Patent ID: 7025615
Filing Date: 2006-04-11
Classification: H01L

Abstract:
1. A method in the fabrication of an integrated bipolar circuit for forming a pt + /n-junction varactor, comprising the steps of: providing a p-doped substrate; forming a buried n forming in said substrate an essentially n-doped region above the buried n forming field isolation around, in a horizontal plane, said n-doped region; doping said essentially n-doped region by a multiple ion implant; forming a p forming an n+-doped contact region to the buried n+-doped region; said contact region being separated from, in a lateral plane, said n-doped region by said field isolation; and heat-treating the hereby-obtained structure to set the final doping profiles of the doped regions, wherein said steps of doping said essentially n-doped region by a multiple ion implant; forming a p + -doped region on said essentially n-doped region; and heat treating the hereby obtained structure are performed to obtain a hyper-abrupt p + /n-junction with a n-type dopant concentration N on the n-side of the hyper-abrupt p + /n-junction, which substantially varies according to where B is an arbitrary constant, W is the vertical distance from the p + /n-junction, and m is −3/2 to thereby create a varactor with a capacitance that is proportional to the inverse of the square of a voltage applied to said varactor.