JP6896992B2 - Wafer grinding method and wafer grinding equipment - Google Patents

Description

The present invention relates to a wafer grinding method and a wafer grinding apparatus, and in particular, groove processing for processing a groove shallower than the thickness of the wafer from the surface side of the wafer along a dicing line for partitioning a plurality of semiconductor elements formed on the surface of the wafer. The present invention relates to a wafer grinding method and a wafer grinding apparatus in which the front surface side of a wafer to which a protective tape is attached to the front surface is held by a table and the back surface of the wafer is ground to thin the wafer to a finished thickness after the step.

Patent Document 1 describes a method for manufacturing a semiconductor device that separates a chip on which a plurality of semiconductor elements are formed from a wafer, and manufactures a semiconductor device to which a dicing method called a DBG method (Dicing Before Grinding) is applied. The method is disclosed.

The DBG method includes a dicing step, a pasting step, and a back surface grinding step.

In the dicing step of the DBG method, as shown in the cross-sectional view of the wafer W in FIG. 9A, the front surface of the wafer W is cut by the blade 1 and a groove having a depth that does not penetrate the back surface of the wafer W, that is, the wafer W. A cutting groove 2 for separation is formed, which is shallower than the thickness of the above. As a result, as shown in the plan view of the wafer W in FIG. 10, a grid-like cutting groove 2 along the dicing line is formed on the surface of the wafer W.

Next, in the sticking step, as shown in FIG. 9B, the wafer W is turned upside down, and a back grinding tape (protective tape; hereinafter, a protective tape) is placed on the surface of the semiconductor element SD (Semiconductor Device) which is the lower side in the drawing. , BG tape.) 3 is pasted.

Next, in the back surface grinding step, as shown in FIG. 9C, the back surface of the wafer W, which is the upper surface in the drawing, is ground by the wafer grinding device 4 until it reaches the cutting groove 2, and the wafer W is formed. It is individualized into individual chips T. In the back surface grinding step, the front surface side of the wafer W is held by the table 5 via the BG tape 3, the table 5 and the wafer grinding device 4 are rotated in the directions a and b, and the wafer grinding device 4 is rotated in the arrow c direction. Carry out while sending to.

After that, a wafer holding tape (not shown) is attached to the back surface of the separated chip T to remove the BG tape 3 from the table 5, then the BG tape 3 is removed from the chip T, and then the chip is removed from the wafer holding tape. Take out T.

Japanese Unexamined Patent Publication No. 2002-100588

However, in the wafer grinding method by the DBG method as in Patent Document 1, when the chips T are fragmented, sludge generated by the grinding process enters the gap 6 between the adjacent chips T, and the chips There was a problem that sludge adhered to the side surface of T.

Such a problem can be alleviated if the back surface grinding process is completed immediately after the back surface grinding by the wafer grinding device 4 reaches the cutting groove 2. Therefore, the thickness of the wafer W may be measured while grinding the back surface of the wafer W, and the back surface grinding process may be terminated immediately after the thickness reaches the depth of the cutting groove 2.

Here, as an apparatus for measuring the thickness of the wafer W during the back surface grinding process, for example, it is conceivable to use a known contact type thickness measuring gauge (also referred to as an electric micrometer or an in-process gauge). This contact thickness measuring gauge has a pair of stylus. With the back surface of the wafer W held by the table 5, one of the pair of stylus is in contact with the back surface of the wafer, the other stylus is in contact with the top surface of the table, and the top surface of the table is used as a reference. The thickness of the wafer W is measured.

However, since the BG tape 3 is attached to the surface of the wafer W, the contact type thickness measuring gauge detects the thickness of the wafer W including the thickness of the BG tape 3, but the thickness of the BG tape 3 Is non-uniform, so it is difficult to accurately measure the thickness of the wafer W alone. Further, there is also a problem that the back surface of the individualized chip T is scratched due to the contact of one of the contacts.

Therefore, instead of the contact type thickness measuring gauge, an ultrasonic wave or a laser is sent to the back surface of the wafer W, and the reflected wave is received to measure the thickness of only the wafer W, which is a known non-contact type thickness. It is conceivable to use a measuring gauge (also referred to as a non-contact in-process gauge).

However, since the back surface of the wafer W being ground is rough, the transmitted ultrasonic waves or laser are diffused on the back surface. As a result, it is difficult to accurately measure the thickness of the wafer W alone.

The present invention has been made in view of such circumstances, and is a wafer grinding method capable of grinding the back surface of a wafer while accurately measuring the thickness of only the wafer to thin the wafer to a finished thickness. And to provide a wafer grinding device.

One aspect of the wafer grinding method of the present invention is more than the thickness of the wafer from the surface side of the wafer along a dicing line for partitioning a plurality of semiconductor elements formed on the surface of the wafer in order to achieve the object of the present invention. After the grooving process for machining shallow grooves is performed, the front side of the wafer with the protective tape attached to the front surface is held by a table, and the back surface of the wafer is ground to finish the wafer, which is the first thickness. It is a wafer grinding method that thins the wafer to the extent that it is measured by the contact type thickness measuring means while measuring the thickness of the wafer by the contact type thickness measuring means that contacts the back surface of the wafer and measures the thickness of the wafer. After the rough grinding step of rough grinding the back surface of the wafer by the rough grinding means and the rough grinding step until the thickness of the wafer becomes the second thickness thicker than the first thickness based on the thickness of the wafer. Based on the thickness of the wafer measured by the non-contact thickness measuring means while measuring the thickness of the wafer by the non-contact thickness measuring means that measures the thickness of the wafer from a position away from the back surface of the wafer. The present invention includes a fine grinding step of finely grinding the back surface of the wafer by a fine grinding means until the thickness of the wafer reaches the first thickness.

