CN111276533B - 一种选择区域凹槽栅GaN电流孔径垂直结构晶体管结构及实现方法 - Google Patents

一种选择区域凹槽栅GaN电流孔径垂直结构晶体管结构及实现方法 Download PDF

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CN111276533B
CN111276533B CN201811479104.XA CN201811479104A CN111276533B CN 111276533 B CN111276533 B CN 111276533B CN 201811479104 A CN201811479104 A CN 201811479104A CN 111276533 B CN111276533 B CN 111276533B
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王茂俊
尹瑞苑
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Abstract

本发明公开了一种选择区域凹槽栅GaN电流孔径垂直结构晶体管结构及实现方法,本发明属于微电子技术领域,涉及氮化镓垂直结构电力电子器件制作。所述结构包括漏极金属、GaN自支撑衬底、漂移区、P型GaN、非故意掺杂GaN、AlGaN势垒、栅介质、栅极和源极金属。在衬底上生长漂移区,P型GaN,并在P型GaN上形成电流孔径结构、再生长非故意掺杂GaN和AlGaN势垒层,去除电流孔径周围AlGaN势垒层,淀积栅介质,源极、栅极和漏极金属。本发明去除AlGaN势垒层,形成增强型沟道,避免了对电流孔径上方区域的损伤,栅漏电得到有效控制,同时提高了器件的阈值电压,拓展了GaN电流孔径垂直结构晶体管的应用范围。

Description

一种选择区域凹槽栅GaN电流孔径垂直结构晶体管结构及实 现方法
技术领域
本发明属于微电子技术领域,涉及氮化镓垂直结构电力电子器件制作。
背景技术
GaN材料由于其击穿电场强、迁移率高以及AlGaN/GaN异质结界面处高浓度的二维电子气而被视为功率器件领域重要替代材料。GaN材料有望进一步降低器件的静态损耗和开关损耗,从而进一步提高系统效率。
近年来,随着GaN在光电领域的发展,GaN自支撑衬底的成本不断降低,质量不断提高,这为GaN垂直结构器件的发展提供了有利的条件。同时,GaN材料生长技术不断发展,不论是同质外延还是异质外延,生长的GaN晶体背景载流子浓度和位错密度很低,迁移率较高,能完全满足GaN垂直结构器件发展的需求。
GaN垂直结构器件由于其特有的材料特性,电流输出能力和耐压能力很强,而且其受表面态的影响较小,因此适于新型功率系统对于功率开关器件的需求。
目前,GaN垂直结构三极管主要分为两类。一种是槽型金属氧化物半导体晶体管(Trench MOSFET),在GaN领域,Mg掺杂的激活率很低,导致实现P型GaN要掺杂大量Mg,导致MOSFET的沟道迁移率很低,另一方面,刻蚀栅槽降低了器件的击穿电压;另一种是电流孔径垂直结构晶体管(CAVET),这种结构利用背势垒实现器件的关断,同时利用AlGaN/GaN异质结界面处高浓度的二维电子气降低导通电阻,这种结构的缺点是增强型实现困难,而增强型器件有利于减小功率系统电路复杂度以及具有失效保护机制。为实现增强型,采用P型栅技术,可以耗尽栅下方的二维电子气,但是P型栅构成的pn结其开启电压限制了栅极摆幅,在实用中往往需要较大的栅极摆幅以屏蔽电路串扰从而提高系统的容错能力,因此实现高阈值电压的CAVET增强型结构在实际应用中意义重大。
发明内容
本发明为了提高电流孔径垂直结构晶体管的阈值电压,在传统电流孔径垂直结构晶体管结构的基础上,进行选择性栅刻蚀,去除部分栅极下方的AlGaN,以形成增强型沟道,只有在栅极施加一定的正电压以后,栅极下方积累电子,形成沟道,器件导通。
本发明的技术思路如下:传统电流孔径垂直结构晶体管结构中,P-GaN背势垒耗尽部分二维电子气,P-GaN上生长了一层非故意掺杂的GaN,GaN之上生长了一层AlGaN,利用AlGaN和GaN之间的极化诱导出高浓度的二维电子气,为防止P型GaN中Mg扩散到AlGaN/GaN界面,非故意掺杂的GaN有一定厚度,因此P型GaN距离二维电子气沟道有一段距离,耗尽二维电子气的作用有限,即使可以排除Mg扩散的影响,P-GaN与AlGaN/GaN界面的距离较近时,耗尽效果明显,器件导通电阻急剧上升,CAVET失去其特有的结构优势。在不影响器件导通电阻的基础上,本发明通过选择性刻蚀部分栅极下方的AlGaN,形成局部的增强型沟道,从而提高阈值电压。
依据上述技术思路,为了提高电流孔径垂直结构晶体管阈值电压,一种选择区域凹槽栅GaN电流孔径垂直结构晶体管结构及实现方法,所述结构包括GaN自支撑衬底、n-漂移区、P型GaN、电流孔径、再生长的非故意掺杂的GaN、AlGaN势垒层、栅介质层、栅极金属和源极金属。
在GaN自支撑衬底上生长近本征的高阻n型GaN,之后生长背势垒P型GaN,然后对P型GaN进行选择性刻蚀,直至露出n型GaN表面,从而形成电流孔径。
在形成电流孔径的晶圆上再生长一定厚度非故意掺杂的GaN,然后生长AlGaN势垒层,以形成高浓度的二维电子气。
对生长好势垒层的基片进行区域选择性刻蚀,去除部分区域的AlGaN,电流孔径上方区域容易受到高场的影响,为降低栅漏电,保护电流孔径上方的AlGaN势垒层,只去除电流孔径周围的AlGaN。
在选择区域刻蚀形成的基片上,淀积栅极介质,对源极区域进行刻蚀去除源极区域上方的栅介质,同时刻蚀非故意搀杂GaN和AlGaN势垒层露出P型GaN;
淀积P-GaN接触金属,再淀积源极金属,形成对n-GaN和AlGaN势垒层的接触,然后快速热退火,形成源极欧姆接触,淀积栅极金属和互连金属,形成栅极金属。
在晶圆背面淀积金属,形成漏极欧姆接触。
附图说明
通过参照附图能更加详尽地阐明本发明二极管的原理及其结构,并进一步描述本发明的示例性实施例,在附图中:
图1是本发明选择区域凹槽栅GaN电流孔径垂直结构晶体管结构示意图;
图2是传统GaN电流孔径垂直结构晶体管的整体剖面结构图,帮助更好地阐明本发明的设计思路;
图3~图11是本发明中的选择区域凹槽栅GaN电流孔径垂直结构晶体管结构示意图,反映了本发明的工艺制造流程。
具体实施方式
在下文中,将参照附图更充分地描述本发明,在附图中示出了实施例及其实现过程,所描述的实施例仅仅是本发明中的一种实现形式,即本发明不应该解释为局限于在此阐述的实施例。基于该实施例,将本发明的范围充分地传达给本领域技术人员。
在下文中,将参照附图更详细地描述本发明的示例性实施例。
参照图1,该器件结构自下而上的顺序依次包括漏极金属、GaN自支撑衬底、n-漂移区、P型GaN、非故意掺杂GaN、AlGaN势垒层、栅介质层、栅极金属和源极金属。其制备方法包括以下具体步骤:
(1)如图3所示,在GaN自支撑衬底上,首先用MOCVD或者MBE生长一层n--GaN漂移区,然后用MOCVD或者MBE生长一层P型GaN;
(2)在图3所示结构基础上,用ICP-RIE对P-GaN进行刻蚀形成电流孔径结构如图4所示;
(3)在图4所示结构基础上,用MOCVD或者MBE再生长一层非故意掺杂的GaN,之后再生长一层AlGaN势垒层,如图5所示;
(4)在图5所示结构基础上,用ICP-RIE对电流孔径周围区域进行刻蚀,去除该区域AlGaN势垒层,形成图6所示所示结构;
(5)在图6所示结构基础上,用ALD、PECVD、ICPCVD或者LPCVD生长一层栅极介质层,形成图7所示结构;
(6)在图7所示结构基础上,用RIE去除源极区域栅介质层,如图8所示;
(7)用ICP-RIE去除再生长的非故意掺杂的GaN和AlGaN势垒层,露出P-GaN表面,如图9所示;
(8)在图9所示结构基础上,淀积P-GaN接触金属,然后淀积源极金属,快速热退火形成,源极欧姆接触,如图10所示;
(9)在图10所示结构基础上,淀积栅金属和互连金属,形成如图11所示结构;
(10)在图11所示结构基础上,在晶圆背面淀积漏极接触金属,形成漏极欧姆接触,如图1所示。

