JP6117134B2 - Manufacturing method of composite substrate - Google Patents

Description

The present invention relates to a method for manufacturing a composite substrate having a semiconductor layer such as a single crystal silicon layer on a handle substrate, and relates to a method for manufacturing a composite substrate having substantially no SiO ₂ layer at the bonding interface between the handle substrate and the semiconductor layer. .

  SOI (Silicon On Insulator) wafers are used in applications such as power devices and high-frequency devices from the viewpoint of reducing junction capacitance, suppressing leakage current, high-frequency characteristics, and the like in semiconductor elements.

  As a typical method for manufacturing an SOI wafer, there is a SIMOX (Separation by IM plantation of Oxygen) method and a bonding method. In the SIMOX method, oxygen ions are implanted at a high concentration into a silicon wafer, which is a semiconductor, and then heat treatment is performed at a high temperature to form an oxide film serving as an insulator in the wafer, thereby obtaining an SOI wafer. On the other hand, in the bonding method, a silicon wafer that is a semiconductor and an insulator handle wafer are bonded together, and then the silicon wafer is thinned to form an SOI wafer (Patent Document 1, Non-Patent Document 1).

  As a method of thinning the silicon wafer in the bonding method, hydrogen ions or rare gas ions are implanted from the surfaces to be bonded, and the silicon wafer having an ion implantation layer inside is bonded to the handle wafer. SmartCut method that embrittles and peels the ion-implanted layer by performing heat treatment, or before bonding the silicon wafer having the ion-implanted layer inside by implanting hydrogen ions from the surface to be bonded and the handle wafer In addition, after the surface activation treatment is performed on the bonding surfaces of these wafers, the wafers are bonded together, heat-treated at a low temperature (for example, 100 to 300 ° C.) to increase the bonding strength, and then mechanically peeled off at room temperature. Thus, a method by bonding such as SiGen method for obtaining an SOI wafer is known. Such a bonding method can use another single crystal semiconductor bond wafer instead of a silicon wafer, or a handle wafer made of a material different from the material of the bond wafer. In addition, it is possible to obtain a composite substrate provided with a single crystal semiconductor thin film with good film thickness uniformity.

Japanese Patent No. 4407127

H. Takagi et al. , Appl. Phys. Lett. Vol. 68, 2222-2224 (1996)

A composite substrate obtained by using the bonding method as described above may have a buried oxide film serving as an insulator at the bonding interface between the handle wafer and the bond wafer. For example, in high-frequency device applications, insulation and dielectric loss are required to be small, so sapphire, silicon nitride, aluminum nitride, etc. are used as handle wafers, and a single crystal silicon layer is formed on the composite substrate by bonding. Has been developed, but an SiO ₂ film is provided on the bonding surface.

In recent years, due to higher power and higher integration of devices, the amount of heat generated from the device layer has increased, and heat dissipation has become a problem. In composite substrate SiO ₂ film at the bottom of the device layer is an insulator layer is present, while the SiO ₂ film has good insulating properties, thermal conductivity is as low as about 1.5 W / m · K, the device side It is difficult to dissipate the generated heat. Therefore, it is desirable to eliminate the SiO ₂ film in order to improve heat dissipation.

However, when the SiO ₂ film is thinned, voids and blisters are likely to occur at the bonding interface. Further, as a method for performing bonding without using an SiO ₂ film, there is a room temperature bonding method (Non-Patent Document 1) in which bonding is performed after activation of a bonding surface under vacuum, but in an ultrahigh vacuum atmosphere. In this case, the surface is activated and bonded together, so that the throughput is low and the productivity is sometimes low. Furthermore, the device is expensive, and the cost of the composite substrate may be high.
Thus, it has been difficult to produce a composite substrate that is low in cost and has few defects at the bonding interface without using an SiO ₂ film.

