TW202336831A - Nitride semiconductor substrate and manufacturing method therefor - Google Patents

Abstract

The present invention is a nitride semiconductor substrate comprising: a growth substrate in which a single crystal silicon layer is formed on a composite substrate obtained by laminating a plurality of layers; and a nitride semiconductor thin film formed on the single crystal silicon layer of the growth substrate, the nitride semiconductor substrate being characterized in that the carbon concentration of the single crystal silicon layer is 5E17 atoms/cm3 to 1E22 atoms/cm3. Consequently, provided are: a nitride semiconductor substrate in which the resistivity becomes low by diffusing Al in a single crystal silicon layer during the growth of a nitride semiconductor, and deterioration in high frequency characteristics is suppressed; and a manufacturing method therefor.

Description

Nitride semiconductor substrate and manufacturing method thereof

The present invention relates to a nitride semiconductor substrate and a manufacturing method thereof.

The MOCVD method, one of the semiconductor thin film manufacturing methods, is widely used because it is excellent in large-diameter and mass-produced and can form uniform thin film crystals. In addition, nitride semiconductors represented by GaN are expected to be next-generation semiconductor materials that can break through the limits of Si (silicon) as a material.

Because GaN has characteristics such as a high saturation electron velocity, it is possible to create a device that can operate at high frequencies. In addition, because the insulation breakdown electric field is large, it can be operated at high output. In addition, weight reduction, miniaturization, and low power consumption are also expected. In recent years, due to the increase in communication speed represented by 5G and others, and the accompanying demand for higher output, GaN HEMTs that can operate at high frequencies and at high output have attracted attention.

As a substrate for GaN epitaxial wafers used to manufacture GaN devices, Si substrates are the cheapest and are advantageous in increasing the diameter. In addition, SiC substrates are also used due to their high thermal conductivity and good heat dissipation characteristics. However, the thermal expansion coefficients of these substrates and GaN are different, so stress is applied during the cooling step after epitaxial film formation, and cracks are prone to occur. In addition, by applying strong stress, wafer cracks sometimes occur during device manufacturing. In addition, it is impossible to form a thick GaN film, so even if a complex stress relaxation layer is formed in the epitaxial layer, the limit will be reached at about 5 μm without cracks.

On the other hand, because the GaN substrate has the same (or very similar) thermal expansion coefficient as the GaN epitaxial layer, the above-mentioned problems are less likely to occur. However, the production of a self-supporting GaN substrate is not only difficult, but also extremely expensive and cannot be produced with a large aperture. substrate, so it is not suitable for mass production.

Therefore, Patent Document 1 discloses a large-diameter substrate for GaN epitaxial crystals (hereinafter, GaN support substrate), which has a large diameter and has a thermal expansion coefficient close to that of GaN. The GaN support substrate is composed of a support structure, a planarization layer laminated on one side of the support structure, and a single crystal silicon layer laminated on the planarization layer. The support structure includes a polycrystalline ceramic core, a third An adhesive layer, a conductive layer, a second adhesive layer and a barrier layer.

By using this growth support substrate, it is possible to produce a nitride semiconductor substrate having a large diameter, a thick epitaxial layer, and no cracks. In addition, since the difference in thermal expansion coefficient between GaN and GaN is extremely small, it is less likely to warp when GaN is grown or cooled. Therefore, warpage of the substrate after film formation can be controlled to be small, and there is no need to install an epitaxial layer in the epitaxial layer. The complex stress relaxation layer shortens the epitaxial film formation time and can significantly reduce the cost of epitaxial growth. Furthermore, most of the growth support substrates are made of ceramics, so the substrate itself is very hard and not only difficult to undergo plastic deformation, but also does not cause wafer cracks that cannot be solved with large-diameter GaN on Si. [Prior technical literature] (patent document)

Patent Document 1: Japanese Special List 2020-505767.

[Problem to be solved by the invention] GaN on Si devices for high-frequency applications use single-crystal silicon substrates with high resistance. However, during the film formation process of AlN, AlGaN, GaN, etc. on a single crystal silicon substrate, Al and Ga will diffuse in the single crystal silicon substrate, causing an interface between the surface layer of the single crystal silicon substrate (and the nitride semiconductor epitaxial layer). Nearby), the resistance becomes low, and there is a problem of deterioration of high-frequency characteristics.

The surface layer of the GaN supporting substrate is also a single crystal silicon layer. Therefore, when used for high-frequency applications, during the growth of AlN, AlGaN, GaN, etc., Al and Ga will diffuse in the single crystal silicon layer, and the same high-frequency will occur. frequency loss problem.

The present invention is made to solve the above problems, and aims to provide a nitride semiconductor substrate in which Al diffuses in the single crystal silicon layer during the growth of the nitride semiconductor to reduce the resistance and a manufacturing method thereof. This suppresses the deterioration of high-frequency characteristics. [Technical means to solve problems]

In order to solve the above problems, the present invention provides a nitride semiconductor substrate including: a growth substrate in which a single crystal silicon layer is formed on a composite substrate in which a plurality of layers are laminated; and the aforementioned growth substrate formed into a film. A nitride semiconductor thin film on a single crystal silicon layer; the carbon concentration of the single crystal silicon layer is 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less.

As long as the carbon concentration of the single crystal silicon layer is 5E17 atoms/cm ³ or more, the diffusion of Al and Ga into the single crystal silicon layer can be suppressed, and the resistance of the single crystal silicon layer can be suppressed from becoming low. In addition, as long as the carbon concentration of the single crystal silicon layer is 1E22 atoms/cm ³ or less, deterioration of crystallinity can be prevented, and therefore a substrate with good crystallinity can be produced. As a result, a nitride semiconductor substrate with excellent high-frequency characteristics can be provided.

