TWI620247B - Method for forming through-silicon via etching and through-silicon via etching device - Google Patents

Abstract

The invention provides a method for forming a TSV and a TSV etching device. The method for etching and forming a through-silicon via on the back surface of a silicon substrate includes: placing the silicon substrate in a reaction chamber of a plasma etching device with the back surface facing upward, and forming a silicon material layer on the back surface of the silicon substrate. There is a hard mask layer, and a photoresist pattern is formed above the hard mask layer; using the photoresist pattern as a mask, the hard mask layer is etched to form a hard mask pattern; the remaining photoresist pattern is removed; The hard mask pattern is used as a mask to etch the underlying silicon material layer to initially form a through silicon via; remove the remaining hard mask pattern; globally etch the silicon material layer; and remove the silicon substrate from the reaction chamber.

Description

Method for forming through silicon via and etching through silicon via

The invention relates to a plasma etching device and method, in particular to a through-silicon via (TSV, namely Through-Silicon Via).

A typical TSV manufacturing process usually includes multiple steps: (a) forming a photoresist pattern on a silicon material layer of a silicon substrate; (b) using the photoresist pattern as a mask, and plasma etching the silicon material layer to A through-silicon via is initially formed in the silicon material layer; (c) the remaining photoresist pattern is removed; (d) the silicon material layer is etched by a global plasma in a state without a mask to reduce the through-silicon via to a predetermined thickness the height of.

Each of the above steps needs to be performed in a specific processing device. For example, step (a) is usually performed in a lithographic apparatus; step (b) is usually performed in an inductive coupled plasma (ICP) processing device; step (c) is usually performed in an ashes Performed in a device; step (d) is usually performed in another plasma processing device. In other words, during the entire TSV fabrication process, the silicon substrate needs to be transferred back and forth between the different processing devices.

It is an object of the present invention to provide a TSV etching device capable of continuously performing a plurality of TSV fabrication processes (in the present invention, unless otherwise specified, "multiple" means Are two or more) adjacent steps (as before The listed steps (b) to (d)) in the prior art originally need to be completed in different processing devices.

Another object of the present invention is to provide a method for forming TSVs by etching. Multiple adjacent steps in the method can be implemented in the same processing device, thereby reducing the silicon substrate being transferred during the TSV fabrication process. frequency.

Another object of the present invention is to provide a TSV etching device capable of performing a plurality of steps in a TSV fabrication process. These steps (such as the steps (b) and (d) listed above) In the prior art, it was originally required to be completed in different processing devices, thereby reducing the number of equipment to be applied in the entire TSV manufacturing process.

According to one aspect of the present invention, a method for forming a through-silicon via on the back surface of a silicon substrate is provided, which comprises: placing the silicon substrate in a reaction chamber of a plasma etching apparatus with the back side facing up, and the silicon substrate A hard mask layer is formed above the silicon material layer on the back of the sheet, and a photoresist pattern is formed above the hard mask layer; using the photoresist pattern as a mask, the hard mask layer is etched to form a hard mask pattern; the remaining Photoresist pattern; using the hard mask pattern as a mask, etching the underlying silicon material layer to form a TSV initially; removing the remaining hard mask pattern; globally etching the silicon material layer; removing the silicon substrate from the reaction chamber.

Preferably, the reaction chamber includes at least: an air inlet area connected to the gas supply device, a processing area where the silicon substrate to be processed is located, and a gas focus ring is set between the air inlet area and the processing area, and the center of the gas focus ring An opening is provided, and the opening serves as a channel for gas to flow from the air inlet area to the processing area; the size of the opening can be adjusted during the processing of the silicon substrate; in the global etching stage, the size of the opening is smaller than that in the initial stage of forming a TSV or forming The size of the openings in the hard mask pattern stage or the remaining hard mask pattern stage.

Preferably, the periphery of the base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; the size of the opening of the gas focus ring can be adjusted by the following methods: When a larger opening size is required, the edge ring is kept on the base; when a smaller opening size is required, the edge ring is raised to a certain height so that the edge ring can cover a part of the opening space.

Preferably, the peripheral edge of the base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; the edge ring is held on the base during the initial stage of forming the TSV or forming the hard mask pattern; During the global etching phase, the edge ring is maintained at a height significantly higher than the base.

Preferably, the height of the edge ring in the global etching stage is higher than that in the stage of initially forming the TSV or the stage of forming the hard mask pattern by 5 mm to 15 mm.

Preferably, the through-silicon via that is finally formed is generally tapered or trapezoidal with a wide width and a narrow width.

Preferably, the residual photoresist pattern is removed by an ashing method.

Preferably, the step of forming a hard mask pattern, the step of initially forming a TSV, the step of removing the remaining hard mask pattern, and the step of globally etching the silicon material layer are all performed by plasma etching.