As a result of intensive studies by the inventor on the above problems, the SiO ₂ film is intentionally not provided on the bonding surface between the single crystal semiconductor substrate into which the hydrogen ions have been implanted and the handle substrate before bonding. It has been found that by performing surface activation treatment in an oxygen atmosphere and further performing bonding at a temperature of 200 ° C. or higher, generation of voids at the bonding interface is suppressed, and the number of voids is reduced. It was. Further, the bonded substrate is heat-treated at a temperature lower than that used in the case of heat peeling in the past to form a bonded body, and then mechanical energy or light energy is applied to peel off the single crystal semiconductor substrate. Thus, it has been found that a composite substrate having very few void defects at the bonding interface (bonding interface) can be produced.

That is, in one aspect of the present invention, the ion-implanted surface of a single-crystal semiconductor substrate having an ion-implanted layer formed by implanting ions from a surface having a SiO ₂ film of zero or 1 nm or less, and the single-crystal semiconductor A step of subjecting at least one of the surface of the handle substrate to be bonded to the substrate and a surface activation treatment in an oxygen atmosphere having an oxygen concentration of 80 to 100 vol%; The step of bonding the ion-implanted surface and the surface of the handle substrate at 200 to 400 ° C., the step of heat-treating the bonded substrate at 200 to 400 ° C. to obtain a bonded body, and the bonding Peeling the body along the ion implantation layer, and transferring the single crystal semiconductor thin film onto the handle substrate. It is possible to provide a method of manufacturing a composite substrate provided for the handle substrate.

According to the present invention, the number of voids at the bonding interface can be reduced without intentionally providing a SiO ₂ film on the bonding surface between the single crystal semiconductor substrate and the handle substrate. That is, since the generation of void defects can be suppressed by performing the surface activation treatment in an oxygen atmosphere, the composite substrate has a very small number of void defects at the bonding interface (bonding interface).

It is a schematic diagram which shows the one aspect | mode of the manufacturing process of the composite substrate concerning this invention. It is an ultrasonic microscope image in the bonding interface of (a) the board | substrate bonded together of Example 1, and (b) joined body. It is an ultrasonic microscope image in the bonding interface of (a) the board | substrate bonded together of the comparative example 1, and (b) conjugate | zygote. It is an ultrasonic microscope image in the bonding interface of (a) the board | substrate bonded together of the comparative example 2, and the (b) joined body. It is an ultrasonic microscope image in the bonding interface of (a) the board | substrate bonded together of the comparative example 3, and (b) conjugate | zygote. It is an ultrasonic microscope image in the bonding interface of (a) the board | substrate bonded together of the comparative example 4, and the (b) joined body. It is an ultrasonic microscope image in the bonding interface of (a) the board | substrate bonded together of the comparative example 5, and (b) joined body.

  Hereinafter, the best mode which is an example for carrying out the present invention will be described in detail, but the scope of the present invention is not limited to this mode.

The present invention, according to one embodiment, relates to a method of manufacturing a composite substrate having a single crystal semiconductor thin film on a handle substrate. That is, according to one aspect of the present invention, an ion-implanted surface of a single-crystal semiconductor substrate having an ion-implanted layer formed by implanting ions from a surface having a SiO ₂ film of zero or 1 nm or less, a single-crystal semiconductor substrate, A step of subjecting at least one of the surfaces of the handle substrate to be bonded to a surface activation treatment in an oxygen atmosphere having an oxygen concentration of 80 to 100 vol%, and an ion-implanted surface of the single crystal semiconductor substrate after the surface activation treatment And the surface of the handle substrate are bonded to each other at 200 to 400 ° C., the bonded substrate is heat-treated at 200 to 400 ° C. to obtain a bonded body, and the bonded body along the ion implantation layer. And a step of peeling and transferring the single crystal semiconductor thin film onto the handle substrate. .

Handle substrate and the single crystal semiconductor substrate of the present invention has no SiO ₂ film is deliberately surface, for example, thermal oxidation or CVD, by PVD method such as vapor deposition or sputtering, actively SiO ₂ The film is not provided. In the case of using a silicon substrate, a natural oxide film of 1 nm or less is usually formed unless treated with HF or the like. However, even if it is used as it is, the SiO ₂ film of the natural oxide film is removed by treating with HF. You can use it.

