GaN-based device based on novel ohmic regrowth and preparation method thereof

Abstract

The application provides a GaN-based device based on novel ohmic regrowth and a preparation method thereof, wherein an AlN cap layer is epitaxially formed on a GaN cap layer; since the AlN has a larger Al component than AlGaN, the generation of AlF3 is more favorable in the self-termination etching process, the selectivity of the self-termination etching can be effectively improved, the damage of the etching to the two-dimensional electron gas in the channel can be reduced, and a larger output current can be obtained; meanwhile, the application uses AlN as an etching stop layer, the etching surface obtained is more flat, the surface defects are less, and thus the surface leakage of the device is reduced; compared with conventional maskless regrowth, the application can effectively improve the reliability of the device, can avoid the degradation of the barrier layer caused by the component diffusion and stress effect of the mask in the MOCVD high-temperature epitaxy process; meanwhile, the advantages of the traditional MBE regrowth are retained, the contact resistance can be effectively reduced, and the DC characteristics of the device are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microelectronics, and relates to a GaN-based device based on a novel ohmic regrowth and a preparation method thereof. BACKGROUND

[0002] The GaN-based HEMT device not only has the high-conductivity characteristic of the two-dimensional electron gas, but also has the high-voltage resistance of GaN, so that it becomes a research hotspot of microwave power devices. With the popularization of 5G and the proposal of 6G, the GaN-based HEMT device faces new challenges, in order to break through the output power and efficiency of the GaN radio frequency power device at a high working frequency, reducing the parasitic resistance of the device is the most fundamental solution, and in the process of reducing the parasitic resistance of the device, the ohmic regrowth process plays a crucial role.

[0003] Compared with the conventional ohmic annealing process, the ohmic regrowth process can not only greatly reduce the ohmic contact resistance, but also can avoid the phenomenon of spikes formed due to the outward expansion of the metal alloy, improve the metal morphology, and improve the breakdown characteristics of the device. The ohmic regrowth is usually based on the MOCVD or MBE epitaxy n + material, and the commonly used method is to epitaxially grow n + material by MBE. However, MBE has a high requirement for temperature, and a lower temperature will lead to polycrystalline or amorphous growth, and a higher temperature will lead to the evaporation and falling off of the adsorbed atoms. Moreover, MBE belongs to beam epitaxy, and has a slow growth rate and low efficiency, which is not conducive to industrialization.

[0004] The ohmic regrowth process includes mask-free regrowth and mask regrowth. The mask regrowth process will cause the degradation of the barrier layer due to the component diffusion and stress effect of the mask during the MOCVD high-temperature epitaxy process, thereby increasing the heterojunction resistance and reducing the reliability of the device. Therefore, it is necessary to introduce mask-free regrowth. In the mask-free regrowth process, the most important thing is to remove the n + material covering the surface of the barrier layer after epitaxy by self-terminating etching. The reaction gas for self-terminating etching is SF6 and BCl3. After etching the n+ material to the barrier interface, SF6 reacts with Al in the AlGaN to generate AlF3, and AlF3 attached to the surface of the sample can prevent further reaction of BCl3 with the AlGaN. However, in the conventional mask-free regrowth process, the Al component of the AlGaN barrier layer is low, the blocking ability of the generated AlF3 is weak, and the etching process will still cause certain damage to the barrier layer, thereby increasing the gate leakage of the device and deteriorating the off-state. SUMMARY

[0005] In order to solve the above problems in the prior art, the application provides a GaN-based device based on a novel ohmic regrowth and a preparation method thereof. The technical problems to be solved by the application are solved by the following technical scheme.

[0006] In a first aspect, the present invention provides a method for fabricating a GaN-based device based on a novel ohmic regenerating length, comprising:

[0007] Step 1: Select a device substrate;

[0008] Step 2: Epitaxially grow a core layer, a buffer layer, a barrier layer, a GaN cap layer, and an AlN cap layer sequentially from bottom to top on the substrate to form a GaN device structure;

[0009] Step 3: In the ohmic regrowth region on the GaN device structure, a dry etching process is used to etch from top to bottom to remove the AlN cap layer, GaN cap layer, barrier layer and part of the buffer layer in the ohmic regrowth region, so that the buffer layer presents a stepped structure between the ohmic regrowth region and the central region.

