JP7041648B2 - Manufacturing method of composite substrate - Google Patents

Description

The present invention relates to a composite substrate having an insulating film on a single crystal silicon substrate, and more specifically, has high thermal conductivity on a single crystal silicon substrate used for semiconductor devices and MEMS (Micro Electro Mechanical System) applications. It relates to a bonded substrate provided with an insulating substrate such as silicon nitride or aluminum nitride.

There are many studies on improving the performance of semiconductor devices by combining silicon substrates, including SOI (Silicon on insulator). Among them, SOQ (Silicon on Quartz), which is used for optoelectronic applications due to its high transparency, and SOS (Silicon on Sapphire), which is used for high frequency applications due to its high insulation and good thermal conductivity, have been enhanced. There is a board. For example, in Patent Document 1, SOS in which silicon and sapphire are bonded is produced by devising the heat treatment temperature before and after bonding. However, these composite substrates (hybrid substrates) are a combination of materials with different coefficients of thermal expansion than silicon (Si) used as a semiconductor layer, and when manufactured by bonding, the heat of each substrate is high. It is known that it is difficult to manufacture due to the difference in expansion coefficient.

In recent years, with the progress of power electronics, power devices that convert and control electric power with high efficiency have rapidly become widespread, and are used for motor control of transportation equipment such as industrial robots and trains. Furthermore, the market for high-output power modules is rapidly expanding due to the progress of hybridization of automobile power and electric motors. Since a power module converts and controls a large amount of power of several tens to several hundreds of kW, its circuit board is required to have high insulation, heat dissipation, and heat resistance. Substrates having a thermal conductivity of more than 50 W / (m · K), such as silicon nitride and aluminum nitride, are used for circuit boards of power modules such as in-vehicle inverters. Insulating substrates with higher thermal conductivity by combining these high thermal conductive substrates and Si are also expected as next-generation materials, but like SOQ and SOS, the difference in the coefficient of thermal expansion between the substrates is 4 inches. In the case of a large-diameter substrate exceeding 300 ° C, the sintered body is generally popular and has a large surface roughness, which is a problem, and there is a problem that the bonded substrate is separated during a high temperature process exceeding 300 ° C. .. For example, Patent Document 2 shows an example of forming an amorphous layer on the bonded surface to improve a sintered body having a large surface roughness, but in the experiments of the present inventors, the same applies to the aluminum nitride sintered body. It was found that when the treatment was performed and the substrate bonded to the single crystal silicon substrate was treated at a high temperature, the substrate was peeled off at the amorphous layer forming interface, and only the amorphous layer was transferred to the single crystal silicon substrate.

Japanese Patent No. 5643509 Japanese Patent No. 6182661

In view of the above situation, it is an object of the present invention to provide a composite substrate that can withstand high temperatures.

The present inventors have improved the surface roughness of a composite substrate of a single crystal silicon substrate and an insulating substrate by subjecting the surface of the insulating substrate to a hydrophilic treatment and then providing an intervening layer on the hydrophilic surface. It has been found that a composite substrate can be obtained that can withstand high temperature treatment exceeding 300 ° C. by achieving improvement in the adhesion of each bonded interface of the crystalline silicon substrate-intervening layer-insulating substrate.

That is, the method for manufacturing a composite substrate according to an embodiment of the present invention is a first layer which is an insulating substrate containing Si or Al, a second layer which is an amorphous layer containing Si, and a single crystal silicon substrate. This is a method of manufacturing a composite substrate having a diameter of 100 to 300 mm by laminating the third layer in order. The manufacturing method includes a step of subjecting at least one surface of the first layer to a hydrophilization treatment to bring the contact angle with water to 60 degrees or less, a step of forming a second layer on the surface subjected to the hydrophilic treatment, It includes a step of bonding the first layer and the third layer via the second layer, a step of thinning the first layer, and a step of heating the composite substrate at a temperature of 400 ° C to 700 ° C. The ratio of the thickness of the first layer in the stacking direction to the thickness of the third layer in the stacking direction after thinning is 0.5 or less, and the heat of the first layer and the third layer at 40 ° C to 400 ° C. The difference in expansion coefficient is 3 ppm or less. The insulating substrate may contain Si ₃ N ₄ or Al N.