One aspect of the wafer grinding apparatus of the present invention is more than the thickness of the wafer from the surface side of the wafer along a dicing line for partitioning a plurality of semiconductor elements formed on the surface of the wafer in order to achieve the object of the present invention. After the grooving process for machining shallow grooves is performed, the front side of the wafer with the protective tape attached to the front surface is held by a table, and the back surface of the wafer is ground to finish the wafer, which is the first thickness. It is a wafer grinding device that thins down to that extent, and is a rough grinding means that roughly grinds the back surface of the wafer held on the table, and a contact type thickness that contacts the back surface of the wafer held on the table and measures the thickness of the wafer. A non-contact thickness measuring means for precisely grinding the back surface of the wafer held on the table, and a non-contact thickness measuring means for measuring the thickness of the wafer from a position away from the back surface of the wafer held on the table. And, while measuring the thickness of the wafer by the contact type thickness measuring means, the thickness of the wafer is thicker than the first thickness based on the thickness of the wafer measured by the contact type thickness measuring means. It is a control means for rough grinding the back surface of the wafer by the rough grinding means until the rough grinding process is performed, and then the non-contact type thickness is measured while measuring the thickness of the wafer by the non-contact type thickness measuring means. Based on the thickness of the wafer measured by the measuring means, the control means for finely grinding the back surface of the wafer by the fine grinding means until the thickness of the wafer becomes the first thickness is provided.

According to one aspect of the present invention, the back surface grinding step of the wafer is divided into a rough grinding step in which the grinding amount per unit time is large and a fine grinding step in which the grinding amount per unit time is small. In the rough grinding process, a contact-type thickness measuring means capable of measuring the thickness of the wafer even if the surface roughness of the back surface of the wafer is rough is used. While contacting the contact type thickness measuring means with the back surface of the wafer and measuring the thickness of the wafer, the thickness of the wafer is the finish thickness based on the thickness of the wafer measured by the contact type thickness measuring means. Rough grinding is performed by the rough grinding means until the second thickness becomes thicker than the first thickness. After that, the rough grinding process is switched to the fine grinding process.

In the fine grinding process, the back surface of the wafer is finely ground by the fine grinding means, that is, the back surface of the wafer is ground so as to have a small surface roughness. Use contact-type thickness measuring means. While only the thickness of the wafer is measured non-contactly by the non-contact thickness measuring means, until the thickness of the wafer becomes the first thickness based on the thickness of the wafer measured by the non-contact thickness measuring means. Fine grinding is performed by fine grinding means.

Thereby, according to one aspect of the present invention, the back surface of the wafer can be ground while accurately measuring the thickness of only the wafer, and the wafer can be thinned to the finished thickness.

In one aspect of the wafer grinding method of the present invention, the rough grinding step controls the feeding speed by the rough grinding means to the first speed to roughly grind the back surface of the wafer to the second thickness, and the fine grinding step is fine grinding. A first fine grinding step in which the feeding speed by means is controlled to a second speed lower than the first speed, and the wafer is finely ground to a third thickness thinner than the second thickness and thicker than the first thickness. After the first fine grinding step is performed, the second fine grinding step of finely grinding the wafer to the first thickness by controlling the feeding speed by the fine grinding means to a third speed lower than the second speed. And, it is preferable to have.

In one aspect of the wafer grinding apparatus of the present invention, the control means controls the feeding speed by the rough grinding means to the first speed to roughly grind the back surface of the wafer to the second thickness, and then feeds by the fine grinding means. The speed is controlled to a second speed, which is slower than the first speed, and the wafer is finely ground until it has a third thickness that is thinner than the second thickness and thicker than the first thickness, and then the feeding speed by the fine grinding means. Is preferably controlled to a third speed, which is slower than the second speed, to finely grind the wafer until it reaches the first thickness.

According to one aspect of the present invention, in the rough grinding step, the back surface of the wafer is roughly ground to a second thickness by controlling the feed speed by the rough grinding means to the first speed.

The fine grinding step is divided into a first fine grinding step and a second fine grinding step. In the first fine grinding step, the feeding speed by the fine grinding means is controlled to a second speed lower than the first speed until the wafer becomes a third thickness thinner than the second thickness and thicker than the first thickness. Fine grind. As a result, the back surface of the wafer W is mirror-ground. Then, in the second fine grinding step, the feeding speed by the fine grinding means is controlled to a third speed lower than the second speed, and the wafer is finely ground until it reaches the first thickness. As a result, the wafer W is gradually ground from the third thickness to the first thickness, so that the grinding process of the back surface of the wafer can be completed immediately after the wafer W is ground to the first thickness which is the finishing thickness. .. That is, by setting the first thickness to the depth of the groove, it is possible to reduce the problem that the sludge generated by the grinding process enters the gap between the adjacent chips and the sludge adheres to the side surface of the chip. ..

