High-voltage-withstanding AlGaN HEMT device based on P-type AlGaN back barrier structure and preparation method

Abstract

The invention discloses a high-voltage-resistance AlGaN HEMT device based on a P-type AlGaN back barrier structure and a preparation method. The high-voltage-resistance AlGaN HEMT device comprises a substrate, an AlN nucleating layer, a first AlGaN buffer layer, a P-type AlGaN back barrier layer, a second AlGaN buffer layer, an AlGaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer which are sequentially stacked from bottom to top. The Al component in the first AlGaN buffer layer is gradually reduced in a stepped manner and is reduced to the size of the Al component in the AlGaN back barrier layer to the minimum; the Al component in the second AlGaN buffer layer is gradually reduced in a stepped manner and is reduced to the size of the Al component in the AlGaN channel layer to the minimum; the source electrode and the drain electrode are located at the two ends of the device and penetrate through the GaN cap layer to the inside of the AlGaN barrier layer. The grid electrode is located on the GaN cap layer. The invention relates to an AlGaN-based HEMT (High Electron Mobility Transistor), which has higher breakdown characteristic and reliability.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure and a preparation method thereof. Background Art

[0002] In recent years, GaN materials, as the third-generation semiconductor, have been widely used in power electronics, radio frequency devices, optoelectronic devices, consumer electronics, energy and environment, medical equipment, the Internet of Things and sensors due to their unique physical properties, such as high bandgap, high breakdown field strength, high electron mobility and high thermal conductivity.

[0003] Based on the high electron mobility of GaN materials, AlGaN / GaN heterojunctions are used. Due to the existence of spontaneous polarization effects and piezoelectric polarization effects, a high concentration of two-dimensional electron gas will be generated at the AlGaN / GaN heterojunction interface, thereby manufacturing a high electron mobility transistor (HEMT). The two-dimensional electron gas has the characteristics of high electron saturation drift velocity and high mobility, so the high electron mobility transistor based on the AlGaN / GaN heterojunction has the characteristics of high output current and high power density. However, in high voltage scenarios, it is often accompanied by a higher leakage current. Reducing leakage current is conducive to reducing unnecessary losses, improving energy utilization efficiency, reducing heat loss of devices during operation, and improving device performance and reliability. Therefore, reducing the leakage current of GaN-based HEMTs is of great significance. At present, conventional GaN power devices mainly reduce the trap state density in the GaN bulk material by improving the lattice quality, thereby suppressing the leakage current in the GaN bulk material. One way is to perform epitaxy of GaN heterojunction materials by homoepitaxial growth; another way is to grow epitaxial materials by using a molecular beam epitaxy (MBE) process.

[0004] However, it is difficult to obtain large-sized wafers using homoepitaxial growth and the cost is extremely high. Although the MBE process can produce GaN epitaxial materials with higher crystal quality, the growth rate is slow and the cost is high. Both methods have the problems of high cost and low efficiency. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure and a preparation method. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure, the device comprising:

[0007] A substrate, an AlN nucleation layer, a first AlGaN buffer layer, a P-type AlGaN back barrier layer, a second AlGaN buffer layer, an AlGaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer are stacked in sequence from bottom to top; wherein the Al component in the first AlGaN buffer layer gradually decreases in a step-like manner from bottom to top, and decreases to the minimum value of the Al component in the P-type AlGaN back barrier layer; the Al component in the second AlGaN buffer layer gradually decreases in a step-like manner from bottom to top, and decreases to the minimum value of the Al component in the AlGaN channel layer; the Al component in the AlGaN barrier layer is greater than the Al component in the AlGaN channel layer;

[0008] The source and drain are located at two ends of the device and respectively penetrate the GaN cap layer into the AlGaN barrier layer;

[0009] The gate is located on the GaN cap layer close to the source.

[0010] In one embodiment of the present invention, the thickness of the AlN nucleation layer is 30 nm to 100 nm.

[0011] In one embodiment of the present invention, the thickness of the first AlGaN buffer layer is 0.1 μm to 3 μm.

