Effect of silicide process on bipolar transistor current gain

Emitter Gummel number of modern bipolar transistors is an important factor in determining device performance, especially for heavily doped, shallow junction transistors. Removal of even small amounts of the active dopant from the shallow emitter, e.g., Ar sputteretch and PtSi formation, can significantly reduce the current gain of bipolar transistors. A simple theory of bipolar transistor gain shows that degradation of current gain is due to the reduction of emitter Gummel number. Emphasis is placed on the control of the Ar sputteretch and PtSi formation to obtain desired current gain and to determine its implication in the development of advanced bipolar transistors with very shallow emitter junctions.