GaN HEMT epitaxial wafer based on AlN thick film and manufacturing method thereof
By introducing an AlN thick film structure into the GaN HEMT epitaxial wafer, the leakage current and heat release problems caused by damage to the growth substrate surface are solved, excellent electrical insulation and high thermal conductivity are achieved, and the performance and quality of the wafer are improved.
Patent Information
- Application Number
- CN202510463065.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-02-17
- Filing Date
- 2025-04-14
- Publication Date
- 2025-10-21
AI Technical Summary
Existing GaN HEMT power semiconductor epitaxial wafers suffer from performance and quality degradation due to vertical leakage current caused by damage to the growth substrate surface, and it is difficult to quickly release heat during operation.
The AlN thick film-based structure includes an AlN nucleation region, an AlN stress control region, and an AlN buffer region, combined with a Si or 4H-SiC growth substrate to form an active region with excellent electrical insulation and high thermal conductivity by controlling air voids and Al vacancies.
It effectively prevents vertical leakage current, improves electrical insulation performance, quickly releases heat, reduces production costs, and improves wafer quality and performance.
Smart Images
Figure CN120825980A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a GaN HEMT power semiconductor epitaxial wafer and a manufacturing method thereof, wherein the GaN HEMT power semiconductor epitaxial wafer has excellent electrical insulation and heat dissipation physical properties by utilizing an AlN thick film with a specific structure. Background Art
[0002] The GaN HEMT power semiconductor epitaxial structure generally has a structure in which a nucleation region, a stress relief region, a buffer region, a channel region, and a barrier region are sequentially stacked on a growth substrate.
[0003] In the GaN HEMT power semiconductor epitaxial structure, the channel region and barrier region are key active regions separated from the substructure.
[0004] In the active region, due to the polarization phenomenon of the III-nitride semiconductor at the interface of the channel region, a high electron density 2DEG (two-dimensional electron gas) is formed, which is called a horizontal channel structure.
[0005] GaN HEMT power semiconductor epitaxial wafers with a horizontal channel structure have performance and quality degradation problems due to vertical leakage current in the direction of the active region substructure, and in order to solve this problem, an active region substructure with further enhanced electrical insulation is required.
[0006] In addition, in order to quickly and easily release the large amount of heat generated when operating the GaN HEMT power semiconductor device to the outside, it is necessary to configure the substructure of the active area with a material having high thermal conductivity.
[0007] The buffer region has a current blocking function of reducing vertical leakage current by imparting high resistance characteristics, and is generally made of a GaN material doped with carbon (C) or iron (Fe) as a dopant (C-doped or Fe-doped GaN) to achieve the intended purpose.
[0008] However, when growing GaN doped with C or Fe, the quality of the GaN crystal deteriorates. Therefore, forming the optimal growth conditions between the growth substrate and the active region is a challenge in the related art. Summary of the Invention
[0009] Technical issues
[0010] The present invention provides a structure and method for solving the problem of performance and quality degradation caused by vertical leakage current resulting from surface damage of a growth substrate during the epitaxial growth process of a GaN HEMT power semiconductor epitaxial wafer having a horizontal channel structure.
[0011] The present invention provides a substructure of an active region having enhanced electrical insulation and a method for manufacturing the same, so that not only a growth substrate made of a semi-insulating material (SiC, Si) can be used, but also a low-cost conductive growth substrate can be used.
[0012] The present invention provides a substructure of an active region having a material with high thermal conductivity and a method for manufacturing the same, the material being capable of quickly and easily dissipating a large amount of heat generated during the operation of a GaN HEMT power semiconductor device.
[0013] Technical solution
[0014] An embodiment according to the present invention is a GaN HEMT epitaxial wafer based on an AlN thick film, the GaN HEMT epitaxial wafer based on an AlN thick film including: a growth substrate made of a semi-insulating material or a conductive material; an AlN nucleation region grown on the growth substrate; an AlN stress control region grown on the AlN nucleation region and having air voids or Al vacancies; an AlN buffer region grown on the AlN stress control region and not including the air voids and the Al vacancies; and an active region grown on the AlN buffer region and including a GaN channel region and an AlGaN barrier region.
