CN113990940B - Silicon carbide epitaxial structure and manufacturing method thereof - Google Patents

Abstract

The present disclosure provides a silicon carbide epitaxial structure and a method for manufacturing the same, which belong to the technical field of semiconductors. The silicon carbide epitaxial structure comprises a substrate and an interface treatment layer, a nucleation layer and a SiC thick layer which are sequentially laminated on the substrate, wherein the substrate comprises a plurality of GaN layers and AlN layers which alternately grow in a period, the interface treatment layer comprises a first sub-layer and a second sub-layer which are sequentially laminated, the first sub-layer is an undoped SiC layer, the second sub-layer is an Si-doped SiC layer, the nucleation layer is an SiC layer with a plurality of triangular cone-shaped bulges on the surface, and the thickness of the SiC thick layer is 80-100 microns. The silicon carbide epitaxial structure can be used for growing a thicker SiC layer and ensuring the quality of the grown SiC epitaxial structure.

Description

Silicon carbide epitaxial structure and manufacturing method thereof

technical field

The present disclosure relates to the technical field of semiconductors, in particular to a silicon carbide epitaxial structure and a manufacturing method thereof.

Background technique

Silicon carbide (SiC) has attracted more and more attention due to its high thermal conductivity, high breakdown voltage, and high saturation carrier concentration, and is widely used in various power conversion devices.

In the related art, a silicon wafer is usually used as a substrate, and a SiC layer is epitaxially grown on the silicon wafer. However, there are differences in lattice constants and thermal expansion coefficients between silicon wafers and SiC materials, which can easily cause tensile stress in the SiC film and compressive stress in the substrate. As the film thickness increases, the stress accumulation will also increase rapidly, and due to the high growth temperature during SiC epitaxial growth, high temperature growth will further aggravate the stress accumulation, and in severe cases, cracks and other problems will occur. Therefore, it is difficult to grow thicker SiC of tens or even hundreds of microns on silicon wafers.

Contents of the invention

Embodiments of the present disclosure provide a silicon carbide epitaxial structure and a manufacturing method thereof, which can grow a thicker SiC layer and ensure the quality of the grown SiC epitaxial structure. Described technical scheme is as follows:

In one aspect, a silicon carbide epitaxial structure is provided, the silicon carbide epitaxial structure includes a substrate and an interface treatment layer, a nucleation layer, and a thick SiC layer stacked on the substrate in sequence, and the substrate includes a plurality of periodic alternate growth GaN layer and AlN layer, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, the first sublayer is an undoped SiC layer, and the second sublayer is a Si-doped SiC layer, the nucleation layer is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface, and the thickness of the SiC thick layer is 80-100um.

Optionally, the interface treatment layer has a thickness of 20-50 nm.

Optionally, the thickness ratio of the first sublayer and the second sublayer in the interface treatment layer is 1:1˜1:5.

Optionally, the doping concentration of Si in the second sublayer in the interface treatment layer is 10 ¹⁷ -10 ¹⁸ cm ^-3 .

Optionally, the distance between the plurality of triangular pyramid-shaped protrusions on the surface of the nucleation layer is 2-50 um.

Optionally, the substrate includes n+1 GaN layers and n AlN layers alternately grown in sequence, 20≤n≤50.

Optionally, the thickness ratio of the GaN layer and the AlN layer in the substrate is 1:1˜1:5.

Optionally, the silicon carbide epitaxial wafer further includes a transition layer between the nucleation layer and the SiC thick layer, the transition layer is a SiC layer treated at high temperature, and the thickness of the transition layer is 20-80um .

In another aspect, a method for manufacturing a silicon carbide epitaxial structure is provided, the method comprising:

A substrate is provided, and the substrate includes a plurality of alternately grown GaN layers and AlN layers;

An interface treatment layer is grown on the substrate, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, the first sublayer is an undoped SiC layer, and the second sublayer is SiC layer doped with Si;

A nucleation layer and a SiC thick layer are sequentially grown on the interface treatment layer, the nucleation layer is a SiC layer with a plurality of triangular pyramid-shaped protrusions on the surface, and the thickness of the SiC thick layer is 80-100 um.

