TECHNIQUE FOR REDUCING SILICIDE NON-UNIFORMITIES IN POLYSILICON GATE ELECTRODES BY AN INTERMEDIATE DIFFUSION BLOCKING LAYER
Threshold variability in advanced transistor elements, as well as increased leakage currents, may be reduced by incorporating a barrier material in a polysilicon gate electrode. The barrier material results in a well-controllable and well-defined metal silicide in the polysilicon gate electrode during the silicidation sequence and during the further processing by significantly reducing the diffusion of a metal species, such as nickel, into the vicinity of the gate dielectric material.
1 . A semiconductor device, comprising:
a silicon-containing gate electrode formed above at least a semiconductor region, said silicon-containing gate electrode comprising a first layer comprised of polysilicon and a second layer comprising a metal silicide material, said first and second layers being separated by a barrier material; and
an insulation layer positioned between said silicon-containing gate electrode and said semiconductor region.
2 . The semiconductor device of claim 1 , wherein said metal silicide comprises nickel.
3 . The semiconductor device of claim 1 , wherein said barrier material comprises a metal.
4 . The semiconductor device of claim 3 , wherein said barrier material comprises at least one of tungsten, titanium and cobalt.
5 . The semiconductor device of claim 1 , wherein said barrier material comprises a doped semiconductor material.
6 . The semiconductor device of claim 1 , wherein said gate electrode has a length of approximately 50 nm or less.
7 . The semiconductor device of claim 6 , wherein said length is approximately 30 nm or less.
8 . A method, comprising:
identifying a target depth of a metal silicide region to be formed in a silicon-containing gate electrode;
forming said silicon-containing gate electrode above a semiconductor region so as to include a barrier material at said target depth; and
forming said metal silicide region in said silicon-containing gate electrode above said barrier material.
9 . The method of claim 8 , wherein forming said silicon-containing gate electrode comprises forming a first silicon-containing electrode layer, forming said barrier material on said first silicon-containing electrode layer and forming a second silicon-containing electrode layer.
10 . The method of claim 9 , wherein forming said barrier material on said first silicon-containing layer comprises depositing a conductive material on said first silicon-containing electrode layer having a higher diffusion blocking effect with respect to a metal used for forming said metal silicide region.
11 . The method of claim 10 , wherein said conductive material comprises a metal.
12 . The method of claim 11 , wherein said metal comprises at least one of tungsten and titanium.
13 . The method of claim 9 , wherein forming said barrier material on said first silicon-containing layer comprises incorporating a barrier species through a surface of said first silicon-containing layer.
14 . The method of claim 13 , wherein said barrier species is incorporated by performing a plasma treatment.
15 . The method of claim 8 , wherein forming said silicon-containing gate electrode comprises forming a silicon-containing layer and incorporating a barrier species by performing an ion implantation process so as to form said barrier material.
16 . The method of claim 8 , wherein said metal silicide region is formed by using nickel.
17 . A method, comprising:
forming a layer stack above at least a semiconductor region, said layer stack comprising a first silicon-containing layer, a second silicon-containing layer formed above said first silicon-containing layer and a barrier layer positioned between said first and second silicon-containing layers;
forming a gate electrode from said layer stack; and
forming a metal silicide in said gate electrode.
18 . The method of claim 17 , wherein forming said layer stack comprises depositing said barrier layer on said first silicon-containing layer and depositing said second silicon-containing layer on said barrier layer.
19 . The method of claim 17 , wherein said metal silicide is formed on the basis of nickel.
20 . The method of claim 17 , wherein said barrier layer is provided as a metal-containing material.