Temporary adhesive for substrates and substrate processing method

Abstract

To provide a temporary substrate adhesive that has excellent heat resistance after bonding and prevents the adhesive from being left after peeling.SOLUTION: A temporary substrate adhesive according to an embodiment includes a silane coupling agent and a photobase generator, but does not include a resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a temporary adhesive for substrates and a method for processing substrates. [Background technology]

[0002] There is a substrate processing method in which a substrate to be processed and a support substrate are bonded together using a temporary adhesive for substrates, and after processing the substrate, the substrate to be processed and the support substrate are peeled apart. The temporary adhesive for substrates used in such a processing method is required to have excellent heat resistance after bonding and to suppress adhesive residue after peeling. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5397378 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a temporary adhesive for substrates that has excellent heat resistance after bonding and can prevent adhesive residue after peeling, and a method for processing substrates. [Means for solving the problem]

[0005] The temporary adhesive for substrates according to the embodiment contains a silane coupling agent and a photobase generator, but does not contain a resin. [Brief explanation of the drawings]

[0006] [Figure 1] 1(a) to 1(f) are explanatory views showing a substrate processing method according to an embodiment. [Figure 2] 2(a) and 2(b) are explanatory diagrams of an experimental example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and in each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0008] <Temporary adhesive for circuit boards> The temporary adhesive for substrates according to the embodiment contains a silane coupling agent and a photobase generator. The temporary adhesive for substrates according to the embodiment does not contain a resin.

[0009] The silane coupling agent contains, for example, a silanol group. The silane coupling agent contains, for example, at least one selected from the group consisting of an amino group, an epoxy group, an azide group, and an isocyanate group. When the silane coupling agent contains these functional groups, it can bond with hydroxyl groups on the surface of the substrate to be processed or with amino groups or carboxyl groups formed by partial cleavage of imide bonds in a polyimide film formed on the surface of the substrate to be processed. The silane coupling agent may also contain other functional groups that can bond with hydroxyl groups on the surface of the substrate to be processed or with amino groups or carboxyl groups formed by partial cleavage of imide bonds in a polyimide film. These functional groups are bonded to, for example, silicon atoms constituting siloxane bonds.

[0010] The silane coupling agent contains a silanol group, which allows it to easily bond with the hydroxyl groups on the surface of the support substrate. The silane coupling agent may also contain other functional groups that can bond with the hydroxyl groups on the surface of the support substrate.

[0011] The silane coupling agent has, for example, a structure represented by the following formula (1) or formula (2): Formula (2) shows a reaction in which a silane coupling agent having a basic chemical structure is hydrolyzed. [ka] [ka] (In the formula, R1, R2, and R4 are each an amino group, an epoxy group, an azide group, or an isocyanate group, and R3 is a methyl group or an ethyl group.)

[0012] The blend amount of the silane coupling agent is, for example, 0.1% by mass or more and 1% by mass or less of the temporary adhesive for substrates.

[0013] The photobase generator absorbs, for example, ultraviolet light having a wavelength of 400 nm or less to generate a base.The photobase generator absorbs, for example, ultraviolet light having a wavelength of 254 nm or less to generate a base.

[0014] The photobase generator has, for example, a structure represented by the following formula (3), formula (4), or formula (5). [ka] [ka] (In the formula, Et is an ethyl group.) [ka]

[0015] The amount of the photobase generator blended is, for example, 0.01% by mass or more and 0.1% by mass or less of the temporary adhesive for substrates.

[0016] The temporary adhesive for substrates according to the embodiment may contain, for example, a solvent. Examples of the solvent include methanol, ethanol, and isopropyl alcohol.

[0017] <Substrate processing method> 1(a) to 1(f) are explanatory views showing a substrate processing method according to an embodiment. 1(a) to 1(f), the substrate processing method according to the embodiment is a method for processing one surface (a second surface 12 described below) of a substrate 10 to be processed. The substrate processing method according to the embodiment includes a bonding step, a processing step, and a peeling step. The substrate processing method according to the embodiment will be described in more detail below.