[0015] In an embodiment according to the present invention, the growth substrate is made of Si having a (111) plane as a growth surface or 4H-SiC having a Si polar plane as a growth surface.
[0016] In an embodiment according to the present invention, the AlN stress control region is formed to be relatively thicker than the AlN buffer region, and the AlN stress control region is provided with a large number of air voids having a micron-scale size or Al vacancies having a nano-scale size.
[0017] An embodiment according to the present invention further includes a back barrier region formed of Al(1-z)Ga(z)N (0 < z < 1), the back barrier region being grown on the AlN buffer region before the growth of the active region.
[0018] An embodiment according to the present invention is a method for manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film, wherein the step of forming an AlN stress control region having a large number of air voids includes a carrier gas that moves an aluminum organometallic source (TMAl, TEAl) into a MOCVD chamber, the carrier gas being made of separate N2 or a gas mixed with a small amount of H2 (i.e., an N2-rich atmosphere).
[0019] Here, the step of forming the AlN stress control region may include the following steps: forming an AlN surface patterning structure by photolithography and etching after growing the AlN nucleation region by an MOCVD process or after growing a portion of the AlN stress control region to a predetermined thickness; and completing the AlN stress control region by re-growth on the AlN surface patterning structure in MOCVD.
[0020] The step of forming the AlN stress control region may include the following steps: after growing the AlN nucleation region, growing AlGaN or AlInN material at a predetermined temperature (Tg) as a subsequent process, and decomposing and evaporating Ga or In at a high temperature above Tg and in an H2 reducing atmosphere.
[0021] The step of forming the AlN stress control region can be formed to a preset thickness by using a 2-dimensional growth mode and a 3-dimensional growth mode, wherein the AlN is preferentially grown in the horizontal direction by a pulsed NH3 source supply and the AlN is preferentially grown in the vertical direction by a continuous NH3 source supply.
[0022] The step of forming the AlN stress control region is preferably performed by controlling the V (N source) / III (Al source) ratio below a predetermined growth pressure in MOCVD and supplying Ga and In sources during AlN growth for isoelectric co-doping, thereby generating a large number of Al vacancies.
[0023] The step of forming the AlN buffer region may be performed in a 2D growth mode using a carrier gas (H 2 alone or a gas mixed with a small amount of N 2 (ie, H 2 -rich atmosphere)) for moving an aluminum organometallic source (TMAl, TEAl) into the MOCVD chamber.
[0024] Here, the 2D growth mode is used to eliminate or minimize the density of threading dislocations and the induced crystal defects in the AlN nucleation region.
[0025] Beneficial effects
[0026] According to the present invention, by introducing an AlN stress control region and an AlN buffer region defined as an "AlN thick film", a substructure with excellent electrical insulation for the active area can be formed not only on a semi-insulating growth substrate but also on a relatively inexpensive conductive growth substrate.
[0027] According to the present invention, the "AlN thick film" prevents vertical leakage current caused by surface damage of the growth substrate during the growth process. This prevents performance and quality degradation.
[0028] According to the present invention, since the "AlN thick film" has sufficient thermal conductivity, a large amount of heat generated when operating the GaN HEMT power semiconductor device can be released quickly and easily.
[0029] According to the present invention, by forming a back barrier region made of Al(1-z)Ga(z)N (0 < z < 1) on the AlN buffer region, the effect of confining 2DEG carrier electrons in the channel region can be maximized.
[0030] In addition, the back barrier region minimizes crystal defects by reducing the lattice constant difference between the AlN buffer region and the GaN channel region, and at the same time induces compressive stress that compensates for tensile stress to eliminate microcracks.
[0031] According to the present invention, since the "AlN thick film" is composed of a single material, the growth process time can be shortened, and thus the GaN HEMT device can be manufactured with high cost-effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 is a cross-section of a GaN HEMT power semiconductor epitaxial wafer according to an embodiment of the present invention.
[0033] Figure 2 is a cross-section of a GaN HEMT power semiconductor epitaxial wafer according to another embodiment of the present invention.
[0034] Figure 3 is a diagram for explaining a method of manufacturing a GaN HEMT power semiconductor epitaxial wafer according to an embodiment of the present invention. DETAILED DESCRIPTION
[0035] Hereinafter, embodiments of an AlN thick film-based GaN HEMT epitaxial wafer and a method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.