One aspect of the wafer grinding method of the present invention preferably includes a spark-out step of stopping the feeding of the precision grinding means and executing the spark-out by the precision grinding means after the precision grinding step is performed.

In one aspect of the wafer grinding apparatus of the present invention, it is preferable that the control means stops the feeding of the fine grinding means and causes the fine grinding means to perform spark-out after the fine grinding step is performed.

According to one aspect of the present invention, the uncut portion on the back surface of the wafer that has reached the first thickness by the fine grinding step can be removed by the sparkout step. As a result, the quality of the back surface, which is the finished surface, can be improved.

According to the wafer grinding method and the wafer grinding apparatus of the present invention, the back surface of the wafer can be ground while accurately measuring the thickness of only the wafer, and the wafer can be thinned to the finished thickness.

External perspective view of the wafer grinding apparatus of the embodiment Top view of the wafer grinding apparatus shown in FIG. A block diagram showing the configuration of the wafer grinding apparatus shown in FIG. Block diagram showing the configuration of IPG Block diagram showing the configuration of NCIG Flow chart showing the process of the rough grinding part and the fine grinding part Graph showing the amount of wafer ground by the process of the rough grinding part and the fine grinding part Explanatory drawing showing operation of rough grinding part and fine grinding part Explanatory drawing showing the manufacturing method of a semiconductor device in chronological order Top view of a wafer in which a cutting groove is formed in the dicing process

Hereinafter, preferred embodiments of the wafer grinding method and the wafer grinding apparatus according to the present invention will be described with reference to the accompanying drawings.

[Wafer Grinding Device 10]
FIG. 1 is a perspective view of the wafer grinding device 10 of the embodiment, and FIG. 2 is a plan view of the wafer grinding device 10. Further, FIG. 3 is a block diagram showing the configuration of the wafer grinding apparatus 10.

As shown in FIGS. 1 and 2, a cassette storage unit 14, a wafer transfer device 16, an alignment unit 18, an index table 20, a rough grinding unit 22, and a fine grinding unit 24 are located at predetermined positions in the main body 12 of the wafer grinding apparatus 10. It is provided in. These devices and each part are collectively controlled by the controller (control means) 26 shown in FIG. The controller 26 controls these devices and each unit based on the information indicating the type of wafer W input from the input device 28. The control content will be described later. The rough grinding section 22 and the precision grinding section 24 of FIGS. 1 and 2 are covered with a cover (not shown), so that the machining fluid used in the rough grinding section 22 and the precision grinding section 24 is scattered to the outside. It is preventing.

<Cassette storage unit 14>
A cassette 30 containing a plurality of wafers W before backside grinding and a cassette 32 containing wafers W after backside grinding are detachably mounted on the cassette storage unit 14.

A cutting groove 2 (see FIG. 8) for separating semiconductor elements is formed on the surface of the wafer W before backside grinding by undergoing a grooving process using a dicing device (not shown). That is, on the surface of the wafer W, a cutting groove 2 shallower than the initial thickness of the wafer W is machined from the surface side of the wafer along the dicing line for partitioning the plurality of semiconductor elements. A BG tape 3 (see FIG. 8) that protects the semiconductor element is attached to the surface of the wafer W.

The wafers W housed in the cassette 30 are held one by one by the suction unit 34 of the wafer transfer device 16 and transferred to the alignment unit 18. Since the wafer transfer device 16 is a general-purpose 6-axis joint robot and its configuration is well known, the description thereof will be omitted here.

<Alignment unit 18>
The alignment unit 18 is a device for aligning the wafer W carried out from the cassette 30 at a predetermined position. The wafer W aligned by the alignment unit 18 is sucked and held again by the suction portion 34 of the wafer transfer device 16 and then transported to an empty table 36, and the surface side of the wafer W is attracted to the suction surface on the upper surface of the table 36. Be retained. The table 36 is installed on the upper surface of the index table 20, and the tables 38, 40, and 42 having the same function are installed on the upper surface of the index table 20.

<Index table 20>
The index table 20 is formed in a disk shape and is rotatably supported by the main body 12 via a rotation shaft 44 shown by a broken line in FIG. Further, a rotating shaft (not shown) of the motor 46 shown by the broken line in FIG. 2 is connected to the rotating shaft 44. Therefore, the index table 20 is rotated by the power of the motor 46, and the motor 46 is controlled by the controller 26 of FIG. The four tables 36 to 42 described above are installed at intervals of 90 degrees on concentric circles centered on the rotation axis 44 of the index table 20.

<Tables 36-42>
In FIGS. 1 and 2, the table 36 is at the receiving position of the wafer W, the table 38 is at the rough grinding position by the rough grinding unit 22, the table 40 is at the fine grinding position by the fine grinding unit 24, and the table 42 is at the wafer W. It is placed at each delivery position.

