JP2002309187A - Multilayer adhesive film and holding substrate suitable for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a thin semiconductor wafer. SOLUTION: The multilayer adhesive film is provided which is used in a method for producing a thin semiconductor wafer by temporarily bonding a semiconductor wafer on which a circuit pattern is formed to a holding substrate through an adhesive film, grinding and processing the back of the wafer, and peeling the film from the wafer and is characterized by being prepared by laminating (a) hot-melt polyimide films or prepared by laminating a hot-melt polyimide film on a non-hot-melt polyimide film, (b) being capable of being bonded to a silicon wafer by thermocompression through the hot-melt polyimide layer on each side, and (c) being capable of being separated at a separation surface when water penetrates into the adhesive film, the separate surface being formed by laminating a polyimide film surface-treated with a silicone resin or a silylating agent in the inside. The holding substrate is also provided which is used in a process using the above adhesive film and is prepared by coating the surface of a silicon wafer with an acid-resistance material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a thin semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, thin chips have been produced to reduce the size of devices and to prevent heat generation of power devices. In the future, mounting technology called bumpless super connect is being studied to increase the transfer rate between chips, and technology to make the chip as thin as possible to connect without bumps is being studied. It has been demanded.

Conventionally, a thin IC chip is formed by forming an integrated circuit on the surface of a high-purity silicon single crystal wafer by ion implantation, etching or the like, and then thinning the back surface to a thickness of 100 to 200 μm by grinding, polishing or etching. After that, it is manufactured in the process of dicing into chips.

[0004] In these steps, a method is used in which an adhesive tape is adhered to the front surface (hereinafter referred to as a circuit surface) of the wafer in order to prevent damage during grinding of the back surface of the wafer and facilitate the grinding process. Have been. This pressure-sensitive adhesive tape contains acrylic or rubber as a component of the pressure-sensitive adhesive, and is used at around room temperature.

[0005]

On the other hand, IGBTs and GTs
In the case of a power device such as an O 2 thyristor, electrodes such as a collector and an anode are formed on the back surface of the chip. The formation method is chrome, nickel,
After forming an alloy such as silver by vapor deposition, a metal sintering process is performed at 400 to 500 ° C.

In the production of these power devices,
Since the adhesive tape shown above lacks heat resistance,
In place of the above process, after grinding and polishing, the adhesive tape, which was also used for maintaining strength, was peeled off, and after cleaning the wafer, it was necessary to form the back electrode by sputtering or the like, thus complicating the process. There are problems such as a decrease in yield due to cracks and the like.

The present invention has been made in view of the above-mentioned prior art, and is directed to a multilayer adhesive film and a holding substrate which can be used from the back surface grinding of a semiconductor wafer to a metal sintering process, and a thin semiconductor wafer using the same. It is intended to provide a manufacturing method.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a thin semiconductor wafer in which a semiconductor wafer on which a circuit pattern is formed is temporarily bonded to a holding substrate via an adhesive film, and the back surface is ground and processed and then peeled off from the holding substrate. (A) a heat-fusible polyimide film, or a multilayer adhesive film formed by laminating a heat-fusible polyimide film and a non-heat-fusible polyimide film, b) A heat-sealed polyimide layer is provided on both sides to enable adhesion to a silicon wafer by thermocompression bonding. (d) A polyimide film surface-treated with a silicone resin or a silylating agent is laminated inside. A multi-layer adhesive film characterized by the fact that a separate surface is formed by leaving it in place, and peels off from the separate surface when water permeates. It is.

Further, the present invention provides a method of manufacturing a thin semiconductor wafer in which a semiconductor wafer on which a circuit pattern is formed is temporarily bonded to a holding substrate via the multilayer adhesive film, the back surface is ground and processed, and then peeled off from the holding substrate. A holding substrate used in the method, wherein the surface of the silicon wafer is coated with an acid-resistant material.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multilayer adhesive film, a holding substrate, and a method for manufacturing a thin semiconductor wafer using the same according to the present invention will be described below with reference to a silicon IC as an example.

