We use inductively coupled plasma chemical etching technology (PCET) operating at atmospheric pressure to fabricate an optical mirror whose materials are fused silica, reaction bonded SiC, sintered SiC, and Si for the first time, to our best knowledge. This Letter is focused on a primary study of the mirror surface roughness fabricated with a plasma torch on different wafers. The four wafers’ surface roughness after PCET fabrication are Ra 0.053, 0.223, 0.612, and 0.027 μm, respectively (increased 5, 40, 1.07, and 2 times, respectively). The micro-transformation principle of the surface roughness is researched with an Olympus LEXT 450. We analyze the main reasons that underpin the surface roughness increase. The experimental results show that the new technology is valid for fabricating Si-based materials. Consequently, inductively coupled PCET operating at atmospheric pressure shows promise for the future.