GaN millimeter wave power device based on MOCVD ohm regrowth and preparation method

Abstract

The invention discloses a GaN millimeter wave power device based on MOCVD ohm regrowth and a preparation method thereof, and relates to the field of semiconductor devices.On the basis of ingenious design of an improved photoetching mask plate and a device process, the hard mask area on the surface of a wafer and the negative influence of the hard mask area are reduced to the minimum, and the yield of the wafer is improved. The problems that the surface of conventional MOCVD ohmic regrowth n + nitride is uneven, the actual epitaxial thickness deviates from a design value, and the uniformity is poor are solved, the ohmic contact resistance is further reduced by maximizing the area of an ohmic regrowth region, and meanwhile the performance and reliability of an MOCVD ohmic regrowth GaN-based millimeter wave power device are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor devices, and particularly relates to a GaN millimeter wave power device based on MOCVD ohmic regrowth and a preparation method thereof. BACKGROUND

[0002] Millimeter wave technology has great bandwidth, high data transmission rate, low delay, high resolution and device miniaturization capability, making it a key technology in the fields of 5G / 6G communication, high-precision radar, etc. Compared with the first generation of semiconductor silicon (Si) and the second generation of semiconductor gallium arsenide (GaAs), the third generation of semiconductor gallium nitride (GaN) is expected to become the preferred material for preparing high-performance and high-reliability millimeter wave power devices due to its material advantages such as large band gap, high critical breakdown field, high two-dimensional electron gas density and high electron saturation drift speed.

[0003] The core indicators of GaN-based millimeter wave power devices include high cutoff frequency to ensure that the device has millimeter wave frequency band working capability, high power added efficiency to realize low power consumption of the device, and high output power to increase signal transmission distance. The improvement of the above three core parameters can be realized at the same time by reducing the parasitic resistance loss of the device. The specific method for reducing the parasitic resistance loss of the device includes reducing the heterojunction sheet resistance, ohmic contact resistance and device source-drain spacing. Using a strong polarization high-Al component barrier material helps to reduce the heterojunction sheet resistance. After the wafer material is determined, an alloyed ohmic contact is usually formed based on a high-temperature thermal annealing process, which can realize a contact resistance value at the level of 0.2-0.5 Ω·mm. However, the ohmic metal surface is rough and the edge is uneven after high-temperature annealing, with burrs, so that the degree of scaling-down of the device source-drain is limited, and the minimum source-drain spacing is usually 1 μm. Although the high-temperature annealing ohmic contact process is convenient, it cannot meet the requirements for realizing ultra-low parasitic resistance loss. Therefore, an advanced ohmic regrowth process is used to form a non-alloyed ohmic contact, which can further reduce the contact resistance to the level of 0.1 Ω·mm, and the ohmic metal surface is smooth and the edge is flat, which makes it easy to scale down the device source-drain spacing to less than 1 μm, which helps to realize ultra-low parasitic resistance loss.

[0004] The ohmic regrowth process refers to etching a heterojunction material in an ohmic electrode region, growing a high-concentration Si-doped low-resistance nitride material in the etching well, and then depositing an ohmic metal stack, without annealing, to achieve a low-ohmic contact resistance; at the same time, the size of the device source and drain is no longer determined by the spacing of the source and drain ohmic metal, but by the spacing between the source and drain ohmic regrowth etching wells, so that the actual device source and drain size is further reduced. The implementation of the ohmic regrowth process can be based on a molecular beam epitaxy (MBE) or a metal organic chemical vapor deposition (MOCVD) device. The MBE device has a slow growth rate, low growth efficiency, and high equipment use and maintenance costs; however, the MOCVD device has a higher growth rate, supports multi-piece "planetary" growth in the same furnace, and has lower equipment use and maintenance costs, thus having the advantages of low-cost and large-batch epitaxial growth, and being more suitable for industrial application.