In addition, it is preferable that the nitride semiconductor thin film contains one or more types of GaN, AIN, and AlGaN.

Such a nitride semiconductor thin film can reliably provide a nitride semiconductor substrate with excellent high-frequency characteristics.

Furthermore, it is preferable that the single crystal silicon layer has a thickness of 100 to 500 nm, and the total film thickness of the nitride semiconductor thin film is 2 μm or more and 10 μm or less.

In the present invention, the single crystal silicon layer and the nitride semiconductor thin film can be made to have such thickness.

In addition, preferably, the composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a second adhesive layer laminated on the entire first adhesive layer. the barrier layer of the second adhesive layer, and The single crystal silicon layer is formed on a planarization layer, and the planarization layer is laminated on only one side of the composite substrate.

With such a structure, most of the growth substrate is made of ceramic, so the substrate itself is very hard and is not prone to plastic deformation or wafer cracking that cannot be solved with a silicon substrate.

In addition, the composite substrate may have a conductive layer laminated on the entire first adhesive layer between the first adhesive layer and the second adhesive layer.

Conductivity can be imparted to the composite substrate as needed.

Furthermore, it is preferable that the composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, a barrier layer laminated on the entire first adhesive layer, and a barrier layer laminated on the entire first adhesive layer. a second adhesive layer on the back side of the barrier layer and a conductive layer laminated on the back side of the second adhesive layer, and The single crystal silicon layer is formed on a planarization layer, and the planarization layer is laminated on the front surface of the barrier layer of the composite substrate.

A nitride semiconductor substrate using such a growth substrate can have excellent high-frequency characteristics without generating a leakage path due to the front-side conductive layer of the growth substrate.

Furthermore, it is preferable that the composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, a conductive layer laminated on the back surface of the first adhesive layer, and a conductive layer laminated on the back surface of the first adhesive layer. The second adhesive layer and barrier layer on the back side of the conductive layer, the barrier layer is laminated on the front and side surfaces of the aforementioned first adhesive layer, the side surfaces of the aforementioned conductive layer, and the side surfaces and back surface of the aforementioned second adhesive layer, and The single crystal silicon layer is formed on a planarization layer, and the planarization layer is laminated on the front surface of the barrier layer of the composite substrate.

A nitride semiconductor substrate using such a growth substrate can have excellent high-frequency characteristics without generating a leakage path due to the front-side conductive layer of the growth substrate.

At this time, it is preferable that the conductive layer includes a polycrystalline silicon layer.

The conductive layer can be formed into such a layer.

At this time, it is preferable that the polycrystalline ceramic core contains aluminum nitride.

With such a composite substrate, the difference in thermal expansion coefficient with the nitride semiconductor can be minimized.

In addition, preferably, the first adhesive layer and the second adhesive layer include a tetraethyl orthosilicate (TEOS) layer or a silicon oxide (SiO ₂ ) layer, and the barrier layer includes silicon nitride.

The thickness of the first adhesive layer, the second adhesive layer, and the barrier layer can be such a layer.

Furthermore, it is preferable that the planarization layer contains tetraethylsiloxane (TEOS) or silicon oxide (SiO ₂ ) and has a thickness of 500 to 3000 nm.

The planarization layer can be such a layer.

In addition, the present invention provides a method for manufacturing a nitride semiconductor substrate, which includes a growth substrate and a nitride semiconductor thin film formed on the growth substrate. The manufacturing method includes the following steps: Step ( 1), forming a single crystal silicon layer with a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less on a composite substrate in which a plurality of layers are laminated, to produce a substrate for growth; and, step (2) In this method, the nitride semiconductor thin film is epitaxially grown on the single crystal silicon layer of the growth substrate to produce a nitride semiconductor substrate.

As long as the manufacturing method of a nitride semiconductor substrate using a growth substrate with a carbon concentration of a single crystal silicon layer of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less is performed in this way, high-frequency production can be easily produced. Nitride semiconductor substrate with excellent characteristics.

In addition, it is preferable that the aforementioned step (1) includes the following steps: Step (1-1), which prepares a composite substrate as the aforementioned composite substrate. The composite substrate includes a polycrystalline ceramic core laminated throughout the The first adhesive layer of the polycrystalline ceramic core, the second adhesive layer laminated on the entire first adhesive layer, and the barrier layer laminated on the entire second adhesive layer; Step (1-2), which is described above The planarization layer is laminated on only one side of the composite substrate; and, step (1-3), which forms the single crystal silicon layer by bonding a donor substrate with a single crystal silicon layer to the planarization layer. , the single crystal silicon layer has a thickness of 100 to 500 nm and is doped with carbon at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ^{3 or} less.

With this configuration, most of the growth substrate is made of ceramic, so the substrate itself is very hard and is not easily plastically deformed. It is also possible to reliably produce a nitride semiconductor substrate that does not produce crystallization problems that cannot be solved with silicon substrates. The circle breaks.

In this case, in the step (1-1), the composite substrate can be made to have a conductive layer laminated on the entire first adhesive layer between the first adhesive layer and the second adhesive layer.

Conductivity can be imparted to the composite substrate as needed.

In addition, it is preferable that the aforementioned step (1) includes the following steps: Step (1-1), which prepares a composite substrate as the aforementioned composite substrate. The composite substrate includes a polycrystalline ceramic core laminated throughout the A first adhesive layer of the polycrystalline ceramic core, a barrier layer laminated on the entire first adhesive layer, a second adhesive layer laminated on the back side of the barrier layer, and a second adhesive layer laminated on the back side of the second adhesive layer a conductive layer; step (1-2), which laminates a planarization layer on the front surface of the barrier layer of the composite substrate; and step (1-3), which involves laminating a layer with a single crystal silicon layer The substrate is bonded to the planarization layer to form the single crystal silicon layer, which has a thickness of 100 to 500 nm and is carbon doped at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less. Mixed up.

