A true polysilicon emitter transistor

Abstract

A polysilicon emitter transistor has been fabricated in which the metallurgical base/emitter junction coincides with the interface between polycrystalline and monocrystalline material. The emitter region was formed by deposition of heavily phosphorus-doped polysilicon in an LPCVD reactor at 627°C, a temperature low enough to prevent diffusion of phosphorus into the substrate. Emitter Gummel numbers of over 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> scm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> have been obtained with this structure, allowing common emitter current gains in excess of 10000 to be reached for base implant doses of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> .