GaN HEMT epitaxial wafer based on AlN thick film and manufacturing method of the same

Abstract

The disclosed AlN thick film-based GaN HEMT epitaxy wafer comprises: a growth substrate provided with 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 an air void or an Al vacancy; an AlN buffer region grown on the AlN stress control region and not containing an air void or an Al vacancy; and an active region grown on the AlN buffer region and including a GaN channel region and an AlGaN barrier region.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a GaN HEMT power semiconductor epitaxy wafer, and to a GaN HEMT power semiconductor epitaxy wafer and a method for manufacturing the same, characterized by utilizing an AlN thick film having excellent physical properties of both electrical insulation and heat dissipation ability. Background Technology

[0002] The epitaxy structure of a GaN HEMT power semiconductor typically has a structure in which a nucleation region, a stress-relieving region, a buffer region, a channel region, and a barrier region are sequentially stacked on a growth substrate.

[0003] In the epitaxy structure of a GaN HEMT power semiconductor, the channel and barrier regions are key active regions, separate from the underlying structure.

[0004] Al 1-y Ga y Even without intentional dopant doping at the interface of the GaN channel region, which has a small energy bandgap, at the N (barrier) / GaN (channel) heterojunction, a horizontal channel with a high electron density of 2DEG (2-dimensional electron gas) is formed due to the polarization phenomenon of the group 3 nitride semiconductor.

[0005] Polarization intensity is Al 1-y Ga y N's Al composition and Al 1-y Ga y It is determined by the thickness of N, and typically, the thickness is controlled by the Al composition.

[0006] In some cases, Al on top of the GaN channel region 1-y Ga yPrior to growing the N barrier region, it is possible to introduce an AlN thin film with a thickness of less than 5 nm.

[0007] Al 1-y Ga y Depending on the case, a capping region or p-type group 3 nitride (GaN, AlGaN, AlInN, AlGaInN) thin film can be grown on top of the N barrier region.

[0008] The buffer region performs the role of current blocking by reducing vertical leakage current through high-resistive properties, and typically achieves this purpose using GaN materials doped with carbon (C) or iron (Fe) as a dopant (C-doped or Fe-doped GaN).

[0009] However, typically, when growing C- or Fe-doped GaN, a phenomenon occurs in which the GaN crystal quality deteriorates.

[0010] Therefore, developing optimal growth conditions between the growth substrate and the active region is a challenge in the relevant technology field. Prior art literature

[0011] Korean Registered Patent No. 10-2615809 The problem to be solved

[0012] The present invention aims to provide a structure and method for solving the problem of performance and quality degradation caused by vertical leakage current resulting from surface damage to the growth substrate during growth, which occurs when silicon carbide (SiC) or silicon (Si) material is generally used as a semi-insulating growth substrate to design and fabricate a GaN HEMT power semiconductor epitaxy wafer having a horizontal channel structure.

[0013] The present invention aims to provide a structure and method that can solve the problem that, although an electrically conductive growth substrate is much less expensive than a semi-insulating growth substrate material (SiC, Si), a sublayer of an active region (channel & barrier) with enhanced electrical insulation is absolutely necessary before growing a GaN HEMT active region (channel, barrier) in order to use a conductive growth substrate.

[0014] The present invention aims to provide a structure and method capable of solving the problem that a lower layer of the active region (channel & barrier) must be made of a material with high thermal conductivity in order to quickly and easily dissipate a large amount of heat generated during the operation of a GaN HEMT power semiconductor device designed and fabricated on a silicon carbide (SiC) or silicon (Si) growth substrate. means of solving the problem

[0015] Embodiments according to the present invention include an AlN thick film-based GaN HEMT epitaxy wafer comprising: a growth substrate provided with 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 an air void or an Al vacancy; an AlN buffer region grown on the AlN stress control region and not containing an air void or an Al vacancy; and an active region grown on the AlN buffer region and including a GaN channel region and an AlGaN barrier region.

[0016] Here, the growth substrate may be provided with Si having a (111) plane as the growth plane or 4H-SiC having a Si-polar face as the growth plane.

[0017] The above AlN stress control region is formed relatively thicker than the above AlN buffer region, and the above AlN stress control region may be provided with a large amount of micro-level size air voids or nano-level size Al vacancies.

