GaAs MMICs: development and manufacture

Summary form only given. The development of electronic devices from initial feasibility studies to a commercially viable products is lengthy and expensive. For example, it is almost exactly twenty years since the first GaAs MMIC was demonstrated at Caswell, but it is only in the last year or so that there has been large scale production worldwide, based on the advantages of low noise and high power efficiency in mobile communications applications. To a large extent this slow exploitation reflects the lack of a mass market opportunity, but it is also intrinsic to the development process itself. This paper traces the various stages in the process, using the GMMT H40 pHEMT as an example. Process development is controlled by formal review procedures, designed to achieve release of a commercial foundry process. The initial stages concentrate on the feasibility of the process in terms of various process steps, market information and key specifications. Important aspects of the H40 process are the 0.25 μm gate, the double gate recess to reduce gate-drain capacitance and improve breakdown voltage, the mushroom gate structure to reduce gate resistance and so Improve associated gain and noise, and the carefully designed material structure with a 20% InGaAs channel. In parallel with process development, process monitors are developed with test devices and controlled test procedures. Standard transistor structures are used for initial characterisation and modelling