The handle substrate is not particularly limited as long as it can support a single crystal semiconductor thin film,
Examples include substrates such as silicon, silicon carbide, silicon nitride, sapphire, diamond, aluminum nitride, gallium nitride, and zinc oxide.

  Examples of the single crystal semiconductor substrate include substrates such as silicon, silicon-germanium, silicon carbide, germanium, gallium nitride, and gallium arsenide.

A single crystal semiconductor substrate has ions implanted from the surface having a SiO ₂ film of zero or 1 nm or less and has an ion implantation layer inside. The ion implantation layer has a predetermined dose of hydrogen ions (H ⁺ ) or an implantation energy that can form an ion implantation layer at a desired depth from the surface of the single crystal semiconductor substrate having a SiO ₂ film of zero or 1 nm or less. It is formed by implanting hydrogen molecular ions (H ₂ ⁺ ). As a condition at this time, for example, the implantation energy can be set to 50 to 100 keV. The dose amount of hydrogen ions (H ⁺ ) to be implanted is preferably 5.0 × 10 ¹⁶ atoms / cm ^{2 to} 2.0 × 10 ¹⁷ atoms / cm ² . If it is less than 5.0 × 10 ¹⁶ atoms / cm ² , the ion implantation layer may not be embrittled in a later step. If it exceeds 2.0 × 10 ¹⁷ atoms / cm ² , In some cases, bubbles may be formed during heat treatment, resulting in poor transfer. When hydrogen molecular ions (H ₂ ⁺ ) are used as implanted ions, the dose is preferably 2.5 × 10 ¹⁵ atoms / cm ^{2 to} 1.0 × 10 ¹⁷ atoms / cm ² . If it is less than 2.5 × 10 ¹⁵ atoms / cm ² , the ion implantation layer may not be embrittled in a later step. If it exceeds 1.0 × 10 ¹⁷ atoms / cm ² , In some cases, bubbles may be formed during heat treatment, resulting in poor transfer.

  The combination of the handle substrate and the single crystal semiconductor substrate is not particularly limited, and the substrate can be selected according to the application.

The handle substrate and the single crystal semiconductor substrate may be formed of amorphous silicon, alumina, silicon nitride, carbonized on at least one of an ion-implanted surface of the single crystal semiconductor substrate and a surface of the handle substrate to be bonded to the single crystal semiconductor substrate. A film made of silicon, aluminum nitride, or the like may be provided. These films can be formed by a CVD method such as atmospheric pressure CVD, low pressure CVD, or plasma CVD, or a PVD method such as sputtering, electron beam evaporation, or ion beam evaporation. The thickness of the film is preferably 5 nm to 10 μm. If it is thinner than 5 nm, it is difficult to obtain the effect of improving the flatness due to the application of the film. If it is thicker than 10 μm, the film itself may be cracked. The surface of the formed film may be mirror-finished with a polishing machine or the like. Unlike the SiO ₂ film, these films have thermal conductivity, so that a composite substrate having desired heat dissipation can be obtained. In addition, when these films are made of the same material as the handle substrate, for example, when a silicon nitride substrate is used as the handle substrate and silicon nitride is deposited on the surface thereof, the flatness and smoothness of the substrate surface is improved by vapor deposition (and polishing). In addition to being able to improve, silicon nitride substrates generally contain metal impurities, so that diffusion of impurities can be prevented by forming a film on the substrate surface. In this case, if low pressure CVD (LPCVD) is used, not only one surface of the substrate but also the top, bottom, and side surfaces can be deposited to form a film, thus preventing diffusion of impurities from the bottom surface and edges. obtain.