Optionally, the providing a substrate includes:

sequentially growing a buffer layer, an N-type gallium nitride layer and a superlattice layer on the silicon wafer, the superlattice layer comprising a plurality of alternately grown GaN layers and AlN layers;

Etching away the N-type gallium nitride layer by electrochemical means, removing the silicon wafer on which the buffer layer is grown, and obtaining the superlattice layer;

The superlattice layer is used as the substrate.

Optionally, the growing the interface treatment layer on the substrate includes:

controlling the temperature of the reaction chamber to be 800-1000° C., and growing the first sublayer under a hydrogen atmosphere;

Stop feeding hydrogen into the reaction chamber, and feed SiHCl ₃ or SiH ₄ , control the temperature of the reaction chamber to rise to 1000-1500°C, and the feeding time is 50-200s, and grow the second sub-layer on the first sub-layer sublayer.

The beneficial effects brought by the technical solutions provided by the embodiments of the present disclosure are:

By providing a silicon carbide epitaxial structure, the substrate of the silicon carbide epitaxial structure includes a plurality of alternately grown GaN layers and AlN layers, GaN and SiC lattice constants are close, and the crystal quality of the SiC epitaxial layer grown thereon can be guaranteed . However, AlN has better thermal conductivity, which can have a good heat dissipation effect, and is conducive to coordinating the difference in thermal expansion coefficient between GaN and SiC. Therefore, the GaN layer and AlN layer grown alternately in multiple periods can take into account the difference in lattice constant and thermal expansion coefficient at the same time, and provide a substrate with equivalent lattice constant and thermal expansion coefficient for the subsequent SiC epitaxial layer growth. At the same time, it can also ensure that the substrate will not produce defects such as cracks when the SiC epitaxial layer is grown at a subsequent high temperature. Before growing the thick SiC layer, an interface treatment layer and a nucleation layer are grown separately. Wherein, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, and the first sublayer is an undoped SiC layer, which can play a role of lattice transition. The second sublayer is a SiC layer doped with Si, and doping with Si can further improve the crystal quality of SiC. The nucleation layer is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface. Multiple triangular pyramid-shaped protrusions divide the growth of the SiC thick layer into multiple small areas. dislocations, reducing stress. Therefore, on the basis of the above layers, a relatively thick SiC layer with a thickness of 80-100 um can be grown finally, and problems such as cracks will not occur, ensuring the quality of the grown SiC epitaxial structure.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

FIG. 1 is a schematic structural diagram of a silicon carbide epitaxial structure provided by an embodiment of the present disclosure;

2 is a flowchart of a method for manufacturing a silicon carbide epitaxial structure provided by an embodiment of the present disclosure;

FIG. 3 is a flow chart of another method for manufacturing a silicon carbide epitaxial structure provided by an embodiment of the present disclosure.

Detailed ways

In order to make the purpose, technical solution and advantages of the present disclosure clearer, the implementation manners of the present disclosure will be further described in detail below in conjunction with the accompanying drawings.

FIG. 1 is a schematic structural diagram of a silicon carbide epitaxial structure provided by an embodiment of the present disclosure. As shown in FIG. 1 , the silicon carbide epitaxial structure includes a substrate 10 and an interface treatment layer 20 and a nucleation layer 30 stacked on the substrate 10 in sequence. and SiC thick layer 50.

The substrate 10 includes a plurality of periodically alternately grown GaN layers 11 and AlN layers 12 . The interface treatment layer 20 includes a first sublayer 21 and a second sublayer 22 stacked in sequence, the first sublayer 21 is an undoped SiC layer, and the second sublayer 22 is a Si-doped SiC layer. The nucleation layer 30 is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface, and the SiC thick layer 50 has a thickness of 80-100 um.

The silicon carbide epitaxial structure provided by the embodiments of the present disclosure has a substrate comprising a plurality of alternately grown GaN layers and AlN layers, and the GaN and SiC lattice constants are close to each other, which can ensure the crystal quality of the SiC epitaxial layer grown thereon. However, AlN has better thermal conductivity, which can have a good heat dissipation effect, and is conducive to coordinating the difference in thermal expansion coefficient between GaN and SiC. Therefore, the GaN layer and AlN layer grown alternately in multiple periods can take into account the difference in lattice constant and thermal expansion coefficient at the same time, and provide a substrate with equivalent lattice constant and thermal expansion coefficient for the subsequent SiC epitaxial layer growth. At the same time, it can also ensure that the substrate will not produce defects such as cracks when the SiC epitaxial layer is grown at a subsequent high temperature. Before growing the thick SiC layer, an interface treatment layer and a nucleation layer are grown separately. Wherein, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, and the first sublayer is an undoped SiC layer, which can play a role of lattice transition. The second sublayer is a SiC layer doped with Si, and doping with Si can further improve the crystal quality of SiC. The nucleation layer is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface. Multiple triangular pyramid-shaped protrusions divide the growth of the SiC thick layer into multiple small areas. dislocations, reducing stress. Therefore, on the basis of the above layers, a relatively thick SiC layer with a thickness of 80-100um can be grown eventually, and problems such as cracks will not occur, ensuring the quality of the grown SiC epitaxial structure.

