Abrading – Accessory – Dressing
Reexamination Certificate
1999-04-19
2001-04-10
Scherbel, David A. (Department: 3723)
Abrading
Accessory
Dressing
Reexamination Certificate
active
06213856
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to chemical mechanical polishing (CMP), and more particularly, to a conditioner and a conditioning disk for conditioning a CMP pad, and a method of fabricating, reworking, and cleaning the conditioning disk.
2. Background of the Related Art
Highly integrated semiconductor devices require a sophisticated pattern formation technique, and use a multilayer structure for circuit distribution. This means that the surface structure of these semiconductor devices is more complicated, and step height differences between intermediary layers are more severe.
These step height differences cause many process failures in the semiconductor device fabrication process, for example, in the photolithography process for forming a photoresist pattern on a semiconductor wafer, which comprises the steps of coating the wafer with photoresist, aligning a mask having circuit patterns with the wafer having photoresist thereon, and performing an exposure process and a development process.
In the past, the formation method for precise patterns was easier, because the critical dimension (CD) of the pattern was relatively wide, and the semiconductor devices had fewer structural layers. However, the step height difference is increasing due to the finer patterns and multilayered structure of the modem devices. Therefore, it is more difficult to focus between the upper and the lower position of the step height during the exposure process, and it is also difficult to obtain more precise patterns.
Therefore, in order to reduce the step height difference, a planarization technique for the wafer has become important. A planarization technique such as SOG (Spin On Glass) film deposition has been introduced, or a partial planarization technique, such as etch back or reflow, etc., has been used, but many problems persist. Accordingly, a CMP (chemical mechanical polishing) technique for global planarization has been introduced, wherein the planarization is performed throughout the whole surface of the wafer.
The CMP technique planarizes the wafer surface through both chemical and mechanical reactions, whereby the protrusions existing on the surface of the thin film on the wafer chemically react with a slurry supplied to the wafer, with the surface of the wafer having the device pattern contacting a polishing pad surface. At the same time, the protrusions are planarized mechanically by rotation of a polishing table and the wafer.
Referring to
FIGS. 1 and 2
, the CMP apparatus
1
comprises a polishing table
10
having a polishing pad
12
made of polyurethane attached thereon, a wafer carrier
20
for fixing and rotating a wafer
16
, with the thin film pattern
18
on the wafer
16
contacting the polishing pad
12
, a slurry
14
supplied on the polishing pad
12
, and a conditioner
22
displaced on the opposite side of the wafer carrier
20
and having a conditioning disk
24
attached thereon for conditioning the polishing pad
12
.
In the CMP technique using the CMP apparatus
1
, removal rate and planarization uniformity are very important, and these are determined by process conditions of the CMP apparatus
1
, and the type of slurry
14
and polishing pad
12
used. In particular, the polishing pad
12
affects the removal rate, which should be properly maintained within a process specification by monitoring the surface state of the conditioning disk
24
of the conditioner
22
which conditions the polishing pad
12
, and replacing the conditioning disk
24
when necessary.
Referring to
FIG. 3
, the conditioning disk
24
has artificial diamonds
26
attached to its surface by a nickel thin film used as an adhesive film
25
, and the artificial diamond
26
abrades the surface of the polishing pad
12
which is made of polyurethane and has fine protrusions
27
.
While the CMP process is continuously being performed for the wafer
16
on the polishing pad
12
by the supplied slurry
14
, by-products
28
entrained in the slurry
14
are deposited between the protrusions
27
.
Therefore, the surface of the polishing pad
12
becomes slippery with repeated CMP processing, thereby abruptly decreasing the removal rate for subsequent wafers. In order to restore the required removal rate, and maintain the condition of the polishing pad
12
, a conditioning is performed to remove the by-products
28
. The conditioning is performed by first placing the conditioning disk
24
with the artificial diamond
26
into contact with the surface of the polishing pad
12
, and then, rotating the conditioning disk
24
at a certain speed so as to increase the roughness of the polishing pad
12
. Therefore, the film of each wafer planarized during the CMP process is within a certain specification.
The conditioning method for the polishing pad
12
is different for a metallic film CMP than for an oxide film CMP. In the case of metallic film CMP, the conditioner
22
conditions the surface of the polishing pad
12
after the CMP for a wafer is preformed. For the oxide film, the CMP process is carried out by simultaneously performing the conditioning of the polishing pad
12
by the conditioner
22
and the CMP for the wafer.
Referring to
FIGS. 4 and 5
, the conditioning disk
24
has artificial diamonds
26
of a certain size attached on its surface with a nickel thin film
25
functioning as the adhesive. With the continuously-carried out CMP, the by-product
28
including the slurry
14
also accumulates between the artificial diamonds
26
on the conditioning disk
24
as well as on the polishing pad
12
. The abrasion of the artificial diamonds
26
itself as well as the accumulation of the by-products
28
between the artificial diamonds
26
decreases the efficiency of the conditioning for the polishing pad
12
.
That is, the conditioning effect of the conditioning disk
24
on the polishing pad
12
changes according to the state of the artificial diamonds
26
on the conditioning disk
24
.
The size of the artificial diamonds
26
is approximately 68 &mgr;m, with approximately 30 to 40 &mgr;m protruding from the nickel thin film
25
. As a result, the conditioning disk
24
has a short life time, and frequent replacement of the conditioning disk
24
results in decreased productivity and deterioration of production yield due to increased process failures.
SUMMARY OF THE INVENTION
The present invention is directed to providing a conditioning disk for a chemical mechanical polishing (CMP) pad for efficiently conditioning the polishing pad, and a method of fabricating the conditioning disk.
Another object of the present invention is to provide a method of reworking the conditioning disk, and a method of cleaning the conditioning disk to reduce production costs and lengthen the life of the disk by reworking a used conditioning disk.
To achieve these and other advantages and in accordance with the purpose of the present invention as embodied and broadly described, the conditioning disk for a CMP pad is divided into regions according to a size difference of the abrasive grains formed on each region of the body surface of the conditioning disk.
The abrasive grains may be artificial diamonds, which are attached to the regions of the body surface of the conditioning disk depending upon their size, one region having artificial diamonds of size greater than 200 &mgr;m, and another region having artificial diamonds of size less than 200 &mgr;m. The regions on the body surface of the conditioning disk are preferably formed to be concentric rings forming an inner region and an outer region.
The conditioning disk may be ring-shaped with an opening of a certain area in the center. Preferably, the inner region has artificial diamonds having a size of 200 to 300 &mgr;m provided thereon, and the outer region has artificial diamonds having a size of 100 to 200 &mgr;m provided thereon.
In another embodiment, the conditioning disk has a cross-shaped portion having an opening in its center with a certain area, and a ring-shaped portion adjacent to outer ends
Cho Sung-Bum
Choi Baik-soon
Choi Kyue-sang
Kim Jin-Sung
Jones Volentine, L.L.C.
Nguyen George
Samsung Electronics Co,. Ltd.
Scherbel David A.
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