[0018] Al containing gallium (Ga) is grown on the above AlN buffer region prior to the growth of the above active region. 1-z Ga z It may include a back barrier region equipped with N.

[0019] Embodiments according to the present invention are a method for manufacturing an AlN thick film-based GaN HEMT epitaxial wafer, wherein the step of forming an AlN stress control region having a large amount of air voids is performed by using a carrier gas that moves an aluminum organometallic source (TMAl, TEAl) into an MOCVD chamber as N2 alone or a gas mixed with a small amount of H2 (i.e., an atmosphere with an excess of N2).

[0020] Here, the step of forming the AlN stress control region may include: a step of forming an AlN surface patterning through lithography and etching after growing the AlN nucleation region by an MOCVD process or after growing a part of the AlN stress control region to a predetermined thickness; and a step of completing the AlN stress control region by regrowth on the AlN surface patterning within the MOCVD.

[0021] The step of forming the AlN stress control region may include growing the AlN nucleation region, then growing an AlGaN or AlInN material in a continuous subsequent process at a predetermined temperature (Tg), and decomposing and evaporating Ga or In at a high temperature higher than Tg and in an H2 reducing atmosphere.

[0022] The step of forming the above AlN stress control region can be formed with a set thickness using a 2-dimensional growth mode that preferentially grows AlN in the horizontal direction through pulsed NH3 source supply and a 3-dimensional growth mode that preferentially grows AlN in the vertical direction through continuous NH3 source supply.

[0023] The step of forming an AlN stress control region that is grown on the above AlN nucleation region and has a large amount of Al vacancies; is preferably to generate a large amount of Al vacancies by controlling the V (N source) / III (Al source) ratio at a growth pressure below a predetermined growth pressure in MOCVD, and to supply a Ga or In source during AlN growth using the concept of isoelectric co-doping.

[0024] The step of forming an AlN buffer region on the above AlN stress control region can be formed in a 2D growth mode by using a carrier gas that moves an aluminum organometallic source (TMAl, TEAl) into the MOCVD chamber, either H2 alone or a gas mixed with a small amount of N2.

[0025] Here, the 2D growth mode functions to minimize the density of threading dislocations and crystal defects caused in the AlN nucleation region. Effects of the invention

[0026] According to the present invention, by introducing an AlN stress control region and an AlN buffer region defined as an 'AlN thick film,' it is possible to form a sublayer having excellent electrical insulation for the active region not only on semi-insulating growth substrates but also on relatively low-cost conductive growth substrates.

[0027] According to the present invention, the 'AlN thick film' can prevent performance and quality degradation caused by vertical leakage current resulting from surface damage to the growth substrate during growth.

[0028] According to the present invention, sufficient thermal conductivity can be secured to quickly and easily dissipate a large amount of heat generated during the operation of a GaN HEMT power semiconductor device by means of an 'AlN thick film'.

[0029] According to the present invention, Al on the AlN buffer region 1-z Ga z By forming a back barrier region equipped with N, the confinement effect of 2DEG carrier electrons generated on the side of the channel region at the barrier / channel interface can be maximized.

[0030] In addition, it functions to minimize crystal defects by mitigating the difference in lattice constants between the AlN buffer region and the GaN channel region, and simultaneously eliminate microcracks by inducing condensation stress that compensates for tensile stress.

[0031] According to the present invention, when designing and fabricating GaN power semiconductor HEMT devices using an 'AlN thick film' having excellent properties of both electrical insulation and heat dissipation, performance and quality can be dramatically improved.

[0032] In addition, since the 'AlN thick film' is composed of a single material, the growth process time is shortened, enabling the mass production of high-cost GaN HEMT devices at a reduced cost. Brief explanation of the drawing

[0033] FIG. 1 is a cross-section of a GaN HEMT power semiconductor epitaxy wafer according to one embodiment of the present invention. FIG. 2 is a cross-section of a GaN HEMT power semiconductor epitaxy wafer according to another embodiment of the present invention. FIG. 3 is a drawing for explaining a method for manufacturing a GaN HEMT power semiconductor epitaxy wafer according to an embodiment of the present invention. Specific details for implementing the invention

[0034] Hereinafter, an AlN thick film-based GaN HEMT epitaxy wafer and a method for manufacturing the same according to embodiments of the present invention will be described in detail with reference to the drawings.