And for SiC devices with a high voltage above 10Kv, a SiC thick layer with a thickness of more than 60um is required, and the epitaxial structure provided by the embodiment of the present disclosure can be used to grow a SiC thick layer with a thickness of 80-100um, so as to meet the requirements of SiC with a high voltage above 10Kv. Device requirements, providing wafers for low-cost mass production of SiC high-voltage devices.

Optionally, the substrate 10 includes n+1 GaN layers 11 and n AlN layers 12 alternately grown in sequence, 20≤n≤50.

That is to say, the layer in contact with the interface treatment layer 20 in the substrate 10 is the GaN layer 11, which can prevent the abnormality between it and the SiC epitaxial structure due to the large difference in lattice constant and thermal expansion coefficient, so that the epitaxial layer 11 can be guaranteed. Growth quality of the grown SiC epitaxial structures.

If the number of periods in the substrate 10 is too large, the thickness of the substrate 10 will be thicker, and the lattice and thermal expansion differences of AlN and GaN will continue to accumulate, resulting in increased defects and stress; if the number of periods in the substrate 10 is too small, on the one hand, It is easy to break at high temperature, and on the other hand, the quality of the substrate crystal is poor, and it is difficult to continue to grow high-quality thick-layer SiC.

Optionally, the thickness ratio of the GaN layer 11 and the AlN layer 12 in the substrate 10 is 1:1˜1:5.

Since the difference in thermal expansion coefficient will cause the SiC epitaxial layer to appear convex and concave changes during growth, and the thermal expansion coefficient of GaN and AlN is different, setting the thickness of each layer within the above range can neutralize the warpage change caused by the difference in thermal expansion, which is beneficial achieve better planar growth.

Wherein, the thickness of the AlN layer 12 is greater than the thickness of the GaN layer 11. If the thickness of the AlN layer 12 is thinner, it is difficult to effectively balance the warpage caused by the temperature difference, and the stress is easy to accumulate in the film during the growth process. Therefore, the AlN layer 12 Thickness is set thicker.

Optionally, the thickness of the substrate 10 is 50-500 nm.

If the thickness of the substrate 10 is too thin, it is easy to break during high-temperature growth; if the thickness of the substrate 10 is too thick, the differences in lattice and stress between AlN and GaN will continue to accumulate, affecting the growth quality of the subsequent SiC epitaxial layer.

Optionally, the substrate 10 further includes a protective layer 13 located on the surface of the last GaN layer 11 , and the protective layer 13 is a Si-doped GaN layer.

Since Si is doped in the protective layer 13 , Si dangling bonds can be formed on the surface of the last GaN layer 11 , which is beneficial for subsequent bonding with the SiC epitaxial structure. At the same time, the doping of Si in the protection layer 13 can also play an anti-oxidation role, preventing the surface of the GaN layer 110 from being oxidized, and finally affecting the crystal quality of the SiC epitaxial structure grown thereon.

Optionally, the protective layer 13 has a thickness of 5-10 nm.

If the thickness of the protective layer 13 is too thin, it is easy to be affected by impurity elements such as adsorbed C/H/O/Si, and thermal decomposition is also easy to damage the protective layer during high-temperature epitaxy; if the thickness of the protective layer 13 is too thick, due to The difference in thermal expansion coefficient is easy to introduce internal stress in the film during the subsequent high-temperature epitaxy of SiC, resulting in abnormal SiC thick film.

Optionally, the thickness of the interface treatment layer 20 is 20-50 nm.

If the thickness of the interface treatment layer 20 is too thick, it will lead to the deviation of the crystal quality of the bottom layer, and it is difficult to improve the quality of the subsequent epitaxial crystal; if the thickness of the interface treatment layer 20 is too thin, the lattice transition cannot be effectively completed. Crystal quality is also difficult to improve.

