Manufacturing method of gallium nitride device

Abstract

The invention provides a manufacturing method of a gallium nitride device, and relates to the technical field of semiconductor photoelectric devices. According to the method, an AlN nucleating layer, an AlN buffer layer, an AlGaN shielding layer, an AlN etching stop layer and a p-GaN layer are sequentially grown on a substrate to form an epitaxial layer, and an ultrathin nanoscale doping layer is introduced between the AlN buffer layer and the AlGaN shielding layer. And removing the p-GaN layer in a non-gate region through a composite etching technology, and carrying out surface treatment after etching to further reduce the surface roughness. A multi-layer metal structure is deposited on the surface of the p-GaN layer in the grid electrode area, a Ti / Al / Ni / Au layer is deposited on the surface of the AlGaN / GaN shielding layer, ohmic contact is formed, and the contact performance is optimized through the laser annealing technology. By means of the innovative manufacturing process, the problems of high-temperature stability, surface roughness, interface defects and the like of a traditional gallium nitride device are solved, and the gallium nitride device is suitable for being applied to high-power and high-frequency circuits.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and specifically to a manufacturing method of a gallium nitride device. Background Art

[0002] Most of the general traditional power devices are mainly made of silicon (Si) material. The main reason is that silicon is a material with a relatively large content on the earth, with a low price and more mature technology development compared to other materials. However, due to the physical properties of the material and the large leakage loss of the substrate, it can no longer be applied to high-power and high-frequency circuits, resulting in a bottleneck in the energy conversion efficiency of silicon-based devices. Gradually, the development focus has shifted to wide bandgap semiconductor materials.

[0003] Gallium nitride has the following advantages compared with silicon: such as a wider bandgap, higher breakdown electric field, electron mobility, electron saturation velocity, heat conduction rate, etc. The main reason why gallium nitride has the above advantages is that gallium nitride has a unique polarization effect. A triangular potential well will be formed at the heterointerface of gallium nitride and aluminum gallium nitride, triggering a two-dimensional electron gas (2DEG) channel with high electron mobility, which is very helpful for the performance of field-effect transistors.

[0004] CN112542384B proposes a manufacturing method of a gallium nitride enhancement device. In this method, since the surface material of the AlN etch stop layer is oxidized to form Al2O3 during the oxidation treatment, the etch selectivity is improved, the etch uniformity can be improved, and the device stability can be further enhanced. In addition, compared with traditional dry etching, the compound etching technology can effectively reduce the surface roughness of the gallium nitride enhancement device and remove surface damage, improving the on-resistance and breakdown voltage characteristics of the device.

[0005] However, due to the original characteristics of the gallium nitride material, traditional gallium nitride devices may exhibit poor thermal stability at high temperatures and may experience performance degradation during long-term use, such as an increase in leakage current and a drift in the threshold voltage, affecting the reliability of the device. In addition, the gallium nitride material itself may have a relatively high dislocation density, and these dislocations will affect the performance of the device, such as increasing the leakage current and reducing the breakdown voltage resistance. There may be defects at the interface between gallium nitride and the buffer layer or substrate, and these defects will affect the performance and reliability of the device. Summary of the Invention

[0006] (I) Technical Problems to be Solved

[0007] In view of the deficiencies of the prior art, the present invention provides a manufacturing method of a gallium nitride device, which solves the problems raised in the above background art.

[0008] (II) Technical Solutions

[0009] To achieve the above object, the present invention is realized by the following technical solutions: A manufacturing method of a gallium nitride device, comprising the following steps:

[0010] S1. Sequentially grow an AlN nucleation layer, an AlN buffer layer, an AlGaN shielding layer, an AlN etch stop layer, and a p-GaN layer on a substrate to form an epitaxial layer, and introduce an ultra-thin nanoscale doping layer between the AlN buffer layer and the AlGaN shielding layer;

[0011] S2. Define a gate region and a non-gate region on the surface of the epitaxial layer through a yellow light lithography process, use the non-gate region as an etching area, adopt a compound etching technology to remove the p-GaN layer in the non-gate region, and perform surface treatment after etching, and further reduce the surface roughness through chemical mechanical polishing;

[0012] S3. Deposit a multi-layer metal structure on the surface of the p-GaN layer in the gate region, deposit a Ti / Al / Ni / Au layer on the surface of the AlGaN / GaN shielding layer and prepare source metal and drain metal to form an ohmic contact, and use a laser annealing technology to process the source metal and the drain metal;

[0013] S4. Introduce a nanoscale doping technology in the p-GaN layer and introduce an ultra-thin nanoscale doping layer on the surface of the AlGaN shielding layer;

[0014] S5. Perform device packaging and performance testing to verify the device performance.

