Wafer edge scrubber and method

Details Wafer edge scrubber and method Wafer edge scrubber and method

1998-07-10

2001-10-09

Spisich, Mark (Department: 1744)

Cleaning and liquid contact with solids

Processes

Using solid work treating agents

C015S077000, C015S088200, C015S088300, C015S102000

Reexamination Certificate

active

06299698

ABSTRACT:

The present invention relates generally to apparatuses and methods for cleaning thin discs, such as semiconductor wafers, compact discs, glass substrates and the like. More particularly, the invention relates to a scrubbing device for simultaneously scrubbing the entire surface of the thin disc, including the edges thereof.
BACKGROUND OF THE INVENTION
To manufacture a thin disc such as a semiconductor wafer, an elongated billet of semiconductor material is cut into very thin slices, about ½ mm in thickness. The slices or wafers of semiconductor material are then lapped and polished by a process that applies an abrasive slurry to the wafer's surfaces. After polishing, slurry residue conventionally is cleaned or scrubbed from wafer surfaces via a scrubbing device which employs polyvinyl acetate (PVA) brushes, brushes made from other porous or sponge-like material, or brushes made from nylon bristles or similar materials. Although these conventional cleaning devices remove a substantial portion of the slurry residue which adheres to wafer edges, slurry particles nonetheless remain and produce defects during subsequent processing.
A conventional PVA brush scrubber disclosed in U.S. Pat. No. 5,675,856 is shown in the side elevational view of FIG.
1
. The conventional scrubber
11
, shown in
FIG. 1
, comprises a pair of PVA brushes
13
a
,
13
b
. Each brush comprises a plurality of raised nodules
15
across the surface thereof, and a plurality of valleys
17
located among the nodules
15
. The scrubber
11
also comprises a platform
19
for supporting a wafer W and a mechanism (not shown) for rotating the pair of PVA brushes
13
a
,
13
b
. The platform
19
comprises a plurality of spinning mechanisms
19
a-c
for spinning the wafer W.
Preferably, the pair of PVA brushes
13
a
,
13
b
are positioned to extend beyond the edge of the wafer W, so as to facilitate cleaning the wafer's edges thereof. However, research shows that slurry induced defects still occur, and are caused by slurry residue remaining along the edges of the wafer despite cleaning with apparatuses such as that described above. Specifically, subsequent processing has been found to redistribute slurry residue from the wafer edges to the front of the wafer, causing defects.
A number of devices have been developed to improve wafer edge cleaning. One such device is shown in the side elevational view of FIG.
2
. This mechanism employs a separate edge brush
21
, which is driven by a separate motor (not shown), that causes the edge brush
21
to rotate. The edge brush
21
fits over the edge of the wafer W as shown in
FIG. 2
, providing more effective wafer edge cleaning. Although the edge brush
21
addresses the need to clean slurry residue from wafer edges, it does so at the expense of increased scrubber complexity and cost, and requires additional solvents (e.g., water and ammonia) to maintain the cleanness of the edge brush
21
over an extended numbers of wafers.
Accordingly the field of wafer cleaning requires a method and apparatus which effectively cleans both the flat surfaces and the edge surfaces of a semiconductor wafer, and that does so without increased cost and complexity. In short, the semiconductor processing field needs an effective scrubber that satisfies the ever-present demand for reduced cost per unit wafer processed.
SUMMARY OF THE INVENTION
The present invention addresses the need for a more effective edge cleaner by providing a single brush which simultaneously scrubs both a planar surface and an edge surface of a thin disk such as semiconductor wafer. The brush comprises a wafer contacting surface which, during operation, cleans a wafer surface in contact therewith. The wafer contacting surface comprises a first portion for contacting the wafer along a substantially uniform plane; and a second portion for contacting the wafer along a profiled plane, such as an edge surface of the wafer.
The inventive brush preferably comprises a plurality of planar nodules for contacting the top or bottom planar surface of the wafer, and a plurality of profiled nodules for contacting the edge surface of the wafer. The profiled nodules are preferably elongated and extend to the end of the brush, having a profile which corresponds to the edge profile of a wafer to be cleaned by the inventive brush. It should be understood that as used herein, the profiled portion of the brush for contacting a wafer along a profiled plane has a profiled surface prior to contacting the wafer. The profiled nodules also may have a higher modulus of elasticity than that of the planar nodules.
A recessed area surrounds both the planar nodules and the profiled nodules forming a channel through which solvents and slurries may travel. The shape, spacing and number of nodules may vary broadly and still provide adequate wafer cleaning, as will be apparent to a worker of ordinary skill in the art.
The inventive brush may assume any shape required by a given wafer scrubbing device, the most common shapes being rollers or flat scrubbing surface devices (i.e., pancakes). Scrubbing devices which employ the inventive brush solve the long felt need for a highly effective and economical edge cleaner that reduces both manufacturing costs and costs associated with slurry induced defects.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.


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patent: 5729856 (1998-03-01), Jang et al.
patent: 5870793 (1999-02-01), Choffat et al.
patent: 5937469 (1999-08-01), Culkins et al.
patent: 123574 (1919-02-01), None
patent: 711598 (1954-07-01), None
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