A method for epitaxial growth of gallium nitride and a method for preparing a gallium nitride layer

Abstract

The application discloses a gallium nitride epitaxial growth method and a gallium nitride layer preparation method. The gallium nitride epitaxial growth method comprises the following steps: growing a sacrifice layer on a substrate; the sacrifice layer has a plurality of epitaxial holes forming a honeycomb structure, the epitaxial holes penetrate through the sacrifice layer, and the diameter of the end of the epitaxial hole far from the substrate is smaller than the diameter of the end of the epitaxial hole close to the substrate; and epitaxial growth of a gallium nitride layer in the epitaxial hole and on the sacrifice layer. The method can filter the penetrating dislocation from the substrate, reduce the cracking possibility of the gallium nitride layer grown above the sacrifice layer, and realize epitaxial growth of a high-quality gallium nitride layer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an epitaxial growth method for gallium nitride and a method for preparing gallium nitride layers. Background Technology

[0002] With the development and application of silicon, germanium, gallium arsenide, and indium phosphide semiconductor materials, efficient and reliable application scenarios rely on the superior performance of semiconductor materials. In order to realize applications under extreme conditions such as high temperature, high frequency, high power, strong radiation, and full wavelength, the research and application of third-generation semiconductor materials, namely wide bandgap semiconductors (WBGS), is a hot topic in the semiconductor industry.

[0003] Gallium nitride (GaN), as a wide bandgap semiconductor material, has the characteristics of a large adjustable bandgap, high breakdown field strength, low dielectric constant, high electron saturation, high drift velocity, strong radiation resistance, and excellent chemical stability. High electron mobility field-effect transistors and photodetectors fabricated with GaN as the core are widely used in high-tech fields such as microelectronics, power electronics, and optoelectronics, as well as in the defense industry, information industry, electromechanical industry, and energy industry. It is also a key basic material for the continued development of these pillar industries in the 21st century.

[0004] Silicon carbide (SiC) and gallium nitride (GaN) substrates, due to their low lattice and thermal mismatch rates with GaN, can grow high-quality epitaxial layers. However, commercially available SiC and GaN substrates are expensive. Currently, commercially available GaN is typically grown on sapphire or silicon substrates, especially silicon substrates, because they are mass-producible and can be grown in large sizes. Therefore, epitaxial growth of GaN devices on silicon substrates can significantly increase the number of devices and effectively reduce the epitaxial cost of GaN-based devices. However, there is a large difference in lattice constant and thermal mismatch between the silicon substrate and the epitaxial layer, resulting in high dislocation density and high stress in the GaN epitaxial material. This makes it difficult to grow high-crystallinity, thick, crack-free silicon-based GaN epitaxial layers. Therefore, the most mainstream method currently is to use an AlGaN buffer layer to introduce compressive stress and prevent silicon-based GaN material from cracking due to thermal stress during the cooling process. However, through-dislocations in the silicon-based gallium nitride material system will climb and tilt under compressive stress, thus forming vertically growing mismatched dislocations. This weakens the compressive stress introduced by the AlGaN buffer layer, resulting in insufficient compressive stress compensation during the cooling process, and the gallium nitride epitaxial layer is still prone to cracking. Summary of the Invention

[0005] Therefore, the present invention provides a gallium nitride epitaxial growth method that can effectively filter through dislocations conducted from the substrate, reduce the possibility of cracking in the epitaxially grown gallium nitride layer, and improve its quality, and further provides a method for preparing gallium nitride layers that can achieve high-quality gallium nitride layer preparation.

[0006] According to a first aspect, the present invention provides a method for epitaxial growth of gallium nitride, comprising the following steps:

[0007] A sacrificial layer is grown on a substrate; the sacrificial layer has multiple epitaxial holes forming a honeycomb structure, the epitaxial holes penetrate the sacrificial layer, and the diameter of the end of the epitaxial hole away from the substrate is smaller than the diameter of the end closer to the substrate;

[0008] Gallium nitride layers are epitaxially grown inside the epitaxial holes and on the sacrificial layer.

