Abstract: A plasma etch process is described for the etching of oxide with a high selectivity to nitride, including nitride formed on uneven surfaces of a substrate, e.g., on sidewalls of steps on an integrated circuit structure. The addition of a hydrogen-bearing gas to C4F8 or C2F6 etch gases and a scavenger for fluorine, in a plasma etch process for etching oxide in preference to nitride, results in a high selectivity to nitride which is preserved regardless of the topography of the nitride portions of the substrate surface.

Abstract: N bit-collision circuits of a collision detection circuit each include a bit-collision circuit driver connected to drive an x-th line of the common collision detection bus if the x-th line of the station's corresponding identifier signal is at a low level. The bits of the identifier signal are only provided to the bit-collision circuit drivers while an enable signal is asserted. The driver has an open-collector-type connection to the x-th line of the common collision detection bus. That is, the bit-collision circuit driver, when not driving, presents a high impedance at its output. Each bit-collision circuit further includes an XOR device for use in comparing the level of the x-th line of the collision bus with the level of the x-th bit of the station's identifier signal. A NOR device is for combining receives the comparison results from the XOR devices of the bit-collision circuits and provides a combined bit-collision result.