[0035] In this process, the thicknesses of the layers or regions depicted in the drawings are exaggerated for the sake of clarity in the specification. Furthermore, the terms used below are selected for the convenience of explanation and should not be limited to their dictionary meanings but should be interpreted in a sense consistent with the technical concept of the present invention.

[0036] First, the structure of a GaN HEMT power semiconductor epitaxy wafer according to one embodiment of the present invention will be described.

[0037] Referring to FIG. 1, 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) may be provided with a semi-insulating material or a conductive material.

[0039] The growth substrate (110) may be, for example, a silicon (Si) substrate, a silicon carbide (SiC) substrate, or an aluminum oxide substrate. The aluminum oxide substrate may be, for example, a sapphire (Al2O3) substrate.

[0040] It is preferable that the silicon (Si) growth substrate be grown on the (111) plane, which has a higher atomic packing rate than the (100) and (110) planes, such as the group 3 nitride crystal structure (HCP).

[0041] For silicon carbide (SiC) growth substrates, a 4H-SiC growth substrate with the smallest difference in lattice constants and a crystal structure identical to that of group 3 nitride crystal structure (HCP) is preferred, and it is desirable to grow on a Si-polar face.

[0042] The AlN nucleation region (120) is grown on the growth substrate (110).

[0043] The AlN nucleation region (120) is a region that promotes the growth of the 'AlN thick film' and the active region (160). In addition, in the case of a Si growth substrate, it suppresses the Melt Back Etching phenomenon caused by the Si-Ga eutectic reaction.

[0044] The AlN nucleation region (120) is not limited to growing separately from the AlN stress control region (130), but includes growing simultaneously as part of the AlN stress control region (130) under the same growth conditions as the AlN stress control region (130).

[0045] The present embodiment is characterized by having an AlN stress control region (130) and an AlN buffer region (140) as an AlN thick film between the growth substrate (110) and the active region (160).

[0046] The AlN stress control region (130) is a conventional Al composed of two or three layers through a change in gallium (Ga) composition (x).1-x Ga x Instead of N material, it is composed of a high-resistance AlN material having an energy band gap of 6.2 eV.

[0047] Additionally, the AlN stress control region (130) contains a large amount of micro-level sized air voids or nano-level sized Al vacancies for stress control.

[0048] The AlN buffer region (140) solves the problem of quality and reliability degradation that occurs in the process of doping carbon (C) or iron (Fe) ions to grow conventional high-resistance GaN materials, and does not contain air voids or Al vacancies.

[0049] Here, the AlN stress control region (130) and the AlN buffer region (140) differ in thickness.

[0050] The AlN stress control region (130) is provided relatively thick, and it is preferable to provide a thickness of 0.2 to 3 μm.

[0051] The AlN buffer region (140) is provided with a relatively thin thickness, and preferably with a thickness of 0.01 to 1 μm.

[0052] The AlN stress control region (130) and the AlN buffer region (140) are defined as an 'AlN thick film', and the 'AlN thick film' prevents damage to the crystal quality of the active region (160) and the resulting leakage current.

[0053] In addition, by adding an expensive semi-insulating material as a growth substrate, it enables the use of an inexpensive electrically conductive material to provide electrical insulation.

[0054] In addition, a large amount of heat generated when operating a GaN HEMT power semiconductor device designed and manufactured in the active area (160) is quickly and easily released to the outside.

[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] Referring to FIG. 2, another embodiment of the present invention adds a back barrier region (150) to the embodiment of FIG. 1.

[0057] The back barrier region (150) is grown on the AlN buffer region (140) before the growth of the active region (160), and is an Al containing gallium (Ga). 1-z Ga z N(0 <z<1)로 구비된다.

[0058] Additionally, the back barrier region (150) may be provided with a multi-layer structure or a superlattice structure composed of AlN, AlGaN, and GaN materials, respectively.

[0059] The back barrier region (150) functions to maximize the confinement of 2DEG carrier electrons generated on the side of the channel region of the barrier / channel interface.

[0060] Additionally, the back barrier region (150) functions to minimize crystal defects by mitigating the difference in lattice constants between the materials of the AlN buffer region (140) and the GaN channel region (161), and simultaneously eliminate microcracks by inducing condensation stress that compensates for tensile stress.

