Abstract: An optical bench on which an optical component is mounted comprises an Si substrate made of a silicon wafer, a groove disposed on the Si substrate and designed to mount the optical component thereon, and a metal thin-film wiring for driving the optical component or a driver component. The metal thin-film wiring is formed in an electroless plating process before a groove manufacturing process which forms the groove by micromachining by means of wet processing.

Abstract: A process for forming trenches on a surface of a semiconductor substrate by dry etching using a gas mixture. The gas mixture comprises; (1) an etchant gas comprising at least bromine which etches the semiconductor surface to form trenches, (2) a cleaning gas comprising a halogen which evaporates residue formed by the etching, and (3) a reactive gas, e.g. N.sub.2, capable of reacting with material formed during the etching and capable of controlling the inclination of the trenches.

Abstract: A process for forming deep trenches on a surface of a semiconductor substrate by forming a mask on the surface of the semiconductor, which prescribes the position of the trenches; and then dry etching the semiconductor surface using a gas mixture comprising (1) an etchant, bromine containing, gas which etches the semiconductor surface to form trenches, (2) a cleaning, halogen containing, gas which evaporates the residue formed by the etching; and (3) a reactive gas capable of reacting with material formed during the etching and capable of decreasing the wastage of the mask by the etchant gas.