JP7637566B2 - Processing system and processing method - Google Patents

Description

This disclosure relates to a processing system and a processing method.

Patent Document 1 discloses a method for processing a wafer having multiple devices formed on its surface side. In this processing method, the wafer is separated and thinned using a modified layer formed inside the wafer by irradiation with laser light as a base point, and the separated surface of the wafer is then ground to remove the modified layer remaining on the separated surface.

International Publication No. 2020/66492

The technology disclosed herein appropriately flattens the peeled surface of a substrate that has been peeled off starting from a modified layer formed by irradiation with laser light.

One aspect of the present disclosure is a processing system for processing a processing object, the processing system including a displacement amount acquisition device that acquires the displacement amount of a separation surface of a separation object separated from a modified layer formed inside the processing object as a base point, a planarization device that irradiates the separation surface with laser light to planarize the separation surface, and a control device, the control device controlling the displacement amount acquisition device to acquire the displacement amount of the separation surface, controlling the planarization device to execute a first planarization process in which a first laser light is irradiated to a convex portion on the separation surface with a large displacement amount, and controlling the planarization device to execute a second planarization process in which a second laser light having a power at least lower than that of the first laser light is irradiated to the separation surface.

According to the present disclosure, when a substrate is peeled off starting from a modified layer formed by irradiation with laser light, the peeled surface of the substrate can be appropriately flattened.

FIG. 2 is a side view showing an outline of a configuration of an overlapping wafer. FIG. 2 is a side view showing the state after separation of the first wafer. 1 is a plan view showing a configuration example of a wafer processing system according to an embodiment of the present invention. FIG. 2 is a side view showing a configuration example of a planarization apparatus according to the present embodiment. 1 is a side view showing a configuration example of a reforming separation device according to an embodiment of the present invention. FIG. 2 is a flow chart showing main steps of wafer processing according to the present embodiment. 1A to 1C are explanatory diagrams of main steps of wafer processing according to the present embodiment. 1 is a plan view showing a state in which an internal surface modification layer is formed on a first wafer. FIG. 1 is a vertical cross-sectional view showing a state in which an internal surface modification layer is formed on a first wafer. FIG. 4 is a vertical cross-sectional view showing a state of a separation surface of a separation wafer immediately after separation. FIG. 5A and 5B are explanatory diagrams showing how a separation surface is flattened in the present embodiment. 13 is an explanatory diagram showing how a separation surface is flattened in accordance with another embodiment. FIG. 13 is an explanatory diagram showing how a separation surface is flattened in accordance with another embodiment. FIG. 13 is an explanatory diagram showing how a separation surface is flattened in accordance with another embodiment. FIG. 13 is an explanatory diagram showing how a separation surface is flattened in accordance with another embodiment. FIG. 10A to 10C are explanatory diagrams of main steps of a wafer processing according to another embodiment.

In the manufacturing process of semiconductor devices, a semiconductor wafer (hereinafter referred to as a wafer) having multiple devices formed on its surface is thinned. There are various methods for thinning a wafer, such as a method of grinding the wafer by contacting a grinding wheel with the back surface of the wafer, or a method of separating the wafer by irradiating the inside of the wafer with laser light to form a modified layer as a base point, as disclosed in Patent Document 1.

However, when the wafer is thinned by separation based on the modified layer, the separation surface of the wafer may have unevenness due to the mixture of positions irradiated and non-irradiated by the laser light when the modified layer is formed, resulting in rough surface accuracy. As disclosed in Patent Document 1, the separation surface of the wafer may be ground to remove the remaining modified layer. However, if the surface accuracy of the separation surface is rough, the grinding resistance may increase, making it difficult to remove the modified layer. In order to properly remove the modified layer remaining on the separation surface, for example, it is possible to improve the surface accuracy prior to grinding the separation surface, that is, to flatten the separation surface, but Patent Document 1 does not disclose or suggest anything about flattening the separation surface prior to this grinding. Therefore, there is room for improvement in conventional wafer processing when separating a wafer based on the modified layer.

The technology disclosed herein has been made in consideration of the above circumstances, and appropriately flattens the peeled surface of a substrate that has been peeled off starting from a modified layer formed by irradiation with laser light. Below, a wafer processing system as a processing system according to this embodiment, and a wafer processing method as a processing method, will be described with reference to the drawings. Note that in this specification and the drawings, elements that have substantially the same functional configuration are denoted with the same reference numerals to avoid redundant description.

In the wafer processing system 1 according to this embodiment, which will be described later, processing is performed on a laminated wafer T, which is a laminated substrate in which a first wafer W as a first substrate and a second wafer S as a second substrate are bonded together, as shown in FIG. 1. Hereinafter, the surface of the first wafer W that is bonded to the second wafer S is referred to as the front surface Wa, and the surface opposite the front surface Wa is referred to as the back surface Wb. Similarly, the surface of the second wafer S that is bonded to the first wafer W is referred to as the front surface Sa, and the surface opposite the front surface Sa is referred to as the back surface Sb.

The first wafer W is a semiconductor wafer such as a silicon substrate, and a device layer Dv including a plurality of devices is formed on the front surface Wa side of the first wafer W. A surface film Fw is further formed on the front surface Wa side of the first wafer W, and the surface film Fw is bonded to a surface film Fs of the second wafer S. Examples of the surface film Fw include an oxide film (THOX film, _SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. The peripheral portion of the first wafer W is chamfered, and the cross section of the peripheral portion has a smaller thickness toward its tip.

The second wafer S is, for example, a wafer that supports the first wafer W. A surface film Fs is formed on the surface Sa of the second wafer S. Examples of the surface film Fs include an oxide film (THOX film, _SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. The second wafer S also functions as a protective material (support wafer) that protects the device layer Dv of the first wafer W. The second wafer S does not need to be a support wafer, and may be a device wafer in which a device layer (not shown) is formed, similar to the first wafer W.

In the drawings used in the following explanation, the device layer Dv and surface films Fw and Fs may be omitted in order to avoid complexity of illustration.

In addition, in the wafer processing system 1 of this embodiment described later, the first wafer W in the overlapped wafer T is separated and thinned as shown in FIG. 2. In the following description, the first wafer W on the separated front surface Wa side is referred to as the first separated wafer W1, and the first wafer W on the separated back surface Wb side is referred to as the second separated wafer W2. Note that the first separated wafer W1 refers to the first wafer W supported by the second wafer S, and may be referred to as the first separated wafer W1 including the second wafer S. The separated sides of the first separated wafer W1 and the second separated wafer W2 may be referred to as the separated surfaces W1a and W2a, respectively.