Optionally, the thickness ratio of the first sublayer 21 and the second sublayer 22 in the interface treatment layer 20 is 1:1˜1:5.

Optionally, the doping concentration of Si in the second sub-layer 22 in the interface treatment layer 20 is 10 ¹⁷ -10 ¹⁸ cm ⁻³ .

If the doping concentration of Si in the second sublayer 22 is too large, then Si will exist as an impurity and affect the crystal quality; if the doping concentration of Si in the second sublayer 22 is too small, it will be difficult to improve point defects and improve Effect of crystal quality.

Optionally, the distance between the plurality of triangular pyramid-shaped protrusions on the surface of the nucleation layer 30 is 2-50 um.

If the distance between multiple triangular pyramid-shaped protrusions is too small, it will be easy to quickly fill up later, and it is difficult to achieve the purpose of reducing dislocations and stress; if the distance between multiple triangular pyramid-shaped protrusions is too large, the Differences can become apparent, affecting intra-chip consistency and uniformity.

Exemplarily, the diameter of the bottom of each triangular pyramid-shaped protrusion is 2˜10 μm.

Optionally, the silicon carbide epitaxial structure further includes a transition layer 40 located between the nucleation layer 30 and the thick SiC layer 50 , the transition layer 40 is a SiC layer treated at high temperature, and the thickness of the transition layer 40 is 20-80 um.

High-temperature treatment can make Si and C carry out atomic rearrangement with the help of thermal kinetic energy to obtain a high-quality SiC layer, which can have a better transition effect and provide a good growth basis for the subsequent SiC thick layer growth.

An embodiment of the present disclosure also provides a method for manufacturing a silicon carbide epitaxial structure, which is used for manufacturing the silicon carbide epitaxial structure as shown in FIG. 1 .

Fig. 2 is a flow chart of a method for manufacturing a silicon carbide epitaxial structure provided by an embodiment of the present disclosure. As shown in Fig. 2 , the method includes:

Step 201, providing a substrate.

Wherein, the substrate includes a plurality of alternately grown GaN layers and AlN layers.

Step 202 , growing an interface treatment layer on the substrate.

Wherein, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, the first sublayer is an undoped SiC layer, and the second sublayer is a Si-doped SiC layer.

Step 203 , growing a nucleation layer and a SiC thick layer sequentially on the interface treatment layer.

Wherein, the nucleation layer is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface, and the thickness of the SiC thick layer is 80-100um.

The silicon carbide epitaxial structure grown in the embodiment of the present disclosure has a substrate including GaN layers and AlN layers alternately grown in multiple periods. The lattice constant of GaN and SiC is close, which can ensure the crystal quality of the SiC epitaxial layer grown thereon. However, AlN has better thermal conductivity, which can have a good heat dissipation effect, and is conducive to coordinating the difference in thermal expansion coefficient between GaN and SiC. Therefore, the GaN layer and AlN layer grown alternately in multiple periods can take into account the difference in lattice constant and thermal expansion coefficient at the same time, and provide a substrate with equivalent lattice constant and thermal expansion coefficient for the subsequent SiC epitaxial layer growth. At the same time, it can also ensure that the substrate will not produce defects such as cracks when the SiC epitaxial layer is grown at a subsequent high temperature. Before growing the thick SiC layer, an interface treatment layer and a nucleation layer are grown separately. Wherein, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, and the first sublayer is an undoped SiC layer, which can play a role of lattice transition. The second sublayer is a SiC layer doped with Si, and doping with Si can further improve the crystal quality of SiC. The nucleation layer is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface. Multiple triangular pyramid-shaped protrusions divide the growth of the SiC thick layer into multiple small areas. dislocations, reducing stress. Therefore, on the basis of the above layers, a relatively thick SiC layer with a thickness of 80-100um can be grown eventually, and problems such as cracks will not occur, ensuring the quality of the grown SiC epitaxial structure.

Embodiments of the present disclosure also provide another method for manufacturing a silicon carbide epitaxial structure, which is used to manufacture the silicon carbide epitaxial structure as shown in FIG. 1 .

Fig. 3 is a flowchart of a method for manufacturing a silicon carbide epitaxial structure provided by an embodiment of the present disclosure. As shown in Fig. 3 , the method includes:

Step 301, providing a substrate.