[0009] In one possible implementation, the epitaxial via includes a first via segment and a second via segment, the first via segment being located at the end of the sacrificial layer near the substrate, and the diameter of the second via segment being smaller than the diameter of the first via segment.

[0010] In one possible implementation, the step of growing the sacrificial layer on the substrate specifically includes:

[0011] A first mask layer is grown on the substrate;

[0012] The first mask layer is etched to form a plurality of first mask holes penetrating the first mask layer; the plurality of first mask holes form a honeycomb structure;

[0013] The first mask aperture is filled with a dielectric material;

[0014] A second mask layer is grown on top of the first mask layer;

[0015] The second mask layer is etched to form a plurality of second mask holes penetrating the second mask layer; the plurality of second mask holes form a honeycomb structure, and the positions of the plurality of second mask holes correspond one-to-one with the positions of the plurality of first mask holes, and the diameter of the second mask holes is smaller than the diameter of the first mask holes;

[0016] Remove the dielectric material inside the first mask hole to complete the growth of the sacrificial layer; the first mask hole is the first hole segment, and the second mask hole is the second hole segment.

[0017] In one possible implementation, the thickness of the second mask layer is less than the thickness of the first mask layer.

[0018] In one possible implementation, the step of epitaxially growing a gallium nitride layer within the epitaxial via and on the sacrificial layer specifically includes:

[0019] Gallium nitride filling layers are grown in epitaxial holes sequentially under first preset growth conditions and second preset growth conditions in a chemical vapor deposition apparatus.

[0020] Under the second preset growth conditions, a gallium nitride epitaxial layer on the sacrificial layer is grown in a chemical vapor deposition apparatus; the first growth temperature in the first preset growth conditions is lower than the second growth temperature in the second preset growth conditions, and the first growth pressure in the first preset growth conditions is greater than the second growth pressure in the second preset growth conditions.

[0021] In one possible implementation, the first growth temperature is between 500°C and 800°C, the second growth temperature is between 900°C and 1200°C, the first growth pressure is between 200 torr and 600 torr, and the second growth pressure is between 40 torr and 150 torr.

[0022] According to a second aspect, the present invention also provides a method for preparing a gallium nitride layer, comprising the following steps:

[0023] The gallium nitride layer is grown using the gallium nitride epitaxial growth method in any of the embodiments of the first aspect described above.

[0024] After removing the sacrificial layer, the gallium nitride layer is peeled off from the substrate.

[0025] The technical solution provided by this invention has the following advantages:

[0026] 1. The gallium nitride epitaxial growth method provided by the present invention involves setting epitaxial holes with a honeycomb structure in the sacrificial layer on the substrate, and setting the diameter of the end of the epitaxial hole away from the substrate to be smaller than the diameter of the end closer to the substrate. This results in the gallium nitride layer growing in the epitaxial hole forming a structure that is smaller at the top and larger at the bottom. As a result, through-dislocations extending from the substrate can be blocked by the upper end (the end away from the substrate) of the sacrificial layer as the diameter of the gallium nitride structure decreases, thereby achieving the effect of filtering through dislocations and reducing the possibility of cracking in the part of the gallium nitride layer growing above the sacrificial layer, thus realizing the epitaxial growth of a high-quality gallium nitride layer.

[0027] 2. The gallium nitride epitaxial growth method provided by the present invention first grows a gallium nitride filling layer in the epitaxial hole under a first preset growth condition with relatively low temperature and relatively high pressure, and then switches to a second preset growth condition with relatively high temperature and relatively low pressure to continue growing the gallium nitride filling layer in the epitaxial hole. This achieves a rapid conversion of three-dimensional gallium nitride growth to two-dimensional growth mode, thereby introducing nanopores in the gallium nitride filling layer, forming a porous structure in the sacrificial layer, which is conducive to the subsequent lift-off process, can reduce the damage to the gallium nitride layer by the subsequent lift-off process, and achieve high-quality gallium nitride epitaxial growth. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 A flowchart of a gallium nitride epitaxial growth method provided in an embodiment of the present invention;

