Abstract: An apparatus may be used to deposit metal or conductive layers upon semiconductor wafers using an electrochemical process. The apparatus comprises a housing for retaining a first electrode (e.g., anode) and a second electrode (e.g., cathode), in a fixed spaced-apart relation to each other, with the surface area of the anode exceeding the surface area of the cathode (the wafer). The back surface of the wafer is mounted on a handling disk; the disk has an aperture for accessing the wafer and is held in the housing. A contact probe passes through the aperture to touch the back surface of the wafer, the probe having a spring-loaded spherical radius head for depressurizing the head as it touches the wafer. This apparatus permits a uniform current distribution as the contact probe is not interposed between the electrodes, and the larger surface area of the anode relative to the wafer enhances the production of uniform and reproducible films.

Abstract: An optically toggled bidirectional normally-on switch is provided with protection against bilateral voltage and bidirectional current surges by the inclusion of a pair of oppositely poled thyristors. One version uses a large junction-type field-effect transistor in its main path and a pair of smaller junction-type transistors in the subsidiary path. A photodiode array controls the gate voltage on each of the transistors and turns them off when illuminated. A control node in the subsidiary path is connected to the gates of the SCRs so that excess current in this path turns on the appropriately-poled thyristor to provide an additional shunt path for the current.