Method for making improved polysilicon FET gate electrodes havin

Details Method for making improved polysilicon FET gate electrodes havin Method for making improved polysilicon FET gate electrodes havin

1999-08-13

2000-03-21

Bowers, Charles

Semiconductor device manufacturing: process

Making field effect device having pair of active regions...

Having insulated gate

438305, 438595, H01L 21336

Patent

active

060402237

ABSTRACT:
A method for making improved polysilicon FET gate electrodes having composite sidewall spacers is achieved. After forming the polysilicon gate electrodes on the substrate, a SiO.sub.2 stress-release layer is deposited having a trapezoidal shape. A Si.sub.3 N.sub.4 layer is deposited and plasma etched back using the SiO.sub.2 layer as an etch-endpoint-detect layer to form composite sidewall spacers that include portions of the trapezoidal-shaped oxide layer. The SiO.sub.2 layer protects the source/drain areas from plasma etch damage that could cause high leakage currents. The Si.sub.3 N.sub.4 also extends over the SiO.sub.2 layer at the upper edges of the polysilicon gate electrodes. This prevents erosion of the SiO.sub.2 along the gate electrodes when the remaining oxide is removed from the source/drain areas using hydrofluoric acid wet etching. When an insulating layer is deposited over the FETs, and self-aligned contact openings are etched to the source/drain areas and extending over the gate electrodes, the Si.sub.3 N.sub.4 extending over the portion of the trapezoidal-shaped SiO.sub.2 layer that forms part of the composite sidewall spacer protects the SiO.sub.2 from etching. This results in more reliable contacts without degrading the FET performance.

REFERENCES:
patent: 5405791 (1995-04-01), Ahmad et al.
patent: 5656533 (1997-08-01), Kim
patent: 5747373 (1998-05-01), Yu
patent: 5824588 (1998-10-01), Liu

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