Abrading – Machine – Combined
Reexamination Certificate
2001-10-05
2003-07-22
Wilson, Lee D. (Department: 3723)
Abrading
Machine
Combined
C451S287000, C451S285000, C033S483000, C033S679100
Reexamination Certificate
active
06595836
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the chemical-mechanical polishing (CMP) process used in the manufacturing of semiconductor devices. More particularly, the present invention relates to the pad conditioner head of a CMP machine.
2. Description of the Related Art
In the fabrication of integrated circuits of a semiconductor device, a chemical-mechanical polishing (CMP) process is generally used to reduce step coverage, or to form contact plugs and wires in a damascene manner. To this end, the CMP process uses mechanical friction and a chemical reaction to remove material from the surface of a wafer. In the CMP process, a polishing head presses a wafer against an abrasive pad and rotates the wafer, whereby the wafer is mechanically polished. Also, during this time, a slurry arm supplies a slurry of abrasive particles into a small gap between the wafer and the abrasive pad to chemically remove silicon oxides from the wafer. CMP is very efficient in removing material from the surface of a wafer because CMP makes use of both mechanical and chemical processes. Also, the use of a chemical reaction allows for only selected material to be removed from the surface of a wafer.
However, a precise surface roughness and elasticity of the abrasive pad and a specified contact pressure between the wafer and the abrasive pad have to be established if the CMP process is to remove material precisely from the surface of a wafer. Also, the slurry has to be uniformly distributed in the gap between the surface of the wafer and the abrasive pad. Accordingly, the abrasive pad is precisely fabricated to satisfy these requirements. If, however, the characteristics of the abrasive pad change significantly after the pad has been used for a given period of time, it has to be replaced. Moreover, the abrasive pad is an expensive consumable article of manufacture. Therefore, its frequent replacing has a noticeable impact on the manufacturing cost of the semiconductor devices.
Accordingly, the abrasive pad needs to be maintained for a long period of time. To meet this need, a pad conditioner is used to condition the surface of the abrasive pad so that the surface remains uniform for as long as possible. The pad conditioner evens out irregularities in the surface contour of the abrasive pad and remove surplus slurry from the surface of the abrasive pad so that the slurry is distributed uniformly across the surface of the abrasive pad. The pad conditioner also trims the surface of the abrasive pad so that a given surface roughness is maintained. Thus, the pad conditioner prolongs the useful life of the abrasive pad and maintains the condition of the pad until its useful life is over.
FIG. 1
is a schematic plan view of a conventional CMP machine. The CMP machine has several working area P
1
, P
2
, P
3
. A respective abrasive pad
11
, a slurry arm
13
, and a pad conditioner
15
having a head
21
are disposed in each working area. The abrasive pad
11
is mounted on a circular platen (
23
of FIG.
3
). The slurry arm
13
and the pad conditioner
15
are disposed in a first corner of the working area. On the other hand, a respective polishing head
19
is disposed over the abrasive pad
11
at a second corner of each working area opposite to that corner at which the slurry arm
13
and the pad conditioner
15
are disposed. The polishing head
19
chucks a wafer
17
by vacuum or surface tension during the CMP process in which, as mentioned above, the wafer
17
is pressed by the polishing head against the abrasive pad
11
while the abrasive pad
11
is rotated (by the platen
23
) and the slurry arm
13
supplies slurry into the gap between the contacting surfaces of the wafer
17
and the abrasive pad
11
.
Subsequently, the head
21
of the pad conditioner
15
is moved onto the abrasive pad
11
from a stand-by position in a clean cup. The head
21
has a diamond-encrusted disk mounted thereto. The head
21
evens out the surface of the abrasive pad
11
by sweeping the disk across the pad
11
over a certain angle, whereby the centers of the platen
23
and the head
21
of the pad conditioner
15
are moved within a certain range relative to each other.
To maintain a sufficient surface roughness of the abrasive pad
11
, the head
21
of the pad conditioner
15
has to be swung to the left and right within a given working range. If the movement of the pad conditioner
15
deviates from the given working range, excess slurry can remain on a portion of the abrasive pad
11
, or steps or defective abrasive portions can be formed on the surface of the abrasive pad
11
. Steps at the surface of the abrasive pad
11
may cause the wafer to be improperly polished. As a result, chips of inferior quality may be produced at a portion of the wafer
17
.
Therefore, in preparation for the CMP process, the pad conditioner
15
is first adjusted to limit its movement within the desired given working range, however, components of the CMP machine may be mechanically altered as the CMP process is being carried out. Accordingly, it is necessary to frequently calibrate the head
21
of the pad conditioner
21
, i.e., set the head
21
in place in a reference position.
Referring to FIG.
2
and
FIG. 3
, the head
21
is so calibrated by vertically aligning the outer peripheral edge thereof with the outer peripheral edge of the platen
23
. Up until now, the pad conditioner head
21
has been calibrated in this way by eye. However, it is not possible to accurately calibrate the head
21
consistently and correctly by eye. In particular, it is very difficult to discern whether the edge of the head
21
is vertically aligned with the edge of the platen
23
because the abrasive pad
11
protrudes outwardly beyond the edge of the platen
23
.
Accordingly, the head
21
is often improperly calibrated, whereby the pad conditioner
15
operates outside the desired working range when conditioning the abrasive pad. As a result, excess slurry can be remain on a portion of the abrasive pad
11
, or steps or defective abrasive portions can be formed on the surface of the abrasive pad
11
. As a result, inferior chips are often produced.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device by which a pad conditioner head of a CMP machine can be correctly calibrated, especially in the case in which the abrasive pad of the CMP machine protrudes radially outwardly beyond an outer peripheral edge of the circular platen to which the pad is mounted.
The present invention achieves this abject by providing by a calibration device that includes a first horizontal member having a radially innermost end defining a concave arcuate reference surface having a shape complementary to that of a portion of the outer peripheral edge of the platen, a second horizontal member extending radially relative to the concave arcuate reference surface of the first horizontal member and bearing a reference mark located in the projected plane of the reference surface, and a connecting member interconnecting and vertically spacing the first and second horizontal members.
The innermost end of the first horizontal member is elongate relative to the outermost end thereof, in the circumferential direction of the platen, so that the reference surface can engage the outer peripheral edge of the platen over a rather wide area. Furthermore, when the calibration device is in use, the outermost end of the first horizontal member and an outermost end of the second horizontal member opposite thereto are located further out than a portion of the outer peripheral edge of the abrasive pad that extended outwardly beyond the outer peripheral edge of the platen. Thus, the abrasive pad can be accommodated in a space between the horizontal members of the calibration device.
The connecting member can be unitary with the first and second horizontal members. In addition, a handle can be integrated with the connecting member so that the calibration device can be grasped.
The reference mark can be part of
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
Wilson Lee D.
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