A method for atomic layer etching of GaN-based materials
By employing an atomic layer etching method based on GaN-based materials and utilizing plasma bombardment with modified and inert gases, the problems of inaccurate AlGaN layer thickness and surface damage during the etching process of GaN-based devices have been solved, achieving high-precision and low-damage etching results and improving device performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU LEUVEN INSTR CO LTD
- Filing Date
- 2021-06-25
- Publication Date
- 2026-07-10
AI Technical Summary
In the existing technology, the etching process of the groove gate of GaN-based devices has problems such as inaccurate residual thickness of AlGaN layer, large surface roughness and severe plasma damage, which affect the performance and reliability of the device.
An atomic layer etching method based on GaN-based materials is adopted, which uses modified gases such as Cl2 and BCl3 and inert gases for plasma bombardment. By controlling the modification and etching process parameters, precise control and low-damage etching of AlGaN layers can be achieved.
This technology enables high-precision etching control of the AlGaN layer, reducing surface roughness and plasma damage, and improving the electrical performance and reliability of the device.
Smart Images
Figure CN115527849B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of atomic layer etching, and particularly relates to a method for etching atomic layers based on GaN-based materials. Background Technology
[0002] GaN, or gallium nitride, is a third-generation semiconductor material with a hexagonal wurtzite structure. GaN possesses characteristics such as a large bandgap (Eg=3.4eV), high thermal conductivity, high temperature resistance, radiation resistance, acid and alkali resistance, high strength, and high hardness, making it one of the most interesting semiconductor materials in the world today.
[0003] Due to its large bandgap and high thermal conductivity, GaN devices can operate at temperatures above 200°C, enabling them to carry higher energy densities and have higher reliability. The large bandgap also results in lower on-state resistance in transistors, which helps improve the overall energy efficiency of the device. The fast electron saturation velocity and high electron mobility allow the device to operate at high speeds.
[0004] The high electron mobility of GaN-based devices is achieved through AlGaN=GaN heterojunctions. Although normally-off operation is strongly required for power switching applications from a fail-safe perspective, achieving normally-off operation in GaN / AlGaN HEMTs remains a challenge. Several normally-off structures have been investigated, such as recessed gate, fluoride ion treatment, and p-GaN gate structures. Recessed gates are generally considered a simple structure, requiring less complex fabrication steps compared to other structures. Recessed gate HEMTs use dry etching to partially remove the AlGaN layer, resulting in an in-plane AlGaN / GaN heterojunction. In this structure, a gate insulator can be used to suppress gate leakage current and increase on-state oscillation. However, three main challenges exist during the etching process of recessed gates: residual AlGaN layer thickness, surface roughness, and plasma-induced damage. First, the residual AlGaN layer thickness directly affects the gate threshold voltage (Vth). th Therefore, the thickness of the AlGaN layer needs to be controlled very precisely. Furthermore, from a manufacturing perspective, the controllability, uniformity, and repeatability of the etching depth across the entire wafer are also major challenges. Secondly, a rough surface increases the interface state density, reducing electron density. Thirdly, plasma can cause surface damage, such as lattice defects, which degrade the electrical properties of the device.
[0005] In existing technologies, some etching damage can be improved by an additional thermal annealing process after etching. The higher the temperature during annealing, the greater the degree to which the damage can be reversed. However, it is difficult to completely reverse etching damage. Therefore, one approach to solving the above three problems in AlGaN etching is atomic layer etching (ALE).
[0006] ALE (Atomic Etching) is an atomically controlled etching method for fabricating nanoscale devices, primarily consisting of two steps: surface modification and modified layer removal. Both surface modification and modified layer removal are self-limiting; therefore, compared to traditional reactive ion etching (RIE), ALE offers superior controllability of etching depth. In previous studies on ALE for GaN or AlGaN, the surface was oxidized by O2 plasma and then removed by BCl3 plasma. This oxidation step is a self-limiting process, but the BCl3 plasma etching in the removal step is not. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to provide an atomic layer etching method based on GaN-based materials to address the shortcomings of the prior art, thereby optimizing the fabrication process of GaN-based materials and achieving more precise control and lower damage.
[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0009] An atomic layer etching method based on GaN-based materials includes the following steps:
[0010] Step 1: The material to be modified is transported to the vacuum chamber of the plasma etching machine for vacuuming.