The multilayer adhesive film of the present invention refers to a thin semiconductor wafer which is formed by temporarily adhering a semiconductor wafer on which a circuit pattern is formed to a holding substrate via an adhesive film, grinding and processing the back surface, and then peeling off the holding substrate. A multilayer adhesive film used in a production method, comprising: (a) a heat-fusible polyimide film having two or more layers;
A heat-fusible polyimide film is present on the two surface layers, and the surfaces thereof can be bonded to the silicon wafer by thermocompression bonding. (C) Surface treatment with a silicone resin or silylating agent on the back surface of the polyimide film on the surface layer Is applied to form a separate surface, or a polyimide film which has been subjected to a surface treatment with a silicone resin or a silylating agent is laminated inside to form a separate surface, and optionally (d) 1 A multilayer adhesive film characterized in that one or more heat-fusible polyimide films or non-heat-fusible polyimide films are present inside and peel off from the separate surface when water permeates.

This multilayer adhesive film has an adhesive property to a silicon wafer or a holding substrate because the outermost layer, which is a heat-sealed polyimide layer, is provided. Also,
Since the polyimide has acid resistance, the multilayer adhesive film is also resistant to silicon wafer etchants (such as hydrofluoric nitric acid). In addition, since polyimide has a high thermal decomposition temperature, the present multilayer adhesive film also has heat resistance and can withstand the above-described metal sintering step.

When water penetrates into the heat-fused polyimide film, the adhesive strength is reduced and the separation of the holding substrate and the silicon wafer becomes easy. The thicker the film, the more easily the water permeates, and the easier the separation of the holding substrate and the silicon wafer. The preferred thickness of the multilayer adhesive film that is not peeled off by water washing but is peeled off in a peeling step described later is 50 μm or more and 500 μm or less.

Further, in the step of separating the wafer after the back surface grinding and processing from the holding substrate which is a hard material, the separation is performed preferentially within the multilayer adhesive film in order to prevent the silicon wafer from being concentrated and cracked. A surface is formed. After separating the silicon wafer and the holding substrate, the adhesive film remaining on the wafer and the holding substrate is a soft material, and it is easy to peel off the brittle silicon wafer or the holding substrate.

A method for producing a multilayer adhesive film will be described using a multilayer adhesive film composed of four layers as an example. First, a first heat-fusible polyimide film serving as a bonding surface with a silicon wafer, a second polyimide film forming a separate surface by surface treatment, and a third polyimide film bonded to the separate surface and separated from the separate surface in a peeling step. And a fourth heat-fused polyimide film that adheres to the holding substrate. In addition, the multilayer adhesive film of the present invention has 4
It is not limited to the use of a single film, the first and second polyimide films can be used on both sides of one polyimide film, and the third and fourth polyimide films are also formed of one polyimide film. Can be used on both sides. Further, another polyimide film may be inserted between the first and second polyimide films and between the third and fourth polyimide films to adjust the thickness.

First, the first polyimide film is a heat-sealing type polyimide film, and is responsible for bonding to a silicon wafer. The surface to be bonded to the silicon wafer may be subjected to an appropriate surface treatment for adjusting the adhesive force and water repellency.

The second polyimide film is subjected to a surface treatment for improving the releasability of the third heat-fusible polyimide film so that the treated surface becomes a separate surface.
As the surface treatment agent, a silylating agent or a silicone resin is used. The silylating agent only needs to have the ability to inactivate hydrophilic groups (carboxyl group, amino group, hydroxyl group, etc.) on the polyimide film surface. Preferably, the silylating agent is trimethylchlorosilane, dimethyldichlorosilane, hexamethyldisilazane, N, O-bis (trimethylsilyl)
Acetamide, N-trimethylsilylacetamide,
N, N'-bis (trimethylsilyl) urea, N-trimethylsilyldiethylamine, N-trimethylsilylimidazole, tert. -Butyldimethylchlorosilane. Further, those suitable as silicone resins are represented by general formula 1

Embedded image (Wherein, R ¹ and R ² are an aryl group, a hydrogen atom, an aliphatic alkyl group or a functional group having an unsaturated bond and may be the same or different, and R ³ , R ⁴ , R ⁵ and R ⁶ are hydrogen atoms , An aryl group, an aliphatic alkyl group, a trialkylsilyl group, or a functional group having an unsaturated bond, which may be the same or different).

