Enhanced multi-channel gan power device and method of fabrication

Abstract

The application relates to an enhanced multi-channel GaN power device and a manufacturing method, the power device comprising a substrate, a buffer layer, a first channel layer and at least one group of second channel layers arranged in sequence from bottom to top, the first channel layer comprising a first GaN layer, a first AlGaN layer and a first C single crystal thin film layer arranged in sequence from bottom to top, each group of the second channel layers comprising a second GaN layer, a second AlGaN layer and a second C single crystal thin film layer arranged in sequence from bottom to top, the thicknesses of the first C single crystal thin film layer and the second C single crystal thin film layer are less than or equal to 2 nm, and the thickness of the second GaN layer is 2-10 nm. The C single crystal thin film layer forms an electron dielectric layer and an electric field buffer layer, not only enhances a two-dimensional electron gas channel, improves the working voltage and current of the device, but also reduces the processing difficulty of the device; and the C single crystal thin film layer can relieve stress in the device structure, so that the device structure can be designed to be more complex and diversified.

Description

Technical Field

[0001] This invention relates to an enhanced multi-channel GaN power device and its fabrication method, and is applicable to the field of semiconductor materials technology. Background Technology

[0002] In semiconductor materials research, GaN, as a representative of third-generation wide-bandgap semiconductor materials, possesses significant advantages and potential in power device fabrication. Currently, devices based on AlGaN / GaN heterostructures typically consist of a substrate, buffer layer, GaN layer, AlGaN layer, and electrodes, arranged from bottom to top. By introducing the AlGaN / GaN heterostructure, the polarization effect is achieved through the positive polarization of the upper AlGaN layer and the negative polarization of the lower GaN layer, forming a two-dimensional electron gas conductive channel between them, thus improving electron mobility. Compared to Si devices that rely on P-type holes or N-type electrons for carrier transport, AlGaN / GaN heterostructure devices exhibit higher breakdown voltage, lower turn-on resistance, and shorter reverse recovery time.

[0003] However, with increasing application demands, conventional single-channel heterostructures, limited by their two-dimensional electron gas concentration, can no longer meet the required operating voltage and current. Based on this, multi-channel devices have emerged. Most current multi-channel devices are formed by repeatedly depositing and stacking AlGaN / GaN heterostructures from a single channel, creating a multi-channel structure consisting of GaN layers, AlGaN layers, GaN layers, AlGaN layers, ..., GaN layers, AlGaN layers, from bottom to top. However, because the AlGaN layers in the lower heterostructure and the GaN layers in the upper heterostructure carry opposite polarization charges, although they do not produce a polarization effect, they easily neutralize each other. This interferes with the two-dimensional electron gas channels in each AlGaN / GaN heterostructure, limiting the operating voltage and current it can carry. In order to reduce this interference, existing technologies typically increase the thickness of the GaN layer to more than 100nm. However, increasing the thickness of the GaN layer not only increases the difficulty of device fabrication but also affects the operating voltage and weakens the effect of multi-channel layers. At the same time, it also restricts device design and makes it difficult to meet diverse design requirements. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention proposes an enhanced multi-channel GaN power device and its fabrication method.

[0005] The technical solution adopted in this invention is as follows: On the one hand, an enhanced multi-channel GaN power device is provided, comprising a substrate, a buffer layer, a first channel layer and at least one set of second channel layers arranged sequentially from bottom to top. The first channel layer includes a first GaN layer, a first AlGaN layer and a first C single crystal thin film layer arranged sequentially from bottom to top. Each set of second channel layers includes a second GaN layer, a second AlGaN layer and a second C single crystal thin film layer arranged sequentially from bottom to top. The thickness of the first C single crystal thin film layer and the thickness of the second C single crystal thin film layer are both less than or equal to 2 nm, and the thickness of the second GaN layer is 2~10 nm. A quasi-two-dimensional C single-crystal thin film layer is placed between adjacent AlGaN / GaN heterostructures. This C single-crystal thin film layer forms a good electronic dielectric layer, ensuring insulation between adjacent AlGaN / GaN heterostructures and preventing electrical neutralization between the lower AlGaN layer and the upper GaN layer. This enhances the two-dimensional electron gas conductive channels, increasing the operating voltage and current that the device can withstand. Furthermore, the GaN layer thickness can be significantly reduced, lowering the device fabrication difficulty. Since the device operating voltage is much higher than the polarization voltage between the AlGaN / GaN heterostructures, the C single-crystal thin film layer does not affect the operating voltage while isolating adjacent channel layers, further enhancing the multi-channel effect. Simultaneously, the C single-crystal thin film layer also serves as a good electric field buffer layer, alleviating stress in the device's various structural layers, allowing for more complex and diverse device designs.