Wherein, the substrate includes a plurality of alternately grown GaN layers and AlN layers.

Optionally, the substrate includes n+1 GaN layers and n AlN layers alternately grown in sequence, 20≤n≤50.

That is to say, the layer in the substrate that is in contact with the interface treatment layer is a GaN layer, which can prevent abnormalities between it and the SiC epitaxial structure due to excessive differences in lattice constant and thermal expansion coefficient, thereby ensuring that the SiC epitaxially grown on it Growth quality of epitaxial structures.

If the number of periods in the substrate is too large, the thickness of the substrate will be thicker, and the difference between the lattice and thermal expansion of AlN and GaN will continue to accumulate, resulting in increased defects and stress; if the number of periods in the substrate is too small, on the one hand, at high temperature It is easy to break, and on the other hand, the quality of the substrate crystal is poor, and it is difficult to continue to grow high-quality thick-layer SiC.

Optionally, the thickness ratio of the GaN layer and the AlN layer in the substrate is 1:1˜1:5.

Since the difference in thermal expansion coefficient will cause the SiC epitaxial layer to appear convex and concave changes during growth, and the thermal expansion coefficient of GaN and AlN is different, setting the thickness of each layer within the above range can neutralize the warpage change caused by the difference in thermal expansion, which is beneficial achieve better planar growth.

Wherein, the thickness of the AlN layer is greater than the thickness of the GaN layer. If the thickness of the AlN layer is thinner, it is difficult to effectively balance the warpage caused by the temperature difference, and the stress is easy to accumulate in the film during the growth process. Therefore, the thickness of the AlN layer 12 is set to thicker.

Optionally, the substrate has a thickness of 50-500 nm.

If the thickness of the substrate is too thin, it is easy to break during high-temperature growth; if the thickness of the substrate is too thick, the difference in lattice and stress between AlN and GaN will continue to accumulate, affecting the growth quality of the subsequent SiC epitaxial layer.

Optionally, the substrate further includes a protective layer on the surface of the last GaN layer, and the protective layer is a Si-doped GaN layer.

Since Si is doped in the protective layer, Si dangling bonds can be formed on the surface of the last GaN layer, which is beneficial for subsequent bonding with the SiC epitaxial structure. At the same time, the doping of Si in the protective layer can also play a role of anti-oxidation, prevent the surface of GaN layer 1 from being oxidized, and ultimately affect the crystal quality of the SiC epitaxial structure grown thereon.

Optionally, the protective layer 13 has a thickness of 5-10 nm.

If the thickness of the protective layer 30 is too thin, it is easy to be affected by impurity elements such as adsorbed C/H/O/Si, and thermal decomposition is also easy to damage the protective layer during high-temperature epitaxy; if the thickness of the protective layer 30 is too thick, due to The difference in thermal expansion coefficient is easy to introduce internal stress in the film during the subsequent high-temperature epitaxy of SiC, resulting in abnormal SiC thick film.

Exemplarily, step 301 may include:

In the first step, a buffer layer, an N-type gallium nitride layer and a superlattice layer are sequentially grown on the silicon wafer, and the superlattice layer includes a plurality of alternately grown GaN layers and AlN layers.

Wherein, the buffer layer is an undoped GaN layer or an AlGaN layer with a thickness of 15-30 nm. The N-type gallium nitride layer is a Si-doped GaN layer, and the thickness of the N-type gallium nitride layer is 200-500 nm.

Optionally, the buffer layer is an undoped GaN layer or an AlGaN layer with a thickness of 15-30 nm. The nucleation layer can serve as a crystal nucleus for subsequent epitaxial growth.

In the embodiment of the present disclosure, the doping concentration of Si in the N-type GaN layer is 5E18-5E19 cm ⁻³ .

Control the temperature of the reaction chamber at 600-900°C and the pressure at 100-500 torr, and grow the nucleation layer on the silicon wafer;

The temperature of the reaction chamber is controlled to be 950-1150° C., and the pressure is 100-500 torr. In a nitrogen atmosphere, feed Ga source, NH ₃ and SiH ₄ into the reaction chamber to grow an N-type gallium nitride layer with a thickness of 200-500nm and a Si doping concentration of 5E18-5E19cm ^-3 ;

The temperature of the reaction chamber is controlled to be 1150-1350° C., the pressure is 100-300 torr, and the superlattice layer is grown on the N-type gallium nitride layer.

