CN111211160B - 一种垂直GaN功率二极管 - Google Patents

一种垂直GaN功率二极管 Download PDF

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CN111211160B
CN111211160B CN202010040170.8A CN202010040170A CN111211160B CN 111211160 B CN111211160 B CN 111211160B CN 202010040170 A CN202010040170 A CN 202010040170A CN 111211160 B CN111211160 B CN 111211160B
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罗小蓉
孙涛
欧阳东法
郗路凡
邓思宇
魏杰
张波
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University of Electronic Science and Technology of China
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Abstract

本发明属于功率半导体技术领域，涉及一种垂直GaN功率二极管。本发明在阳极电压为0V时，利用阳极金属与GaN半导体之间功函数差耗尽二极管阳极和阴极之间的导电沟道，实现二极管关断及耐压的功能，避免了GaN肖特基二极管因肖特基结因漏电而导致的提前击穿，获得高反向击穿电压和低泄漏电流；当阳极电压大于电压临界值时，耗尽区变窄,器件导通；当阳极电压进一步增大，凸出部分的漂移区侧壁开始出现高浓度电子积累层，通过调节凸出部分的漂移区的宽度以及选择合适的阳极金属，从而获得低开启电压和极低导通电阻。此外，沟道区势垒高度随温度几乎不变，具有很高的温度稳定性。本发明具有开启电压小，击穿电压高，比导通电阻低，温度稳定性好等优点。