With this method of manufacturing a nitride semiconductor substrate, a nitride semiconductor substrate having excellent high-frequency characteristics can be manufactured without generating a leakage path due to the front-side conductive layer of the composite substrate.

In addition, it is preferable that the aforementioned step (1) includes the following steps: Step (1-1), which prepares a composite substrate as the aforementioned composite substrate. The composite substrate includes a polycrystalline ceramic core laminated throughout the The first adhesive layer of the polycrystalline ceramic core, the conductive layer laminated on the back side of the first adhesive layer, the second adhesive layer laminated on the back side of the conductive layer and the barrier layer, the barrier layer is laminated on The front and side surfaces of the first adhesive layer, the side surfaces of the conductive layer, and the side and back surfaces of the second adhesive layer; Step (1-2), which is to perform a planarization layer on the front surface of the barrier layer of the composite substrate Lamination; and, step (1-3), which forms the aforementioned single crystal silicon layer by bonding a substrate having a single crystal silicon layer to the aforementioned planarization layer, and the single crystal silicon layer has a wavelength of 100 to 500 nm. thickness and carbon doping at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less.

With this method of manufacturing a nitride semiconductor substrate, a nitride semiconductor substrate having excellent high-frequency characteristics can be manufactured without generating a leakage path due to the front-side conductive layer of the composite substrate.

In addition, it is preferable that the aforementioned step (1-3) includes the following steps: Step (1-3-1), which uses a CVD method to form a film of the aforementioned carbon-doped single crystal silicon film on On a single crystal silicon substrate, the aforementioned application substrate is produced; step (1-3-2), which involves laminating the aforementioned carbon-doped single crystal silicon film of the aforementioned application substrate to the aforementioned planarization layer; and, steps (1-3-3), which removes the single crystal silicon substrate of the applied substrate and further processes the carbon-doped single crystal silicon thin film of the applied substrate to a desired thickness, A single crystal silicon layer having a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less is formed.

By such an operation, not only can a substrate having a single crystal silicon thin film with a high carbon concentration be produced relatively simply and reliably, but also a single crystal silicon layer of a desired thickness can be easily formed on the planarization layer. [Effects of the invention]

As described above, according to the present invention, it is possible to provide a nitride semiconductor substrate and a manufacturing method thereof. In the nitride semiconductor substrate, during the growth of the nitride semiconductor, Al and Ga diffuse in the single crystal silicon layer to reduce the resistance. This suppresses the deterioration of high-frequency characteristics.

As mentioned above, during the process of forming a nitride semiconductor film on a single crystal silicon layer, Al and Ga will diffuse in the single crystal silicon layer, causing the surface layer of the single crystal silicon layer (near the interface with the GaN epitaxial layer) to become The resistance has to be lowered, which leads to the problem of deterioration of high-frequency characteristics.

The inventors have devoted themselves to research on methods to suppress the diffusion of Al and Ga in the single crystal silicon layer during the growth of GaN, resulting in low resistivity and deterioration of high frequency characteristics, and found that by setting the carbon concentration of the single crystal silicon layer to 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less can suppress the diffusion of Al and Ga into the single crystal silicon layer, and can suppress the single crystal silicon layer from becoming low-resistance, thereby achieving both a substrate with good crystallinity and a By using the diffusion barrier of carbon, a nitride semiconductor substrate with good high-frequency characteristics can be produced, and the present invention is completed.

That is, the present invention is a nitride semiconductor substrate including a growth substrate in which a single crystal silicon layer is formed on a composite substrate in which a plurality of layers are laminated, and the single crystal film formed on the growth substrate. Nitride semiconductor thin film on the silicon layer; The carbon concentration of the single crystal silicon layer is 5E17atoms/cm ³ or more and 1E22atoms/cm ³ or less.

In addition, the present invention is a method for manufacturing a nitride semiconductor substrate, which includes a growth substrate and a nitride semiconductor thin film formed on the growth substrate. The manufacturing method includes the following steps: Step ( 1), forming a single crystal silicon layer with a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less on a composite substrate in which a plurality of layers are laminated, to produce a substrate for growth; and, step (2) In this method, the nitride semiconductor thin film is epitaxially grown on the single crystal silicon layer of the growth substrate to produce a nitride semiconductor substrate.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[Nitride Semiconductor Substrate] The nitride semiconductor substrate of the present invention, for example, the nitride semiconductor substrate 300 shown in FIG. 1, has a single crystal silicon layer 7 formed on a composite substrate 200 in which a plurality of layers are laminated. The growth substrate 100, and the nitride semiconductor thin film 8 formed on the single crystal silicon layer 7 of the growth substrate 100, and the carbon concentration of the single crystal silicon layer 7 is 5E17atoms/ ^cm3 or more and 1E22atoms/ cm ³ or less.

As long as the carbon concentration of the single crystal silicon layer 7 is 5E17 atoms/cm ³ or more, the diffusion of Al and Ga into the single crystal silicon layer 7 can be suppressed, and the resistance of the single crystal silicon layer 7 can be suppressed from becoming low. In addition, as long as the carbon concentration of the single crystal silicon layer 7 is 1E22 atoms/cm ³ or less, deterioration of the crystallinity can be prevented, and therefore a substrate with good crystallinity can be produced. As a result, a nitride semiconductor substrate with excellent high-frequency characteristics can be provided.