[0005] Currently, the main problems faced by the MOCVD ohmic regrowth technology include: the MOCVD ohmic regrowth contact resistance is not as good as that of the MBE ohmic regrowth contact resistance; the MOCVD ohmic regrowth n + The nitride surface is extremely uneven, the actual epitaxial thickness deviates from the design, and the uniformity is poor, which significantly affects the reliability of the regrowth device. SUMMARY

[0006] In order to solve the above problems in the prior art, the present application provides a GaN millimeter wave power device based on MOCVD ohmic regrowth and a preparation method thereof. The technical problems to be solved by the present application are solved by the following technical solutions: The present application provides a preparation method of a GaN millimeter wave power device based on MOCVD ohmic regrowth, comprising: Step 1: forming a laminated buffer layer, channel layer, barrier layer and hard mask dielectric layer on the substrate in sequence, and forming a two-dimensional electron gas between the channel layer and the barrier layer; Step 2: spin-coating a positive photoresist on the surface of the hard mask dielectric layer, and exposing the positive photoresist to light using an improved photomask, wherein the improved photomask is opaque in the device source and drain channel region, and transparent in the remaining regions; Step 3: developing and hardening the exposed positive photoresist, retaining the positive photoresist in the device source and drain channel region, defining an ohmic regrowth region, and removing the hard mask dielectric layer in the ohmic regrowth region; Step 4: etching the barrier layer and the channel layer in the ohmic regrowth region under the masking effect of the retained positive photoresist, and etching to below the interface between the barrier layer and the channel layer to form an ohmic regrowth well; Step 5: removing the positive photoresist in the device source and drain channel region, and repairing the damage to the etching interface of the ohmic regrowth well. Step 6: Forming a second-growth n + nitride on the position of the ohmic regrowth well by using a MOCVD equipment. Step 7: Injecting ions into the isolation region by using an ion implantation equipment to realize device isolation. Step 8: Preparing source, drain and gate of the device.

[0007] In one embodiment of the present application, the material of the substrate is SiC or Si; the material of the barrier layer is AlN, ScAl 0.82 N, InAl 0.83 N or Al >0.5 GaN; and the material of the hard mask medium layer is SiO2.

[0008] In one embodiment of the present application, the width of the device source-drain channel region is not more than 1 μm.

[0009] In one embodiment of the present application, in the step 3, the hard mask medium layer of the ohmic regrowth region is removed by using a dry etching process of an ICP etching equipment, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching equipment is 80 W, and the lower electrode power is 10 W.

[0010] In one embodiment of the present application, in the step 4, the barrier layer and the channel layer of the ohmic regrowth region are etched by using a dry etching process of an ICP etching equipment to at least 30 nm below the interface of the barrier layer and the channel layer to form the ohmic regrowth well, wherein the etching gas is BCl3 / Cl2, the flow rate is 20 / 8 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching equipment is 51 W, and the lower electrode power is 14 W.

[0011] In one embodiment of the present application, the step 5 comprises: Step 5.1: Removing the positive photoresist of the device source-drain channel region by using a wet process. Step 5.2: Immersing the wafer in ammonia water heated by water bath to repair the etching interface of the device ohmic regrowth well.

[0012] In one embodiment of the present application, the step 6 comprises: Step 6.1: Forming a second-growth n + nitride on the surface of the device by using a MOCVD equipment. + The n +The nitride is in an amorphous or disordered state. Step 6.2: removing the hard mask medium layer and the n + The nitride is in an amorphous or disordered state.

[0013] In an embodiment of the present application, the n + The nitride is in an amorphous or disordered state. + The nitride is in an amorphous or disordered state. + The nitride is in an amorphous or disordered state.

[0014] In an embodiment of the present application, the step 8 comprises: Step 8.1: depositing an ohmic stack metal on the upper surface of the n + The nitride is in an amorphous or disordered state. Step 8.2: depositing a SiN passivation layer on the surface of the device by using a PECVD device, and removing the SiN passivation layer on the source and drain by using an ICP etching device through a dry etching process, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W. Step 8.3: removing the SiN passivation layer in the gate leg area by using an ICP etching device through a dry etching process, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W. Step 8.4: depositing a gate stack metal in the gate leg area and the gate cap area by using an electron beam evaporation device to form a gate.

[0015] The present application provides a GaN millimeter wave power device based on MOCVD ohmic regrowth, which is prepared by the preparation method of the GaN millimeter wave power device based on MOCVD ohmic regrowth.

[0016] Compared with the prior art, the present application has the following beneficial effects: The preparation method of the GaN millimeter wave power device based on MOCVD ohmic regrowth of the present application reduces the area of the hard mask on the wafer surface and its negative effects to the minimum through the ingenious design of the improved photoetching mask and device process, improves the conventional MOCVD ohmic regrowth n + The nitride is in an amorphous or disordered state.

