Epitaxial wafer for GaN HEMT with enhanced electrical insulation and method of manufacturing same

Abstract

An epitaxial wafer for a GaN HEMT having enhanced electrical insulation and a method of manufacturing the same are provided according to an embodiment of the present invention, the epitaxial wafer comprising: a growth substrate; a nucleation region, wherein the nucleation region is grown on the growth substrate; and a high resistance region having high resistance characteristics, the high resistance region including a high resistance cell region defined by a first region grown as a group III nitride semiconductor doped with carbon and a second region grown as a group III nitride semiconductor on the first region, the high-resistance region is arranged on the nucleation region; and an active region including a channel region grown on the high resistance region and a barrier region grown on the channel region.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an epitaxial wafer for a GaN HEMT having enhanced electrical insulation and a method of manufacturing the same, and more particularly, to an epitaxial wafer for a GaN HEMT having enhanced electrical insulation and a method of manufacturing the same, which can electrically insulate a channel region and a growth substrate while using a semi-electrically insulating substrate and an inexpensive electrically conductive substrate as the growth substrate, and can significantly improve the film quality of the channel region. BACKGROUND

[0002] An epitaxial wafer for a GaN HEMT power semiconductor having a horizontal channel structure generally requires a semi-insulating growth substrate, and uses materials such as silicon carbide (SiC) and silicon (Si).

[0003] The semi-insulating SiC substrate and the Si material growth substrate have surface damage (surface damage) during the growth of the epitaxial layer, which creates a leakage current path in the vertical direction, resulting in degradation of performance and quality.

[0004] To solve this problem, a high-resistance region grown of GaN doped with carbon or iron is introduced before growing the active region (channel region, barrier region).

[0005] However, this causes degradation of the crystal quality of the active region.

[0006] Therefore, it is essential to develop a technology that can use a semi-insulating substrate or an electrically conductive substrate as a growth substrate while minimizing the occurrence of crystal defects on the surface of the active region, improving the film quality of the active region, and minimizing the possibility of a leakage current path in the vertical direction. SUMMARY

[0007] TECHNICAL PROBLEM

[0008] The present invention aims to provide an epitaxial wafer for a GaN HEMT having enhanced electrical insulation and a method of manufacturing the same, which can not only use a semi-insulating substrate but also use an inexpensive electrically conductive substrate as a growth substrate, and can improve the high-resistance characteristics and film formation quality of the active region.

[0009] TECHNICAL SOLUTION

[0010] An epitaxial wafer for a GaN HEMT having enhanced electrical insulation according to an embodiment of the present application includes: a growth substrate; a nucleation region grown on the growth substrate; a high-resistance region having a high-resistance characteristic, the high-resistance region including a high-resistance unit region defined by a first region grown as a Group III nitride semiconductor doped with carbon and a second region grown as a Group III nitride semiconductor on the first region, the high-resistance region disposed on the nucleation region; and an active region including a channel region grown on the high-resistance region and a barrier region grown on the channel region.

[0011] In an embodiment according to the present application, the high-resistance region is provided by laminating the high-resistance unit region two or more times.

[0012] In an embodiment according to the present application, the first region is provided with a carbon doping concentration of 5 x 10 17 / cm 3 or more, preferably 1 x 10 18 / cm 3 or more.

[0013] In an embodiment according to the present application, the first region is formed of one of aluminum nitride (AlN), aluminum gallium nitride (AlGaN), or gallium nitride (GaN), and the second region is formed of aluminum nitride (AlN).

[0014] In an embodiment according to the present application, a high-resistance GaN region made of aluminum gallium nitride (AlGaN) or gallium nitride (GaN) can be further included between the high-resistance region and the active region.

[0015] An embodiment of a manufacturing method according to the present application provides a method for manufacturing an epitaxial wafer for a GaN HEMT having enhanced electrical insulation, the method including the steps of: preparing a growth substrate; forming a nucleation region by epitaxially growing a nucleation region on the growth substrate; forming a first region by epitaxially growing a carbon-doped Group III nitride semiconductor layer on the nucleation region; forming a second region by epitaxially growing a Group III nitride semiconductor layer on the first region at a relatively higher temperature than that of the first region forming step; repeating the steps of forming the first region and the second region; and forming an active region by a channel region formed on the second region and a barrier region grown on the channel region, the channel region having a band gap smaller than that of the second region.