Using the above-described handle substrate and single crystal semiconductor substrate, first, surface activation is performed in an oxygen atmosphere on at least one of the ion-implanted surface of the single crystal semiconductor substrate and the handle substrate surface to be bonded to the single crystal semiconductor substrate. Apply processing. As the surface activation treatment, a plasma activation treatment, ion beam irradiation treatment, etc. UV ozone treatment and the like, plasma treatment or ion beam treatment. The surface activation treatment is performed in an oxygen atmosphere in a closed system. In the oxygen atmosphere, the substrate surface is activated, and at the same time, the amount of water physically adsorbed on the substrate surface can be kept low, so that the amount of adsorbed water trapped at the substrate interface at the time of bonding can be reduced. . The oxygen concentration in the oxygen atmosphere is 80 to 100 vol%. When the oxygen concentration is less than 100 vol%, nitrogen, argon and a mixed gas thereof may be included. If it is less than 80 vol%, the amount of moisture physically adsorbed on the substrate surface increases, and voids are likely to occur at the bonding interface due to heat treatment during bonding after bonding. The oxygen concentration can be measured, for example, by monitoring the inside of the processing chamber as well as the inside of the closed system with an oxygen concentration meter in an inlet line for supplying oxygen into the closed system by piping or the like from an oxygen supply source. it can. In addition, when the amount of moisture contained in the atmosphere is large, the amount of moisture that is physically adsorbed on the substrate surface after the surface activation treatment increases, so it is desirable to control the moisture. The moisture in the atmosphere can be adjusted, for example, by using high-purity oxygen gas or by removing moisture contained in the oxygen introduction line. By activating the bonded surface in an oxygen atmosphere and in a state where the amount of moisture contained in the atmosphere is low, the surface can be modified so that moisture is hardly physically adsorbed. This makes it possible to suppress the generation of voids at the bonding interface in the heat treatment during bonding after bonding.

  In the case of plasma treatment, for example, a single crystal semiconductor substrate and / or a handle substrate is placed in a chamber, oxygen gas is introduced as a plasma gas under reduced pressure, and then the oxygen concentration in the chamber is set to 80 to 100 vol%. Then, the surface is treated by exposing to high frequency plasma of about 50 to 500 W for 5 to 120 seconds. By this treatment, organic substances on the surface of the single crystal semiconductor substrate and / or the handle substrate are oxidized and removed, and the OH groups on the surface are increased and activated.

  In the case of processing with an ion beam, for example, a single crystal semiconductor substrate and / or a handle substrate is placed in a chamber equipped with a gas cluster ion beam, oxygen gas is introduced under reduced pressure, and then the oxygen concentration in the chamber is set to 80. It can be processed by irradiating an ion beam for 30 seconds to 30 minutes with an acceleration voltage of 10 V to 5 kV at ˜100 vol%.

  When processing with UV ozone, for example, a single crystal semiconductor substrate and / or a handle substrate is placed in the chamber, the oxygen concentration in the chamber is set to 80 to 100 vol%, and the processing is performed by irradiating UV light such as a low-pressure mercury lamp. Is possible.

  The above treatment is preferably performed on both the ion-implanted surface of the single crystal semiconductor substrate and the bonding surface of the handle substrate, but only one of them may be performed. The surface activation can be confirmed by looking at the degree of hydrophilicity (wetting). Specifically, the measurement can be performed simply by putting water on the substrate surface and measuring the contact angle.

  After the surface activation treatment, the ion-implanted surface of the single crystal semiconductor substrate is bonded to the surface of the handle substrate to be bonded to the single crystal semiconductor substrate at 200 to 400 ° C. The temperature at the time of bonding differs depending on the type and combination of the single crystal semiconductor substrate and the handle substrate, and the dose of hydrogen ions implanted into the single crystal semiconductor substrate. In any case, the temperature at which the ion implanted layer is not embrittled is preferable. Specifically, it is 200-400 degreeC. If it is lower than 200 ° C., it is difficult to suppress the generation of voids. When the temperature is higher than 400 ° C., the difference in linear expansion coefficient between the single crystal semiconductor substrate and the handle substrate increases, and one or both of the substrates are easily cracked during subsequent cooling. At the time of bonding, for example, it is preferable to bond the single crystal semiconductor substrate and the handle substrate in an oven at 200 to 400 ° C., and the time for performing the bonding is not particularly limited as long as the bonding can be performed. Second to 1 minute. A single crystal semiconductor substrate whose surface is modified by removing the physical adsorbed water adsorbed on the substrate surface before the surface activation treatment by performing the surface activation treatment in an oxygen atmosphere (oxygen concentration of 80 to 100 vol%). By bonding the handle substrate and the handle substrate at 200 to 400 ° C., the amount of moisture trapped at the bonding interface of the bonded substrates becomes extremely small, and it becomes possible to suppress the generation of voids at the bonding interface. .