[0010] Wherein, the ohmic regrowth region is a pre-region, and the buffer layer is the first surface on the lower step surface of the ohmic regrowth region;

[0011] Step 4: Epitaxially grow n on the entire wafer + InGaN layer;

[0012] Step 5: Remove n outside the ohmic region using self-terminating etch. + InGaN;

[0013] Among them, the ohmic region is formed by the ohmic regeneration region and the regions extending on both sides of the ohmic region.

[0014] Step 6: In the ohmic regrowth region n + Metal is deposited on the InGaN layer to fabricate the source and drain electrodes;

[0015] Step 7: Based on mesa etching, from top to bottom, the AlN cap layer, GaN cap layer, barrier layer and part of the buffer layer on the outside of the ohmic regrowth region are formed to create a device with isolation regions on both sides.

[0016] Among them, after the platform is etched, the buffer layer presents a three-step structure, with the upper surface of the bottom step being the second surface;

[0017] Step 8: Deposit a passivation layer on the device surface;

[0018] Step 9: Use a dry etching process to remove the passivation layer covering the source electrode region and the drain electrode region to form vias;

[0019] Step 10: Use a dry etching process to remove the passivation layer in the gate region down to the AlN cap layer to form a gate trench;

[0020] The gate region is a non-adjacent region between the source electrode and the drain electrode.

[0021] Step 11: depositing metal in the gate recess to form a T-shaped gate electrode, and completing the preparation process of the new ohmic regrowth GaN-based device.

[0022] Optionally, the step 2 comprises:

[0023] The nucleation layer, the buffer layer, the barrier layer, the GaN cap layer and the AlN cap layer are sequentially epitaxially grown from bottom to top on the substrate by MOCVD to form a GaN device structure.

[0024] Optionally, the step 3 comprises:

[0025] After step 2, the wafer is sequentially subjected to pre-baking, glue spinning and glue baking;

[0026] The ohmic regrowth region is exposed, post-baked and developed by a photoetching machine;

[0027] The photoresist of the ohmic regrowth region is removed, and a hardening operation is performed to complete photoetching;

[0028] The wafer after photoetching is subjected to Cl-based etching by an ICP device, and the reaction gas is BCl3 and Cl2;

[0029] The ohmic regrowth region on the GaN device structure is etched from top to bottom by a Cl-based etching process using an ICP machine to remove the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the ohmic regrowth region to form a recess, so that the buffer layer presents a stepped structure in the ohmic regrowth region and the central region;

[0030] After etching, the wafer is sequentially placed in acetone, stripping liquid, acetone and isopropyl alcohol for ultrasonic cleaning to remove the surface photoresist;

[0031] The wafer after removing the surface photoresist is rinsed with ultrapure water and is blow-dried.

[0032] Optionally, the step 4 comprises:

[0033] The n-InGaN layer is epitaxially grown on the whole wafer by MOCVD or MBE process; +

[0034] The doping concentration of Si is 5×10 19 cm 3 -5×10 20 cm 3 .

[0035] Optionally, the step 5 comprises:

[0036] The wafer formed in step 4 is sequentially subjected to pre-baking, glue spinning and glue baking; ​

[0037] Exposing, post-baking and developing the self-terminating etching region outside the ohmic region by a photoetching machine to remove the photoresist of the self-terminating etching region;

[0038] Hardening the sample after development to complete photoetching;

[0039] Self-terminating etching the sample after photoetching by a Samco device to remove the n + InGaN, self-terminating on an AlN cap layer;

[0040] The reaction gas for self-terminating etching is SF6 and BCl3.

[0041] Optionally, the step 6 comprises:

[0042] Depositing Ti / Au ohmic stack metal on the n + InGaN to prepare a source electrode and a drain electrode.

[0043] Optionally, the step 7 comprises:

[0044] Removing the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the passive region to reach a second surface to form an isolation region on both sides of the device by Cl-based etching based on an ICP device; the Cl-based etching reaction gas is BCl3 and Cl2.