[0015] Preferably, in step S1, the thickness of the ultra-thin nanoscale doping layer is 1-5 nm, the doping element is Si, and it is grown by atomic layer deposition technology.

[0016] Preferably, in step S2, the compound etching technology includes two steps of dry etching and wet etching. Among them, for dry etching, N2O gas is used, the ICP power is 30 W, the chamber pressure is 60 mTorr, the gas flow rate is 30 sccm, the etching time is 150 s, and the surface of the p-GaN layer is oxidized to form 4 nm thick Ga2O3; for wet etching, an HCl solution is used, the etching time is 120 seconds, and Ga2O3 is removed; the dry etching and wet etching steps are repeated 15 times to completely remove the 60 nm thick p-GaN layer.

[0017] Preferably, in step S3, the multi-layer metal structure is Ni / Au / TiN, with thicknesses of 25 nm, 120 nm, and 30 nm respectively, and it is deposited by electron beam evaporation method. The thicknesses of the Ti / Al / Ni / Au layer are 30 nm, 125 nm, 50 nm, and 200 nm respectively, and it is deposited by electron beam evaporation method. The processing conditions of the laser annealing technology are rapid annealing at 750 °C for 20 seconds.

[0018] Preferably, in step S4, the doping element of the nanoscale doping technology is Mg, and the doping concentration is 3e19 cm -3 . By precisely controlling the flow rate of the doping source gas, precise control of the nanoscale doping concentration is achieved during the MOCVD growth process.

[0019] Preferably, in step S4, the thickness of the ultra-thin nanoscale doping layer is 2 nm, the doping element is Si, and it is grown using ALD technology. By precisely controlling the number of ALD cycles, precise control of the thickness of the ultra-thin layer is achieved.

[0020] Preferably, in step S2, the number of cycles of the combined etching is adjusted according to the thickness of the p-GaN layer. The etching depth per cycle is approximately 4 nm, and the etching depth has a linear relationship with the number of cycles.

[0021] Preferably, in step S4, the doping uniformity of the nanoscale doping technology is monitored in real time through in-situ monitoring technology to ensure that the doping effect meets the design requirements.

[0022] (III) Beneficial Effects

[0023] The present invention provides a method for manufacturing a gallium nitride device, which has the following beneficial effects:

[0024] 1. By optimizing the epitaxial layer structure and growth process, the thermal stress at high temperatures is reduced, and the high-temperature stability of the device is improved. When aging tests are carried out in an environment of 150 °C, both the leakage current and the threshold voltage drift of the device are within the design range, indicating that the device has good high-temperature stability.

[0025] 2. The combined etching technology combined with chemical mechanical polishing significantly reduces the surface roughness, from 0.401 nm of traditional dry etching to 0.273 nm, thereby reducing the surface state density, increasing the electron mobility, and reducing the on-resistance.

[0026] 3. By introducing the nanoscale doping technology and the ultra-thin nanoscale doping layer, the interface defects and dislocation density are reduced, and the breakdown voltage capability and long-term reliability of the device are improved. After the device operates continuously for 1000 hours, the performance does not show obvious degradation, verifying the reliability of the manufacturing method. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the gallium nitride device in the present invention.

[0028] Legend Explanation:

[0029] 1. Substrate; 2. AlN nucleation layer; 3. AlN buffer layer; 4. Ultra-thin nanoscale doping layer; 5. AlGaN shielding layer; 6. AlN etching stop layer; 7. p-GaN layer; 8. Gate metal Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Embodiment 1:

[0032] As Figure 1 shown, the embodiment of the present invention provides a manufacturing method for a gallium nitride device, including the following steps:

[0033] S1 Epitaxial layer growth

[0034] Metal organic chemical vapor deposition (MOCVD) growth is carried out on a 6-inch silicon-based (111) p-type substrate with low resistivity to grow a 4-μm-thick AlN nucleation layer and an AlN buffer layer. A 2-nm-thick Si-doped layer is introduced between the AlN buffer layer and the AlGaN shielding layer, and atomic layer deposition (ALD) technology is used for growth to reduce interface defects and improve interface quality. Then, a 12-nm-thick Al 0.17 Ga 0.83 N shielding layer is grown, a 1-nm-thick AlN etch stop layer is grown, and a 60-nm-thick p-GaN layer with a Mg doping concentration of 3e19 cm -3 is grown. By precisely controlling the doping concentration and distribution, the electron mobility and on-resistance are optimized.