In the second step, the N-type gallium nitride layer is etched away by electrochemical methods, and the silicon wafer with the buffer layer is removed to obtain the superlattice layer;

The third step is to use the superlattice layer as a base.

Exemplarily, step 301 may also include:

A protection layer is grown on the superlattice layer, the protection layer is a GaN layer doped with Si, and the thickness of the protection layer is 5-10 nm.

Exemplarily, the temperature and pressure in the reaction chamber are kept constant, the Ga source and NH ₃ are turned off, and SiH ₄ is introduced to form a protective layer on the surface of the second sub-layer.

Step 302 , growing an interface treatment layer on the substrate.

Wherein, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, the first sublayer is an undoped SiC layer, and the second sublayer is a Si-doped SiC layer.

Optionally, the thickness of the interface treatment layer is 20-50 nm.

Optionally, the thickness ratio of the first sublayer and the second sublayer 22 in the interface treatment layer is 1:1˜1:5.

Optionally, the doping concentration of Si in the second sublayer in the interface treatment layer is 10 ¹⁷ -10 ¹⁸ cm ^-3 .

Exemplarily, step 302 may include:

The temperature of the reaction chamber is controlled to be 1200-1400° C., the pressure is 1-10 Torr, and the interface treatment layer is grown on the substrate.

Step 303 , growing a nucleation layer on the interface treatment layer.

Wherein, the nucleation layer is a SiC layer with a plurality of triangular pyramid-shaped protrusions on the surface.

Optionally, the distance between the plurality of triangular pyramid-shaped protrusions on the surface of the nucleation layer 30 is 2-50 um.

Exemplarily, the diameter of the bottom of each triangular pyramid-shaped protrusion is 2-10 nm.

Exemplarily, step 303 may include:

The temperature of the reaction chamber is controlled to be 1100-1300° C., the pressure is 1-10 Torr, and a nucleation layer is grown on the interface treatment layer.

Step 304 , growing a transition layer on the nucleation layer.

Wherein, the transition layer is a high temperature treated SiC layer, and the thickness of the transition layer is 20-80um.

High-temperature treatment can make Si and C carry out atomic rearrangement with the help of thermal kinetic energy to obtain a high-quality SiC layer, which can have a better transition effect and provide a good growth basis for the subsequent SiC thick layer growth.

Exemplarily, step 304 may include:

The temperature of the reaction chamber is controlled at 1500-1750° C., the pressure is 1-10 Torr, and a transition layer is formed on the nucleation layer.

Step 305 , growing a SiC thick layer on the transition layer.

Wherein, the SiC thick layer has a thickness of 80-100um.

Exemplarily, the temperature of the reaction chamber is controlled to be 1400-1750° C., the pressure is 1-10 Torr, and a SiC thick layer is grown on the transition layer.

It should be noted that, in the embodiments of the present disclosure, controlling the temperature and pressure refers to controlling the temperature and pressure in the reaction chamber for growing the epitaxial structure, specifically Metal-organic Chemical Vapor Deposition (English: Metal-organic Chemical Vapor Deposition, referred to as : The reaction chamber of MOCVD) equipment. Use high-purity H ₂ (hydrogen) or high-purity N ₂ (nitrogen) or a mixture of high-purity H ₂ and high-purity N ₂ as carrier gas, high-purity NH ₃ as nitrogen source, trimethylgallium (TMGa) and three Ethylgallium (TEGa) as gallium source, trimethylindium (TMIn) as indium source, silane (SiH4) as N-type dopant, ie Si source, trimethylaluminum (TMAl) as aluminum source, magnesocene (CP ₂ Mg) is used as a P-type dopant, that is, a source of Mg.

