Abrading – Precision device or process - or with condition responsive... – With indicating
Reexamination Certificate
2001-06-29
2003-09-30
Morgan, Eileen P. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
With indicating
C451S010000, C451S011000, C451S041000, C451S307000
Reexamination Certificate
active
06626736
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a rotary-type polishing apparatus which allows a polishing pad to be automatically replaced without stopping rotary or circulatory motion of a polishing table.
2. Description of the Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of processes available for forming such interconnections is photolithography. Though a photolithographic process can form interconnections that are at most 0.5 &mgr;m wide, it requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because depth of focus of an optical system is relatively small.
It is therefore necessary to make surfaces of semiconductor wafers flat for photolithography. One customary way of flattening surfaces of semiconductor wafers is to polish them with a polishing apparatus, and such a process is called Chemical Mechanical Polishing (CMP) in which semiconductor wafers are chemically and mechanically polished while supplying a polishing liquid comprising abrasive grains and chemical solution such as alkaline solution.
In a manufacturing process of a semiconductor device, a thin film is formed on a semiconductor device, and then micromachining processes, such as patterning or forming holes, are performed thereon. Thereafter, the above processes are repeated to form thin films on the semiconductor device. Recently, semiconductor devices have become more integrated, and structure of semiconductor elements has become more complicated. In addition, the number of layers in multilayer interconnections used for a logical system has been increased. Therefore, irregularities on a surface of a semiconductor device are increased, so that step height on the surface of the semiconductor device becomes larger.
When irregularities of a surface of a semiconductor device are increased, the following problems arise. Thickness of a film formed in a portion having a step is relatively small. An open circuit is caused by disconnection of interconnections, or a short circuit is caused by insufficient insulation between layers. As a result, good products cannot be obtained, and yield is lowered. Further, even if a semiconductor device initially works normally, reliability of the semiconductor device is lowered after a long-term use.
Thus, during a manufacturing process of a semiconductor device, it is increasingly important to planarize a surface of the semiconductor device. The most important one of planarizing technologies is chemical mechanical polishing (CMP). During chemical mechanical polishing, a polishing apparatus is employed. While a polishing liquid containing abrasive particles such as silica (SiO
2
) therein is supplied onto a polishing surface such as a polishing pad, a substrate such a semiconductor wafer is brought into sliding contact with the polishing surface, so that the substrate is polished.
FIGS. 16 and 17
of the accompanying drawings show a conventional polishing apparatus for carrying out a CMP process. As shown in
FIGS. 16 and 17
, the conventional polishing apparatus comprises a polishing table
102
having a polishing pad (polishing cloth)
100
attached to its upper surface, a motor
104
for rotating the polishing table
102
, and a vertically movable top ring
106
for holding a substrate W such as a semiconductor wafer with its surface, to be polished, facing the polishing pad
100
. While the polishing table
102
and the top ring
106
are being rotated independently about their own axes, the substrate W is pressed against the polishing pad
100
under a constant pressure by the top ring
106
, and a polishing liquid is supplied from a nozzle (not shown) to the polishing pad
100
, thereby polishing the surface of the substrate W to a flat mirror finish. The polishing liquid comprises fine abrasive particles of silica or the like suspended in an alkaline solution or the like. The substrate W is polished by a chemical mechanical polishing action which is a combination of a chemical polishing action performed by the alkaline solution and a mechanical polishing action performed by the abrasive particles of silica or the like.
The polishing pad
100
is usually regenerated by a dresser which comprises a nylon brush, diamond particles, or the like. When the polishing pad
100
is worn to an extent that its polishing capability can no longer be restored by the dresser, the polishing pad
100
is replaced with a new one.
The polishing pad
100
is generally attached to an upper surface of the polishing table
102
by an adhesive tape. For replacing the polishing pad
100
with a new one, it is necessary to temporarily stop a CMP process, and a skilled operator is required to peel off the polishing pad
100
and attach a new polishing pad
100
to the polishing table
102
.
FIG. 18
of the accompanying drawings shows another conventional polishing apparatus for eliminating the above drawbacks. The polishing apparatus shown in
FIG. 18
has a polishing pad
100
attached to a polishing table
102
under vacuum developed by a vacuum attraction section
108
provided in the polishing table
102
. Since the polishing pad
100
is removed from the polishing table
102
by releasing the vacuum, the polishing pad
100
can easily and quickly be replaced with a new one. However, replacing the polishing pad
100
requires temporarily stopping a CMP process because the polishing pad cannot be replaced while the polishing pad table
102
is rotating.
Still another conventional polishing apparatus is shown in
FIG. 19
of the accompanying drawings. In
FIG. 19
, a polishing table
110
is fixed in position, and a pair of rolls
112
,
114
are rotatably disposed one on each side of the polishing table
110
. An elongate polishing pad
116
wound onto the roll
112
is continuously fed at a constant speed along an upper surface of the polishing table
110
, and beneath a substrate W, toward the other roll
114
onto which the polishing pad
116
is wound. The substrate W is polished by the elongate polishing pad
116
as the polishing pad travels over the polishing table
110
in one direction. Principles of the polishing apparatus shown in
FIG. 19
are not applicable to a rotary-type polishing apparatus in which a polishing table makes rotary or circulatory motion.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a rotary-type polishing apparatus which has a polishing table that makes rotary or circulatory motion, and which allows a polishing pad to be automatically replaced without stopping a CMP process.
Another object of the present invention is to provide a polishing apparatus which has a polishing table that makes predetermined motion, and which allows a polishing pad to be automatically replaced without stopping a CMP process.
According to a first aspect of the present invention, there is provded a polishing apparatus comprising: a polishing table for making rotary or circulatory motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a pair of rolls rotatable about their own axes and movable in unison with the polishing table; and a polishing pad which is wound on one of the rolls and supplied over an upper surface of the polishing table toward the other of the rolls.
Even when the polishing table is in rotary or circulatory motion, the polishing pad can be transported from one of the rolls over the upper surface of the polishing table toward the other roll by a distance corresponding to a region of the polishing pad that has been used to polish workpieces. A used region of the polishing pad can thus automatically be replaced with a new region thereof.
In a preferred aspect of the present invention, the pol
Kimura Norio
Tsujimura Manabu
Ebara Corporation
Morgan Eileen P.
Wenderoth , Lind & Ponack, L.L.P.
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