In addition, from the viewpoint of obtaining more excellent second harmonic characteristics, the carbon concentration of the single crystal silicon layer 7 is preferably 1E18 atoms/cm ³ or more.

Growth substrate As shown in FIG. 1 , the growth substrate 100 can be composed of, for example, a composite substrate 200 (support structure), a planarization layer 6 laminated on only one side of the composite substrate 200 , and the above-described planarization layer 6 laminated on the planarization layer 6 . Composed of a carbon-concentrated single crystal silicon layer 7 (substantial single crystal silicon layer), the composite substrate includes a polycrystalline ceramic core 1, a first adhesive layer 2 laminated on the entire polycrystalline ceramic core 1, and a first adhesive layer 2 laminated on the entire polycrystalline ceramic core 1. The entire conductive layer 3 of the first adhesive layer 2 , the second adhesive layer 4 laminated on the entire conductive layer 3 , and the barrier layer 5 laminated on the entire second adhesive layer 4 . Furthermore, the above-mentioned conductive layer 3 and the first adhesive layer 2 can be formed as needed, but do not necessarily exist, or sometimes they are only formed on one side.

Here, the polycrystalline ceramic core 1 contains aluminum nitride and is calcined using a calcining aid at a high temperature of, for example, 1800° C. to have a thickness of approximately 600 to 1150 μm. Basically, most of them are formed with the thickness of the SEMI standard of the Si substrate.

The first adhesive layer 2 and the second adhesive layer 4 include a tetraethylsiloxane (TEOS) layer or a silicon oxide (SiO ₂ ) layer, or a layer including both, and are formed by a LPCVD process or a CVD process. Stacked and have a thickness of approximately 50 to 200 nm.

The conductive layer 3 includes polycrystalline silicon and is deposited by a LPCVD process or the like and has a thickness of approximately 150 to 500 nm. The conductive layer is a layer for imparting conductivity, and may be doped with boron (B), phosphorus (P), or the like, for example. The conductive layer 3 containing polycrystalline silicon may be provided as needed, or may not be provided, or may be formed on only one side.

In addition, the barrier layer 5 includes a silicon nitride layer and is deposited by a LPCVD process or the like, and has a thickness of, for example, 100-1000 nm.

The planarization layer 6 is deposited by a LPCVD process or the like, and has a thickness of about 500 to 3000 nm. The planarization layer 6 is deposited for the purpose of planarizing the upper surface, and preferably contains tetraethylsiloxane (TEOS) or silicon oxide (SiO ₂ ), but may be SiO ₂ , Al ₂ O ₃ , Si General ceramic membrane materials such as ₃ N ₄ or silicon oxynitride ( _Six O _y N _z ).

The single crystal silicon layer 7 has a thickness of, for example, about 100 to 500 nm and is used as a growth surface for growing other epitaxial crystals such as GaN. It can be bonded to the planarization layer 6 using a layer transfer process or the like. As mentioned above, the single crystal silicon layer 7 is doped with a specific concentration of carbon.

Furthermore, the thickness, manufacturing method, and materials used of each layer are not limited to the thickness, manufacturing method, and materials used, and all layers do not need to be present.

In addition, as another example of the growth substrate, for example, as shown in FIG. 4 , a composite substrate, a planarization layer 6 bonded only to the front surface of the composite substrate, and a single crystal silicon layer 7 bonded to the planarization layer can be used. The composite substrate includes: a polycrystalline ceramic core 1, a first adhesive layer 2 laminated on the entire polycrystalline ceramic core, a barrier layer 5 laminated on the entire first adhesive layer, and a barrier layer 5 laminated on the entire first adhesive layer. The second adhesive layer 4 on the back side of the barrier layer and the conductive layer 3 laminated on the back side of the second adhesive layer.

As long as a nitride semiconductor substrate is used as a growth substrate in which the conductive layer 3 is formed only on the back side, when a high-frequency device is manufactured, leakage due to the front side conductive layer of the growth substrate will not occur. path, and can produce one with excellent high-frequency characteristics.

In addition, as yet another example of the growth substrate, for example, as shown in FIG. 5 , a composite substrate, a planarization layer 6 bonded only to the front surface of the composite substrate, and a single crystal silicon layer bonded to the planarization layer can be used. 7, the composite substrate includes: a polycrystalline ceramic core 1, a first adhesive layer 2 laminated on the entire polycrystalline ceramic core, a conductive layer 3 laminated on the back of the first adhesive layer, The second adhesive layer 4 and the barrier layer 5 on the back side of the conductive layer. The barrier layer 5 is laminated on the front and side surfaces of the first adhesive layer, the side surfaces of the conductive layer, and the side and back surfaces of the second adhesive layer.

As long as a nitride semiconductor substrate is used as a growth substrate in which the conductive layer 3 is formed only on the back side, when a high-frequency device is manufactured, leakage due to the front side conductive layer of the growth substrate will not occur. path, and can produce one with excellent high-frequency characteristics.

Nitride semiconductor thin film The nitride semiconductor thin film 8 formed on the single crystal silicon layer 7 of the growth substrate 100 is not particularly limited, and may include, for example, one or more types of GaN, AlN, and AlGaN.

That is, the nitride semiconductor thin film can be an epitaxial growth layer of AlN, AlGaN, GaN, etc., but the structure of the epitaxial layer is not limited to this, and includes a case where AlGaN is not formed, and a case where AlN is further formed after the AlGaN film is formed. condition. In addition, it also includes the case where a plurality of layers of AlGaN are formed to change the Al composition.

