技术领域technical field
本发明是关于半导体技术领域氮化镓基（GaN）材料，具体涉及一种基于GaN基材料的自停止刻蚀方法。The invention relates to gallium nitride-based (GaN) materials in the technical field of semiconductors, in particular to a self-stop etching method based on GaN-based materials.
背景技术Background technique
以AlGaN/GaN、InGaN/GaN、InAlGa/GaN等为材料基础的器件统称为氮化镓基器件，例如AlGaN/GaN异质结场效应管（heterostructurefieldeffecttransistors,HFET），异质结双极晶体管（heterostructurebipolartransistor,HBT）等。氮化镓基器件具有击穿场强大、电子迁移率高、饱和速度大等优点，被认为是下一代功率开关器件的有力竞争者，近年来备受研究者青睐。Devices based on AlGaN/GaN, InGaN/GaN, InAlGa/GaN, etc. are collectively referred to as gallium nitride-based devices, such as AlGaN/GaN heterojunction field effect transistors (heterostructure field effect transistors, HFET), heterojunction bipolar transistors (heterostructure bipolar transistors) ,HBT) etc. Gallium nitride-based devices have the advantages of strong breakdown field, high electron mobility, and high saturation speed. They are considered to be strong competitors for the next generation of power switching devices, and have been favored by researchers in recent years.
然而由于GaN基材料具有很强的抗腐蚀特性，对于GaN基材料的刻蚀工艺很多采用干法刻蚀，然而干法刻蚀具有很大的不稳定行，可操作性差；同时对材料本身可能引起各种缺陷因而可能会对后续的器件采用不利的影响。However, due to the strong corrosion resistance of GaN-based materials, dry etching is often used in the etching process of GaN-based materials. However, dry etching has great instability and poor operability; at the same time, it may affect the material itself. Various defects are caused and thus may adversely affect subsequent device adoption.
发明内容Contents of the invention
本发明的目的在于针对上述问题，提供一种氮化镓基材料的自停止刻蚀方法，这种方法基于湿法腐蚀工艺技术，可实现自停止特性，从而具有很高的可操作性和可重复性，更利于工业化生产；同时对后续器件制作不会造成影响。The object of the present invention is to address the above problems and provide a self-stop etching method for gallium nitride-based materials. This method is based on wet etching technology and can achieve self-stop characteristics, thus having high operability and operability. Repeatability is more conducive to industrial production; at the same time, it will not affect the subsequent device production.
为实现上述目的，本发明采用如下技术方案：To achieve the above object, the present invention adopts the following technical solutions:
一种基于氮化镓基材料的自停止刻蚀方法，其步骤包括：A self-stop etching method based on gallium nitride-based materials, the steps comprising:
1）在氮化镓基材料表面淀积保护层；1) Deposit a protective layer on the surface of gallium nitride-based materials;
2）在所述保护层上涂敷光刻胶，并光刻待做刻蚀区域图形；2) Coating photoresist on the protective layer, and photoetching the pattern of the area to be etched;
3）去除待做刻蚀区域的保护层；3) Remove the protective layer of the area to be etched;
4）去除剩余光刻胶；4) Remove remaining photoresist;
5）对氮化镓基材料在高温条件下进行氧化处理；5) Oxidation treatment of gallium nitride-based materials under high temperature conditions;
6）将氧化处理后的氮化镓基材料置于腐蚀性溶液中进行腐蚀；6) Corroding the oxidized GaN-based material in a corrosive solution;
7）将非刻蚀区域的保护层置于腐蚀性溶液中去除。7) Remove the protective layer of the non-etching area in a corrosive solution.
进一步地，所述氮化镓基材料主要包括AlGaN/GaN、InGaN/GaN、InAlGa/GaN等。Further, the gallium nitride-based material mainly includes AlGaN/GaN, InGaN/GaN, InAlGa/GaN and the like.
进一步地，所述保护层可以采用但不限于SiO2或SiN等材料。Further, the protective layer may be made of materials such as but not limited to SiO2 or SiN.