[0035] S2. Region definition and combined etching

[0036] A photoresist layer is coated on the surface of the p-GaN layer. The gate region and the non-gate region are defined through exposure and development. The combined etching technology is used to remove the p-GaN layer in the non-gate region. Among them, for dry etching, N2O gas is used, the ICP power is 30 W, the chamber pressure is 60 mTorr, the gas flow rate is 30 sccm, and the etching time is 150 s to oxidize the surface of the p-GaN layer into a 4-nm-thick Ga2O3. For wet etching, an HCl solution is used, and the etching time is 120 seconds to remove Ga2O3. The dry etching and wet etching steps are repeated 15 times to completely remove the 60-nm-thick p-GaN layer. After etching, chemical mechanical polishing (CMP) is carried out to further reduce the surface roughness, from 0.401 nm of traditional dry etching to 0.273 nm, reduce the surface state density, and improve the electron mobility.

[0037] S3. Metal layer deposition and laser annealing

[0038] Deposit a Ni / Au / TiN multi-layer metal structure on the surface of the p-GaN layer in the gate region, with thicknesses of 25 nm, 120 nm, and 30 nm respectively. Use the electron beam evaporation method to optimize the gate performance. Deposit a Ti / Al / Ni / Au layer on the surface of the AlGaN / GaN shielding layer, with thicknesses of 30 nm, 125 nm, 50 nm, and 200 nm respectively. Use the electron beam evaporation method to form a good ohmic contact. Use the laser annealing technique to process the source metal and drain metal, and perform a rapid annealing at 750 °C for 20 seconds to optimize the ohmic contact performance and reduce thermal damage.

[0039] S4, Nano-scale doping and structure optimization

[0040] Introduce Mg doping into the p-GaN layer, with a doping concentration of 3e19 cm -3 , and precisely control the nano-scale doping concentration during the MOCVD growth process by precisely controlling the flow rate of the doping source gas (Cp2Mg) to improve the p-type conductivity. Introduce a 2-nm-thick Si doping layer on the surface of the AlGaN shielding layer, which is grown using the ALD technique. By precisely controlling the number of ALD cycles, achieve precise thickness control of the ultra-thin layer and reduce interface defects.

[0041] S5, Device packaging and performance testing

[0042] Use the standard packaging process for device packaging to ensure the stability and reliability of the device, and perform performance testing, including high-temperature stability testing, leakage current testing, threshold voltage drift testing, etc.:

[0043] Surface roughness, measure the surface roughness of the device using an atomic force microscope (AFM). The average surface roughness after compound etching is 0.273 nm, which is significantly lower than 0.401 nm of traditional dry etching.

[0044] Threshold voltage and sub-threshold characteristics, the test results show that the threshold voltage of the device is about 1.7 V, and the sub-threshold current (S.S.) is 60 mV / dec, indicating that the device has good switching characteristics and low surface defects.

[0045] On-resistance and breakdown voltage, the on-resistance of the device is about 14.6 Ω·mm, and the breakdown voltage reaches 423 V, which is significantly higher than 352 V of traditional dry-etched devices.

[0046] High-temperature stability, perform an aging test in an environment of 150 °C. The leakage current and threshold voltage drift of the device are within the design range, indicating that the device has good high-temperature stability.

[0047] Reliability test, after the device has been continuously working for 1000 hours, the performance has not shown obvious degradation, verifying the reliability of the manufacturing method.

[0048] Example 2:

[0049] The difference between this example and Example 1 lies in: The difference between this example and Example 1 lies in:

[0050] The thickness of the ultra-thin nanoscale doping layer introduced between the AlN buffer layer and the AlGaN shielding layer is 3 nm, and the doping element is C;

[0051] The doping element introduced into the p-GaN layer is Be, and the doping concentration is 2e19 cm -3 ;

[0052] The processing conditions of the laser annealing technique are rapid annealing at 700 °C for 30 seconds.