[0012] In one embodiment of the present invention, the doped material of the P-type AlGaN back barrier layer includes Mg and Zn; the doping concentration of the P-type AlGaN back barrier layer is 10 15 cm -3 ~10 20 cm -3 , thickness is 100nm~400nm.

[0013] In one embodiment of the present invention, the thickness of the second AlGaN buffer layer is 0.1 μm to 3 μm.

[0014] In one embodiment of the present invention, the thickness of the AlGaN channel layer is 300 nm to 800 nm.

[0015] In one embodiment of the present invention, the thickness of the AlGaN barrier layer is 10 nm to 40 nm.

[0016] In one embodiment of the present invention, the device further comprises:

[0017] A passivation layer is located on the gate, the source, the drain and the GaN cap layer.

[0018] In a second aspect, an embodiment of the present invention provides a method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure, the preparation method comprising:

[0019] Obtaining a substrate and pre-treating the substrate;

[0020] depositing an AlN nucleation layer on the substrate;

[0021] Depositing a first AlGaN buffer layer on the AlN nucleation layer; wherein the Al component in the first AlGaN buffer layer decreases gradually from bottom to top in a step-by-step manner;

[0022] Depositing a P-type AlGaN back barrier layer on the first AlGaN buffer layer; wherein the Al component in the P-type AlGaN back barrier layer is the minimum Al component of the first AlGaN buffer layer;

[0023] Depositing a second AlGaN buffer layer on the P-type AlGaN back barrier layer; wherein the Al component in the second AlGaN buffer layer decreases gradually from bottom to top in a step-by-step manner;

[0024] Depositing an AlGaN channel layer on the second AlGaN buffer layer; wherein the Al component in the AlGaN channel layer is the minimum Al component of the second AlGaN buffer layer;

[0025] Depositing an AlN insertion layer on the AlGaN channel layer;

[0026] Depositing an AlGaN barrier layer on the AlN insertion layer; wherein the Al component in the AlGaN barrier layer is greater than the Al component in the AlGaN channel layer;

[0027] depositing a GaN cap layer on the AlGaN barrier layer;

[0028] Etching the GaN cap layer at both ends of the device into the AlGaN barrier layer, and depositing source and drain metals on the AlGaN barrier layer at both ends of the device to form a source and a drain;

[0029] A gate metal is deposited on the GaN cap layer close to the source to form a gate.

[0030] In one embodiment of the present invention, the preparation method further comprises:

[0031] A passivation layer is formed on the gate, the source, the drain and the GaN cap layer, and a portion of the passivation layer on the gate, the source and the drain is etched away to form a gate contact hole, a source contact hole and a drain contact hole.

[0032] Beneficial effects of the present invention:

[0033] The high-voltage AlGaN HEMT device based on the P-type AlGaN back barrier structure proposed in the present invention designs an AlGaN-based HEMT device suitable for high-voltage, high-temperature and high-power application scenarios based on the improvement of the device structure. Specifically: the device channel layer and the buffer layer are both made of ultra-wide bandgap AlGaN material, which can effectively improve the lateral and longitudinal breakdown characteristics of the device, and improve the breakdown characteristics and reliability of the device; the first AlGaN buffer layer with a gradient Al component can regulate the stress between the substrate material and the P-type AlGaN back barrier layer. At the same time, this design can avoid the parasitic channel generated between the P-type AlGaN back barrier layer and the conventional GaN buffer layer, thereby avoiding the leakage current caused by the parasitic channel, and can effectively reduce the lattice mismatch and thermal mismatch in the epitaxial material, thereby improving the structure of the entire epitaxial structure. The invention discloses a novel method for improving the crystal quality of the epitaxial structure of the present invention. The method comprises the following steps: a first AlGaN buffer layer and an AlGaN channel layer are provided with a P-type AlGaN back barrier layer, which can raise the energy level of the epitaxial layer in a larger range by changing the P-type doping concentration and the Al component, and can suppress the leakage current formed by the two-dimensional electron gas in the channel layer through the trap state of the bulk material to a greater extent, thereby improving the reliability of the device and improving the breakdown characteristics of the device; a second AlGaN buffer layer is designed between the P-type AlGaN back barrier layer and the AlGaN channel layer, which can effectively alleviate the tailing effect in the preparation of the P-type AlGaN back barrier layer, and can also effectively alleviate the stress mutation that may exist between the P-type back barrier layer and the AlGaN channel layer, and further improve the crystal quality of the overall epitaxial structure.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure provided by an embodiment of the present invention;