进一步地，所述淀积保护层的方法包括但不限于：PECVD（PlasmaEnhancedChemicalVaporDeposition，等离子体增强化学气相沉积）、ICP-CVD（InductivelyCoupledPlasmaChemicalVaporDeposition,电感耦合等离子体化学气相淀积）、光学薄膜沉积；优选采用PECVD方法。Further, the method for depositing the protective layer includes but is not limited to: PECVD (PlasmaEnhancedChemicalVaporDeposition, plasma enhanced chemical vapor deposition), ICP-CVD (InductivelyCoupledPlasmaChemicalVaporDeposition, inductively coupled plasma chemical vapor deposition), optical film deposition; preferably using PECVD method.
进一步地，所述光刻胶可以采用AZ5214等材质；所述光刻采用接触式光刻等方式。Further, the photoresist can be made of AZ5214 and other materials; the photolithography adopts methods such as contact photolithography.
进一步地，步骤3）去除保护层刻蚀的方法包括但不限于：1）RIE（反应离子刻蚀，ReactiveIonEtching）处理；2）BOE（BufferOxideEtch，缓冲蚀刻液）溶液浸泡处理。Further, the etching method of step 3) removing the protective layer includes but is not limited to: 1) RIE (Reactive Ion Etching, Reactive Ion Etching) treatment; 2) BOE (Buffer Oxide Etch, buffer etchant) solution soaking treatment.
进一步地，步骤5）进行氧化处理的温度为590-640℃，时间为40min-80min；优先选用快速退火炉进行氧化处理，气氛为氧气；Further, in step 5), the temperature for oxidation treatment is 590-640°C, and the time is 40min-80min; the oxidation treatment is preferably performed in a rapid annealing furnace, and the atmosphere is oxygen;
进一步地，步骤6）所述腐蚀性溶液为碱性溶液，如氢氧化钾溶液或氢氧化钠溶液：其质量浓度为10%-70%，其温度为50-90℃，腐蚀时间为45min-60min；Further, the corrosive solution in step 6) is an alkaline solution, such as potassium hydroxide solution or sodium hydroxide solution: its mass concentration is 10%-70%, its temperature is 50-90°C, and the corrosion time is 45min- 60min;
进一步地，步骤7）所述腐蚀容易采用酸性腐蚀液，所述酸性腐蚀液包括但不限于：1）BOE（BufferOxideEtch，缓冲蚀刻液）溶液浸泡处理，可调整浓度范围；2）HF（氢氟酸）溶液浸泡处理，可调整浓度范围。Further, the etching in step 7) is easy to use acidic etching solution, the acidic etching solution includes but not limited to: 1) BOE (BufferOxideEtch, buffer etching solution) solution soaking treatment, the concentration range can be adjusted; 2) HF (hydrogen fluorine Acid) solution soaking treatment, the concentration range can be adjusted.
本发明的基于氮化镓基材料的刻蚀工艺，其刻蚀深度不随设定的氧化时间和腐蚀时间变化，因而可实现自停止刻蚀，其槽底平整，台阶边缘光滑，提供了一种具有很高的可操作性和可重复性刻蚀氮化镓基材料的制备方法，同时为实现氮化镓增强型器件的工业化生产提供了一种很好的方法。The etching process based on gallium nitride-based materials of the present invention does not change the etching depth with the set oxidation time and etching time, so it can realize self-stop etching, the bottom of the groove is flat, and the edge of the step is smooth, providing a The preparation method of etching GaN-based materials with high operability and repeatability provides a good method for realizing the industrial production of GaN-enhanced devices.
附图说明Description of drawings
图1是本发明实施例的氮化镓基材料自停止刻蚀方法的步骤流程图。FIG. 1 is a flowchart of steps of a self-stop etching method for GaN-based materials according to an embodiment of the present invention.
图2为本发明实施例样品一的刻蚀深度的原子力显微镜图像。FIG. 2 is an atomic force microscope image of the etching depth of sample 1 of the embodiment of the present invention.
图3为本发明实施例样品一的刻蚀区域的槽底原子形貌图像。FIG. 3 is an atomic topography image of the groove bottom of the etched region of Sample 1 of the embodiment of the present invention.
图4为本发明实施例样品二的刻蚀区域深度的原子力显微镜图像。FIG. 4 is an atomic force microscope image of the depth of the etched region of Sample 2 of the embodiment of the present invention.
图5为本发明实施例样品三的刻蚀区域深度的原子力显微镜图像。Fig. 5 is an atomic force microscope image of the depth of the etched region of sample 3 of the embodiment of the present invention.
图6为本发明实施例样品四的刻蚀区域深度的原子力显微镜图像。FIG. 6 is an atomic force microscope image of the depth of the etched region of sample 4 of the embodiment of the present invention.
