Patterning of Si(100) in microwave assisted LDE (Laser dry etching)

With the MALDE process high etch rates up to 1 mu m/min are obtained for p-Si(100) and P-Si(111) at room temperature by using excited CF4 and non-excited CC14 as processing gases. XPS measurements show that the formation of SiCl2 and F atom etching compete. A maximum in the etch rate is observed for a suitable CF4:CCl4 ratio (CCl4/[CF4+CCl4] = 0.20). The formation of CIF3in the MALDE process is proposed as a possible mechanism to explain the high Si etch rates. Spontaneous etching plays an important role in MALDE. For temperatures up to 350 deg C etch rates of 2.6 mu m/min are obtained via thermal evaporation without laser radiation. Polymerization (e.g., of MMA) can be used to protect the Si surface and the sidewalls against spontaneous etching and to make the process more anisotropic. For applications in microsystem technologies (e.g., sensors or actuators), large areas (> 4 mm2) can be etched by mask projection techniques.