[0016] In an embodiment of the manufacturing method according to the present application, the growth substrate is formed of silicon carbide (SiC) and silicon (Si) materials, the nucleation region is formed of aluminum nitride (AIN), the first region is formed of one of aluminum nitride (AIN), aluminum gallium nitride (AlGaN), and gallium nitride (GaN), and the second region is formed of aluminum nitride (AIN).

[0017] In an embodiment of the manufacturing method according to the present application, the first region forming step is performed at a temperature of 900°C to 1100°C, and the second region forming step is performed at a temperature of 1150°C to 1300°C.

[0018] In an embodiment of the manufacturing method according to the present application, the method further includes a step of forming a high-resistance GaN region made of aluminum gallium nitride (AlGaN) or gallium nitride (GaN) between the high-resistance region and the active region.

[0019] In an embodiment of the manufacturing method according to the present application, the first region forming step is performed at a V / III ratio of 250 to 400 and a pressure of 50 mbar to 70 mbar.

[0020] Advantageous Effects

[0021] According to the present application, by employing a high-resistance region structure in which a high-concentration carbon-doped group III nitride semiconductor layer epitaxially grown at a low temperature and a group III nitride semiconductor layer grown at a high temperature are repeatedly laminated, even when a semi-electrically insulating substrate and an electrically conductive substrate are used as a growth substrate, electrical insulation between a channel region and a growth substrate can be achieved, and film formation quality of the channel region can be significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a diagram illustrating an epitaxial wafer for a GaN HEMT with enhanced electrical insulation according to an embodiment of the present application.

[0023] Figure 2 is a diagram illustrating an epitaxial wafer for a GaN HEMT with enhanced electrical insulation according to another embodiment of the present application.

[0024] Figures 3 to 8 is a diagram illustrating a method for manufacturing an epitaxial wafer for a GaN HEMT with enhanced electrical insulation according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of an epitaxial wafer for a GaN HEMT with enhanced electrical insulation and a manufacturing method thereof according to the present application will be described in detail with reference to the accompanying drawings.

[0026] The terms used in the following are selected for the purpose of facilitating description and should be appropriately interpreted as having meanings consistent with the inherent spirit of the disclosure, and are not limited to the meanings in the dictionaries at the time of finding the spirit of the disclosure.

[0027] Reference Figure 1 An epitaxial wafer for a GaN HEMT having enhanced electrical insulation according to an embodiment of the present application includes a growth substrate 100, a nucleation region 200, a high resistance region 300, and an active region 400.

[0028] The growth substrate 100 can be a conductive or semi-insulating substrate.

[0029] The nucleation region 200 is epitaxially grown on the growth substrate 100.

[0030] The high resistance region 300 has a first region 310 on a lower side and a second region 320 on an upper side.

[0031] The first region 310 is formed as a carbon-doped group III nitride semiconductor layer on the nucleation region 200.

[0032] The second region 320 is formed as a group III nitride semiconductor layer on the first region 310.

[0033] The second region 320 has a function of recovering crystallinity damaged by carbon (C) doping during growth of the first region 310.

[0034] To this end, it is desirable to make the growth temperature of the second region 320 higher than the growth temperature of the first region 310.

[0035] The active region 400 includes a channel region 410 formed on the second region 320 and a barrier region 420 formed on the channel region 410.

[0036] The channel region 410 has a 2DEG (two-dimensional electron gas) formed by a gate voltage applied by a gate electrode formed on an upper side of the barrier region 420.

[0037] The active region 400 can further include a group III nitride p-type semiconductor layer, a passivation layer, or a cap layer formed on the barrier region 420.

[0038] The band gap of the second region 320 is set to be greater than the band gap of the channel region 410.

[0039] The channel region 410 is electrically insulated due to the second region 320 having a greater band gap than the channel region 410.