[0036] Figure 2 It is a structural schematic diagram of another high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure provided by an embodiment of the present invention;

[0037] Figure 3 It is a schematic flow chart of a method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure provided by an embodiment of the present invention;

[0038] Figure 4It is a schematic flow chart of another method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0040] Compared with GaN materials, AlGaN materials have a larger bandgap, a higher critical breakdown electric field, and better stability at high temperatures. Therefore, HEMTs based on AlGaN channels can have better breakdown characteristics and high-temperature characteristics than GaN-based HEMTs. In other words, AlGaN-based HEMTs have greater advantages in high-voltage, high-temperature, and high-power application scenarios. However, in higher voltage scenarios, AlGaN-based HEMTs have higher leakage current problems. Although the leakage current problem can be improved by using a processing method similar to that of GaN-based HEMTs, there are still problems of high cost and low efficiency. To address this problem, an embodiment of the present invention proposes a high-voltage AlGaN HEMT device and a preparation method based on a P-type AlGaN back barrier structure, which improves the leakage current problem by improving the device structure, and the proposed preparation scheme has the advantages of low preparation cost and high efficiency. Specifically:

[0041] First, see Figure 1 The embodiment of the present invention provides a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure, the device comprising:

[0042] The substrate, AlN nucleation layer, first AlGaN buffer layer, P-type AlGaN back barrier layer, second AlGaN buffer layer, AlGaN channel layer, AlN insertion layer, AlGaN barrier layer and GaN cap layer are stacked in sequence from bottom to top; wherein the Al component in the first AlGaN buffer layer decreases stepwise from bottom to top, and decreases to the minimum to the size of the Al component in the P-type AlGaN back barrier layer; the Al component in the second AlGaN buffer layer decreases stepwise from bottom to top, and decreases to the minimum to the size of the Al component in the AlGaN channel layer; the Al component in the AlGaN barrier layer is greater than the Al component in the AlGaN channel layer; for example, the P-type AlGaN back barrier layer adopts P-type Al x Ga 1-x N material, the AlGaN channel layer uses Al y Ga 1-y N material, the AlGaN barrier layer uses Al z Ga 1-zN material, x>y and z>y, x, y, z are 0~1, then the Al component in the first AlGaN buffer layer gradually decreases from 1~x in a step-by-step manner, and the Al component in the second AlGaN buffer layer gradually decreases from x~y in a step-by-step manner; wherein the Al component represents the content of Al in the corresponding material, i.e., the percentage, for example, Al x Ga 1-x N, means Al in Al x Ga 1-x The content of N is x, and the content of Ga in Al x Ga 1-x The content of N is 1-x.

[0043] The source and drain are located at two ends of the device and respectively penetrate the GaN cap layer into the AlGaN barrier layer; the gate is located on the GaN cap layer close to the source.

[0044] The substrate of the embodiment of the present invention may be made of sapphire, Si, SiC or GaN bulk material.

[0045] The thickness of the AlN nucleation layer in the embodiment of the present invention is 30nm to 100nm. Compared with the conventional AlN nucleation layer (usually 30nm), the thicker AlN nucleation layer used in the embodiment of the present invention can effectively alleviate the lattice mismatch and thermal mismatch between the AlGaN material and the substrate material, which is beneficial to the improvement of the crystallization quality of the epitaxial material and thus improves the crystallization quality of the entire epitaxial structure.

[0046] The thickness of the first AlGaN buffer layer in the embodiment of the present invention is 0.1 μm to 3 μm, and the Al component in the first AlGaN buffer layer decreases gradually from bottom to top in a step-like manner. The embodiment of the present invention uses AlGaN material with a step-like change in Al component as a buffer layer, which can avoid stress mutations at local locations and effectively alleviate stress relaxation. On the other hand, it can avoid the generation of parasitic channels when using conventional GaN buffer layers, thereby avoiding leakage current caused by parasitic channels.