  The bonded substrates as described above are further heat-treated at 200 to 400 ° C. to obtain a joined body. When the heat treatment temperature is lower than 200 ° C., the bonding strength does not increase, and when it is higher than 400, the bonded body may be damaged, which is not preferable. The heat treatment is performed in order to increase the bonding strength at the bonding interface and embrittle the hydrogen ion implanted layer. For this reason, it is preferable that the heat processing temperature is higher than the temperature at the time of bonding, for example, it is preferable that it is 20-100 degreeC higher than the temperature at the time of bonding. Further, the heat treatment temperature varies depending on the types and combinations of the single crystal semiconductor substrate and the handle substrate, and in any case, a temperature that does not reach thermal separation is preferable. The heat treatment may be performed by dividing the temperature into two or more stages. The heat treatment time is preferably 12 hours to 72 hours, although depending on the temperature to some extent.

  The bonded body obtained by the heat treatment is peeled along the ion implantation layer of the bonded body, and the single crystal semiconductor thin film is transferred onto the handle substrate. As a method for performing peeling, for example, peeling may be caused by applying mechanical impact and / or light irradiation toward the ion implantation layer. The method of performing peeling may be used alone or in combination.

  When mechanical peeling is performed by applying an impact to the ion-implanted layer, there is no possibility that thermal strain, cracks, peeling of the bonded surfaces, and the like accompanying heating occur. The mechanical peeling is preferably by cleavage from one end to the other end. As the cleavage member, a wedge-shaped member, for example, a wedge (wedge) is preferably inserted into the ion implantation layer (implantation interface), and the cleavage is progressed by the deformation by the wedge, and the separation may be performed. When using this method, care should be taken to avoid generation of scratches and particles at the contacted portion of the wedge, and generation of substrate cracking due to excessive deformation of the substrate caused by driving the wedge. In order to give an impact to the ion-implanted layer, for example, a jet of a fluid such as a gas or a liquid may be sprayed continuously or intermittently from the side surface of the bonded substrate. If there is no particular limitation.

  When the single crystal semiconductor substrate and / or the handle substrate is transparent, the ion implantation layer can be peeled off by irradiating light from the transparent substrate. In this case, the light source is preferably visible light. Since the vicinity of the ion implantation interface formed inside the single crystal semiconductor substrate is amorphized, the ion implantation layer becomes brittle and peels by a mechanism that easily absorbs visible light and easily accepts energy. It is possible. Moreover, this peeling method is preferable because it is simpler than mechanical peeling. The visible light source is preferably a Rapid Thermal Annealer (RTA), a green laser light, a flash lamp light, or the like.

  In peeling by light irradiation, prior to light irradiation, a mechanical shock is applied to the edge of the joined body and the vicinity of the bonding surface, and the heat shock due to light irradiation is bonded from the mechanical shock starting point of the edge. Destruction may occur at the ion implantation interface over the entire surface of the substrate. Alternatively, after light irradiation, mechanical impact may be applied to the interface of the ion implantation layer, and the bonded substrate may be peeled along the ion implantation interface. In this way, it is possible to obtain a composite substrate that is peeled along the ion-implanted layer of the bonded body and has a single crystal semiconductor thin film on the handle substrate.

  Although the manufacturing process of the composite substrate concerning this invention is not specifically limited, The one aspect | mode is shown in FIG. According to this, the ion implantation layer 4 is formed by implanting ions 3 from one surface of the single crystal semiconductor substrate 1 (a). A surface activation treatment by plasma 5 is performed on the bonded surface 2s of the ion-implanted surface 1s and the handle substrate 2 under an oxygen atmosphere (oxygen concentration 80 vol%) (b and c). Next, at 250 ° C., the surfaces 1s and 2s of the substrate subjected to the surface activation treatment are overlapped and bonded together (d). The bonded substrate 6 is heat treated at 300 ° C. to obtain a bonded body 7 (e). Next, a wedge-shaped jig is inserted into the ion implantation layer 4 of the bonded body 7, and the single crystal semiconductor substrate 1 b is peeled along the ion implantation layer 4, whereby the single crystal semiconductor substrate 1 a is transferred onto the handle substrate 2. The composite substrate 8 can be obtained (f).

