Wafer scrubbing brush core

Details Wafer scrubbing brush core Wafer scrubbing brush core

1999-12-03

2001-06-05

Till, Terrence R. (Department: 1744)

Brushing, scrubbing, and general cleaning

Machines

Brushing

C015S102000

Reexamination Certificate

active

06240588

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to semiconductor wafer fabrication, and more particularly to semiconductor wafer scrubbing equipment.
2. Description of the Related Art
As is well known, semiconductor devices are fabricated from semiconductor wafers, which are subjected to numerous processing operations. These operations include, for example, impurity implants, gate oxide generation, inter-metal oxide depositions, metallization depositions, photolithography pattering, etching operations, chemical mechanical polishing (CMP), etc. Although these processes are performed in ultra clean environments, the very nature of many of the process operations is to blame for the generation of surface particles and residues. For instance, when CMP operations are performed, a film of particles and/or metal contaminants are commonly left behind.
Because surface particles can detrimentally impact the performance of an integrated circuit device, wafer cleaning operations have become a standard procedural requirement after certain process steps. Although cleaning operations are rather procedural, the equipment and chemicals implemented to perform the actual cleaning are highly specialized. This specialization is important because each wafer, being at different stages of fabrication, represents a significant investment in terms of raw materials, equipment fabrication time, and associated research and development.
To perform the cleaning operations in an automated manner, fabrication labs employ cleaning systems. The cleaning systems typically include one or more brush boxes in which wafers are scrubbed. Each brush box includes a pair of brushes, such that each brush scrubs a respective side of a wafer. To enhance the cleaning ability of such brush boxes, it is common practice to deliver cleaning fluids through the brush (TTB). TTB fluid delivery is accomplished by implementing brush cores that have a plurality of holes that allow fluids being fed into the brush core at a particular pressure to be released into an outer brush surface. The outer brush surface is made out of a very porous and soft material so that direct contact with the delicate surface of a wafer does not cause scratches or other damage. Typically, the outer brush surface is a made out of polyvinyl alcohol (PVA) foam. Although, other materials such as nylon, mohair or a mandrel wrapped with a polishing pad material can be used.
As semiconductor design and performance requirements continue increase, cleaning engineers are also challenged to improve their associated processes. To meet these demands, the same cleaning equipment is now being used to perform operations other than basic de-ionized (DI) water cleaning. Such operations include the application of sophisticated chemicals TTB to remove particulates and/or to etch precision amounts of materials from the surfaces of a wafer. Although much research and development goes into the design of cleaning and etching chemicals, the effectiveness of such chemicals is only as good as their delivery and application onto the surface of a wafer.
Recent research of conventional brush core technology has uncovered non-uniformities in the application of the chemicals onto the surface of wafers. The research indicates that although chemicals are being flushed out of the brush cores and onto the wafer surfaces, the applied chemicals do exit the holes of the brush core at the same rate over the length of a core. For instance, chemicals are generally supplied to an internal bore of a brush core from one end of the brush core at a given pressure. Ideally, the chemicals are expected to flow through the bore and drip or flow out of the core equally from all of the brush core holes (e.g., the same amount drips out each of holes all along the brush core). Unfortunately, research shows that chemicals are not dripping out of all of the holes at the same or substantially the same rate. In fact, much of the research indicates that the brush core holes near the chemical receiving end drip out chemicals at a substantially faster rate than holes at the opposite side of the chemical receiving end.
Because traditional cleaning typically only included the application of DI water and/or ammonia based chemicals, the uneven application of these fluids through the brush core did not in many cases detrimentally impact cleaning performance. However, because most cleaning systems are now required to also apply engineered chemicals, such as hydrofluoric acid (HF) containing etch chemicals, any uneven application will have a severe impact on the wafer being processed. For instance, if more HF is applied to one part of the wafer and less is applied to another part of the wafer, the surface of the processed wafer may exhibit performance impacting etch variations due to experienced chemical concentration variations.
FIG. 1A
provides a simplified diagram
10
of a prior art brush core
12
having a plurality of holes
12
a
. The brush core
12
has a center bore
12
b
which is configured to receive fluids from a fluid input
16
at one end of the brush core
12
. The brush core
12
is shown having a brush
14
mounted thereon to illustrate that fluid that enters the bore
12
b
exits the holes
12
a
soaks the brush
14
that is designed to contact a wafer. This simplistic diagram also illustrates fluid flow lines
18
a
and
18
b
, in which fluid lines
18
a
illustrate that more fluid tends to flow out of holes
12
a
near the fluid input than at the opposite end. It is believed that this occurs because chemicals are either not applied to the brush core
12
at a sufficient pressure or the holes
12
are too large and/or are improperly arranged and thus allow gravity to pull more fluid out of the brush core
12
near the fluid input
16
than at the opposite end.
Some of these prior art brush cores
12
have a center bore
12
b
that is about 0.36 inch in diameter or larger and holes
12
a
that are about 0.13 inch in diameter or larger. To compensate for the larger size of these dimensions and to attempt to prevent the uneven delivery of fluids, cleaning systems need to deliver fluids to the brush cores
12
at higher pressures. These higher pressures range between 30 to 35 PSI or higher. However, the application of higher pressures require the cleaning system to have access to facilities and associated equipment that can deliver the desired controlled pressures at all times. However, cleaning systems are installed in clean rooms around the world having different facilities which may or may not be able to deliver the recommended pressures. Additionally, the holes
12
a
of most prior art brush cores
12
are arranged such that one hole
12
a
′ is directly opposite of another hole
12
a
′. This arrangement is also believed to contribute to the higher outflow of fluids near the fluid input
16
than at the opposite end.
In view of the foregoing, there is a need for improved brush core designs that enable controlled amounts of fluid to be evenly delivered and distributed over the surface areas of a brush core.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing a brush core for use in scrubbing substrates. The substrate can be any substrate that may need to undergo a scrubbing operation to complete a cleaning operation, etching operation, or other preparation. For instance, the substrate can be a semiconductor wafer, a disk, or any other type of work piece that will benefit from a brush core that can deliver uniform controlled amounts of fluid through the brush along an entire length of the brush core. 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 brush core for use in substrate scrubbing is disclosed. The brush core is defined by a tubular core extending between a first end and a second end. A bore is define

Affiliated with

Also associated with

Rating

Wafer scrubbing brush core does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Wafer scrubbing brush core, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wafer scrubbing brush core will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2493661