A device layer can be provided on the surface side of the epitaxial layer. The device layer can have a structure provided with the following layers: a layer (channel layer) that generates two-dimensional electron gas and has high crystallinity, a layer that generates two-dimensional electron gas (barrier layer), and a cap layer at the outermost layer (top layer). The channel layer can be a GaN layer, for example, but is not limited thereto. The barrier layer can use AlGaN with an Al composition of about 20%. However, for example, InGaN can also be used, and is not limited thereto. The Cap layer can be a GaN layer or a SiN layer, for example, and is not limited thereto. In addition, the thickness of the device layers and the Al composition of the barrier layer can be changed according to the design of the device.

The film thickness of the nitride semiconductor thin film can be changed depending on the application, but is not particularly limited. Preferably, the total film thickness of the nitride semiconductor thin film is 2 μm or more and 10 μm or less.

[Method for manufacturing nitride semiconductor substrate] The above-mentioned nitride semiconductor substrate of the present invention can be manufactured according to the following operations. Hereinafter, the method for manufacturing the nitride semiconductor substrate of the present invention will be described.

<Step (1)> Step (1) is to form a single crystal silicon layer with a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less on a composite substrate in which a plurality of layers are laminated to produce a substrate for growth. steps. Examples of implementation aspects of step (1) include the following first, second, and third aspects.

first form The first aspect of step (1) can be a step including the following steps (1-1) to (1-3).

Steps (1-1) Step (1-1) is a step of preparing a composite substrate as a composite substrate. The composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, and a first adhesive layer laminated on the entire polycrystalline ceramic core. a second adhesive layer and a barrier layer laminated throughout the second adhesive layer. The composite substrate prepared here may be the above-mentioned composite substrate.

Steps (1-2) Step (1-2) is a step of laminating a planarizing layer on only one side of the composite substrate. The planarization layer only needs to be laminated using the above-mentioned materials and methods.

Step (1-3) Step (1-3) is a step of forming a single crystal silicon layer by bonding a substrate having a single crystal silicon layer to a planarization layer. The single crystal silicon layer has a thickness of 100 to 500 nm thickness and carbon doping at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less. Step (1-3) can include the following steps (1-3-1) to (1-3-3).

Steps (1-3-1) Step (1-3-1) is a step of forming a single crystal silicon thin film doped with carbon on a single crystal silicon substrate by a CVD method to produce a substrate. More specifically, the donor substrate can be produced as follows.

A single crystal silicon substrate is prepared, and a single crystal silicon thin film (layer) with a high carbon concentration is formed on the single crystal silicon substrate using a CVD film forming device. As the raw material gas used for film formation, monomethylsilane and trimethylsilane are used as carbon sources. Dichlorosilane and monosilane are used as silicon sources. The raw material gas is not limited to this. The film forming temperature can be, for example, 600 to 1200°C, but is not limited thereto. The carbon concentration for doping the silicon layer can be adjusted by the flow rate of the raw material gas and the film-forming temperature.

The thickness of the single crystal silicon thin film to be formed can be controlled by the film formation time, etc., and is not limited to a thicker one. However, it must be at least the single crystal silicon layer bonded to the outermost surface layer of the growth substrate. thickness.

Furthermore, the donor substrate produced in this step may be undoped, n-type, or p-type, but is preferably an n-type single crystal silicon substrate.

Steps (1-3-2) Step (1-3-2) is a step of bonding the carbon-doped single crystal silicon film applied to the substrate to the planarization layer.

The substrate used here as the application substrate is a single crystal silicon substrate with a single crystal silicon thin film formed on the surface produced in the above step (1-3-1), and the single crystal silicon thin film with a high carbon concentration is combined with the single crystal silicon thin film. The lamination is performed by connecting the planarized layers on the composite substrate.

Step (1-3-3) Step (1-3-3) is to remove the single crystal silicon substrate applied to the substrate, and further to make the carbon-doped single crystal silicon thin film applied to the substrate a desired thickness. A step of processing in a manner to form a single crystal silicon layer with a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less.

In this step, after the applied substrate and the planarization layer are bonded, a single crystal silicon film with a target thickness and doped with carbon is left. The single crystal silicon substrate and the unnecessary single crystal silicon film are peeled off and polished. The surface of the remaining single crystal silicon film is left to improve flatness. For peeling, a conventional technique such as a hydrogen ion implantation peeling method may be used. In this step, the thickness of the high carbon concentration single crystal silicon layer formed on the surface layer of the growth substrate on the planarization layer is preferably 100 to 500 nm. The film-forming substrate can be produced by performing the above operations.

second form The second aspect of step (1) can be a step including the following steps (1-1) to (1-3).

Steps (1-1) Step (1-1) is a step of preparing a composite substrate as a composite substrate. The composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, and a first adhesive layer laminated on the entire polycrystalline ceramic core. A barrier layer, a second adhesive layer laminated on the back side of the barrier layer, and a conductive layer laminated on the back side of the second adhesive layer. The composite substrate prepared here may be the above-mentioned composite substrate.

Steps (1-2) Step (1-2) is a step of laminating a planarization layer on the front surface of the barrier layer of the composite substrate. The planarization layer only needs to be laminated using the above-mentioned materials and methods.

Step (1-3) Step (1-3) is a step of forming a single crystal silicon layer by bonding a substrate having a single crystal silicon layer to a planarization layer. The single crystal silicon layer has a thickness of 100 to 500 nm thickness and carbon doping at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less. Step (1-3) can be performed in the same manner as in the first aspect.

third aspect The third aspect of step (1) can be a step including the following steps (1-1) to (1-3).