[0045] Optionally, the step 9 comprises:

[0046] Removing the passivation layer of the source electrode region and the drain electrode region to form a via hole by F-based etching process based on an ICP machine.

[0047] Optionally, the step 10 comprises:

[0048] Removing the passivation layer of the gate region to form a gate recess by F-based etching process based on an ICP machine.

[0049] The step 11 comprises depositing Ni / Au metal stack in the gate recess to form a gate electrode by an electron beam evaporation device.

[0050] In a second aspect, the application provides a GaN-based device based on novel ohmic regrowth, which is prepared by the preparation method in the first aspect, and comprises:

[0051] A substrate layer;

[0052] A nucleation layer, which is located on the substrate layer;

[0053] a GaN buffer layer on the nucleation layer;

[0054] the GaN buffer layer comprises three steps, the upper surface of the middle step is the first surface, the upper surface of the lower step is the second surface, the step surface higher than the second surface is the first surface, and the step surface higher than the first surface is the third surface;

[0055] a barrier layer on the third surface of the GaN buffer layer;

[0056] a GaN cap layer on the barrier layer;

[0057] an AlN cap layer on the GaN cap layer;

[0058] n + an InGaN layer on the first surface of the GaN buffer layer and partially on the AlN cap layer; + an InGaN layer on the first surface of the GaN buffer layer and partially on the AlN cap layer;

[0059] a source electrode and a drain electrode on the n + InGaN layer;

[0060] a passivation layer on the AlN cap layer and the n + InGaN layer, covering the n + InGaN layer and the AlN cap layer;

[0061] a gate electrode, a gate leg of the gate electrode on the AlN cap layer, a gate cap of the gate electrode on the passivation layer, and the gate electrode between the source electrode and the drain electrode.

[0062] The application provides a GaN-based device based on novel ohmic regrowth and a preparation method thereof. An AlN cap layer is epitaxially formed on a GaN cap layer. Since the AlN has a larger Al component than AlGaN, the generation of AlF3 is more favorable in the self-terminating etching process, the selectivity of the self-terminating etching is effectively improved, the damage of the etching to the two-dimensional electron gas in the channel is reduced, and a larger output current can be obtained. Meanwhile, the AlN is used as the etching stop layer, the etching surface is more planar, and the surface defects are fewer, thereby reducing the surface leakage of the device. Compared with conventional mask-free regrowth, the reliability of the device can be effectively improved, the degradation of the barrier layer caused by the component diffusion and stress effect of the mask in the MOCVD high-temperature epitaxy process can be avoided, and the advantages of traditional MBE regrowth are retained, the contact resistance is effectively reduced, and the DC characteristics of the device are improved.

[0063] The application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 is a flow chart of a preparation method of a GaN-based device based on novel ohmic regrowth provided by an embodiment of the application;

[0065] Figure 2a is a GaN device structure formed in step 2 provided by an embodiment of the application;

[0066] Figure 2b is a GaN device structure formed in step 3 provided by an embodiment of the application;

[0067] Figure 2c is a GaN device structure formed in step 4 provided by an embodiment of the application;

[0068] Figure 2d is a GaN device structure formed after self-terminating etching photolithography in step 5 provided by an embodiment of the application;

[0069] Figure 2e is a GaN device structure formed after self-terminating etching in step 5 provided by an embodiment of the application;

[0070] Figure 2f is a GaN device structure formed in step 6 provided by an embodiment of the application;

[0071] Figure 2g is a GaN device structure formed in step 7 provided by an embodiment of the application;

[0072] Figure 2h is a GaN device structure formed in step 8 provided by an embodiment of the application;

[0073] Figure 2i is a GaN device structure formed in step 10 provided by an embodiment of the application;

[0074] Figure 2j is a GaN device structure formed in step 11 provided by an embodiment of the application;

[0075] Figure 3 is a structure schematic diagram of a GaN-based device based on novel ohmic regrowth provided by an embodiment of the application. DETAILED DESCRIPTION

[0076] The application will be further described in detail below with reference to the accompanying drawings and embodiments, but the embodiments of the application are not limited thereto.