[0047] In the embodiment of the present invention, the doping material of the P-type AlGaN back barrier layer includes Mg and Zn; the doping concentration of the P-type AlGaN back barrier layer is 10 15 cm -3 ~10 20 cm -3, thickness is 100nm~400nm. The conventional back barrier structure uses non-intentionally doped AlGaN material. This is because AlGaN material has a larger bandgap width compared to GaN, and has a larger bandgap width between the Fermi level and the bottom of the conduction band compared to GaN material, which can raise the energy level of the epitaxial structure above the back barrier layer and reduce the leakage current of the buffer layer. However, for high-power application scenarios with high voltage and high temperature, a back barrier structure of non-intentionally doped AlGaN material is used. Since the Al component in the AlGaN material is fixed, the corresponding bandgap width is fixed. For this reason, the embodiment of the present invention proposes to use a P-type AlGaN back barrier layer. The P-type AlGaN back barrier layer is an AlGaN back barrier layer doped with Mg or Zn. The band gap width between the Fermi level and the top of the valence band of the AlGaN back barrier layer can be reduced, thereby effectively increasing the band gap width between the Fermi level and the bottom of the conduction band, and further more effectively increasing the barrier height between the conventional AlGaN back barrier layer and the AlGaN channel layer. As the effective doping concentration increases, the barrier height will become higher. A higher barrier height can bring better suppression of leakage current in the bulk material. Suppression of leakage current in the bulk material can bring advantages such as reduced power consumption, better high voltage resistance, and better reliability to the device.

[0048] The thickness of the second AlGaN buffer layer in the embodiment of the present invention is 0.1μm to 3μm, and the Al component in the second AlGaN buffer layer gradually decreases from bottom to top in a step-like manner. In the embodiment of the present invention, a layer of AlGaN material with a gradient Al component is also used between the P-type AlGaN back barrier layer and the AlGaN channel layer. This is because: the inventor found that there is a tailing phenomenon in the preparation process of the P-type AlGaN back barrier layer, and Mg or Zn spreads to the AlGaN channel layer. The second AlGaN buffer layer is designed between the P-type AlGaN back barrier layer and the AlGaN channel layer: on the one hand, it can effectively alleviate the problem of the tailing effect affecting the AlGaN channel layer in the preparation of the P-type AlGaN back barrier layer, and avoid Mg or Zn from diffusing into the AlGaN channel layer; on the other hand, the second AlGaN buffer layer with a gradient layer design can effectively alleviate the stress mutation that may exist between the P-type back barrier layer and the AlGaN channel layer, so that the stress between the two can be gradually released, and the crystal quality of the overall epitaxial structure is improved.

[0049] The AlGaN channel layer in the embodiment of the present invention is an unintentionally doped AlGaN material, and the thickness of the AlGaN channel layer is 300 nm to 800 nm.

[0050] The thickness of the AlN insertion layer in the embodiment of the present invention is 1 nm to 3 nm.

[0051] The thickness of the AlGaN barrier layer in the embodiment of the present invention is 10 nm to 40 nm.

[0052] The GaN cap layer in the embodiment of the present invention is a non-intentionally doped GaN material, and the thickness of the GaN cap layer is 1 nm to 3 nm.

[0053] In the embodiment of the present invention, the source and drain metals can adopt a metal layer combination of Ti / Al or Ti / Al / Ni / Au or Ti / Al / Mo / Au; the gate metal can adopt a metal layer combination of Ni / Au / Ni or Ni / Au or W / Au or Mo / Au or Ti / Au.

[0054] See also Figure 2 The high withstand voltage AlGaN HEMT device based on the P-type AlGaN back barrier structure provided by the embodiment of the present invention further includes: a passivation layer located on the gate, source, drain and GaN cap layer. The passivation layer can be made of SiN or SiO2 or Al2O3 or HfO2 medium; the thickness of the passivation layer is 20nm to 50nm.