The silicon carbide epitaxial structure grown in the embodiment of the present disclosure has a substrate including GaN layers and AlN layers alternately grown in multiple periods. The lattice constant of GaN and SiC is close, which can ensure the crystal quality of the SiC epitaxial layer grown thereon. However, AlN has better thermal conductivity, which can have a good heat dissipation effect, and is conducive to coordinating the difference in thermal expansion coefficient between GaN and SiC. Therefore, the GaN layer and AlN layer grown alternately in multiple periods can take into account the difference in lattice constant and thermal expansion coefficient at the same time, and provide a substrate with equivalent lattice constant and thermal expansion coefficient for the subsequent SiC epitaxial layer growth. At the same time, it can also ensure that the substrate will not produce defects such as cracks when the SiC epitaxial layer is grown at a subsequent high temperature. Before growing the thick SiC layer, an interface treatment layer and a nucleation layer are grown separately. Wherein, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, and the first sublayer is an undoped SiC layer, which can play a role of lattice transition. The second sublayer is a SiC layer doped with Si, and doping with Si can further improve the crystal quality of SiC. The nucleation layer is a SiC layer with multiple triangular pyramid-shaped protrusions on the surface. Multiple triangular pyramid-shaped protrusions divide the growth of the SiC thick layer into multiple small areas. dislocations, reducing stress. Therefore, on the basis of the above layers, a relatively thick SiC layer with a thickness of 80-100um can be grown eventually, and problems such as cracks will not occur, ensuring the quality of the grown SiC epitaxial structure.

The above descriptions are only optional embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection of the present disclosure. within range.

Claims (10)

1. A silicon carbide epitaxial structure, characterized in that the silicon carbide epitaxial structure comprises a substrate and an interface treatment layer, a nucleation layer and a SiC thick layer stacked on the substrate in sequence, and the substrate comprises a plurality of periodic alternating grown GaN layer and AlN layer, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, the first sublayer is an undoped SiC layer, and the second sublayer is an Si-doped SiC layer, the nucleation layer is a SiC layer with a plurality of triangular pyramid-shaped protrusions on the surface, and the thickness of the SiC thick layer is 80-100um. 2 . The silicon carbide epitaxial structure according to claim 1 , wherein the interface treatment layer has a thickness of 20-50 nm. 3 . The silicon carbide epitaxial structure according to claim 2 , wherein the thickness ratio of the first sublayer and the second sublayer in the interface treatment layer is 1:1˜1:5. 4 . 4 . The silicon carbide epitaxial structure according to claim 1 , wherein the doping concentration of Si in the second sublayer of the interface treatment layer is 10 ¹⁷ -10 ¹⁸ cm ^-3 . 5 . The silicon carbide epitaxial structure according to claim 1 , wherein the distance between the plurality of triangular pyramid-shaped protrusions on the surface of the nucleation layer is 2-50 um. 6 . The silicon carbide epitaxial structure according to claim 1 , wherein the substrate comprises n+1 GaN layers and n AlN layers alternately grown in sequence, 20≤n≤50. 7. The silicon carbide epitaxial structure according to any one of claims 1 to 6, characterized in that, the silicon carbide epitaxial structure further comprises a transition layer between the nucleation layer and the SiC thick layer, the transition The layer is a SiC layer treated at high temperature, and the thickness of the transition layer is 20-80um. 8. A method of manufacturing a silicon carbide epitaxial structure, characterized in that the method of manufacturing comprises: A substrate is provided, and the substrate includes a plurality of alternately grown GaN layers and AlN layers; An interface treatment layer is grown on the substrate, the interface treatment layer includes a first sublayer and a second sublayer stacked in sequence, the first sublayer is an undoped SiC layer, and the second sublayer is SiC layer doped with Si; A nucleation layer and a SiC thick layer are sequentially grown on the interface treatment layer, the nucleation layer is a SiC layer with a plurality of triangular pyramid-shaped protrusions on the surface, and the thickness of the SiC thick layer is 80-100 um. 9. The manufacturing method according to claim 8, wherein said providing a base comprises: sequentially growing a buffer layer, an N-type gallium nitride layer and a superlattice layer on the silicon wafer, the superlattice layer comprising a plurality of alternately grown GaN layers and AlN layers; Etching away the N-type gallium nitride layer by electrochemical means, removing the silicon wafer on which the buffer layer is grown, and obtaining the superlattice layer; The superlattice layer is used as the substrate. 10. The manufacturing method according to claim 8, wherein the growing the interface treatment layer on the substrate comprises: controlling the temperature of the reaction chamber to be 800-1000° C., and growing the first sublayer under a hydrogen atmosphere; Stop feeding hydrogen into the reaction chamber, and feed SiHCl ₃ or SiH ₄ for 50-200s, control the temperature of the reaction chamber to rise to 1000-1500°C, and grow the second sub-layer on the first sub-layer sublayer.

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