In the present invention, the amorphous layer is selected from amorphous Si, SiO ₂ and Si _{3N 4 ,} and may be formed by sputtering, CVD or spin coating.

Further, in the present invention, the hydrophilization treatment is one or a plurality of methods of ozone treatment, UV treatment, plasma treatment, ion beam treatment, ultrasonic cleaning, and cleaning with an acidic solution containing hydrofluoric acid or hydrochloric acid. good.

Further, the composite substrate according to the embodiment of the present invention includes a first layer which is an insulating substrate containing Si or Al, a second layer which is an amorphous layer containing Si, and a third layer which is a single crystal silicon substrate. And is a composite substrate having a diameter of 100 to 300 mm, which is formed by laminating in order. When the surface of the first layer in direct contact with the second layer of the composite substrate is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), The intensity ratio of the peak of the positive secondary ion detected as Si or Al to the peak of the positive secondary ion of the hydrocarbon detected as C _n H _m (n, m = 1 to 20) is Si / C. It is characterized in that _n H _m or Al / C _n H _m is 1 or more. The insulating substrate may contain Si ₃ N ₄ or Al N.

In the present invention, the amorphous layer may be selected from amorphous Si, SiO ₂ and Si ₃ N ₄ .

In the present invention, the surface of the first layer in direct contact with the second layer may be treated with ozone, UV, plasma, ion beam, ultrasonic cleaning, or cleaning with an acidic solution containing hydrofluoric acid or hydrochloric acid. Alternatively, the surface may be hydrolyzed by a plurality of methods.

It is a schematic cross-sectional view which shows the structure of a composite substrate. It is a flowchart which shows the procedure of the manufacturing method of a composite substrate. It is a photograph which shows the contact angle before and after the hydrophilization treatment to the surface of an insulating substrate. The ToF-SIMS measurement results before and after the plasma activation treatment on the surface of the insulating substrate are shown.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.
FIG. 1 shows the structure of the composite substrate 1 according to the present embodiment. As shown in FIG. 1, the insulating substrate 2 forming the first layer (surface layer) in the composite substrate 1, the amorphous layer 3 forming the second layer (intermediate layer) in contact with the insulating substrate 2, the insulating substrate 2 and the amorphous The single crystal silicon substrate 4 forming the third layer, which is the support substrate for the layer 3, has a structure in which they are laminated in this order. The dimensions of the composite substrate are φ100 to 300 mm in diameter.

The insulating substrate 2 is formed of a material containing silicon (Si) or aluminum (Al). As the insulating substrate 2, it is preferable to use a material in which the difference in the coefficient of thermal expansion of the single crystal silicon substrate is 3 ppm or less with respect to the coefficient of thermal expansion from 40 ° C. to 400 ° C. Specifically, the insulating substrate may be an aluminum nitride (AlN) sintered body, a silicon nitride (Si ₃ N ₄ ) sintered body, or the like. The surface of the insulating substrate 2 that comes into direct contact with the amorphous layer 3 is hydrophilized before the amorphous layer 3 is provided. This hydrophilization treatment may be one or more of ozone treatment, UV treatment, plasma treatment, ion beam treatment, ultrasonic cleaning, or cleaning with an acidic solution containing hydrofluoric acid or hydrochloric acid.

The hydrophilization treatment may be performed so that the contact angle with water on the treated surface of the insulating substrate 2 is 60 degrees or less. In the hydrophilization treatment, Si or Al is used when the treated surface of the insulating substrate 2 is analyzed by the time-of-flight secondary ion mass spectrometry (ToF-SIMS). The intensity ratio of the peak of the positive secondary ion detected as C _n H _m (n, m = 1 to 20) and the peak of the positive secondary ion of the hydrocarbon detected as C n H m (that is, Si / C _n H _m or It is preferable to carry out so that Al / C _n H _m ) is 1 or more.

The amorphous layer 3 is an amorphous layer containing Si. Specifically, the amorphous layer 3 containing Si may be any of amorphous Si, SiO ₂ or Si ₃ N ₄ . Such an amorphous layer 3 may be formed by sputtering, CVD or spin coating.