[0055] In summary, the high-voltage AlGaN HEMT device based on the P-type AlGaN back barrier structure proposed in the embodiment of the present invention designs an AlGaN-based HEMT device suitable for high-voltage, high-temperature and high-power application scenarios based on the improvement of the device structure. Specifically: the device channel layer and the buffer layer are both made of ultra-wide bandgap AlGaN material, which can effectively improve the lateral and longitudinal breakdown characteristics of the device, and improve the breakdown characteristics and reliability of the device; the first AlGaN buffer layer with a gradient Al component is used to regulate the stress between the substrate material and the P-type AlGaN back barrier layer. At the same time, this design can avoid the parasitic channel generated between the P-type AlGaN back barrier layer and the conventional GaN buffer layer, thereby avoiding the leakage current caused by the parasitic channel, and can effectively reduce the lattice mismatch and thermal mismatch in the epitaxial material, thereby improving the crystallinity of the entire epitaxial structure. Quality; a P-type AlGaN back barrier layer is added between the first AlGaN buffer layer and the AlGaN channel layer. The P-type AlGaN back barrier layer can raise the energy level of the epitaxial layer in a wider range by changing the P-type doping concentration and the Al component, and can suppress the leakage current formed by the two-dimensional electron gas in the channel layer through the trap state of the bulk material to a greater extent, thereby improving the reliability of the device and improving the breakdown characteristics of the device; a second AlGaN buffer layer is designed between the P-type AlGaN back barrier layer and the AlGaN channel layer, which can effectively alleviate the tailing effect in the preparation of the P-type AlGaN back barrier layer, and can also effectively alleviate the possible stress mutation between the P-type back barrier layer and the AlGaN channel layer, and further improve the crystallization quality of the overall epitaxial structure.

[0056] Second, see Figure 3, a method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure provided by an embodiment of the present invention, the preparation method comprising:

[0057] S10, obtaining a substrate and pre-processing the substrate.

[0058] The embodiment of the present invention obtains a substrate, which can be made of sapphire or Si or SiC or GaN bulk material. The substrate surface is pretreated to eliminate dangling bonds, and the pretreatment process includes: soaking the substrate in HF acid solution for 1 minute, then ultrasonically cleaning it in acetone solution, anhydrous ethanol solution and deionized water for 10 minutes each, blowing the cleaned substrate dry with nitrogen; and heat treating it at 1000°C in a H2 atmosphere reaction chamber to remove surface contaminants.

[0059] S20, depositing an AlN nucleation layer on the substrate.

[0060] In the embodiment of the present invention, the pretreated substrate is placed in a metal-organic chemical vapor deposition (MOCVD) system, and an AlN nucleation layer with a thickness of 30nm to 100nm is grown on the pretreated substrate by a MOCVD process, and the process conditions are as follows: the chamber pressure is set to 20Torr and the temperature is set to 900°C; at the same time, an Al source with a flow rate of 200μmol / min to 300μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm are introduced into the MOCVD reaction chamber to grow an AlN nucleation layer with a thickness of 30nm to 100nm on the substrate.

[0061] S30, depositing a first AlGaN buffer layer on the AlN nucleation layer; wherein the Al component in the first AlGaN buffer layer decreases gradually in a step-by-step manner.

[0062] In the embodiment of the present invention, a first AlGaN buffer layer with a thickness of 0.1 μm to 3 μm is deposited on the AlN nucleation layer by MOCVD process; wherein the Al component in the first AlGaN buffer layer gradually decreases from bottom to top in a step-by-step manner. Specifically:

[0063] Taking the deposition of the first AlGaN buffer layer with a thickness of 0.1μm as an example, the process is as follows: simultaneously, MOCVD introduces into the reaction chamber an Al source with a flow rate of 200μmol / min to 10μmol / min, a Ga source with a flow rate of 35μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm to grow a first AlGaN buffer layer with a thickness of 0.1μm on the AlN nucleation layer.

[0064] Taking the deposition of the first AlGaN buffer layer with a thickness of 2μm as an example, the process is as follows: simultaneously, MOCVD introduces into the reaction chamber a gradually decreasing Al source with a flow rate of 250μmol / min to 15μmol / min, a Ga source with a flow rate of 30μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm to grow a second AlGaN buffer layer with a thickness of 2μm on the AlN nucleation layer.