In the following embodiments, the laminated substrate corresponds to the "processing target" according to the technology disclosed herein, and the separated wafers W1 and W2 correspond to the "separated body" according to the technology disclosed herein.

As shown in FIG. 3, the wafer processing system 1 has a configuration in which the loading/unloading station 2 and processing station 3 are connected together. The loading/unloading station 2 and processing station 3 are arranged side by side from the positive side of the X-axis to the negative side. The loading/unloading station 2 loads/unloads cassettes Ct, Cw1, and Cw2, each capable of housing a plurality of overlapped wafers T, a plurality of first separated wafers W1, and a plurality of second separated wafers W2, for example, between the outside. The processing station 3 is equipped with various processing devices that perform the desired processing on the overlapped wafers T and the separated wafers W1 and W2.

The loading/unloading station 2 is provided with a cassette loading table 10. In the illustrated example, the cassette loading table 10 can freely load multiple cassettes, for example, three cassettes Ct, Cw1, and Cw2, in a row in the Y-axis direction. Note that the number of cassettes Ct, Cw1, and Cw2 loaded on the cassette loading table 10 is not limited to this embodiment and can be determined arbitrarily.

In the loading/unloading station 2, a wafer transport area 20 is provided adjacent to the cassette mounting table 10 on the negative X-axis side of the cassette mounting table 10. The wafer transport area 20 is provided with a wafer transport device 22 that is movable on a transport path 21 extending in the Y-axis direction. The wafer transport device 22 has two transport arms 23, 23 that hold and transport the overlapped wafer T and the separated wafers W1 and W2. Each transport arm 23 is configured to be movable in the horizontal direction (X-axis direction and Y-axis direction), the vertical direction, and around the horizontal axis and the vertical axis. The configuration of the transport arm 23 is not limited to this embodiment and may be any configuration.

The processing station 3 is provided with, for example, three processing blocks G1 to G3 and a wafer transfer area 30. The first processing block G1, the second processing block G2, and the third processing block G3 are arranged in this order from the positive side of the X-axis (the load/unload station 2 side) to the negative side. The first processing block G1 is arranged on the positive side of the X-axis of the wafer transfer area 30, and the second processing block G2 and the third processing block G3 are each arranged on the positive side of the Y-axis of the wafer transfer area 30.

The wafer transport area 30 is provided with a wafer transport device 32 that can move freely on a transport path 31 extending in the X-axis direction. The wafer transport device 32 is configured to be able to transport the overlapped wafer T and the separated wafers W1 and W2 to each processing device in the processing blocks G1 to G3. The wafer transport device 32 also has two transport arms 33, 33 that hold and transport the overlapped wafer T and the separated wafers W1 and W2. Each transport arm 33 is supported by a multi-joint arm member 34 and is configured to be able to move freely in the horizontal direction, vertical direction, around a horizontal axis, and around a vertical axis. The configuration of the transport arm 33 is not limited to this embodiment and may be any configuration.

The first processing block G1 is provided with two wet etching devices 40, 40, two cleaning devices 50, 50, a buffer device 60, and a modified separation device 70. The wet etching device 40, the cleaning device 50, and the buffer device 60 are arranged in this order from the positive side to the negative side of the Y axis. The two wet etching devices 40, 40 are arranged in a stacked configuration. The two cleaning devices 50, 50 are arranged in a stacked configuration. The buffer device 60 and modified separation device 70 are also arranged in a stacked configuration.

The second processing block G2 has an inversion device 80 and a flattening device 90 stacked in this order from the top.

The third processing block G3 is provided with a processing device 100.

The two wet etching devices 40 each etch the separation surfaces W1a, W2a of the separated wafers W1, W2 ground by the processing device 100. For example, a chemical solution (etching solution) is supplied to the separation surfaces W1a, W2a of the separated wafers W1, _W2 . For example, HF, _HNO3 , _H3PO4 , TMAH, Choline, KOH, or the like is used as the chemical solution.

The two cleaning devices 50 each clean the separation surfaces W1a, W2a of the separation wafers W1, W2 ground by the processing device 100. For example, a brush is brought into contact with the separation surfaces W1a, W2a to scrub the separation surfaces W1a, W2a. Note that pressurized cleaning liquid may be used to clean the separation surfaces W1a, W2a.

The buffer device 60 temporarily holds the unprocessed laminated wafer T that is transferred from the wafer transfer area 20 to the wafer transfer area 30. The buffer device 60 may also be configured to adjust the horizontal orientation of the laminated wafer T by detecting the position of the notch portion of the first wafer W with a detection unit (not shown) while rotating the laminated wafer T held on a chuck (not shown), for example, and adjusting the position of the notch portion.

The modification separation device 70, which serves as a separation device, irradiates the inside of the first wafer W with laser light to form an internal surface modification layer, which will be described later, and then separates the first wafer W into a first separation wafer W1 and a second separation wafer W2 using the internal surface modification layer as a base point.

The modified separation device 70 has a chuck 71 that holds the overlapped wafer T with the first wafer W on top and the second wafer S on the bottom as shown in FIG. 4. The chuck 71 is configured to be movable in the X-axis direction and/or the Y-axis direction by a moving unit 72. The moving unit 72 is configured as a precision XY stage, for example. The chuck 71 is also configured to be rotatable around a vertical axis by a rotating unit 73.

A laser head 74 is provided above the chuck 71, which irradiates the inside of the first wafer W with laser light. The laser head 74 irradiates a desired position inside the first wafer W with high-frequency pulsed laser light (e.g., YAG laser) oscillated from a laser light oscillator (not shown) and having a wavelength that is transparent to the first wafer W. As a result, the portion inside the first wafer W where the laser light is focused is modified, and an internal surface modification layer is formed. The laser head 74 is configured to be movable in the X-axis direction and/or the Y-axis direction by the moving unit 75. The moving unit 75 is configured, for example, as a precision XY stage. The laser head 74 is also configured to be movable in the Z-axis direction by the lifting unit 76.