[0077] As shown in Figure 1 , a preparation method of a GaN-based device based on novel ohmic regrowth provided by the application comprises:

[0078] Step 1: Selecting a device substrate;

[0079] Wherein, the substrate is Si, sapphire and SiC material.

[0080] Step 2: Epitaxially growing a nucleation layer, a buffer layer, a barrier layer, a GaN cap layer and an AlN cap layer on the substrate from bottom to top, to form a GaN device structure;

[0081] In an embodiment, referring to Figure 2a , Step 2 comprises:

[0082] Epitaxially growing a nucleation layer 2, a buffer layer 3, a barrier layer 4, a GaN cap layer 5 and an AlN cap layer 6 on the substrate 1 from bottom to top by MOCVD, to form a GaN device structure.

[0083] Step 3: Etching the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the ohmic regrowth region on the GaN device structure from top to bottom by dry etching, to make the buffer layer present a step structure between the ohmic regrowth region and the center region;

[0084] Wherein, the ohmic regrowth region is a pre-region, and the lower step surface of the buffer layer in the ohmic regrowth region is a first surface;

[0085] In an embodiment, referring to Figure 2b , Step 3 comprises:

[0086] Step 31: After Step 2, forming a wafer and sequentially performing pre-baking, spin-coating and baking;

[0087] Step 32: Exposing, post-baking and developing the ohmic regrowth region by a photoetching machine;

[0088] Step 33: Removing the photoresist of the ohmic regrowth region and performing hardening operation to complete photoetching;

[0089] Step 34: Using an ICP device to perform Cl-based etching on the wafer after photoetching, and the reaction gas is BCl3 and Cl2;

[0090] Step 35: Using an ICP machine, performing Cl-based etching on the ohmic regrowth region of the GaN device structure from top to bottom, to remove the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the ohmic regrowth region to form a groove, so that the buffer layer presents a step structure between the ohmic regrowth region and the center region;

[0091] In Figure 2bIn the process, after photolithography, the sample is etched with Cl-based material using an ICP device. The reaction gases are BCl3 and Cl2. All AlN cap layer, GaN cap layer, barrier layer and part of buffer layer are removed to the first surface 3-1, so that the buffer layer presents a stepped structure in the ohmic regrowth region and the central region.

[0092] Step 36: After etching, the sample is placed in acetone, stripping solution, acetone and isopropanol in sequence for ultrasonic cleaning to remove the surface photoresist;

[0093] Step 37: Rinse the sample after removing the photoresist with ultrapure water and then blow it dry.

[0094] Step 4: Grow an n+InGaN layer on the entire epitaxial wafer;

[0095] In one embodiment, step 4 includes:

[0096] Using MOCVD or MBE processes, n is epitaxially grown on a whole wafer. + InGaN layer 7;

[0097] The Si doping concentration is 5 × 10⁻⁶. 19 cm -3 -5×10 20 cm -3 .

[0098] See Figure 2c ,exist Figure 2c n + InGaN layer 7 is grown on the ohmic region and AlN cap layer 6, respectively, so that n + InGaN layer 7 covers the ohmic region and AlN cap layer 6, i.e., it grows on the entire n-layer. + InGaN layer.

[0099] Step 5: Remove n outside the ohmic region using self-terminating etch. + InGaN;

[0100] Among them, the ohmic region is formed by the ohmic regeneration region and the regions extending on both sides of the ohmic region.

[0101] In one embodiment, step 5 includes:

[0102] Step 51: Perform pre-baking, spin coating, and glue drying on the sample formed in step 4 in sequence;

[0103] Step 52: Expose, bake, and develop the self-terminating etched region outside the ohmic region using a photolithography machine to remove the photoresist in the self-terminating etched region. See [link to previous step]. Figure 2d ;

[0104] Step 53: harden the sample after development to complete the photoetch;

[0105] Step 54: see Figure 2e , use Samco equipment to perform self-terminating etching on the sample after photoetching, to remove the n + InGaN outside the ohmic region, and self-terminate on the AlN cap layer;

[0106] wherein the reaction gas for self-terminating etching is SF6 and BCl3.