[0040] The growth substrate 100 is preferably made of silicon carbide (SiC) or silicon (Si), which is a semi-insulating or conductive material. Since it is relatively inexpensive, it can ensure high cost-effectiveness of the GaN HEMT.

[0041] The nucleation region 200 can be formed of aluminum nitride (AlN).

[0042] The first region 310 is preferably formed of one of aluminum nitride (AlN), aluminum gallium nitride (AlGaN), and gallium nitride (GaN), and the second region 320 is preferably formed of aluminum nitride (AlN).

[0043] The second region 320 minimizes an adverse effect on the film quality of the channel region 410, thereby achieving high quality of the channel region 410.

[0044] Since the energy band gap of the second region 320 is greater than that of the channel region 410, the channel region 410 and the second region 320 are a heterojunction structure.

[0045] Accordingly, an energy barrier is formed in each of the conduction band and the valence band from the channel region 410 toward the second region 320.

[0046] The energy barrier prevents electrons in the conduction band and holes in the valence band from leaking outside the lower portion of the channel region 410, i.e., the second region 320.

[0047] Accordingly, the second region 320 has a high resistance characteristic, i.e., an electrically insulating characteristic.

[0048] The resistance characteristic of the second region 320 formed due to the difference in the energy band gap is more stable than a high resistance characteristic formed by implanting impurities or the like.

[0049] A high-resistivity region grown with carbon or iron-doped GaN used in a conventional GaN HEMT structure obtains its resistivity by internally implanting carbon or iron as a trap.

[0050] However, since carbon or iron has an energy level that varies depending on temperature, there is a problem in ensuring resistance over a wide temperature range, particularly at high temperatures.

[0051] In contrast, as in the present embodiment, since the high resistance due to the energy barrier formed due to the difference in the band gap between different materials is not sensitive to temperature changes, even over a wide temperature range, the phenomenon of an increase in leakage current is minimized, thus having the advantage of being usable over a wide temperature range.

[0052] The first region 310 is resistive due to carbon doping.

[0053] The carbon doping concentration of the first region 310 is 5 x 10 17 / cm 3 or more, preferably 1 x 10 18 / cm 3 or more.

[0054] The first region 310 formed using AlN or GaN doped with a high concentration of carbon together with the undoped second region 320 forms a high resistance region and provides enhanced high resistance characteristics.

[0055] Next, referring to Figure 2 , the first region 310 and the second region 320 are sequentially and repeatedly grown two or more times to form the high resistance region 300.

[0056] At this time, the laminated first region 310 and the second region 320 are defined as a high resistance cell region. That is, the present embodiment is provided with a high resistance cell region laminated two or more times.

[0057] Accordingly, electrical insulation is enhanced, and it is advantageous to minimize tensile stress applied to the active region 400, particularly the channel region 410.

[0058] In addition, when the first region 310 and the second region 320 are repeatedly laminated, stress applied from the growth substrate is reduced in the second region 320 laminated on the upper side and the first region 310.

[0059] Accordingly, the second region 320 repeatedly laminated has the effect of further improving the film formation quality of the uppermost second region 320 in proportion to the number of times it is laminated.

[0060] Meanwhile, Figure 1 and Figure 2 The embodiment of the present application can further include a carbon layer (carbonization layer) formed as a Si-C bonding layer between the growth substrate 100 and the nucleation region 200.

[0061] It is preferable that the carbonization layer 150 be formed in an amorphous, polycrystalline, or single-crystal form to have a thickness of 0.1 nm to 10 nm.

[0062] Figure 1 and Figure 2 The embodiment of the present application forms a further enhanced high resistance region by sequentially growing the first region 310 and the second region 320 to overlap the unique high resistance characteristics of each region.

[0063] The first region 310 achieves a high resistance characteristic through carbon doping, and the second region 320 achieves a high resistance characteristic by utilizing an energy barrier due to a band gap difference.

[0064] The second region 320 must be epitaxially grown to have excellent film quality and a low defect density.

[0065] To this end, the second region 320 is grown at a temperature higher than the growth temperature of the first region 310.

[0066] The second region 320 having excellent film quality and a low defect density maintains excellent film quality of the channel region 410.