According to another aspect of the present invention, a method for forming a through-silicon via plasma etching is provided. The method includes: placing a silicon substrate in a reaction chamber of a plasma etching device, and forming a pattern on a silicon material layer of the silicon substrate. The reaction chamber includes at least: an air inlet area connected to the gas supply device, a processing area where the silicon substrate to be processed is located, and a gas focus ring is provided between the air inlet area and the processing area. An opening is provided in the center, and the opening serves as a channel for gas to flow from the intake area to the processing area; the size of the opening can be adjusted during the processing of the silicon substrate; while the opening of the gas focusing ring is maintained at the first size, the plasma The silicon material layer is etched to form a through-silicon via in the silicon material layer; the remaining mask is removed; while the opening of the gas focus ring is maintained at the second size, the silicon material layer is globally etched, and the second The size is smaller than the first size; the silicon substrate is removed from the reaction chamber.

Preferably, the mask comprises a hard mask pattern.

Preferably, the periphery of the base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; the size of the opening of the gas focusing ring can be adjusted by the following method: when a larger opening size is required, Keep the edge ring on the base; when a smaller opening size is required, raise the edge ring to a certain height so that the edge ring can cover a part of the space of the opening.

According to another aspect of the present invention, a method for forming a through-silicon via plasma etching is provided. The method includes: placing a silicon substrate in a reaction chamber of a plasma etching device, and forming a pattern on a silicon material layer of the silicon substrate. A mask; a base for placing a silicon substrate in the reaction chamber, and an edge ring that can be raised and lowered around the silicon substrate; while the edge ring is held at the base, the silicon material is etched by plasma Layer to form a TSV in the silicon material layer; remove the remaining mask; while the edge ring is maintained at a height significantly higher than the base, the global plasma etches the silicon material layer; the silicon substrate is removed Reaction chamber.

Preferably, the mask comprises a hard mask pattern.

Preferably, the height of the edge ring in the global plasma etching step is 5 mm to 15 mm higher than that in the step of initially forming the TSV.

According to another aspect of the present invention, a through-silicon via etching apparatus is provided, which includes a reaction chamber surrounded by a plurality of walls, and the reaction chamber is divided into at least three regions, namely: (1) an air inlet region Is connected to the gas supply device so that the gas can enter the reaction chamber; (2) the processing area, the silicon substrate to be processed is set in the processing area, and the processing area is connected to the gas inlet area so that the gas can diffuse from the gas inlet area to Treatment area; (3) Exhaust area, which is connected to the treatment area and the exhaust device, so that the gas can be discharged from the treatment area to the outside of the reaction chamber through the exhaust device; the plasma generating device is used to act on the gas in the reaction chamber In order to generate the plasma required in the processing process; a gas focusing ring is provided between the inlet area and the processing area, and an opening is provided in the center of the gas focusing ring, and the opening serves as a channel for gas to flow from the inlet area to the processing area; The size of the opening can be adjusted during the processing of the silicon substrate; A device for controlling the process of TSV etching; in the step of plasma-etching a silicon material layer protected by a mask to form a TSV initially, the control device controls the opening of the gas focusing ring to remain at the first size; In the step of performing global plasma etching of the silicon material layer without mask protection after the step of initially forming the TSV, the control device controls the opening of the gas focus ring to remain at the second size, and the second size is smaller than the first size.

Preferably, the periphery of the base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; the control device adjusts the size of the opening of the gas focusing ring by controlling the raising and lowering of the edge ring: When a larger opening size is required, the control device controls the edge ring to remain on the base; when a smaller opening size is required, the control device controls the edge ring to be raised to a certain height so that the edge ring can cover a part of the opening space.

According to another aspect of the present invention, a through-silicon via etching apparatus is provided, which includes: a vacuum-tight, air-tight reaction chamber; a pedestal located in the reaction chamber for placing a silicon substrate; and surrounding the silicon substrate The edge ring that can be set up and down; the gas supply device is connected to the reaction chamber for supplying gas to the reaction chamber; the plasma generating device is used to act on the gas in the reaction chamber to generate the required gas in the processing process Plasma; control device for controlling the process of TSV etching; during the step of plasma etching the silicon material layer protected by the mask to initially form the TSV, the control device controls the edge ring to remain at the base In the step of performing global plasma etching of the silicon material layer without mask protection after the step of initially forming the TSV, the control device controls the edge ring to be maintained at a height significantly higher than the base.

Preferably, the height of the edge ring in the global plasma etching step is 5 mm to 15 mm higher than that in the step of initially forming the TSV.

Preferably, it further comprises a gas focusing ring. An opening is provided in the center of the gas focusing ring, and the opening serves as a channel for the gas to flow from the gas supply device to the base.

Preferably, in the global plasma etching step, the control device controls the edge ring dimension. Hold it at the same level as the gas focus ring or make the edge ring close to the lower surface of the gas focus ring, so that the edge ring can cover part of the space of the opening.

