Semiconductor device manufacturing: process – Including control responsive to sensed condition – Optical characteristic sensed
Reexamination Certificate
1999-03-01
2001-02-27
Gulakowski, Randy (Department: 1746)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
Optical characteristic sensed
C438S016000, C438S692000, C451S006000, C216S084000
Reexamination Certificate
active
06194231
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to a method for monitoring a condition of a polishing pad used in a chemical-mechanical planarization (CMP) process to polish a semiconductor wafer so as to, for example, determine whether the polishing pad is suitable for polishing or should be changed.
BACKGROUND OF THE INVENTION
A chemical-mechanical planarization (CMP) procedure is widely used in a semiconductor manufacturing process for planarizing a wafer. The apparatus and the operating cycle for a CMP process is briefly described with reference to
FIG. 1
which is a schematic cross-sectional view of a conventional CMP apparatus. In the CMP apparatus, a platen
6
is rotatably mounted, and a polishing pad
4
is secured on and rotated with the platen
6
. The back surface of a wafer
8
to be polished is held by a carrier
7
and parallelly placed on the platen
6
so that the front surface of the wafer
8
is in contact with the polishing pad
4
. The carrier
7
also rotates during the CMP process in a direction the same as the platen
6
. During the CMP process, polishing slurry
9
is continuously provided onto the polishing pad
4
for facilitating to polish the wafer
8
. The slurry
9
is supplied through a pipeline
5
arranged above the platen
6
. After a CMP cycle in which a wafer or several wafers is or are simultaneously planarized is completed, the polishing pad
4
is subjected to a conditioning cycle to restore its proper function. Therefore, in brief, the purpose for polishing a wafer can be achieved by gradually removing bumps on the surface of the wafer via a chemical reaction conducted by the polishing slurry and a mechanical force applied to the wafer through the operations of the above devices.
The control of the CMP process for precisely planarizing a semiconductor wafer, however, is relatively complicated because of a great number of variations in the process. The condition of the polishing pad is one of the variations which are considered uneasy to be controlled. In other words, with the increasing abrasion in the CMP cycles and the conditioning cycles, the condition of the polishing pad is gradually deteriorated, and the pad should be changed when the pad surface is lowered to an unacceptable value. Therefore, it is important to monitor the condition of the polishing pad frequently.
Monitoring methods used in a CMP process is various. For example, Sandhu et al, U.S. Pat. No. 5,036,015, monitors a planar endpoint by measuring the current change in the driving motor of the carrier. Yu et al, U.S. Pat. Nos. 5,222,329 and 5,240,552, monitor an endpoint and thickness of films formed on a wafer by analyzing acoustical waves and reflected acoustical waves from the wafer. Yano et al, U.S. Pat. No. 5,483,568, monitors a polishing rate by detecting the intensity of the X-ray fluorescence resulting from an X-ray beam illuminating the polishing pad.
Meikle et al., U.S. Pat. Nos. 5,609,718, 5,655,951 and 5,801,066, disclose a method and an apparatus for measuring a change in the thickness of the polishing pad by using a laser beam detector. This method for monitoring the thickness change of the polishing pad is conducted by measuring the thickness change at a plurality of specified points after the pad is conditioned. In other words, the thickness of discontinuous points on the surface of the polishing pad is measured. As known to those skilled in the art, however, thickness measurement may be interfered by the polishing slurry so that there may be some irreliable data present. For such a sampling way, it is difficult to determine which data points are not reliable and should be ignored. On the other hand, the thickness measurement of the above method is conducted after the pad is conditioned and cannot be performed during the CMP cycle so that a thickness-measuring step is required in addition to the CMP cycle and the conditioning cycle, and the purpose for on-line monitoring of the polishing pad cannot be achieved.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for monitoring a condition of a polishing pad used in a CMP process, by which the time to change a polishing pad can be easily determined.
Another object of the present invention is to provide a method for monitoring a condition of a polishing pad used in a CMP process, by which an on-line monitoring of the condition of the polishing pad can be performed.
A further object of the present invention is to provide a method for monitoring a condition of a polishing pad used in a CMP process, in which a profile information rather than thickness data of separated points is used to determine the condition of the polishing pad so as to lower the probability of errors.
According to the present invention, a method for monitoring a polishing pad used for polishing a semiconductor wafer in a CMP cycle, includes steps of:
a) installing a linear multi-dimensional scanning device above the polishing pad in a radial direction without overlapping the semiconductor wafer, the linear multi-dimensional scanning device including a first section for scanning a first portion of the polishing pad which is in intermittent contact with and polishes the semiconductor wafer during the CMP cycle, and a second section for scanning a second portion of the polishing pad which is never in contact with the semiconductor wafer during the CMP cycle;
b) reading and comparing scanning data in both of the first and the second portions to realize a surface profile information of the polishing pad; and
c) determining a condition of the polishing pad according to the profile information of the polishing pad.
In the step a), while the pad surface in the first portion will be lowered after a period of polishing time, the pad surface in the second portion is not lowered.
The linear multi-dimensional scanning device can be a scanning head of a commercial reverse engineering 3D laser scanning system. If a relatively long scanning head is used, one scanning head is enough for serving as both of the first and the second sections. Alternatively, if the selected scanning head is relatively short, two scanning heads may be needed to serve as the first section and the second section, respectively.
Preferably, the step b) is conducted during the CMP cycle. However, the step b) can also be conducted before or after the CMP cycle, or after a conditioning cycle.
In accordance with an aspect of the present invention, the scanning data are relative levels along a radius on a surface of the polishing pad in contact with the semiconductor wafer. Preferably, a step of ignoring any data point of the relative levels which are beyond a preset range is performed before the step c) in order to lower the probability of errors. Meanwhile, according to another aspect of the present invention, the condition of the polishing pad is determined to be deteriorated when a maximal difference among the relative levels irrespective of the ignored data point exceeds a preset value.
REFERENCES:
patent: 5036015 (1991-07-01), Sandhue et al.
patent: 5222329 (1993-06-01), Yu
patent: 5240552 (1993-08-01), Yu et al.
patent: 5483568 (1996-01-01), Yano et al.
patent: 5609718 (1997-03-01), Meikle et al.
patent: 5655951 (1997-08-01), Meikle et al.
patent: 5664987 (1997-09-01), Renteln
patent: 5708506 (1998-01-01), Birang
patent: 5801066 (1998-09-01), Meikle et al.
patent: 5835225 (1998-11-01), Thakur
patent: 5951370 (1999-09-01), Cesna
Ho-Cheng Hong
Liu Kuo-Hsing
Gulakowski Randy
Laff Charles A.
Laff, Whitesel & Saret, Ltd.
National Tsing Hua University
Smetana Jiri F.
LandOfFree
Method for monitoring polishing pad used in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for monitoring polishing pad used in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for monitoring polishing pad used in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2601923