[0067] The nucleation region 200 has a thickness of less than 100 nm, and is generally grown on the growth substrate 100 with a thickness of several tens of nm.

[0068] If the second region 320 is directly grown on the nucleation region 200, problems such as cracking and delamination are expected to occur due to stress generated due to a difference in a lattice constant from the growth substrate 100.

[0069] The stress generation forms various leakage paths, which is a main cause of loss of the high resistance characteristic, i.e., the insulation function, of the second region 320.

[0070] To this end, in order to achieve stable growth of the second region 320 grown at a high temperature, it is necessary to first form the first region 310 between the nucleation region 200 and the second region 320.

[0071] The first region 310 serves as a stress buffer, which can minimize stress generated when the second region 320 is grown at a high temperature.

[0072] Meanwhile, in order to minimize stress generated due to a difference in a lattice constant and a thermal expansion coefficient between the first region 310 and the second region 320, it is preferable that the first region 310 be made of the same material as the second region 320.

[0073] Meanwhile, it is desirable to minimize stress generation between the first region 310 and the growth substrate 100.

[0074] To this end, the first region 310 is grown at a relatively low temperature.

[0075] In addition, the first region 310 should be carbon-doped to prevent crystal defects and deterioration of resistance characteristics due to low-temperature growth, and a high concentration of at least 5 x 1019 17 / cm 3 is desirable.

[0076] Next, an embodiment of a manufacturing method according to the present application will be described with reference to Figures 3 to 8 This is characterized by a method of forming the first region 310 and the second region 320.

[0077] Referring to

[0078] Figures 3 to 8 ​The method for manufacturing an epitaxial wafer for a GaN HEMT having enhanced electrical insulation according to the present embodiment includes a growth substrate preparation step (S100), a nucleation region formation step (S200), a first region formation step (S300), a second region formation step (S400), and an active region formation step (S500).

[0079] Before the active region is formed, it is preferable to include a step of repeating the steps of forming the first region and the second region (S300, S400).

[0080] The growth substrate preparation step (S100) prepares a conductive or semi-insulating growth substrate 100.

[0081] The growth substrate 100 is preferably selected from silicon carbide (SiC) and silicon (Si) wafer materials.

[0082] The nucleation region formation step (S200) epitaxially grows a nucleation region 200 on the growth substrate 100.

[0083] The nucleation region 200 is preferably made of an aluminum nitride (AlN) material.

[0084] The first region formation step (S300) grows a first region 310 as a carbon-doped III-nitride semiconductor layer on the nucleation region 200.

[0085] The second region formation step (S400) forms a second region 320 as a III-nitride semiconductor layer on the first region 310 at a relatively higher temperature than the first region formation step (S300).

[0086] In the active region formation step (S500), a channel region 410 and a barrier region 420 are sequentially formed.

[0087] The material forming the second region 320 has a higher energy band gap than the material forming the channel region 410.

[0088] The first region 310 is preferably made of aluminum nitride (AlN), aluminum gallium nitride (AlGaN), and gallium nitride (GaN), and the second region 320 is preferably made of aluminum nitride (AlN).

[0089] The first region formation step (S300) is performed at a temperature of 900°C to 1100°C, and the second region formation step (S400) is performed at a temperature of 1150°C to 1300°C.

[0090] The first region formation step (S300) is performed such that the carbon-doped concentration of the first region 310 is 5 x 10 17 / cm 3or more. Preferably, it is 1 x 10 18 / cm 3 or more.

[0091] At this time, the first region forming step S300 is preferably performed at a V / III ratio of 250 to 400 and a pressure of 50 mbar to 70 mbar.

[0092] The second region forming step (S400) can be implemented with aluminum nitride (AlN) having excellent crystallinity.

[0093] Due to the large energy band gap (6.2 eV) of aluminum nitride (AlN), the flow of electrons as conduction band carriers and holes as valence band carriers is blocked.

[0094] Therefore, since it has resistance, it hardly generates heat and can maintain high resistance while being stable regardless of temperature changes.

[0095] In addition, the second region 320 having excellent crystallinity can achieve excellent film quality of the channel region 410 grown thereon.

