A low noise silicon microwave transistor made by ion-implantation

A low noise silicon microwave transistor has been developed using ion-implantation technology. For reduction of the noise figure of microwave transistors, it is necessary to keep the base width small enough while maintaining the total base impurity above a certain limit. It has not been possible to meet this requirement with conventional double diffused structures because of the error function-like impurity profile and the undesirable emitter dip effect. The impurity profile of an ion-implanted base is more step-like and can be advantageously used for the base region of microwave transistors if the profile is not substantially disturbed by subsequent heat treatments. An arsenic-diffused and washed emitter method has been developed. An arsenic doped germano-silicate glass film which has a very fast etch rate was used as a diffusion source. Emitter dip free structures with arsenic surface concentrations in excess of 1.5 × 10²⁰cm^-3have been realized with this method.