[0017] The above description is only a summary of the technical scheme of the present application, in order to enable the technical means of the present application to be implemented more clearly, and in order to enable the above and other purposes, characteristics and advantages of the present application to be more apparent and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of a preparation method of a GaN millimeter wave power device based on MOCVD ohmic regrowth provided by an embodiment of the present application; Figure 2 is a process schematic diagram of a preparation process of a GaN millimeter wave power device based on MOCVD ohmic regrowth provided by an embodiment of the present application; Figure 3 is a process schematic diagram of a preparation process of a GaN millimeter wave power device prepared by a conventional MOCVD ohmic regrowth process.

[0019] Figure 4 is a field area schematic diagram of a 6-inch wafer provided by an embodiment of the present application; Figure 5 is a complete layout example diagram of one field area in a wafer provided by an embodiment of the present application; Figure 6 is a layout of a conventional MOCVD ohmic regrowth process; Figure 7 is a layout of a MOCVD ohmic regrowth process of the method of the present application.

[0020] Figure legend: 1-substrate; 2-buffer layer; 3-channel layer; 4-potential barrier layer; 5-hard mask dielectric layer; 6-positive photoresist; 7-n + nitride; 8-isolation region; 9-source electrode; 10-drain electrode; 11-gate electrode; 12-SiN passivation layer. DETAILED DESCRIPTION

[0021] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined purpose, the following describes in detail a GaN millimeter wave power device and a preparation method based on MOCVD ohmic regrowth according to the present application, in combination with the accompanying drawings and specific embodiments.

[0022] The foregoing and other technical contents, characteristics and effects of the present application can be clearly presented in the following detailed description of the specific embodiments in combination with the accompanying drawings. Through the description of the specific embodiments, the technical means and effects adopted by the present application to achieve the predetermined purpose can be understood more deeply and specifically. However, the accompanying drawings are provided for reference and explanation only, and are not used to limit the technical scheme of the present application.

[0023] In a first aspect, an embodiment of the present application provides a preparation method of a GaN millimeter wave power device based on MOCVD ohmic regrowth. + The nitride surface is extremely uneven, the actual epitaxial thickness deviates from the design, and the uniformity is poor, which is mainly affected by the "surface mask structure" in the process.

[0024] Specifically, the conventional MOCVD ohmic regrowth n + In the nitride process, most of the wafer surface is covered by a hard mask (such as SiO2), and a small number of areas correspond to the mask opening and the ohmic regrowth well area after nitride etching. From the mask surface to the ohmic regrowth well, the transport and reaction of the growth source gas are seriously affected by the adjacent mask, resulting in n + The nitride epitaxy is non-uniform, which is manifested in that the n + The nitride epitaxy thickness is thick (forming a protrusion), and the n + The nitride epitaxy thickness is thin (forming a recess), the actual epitaxial thickness deviates from the growth design value, and changes significantly with the position, which significantly affects the reliability of the ohmic regrowth device. At the same time, it is found that the smaller the mask opening area, that is, the smaller the area of the ohmic regrowth well, the n + The nitride epitaxy is more affected by the surrounding mask, and the prepared device has a higher ohmic contact resistance, which is not conducive to the improvement of the device performance.

[0025] Based on this, the present application improves the conventional MOCVD ohmic regrowth process and proposes a new MOCVD ohmic regrowth technical solution, which can minimize the area of the hard mask on the wafer surface and its negative effects, while maximizing the area of the ohmic regrowth region, significantly improving the performance and reliability of the MOCVD ohmic regrowth GaN-based millimeter wave power device.

[0026] Please refer to Figure 1 , Figure 1 is a schematic diagram of a preparation method of a GaN millimeter wave power device based on MOCVD ohmic regrowth provided by an embodiment of the present application, as Figure 1 shown, the preparation method of the GaN millimeter wave power device based on MOCVD ohmic regrowth of the present embodiment includes the following steps: Step 1: Forming a laminated buffer layer, channel layer, barrier layer and hard mask dielectric layer on the substrate in sequence, forming a two-dimensional electron gas between the channel layer and the barrier layer.

[0027] Optionally, the material of the substrate is SiC or Si; the material of the barrier layer is a high Al component material, such as AlN, ScAl 0.82 N, InAl 0.83 N or Al >0.5 GaN; the material of the hard mask dielectric layer is SiO2.