[0018] In the substrate processing method according to the embodiment, first, as shown in FIG. 1(a), a substrate 10 to be processed and a support substrate 20 are prepared.

[0019] The substrate 10 to be processed is, for example, a wafer. The substrate 10 to be processed has, for example, a device structure. The substrate 10 to be processed includes, for example, a semiconductor.

[0020] The workpiece substrate 10 has a first surface 11 and a second surface 12. The first surface 11 is a bonding surface that is bonded to the support substrate 20. The second surface 12 faces the opposite side to the first surface 11. If the first surface 11 is the front surface, the second surface 12 is the back surface. The second surface 12 is a surface to be processed that is processed in a processing step. For example, a circuit is formed on the first surface 11 in advance. For example, the first surface 11 is a circuit-formed surface. For example, a circuit is not formed on the second surface 12 in advance. The second surface 12 is a non-circuit-formed surface. A film containing polyimide may be formed on the first surface 11.

[0021] The support substrate 20 is capable of transmitting ultraviolet light. For example, the support substrate 20 is capable of transmitting ultraviolet light having a wavelength of 300 nm or less. For example, the support substrate 20 is capable of transmitting ultraviolet light having a wavelength of 254 nm or less. The support substrate 20 is, for example, transparent. The light transmittance of the support substrate 20 is, for example, higher than the light transmittance of the workpiece substrate 10. The support substrate 20 includes, for example, synthetic quartz.

[0022] The support substrate 20 has a third surface 21 and a fourth surface 22. The third surface 21 is a bonding surface that is bonded to the workpiece substrate 10. The fourth surface 22 faces the opposite side to the third surface 21. If the third surface 21 is the front surface, the fourth surface 22 is the back surface.

[0023] In the substrate processing method according to the embodiment, next, as shown in FIG. 1(b), a temporary adhesive for substrates 30 is applied between the workpiece substrate 10 and the support substrate 20. The temporary adhesive for substrates 30 is the temporary adhesive for substrates according to the embodiment described above. That is, the temporary adhesive for substrates 30 contains a silane coupling agent and a photobase generator, but does not contain a resin. The temporary adhesive for substrates 30 is applied by, for example, spin coating.

[0024] The temporary adhesive for substrates 30 is applied to at least one of the first surface 11 of the workpiece substrate 10 and the third surface 21 of the support substrate 20. In this example, the temporary adhesive for substrates 30 is applied to the third surface 21 of the support substrate 20. The temporary adhesive for substrates 30 may be applied to the first surface 11 of the workpiece substrate 10, or may be applied to both the first surface 11 of the workpiece substrate 10 and the third surface 21 of the support substrate 20.

[0025] In the substrate processing method according to the embodiment, next, as shown in FIG. 1(c), the workpiece substrate 10 and the support substrate 20 are bonded by thermocompression bonding. By thermocompression bonding, the first surface 11 of the workpiece substrate 10 and the third surface 21 of the support substrate 20 are chemically bonded via a temporary substrate adhesive 30 (silane coupling agent). If a polyimide-containing film is formed on the first surface 11, the polyimide-containing film and the third surface 21 of the support substrate 20 are chemically bonded via the temporary substrate adhesive 30 (silane coupling agent). The thermocompression bonding is performed, for example, under conditions of 100°C to 160°C, 1.25 MPa to 5 MPa, and 15 minutes to 30 minutes.

[0026] The application of the temporary adhesive for substrates 30 shown in FIG. 1(b) and the thermocompression bonding shown in FIG. 1(c) correspond to the bonding step.

[0027] 1(d), the second surface 12 of the workpiece substrate 10 is then processed (processing step). The processing step includes, for example, at least one of grinding the second surface 12, polishing the second surface 12, forming a film on the second surface 12, and heating the second surface 12. The processing step is performed after the bonding step.

