"Non-Fowl Mouth" Symmetric Transistor
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Disclosed is a process which eliminates the "bird's beak" at the perimeter of the emitter/base junction in semiconductor devices. The process employs a double sidewall structure to retain a Si3N4/SiO2 plug which serves as the dielectric spacer providing the isolation between the emitter and the base. In symmetric transistor fabrication using previous methods, there has been a problem with the formation of an oxidation bird's beak near the perimeter of the emitter-base junction. This is normally an uncontrollable process step in the transistor fabrication and is a potential source of parameter variability. The present process eliminates the bird's beak completely. In the process, a thin layer of SiO2, designated as 2 in Fig. 1, is grown upon the Si substrate 1.