CN112713188B - 一种GaN基增强型MIS-HEMT器件及其制备方法 - Google Patents
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Abstract
本发明公开了一种GAN基增强型MIS‑HEMT器件,属于微电子技术领域,包括从下至上依次层叠设置的衬底、成核层、应力调控层、GaN沟道层、***层、AlxGa1‑XN势垒层以及帽层,所述应力调控层是由AlN/AlGaN/SiNX/GaN循环生长组成,具体包括AlN晶核层、AlGaN应力控制层、网状结构SiNx薄层及GaN填平层,外延材料方面,本发明应力调控层为AlN/AlGaN/SiNX/GaN循环生长复合层,降低了材料的位错密度,提高晶格质量,从而提升器件的电子迁移率、击穿电压等特性;在器件工艺方面,凹栅槽刻蚀通过两步法刻蚀直到将AlxGa1‑xN势垒层刻蚀完,充分结合了干法刻蚀的高效率特点和湿法刻蚀的低界面损伤优势,此外,本发明的TMAH溶液有效降低由于热氧化不均匀造成的栅极凹槽界面不平整问题。
Description
技术领域
本发明属于微电子技术领域,具体涉及一种GaN基增强型MIS-HEMT器件及其制备方法。
背景技术
基于AGaN/GaN异质结的高电子迁移率晶体管(High Electron MobilityTransistor,HEMT)因其拥有诸多优异特性,已经被广泛应用于高温、高频、高压、高功率、抗辐射的微波电子器件和电力电子器件中。然而,因各领域应用对性能需求不断加大,不论是外延材料还是器件工艺方面,依然存在着一些急需解决的问题。
在外延材料方面,由于氮化镓材料与硅衬底之间均存在较大的晶格失配和热失配,通过传统的成核层与AlGaN或GaN缓冲层在衬底与GaN层之间虽然起到缓冲作用,但生长得到的GaN层的晶体质量不够好,这样就会降低器件击穿电压,减小电子迁移率,从而使当前氮化镓HEMT器件的性能远低于理论极限。
在器件工艺方面,由于极化效应,基于AlGaN/GaN异质结的HEMT一般是耗尽型(常开),该类型的器件应用于电路级***中时,需要设计负极性栅极驱动电路,以实现对器件的开关控制,这极大增加了电路的复杂性与成本。为此,研制各种增强型GaN器件成为该领域研究人员尤为热衷的课题。而凹槽栅技术则是一种简单高效的实现增强型GaN器件的方式,但也具有明显的缺点,尤其是栅槽刻蚀带来的损伤以及界面态会影响器件性能,造成栅极泄漏电流增加、沟道电子迁移率降低、导通电阻增大等问题。针对上述问题,在器件结构方面,人们提出了MIS(Metal-Insulator-Semiconductor)栅结构,即在肖特基栅金属与势垒层之间***一层高k栅介质,有效地降低了栅极泄漏电流、提高栅压摆幅;在器件制备方面,栅槽刻蚀工艺最为关键,目前主要的刻蚀方法有:感应耦合等离子体(ICP)干法刻蚀、数字刻蚀(digital etch)和高温热氧化湿法刻蚀。ICP干法刻蚀是一种最常用的栅槽刻蚀技术,该技术具有刻蚀速率快、工艺简单、高各向异性等优势,但其弊端在于刻蚀速率非线性、刻蚀损伤大等方面。数字刻蚀技术是一种损伤较低的刻蚀方法,消除了由ICP干法刻蚀中等离子体轰击引起的损伤,但是其刻蚀速率很慢。相比于前两种方法,高温热氧化湿法刻蚀不存在物理轰击过程,能够很好地解决干法刻蚀所带来的界面损伤以及界面态问题,进一步降低了刻蚀损伤,并且在一定的温度范围内具有自停止效应,但其弊端在于整个栅槽刻蚀过程需要多个氧化/腐蚀周期,工艺流程繁琐,时间成本较高。
发明内容
