Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – For liquid etchant
Reexamination Certificate
2001-12-20
2004-07-27
Hassanzadeh, P. (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
For liquid etchant
C451S268000, C451S066000, C451S072000
Reexamination Certificate
active
06767428
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to chemical mechanical planarization apparatuses, and more particularly to methods and apparatuses for improved uniformity in chemical mechanical planarization applications via a membrane based chemical mechanical planarization apparatus.
2. Description of the Related Art
In the fabrication of semiconductor devices, planarization operations, which can include polishing, buffing, and wafer cleaning, are often performed. Typically, integrated circuit devices are in the form of multi-level structures. At the substrate level, transistor devices having diffusion regions are formed. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define the desired functional device. Patterned conductive layers are insulated from other conductive layers by dielectric materials, such as silicon dioxide. As more metallization levels and associated dielectric layers are formed, the need to planarize the dielectric material increases. Without planarization, fabrication of additional metallization layers becomes substantially more difficult due to the higher variations in the surface topography. In other applications, metallization line patterns are formed in the dielectric material, and then metal planarization operations are performed to remove excess metallization. Further applications include planarization of dielectric films deposited prior to the metallization process, such as dielectrics used for shallow trench isolation or for poly-metal insulation. One method for achieving semiconductor wafer planarization is the chemical mechanical planarization (CMP) process.
In general, the CMP process involves holding and rubbing a typically rotating wafer against a moving polishing pad under a controlled pressure and relative speed. CMP systems typically implement orbital, belt, or brush stations in which pads or brushes are used to scrub, buff, and polish one or both sides of a wafer. Slurry is used to facilitate and enhance the CMP operation. Slurry is most usually introduced onto a moving preparation surface and distributed over the preparation surface as well as the surface of the semiconductor wafer being buffed, polished, or otherwise prepared by the CMP process. The distribution is generally accomplished by a combination of the movement of the preparation surface, the movement of the semiconductor wafer and the friction created between the semiconductor wafer and the preparation surface.
FIG. 1A
is a diagram showing a conventional table based CMP apparatus
50
. The conventional table based CMP apparatus
50
includes a polishing head
52
, which holds a wafer
54
, and is attached to a translation arm
64
. In addition, the table based CMP apparatus
50
includes a polishing pad
56
that is disposed above a polishing table
58
, which is often referred to as a polishing platen.
In operation, the polishing head
52
applies downward force to the wafer
54
, which contacts the polishing pad
56
. Reactive force is provided by the polishing table
58
, which resists the downward force applied by the polishing head
52
. The polishing pad
56
is used in conjunction with slurry to polish the wafer
54
. Typically, the polishing pad
56
comprises foamed polyurethane or a sheet of polyurethane having a grooved surface. The polishing pad
56
is wetted with a polishing slurry having both an abrasive and other polishing chemicals. In addition, the polishing table
58
is rotated about its central axis
60
, and the polishing head
52
is rotated about its central axis
62
. Further, the polishing head can be translated across the polishing pad
56
surface using the translation arm
64
. In addition to the table based CMP apparatus
50
discussed above, linear CMP systems have been conventionally used to perform CMP.
FIG. 1B
shows a side view of a conventional linear wafer polishing apparatus
100
. The linear wafer polishing apparatus
100
includes a polishing head
108
, which secures and holds a wafer
104
in place during processing. A polishing pad
102
forms a continuous loop around rotating drums
112
, and generally moves in a direction
106
at a speed of about 400 feet per minute, however this speed may vary depending upon the specific CMP operation. As the polishing pad
102
moves, the polishing head
108
rotates and lowers the wafer
104
onto the top surface of the polishing pad
102
.
A platen manifold assembly
110
supports the polishing pad
102
during the polishing process. The platen manifold assembly
110
may utilize any type of bearing such as a fluid bearing or a gas bearing. The platen manifold assembly
110
is supported and held into place by a platen surround plate
116
. Gas pressure from a gas source
114
is inputted through the platen manifold assembly
110
via a plurality of independently controlled of output holes that provide upward force on the polishing pad
102
to control the polishing pad profile.
Unfortunately, in each of the above CMP systems non-uniformities in material removal rate and process instability can occur. Generally, uniformity requires all parameters defining the material removal rate to be evenly distributed across the entire contact surface that interfaces with the wafer. In addition, process stability generally requires the properties of the contacting surface to remain essentially constant.
Edge instabilities in CMP are among the most significant performance affecting issues and among the most complicated problems to resolve.
FIG. 2
is a diagram showing a wafer pad interface
200
, illustrating edge effect non-uniformity factors. As shown in
FIG. 2
, when the wafer
54
contacts the polishing pad
56
during the CMP process, the flexibility in the polishing pad
56
allows the wafer
54
to form a depression in the polishing pad
56
. More particularly, although the polishing pad
56
is a compressible medium, the polishing pad
56
has limited flexibility, which prevents the polishing pad
56
from conforming to the exact shape of the wafer
54
, forming transient deformation zones. As a result, edge effects occur at the wafer edge
202
from a non-flat contact field resulting from redistributed contact forces. Hence, large variations in removal rates occur at the wafer edge
202
.
Process instability is another problem occurring in prior art CMP systems. Efficient CMP systems allow the use of a given set of consumables for processing of a significant number of wafers, at least several hundred, before the consumables require replacement. Unfortunately, prior art CMP systems inject process instabilities into the CMP process through wear on the polishing surface, as illustrated in
FIGS. 3A and 3B
.
FIG. 3A
is a diagram showing a top view of a prior art table based CMP apparatus
300
. As shown in
FIG. 3A
, when a wafer
54
undergoes planarization using the polishing pad
56
, material is eroded from the polishing pad
56
in addition to the material removed from the surface of the wafer
54
. Pad material is removed from the polishing pad
56
in a wafer path that contacts the wafer
54
during the CMP process. Moreover, the pad erosion rate is distributed non-evenly, being higher at the central path
304
, less near the edge sections
304
a
of the wafer path, and remaining non-eroded in outer pad regions
302
that are outside the wafer path. As similar behavior occurs on a linear apparatus, as shown in FIG.
3
B.
FIG. 3B
is a diagram showing a top view of a prior art linear wafer polishing apparatus
350
. As shown in
FIG. 3B
, when a wafer
104
undergoes planarization using the polishing pad
102
, material is eroded from the polishing pad
102
in addition to the material removed from the surface of the wafer
104
. As above, material is removed from the polishing pad
102
in a wafer path
352
that contacts the wafer
104
during the CMP process. As with table based CMP apparatus
300
, the pad erosion rate is distributed non-evenly. The pad erosion rate is highe
Gotkis Yehiel
Kistler Rod
Owczarz Aleksandar
Hassanzadeh P.
Lam Research Corporation
MacArthur Sylvia R.
Martine & Penilla LLP
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