10, 20‧‧‧ reaction chamber

11, 21‧‧‧ insulated cover

12, 22‧‧‧air inlet

13, 23‧‧‧ inductive coupling coils

14, 24‧‧‧ base

15‧‧‧ cover ring

16, 28‧‧‧gas focus ring

17, 25b‧‧‧Edge ring

18, 27‧‧‧ drive unit

251‧‧‧ protrusion

25a‧‧‧Focus ring

26‧‧‧ support bar

29‧‧‧ insulating ring

300‧‧‧ silicon material layer

305‧‧‧Silicon Via

310‧‧‧Semiconductor layer

320‧‧‧ hard mask layer

322‧‧‧hard mask pattern

325, 345‧‧‧ opening

342‧‧‧Photoresist pattern

Steps S1 ~ S6‧‧‧‧

W‧‧‧ Substrate

ΦD1, ΦD2‧‧‧Inner diameter

Figures 1 and 2 are schematic diagrams of the structure of a TSV etching apparatus according to an embodiment of the present invention; Figure 3 is a schematic diagram of the structure of a TSV etching apparatus according to another embodiment of the present invention; Figures 4 to 9 It is a schematic diagram of a method for forming a TSV by etching according to an embodiment of the present invention.

The method for forming through-silicon vias by plasma etching and the through-silicon via etching apparatus of the present invention will be described below with reference to the drawings. It should be emphasized that this is only an exemplary explanation and does not exclude other embodiments using the present invention.

As a more common high-aspect-ratio structure, TSVs usually have large depths (several hundreds to thousands of microns), so inductively coupled plasma (ICP) processing devices with faster etching rates are usually used to perform the main etching step. The main etching steps of the TSV fabrication process usually include: a step of local plasma etching to initially form a TSV (equivalent to the aforementioned step (b)) and a step of global plasma etching (equivalent to the aforementioned step (d) ).

Before the local etching described above, a patterned photoresist layer or hard mask layer is usually formed on the silicon material layer to be etched in advance (the patterned photoresist layer or hard mask layer can be referred to as a photoresist pattern) Or hard mask pattern). During the local etching process, the patterned photoresist layer is used Or use a hard mask layer as a mask, and then use a suitable process gas to generate a plasma and apply it to the area of the silicon material that is not protected by the mask to etch through silicon vias. Because a patterned photoresist layer or hard mask layer is usually required as a protective layer, the above-mentioned local etching step / process is sometimes referred to as a pattern etching step / process or mask etching as needed in the description of the present invention. Steps / processes.

After the TSVs are initially etched, it is usually necessary to perform a global etching (also known as blank etching) process that does not require a mask to thin the formed TSVs for final formation. Vias of desired depth.

If a plasma etching device designed or configured for a mask etching process is used to perform the above-mentioned global etching process, it will usually happen that the etching rate of the edge region of the substrate is significantly faster than that of the central region, which will cause the entire substrate range The through-silicon structure is inconsistent in various aspects such as the depth of being thinned, the feature size at the top and the feature size at the bottom, which further affects the product yield. Therefore, the above-mentioned mask etching and global etching processes are usually implemented in different etching apparatuses; however, this will increase the cost (because it is necessary to purchase two different etching apparatuses).

In view of the above defects, the present invention provides a gas focus ring with adjustable opening width in a reaction chamber in a TSV etching device. The gas focus ring is used in different applications (such as a global etching process or a mask etching process). The opening width can be adaptively adjusted, so that it can ensure or improve the uniformity of etching in different application situations.

FIG. 1 and FIG. 2 are schematic structural diagrams of a TSV etching apparatus according to an embodiment of the present invention. The TSV etching device is typically an inductively coupled plasma processing device. As shown in FIG. 1 and FIG. 2, it includes an air-tight reaction chamber 10 surrounded by various walls. The reaction chamber 10 has an insulating cover plate 11 at the top, and a base 14 for holding the substrate W to be processed is provided at the bottom.

And a gas supply device (not shown in the figure) provided outside the reaction chamber; it may include a gas The air inlet 12 connected to the source, the air inlet pipe and the flow control device is provided on the side wall of the reaction chamber for the process gas to enter the reaction chamber 10. In other embodiments, the air inlet may be provided on the insulating cover 11.

An exhaust port (not shown) may be generally provided on the bottom wall of the reaction chamber 10. The exhaust port can be connected to an exhaust device (such as a pump) outside the reaction chamber, so that the reaction process gas can be continuously discharged under the action of the air extraction device, so that the reaction chamber can be maintained within a specific pressure range; The continuous discharge of impurities generated after the reaction can also avoid or reduce the risk of substrate contamination.

The insulative cover plate 11 is provided with an inductive coupling coil 13, and the coil 13 is connected to a radio frequency source (not shown) through a matching device (not shown). An alternating magnetic field is generated by passing a radio frequency current through the coil 13, and an electric field is induced in the reaction chamber 10 to ionize the process gas to generate a plasma. Therefore, the coil 13, the matching device, the radio frequency source, and the like herein may be collectively referred to as a plasma generating device.