The wafer W is held by the table 36 located at the receiving position, and then moved to the rough grinding position by the intermittent rotation of the index table 20 by 90 degrees, where the rough grinding is performed. When the rough grinding process is completed, the wafer W is moved to the fine grinding process position by intermittent rotation of the index table 20 in the same direction by 90 degrees, where the fine grinding process and the spark out process are performed. When the precision grinding process is completed, the wafer W is moved to the delivery position by intermittent rotation of the index table 20 in the same direction by 90 degrees, held in the wafer transfer device 16 here, and then stored in the cassette 32. ..

The tables 36 to 42 are connected to a rotation shaft of a motor (not shown) supported on the lower surface of the index table 20, and are rotated by the driving force of the motor.

The suction surfaces of the tables 36 to 42 are made of a porous material made of a sintered body such as ceramics, and are connected to a suction pump (not shown). By applying the suction force of the suction pump to the suction surface, the surface side of the wafer W is suction-held on the suction surface.

<Rough grinding unit 22>
The rough grinding section 22 includes a cup-shaped grindstone (rough grinding means) 48 for rough grinding the back surface of the wafer W, a motor 50, a feeding device 52, and an in-process gauge (Tokyo Seimitsu Co., Ltd.) which is a contact type thickness measuring means. Palcom series. In Process Gage. Hereinafter referred to as "IPG") 54.

As shown in FIG. 1, the cup-shaped grindstone 48 is connected to a rotating shaft (not shown) of the motor 50 and is rotated by the driving force of the motor 50. Further, the cup type grindstone 48 is attached to the feeding device 52 via the motor 50 and the motor support portion 56.

The feeding device 52 is a device that moves the cup-shaped grindstone 48 together with the motor 50 up and down with respect to the rough grinding processing position, and the cup-shaped grindstone 48 can be pressed against the back surface of the wafer W by the feeding movement by the downward movement. .. As a result, the back surface rough grinding process of the wafer W is performed.

The feeding speed of the cup-shaped grindstone 48 by the feeding device 52 is set to a constant speed based on the specifications of the grindstone such as the number of abrasive grains of the cup-shaped grindstone 48 and the grinding conditions such as the material of the wafer W.

Further, the amount of the cup-shaped grindstone 48 fed to the back surface of the wafer W by the feeding device 52 is the initial thickness of the wafer W, the thickness of the wafer W during rough grinding measured by the IPG 54, and the grooving step. The controller 26 in FIG. 3 controls based on the depth of the groove 2 formed in.

FIG. 4 is a block diagram showing the configuration of the IPG 54.

The IPG 54 includes a pair of contacts 58, 60 and a calculation unit 62. The contactor 58 is brought into contact with the back surface of the wafer W, and the contactor 60 is brought into contact with the upper surface of the table 36 located at the rough grinding position (see FIG. 8). The calculation unit 62 obtains the thickness of the wafer W by subtracting the height of the upper surface of the table 36 measured by the contact 60 from the height of the back surface of the wafer W measured by the contact 60. The thickness of the wafer W measured by the IPG 54 is output to the controller 26 of FIG. 3, and the controller 26 controls the rough grinding unit 22 based on the thickness. The thickness of the wafer W measured by the IPG 54 includes the thickness of the BG tape 3.

The wafer W subjected to the rough grinding process in the rough grinding section 22 is moved to the fine grinding section 24 by rotating the index table 20 by 90 degrees after the cup-shaped grindstone 48 is retracted and moved upward from the wafer W. ..

<Precision section 24>
As shown in FIGS. 1 and 2, the fine grinding unit 24 includes a cup-type grindstone (fine grinding means) 64 for finely grinding the back surface of the wafer W, a motor 66, a feeding device 68, and a non-contact type thickness measuring means. A contact in process gauge (No Contact In Process Gage; hereinafter referred to as “NCIG”) 70 is provided.

The cup-shaped grindstone 64 is connected to a rotating shaft (not shown) of the motor 66 and is rotated by the driving force of the motor 66. Further, the cup type grindstone 64 is attached to the feeding device 68 via the motor 66 and the motor support portion 72.

The feeding device 68 is a device that moves the cup-shaped grindstone 64 together with the motor 66 up and down with respect to the fine grinding processing position, and the cup-shaped grindstone 64 can be pressed against the back surface of the wafer W by the feeding movement by the downward movement. .. As a result, the back surface of the wafer W is finely ground.

The feeding speed of the cup-type grindstone 64 by the feeding device 68 is set based on the specifications of the grindstone such as the number of abrasive grains of the cup-type grindstone 64 and the grinding conditions such as the material of the wafer W.

Further, the amount of the cup-shaped grindstone 64 fed to the back surface of the wafer W by the feeding device 68 is the thickness of the wafer W during the fine grinding process measured by NCIG70 and the groove 2 formed in the grooving process. The controller 26 in FIG. 3 controls based on the depth of.

FIG. 5 is a block diagram showing the configuration of NCIG70.

The NCIG70 has a wave transmitting unit 76 that transmits ultrasonic waves U such as pulsed ultrasonic waves oscillated from the ultrasonic oscillating unit toward the lower wafer W, and a wave transmitting unit 76 that is transmitted from the transmitting unit 76 and reflected on the wafer W. It includes a receiving unit 78 that receives the reflected wave of ultrasonic waves and a calculation unit 80.