[0107] Step 6: deposit metal on the n+InGaN layer of the ohmic regrowth region to prepare the source electrode and the drain electrode;

[0108] In one embodiment, step 6 includes:

[0109] Use an electron beam evaporation device to deposit Ti / Au ohmic stack metal on the n + InGaN of the ohmic regrowth region to prepare the source electrode 8 and the drain electrode 9.

[0110] First, pre-bake the sample, then coat the sample with two layers of photoresist, bake the photoresist, expose the ohmic regrowth electrode region using a photoetching machine, then post-bake and develop to remove the photoresist from the ohmic regrowth electrode region, and complete the photoetching. See Figure 2f , then use a plasma photoresist remover to remove the residual photoresist from the ohmic regrowth electrode region, and then use an electron beam evaporation station to evaporate Ti / Au metal stacks to form the source electrode 8 and the drain electrode 9. Place the sample after metal evaporation in acetone for more than 3 hours, then perform ultrasonic cleaning until the metal in the unexposed region is completely removed; place the sample in a 60°C stripping solution and heat in a water bath for 15 minutes; sequentially place the sample in acetone and isopropanol and perform ultrasonic cleaning for 3 minutes, then rinse with ultrapure water for 2 minutes and dry with N2.

[0111] Step 7: based on mesa etching, self-terminate from the top to the AlN cap layer, the GaN cap layer, the barrier layer, and part of the buffer layer outside the ohmic regrowth region to form a device with isolation regions on both sides;

[0112] wherein after mesa etching, the buffer layer presents a three-step structure, and the upper surface of the lowermost step is the second surface;

[0113] In one embodiment, referring to Figure 2g , step 7 includes:

[0114] Use an ICP device to remove the AlN cap layer, the GaN cap layer, the barrier layer, and part of the buffer layer of the passive region based on Cl-based etching to reach the second surface 3-2, and form isolation regions on both sides of the device;

[0115] The Cl-based etching reaction gas is BCl3 and Cl2, and the passive region is located on both sides of the ohmic region.

[0116] After the etching is completed, the sample is sequentially placed in acetone, stripping liquid, acetone and isopropyl alcohol for ultrasonic cleaning to remove the surface photoresist, and then washed with ultrapure water and dried.

[0117] Step 8: depositing a passivation layer 10 on the surface of the device;

[0118] After the passivation layer is deposited, the passivation layer of the isolation region can be removed to improve the performance of the device.

[0119] In one embodiment, referring to Figure 2h , step 8 comprises:

[0120] SiH4 and NH3 are used as Si source and N source respectively by using a PECVD device to deposit 120 nm SiN on the sample under the conditions of a radio frequency power of 22 W and a growth temperature of 250°C.

[0121] Step 9: removing the passivation layer covering the source electrode region and the drain electrode region by using a dry etching process to form a via hole;

[0122] In one embodiment, step 9 comprises:

[0123] The passivation layer of the source electrode region and the drain electrode region is removed by using an ICP machine to form a via hole by using an F-based etching process.

[0124] In this step, the sample can be first pre-baked, then glue is spun, the glue is baked, the surface region of the source electrode and the drain electrode is exposed by using a photoetching machine, then post-baking and development are performed to remove the photoresist on the surface region of the source electrode and the drain electrode, and finally the film is hardened. After the photoetching is completed, the sample is subjected to F-based etching by using an ICP device, the reaction gas is CF4 and O2, the SiN on the surface region of the source electrode and the drain electrode is removed, the source metal electrode and the drain metal electrode are exposed, and the testing is facilitated. After the etching is completed, the sample is sequentially placed in acetone, stripping liquid, acetone and isopropyl alcohol for ultrasonic cleaning to remove the surface photoresist, and then washed with ultrapure water and dried.

[0125] Step 10: removing the passivation layer of the gate region until the AlN cap layer by using a dry etching process to form a gate recess;

[0126] The gate region is between the source electrode 8 and the drain electrode 9, and is not adjacent to the region.

[0127] In one embodiment, step 10 comprises:

[0128] The passivation layer of the gate region is removed by using an ICP machine to form a gate recess by using an F-based etching process.

[0129] Reference Figure 2i The step is divided into grid slot area photoetching, grid slot etching and organic cleaning.

