A high-voltage, medium-power silicon planar epitaxial switching transistor

Since transistors have been used as drivers in ferrite core solid-state memories, the push for increased performance has been relentless. To compound the problem, the increased performance has always been required in all directions simultaneously, such as higher operating voltage, higher current capability, higher speed, and lower saturation drops. Along with the foregoing requirements, high reliability is also mandatory. This paper describes the development of a transistor with improved performance in all of the categories mentioned above. It is a double-diffused, epitaxial, silicon NPN planar structure employing a unique impurity gradient in the epitaxial layer and a unique ohmic contact geometry. The result is a transistor with a BVCBO> 180 v., a BVCEO> 90 v., that will switch 600 ma. through a 90 volt collector voltage swing in 35 nsec., 10 to 90%, with a 60 ma. base drive. With increased base drive, 100 ma., the switching time can be reduced to < 25 nsec. VBE(SAT)is less than 1.5 v. and VCE(SAT)is less than 1.0 v.