[0006] Furthermore, the substrate is made of one of Si, SiC, or GaN, and the buffer layer is made of C-doped AlN material, which can improve the structural quality of the device.

[0007] Furthermore, the thicknesses of both the first AlGaN layer and the second AlGaN layer are less than 20 nm.

[0008] On the other hand, a method for fabricating the above-mentioned enhanced multi-channel GaN power device is provided, the method comprising: S1. Place the substrate in the MOCVD reaction chamber, and grow a buffer layer, a first GaN layer, and a first AlGaN layer sequentially on the substrate. The thickness of the first GaN layer is 2~3μm. Specifically, the growth temperature of the buffer layer, the first GaN layer, and the first AlGaN layer is 800~1400℃, the gas pressure in the reaction chamber is 10~100Torr, and the gas atmosphere in the reaction chamber is nitrogen or hydrogen. S2. A C2H4 gas atmosphere is created in the MOCVD reaction chamber, and a first C single-crystal thin film layer is grown on the first AlGaN layer. The first C single-crystal thin film layer is then subjected to high-temperature annealing. Specifically, the growth temperature of the first C single-crystal thin film layer is 800~1400℃, and the gas pressure in the reaction chamber is 100~700 Torr. The high-temperature annealing temperature of the first C single-crystal thin film layer is 600~1200℃, and the treatment time is 100~130 seconds. By using C2H4 gas as a gas source, MOCVD chemical vapor deposition is employed at high temperature to... C source is decomposed and deposited onto the first AlGaN layer to grow a first C single crystal thin film layer with high single crystal orientation, low defect density and extremely thin thickness. After the first C single crystal thin film layer is grown, the temperature in the reaction chamber is rapidly reduced by about 200°C to perform high-temperature annealing treatment on the first C single crystal thin film layer to improve its activation degree and reduce its defect density, making it a good electronic dielectric layer and electric field buffer layer. This facilitates the isolation of the neutralization reaction between the lower first AlGaN layer and the upper second GaN layer to be grown subsequently, and enhances the net polarization effect of the two-dimensional electron gas conductive channel. S3. Remove C2H4 from the MOCVD reaction chamber and grow a second GaN layer and a second AlGaN layer sequentially on the first C single crystal thin film layer; specifically, the growth temperature of the second GaN layer and the second AlGaN layer is 800~1400℃, the gas pressure in the reaction chamber is 10~100Torr, and the gas atmosphere in the reaction chamber is nitrogen or hydrogen. S4. Grow a second C single crystal thin film layer on the second AlGaN layer according to the method in step S2, and perform high-temperature annealing treatment on the second C single crystal thin film layer. S5. Repeat steps S3 and S4 n times, where 0 ≤ n ≤ 18. By repeatedly growing the second GaN layer and the second AlGaN layer, a multi-channel structure of the device is formed. Due to the presence of the C single crystal thin film layer, the required thickness of the second GaN layer is reduced, the fabrication difficulty of the device is reduced, the number of channel structures that can be constructed in the device is greatly increased, the working performance of the device is improved, and a basis for realizing diverse design requirements is provided.

[0009] S6. Etch and grow the source, gate, and drain on the uppermost second C single crystal thin film layer of the GaN power device, and then complete the device fabrication.

[0010] Furthermore, in step S6, the methods for growing the source, gate, and drain include: S6.1. Two first electrode regions and one second electrode region are etched on the uppermost second C single crystal thin film layer of the GaN power device using reactive ion etching or inductively coupled plasma etching. The two first electrode regions are located on both sides of the second C single crystal thin film layer, and the second electrode region is located between the two first electrode regions. S6.2. The source and drain are generated in the two first electrode regions respectively using MOCVD process, and the gate is generated in the second electrode region. S6.3. Anneal the product obtained in step b at high temperature to form an ohmic contact between the electrode metal and the contact interface.

[0011] Furthermore, the depth of the first electrode region and the depth of the second electrode region are both greater than or equal to the thickness of the second C single crystal thin film layer. Specifically, the depths of the first electrode region and the second electrode region can be etched according to design requirements.