本发明的目的在于克服上述问题,提供一种P-GaN帽层增强型HEMT器件外延制备方法,在外延材料方面,本发明采用AlN/AlGaN/SiNx/GaN循环生长复合层作为应力调控层,可改善晶体质量;在器件工艺方面,凹栅槽刻蚀通过两步法刻蚀直到将AlXGa1-XN势垒层刻蚀完。先通过ICP干法刻蚀去除大部分AlXGa1-XN势垒层,再通过高温热氧化余下的AlXGa1-XN势垒层,并且氧化会在AlXGa1-XN界面实现自终止,再通过湿法腐蚀氧化层。两步法刻蚀充分结合了干法刻蚀的高效率特点和湿法刻蚀的低界面损伤优势。
本发明的器件结构包括从下至上依次层叠设置的衬底、成核层、应力调控层、GaN沟道层、***层、AlxGa1-XN势垒层以及帽层,所述应力调控层是由AlN/AlGaN/SiNX/GaN循环生长组成,具体包括AlN晶核层、AlGaN应力控制层、网状结构SiNx薄层及GaN填平层;
先通过RIE刻蚀栅极区域SiNx钝化层,再通过ICP干法、高温热氧化后湿法两步法完全刻蚀掉AlXGa1-XN势垒层形成凹栅槽,Al2O3栅介质层分布在钝化层上、凹栅槽侧壁及底部,实现增强型MIS-HEMT;
源极、漏极位于T型栅极两侧,源极、漏极与AlXGa1-XN势垒层之间形成欧姆接触;
凹栅槽刻蚀通过两步法刻蚀直到将AlXGa1-XN势垒层刻蚀完,具体方法为:先通过ICP干法刻蚀去除大部分AlXGa1-XN势垒层,再通过高温热氧化后TMAH湿法刻蚀去除余下的AlXGa1-XN势垒层。
优选的,所述衬底尺寸大小为2~6inch,材质为硅。
优选的,所述成核层采用PECVD方法生长,温度在450~550℃,其总厚度在5~15nm,在N2/Ar/O2的混合气氛下以生长速度为1~10nm/S生长。
优选的,所述应力调控层中,所述AlN子层厚度在1~5nm,AlGaN子层的厚度在2~10nm,网状结构SiNX子层厚度在0.5~2nm、GaN子层的厚度为2~10nm,循环数为5~30。
优选的,所述GaN沟道层的生长温度为1050~1150℃,厚度为1.0~2.5μm。
优选的,所述***层为AlN***层,厚度为0.5~1.5nm,生长压力为50~100mbar,生长温度为1000~1200℃;
优选的,所述AlXGa1-XN势垒层生长厚度为10~25nm,生长压力为50~100mbar,生长温度为900~1200℃,其中0<x<1;
优选的,所述帽层为GaN帽层,该帽层生长厚度为1~3nm,生长压力为50~100mbar,生长温度为900~1200℃;
优选的,所述源极、漏极欧姆金属淀积采用电子束蒸发的方式淀积Ti/Al/Ni/Au四层欧姆金属,表面势垒层的刻蚀深度为5~15nm;
优选的,所述SiNX钝化层由PECVD生长,生长温度为100~350℃,厚度为50~300nm;
优选的,ICP干法刻蚀使用气体为Cl2和BCl3,Cl2流量为10~100sccm,BCl3流量为10~100sccm,刻蚀腔体压强为10~100mTorr,RF功率为10~100W,ICP功率为200~2000W;
高温热氧化后TMAH湿法刻蚀中,高温热氧化在退火炉氧气氛围中550~650℃下进行,TMAH采用5%~35%体积比的水溶液,腐蚀温度在40~120℃,氧化/腐蚀过程循环处理次数为1~10次。
优选的,分布在钝化层上、凹槽侧壁及底部的栅介质层为Al2O3,通过ALD(AtomLayer Deposition,原子层沉积)技术进行栅介质层Al2O3沉积,厚度为2~50nm。
优选的,T型栅极金属淀积采用电子束蒸发的方式淀积Ni/Au两层金属。引线电极为金属Ni/Au,厚度为50nm/450nm。
与现有技术相比,本发明具有如下优点:提供了一种新的外延结构及长法,并实现增强型HEMT器件的工艺优化。其主要技术包括:
1.在外延材料方面,在现有的AlN/AlGaN/GaN、AlN/SiNX/GaN循环生长复合层作为应力调控层基础上,本发明提出了AlN/AlGaN/SiNX/GaN循环生长复合层作为应力调控层。在AlN晶核层和GaN填平层中间同时引入AlGaN应力控制层和网状结构SiNX薄层,AlGaN的引入,产生的压应力与外延生长过程中、以及降温过程中的张应力相互抵消,从而起到应力调控的作用;网状结构SiNX薄层为填平层提供均匀的裸露的晶核,并且可以遮挡部分缺陷的延伸。这样充分结合了AlGaN应力控制层和网状SiNX薄层的作用。
2.在器件工艺方面,凹栅槽刻蚀通过两步法刻蚀直到将AlXGa1-XN势垒层刻蚀完。先通过ICP干法刻蚀去除大部分AlXGa1-XN势垒层,再通过高温热氧化余下的AlXGa1-XN势垒层,因在低于700℃下GaN不会被氧化,氧化会在AlXGa1-XN界面实现自终止,再通过湿法腐蚀氧化层。两步法刻蚀充分结合了干法刻蚀的高效率特点和湿法刻蚀的低界面损伤优势。
3.本发明中高温热氧化后用TMAH溶液代替传统的KOH溶液进行湿法腐蚀,利用其特有的侧向腐蚀机理,有效降低由于热氧化不均匀造成的栅极凹槽界面不平整问题。
附图说明
图1为本发明实施例提供的一种GaN基增强型MIS-HEMT器件的结构示意图。
图2为本发明实施例提供的应力控制层结构示意图。
图3a~3e为本发明实施例提供的两步法栅槽刻蚀过程示意图。
图3a为SiNx钝化层(掩膜层)生长。
图3b为AZ5214光刻胶保护下,RIE刻蚀SiNx钝化层。
图3c为ICP干法刻蚀帽层及大部分势垒层。
图3d为未刻蚀的势垒层及***层进行高温氧化。
图3e为余下的势垒层及***层高温氧化后进行TMAH溶液湿法刻蚀。
图4为本发明实施例提供的两步法与干法槽栅刻蚀后泄漏电流(I)-漏源电压(V)曲线对比。
图5为本发明实施例提供的另一制备方法下得到的GaN基增强型MIS-HEMT器件的结构示意图。
其中:11-衬底,12-成核层,13-应力调控层,131-AlN晶核层,132-AlGaN应力控制层,133-网状结构SiNX薄层,134-GaN填平层,14-GaN沟道层,15-***层,16-AlXGa1-XN势垒层,17-帽层,2-SiNx钝化层,3-Al2O3栅介质层,4-源极,5-漏极,6-T型栅极。
具体实施方式
为使本发明实现的技术手段、创作特征、达成目的与功效易于明白了解,下面结合具体实施方式,进一步阐述本发明。
制备该GaN基MIS-HEMT器件的异质结材料结构自下而上包括衬底11、成核层12、应力调控层13、GaN沟道层14、AlN***层15、AlXGa1-XN势垒层16及GaN帽层17。先通过RIE刻蚀栅极区域SiNx钝化层2,再通过ICP干法、高温热氧化后湿法两步法完全刻蚀掉AlXGa1-XN势垒层16形成凹栅槽,Al2O3栅介质层3分布在钝化层2上、凹栅槽侧壁及底部,实现增强型MIS-HEMT。源极4、漏极5位于T型栅极6两侧,源极4、漏极5金属与AlGaN势垒层16之间形成欧姆接触。可按照先欧姆接触后钝化的方式(如图1),也可按照先钝化后欧姆接触的方式(如图5)进行器件制备。
本发明的器件结构具体采用以下步骤制得:
实施例1:
本案例按照先欧姆接触后钝化的方式(如图1)进行器件制备。具体步骤及工艺条件如下:
S1.首先将Si衬底11放入反应室中并升温至1050~1150℃,在H2条件下去除表面的氧化膜;
S2.在衬底11上采用PECVD方法生长AlN成核层12,温度在350~550℃,其总厚度在5~15nm,在N2/Ar/O2的混合气氛下以生长速度为1~10nm/S生长;