[0061] Next, a method for manufacturing an AlN thick film-based GaN HEMT epitaxy wafer according to the present invention will be described.

[0062] Referring to FIG. 3, the method for manufacturing an AlN thick film-based GaN HEMT epitaxy wafer according to the present invention comprises, on a prepared growth substrate (110), 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).

[0063] Here, since the present invention is characterized by an 'AlN thick film', there are no special limitations on the AlN nucleation region growth step (S12) and the active region growth step (S16).

[0064] Below, examples of the AlN stress control region growth step (S13) and the AlN buffer region growth step (S14) will be described.

[0065] As previously explained, the AlN stress control region (130) contains a large amount of micro-level sized air voids or nano-level sized Al vacancies for stress control.

[0066] An AlN stress-controlled region having a large amount of air voids can be grown by using N2 alone or a gas mixed with a small amount of H2 (i.e., an atmosphere with excess N2) as the carrier gas that moves the aluminum organometallic source (TMAl, TEAl) into the MOCVD chamber.

[0067] Typically, H2 carrier gas has an etching function, whereas N2 gas does not.

[0068] Therefore, when growing AlN thin films using a carrier gas with an atmosphere of N2 alone or an excess of N2, the AlN island particle diameter tends to be large and non-uniform, resulting in a rough surface; thus, air voids can be formed inside the AlN thin film by controlling the growth pressure, V (N source) / III (Al source) ratio, and growth temperature to control the growth rate in the vertical direction (3D growth mode) and the growth rate in the horizontal direction (2D growth mode).

[0069] An AlN stress control region having a large amount of air voids can be formed by growing an AlN nucleation region (120) in an MOCVD process, or growing a part of the AlN stress control region to a predetermined thickness on the AlN nucleation region (120), then forming an AlN surface patterning through lithography and etching, and subsequently completing the AlN stress control region by regrowth on the AlN surface patterning in MOCVD.

[0070] Specifically, air voids can be formed on the pattern by patterning at the nanometer scale and lowering the growth rate in the horizontal direction (2D growth mode) compared to the growth rate in the vertical direction.

[0071] An AlN stress control region having a large amount of air voids is formed by growing an AlGaN or AlInN material in a continuous subsequent process at a predetermined temperature (Tg) after growing an AlN nucleation region (120), and then decomposing and evaporating Ga or In at a high temperature higher than Tg and in an H2 reducing atmosphere.

[0072] AlGaN compounds grown at a specific temperature (Tg) are alloyed with AlN and GaN materials, each with different growth temperatures. If maintained for a specified time in an atmosphere of H2 alone or an excess reduction of H2 at a temperature higher than Tg, the AlGaN compound decomposes, and the GaN, which is a relatively low-temperature forming material, evaporates, resulting in porous AlN or a thick AlGaN film containing a large amount of air voids. Like AlGaN compounds, AlInN compounds are formed by the same mechanism, but they decompose and evaporate at a relatively lower temperature than AlGaN compounds.

[0073] An AlN stress control region having a large amount of air voids is formed to a set thickness using a 2-dimensional growth mode that preferentially grows AlN in the horizontal direction through pulsed NH3 source supply and a 3-dimensional growth mode that preferentially grows AlN in the vertical direction through continuous NH3 source supply.

[0074] By combining a mechanism in which an AlN material layer is grown in a 3D growth mode when an ammonia (NH3) source is injected into an MOCVD reaction chamber together with an aluminum source (TMAl), while an AlN material layer is formed in a 2D growth mode when the ammonia source is injected at predetermined time intervals while the aluminum source is continuously injected, a thick AlN film containing air voids can be formed. In particular, it is desirable to have a longer process time in the 2D growth mode than in the 3D growth mode.

[0075] Meanwhile, the AlN stress control region having a large amount of Al vacancies is formed by generating a large amount of Al vacancies through V (N source) / III (Al source) ratio control at a growth pressure below a predetermined level in MOCVD, and by supplying a Ga or In source during AlN growth using the concept of isoelectric co-doping.

[0076] When forming an AlN material layer in 3D growth mode, if the aluminum source is injected relatively less than the ammonia source to control the V(N source) / III(Al source) ratio to be high, it is possible to grow an AlN thin film containing a large amount of aluminum vacancies.