A gas focus ring 16 having an inner diameter ΦD1 is provided below the air inlet 12 (the inner diameter ΦD1 is the width or diameter of an opening provided in the central region of the gas focus ring 16). The gas collection ring 16 may be made of an aluminum alloy material. The gas focusing ring 16 can restrict the process gas and the plasma distribution near the air inlet 12 according to its inner diameter.

The setting of the gas focusing ring 16 enables the gas entering from the air inlet 12 and the plasma and radicals generated by the ionization of the gas to pass through the opening of the gas focusing ring 16 to reach the surface of the substrate. Processing. The gas after the reaction and a part of the gas that is too late to participate in the reaction will be discharged downward from the channel around the base 14 from the exhaust port. From the above analysis of the gas flow path, the internal space of the reaction chamber 10 can be roughly divided into three regions: (1) the air inlet region located above the gas focusing ring 16; (2) the gas focusing ring 16 and the substrate W Between the processing area; (3) the exhaust area located below the substrate W.

A cover ring 15 is provided around the substrate W to protect the base 14 from the plasma. Damaged by bombardment. An edge ring 17 which is also arranged around the substrate W and can be raised and lowered is located above the cover ring 15. The edge ring 17 may be made of an insulating material such as ceramic. The edge ring 17 has a smaller inner diameter ΦD2 (relative to the inner diameter ΦD1 of the gas focusing ring 16). In the illustrated embodiment, the inner diameter ΦD2 of the edge ring 17 is smaller than the diameter of the substrate W. Therefore, part of the edge ring 17 may extend directly above the substrate W. In other embodiments, the inner diameter ΦD2 of the edge ring 17 may be slightly larger than the diameter of the substrate W, so that the edge ring 17 does not cover the substrate W even when it is lowered to the lowest position.

The raising and lowering of the edge ring 17 is driven by the driving unit 18. The driving of the edge ring 17 by the driving unit 18 and the process control in the entire etching process are controlled by a control device (not shown). When a global etching process is required, under the control of the control device, the driving unit 18 brings the edge ring 17 close to the gas focus ring 16 (the state shown in FIG. 2). Because the inner diameter of the edge ring 17 is small, the process gas and plasma passed by the gas focusing ring 16 are limited to the range of the edge ring 17, thereby preventing or inhibiting the plasma from contacting the periphery of the substrate and reducing the etching rate of the edge of the substrate. . When a mask etching process is needed, under the control of the control device, the drive unit 18 will bring the edge ring 17 close to the surface of the base 14 (as shown in Figure 1), and the gas focusing ring 16 enables the process gas and plasma to be able to Diffusion decreases over a wide range.

In other embodiments, the outer diameter of the edge ring 17 may be smaller than or substantially equal to the inner diameter ΦD1 of the gas focusing ring 16, so that when the edge ring 17 rises to the height of the gas focusing ring 16, the edge ring 17 will no longer stop at the gas The lower surface of the focus ring 16 can further enter the opening of the gas focus ring 16. In the global etching process, maintaining the edge ring 17 within or near the opening of the gas focus ring 16 can also achieve better process results.

FIG. 3 is a schematic structural diagram of a TSV etching apparatus according to another embodiment of the present invention. As shown in FIG. 3, the TSV etching apparatus includes a reaction chamber 20. Above the reaction chamber 20, there is an insulating cover plate 21, which is usually a ceramic dielectric material. The side wall of the reaction chamber An air inlet 22 is provided near the top for inputting a process gas into the reaction chamber 20. A base 24 (usually an electrostatic chuck) for holding the substrate W to be processed is provided at the bottom of the reaction chamber 20. An inductive coupling coil 23 is arranged above the outer side of the insulating cover plate 21, and a radio frequency current is provided to the coil 23 by a radio frequency source (not shown) to induce an electric field in the reaction chamber 20, thereby introducing the electric current from the air inlet 22 into the chamber. The process gas in the room is ionized and a plasma is generated to perform processes such as etching on the substrate W. In addition, in this embodiment, the air inlet 22 is formed on the side wall of the reaction chamber 20 near the insulating cover, but in other embodiments, it may be formed in the insulating cover, which is not limited in the present invention.