  Hereinafter, the method for producing a composite substrate according to the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these.

<Example 1>
As the single crystal semiconductor substrate, a single crystal Si wafer having an outer diameter of 6 inches and a thickness of 625 μm was used. From the mirror surface side of the single crystal Si wafer, H ⁺ ions were implanted under the conditions of a dose amount of 7.0 × 10 ¹⁶ atoms / cm ² and an acceleration voltage of 70 keV.

  A silicon nitride substrate having the same size as the single crystal Si wafer was used as the handle substrate. On the silicon nitride substrate, SiN was vapor-deposited with a LP-CVD apparatus (manufactured by Hitachi Kokusai Electric Co., Ltd.) so as to have a thickness of 1 μm, and then polished to be mirror-finished.

Each substrate was impregnated with an SC-1 cleaning solution (NH ₄ OH + H ₂ O ₂ + H ₂ O) to perform particle removal and hydrophilic treatment. Then, in a chamber equipped with a gas cluster ion beam (manufactured by ULVAC) on an ion-implanted surface of the single crystal Si wafer and a surface of the silicon nitride substrate to be bonded to the single crystal Si wafer on which SiN is vapor-deposited in an oxygen atmosphere. The surface activation treatment was performed by ion beam irradiation. The atmosphere in the chamber was controlled by selecting the type of gas to be supplied. That is, oxygen gas was supplied into the chamber, and the oxygen concentration was set to 100 vol%.

  Next, the ion-implanted surface of the surface activated single crystal Si wafer and the surface of the silicon nitride substrate were bonded at 280 ° C. using a bonding apparatus.

  The bonded substrate was heat-treated at 300 ° C. for 10 hours to obtain a joined body. Thereafter, a mechanical impact is applied to the ion implantation layer of the single crystal Si wafer using a blade, the single crystal Si wafer is peeled along the ion implantation layer, and the single crystal Si wafer is transferred onto the silicon nitride substrate. Got.

  The presence or absence of defects at the bonding interface of the bonded substrate and the bonded body after 300 ° C. heat treatment was evaluated with an ultrasonic microscope (Fine SAT FS200II manufactured by Hitachi Construction Machinery Finetech). Ultrasonic microscope images of the bonded substrate and bonded body are shown in FIGS. 2 (a) and 2 (b). In both the bonded substrate and the bonded body, no defect was observed at the bonded interface. In addition, no defects were found in the obtained composite substrate.

<Example 2>
The single crystal Si wafer was formed on the silicon nitride substrate in the same manner as in Example 1 except that the ion-implanted surface of the surface activated single crystal Si wafer and the surface of the silicon nitride substrate were bonded together at 200 ° C. A composite substrate to which was transferred was obtained.

  The obtained composite substrate was confirmed by observation with an optical microscope that the single crystal Si wafer was transferred to the entire surface of the silicon nitride substrate. When the bonded substrate and bonded body were evaluated by an ultrasonic microscope, no defect was observed at the bonded interface in both the bonded substrate and bonded body.

<Comparative Example 1>
Example 1 except that the ion-implanted surface of the single crystal Si wafer and the surface of the silicon nitride substrate were bonded together at room temperature (25 ° C.) without being subjected to surface activation treatment and heat-treated at 150 ° C. for 10 hours. In the same manner as above, a joined body was obtained. The obtained bonded body was further heat-treated at 300 ° C. for 24 hours, and a mechanical impact was applied to the ion implantation layer of the single crystal Si wafer using a blade, and the single crystal Si wafer was peeled along the ion implantation layer. As a result, a composite substrate in which a single crystal Si wafer was transferred onto a silicon nitride substrate was obtained.