The role of the third heat-fusible polyimide film is to adhere to the separate surface of the second polyimide film to become a part of the multilayer adhesive film and to separate from the separate surface in the peeling step.

After the circuit surface of the wafer is thermocompression-bonded to the holding substrate via the multilayer adhesive film, the adhesive force is maintained so that the adhesive force is sufficiently reduced in the peeling step.
It is desirable that not only the second polyimide film but also the third polyimide film be subjected to an appropriate surface treatment.
Specifically, it is preferable to apply a 0.1% to 10% solution of a silylating agent or a 1% to 20% solution of a silicone resin to the second polyimide film. The third heat-fused polyimide film has a silylating agent of 10 to 1000 p.
pm solution application, or 100-5 of silicone resin
The application of a 000 ppm solution is preferred. The coating method is not particularly limited, and is selected from an air doctor coater, a blade coater, a knife coater, a roll coater, a cast coater, a spray coater and the like. The fourth polyimide film is a heat-fusible polyimide film, and is responsible for bonding to the holding substrate. The surface to be bonded may be subjected to an appropriate surface treatment for adjusting the bonding strength. For example, when the surface of the holding substrate is diamond-like carbon, a 0.1% to 10% solution of a silicone resin is preferably applied, and when chromium nitride is used, a 0.01% to 1% solution of a silicone resin is preferably applied. It is.

The first surface having been subjected to the appropriate surface treatment as described above
The fourth to fourth polyimide films are integrated by thermocompression bonding.

The apparatus used for thermocompression bonding is not particularly limited, but can be thermocompression bonded with a hot roll, a hot press, or an oven. The thermocompression bonding is performed at a temperature higher than the glass transition point of the film. However, in order to prevent the film from adhering to a heating hot plate or a roller, it is desirable to perform the heating at a temperature equal to or lower than the heat fusing temperature. Specifically, the temperature may be 230 ° C. or higher, and desirably 310 ° C. or lower. The pressure may be such that the films adhere sufficiently to each other, and specifically, is 10 kPa or more.

Next, the structure and manufacturing method of the holding substrate will be described. The holding substrate is used to temporarily hold the silicon wafer on which the circuit pattern is formed, and to prevent damage to the silicon wafer during processing such as backside grinding, polishing, etching, sputtering, vapor deposition, and metal sintering of the silicon wafer. Can be

The holding substrate of the present invention is a plate in which an acid-resistant material is coated on the entire surface of a silicon wafer.
Since the holding substrate has the same thermal expansion coefficient as the silicon semiconductor wafer on which the circuit pattern to be thinned is formed, the bonding substrate of the silicon semiconductor wafer on which the circuit pattern is formed and the holding substrate is curved even in the heating / cooling process. do not do. Furthermore, since it has acid resistance, it is characterized in that it is not corroded even in the etching step of the back surface of the silicon wafer on which the circuit pattern is formed.

The acid-resistant coating material is selected from materials having resistance to the etching solution of the silicon wafer and heat resistance enough to withstand the heat diffusion process. In particular,
Aluminum oxide, chromium oxide, composite oxide of aluminum oxide and chromium oxide, chromium nitride, titanium nitride, aluminum nitride, zirconium nitride, composite nitride of any combination of two or more of the nitrides, titanium carbide,
Gold, diamond-like carbon and polyimide are preferred.

The purpose of the coating is to impart acid resistance, and the coating method is not particularly limited. Oxides such as aluminum oxide, chromium oxide, and a composite oxide of aluminum oxide and chromium oxide can be coated by a wet method such as a sol-gel method in addition to a dry method such as an evaporation method, an ion plating method, sputtering, and CVD. . Inorganic materials such as chromium nitride, titanium nitride, aluminum nitride, zirconium nitride, a composite nitride of any combination of two or more of the above nitrides, titanium carbide, gold, diamond-like carbon gold, and diamond-like carbon are deposited by evaporation, Ion plating method, sputtering, CVD
Etc. can be coated. Polyimide can be used by a wet method such as a spin coating method, a dip coating method, a spray coating method, or a dry method such as a vapor deposition polymerization method.