Steps (1-1) Step (1-1) is a step of preparing a composite substrate as a composite substrate. The composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, and a first adhesive layer laminated on the first adhesive layer. The conductive layer on the back side, the second adhesive layer and the barrier layer laminated on the back side of the conductive layer. The barrier layer is laminated on the front and side surfaces of the first adhesive layer, the side surfaces of the conductive layer and the second adhesive layer. sides and back of the layer. The composite substrate prepared here may be the above-mentioned composite substrate.

Steps (1-2) Step (1-2) is a step of laminating a planarization layer on the front surface of the barrier layer of the composite substrate. The planarization layer only needs to be laminated using the above-mentioned materials and methods.

Step (1-3) Step (1-3) is a step of forming a single crystal silicon layer by bonding a substrate having a single crystal silicon layer to a planarization layer. The single crystal silicon layer has a thickness of 100 to 500 nm thickness and carbon doping at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less. Step (1-3) can be performed in the same manner as in the first aspect.

＜Step (2)＞ Step (2) is a step of manufacturing a nitride semiconductor substrate by epitaxially growing a nitride semiconductor thin film on the single crystal silicon layer of the growth substrate.

In the MOCVD reactor, nitrides such as AlN, AlGaN and GaN are carried out on the single crystal silicon layer with a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less on the growth substrate produced in step (1). Epitaxial growth of semiconductor thin films. In this step, the nitride semiconductor thin film as described above can be epitaxially grown.

During epitaxial growth, TMAl can be used as the Al source, TMGa can be used as the Ga source, and _NH3 can be used as the N source. In addition, the carrier gas can be set to N ₂ and H ₂ or any one of the two gases, and the process temperature can be set to about 900 to 1200°C.

Through the above operation, a nitride semiconductor thin film can be formed to produce a nitride semiconductor substrate. [Example]

Hereinafter, the present invention will be described in more detail using examples and comparative examples, but the present invention is not limited to these examples.

(Example) Prepare a single crystal silicon substrate, and use a CVD film forming furnace to form a high carbon concentration single crystal silicon thin film on the single crystal silicon substrate. As raw material gases used for film formation, trimethylsilane was used as the carbon source and dichlorosilane was used as the silicon source. The film formation temperature of the high carbon concentration single crystal silicon layer was set to 1130°C.

The film thickness is controlled by the film formation time, and a 2 μm high carbon concentration single crystal silicon film is formed. The carbon concentration doped into a single crystal silicon thin film with a high carbon concentration can be adjusted to the following eight levels by adjusting the flow rate of the raw material gas and the film formation temperature. ･5E17 atoms/cm ³ ･2E18 atoms/cm ³ ･7E18 atoms/cm ³ ･2E19 atoms/cm ³ ･2E20 atoms/cm ³ ･4E20 atoms/cm ³ ･2E21 atoms/cm ³ ･4E21 atoms/cm ³

Next, a substrate for epitaxial growth, that is, a growth substrate, is produced. The growth substrate is composed of a support structure including a polycrystalline ceramic core (aluminum nitride core) and a planarization layer (silicon oxide layer) laminated on only one side of the support structure. The first adhesive layer (silicon oxide layer) of the crystalline ceramic core, the conductive layer (polycrystalline silicon layer) laminated on the entire first adhesive layer, the second adhesive layer (silicon oxide layer) laminated on the entire conductive layer, and the The entire barrier layer (silicon nitride layer) of the second adhesive layer.

Next, on the above-described planarization layer, single-crystal silicon substrates on which single-crystal silicon thin films having the above-mentioned eight levels of high carbon concentrations were respectively formed were bonded together as a substrate. At this time, hydrogen ions are implanted from the surface of the single crystal film in advance, and then the planarization layer is in contact with the single crystal silicon film with a high carbon concentration and is bonded together.

After that, a 450 nm single-crystal silicon film with a high carbon concentration is left, and the ion implantation layer is peeled off. After peeling off, the single-crystal silicon thin film with a high carbon concentration is polished to a thickness of 300 nm to form a single-crystal silicon layer on the surface of the growth substrate. Follow the above steps to prepare a substrate for growth.

This growth substrate is placed in a MOCVD reactor, and epitaxial growth of a Group III nitride semiconductor thin film such as AlN, AlGaN, and GaN is performed on the growth substrate. The growth substrate is placed in a wafer pocket called a satellite pallet. When epitaxially growing, TMAl is used as the Al source, TMGa is used as the Ga source, and _NH3 is used as the N source.

As the carrier gas, either N ₂ or H ₂ gas is used. The process temperature is set to about 900~1200℃. When the growth substrate is placed on the satellite tray to perform epitaxial growth, the epitaxial layer is formed by sequentially forming AlN and AlGaN films from the substrate side toward the growth direction, and then epitaxially growing GaN.

A device layer is provided on the surface side of the epitaxial layer. The device layer has a structure in which a GaN layer (channel layer) of about 400 nm that generates two-dimensional electron gas and has high crystallinity, a layer that generates two-dimensional electron gas (barrier layer) of about 20 nm is provided, and Set a cap layer of about 3 nm on the outermost layer. The barrier layer uses AlGaN whose Al composition is set to 20%. The Cap layer is set to a GaN layer. In addition, the thickness of the device layers and the Al composition of the barrier layer can be changed according to the design of the device, and are therefore not limited thereto.

The total film thickness of the epitaxial layer including the device layer is set to 3.5 μm.

After the epitaxial growth is completed, an electrode (CPW: Coplanar Waveguide) is formed on the surface of the epitaxial layer, and a high-frequency signal with a frequency of 1 GHz is input to evaluate the second harmonic characteristics. The second harmonic characteristic uses the value when Pin=15dBm. The results are shown in Figure 2.