[0011] Step 2: The modified material after vacuuming is sent to the modification process chamber;
[0012] Step 3: Modify the material using a modifying gas, wherein the modifying gas is Cl. 2、 BCl 3、 Any one or any combination of chlorine-based gases;
[0013] Step 4: Extract the modified gas and fill it with etching gas for plasma bombardment. The etching gas is an inert gas or a combination of multiple inert gases.
[0014] Step 5: Extract the etching gas and repeat steps 3 and 4 until the GaN-based material reaches the required process parameters.
[0015] Furthermore, in step 3, the modified gas is a combination of Cl2 and BCl3. The conditions for the modification process are as follows: upper RF power 100-500W, lower RF power 0W, total inlet flow rate 50-200sccm, BCl3 accounting for 10%-90% of the Cl2 and BCl3 gas flow rate, Cl2 accounting for 10%-90% of the total gas flow rate, cavity pressure 20mT-90mT, and coolant temperature 40-80℃ during the process.
[0016] Furthermore, in step 3, BCl3 is selected as the modified gas. The conditions for the modification process are: upper RF power 100-500W, lower RF power 0W, BCl3 inlet flow rate 50-200sccm, cavity pressure 20mT-90mT, and coolant temperature 40-80℃ during the process.
[0017] Furthermore, in step 4, the processing conditions for plasma bombardment using inert gas ionization are as follows: upper radio frequency power 100-500W, lower radio frequency power 10-50W, lower radio frequency 100-800Hz, inert gas duty cycle 10%-80%, inert gas flow rate 100-300sccm, cavity pressure 5-50mT, and coolant temperature 40-80℃ during the process.
[0018] Furthermore, it also includes: Step 6, after Step 5 is completed, the sample is taken out and confirmed by morphological analysis using SEM or TEM.
[0019] Furthermore, if the modified material is GaN or AlGaN and the etching rate is less than or equal to 2 nm / loop, then the roughness increment ΔRMS of the modified material is in the range of -0.352~0.03 nm.
[0020] Furthermore, the modified material is AlGaN or GaN, the cavity pressure is 40-80 mT, and the modification process time is set to 10-60 s.
[0021] Furthermore, 100 sccm Ar was used for pure physical bombardment, with process conditions of 200-500W upper RF power, 10-50W lower RF power, pulse frequency range of 100-800Hz, duty cycle range of 10-80%, cavity pressure of 5-20mT, and process time of 20-40s.
[0022] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:
[0023] 1. Compared with traditional ICP etching process, it has higher etching precision and controllability for AlGaN layer;
[0024] 2. Compared to traditional ICP etching processes, the surface roughness is significantly improved;
[0025] 3. Compared to traditional ICP etching processes, equal etching amounts can be achieved even with different aspect ratios. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the process flow;
[0027] Figure 2 This is a schematic diagram of the roughness of AlGaN before etching.
[0028] Figure 3 Three sets of schematic diagrams showing the roughness of AlGaN after etching;
[0029] Figure 4 This is a schematic diagram of the roughness of AlGaN etched by conventional ICP.
[0030] Figure 5 This is a schematic diagram of the roughness of AlGaN etched by conventional ICP.
[0031] Figure 6 This is a schematic diagram of the AlGaN experimental sheet in Example 1;
[0032] Figure 7 This is a schematic diagram of different cycle numbers of an AlGaN experimental wafer used in the ALE process of Example 1.
[0033] Figure 8 This is a schematic diagram of different cycle numbers of an AlGaN experimental wafer used in the ALE process of Example 1.
[0034] Figure 9 This is a schematic diagram of the GaN experimental wafer with different cycle numbers in the ALE process of Example 2;
[0035] Figure 10 This is a schematic diagram of the GaN experimental wafer with different number of cycles in the ALE process of Example 3. Detailed Implementation
[0036] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:
[0037] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.
[0038] This invention provides an atomic layer etching method based on GaN-based materials, such as... Figure 1 , 2 As shown in points 3, 4, and 5, the steps include the following:
[0039] Step 1: The material to be modified is transported to the vacuum chamber of the plasma etching machine for vacuuming.
[0040] Step 2: The modified material after vacuuming is sent to the modification process chamber;
[0041] Step 3: Modify the material using a modifying gas; the modifying gas is Cl2, BCl3, chlorine-based gas, or any combination thereof;
[0042] Step 4: Extract the modified gas and fill it with etching gas for plasma bombardment; the etching gas is an inert gas or a combination of multiple inert gases.