[0036] The terms used below are selected for convenience of explanation and should be appropriately interpreted to conform to the meaning of the technical concept of the present invention, rather than being limited to the dictionary meaning.
[0037] Referring to Figure 1 , in a GaN HEMT power semiconductor epitaxial wafer according to an embodiment of the present invention, an AlN nucleation region (120), an AlN stress control region (130), and an AlN buffer region (140) are sequentially stacked and grown on a growth substrate (110), and a channel region (161) and a barrier region (162) are formed as an active region (160) thereon.
[0038] The growth substrate (110) is provided with a semi-insulating material or a conductive material.
[0039] The growth substrate (110) may be a silicon (Si) substrate, a silicon carbide (SiC) substrate or an aluminum oxide substrate. The aluminum oxide substrate may be a sapphire (Al2O3) substrate.
[0040] The silicon (Si) substrate preferably has a (111) plane (which has a high atomic filling rate, such as a group III nitride crystal structure (HCP, hexagonal close packing)) as a growth plane, rather than a (100) plane and a (110) plane.
[0041] The silicon carbide (SiC) substrate is preferably a 4H-SiC substrate, which has the same crystal structure as the Group III nitride crystal structure (HCP) and has a minimal lattice constant difference, and is preferably grown on a Si polar surface.
[0042] An AlN nucleation region (120) is grown on a growth substrate (110).
[0043] The AlN nucleation region (120) is a region that promotes high-quality growth of the "AlN thick film" and the active region (160). In addition, in the case of a Si growth substrate, the AlN nucleation region (120) suppresses the melt-back etching phenomenon caused by the Si-Ga process reaction.
[0044] The AlN nucleation region (120) is part of the AlN stress control region (130) and can be grown under the same growth conditions as the AlN stress control region (130).
[0045] This embodiment is characterized by having an AlN stress control region (130) defined as an "AlN thick film" and an AlN buffer region (140) as substructures of an active region (160).
[0046] The AlN stress control region (130) is provided with AlN having an energy band gap of 6.2 eV and high resistivity.
[0047] The AlN stress control region (130) contains a large number of micron-sized air voids and / or nano-sized Al vacancies for stress control.
[0048] An AlN buffer region (140) is provided to address quality and reliability degradation phenomena occurring during doping of carbon (C) or iron (Fe) ions to grow conventional high-resistivity GaN materials, and is provided with AlN and does not include air voids or Al vacancies.
[0049] Here, the AlN stress control region (130) and the AlN buffer region (140) have a thickness difference.
[0050] The AlN stress control region (130) is set to be relatively thick and preferably has a thickness of 0.2 μm to 3 μm.
[0051] The AlN buffer region (140) is set to have a relatively thin thickness and preferably has a thickness of 0.01 μm to 1 μm.
[0052] The AlN stress control region (130) and the AlN buffer region (140), which are defined as "AlN thick films", prevent damage to the crystal quality of the active region (160) and the resulting leakage current.
[0053] In addition, since it has high electrical insulation, in addition to expensive semi-insulating materials, inexpensive conductive materials can also be used as the growth substrate.
[0054] In addition, it allows the rapid and easy release of a large amount of heat generated when driving a GaN HEMT power semiconductor device.
[0055] The active region (160) is grown on the AlN buffer region (140) and includes a GaN channel region (161) and an AlGaN barrier region (162).
[0056] Refer to Figure 2 Another embodiment of the present invention adds a back barrier region (150) to the Figure 1 embodiment.
[0057] The back barrier region (150) is grown on the AlN buffer region (140) before the growth of the active region (160) and is made of Al(1-z)Ga(z)N (0 < z < 1) containing gallium (Ga).
[0058] In addition, the back barrier region (150) can be formed of a multi-layer structure or a superlattice structure each composed of AlN, AlGaN, and GaN materials.
[0059] The back barrier region (150) has the following function: maximizing the effect of confining carrier electrons in the 2DEG generated in the channel region at the barrier / channel interface.
[0060] In addition, the back barrier region (150) has the following function: minimizing crystal defects by reducing the lattice constant difference between the materials of the AlN buffer region (140) and the GaN channel region (161), and eliminating microcracks by inducing compressive stress that compensates for tensile stress.