FIG. 2 is a flowchart showing a procedure of a manufacturing method of the composite substrate 1 according to the present embodiment.
First, an insulating substrate 2 having a diameter of φ100 to 300 mm is prepared (step S10). Subsequently, one surface of the prepared insulating substrate 2 is subjected to a hydrophilization treatment (step S11). The method of hydrophilization is optional, but may be, for example, ozone treatment, UV treatment, plasma treatment, ion beam treatment, ultrasonic cleaning, or cleaning with an acidic solution containing hydrofluoric acid or hydrochloric acid, or a plurality of methods. It is good to say. The hydrophilization treatment may be performed so that the contact angle with water on the treated surface of the insulating substrate 2 is 60 degrees or less. In the hydrophilization treatment, Si or Al is used when the treated surface of the insulating substrate 2 is analyzed by the time-of-flight secondary ion mass spectrometry (ToF-SIMS). The intensity ratio of the peak of the positive secondary ion detected as C _n H _m (n, m = 1 to 20) and the peak of the positive secondary ion of the hydrocarbon detected as C n H m (that is, Si / C _n H _m or It is preferable to carry out so that Al / C _n H _m ) is 1 or more.

Subsequently, the amorphous layer 3 is formed on the surface of the insulating substrate 2 that has been hydrophilized (step S12). The amorphous layer 3 may be formed into a film by, for example, sputtering, CVD or spin coating. Then, the formed amorphous layer 3 is polished and flattened (step S13). At this time, it is preferable to polish the amorphous layer 3 so that the surface roughness is 0.3 nm or less.

In parallel with the steps (steps S10 to S13) before bonding to the insulating substrate 2, the single crystal silicon substrate 4 to be the support substrate is prepared (step S20). The size of the single crystal silicon substrate 4 may be φ100 to 300 mm in diameter, but it is preferable that the diameter is substantially equal to that of the insulating substrate 2 prepared in step S10. Further, the single crystal silicon substrate 4 may have a thickness of about 600 μm so as to have sufficient strength when the composite substrate 1 is formed by laminating the single crystal silicon substrate 4 with the insulating substrate 2 and the amorphous layer 3.

Subsequently, plasma activation treatment is performed on the surface of the amorphous layer 3 formed in step S13 and the surface of the single crystal silicon substrate 4 prepared in step S20, respectively (step S30). Then, the surface of the amorphous layer 3 subjected to the plasma activation treatment and the surface of the single crystal silicon substrate 4 are bonded to each other (step S31). That is, the insulating substrate 2 and the single crystal silicon substrate 4 are bonded together via the amorphous layer 3. Subsequently, the insulating substrate 2 is ground and polished to a thin film (step S32) to form a composite substrate 1. In step S32, the insulating substrate 2 is thinned so that the ratio of the thickness of the insulating substrate 2 in the stacking direction to the thickness of the single crystal silicon substrate 4 in the stacking direction is 0.5 or less. Finally, the composite substrate 1 is heated at a temperature of 400 ° C to 700 ° C (step S33).

[Example 1]
As an insulating substrate, an aluminum nitride (AlN) sintered body having an outer diameter of 150 mm and a thickness of 380 μm was prepared, and one surface was plasma-activated in a nitrogen atmosphere for 60 seconds. When the contact angle of water on this treated surface was measured with a contact angle meter (dropmaster manufactured by Kyowa Interface Science Co., Ltd.), it was confirmed that the water was hydrophilized at a contact angle of 20 degrees. FIG. 3 is a photograph showing the contact angle of water before and after the hydrophilization treatment. FIG. 3A is a photograph before the hydrophilization treatment, and the contact angle is 80 degrees. On the other hand, FIG. 3B is a photograph after the hydrophilization treatment, and the contact angle is 20 degrees. A silicon oxide film (SiO ₂ ) of 1 μm was formed on this hydrophilized surface as an amorphous layer by plasma CVD, and the silicon oxide film was polished to reduce the surface roughness to 0.3 nm or less. Subsequently, a single crystal silicon substrate having an outer diameter of 150 mm and a thickness of 600 μm was prepared as a support substrate, and the silicon substrate surface and the silicon oxide film on the above-mentioned AlN sintered substrate were subjected to plasma activation treatment, respectively, and both substrates were attached. I matched it. The bonded substrate was heated at 300 ° C. for 12 hours to confirm that there was no damage, and then the AlN sintered body was ground and polished to 100 μm. After that, it was further heated at 700 ° C. for 12 hours, but no damage was observed. In this way, an AlN on silicon substrate having a heat resistance of 700 ° C. was produced.