S3.在成核层12上采用金属有机源化学气相沉积(MOCVD)生长应力调控层13,如图2所示,应力调控层13为AlN/AlGaN/SiNX/GaN循环生长复合层,氢气和氮气作为载气,生长温度在1050~1150℃,反应室压力为50torr~200torr,AlN子层厚度在1~5nm,AlGaN子层厚度在2~10nm,网状结构SiNX子层厚度在0.5~2nm,GaN子层厚度为2~10nm,循环数为5~30;
S4.在应力调控层13上采用金属有机源化学气相沉积(MOCVD)生长GaN沟道层14,生长温度为1050~1150℃;
S5.在GaN沟道层14上采用金属有机源化学气相沉积(MOCVD)生长AlN***层15,生长压力为50~100mbar,生长温度为1000~1200℃;
S6.在AlN***层15上采用金属有机源化学气相沉积(MOCVD)生长AlXGa1-XN势垒层16,生长压力为50~100mbar,生长温度为900~1200℃,生长厚度为25nm;
S7.在AlXGa1-XN势垒层16上采用金属有机源化学气相沉积(MOCVD)生长GaN帽层17,生长压力为50~100mbar,生长温度为900~1200℃;
S8.刻蚀源、漏欧姆接触凹槽。采用光刻胶AZ5214作掩膜,采用ICP(InductiveCoupled Plasma,电感耦合等离子体)刻蚀技术对势垒层16进行刻蚀。表面势垒层16的刻蚀深度为5~15nm,实现源、漏欧姆接触开窗;
S9.源漏欧姆接触。采用电子束蒸发技术,制备条件:金属Ti/Al/Ni/Au,厚度为20nm/140nm/50nm/150nm。退火条件为100~800℃,20~60s,氮气气氛
S10.有源区隔离。采用N离子注入技术进行隔离,离子注入能量为100~400KeV,注入深度为超过沟道层0.5~1.0μm左右;
S11.采用等离子体增强化学的气相沉积法(PECVD)生长SiNX钝化层2,如图3a所示,SiNX钝化层2具有抑制电流崩塌、保护器件表面、充当工艺阻挡层等作用,生长温度为100~350℃,厚度50~500nm;
S12.槽栅开窗。以光刻胶AZ5214为掩膜(1~2μm)通过RIE(Reactive Ion Etch,反应离子刻蚀)对栅极区域的SiNX钝化层2进行刻蚀,实现栅极开窗,如图3b所示;
S13.栅槽刻蚀。在槽栅开窗的基础上,进行凹槽的刻蚀。第一步为ICP干法刻蚀,如图3c所示,刻蚀AlXGa1-XN势垒层16厚度为23nm。采用光刻胶AZ5214作掩膜,SiNX钝化层2作阻挡层,Cl2流量为10~100sccm,BCl3流量为10~100sccm,刻蚀腔体压强为10~100mTorr,RF功率为10~100W,ICP功率为200~2000W;第二步为高温热氧化(如图3d)后TMAH湿法刻蚀(如图3e)余下的AlXGa1-XN势垒层16及AlN***层15。高温热氧化在退火炉氧气氛围中550~650℃下进行,湿法刻蚀溶液TMAH采用5%~35%体积比的水溶液,腐蚀温度在40~120℃,氧化/腐蚀过程循环处理次数为1~10次;
S14.栅介质层3沉积。除去光刻胶,通过ALD(Atom Layer Deposition,原子层沉积)技术,进行栅介质层Al2O3 3沉积,厚度为2~50nm;
S15.栅极金属沉积。采用电子束蒸发技术,制备条件:金属Ni/Au,厚度为50nm/300nm。
S16.引线电极制备。在引线电极开窗后进行引线电极金属的制备,材料为Ni/Au,厚度为50nm/450nm。
实施例2:
本案例按照先欧姆接触后钝化的方式(如图1)进行器件制备。具体步骤及工艺条件如下:
S1.首先将Si衬底11放入反应室中并升温至1050~1150℃,在H2条件下去除表面的氧化膜;
S2.在衬底11上采用PECVD方法生长AlN成核层12,温度在350~550℃,其总厚度在5~15nm,在N2/Ar/O2的混合气氛下以生长速度为1~10nm/S生长;