[0012] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The enhanced multi-channel GaN power device and its fabrication method of the present invention generate a C single-crystal thin film layer with high unidirectional crystal orientation and low defect density between adjacent AlGaN / GaN heterostructures, and improve its activation degree by rapidly annealing it at high temperature, making it a good electronic dielectric layer and electric field buffer layer. This not only avoids electrical neutralization between the lower AlGaN layer and the upper GaN layer, but also enhances the two-dimensional electron gas conductive channels of each layer, increasing the operating voltage and current that the device can carry; it also greatly reduces the thickness of the GaN layer, reducing the fabrication difficulty of the device; furthermore, the C single-crystal thin film layer does not affect the operating voltage while isolating adjacent channel layers, further enhancing the effect of the multi-channel layer; at the same time, the C single-crystal thin film layer can alleviate the stress in each layer of the device structure, allowing for more complex and diversified device structure designs. Attached Figure Description

[0013] The following sections will describe some specific embodiments of the invention in a detailed manner, by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic diagram of the structure of the device obtained in step S1 in one embodiment of the present invention; Figure 2 yes Figure 1 A schematic diagram of the device obtained in step S2 of the embodiment shown; Figure 3 yes Figure 1 A schematic diagram of the device obtained in step S3 of the embodiment shown; Figure 4 yes Figure 1 A schematic diagram of the device obtained in step S4 of the embodiment shown; Figure 5 yes Figure 1 A schematic diagram of the device obtained in step S5 of the embodiment shown; Figure 6 yes Figure 1 A schematic diagram of the device obtained in step S6.1 in the illustrated embodiment; Figure 7 yes Figure 1 A schematic diagram of the device obtained in step S6.2 of the embodiment shown; The reference numerals in the attached figures are explained as follows: 1. Substrate; 2. Buffer layer; 3. First channel layer; 31. First GaN layer; 32. First AlGaN layer; 33. First C single crystal thin film layer; 4. Second channel layer; 41. Second GaN layer; 42. Second AlGaN layer; 43. Second C single crystal thin film layer; 5. First electrode region; 51. Source; 52. Drain; 6. Second electrode region; 61. Gate. Implementation

[0014] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] In the description of this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0016] Reference Appendix Figure 1-7On one hand, this embodiment provides an enhanced multi-channel GaN power device, including a substrate 1, a buffer layer 2, a first channel layer 3 and at least one set of second channel layers 4 arranged sequentially from bottom to top. The first channel layer 3 includes a first GaN layer 31, a first AlGaN layer 32 and a first C single crystal thin film layer 33 arranged sequentially from bottom to top. Each set of second channel layers 4 includes a second GaN layer 41, a second AlGaN layer 42 and a second C single crystal thin film layer 43 arranged sequentially from bottom to top. The thickness of the first C single crystal thin film layer 33 and the thickness of the second C single crystal thin film layer 43 are both less than or equal to 2 nm, and the thickness of the second GaN layer 41 is 2~10 nm. A quasi-two-dimensional C single-crystal thin film layer is placed between adjacent AlGaN / GaN heterostructures. This C single-crystal thin film layer forms a good electronic dielectric layer, ensuring insulation between adjacent AlGaN / GaN heterostructures and preventing electrical neutralization between the lower AlGaN layer and the upper GaN layer. This enhances the conductive channels of each two-dimensional electron gas, increasing the operating voltage and current that the device can withstand. Furthermore, the GaN layer thickness can be significantly reduced, lowering the device fabrication difficulty. Since the device operating voltage is much higher than the polarization voltage between the AlGaN / GaN heterostructures, the C single-crystal thin film layer does not affect the operating voltage while isolating adjacent heterostructures, further enhancing the multi-channel effect. Simultaneously, the C single-crystal thin film layer also serves as a good electric field buffer layer, alleviating stress in the device's various structural layers, allowing for more complex and diverse device designs.

[0017] In a more preferred embodiment, the substrate 1 is made of one of Si, SiC, or GaN, and the buffer layer 2 is made of C-doped AlN material, which can improve the structural quality of the device.

[0018] In a more preferred embodiment, the thickness of both the first AlGaN layer 32 and the second AlGaN layer 42 is less than 20 nm.

[0019] On the other hand, this embodiment provides a method for fabricating the above-mentioned enhanced multi-channel GaN power device, the method comprising: S1, such as Figure 1 As shown, substrate 1 is placed in an MOCVD reaction chamber, and a buffer layer 2, a first GaN layer 31, and a first AlGaN layer 32 are sequentially grown on substrate 1. The thickness of the first GaN layer 31 is 2~3μm. Specifically, the growth temperature of the buffer layer 2, the first GaN layer 31, and the first AlGaN layer 32 is 800~1400℃, the gas pressure in the reaction chamber is 10~100Torr, and the gas atmosphere in the reaction chamber is nitrogen or hydrogen.