[0130] Specifically, first, the sample is pre-baked, then the glue is spun, the glue is baked, the grid slot area is exposed by a photoetching machine, then post-baking and development are performed, the photoresist in the grid slot area is removed, and finally, the film is hardened, and the photoetching is completed. After the photoetching is completed, the sample is subjected to F-based etching by using an ICP device, the reaction gas is CF4 and O2, the SiN in the grid slot area is removed, and the gate recess is formed. After the etching is completed, the sample is sequentially placed in acetone, stripping liquid, acetone and isopropyl alcohol for ultrasonic cleaning, the surface photoresist is removed, and then the sample is rinsed with ultrapure water and dried.

[0131] Step 11: depositing metal in the gate recess to form a T-shaped gate electrode 11, and completing the preparation process of the new ohmic regrowth GaN-based device.

[0132] Step 11 includes: depositing Ni / Au metal layers in the gate recess by using an electron beam evaporation device to form the gate electrode 11.

[0133] Reference Figure 2j First, the sample is pre-baked, then the sample is coated with double-layer photoresist, the glue is baked, the gate electrode area is exposed by a photoetching machine, then post-baking and development are performed, the photoresist in the gate area is removed, and the photoetching is completed. First, the residual photoresist in the gate area is removed by using a plasma stripper, then a Ni / Au metal layer is evaporated by using an electron beam evaporation station to form a gate electrode. The sample after completing the metal evaporation is soaked in acetone for more than 3 hours, then ultrasonic cleaning is performed until the metal in the unexposed area completely falls off; the sample is placed in a 60℃ stripping liquid for water bath heating for 15 min; the sample is sequentially placed in acetone and isopropyl alcohol for ultrasonic cleaning for 3 min, then rinsed with ultrapure water for 2 min and dried with N2.

[0134] After the device preparation is completed, the device is tested, metal interconnection can be deposited on the device, the small-area device electrode is led out as a large-area metal pattern, and the connection between the probe and the device in the electrical test is facilitated.

[0135] The present application firstly pre-bakes the sample, then coats double-layer photoresist on the sample, bakes the photoresist, exposes the interconnection area through a photoetching machine, then post-bakes and develops, removes the photoresist in the interconnection area, and completes photoetching. The residual photoresist in the interconnection area is removed by using a plasma photoresist remover, then a Ti / Au metal layer is evaporated by using an electron beam evaporation table to form the interconnection. The sample after completing metal evaporation is soaked in acetone for more than 3 hours, then is ultrasonically cleaned until the metal in the unexposed area completely falls off; the sample is placed in a 60 DEG C stripping liquid for water bath heating for 15 min; the sample is sequentially placed in acetone and isopropyl alcohol for ultrasonic cleaning for 3 min, is washed with ultrapure water for 2 min, and is dried by blowing N2.

[0136] The present application provides a preparation method of a GaN-based device based on novel ohmic regrowth, which epitaxially grows an AlN cap layer on a GaN cap layer. Since the AlN has a larger Al component than AlGaN, it is more conducive to the generation of AlF3 in the self-termination etching process, can effectively improve the selectivity of the self-termination etching, reduce the damage of the etching to the two-dimensional electron gas in the channel, and can obtain a larger output current. Meanwhile, the present application uses AlN as the etching stop layer, and the etching surface obtained is more flat and has fewer surface defects, thereby reducing the surface leakage of the device. Compared with the conventional maskless regrowth, the present application can effectively improve the reliability of the device, can avoid the degradation of the barrier layer caused by the component diffusion and stress effect of the mask in the MOCVD high-temperature epitaxial process, and also retains the advantages of the traditional MBE regrowth, can effectively reduce the contact resistance, and improve the direct current characteristics of the device.