[0030] Figure 2 for Figure 1 Flowchart of the specific steps in step S100;

[0031] Figure 3A and Figure 3B This is a schematic diagram of the structure of the first mask layer and the first mask aperture;

[0032] Figure 3C and Figure 3D This is a schematic diagram of the structure of the second mask layer and the second mask aperture;

[0033] Figure 4 for Figure 1 Flowchart of the specific steps in step S200;

[0034] Explanation of reference numerals in the attached figures:

[0035] 1-Substrate; 21-First mask layer; 22-Second mask layer; 3a-First mask aperture; 3b-Second mask aperture; 4-Dielectric material. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] Example 1

[0039] Figure 1 A flowchart illustrating a gallium nitride epitaxial growth method provided in this embodiment is shown. Figure 1 As shown, the method includes the following steps:

[0040] S100: A sacrificial layer is grown on the substrate.

[0041] In this embodiment, the sacrificial layer has multiple epitaxial holes forming a honeycomb structure. The epitaxial holes penetrate the sacrificial layer, and the diameter of the end of the epitaxial hole away from the substrate is smaller than the diameter of the end closer to the substrate.

[0042] Specifically, the diameter of the epitaxial via can gradually decrease from the end closer to the substrate to the end farther from the substrate, or it can decrease in a step manner. In this case, the epitaxial via includes at least two segments, and the diameter of the segment farther from the substrate is smaller than the diameter of the segment closer to the substrate.

[0043] Specifically, the substrate can be a silicon substrate or an SOI substrate, or a composite substrate with a silicon carbide top structure formed by heat treatment, carbonization, or epitaxial growth, such as a SiC-on-Si substrate, a SiC-on-SOI substrate, or a SiC substrate. Furthermore, the substrate in this step can be a directly obtained finished substrate or a substrate grown prior to this step.

[0044] Specifically, the sacrificial layer can be a SiNx layer, a TiN layer, or an AlN layer, etc. The growth process of the sacrificial layer can be magnetron sputtering, atomic layer deposition, or PECVD, etc.

[0045] S200: Gallium nitride layers are epitaxially grown inside the epitaxial holes and on the sacrificial layer.

[0046] Specifically, the gallium nitride layer can be an unintentionally doped gallium nitride layer or an N-doped gallium nitride layer; its doping configuration can be set according to the needs of specific application scenarios, and there are no restrictions here.

[0047] Specifically, gallium nitride layers can be epitaxially grown using metal-organic source chemical vapor deposition (MOCVD) technology.

[0048] The gallium nitride epitaxial growth method in this embodiment involves setting epitaxial holes with a honeycomb structure within the sacrificial layer on the substrate, and setting the diameter of the end of the epitaxial hole away from the substrate to be smaller than the diameter of the end closer to the substrate. This results in the gallium nitride layer growing in the epitaxial hole forming a structure that is smaller at the top and larger at the bottom. Consequently, through-dislocations extending from the substrate can be blocked by the upper (the end away from the substrate) sacrificial layer as the diameter of the gallium nitride structure decreases, achieving the effect of filtering through dislocations. This reduces the possibility of cracking in the part of the gallium nitride layer growing above the sacrificial layer, thus achieving high-quality gallium nitride epitaxial growth.

[0049] In one specific embodiment of this invention, the diameter of the epitaxial via decreases in a stepped manner, and there are two segments, namely, the epitaxial via includes a first segment and a second segment. The first segment is located at the end of the sacrificial layer near the substrate, and the diameter of the second segment is smaller than the diameter of the first segment. Figure 2 As shown, step S100 above may specifically include the following steps:

[0050] S101: Grow the first mask layer 21 on the substrate 1.