  The bonded substrate and the bonded body after heat treatment at 150 ° C. were evaluated with an ultrasonic microscope. The results are shown in FIGS. 3 (a) and (b). No defects were found on the bonded substrates, but many blister-like defects were observed on the entire bonded interface in the bonded body after the heat treatment. Moreover, many voids were seen in the obtained composite substrate.

<Comparative example 2>
Ion beam irradiation in a nitrogen atmosphere (oxygen concentration 0 vol%) containing nitrogen alone as the gas species supplied into the chamber between the surface of the single crystal Si wafer implanted with ions and the surface of the silicon nitride substrate. Then, surface activation treatment was performed, and the activated wafers were bonded to each other at room temperature and heat treated at 150 ° C. for 10 hours to obtain a joined body. The obtained bonded body was further heat-treated at 300 ° C. for 24 hours, and a mechanical impact was applied to the ion implantation layer of the single crystal Si wafer using a blade, and the single crystal Si wafer was moved along the ion implantation layer. The composite substrate which peeled and transferred the single crystal Si wafer on the silicon nitride substrate was obtained.

  The bonded substrate and the bonded body after heat treatment at 150 ° C. were evaluated with an ultrasonic microscope. The results are shown in FIGS. 4 (a) and (b). No defects were found on the bonded substrates, but many defects were observed on the entire bonded interface in the bonded body after the heat treatment. Moreover, many voids were seen in the obtained composite substrate.

<Comparative Example 3>
The ion beam of the surface of the single crystal Si wafer and the surface of the silicon nitride substrate that is supplied into the chamber is only nitrogen, and the ion beam is substantially contained in an oxygen-free nitrogen atmosphere (oxygen concentration 0 vol%). After irradiating and performing surface activation treatment, a bonded body was obtained in the same manner as in Example 1 except that bonding was performed at 100 ° C. and heat treatment was performed at 150 ° C. for 10 hours. The obtained bonded body was further heat-treated at 300 ° C. for 24 hours, and a mechanical impact was applied to the ion implantation layer of the single crystal Si wafer using a blade, and the single crystal Si wafer was moved along the ion implantation layer. The composite substrate which peeled and transferred the single crystal Si wafer on the silicon nitride substrate was obtained.

  The bonded substrate and the bonded body by heat treatment at 150 ° C. were evaluated with an ultrasonic microscope. The results are shown in FIGS. 5 (a) and (b). Although no defect was found in the bonded substrate, two void defects having a diameter of 2.0 cm were observed at the bonded interface in the bonded body after the heat treatment. Further, in the obtained composite substrate, a void having a diameter of 2.0 cm was observed at the same position as the void defect observed in the bonded body after the heat treatment.

<Comparative example 4>
In an oxygen atmosphere (oxygen concentration 70 vol%), the gas species supplied into the chamber between the ion-implanted surface of the single-crystal Si wafer and the surface of the silicon nitride substrate is oxygen and nitrogen, and the oxygen / nitrogen flow ratio is 70:30. ), Ion beam irradiation was performed, surface activation treatment was performed, bonding was performed at 200 ° C., and heat treatment was performed at 250 ° C. for 10 hours to obtain a joined body. The obtained bonded body was further heat-treated at 300 ° C. for 24 hours, and a mechanical impact was applied to the ion implantation layer of the single crystal Si wafer using a blade, and the single crystal Si wafer was moved along the ion implantation layer. The composite substrate which peeled and transferred the single crystal Si wafer on the silicon nitride substrate was obtained.

  The bonded substrate and the bonded body at 250 ° C. heat treatment were evaluated with an ultrasonic microscope. The results are shown in FIGS. 6 (a) and (b). Although no defect was found on the bonded substrate, one void defect having a diameter of 2.5 cm was observed at the bonding interface in the bonded body after the heat treatment. Further, in the obtained composite substrate, a void having a diameter of 2.5 cm was observed at the same position as a void defect observed in the bonded body after the heat treatment.

<Comparative Example 5>
Except that the ion-implanted surface of the surface activated single crystal Si wafer and the surface of the silicon nitride substrate were bonded together at 100 ° C. and heat-treated at 250 ° C. for 10 hours. A joined body was obtained. The obtained bonded body is further heat-treated at 300 ° C., mechanical impact is applied to the ion implantation layer of the single crystal Si wafer using a blade, the single crystal Si wafer is peeled along the ion implantation layer, and nitriding is performed. A composite substrate in which a single crystal Si wafer was transferred onto a silicon substrate was obtained.