The thickness of the coating layer may be such that corrosion of the base material (silicon wafer) by the etchant can be prevented.
What is necessary is just 0.01 micrometer or more. Note that the above description is not limited to only a single-layer film, even if a primer layer is formed to increase the adhesion strength between the outermost acid-resistant coating layer and the silicon wafer as the base material. I do not care.

Further, in order to adjust the adhesion and release characteristics with the multilayer adhesive film, the surface of the holding substrate may be further treated with a silicone-based resin. For example, the coating surface with diamond-like carbon or polyimide has too strong an adhesive force with the multilayer adhesive film,
It is desirable to apply a silicone resin to the adhesive surface of the holding substrate. A preferred silicone resin has the general formula 1

Embedded image (Wherein, R ¹ and R ² are an aryl group, a hydrogen atom, an aliphatic alkyl group or a functional group having an unsaturated bond and may be the same or different, and R ³ , R ⁴ , R ⁵ and R ⁶ are hydrogen atoms , An aryl group, an aliphatic alkyl group, a trialkylsilyl group or a functional group having an unsaturated bond, which may be the same or different.)

A method of bonding the silicon wafer to the holding substrate will be described. The multilayer adhesive film is placed on the circuit surface of a silicon wafer on which a circuit pattern is formed, and a holding substrate is placed thereon, and thermocompression bonding is performed. The heating temperature is higher than the heat fusion temperature. Specifically, the temperature is 310 ° C. or higher. The pressure may be such that the holding substrate and the silicon wafer sufficiently adhere to the multilayer adhesive film, and more specifically, 50 kPa or more.

The silicon wafer on which the circuit pattern has been formed by the above process is fixed on a holding substrate, and the circuit surface is protected by a multilayer adhesive film. Since the holding substrate and the multilayer adhesive film have acid resistance and heat resistance, the bonded substrate can be exposed to an acidic solution or heated. Therefore, the back surface of the silicon wafer bonded to the holding substrate can be mechanically processed by grinding, polishing, etching, or the like. Further, a film can be formed on the back surface of the silicon wafer by a process such as sputtering or vapor deposition. Further, a heat treatment such as a metal sintering step is also possible.

A method for separating the silicon wafer and the holding substrate will be described.

The peeling of the silicon wafer after the back surface processing is 2
The process is performed separately. In the first step, the bonded substrate of the silicon wafer and the holding substrate is immersed in water and then pulled from both sides to separate the holding substrate and the silicon wafer.
At this time, since the separation proceeds from the separate surface of the multilayer adhesive film, the adhesive film remains on the silicon wafer and the holding substrate. In the second step, the adhesive film remaining on the silicon wafer is peeled off.

Since the peeling conditions such as the pH of the peeling water, the liquid temperature, and the immersion time in the first step are influenced by the thickness of the multilayer adhesive film, the bonding conditions, and the heat history after bonding, they should be generally limited. Can not. The thicker the multilayer adhesive film, the more quickly the adhesive force is reduced and the easier it is to peel off. The higher the maximum temperature in the heat history including the bonding, the higher the adhesive strength, the more difficult it is to peel off, and the longer the immersion time. The higher the temperature of the water to be immersed and the higher the basicity, the easier the peeling.

As a method for pulling the holding substrate and the silicon wafer, there is a method in which the silicon wafer is fixed to a vacuum suction type suction pad and pulled on both sides. At this time, in order to prevent the silicon wafer with circuit from being damaged, a protective film is stuck on the back surface of the silicon wafer, or the back surface of the silicon wafer is fixed to a second hard holding substrate such as a glass plate with a double-sided tape, and then sucked. It may be pulled on both sides using a pad.
Since the protective film and the double-sided tape need to peel the silicon wafer later, an ultraviolet-curable or heat-peelable pressure-sensitive adhesive tape is preferable.

In the second step, after fixing the back surface of the silicon wafer with the suction pad, an adhesive tape was stuck on the film remaining on the wafer, and the end of the adhesive tape was pulled up and remained on the wafer. Peel off the adhesive film.