[0051] Correspondingly, the first mask layer 21 can also be a SiNx layer, a TiN layer, or an AlN layer, etc. Taking the growth of the first mask layer 21 (such as a SiNx layer) using PECVD process as an example, the temperature inside the PECVD equipment during growth can be between 100℃ and 150℃, and the pressure can be between 2Pa and 4Pa.

[0052] Specifically, the thickness of the first mask layer 21 is greater than the thickness of the second mask layer 22 described below, and the thickness of the first mask layer 21 can be between 600nm and 1000nm.

[0053] S102: Etch the first mask layer 21 to form a plurality of first mask holes 3a penetrating the first mask layer 21.

[0054] In this embodiment, such as Figure 3A and Figure 3B As shown, multiple first mask holes 3a form a honeycomb structure.

[0055] Specifically, the first mask layer 21 can be etched using ICP etching or RIE etching, and the diameter of the first mask hole 3a obtained by etching can be between 200nm and 400nm.

[0056] S103: Fill the first mask hole 3a with dielectric material 4.

[0057] Specifically, the dielectric material 4 can be Al2O3 or ZnO, etc., and the process of filling it into the first mask hole 3a can be magnetron sputtering or PECVD. Taking PECVD as an example, the temperature of the PECVD equipment during filling can be between 100℃ and 150℃, and the pressure can be 1Pa.

[0058] S104: Grow a second mask layer 22 on the first mask layer 21.

[0059] Specifically, the material of the second mask layer 22 is the same as that of the first mask layer 21, and the growth process can also be the same.

[0060] Specifically, the thickness of the second mask layer 22 can be between 100nm and 300nm.

[0061] S105: Etch the second mask layer 22 to form a plurality of second mask holes 3b penetrating the second mask layer 22.

[0062] In this embodiment, such as Figure 3C and Figure 3D As shown, multiple second mask holes 3b form a honeycomb structure, and the positions of multiple second mask holes 3b correspond one-to-one with the positions of multiple first mask holes 3a. The diameter of the second mask holes 3b is smaller than the diameter of the first mask holes 3a.

[0063] Specifically, the second mask layer 22 can also be etched using ICP etching or RIE etching, and the diameter of the second mask hole 3b obtained by etching can be between 100nm and 140nm.

[0064] S106: Remove the dielectric material 4 inside the first mask hole 3a to complete the growth of the sacrificial layer.

[0065] In this embodiment, the first mask hole 3a is the first hole segment, and the second mask hole 3b is the second hole segment.

[0066] Specifically, the dielectric material 4 inside the first mask hole 3a can be removed by cleaning with an alkaline solution.

[0067] For subsequent applications of the gallium nitride layer grown by the epitaxial growth method in this embodiment (such as use as a gallium nitride thin film, or application in the fabrication of HEMT devices and LEDs), it is generally necessary to peel the gallium nitride layer off the substrate. Therefore, minimizing the damage to the gallium nitride layer caused by the subsequent peeling process is also an important part of achieving high-quality epitaxial growth of gallium nitride layers using this method. To this end, in one specific embodiment of this invention, such as... Figure 4 As shown, step S200 above may specifically include the following steps:

[0068] S201: Under the first preset growth conditions and the second preset growth conditions, a gallium nitride filling layer is grown in the epitaxial hole in a chemical vapor deposition apparatus.

[0069] In this embodiment, the first growth temperature in the first preset growth condition is lower than the second growth temperature in the second preset growth condition, and the first growth pressure in the first preset growth condition is greater than the second growth pressure in the second preset growth condition.

[0070] Specifically, the first growth temperature in the first preset growth conditions can be between 500℃ and 800℃, and the first growth pressure can be between 200 torr and 600 torr. The second growth temperature in the second preset growth conditions is between 900℃ and 1200℃, and the second growth pressure is between 40 torr and 150 torr.