S3.在成核层12上采用金属有机源化学气相沉积(MOCVD)生长应力调控层13,如图2所示,应力调控层13为AlN/AlGaN/SiNX/GaN循环生长复合层,氢气和氮气作为载气,生长温度在1050~1150℃,反应室压力为50torr~200torr,AlN子层厚度在1~5nm,AlGaN子层厚度在2~10nm,网状结构SiNX子层厚度在0.5~2nm,GaN子层厚度为2~10nm,循环数为5~30;
S4.在应力调控层13上采用金属有机源化学气相沉积(MOCVD)生长GaN沟道层14,生长温度为1050~1150℃;
S5.在GaN沟道层14上采用金属有机源化学气相沉积(MOCVD)生长AlN***层15,生长压力为50~100mbar,生长温度为1000~1200℃;
S6.在AlN***层15上采用金属有机源化学气相沉积(MOCVD)生长AlXGa1-XN势垒层16,生长压力为50~100mbar,生长温度为900~1200℃,生长厚度为25nm;
S7.在AlXGa1-XN势垒层16上采用金属有机源化学气相沉积(MOCVD)生长GaN帽层17,生长压力为50~100mbar,生长温度为900~1200℃;
S8.刻蚀源、漏欧姆接触凹槽。采用光刻胶AZ5214作掩膜,采用ICP(InductiveCoupled Plasma,电感耦合等离子体)刻蚀技术对势垒层16进行刻蚀。表面势垒层16的刻蚀深度为5~15nm,实现源、漏欧姆接触开窗;
S9.源漏欧姆接触。采用电子束蒸发技术,制备条件:金属Ti/Al/Ni/Au,厚度为20nm/140nm/50nm/150nm。退火条件为100~800℃,20~60s,氮气气氛;
S10.有源区隔离。采用N离子注入技术进行隔离,离子注入能量为100~400KeV,注入深度为超过沟道层0.5~1.0μm左右;
S11.采用等离子体增强化学的气相沉积法(PECVD)生长SiNX钝化层2,如图3a所示,SiNX钝化层2具有抑制电流崩塌、保护器件表面、充当工艺阻挡层等作用,生长温度为100~350℃,厚度50~500nm;
S12.槽栅开窗。以光刻胶AZ5214为掩膜(1~2μm)通过RIE(Reactive Ion Etch,反应离子刻蚀)对栅极区域的SiNX钝化层2进行刻蚀,实现栅极开窗,如图3b所示;
S13.栅槽刻蚀。在槽栅开窗的基础上,进行凹槽的刻蚀。第一步为ICP干法刻蚀,如图3c所示,刻蚀AlXGa1-XN势垒层16厚度为21nm。采用光刻胶AZ5214作掩膜,SiNX钝化层2作阻挡层,Cl2流量为10~100sccm,BCl3流量为10~100sccm,刻蚀腔体压强为10~100mTorr,RF功率为10~100W,ICP功率为200~2000W;第二步为高温热氧化(如图3d)后TMAH湿法刻蚀(如图3e)余下的AlXGa1-XN势垒层16及AlN***层15。高温热氧化在退火炉氧气氛围中550~650℃下进行,湿法刻蚀溶液TMAH采用5%~35%体积比的水溶液,腐蚀温度在40~120℃,氧化/腐蚀过程循环处理次数为1~10次;
S14.栅介质层3沉积。除去光刻胶,通过ALD(Atom Layer Deposition,原子层沉积)技术,进行栅介质层Al2O3 3沉积,厚度为2~50nm;
S15.栅极金属沉积。采用电子束蒸发技术,制备条件:金属Ni/Au,厚度为50nm/300nm。
S16.引线电极制备。在引线电极开窗后进行引线电极金属的制备,材料为Ni/Au,厚度为50nm/450nm。
实施例3:
本案例按照先钝化后欧姆接触的方式(如图5)进行器件制备。具体步骤及工艺条件如下:
S1.首先将Si衬底11放入反应室中并升温至1050~1150℃,在H2条件下去除表面的氧化膜;
