Composite gate electrode incorporating dopant diffusion-retardin

Details Composite gate electrode incorporating dopant diffusion-retardin Composite gate electrode incorporating dopant diffusion-retardin

1997-04-21

1999-03-23

Niebling, John F.

Semiconductor device manufacturing: process

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

Having insulated gate

438303, 438593, H01L 21336, H01L 213205

Patent

active

058858776

ABSTRACT:
A composite gate electrode layer incorporates a diffusion-retarding barrier layer disposed at the bottom of the gate electrode layer to reduce the amount of dopant which diffuses into the gate dielectric layer from the gate electrode layer. A lower nitrogen-containing gate electrode layer provides a diffusion-retarding barrier layer against dopant diffusion into the gate dielectric layer disposed therebelow, and an upper gate electrode layer is formed upon the lower layer and is doped to form a highly conductive layer. Together the first and second gate electrode layers form a composite gate electrode layer which incorporates a diffusion-retarding barrier layer adjacent to the underlying gate dielectric layer. The barrier layer may be formed by annealing a first polysilicon layer in a nitrogen-containing ambient, such as N.sub.2, NO, N.sub.2 O, and NH.sub.3, by implanting a nitrogen-containing material, such as elemental or molecular nitrogen, into a first polysilicon layer, and by in-situ depositing a nitrogen-doped first polysilicon layer. Diffusion of dopants into the gate dielectric layer may be retarded, as most dopant atoms are prevented from diffusing from the composite gate electrode layer at all. In addition, the nitrogen concentration within the gate dielectric layer, particularly at or near the substrate interface, may be maintained at lower concentrations than otherwise necessary to prevent dopant diffusion into the underlying substrate. The present invention is particularly well suited to thin gate dielectrics, such as a those having a thickness less than approximately 60 .ANG. when using a p-type dopant, such as boron.

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