[0028] 1(e) and 1(f), ultraviolet light is then applied from the fourth surface 22 side of the support substrate 20 to separate the workpiece substrate 10 and the support substrate 20. More specifically, the first surface 11 of the workpiece substrate 10 and the third surface 21 of the support substrate 20 are separated. If a film containing polyimide is formed on the first surface 11, the film containing polyimide is separated from the third surface 21 of the support substrate 20. The separation step is performed after the processing step.

[0029] The irradiated ultraviolet light has a wavelength of, for example, 400 nm or less. The irradiated ultraviolet light has a wavelength of, for example, 200 to 280 nm. The irradiated light amount of the ultraviolet light is, for example, 190 J / cm 2 More than 300J / cm 2 After irradiation with ultraviolet light, the film may be left for a predetermined time (for example, about 15 minutes) before being peeled off.

[0030] When irradiated with ultraviolet light, the photobase generator contained in the temporary adhesive for substrates 30 absorbs the ultraviolet light and generates a base. For example, the generated base cuts the bond between the silane coupling agent and the first surface 11 of the substrate 10 to be processed. If a film containing polyimide is formed on the first surface 11, for example, the generated base cuts the bond between the silane coupling agent and the film containing polyimide. For example, the generated base cuts the bond between the silane coupling agent and the third surface 21 of the support substrate 20. As a result, the substrate 10 to be processed and the support substrate 20 can be peeled off.

[0031] The peeled support substrate 20 can be reused, for example, as the support substrate 20 in the next processing.

[0032] Hereinafter, the effects of the temporary adhesive for substrates and the substrate processing method according to the embodiment will be described. Conventionally, temporary adhesives for substrates have been used that contain thermosetting resins or photocurable resins (e.g., acrylic resins, silicone resins, etc.). However, when a temporary adhesive for substrates containing such resins is used to bond a substrate to a support substrate, the heat resistance temperature of the bonded portion depends on the heat resistance temperature of the resin and is approximately 200°C or less. Therefore, for example, if the temperature of the substrate to be processed exceeds 200°C during processing after bonding, there is a problem in that the substrate to be processed may unintentionally peel off from the support substrate.

[0033] Furthermore, when a substrate temporary adhesive containing such a resin is used to bond a substrate to a support substrate, after the substrate to be processed and the support substrate are peeled off, a "residual adhesive" may occur, in which part of the temporary adhesive remains on the substrate to be processed or the support substrate. If residual adhesive occurs, a process of cleaning the substrate to be processed or the support substrate after peeling with an organic solvent or the like is required, which may cause a decrease in the yield of substrate processing. Therefore, there has been a demand for a temporary adhesive for substrates used in such substrate processing methods that has excellent heat resistance after bonding and suppresses adhesive residue after peeling.

[0034] In contrast, the temporary adhesive for substrates according to the embodiment contains a silane coupling agent and a photobase generator, but does not contain resin, and therefore can reliably bond the workpiece substrate and the support substrate, has excellent heat resistance after bonding, and can prevent adhesive residue after peeling.

[0035] Furthermore, according to the substrate processing method of the embodiment, by using such a temporary adhesive for substrates according to the embodiment, it is possible to provide excellent heat resistance after bonding and to suppress adhesive residue after peeling, which improves the degree of freedom in processing in the processing step, and also makes it possible to omit the cleaning step after peeling, thereby improving yield.

[0036] The temporary adhesive for substrates and the substrate processing method according to the embodiment are used, for example, in the manufacture of power devices and LED devices.

[0037] <Experimental Example> An experimental example will be described below. 2(a) and 2(b) are explanatory diagrams of an experimental example. In the experimental example, first, as shown in Fig. 2(a), a test piece 110 having a polyimide film 112 formed on the surface of a metal plate 111 and a 1.0 mm thick support substrate 120 made of synthetic quartz were prepared. Next, the test piece 110 and the support substrate 120 were bonded by thermocompression using a temporary substrate adhesive 130 to produce a bonded sample 150. The temporary substrate adhesive 130 used was a temporary substrate adhesive composed of a silane coupling agent represented by the above formula (1) in which R1 and R2 are ethylenediamine groups, and a photobase generator represented by the above formula (2).

