A method for isolating a GaN-based device

Abstract

The application discloses a method for isolating GaN-based devices, wherein a Fe film is evaporated on a region requiring device isolation on a surface of a GaN HEMT structure, a pulse laser is used to heat the Fe film covering region, laser pulse energy is reasonably controlled, Fe is accelerated to diffuse into the sample and the sample is recrystallized, so that Fe is incorporated into the sample lattice. Fe impurities are deep level impurities in GaN-based materials, and doping Fe in the region requiring isolation can form a high resistance state, so that the purpose of device isolation is achieved. The method can reduce the defect density of the isolation region by recrystallizing the sample through high-energy laser pulses and introducing Fe impurities in the recrystallization process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor device manufacturing, and relates to a GaN-based device isolation method. BACKGROUND

[0002] III-nitride materials represented by GaN are direct bandgap semiconductors, and have advantages such as high breakdown electric field, high electron saturation drift speed, radiation resistance, and high temperature resistance, and are widely applied in the fields of high-efficiency light-emitting devices and electronic devices. A heterojunction represented by AlGaN / GaN has a high electron mobility and a high-concentration two-dimensional electron gas (2DEG) formed at the heterojunction interface due to the strong polarization effect of the nitride, and a high electron mobility transistor (HEMT) prepared based on the structure has advantages such as large current density, high output power, and high working frequency, and has great application potential in the fields of high frequency and high power.

[0003] In the process of preparing the HEMT device, multiple devices or even multiple circuits are usually prepared on the same heterojunction material, and in order to avoid crosstalk and connection between the devices, each active region needs to be isolated.

[0004] Currently, there are two isolation methods in the preparation process of the AlGaN / GaN HEMT, one is mesa etching, and the other is ion implantation. The mesa isolation realizes device isolation by etching away the AlGaN / GaN heterojunction between two active regions. In the mesa etching process, the etching damage caused by the etching process at the edge and the bottom of the mesa forms a leakage channel, which affects the reliability of the device. The ion implantation realizes device isolation by implanting H + ions, He + ions, N - ions, F + ions and the like into the GaN epitaxial layer between the two active regions. The high-energy ion implantation sample causes problems such as lattice damage and interface state, causing device leakage.

[0005] Therefore, the defects caused by the traditional device isolation process form a leakage channel, thereby affecting the reliability of the device. SUMMARY

[0006] In order to solve the problem that the defects caused by the traditional device isolation process form a leakage channel, thereby affecting the reliability of the device, the application provides a GaN-based device isolation method. The device isolation region prepared by the method has small defect density, high resistance and small leakage, and solves the problem of device reliability reduction caused by the defects generated by the traditional device isolation method.

[0007] In order to achieve the above purpose, the application adopts the following technical scheme:

[0008] A method for isolating a GaN-based device, the method comprising the steps of:

[0009] 1) providing a sample, exposing the area where device isolation is needed on the surface of the sample by photolithography;

[0010] 2) evaporating a metal film on the surface of the sample in step 1);

[0011] 3) removing the remaining metal film except the area where device isolation is needed;

[0012] 4) irradiating the remaining metal film covering area in step 3) with laser pulses to diffuse the metal into the sample and recrystallize the sample, incorporating the metal into the lattice of the sample;

[0013] 5) removing the residual metal film in step 4).

[0014] In the present application, it has been reported that high-energy laser pulses can locally heat the sample to recrystallize it, and single-crystal Ge can be synthesized on a Ge substrate using high-energy laser by pulsed laser melting (PLM) 1-x Sn x with controllable synthesis ratio and no amorphous region. Recrystallization of GaN-based samples at high temperature can improve the crystalline quality. According to the diffusion theory, atoms diffuse from high-concentration areas to low-concentration areas, and high temperature accelerates the diffusion speed.

[0015] As a preferred embodiment of the present application, the metal film is a Fe metal film, and the purity of the Fe source used is 99.999%.

[0016] As a preferred embodiment of the present application, the thickness of the metal film is 1-60 nm.

[0017] As a preferred embodiment of the present application, the thickness of the metal film is 1-20 nm.

[0018] As a preferred embodiment of the present application, in step 2), the method for evaporating the metal film includes electron beam evaporation, thermal evaporation or magnetron sputtering.

[0019] As a preferred embodiment of the present application, the method for evaporating the metal film is electron beam evaporation, and the process conditions are: electron beam pressure is 10 -6 Torr, and evaporation speed is 0.5-3 nm / min.

[0020] As a preferred embodiment of the present application, in step 3), the method for removing the remaining metal film is Lift-off method.

[0021] As a preferred scheme of the present application, in step 4), the wavelength of the laser pulse is 1030 nm, the pulse width is 0.13 ps, the average power is 30-70 mW, the laser repetition frequency is 2000 Hz, and the irradiation angle of the laser pulse is vertical.

[0022] As a preferred scheme of the present application, in step 4), the doping concentration of the metal in the sample recrystallization process is 1×10 18 cm -3 -1×10 20 cm -3 .

[0023] As a preferred scheme of the present application, in step 5), the method for removing the residual metal film is acid pickling.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1) The present application proposes to evaporate a Fe film on the region of the GaN HEMT structure surface where device isolation is needed, to accelerate Fe diffusion into the sample and make the sample recrystallize by reasonably controlling the laser pulse energy using a pulsed laser to heat the Fe film covering region, so as to incorporate Fe into the sample lattice. Fe impurities are deep level impurities in GaN-based materials, and doping Fe in the region where isolation is needed can form a high resistance state, thereby achieving the purpose of device isolation. This method can reduce the defect density of the isolation region by recrystallizing the sample through high-energy laser pulses and introducing Fe impurities in the recrystallization process.

