Manufacturing method of GaN HEMT (High Electron Mobility Transistor) power semiconductor epitaxial wafer with high-quality high-resistance buffer region

Abstract

An embodiment of the present invention provides a method for manufacturing a GaN HEMT power semiconductor epitaxial wafer having a high-quality and high-resistance buffer, comprising: a first GaN buffer layer formation step in which carbon is doped using a metal-organic source as a precursor for carbon doping in a source supplied for GaN growth; and a second GaN buffer layer forming step in which carbon is doped by supplying a carbon doping precursor separately from the source supplied for GaN growth; wherein the precursor for carbon doping in the second GaN buffer layer formation step is at least one of CH4 (methane), C2H4 (ethylene), C2H2 (acetylene), C3H8 (propane), i-C4H10 (isobutane), and [N (CH3) 3] (trimethylamine).

Description

Technical Field

[0001] This invention relates to a method for manufacturing a GaN HEMT power semiconductor epitaxial wafer, and more specifically, to a method for manufacturing a GaN HEMT power semiconductor epitaxial wafer characterized by forming a high-quality, high-resistance buffer. Background Technology

[0002] GaN HEMT power semiconductor epitaxial structures typically consist of nucleation regions, stress-relieving regions, buffer zones, channel regions, and barrier regions stacked sequentially on a growth substrate.

[0003] In the Al(1-y)Ga(y)N (barrier) / GaN (channel) heterojunction, a horizontal channel with a two-dimensional electron gas (2DEG) is formed at the interface of the GaN channel region, exhibiting a small band gap without intentional doping. This is attributed to the polarization phenomenon of group III nitride semiconductors.

[0004] The polarization intensity is determined by the Al(1-y)Ga(y)N thickness and the Al composition (1-y), and the thickness is usually controlled by the Al composition (1-y).

[0005] In some cases, an AlN film less than 5 nm thick can be introduced before growing the Al(1-y)Ga(y)N barrier region on the GaN channel region.

[0006] In some cases, capping regions or p-type group III nitride (GaN, AlGaN, AlInN, AlGaInN) films can be grown on the Al(1-y)Ga(y)N barrier region.

[0007] The buffer acts as a current blocker, reducing vertical leakage current by imparting high resistivity characteristics. This function is typically achieved by doping with carbon (C) or iron (Fe).

[0008] However, growing C- or Fe-doped GaN leads to a deterioration in GaN crystal quality. Therefore, developing optimal growth conditions is a key challenge in related technological fields. Summary of the Invention

[0009] Technical issues

[0010] This invention provides a method for improving the poor crystal quality of a high-resistivity buffer formed by GaN doped with C or Fe.

[0011] The present invention also provides a method for improving leakage current through a high-resistance buffer.

[0012] The present invention also provides a method for improving the crystal quality and device reliability of the active region of a GaN HEMT by improving the crystal quality of the high-resistivity buffer, which includes a subsequently grown GaN channel region and an AlGaN barrier region.

[0013] [Technical Solution]

[0014] According to an embodiment of the present invention, a method for manufacturing a GaN HEMT power semiconductor epitaxial wafer with a high-quality, high-resistivity buffer is provided. The method includes: a first GaN buffer layer formation step, wherein a metal-organic source is used as a carbon doping precursor in a source supplied for GaN growth to dope carbon; and a second GaN buffer layer formation step, wherein carbon is doped by supplying a carbon doping precursor separately from the source supplied for GaN growth; wherein the carbon doping precursor in the second GaN buffer layer formation step is CH4 (methane), C2H4 (ethylene), C2H2 (acetylene), C3H8 (propane), i-C4H... 10 At least one of isobutane and [N(CH3)3](trimethylamine).

[0015] In an embodiment of the invention, the metal-organic source is a TMGa source, and carbon is doped by controlling the carbon concentration in the TMGa source by changing at least one of the growth pressure, growth temperature, and V / III ratio, which are growth conditions for GaN growth.

[0016] In an embodiment of the invention, the growth conditions are altered by relatively reducing the growth pressure and / or the growth temperature to increase the carbon concentration.

[0017] In an embodiment of the present invention, the thickness of the first GaN buffer layer is formed to be thicker than the thickness of the second GaN buffer layer.

[0018] In an embodiment of the present invention, the thickness of the second GaN buffer layer is 50% to 99% of the thickness of the first GaN buffer layer.

[0019] In an embodiment of the invention, the first GaN buffer layer and the second GaN buffer layer constitute the buffer, and the buffer is formed by alternately stacking the first GaN buffer layer and the second GaN buffer layer at least once.

[0020] According to embodiments of the present invention, the step of forming an AlGaN buffer layer formed of Al(1-z)Ga(z)N (0.5≤z≤0.99) is further included.