[0065] Taking the deposition of the first AlGaN buffer layer with a thickness of 3μm as an example, the process is as follows: simultaneously, MOCVD introduces into the reaction chamber an Al source with a flow rate of 300μmol / min to 20μmol / min, a Ga source with a flow rate of 25μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm to grow a first AlGaN buffer layer with a thickness of 3μm on the AlN nucleation layer.

[0066] S40, depositing a P-type AlGaN back barrier layer on the first AlGaN buffer layer; wherein the Al component in the P-type AlGaN back barrier layer is the minimum Al component of the first AlGaN buffer layer in a decreasing manner.

[0067] In the embodiment of the present invention, an Al source with a flow rate of 20 μmol / min to 40 μmol / min, a Ga source with a flow rate of 70 μmol / min to 50 μmol / min, a Mg source or a Zn source with a flow rate of 1 μmol / min to 3 μmol / min, a hydrogen gas with a flow rate of 1000 sccm to 2000 sccm, and an ammonia gas with a flow rate of 2000 sccm to 5000 sccm are simultaneously introduced into the MOCVD reaction chamber, and a MOCVD process is used to grow a first AlGaN buffer layer with a thickness of 100 nm to 400 nm and a doping concentration of 10 15 cm -3 ~10 20 cm -3A P-type AlGaN back barrier layer is provided, and the Al composition in the P-type AlGaN back barrier layer is a minimum Al composition of the first AlGaN buffer layer that decreases gradually.

[0068] S50, depositing a second AlGaN buffer layer on the P-type AlGaN back barrier layer; wherein the Al component in the second AlGaN buffer layer gradually decreases in a step-by-step manner.

[0069] In the embodiment of the present invention, a second AlGaN buffer layer with a thickness of 0.1 μm to 3 μm is deposited on the P-type AlGaN back barrier layer using an MOCVD process; wherein the Al component in the second AlGaN buffer layer gradually decreases from bottom to top in a step-by-step manner. Specifically:

[0070] Taking the deposition of a second AlGaN buffer layer with a thickness of 0.1 μm as an example, the process is as follows: simultaneously, an Al source with a flow rate of 25 μmol / min to 20 μmol / min, a Ga source with a flow rate of 90 μmol / min, a hydrogen with a flow rate of 1000 sccm to 2000 sccm, and an ammonia with a flow rate of 2000 sccm to 5000 sccm are introduced into the reaction chamber by MOCVD to grow a second AlGaN buffer layer with a thickness of 0.1 μm on the P-type AlGaN back barrier layer;

[0071] Taking the deposition of a second AlGaN buffer layer with a thickness of 2μm as an example, the process is as follows: simultaneously, MOCVD introduces into the reaction chamber a gradually decreasing Al source with a flow rate of 40μmol / min to 30μmol / min, a Ga source with a flow rate of 80μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm to grow a second AlGaN buffer layer with a thickness of 2μm on the P-type AlGaN back barrier layer.

[0072] Taking the deposition of a second AlGaN buffer layer with a thickness of 3μm as an example, the process is as follows: simultaneously, MOCVD introduces into the reaction chamber a gradually decreasing Al source with a flow rate of 55μmol / min to 40μmol / min, a Ga source with a flow rate of 70μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm to grow a second AlGaN buffer layer with a thickness of 3μm on the P-type AlGaN back barrier layer.

[0073] S60, depositing an AlGaN channel layer on the second AlGaN buffer layer; wherein the Al component in the AlGaN channel layer is the minimum Al component of the second AlGaN buffer layer.

[0074] In the embodiment of the present invention, an Al source with a flow rate of 20 μmol / min to 40 μmol / min, a Ga source with a flow rate of 90 μmol / min to 70 μmol / min, a hydrogen with a flow rate of 1000 sccm to 2000 sccm, and an ammonia with a flow rate of 2000 sccm to 5000 sccm are simultaneously introduced into the MOCVD reaction chamber to grow an AlGaN channel layer with a thickness of 300 nm to 800 nm on the second AlGaN buffer layer, and the Al component in the AlGaN channel layer is the minimum Al component of the second AlGaN buffer layer that decreases.

