Patent ID: 9401410
Filing Date: 2016-07-26
CPC Classification: H01L

Claim Text:
1. A method of forming a semiconductor device, comprising the steps: providing a substrate comprising a semiconductor material; forming a deep trench at least 10 microns deep in the substrate, the deep trench being 1.5 microns to 3.5 microns wide; forming a dielectric liner on sidewalls of the deep trench; forming a first layer of polysilicon on the dielectric liner so that the first layer of polysilicon extends into the deep trench, the first layer of polysilicon being formed as an undoped layer; implanting dopants into the first layer of polysilicon; forming a second layer of polysilicon on the first layer of polysilicon so that the second layer of polysilicon extends into the deep trench, the second layer of polysilicon being formed as an undoped layer; and annealing the substrate so as to activate and diffuse the implanted dopants, so that an average doping density in the first layer of polysilicon and the second layer of polysilicon is at least 1×10