Fluid venting platen for optimizing wafer polishing

Details Fluid venting platen for optimizing wafer polishing Fluid venting platen for optimizing wafer polishing

2002-06-28

2004-08-03

Hail, III, Joseph J. (Department: 3723)

Abrading

Abrading process

Utilizing nonrigid tool

C451S041000, C451S288000

Reexamination Certificate

active

06769970

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 optimizing chemical mechanical planarization applications by optimizing the controllability of a fluid bearing generated by a platen.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform chemical mechanical planarization (CMP) operations. 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. As is well known, 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 grows. Without planarization, fabrication of further metallization layers becomes substantially more difficult due to the variations in the surface topography. In other applications, metallization line patterns are formed in the dielectric material, and then, metal CMP operations are performed to remove excess material.
A chemical mechanical planarization (CMP) system is typically utilized to polish a wafer as described above. A CMP system typically includes system components for handling and polishing the surface of a wafer. Such components can be, for example, a rotary polishing pad, an orbital polishing pad, or a linear belt polishing pad. The pad itself is typically made of a polyurethane material or polyurethane in conjunction with other materials such as, for example a stainless steel belt. In operation, the belt pad is put in motion and then a slurry material is applied and spread over the surface of the belt pad. Once the belt pad having slurry on it is moving at a desired rate, the wafer is lowered onto the surface of the belt pad. In this manner, wafer surface is planarized substantially. The wafer may then be cleaned in a wafer cleaning system.
FIG. 1A
shows a linear polishing apparatus
10
which is typically utilized in a CMP system. The linear polishing apparatus
10
polishes away materials on a surface of a semiconductor wafer
16
. The material being removed may be a substrate material of the wafer
16
or one or more layers formed on the wafer
16
. Such a layer typically includes one or more of any type of material formed or present during a CMP process such as, for example, dielectric materials, silicon nitride, metals (e.g., aluminum and copper), metal alloys, semiconductor materials, etc. Typically, CMP may be utilized to polish the one or more of the layers on the wafer
16
to planarize a surface layer of the wafer
16
. The linear polishing apparatus
10
utilizes a polishing belt
12
, which moves linearly in respect to the surface of the wafer
16
. The belt
12
is a continuous belt rotating about rollers (or spindles)
20
. A motor typically drives the rollers so that the rotational motion of the rollers
20
causes the polishing belt
12
to be driven in a linear motion
22
with respect to the wafer
16
.
A wafer carrier
18
holds the wafer
16
. The wafer
16
is typically held in position by mechanical retaining ring and/or by vacuum. The wafer carrier positions the wafer atop the polishing belt
12
so that the surface of the wafer
16
comes in contact with a polishing surface of the polishing belt
12
.
FIG. 1B
shows a side view of the linear polishing apparatus
10
. As discussed above in reference to
FIG. 1A
, the wafer carrier
18
holds the wafer
16
in position over the polishing belt
12
while applying pressure to the polishing belt. The polishing belt
12
is a continuous belt typically made up of a polymer material such as, for example, the IC
1000
made by Rodel, Inc. layered upon a supporting layer. The polishing belt
12
is rotated by the rollers
20
which drives the polishing belt in the linear motion
22
with respect to the wafer
16
. In one example, a fluid bearing platen
24
supports a section of the polishing belt under the region where the wafer
16
is applied. The platen
24
can then be used to apply fluid against the under surface of the supporting layer. The applied fluid thus forms a fluid bearing that creates a fluid pressure on the underside of the polishing belt
12
which is applied against the surface of the wafer
16
. Additionally, typical platen designs tend to use a significant amount of fluid to produce a fluid bearing between the platen
24
and the polishing pad
12
. In one example, high flow regulators are utilized to input air through the platen
24
. Unfortunately, by use of a high flow regulator, large amounts of air are utilized during a CMP operation. Large usage of fluid can lead to increased wafer production cost and therefore is generally undesirable. Generally, uniformity is desired where the material removal rate is evenly distributed across the entire contact surface that interfaces with the wafer so the wafer surface becomes substantially planar. This typically requires control of polishing pressure applied by the fluid bearing. But, there can be times where polishing pressure in different regions of the wafer is desired to be varied such as times when oxide deposition on the wafer has a distinctive thickness profile as discussed below in reference to
FIGS. 1C and 1D
.
FIG. 1C
shows a graph
30
illustrating a profile of non-uniform oxide deposition on a wafer. In this example, the oxide layer that has been deposited is thicker in the center and the edge of the wafer and thinner in the area between the center and the edge. This can occur due to equipment optimization limitations. Therefore, when platens that apply uniform polishing pressure across the wafer are utilized resulting in a uniform removal rate, the original non-uniformity from the deposition is preserved after planarization. Thus, when, for example, the oxide layer that has been applied is thicker in the center and the edge and thinner in the areas in between, this may result in too little polishing in the edge and center portions of the wafer and too much polishing in the other regions of the wafer. Unfortunately, because prior art platens are configured to only outputs fluids from outlets, wafer polishing profiles typically cannot be managed to match many wafer thickness profiles.
FIG. 1D
shows a graph
40
of another exemplary profile of an non-uniform oxide layer that has been deposited on the wafer. In this example, if a wafer that is thicker in the edge and thinner in the middle is polished, the polishing can result in too much removal of oxide in the center region while too little removal takes place in the edge regions of the wafer. Therefore, the wafer with the thickness profile as shown in graph
40
may not polished to a substantially planar surface.
As shown by
FIGS. 1C and 1D
, there are numerous types of wafer thickness profiles that can occur with different oxide deposition equipment from different manufacturers. Therefore, wafer polishing equipment attempting to apply uniform polishing pressure across the wafer is not able to adjust polishing pressures throughout the various portions of the wafer. Such resultant non-uniform wafer thicknesses may be undesired and can be detrimental to efficient wafer processing operations.
In view of the foregoing, there is a need for an apparatus that overcomes the problems of the prior art by having a platen that can effectively control different polishing pressure profiles during CMP operations.
SUMMARY OF THE INVENTION
Broadly speaking, embodiments of the present invention fill these needs by providing a platen that enables management and control of polishing pressure in different parts of the wafer during a CMP process by having the ability to increase or decrease fluid pressure in different areas over the platen. The

Affiliated with

Also associated with

Rating

Fluid venting platen for optimizing wafer polishing does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Fluid venting platen for optimizing wafer polishing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluid venting platen for optimizing wafer polishing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3349335