Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-07-13
2001-10-23
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S649000, C438S655000
Reexamination Certificate
active
06306766
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to formation of crystalline phase materials in semiconductor wafer processing and more particularly to formation of refractory metal silicides and crystalline phase transformation thereof as well as to conductive lines incorporating such materials.
BACKGROUND OF THE INVENTION
Silicides, such as titanium silicide and tungsten silicide, are commonly utilized electrically conductive materials in semiconductor wafer integrated circuitry fabrication. Such materials are utilized, for example, as capping layers over underlying conductively doped polysilicon material to form electrically conductive lines or interconnects. Such silicide materials are also utilized at contact bases intermediate an underlying silicon substrate and overlying conductive polysilicon contact plugging material. Silicides can be provided by chemical vapor deposition, or by deposition of elemental titanium or tungsten over an underlying silicon surface. Subsequent high temperature annealing causes a chemical reaction of the tungsten or titanium with the underlying silicon to form the silicide compound.
Titanium silicide (TiSi
2
) occurs in two different crystalline structures or phases referred to as the C49 and C54 phase. The C49 structure is base-centered orthorhombic, while the C54 is face orthorhombic. The C54 phase occurs in the binary-phase diagram while the C49 phase does not. The C49 phase is therefor considered to be metastable. The C54 phase is a densely packed structure having 7% less volume than the C49 phase. The C54 phase also has lower resistivity (higher conductivity) than the C49 phase.
The C49 phase forms at lower temperatures during a typical refractory metal silicide formation anneal (i.e. at from 500° C.-600° C.) and transforms to the C54 phase at higher elevated temperatures (i.e., greater than or equal to about 650° C.). The formation of the higher resistive C49 phase has been observed to be almost inevitable due to the lower activation energies associated with it (2.1-2.4 eV) which arises from the lower surface energy of the C49 phase compared to that of the more thermodynamically stable C54 phase. Hence, the desired C54 phase can be obtained by transforming the C49 phase at elevated temperatures.
Due at least in part to its greater conductivity, the C54 phase is much more desirable as contact or conductive line cladding material. Continued semiconductive wafer fabrication has achieved denser and smaller circuitry making silicide layers thinner and narrower in each subsequent processing generation. As the silicide layers become thinner and narrower, the ratio of surface area to volume of material to be transformed from the C49 to the C54 phase increases. This requires ever increasing activation energies to cause the desired transformation, which translates to higher anneal temperatures to effect the desired phase transformation. In some instances, the temperature must be at least equal to or greater than 800° C. Unfortunately, heating a silicide layer to a higher temperature can result in undesired precipitation and agglomeration of silicon in such layer, and also adversely exposes the wafer being processed to undesired and ever increasing thermal exposure. The processing window for achieving or obtaining low resistance silicide phases for smaller line widths and contacts continues to be reduced, making fabrication difficult.
It would be desirable to develop methods which facilitate the C49 to C54 phase transformation in titanium silicide films. It would also be desirable to develop methods which initially, or which appear to initially, form C54 phase titanium silicide during deposition to minimize or eliminate subsequent dedicated or separate anneal processing in separate equipment. Although the invention was developed with an eye towards overcoming this specific problem, the artisan will appreciate applicability of the invention in other areas, with the invention only being limited by the accompanying claims appropriately interpreted in accordance with the Doctrine of Equivalents.
SUMMARY
In but one aspect, the invention provides a method of forming a crystalline phase material capable of first and second crystalline phases, where said first and second phases are of different densities. In one implementation, a method is performed by providing a stress-inducing material on a substrate and, after providing the stress-inducing material on the substrate, depositing a crystalline phase material over the substrate in a substantially continuous manner and changing deposition temperature at least once during the depositing, and forming the second crystalline phase of the crystalline phase material. Where the second density is greater than the first density, the stress inducing material is chosen to impart compressive stress during the temperature changing. Where the second density is less than the first density, the stress inducing material is chosen to impart tensile stress during the temperature changing.
In accordance another aspect, a method is performed by providing a stress-inducing material on a substrate and, after providing the stress-inducing material on the substrate, forming a crystalline phase material over the substrate in at least two discrete crystalline phase material depositions, a later of the depositions being conducted at a different temperature from an earlier of the depositions and forming the second crystalline phase of the crystalline phase material.
In another implementation, a method is performed by forming a refractory metal silicide layer of C54 crystalline phase on a substrate, and depositing refractory metal silicide material onto the C54 refractory metal silicide layer with the C54 crystalline phase being induced into the refractory metal silicide material from the C
54
crystalline phase in the refractory metal silicide layer.
In another aspect, the invention provides a method of forming a crystalline phase material capable of first and second crystalline phases, where said second phase is less dense than said first phase. In one implementation, a method is performed by providing a stress-inducing material on a substrate and, after providing the stress-inducing material on the substrate, depositing a crystalline phase material over the substrate in a substantially continuous manner and changing deposition temperature at least once during the depositing, and forming the second crystalline phase of the crystalline phase material.
REFERENCES:
patent: 4568565 (1986-02-01), Gupta et al.
patent: 4971655 (1990-11-01), Stefano et al.
patent: 5240739 (1993-08-01), Doan et al.
patent: 5376405 (1994-12-01), Doan et al.
patent: 5593924 (1997-01-01), Apte et al.
patent: 5608266 (1997-03-01), Agnello et al.
patent: 5665646 (1997-09-01), Kitano
patent: 5828131 (1998-10-01), Cabral, Jr. et al.
patent: 5874351 (1999-02-01), Hu et al.
patent: 5997634 (1999-12-01), Sandhu et al.
patent: 6090708 (2000-07-01), Sandhu et al.
patent: 8-139056 (1996-05-01), None
Ilderem, V., et al., “Optimized Deposition Parameters For Low Pressure Chemical Vapor Deposited Titanium Silicide”,Massachusetts Institute of Technology, vol. 135, No. 10, pp. 2590-2596 (Feb. 1988).
Nagabushnam, R.V., et al., “Kinetics And Mechanism Of The C49 to C54 Titanium Disilicide Phase Transformation Formation In Nitrogen Ambient”, 5 pages (Nov. 1995).
Huang, et al. The Influence of Ge-Implantation on the Electrical Characteristics of the Ultra-Shallow . . . IEEE Electron Device Letters, vol. 17, No. 3, Mar. 1996, pp. 88-90.
Hill Chris
Sandhu Gurtej S.
Sharan Sujit
Micro)n Technology, Inc.
Picardat Kevin M.
Wells, St. John, Roberts Gregory & Matkin P.S.
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