Method of fabricating a semiconductor device having a decreased concentration of phosphorus impurities in polysilicon
View Patent ↗In a method for manufacturing a semiconductor device having a laminated gate electrode, a phosphorus-doped polysilicon is formed on a gate oxide film. A high-melting metal or a compound of a high-melting metal and silicon is formed on the polysilicon. Phosphorus is doped into the polysilicon so that a concentration of the phosphorus in the polysilicon at an interface between the polysilicon and the gate oxide film is 2×10 20 (1/cm 3 ) or less. Then, thermal oxidation is carried out in a wet-hydrogen atmosphere containing water vapor.
1. A method for manufacturing a semiconductor device having a laminated gate electrode, comprising:
forming a phosphorus-doped polysilicon layer on a gate oxide film;
forming a high-melting metal or a compound of a high-melting metal and silicon on the polysilicon layer;
doping phosphorus into the polysilicon layer so that a concentration of the phosphorus in the polysilicon layer at an interface between the polysilicon layer and the gate oxide film is 2×10 20 (1/cm 3 ) or less; and
carrying out thermal oxidation of about 3 to 5 nm of the polysilicon layer without oxidizing the high-melting metal by treating in a wet-hydrogen atmosphere containing water vapor,
wherein the wet-hydrogen atmosphere contains 5 to 10% by volume of water vapor, and
wherein the thermal oxidation is carried out under conditions of a temperature of 800 to 900° C.
2. A method as claimed in claim 1 , wherein:
the wet-hydrogen atmosphere is a mixed atmosphere of H 2 O and H 2 .
3. A method as claimed in claim 1 , wherein:
a bird's beak is formed in a lower end of the polysilicon layer during the thermal oxidation in the wet-hydrogen atmosphere.
4. A method as claimed in claim 3 , wherein:
the bird's beak is formed so as to reduce a concentration of an electric field in the end of the polysilicon layer.
5. A method as claimed in claim 3 , wherein:
the phosphorus is doped so as to suppress a reduction in adhesion strength between the polysilicon layer and the gate oxide film caused by a stress of the bird's beak.
6. A method as claimed in claim 1 , wherein:
the concentration of the phosphorus is equal to 1×10 20 (1/cm 3 ).
7. A method as claimed in claim 1 , wherein:
the high-melting metal contains tungsten.
8. A method for manufacturing a semiconductor device having a laminated gate electrode, comprising:
forming a phosphorus-doped polysilicon layer on a gate oxide film;
forming a layer consisting of a high-melting metal on the polysilicon layer;
doping phosphorus into the polysilicon layer so that a concentration of the phosphorus in the polysilicon at an interface between the polysilicon layer and the gate oxide film is 2×10 20 (1/cm 3 ) or less; and
carrying out thermal oxidation of about 3 to 5 nm of the polysilicon layer without oxidizing the high-melting metal by treating in a wet-hydrogen atmosphere containing water vapor,
wherein the wet-hydrogen atmosphere contains 5 to 10% by volume of water vapor, and
wherein the thermal oxidation is carried out under conditions of a temperature of 800 to 900° C.
9. A method as claimed in claim 8 , wherein:
the wet-hydrogen atmosphere is a mixed atmosphere of H 2 O and H 2 .
10. A method as claimed in claim 8 , wherein:
a bird's beak is formed in a lower end of the polysilicon layer during the thermal oxidation in the wet-hydrogen atmosphere.
11. A method as claimed in claim 10 , wherein:
the bird's beak is formed so as to reduce a concentration of an electric field in the end of the polysilicon layer.
12. A method as claimed in claim 10 , wherein:
the phosphorus is doped so as to suppress a reduction in adhesion strength between the polysilicon layer and the gate oxide film caused by a stress of the bird's beak.
13. A method as claimed in claim 8 , wherein:
the concentration of the phosphorus is equal to 1×10 20 (1/cm 3 ).
14. A method as claimed in claim 8 , wherein:
the high-melting metal contains tungsten.