Description

一种垂直GaN功率二极管
技术领域
本发明属于功率半导体技术领域，涉及一种垂直GaN功率二极管。
背景技术
横向GaN晶体管击穿电压和电流能力的提升需要更大的芯片面积，同时，栅介质与宽禁带半导体材料界面的强电场会影响器件可靠性，导致器件提前击穿，无法充分发挥材料的优势。相比之下，垂直GaN晶体管器件结构耐压不受横向尺寸的限制，一方面，有效减小芯片面积、降低芯片成本；另一方面，耐压时的电场峰值远离器件表面，提高器件可靠性。其中，垂直GaN肖特基二极管由于具有低正向导通压降和快反向恢复的特性，能够实现低导通损耗和关断损耗，十分适合于高频低功耗应用。然而，由于受到镜像力势垒降低和隧穿电流的影响，导致垂直GaN肖特基二极管反向泄漏电流增大，器件发生提前击穿。垂直GaN PiN二极管正向导通时是PN结开启，由于GaN禁带宽度较大为3.4eV，因此其开启电压较大，同时，少子会影响反向恢复特性。
发明内容
针对上述问题，本发明提出一种具有高反向击穿电压和低泄漏电流的垂直GaN功率二极管。
本发明的技术方案是，一种垂直GaN功率二极，包括阳极结构、N型漂移区1和阴极结构，其中阳极结构位于N型漂移区1之上，阴极结构位于N型漂移区1下端；
所述N型漂移区1的中部向上凸起从而呈倒“T”字形结构；所述阳极结构包括第一导电材料2、第一材料层3、第一绝缘材料层4、第二绝缘材料层5和第一高掺杂N型半导体层6，第二绝缘材料层5覆盖在N型漂移区1除凸起部位以外的上表面；所述第一绝缘材料层4覆盖在N型漂移区1凸起部分两侧及第二绝缘材料层5上；所述第一高掺杂N型半导体层6位于N型漂移区1凸起部位的顶部；所述第一材料层3位于第一高掺杂N型半导体层6的两侧，且沿N型漂移区1凸起部位的侧面向下延伸至与第一绝缘材料层4接触；所述第一导电材料2覆盖在第一高掺杂N型半导体层6、第一材料层3和第一绝缘材料层4上；
所述阴极结构包括第二导电材料层8和第二高掺杂N型半导体层7，第二N型层7位于N型漂移区1和第二导电材料层8之间；
所述第一导电材料2与第一高掺杂N型半导体层6形成欧姆接触，第一导电材料2的材料包括但不限于金属、多层金属堆栈结构及合金。
本发明提出一种高压垂直GaN功率二极管，该结构通过阳极金属与GaN之间的功函数差耗尽二极管阳极和阴极之间的导电沟道，实现二极管关断和耐压的功能，避免了GaN肖特基二极管因肖特基结因漏电而导致的提前击穿，从而获得高反向击穿电压和低泄漏电流；当阳极电压大于电压临界值时，耗尽区变窄，器件导通，当阳极电压进一步增大，凸出部分的漂移区侧壁开始出现高浓度电子积累层，从而获得低开启电压和极低导通电阻。此外，沟道区势垒高度随温度几乎不变，具有很高的温度稳定性。
进一步的，所述第一材料层3和第一绝缘材料层4为同种绝缘材料。
进一步的，所述第一材料层3与N型漂移区1为肖特基接触，第一材料层3是金属或者是包含金属的复合结构。
更进一步的，第二绝缘材料层5覆盖在N型漂移区1除凸起部位外的上表面，并沿N型漂移区1凸起部位的侧面向上延伸，从而使位于第二绝缘材料层5上方的第一绝缘材料层4和第一导电材料2皆呈阶梯状。
本发明方案的器件，其版图为条形元胞、多边形元胞或者为圆形元胞。
本发明的有益效果是，本发明相对于传统结构，在阳极电压为0V时，利用阳极金属与GaN半导体之间功函数差耗尽二极管阳极和阴极之间的导电沟道，实现二极管关断及耐压的功能，避免了GaN肖特基二极管因肖特基结因漏电而导致的提前击穿，从而获得高反向击穿电压和低泄漏电流；当阳极电压大于电压临界值时，耗尽区变窄,器件导通；当阳极电压进一步增大，凸出部分的漂移区侧壁开始出现高浓度电子积累层，通过调节凸出部分的漂移区的宽度以及选择合适的阳极金属，从而获得低开启电压和极低导通电阻。此外，沟道区势垒高度随温度几乎不变，具有很高的温度稳定性。因此，本发明具有开启电压小，击穿电压高，比导通电阻低，温度稳定性好等优点。
附图说明
图1是实施例1的结构示意图；
图2是实施例2的结构示意图；
图3是条形元胞及AA’、BB’及CC’剖面示意图，并沿DD’画出了耗尽区交叠示意图；
图4是多边形元胞及AA’及BB’剖面示意图，并沿DD’画出了耗尽区交叠示意图；
图5是圆形元胞及AA’及BB’剖面示意图；
具体实施方式
下面结合附图和实施例对本发明的方案做进一步的描述。
实施例1
如图1所示，本例包括阳极结构、N型漂移区1和阴极结构，其中阳极结构位于N型漂移区1之上，阴极结构位于N型漂移区1下端；N型漂移区1的中部向上凸起从而呈倒“T”字形结构；所述阳极结构包括第一导电材料2、第一材料层3、第一绝缘材料层4、第二绝缘材料层5和第一高掺杂N型半导体层6，第二绝缘材料层5覆盖在N型漂移区1除凸起部位以外的上表面；所述第一绝缘材料层4覆盖在N型漂移区1凸起部分两侧及第二绝缘材料层5上；所述第一高掺杂N型半导体层6位于N型漂移区1凸起部位的顶部；所述第一材料层3位于第一高掺杂N型半导体层6的两侧，且沿N型漂移区1凸起部位的侧面向下延伸至与第一绝缘材料层4接触；所述第一导电材料2覆盖在第一高掺杂N型半导体层6、第一材料层3和第一绝缘材料层4上；阴极结构包括第二导电材料层8和第二高掺杂N型半导体层7，第二N型层7位于N型漂移区1和第二导电材料层8之间；第一导电材料2与第一高掺杂N型半导体层6形成欧姆接触。
本例的工作原理：在阳极电压为0V时，利用阳极金属与GaN半导体之间功函数差耗尽二极管阳极和阴极之间的导电沟道，实现二极管关断及耐压的功能；当阳极电压大于电压临界值时，耗尽区变窄,器件导通；当阳极电压进一步增大，凸出部分的漂移区侧壁开始出现高浓度电子积累层，通过调节凸出部分的漂移区的宽度以及选择合适的阳极金属，从而获得低开启电压和极低导通电阻。
相比于传统结构，本发明避免了GaN肖特基二极管因肖特基结因漏电而导致的提前击穿，获得高反向击穿电压和低泄漏电流。此外，沟道区势垒高度随温度几乎不变，具有很高的温度稳定性。本发明具有开启电压小，击穿电压高，比导通电阻低，温度稳定性好等优点。
实施例2
如图2所示，本例与实施例1的区别在于，第二绝缘材料层5覆盖在N型漂移区1除凸起部位外的上表面，并沿N型漂移区1凸起部位的侧面向上延伸，从而使位于第二绝缘材料层5上方的第一绝缘材料层4和第一导电材料2皆呈阶梯状。
相比于实施例1，本例结构的特点是覆盖在材料层5的第一导电材料呈阶梯状，起到阶梯场板的作用，缓解电场集中现象，优化电场分布，提高器件击穿电压。
图3是条形元胞及AA’、BB’及CC’剖面示意图，并沿DD’画出了耗尽区交叠示意图。耗尽区的交叠由左右两个侧壁的耗尽区的展宽和缩小决定。
图4是多边形元胞及AA’及BB’剖面示意图，并沿DD’画出了耗尽区交叠示意图。相比于条形元胞具有多方向的耗尽作用。
图5是圆形形元胞及AA’及BB’剖面示意图。相比于多边形元胞具有更多方向的耗尽作用。
本发明的开启电压取决于耗尽区的交叠程度，若交叠程度较小，则在较小的阳极电压下器件就开启，即具有更小的开启电压。但反向耐压时需要耗尽区阻断，若耗尽区交叠程度较小，无法具有较高的击穿电压。因此，要获得较高的击穿电压和较小的开启电压需要对耗尽区交叠程度进行折中。而图4及图5所示的版图具有更好的折中。