[0028] In the embodiment, the MOCVD device can be used to grow the high Al component low sheet resistance heterojunction material on the substrate, i.e., the buffer layer, the channel layer and the barrier layer are stacked from bottom to top; the PECVD device can be used to deposit the hard mask dielectric layer on the surface of the barrier layer.

[0029] Step 2: spin-coat the positive photoresist on the surface of the hard mask dielectric layer, and expose the positive photoresist by using the improved photomask, wherein the improved photomask is opaque in the device source-drain channel region and transparent in the rest region.

[0030] In the embodiment, the improved photomask is opaque in the device source-drain channel region, i.e., dark region, and transparent in the rest region, i.e., clear region, and the width of the device source-drain channel region is not more than 1 μm.

[0031] It can be understood that the width of the device source-drain channel region is subject to the equipment parameters of the photolithography machine, and exemplarily, the width of the device source-drain channel region can be 0.3-0.5 μm.

[0032] Step 3: develop and harden the exposed positive photoresist, retain the positive photoresist in the device source-drain channel region, define the ohmic regrowth region, and remove the hard mask dielectric layer in the ohmic regrowth region.

[0033] Optionally, the ICP etching device is used to remove the hard mask dielectric layer in the ohmic regrowth region by using the dry etching process, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W.

[0034] Step 4: etch the barrier layer and the channel layer in the ohmic regrowth region under the masking effect of the retained positive photoresist, and etch to below the interface between the barrier layer and the channel layer to form the ohmic regrowth well.

[0035] Optionally, the ICP etching device is used to etch the barrier layer and the channel layer in the ohmic regrowth region by using the dry etching process, and etch to at least 30 nm below the interface between the barrier layer and the channel layer to form the ohmic regrowth well, wherein the etching gas is BCl3 / Cl2, the flow rate is 20 / 8 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 51 W, and the lower electrode power is 14 W.

[0036] Step 5: Remove the positive photoresist in the source / drain channel region of the device and repair the damage to the etched interface of the ohmic regrowth well.

[0037] Optionally, step 5 includes: Step 5.1: Remove the positive photoresist in the source / drain channel region of the device using a wet process; Step 5.2: Immerse the wafer in ammonia water heated in a water bath to repair the damage to the etched interface of the ohmic regrowth well of the device.

[0038] At this point, the area of ​​the hard mask dielectric layer on the wafer surface is reduced from initially covering the entire wafer to only covering the source and drain channel regions of the devices, minimizing the surface mask area and its impact on subsequent secondary growth. + The negative impact of nitrides is to minimize the surface mask area, i.e., to maximize the area of ​​the ohmic regeneration well region.

[0039] Step 6: Use MOCVD equipment to form a secondary growth n at the location of the ohmic regrowth well. + Nitrogen compounds.

[0040] Optionally, step 6 includes: Step 6.1: Use MOCVD equipment to perform secondary growth of n on the device surface + Nitrides, wherein n is located at the site of the ohmic regeneration well. + The nitride is a single crystal, and the n on the upper surface of the hard mask dielectric layer is... + Nitrides are in an amorphous or non-crystalline state; Step 6.2: Remove the hard mask dielectric layer and its upper surface n + Nitrogen compounds.

[0041] In this embodiment, n + Nitrogen compounds are n + GaN or n + InGaN. Optionally, the hard mask dielectric layer and its upper surface can be removed by BOE wet processing. + Nitrogen compounds.

[0042] At this point, except for the device source / drain channel regions which retain the initial heterojunction structure—that is, the channel layer, the barrier layer, and the two-dimensional electron gas formed between the channel layer and the barrier layer—the rest of the wafer has undergone secondary growth of n... + The use of nitrides maximizes the ohmic regrowth area of ​​MOCVD, approaching the entire wafer area, and minimizes ohmic contact resistance. This is something that conventional MOCVD ohmic regrowth processes cannot match, as the conventional ohmic regrowth area is limited and far less than the MOCVD ohmic regrowth area of ​​this invention.

[0043] Step 7: Use an ion implantation device to implant ions into the isolation region to achieve device isolation.

[0044] Alternatively, ion implantation equipment can be used to implant, for example, boron ions, nitrogen ions or argon ions into the isolation region to achieve device isolation.

[0045] Step 8: Fabricate the source, drain, and gate of the device.

