Abrading – Machine – Rotary tool
Reexamination Certificate
2003-02-04
2004-08-10
Hall, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S008000, C451S009000, C451S285000, C451S390000, C451S398000, C451S041000
Reexamination Certificate
active
06773338
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing head of a chemical mechanical polishing apparatus used for manufacturing semiconductor devices and a chemical mechanical polishing apparatus including the same. More particularly, the present invention relates to a polishing head capable of adjusting a height of a retainer ring after measuring a step height difference between the retainer ring and a semiconductor wafer.
2. Description of the Related Art
The manufacturing process of semiconductor devices demands a degree of integration, a fine pitch and a multi-layered structure of wires. As the demand increases, the surface roughness of a semiconductor wafer becomes increasingly uneven. Therefore, significant attention is paid to a technology for smoothing or planarizing a surface of the semiconductor wafer.
Known planarizing techniques include reflowing, spin on glass (SOG), etch back, and chemical mechanical polishing (CMP). Among these techniques, CMP is widely used in semiconductor device manufacturing due to an advantage of global planarization achievement, particularly in the manufacture of a semiconductor device having four wiring layers.
To perform CMP, a polishing head moves down to the semiconductor wafer, and holds the semiconductor wafer in a retainer ring thereof. Then, the polishing head presses a surface of the semiconductor wafer against a pad covering a polishing table, which is rotating. A polishing slurry is applied onto the pad during the polishing.
In addition, not only does the semiconductor wafer contact the polishing pad, but the retainer ring holding the semiconductor wafer contacts the polishing pad during the polishing, thus causing wear on the retainer ring. As the retainer ring becomes worn, a step height difference between a bottom surface of the retainer ring and the surface of the semiconductor wafer is reduced. As a result, polishing uniformity is degraded.
Several conventional apparatus have been proposed to improve polishing uniformity.
One conventional apparatus includes a polishing head having a pushing force distribution plate on a bottom thereof, the pushing force distribution plate including a plurality of segments in which a thickness of the segments is adjusted by a controller, for improving polishing uniformity by adjusting the pushing force of the semiconductor wafer.
Another conventional apparatus provides a polishing system including a modulation unit that includes a plurality of capacitors each of which includes a flexible lower plate and a plurality of smaller upper plate segments. In the polishing system, a controller monitors and adjusts the capacitance between each of the upper plate segments and the flexible lower plate, so that dynamic and localized control of polishing is achieved.
FIG. 1
illustrates a schematic view of a conventional chemical mechanical polishing (CMP) apparatus. The conventional CMP apparatus includes a polishing table
10
covered with a pad
12
that directly contacts a wafer and is rotated during polishing, a polishing head
14
, that is installed over the polishing table
10
and holds a wafer
2
by vacuum suction, and a slurry supplying nozzle
18
installed over the polishing table
10
for supplying slurry from a slurry tank
16
onto the polishing table
10
. The polishing head
14
is shown in greater detail in FIG.
2
.
Referring to
FIG. 2
, the polishing head
14
includes an upper plate
20
where a vacuum tube
21
passes through at a portion thereof, and an outer ring
22
being attached to the upper plate
20
by a bolt
22
a
at an edge portion thereof. Inside the outer ring
22
, an inner ring
24
is fixed to an inner sidewall of the outer ring
22
by pins
24
a
. Inside the inner ring
24
, an inner plate
26
having a penetrating hole
28
connected to one end of the vacuum tube
21
is provided by being fixed to the inner ring
24
using pins
26
a.
As shown in FIG.
2
and an enlarged portion of
FIG. 2
, a lower plate
30
is provided under the inner plate
26
being apart from the inner plate
26
a predetermined distance and fixed to the inner plate
26
by bolts
30
a
. The lower plate
30
has a recess around an edge portion thereof and a plurality of vacuum holes
32
at an inner part of the recess. A porous film
34
having a plurality of holes
36
corresponding in location to the vacuum holes
32
of the lower plate
30
is provided under the lower plate
30
. The wafer
2
is attached to the porous film
34
by a vacuum pumping force transferred though the vacuum holes
32
of the lower plate
30
and holes
36
of the porous film
34
from the vacuum tube
21
.
Referring to the enlarged portion of
FIG. 2
, a retainer ring
38
is provided at the recess formed on the bottom of the lower plate
30
and clamped by a clamp ring
44
installed on an exterior of the retainer ring
38
wherein an inner tube
42
is interposed between the clamp ring
44
and the retainer ring
38
. The clamp ring
44
is fixed to the lower plate
30
by bolts
44
a
. The retainer ring
38
is provided to prevent the wafer
2
from being pulled off outside the lower plate
30
. Additionally, a shim
40
is interposed between the lower plate
30
and the retainer ring
38
at the recess to adjust a step height between a bottom of the wafer
2
and a bottom of the retainer ring
38
.
The polishing head
14
contacts a back surface of the wafer
2
and tightly holds the wafer
2
using vacuum suction. The wafer
2
is fixed to the porous film
34
attached to the bottom of the polishing head
14
by a vacuum pumping force that is transferred through the vacuum tube
21
, the penetrating holes
28
of the inner plate
26
, the vacuum holes
32
of the lower plate
30
and holes
36
of the porous film
34
.
The polishing head holding the wafer
2
by the bottom thereof using the vacuum pumping force contacts the pad
12
of the polishing table
10
, which is rotating and presses the wafer against the pad
12
, thereby polishing the surface of the wafer.
At this time, a slurry is supplied onto the polishing table
10
from the slurry tank
16
via the slurry nozzle
18
, so that mechanical and chemical polishing is accomplished.
The wafer
2
may not be detached from the polishing head
14
, even though the vacuum pumping force is removed from the vacuum tube
21
, due to a pressing force of the polishing head
14
and a clamping force of the retainer ring
38
during polishing.
The retainer ring
38
, however, is gradually worn-out as the polishing proceeds due to the nonuniform distribution of the pressing force. Further, the retainer ring
38
may be worn-out due to the internal pressure variation of the internal tube
42
pressing the retainer ring
38
. As a result, polishing uniformity of the wafer is degraded.
In a case when the retainer ring
38
becomes worn-out, an operator releases the retainer ring
38
from the polishing head
14
and replaces the shim
40
installed between the lower plate
30
and the retainer ring
38
, thereby increasing a step height difference between the wafer
2
and the retainer ring
38
. However, it is difficult to detect the worn-out status of the retainer ring in real time. Accordingly, inferior polishing frequently occurs.
Further, such replacements are labor-intensive work and an accuracy of adjustment of the step height difference between the wafer and the retainer ring is low because the replacement is performed manually.
SUMMARY OF THE INVENTION
It is a feature of an embodiment of the present invention to provide a polishing head capable of automatically detecting a step height difference between a wafer and a retainer ring and accurately adjusting the step height difference, and a chemical mechanical polishing apparatus including the same polishing head.
In accordance with one aspect of the present invention, there is provided a polishing head for a chemical mechanical polishing apparatus including a plate having a plurality of vacuum holes for transferring a vacuum pumping force; a porous film having
Kim Young-Min
Yun Cheol-Ju
Hall, III Joseph J.
Lee & Sterba, P.C.
Ojini Anthony
Samsung Electronics Co,. Ltd.
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