图7为本发明实施例自停止刻蚀方法对氧化温度的依赖关系图。FIG. 7 is a graph showing the dependence of the self-stop etching method on the oxidation temperature according to the embodiment of the present invention.
具体实施方式detailed description
下面通过具体实施例并配合附图，对本发明做详细的说明。The present invention will be described in detail below through specific embodiments and accompanying drawings.
本发明可实现基于GaN基材料的自停止刻蚀工艺的原理是：在AlGaN/GaN、InGaN/GaN、InAlGa/GaN等氮化镓基材料中，由于GaN比AlGaN等其他材料层具有更高的抗氧化特性，在氧化处理时，使AlGaN等材料层被氧化而不影响其下面的GaN层，形成的氧化物容易被KOH等碱性溶液腐蚀，同时该碱性溶液对GaN层没有任何影响，因而可以实现自停止特性。The principle that the present invention can realize the self-stop etching process based on GaN-based materials is: in gallium nitride-based materials such as AlGaN/GaN, InGaN/GaN, InAlGa/GaN, etc., because GaN has a higher Anti-oxidation properties, during oxidation treatment, the material layer such as AlGaN is oxidized without affecting the GaN layer below it, and the formed oxide is easily corroded by alkaline solutions such as KOH, and the alkaline solution has no effect on the GaN layer. Therefore, the self-stop characteristic can be realized.
以氮化镓材料AlGaN/GaN为例，由于GaN比AlGaN的具有更高的抗氧化特性，在温度为615℃时，只有AlGaN层被氧化而不影响其下面的GaN层，在经过40min氧化后AlGaN层已全部被氧化，形成的氧化物为Al2O3和Ga2O3，这些氧化物是很容易被70℃时的KOH溶液腐蚀的，同时KOH溶液对GaN层也没有任何影响，因而可以实现自停止特性。Taking the gallium nitride material AlGaN/GaN as an example, because GaN has higher oxidation resistance than AlGaN, at a temperature of 615°C, only the AlGaN layer is oxidized without affecting the underlying GaN layer. After 40 minutes of oxidation The AlGaN layer has been completely oxidized, and the oxides formed are Al2 O3 and Ga2 O3 . These oxides are easily corroded by the KOH solution at 70°C. At the same time, the KOH solution has no effect on the GaN layer, so Self-stop feature can be realized.
图1是本实施例的基于氮化镓基材料的自停止刻蚀工艺的步骤流程图。下面以AlGaN/GaN材料为例，对该方法进行具体说明。该自停止刻蚀工艺的步骤包括：FIG. 1 is a flow chart of the steps of the gallium nitride-based material-based self-stop etching process in this embodiment. The method will be specifically described below by taking AlGaN/GaN material as an example. The steps of the self-stop etching process include:
1）在GaN基材料表面采用PECVD方法制备厚度为200nm的SiO2保护层。1) Prepare a SiO2 protective layer with a thickness of 200nm on the surface of the GaN-based material by PECVD method.
该步骤制备SiO2层的目的是保护非凹槽区域，即刻蚀区域以外的区域在高温氧气环境下不被氧化和损坏。The purpose of preparing theSiO2 layer in this step is to protect the non-groove area, that is, the area other than the etched area from being oxidized and damaged in a high-temperature oxygen environment.
2）在所述SiO2层上涂敷光刻胶，并光刻待做刻蚀区域的图形。2) Coating photoresist on the SiO2 layer, and photoetching the pattern of the area to be etched.
本实施例采用的版图是栅结构版图，采用的光刻胶是AZ5214；采用接触式光刻方法进行光刻。The layout used in this embodiment is a gate structure layout, and the photoresist used is AZ5214; photolithography is performed by a contact photolithography method.
3）去除待做刻蚀区域的SiO2保护层。3) Remove the SiO2 protective layer in the area to be etched.
该步骤的目的是去除掉待做刻蚀部分SiO2保护层，使待做刻蚀部分暴露，便于后续的氧化，而非刻蚀区域的SiO2保护层由于有光刻胶的保护，不会被刻蚀掉。该步骤采用RIE（反应离子刻蚀）方法进行刻蚀。The purpose of this step is to remove theSiO2 protective layer of the part to be etched, so that the part to be etched is exposed, which is convenient for subsequent oxidation, and theSiO2 protective layer in the non-etched area is protected by photoresist. is etched away. This step uses the RIE (Reactive Ion Etching) method for etching.