[0046] Optionally, step 8 includes: Step 8.1: Using an electron beam evaporation device to evaporate the n in the source / drain region of the device + An ohmic multilayer metal is deposited on the upper surface of the nitride to form the source and drain. In this embodiment, the ohmic multilayer metal can be a Ti / Au multilayer metal. This ohmic multilayer metal is deposited on a flat n-type surface. + The nitride top surface can achieve low ohmic contact resistance without annealing.

[0047] Step 8.2: Deposit a SiN passivation layer on the device surface using a PECVD device, and remove the SiN passivation layer on the source and drain electrodes using an ICP etching device with a dry etching process. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching device is 80 W and the lower electrode power is 10 W. Step 8.3: Use an ICP etching equipment to remove the SiN passivation layer in the gate area using a dry etching process. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm and a chamber pressure of 5 mTorr. The upper electrode power of the ICP etching equipment is 80W and the lower electrode power is 10W. Step 8.4: Deposit gate stack metal in the gate foot region and gate cap region using an electron beam evaporation device to form the gate.

[0048] In this embodiment, the gate stack metal can be a Ni / Au stack metal.

[0049] This invention relates to a method for fabricating GaN millimeter-wave power devices based on MOCVD ohmic regeneration. Through ingenious design of an improved photolithography mask and device process, the method minimizes the hard mask area on the wafer surface and its negative impacts. This significantly reduces the adverse effects of the "near-whole wafer-wide surface mask structure" and "small ohmic regeneration area" on device performance and reliability in conventional MOCVD ohmic regeneration processes. It improves upon the conventional MOCVD ohmic regeneration method. +The problems of uneven nitride surfaces, actual epitaxial thickness deviating from the design value, and poor uniformity are addressed. By maximizing the area of ​​the ohmic regrowth region, the ohmic contact resistance is further reduced, thereby improving the performance and reliability of MOCVD ohmic regrowth GaN-based millimeter-wave power devices.

[0050] Furthermore, the process flow of the fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length of the present invention is illustrated by comparative examples.

[0051] Example 1 Please see Figure 2 , Figure 2 This is a schematic diagram illustrating the fabrication process of a GaN millimeter-wave power device based on MOCVD ohmic regeneration length, as provided in an embodiment of the present invention. Figure 2 As shown, the fabrication process of the GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to the present invention includes the following steps: Step 1: Using an MOCVD device, a stacked buffer layer 2, a channel layer 3, and a barrier layer 4 are grown on substrate 1. The substrate 1 is made of SiC, a two-dimensional electron gas (2DEG) is formed between the channel layer 3 and the barrier layer 4, and the barrier layer 4 is made of AlN.

[0052] Step 2: Deposit a hard mask dielectric layer 5 on the surface of the barrier layer 4 using a PECVD device. The material of the hard mask dielectric layer 5 is SiO2.

[0053] Step 3: Spin-coat positive photoresist 6 onto the surface of the hard mask dielectric layer 5. Expose the positive photoresist 6 using an improved photomask. The improved photomask is opaque in the device source / drain channel region and transparent in the remaining regions. The width of the device source / drain channel region does not exceed 1 μm.

[0054] Step 4: Develop and harden the exposed positive photoresist 6 to retain the positive photoresist 6 in the source and drain channel regions of the device and define the ohmic regrowth region.

[0055] Step 5: Under the masking effect of the retained positive photoresist 6, the hard mask dielectric layer 5 of the ohmic regrowth region is removed using a dry etching process in an ICP etching apparatus. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching apparatus is 80 W, while the lower electrode power is 10 W.

[0056] Step 6: Under the masking effect of the retained positive photoresist 6, the barrier layer 4 and the channel layer 3 of the ohmic regrowth region are etched using a dry etching process on an ICP etching device, etching to at least 30 nm below the interface between the barrier layer 4 and the channel layer 3, forming an ohmic regrowth well. The etching gas is BCl3 / Cl2 with a flow rate of 20 / 8 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching device is 51 W and the lower electrode power is 14 W.

[0057] Step 7: Remove the positive photoresist 6 from the source and drain channel regions of the device using a wet process, and immerse the wafer in ammonia water heated in a water bath to repair the damage to the etched interface of the ohmic regrowth well of the device.

[0058] Step 8: Use MOCVD equipment to perform secondary growth of n on the device surface + Nitride 7, where n + Nitride 7 is n + GaN, n at the location of the ohmic regeneration well + Nitride 7 is a single crystal, and the n on the upper surface of the hard mask dielectric layer 5 is... + Nitride 7 is in an amorphous or non-crystalline state.

