HCl Selective Etching of SiGe versus Si in Stacks Grown on (110)

Abstract

We have investigated the lateral HCl selective etching of SiGe versus Si in various patterned (110) SiGe/Si stacks. Given that Si(110) vertical etch rates are roughly 4 times higher than Si(100) ones, a moderate HCl partial pressure (0.4 Torr) was adopted for this 600-700C study. A definite SiGe versus Si etch selectivity has been demonstrated on (110) for 30-40% of Ge (none for 20% of Ge). SiGe lateral etch rates higher in the [1-10] than in the [001] direction have also been evidenced. A definite increase of both [1-10] and [001] lateral etch rates occurred when increasing the Ge content, the SiGe layer thickness and the etch temperature. Mean selectivities for 15 nm thick layers were however not that high, 20 for Si0.7Ge0.3 and 60 for Si0.6Ge0.4. [1-10] versus [001] etch anisotropy was otherwise minimized for low temperature etches, high Ge content and thick SiGe layers.