Method to form uniform silicide features

Details Method to form uniform silicide features Method to form uniform silicide features

1999-10-25

2001-08-28

Tsai, Jey (Department: 2812)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S651000, C438S682000

Reexamination Certificate

active

06281117

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of forming uniform ultrathin silicide features in the fabrication of integrated circuits.
(2) Description of the Prior Art
In the fabrication of integrated circuits, the fabrication of ultrathin uniform silicide layers on sub 0.1 micron features is expected to be extremely difficult using the standard salicide (self-aligned silicide) process. A key problem is the interfacial non-uniformity as the silicide thickness is scaled down from about 1000 Angstroms to about 300 Angstroms. This non-uniformity issue of. ultrathin silicide films is mainly related to the statistical nature of the nucleation events required to form the resulting low-resistivity phase, as well as the non-uniformity of the existing rapid thermal annealing (RTA) process.
U. S. Pat. No. 5,712,191 to Nakajima et al teaches spin coating a nickel acetate solution onto a silicon layer and heat treating at 300-500° C. to form nickel suicide. A laser light is then irradiated to promote crystal growth in the area of the nickel silicide. However, laser irradiation or modification may not allow features smaller than submicron scale to be fabricated. Laser irradiation only allows a single localized modification at any one time. Additionally, laser irradiation has been observed experimentally to induce cracks and film peelings due to the large thermal shock induced in the localized nickel oxide regions at any one time within an extremely short time period. U.S. Pat. No. 5,510,295 to Cabral, Jr. et al teaches depositing a cobalt layer over silicon, annealing the cobalt layer at 900-1000° C. in a N
2
ambient, then depositing a titanium layer thereover and annealing to form titanium silicide. U.S. Pat. No. 4,908,334 to Zuhr et al forms a silicide film by ion beam deposition of metal onto silicon at 400-600° C. U.S. Pat. No. 5,728,625 to Tung discloses growing cobalt silicide on silicon in ultra-high vacuum and growing cobalt on silicon and then annealing at 450-800° C. to form cobalt silicide. U.S. Pat. No. 5,702,972 to Tsai et al teaches depositing titanium onto silicide to form titanium silicide and then annealing to change the titanium silicide from phase C49 to phase C54. U.S. Pat. No. 4,957,777 to Ilderem et al teaches depositing titanium silicide over polysilicon using silane.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide an effective and very manufacturable method of fabricating a uniform silicide film in the fabrication of an integrated circuit.
A further object of the invention is to provide a method of fabricating uniform ultrathin silicide features in the fabrication of an integrated circuit.
Yet another object is to provide a method of forming uniform silicide features having a spatial width of 0.1 microns and below.
Yet another object is to provide a method of localized and uniform formation of silicide.
Yet another object of the invention is to provide a method for uniform formation of silicide utilizing a cost-effective precursor for silicide formation.
A still further object of the invention is to provide a method for uniform formation of silicide wherein oxidation of a metallic oxide is avoided.
In accordance with the objects of the invention a method for forming uniform ultrathin silicide features in the fabrication of an integrated circuit is achieved. A metal layer is deposited over the surface of a silicon semiconductor substrate. An array of heated metallic tips contact the metal layer whereby the metal layer is transformed to a metal silicide where it is contacted by the metallic tips and wherein the metal layer not contacted by the metallic tips is unreacted. The unreacted metal layer is removed leaving the metal silicide as uniform ultrathin silicide features.
Also, in accordance with the objects of the invention, a metal acetate layer is spin-coated over the surface of a silicon semiconductor substrate. An array of heated metallic tips contacts the metal acetate layer whereby the metal acetate layer is transformed to a metal silicide where the metallic tips contact the metal acetate layer and wherein the metal acetate layer not contacted by the metallic tips is unreacted. The unreacted metal acetate layer is removed leaving the metal silicide as the uniform ultrathin silicide features.
Also, in accordance with the objects of the invention, a metal acetate layer is spin-coated over the surface of a silicon semiconductor substrate. An array of heated metallic tips contacts the metal acetate layer on polysilicon gates and diffusion regions whereby the metal acetate layer is transformed to a metal silicide where the metallic tips contact the metal acetate layer and wherein the metal acetate layer not contacted by the metallic tips is unreacted. The heating is performed in a H
2
or N
2
ambient under high vacuum to prevent oxidation of the metal surfaces. The unreacted metal acetate layer is removed leaving the metal silicide as the uniform ultrathin silicide features.


REFERENCES:
patent: 4908334 (1990-03-01), Zuhr et al.
patent: 4957777 (1990-09-01), Ilderem et al.
patent: 5075243 (1991-12-01), Nieh et al.
patent: 5510295 (1996-04-01), Cabral, Jr. et al.
patent: 5702972 (1997-12-01), Tsai et al.
patent: 5712191 (1998-01-01), Nakajima et al.
patent: 5728625 (1998-03-01), Tung
patent: 5918143 (1999-06-01), Beauvais et al.

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