Abstract: A system for reducing the concentration of foreign material on a wafer etched in a reactive ion etch chamber is disclosed. As a radio frequency voltage is applied within the etch chamber, the pressure within the etch chamber may be reduced to a base pressure. Also, the flow of gas into the etch chamber may be maintained. This may include minimizing the flow of high reactive gas into the etch chamber while maintaining the flow of low reactive gas therein. The system further includes deactivating the radio frequency voltage. Deactivating the radio frequency voltage may be accomplished by gradually reducing the voltage to a minimum voltage. The gradual reduction may be accomplished by incrementally reducing the voltage in a series of steps. If reactive ion etching occurs with magnetic enhancements, the magnetic field applied to the etch chamber may be deactivated, typically prior to the reduction of the radio frequency voltage.

Abstract: A process for forming deep (>6.mu.m) trenches in a silicon substrate. The substrate is etched through a silicon oxide mask in a plasma having 75%-86% HCl, 9%-16% O.sub.2, and 1%-8% BCl.sub.3. The resulting trenches have substantially vertical sidewalls and rounded bottom surfaces. The plasma etch is performed at high power and low pressure, so that it achieves a high aspect ratio at a minimum etch bias.

Abstract: This describes different methods of using a single photoresist layer to define both metal contact vias and metal lift-off areas on semiconductor integrated circuits. The methods use positive photoresist containing a small amount of base such as imidazole to provide a lift-off overhang when the resist is exposed and developed to provide a reversal image.