Polysilicon contact

Details Polysilicon contact Polysilicon contact

1993-01-15

1994-07-05

Chaudhuri, Olik

Fishing, trapping, and vermin destroying

437968, 437983, 437 31, 437239, H01L 21329

Patent

active

053267222

ABSTRACT:
A new method of forming polysilicon buried contact to source/drain or emitter regions is described. A silicon oxide layer is formed over the silicon substrate. An opening is formed to the silicon substrate at the location of the desired buried contact to source/drain or emitter region via conventional techniques. A hydrofluoric acid solution is used to remove the native silicon oxide which forms on the exposed surface of the silicon substrate. Some native silicon oxide is formed in a controlled manner again on the surface of the silicon substrate. The wafer is put into a low pressure chemical vapor deposition (LPCVD) apparatus and a layer of undoped polysilicon or amorphous silicon is deposited. An oxidizer is added to the deposition chamber or the wafer is exposed to ambient air so that a thin layer of native silicon oxide is formed in a controlled manner overlying the polysilicon layer. Additional alternating layers of polysilicon and native silicon oxide are formed as desired. The wafer is annealed at between about 800.degree. to 1000.degree. C. This causes, it is believed, the silicon oxide gas from the multiple native silicon oxide very thin layers to be exhausted resulting in the removal of all silicon oxide islands within the interface between the polysilicon and the buried contact to source/drain or emitter regions. Ions are implanted through the polysilicon layer or layers in the opening to the silicon substrate to form the source and drain regions.

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G. Akinai, et al. "NiSi.sub.2 ON Si(111), I. Effects of Substrate Cleaning Procedure and Reconstruction" Surface Science 193 (1988) pp. 534-548.

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