A ring assembly is provided around the outer peripheral side of the substrate W. As shown, the ring assembly may include at least two parts: a focus ring 25a and an edge ring 25b. The focus ring 25a is fixed around the outer periphery of the substrate W, and its inner diameter is larger than the outer diameter of the substrate W, so as to provide a relatively closed environment around the substrate W while preventing the edge region of the substrate W from being shielded. The edge ring 25b is disposed on the focus ring 25a in a movable / liftable manner, and its cross-sectional shape may be rectangular or trapezoidal, but its inner diameter is larger than the inner diameter of the focus ring 25a (in the embodiment shown in the figure, the focus The inner diameter of the ring 25a is approximately equal to the outer diameter of the base 24, and the inner diameter of the edge ring 25b is significantly larger than the outer diameter of the base 24). Therefore, the minimum horizontal distance from the inner periphery of the edge ring 25b to the substrate W is greater than the horizontal distance from the inner periphery of the focus ring 25a to the substrate W. When the cross-sectional shape of the edge ring 25b is rectangular, the width of the rectangle is about 1/4 to 2/3 of the radius of the cavity 20, which can achieve a better effect of plasma adjustment. The focus ring 25a and the edge ring 25b are each made of an insulating material such as ceramic. The edge ring 25b is positioned on the surface of the focus ring 25a by the support rod 26. The support rods 26 are preferably uniformly distributed in a plurality along the circumferential direction of the edge ring 25b, such as three. One end of each support rod 26 is fixedly connected to the edge ring 25b, and the other end is connected to the driving unit 27. In this embodiment, the driving unit 27 is provided outside the reaction chamber 20, and may include equipment such as a motor and an air cylinder for raising and lowering the support rod 26 and the edge ring 25b in a vertical direction so that the edge ring 25b approaches or leaves the substrate W. Specifically, the driving unit 27 drives the first position and the second position of the edge ring 25b in the vertical direction. Move between positions, and position the edge ring 25b in the first position or the second position as needed. Similar to the previous embodiments corresponding to FIG. 1 and FIG. 2, the driving of the edge ring 25 b by the driving unit 27 and the process control in the entire etching process are controlled by a control device (not shown).

When the edge ring 25b is positioned in the first position, it contacts the focus ring 25a, and cooperates with the focus ring 25a to adjust the distribution of the process gas and the plasma near the substrate. Specifically, the two parts form an integrated ring assembly, and the focus ring 25a plays the main plasma convergence effect. As shown by the solid line arrows in the figure, the edge ring 25b has very little shielding effect on the edge of the substrate. There is no shielding effect, so when the edge ring 25b is positioned at the first position, a mask etching process can be performed. The plasma density near the surface of the substrate W is not easily affected by the edge ring 25b, and the edge area of the substrate W is etched. The cross-sectional shape of the TSV is guaranteed.

Preferably, as shown in the figure, the focus ring 25a has a main body portion (not labeled) and a protruding portion 251 that protrudes from the upper surface of the main body portion in a narrow ring structure and surrounds the outer peripheral side of the substrate W . The edge ring 25b is movably provided on the outer peripheral side of the protruding portion 251 of the focus ring 25a. When it is positioned at the first position, its lower surface is in contact with the upper surface of the main body portion of the focus ring 25a. The ring 25a has fewer parts protruding from the focusing ring 25a, and has a smaller shielding effect on the plasma of the substrate edge. More preferably, the upper surface of the edge ring 25b is flush with the upper surface of the protruding portion 251, so that during the mask etching process of the TSV, the edge ring 25b does not affect the plasma density of the edge region of the substrate W at all.

When the edge ring 25b is positioned at the second position, its distance from the upper surface of the main body of the focus ring 25a is about 5 ~ 15mm. As shown by the dotted arrow in Figure 3, it can effectively block the free radicals in the reaction chamber from affecting the edge of the substrate. Etching plays a role of shielding or inhibiting the plasma from contacting the periphery of the substrate W. At this time, the edge ring 25b can reduce the process gas and plasma distribution at the edge of the substrate, reduce the etching rate at the edge of the substrate, and ensure the etching of the entire substrate surface. Uniformity. Therefore, when the edge ring 25b is positioned at the second position, the global etching process can be performed better.

In order to prevent the substrate W from flying out during the plasma treatment process, the protruding portion 251 may protrude from the upper surface of the substrate by 1 to 3 mm to prevent the substrate from flying out. In other embodiments, the focusing ring 25a may not be provided with a protruding portion but the entire upper surface protrudes from the upper surface of the substrate W by 1 to 3 mm to prevent the substrate from flying out.

In addition, the reaction chamber 20 may further include a gas gathering ring 28, which is horizontally disposed below the air inlet 22, and can restrict the process gas and the plasma distribution near the air inlet 22 according to its inner diameter. The gas accumulation ring 28 may be made of an aluminum alloy material. The reaction chamber 20 further includes an insulating ring 29 surrounding the base 24. The focusing ring 25a is fixedly disposed on the insulating ring 29 and covers the upper surface of the insulating ring 29, so that the insulating ring 29 can play a role of fixing and supporting the focusing ring 25a. The cross-sectional shape of the insulating ring 29 may be L-shaped or rectangular, which is not limited in the present invention. The inner side wall of the insulating ring 29 and the outer side wall of the base 24 are as close as possible to prevent the plasma from entering the surface of the base 24 and protect the base 24 from damage. The insulating ring 29 may be formed of an insulating material such as ceramic or quartz.

To explain, raising the edge ring 25b to the gas accumulation ring 28 (that is, the upper surface of the edge ring 25b is in close contact with the lower surface of the gas accumulation ring 28) can also achieve a better global etching effect. The function mechanism is similar to the embodiment in FIG. 2 and will not be repeated here.

FIG. 4 is a flowchart of a method for forming through-silicon via plasma etching according to an embodiment of the present invention. Multiple adjacent steps in this method can be performed continuously in the same plasma processing device, which can reduce the number of times the substrate is transferred throughout the TSV fabrication process.

