Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1997-03-24
2001-03-20
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S628000, C438S629000, C438S644000, C438S652000, C438S654000, C438S626000, C438S633000, C438S689000, C438S690000, C438S691000, C438S692000, C438S693000, C451S057000, C451S059000, C451S037000, C451S041000
Reexamination Certificate
active
06204169
ABSTRACT:
CROSS-REFERENCE TO RELATEED APPLICATION
The present invention relates to the following commonly assigned, copending applications:
1) “Process for Polishing A Semiconductor Device Substrate,” by Kim et al., Ser. No. 08/780,113, filed Dec. 26,1996; and
2) “Process for Forming A Semiconductor Device,” by Nagabushnam et al., Ser. No. 08/783,975, filed Jan. 15, 1997; and
3) “Slurry for Chemically-Mechanically Polishing a Layer and Method of Use,” by Farkas et al., Ser. No. 08/684,782, filed Jul. 22, 1996.
FIELD OF THE INVENTION
The present invention relates generally to processes for polishing, and more particularly, to processes for polishing semiconductor device substrates.
BACKGROUND OF THE INVENTION
Chemical mechanical polishing (CMP) is presently used to polish a variety of materials found in semiconductor devices. Those materials include metals, such as tungsten, aluminum, and copper. Regardless of the type of material being polished, similar techniques are used. For example, a polishing system typically includes a polishing platen, on which is attached a polishing pad. While the platen is being rotated, a slurry is dispensed while a semiconductor wafer is pressed against the pad. A combination of the chemical reaction between the slurry and the layer being polished and the mechanical interaction between abrasives within the slurry and the layer being polished cause the planarization of the layer.
In some instances, two layers of different materials are deposited on each other in a semiconductor substrate, and both materials need to be polished, preferably in a continuous polishing operation to minimize cycle time. Commercially available polishing slurries do not provide ideal properties for polishing two dissimilar materials during the same polishing operation. For example, when polishing tungsten that is deposited on a titanium/titanium nitride layer, the polishing properties of tungsten and the titanium layer differ greatly. Titanium is a relatively difficult material to polish using a slurry composition optimized for tungsten polishing. Slurry formulations that successfully polish titanium typically do not polish tungsten as fast as other slurries. In most cases, optimizing the polishing conditions for one material, for example tungsten, leads to a degradation of the polishing characteristics of the other materials, such as titanium.
One known method for polishing a combination of tungsten and titanium is to use a relatively hard or abrasive polishing pad, such as a Suba 500 made by Rodel, Inc. of Delaware, with a slurry formulated for tungsten polishing (e.g. a ferric nitrate slurry). The polishing slurry does not significantly chemically react with the titanium, therefore use of a harder polishing pad is effective in mechanically removing titanium. However, problems with this method include 1) a lower tungsten polishing rate than if a softer pad is used; and 2) high oxide removal or erosion during polishing. Oxide removal or erosion is undesirable because it is generally non-uniform across the wafer, being faster in dense feature arrays and slower in peripheral areas. Use of a softer pad, such as a Politex pad, also by Rodel, Inc. of Wilmington Delaware, results in less removal of oxide, but inadequately removes titanium.
Another method for overcoming the problem of polishing tungsten and titanium is to polish the tungsten away, but leave the titanium layer in place. An interconnect metal layer(s), such as aluminum, is then deposited on the remaining titanium layer, and the aluminum and titanium layers are simultaneously patterned and etched. By etching the titanium layer with the aluminum, the need to polish away the titanium is eliminated. However, the titanium layer is nonetheless exposed to the polishing process during the polishing of tungsten. Consequently, the quality of titanium under the aluminum is poor and reliability of the resulting aluminum interconnects is degraded.
Accordingly, there is a need in the industry to establish a polishing process that can effectively polish two dissimilar conductive materials in a cost effective manner that is conducive to a manufacturing environment.
REFERENCES:
patent: 4448634 (1984-05-01), Lampert
patent: 5209816 (1993-05-01), Yu et al.
patent: 5340370 (1994-08-01), Cadien et al.
patent: 5352277 (1994-10-01), Sasaki
patent: 5516346 (1996-05-01), Cadien et al.
patent: 5676587 (1997-10-01), Landers et al.
patent: 5700383 (1997-12-01), Feller et al.
patent: 5756398 (1998-05-01), Wang et al.
patent: 5858813 (1999-01-01), Scherber et al.
patent: 9800501-0 (1998-03-01), None
patent: 1133218 (1989-05-01), None
patent: 2285518 (1990-11-01), None
Brown et al., “Electrochemical and in situ atomic force microscopy and scanning tunneling microscopy investigations of titanium in oxalic acid solution”; J. Vac. Technl. vol. 10 No. 5 Sep./Oct. 1992, pp. 3001-3006.
Bajaj Rajeev
Farkas Janos
Kim Sung C.
Saravia Jaime
Motorola Inc.
Niebling John F.
Zarneke David A.
LandOfFree
Processing for polishing dissimilar conductive layers in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Processing for polishing dissimilar conductive layers in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Processing for polishing dissimilar conductive layers in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438798