A suction pad 77 is provided above the chuck 71 to suction-hold the back surface Wb of the first wafer W. The suction pad 77 is configured to be rotatable around a vertical axis by a rotating part 78. The suction pad 77 is also configured to be movable in the Z-axis direction by a lifting part 79.

The modification separation device 70 may also be configured to acquire the position of the internal surface modification layer formed inside the first wafer W, or the position of the internal surface modification layer remaining on the separation surfaces of the separation wafers W1 and W2, for example, by imaging the polymerized wafer T held on the chuck 71 with an imaging mechanism (not shown), such as a CCD camera.

The inversion device 80 inverts the front and back sides of the second separated wafer W2 separated by the modification separation device 70. The configuration of the inversion device 80 is optional.

The two planarization devices 90 each irradiate laser light onto the separation surfaces W1a, W2a of the separated wafers W1, W2 separated by the modification separation device 70, and planarize the separation surfaces W1a, W2a prior to the grinding process in the processing device 100. In the following description, "planarization" refers to a process that improves the surface precision (surface roughness) of the separation surfaces W1a, W2a of the first wafer W (separated wafers W1, W2) after separation in the modification separation device 70, thereby reducing the grinding resistance during the grinding process in the processing device 100 described below.

The flattening device 90 has a chuck 91 that holds the first separated wafer W1 with the separation surface W1a on the upper side and the back surface Sb of the second wafer S on the lower side, as shown in FIG. 5. The chuck 91 is configured to be movable in the X-axis direction and/or the Y-axis direction by a moving part 92. The moving part 92 is configured as a precision XY stage, for example. The chuck 91 is also configured to be rotatable around a vertical axis by a rotating part 93. When flattening the second separated wafer W2 in the flattening device 90, the chuck 91 holds the second separated wafer W2 with the separation surface W2a on the upper side and the back surface Wb of the first wafer W on the lower side.

Above the chuck 91, a laser head 94 is provided for irradiating the separation surfaces W1a and W2a of the separation wafers W1 and W2 with laser light. The laser head 94 irradiates the desired positions of the separation surfaces W1a and W2a of the separation wafers W1 and W2 with high-frequency pulsed laser light (for example, an ultrashort pulse laser such as a picosecond laser or a femtosecond laser) oscillated from a laser light oscillator (not shown). This removes the portion of the separation surfaces W1a and W2a of the separation wafers W1 and W2 where the laser light is focused, thereby flattening the separation surfaces W1a and W2a (improving the surface accuracy). The laser head 94 is configured to be movable in the X-axis direction and/or the Y-axis direction by the moving unit 95, and is configured to be able to arbitrarily adjust the irradiation position of the laser light on the separation surfaces W1a and W2a by, for example, a galvano scanner. The moving unit 95 is configured as a precision XY stage, for example. The laser head 94 is also configured to be movable in the Z-axis direction by the lifting unit 96.

The laser head 94 may further include a spatial light modulator (not shown). The spatial light modulator modulates and outputs the laser light. Specifically, the spatial light modulator can control the focal position and phase of the laser light, and can adjust the shape and number (number of branches) of the irradiated laser light. At this time, the branched and irradiated laser light is configured so that the output, etc., of each branch can be adjusted. Note that, for example, LCOS (Liquid Crystal Silicon) can be selected as the spatial light modulator.

The planarization device 90 also has an imaging mechanism 97 that captures images of the separation surfaces W1a, W2a of the separated first wafer W (separated wafers W1, W2) to detect the surface condition. For example, a CCD camera or the like can be used as the imaging mechanism 97. Then, based on the surface condition of the separation surfaces W1a, W2a obtained from the imaging results by the imaging mechanism 97, it is possible to obtain, for example, the position of the internal surface modification layer remaining on the separation surfaces W1a, W2a, the amount of displacement of the separation surfaces W1a, W2a, etc., which will be described later.

As shown in FIG. 3, the processing device 100 grinds the separation surface W1a of the first separated wafer W1 and the separation surface W2a of the second separated wafer W2. The processing device 100 has a rotating table 110, a first grinding unit 120, and a second grinding unit 130.

The rotating table 110 is configured to be freely rotatable around a vertical rotation center line 111 by a rotating mechanism (not shown). Four chucks 112 are provided on the rotating table 110 to suction and hold the separated wafers W1 and W2. The chucks 112 are evenly arranged on the same circumference as the rotating table 110, that is, at 90 degree intervals. The four chucks 112 can be moved to the transfer positions A1 and A2 and the processing positions B1 and B2 by the rotation of the rotating table 110. Each chuck 112 is held by a chuck base (not shown) and configured to be rotatable by a rotating mechanism (not shown).

In this embodiment, the first transfer position A1 is a position on the negative X-axis side and the negative Y-axis side of the rotating table 110, where the first separated wafer W1 is transferred. The second transfer position A2 is a position on the positive X-axis side and the negative Y-axis side of the rotating table 110, where the second separated wafer W2 is transferred. The first processing position B1 is a position on the positive X-axis side and the positive Y-axis side of the rotating table 110, where the first grinding unit 120 is located. The second processing position B2 is a position on the negative X-axis side and the positive Y-axis side of the rotating table 110, where the second grinding unit 130 is located.

In the first grinding unit 120, the separation surface W1a of the first separated wafer W1 is ground. The first grinding unit 120 has a first grinding section 121 equipped with a grinding wheel (not shown) that is annular and can rotate freely. The first grinding section 121 is configured to be movable vertically along a support 122. Then, with the separation surface W1a of the first separated wafer W1 held by the chuck 112 in contact with the grinding wheel, the chuck 112 and the grinding wheel are rotated, and the grinding wheel is lowered to grind the separation surface W1a of the first separated wafer W1. This reduces the thickness of the first separated wafer W1 to a desired thickness and flattens the separation surface W1a of the first separated wafer W1.

In the second grinding unit 130, the separation surface W2a of the second separated wafer W2 is ground. The second grinding unit 130 has a second grinding section 131 equipped with a grinding wheel (not shown) that is annular and can rotate freely. The second grinding section 131 is configured to be movable vertically along a support 132. Then, with the separation surface W2a of the second separated wafer W2 held by the chuck 112 in contact with the grinding wheel, the chuck 112 and the grinding wheel are rotated, and the grinding wheel is lowered to grind the separation surface W2a of the second separated wafer W2. This reduces the thickness of the second separated wafer W2 to a desired thickness and flattens the separation surface W2a of the second separated wafer W2.