[0020] S2, such as Figure 2As shown, a C2H4 gas atmosphere is created in the MOCVD reaction chamber, and a first C single-crystal thin film layer 33 is grown on the first AlGaN layer 32. The first C single-crystal thin film layer 33 is then subjected to high-temperature annealing. Specifically, the growth temperature of the first C single-crystal thin film layer 33 is 800~1400℃, the gas pressure in the reaction chamber is 100~700 Torr, the high-temperature annealing temperature of the first C single-crystal thin film layer 33 is 600~1200℃, and the treatment time is 100~130 seconds. By using C2H4 gas as the gas source, MOCVD chemical vapor deposition is employed at high temperature to... C source is decomposed and deposited onto the first AlGaN layer 32 to grow a first C single crystal thin film layer 33 with high single crystal orientation, low defect density and extremely thin thickness. After the growth of the first C single crystal thin film layer 33 is completed, the temperature in the reaction chamber is rapidly reduced by about 200°C to perform high-temperature annealing treatment on the first C single crystal thin film layer 33 to improve its activation degree and reduce its defect density, making it a good electronic dielectric layer and electric field buffer layer. This facilitates the isolation of the neutralization reaction between the lower first AlGaN layer 32 and the upper second GaN layer 41 to be grown subsequently, and enhances the net polarization effect of the two-dimensional electron gas channel.

[0021] S3, such as Figure 3 As shown, C2H4 in the MOCVD reaction chamber is discharged, and a second GaN layer 41 and a second AlGaN layer 42 are sequentially grown on the first C single crystal thin film layer 33. Specifically, the growth temperature of the second GaN layer 41 and the second AlGaN layer 42 is 800~1400℃, the gas pressure in the reaction chamber is 10~100 Torr, and the gas atmosphere in the reaction chamber is nitrogen or hydrogen.

[0022] S4, such as Figure 4 As shown, a second C single crystal thin film layer 43 is grown on the second AlGaN layer 42 according to the method in step S2, and the second C single crystal thin film layer 43 is subjected to high-temperature annealing treatment. S5, such as Figure 5 As shown, steps S3 and S4 are repeated n times, where 0 ≤ n ≤ 18. Specifically, in this embodiment, n = 2. By repeatedly growing the second GaN layer 41 and the second AlGaN layer 42, a multi-channel structure of the device is formed. Due to the presence of the C single crystal thin film layer, the required thickness of the second GaN layer 41 is reduced, the processing difficulty of the device is reduced, the number of channel structures that can be constructed in the device is greatly increased, the working performance of the device is improved, and a basis for realizing diverse design requirements is provided.

[0023] S6, such as Figures 6-7 As shown, the source 51, gate 61, and drain 52 are etched and grown on the uppermost second C single crystal thin film layer 43 of the GaN power device, and then the device fabrication is completed.

[0024] In a more preferred embodiment, step S6, the method for growing the source 51, gate 61, and drain 52 includes: S6.1, such as Figure 6 As shown, two first electrode regions 5 and one second electrode region 6 are etched on the uppermost second C single crystal thin film layer 43 of the GaN power device using reactive ion etching or inductively coupled plasma etching. The two first electrode regions 5 are located on both sides of the second C single crystal thin film layer 43, and the second electrode region 6 is located between the two first electrode regions 5. S6.2, such as Figure 7 As shown, the source 51 and drain 52 are generated in two first electrode regions 5 using MOCVD process, and the gate 61 is generated in the second electrode region 6. S6.3. The product obtained in step b is annealed at high temperature to form an ohmic contact between the electrode metal and the contact interface. Specifically, the high temperature annealing temperature is 900~1200℃, and the gas atmosphere in the reaction chamber is nitrogen.

[0025] In a more preferred embodiment, the depth of the first electrode region 5 and the depth of the second electrode region 6 are both greater than or equal to the thickness of the second C single crystal thin film layer 43. Specifically, the depths of the first electrode region 5 and the second electrode region 6 can be etched according to design requirements.

[0026] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The enhanced multi-channel GaN power device and its fabrication method of the present invention generate a C single-crystal thin film layer with high unidirectional crystal orientation and low defect density between adjacent AlGaN / GaN heterostructures, and improve its activation degree through rapid high-temperature annealing, making it a good electronic dielectric layer and electric field buffer layer. This not only avoids electrical neutralization between the lower AlGaN layer and the upper GaN layer, but also enhances the two-dimensional electron gas conductive channels of each layer, increasing the operating voltage and current that the device can carry; it also greatly reduces the thickness of the GaN layer, reducing the fabrication difficulty of the device; furthermore, the C single-crystal thin film layer isolates adjacent channel layers without affecting the operating voltage, further enhancing the effect of the multi-channel layer; at the same time, the C single-crystal thin film layer can alleviate the stress in each layer of the device structure, allowing for more complex and diversified device structure designs.