[0137] As shown in Figure 3 The present application provides a GaN-based device based on novel ohmic regrowth, which comprises:

[0138] a substrate layer 1;

[0139] a nucleation layer 2, which is located on the substrate layer 1;

[0140] a GaN buffer layer 3, which is located on the nucleation layer 2;

[0141] The GaN buffer layer comprises three steps, the upper surface of the middle step is a first surface, the upper surface of the lower step is a second surface, the step surface higher than the second surface is a first surface, and the step surface higher than the first surface is a third surface;

[0142] a barrier layer 4, which is located on the third surface of the GaN buffer layer 3;

[0143] a GaN cap layer 5, which is located on the barrier layer;

[0144] an AlN cap layer 6, which is located on the GaN cap layer;

[0145] n+ InGaN layer 7, n + The InGaN layer is located on the first surface of the GaN buffer layer and partially on the AlN cap layer;

[0146] Source electrode 8 and drain electrode 9, the source electrode and the drain electrode are respectively located in the source electrode region and the drain electrode region n + On the InGaN layer;

[0147] Passivation layer 10, the passivation layer is located on the AlN cap layer and n + On the InGaN layer, covering n + InGaN layer and AlN cap layer;

[0148] Gate electrode 11, the gate foot of the gate electrode is located on the AlN cap layer, and the gate cap of the gate electrode is located on the passivation layer, and the gate electrode is located between the source electrode and the drain electrode.

[0149] The application provides a GaN-based device based on novel ohmic regrowth, which is characterized in that an AlN cap layer is epitaxially grown on a GaN cap layer, since the AlN has a larger Al component than AlGaN, the generation of AlF3 is more favorable in the self-terminating etching process, the selectivity of the self-terminating etching can be effectively improved, the damage of the etching to the two-dimensional electron gas in the channel can be reduced, and a larger output current can be obtained. Meanwhile, the application uses AlN as the etching stop layer, the etching surface obtained is more flat, the surface defects are fewer, and thus the surface leakage of the device is reduced. Compared with conventional maskless regrowth, the application can effectively improve the reliability of the device, can avoid the degradation of the barrier layer caused by the component diffusion and stress effect of the mask in the MOCVD high-temperature epitaxy process, and meanwhile, the advantages of traditional MBE regrowth are retained, the contact resistance can be effectively reduced, and the direct current characteristics of the device can be improved.

[0150] The above is a further detailed description of the application in combination with specific preferred embodiments, and the specific implementation of the application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the application belongs, some simple deductions or replacements can be made without departing from the concept of the application, and all of them should be regarded as falling within the protection scope of the application.

Claims

1. A method for fabricating GaN-based devices based on a novel ohmic regenerating length, characterized in that, The application relates to a preparation method of a novel ohmic regrowth GaN-based device. The method comprises the following steps: Step 1: selecting a device substrate; Step 2: sequentially epitaxially growing a nucleation layer, a buffer layer, a barrier layer, a GaN cap layer and an AlN cap layer on the substrate from bottom to top to form a GaN device structure; Step 3: adopting a dry etching process to etch from top to bottom on an ohmic regrowth region of the GaN device structure, and removing the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the ohmic regrowth region so that the buffer layer presents a step structure in the ohmic regrowth region and a central region; Wherein, the ohmic regrowth region is a pre-region, and a lower step surface of the buffer layer in the ohmic regrowth region is a first surface; the step 3 comprises: After the step 2, a sample is formed and sequentially subjected to pre-baking, glue spinning and glue baking; The ohmic regrowth region is exposed, post-baked and developed by using a photoetching machine; The photoresist of the ohmic regrowth region is removed, and a hard film operation is conducted to complete photoetching; An ICP device is used to perform Cl-based etching on the sample after photoetching, and the reaction gas is BCl3 and Cl2; An ICP machine is used to perform Cl-based etching on the ohmic regrowth region of the GaN device structure from top to bottom, the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the ohmic regrowth region are removed to form a groove, so that the buffer layer presents a step structure in the ohmic regrowth region and the central region; After etching is completed, the sample is sequentially placed into acetone, a stripping liquid, acetone and isopropyl alcohol for ultrasonic cleaning to remove the surface photoresist; Step 4: Epitaxial growth of n + InGaN layer; Step 5: n-type layer is removed by self-terminating etching outside the ohmic region + InGaN; The sample after the surface photoresist is removed is washed by using ultrapure water and is blow-dried; Step 6: n + Depositing metal on the InGaN layer to make the source electrode and the drain electrode; Wherein, the ohmic region is a part of the region formed on both sides of the ohmic regrowth region and the ohmic region; Step 7: based on mesa etching, the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer outside the ohmic regrowth region are etched from top to bottom to form a device with isolation regions on both sides; Wherein, after mesa etching, the buffer layer presents a three-layer step structure, and the upper surface of the lowermost layer is a second surface; Step 8: a passivation layer is deposited on the surface of the device; Step 9: a dry etching process is adopted to remove the passivation layer covering the source electrode region and the drain electrode region to form a through hole; Step 10: a dry etching process is adopted to remove the passivation layer of the gate region until the AlN cap layer to form a gate groove; Wherein, the gate region is between the source electrode and the drain electrode, and the regions are not adjacent; 2. The method of claim 1, wherein the method further comprises: Step 11: a T-shaped gate electrode is deposited in the gate groove to complete the preparation process of the novel ohmic regrowth GaN-based device. The step 2 comprises:

3. The method of claim 1, wherein the method further comprises: A nucleation layer, a buffer layer, a barrier layer, a GaN cap layer and an AlN cap layer are sequentially epitaxially grown on the substrate from bottom to top by using MOCVD to form a GaN device structure. n + InGaN layers; wherein the doping concentration of Si is .

4. The method of claim 1, wherein the method further comprises: The step 4 comprises: The step 5 comprises: The sample formed in the step 4 is sequentially subjected to pre-baking, glue spinning and glue baking; The self-termination etching region outside the ohmic region is exposed, post-baked and developed by using a photoetching machine, and the photoresist of the self-termination etching region is removed; The Samco equipment was used to self-terminate etch the sample after lithography, removing n + InGaN, self-terminated in an AlN cap layer; The sample after development is subjected to hard film operation to complete photoetching; 5. The method of claim 1, wherein the method further comprises: Wherein, the reaction gas of the self-termination etching is SF6 and BCl3. The n + On InGaN, Ti / Au ohmic stack metal is deposited to fabricate source and drain electrodes.

6. The method of claim 1, wherein the method further comprises: The step 6 comprises: The step 7 comprises: Utilizing ICP equipment, based on Cl-based etching, the AlN cap layer, the GaN cap layer, the barrier layer and part of the buffer layer of the passive region are removed to reach the second surface, forming an isolation region on both sides of the device; wherein the Cl-based etching reaction gas is BCl3 and Cl2.

7. The method of claim 1, wherein the method further comprises: The step 9 comprises: Utilizing ICP equipment, the passivation layer of the source electrode region and the drain electrode region is removed to form a via hole by F-based etching process.

8. The method of claim 1, wherein the method further comprises: The step 10 comprises: Utilizing ICP equipment, the passivation layer of the gate region is removed to form a gate recess by F-based etching process. The step 11 comprises: utilizing electron beam evaporation equipment, depositing Ni / Au metal stack in the gate recess to form a gate electrode.

9. A GaN-based device based on novel ohmic regrowth, characterized by, The GaN-based device based on novel ohmic regrowth is prepared by the preparation method of any one of claims 1-8, and the GaN-based device based on novel ohmic regrowth comprises: a substrate layer; a nucleation layer, which is located on the substrate layer; a GaN buffer layer, which is located on the nucleation layer; the GaN buffer layer comprises three layers of steps, the upper surface of the middle step is a first surface, the upper surface of the lower step is a second surface, the step surface higher than the second surface is a first surface, and the step surface higher than the first surface is a third surface; a barrier layer, which is located on the third surface of the GaN buffer layer; a GaN cap layer, which is located on the barrier layer; an AlN cap layer, which is located on the GaN cap layer; n + InGaN layer, said n + InGaN layer is located on the first surface of the GaN buffer layer and partially on the AlN cap layer; a source electrode and a drain electrode, respectively, in the n + over the InGaN layer; a passivation layer located between the AlN cap layer and the n + over the InGaN layer, covering the n + InGaN layer and the AlN cap layer; a gate electrode, a gate leg of which is located on the AlN cap layer, a gate cap of which is located on the passivation layer, and which is located between the source electrode and the drain electrode.

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