Characteristics of RIE SF6/O2/Ar Plasmas on n-Silicon Etching

In this work, highly anisotropic Si plasma etching process has been developed in reactive ion etching (RIE) reactor. The etch chemistry utilized consists of a mixture of sulphur tetra fluoride (SF6), oxygen (02) and argon (Ar). The use of nickel as masks was successfully patterned on Si by lift-off. Lines of 50 mum feature size were patterned on Si, resulting in perpendicular sidewalls and no observable undercutting. Etch rates were studied for gas compositions of SF₆/O₂/Ar, chamber pressures and DC bias. For chamber pressure in the range of 5 mTorr to 20 mTorr, the etch rates is found to increase with increasing dc bias, attaining a maximum rate of 2997 A/min at 20 mTorr. Surface morphology after etching is checked by atomic force microscopy and scanning electron microscopy, which show that the anisotropic of the etched surface and the smoothness of the etched surface is comparable to that of the etched.