According to NCIG70, the ultrasonic wave U transmitted from the wave transmitting unit 76 toward the wafer W is reflected by the back surface W1 and the front surface W2 of the wafer W, and are reflected by the first reflected wave U1 and the second reflected wave U2, respectively. As a result, the wave is received by the wave receiving unit 78. Since the second reflected wave U2 reaches the receiving portion 78 later than the first reflected wave U1 by the thickness of the wafer W, the calculation unit 80 obtains the thickness of only the wafer W based on this time difference. The thickness of only the wafer W measured by the NCIG 70 is output to the controller 26 in FIG. 3, and the controller 26 controls the fine grinding unit 24 based on the thickness. Although NCIG70 using ultrasonic waves has been described as a non-contact type thickness measuring means, a measuring means using a laser beam can also be used as a non-contact type form.

Further, in the fine grinding unit 24, after the fine grinding step by the cup type grindstone 64, it is possible to shift to the spark out step by the cup type grindstone 64. The spark-out process is a process performed at the final stage of grinding. The feeding of the cup-shaped grindstone 64 is stopped, the cup-shaped grindstone 64 is rotated, and the back surface of the wafer W is pressed until sparks and grinding noise due to grinding disappear. This is the process of processing.

The wafer W whose back surface is sparked out by the precision grinding unit 24 is moved to the delivery position by rotating the index table 20 in the same direction by 90 degrees after the cup-shaped grindstone 64 is retracted and moved upward from the wafer W. ..

[Actions of Rough Grinding Unit 22 and Fine Grinding Unit 24]
FIG. 6 is a flowchart of a wafer grinding method including a rough grinding step (S (Step) 10, S20) by the rough grinding section 22 and a fine grinding step (S40, S50, S60, S70) by the fine grinding section 24.

FIG. 7 is a graph showing the thickness of the wafer W gradually decreasing by the rough grinding steps (S10, S20) and the fine grinding steps (S40, S50, S60, S70) over time. That is, the vertical axis represents the thickness of the wafer W, and the horizontal axis represents the elapsed time of the grinding process.

8 (A) to 8 (E) are explanatory views showing the grinding operation of the rough grinding section 22 and the precision grinding section 24.

In FIG. 3, the rotation speed of the motor 50 of the rough grinding unit 22, the feeding speed of the feeding device 52, the feeding end position, the rotation speed of the motor 66 of the fine grinding unit 24, the feeding speed of the feeding device 68, The delivery end position is controlled by the controller 26.

Hereinafter, description will be made with reference to FIGS. 3 and 6 to 8.

The controller 26 has an initial thickness A of the wafer W input from the input device 28, a depth d of the cutting groove 2 formed on the surface, a first thickness B (B = d) which is a finishing thickness, and a cup. First feed speed V1 of the grindstone 48, second thickness C after grinding in the rough grinding process, third thickness D after fine grinding in the first fine grinding step, first fine grinding Rough grinding section 22 and fine grinding based on the second feed speed V2 of the cup-type grindstone 64 in the process, the third feed speed V3 of the cup-type grindstone 64 in the second fine grinding step, and the set time S1 of the spark-out step. The operation of each part of the part 24 is controlled.

First, the rough grinding steps (S10, S20) and the fine grinding steps (S40, S50, S60, S70) will be outlined.

<Rough grinding process (S10, S20)>
FIG. 8A is a view in which the table 36 is moved to the rough grinding position. After that, as shown in FIG. 8B, the cup-shaped grindstone 48 is moved downward from above the wafer W, and rough grinding is started when the cup-shaped grindstone 48 comes into contact with the back surface of the wafer W (S10).

When the rough grinding is started, the thickness of the wafer W measured by the IPG 54 is measured while the thickness of the wafer W is measured by the IPG 54 which contacts the back surface of the wafer W held on the table 36 and measures the thickness of the wafer. Based on the thickness (including the thickness of the BG tape), the thickness of the wafer W is changed from the initial thickness A to the second thickness C, which is thicker than the first thickness B, which is the finishing thickness. Roughly grind the back surface of the wafer W (S20).

As shown in FIG. 8B, when the thickness of the wafer W reaches the second thickness C, the cup-shaped grindstone 48 is retracted and moved upward. After that, the index table 20 is rotated 90 degrees to move the table 36 to the fine grinding position (S30).

<Precision grinding process>
After the rough grinding step is performed, fine grinding with the cup type grindstone 64 is started as shown in FIG. 8 (C) (S40). In the fine grinding process, the thickness of only the wafer W is measured by the NCIG70, which measures the thickness of the wafer W from a position away from the back surface of the wafer W, and the wafer is based on the thickness of the wafer W measured by the NCIG70. The back surface of the wafer W is finely ground with a cup-shaped grindstone 64 until the thickness of W becomes the first thickness B (S70). When the thickness of the wafer W reaches the first thickness B, the cup-shaped grindstone 48 is retracted and moved upward. After that, the index table 20 is rotated 90 degrees to move the table 36 to the delivery position.

According to the wafer grinding apparatus 10 of the embodiment, the back surface grinding process of the wafer W includes a rough grinding step (S10, S20) in which the grinding amount per unit time is large and a fine grinding step (S40) in which the grinding amount per unit time is small. , S50, S60, S70).