Step S1 shown in FIG. 4 may be performed first: forming a photoresist pattern. This can be achieved with a commonly used lithography system. The process of forming a photoresist pattern may generally include: forming a photoresist layer on the entire surface of the substrate by spin coating; exposing and developing the photoresist layer, To form a photoresist pattern with an opening.

Usually, the semiconductor layer 310 (shown in Figure 5) and various functional elements (not shown in the figure; it can be a transistor, etc.) have been formed on the front surface of the silicon substrate, and then it will start on the back surface of the silicon substrate. The process of forming TSVs. In a specific embodiment, in order to reduce the required photoresist thickness, a hard mask layer 320 may be formed on the silicon material layer 300 first, as shown in FIG. 5. Compared with the photoresist, the hard mask layer 320 has a larger etching selection ratio than the silicon material layer 300. The material of the hard mask layer 320 may be a commonly used oxide layer, such as silicon oxide or silicon oxynitride. Then, a photoresist pattern 342 is formed above the hard mask layer 320. The photoresist pattern 342 has an opening 345 therein, and the position of the opening 345 corresponds to the position of the through silicon via to be formed.

Step S2 shown in FIG. 4 is performed: plasma etching is performed to form a hard mask pattern. This step can be implemented in any of the TSV etching apparatuses given in the previous embodiments. In order to obtain a better hard mask pattern, the corresponding TSV etching device can be adjusted to a mask etching mode for the mask etching process. In the process of forming a hard mask layer pattern by etching, the photoresist pattern used as a mask is usually not completely lost, and a part thereof is usually left.

The specific process of the plasma etching to form the hard mask layer may generally include: placing the silicon substrate in a reaction chamber of the etching device with the back side facing up, and putting the etching device in a mask etching mode; Under the environmental conditions of the reaction chamber (including temperature, air pressure, etc.), a process gas is passed to etch the hard mask layer to form a hard mask pattern. The composition of the process gas that is passed in is designed for the material of the hard mask layer. At the same time, in order to avoid the erroneous damage of the underlying silicon material layer by the etching process, the process gas that is passed in is relatively slow to silicon (that is, the etching rate of the silicon material layer is very slow).

The hard mask pattern 322 formed at the end of the etching in this step and the opening 325 located in the hard mask pattern 322 can be shown in FIG. 6.

Step S3 shown in FIG. 4 is performed: the remaining photoresist pattern is removed.

The traditional method of removing photoresist is usually ashing, and the device used is usually a special ashing device. Put the substrate with photoresist on the surface into this special ashing device, and then pass in the ashing gas (such as oxygen), and some of the ashing gas is ionized into plasma and radical. Wait. The main effect on photoresist ashing is free radicals. The existence of plasma may damage the formed semiconductor layer and functional components. Therefore, special ashing devices are usually provided with filter elements to intercept the plasma, and only ash is allowed. The chemical gas carries free radicals to the photoresist.

In one embodiment of the present invention, the above-mentioned dedicated ashing device may not be used, but the through-silicon via etching device for completing the hard mask layer etching may be continued to perform the ashing process. That is, after step S2 (etching to form a hard mask pattern) is completed in the reaction chamber of the through-silicon via etching device, the silicon substrate is not removed from the reaction chamber, but ashing is continued using the through-silicon via etching device. Process (ie, step S3). The specific process may include: passing ashing gas (such as oxygen) to the reaction chamber; ionizing at least a part of the ashing gas using a plasma generating device to form free radicals and plasmas; etc .; The chemical gas flows to the back of the silicon substrate to achieve ashing of the residual photoresist pattern. The plasma present during the ashing process can also reach the back of the silicon substrate, which may cause a corrosive effect on the back of the silicon substrate. However, since there is no functional element or a truly functioning semiconductor layer on the back of the silicon substrate at this moment, there is no major damage or defect on the back of the silicon substrate. What's more, the subsequent thinning step on the back of the silicon substrate will also eliminate this defect.

When the through-silicon via etching device is used to implement the ashing process, it can be maintained in the mask etching mode for the mask etching process, so as to reduce the frequency of switching the etching mode.

After the step of removing the remaining photoresist pattern is completed, the obtained device structure can be as shown in FIG. 7.

Perform step S4 as shown in FIG. 4: mask etching to initially form a through silicon hole.

In one embodiment, the silicon substrate can be kept in the reaction chamber of the TSV etching device to complete the step of etching to form a TSV initially. In order to obtain better TSV etching results, the corresponding TSV etching device can be adjusted to a mask etching mode for the mask etching process. In this step, the composition of the process gas that is passed in is designed for the silicon material layer and has a very low etch rate for the hard mask pattern as a mask; for example, in one embodiment, the selected process gas pair The etch selection ratio of the hard mask pattern to the silicon material layer may be 1: 100 or lower. At the end of this step, the hard mask pattern is usually not completely consumed, but a part of it remains.