Example

EXAMPLES 1-3 Preparation of Holding Substrate A silicon wafer having a diameter of 6 inches and a thickness of 640 μm was prepared. The silicon wafer was coated with an acid-resistant material by the method shown in Table 1. In Example 2, a silicone resin represented by the general formula 1 (GR650 manufactured by Showa Denko KK, diluted to 10% by weight with methyl ethyl ketone) was applied to the surface on which the multilayer adhesive film was to be adhered, and the adhesion was adjusted. .

[Table 1]

[0036]

Examples 4 to 9 Production of Multi-layer Adhesive Film (1) Three heat-fusible polyimide films Upilex VT441S (25 μm thick) manufactured by Ube Industries, Ltd. were prepared. (VT441S is a multilayer heat-sealing film in which a heat-fusible polyimide layer is formed on both sides of a polyimide film.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first polyimide film in the description corresponds to the first "surface to be an outer layer" in the example. Similarly, the second polyimide film is on the “bonding face with the first sheet”, the third polyimide film is on the “sticking face with the first sheet”, and the fourth polyimide film is 3 on the “sticking face with the first sheet”.
Each corresponds to the “surface to be the outer layer” of the sheet. ) The surface treatment liquid shown in Table 2 was applied to each of the bonded surfaces and the surface that became an outer layer when integrated, dried, and heated at 210 ° C for 30 minutes. Next, the two films were laminated, thermocompression-bonded at 300 ° C. for 15 minutes at 0.1 MPa, and integrated to form a multilayer adhesive film. The thickness after integration was 70 to 75 μm.

[Table 2]

[0037]

Examples 10 to 17 Production of multilayer adhesive film (2) In the same manner as in Examples 4 to 9, a multilayer adhesive film having the structure shown in Table 3 was prepared by using a polyimide film shown in Table 3 and a surface treating agent shown in Table 4. It produced using it. The thickness after integration is 190-
It was 200 μm.

[Table 3]

[Table 4]

[0038]

Examples 18 to 21 Production of multilayer adhesive film (3) In the same manner as in Examples 4 to 9, the multilayer adhesive film having the structure shown in Table 5 was replaced with the number of heat-fusible polyimide films shown in Table 6 (Ube Industries, Ltd.). (VT441S, manufactured by Co., Ltd., thickness: 25 μm) and the surface treatment agents shown in Table 5.

[Table 5]

[Table 6]

[0039]

Examples 22 to 39 Adhesion and peeling of holding substrate and silicon wafer A silicon wafer, the heat-sealed film prepared in Examples 4 to 21, and the holding substrate prepared in Examples 1 to 3 were stacked. Table 7 shows the multilayer adhesive film and the holding substrate used. The stacking order was such that the silicon wafer and the first film were bonded, and the holding substrate and the last film were bonded.
Next, thermocompression bonding was performed to bond the silicon wafer, the multilayer adhesive film, and the holding substrate. Thermocompression bonding conditions: 330 ° C, 1
0 min, 0.1 MPa. The warpage of each of the bonded plates was 20 μm or less. The warpage of the silicon wafer before bonding was 20 μm or less, and it can be seen that warping did not occur even after bonding. Next, after being immersed in water at 80 ° C., the holding substrate and the silicon wafer were vacuum-suctioned from both sides using a vacuum pad and pulled to both sides, and both could be peeled off into two sheets. At this time, the film was peeled off on the separate surface of the heat sealing film, and the film was stuck to both the holding substrate and the silicon wafer and remained. Table 7 shows the immersion time. From this table, it can be seen that the greater the thickness of the multilayer adhesive film, the more quickly it can be peeled off. An adhesive tape was stuck to the heat-sealing film remaining on the holding substrate and the silicon wafer, and the heat-sealing film was easily peeled off from the holding substrate and the silicon wafer.

[Table 7]

[0040]

COMPARATIVE EXAMPLES 1 AND 2 Three heat-fused polyimide films (Table 8) were stacked and thermocompressed in the same manner as in Examples 4 to 9 to be integrated. Next, in the same manner as in Examples 22 to 39, a silicon wafer, an integrated heat-fused polyimide film, and the holding substrate prepared in Example 1 were stacked in this order and subjected to thermocompression bonding, immersed in water, and pulled to both sides. The silicon wafer and the holding substrate were separated. (A) peeling is progressing between the silicon wafer and the heat-fusible polyimide film; (b) the heat-fusible polyimide film cannot be peeled one by one; (c)
It was found that separation of the silicon wafer and the holding substrate was not easy, and the silicon wafer was sometimes damaged.