In the rough grinding steps (S10, S20), IPG54, which can measure the thickness of the wafer W even if the surface roughness of the back surface of the wafer W is rough, is used. The contact 58 of the IPG 54 is brought into contact with the back surface of the wafer W, and while measuring the thickness of the wafer W gradually decreasing from the initial thickness A, the thickness of the wafer W is measured based on the thickness of the wafer W measured by the IPG 54. Rough grinding is performed with the cup-type grindstone 48 until the thickness becomes the second thickness C, which is thicker than the first thickness B, which is the finish thickness. After that, the rough grinding process is switched to the fine grinding process.

In the fine grinding step (S40, S50, S60, S70), the back surface of the wafer W is finely ground by the cup type grindstone 64, that is, the back surface of the wafer W is ground so as to have a small surface roughness. Therefore, NCIG70 is used instead of IPG54. While measuring only the thickness of the wafer W with the NCIG70 in a non-contact manner, fine grinding is performed with the cup-type grindstone 64 until the thickness of the wafer W becomes the first thickness B based on the thickness of the wafer W measured by the NCIG70. To do.

As a result, according to the wafer grinding apparatus 10 and the wafer grinding method of the embodiment, the back surface of the wafer W is ground while accurately measuring the thickness of only the wafer W, and the wafer is finished with a first thickness which is the finishing thickness. It can be diluted to B.

Next, the rough grinding steps (S10, S20) and the fine grinding steps (S40, S50, S60, S70) will be described in detail.

<< Rough grinding process (S10, S20) >>
In the rough grinding step (S10, S20), the feeding speed of the cup-shaped grindstone 48 is controlled to the first feeding speed V1, and the back surface of the wafer W is roughly ground from the initial thickness A to the second thickness C.

The first feed rate V1 is set with priority given to shortening the processing time spent in the back surface grinding process and efficiently performing the back surface grinding process without damaging the back surface of the wafer W by the cup type grindstone 48. The speed.

<< Fine grinding process (S40, S50, S60, S70) >>
The fine grinding step is divided into a first fine grinding step (S40, S50) and a second fine grinding step (S60, S70).

As shown in FIG. 8D, in the first fine grinding step (S40, S50), the feeding speed by the cup type grindstone 64 is controlled to the second feeding speed V2, which is lower than the first feeding speed V1. The wafer W is finely ground until it has a third thickness D that is thinner than the second thickness C and thicker than the first thickness B.

The second feeding speed V2 is a speed set with priority given to mirroring the back surface of the wafer W, which was a rough surface, without damaging the back surface of the wafer W by the cup-type grindstone 64. Therefore, the second feed rate V2 is set to be lower than the first feed rate V1 to reduce the grinding amount per unit time. Therefore, in the first fine grinding step (S40, S50), the back surface of the wafer W is mirror-ground.

Then, as shown in FIG. 8 (E), in the second precision grinding step (S60, S70), the feeding speed by the cup type grindstone 64 is controlled to the third feeding speed V3, which is slower than the second feeding speed V2. The wafer W is finely ground to a first thickness B.

The third feed rate V3 is, of course, a speed at which the back surface of the wafer W is not damaged by the cup-type grindstone 64, but the feed rate V3 is immediately after being ground to the first thickness B, which is the finish thickness. The speed is set with priority given to immediately stopping the downward movement of the cup-shaped grindstone 64 by the embedding device 68. That is, the speed is set to prevent an excessive amount of backside grinding due to a slight difference between the time for grinding to the first thickness B and the stop time for the downward movement of the cup-shaped grindstone 64.

Therefore, in the wafer W in the second fine grinding process, the feeding speed is gradually controlled from the third thickness D to the first thickness B by the cup type grindstone 64 whose feeding speed is controlled to the third feeding speed V3 over time. It will be ground. Then, when the first thickness B is detected by the NCIG 70, the controller 26 immediately stops the downward movement of the cup-shaped grindstone 64 by the feeding device 68. This makes it possible to prevent an excessive amount of backside grinding.

That is, by setting the first thickness B to the depth d of the cutting groove 2, the sludge generated by the grinding process enters the gap between the adjacent inserts T, and the sludge adheres to the side surface of the insert T. Can be reduced. Further, since the displacement of the chip T immediately after being separated into individual pieces can be suppressed, it is possible to prevent the chip T from being damaged due to the contact between the chips T.

<< Spark-out process (S80) >>
After the fine grinding step is performed, the feeding of the cup-shaped grindstone 64 is stopped, and the spark-out is executed by the cup-shaped grindstone 64 for S1 hour.

The uncut portion on the back surface of the wafer W that has reached the first thickness B in the second fine grinding step (S60, S70) can be removed in the sparkout step (S80). As a result, the quality of the back surface, which is the finished surface of the wafer W, is improved.

As described above, according to the wafer grinding method of the embodiment, when the back surface of the wafer W is ground to be thinned to a predetermined thickness (finishing thickness, first thickness B, target thickness of chip T), Not only the type of grinding (rough grinding, fine grinding) is changed according to the thickness of the wafer W, but also the means for measuring the thickness of the wafer W is changed. Specifically, the IPG54, which is a contact-type thickness measuring means, is used in the rough grinding process, while the NCIG70, which is a non-contact-type thickness measuring means, is used in the fine grinding process.