To explain, in the expression "preliminarily forming TSV", the meaning of "preliminary" is only to indicate that the TSV formed in this step is not the final TSV, and it will be further processed in the subsequent steps For example, it is thinned as a whole by global etching (step S6)). In other words, the “preliminary” here does not mean to limit the shape of the TSV formed here.

In order to facilitate subsequent filling, the cross-section of the TSV formed here can be tapered, trapezoidal, or irregular in shape with a wide width and a narrow width.

The preliminary shape of the TSV 305 obtained after the etching at this step can be shown in FIG. 8.

Step S5 shown in FIG. 4 is performed: the remaining hard mask pattern is removed.

In one embodiment, the silicon substrate can be kept in the reaction chamber of the TSV etching device to complete the step of removing the residual hard mask pattern. In the etching of this step, the corresponding TSV etching device can be adjusted to a mask etching mode for a mask etching process, or it can be adjusted to a global etching mode for a global etching process. It has been verified that the above two modes can achieve the removal of hard mask patterns that meet the requirements of the process. But compared to In other words, the process results using the mask etching mode are slightly better than those using the global etching mode. In this step, the composition of the process gas that is passed in is designed for the hard mask layer and has a lower etching rate for the underlying silicon material layer.

The device structure obtained at the end of this step can be shown in Figure 9.

Finally, step S6 shown in FIG. 4 is performed: global etching to thin the TSV.

In one embodiment, the silicon substrate can be kept in the reaction chamber of the TSV etching device to complete the global etching step to reduce the TSV. In order to obtain a better etching morphology, the corresponding TSV etching device can be adjusted to a global etching mode for a global etching process. In this step, the composition of the introduced process gas is designed for the silicon material layer.

The depth of the TSV obtained after the etching at this step has met the design requirements.

In the above embodiment, steps S2 to S6 are all performed in the same TSV etching device. In other embodiments, according to requirements, only steps S4 to S6 may be selected and executed in the same TSV etching device.

Although the content of the present invention has been described in detail through the above-mentioned preferred embodiments, it should be recognized that the above description should not be considered as limiting the present invention. Various modifications and alternatives to the present invention will become apparent to those skilled in the art after having read the foregoing. Therefore, the scope of protection of the present invention should be defined by the scope of the attached patent application for invention.

Claims (19)