  The bonded substrate and the bonded body at 250 ° C. heat treatment were evaluated with an ultrasonic microscope. The results are shown in FIGS. 7 (a) and (b). Although no defect was found on the bonded substrate, four void defects having a diameter of 1 to 3 mm were observed at the bonding interface in the bonded body after the heat treatment. Further, in the obtained composite substrate, voids having a diameter of 1 to 3 mm were observed at the same positions as the void defects observed in the bonded body after the heat treatment.

The results are shown in Table 1. If the SiO ₂ film was not intentionally formed on the bonding surface, a large number of voids were generated at a considerably low temperature as shown in Comparative Example 1, and defects remained in the peeled Si layer. In order to eliminate defects in the transferred Si layer, it is necessary to suppress the generation of voids up to a temperature at which the Si layer can be peeled off. Further, when the surface activation treatment was performed in the presence of N ₂ (oxygen concentration 70 vol% or less), voids were generated. On the other hand, the surface activation treatment atmosphere is O ₂ (oxygen concentration 80 to 100 vol%), and the temperature at the time of bonding can be increased to reduce the size and number of voids. By doing so, it was possible to make the void zero. That is, according to the present invention, it was possible to obtain a composite substrate excellent in heat dissipation without intentionally forming a SiO ₂ film at the bonding interface.

DESCRIPTION OF SYMBOLS 1 Single crystal semiconductor substrate 1s Surface activated surface 1a of single crystal semiconductor substrate Single crystal semiconductor thin film 1b Stripped single crystal semiconductor substrate 2 Handle substrate 2s Surface activated surface of handle substrate 3 Ion 4 Ion implantation layer 5 Plasma 6 Bonded substrate 7 Bonded body 8 Composite substrate

Claims (6)

The ion-implanted surface of a single crystal semiconductor substrate having an ion-implanted layer by implanting ions from a surface having a zero or 1 nm or less SiO ₂ film and the surface of a handle substrate to be bonded to the single crystal semiconductor substrate At least one of the steps is to perform surface activation treatment in an oxygen atmosphere having an oxygen concentration of 80 to 100 vol% and when the oxygen concentration is less than 100 vol%, in an oxygen atmosphere containing nitrogen, argon, or a mixed gas thereof. When,
Bonding the ion-implanted surface of the single crystal semiconductor substrate and the surface of the handle substrate after the surface activation treatment at 200 to 400 ° C .;
Heat-treating the bonded substrates at 200 to 400 ° C. to obtain a joined body;
A method of manufacturing a composite substrate including a single crystal semiconductor thin film on a handle substrate, comprising at least a step of peeling the bonded body along the ion implantation layer and transferring the single crystal semiconductor thin film onto the handle substrate. Before the step of performing the surface activation treatment, at least one of the ion-implanted surface of the single crystal semiconductor substrate and the surface of the handle substrate to be bonded to the single crystal semiconductor substrate, amorphous silicon, alumina, silicon nitride, silicon carbide, and further comprising the step of forming a layer selected from aluminum nitride, a manufacturing method of a composite substrate according to claim 1.   The method for manufacturing a composite substrate according to claim 1, wherein the surface activation treatment is a plasma treatment or an ion beam treatment.   4. The method according to claim 1, wherein in the step of transferring the single crystal semiconductor thin film onto the handle substrate, the peeling is caused by mechanical impact and / or light irradiation toward the ion implantation layer. The manufacturing method of the composite substrate of description.   The method for manufacturing a composite substrate according to claim 1, wherein the single crystal semiconductor substrate is selected from silicon, silicon-germanium, silicon carbide, germanium, gallium nitride, and gallium arsenide.   The method for manufacturing a composite substrate according to claim 1, wherein the handle substrate is selected from silicon, silicon carbide, silicon nitride, sapphire, diamond, aluminum nitride, gallium nitride, and zinc oxide.