[0021] In an embodiment of the present invention, the first GaN buffer layer, the second GaN buffer layer, and the AlGaN buffer layer constitute the buffer, and the AlGaN buffer layer is provided as the top layer of the buffer or as an intercalation layer between the first GaN buffer layer and the second GaN buffer layer.

[0022] In an embodiment of the present invention, the AlGaN buffer layer is formed to have a thickness of 5 nm to 500 nm.

[0023] Beneficial effects

[0024] According to the present invention, a high-resistivity GaN buffer can be ensured by dividing the high-resistivity GaN buffer into two or more layers and using different carbon doping methods.

[0025] According to the present invention, by introducing a first GaN buffer layer (i-Carbon GaN layer) and a second GaN buffer layer (e-Carbon GaN layer) together, not only can the epitaxial crystal quality of the GaN HEMT active region composed of the subsequently grown channel and barrier region be significantly improved, but the leakage current of the GaN HEMT device can also be improved.

[0026] According to the present invention, the first GaN buffer layer (i-Carbon GaN layer) prevents epitaxial crystal quality degradation that occurs in the second GaN buffer layer (e-Carbon GaN layer), thereby ensuring a high-quality GaN buffer.

[0027] According to the present invention, the doping concentration of the second GaN buffer layer (e-Carbon GaN layer) is relatively easy to control, which increases the resistance of the buffer and improves the leakage current.

[0028] According to the present invention, an AlGaN buffer layer having a larger band gap than a GaN buffer layer can effectively block leakage current in the buffer. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view of a GaN HEMT power semiconductor epitaxial wafer according to an embodiment of the present invention.

[0030] Figure 2 It is shown in detail Figure 1 A diagram of the buffer in the diagram.

[0031] Figures 3 to 5 This is a diagram showing the growth conditions of the first GaN buffer.

[0032] Figure 6 It is shown Figure 2 The diagram shows an example of buffer modification.

[0033] Figure 7 It is shown Figure 2 A diagram showing another example of a modified buffer. Detailed Implementation

[0034] In the following, a method for manufacturing a GaN HEMT power semiconductor epitaxial wafer with a high-quality, high-resistivity buffer according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0035] The terms used below have been chosen for ease of explanation and should be interpreted appropriately in a meaning consistent with the technical concept of the present invention, and not limited to dictionary definitions.

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

[0037] refer to Figure 1 A buffer zone (40) is formed on the growth substrate (10), and a channel region (50) and a barrier region (60) are formed thereon as active regions.

[0038] Preferably, a nucleation region (20) and a stress relief region (30) are formed on the growth substrate (10) before the buffer zone (40) is formed, but this is not necessary for the practice of the present invention.

[0039] The growth substrate (10) can be, for example, a silicon substrate, a silicon carbide (SiC) substrate, or an alumina substrate. The alumina substrate can be, for example, an Al2O3 substrate.

[0040] For silicon (Si) growth substrates, it is preferable to grow on the (111) plane, which has a high atomic filling ratio similar to the group III nitride crystal structure (HCP), rather than on the (100) and (110) planes.

[0041] For silicon carbide (SiC) growth substrates, 4H-SiC growth substrates are preferred because they have the same crystal structure and minimum lattice constant as group III nitride (HCP) crystal structures. Growth on a Si-polar plane is preferred.

[0042] The nucleation region (20) promotes the growth of the high-quality buffer zone (40), channel region (50), and barrier region (60). Furthermore, for the Si growth substrate, it suppresses melt retreat caused by the Si-Ga eutectic reaction. An AlN thin film is preferred for the nucleation region (20).

[0043] When GaN thin or thick films are grown on Si or SiC growth substrates and cooled to room temperature, tensile stress occurs within the GaN material layer due to thermomechanical stress, leading to wafer warping or cracking. Stress relief regions (30) are introduced to suppress such wafer warping or cracking.

[0044] The stress-relief region (30) is composed of a multilayer structure of Al(1-x)Ga(x)N with different Ga composition ratios (x). Typically, it consists of two (double-layer) or three (triple-layer) layers with different Ga composition ratios. In some cases, the Ga composition ratio (x) gradually increases towards the buffer zone (40) to reach 100%. It can also be formed as an AlN / AlGaN superlattice structure.

[0045] The buffer (40) has high resistance characteristics, which reduces vertical leakage current and acts as a current blocking function.

[0046] The present invention aims to improve the crystal quality degradation of C or Fe doped GaN by using carbon (C) or iron (Fe) as a dopant, which is a common method for forming a buffer (40).

[0047] refer to Figure 2 The buffer (40) is composed of C-doped GaN and includes a first GaN buffer layer (41) and a second GaN buffer layer (42) using different carbon doping methods.