Claims (11)

1.一种选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:所述结构包括:漏极金属、衬底、n-漂移区、P型GaN、电流孔径结构、非故意掺杂GaN、AlGaN势垒层、凹槽结构、栅介质层、栅极金属和源极金属;所述晶体管制备方法包括:在衬底上生长n-漂移区,P型GaN,并在P型GaN刻蚀形成电流孔径结构、再生长非故意掺杂GaN和AlGaN势垒层,去除电流孔径周围、P-GaN和非故意掺杂GaN上方的AlGaN势垒层以形成凹槽结构,淀积栅极介质,在电流孔径和凹槽结构上淀积栅极金属,凹槽栅和电流孔径上方的平面栅共同构成选择区域凹槽栅结构,最后淀积源极和漏极金属。
2.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:其中的衬底材料为GaN自支撑衬底。
3.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:其中的n-漂移区材料为GaN。
4.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,生长n-漂移区和P型GaN的方法有:MOCVD、MBE以及MOCVD和MBE结合的方法。
5.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,在P型GaN上形成电流孔径的方法有:ICP-RIE或者RIE干法刻蚀、KOH或者TMAH溶液的湿法腐蚀以及ICP-RIE或者RIE干法刻蚀和KOH或者TMAH溶液湿法腐蚀相结合的方法。
6.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,再生长非故意掺杂GaN和AlGaN势垒层的方法有:MOCVD、MBE以及MOCVD和MBE结合的方法。
7.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:栅极刻蚀区域的AlGaN势垒层部分或者全部被去除。
8.根据权利要求7所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:去除AlGaN势垒层的方法包括ICP-RIE或者RIE干法刻蚀、KOH或者TMAH溶液的湿法腐蚀以及ICP-RIE或者RIE干法刻蚀和KOH或者TMAH溶液湿法腐蚀相结合的方法。
9.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:栅极介质材料为以下材料中的任意一种:Si3N4、Al2O3、AlN、HfO2、SiO2、HfTiO、Sc2O3、Ga2O3、MgO、SiNO。
10.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:源极由P-GaN接触金属以及非故意掺杂GaN、AlGaN势垒层接触金属构成,为以下导电材料的一种或多种的组合:钛、铝、铂、铱、镍、金、钼、钯、硒、铍、TiN、ITO。
11.根据权利要求1所述的选择区域凹槽栅GaN电流孔径垂直结构晶体管,其特征在于:栅极和漏极金属可以为以下导电材料的一种或多种的组合:钛、铝、铂、铱、镍、金、钼、钯、硒、铍、TiN、ITO。
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CN108598163A (zh) * 2018-05-14 2018-09-28 电子科技大学 一种GaN异质结纵向功率器件

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