[Example 2]
As an insulating substrate, an aluminum nitride (AlN) sintered body having an outer diameter of 150 mm and a thickness of 380 μm was prepared and infiltrated into a hydrofluoric acid aqueous solution (5 wt%, 25 ° C.) for 5 minutes. When the contact angle of water on this treated surface was measured with a contact angle meter (dropmaster manufactured by Kyowa Interface Science Co., Ltd.), it was confirmed that the water was hydrophilized at a contact angle of 20 degrees. A silicon oxide film (SiO ₂ ) of 1 μm was formed on this hydrophilized surface as an amorphous layer by plasma CVD, and the silicon oxide film was polished to reduce the surface roughness to 0.3 nm or less. Subsequently, a single crystal silicon substrate having an outer diameter of 150 mm and a thickness of 600 μm was prepared as a support substrate, and the silicon substrate surface and the silicon oxide film on the above-mentioned AlN sintered substrate were subjected to plasma activation treatment, respectively, and both substrates were attached. I matched it. The bonded substrate was heated at 300 ° C. for 12 hours to confirm that there was no damage, and then the AlN sintered body was ground and polished to 100 μm. After that, it was further heated at 700 ° C. for 12 hours, but no damage was observed. In this way, an AlN on silicon substrate having a heat resistance of 700 ° C. was produced.

[Example 3]
As an insulating substrate, an aluminum nitride (AlN) sintered body having an outer diameter of 150 mm and a thickness of 380 μm was prepared, and one surface was plasma-activated in a nitrogen atmosphere for 60 seconds. Before and after this plasma activation treatment, the AlN surface was measured by ToF-SIMS, and the intensity ratio (Al / C ₂ H ₃ ) of Al (atomic weight 27) and C ₂ H ₃ (molecular weight 27) was determined. As a result, as shown in FIG. 4, the intensity ratio before the treatment (FIG. 4 (a)) was 0.7, but after the treatment (FIG. 4 (b)) it became 13, and the treatment resulted in Al-rich. It was confirmed that it became. A silicon oxide film (SiO ₂ ) of 1 μm was formed on this hydrophilized surface as an amorphous layer by plasma CVD, and the silicon oxide film was polished to reduce the surface roughness to 0.3 nm or less. Subsequently, a single crystal silicon substrate having an outer diameter of 150 mm and a thickness of 600 μm was prepared as a support substrate, and the silicon substrate surface and the silicon oxide film on the above-mentioned AlN sintered substrate were subjected to plasma activation treatment, respectively, and both substrates were attached. I matched it. The bonded substrate was heated at 300 ° C. for 12 hours to confirm that there was no damage, and then the AlN sintered body was ground and polished to 100 μm. After that, it was further heated at 700 ° C. for 12 hours, but no damage was observed. In this way, an AlN on silicon substrate having a heat resistance of 700 ° C. was produced.

[Example 4]
As an insulating substrate, a silicon nitride (Si _{3N 4 )} sintered body having an outer diameter of 150 mm and a thickness of 400 μm was prepared, and one surface was plasma-activated in a nitrogen atmosphere for 60 seconds. When the contact angle of water on this treated surface was measured with a contact angle meter (dropmaster manufactured by Kyowa Interface Science Co., Ltd.), it was confirmed that the water was hydrophilized at a contact angle of 20 degrees. A silicon oxide film (SiO ₂ ) of 1 μm was formed on the hydrophilized surface as an amorphous layer by sputter treatment, and the silicon oxide film was polished to reduce the surface roughness to 0.3 nm or less. Subsequently, a single crystal silicon substrate having an outer diameter of 150 mm and a thickness of 600 μm was prepared as a support substrate, and the silicon substrate surface and the silicon oxide film on the above-mentioned Si _{3N 4 sintered} substrate were subjected to plasma activation treatment, respectively. The substrates were pasted together. This bonded substrate was heated at 300 ° C. for 12 hours to confirm that there was no damage, and then the Si _{3N 4 sintered} body was ground and polished to 100 μm. After that, it was further heated at 550 ° C. for 12 hours, but no damage was observed. In this way, a Si ₃ N ₄ on silicon substrate having a heat resistance of 550 ° C. was produced.