[0077] Next, the method for forming the AlN buffer region (140) is described.

[0078] As previously explained, the AlN buffer region (140) solves the problem of quality and reliability degradation that occurs in the process of doping carbon (C) or iron (Fe) ions to grow conventional high-resistance GaN materials, and does not contain air voids or Al vacancies.

[0079] The growth of the AlN buffer region (140) on the AlN stress control region (130) can be formed in a 2D growth mode using a carrier gas that moves an aluminum organometallic source (TMAl, TEAl) into the MOCVD chamber, either H2 alone or a gas mixed with a small amount of N2 (i.e., an atmosphere with excess H2).

[0080] Growing AlN in an H2-only or H2-excessive atmosphere suppresses the growth rate in the vertical direction through etching, while promoting the growth rate in the horizontal direction, making it possible to form high-quality thin (thick) films with no or minimized air voids and aluminum vacancies.

[0081] Here, the 2D growth mode functions to minimize the density of threading dislocations and crystal defects caused in the AlN nucleation region.

[0082] The embodiments of the present invention described above introduce an AlN stress control region defined as an 'AlN thick film' and an AlN buffer region, wherein the AlN stress control region is configured to contain a large amount of micro-level sized air voids or nano-level sized Al vacancies, and the AlN buffer region does not contain air voids or Al vacancies.

[0083] Accordingly, a sublayer having excellent electrical insulation for the active region can be formed not only on semi-insulating growth substrates but also on relatively low-cost conductive growth substrates.

[0084] In addition, surface damage to the growth substrate during growth can prevent performance and quality degradation caused by vertical leakage current.

[0085] In addition, sufficient thermal conductivity can be secured to quickly and easily dissipate a large amount of heat generated during the operation of GaN HEMT power semiconductor devices.

[0086] In addition, when designing and fabricating GaN power semiconductor HEMT devices by utilizing an 'AlN thick film' that has excellent properties for both electrical insulation and heat dissipation, performance and quality can be dramatically improved.

[0087] In addition, since the 'AlN thick film' is composed of a single material, the growth process time is shortened, enabling the mass production of high-cost GaN HEMT devices at a reduced cost.

Claims

Claim 1 An AlN thick-film based GaN HEMT epitaxy wafer comprising: a growth substrate provided with 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 containing nano-level sized Al vacancies generated by a Ga or In source supplied by an isoelectric co-doping concept; an AlN buffer region grown on the AlN stress control region and not containing air voids or Al vacancies; and an active region grown on the AlN buffer region and including a GaN channel region and an AlGaN barrier region. Claim 2 The GaN HEMT epitaxial wafer based on an AlN thick film according to claim 1, wherein the growth substrate is provided with Si having a (111) plane as the growth plane or 4H-SiC having a Si-polar face as the growth plane. Claim 3 In claim 1, the AlN stress control region is formed relatively thicker than the AlN buffer region, and the AlN stress control region is an AlN thick film-based GaN HEMT epitaxy wafer having a large amount of nano-level sized Al vacancies. Claim 4 In claim 1, Al comprising gallium (Ga) is grown on the AlN buffer region prior to the growth of the active region. 1-z Ga z An AlN thick film-based GaN HEMT epitaxy wafer comprising a back barrier region provided by N. Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 A method for manufacturing an AlN thick film-based GaN HEMT epitaxy wafer according to claim 1, comprising the step of forming an AlN stress control region grown on the AlN nucleation region and having a large amount of Al vacancies; wherein the step of forming the AlN stress control region generates a large amount of Al vacancies by controlling the V (N source) / III (Al source) ratio at a growth pressure below a predetermined growth pressure in the MOCVD, and supplies a Ga or In source during AlN growth under the concept of isoelectric co-doping. Claim 10 A method for manufacturing an AlN thick-film-based GaN HEMT epitaxy wafer according to claim 9, comprising the step of forming an AlN buffer region on the AlN stress control region; wherein the step of forming the AlN buffer region is performed by using a carrier gas that moves an aluminum organometallic source, such as TMAl or TEAl, into an MOCVD chamber, and the carrier gas is H2 alone or a gas mixed with a small amount of N2, and the AlN buffer region is formed in a 2D growth mode.

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