Deep silicon etching for thermopile structures using a modified Bosch process

We present a simple method of deep anisotropic etching of silicon up to 400 μm with nearly vertical sidewall profile for thermopile devices. The method is based on the time-multiplexed etching which is a modified case of the Bosch deep reactive ion etching process. This process is mainly adjusted by chuck power and it is divided into three steps which are zero bias deposition step, high bias polymer removing step, and low bias silicon etching step. Compared with the standard Bosch process, this modified strategy shows advantage of etch rate and selectivity.