Abrading – Accessory – Tool cleaner
Reexamination Certificate
2000-02-18
2001-06-19
Banks, Derrish H. (Department: 3723)
Abrading
Accessory
Tool cleaner
C451S443000
Reexamination Certificate
active
06248009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate cleaning apparatus, and more particularly to a substrate cleaning apparatus suitable for cleaning a substrate which requires a high level of cleanliness, such as a semiconductor wafer, a glass substrate, a liquid crystal panel, etc.
2. Description of the Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of the processes available for forming such interconnection is photolithography. Though the photolithographic process can form interconnections that are spaced by a distance of at most 0.5 &mgr;m, it requires that surface on which pattern images are to be focused by a stepper is as flat as possible because the depth of focus of the optical system is relatively small. If particles larger than the distance between adjacent interconnections are present on a substrate, then they tend to cause a short circuit between the interconnections. Therefore, it is important that the substrate is cleaned as well as planarized in its fabrication process. The same processing requirements apply to other substrates including glass substrates, liquid crystal panels, etc. In view of these requirements, there has been a demand for cleaning techniques for removing smaller particles, i.e., submicrons, from semiconductor substrates or the like.
According to a known process of cleaning a polished semiconductor substrate to a high level of cleanliness, the surface to be cleaned of the substrate is scrubbed by a cleaning member such as a brush or a sponge that is rubbed against the substrate (primary cleaning), and then a stream of water under high pressure, i.e., a high-speed jet of water, is ejected toward the substrate to produce air bubbles due to cavitation to clean the substrate (secondary cleaning).
FIG. 9A
of the accompanying drawings shows a conventional general arrangement of a substrate cleaning apparatus for use in scrubbing a substrate. The substrate cleaning apparatus has a plurality of upstanding substrate-holding rollers
100
openably and closably disposed around a substrate W. The substrate-holding rollers
100
has holding grooves
102
defined in upper ends thereof for holding the edge of the substrate W and rotating the substrate W upon rotation of the rollers
100
. As shown in
FIG. 9B
of the accompanying drawings, a pair of cleaning devices
108
is disposed in sandwiching relationship to the substrate W. The cleaning devices
108
are rotatable about respective axes thereof and movable into and out of contact with the substrate W. Each of the cleaning devices
108
comprises a solid shaft
104
and a cleaning member
106
in the form of a tubular sponge, brush, or the like disposed on the surface of the solid shaft
104
. As shown in
FIG. 9C
of the accompanying drawings, nozzles
110
which supply a cleaning liquid, pure water, or the like to the face and back of the substrate W are provided.
While the substrate W is being held and rotated by the rollers
100
, the cleaning liquid is supplied from the nozzles
110
to the face and back of the substrate W, and the cleaning members
106
are rubbed against the substrate W to scrub the substrate W (primary cleaning) for thereby removing deposits of an abrasive liquid, a polishing residue, etc. from the entire face and back of the substrate W.
Since the scrubbing process is carried out while the cleaning members
106
are being held in contact with the substrate W, the contamination of the cleaning members
106
themselves governs the cleaning effect. If the contamination of the cleaning members
106
progresses, then the contaminant attached to the cleaning members
106
tends to contaminate the substrate W. Therefore, as shown in
FIG. 9C
, a cleaning tank
114
filled with a cleaning liquid
112
is disposed in a retracted position of the cleaning devices
108
, and each of the cleaning devices
108
is cleaned by being dipped and rotated in the cleaning liquid
112
in the cleaning tank
114
.
SUMMARY OF THE INVENTION
With the above conventional arrangement, it is necessary to supply the cleaning liquid to the entire surface of the substrate in order to uniformly clean the substrate, and hence a large amount of cleaning liquid is required. Particularly, if the substrate is rotated at a high speed, then the cleaning liquid is quickly removed from the surface of the substrate, and hence is utilized with low efficiency, resulting in a need for a greater amount of the cleaning liquid which is supplied from nozzles
110
.
Furthermore, since the cleaning devices
108
are dipped in the cleaning liquid
112
in the cleaning tank
114
to clean the cleaning members
106
themselves, the cleaning devices
108
may be contaminated by contaminants contained in the cleaning liquid and ions released into the cleaning liquid.
The shafts
104
of the cleaning devices
108
are rotatably supported by bearings at ends held by the shaft end holders thereof remote from drive ends that are connected to a drive mechanism such as a motor. Therefore, particles are produced and metal and grease are released from the bearings, seals that protect the bearings from corrosive fluids, and springs which bias the cleaning devices in the axial direction. When not in operation, the cleaning liquid is dried to allow the cleaning agent to be solidified, preventing the cleaning devices from operating smoothly. Because the ends of the shafts held by the shaft end holders are combined with a complex mechanism, the diameter of the cleaning devices is so large that it takes a long period of time to impregnate the entire cleaning members of the cleaning devices with the cleaning liquid, and a large amount of cleaning liquid is required.
The present invention has been made in view of the above drawbacks. It is an object of the present invention to provide a substrate cleaning apparatus which has an increased cleaning efficiency of a cleaning liquid and maintains a sufficient cleaning capability, includes durable bearings of a simple structure, and can be operated stably at a low cost.
To achieve the above object, there is provided in accordance with an invention described in claim
1
, a substrate cleaning apparatus comprising a substrate holder for holding a substrate while rotating the substrate in a substantially horizontal plane, a cleaning device for scrubbing a surface to be cleaned of the substrate, a cleaning device holder for holding the cleaning device rotatably about its own axis, the cleaning device having a shaft and a cleaning member disposed around the shaft, the cleaning member being permeable to a cleaning liquid, the shaft having an axially extending shaft hole and a cleaning liquid ejection port extending radially therethrough from the shaft hole, and a fluid-lubricated bearing disposed between the shaft and the cleaning device holder in at least one end thereof and lubricated by a cleaning liquid as a lubricating fluid. The cleaning member which is permeable to a cleaning liquid may be a sponge that is liquid-permeable by itself, a brush which has gaps, or a hydrophobic tube with holes defined at suitable intervals.
Since the cleaning liquid is ejected via the shaft hole in the shaft from the cleaning liquid ejection port and supplied via the cleaning member to the surface to be cleaned of the substrate, the cleaning liquid concentrates on a region to be cleaned of the substrate. Therefore, no wasteful cleaning liquid is supplied to the substrate, which is cleaned efficiently. Because the cleaning member itself is cleaned steadily by the cleaning liquid passing through the cleaning member, the substrate is prevented from being contaminated by the cleaning member which would otherwise be contaminated. Furthermore, inasmuch as the cleaning device is supported by the fluid-lubricated bearing which employs the cleaning liquid as the lubricating fluid, a stable contamination-free support stru
Ato Koji
Ito Kenya
Matsuda Naoki
Oikawa Fumitoshi
Shirakashi Mitsuhiko
Banks Derrish H.
Ebara Corporation
Wenderoth , Lind & Ponack, L.L.P.
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