In addition, for a sample in which epitaxial growth was performed on a single crystal silicon layer with a carbon concentration of 2E19 atoms/cm ³ , the concentration of Al diffused in the single crystal silicon layer on the surface of the growth substrate was investigated by back-crystal SIMS. The results are shown in Figure 3.

(Comparative example 1) For the bonding step of the outermost single crystal silicon layer in the process of manufacturing the growth substrate of the embodiment, in addition to using a single crystal silicon substrate on which a single crystal silicon thin film with a high carbon concentration has not been formed as the application substrate, it is the same as the implementation. In the same manner, a nitride semiconductor thin film is epitaxially grown to produce a nitride semiconductor substrate.

The second harmonic characteristics of the produced nitride semiconductor substrate were evaluated in the same manner as in the Examples. In addition, the concentration of Al diffused in the single crystal silicon layer of the growth substrate was measured by the same method as in the Example. The results are shown in Figure 2 and Figure 3.

(Comparative Example 2) For the bonding step of the outermost single crystal silicon layer in the process of manufacturing the growth substrate of the Example, in addition to using single crystal silicon substrates with the carbon concentration of the single crystal silicon thin film at the following two levels: Except for applying the substrate, the nitride semiconductor thin film is epitaxially grown in the same manner as in the Example to prepare a nitride semiconductor substrate. ･4E16 atoms/cm ³ ･1E17 atoms/cm ³

The second harmonic characteristics of the produced nitride semiconductor substrate were evaluated in the same manner as in the Examples. The results are shown in Figure 2.

As shown in Figure 2, in the embodiment, by setting the carbon concentration of the single crystal silicon layer, which is the growth surface of the nitride semiconductor thin film, to 5E17atoms/cm3 or ^more and 1E22atoms/ ^cm3 or less, the second harmonic Characteristics get better. On the other hand, in Comparative Example 1 in which the single crystal silicon layer, which is the growth surface of the nitride semiconductor thin film, was not doped with carbon, and in Comparative Example 2 in which the carbon concentration of the single crystal silicon layer was less than 5E17 atoms/cm ³ , good second harmonic characteristics are not obtained.

Furthermore, as shown in FIG. 3 , in the nitride semiconductor substrate of the Example, diffusion of Al was not found in the high carbon concentration single crystal silicon layer of the growth substrate. On the other hand, in Comparative Example 1, the diffusion of Al was observed in the single crystal silicon layer without carbon doping. In addition, in the nitride semiconductor substrate of the Example, Ga diffusion was not found in the single crystal silicon layer with a high carbon concentration.

From the above, it can be seen that the nitride semiconductor substrate and its manufacturing method of the present invention can suppress the deterioration of high-frequency characteristics by diffusing Al in the single crystal silicon layer during the growth of the nitride semiconductor to reduce the resistance.

In addition, the present invention is not limited to the above-described embodiment. The above-mentioned embodiments are only examples, and any embodiments that have substantially the same configuration as the technical ideas described in the patent application scope of the present invention and exhibit the same functions and effects are all included in the technical scope of the present invention.

1: Polycrystalline ceramic core 2: First adhesive layer 3: Conductive layer 4: Second adhesive layer 5: Barrier layer 6: Planarization layer 7:Single crystal silicon layer 8:Nitride semiconductor film 100: Substrate for growth 200:Composite substrate 300:Nitride semiconductor substrate

FIG. 1 is a schematic diagram showing an example of the nitride semiconductor substrate of the present invention. FIG. 2 is a graph showing the relationship between the carbon concentration and the second harmonic characteristics of the single crystal silicon layer on the surface layer of the growth substrate of the nitride semiconductor substrate produced in Examples and Comparative Examples. FIG. 3 shows a growth substrate including a high carbon concentration single crystal silicon layer of the nitride semiconductor substrate of the Example and a growth substrate including a general single crystal silicon layer of the nitride semiconductor substrate of Comparative Example 1. Graph of crystal back SIMS results. FIG. 4 is a schematic diagram showing another example of the growth substrate used in the present invention. FIG. 5 is a schematic diagram showing yet another example of the growth substrate used in the present invention.

Domestic storage information (please note in order of storage institution, date and number) without Overseas storage information (please note in order of storage country, institution, date, and number) without

1: Polycrystalline ceramic core

2: First adhesive layer

3: Conductive layer

4: Second adhesive layer

5: Barrier layer

6: Planarization layer

7:Single crystal silicon layer

8:Nitride semiconductor film

100: Substrate for growth

200:Composite substrate

300:Nitride semiconductor substrate

Claims (18)

