Abrading – Machine – Rotary tool
Reexamination Certificate
2000-08-30
2002-12-03
Eley, Timothy V. (Department: 3723)
Abrading
Machine
Rotary tool
C451S443000, C451S444000
Reexamination Certificate
active
06488573
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for polishing a material such as a semiconductor wafer, and a method of conditioning a surface state of a polishing pad used for polishing the material to be polished.
This specification is on the basis of Japanese Patent Applications (Japanese Unexamined Patent Application Publication No. 11-244120, No. 2000-004058, No. 2000-093834, and No. 2000-099648), and the disclosures of these Japanese Patent Applications are incorporated herein as a part of this specification by reference.
2. Description of the Related Art
A semiconductor wafer cut out of a silicon ingot, for example, from which a semiconductor device is formed, must be polished for realizing fine device structures, in such a manner that the wafer surface acquires a mirror surface free from defects and having high accuracy. A chemical mechanical polishing process (CMP process) capable of providing a high degree of planarity has been employed to polish surfaces of materials for which high polishing accuracy is required, including semiconductor wafers and wafers having devices formed thereon (hereinafter referred to simply as wafers).
The CMP process chemically and mechanically polishes and flattens surfaces of materials to be polished by employing, for example, an alkaline slurry using SiO
2
, a neutral slurry using CeO
2
or an acid slurry using Al
2
O
3
.
A known polishing apparatus
1
for polishing a wafer surface using a CMP process is schematically shown in
FIG. 23
which is an enlarged perspective view of principal part of the apparatus. As shown, a polishing pad
4
made of hard urethane, for example, is affixed to a disk-shaped platen
3
attached to a central shaft
2
, and a polishing head
5
holding a wafer W is from the central shaft
2
of the platen
3
. The polishing apparatus
1
polishes one surface of the wafer W by moving the polishing pad
4
and the wafer W relative to each other, while the polishing head
5
holds the wafer W in contact with the surface of the polishing pad
4
, and a slurry S is supplied between the wafer W and the polishing pad
4
.
Another known example of a apparatus for polishing a wafer surface with the CMP process is shown in FIG.
24
. In the following description, components in
FIG. 24
having essentially the same construction as those of the polishing apparatus
1
shown in
FIG. 23
are denoted by the same reference numerals. Referring to
FIG. 24
, a polishing apparatus
10
comprises a polishing head
5
holding a wafer W to be polished, and a polishing pad
4
affixed to an upper surface of a disk-shaped platen
3
. A plurality of polishing heads
5
are attached to the underside of a carousel
11
serving as a head driving mechanism. The polishing heads
5
are each supported by a spindle
16
to rotate on the polishing pad
4
in planetary motion. In this connection, the center of the platen
3
may be positioned offset from the center about which the polishing heads
5
revolve.
The platen
3
is horizontally disposed at the center of a base
12
and rotated about its own axis by a platen driving mechanism (not shown) provided within the base
12
. Posts
13
are vertically provided on both side portions of the base
12
, and an upper attachment plate
14
is disposed between the posts
13
to support a carousel driving mechanism
15
. The carousel driving mechanism
15
has the function of rotating the carousel
11
provided below the carousel driving mechanism
15
about its own axis.
Abutment portions
17
are disposed on the base
12
to project upward therefrom, and a gap adjusting mechanism
18
is provided at a top of each of the abutment portions
17
. Above the abutment portions
17
, engaging portions
19
are provided in one-to-one opposite relation. The engaging portions
19
are fixed to the upper attachment plate
14
and project downward from the upper attachment plate
14
. By regulating the gap adjusting mechanisms
18
and bringing the engaging portions
19
into contact with the abutment portions
17
, the distance between the polishing head
5
and the polishing pad
4
is set to an appropriate value. The wafers W are then polished by rotating the carousel
11
, the polishing heads
5
and the platen
3
while the wafers W held by the polishing heads
5
are kept in contact with the surface of the polishing pad
4
.
In any of such polishing apparatuses employing the CMP process, properties of the polishing pad and the slurry, polishing time, etc. are changed depending on the wafer polishing conditions, to adjust those parameters so that wafers are polished under the optimum conditions. Here, the term “properties of the slurry” means the material characteristics and size of abrasives forming the slurry, properties of a solution (such as pH and concentration of the solution) in which the abrasives are suspended, etc.
Furthermore, in the polishing apparatuses described above, a step of polishing a wafer surface is divided into several stages, for example a rough polishing stage for eliminating roughness on the wafer surface, a fine polishing stage for flattening the wafer surface, and a finish polishing stage for finishing the wafer surface to a mirror surface. In each stage, the wafer is polished under the respective optimum conditions.
In addition, thin films such as an oxide film and a metal film are formed on a wafer surface to form a circuit on the wafer. Therefore, the polishing conditions are also changed depending on material characteristics of the thin films formed on the wafer surface.
To enable a wafer to be polished successively under plural sets of different polishing conditions, there is known a polishing apparatus comprising a plurality of polishing stations, each of which includes a platen provided with a polishing pad and a driving device for driving the platen for rotation.
In such a polishing apparatus designed to move a wafer between the polishing stations operated under the different polishing conditions, if the slurry adhering to the wafer and the polishing head is not completely removed, the polishing station to which the wafer is transferred from a preceding one is contaminated with the slurry adhering to the wafer and the polishing head, because the properties of the slurry, i.e., the material characteristics and size of abrasives, properties of a solution, etc., differ between the polishing stations. Such mixing of slurries having different properties not only changes the polishing conditions in the polishing station of subsequent stage, but also may bring the slurry into a cohered or gelled state, thereby damaging the wafer surface, or may cause abnormal corrosion of the wafer.
For preventing such drawbacks, a cleaning device has been hitherto provided between the polishing stations to clean the wafer and the polishing head when the wafer and the polishing head are moved from one polishing station to another. However, the cleaning is usually carried out with the wafer kept supported by the polishing head, and the slurry having intruded into, e.g., between the wafer and the polishing head, cannot be completely removed. The remaining slurry is therefore caused to flow out and mix with a new slurry while the wafer is polished in the subsequent polishing station. As a result, the above-described drawbacks cannot be avoided using the present methods.
Further, in any of the polishing apparatuses described above, a number of fine holes, grooves or the like are formed in the polishing pad
4
to hold a slurry, and a wafer is polished with the slurry held on the surface of the polishing pad
4
with the aid of those holes, grooves or the like. However, repeating the wafer polishing gives rise to a problem of reducing the polishing accuracy and the polishing efficiency of wafers, because the slurry and other foreign matter (such as chips or debris particles of the polishing pad
4
and the wafer) adhere to the surface of the polishing pad
4
, and the polishing pad
4
is loaded with them. Also, there is a risk that
Harada Seiji
Hosoki Kanji
Kobayashi Tatsunori
Morita Eturo
Ogata Yasuyuki
Eley Timothy V.
Mitsubishi Materials Corporation
Nguyen Dung Van
LandOfFree
Polishing apparatus, polishing method and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polishing apparatus, polishing method and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polishing apparatus, polishing method and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2954061