Abrading – Abrading process – Utilizing nonrigid tool
Reexamination Certificate
2001-12-20
2004-10-26
Eley, Timothy V. (Department: 3724)
Abrading
Abrading process
Utilizing nonrigid tool
C451S041000, C451S288000, C451S290000, C451S303000, C451S311000, C451S495000
Reexamination Certificate
active
06808442
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 side double roller 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 belt 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
, loading it with required polishing pressure.
A bearing 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 can occur in material removal rate. Generally, to achieve uniform material removal, all parameters defining the material removal rate are required to be evenly distributed across the entire contact surface that interfaces with the wafer.
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 force field resulting from redistributed contact load. Hence, large variations in removal rates occur at the wafer edge
202
.
Although the air bearing platen approach utilized in a linear wafer polishing apparatus can allow significant compensation for the above mentioned non-uniformity in the CMP process, the coupling of support and pad flexing functions limits the degrees of freedom available for each function. For example, if a process engineer adjusts the air pressure to provide additional support for the wafer and polishing pad, the pressure change will also affect pad flexing, which is also being performed by the air bearing. In addition, the conventional approaches require significant air consumption to meet uniformity targets.
In view of the foregoing, there is a need for CMP systems capable of compensating for process non-uniformity. The CMP systems should be capable of compensating for non-uniformity, such as edge effect, independently of other process functions, such as wafer and pad support.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing polishing pad flexing techniques that allow independent flexing of a polishing pad for resolving non-uniformity during a CMP process. In one embodiment, an apparatus for removal rate profile manipulation during a CMP process is disclosed. The apparatus includes an actuator capable of vertical movement perpendicular to a polishing surface of a polishing pad. The actuator is further capable of flexing the polishing pad independently of a pad support device. Also included in the apparatus is an actuator control mechanism that is in communication with the actuator. The actuator control mechanism is capable of controlling an amount of vertical movement of the actuator, allowing the actuator to provide local flexing of the polishing pad to achieve a particular removal rate profile. The actuator can also be capable
Boyd John M.
Gotkis Yehiel
Kistler Rod
Owczarz Aleksander
Wei David
Eley Timothy V.
Lam Research Corporation
Martine & Penilla LLP
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