[0059] Step 9: Remove the hard mask dielectric layer 5 and its upper surface n by BOE wet processing. + Nitrogen compound 7.

[0060] Step 10: Using an ion implantation device, boron ions are implanted into the isolation region 8 to achieve device isolation.

[0061] Step 11: Using an electron beam evaporation device, n in the source / drain region of the device + Ti / Au multilayer metal is deposited on the upper surface of nitride 7 to form source 9 and drain 10.

[0062] Step 12: Deposit a SiN passivation layer 12 on the device surface using a PECVD device, and remove the SiN passivation layer 12 on the source electrode 9 and drain electrode 10 using an ICP etching device with a dry etching process. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W.

[0063] Step 13: Using an ICP etching apparatus, the SiN passivation layer 12 in the gate pin region is removed using a dry etching process. Then, an electron beam evaporation apparatus is used to deposit a Ni / Au multilayer metal in the gate pin and gate cap regions to form the gate 11. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching apparatus is 80 W, while the lower electrode power is 10 W.

[0064] Comparative Example 1 Please see Figure 3 , Figure 3 This is a schematic diagram illustrating the fabrication process of GaN millimeter-wave power devices using conventional MOCVD ohmic regrowth technology, as shown below. Figure 3 As shown, the fabrication process of GaN millimeter-wave power devices using conventional MOCVD ohmic regrowth technology includes the following steps: Step 1: Using an MOCVD device, a stacked buffer layer 2, a channel layer 3, and a barrier layer 4 are grown on substrate 1. The substrate 1 is made of SiC, a two-dimensional electron gas (2DEG) is formed between the channel layer 3 and the barrier layer 4, and the barrier layer 4 is made of AlN.

[0065] Step 2: Deposit a hard mask dielectric layer 5 on the surface of the barrier layer 4 using a PECVD device. The material of the hard mask dielectric layer 5 is SiO2.

[0066] Step 3: Spin-coat positive photoresist 6 onto the surface of the hard mask dielectric layer 5, and expose the positive photoresist 6 using a conventional photomask. The conventional photomask is transparent in the source and drain areas of the device, and opaque in the remaining areas.

[0067] Step 4: Develop and harden the exposed positive photoresist 6, retaining the positive photoresist 6 outside the source and drain regions of the device, and define the ohmic regrowth region.

[0068] Step 5: Under the masking effect of the retained positive photoresist 6, the hard mask dielectric layer 5 of the ohmic regrowth region is removed using a dry etching process in an ICP etching apparatus. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching apparatus is 80 W, while the lower electrode power is 10 W.

[0069] Step 6: Under the masking effect of the retained positive photoresist 6, the barrier layer 4 and the channel layer 3 of the ohmic regrowth region are etched using a dry etching process on an ICP etching device, etching to at least 30 nm below the interface between the barrier layer 4 and the channel layer 3, forming an ohmic regrowth well. The etching gas is BCl3 / Cl2 with a flow rate of 20 / 8 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching device is 51 W and the lower electrode power is 14 W.

[0070] Step 7: Use a wet process to remove the positive photoresist 6 outside the source and drain areas of the device, and soak the wafer in ammonia water heated in a water bath to repair the damage to the etched interface of the ohmic regrowth well of the device.

[0071] Step 8: Use MOCVD equipment to perform secondary growth of n on the device surface + Nitride 7, where n + Nitride 7 is n + GaN, n at the location of the ohmic regeneration well + Nitride 7 is a single crystal, and the n on the upper surface of the hard mask dielectric layer 5 is... + Nitride 7 is in an amorphous or non-crystalline state.

[0072] Step 9: Remove the hard mask dielectric layer 5 and its upper surface n by BOE wet processing. + Nitrogen compound 7.

[0073] Step 10: Using an ion implantation device, boron ions are implanted into the isolation region 8 to achieve device isolation.

[0074] Step 11: Using an electron beam evaporation device, n in the source / drain region of the device + Ti / Au multilayer metal is deposited on the upper surface of nitride 7 to form source 9 and drain 10.

[0075] Step 12: Deposit a SiN passivation layer 12 on the device surface using a PECVD device, and remove the SiN passivation layer 12 on the source electrode 9 and drain electrode 10 using an ICP etching device with a dry etching process. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W.

