Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Contacting coating as it forms with solid member or material...
Reexamination Certificate
1998-11-24
2001-01-09
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Contacting coating as it forms with solid member or material...
C156S345420, C204S22400M, C204S22400M, C205S123000, C205S662000, C205S663000, C216S038000, C216S089000, C438S692000, C438S693000, C451S287000
Reexamination Certificate
active
06171467
ABSTRACT:
BACKGROUND OF THE INVENTION
In the process of semiconductor fabrication, layers of material are deposited onto substrate surfaces to form interconnects. Excess layer material is removed so that a further level of interconnects may be placed on top of the material. In this way, many layers can be created. In such structures, however, the topography of each layer must be precisely controlled so that successive layers and photolithographic processes can be accurately applied.
A process known as planarization is performed on the surface of each layer to prepare the surface of each layer for subsequent levels. Currently, surface planarization is achieved using mechanical polishing, mechanical machining, and chemo-mechanical polishing (CMP).
Mechanical polishing, for example, utilizes an abrasive material, typically in the form of a pad or slurry, which is moved repetitively over the surface to be polished. This causes small particles of the surface to be removed from the highest surface features while the lower features remain relatively untouched. In this way, a high degree of planarization is achieved.
Mechanical machining, on the other hand, involves the selective removal of material from specific sites by the application of a hard, abrasive machining piece, as used for instance in a lathe.
Both mechanical machining and mechanical polishing involve the mechanical breaking of bonds between the material being abraded and the surface itself. At present, the success of each of these methods is limited since there is no way of controlling the hardness of the surface being planarized. Rather, planarization is currently achieved by controlling the abrasive qualities of the polishing pad or slurry. This allows for only an indirect control of the planarization. As an example, Murarka et al. (U.S. Pat. No. 5,637,185) teaches measuring the electrical potential of the slurry in order to detect the end of the polishing process. Similarly, Tsal et al. (U.S. Pat. No. 5,575,706) teaches the utilization of electric fields to control the density of the abrasive slurry particles between the polishing pad and the Si-wafer. In addition, Kishii et al. (U.S. Pat. No. 5,562,529) teaches the use of electrochemistry to increase the density of ions in the slurry.
In yet another method of effecting planarization, chemo-mechanical polishing (CMP) uses chemical means to break chemical bonds at the surface during polishing or machining of a surface. Similar to the mechanical methods, CMP is currently limited since there is presently no way of controlling the hardness of the surface being planarized. Rather, CMP processes rely upon measuring the rate of surface layer formation, dissolution rates, and rate of chemical acceleration of polish rates in order to control surface planarization.
Surface Layer Formation During The Chemical Mechanical Polishing of Copper Thin Films
, J. M. Steigerwald et al., MRS Symp. Proc. 337, 133, 1994
; Mechanisms of Copper Removal During Chemical Mechanical Polishing
, J. M Steigerwald, J. Vac. Sci. Tech. B 13, 2215, 1995. In addition, other chemical techniques, as taught by Chen, (U.S. Pat. No. 5,637,031) control slurry density and wear rates using the addition of ions from a variety of elements.
Effect of Copper Ions in The Slurry on The Chemical
-
Mechanical Polish Rate of Titanium
, J. M Steigerwald et al.,
J. Electrochem. Soc.
141, 3512, 1994
; The Effect of The Polishing Pad Treatments on The Chemical
-
Mechanical Polishing of SiO
2
Films
, W. Li, D. W. Shin et al.,
Thin Solid Films
270, 601, 1995
; Electrochemical Potential Measurements During The Chemical
-
Mechanical Polishing of Copper Thin Films
, J. M. Steigerwald et al., J. Electrochem. Soc. 142, 2379, 1995.
Each of these CMP methods are limited in controlling planarization as they do not allow for the direct control of the surface wear properties of a surface being planarized.
SUMMARY OF THE INVENTION
It is an object of the invention to provide the ability to control or inhibit wear on the surface of a material such as a semiconductor.
Another object of the invention is to control the surface conditions of a material such as a semiconductor using electrochemistry.
Yet another object of the invention is to control the wear rate of the semiconductor material using electrochemistry.
The present invention accomplishes the above and other objects and advantages by providing a method of and apparatus for using electrochemistry to selectively grow or remove oxide coatings on metals or to create a capacitive double layer on non-metals in order to directly control the surface wear properties of a surface being planarized.
For many materials, the application of an electric potential to the surface when it is immersed in an electrolyte permits the controlled growth of a surface layer.
According to the present invention, the chemical and physical properties of a surface (e.g., hardness of a surface, oxide composition, etc.) and its rate of abrasive wear are directly linked so that the electrochemical growth of the oxide layer and the creation of a double capacitive layer provides a means to control the wear rate of the surface.
REFERENCES:
patent: 4839005 (1989-06-01), Katsumoto et al.
patent: 4956056 (1990-09-01), Zubatova et al.
patent: 5562529 (1996-10-01), Kishii et al.
patent: 5575706 (1996-11-01), Tsai et al.
patent: 5637031 (1997-06-01), Chen
patent: 5637185 (1997-06-01), Murake et al.
patent: 5639363 (1997-06-01), Ohmori et al.
F. A. Lowerheim,Electroplating, McGraw-Hill book Co., New York, pp. 137-139, 1978.
Surface Layer Formation During the Chemical Mechanical Polishing of Copper Thin Films, J.M. Steigerwald et al., 337 MRS Symp. Proc., 133-138 (1994).
Mechanisms of Copper Removal During Chemical Mechanical Polishing, J.M. Steigerwald, J. Vac. Sci. Tech. B 13, 2215-2218 (1995).
Effect of Copper Ions in the Slurry on the Chemical-Mechanical Polish Rate of Titanium, J.M. Steigerwald et al., 141 J. Electrochem. Soc., 3512-3516 (1994).
the Effect of the Polishing Pad Treatments on the Chemical-Mechanical Polishing of SiO2Films, W. Li, D.W. Shin et al., 270 Thin Solid Films, 601-606 (1995).
Mann Adrian B.
Searson Peter C.
Weihs Timothy P.
Dickstein , Shapiro, Morin & Oshinsky, LLP
Gorgos Kathryn
Leader William T.
The John Hopkins University
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