[0027] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An enhanced multi-channel GaN power device, characterized in that: The system includes a substrate (1), a buffer layer (2), a first channel layer (3), and at least one set of second channel layers (4) arranged from bottom to top. The first channel layer (3) includes a first GaN layer (31), a first AlGaN layer (32), and a first C single crystal thin film layer (33) arranged from bottom to top. Each set of second channel layers (4) includes a second GaN layer (41), a second AlGaN layer (42), and a second C single crystal thin film layer (43) arranged from bottom to top. The thickness of the first C single crystal thin film layer (33) and the thickness of the second C single crystal thin film layer (43) are both less than or equal to 2 nm. The thickness of the second GaN layer (41) is 2~10 nm. The thickness of the first AlGaN layer (32) and the second AlGaN layer (42) are both less than 20 nm.

2. The enhanced multi-channel GaN power device according to claim 1, characterized in that: The substrate (1) is made of one of Si, SiC, or GaN, and the buffer layer (2) is an AlN material doped with C.

3. A method for fabricating the enhancement-mode multichannel GaN power device according to any one of claims 1 to 2, characterized in that, The method includes: S1. Place the substrate (1) in the MOCVD reaction chamber, and grow the buffer layer (2), the first GaN layer (31), and the first AlGaN layer (32) sequentially on the substrate (1). The thickness of the first GaN layer (31) is 2~3μm. S2. Create a C2H4 gas atmosphere in the MOCVD reaction chamber, grow the first C single crystal thin film layer (33) on the first AlGaN layer (32), and perform high-temperature annealing on the first C single crystal thin film layer (33); the temperature for growing the first C single crystal thin film layer (33) is 800~1400℃, the gas pressure in the reaction chamber is 100~700Torr, the processing temperature for high-temperature annealing of the first C single crystal thin film layer (33) is 600~1200℃, and the processing time is 100~130 seconds; S3. Remove C2H4 from the MOCVD reaction chamber and grow the second GaN layer (41) and the second AlGaN layer (42) sequentially on the first C single crystal thin film layer (33). S4. The second C single crystal thin film layer (43) is grown on the second AlGaN layer (42) according to the method in step S2, and the second C single crystal thin film layer (43) is subjected to high temperature annealing. S5. Repeat steps S3 and S4 n times, where 0 ≤ n ≤ 18; S6. Etch and grow the source (51), gate (61) and drain (52) on the uppermost second C single crystal thin film layer (43) of the GaN power device, and then complete the device fabrication.

4. The method for fabricating the enhanced multi-channel GaN power device according to claim 3, characterized in that: In step S1, the growth temperature of the buffer layer (2), the first GaN layer (31), and the first AlGaN layer (32) is 800~1400℃, the gas pressure in the reaction chamber is 10~100Torr, and the gas atmosphere in the reaction chamber is nitrogen or hydrogen.

5. The method for fabricating the enhanced multi-channel GaN power device according to claim 3, characterized in that: In step S3, the growth temperature of the second GaN layer (41) and the second AlGaN layer (42) is 800~1400℃, the gas pressure in the reaction chamber is 10~100Torr, and the gas atmosphere in the reaction chamber is nitrogen or hydrogen.

6. The method for fabricating the enhanced multi-channel GaN power device according to claim 3, characterized in that, In step S6, the method for growing the source (51), gate (61), and drain (52) includes: S6.1 Two first electrode regions (5) and one second electrode region (6) are etched on the uppermost second C single crystal thin film layer (43) of the GaN power device using reactive ion etching or inductively coupled plasma etching. The two first electrode regions (5) are located on both sides of the second C single crystal thin film layer (43), and the second electrode region (6) is located between the two first electrode regions (5). S6.

2. The source (51) and drain (52) are generated in the two first electrode regions (5) respectively using MOCVD process, and the gate (61) is generated in the second electrode region (6). S6.

3. Anneal the product obtained in step S6.2 at a high temperature.

7. The method for fabricating an enhanced multi-channel GaN power device according to claim 6, characterized in that: The depth of the first electrode region (5) and the depth of the second electrode region (6) are both greater than or equal to the thickness of the second C single crystal thin film layer (43).

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