[0043] Step 5: Extract the etching gas and repeat steps 3 and 4 until the GaN material meets the process specifications.
[0044] In step 3, the modified gas is a combination of Cl2 and BCl3. The modification processing conditions are as follows: upper RF power 100-500W, lower RF power 0W, total inlet flow rate 50-200sccm, BCl3 accounts for 10%-90% of the Cl2 and BCl3 gas flow rate, Cl2 accounts for 10%-90% of the total gas flow rate, cavity pressure 20mT-90mT, and coolant temperature during the process is 40-80℃.
[0045] In step 3, BCl3 is selected as the modified gas. The modification processing conditions are as follows: upper RF power 100-500W, lower RF power 0W, BCl3 inlet flow rate 50-200sccm, cavity pressure 20mT-90mT, and coolant temperature 40-80℃ during the process.
[0046] In step 4, the processing conditions for plasma bombardment using inert gas ionization are as follows: upper radio frequency power 100-500W, lower radio frequency power 10-50W, lower radio frequency 100-800Hz, duty cycle 10%-80%, inert gas flow rate 100-300sccm, cavity pressure 5-50mT, and coolant temperature 40-80℃ during the process.
[0047] The modified material is GaN or AlGaN. Figure 1 For space or line, under appropriate parameters, the etching process can achieve ideal morphology, the etching rate is controllable below 2nm / loop, and the ΔRMS increment is between -0.352~0.03nm. Figure 3 The three images are all roughness data after etching, and... Figure 2 (Before etching) echoes each other. Figure 2 and Figure 3 The data presented is shown in the table below.
[0048] Roughness data (ALE):
[0049] Before etching After etching RMS increment Scan area 0.710nm 0.358~0.740nm -0.352~0.03nm 5μm*5μm
[0050] Roughness data (ICP):
[0051] Before etching After etching RMS increment Scan area 1.8nm 3.02nm 1.22nm 5μm*5μm
[0052] A comparison of AFM characterization after etching AlGaN using ALE and ICP respectively revealed (see...) Figure 4 and Figure 5 The ALE process provides far better control over the surface roughness of AlGaN than the conventional ICP process.
[0053] This invention employs a lower-energy bombardment method (such as pulse function) and controls the surface roughness of AlGaN by setting the duty cycle, so that the surface roughness of AlGaN can be maintained in the negative range, and the roughness performance is greatly improved.
[0054] Example 1
[0055] like Figure 6 , 7 As shown in Figure 8, in this embodiment, the etching process uses an inductively coupled plasma (ICP) etching machine. The sample used is an AlGaN structure wafer with the following film structure: 2μm PR Softmask / 90nm SiN Hardmask / 20~25nm AlGaN / 2μm GaN / Si Sub. The CD is a 5μm line. The open ratio is >90%. The open mask process has been completed.
[0056] Step 1: The sample is sent to the vacuum chamber (LoadLock) of the inductively coupled plasma etching machine for evacuation.
[0057] Step 2: After vacuuming, the sample is sent to the modified process chamber.
[0058] Step 3, Modification: Set the corresponding process parameters as follows: RF power 100-500W in the upper step of modification, RF power 0W in the lower step, cavity voltage 40-80mT, process time 10-60s, and perform modification at Cl2+ BCl3=100sccm.
[0059] Step 4, Etching: Use 200-500W upper RF power and 10-50W lower RF power. Pulse function: frequency range 100-800Hz; duty cycle range: 10-80%, used in combination. Cavity pressure 5-20mT, process time 20-40s, using 100sccm Ar for pure physical bombardment.
[0060] Step 5: The number of process cycles was 58 and 63, respectively. After the process was completed, the samples were removed and their morphology was confirmed using SEM.
[0061] 58 loops: ED ~24.28nm, ER ~0.42nm / loop, with superior overall morphology and no footing / trench. Footing refers to a foot-shaped pattern; Trench refers to a micro-groove.
[0062] 63 loop: ED~26.98nm, ER~0.42nm / loop, with better overall morphology and no footing / trench.
[0063] Based on this set of examples, it can be concluded that precise control exists for the ER / loop.
[0064] Example 2
[0065] like Figure 9 As shown, the difference from Example 1 is that in this example, the etching process uses an inductively coupled plasma (ICP) etching machine. The sample used is an AlGaN structure wafer with the following film structure: 2μm PR softmask / 90nm SiN hardmask / 20~25nm AlGaN / 2μm GaN / Si Sub. The CD is a 5μm line. The open ratio is ~40%. The open mask process has been completed.