The wafer processing system 1 described above is provided with a control device 140. The control device 140 is, for example, a computer, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the laminated wafer T in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of the drive systems of the various processing devices and transport devices described above to realize the wafer processing described below in the wafer processing system 1. The above program may be recorded on a computer-readable storage medium and installed from the storage medium into the control device 140. The above storage medium may be temporary or non-temporary.

Next, we will explain the wafer processing performed using the wafer processing system 1 configured as described above. In this embodiment, the first wafer W and the second wafer S are bonded together to form a laminated wafer T in advance.

First, a cassette Ct containing multiple overlapping wafers T is placed on the cassette placement table 10 of the loading/unloading station 2. Next, the overlapping wafers T in the cassette Ct are removed by the wafer transfer device 22 and transferred to the buffer device 60. In the buffer device 60, the horizontal orientation of the overlapping wafers T (first wafer W) may be adjusted.

Next, the laminated wafer T is transported by the wafer transport device 32 to the modified separation device 70. In the modified separation device 70, an internal surface modified layer M1 is formed inside the first wafer W as shown in FIG. 7(a) (step P1 in FIG. 6). The internal surface modified layer M1 serves as the base point when the first wafer W is separated into the first separated wafer W1 and the second separated wafer W2.

Specifically, as shown in FIG. 8, the chuck 71 (superimposed wafer T) is rotated by the rotating unit 73, and the superimposed wafer T and the laser head 74 are moved horizontally relative to each other to form multiple internal surface modification layers M1, for example, in a spiral shape in a cross-sectional view, inside the first wafer W. These multiple internal surface modification layers M1 are formed at the same height inside the first wafer W. Then, the internal surface modification layers M1 are formed on the entire internal surface of the first wafer W. Here, the internal surface modification layers M1 are formed at a circumferential interval P (pulse pitch) and a radial interval Q (index pitch). The circumferential interval P (pulse pitch) and the radial interval Q (index pitch) may be changed midway, that is, the circumferential interval P (pulse pitch) and/or the radial interval Q (index pitch) may be different between the outer circumference and the inner circumference of the first wafer W.

In FIG. 8, the dashed arrow indicates the trajectory of movement of the position of the laser head 74 (the irradiation position of the laser light L) relative to the first wafer W, and the open circle within the surface of the first wafer W indicates the formed internal surface modification layer M1.

The internal surface modification layer M1 is formed by irradiating the inside of the first wafer W with laser light L from the laser head 74 as shown in FIG. 9. The lower end of the internal surface modification layer M1 is located above the target surface (dotted line in FIG. 9) of the first wafer W after grinding in the processing device 100. In addition, a crack C1 propagates from the internal surface modification layer M1 in the surface direction.

After the internal surface modification layer M1 is formed inside the first wafer W, the first wafer W is then separated into a first separated wafer W1 and a second separated wafer W2 using the internal surface modification layer M1 as a base point, as shown in FIG. 7(b) (step P2 in FIG. 6). Specifically, in the modification separation device 70, the back surface Wb of the first wafer W is suction-held by an adsorption pad 77. The adsorption pad 77 is then raised to separate the second separated wafer W2 from the first separated wafer W1. At this time, the adsorption pad 77 may be rotated to separate the first separated wafer W1 and the second separated wafer W2 at the boundary of the internal surface modification layer M1.

As shown in FIG. 7B and FIG. 10, an inner surface modification layer M1 remains on the separation surface W1a of the first separated wafer W1 and the separation surface W2a of the second separated wafer W2, respectively.
8 and 9, the surface of the first wafer W after the laser light L is irradiated includes a portion that is not directly irradiated with the laser light L, i.e., a portion where the internal surface modification layer M1 is formed, and a portion where the crack C1 has progressed. In other words, the separation surface W1a of the first separation wafer W1 and the separation surface W2a of the second separation wafer W2 each include a portion separated with the internal surface modification layer M1 as a base point and a portion separated with the crack C1 as a base point. As a result, uneven portions are formed on the separation surfaces W1a and W2a as shown in FIG. 7B and FIG. 10, respectively, and the surface accuracy is reduced.

Here, in the processing device 100, if the surface precision of the separation surfaces W1a, W2a is reduced as shown in FIG. 10, there is a risk that the removal of the internal surface modification layer M1 cannot be properly performed as described above. Therefore, in the wafer processing system 1 according to this embodiment, prior to the grinding process in the processing device 100, the uneven portions formed on the separation surfaces W1a, W2a in this manner are removed to improve the surface precision (flatten).

After the first wafer W is separated into the first separated wafer W1 and the second separated wafer W2, the first separated wafer W1 is then transported to the planarization device 90 by the wafer transport device 32. In the planarization device 90, the image capturing mechanism 97 first captures an image of the separated surface W1a of the first separated wafer W1, and the displacement amount H of the uneven portion of the separated surface W1a shown in FIG. 10 (the distance from a reference surface (e.g., the bonding surface between the first wafer W and the second wafer S) to the separated surface W1a) is calculated (step P3 in FIG. 6). At this time, the chuck 91 may be rotated to adjust the horizontal orientation of the first separated wafer W1.

The amount of displacement H of the uneven portion can be calculated based on the distance between adjacent recesses (the radial distance Q of the internal surface modification layer M1 shown in FIG. 8) obtained by, for example, imaging the separation surfaces W1a and W2a of the separation wafers W1 and W2.

In parallel with step P3, the second separated wafer W2 is transported by the wafer transport device 32 to the inversion device 80. In the inversion device 80, the front and back sides of the second separated wafer W2 are inverted (step P4 in FIG. 6).

The second separated wafer W2, whose front and back sides have been inverted, is transported to the planarization device 90 by the wafer transport device 32. In the planarization device 90, the separation surface W2a of the second separated wafer W2 is first imaged, and the amount of displacement H of the uneven portion of the separation surface W2a is obtained (step P5 in FIG. 6). At this time, the chuck 91 may be rotated to adjust the horizontal orientation of the second separated wafer W2.