[Comparative Example 1]
As an insulating substrate, an aluminum nitride (AlN) sintered body having an outer diameter of 150 mm and a thickness of 380 μm was prepared. When the contact angle of water was measured with a contact angle meter (dropmaster manufactured by Kyowa Interface Science Co., Ltd.) without performing treatment such as plasma activation, the contact angle was 80 degrees. Moreover, when this AlN surface was measured by ToF-SIMS, the intensity ratio (Al / C ₂ H ₃ ) of Al (atomic weight 27) and C ₂ H ₃ (molecular weight 27) was 0.8. A silicon oxide film (SiO ₂ ) was formed on the surface of this substrate by 1 μm as an amorphous layer by a sbatter treatment, and the silicon oxide film was polished to reduce the surface roughness to 0.3 nm or less. Subsequently, a single crystal silicon substrate having an outer diameter of 150 mm and a thickness of 600 μm was prepared as a support substrate, and the silicon substrate surface and the silicon oxide film on the above-mentioned AlN sintered substrate were subjected to plasma activation treatment, respectively, and both substrates were attached. I matched it. When this bonded substrate was heated at 150 ° C. for 12 hours, a void of Φ30 mm was generated. This AlN sintered body was ground and polished to 100 μm, and heat treatment was attempted again. When heated at 200 ° C. for 12 hours, the bonded substrate was separated, and the silicon oxide film formed on the insulating substrate by CVD was partially transferred to the silicon substrate side.

[Comparative Example 2]
As an insulating substrate, an aluminum nitride (AlN) sintered body having an outer diameter of 150 mm and a thickness of 380 μm was prepared, and one surface was plasma-activated in a nitrogen atmosphere for 60 seconds. When the contact angle of water on this treated surface was measured with a contact angle meter (dropmaster manufactured by Kyowa Interface Science Co., Ltd.), it was confirmed that the water was hydrophilized at a contact angle of 20 degrees. A silicon oxide film (SiO ₂ ) of 1 μm was formed on this hydrophilized surface as an amorphous layer by plasma CVD, and the silicon oxide film was polished to reduce the surface roughness to 0.3 nm or less. Subsequently, a single crystal silicon substrate having an outer diameter of 150 mm and a thickness of 600 μm was prepared as a support substrate, and the silicon substrate surface and the silicon oxide film on the above-mentioned AlN sintered substrate were subjected to plasma activation treatment, respectively, and both substrates were attached. I matched it. The bonded substrate was heated at 300 ° C. for 12 hours to confirm that there was no damage, and then the AlN sintered body was ground and polished to 100 μm. After that, when it was further heated at 750 ° C. for 12 hours, it was damaged.

As described above, according to the above, it is possible to obtain a composite substrate that can withstand high temperature treatment exceeding 300 ° C.

1 Composite substrate 2 Insulating substrate 3 Amorphous layer 4 Single crystal silicon substrate

Claims (4)

A composite substrate having a diameter of 100 to 300 mm is manufactured by sequentially laminating a first layer, which is an insulating substrate containing Si or Al, a second layer, which is an amorphous layer containing Si, and a third layer, which is a single crystal silicon substrate. How to do
A step of hydrophilizing at least one surface of the first layer so that the contact angle with water is 60 degrees or less.
A step of forming the second layer on the surface subjected to the hydrophilization treatment,
The process of bonding the first layer and the third layer via the second layer,
The process of thinning the first layer and
A step of heating the composite substrate at a temperature of 400 ° C to 700 ° C is included.
The ratio of the thickness of the first layer in the stacking direction to the thickness of the third layer in the stacking direction after the thinning is 0.5 or less, and the temperature of the first layer and the third layer is 40 ° C to 400. A method for manufacturing a composite substrate, characterized in that the difference in thermal expansion coefficient at ° C. is 3 ppm or less. The manufacturing method according to claim 1, wherein the insulating substrate contains Si ₃ N ₄ or Al N. The manufacturing method according to claim 1 or 2, wherein the amorphous layer is selected from amorphous Si, SiO ₂ and Si _{3N 4 and} is formed by sputtering, CVD or spin coating. The hydrophilization treatment is characterized by one or a plurality of methods of ozone treatment, UV treatment, plasma treatment, ion beam treatment, ultrasonic cleaning, and cleaning with an acidic solution containing hydrofluoric acid or hydrochloric acid. Item 6. The manufacturing method according to any one of Items 1 to 3.

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