[0066] The same process parameters as in Example 1 were set, but the number of cycles was changed to 50 loops. After the process was completed, the sample was removed and its morphology was confirmed using SEM.
[0067] 50 loop: ED~51nm, ER~1.02nm / loop, with better overall morphology and no footing / trench.
[0068] Based on Examples 1 and 2, it can be concluded that the etching rate varies with different Open Ratios. Specifically, the etching rate exhibits a higher Low Open Ratio than a higher High Open Ratio.
[0069] Example 3
[0070] like Figure 10 As shown, in this embodiment, the etching process uses an inductively coupled plasma (ICP) etching machine. The sample used is a GaN structure wafer with the following film structure: 2μm PR softmask / 160nm SiN hardmask / 70nm GaN / Si Sub. The CD is a 5μm line. The open ratio is ~40%. The open mask process has been completed.
[0071] Set the same process parameters as Structure 1, but change the number of cycles to 50. After the process is complete, remove the sample and use SEM to confirm its morphology.
[0072] 50 loop: ED~50nm, ER~1nm / loop, with better overall morphology and no footing / trench.
[0073] Based on Examples 2 and 3, it can be concluded that in GaN and AlGaN samples, using the same OpenRatio and the same process menu, the etching rates are basically the same.
[0074] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.
[0075] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention. The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A method for atomic layer etching based on GaN-based materials, characterized in that: Includes the following steps: Step 1: The material to be modified is transported to the vacuum chamber of the plasma etching machine for vacuuming. Step 2: The modified material after vacuuming is sent to the modification process chamber; Step 3: Modify the modified material using a modifying gas, wherein the modifying gas is any one of Cl2, BCl3, chlorine-based gas, or any combination thereof; Step 4: Extract the modified gas and fill it with etching gas for plasma bombardment. The etching gas is an inert gas or a combination of multiple inert gases. Step 5: Extract the etching gas and repeat steps 3 and 4 until the GaN-based material meets the process specifications. The modified material is GaN or AlGaN, and the etching rate is less than or equal to 2nm / loop; Different open ratios result in different etching rates; The roughness increment ΔRMS of the modified material ranges from -0.352 to 0.03 nm; In both GaN and ALGAaN samples, the same Open Ratio and the same process menu were used, resulting in essentially the same etching rate.
2. The atomic layer etching method based on GaN-based materials according to claim 1, characterized in that: In step 3, the modified gas is a combination of Cl2 and BCl3. The conditions for the modification process are as follows: upper RF power 100-500W, lower RF power 0W, total inlet flow rate 50-200sccm, BCl3 accounting for 10%-90% of the Cl2 and BCl3 gas flow rates, Cl2 accounting for 10%-90% of the total gas flow rate, cavity pressure 20mT-90mT, and coolant temperature 40-80℃ during the process.
3. The atomic layer etching method based on GaN-based materials according to claim 1, characterized in that: In step 3, BCl3 is selected as the modified gas. The conditions for the modification process are: upper RF power 100-500W, lower RF power 0W, BCl3 inlet flow rate 50-200sccm, cavity pressure 20mT-90mT, and coolant temperature 40-80℃ during the process.
4. The atomic layer etching method based on GaN-based materials according to claim 1, characterized in that: In step 4, the processing conditions for plasma bombardment using inert gas ionization are as follows: upper radio frequency power 100-500W, lower radio frequency power 10-50W, lower radio frequency 100-800Hz, inert gas duty cycle 10%-80%, inert gas flow rate 100-300sccm, cavity pressure 5-50mT, and coolant temperature 40-80℃ during the process.
5. The atomic layer etching method based on GaN-based materials according to claim 1, characterized in that: Also includes: Step 6: After step 5 is completed, the sample is removed and its morphology is confirmed by SEM or TEM.
6. The atomic layer etching method based on GaN-based materials according to claim 2, characterized in that: The modified material is AlGaN or GaN, the cavity pressure is 40-80 mT, and the modification process time is set to 10-60 s.
7. The atomic layer etching method based on GaN-based materials according to claim 6, characterized in that: Pure physical bombardment was performed using 100 sccm Ar. The process conditions were: upper RF power of 200-500W, lower RF power of 10-50W, pulse frequency range of 100-800Hz, duty cycle range of 10-80%, cavity pressure of 5-20mT, and process time of 20-40s.