A method for forming a through-silicon via by etching on the back surface of a silicon substrate, comprising: placing the silicon substrate in a reaction chamber of a plasma etching device with the back side facing upward, and a silicon on the back surface of the silicon substrate. A hard mask layer is formed over the material layer, and a photoresist pattern is formed over the hard mask layer; using the photoresist pattern as a mask, the hard mask layer is etched to form a hard mask pattern; removing the remaining The photoresist pattern; using the hard mask pattern as a mask, etching the underlying silicon material layer to initially form the TSV; removing the remaining hard mask pattern; globally etching the silicon material layer; the silicon The substrate is removed from the reaction chamber. The reaction chamber includes at least: an air inlet area connected to a gas supply device, a processing area where the silicon substrate to be processed is located, the air inlet area and the processing area. A gas focusing ring is provided therebetween, and an opening is provided in the center of the gas focusing ring, and the opening serves as a channel for gas to flow from the intake area to the processing area; the size of the opening during the processing of the silicon substrate is Adjustable; global eclipse The size of the opening is smaller than in the initial stage of forming the silicon vias stage or stages of forming the hard mask pattern or remove residual size of the opening in the hard mask pattern stage. The method according to item 1 of the scope of patent application, wherein a periphery of a base for supporting the silicon substrate is provided with an edge ring which can be raised and lowered in a vertical direction; The size of the opening of the gas focusing ring is adjusted by the following methods: when a larger opening size is required, the edge ring is kept at a first height close to the base; when a smaller opening size is required, the The edge ring is raised to a second height near the gas focus ring, so that the edge ring covers a part of the space of the opening. The method according to item 1 of the scope of patent application, wherein a periphery of a base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; at the stage of initially forming the TSV or forming the In the hard mask pattern phase, the edge ring is maintained at a first height near the base; in the global etching phase, the edge ring is maintained at a second height near a gas focus ring. The method according to item 3 of the scope of patent application, wherein the height of the edge ring in the global etching stage is higher than that in the stage of initially forming the TSV or the stage of forming the hard mask pattern by 5 mm to 15 mm. The method according to item 1 of the scope of patent application, wherein the TSV formed in the end is a tapered or trapezoidal shape with a wide width and a narrow width. The method according to item 1 of the scope of patent application, wherein the remaining photoresist pattern is removed by ashing. The method according to item 1 of the scope of patent application, wherein the step of forming the hard mask pattern, the step of initially forming the TSV, the step of removing the remaining hard mask pattern, and the step of globally etching the silicon material layer The steps are all performed by plasma etching. A method for forming a silicon through hole by plasma etching includes: placing a silicon substrate in a reaction chamber of a plasma etching device, and forming a patterned mask over a silicon material layer of the silicon substrate; The reaction chamber includes at least: an air inlet area connected to an air supply device, a processing area where the silicon substrate to be processed is located, and a gas focusing ring is provided between the air inlet area and the processing area. An opening is provided in the center of the gas focusing ring, and the opening serves as a channel for gas to flow from the intake area to the processing area; the size of the opening is adjustable during the processing of the silicon substrate; in the gas focusing ring The opening is maintained in a state of a first size, and the silicon material layer is etched by a plasma to form the TSV in the silicon material layer; the remaining mask is removed; the opening in the gas focus ring While maintaining a second size, the silicon material layer is globally etched, the second size is smaller than the first size; the silicon substrate is removed from the reaction chamber. The method according to item 8 of the patent application, wherein the mask comprises a hard mask pattern. The method according to item 8 of the scope of patent application, wherein a periphery of a base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; the size of the opening of the gas focusing ring is borrowed It is adjusted by the following method: when a larger opening size is required, the edge ring is maintained at a first height near the base; When a smaller opening size is required, the edge ring is raised to a second height close to the gas focusing ring, so that the edge ring covers a part of the space of the opening. A method for forming a silicon through hole by plasma etching includes: placing a silicon substrate in a reaction chamber of a plasma etching device, and forming a patterned mask over a silicon material layer of the silicon substrate; A pedestal for placing the silicon substrate and an edge ring that can be raised and lowered around the silicon substrate are provided in the reaction chamber; while the edge ring is maintained at the pedestal, plasma etching is performed The silicon material layer to initially form the through silicon vias in the silicon material layer; remove the remaining mask; and while the edge ring is maintained at a height significantly higher than the base, the global plasma etches the A layer of silicon material; moving the silicon substrate out of the reaction chamber. The method according to item 11 of the patent application, wherein the mask comprises a hard mask pattern. The method according to item 11 of the application, wherein the height of the edge ring in the global plasma etching step is 5 mm to 15 mm higher than that in the step of initially forming the TSV. A through-silicon via etching device includes a reaction chamber surrounded by a plurality of walls. The reaction chamber is divided into at least three areas, namely: (1) an air inlet area and an air supply device. (2) a processing area, a silicon substrate to be processed is set in the processing area, and the processing area is connected to the gas inlet area so that the gas flows from the processing area; The air inlet area diffuses to the processing area; (3) an exhaust area connected to the processing area and an exhaust device, so that gas is discharged from the processing area to the outside of the reaction chamber through the exhaust device; a plasma A generating device is used to act on the gas in the reaction chamber to generate the plasma required in the process; a gas focusing ring is arranged between the inlet area and the processing area, and the center of the gas focusing ring is set There is an opening, which serves as a channel for the gas to flow from the inlet area to the processing area; the size of the opening is adjustable during the processing of the silicon substrate; a control device is used to pass through a silicon through hole The etching process is controlled. In the step of plasma etching a silicon material layer protected by a mask to initially form the TSV, the control device controls the opening of the gas focus ring to remain at a first size; In the step of globally plasma-etching the silicon material layer without mask protection after the step of initially forming the TSV, the control device controls the opening of the gas focus ring to remain at a second size, the second size being smaller than the First size. The through-silicon etching device according to item 14 of the scope of patent application, wherein a periphery of a base for supporting the silicon substrate is provided with an edge ring that can be raised and lowered in a vertical direction; the control device controls the The edge ring is raised and lowered to adjust the size of the opening of the gas focus ring: when a larger opening size is required, the control device controls the edge ring to remain at a first height near the base; When a smaller opening size is required, the control device controls the edge ring to rise to a second height near the gas focus ring, so that the edge ring covers a part of the space of the opening. A through-silicon via etching device includes: a reaction chamber that can be evacuated and hermetically sealed; a base located in the reaction chamber for placing a silicon substrate; An edge ring for lifting; a gas supply device connected to the reaction chamber for supplying gas to the reaction chamber; a plasma generating device for acting on the gas in the reaction chamber to generate the gas required in the processing process A plasma control device for controlling the process of etching through a silicon via; in the step of plasma etching a silicon material layer protected by a mask to initially form the silicon via, the control device controls The edge ring is maintained at the base; in the step of globally plasma-etching the silicon material layer without mask protection after the step of initially forming the TSV, the control device controls the edge ring to be maintained at a level significantly higher than The height of the base. The TSV etching device described in item 16 of the scope of patent application, wherein the height of the edge ring in the global plasma etching step is higher than that in the step of initially forming the TSV by 5 mm to 15 mm. The through-silicon etching device according to item 16 of the patent application scope, further comprising a gas focusing ring, an opening is provided in the center of the gas focusing ring, and the opening serves as a channel for gas to flow from the gas supply device to the base. . The TSV etching device according to item 18 of the scope of patent application, wherein in the global plasma etching step, the control device controls the edge ring to maintain The height of the gas focusing ring is flush, or the edge ring is close to the lower surface of the gas focusing ring, so that the edge ring covers a part of the space of the opening.