A nitride semiconductor substrate comprising: a growth substrate in which a single crystal silicon layer is formed on a composite substrate in which a plurality of layers are laminated; and a nitride film formed on the single crystal silicon layer of the growth substrate. Semiconductor thin film; The carbon concentration of the single crystal silicon layer is 5E17atoms/cm ³ or more and 1E22atoms/cm ³ or less. The nitride semiconductor substrate according to claim 1, wherein the nitride semiconductor film includes at least one of GaN, AlN and AlGaN. The nitride semiconductor substrate according to claim 1, wherein the single crystal silicon layer has a thickness of 100 to 500 nm, and the total film thickness of the nitride semiconductor thin film is 2 μm or more and 10 μm or less. The nitride semiconductor substrate according to claim 2, wherein the single crystal silicon layer has a thickness of 100 to 500 nm, and the total film thickness of the nitride semiconductor thin film is 2 μm or more and 10 μm or less. The nitride semiconductor substrate according to claim 1, wherein the composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, and a second adhesive layer laminated on the entire first adhesive layer. an adhesive layer and a barrier layer laminated throughout the second adhesive layer, and The single crystal silicon layer is formed on a planarization layer, and the planarization layer is laminated on only one side of the composite substrate. The nitride semiconductor substrate according to claim 5, wherein the composite substrate has a conductive layer laminated on the entire first adhesive layer between the first adhesive layer and the second adhesive layer. The nitride semiconductor substrate according to claim 1, wherein the composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, and a barrier laminated on the entire first adhesive layer. layer, a second adhesive layer laminated on the back side of the barrier layer, and a conductive layer laminated on the back side of the second adhesive layer, and The single crystal silicon layer is formed on a planarization layer, and the planarization layer is laminated on the front surface of the barrier layer of the composite substrate. The nitride semiconductor substrate according to claim 1, wherein the composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, and a conductive layer laminated on the back side of the first adhesive layer. layer, a second adhesive layer and a barrier layer laminated on the back of the conductive layer. The barrier layer is laminated on the front and side of the first adhesive layer, the side of the conductive layer and the side of the second adhesive layer. and the back, and The single crystal silicon layer is formed on a planarization layer, and the planarization layer is laminated on the front surface of the barrier layer of the composite substrate. The nitride semiconductor substrate according to any one of claims 6 to 8, wherein the conductive layer includes a polycrystalline silicon layer. The nitride semiconductor substrate according to any one of claims 5 to 8, wherein the polycrystalline ceramic core contains aluminum nitride. The nitride semiconductor substrate according to any one of claims 5 to 8, wherein the first adhesive layer and the second adhesive layer include a tetraethylsiloxane (TEOS) layer or a silicon oxide (SiO ₂ ) layer, And the aforementioned barrier layer contains silicon nitride. The nitride semiconductor substrate according to any one of claims 5 to 8, wherein the planarization layer contains tetraethylsiloxane (TEOS) or silicon oxide (SiO ₂ ) and has a thickness of 500 to 3000 nm. A method for manufacturing a nitride semiconductor substrate, which includes a growth substrate and a nitride semiconductor thin film formed on the growth substrate. The manufacturing method includes the following steps: Step (1), which is: On the composite substrate in which a plurality of layers are laminated, a single crystal silicon layer with a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less is formed to produce a substrate for growth; and, step (2), which uses the nitrogen A compound semiconductor thin film is epitaxially grown on the single crystal silicon layer of the growth substrate to produce a nitride semiconductor substrate. The manufacturing method of a nitride semiconductor substrate according to claim 13, wherein the step (1) is set to include the following steps: Step (1-1), which prepares a composite substrate as the composite substrate, the The composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a barrier laminated on the entire second adhesive layer. layer; step (1-2), which laminates a planarization layer on only one side of the composite substrate; and step (1-3), which involves laminating a substrate having a single crystal silicon layer to The planarization layer is used to form the single crystal silicon layer, which has a thickness of 100 to 500 nm and is carbon doped at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less. The manufacturing method of a nitride semiconductor substrate according to claim 14, wherein in the aforementioned step (1-1), the aforementioned composite substrate is made to have a layer laminated between the aforementioned first adhesive layer and the aforementioned second adhesive layer. The entire conductive layer of the first adhesive layer. The manufacturing method of a nitride semiconductor substrate according to claim 13, wherein the step (1) is set to include the following steps: Step (1-1), which prepares a composite substrate as the composite substrate, the The composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, a barrier layer laminated on the entire first adhesive layer, and a second adhesive layer laminated on the back side of the barrier layer. layer and a conductive layer laminated on the back side of the second adhesive layer; step (1-2), which laminates a planarization layer on the front side of the barrier layer of the composite substrate; and, step (1-3) , which forms the above-mentioned single-crystal silicon layer by bonding a donor substrate with a single-crystal silicon layer to the above-mentioned planarization layer. The single-crystal silicon layer has a thickness of 100 to 500 nm and has a density of 5E17 atoms/cm ³ or more. And it is carbon doped at a concentration of 1E22 atoms/cm ³ or less. The manufacturing method of a nitride semiconductor substrate according to claim 13, wherein the step (1) is set to include the following steps: Step (1-1), which prepares a composite substrate as the composite substrate, the The composite substrate includes a polycrystalline ceramic core, a first adhesive layer laminated on the entire polycrystalline ceramic core, a conductive layer laminated on the back side of the first adhesive layer, and a second adhesive layer laminated on the back side of the conductive layer. and a barrier layer, which is laminated on the front and side surfaces of the first adhesive layer, the side surfaces of the conductive layer, and the side and back surfaces of the second adhesive layer; Step (1-2), in which the barrier layer is formed on the composite substrate A planarization layer is laminated on the front side of the barrier layer; and, step (1-3) is to form the single crystal silicon by bonding a donor substrate having a single crystal silicon layer to the planarization layer. The single crystal silicon layer has a thickness of 100 to 500 nm and is doped with carbon at a concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less. The method for manufacturing a nitride semiconductor substrate according to any one of claims 14 to 17, wherein the step (1-3) includes the following steps: step (1-3-1), wherein The aforementioned carbon-doped single crystal silicon thin film is formed on a single crystal silicon substrate by a CVD method to produce the aforementioned application substrate; step (1-3-2), which involves doping the aforementioned doping of the aforementioned application substrate The single crystal silicon film containing carbon is bonded to the aforementioned planarization layer; and, step (1-3-3), which removes the aforementioned single crystal silicon substrate applied to the substrate, and further makes the aforementioned applied to the substrate The carbon-doped single crystal silicon thin film is processed to have a desired thickness, thereby forming a single crystal silicon layer having a carbon concentration of 5E17 atoms/cm ³ or more and 1E22 atoms/cm ³ or less.

Images