Brushing – scrubbing – and general cleaning – Machines – Wiping
Reexamination Certificate
2000-07-06
2003-05-13
Chin, Randall E. (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
Wiping
C015S021100, C015S077000, C015S088300
Reexamination Certificate
active
06560809
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a cleaning apparatus for cleaning a substrate, such as a semiconductor substrate or wafer and a liquid crystal plate, which are required to have a high degree of cleanliness.
With recent rapid progress in technology for fabricating high-integration semiconductor devices, circuit-wiring patterns have been becoming increasingly fine and, as a result, spaces between wiring patterns have also been decreasing. Especially, in photolithography for formation of wiring patterns with a spacing of less than 0.5 microns, as depth of focus becomes shallower, it is required for an image-formation surface to have an exceptionally high degree of flatness. In addition, it is required for semiconductor substrates to be subjected to fine cleaning in such a manner as to remove sub-micron particles from surfaces on which wiring patterns are to be formed, which particles might otherwise cause short circuits between adjacent wiring patterns. Such fine cleaning is also required in processing a glass substrate to be used as a masking member, a liquid crystal plate or the like.
FIG. 4
illustrates a conventional semiconductor substrate polishing apparatus for conducting fine cleaning as well as planarization or polishing of semiconductors. The apparatus comprises a polishing section
10
, a loading/unloading section
22
, a transfer section including two transfer machines
24
a
,
24
b
, a cleaning section including three cleaning machines
26
a
,
26
b
,
26
c
, and a turning-over machine
28
. Semiconductor substrates to be polished are loaded into the loading/unlading section
22
and, then, transferred to the polishing section
10
by transfer machines
24
a
,
24
b
. Following completion of polishing in the polishing section
10
, the substrate is returned to the loading/unloading section
22
through the cleaning section where the substrate is cleaned by the cleaning machines
26
a
,
26
b
,
26
c
and finally dried.
The transfer machines
24
a
,
24
b
may be of a mobile type or of a stationary robot type having articulated arms provided with robot hands. As shown in
FIG. 5
, the polishing section comprises a turntable
12
provided on its upper surface with a polishing cloth
11
, a substrate carrier
13
for holding a substrate W and bringing it into contact with the polishing cloth
11
to subject the substrate W to polishing, and a nozzle
14
for supplying an abrasive slurry Q (for example, when polishing a dielectric layer or oxide film formed over a silicon substrate, a slurry comprising an alkali solution containing abrasive particles of a predetermined size) to the polishing cloth
11
during polishing of the substrate W.
With reference to FIGS.
6
(
a
)-
6
(
c
), the first cleaning machine
26
a
comprises a plurality of upright substrate support rollers
30
which have annular grooves at their upper ends adapted to be engaged with a peripheral edge of a substrate W to hold the substrate in a horizontal state, and which rotate about their own vertical axes to rotate the substrate at a low speed. The first cleaning machine
26
a
further includes a pair of scrub cleaning rollers
40
a
,
40
b
made of a sponge material or the like which are adapted to be engaged with upper and lower surfaces of the substrate W while it is held and rotated by the rollers
30
, respectively, to effect scrub polishing of these surfaces. Each of the scrub cleaning rollers
40
a
,
40
b
is movable in a vertical direction between a polishing position for effecting the above-stated scrub cleaning, and a retracted position.
With reference to
FIG. 8
, the second and third cleaning machines
26
b
and
26
c
each comprise a disc
36
provided on a top end of a rotational shaft
32
, which disc is provided with a plurality of substrate holding arms
34
extending radially outwardly from a peripheral edge of the disc. The holding arms
34
are provided with upright chuck portions
34
′ at their tip ends for chucking a substrate W. Further, the cleaning machines
26
b
,
26
c
comprise a scrub cleaning member
38
made of a sponge material or the like which is provided on a distal end of an arm
37
which is supported at its proximal end on a top end of a pivotal shaft
35
, and nozzles
39
,
40
for supplying cleaning liquid and pure water, respectively, to the substrate W during polishing thereof.
Upon completion of polishing of a substrate W in the polishing section
10
, the cleaning machines
26
a
,
26
b
,
26
c
effect cleaning of the substrate W as follows.
The substrate W is firstly transferred to the first cleaning machine
26
a
, in which the rollers
30
hold and rotate the substrate about its axis and, simultaneously, the scrub cleaning rollers
40
a
,
40
b
engage with the upper and lower surfaces of the substrate, respectively, to remove particles such as abrasive particles and/or substrate debris from these surfaces, while pure water and/or cleaning liquid is supplied to the surfaces.
Following scrub cleaning by the first cleaning machine
26
a
, the substrate W is transferred successively to the second and third cleaning machines
26
b
and
26
c
, where it is held and rotated by chucks
34
′ at around 100-500 rpm while the scrub cleaning member
38
engages with and sweeps the upper surface of the substrate W, while being rotated about its vertical axis, to thereby effect scrub cleaning of the upper surface. During polishing, the nozzles
39
,
40
supply pure water and/or cleaning water, to which mega-sonic vibration may be imparted. Upon completion of the scrub cleaning in the third cleaning machine
26
c
, speed of rotation of the substrate W is increased to 1500-5000 rpm to effect spin drying of the substrate, while a clean inert gas is supplied around the substrate as required. The dried substrate is thereafter returned to the loading/unloading section
22
by the transfer machine
24
b.
As shown in
FIG. 4
, the polishing apparatus is enclosed in a housing to prevent particles such as abrasive particles and substrate debris from scattering outside the apparatus and, further, the respective sections in the housing including the polishing section
10
and the cleaning section are divided by partition walls which function to prevent particles from being carried to sections other than the polishing section
10
. Further, each of the separated sections is preferably provided with an air-conditioning system for generating an air flow flowing around a substrate treated therein in a downward direction to prevent particles including abrasive particles and substrate debris from scattering outside the section.
The apparatus involves a problem in connection with the first cleaning apparatus
26
a
as follows.
In order to effect scrub cleaning of the entire upper and lower surfaces of a substrate W, the scrub cleaning rollers are brought into contact with the surfaces along a diameter of the substrate in such a manner that, as shown in FIG.
7
(
a
), the scrub cleaning rollers extend, and opposite ends thereof are positioned outside a peripheral edge of the substrate to enable the rollers to engage with the entire opposite side surfaces of the substrate during cleaning. However, as shown in FIG.
7
(
b
), a clearance gap S exists between the upper and lower scrub cleaning rollers
40
a
and
40
b
around peripheral edge B of the substrate W and, as a result, the peripheral edge, specifically a bevel portion thereof is unable to be scrub cleaned. If particles such as abrasive particles remain on the peripheral edge due to incomplete cleaning, there is a possibility that these particles will be displaced or distributed to the side surfaces of the substrate and produce defects in the substrate such as short circuits between adjacent wiring patterns.
To solve this problem, there has been proposed a cleaning device designed specifically for cleaning the peripheral edge of a substrate and adapted to be incorporated into a conventional cleaning machine. However, inclusion of such a device causes the polishing apparatus to become complicated
Chin Randall E.
Ebara Corporation
Wenderoth , Lind & Ponack, L.L.P.
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