As a result, in the rough grinding process, the approximate thickness of the wafer W (that is, the protective tape) is not affected by the surface roughness of the back surface (ground surface) of the wafer W by the contact type thickness measuring means (IPG54). The back surface of the wafer W can be efficiently ground at a relatively high grinding speed while measuring the thickness of the wafer W including the thickness error of the wafer W. Further, in the fine grinding process, the surface roughness of the back surface of the wafer W is smaller than that in the rough grinding process, so that the thickness of the wafer W is accurately measured by the non-contact thickness measuring means (NCIG70). It can be measured well, which makes it possible to control the finish thickness and groove residual film thickness of the wafer W.

Thereby, according to the wafer grinding method of the embodiment, the thickness of the wafer W can be ground to the finish thickness while detecting the thickness of only the wafer W.

The groove residual film thickness described above is the thickness from the back surface of the wafer W to the groove 2, and the groove residual film thickness can also be accurately measured by the non-contact thickness measuring means (NCIG70). By obtaining the groove residual film thickness, the controller 26 can also control the feeding speed of the cup-shaped grindstone 64 of the fine grinding unit 24 to a lower speed and grind the back surface until the groove 2 is reached.

By the way, as a comparative form, when the thickness of the wafer W is measured by the thickness measuring means of the same method regardless of the type of grinding, there are the following problems. That is, when the contact type thickness measuring means (NCIG70) is used not only in the rough grinding process but also in the fine grinding process, the contactor (contactor 58) of the contact type thickness measuring means causes the back surface of the wafer W, that is, , The back surface of the chip T will be damaged. Further, since the contact-type thickness measuring means measures the thickness of the wafer W including the thickness of the protective tape having a non-uniform thickness, it is not possible to measure the thickness of the wafer W alone, thereby finishing. It becomes difficult to properly control the thickness and the residual film thickness of the groove.

On the other hand, when the non-contact type thickness measuring means is used not only in the fine grinding process but also in the rough grinding process, the wafer W is greatly affected by the surface roughness of the back surface of the wafer W in the rough grinding process. It may not be possible to measure the thickness of the wafer. As a result, it may not be possible to confirm the amount of grinding in the rough grinding process.

On the other hand, in the wafer grinding method of the embodiment, as described above, the thickness of the wafer W is a predetermined thickness (second thickness C) while measuring the thickness of the wafer W by the contact type thickness measuring means. After rough grinding the back surface of the wafer W while measuring the thickness of the wafer W until it becomes, the thickness of the wafer W is the finish thickness (the first) while measuring the thickness of the wafer W by the non-contact type thickness measuring means. Since the back surface of the wafer W is finely ground until the thickness becomes 1 B), the problems in the above-mentioned comparative form can be improved.

Further, in the wafer grinding method of the embodiment, when the back surface of the wafer W is ground and thinned to the finish thickness (first thickness B), the cup-shaped grindstones 48 and 64 are fed according to the thickness of the wafer W. The loading speed is gradually reduced. That is, in the rough grinding process, rough grinding is performed from the initial thickness A to the second thickness C at the first feed rate V1, and in the fine grinding process, the second thickness C to the first thickness B is the first. Fine grinding is performed at a feeding speed lower than the 1 feeding speed V1 (second feeding speed V2, third feeding speed V3). Further, in the fine grinding process, the feeding speed is divided into two stages, and the second thickness C to the third thickness D are refined at the second feeding speed V2, which is slower than the first feeding speed V1. Grinding is performed, and fine grinding is performed from the third thickness D to the first thickness B at a third feeding speed V3, which is slower than the second feeding speed V2. That is, in the wafer grinding method of the embodiment, the grinding process is performed while gradually reducing the feeding speed in three stages.

In the embodiment, as an example, the feeding speed is gradually reduced to three stages, but the present invention is not limited to this, and the feeding speed may be changed in four or more steps, for example. Further, the feeding speed may be continuously reduced in proportion to the thickness of the wafer W.

In this way, by gradually or continuously slowing down the feeding speed according to the thickness of the wafer W, the feeding speed (grinding speed) is prioritized over the measurement accuracy of the thickness of the wafer W for rough grinding. In the process, the wafer W having a thick thickness and a large surface roughness on the back surface can be efficiently roughly ground to a second thickness C in a short time. Further, in the fine grinding process in which the accuracy of measuring the thickness of the wafer W is prioritized over the feeding speed, the wafer W having a small thickness and a small surface roughness on the back surface can be finely ground to the finish thickness.

Thereby, in the wafer grinding method of the embodiment, the thickness of the wafer W can be ground to the finish thickness while detecting the thickness of only the wafer W, and the finish thickness of the wafer W can be increased while increasing the throughput. It is possible to properly manage the groove residual film thickness.

