ICP干法刻蚀GaAs背孔工艺研究

Dry Etching of GaAs Backside via with Inductively Coupled Plasma

采用金属Ni作为掩膜,Cl2/BCl3作为刻蚀气体,利用感应耦合等离子体刻蚀(ICP)技术对Ga As HEMT背孔工艺进行研究。本文详细研究了ICP功率、反应室压强、Cl2/BCl3流量比以及RF功率对刻蚀速率、刻蚀形貌以及"长草"效应的影响。实验结果表明:刻蚀速率随ICP功率、Cl2/BCl3流量、RF功率的增加而增加,但随反应室压强的增加,刻蚀速率先增加后降低;相同RF功率条件下,背孔陡直性受ICP功率、反应室压强以及刻蚀气体流量比的影响十分明显;而RF功率则对背孔"长草"效应有较大影响。通过优化刻蚀条件,在ICP功率为500 W,反应室压强为0.4 Pa,Cl2/BCl3流量为20/5 m L/min,RF功率为120 W的刻蚀条件下,刻蚀背孔陡直性好,侧壁平滑,底部平整,刻蚀速率达到3μm/min。

The GaAs backside via of high electron mobility transistor （HEMT） was dry etched by inductively cou- pled plasma （ICP）, with Ni coating as mask and Cl_2/BCl_3 as etching gases. The influence of the etching conditions, in- cluding the ICP power, RF power, pressure, and ratio of Cl_2/BCl_3 flow rates, on the etching rate and via-shape was investi- gated. The results show that the etching conditions strongly affected the etching rate and microstructnres of the back-via. For instance, the etching rate increased with the increases of ICP power, RF powers, and ratio of Cl_2/BCl_3 flow rates; as the pressure increased,the etching rate changed in increase-decrease mode. At a fixed RF power, via-steepness depends on the ICP power, pressure, and ratio of Cl_2/BCl_3 flow rates;and RF power induced “hairy” morphology. Under the opti- mized conditions： ICP power of 500 W, pressure of 0.4 Pa, RF power of 120 W, and ratio of 20 mL/min/5 mL/min, steep via with flat bottom and smooth wall was etched at a rate of 3 gm/min.