[0061] Next, refer to Figure 3The method for manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film according to the present invention comprises an AlN nucleation region growth step (S12), an AlN stress control region growth step (S13), an AlN buffer region growth step (S14) and an active region growth step (S16) on a manufactured growth substrate (110).
[0062] The AlN stress control region (130) contains a large number of micron-sized air voids and / or nano-sized Al vacancies for stress control.
[0063] AlN stress control regions with a large number of air voids can be grown using a carrier gas that moves the aluminum organometallic sources (TMAl, TEAl) into the MOCVD chamber, either as N2 alone or mixed with a small amount of H2 (ie, an N2-rich atmosphere).
[0064] The H2 carrier gas has an etching function, while the N2 gas does not have an etching function.
[0065] Therefore, when AlN thin films are grown using N2 alone or an N2-rich atmosphere, the AlN island particle size tends to be large and non-uniform, resulting in a rough surface.
[0066] At this time, air voids can be formed inside the AlN film by controlling the vertical growth (3D growth mode) speed and the horizontal growth (2D growth mode) speed.
[0067] The growth rate is controlled by controlling the growth pressure, V (N source) / III (Al source) ratio and growth temperature.
[0068] Furthermore, an AlN stress control region having a large number of air voids can be formed in another manner.
[0069] First, an AlN nucleation region (120) or a portion of an AlN stress control region is grown on the AlN nucleation region (120).
[0070] Afterwards, an AlN surface pattern structure is formed on a portion of the AlN nucleation region (120) or the AlN stress control region by photolithography and etching, and the AlN stress control region is completed by re-growth on the AlN surface pattern structure in MOCVD.
[0071] Here, for air void formation on the pattern structure, a nanoscale pattern structure and a horizontal growth rate relatively lower than a vertical growth rate are desired.
[0072] In addition, an AlN stress control region with a large number of air voids can also be formed by growing AlGaN or AlInN on an AlN nucleation region (120) at a predetermined growth temperature (Tg) and decomposing and evaporating Ga or In at a high temperature above Tg and in an H2 reducing atmosphere.
[0073] AlGaN grown at Tg is an alloy of AlN and GaN with different growth temperatures. When it is kept at a temperature higher than Tg and in a H2 or H2 reducing atmosphere for a certain period of time, AlGaN decomposes and GaN, a relatively low-temperature forming material, evaporates. As a result, porous AlN or AlGaN containing a large number of air voids is formed.
[0074] AlInN also has the same mechanism, but decomposes and evaporates at a relatively lower temperature than AlGaN.
[0075] In addition, the AlN stress control region with a large number of air voids can be formed to have a predetermined thickness using a 2-dimensional growth mode and a 3-dimensional growth mode. In the 2-dimensional growth mode, AlN is preferentially grown in the horizontal direction by a pulsed NH3 source supply, and in the 3-dimensional growth mode, AlN is preferentially grown in the vertical direction by a continuous NH3 source supply.
[0076] By combining a mechanism in which an ammonia (NH3) source is injected into an MOCVD reaction chamber along with an aluminum source (TMAl) to grow AlN in a 3D growth mode, and a mechanism in which an aluminum source is continuously injected while interrupting the injection of the ammonia source at predetermined time intervals to form AlN in a 2D growth mode, a thick AlN film including air voids can be formed. Specifically, it is preferred to have a 2D growth mode processing time that is longer than the 3D growth mode processing time.
[0077] In addition, an AlN stress-controlled region with a large number of Al vacancies can be formed by controlling the V (N source) / III (Al source) ratio below a predetermined growth pressure in MOCVD to generate a large number of Al vacancies, while using the concept of isoelectric co-doping to supply Ga or In sources during AlN growth.
[0078] During the process of forming AlN in a 3D growth mode, if the V (N source) / III (Al source) ratio is adjusted to be high, an AlN film containing a large number of aluminum vacancies can be grown.
[0079] The AlN buffer region (140) does not include air voids or Al vacancies and has solved the quality and reliability degradation phenomena that occur during the process of doping carbon (C) or iron (Fe) ions to grow conventional high-resistivity GaN materials.