[0048] The first GaN buffer layer (41) and the second GaN buffer layer (42) are stacked alternately, and the stacking order is not restricted.

[0049] A first GaN buffer layer (41) is introduced to prevent the crystal quality of GaN from deteriorating and to form a high-quality GaN buffer layer (40).

[0050] A second GaN buffer layer (42) is introduced to control the doping concentration of the GaN buffer (40) in order to increase the resistance of the buffer (40) and improve the leakage current.

[0051] Therefore, the first GaN buffer layer (41) is used to prevent epitaxial crystallization degradation that occurs in the second GaN buffer layer (42) and to ensure a high-quality GaN buffer layer (40).

[0052] The metal-organic source material for GaN growth supplied to the MOCVD chamber is used as a precursor for carbon doping to form the first GaN buffer layer (41). In other words, no additional material is supplied for carbon doping.

[0053] Specifically, by changing the growth conditions of GaN growth, the carbon concentration in the TMGa source material supplied to the MOCVD chamber for GaN growth is adjusted, and carbon dopant is automatically supplied to the buffer (40) for doping.

[0054] The first GaN buffer layer (41) can be defined as intrinsically carbon-doped GaN ('i-Carbon GaN) because it uses a metal-organic source material supplied for GaN growth to dope carbon.

[0055] The first GaN buffer layer (41) is grown by changing at least one of the growth pressure, growth temperature, and V / III ratio, which are growth conditions used for GaN growth. Preferably, the growth pressure and / or growth temperature are relatively reduced to increase the carbon concentration in the TMGa source.

[0056] Figure 3 The data shows the carbon concentration at different V / III ratios while maintaining growth temperature and pressure. It can be seen that the carbon concentration is high at V / III ratios of 400 to 500, and decreases rapidly as the V / III ratio increases.

[0057] Figure 4 The data shows carbon concentration as a function of growth temperature while maintaining growth pressure and V / III ratio. It can be seen that the carbon concentration is high at growth temperatures between 1050 and 1100 °C, and then decreases sharply with increasing growth temperature.

[0058] Figure 5 The figure shows carbon concentration as a function of growth pressure while maintaining the growth temperature and V / III ratio. It can be seen that the carbon concentration is high at growth pressures of 40 to 50 Torr, and then decreases sharply with increasing growth pressure.

[0059] Figures 3 to 5 This indicates that reducing any one of the growth pressure, growth temperature, or V / III ratio can increase carbon concentration compared to typical growth conditions. Furthermore, considering... Figures 3 to 5 The carbon concentration unit in the figure indicates that lowering the growth temperature and / or growth pressure results in a higher carbon concentration than lowering the V / III ratio.

[0060] According to tests conducted by the inventors, the first GaN buffer layer (41) is preferably formed by varying the growth conditions within the range of 950 to 1100 °C, 50 to 100 Torr, and 400 to 2000 V / III ratio.

[0061] Next, in addition to providing a source for GaN growth, the second GaN buffer layer (42) is doped with carbon by supplying a carbon doping precursor.

[0062] The second GaN buffer layer (42) can be defined as intrinsic carbon-doped GaN ('e-Carbon GaN', intrinsic carbon-doped GaN) because the carbon doping precursor material is supplied separately.

[0063] The second GaN buffer layer (42) uses CH4 (methane), C2H4 (ethylene), C2H2 (acetylene), C3H8 (propane), and i-C4H 10 At least one of isobutane and [N(CH3)3](trimethylamine) is used as a precursor material for carbon doping.

[0064] The second GaN buffer layer (42) allows for relatively easy control of the doping concentration, which increases the resistance of the buffer and thus improves leakage current.

[0065] In this embodiment, a buffer (40) is formed by sequentially stacking a first GaN buffer layer (41) and a second GaN buffer layer (42).

[0066] As previously described, the first GaN buffer layer (41) prevents crystallinity degradation of the epitaxial layer occurring in the second GaN buffer layer (42) and ensures a high-quality GaN buffer layer (40). Therefore, it is preferable to form the first GaN buffer layer (41) over the second GaN buffer layer (42). However, this is not limited to this configuration; the effects of the invention can also be achieved by forming the second GaN buffer layer (42) over the first GaN buffer layer (41).

[0067] In this embodiment, the thickness of the first GaN buffer layer (41) is preferably greater than the thickness of the second GaN buffer layer (42). This can also be attributed to the function of the first GaN buffer layer (41) in preventing epitaxial crystallinity degradation that occurs in the second GaN buffer layer (42).

[0068] Specifically, the thickness of the second GaN buffer layer (42) is preferably 50% to 99% of the thickness of the first GaN buffer layer (41).