In this embodiment, the displacement amount H of the uneven portion is calculated based on the imaging results of the separation surfaces W1a, W2a by the imaging mechanism 97 as shown in steps P3 and P5, but the displacement amount H of the uneven portion can be acquired by any method. Specifically, for example, the displacement amount H may be directly measured using a laser displacement meter or the like, or, for example, the capacitance distribution within the separation surface W1a may be measured and the displacement amount H may be calculated based on the measured capacitance distribution.
Furthermore, the position where the displacement amount H is acquired is not limited to the planarization device 90, and the displacement amount H may be acquired in the buffer device 60, the modified separation device 70, or the inversion device 80. Alternatively, an independent displacement amount acquisition device (not shown) may be disposed in the wafer processing system 1.

After the images of the separation surfaces W1a and W2a of the separation wafers W1 and W2 are captured, the separation surfaces W1a and W2a of the separation wafers W1 and W2 are then flattened (step P6 in FIG. 6) as shown in FIG. 7(c) and FIG. 7(d). Specifically, the projections formed on the separation surfaces W1a and W2a are irradiated with laser light to remove the projections by ablation processing.

Here, in order to properly remove the convex portions formed on the separation surfaces W1a and W2a, it is necessary to adjust the amount of energy of the irradiated laser light according to the profile of the separation surfaces W1a and W2a. That is, it is necessary to irradiate the laser light with high output at the portions (convex portions) where the displacement amount H is large, and with low output at the portions (concave portions) where the displacement amount H is small. However, since it takes time (approximately 0.5 to 1.0 seconds) to change the output of the laser light irradiated from the laser head 94, if the output is changed sequentially according to the profile of the separation surfaces W1a and W2a, it takes a long time to flatten the entire surfaces of the separation surfaces W1a and W2a.

In this embodiment, therefore, in order to shorten the time required for the planarization process of the separation surfaces W1a and W2a, the following two methods are controlled in the planarization process. The methods below are controlled, for example, by the control device 140. Note that the planarization process for the separation surface W2a is performed in the same manner as the planarization process for the separation surface W1a, so in the following explanation, the planarization process for the separation surface W1a is illustrated as a representative example.

The first method is to independently control the processing using a high-power laser light (first laser light) and the processing using a low-power laser light (second laser light) in order to reduce the number of times the laser light output is changed during the flattening process.

Specifically, first, as shown in FIG. 11(a), a high-power laser beam is irradiated onto a convex portion D with a large displacement amount H, and the displacement amount H1 at the convex portion D is made to substantially coincide with the displacement amount H2 at a concave portion (a portion between adjacent convex portions D) as shown in FIG. 11(b) (first flattening process). The irradiation of the high-power laser beam onto the convex portion D is performed on the entire convex portions D on the separation surfaces W1a and W2a.

Next, low-power laser light is irradiated onto the entire surfaces of the separation surfaces W1a, W2a of the separation wafers W1, W2, which have been displaced by H2, to make the displacement amount H on the entire surfaces of the separation surfaces W1a, W2a approximately equal as shown in FIG. 11(c), i.e., to improve the surface precision of the separation surfaces W1a, W2a (second planarization process). At this time, since the convex portions D formed on the separation surfaces W1a, W2a as shown in FIG. 11(a) and FIG. 11(b) have been removed in advance, the surface precision on the entire surfaces of the separation surfaces W1a, W2a can be appropriately improved without changing the output of the low-power laser light midway.

According to this first method, without sequentially changing the output according to the profile of the separation surfaces W1a, W2a, the convex portion D is removed in advance to make the displacement amount H approximately uniform, and then a low-output laser beam is irradiated to improve the surface precision of the separation surfaces W1a, W2a. This significantly reduces the number of times the output of the laser beam is changed, specifically to just one time, and therefore appropriately shortens the time required to flatten the entire surfaces of the separation surfaces W1a, W2a.

The second method is to split the laser light into multiple beams when the laser head 94 has the spatial light modulator (e.g., LCOS) described above in order to reduce the number of times the laser light output is changed or the number of times the laser light is irradiated during the series of flattening processes.

The specific method is the same as the first method shown in FIG. 11, that is, the surface accuracy over the entire surface of the separation surfaces W1a and W2a is improved by sequentially performing the first planarization process and the second planarization process. In this second method, the laser light L is split into multiple (two in the illustrated example) by a spatial light modulator as shown in FIG. 12, and the laser light L is irradiated simultaneously to multiple points on the separation surfaces W1a and W2a. More specifically, after the first laser light is irradiated simultaneously to multiple convex portions D to perform the above-mentioned first planarization process, the second laser light is irradiated simultaneously to multiple points on the separation surfaces W1a and W2a to perform the above-mentioned second planarization process. This makes it possible to expand the area that can be planarized at one time, thereby shortening the time required for the planarization process of the separation surfaces W1a and W2a.

In FIG. 12, a case is illustrated in which a plurality of first laser beams branched by a spatial light modulator are simultaneously irradiated onto a plurality of convex portions D, and a plurality of second laser beams are simultaneously irradiated onto separation surfaces W1a and W2a. However, as shown in FIG. 13, the first flattening process and the second flattening process described above may be performed simultaneously by simultaneously irradiating laser beam L onto convex portion D and the adjacent concave portion.

More specifically, as shown in FIG. 13, the first laser light is irradiated onto the convex portion D while moving the laser head 94, and the second laser light is irradiated onto the separation surfaces W1a and W2a so as to follow the irradiation of the first laser light onto the convex portion D. That is, in the example shown in FIG. 12, after the first flattening process is performed, the output of the laser light is changed, and the second laser light is then irradiated to perform the second flattening process, but in the example shown in FIG. 13, the second laser light is irradiated onto the separation surfaces W1a and W2a immediately after the first laser light is irradiated onto the convex portion D. This allows the first flattening process and the second flattening process to be performed approximately simultaneously without changing the output of the laser light L.

In such a case, it is desirable to independently control the output of the first laser light L to the convex portion D and the output of the second laser light L to the separation surfaces W1a, W2a after removing the convex portion D. This allows the first planarization process and the second planarization process to be performed substantially simultaneously as described above, so that the entire separation surfaces W1a, W2a can be planarized without changing the output of the laser light, i.e., the time required for the planarization process can be significantly reduced.

The planarization process according to the embodiment is carried out as described above. Next, the first separated wafer W1 that has been subjected to the planarization process is transported by the wafer transport device 32 to the processing device 100 and transferred to the chuck 112 at the first transfer position A1. At the same time, the second separated wafer W2 is inverted in the inversion device 80, and then transported by the wafer transport device 32 to the processing device 100 and transferred to the chuck 112 at the second transfer position A2.