[0053] To verify the effectiveness of the manufacturing method of the present invention, the following comparative experiments were carried out:

[0054] Comparative Experiment 1: A gallium nitride device was manufactured using traditional dry etching technology, without introducing a nanoscale doping layer and a compound etching technology.

[0055] Comparative Experiment 2: The compound etching technology of the present invention was used, but a nanoscale doping layer was not introduced.

[0056] Comparative Experiment 3: The technology used in Example 1.

[0057] Comparative Experiment 4: The technology used in Example 2.

[0058] The test results show that the manufacturing method of the present invention is significantly superior to the comparative experiments in terms of surface roughness, threshold voltage stability, subthreshold current, on-resistance, and breakdown voltage, proving the creativity and novelty of the present invention.

[0059] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A manufacturing method of a gallium nitride device, characterized in that, It includes the following steps: S1. Grow an AlN nucleation layer, an AlN buffer layer, an AlGaN shielding layer, an AlN etch stop layer, and a p-GaN layer on a substrate in sequence to form an epitaxial layer, and introduce an ultra-thin nanoscale doping layer between the AlN buffer layer and the AlGaN shielding layer; S2. Define a gate region and a non-gate region on the surface of the epitaxial layer through a yellow light lithography process, use the non-gate region as an etching area, adopt a compound etching technology to remove the p-GaN layer in the non-gate region, perform surface treatment after etching, and further reduce the surface roughness through chemical mechanical polishing; S3. Deposit a multi-layer metal structure on the surface of the p-GaN layer in the gate region, deposit a Ti / Al / Ni / Au layer on the surface of the AlGaN / GaN shielding layer and prepare source metal and drain metal to form an ohmic contact, and use a laser annealing technology to process the source metal and the drain metal; S4. Introduce a nanoscale doping technology in the p-GaN layer and introduce an ultra-thin nanoscale doping layer on the surface of the AlGaN shielding layer; S5. Perform device packaging and performance testing to verify the device performance.

2. The manufacturing method of a gallium nitride device according to claim 1, wherein: In step S1, the thickness of the ultra-thin nanoscale doping layer is 1-5 nm, the doping element is Si, and it is grown using atomic layer deposition technology.

3. The manufacturing method of a gallium nitride device according to claim 1, characterized in that: In step S2, the compound etching technology includes two steps of dry etching and wet etching. Among them, for dry etching, N2O gas is used, the ICP power is 30 W, the chamber pressure is 60 mTorr, the gas flow rate is 30 sccm, the etching time is 150 s, and the surface of the p-GaN layer is oxidized to form a 4-nm-thick Ga2O3; for wet etching, an HCl solution is used, and the etching time is 120 seconds to remove Ga2O3; repeat the dry etching and wet etching steps 15 times to completely remove the 60-nm-thick p-GaN layer.

4. The manufacturing method of a gallium nitride device according to claim 1, characterized in that: In step S3, the multi-layer metal structure is Ni / Au / TiN, with thicknesses of 25 nm, 120 nm, and 30 nm respectively, and it is deposited using an electron beam evaporation method. The thicknesses of the Ti / Al / Ni / Au layer are 30 nm, 125 nm, 50 nm, and 200 nm respectively, and it is deposited using an electron beam evaporation method. The processing conditions of the laser annealing technology are rapid annealing at 750 °C for 20 seconds.

5. The manufacturing method of a gallium nitride device according to claim 1, characterized in that: In step S4, the doping element of the nanoscale doping technology is Mg, and the doping concentration is 3e19 cm -3 , and by precisely controlling the flow rate of the doping source gas, precise control of the nanoscale doping concentration is achieved during the MOCVD growth process.

6. The manufacturing method of a gallium nitride device according to claim 1, wherein: In step S4, the thickness of the ultra-thin nanoscale doping layer is 2 nm, the doping element is Si, and it is grown using ALD technology. By precisely controlling the number of ALD cycles, precise thickness control of the ultra-thin layer is achieved.

7. A manufacturing method of a gallium nitride device according to claim 1, characterized in that: In step S2, the number of cycles of the compound etching is adjusted according to the thickness of the p-GaN layer. The etching depth per cycle is about 4 nm, and the etching depth has a linear relationship with the number of cycles.

8. The manufacturing method of a gallium nitride device according to claim 1, characterized in that: In step S4, the doping uniformity of the nanoscale doping technology is monitored in real time through an in-situ monitoring technology to ensure that the doping effect meets the design requirements.

Images