Anisotropic etching of silicon

Anisotropic etching of silicon has become an important technology in silicon semiconductor processing during the past ten years. It will continue to gain stature and acceptance as standard processing technology in the next few years. Anisotropic etching of (100) orientation silicon is being widely used today and (110) orientation technology is emerging. This paper discusses both orientation-dependent and concentration-dependent etching of (100) and (110) silicon. Very exact process control steps may be designed into a process by use of (100) anisotropic and concentration-dependent etching. Also, methods of oxide or nitride pin hole detection in (100) silicon are presented. Mask alignments to obtain different etch front termination in both (100) and (110) silicon are shown. Very high packing density structures, less than 1 μm, are obtained in the (110) technology, and extremely high etching ratios of greater than 650 to 1 are obtained in (110) orientation-dependent etching. Some of the many applications for anisotropic and concentration-dependent etching are described.