Next, the rotary table 110 is rotated 180° around the vertical axis to move the first separated wafer W1 to the first processing position B1, and the second separated wafer W2 to the second processing position B2.

Next, the separation surface W1a of the first separated wafer W1 is ground at the first processing position B1, and the height position of the separation surface W1a (thickness of the first separated wafer W1) is reduced to the target surface as shown in FIG. 7(e) and FIG. 11(d). At the same time, the separation surface W2a of the second separated wafer W2 is ground at the second processing position B2 (step P7 in FIG. 6). At this time, the surface accuracy of the separation surfaces W1a, W2a of the separated wafers W1, W2 has been improved by the planarization process of step P6. This allows the grinding units 120, 130 to properly grind the separation surfaces W1a, W2a.

Next, the rotary table 110 is rotated 180° around the vertical axis to move the first separated wafer W1 to the first transfer position A1 and the second separated wafer W2 to the second transfer position A2. At the first transfer position A1, the separated surface W1a of the first separated wafer W1 may be cleaned with a cleaning liquid using a cleaning liquid nozzle (not shown). At the second transfer position A2, the separated surface W2a of the second separated wafer W2 may be cleaned with a cleaning liquid using a cleaning liquid nozzle (not shown).

Next, the first separated wafer W1 is transferred to one cleaning device 50 by the wafer transfer device 32, and the second separated wafer W2 is transferred to the other cleaning device 50 by the wafer transfer device 32. In the cleaning device 50, the separated surfaces W1a and W2a of the separated wafers W1 and W2 are scrubbed and cleaned, respectively (step P8 in FIG. 6).

Next, the first separated wafer W1 is transferred to one wet etching device 40 by the wafer transfer device 22, and the second separated wafer W2 is transferred to the other wet etching device 40 by the wafer transfer device 22. In the wet etching device 40, the separated surfaces W1a, W2a of the separated wafers W1, W2 are wet etched with a chemical solution (step P9 in FIG. 6). Grinding marks may be formed on the separated surfaces W1a, W2a ground by the processing device 100 described above. In this step P9, the grinding marks can be removed by wet etching, and the separated surfaces W1a, W2a can be smoothed.

Then, the first separated wafer W1 and the second separated wafer W2, which have been subjected to all the processes, are transferred by the wafer transfer device 22 to the cassettes Cw1 and Cw2 on the cassette mounting table 10, respectively. This completes the series of wafer processes in the wafer processing system 1. The first separated wafer W1 having the device layer Dv is commercialized. The second separated wafer W2 is reused, for example.

According to the above embodiment, prior to grinding the separation surfaces W1a, W2a of the separation wafers W1, W2, the surface precision is improved by irradiating the separation surfaces W1a, W2a with laser light. This prevents the unevenness formed on the separation surfaces W1a, W2a from interfering with the grinding process, meaning that the separation surfaces W1a, W2a can be appropriately ground.

In addition, in the planarization process aimed at improving surface accuracy according to the embodiment, in order to reduce the number of times the output of the laser light L is changed according to the amount of displacement H of the convex portion D formed on the separation surfaces W1a and W2a, a first planarization process using a high-output laser light L and a second planarization process using a low-output laser light L are each performed independently. As a result, the output of the laser light L needs to be changed only when transitioning from the first planarization process to the second planarization process, and therefore the number of times the output of the laser light L is changed can be appropriately reduced to shorten the time required for the planarization process.

In addition, in the flattening process according to the embodiment, the laser light irradiated from the laser head 94 is split by a spatial light modulator, and the laser light is irradiated simultaneously to multiple points on the separation surfaces W1a and W2a. This increases the area irradiated with the laser light L at one time, shortening the time required for the flattening process, and also reduces the number of times the output of the laser light L is changed, further shortening the time required for the flattening process.

In the above embodiment, the conditions for the planarization process in the planarization device 90 (such as the output and irradiation position of the laser light L) are determined based on the amount of displacement H of the uneven portion calculated based on the imaging results of the separation surfaces W1a and W2a, but the method for determining the conditions for the planarization process is not limited to the above embodiment.

Specifically, the conditions of the planarization process in the planarization device 90 may be controlled based on, for example, the conditions for forming the internal surface modified layer M1 in the modification separation device 70 (the conditions for irradiating the laser light when forming the internal surface modified layer M1 in the modification separation device 70).

As described above, the displacement amount H of the uneven portions of the separation surfaces W1a and W2a can be calculated based on the irradiation conditions of the laser light L (e.g., output, irradiation time, etc.) and the circumferential spacing P and radial spacing Q of the internal surface modified layer M1 shown in FIG. 8. The irradiation conditions of the laser light L and the pitch of the internal surface modified layer M1 can be obtained by referring to the processing recipe in the modified separation device 70. From this perspective, the displacement amount H of the uneven portions of the separation surfaces W1a and W2a may be estimated and calculated by referring to the processing recipe in the modified separation device 70 instead of imaging the separation surfaces W1a and W2a. In other words, the conditions of the planarization process in the planarization device 90 may be determined based on the formation conditions of the internal surface modified layer M1.

In the above embodiment, the separation surfaces W1a, W2a of the separated wafers W1, W2 after separation in the modified separation device 70 are imaged. However, as described above, the displacement amount H of the uneven portion can be calculated based on the circumferential spacing P and radial spacing Q of the internal surface modified layer M1. From this perspective, the circumferential spacing P and radial spacing Q may be detected by imaging the back surface Wb (irradiation surface of the laser light L) of the first wafer W before separation after the formation of the internal surface modified layer M1, instead of imaging the separation surfaces W1a, W2a. In this case, the imaging of the back surface Wb (irradiation surface of the laser light L) of the first wafer W may be performed inside the modified separation device 70 instead of the flattening device 90, or may be performed, for example, in the buffer device 60.

In the above embodiment, the surface precision of the separation surfaces W1a and W2a is improved (flattened) in the flattening device 90, thereby reducing the grinding resistance in the grinding process in the processing device 100. However, the flattening device 90 may further remove the internal surface modification layer M1 remaining on the separation surfaces W1a and W2a. By removing the internal surface modification layer M1, which is the portion where the Si crystal has become amorphous, in the flattening device 90, it is not necessary to grind both the amorphous portion and the Si single crystal portion in the grinding process in the processing device 100. This prevents differences in the grinding resistance value within the separation surfaces W1a and W2a due to differences in the crystal structures of the amorphous portion and the Si single crystal portion, and allows the grinding process to be performed efficiently.