[Table 8]

[0041]

As described above, the multilayer adhesive film and the holding substrate according to the present invention make it possible to handle the semiconductor wafer from the back surface grinding to the metal sintering step with the semiconductor wafer adhered to the holding substrate. After processing, the holding substrate can be separated from the semiconductor wafer.

 ──────────────────────────────────────────────────の Continued on the front page F-term (reference) 4F100 AH06A AH06B AH06C AK49A AK49B AK49C AK49D AK52A AK52B AK52C BA02 BA03 BA04 BA05 BA06 BA07 BA10A BA10B BA16 BA26 JL12A JL12B JL12D JL14A01B04 J004

Claims (7)

[Claims] 1. A multi-layer bonding method used in a method of manufacturing a thin semiconductor wafer in which a semiconductor wafer having a circuit pattern formed thereon is temporarily bonded to a holding substrate via an adhesive film, and a back surface is ground and processed, and then separated from the holding substrate. (A) a heat-fusible polyimide film composed of two or more layers, and (b) a heat-fusible polyimide film on two surface layers, the surface of which is bonded to a silicon wafer by thermocompression bonding. (C) the back surface of the surface polyimide film is subjected to a surface treatment with a silicone resin or a silylating agent to form a separate surface, or is subjected to a surface treatment with a silicone resin or a silylating agent. A separate surface is formed by laminating the polyimide film inside, and optionally (d) one or more Multilayer adhesive film polyimide film without more heat-welding polyimide film or heat-fusible been is present inside, water and then exfoliating the separation plane when penetration. 2. The silylating agent is trimethylchlorosilane,
Dimethyldichlorosilane, hexamethyldisilazane,
N, O-bis (trimethylsilyl) acetamide, N-
Trimethylsilylacetamide, N, N'-bis (trimethylsilyl) urea, N-trimethylsilyldiethylamine, N-trimethylsilylimidazole, ter
t. 2. The multilayer adhesive film according to claim 1, wherein the film is selected from -butyldimethylchlorosilane. 3. The silicone resin has the general formula 1 (In the formula, R ¹ and R ² are independently an aryl group, a hydrogen atom, an aliphatic alkyl group or a functional group having an unsaturated bond, and may be the same or different, and R ³ , R ⁴ , R ⁵ and R ⁶ is independently a hydrogen atom, an aryl group, an aliphatic alkyl group, a trialkylsilyl group or a functional group having an unsaturated bond, and may be the same or different.) Multi-layer adhesive film. 4. The method according to claim 1, wherein the thickness of the multilayer adhesive film is not less than 50 μm and not more than 500 μm.
4. The multilayer adhesive film according to any one of items 3 to 3. 5. A semiconductor wafer having a circuit pattern formed thereon is temporarily bonded to a holding substrate via the multilayer adhesive film according to any one of claims 1 to 4, and after grinding and processing of a back surface, the semiconductor wafer is removed from the holding substrate. A holding substrate used for a method of manufacturing a thin semiconductor wafer to be peeled, wherein the surface of a silicon wafer is coated with an acid-resistant material. 6. An acid-resistant material comprising any combination of at least two of aluminum oxide, chromium oxide, a composite oxide of aluminum oxide and chromium oxide, chromium nitride, titanium nitride, aluminum nitride, zirconium nitride, and the nitride. The holding substrate according to claim 5, wherein the holding substrate is selected from the group consisting of composite nitride, titanium carbide, gold, diamond-like carbon, and polyimide. 7. A holding substrate according to claim 5, wherein the surface of the holding substrate to be bonded to the multilayer adhesive film is coated with a silicone resin, wherein the silicone resin is represented by the general formula (1). (Wherein, R ¹ and R ² are an aryl group, a hydrogen atom, an aliphatic alkyl group or a functional group having an unsaturated bond and may be the same or different, and R ³ , R ⁴ , R ⁵ and R ⁶ are hydrogen atoms , An aryl group, an aliphatic alkyl group, a trialkylsilyl group, or a functional group having an unsaturated bond, which may be the same or different.)