Further, the rough grinding conditions in the rough grinding step so that the machining time in the rough grinding steps (S10 to S20) and the machining time in the fine grinding steps (S40 to S70) including the spark-out step (S80) are substantially equal. (That is, the rough grinding amount, feeding speed, rotation speed, etc. of the cup type grindstone 48), and the fine grinding conditions in the fine grinding process (that is, the fine grinding amount, feeding speed, rotation speed, etc. of the cup type grindstone 64). It is preferable to set.

That is, in the graph of FIG. 7, the machining time of the fine grinding steps (S40 to S70) including the spark-out step (S80) is about three times as long as the machining time of the rough grinding steps (S10 to S20). By making these processing times equal, it is possible to eliminate the waiting time of the wafer W at which the grinding process is completed. Therefore, the grinding time can be further shortened, and the throughput can be further increased.

For example, the wafer W is roughly ground from the initial thickness A to the third thickness D in the rough grinding step, and then the wafer W is finely ground from the third thickness D to the first thickness B in the fine grinding step. As a result, the rough grinding time is slightly longer than the grinding time shown in FIG. 7, but the fine grinding process time is significantly shortened, so that the grinding time is significantly shortened and the throughput is further increased. The feeding speed of fine grinding from the third thickness D to the first thickness B may be divided into two stages (second feeding speed V2, third feeding speed V3), and may be carried out continuously. You may try to slow it down.

The wafer grinding method described above is a grinding method using a wafer grinding device 10 in which one rough grinding section 22 and one precision grinding section 24 are installed. However, when a plurality of precision grinding sections 24 are installed, the wafer grinding method is a grinding method. The wafer W that has been roughly ground by the rough grinding unit 22 may be sequentially transferred to an empty fine grinding unit 24 to perform fine grinding. In this case, it is preferable to shorten the rough grinding time of the rough grinding unit 22 and increase the fine grinding time of the fine grinding unit 24 by the number of fine grinding units 24.

W ... Wafer, 10 ... Wafer grinding device, 12 ... Main body, 14 ... Cassette storage unit, 16 ... Wafer transfer device, 18 ... Alignment unit, 20 ... Index table, 22 ... Rough grinding unit, 24 ... Fine grinding unit, 26 ... Controller, 28 ... Input device, 30, 32 ... Cassette, 34 ... Suction part, 36, 38, 40, 42 ... Table, 44 ... Rotating shaft, 46 ... Motor, 48 ... Cup type grindstone, 50 ... Motor, 52 ... Feed Insertion device, 54 ... IPG, 56 ... Motor support, 58, 60 ... Contact, 62 ... Calculation unit, 64 ... Cup type grindstone, 66 ... Motor, 68 ... Feed device, 70 ... NCIG, 72 ... Motor support , 76 ... Transmitter, 78 ... Receiver, 80 ... Arithmetic

Claims (2)

Shallow trench than the thickness of the wafer to the surface of the window Eha is a by wafer grinding method of thinning to a first thickness which is by grinding the back surface of the wafer which is formed along a dicing line finishing the wafer thickness hand,
While measuring the thickness of the wafer by the contact type thickness measuring means that contacts the back surface of the wafer and measures the thickness of the wafer, the thickness of the wafer measured by the contact type thickness measuring means is obtained. Based on this, a rough grinding step of rough grinding the back surface of the wafer by rough grinding means until the thickness of the wafer becomes a second thickness thicker than the first thickness.
After the rough grinding step is performed, the non-contact type while measuring the thickness of the wafer by a non-contact type thickness measuring means for measuring the thickness of the wafer from a position away from the back surface of the wafer. A fine grinding step of finely grinding the back surface of the wafer by the fine grinding means until the thickness of the wafer becomes the first thickness based on the thickness of the wafer measured by the thickness measuring means.
After the fine grinding step is performed, the feeding of the fine grinding means is stopped, and the spark out is executed by the fine grinding means.
With
The machining time by the rough grinding means and the machining time by the fine grinding means including the sparkout are substantially equal.
Wafer grinding method. Shallow trench than the thickness of the wafer to the surface of the window Eha is a by wafer grinding apparatus for thinning to a first thickness is by grinding the back surface of the wafer which is formed along a dicing line finishing the wafer thickness hand,
A rough grinding means for rough grinding the back surface of the wafer,
A contact-type thickness measuring means that contacts the back surface of the wafer and measures the thickness of the wafer.
A fine grinding means for finely grinding the back surface of the wafer, and
A non-contact thickness measuring means for measuring the thickness of the wafer from a position away from the back surface of the wafer.
While measuring the thickness of the wafer by the contact type thickness measuring means, the thickness of the wafer is thicker than the first thickness based on the thickness of the wafer measured by the contact type thickness measuring means. It is a control means for rough-grinding the back surface of the wafer by the rough grinding means until it reaches the second thickness, and after the rough grinding is performed, the thickness of the wafer is measured by the non-contact thickness measuring means. While controlling the back surface of the wafer to be finely ground by the fine grinding means until the thickness of the wafer becomes the first thickness based on the thickness of the wafer measured by the non-contact thickness measuring means. Means and
With
The control means is a means for stopping the feeding of the fine grinding means and causing the fine grinding means to perform spark-out.
Further, the control means makes the machining time by the rough grinding means substantially equal to the machining time by the fine grinding means including the sparkout.
Wafer grinding equipment.

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