Claims (4)

1.一种垂直GaN功率二极管，包括阳极结构、N型漂移区(1)和阴极结构，其中阳极结构位于N型漂移区(1)之上，阴极结构位于N型漂移区(1)下端；
所述N型漂移区(1)的中部向上凸起从而呈倒“T”字形结构；所述阳极结构包括第一导电材料(2)、第一材料层(3)、第一绝缘材料层(4)、第二绝缘材料层(5)和第一高掺杂N型半导体层(6)，第二绝缘材料层(5)覆盖在N型漂移区(1)除凸起部位以外的上表面；所述第一绝缘材料层(4)覆盖在N型漂移区(1)凸起部分两侧及第二绝缘材料层(5)上；所述第一高掺杂N型半导体层(6)位于N型漂移区(1)凸起部位的顶部；所述第一材料层(3)位于第一高掺杂N型半导体层(6)的两侧，且沿N型漂移区(1)凸起部位的侧面向下延伸至与第一绝缘材料层(4)接触；所述第一导电材料(2)覆盖在第一高掺杂N型半导体层(6)、第一材料层(3)和第一绝缘材料层(4)上；
所述阴极结构包括第二导电材料层(8)和第二高掺杂N型半导体层(7)，第二高掺杂N型半导体层(7)位于N型漂移区(1)和第二导电材料层(8)之间；
所述第一导电材料(2)与第一高掺杂N型半导体层(6)形成欧姆接触；
所述N型漂移区(1)为N型GaN漂移区，第一导电材料(2)与N型GaN漂移区之间功函数差耗尽二极管阳极和阴极之间的导电沟道。
2.根据权利要求1所述的一种垂直GaN功率二极管，其特征在于，所述第一材料层(3)和第一绝缘材料层(4)为同种绝缘材料。
3.根据权利要求1所述的一种垂直GaN功率二极管，其特征在于，所述第一材料层(3)与N型漂移区(1)为肖特基接触，第一材料层(3)是金属或者是包含金属的复合结构。
4.根据权利要求1-3任意一项所述的一种垂直GaN功率二极管，其特征在于，第二绝缘材料层(5)覆盖在N型漂移区(1)除凸起部位外的上表面，并沿N型漂移区(1)凸起部位的侧面向上延伸，从而使位于第二绝缘材料层(5)上方的第一绝缘材料层(4)和第一导电材料(2)皆呈阶梯状。
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