Specifically, first, high-power laser light L is irradiated (first planarization process) to make the displacement amount H1 at the convex portion D approximately equal to the displacement amount H2 at the concave portion D, as shown in FIG. 14(b). Next, as shown in FIG. 14(c), low-power laser light L is irradiated (second planarization process) to reduce the height position (thickness of the first separated wafer W1) of the separation surfaces W1a, W2a to the target surface from which the internal surface modification layer M1 is removed, and the separation surfaces W1a, W2a are planarized at the target surface. In other words, the internal surface modification layer M1 is removed at the same time as the planarization process of the separation surfaces W1a, W2a in the planarization device 90 is performed.

In the example shown in FIG. 14, the internal surface modification layer M1 is removed down to the target surface in the second planarization process in which low-power laser light L is irradiated, but the removal of the internal surface modification layer M1 in the planarization device 90 can be performed by any method. Specifically, for example, as shown in FIG. 15(b), the displacement amount H1 in the convex portion D may be reduced to the target surface in the first planarization process, and then the displacement amount H2 in the concave portion may be reduced to the target surface in the second planarization process.

Furthermore, even when the internal surface modification layer M1 is removed in the flattening device 90, the laser light L from the laser head 94 may be split into multiple beams by a spatial light modulator, as in the above embodiment. In such a case, the split laser light L may be irradiated simultaneously onto the multiple convex portions D, or may be irradiated simultaneously onto both the convex portions D and the concave portions.
Furthermore, when multiple branched laser beams L are simultaneously irradiated onto the convex portions D and concave portions D, respectively, it is desirable to control the output of each laser beam L to an output that can reduce the displacement amount H of the convex portions D and concave portions D to the target surface.

Here, the peripheral portion of the first wafer W is usually chamfered, but if an internal surface modification layer M1 is formed on the entire surface of the first wafer W and then separation is performed as shown in FIG. 7, the peripheral portion of the first wafer W will have a sharply pointed shape (a so-called knife-edge shape). This may cause chipping at the peripheral portion of the first wafer W, which may damage the first wafer W. Therefore, a so-called edge trim may be performed to remove the peripheral portion of the first wafer W before the grinding process.

Therefore, edge trimming may be performed in the wafer processing system 1 of the above embodiment. Below, wafer processing according to other embodiments performed using the wafer processing system 1 will be described. Note that in this embodiment, detailed description of processing similar to that of the above embodiment will be omitted.

The laminated wafer T is transported to the modification separation device 70 by the wafer transport device 32. In the modification separation device 70, as shown in Figures 16(b) and 16(c), a peripheral modification layer M2 and an internal surface modification layer M1 are sequentially formed inside the first wafer W.

The peripheral modified layer serves as a base point for removing the peripheral portion We during edge trimming, and is formed in a ring shape along the boundary between the peripheral portion We and the central portion Wc to be removed in the first wafer W. Furthermore, inside the first wafer W, a crack C2 has developed from the peripheral modified layer M2 and reached the front surface Wa. However, the crack C2 has not reached the back surface Wb.

The internal surface modification layer M1 is formed in the surface direction from the center to the peripheral modification layer M2, i.e., in the central portion Wc. The method for forming the internal surface modification layer M1 is the same as in the above embodiment (step P1 in FIG. 6).

Next, in the same modified separation device 70, the first wafer W is separated into a first separated wafer W1 and a second separated wafer W2 using the inner surface modified layer M1 and the peripheral modified layer M2 as base points, as shown in FIG. 16(d). At this time, the second separated wafer W2 is separated together with the peripheral portion We. The method of separating the first wafer W is the same as in the above embodiment (step P2 in FIG. 6).

Next, the first separated wafer W1 is transported to the planarization device 90 by the wafer transport device 32. In the planarization device 90, the separation surface W1a of the first separated wafer W1 is first imaged, and the amount of displacement H of the uneven portion of the separation surface W1a is obtained. At this time, the horizontal orientation of the first separated wafer W1 may be adjusted.

In parallel with this, the second separated wafer W2 is transported by the wafer transport device 32 to the inversion device 80. In the inversion device 80, the front and back surfaces of the second separated wafer W2 are inverted.

The second separated wafer W2, whose front and back sides have been inverted, is transported to the planarization device 90 by the wafer transport device 32. In the planarization device 90, the separation surface W2a of the second separated wafer W2 is first imaged, and the amount of displacement H of the uneven portion of the separation surface W2a is obtained. At this time, the horizontal orientation of the second separated wafer W2 may be adjusted.

Then, in the planarization device 90, as shown in FIG. 16(e) and FIG. 16(f), the separation surfaces W1a and W2a of the separation wafers W1 and W2 are planarized, respectively. Specifically, the projections formed on the separation surfaces W1a and W2a are irradiated with laser light to remove the projections by ablation processing. The method for planarizing the separation surfaces W1a and W2a is the same as in the above embodiment (step P6 in FIG. 6).

Next, the first separated wafer W1 and the second separated wafer W2 are each transported to the processing device 100 by the wafer transport device 32. In the processing device 100, the separation surface W1a of the first separated wafer W1 is ground as shown in FIG. 16(g) to remove the peripheral modified layer M2 and the internal surface modified layer M1 remaining on the separation surface W1a. At the same time, the separation surface W2a of the second separated wafer W2 is ground as shown in FIG. 16(h) to remove the peripheral modified layer M2 and the internal surface modified layer M1 remaining on the separation surface W2a. The method of grinding the separation surfaces W1a and W2a is the same as in the above embodiment (step P7 in FIG. 6).

The subsequent processing is the same as in the above embodiment (steps P8 and P9 in FIG. 6). That is, the ground separated wafers W1 and W2 are sequentially cleaned in the cleaning device 50 and etched in the wet etching device 40.

In this embodiment, the same effects as those of the above embodiment can be obtained. Moreover, in this embodiment, the peripheral portion We of the first wafer W is removed by edge trimming, which prevents the peripheral portion We from forming a so-called knife edge shape.