[0038] Next, the peel strength (initial peel strength) of the bonded sample 150 produced in this manner was measured when the support substrate 120 was peeled from the test piece 110. Next, the bonded sample 150 produced in the same manner was subjected to a heat treatment at 400°C for 120 minutes in a nitrogen atmosphere, and then the peel strength (post-heating peel strength) of the bonded sample 150 when the support substrate 120 was peeled from the test piece 110 was measured. The results are shown in Figure 2(b).

[0039] 2(b), a peel strength of 7N or more was obtained both when heat treatment was performed and when heat treatment was not performed, and the film 112 was bonded so strongly that it tore upon peeling. This suggests that by bonding the test piece 110 and the support substrate 120 using the temporary adhesive for substrates 130, it is possible to prevent a significant decrease in peel strength after heat treatment. In other words, this suggests that the heat resistance after bonding is excellent.

[0040] Next, the bonded sample 150, which was prepared in the same manner as above and heat-treated at 400°C for 120 minutes in a nitrogen atmosphere, was irradiated with ultraviolet light having a wavelength of 200-280 nm at a light intensity of 287 J / cm. 2The test piece 110 was irradiated with ultraviolet light, and then left for 15 minutes to peel the test piece 110 from the support substrate 120. As a result, the test piece 110 and the support substrate 120 could be easily peeled off without any adhesive remaining on the bonded surface after peeling. This suggests that by bonding the test piece 110 and the support substrate 120 using the temporary adhesive for substrates 130, peeling can be easily performed by irradiation with ultraviolet light without any adhesive remaining after peeling, even after heat treatment. In other words, it suggests that it is possible to suppress the adhesive from remaining after peeling.

[0041] As described above, according to the embodiments, a temporary adhesive for substrates and a substrate processing method are provided that have excellent heat resistance after bonding and can prevent adhesive residue after peeling.

[0042] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0043] 10 substrate to be processed, 11 first surface, 12 second surface, 20 support substrate, 21 third surface, 22 fourth surface, 30 temporary adhesive for substrate, 110 test piece, 111 metal plate, 112 film, 120 support substrate, 130 temporary adhesive for substrate, 150 bonded sample

Claims

1. A temporary adhesive for substrates capable of bonding a workpiece substrate having at least one of a hydroxyl group, an amino group, and a carboxyl group on its surface to a support substrate having a hydroxyl group on its surface, comprising: A temporary adhesive for substrates comprising a silane coupling agent containing a silanol group and a photobase generator, and not containing a resin.

2. The temporary adhesive for substrates according to claim 1 , wherein the silane coupling agent contains at least one selected from the group consisting of an amino group, an epoxy group, an azide group, and an isocyanate group.

3. A method for processing a first surface of a substrate to be processed, the second surface having a first surface including at least one of a hydroxyl group, an amino group, and a carboxyl group, and a second surface facing the opposite side to the first surface, comprising: a bonding step of bonding the first surface of the workpiece substrate and the third surface of a support substrate having a third surface containing a hydroxyl group and capable of transmitting ultraviolet light by thermocompression bonding using the temporary adhesive for substrates according to claim 1 or 2; a processing step of processing the second surface of the workpiece substrate, the processing step being performed after the bonding step; a peeling step, which is carried out after the processing step, of irradiating ultraviolet light having a wavelength of 400 nm or less from the support substrate side to peel off the first surface of the workpiece substrate from the support substrate; A substrate processing method comprising:

4. 4. The substrate processing method according to claim 3, wherein in the bonding step, the first surface on which a circuit is formed in advance is bonded to the third surface of the support substrate.

5. The substrate processing method according to claim 3 , wherein the processing step includes at least one of grinding the second surface, polishing the second surface, forming a film on the second surface, and heating the second surface.

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