[0096] If the growth substrate is Si or SiC, the present embodiment can further include a carbonization layer forming step (S150) for forming a carbonization layer 150 having Si-C bonds in which silicon (Si) and carbon (C) are bonded between the growth substrate preparation step (S100) and the nucleation region forming step (S200).

[0097] The carbonization layer forming step (S150) forms the carbonization layer 150 by carbonizing the surface of the growth substrate using a carbon dopant for carbon doping including C2H4 (ethylene) and propane (C3H8).

[0098] When the materials of the first region 310 and the second region 320 are aluminum nitride (AlN), aluminum gallium nitride (AlGaN), or gallium nitride (GaN), the group III (Al, Ga) or group V (N) elements constituting them can act as a dopant that causes damage (e.g., dangling bonds) to the surface of the SiC or Si growth substrate or diffuses into the inside.

[0099] The carbon layer forms a Si-C bonding layer in advance on the surface of the growth substrate 100, thereby functioning as an isolation layer that isolates the first region 310 and the second region 320 from the growth substrate 100.

[0100] Therefore, it is possible to prevent a phenomenon of damaging the functions of the first region 310 and the second region 320 that can stably maintain high resistance characteristics during the manufacturing process.

[0101] Thus, the carbon layer makes it easier to fabricate GaN HEMTs with enhanced insulation.

Claims

1. An epitaxial wafer for a GaN HEMT with enhanced electrical insulation, the epitaxial wafer comprising: Growth substrate; a nucleation region, the nucleation region growing on the growth substrate; a high-resistance region having a high-resistance characteristic, the high-resistance region including a high-resistance unit region defined by a first region grown as a Group III nitride semiconductor doped with carbon and a second region grown as a Group III nitride semiconductor on the first region, the high-resistance region being disposed on the nucleation region; as well as An active region includes a channel region grown on the high resistance region and a barrier region grown on the channel region.

2. The epitaxial wafer according to claim 1, wherein: The high resistance region is provided by stacking the high resistance cell region two or more times.

3. The epitaxial wafer according to claim 1, wherein: The first area is provided with 5×10 17 / cm 3 or greater carbon doping concentration.

4. The epitaxial wafer according to claim 1, wherein: The first region is formed of one of aluminum nitride AlN, aluminum gallium nitride AlGaN, or gallium nitride GaN, and the second region is formed of aluminum nitride AlN. 5 . The epitaxial wafer according to claim 1 , further comprising a high-resistance GaN region made of aluminum gallium nitride (AlGaN) or gallium nitride (GaN) and disposed between the high-resistance region and the active region.

6. A method for manufacturing an epitaxial wafer for a GaN HEMT with enhanced electrical insulation, the method comprising the steps of: preparing a growth substrate; forming a nucleation region by epitaxially growing the nucleation region on the growth substrate; forming a first region by epitaxially growing a carbon-doped Group III nitride semiconductor layer on the nucleation region; forming a second region by epitaxially growing a Group III nitride semiconductor layer on the first region at a temperature relatively higher than the temperature in the first region forming step; Repeating the steps of forming the first region and forming the second region; as well as An active region is formed by forming a channel region on the second region and growing a barrier region on the channel region, the channel region having an energy band gap smaller than an energy band gap of the second region.

7. The method according to claim 6, wherein: The growth substrate is formed of silicon carbide SiC and silicon Si materials, the nucleation region is formed of aluminum nitride AlN, the first region is formed of one of aluminum nitride AlN, aluminum gallium nitride AlGaN and gallium nitride GaN, and the second region is formed of aluminum nitride AlN.

8. The method according to claim 6, wherein: The first region forming step is performed at a temperature of 900°C to 1100°C, and the second region forming step is performed at a temperature of 1150°C to 1300°C. 9 . The method according to claim 6 , further comprising the step of forming a high-resistance GaN region between the high-resistance region and the active region, the high-resistance GaN region being made of aluminum gallium nitride (AlGaN) or gallium nitride (GaN).

10. The method according to claim 6, wherein: The first region forming step is performed at a V / III ratio of 250 to 400 and a pressure of 50 to 70 mbar.

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