Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-12-12
2003-09-09
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C438S692000, C438S693000, C451S037000
Reexamination Certificate
active
06616510
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application Ser. No. 89125183, filed Nov. 28, 2000.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a chemical-mechanical polishing method. More particularly, the present invention relates to a chemical-mechanical polishing method for polishing a copper layer.
2. Description of Related Art
Chemical mechanical polishing is one of the global planarization methods known and adopted in an ultra-large scale integration (ULSI) integrated circuit fabrication. The method is a planarization technique based on a mechanical polishing theory using an abrasive means. The abrasive means is then supplied with an appropriate reagent to planarize by polishing a non-planar surface profile of the wafer.
In chemical-mechanical polishing, the reagent usually refers to a slurry, which is mainly a colloidal solution of silica or dispersed alumina solution. The hard silica or alumina particles inside the slurry provide the necessary abrasion for polishing a silicon chip.
FIGS. 1A and 1B
are schematic cross-sectional views showing the method of planarizing a copper layer by conventional chemical-mechanical polishing. As shown in
FIG. 1A
, a substrate
100
having a wide opening
102
a
and several densely distributed narrow openings
102
b
is provided. A copper layer
104
is formed to completely cover the substrate
100
and fill the wide opening
102
a
and the narrow openings
102
b
. Since the upper surface of the copper layer
104
is exposed to air, a copper oxide layer
106
is formed over the copper layer
104
.
During the method of forming a damascene structure, the copper oxide layer
106
as well as any excess portion of the copper layer
104
above the substrate
100
must be removed. However, as the copper oxide
106
has an unusual hardness, it would require a long polishing time to remove the copper oxide layer
106
if conventional slurry were used in the polishing method. This leads to a drop in productivity. To speed up the polishing rate, slurry
108
having a high concentration of suspended particles has been conventionally used to polish the copper oxide layer
106
and the copper layer
104
. The suspended particles made up about 5% concentration of the slurry
108
.
Since the copper oxide layer
106
and an excess portion of the copper layer
104
are simultaneously removed using the slurry
108
highly concentrated with the suspended particles, the wide opening
102
a
forms a dish surface as shown in FIG.
1
B. Such dishing problem also occurs in the narrow opening
102
b
. In addition, erosion of the dielectric layer in the substrate
100
occurs in a region densely distributed with narrow openings
102
b
, leading to other problems.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a chemical-mechanical polishing method for copper to prevent dishing problem due to the use of an aqueous solution containing a high concentration of polishing particles, while an erosion of a substrate in a densely distributed copper wire region is avoided.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a chemical-mechanical polishing method for copper. First, an aqueous solution having a high concentration of polishing particles/chelating agent is used to polish away a copper oxide layer naturally formed at the upper surface of a copper layer. A polishing slurry having either a low concentration of polishing particles/chelating agent or free of polishing-particle/chelating agent is then used to continue the polishing of the copper layer.
This invention also provides an alternative chemical-mechanical polishing method for copper. First, the polishing slurry and the aqueous solution having a high concentration of polishing particles/chelating agent are mixed in situ to remove the copper oxide layer at the top surface of the copper layer. After the copper oxide is removed, the polishing slurry having a low concentration of the polishing particles/chelating agent or free of the polishing-particles/chelating agent is used in the polishing step to polish the copper layer.
One major aspect of this invention is an initial increase in the polishing rate of the copper oxide layer, while the dishing of the copper layer and the erosion of the substrate surface that occurred are minimized.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5225034 (1993-07-01), Yu et al.
patent: 5354490 (1994-10-01), Yu et al.
patent: 5840629 (1998-11-01), Carpio
patent: 6083840 (2000-07-01), Mravic et al.
patent: 6242351 (2001-06-01), Li et al.
patent: 6355075 (2002-03-01), Ina et al.
patent: 6375693 (2002-04-01), Cote et al.
Hsu Chia-Lin
Tsai Teng-Chun
Wei Yung-Tsung
Yang Ming-Sheng
Hail III Joseph J.
J. C. Patents
Thomas David B.
United Microelectronics Corp.
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