等离子体低温刻蚀单晶硅高深宽比结构

Plasma Cyro-etching of High Aspect Ratio Silicon Crystal Structures

等离子体低温刻蚀是一种针对高深宽比结构的干法刻蚀技术。本文在低温刻蚀单晶硅样品时得到典型的刻蚀结果为:各向异性值>0.99,硅刻蚀速率>1.5μm/min,对SiO2刻蚀选择比>75,说明该刻蚀方法很具竞争力。通过对载片台温度、反应气体配比、腔体气压和ICP线圈功率等工艺参数的系列实验分析,证明低温刻蚀高深宽比硅微结构必需一定的低温和氧,同时揭示出低温刻蚀过程的主要控制因素是离子轰击而非刻蚀表面的化学反应。本文还对刻蚀过程中刻蚀滞后和凹蚀现象的产生机理进行了分析讨论,指出介电质掩蔽层的充放电效应导致了凹蚀,而刻蚀滞后的诱因则与通常的刻蚀情况不同,主要是台阶对离子轰击的覆盖效应。

High aspect ratio structures have been successfully fabricated by plasma cryo-etching on silicon wafers. The anisotropy, Si etching rate and selectivity of Si to SiO2 are better than 0.99,1.5 μm/min, and 75, respectively. Various factors, including the chuck temperarare, partial pressure ratio of the reactive gases, pressure, and power of the inductively coupled plasma（ICP） coil, were carefully evaluated to optimize the etching conditions. The results show that the anisotrtropic etching significantly depends on the optimal oxygen partial pressure and the low chuck temperature. We found that the ion bombardment plays a more important role in the plasma cryo-etching than the surface reactive etching does and that the discharge of the dielectric layers results in the undercut close to the mask.