4）除去剩余光刻胶。采用有机清洗的方法去除光刻胶，溶剂为丙酮、异丙醇等有机溶剂。4) Remove remaining photoresist. The photoresist is removed by an organic cleaning method, and the solvent is an organic solvent such as acetone and isopropanol.
5）将步骤4）所得氮化镓基材料放于纯氧气环境下的快速退火炉中进行氧化处理。5) The gallium nitride-based material obtained in step 4) is placed in a rapid annealing furnace under a pure oxygen environment for oxidation treatment.
前四步的目的是在样片氧化前，将不需要氧化的区域用SiO2保护层保护起来，需要氧化的区域裸露出来，在该步骤中进行氧化。氧化的温度设定为615℃，时间为40min。The purpose of the first four steps is to protect the area that does not need to be oxidized with a SiO2 protective layer before the oxidation of the sample, and expose the area that needs to be oxidized, and perform oxidation in this step. The oxidation temperature was set at 615° C. and the time was 40 minutes.
6）将氧化处理后的氮化镓基材料浸泡于氢氧化钾溶液进行腐蚀，时间为45min。6) Soak the oxidized gallium nitride-based material in a potassium hydroxide solution for 45 minutes.
该步骤中，氢氧化钾溶液的温度恒定为70℃；其中饱和氢氧化钾溶液和水的比例为1:4，换算成质量浓度为19.7%；腐蚀时间为45min。In this step, the temperature of the potassium hydroxide solution was constant at 70°C; the ratio of the saturated potassium hydroxide solution to water was 1:4, and the converted mass concentration was 19.7%; the corrosion time was 45 minutes.
7）将腐蚀后的氮化镓基材料上的SiO2保护层去除，即得刻蚀区域图形，命名为样品一。7) Remove the SiO2 protective layer on the etched gallium nitride-based material to obtain an etched area pattern, which is named as sample 1.
8）为进一步验证这种刻蚀方法的可自停止特性，另外3个样品做了验证试验，在氧化温度不变的情况下，将氧化时间和腐蚀时间（步骤6）所述的腐蚀）分别设定为：60min，45min；80min，45min；40min，60min。最后将SiO2保护层去除，获得相应的刻蚀区域图形，命名为样品二，三，四。8) In order to further verify the self-stopping characteristics of this etching method, another 3 samples were tested for verification. Under the condition of constant oxidation temperature, the oxidation time and corrosion time (corrosion described in step 6) were respectively The settings are: 60min, 45min; 80min, 45min; 40min, 60min. Finally, the SiO2 protective layer was removed to obtain the corresponding etched area patterns, which were named samples 2, 3, and 4.
图2和图3为采用原子力显微镜（AFM）对上述实施例样品一所得刻蚀区域进行检测所得的图像，其中：图2为刻蚀区域的高度图像，图片中中间深色部分为刻蚀区域，两边浅色部分为未刻蚀区域，右下角的曲线图示意了两边浅色部分和中间深色部分对应的高度（刻蚀深度）；图3为刻蚀区域的槽底形貌图像。图2和图3可以看出其刻蚀深度为22.5nm，槽底平整，其形貌均方根（rms）为0.3nm。Figure 2 and Figure 3 are the images obtained from the detection of the etched area obtained by the sample 1 of the above example using an atomic force microscope (AFM), wherein: Figure 2 is the height image of the etched area, and the dark part in the middle of the picture is the etched area , the light-colored parts on both sides are unetched areas, and the graph in the lower right corner shows the height (etching depth) corresponding to the light-colored parts on both sides and the dark part in the middle; Figure 3 is the topography image of the groove bottom in the etched area. It can be seen from Figure 2 and Figure 3 that the etching depth is 22.5nm, the groove bottom is flat, and the root mean square (rms) of the shape is 0.3nm.
表1给出了上述4个样品的刻蚀深度对比，可以看出，样品二、三、四得到的刻蚀深度和样品一所得的深度几乎相同，可以验证本刻蚀工艺技术具有可自停止特性，从而具有很高的可操作性和可重复性。Table 1 shows the comparison of the etching depths of the above four samples. It can be seen that the etching depths obtained by samples 2, 3, and 4 are almost the same as those obtained by sample 1. It can be verified that this etching process technology has the ability to stop characteristics, which have high operability and repeatability.
