Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-06-08
2004-02-03
Coleman, W. David (Department: 2823)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S655000
Reexamination Certificate
active
06686274
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor device and its production process, particularly to a semiconductor device having a cobalt silicide film and its production process.
BACKGROUND ART
With the recent trend toward higher integration and miniaturization of the semiconductor devices, reduction of contact resistance at the joint of metal wiring and silicon substrate has become essential for high-speed operation. Regarding the techniques for reducing contact resistance, for instance JP-A-08-78357 suggests to form a cobalt silicide film on the diffusion layer (source/drain) or polycrystalline silicon electrodes on a silicon substrate.
DISCLOSURE OF THE INVENTION
However, when the diffusion layer is made shallow and the cobalt silicide film is thinned with miniaturization of the semiconductor devices, there arises the new problem that the cobalt silicide coating, which was film-like when formed, is coagulated by a high-temperature heat treatment in, for instance, the capacitor forming step and takes a partially insular configuration, causing a rise of resistance.
The object of the present invention is to solve the above problem and provide a semiconductor device having a cobalt silicide film which is proof against coagulation and remains low in resistance even if reduced in thickness, and a process for producing such a semiconductor device.
Rise of resistance of the cobalt silicide film is attributable to the insular coagulation of the cobalt silicide which occurs when the cobalt (Co) atoms composing the cobalt silicide film are diffused mostly along the crystal grain boundaries and recombined with silicon in a heat treatment at around 800° C. or above. Therefore, for preventing the rise of resistance due to the coagulation of cobalt silicide film, it is expedient to inhibit the diffusion of cobalt atoms in the cobalt silicide film.
On this concept, the present inventors disclosed that it is possible to inhibit the grain boundary diffusion of Co atoms in the cobalt silicide film when a specific element—an element having a smaller atomic radius than Co atom and specified by the fact that the inter-hetero-atomic energy between this element and Co element is not more than 20% smaller or greater than the inter-iso-atomic energy of Co element—is contained in said cobalt silicide film. That is, it was found the diffusion of Co atoms can be inhibited by containing nickel or iron element in the cobalt silicide film, and that in this case, the ratio of nickel or iron element to cobalt in said film should be preferably 0.05 to 50 atomic %, more preferably 0.05 to 18 atomic %.
It was also found that the use of multi-stage sputtering or an alloy target is suited for forming the said cobalt silicide film.
REFERENCES:
patent: 5897348 (1999-04-01), Wu
patent: 6294420 (2001-09-01), Tsu et al.
patent: 286062 (1991-01-01), None
Mo et al., “Formation and Properties of ternary silicide (CoNi)Si2 thin films”, IEEE, 1998 5thInternational Conference on Solid State and Integrated Circuit Technology, pp 271-274.*
Hong et al., Magneto-optic Kerr effect measurements on FeCoSi epitaxially stabilized on Si (111), Journal of Magetism and Magnetic Materials, vol. 165, pp 212-215.*
http://www.puretechinc.com and http://www.tosohsmd.com/tsprod/tspcobdt.htm, Material Data Sheet MDS 27.000 which includes the total metallics of the cobalt target., pp. 1-4 and pp. 1-3.*
Safety & Health Guide for the Microelectronics Industry, “Hazard Communication”, OSHA 3107, pp 9, 1998.
Ikeda Shuji
Iwasaki Tomio
Miura Hideo
Ohta Hiroyuki
Shimazu Hiromi
Antonelli Terry Stout & Kraus LLP
Coleman W. David
Renesas Technology Corporation
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