[0075] S70 , depositing an AlN insertion layer on the AlGaN channel layer.

[0076] The embodiment of the present invention adopts the MOCVD process to deposit an AlN insertion layer with a thickness of 1nm to 3nm on the AlGaN channel layer. The process is: an Al source with a flow rate of 20μmol / min to 40μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm are simultaneously introduced into the MOCVD reaction chamber to grow an AlN insertion layer with a thickness of 1nm to 3nm on the AlGaN channel layer.

[0077] S80, depositing an AlGaN barrier layer on the AlN insertion layer; wherein the Al component in the AlGaN barrier layer is greater than the Al component in the AlGaN channel layer.

[0078] In the embodiment of the present invention, an Al source with a flow rate of 30 μmol / min to 80 μmol / min, a Ga source with a flow rate of 40 μmol / min to 60 μmol / min, a hydrogen with a flow rate of 1000 sccm to 2000 sccm, and an ammonia with a flow rate of 2000 sccm to 5000 sccm are simultaneously introduced into the MOCVD reaction chamber, and an AlGaN barrier layer with a thickness of 10 nm to 40 nm is grown on the AlN insertion layer using the MOCVD process.

[0079] S90, depositing a GaN cap layer on the AlGaN barrier layer.

[0080] The embodiment of the present invention adopts the MOCVD process to deposit a GaN cap layer with a thickness of 1nm to 3nm on the AlGaN barrier layer. The process is: a Ga source with a flow rate of 40μmol / min to 60μmol / min, a hydrogen with a flow rate of 1000sccm to 2000sccm, and an ammonia with a flow rate of 2000sccm to 5000sccm are simultaneously introduced into the MOCVD reaction chamber to grow a GaN cap layer with a thickness of 1nm to 3nm on the AlGaN barrier layer.

[0081] S100, etching the GaN cap layer at both ends of the device until it reaches the AlGaN barrier layer, and depositing source and drain metals on the AlGaN barrier layer at both ends of the device to form a source and a drain.

[0082] In the embodiment of the present invention, the device structure obtained by S90 is placed in an RIE (Reactive Ion Etching) etching chamber, and CF4 with a flow rate of 20 sccm and O2 with a flow rate of 2 sccm are introduced at the same time. The process conditions are set to 5 mT and the power is 100 W. The source window and the drain window are exposed on the GaN cap layer at both ends of the device, and then it is placed in a magnetron sputtering reaction chamber, and the reaction chamber pressure is maintained at 8.8×10 -2 Pa, using aluminum and titanium targets with a purity of 99.999%, deposit source and drain metals, such as Ti / Al or Ti / Al / Ni / Au or Ti / Al / Mo / Au, in the source window and drain window respectively to form the source and drain, and anneal at a high temperature of 830°C for 30s.

[0083] S101, depositing gate metal on the GaN cap layer close to the source to form a gate.

[0084] In the embodiment of the present invention, the device structure obtained in S100 is placed in a metal evaporation reaction chamber, and the pressure of the reaction chamber is controlled to be 8.8×10 -2 Pa, using nickel and gold targets with a purity of 99.999%, a gate metal such as Ni / Au / Ni or Ni / Au or W / Au or Mo / Au or Ti / Au is deposited on the GaN cap layer close to the source to form a gate.

[0085] See also Figure 4 The method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure provided by an embodiment of the present invention further includes:

[0086] S102, forming a passivation layer on the gate, source, drain and GaN cap layer, and etching away part of the passivation layer on the gate, source and drain to form a gate contact hole, a source contact hole and a drain contact hole.

[0087] In the embodiment of the present invention, the device structure obtained in S101 is placed in a PECVD (Plasma-enhanced chemical vapor deposition) reaction chamber, and a passivation layer with a thickness of 20nm to 50nm is deposited on the gate, source, drain and GaN cap layer at a high temperature of 400°C using a PECVD process. The passivation layer material can be SiN or SiO2 or Al2O3 or HfO2 medium. Finally, the passivation layer on the source, drain and gate is etched to form a source contact hole, a drain contact hole and a gate contact hole.