表1.4个样品的刻蚀深度Table 1. Etching depth of 4 samples
图4,5,6为采用原子力显微镜（AFM）对上述样品二、三、四所得刻蚀区域进行检测所得的图像，可以看出其槽底均很平整，台阶边缘光滑。Figures 4, 5, and 6 are the images obtained by inspecting the etched areas of the above-mentioned samples 2, 3, and 4 using an atomic force microscope (AFM). It can be seen that the groove bottoms are very flat and the edges of the steps are smooth.
9）为进一步说明实施例中的刻蚀方法对氧化温度的依赖性，在氧化时间和腐蚀时间（步骤6）所述的腐蚀）固定为40min和45min的情况下，设定氧化温度分别为590℃和640℃进行试验。图7给出了刻蚀深度和氧化温度的关系图，可以看出在给定氧化温度为590-640℃时，刻蚀深度基本在22nm左右。9) In order to further illustrate the dependence of the etching method in the example on the oxidation temperature, when the oxidation time and corrosion time (corrosion described in step 6) are fixed at 40min and 45min, the oxidation temperature is set to 590 ℃ and 640 ℃ for the test. Figure 7 shows the relationship between etching depth and oxidation temperature. It can be seen that when the oxidation temperature is given at 590-640°C, the etching depth is basically about 22nm.
10）为进一步说明实施例中的刻蚀方法对腐蚀温度及其浓度的依赖性，在氧化温度、时间和腐蚀时间固定为615℃、40min和45min的情况下，表2给出了刻蚀深度与腐蚀温度和浓度的关系。可以看出在给定的腐蚀温度和浓度下实施例中的刻蚀方法都可以实现自停止特性。10) In order to further illustrate the dependence of the etching method in the example on the corrosion temperature and its concentration, when the oxidation temperature, time and corrosion time are fixed at 615°C, 40min and 45min, the etching depth is given in Table 2 The relationship between corrosion temperature and concentration. It can be seen that the etching method in the embodiment can realize the self-stop characteristic under the given etching temperature and concentration.
表2刻蚀深度与腐蚀温度、腐蚀浓度数据列表Table 2 Etching depth, corrosion temperature, and corrosion concentration data list
上述实施例中氮化镓基材料为AlGaN/GaN，在其他实施例中还可以采用InGaN/GaN、InAlGa/GaN等氮化镓基材料。In the above embodiments, the gallium nitride-based material is AlGaN/GaN, and in other embodiments, gallium nitride-based materials such as InGaN/GaN, InAlGa/GaN, etc. may also be used.
上述实施例中保护层除采用SiO2，在其他实施例中还可以采用SiN等材料。In addition to using SiO2 for the protective layer in the above embodiments, materials such as SiN may also be used in other embodiments.
上述实施例中步骤3）采用RIE方法进行刻蚀以去除保护层，在其他实施例中还可以采用BOE（BufferOxideEtch，缓冲蚀刻液）等溶液进行浸泡处理，完成刻蚀。In step 3) of the above embodiment, the RIE method is used to perform etching to remove the protective layer. In other embodiments, a solution such as BOE (Buffer Oxide Etch, buffered etching solution) can also be used for immersion treatment to complete the etching.
上述实施例中淀积保护层采用PECVD方法外，在其他实施例中还可以采用ICP-CVD、光学薄膜沉积等方法。In addition to the PECVD method for depositing the protective layer in the above embodiments, ICP-CVD, optical thin film deposition and other methods can also be used in other embodiments.
上述实施例中，通过快速退火炉进行氧化处理时，温度可在590-640℃范围内调整，时间为40min-80min。In the above embodiment, when the oxidation treatment is carried out by the rapid annealing furnace, the temperature can be adjusted within the range of 590-640° C., and the time is 40 min-80 min.
以上实施例仅用以说明本发明的技术方案而非对其进行限制，本领域的普通技术人员可以对本发明的技术方案进行修改或者等同替换，而不脱离本发明的精神和范围，本发明的保护范围应以权利要求所述为准。The above embodiments are only used to illustrate the technical solution of the present invention and not to limit it. Those of ordinary skill in the art can modify or equivalently replace the technical solution of the present invention without departing from the spirit and scope of the present invention. The scope of protection should be determined by the claims.
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