In addition, in the above embodiment, the planarization process is performed in a planarization device 90 that is independently arranged inside the wafer processing system 1, but the planarization process may be performed, for example, in a modification separation device 70. In such a case, since the laser light (e.g., YAG laser) for forming the internal surface modification layer M1 and the laser light (e.g., picosecond laser) for performing the planarization process are different, it is preferable that the laser heads for irradiating each laser light are independently arranged.

In the above embodiment, the internal surface modified layer M1, which serves as the base point for separating the first wafer W, and the peripheral modified layer M2, which serves as the base point for removing the peripheral portion We, are formed in the modified separation device 70, but the formation positions of these modified layers are not limited to this. Specifically, for example, a separation device (not shown) that separates the first wafer W and a modification device (not shown) that forms the internal surface modified layer M1 and the peripheral modified layer M2 may be independently arranged inside the wafer processing system 1, and these modified layers may be formed inside the modification device.

In the above embodiment, the processing object is a silicon wafer, but the type of processing object is not limited to this. For example, instead of a silicon substrate, a glass substrate, a single crystal substrate, a polycrystalline substrate, or an amorphous substrate may be selected as the processing object. Also, for example, instead of a circular substrate, an ingot, a base, or a thin plate may be selected.

In addition, in the above embodiment, the case of thinning the first wafer W in the overlapped wafer T has been described, but the above embodiment can also be applied to the case of thinning a single wafer.

The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

REFERENCE SIGNS LIST 1 wafer processing system 70 planarization device 140 control device D convex portion H displacement amount L laser light M1 internal surface modified layer S second wafer T overlapped wafer W first wafer W1 first separated wafer W1a separated surface W2 second separated wafer W2a separated surface

Claims (20)

A processing system for processing an object to be processed, comprising:
a displacement acquisition device that acquires a displacement amount of a separation surface of a separated body that is separated from the processing object with respect to a modified layer formed inside the processing object as a base point;
a planarization device that irradiates the separation surface with a laser beam to planarize the separation surface;
A control device,
The control device includes:
performing control to acquire an amount of displacement of the separation surface in the displacement amount acquisition device;
performing control in the planarization device to execute a first planarization process in which a first laser light is irradiated onto a convex portion having a large amount of displacement on the separation surface;
and performing control in the planarization device to perform a second planarization process in which the separation surface is irradiated with a second laser beam having an output lower than that of the first laser beam. The processing system according to claim 1, further comprising a separation device that separates the processing object into a plurality of separated bodies based on the modified layer. The processing system according to claim 1 or 2, wherein the displacement acquisition device is integral with the flattening device. the flattening device is configured to be capable of simultaneously irradiating a plurality of the laser beams onto different positions on the separation surface;
The control device includes:
a control for simultaneously irradiating different convex portions with a plurality of the first laser beams in the first planarization process;
4. The processing system according to claim 1, further comprising: a control for simultaneously irradiating different positions on the separation surface with a plurality of the second laser beams in the second planarization process. the flattening device is configured to be capable of simultaneously irradiating a plurality of the laser beams onto different positions on the separation surface;
The control device includes:
The processing system according to any one of claims 1 to 3, wherein control is performed to simultaneously perform the first planarization process and the second planarization process by simultaneously irradiating the first laser light onto the convex portion and irradiating the second laser light onto a concave portion adjacent to the convex portion and having a smaller displacement than the convex portion. The processing system according to claim 5, wherein the control device performs control to independently adjust the output of the first laser light and the second laser light that are irradiated simultaneously. the processing object is a laminated substrate in which a front surface side of a first substrate and a front surface side of a second substrate are bonded together,
The processing object is separated into a first separation substrate on a front side and a second separation substrate on a back side of the first substrate, using the modified layer formed inside the first substrate as a base point;
7. The processing system according to claim 1, wherein the planarizing device planarizes at least the separation surface of the first separation substrate. A reversing device for reversing the front and back surfaces of the second separation substrate,
The processing system according to claim 7 , wherein the planarizing device planarizes the separation surface of the second separated substrate after inversion. The control device includes:
9. The processing system according to claim 7, wherein control is performed so that the peripheral portion of the first substrate is removed together with the second separated substrate. The processing system according to any one of claims 1 to 9, comprising a processing device that grinds the separation surface after planarization. A method for processing an object to be processed, comprising the steps of:
acquiring a displacement amount of a separation surface of a separated body separated from the processing object with a modified layer formed inside the processing object as a base point;
performing a first planarization process by irradiating the separation surface with a first laser light to remove convex portions on the separation surface that have a large amount of displacement;
and performing a second planarization process by irradiating the separation surface with a second laser beam having a lower output than at least the first laser beam, thereby making the amount of displacement uniform over the entire surface of the separation surface. The processing method according to claim 11, further comprising separating the processing object into a plurality of separate bodies using the modified layer as a base point. The processing method according to claim 11 or 12, in which the acquisition of the displacement amount of the separation surface and the first flattening process and the second flattening process of the separation surface are performed in the same device. In the first planarization process, a plurality of first laser beams are simultaneously irradiated onto different convex portions formed on the separation surface;
The processing method according to claim 11, further comprising: irradiating different positions of the separation surface with a plurality of the second laser beams simultaneously in the second planarization process. The processing method according to any one of claims 11 to 13, in which the first planarization process and the second planarization process are performed simultaneously by simultaneously irradiating the first laser light onto the convex portion and irradiating the second laser light onto a concave portion adjacent to the convex portion and having a smaller displacement than the convex portion. The processing method according to claim 15, wherein the outputs of the first laser light and the second laser light, which are irradiated simultaneously, are adjusted independently. the processing object is a laminated substrate in which a front surface side of a first substrate and a front surface side of a second substrate are bonded together,
The processing object is obtained by separating the first substrate into a first separation substrate on a front side and a second separation substrate on a back side, using the modified layer formed inside the first substrate as a base point;
The processing method according to any one of claims 11 to 16, wherein the first planarization process and the second planarization process are performed on at least the separation surface of the first separation substrate. inverting the second separated substrate after separation;
20. The method of claim 17, further comprising: performing the first planarization process and the second planarization process on the separated surface of the second separated substrate after inversion. The processing method according to claim 17 or 18, wherein the peripheral portion of the first substrate is removed from the first substrate together with the second separation substrate. The method according to any one of claims 11 to 19, further comprising grinding the separated surface after planarization.

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