[0076] Step 13: Using an ICP etching apparatus, the SiN passivation layer 12 in the gate pin region is removed using a dry etching process. Then, an electron beam evaporation apparatus is used to deposit a Ni / Au multilayer metal in the gate pin and gate cap regions to form the gate 11. The etching gas is CF4 / O2 with a flow rate of 25 / 5 sccm, the chamber pressure is 5 mTorr, and the upper electrode power of the ICP etching apparatus is 80 W, while the lower electrode power is 10 W.

[0077] It should be noted that for conventional MOCVD ohmic regeneration processes, the vast majority of the wafer surface is covered by a hard mask, with only a very small area corresponding to the ohmic regeneration region. MOCVD ohmic regeneration n + Nitrides are formed based on the transport of source gases (TMGa, TMIn, NH3, SiH4) and chemical reactions. The source gases need to be transported from the reaction chamber to the sample surface, and then through a hard mask on the sample surface to the ohmic regrowth region. The chemical reaction is completed in the regrowth region to generate nitrides. + Nitrides. The transport of the reaction source gas and its distribution within the ohmic regrowth region are severely affected by the hard mask surrounding the regrowth region, resulting in an extension of n beyond the regrowth region. +Nitride compounds have a concave center and raised edges.

[0078] For the MOCVD ohmic regrowth process of this invention, the hard mask area on the wafer surface is minimized while the ohmic regrowth region area is maximized by improving the photolithography mask and device technology. At this point, the influence of the hard mask on the transport of the reaction source gas and its distribution within the ohmic regrowth region is minimized to the greatest extent, thereby avoiding the problems associated with conventional MOCVD ohmic regrowth. + The problems include uneven nitride surfaces, actual epitaxial thickness deviating from the design value, and poor uniformity.

[0079] Furthermore, the hard mask area and its ratio to the total wafer area, as well as the ohmic regrowth region area and its ratio to the total wafer area, of the MOCVD ohmic regrowth process of the present invention and the conventional MOCVD ohmic regrowth process are described.

[0080] Taking a 6-inch wafer as an example, such as Figure 4 The schematic diagram of the field area of ​​a 6-inch wafer provided in the embodiment of the present invention is shown. The 6-inch wafer may contain 632 field areas, and these 632 field areas are completely identical. Each field area is a small square in the figure.

[0081] Example of a complete layout of a field area in a wafer: Figure 5 As shown, the dimensions are 5000 μm × 5000 μm, and the area is 2.5 × 10. 7 μm 2 This includes numerous test structures, transistor structures, and circuit structures, all of which involve ohmic regeneration processes.

[0082] for Figure 5 The field area shown is the layout used in a conventional MOCVD ohmic regrowth process, as shown below. Figure 6 As shown, the interior of the "closed shape" in the layout corresponds to the ohmic regrowth region, which in turn corresponds to the hard mask region on the exterior of the "closed shape." Using the shape area integration function, the area of ​​the closed shape or the ohmic regrowth region is 1.72216 × 10⁻⁶. 6 μm 2 The proportion of the area occupied by it is: That is, 6.88864%; as the complement, the proportion of the hard mask region to the area of ​​the field is That is, 93.11136%.

[0083] for Figure 5 The field area shown is the layout used in the MOCVD ohmic regrowth process of the present invention, as follows: Figure 7As shown, the interior of the "closed shape" in the layout corresponds to the hard mask region, and the exterior of the "closed shape" corresponds to the ohmic regrowth region. Using the shape area integration function, the area of ​​the closed shape or the hard mask region is 1.28881 × 10⁻⁶. 5 μm 2 The proportion of the area occupied by it is: That is, 0.515524%; as the complement, the proportion of the ohmic regrowth region to the area of ​​the field is That is, 99.484476%.

[0084] It can be clearly seen that the MOCVD ohmic regrowth process of the present invention significantly reduces the area of ​​the hard mask region while maximizing the area of ​​the ohmic regrowth region, thereby improving device performance and reliability.

[0085] Secondly, embodiments of the present invention provide a GaN millimeter-wave power device based on MOCVD ohmic regeneration length, which is fabricated using the fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length provided in the first aspect.