[0026] 2) Fe-doped nitride can increase the resistance of nitride. When the doping concentration reaches 10 19 cm -3 , the resistance can reach 10 9 Ω. Using the method of locally doping Fe, the local resistance of nitride can be improved to achieve the purpose of device isolation.

[0027] 3) In the region of the sample surface where device isolation is needed, a Fe film is evaporated, and Fe atoms diffuse into the nitride under the control of concentration gradient at the interface between the sample and the Fe film. Using the method of pulsed laser doping, a high-energy laser pulse is used to irradiate the Fe film region, the local temperature rises under the action of the high-energy laser pulse, and the thermal diffusion is accelerated, a large number of Fe atoms enter the gallium nitride sample, and are incorporated into the gallium nitride lattice in the process of sample recrystallization, thereby achieving the purpose of Fe doping. In this process, Fe atoms enter the nitride sample through thermal diffusion and are incorporated into the sample without damaging the crystalline quality. At the same time, the local temperature rises in the laser pulse irradiation region, and the sample recrystallization ensures the crystalline quality of the sample. In this diffusion process, the diffusion depth and concentration of Fe in the nitride sample are controlled by the thermal diffusion temperature, and the laser irradiation power and pulse number can be adjusted to control the temperature, thereby controlling the Fe doping concentration.

[0028] 4) The device isolation region prepared by the method of the present application has a small defect density, high resistance and small leakage current. The problem of device reliability reduction caused by defects generated by traditional device isolation methods is solved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flowchart of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] EMBODIMENT

[0032] Referring to Figure 1 , the present application provides a method for GaN-based device isolation, comprising the following steps:

[0033] Step 1): Exposing the region requiring device isolation on the sample surface by photolithography;

[0034] Step 2): Evaporating a layer of Fe metal film on the sample surface by electron beam evaporation, the purity of the Fe source used is 99.999%, the electron beam pressure is 10 -6 Torr, the evaporation speed is 0.5-3 nm / min, and the thickness of the Fe metal film is 1-20 nm;

[0035] Step 3): Removing the excess Fe metal film by Lift-off process, leaving the Fe metal film covering the region requiring device isolation;

[0036] Step 4): Irradiating the Fe metal film with laser pulses, the wavelength of the laser used in the experiment is 1030 nm, the pulse width is 0.13 ps, the average power is 30-70 mW, and the laser repetition rate is 2000 Hz;

[0037] The high-energy laser pulses locally melt the sample, and the Fe element diffuses into the sample interior, and the Fe is incorporated into the crystal lattice during the recrystallization of the sample, so as to form a high-resistance region with a doping purpose concentration (1×10 18 cm -3 -1×10 20 cm -3 ) to achieve the purpose of device isolation;

[0038] Step 5): Washing off the residual Fe film on the surface with acid.

[0039] The application can reduce the defect density of the isolation region by high-energy laser pulse to make the sample recrystallize, reasonably regulating the pulse energy, and introducing Fe impurities in the recrystallization process of the sample.

[0040] The above description is only the preferred embodiment of the present application, and is not any form and substantial limitation of the present application. It should be pointed out that, for ordinary skilled in the art, without departing from the method of the present application, a number of improvements and supplements can also be made, which should be considered as the protection scope of the present application. For those skilled in the art, without departing from the spirit and scope of the present application, some changes, modifications and equivalent changes of the above disclosed technical content can be made, which are equivalent embodiments of the present application; at the same time, any equivalent changes, modifications and evolution of the above-mentioned embodiments according to the essential technology of the present application are still within the scope of the technical solutions of the present application.

Claims

1. A method for isolating GaN-based devices, characterized in that, The method includes the following steps: 1) Provide a sample, and expose the area requiring device isolation on the sample surface using photolithography; 2) A metal film is deposited on the surface of the sample described in step 1); 3) Remove all metal films except those covering the areas where device isolation is required; 4) Irradiate the remaining metal film-covered area from step 3) with a laser pulse to allow the metal to diffuse into the sample and make the sample... Recrystallization incorporates the metal into the sample lattice. 5) Remove the residual metal film from step 4); The metal film is an Fe metal film, and the Fe source used has a purity of 99.999%. The thickness of the metal film is 1-20 nm; In step 2), the method for depositing the metal film includes electron beam evaporation, thermal evaporation, or magnetron sputtering; In step 4), the wavelength of the laser pulse is 1030nm, the pulse width is 0.13ps, the average power is 30-70mW, the laser repetition rate is 2000Hz, and the laser pulse is incident perpendicularly. In step 4), during the sample recrystallization process, the metal doping concentration is 1×10⁻⁶. 18 m -3 -1×10 20 cm -3 .

2. The method for isolating GaN-based devices according to claim 1, characterized in that, The method for depositing metal films is electron beam evaporation, with the following process conditions: electron beam pressure of 10⁻⁶ Torr and evaporation rate of 0.5-3 nm / min.

3. The method for isolating GaN-based devices according to claim 1, characterized in that, In step 3), the method for removing the remaining metal film is the lift-off method.

4. The method for isolating GaN-based devices according to claim 1, characterized in that, In step 5), the method for removing the residual metal film is acid washing.

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