S2.在衬底11上采用PECVD方法生长AlN成核层12,温度在350~550℃,其总厚度在5~15nm,在N2/Ar/O2的混合气氛下以生长速度为1~10nm/S生长;
S3.在成核层12上采用金属有机源化学气相沉积(MOCVD)生长应力调控层13,如图2所示,应力调控层13为AlN/AlGaN/SiNX/GaN循环生长复合层,氢气和氮气作为载气,生长温度在1050~1150℃,反应室压力为50torr~200torr,AlN子层厚度在1~5nm,AlGaN子层厚度在2~10nm,网状结构SiNX子层厚度在0.5~2nm,GaN子层厚度为2~10nm,循环数为5~30;
S4.在应力调控层13上采用金属有机源化学气相沉积(MOCVD)生长GaN沟道层14,生长温度为1050~1150℃;
S5.在GaN沟道层14上采用金属有机源化学气相沉积(MOCVD)生长AlN***层15,生长压力为50~100mbar,生长温度为1000~1200℃;
S6.在AlN***层15上采用金属有机源化学气相沉积(MOCVD)生长AlXGa1-XN势垒层16,生长压力为50~100mbar,生长温度为900~1200℃,生长厚度为25nm;
S7.在AlXGa1-XN势垒层16上采用金属有机源化学气相沉积(MOCVD)生长GaN帽层17,生长压力为50~100mbar,生长温度为900~1200℃;
S8.采用等离子体增强化学的气相沉积法(PECVD)生长SiNX钝化层2,SiNX钝化层2具有抑制电流崩塌、保护器件表面、充当工艺阻挡层等作用,生长温度为100~350℃,厚度50~500nm;
S9.有源区隔离。采用N离子注入技术进行隔离,离子注入能量为100~400KeV,注入深度为超过沟道层0.5~1.0μm左右;
S10.槽栅开窗。以光刻胶AZ5214为掩膜(1~2μm)通过RIE(Reactive Ion Etch,反应离子刻蚀)对栅极区域的SiNX钝化层2进行刻蚀,实现栅极开窗;
S11.栅槽刻蚀。在槽栅开窗的基础上,进行凹槽的刻蚀。第一步为ICP干法刻蚀,如图3c所示,刻蚀AlXGa1-XN势垒层16厚度为23nm。采用光刻胶AZ5214作掩膜,SiNX钝化层2作阻挡层,Cl2流量为10~100sccm,BCl3流量为10~100sccm,刻蚀腔体压强为10~100mTorr,RF功率为10~100W,ICP功率为200~2000W;第二步为高温热氧化后TMAH湿法刻蚀余下的AlXGa1-XN势垒层16及AlN***层15。高温热氧化在退火炉氧气氛围中550~650℃下进行,湿法刻蚀溶液TMAH采用5%~35%体积比的水溶液,腐蚀温度在40~120℃,氧化/腐蚀过程循环处理次数为1~10次;
S12.栅介质层3沉积。除去光刻胶,通过ALD(Atom Layer Deposition,原子层沉积)技术,进行栅介质层Al2O3 3沉积,厚度为2~50nm;
S13.栅极金属沉积。采用电子束蒸发技术,制备条件:金属Ni/Au,厚度为50nm/300nm。
S14.刻蚀源、漏欧姆接触凹槽。采用光刻胶AZ5214作掩膜,通过含氯的等离子体刻蚀Al2O3栅介质层3,含氟的等离子体刻蚀SiNX钝化层2,再采用ICP(Inductive CoupledPlasma,电感耦合等离子体)刻蚀技术对势垒层16进行刻蚀。表面势垒层16的刻蚀深度为5~15nm,实现源、漏欧姆接触开窗;
S15.源漏欧姆接触。采用电子束蒸发技术,制备条件:金属Ti/Al/Ni/Au,厚度为20nm/140nm/50nm/150nm。退火条件为100~800℃,20~60s,氮气气氛。
图4出示了本发明在实施例1条件下制得的GaN基MIS-HEMT器件与现有ICP干法刻蚀栅槽技术下保证其它条件不变制得的器件漏电性能对比:
采用两步法栅槽刻蚀的漏电流远低于ICP干法刻蚀栅槽的漏电流,这是由于ICP干法刻蚀后大量的陷阱电荷以及悬挂键的存在会形成表面漏电通道,而两步法栅槽刻蚀在保证刻蚀效率的同时,能够很好地解决干法刻蚀所带来的界面损伤以及界面态问题,改善漏电性能。
由技术常识可知,本发明可以通过其它的不脱离其精神实质或必要特征的实施方案来实现。因此,上述公开的实施方案,就各方面而言,都只是举例说明,并不是仅有的。所有在本发明范围内或在等同于本发明的范围内的改变均被本发明包含。
Claims (1)
1.一种GaN基增强型MIS-HEMT器件,其特征在于,包括从下至上依次层叠设置的衬底(11)、成核层(12)、应力调控层(13)、GaN沟道层(14)、***层(15)、AlxGa1-XN势垒层(16)以及帽层(17),所述应力调控层(13)是由AlN/AlGaN/SiNX/GaN循环生长组成,具体包括AlN晶核层(131)、AlGaN应力控制层(132)、网状结构SiNx薄层(133)及GaN填平层(134);
先通过RIE刻蚀栅极区域SiNx钝化层(2),再通过ICP干法、高温热氧化后湿法两步法完全刻蚀掉AlXGa1-XN势垒层(16)形成凹栅槽,Al2O3栅介质层(3)分布在钝化层上、凹栅槽侧壁及底部,实现增强型MIS-HEMT;
源极(4)、漏极(5)位于T型栅极(6)两侧,源极(4)、漏极(5)与AlXGa1-XN势垒层(16)之间形成欧姆接触;
凹栅槽刻蚀通过两步法刻蚀直到将AlXGa1-XN势垒层(16)刻蚀完,具体方法为:先通过ICP干法刻蚀去除大部分AlXGa1-XN势垒层(16),再通过高温热氧化后TMAH湿法刻蚀去除余下的AlXGa1-XN势垒层(16);
所述衬底(11)尺寸大小为2~6inch,材质为硅;
所述成核层(12)采用PECVD方法生长,温度在450~550℃,其总厚度在5~15nm,在N2/Ar/O2的混合气氛下以生长速度为1~10nm/S生长;
所述应力调控层(13)中,所述AlN子层(131)厚度在1~5nm,AlGaN子层(132)的厚度在2~10nm,网状结构SiNX子层(133)厚度在0.5~2nm、GaN子层(134)的厚度为2~10nm,循环数为5~30;
所述GaN沟道层(14)的生长温度为1050~1150℃,厚度为1.0~2.5μm;
所述***层(15)为AlN***层,厚度为0.5~1.5nm,生长压力为50~100mbar,生长温度为1000~1200℃;
所述AlXGa1-XN势垒层(16)生长厚度为10~25nm,生长压力为50~100mbar,生长温度为900~1200℃,其中0<x<1;
所述帽层(17)为GaN帽层,该帽层生长厚度为1~3nm,生长压力为50~100mbar,生长温度为900~1200℃;
所述源极(4)、漏极(5)欧姆金属淀积采用电子束蒸发的方式淀积Ti/Al/Ni/Au四层欧姆金属,表面势垒层的刻蚀深度为5~15nm;
所述SiNX钝化层(2)由PECVD生长,生长温度为100~350℃,厚度为50~300nm;
ICP干法刻蚀使用气体为Cl2和BCl3,Cl2流量为10~100sccm,BCl3流量为10~100sccm,刻蚀腔体压强为10~100mTorr,RF功率为10~100W,ICP功率为200~2000W;
高温热氧化后TMAH湿法刻蚀中,高温热氧化在退火炉氧气氛围中550~650℃下进行,TMAH采用5%~35%体积比的水溶液,腐蚀温度在40~120℃,氧化/腐蚀过程循环处理次数为1~10次。
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