[0069] Next, refer to Figure 6 In this embodiment, a buffer (40) is formed by alternately stacking multiple first GaN buffer layers (41) and second GaN buffer layers (42).

[0070] The buffer (40) may include 10 to 300 pairs of first GaN buffer layers (41) and second GaN buffer layers (42).

[0071] The thickness of each of the first GaN buffer layer (41) and the second GaN buffer layer (42) can be set in the range of 10 to 200 nm. This does not limit the first GaN buffer layer (41) (or the second GaN buffer layer (42)) located at different locations to have the same thickness.

[0072] In addition, preferably, the total thickness of the buffer (40) according to this embodiment is formed to be 1 to 5 μm.

[0073] Next, refer to Figure 7 In this embodiment, the buffer (40) is not limited to the first GaN buffer layer (41) and the second GaN buffer layer (42), but an Al(1-z)Ga(z)N buffer layer (43) is added.

[0074] The Al(1-z)Ga(z)N buffer layer (43) has a larger band gap than the GaN buffer layer, and is therefore introduced to more effectively block leakage current in the buffer (40).

[0075] The Al(1-z)Ga(z)N buffer layer (43) is preferably formed to have a thickness of 5 to 500 nm and an Al composition ratio of 1 to 50% (i.e., 0.5 ≤ z ≤ 0.99).

[0076] The Al(1-z)Ga(z)N buffer layer (43) can be formed as part of the buffer (40). However, as a specific example, it can be as follows: Figure 7 As shown, it can also be formed on top of a first GaN buffer layer (41) and a second GaN buffer layer (42) that are alternately stacked multiple times, such as Figure 6 As shown. In addition, an Al(1-z)Ga(z)N buffer layer (43) can be provided as an embedding layer between the first GaN buffer layer (41) and the second GaN buffer layer (42).

[0077] The embodiments of the present invention described above introduce a first GaN buffer layer and a second GaN buffer layer using different carbon doping methods into a high-resistivity GaN buffer layer, thereby preventing the first GaN buffer layer from degrading the epitaxial crystallinity of the second GaN buffer layer and ensuring a high-quality GaN buffer layer.

[0078] Furthermore, since the doping concentration of the second GaN buffer layer is relatively easy to control, this can be used to increase the resistance of the buffer, thereby improving the leakage current.

[0079] As a result, the epitaxial crystal quality of the GaNHEMT active region, which consists of a high-resistivity GaN buffer and subsequently grown channel and barrier regions, was significantly improved, as well as the leakage current of the GaN HEMT device.

[0080] Furthermore, embodiments of the present invention additionally introduce an AlGaN buffer layer having a larger band gap than the GaN buffer layer, thereby effectively blocking leakage current in the buffer.

Claims

1. A method for manufacturing a GaN HEMT power semiconductor epitaxial wafer with a high-quality, high-resistivity buffer, the method comprising: The first GaN buffer layer formation step involves using a metal-organic source as a precursor for carbon doping in a source supplied for GaN growth; as well as The second GaN buffer layer formation step, wherein carbon is doped by supplying a carbon doping precursor separately from the source supplied for GaN growth; In the second GaN buffer layer formation step, the carbon doping precursor is CH4 (methane), C2H4 (ethylene), C2H2 (acetylene), C3H8 (propane), or i-C4H... 10 At least one of isobutane and [N(CH3)3](trimethylamine).

2. The method according to claim 1, wherein, The metal-organic source is a TMGa source, and carbon is doped by controlling the carbon concentration in the TMGa source by changing at least one of the growth pressure, growth temperature, and V / III ratio, which are growth conditions for GaN growth.

3. The method according to claim 2, wherein, The growth conditions are altered by relatively reducing the growth pressure and / or the growth temperature to increase the carbon concentration.

4. The method according to claim 1, wherein, The thickness of the first GaN buffer layer is made to be thicker than the thickness of the second GaN buffer layer.

5. The method according to claim 4, wherein, The thickness of the second GaN buffer layer is 50% to 99% of the thickness of the first GaN buffer layer.

6. The method according to claim 1, wherein, The first GaN buffer layer and the second GaN buffer layer constitute the buffer, and the buffer is formed by alternately stacking the first GaN buffer layer and the second GaN buffer layer at least once.

7. The method according to claim 1, further comprising: The steps for forming an AlGaN buffer layer composed of Al(1-z)Ga(z)N (0.5≤z≤0.99).

8. The method according to claim 7, wherein, The first GaN buffer layer, the second GaN buffer layer, and the AlGaN buffer layer constitute the buffer, and the AlGaN buffer layer is provided as the top layer of the buffer or as an intercalation layer between the first GaN buffer layer and the second GaN buffer layer.

9. The method according to claim 7, wherein, The AlGaN buffer layer is formed to have a thickness of 5 nm to 500 nm.

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