Poly sandwich for deep trench fill

摘要

A semiconductor device is formed by forming a deep trench in a substrate and a dielectric liner on sidewalls of the deep trench. A first undoped polysilicon layer is formed on the semiconductor device, extending into the deep trench on the dielectric liner, but not filling the deep trench. Dopants are implanted into the first polysilicon layer. A second layer of polysilicon is formed on the first layer of polysilicon. A thermal drive anneal activates and diffuses the dopants. In one version, the dielectric liner is removed at the bottom of the deep trench before the first polysilicon layer is formed, so that the polysilicon in the deep trench provides a contact to the substrate. In another version, the polysilicon in the deep trench is isolated from the substrate by the dielectric liner.

主权项

1. A semiconductor device, comprising:
a substrate comprising a semiconductor material; a deep trench structure in the substrate, comprising: a deep trench at least 10 microns deep in the substrate; a dielectric liner disposed on sidewalls of the deep trench; a first layer of polysilicon disposed on the dielectric liner and extending to a bottom of the deep trench; and a second layer of polysilicon disposed on the first layer of polysilicon and extending into the deep trench, wherein dopants are distributed throughout the first layer of polysilicon and the second layer of polysilicon with an average doping density of at least 1×1018 cm−3, and wherein a width of the deep trench structure is 1.5 microns to 3.5 microns.