[0086] For details regarding the GaN millimeter-wave power device based on MOCVD ohmic regeneration and its corresponding beneficial effects, please refer to the relevant content on the fabrication method of the GaN millimeter-wave power device based on MOCVD ohmic regeneration provided in the first aspect, which will not be repeated here.

[0087] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0088] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0089] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a GaN millimeter wave power device based on MOCVD ohmic regrowth, characterized in that, The method comprises the following steps: Step 1: sequentially forming a laminated buffer layer, a channel layer, a barrier layer and a hard mask medium layer on a substrate, and forming a two-dimensional electron gas between the channel layer and the barrier layer; Step 2: spin-coating a positive photoresist on the surface of the hard mask medium layer, and exposing the positive photoresist by using an improved photomask, wherein the photomask is opaque in the device source-drain channel region and transparent in the remaining region; Step 3: developing and hardening the exposed positive photoresist, retaining the positive photoresist in the device source-drain channel region, defining an ohmic regrowth region, and removing the hard mask medium layer in the ohmic regrowth region; Step 4: etching the barrier layer and the channel layer in the ohmic regrowth region under the masking effect of the retained positive photoresist, and etching to below the interface between the barrier layer and the channel layer to form an ohmic regrowth well; Step 5: removing the positive photoresist in the device source-drain channel region, and repairing the etching interface of the ohmic regrowth well; Step 6: Form a second growth n- type epitaxial layer using an MOCVD apparatus at the location of the ohmic regrown well + nitride; Step 7: implanting ions in the isolation region by using an ion implantation device to realize device isolation; Step 8: preparing a source electrode, a drain electrode and a gate electrode of the device.

2. The fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, The material of the substrate is SiC or Si; the material of the barrier layer is AlN, ScAl 0.82 N, InAl 0.83 N or Al >0.5 GaN; the material of the hard mask medium layer is SiO2.

3. The fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, The width of the device source-drain channel region is not more than 1 μm.

4. The fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, In the step 3, the hard mask medium layer in the ohmic regrowth region is removed by using an ICP etching device and a dry etching process, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W.

5. The fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, In the step 4, the barrier layer and the channel layer in the ohmic regrowth region are etched by using an ICP etching device and a dry etching process, and etching to at least 30 nm below the interface between the barrier layer and the channel layer to form the ohmic regrowth well, wherein the etching gas is BCl3 / Cl2, the flow rate is 20 / 8 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 51 W, and the lower electrode power is 14 W.

6. The method for fabricating a GaN millimeter-wave power device based on MOCVD ohmic regeneration as described in claim 1, characterized in that, The step 5 comprises: Step 5.1: removing the positive photoresist in the device source-drain channel region by using a wet process; Step 5.2: soaking the wafer in ammonia water by using water bath heating to repair the etching interface of the ohmic regrowth well of the device.

7. The fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, The step 6 comprises: Step 6.1: n-growth on the device surface by MOCVD equipment + nitride, wherein the n-growth well of the ohmic regrowth well is located at the n + nitride is single crystal, the n-growth well of the ohmic regrowth well is located at the n + nitride is amorphous or in an amorphous state; Step 6.2: Removal of the hard mask dielectric layer and its upper surface n + nitride.

8. The fabrication method of GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, The n + Nitride is n + GaN or n + InGaN.

9. The method for fabricating a GaN millimeter-wave power device based on MOCVD ohmic regeneration length according to claim 1, characterized in that, The step 8 comprises: Step 8.1: n-type ohmic metal is deposited on the source and drain regions of the device using an e-beam evaporation apparatus + The upper surface of the nitride is deposited with ohmic metal to form the source and drain electrodes. Step 8.2: depositing a SiN passivation layer on the surface of the device by using a PECVD device, and removing the SiN passivation layer on the source electrode and the drain electrode by using an ICP etching device and a dry etching process, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W; Step 8.3: removing the SiN passivation layer in the gate leg region by a dry etching process using an ICP etching device, wherein the etching gas is CF4 / O2, the flow rate is 25 / 5 sccm, the chamber pressure is 5 mTorr, the upper electrode power of the ICP etching device is 80 W, and the lower electrode power is 10 W; Step 8.4: depositing a gate stack metal in the gate leg region and the gate cap region by an e-beam evaporation device to form a gate.

10. A GaN millimeter wave power device based on MOCVD ohmic regrowth, characterized in that, The GaN millimeter wave power device based on MOCVD ohmic regrowth is prepared by the method according to any one of claims 1-9.

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