Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-02-03
2002-08-20
Christianson, Keith (Department: 2813)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S663000, C438S680000, C438S685000, C427S255391
Reexamination Certificate
active
06436820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for producing thick titanium nitride film for plug-fill type applications. More specifically, the present invention relates to a method for producing TiN depositions having a thickness of about 400 Å or more (and typically 1000 Å or more), where the deposited material maintains low resistivity, low stress, and low chlorine content.
2. Brief Description of Background Art
Titanium nitride layers have been used in semiconductor device structures as barrier layers for preventing the interdiffusion of adjacent layers of materials such as aluminum and silicon, for example. However, the resistivity of a conventional titanium nitride film is frequently greater than 150 &mgr;&OHgr;cm, which detracts from the overall conductivity of the layered conductive structure to which it contributes. Further, high residual film stress can cause a titanium nitride film to peel off from the surface of an underlying layer (typically silicon oxide, titanium, or titanium silicide). In the alternative, if the film does not peel off, the film stress can cause feature distortion on the substrate (typically a silicon wafer) surface or even deformation of a thin wafer.
U.S. Pat. No. 5,610,106 to Foster et al., issued on Mar. 11, 1997 and assigned to Sony Corporation, describes TiN films as typically being deposited over a substrate by reactively sputtering titanium in a nitrogen-argon mixture, or by evaporating titanium in a nitrogen atmosphere. The disclosure adds that sputtered films provide poor conformity while chemical vapor deposited films require the use of high temperatures which make the process impractical for use in multi-level metalization schemes. Foster suggests a plasma enhanced CVD process to overcome these deficiencies. The method disclosed by Foster et al. is for the deposition of films having a thickness ranging from about 200 Å to about 500 Å, and the deposition is carried out at a temperature of about 400 ° C. to about 500 ° C. and a process chamber pressure of about 5 Torr.
U.S. Pat. Nos. 5,279,857 and 5,308,655 to Eichman et al., issued on Jan. 18, 1994 and May 3, 1994, respectively, describe a method for reducing the chlorine content of TiN films by first forming a TiN film on a wafer, and then reacting the residual chlorine in the film with ammonia at a temperature of 600-700° C. and pressure of 115-300 mTorr to remove the residual chlorine. The theory presented is that low pressure chemical vapor deposition titanium nitride films deposited from TiCl
4
and NH
3
gas incorporates a large amount of chlorine in the film. This chlorine is said to be found to be concentrated at the grain boundaries and film interfaces. The Eichman et al. patents refer to “thin films” of titanium nitride, but are silent as to the thickness of such a film.
U.S. Pat. No. 4,570,328 to Price et al., issued on Feb. 18, 1986 describes a method of producing titanium nitride MOS device gate electrodes. In particular, the gate electrode and interconnect are fabricated from low pressure chemical vapor deposited titanium nitride. The film thicknesses described are between about 100 nm and 200 nm (1,000 Å and 2,000 Å). The films are deposited from a feed gas of titanium tetrachloride, ammonia and hydrogen, at temperatures between about 680° C. and 800° C. and at a pressure ranging between 100 mTorr and 300 mTorr. The films are subsequently annealed in a nitrogen atmosphere at a temperature between 900° C. and 1,000° C., to reduce resistivity. Price et al. explains that at film formation temperatures greater than approximately 800° C., severe gas phase depletion occurs resulting in a loss of control of the film thickness' uniformity. At temperatures less than approximately 680° C., TiNCl
x
is grown instead of the desired TiN, and annealing of the film causes ‘cracks’ and ‘blisters’ that form when chlorine atoms escape the film.
As indicated by the references cited above, there is a need for a method for removing halogen-comprising (typically chlorine-comprising) residues from TiN films deposited using CVD. The residual halogen content increases resistivity and can cause damage to the film structure during subsequent processing at elevated temperatures. There is a particular need for a method of removing halogen-comprising residues from a thick TiN film, where the method has minimal effect on the final film structure while providing a film having a low resistivity, preferably less than about 175 &mgr;&OHgr;cm.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for producing a substantially uniform TiN film of a thickness of 400 Å or higher, preferably 1,000 Å or higher, where the resistivity of the deposited film is less than about 175 &mgr;&OHgr;cm. The method comprises forming a layer of TiN having a thickness of 400 Å or less by chemical vapor deposition using a halogen-comprising precursor and a nitrogen-comprising precursor; a halogen residue removal step which includes annealing the layer of TiN film in the presence of at least one gas which reacts with the halogen to produce a reaction product which is volatile under the precessing conditions; and, repeating the film forming and halogen residue removal steps multiple times, to form a multi-layer TiN film having the desired thickness. Preferably the halogen residue removal step is carried out in the chemical vapor deposition chamber used for deposition of the TiN film, so that a series of TiN deposition and halogen removal steps can be carried out rapidly. The use of a series of deposition-anneal steps provides for a more complete removal of halogen residues from the thick titanium nitride film while permitting a rapid film deposition rate. Preferably, the residual halogen content in the TiN film produced by the method of the invention is less than about 1.5 atomic percent, and the film is free from blisters and cracks.
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K. Ohto et al., “A Novel TiN/Ti Contact Plug Technology for Gigabit Scale DRAM Using T-PECVD and TiN-LPCVD,” IEEE 1996 International Electronic Devices Meeting, pp. 361-364 (1996).*
Translation of Japanese Published Patent Application 8-279558 A, Kenshi Kaizuka and Hiroshi Shinriki, “Semiconductor Device Manufacturing Method,” Japanese Patent Office, Oct. 1996.*
J. Hu et al., “Electrical properties of Ti/TiN films prepared by chemical vapor deposition and their applications in submicron structures as contact and barrier materials”,Thin Solid Films, 308-309, pp. 589-593 (1997).
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Chen Fufa
Demayo Yehuda
Hu Jianhua
Lin Yin
Xi Ming
Applied Materials Inc
Bean Kathi
Christianson Keith
Church Shirley L.
Smoot Stephen W.
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