Fluid conserving platen for optimizing edge polishing

Details Fluid conserving platen for optimizing edge polishing Fluid conserving platen for optimizing edge polishing

2002-03-29

2004-09-14

Morgan, Eileen P. (Department: 3723)

Abrading

Abrading process

Glass or stone abrading

C451S054000, C451S307000

Reexamination Certificate

active

06790128

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 asymmetric platen pressure zones.
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, 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 that is desired to be planarized is substantially smoothed, much like sandpaper may be used to sand wood. 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 with 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 polishing pressure on the underside of the polishing belt
12
which is applied against the surface of the wafer
16
. Unfortunately, because the polishing pressure produced by the fluid bearing typically cannot be controlled very well, the polishing pressure applied by the fluid bearing to different parts of the wafer
16
generally is non-uniform. Generally, uniformity requires all parameters defining the material removal rate 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. 1C
shows a linear polishing apparatus
10
illustrating edge effect non-uniformity factors. In this example, a wafer
16
is attached to a carrier
18
, which applies pressure
13
to push the wafer
16
down on the polishing belt
12
that is moving over the platen
24
. However, the polishing belt
12
deforms when the wafer contacts the polishing belt
12
. Although the polishing belt
12
is a compressible medium, the polishing belt
12
has limited flexibility, which prevents the polishing belt
12
from conforming to the exact shape of the wafer
16
, forming transient deformation zones
22
and
26
. As a result, edge effects occur at the wafer edge
16
a
and
16
b
from a non-flat contact field resulting from redistributed contact forces. Hence, large variations in removal rates occur at the wafer edge
16
a
and
16
b
. Consequently, due to the fact that the prior art polishing belt designs do not properly control polishing dynamics, uneven polishing and inconsistent wafer polishing may result thereby decreasing wafer yield and increasing wafer costs.
In addition to the aforementioned problem of non-uniform wafer polishing, typical air bearing platens utilize a very large amount of air to apply air pressure to the polishing belt. For example, in platens used for 200 mm wafer CMP operations, as much as 100 SCFM (Standard Cubic Feet per Minute) of air may be utilized, and in 300 mm wafer CMP operations as much as 200 SCFM of air may be used. As a result, a large source of air must be utilized to be able to provide sufficient air to create the air bearing. Consequently, prior art air bearing platens have a problem of large air consumption.
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 improves polishing pressure control and reduces polishing pad deformation and at the same time reduce fluid consumption during CMP operations.
SUMMARY OF THE INVENTION
Broadly speaking, embodiments of the present invention fill these needs by providing a platen design that provides edge polishing uniformity control during a CMP process utilizing a fluid conserving platen. It should be appreciated that the present invention can be implemented in numerous ways, including as a process; an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a platen is disclosed. The platen includes a support surface for supporting a portion of a linear polishing belt during a chemical mechanical polishing (CMP) operation. The platen also includes a plurality of fluid outlets oriented throughout the support surface. The orientation defines an asymmetric pattern where each of the plurality of fluid outlets is capable of outputting a controlled fluid toward an underside of the linear polishing belt.
In another embodiment, a method for wafer p

Affiliated with

Also associated with

Rating

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

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3254130