[0080] The growth of the AlN buffer region (140) can be formed in a 2D growth mode using a carrier gas (H2 alone or mixed with a small amount of N2 (i.e., an H2-rich atmosphere)) used to move the aluminum organic metal source (TMAl, TEAl) into the MOCVD chamber.
[0081] When growing AlN in H2 alone or in an H2-rich atmosphere, the etching function of H2 suppresses the vertical growth rate while promoting the horizontal growth rate, thereby forming high-quality films with no or minimal air voids and aluminum vacancies.
[0082] Here, a 2D growth mode is used to minimize the density of threading dislocations, induced crystal defects in the AlN nucleation region.
Claims
1. A GaN HEMT epitaxial wafer based on an AlN thick film, the GaN HEMT epitaxial wafer based on an AlN thick film comprising: A growth substrate made of a semi-insulating material or a conductive material; An AlN nucleation region grown on the growth substrate; An AlN stress control region grown on the AlN nucleation region and having air voids or Al vacancies; An AlN buffer region grown on the AlN stress control region and not including the air voids and the Al vacancies; And An active region grown on the AlN buffer region and including a GaN channel region and an AlGaN barrier region.
2. The AlN thick film-based GaN HEMT epitaxial wafer according to claim 1, wherein: The growth substrate is made of Si having a (111) plane as a growth surface or 4H-SiC having a Si polar plane as a growth surface.
3. The AlN thick film-based GaN HEMT epitaxial wafer according to claim 1, wherein: The AlN stress control region is formed to be relatively thicker than the AlN buffer region, and the AlN stress control region is provided with a large number of air voids with a micron-sized dimension or Al vacancies with a nanometer-sized dimension.
4. The AlN thick film-based GaN HEMT epitaxial wafer according to claim 1 , further comprising a back barrier region formed of Al(1-z)Ga(z)N, wherein: 0 < z < 1, the back barrier region is grown on the AlN buffer region before the growth of the active region.
5. A method of manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film according to claim 1, the method comprising the following steps: Forming the AlN stress control region having a large number of air voids on the AlN nucleation region, and Wherein, the step of forming the AlN stress control region is performed using a carrier gas that moves an aluminum organometallic source TMAl, TEAl into a MOCVD chamber, and the carrier gas is a separate N2 or a gas mixed with a small amount of H2.
6. The method for manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film according to claim 5, wherein: The step of forming the AlN stress control region includes the following steps: after growing the AlN nucleation region by a MOCVD process or after growing a part of the AlN stress control region to a predetermined thickness, forming an AlN surface pattern structure by photolithography and etching; and completing the AlN stress control region by re-growth on the AlN surface pattern structure in MOCVD.
7. The method for manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film according to claim 5, wherein: The step of forming the AlN stress control region includes the following steps: after growing the AlN nucleation region, growing an AlGaN or AlInN material at a predetermined temperature (Tg) as a subsequent process, and decomposing and evaporating Ga or In in a high-temperature and H2 reduction atmosphere higher than Tg.
8. The method for manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film according to claim 5, wherein: The step of forming the AlN stress control region is performed by the following operation: forming a predetermined thickness by using a 2D growth mode and a 3D growth mode, in the 2D growth mode, AlN is preferentially grown in the horizontal direction by supplying a pulsed NH3 source, and in the 3D growth mode, AlN is preferentially grown in the vertical direction by supplying a continuous NH3 source.
9. A method of manufacturing a GaN HEMT epitaxial wafer based on an AlN thick film according to claim 1, the method comprising the following steps: forming the AlN stress control region having a large number of Al vacancies on the AlN nucleation region, and The step of forming the AlN stress control region with a large number of Al vacancies is performed by controlling the N source V / Al source III ratio below a predetermined growth pressure in MOCVD, and supplying Ga source and In source for isoelectric co-doping during AlN growth.
10. The method for manufacturing an AlN thick film-based GaN HEMT epitaxial wafer according to claim 5, further comprising the following steps: forming the AlN buffer region on the AlN stress control region, and The step of forming the AlN buffer region is performed in a 2D growth mode and by using H 2 alone or an H 2 -rich atmosphere as a carrier gas for moving the aluminum organic metal sources TMAl and TEAl into the MOCVD chamber.