CMP endpoint detection system

Details CMP endpoint detection system CMP endpoint detection system

2002-03-25

2004-02-10

Nguyen, George (Department: 3723)

Abrading

Precision device or process - or with condition responsive...

By optical sensor

C451S005000, C451S007000, C451S285000, C451S286000, C451S287000, C451S053000, C356S500000

Reexamination Certificate

active

06688945

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of the Invention
The invention relates to an endpoint detection system in a chemical mechanical polishing (CMP) apparatus, and more particularly, to an endpoint detection system utilizing a gas flow system to evacuate water vapor.
2. Description of the Prior Art
When fabricating modern semiconductor integrated circuits (ICs), to prevent subsequent manufacturing processes from being adversely affected, the flatness of each deposition layer of an integrated circuit has to be considered. In fact, most high-density IC fabrication techniques make use of some method to form a planarized wafer surface at critical points in the manufacturing process. One method for achieving semiconductor wafer planarization or topography removal is the chemical mechanical polishing (CMP) process. The CMP process is a well-known technique for removing materials on a semiconductor wafer using a polishing device and polishing slurry. The combination of the mechanical movement of the polishing device relative to the wafer and the chemical reaction of the polishing slurry provides an effective abrasive force with chemical erosion to planarize the exposed surface of the wafer or a layer formed on the wafer.
Please refer to FIG.
1
.
FIG. 1
is a schematic diagram of an endpoint detection system
10
in a prior art CMP apparatus. The endpoint detection system
10
in the CMP apparatus includes a polishing platen
12
covered with a polishing pad
14
. The polishing pad
14
comprises a hard polishing pad
16
and a soft polishing pad
18
. The soft polishing pad
18
interfaces with the hard polishing pad
16
and the polishing platen
12
and the hard polishing pad
16
is used in conjunction with polishing slurry
20
to polish a semiconductor wafer
22
disposed on the polishing platen
12
. Furthermore, a window
24
is formed in the hard polishing pad
16
, and a chamber
26
is formed below the window
24
in the soft polishing pad
18
and the polishing platen
12
. This window
24
is positioned such that it has a view of the semiconductor wafer
22
held by a polishing head during a portion of a platen's rotation. A laser interferometer
28
is fixed below the polishing platen
12
in a position enabling a laser beam to pass through the window
24
and than strike the surface of the overlying semiconductor wafer
22
during a time when the window
24
is adjacent the semiconductor wafer
22
. Thereafter, the CMP apparatus
10
analyzes the reflected laser beam from the semiconductor wafer
22
to determine the endpoint of the CMP process.
However, there may be contaminants such as coagulated polishing slurry or fine water mist deposited on the bottom surface of the window
24
and exposed surfaces of the chamber
26
in the polishing platen
12
in the endpoint detection system
10
of the prior art CMP apparatus. Thus, the laser beam traveling through the window
24
and the chamber
26
in the polishing platen
12
is scattered by the contaminants. That is, either the laser beam emitted from the laser interferometer
28
or the laser beam reflected from the semiconductor wafer
22
is attenuated. Consequently, the endpoint detection of the CMP process is interfered with and the planarization of the semiconductor wafer
22
cannot be achieved.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide an endpoint detection system in a chemical mechanical polishing (CMP) apparatus to solve the above-mentioned problem.
According to the claimed invention, an endpoint detection system in a CMP apparatus has a polishing platen, a polishing pad covering the polishing platen, a chamber located in the polishing platen, and a gas flow system arranged in a periphery of the chamber. The gas flow system has a gas inlet used to flow dry gas into the chamber and a gas outlet used to evacuate water vapor in the chamber.
It is an advantage of the claimed invention that the endpoint detection system in the CMP apparatus has the gas flow system arranged in a periphery of the chamber so as to evacuate water vapor deposited on the bottom surface of a window or exposed surfaces of the chamber. Thus, the problem of contaminants such as water droplets has been solved and the endpoint of a CMP process can be precisely controlled. Consequently, the yield of the manufacturing process for integrated circuits is substantially improved and the cost of fabrication is significantly reduced.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.


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