[0071] Specifically, the thickness of the gallium nitride filling layer under the first preset growth condition and the thickness of the gallium nitride filling layer under the second preset growth condition can be set according to the needs of specific application scenarios. As long as the conversion from the first preset growth condition to the second preset growth condition is completed during the entire growth process of the gallium nitride filling layer, the growth mode of rapidly converting three-dimensional gallium nitride growth to two-dimensional growth can be realized. This allows the introduction of nanopores in the gallium nitride filling layer, forming a porous structure within the sacrificial layer. This facilitates the subsequent lift-off process, reduces damage to the gallium nitride layer caused by the subsequent lift-off process, and further achieves the epitaxial growth of high-quality gallium nitride layers.

[0072] S202: Under the second preset growth conditions, a gallium nitride epitaxial layer on the sacrificial layer is grown in a chemical vapor deposition apparatus.

[0073] Example 2

[0074] This embodiment provides a method for preparing a gallium nitride layer, which includes the following steps:

[0075] S10: The gallium nitride layer is grown using the gallium nitride epitaxial growth method in any of the embodiments of Example 1 described above.

[0076] S20: After removing the sacrificial layer, peel the gallium nitride layer off the substrate.

[0077] The method in this embodiment can prepare a high-quality gallium nitride layer.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for epitaxial growth of gallium nitride, characterized in that, Includes the following steps: A sacrificial layer is grown on a substrate; the sacrificial layer has a plurality of epitaxial holes forming a honeycomb structure, the epitaxial holes penetrating the sacrificial layer, and the diameter of the end of the epitaxial hole away from the substrate is smaller than the diameter of the end closer to the substrate; Gallium nitride layers are epitaxially grown inside the epitaxial holes and on the sacrificial layer; The step of epitaxially growing a gallium nitride layer within the epitaxial hole and on the sacrificial layer specifically includes: Gallium nitride filling layers are grown in the epitaxial holes sequentially under first preset growth conditions and second preset growth conditions in a chemical vapor deposition apparatus. Under the second preset growth conditions, a gallium nitride epitaxial layer on the sacrificial layer is grown in a chemical vapor deposition apparatus; the first growth temperature in the first preset growth conditions is lower than the second growth temperature in the second preset growth conditions, and the first growth pressure in the first preset growth conditions is greater than the second growth pressure in the second preset growth conditions.

2. The gallium nitride epitaxial growth method according to claim 1, characterized in that, The epitaxial via includes a first via segment and a second via segment. The first via segment is located at one end of the sacrificial layer near the substrate, and the diameter of the second via segment is smaller than the diameter of the first via segment.

3. The gallium nitride epitaxial growth method according to claim 2, characterized in that, The step of growing a sacrificial layer on the substrate specifically includes: A first mask layer is grown on the substrate; The first mask layer is etched to form a plurality of first mask holes penetrating the first mask layer; the plurality of first mask holes form a honeycomb structure; The first mask aperture is filled with a dielectric material; A second mask layer is grown on the first mask layer; The second mask layer is etched to form a plurality of second mask holes penetrating the second mask layer; the plurality of second mask holes form a honeycomb structure, and the positions of the plurality of second mask holes correspond one-to-one with the positions of the plurality of first mask holes, and the diameter of the second mask holes is smaller than the diameter of the first mask holes; Remove the dielectric material inside the first mask hole to complete the growth of the sacrificial layer; the first mask hole is the first hole segment, and the second mask hole is the second hole segment.

4. The gallium nitride epitaxial growth method according to claim 3, characterized in that, The thickness of the second mask layer is less than the thickness of the first mask layer.

5. The gallium nitride epitaxial growth method according to claim 1, characterized in that, The first growth temperature is between 500℃ and 800℃, the second growth temperature is between 900℃ and 1200℃, the first growth pressure is between 200 torr and 600 torr, and the second growth pressure is between 40 torr and 150 torr.

6. A method for preparing a gallium nitride layer, characterized in that, Includes the following steps: The gallium nitride layer is grown using the gallium nitride epitaxial growth method described in any one of claims 1-5. After removing the sacrificial layer, the gallium nitride layer is peeled off from the substrate.

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