VIA GaAsFETs connected by photoelectrochemical plating

The advantages of via transistors made by plasma etching are higher gain, wider bandwidth, and increased packing density compared to wire bonded devices. These advantages become increasingly important at frequencies above 4 GHz. In order to obtain low thermal resistance and stable metallurgy the vias must be filled with metal. To accomplish this result, we have developed a new photoelectrochemical technique for filling the vias with a solid metal deposit such as gold. The method produces reliable devices and is suitable for manufacture.