A new process for combining anisotropic bulk etching with subsequent precision lithography

We present a new method to combine deep anisotropic silicon etching with subsequent precision thin film lithography. The method is based on etching out the deep structures through a perforated silicon nitride membrane, followed by sealing the membrane with LPCVD deposition. By using polysilicon as a sacrificial layer defining the deep structure only one etching step is required. Ultrasonically agitated KOH etch was used to improve the etching performance. The process technology was demonstrated on the fabrication of a laser chip carrier with V-grooves for optical fibre alignment and electrodes for flip-chip mounting of lasers.