[0088] The embodiment of the present invention proposes a preparation method based on the device structure of the first aspect. In addition to having the advantages of the device structure of the first aspect, the preparation process is simple, the preparation cost is reduced, the preparation efficiency is improved, and it is suitable for the preparation of large-size wafers.

[0089] As for the device structure embodiment of the first aspect, since it is basically similar to the preparation method embodiment of the second aspect, the description is relatively simple, and the relevant parts can be referred to the partial description of the preparation method embodiment of the second aspect.

[0090] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0091] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the specification and its drawings. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude multiple situations. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0092] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure, characterized in that: The device comprises: A substrate, an AlN nucleation layer, a first AlGaN buffer layer, a P-type AlGaN back barrier layer, a second AlGaN buffer layer, an AlGaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer are stacked in sequence from bottom to top; wherein the Al component in the first AlGaN buffer layer gradually decreases in a step-like manner from bottom to top, and decreases to the minimum value of the Al component in the P-type AlGaN back barrier layer; the Al component in the second AlGaN buffer layer gradually decreases in a step-like manner from bottom to top, and decreases to the minimum value of the Al component in the AlGaN channel layer; the Al component in the AlGaN barrier layer is greater than the Al component in the AlGaN channel layer; The source and drain are located at two ends of the device and respectively penetrate the GaN cap layer into the AlGaN barrier layer; The gate is located on the GaN cap layer close to the source.

2. The high withstand voltage AlGaN HEMT device based on the P-type AlGaN back barrier structure according to claim 1, characterized in that: The thickness of the AlN nucleation layer is 30nm-100nm.

3. The high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 1, characterized in that: The thickness of the first AlGaN buffer layer is 0.1 μm to 3 μm.

4. The high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 1, characterized in that: The doping material of the P-type AlGaN back barrier layer includes Mg and Zn; the doping concentration of the P-type AlGaN back barrier layer is 10 15 cm -3 ~10 20 cm -3 , thickness is 100nm~400nm.

5. The high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 1, characterized in that: The thickness of the second AlGaN buffer layer is 0.1 μm to 3 μm.

6. The high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 1, characterized in that: The thickness of the AlGaN channel layer is 300nm-800nm.

7. The high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 1, characterized in that: The thickness of the AlGaN barrier layer is 10 nm to 40 nm.

8. The high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 1, characterized in that: The device further comprises: A passivation layer is located on the gate, the source, the drain and the GaN cap layer.

9. A method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure, characterized in that: The preparation method comprises: Obtaining a substrate and pre-treating the substrate; depositing an AlN nucleation layer on the substrate; Depositing a first AlGaN buffer layer on the AlN nucleation layer; wherein the Al component in the first AlGaN buffer layer decreases gradually from bottom to top in a step-by-step manner; Depositing a P-type AlGaN back barrier layer on the first AlGaN buffer layer; wherein the Al component in the P-type AlGaN back barrier layer is the minimum Al component of the first AlGaN buffer layer; Depositing a second AlGaN buffer layer on the P-type AlGaN back barrier layer; wherein the Al component in the second AlGaN buffer layer decreases gradually from bottom to top in a step-by-step manner; Depositing an AlGaN channel layer on the second AlGaN buffer layer; wherein the Al component in the AlGaN channel layer is the minimum Al component of the second AlGaN buffer layer; Depositing an AlN insertion layer on the AlGaN channel layer; Depositing an AlGaN barrier layer on the AlN insertion layer; wherein the Al component in the AlGaN barrier layer is greater than the Al component in the AlGaN channel layer; depositing a GaN cap layer on the AlGaN barrier layer; Etching the GaN cap layer at both ends of the device into the AlGaN barrier layer, and depositing source and drain metals on the AlGaN barrier layer at both ends of the device to form a source and a drain; A gate metal is deposited on the GaN cap layer close to the source to form a gate.

10. The method for preparing a high withstand voltage AlGaN HEMT device based on a P-type AlGaN back barrier structure according to claim 9, characterized in that: The preparation method further comprises: A passivation layer is formed on the gate, the source, the drain and the GaN cap layer, and a portion of the passivation layer on the gate, the source and the drain is etched away to form a gate contact hole, a source contact hole and a drain contact hole.

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