Information
-
Patent Grant
-
6306016
-
Patent Number
6,306,016
-
Date Filed
Thursday, August 3, 200024 years ago
-
Date Issued
Tuesday, October 23, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Eley; Timothy V.
- Nguyen; Dung Van
Agents
- Hand; Francis C.
- Carella, Byrne, Bain, Gilfillan, Cecchi, Stewart & Olstein
-
CPC
-
US Classifications
Field of Search
US
- 451 44
- 451 41
- 451 42
- 451 43
- 451 168
- 451 296
- 451 11
-
International Classifications
-
Abstract
The notch polishing machine employs a plurality of polishing tapes which can be sequentially introduced into the notch of a wafer to polish both sides of the notch, i.e. the top and bottom surfaces. Each tape is pulled off a supply reel and passed into a mounting block sized to fit into the wafer notch. Each block is also mounted to be oscillated to effect a polishing action. Also, all the blocks are mounted in common to be pivoted between a position angularly disposed relative to the top of the top of the wafer and a position angularly disposed relative to the bottom of the wafer.
Description
This invention relates to a wafer notch polishing machine and method of polishing an orientation notch in a wafer.
As is known, various types of wafers, such silicon wafers, have been employed in the manufacture semi-conductor chips. Typically, the wafers have been obtained by the slicing of a solid cylindrical ingot into individual wafers. Once cut, the wafers are processed in various manners and particularly to provide a peripheral edge of a predetermined contour. Various type of grinding and polishing machines have also been employed for this purpose.
As is also known, ingots have been provided with a groove to serve for orientation of the crystalline structure of the ingot so that the wafers which are obtained have a notch in the periphery. This notch serves as a reference point for the further processing of the wafers into semi-conductor chips.
During the processing of a wafer into semi-conductor chips, small subsurface cracks or fractures on the peripheral edge of the wafer have been found to have a tendency of migrating into the wafer to such an extent that a significant portion of the wafer becomes unusable for the manufacture of the semi-conductor chips. Hence, the reason for polishing the peripheral edge of the wafer is to avoid such cracks or fractures. However, one of the problems attendant with the polishing of the peripheral edge of the wafer is the need to polish the notch. To date, the techniques which have been available have been cumbersome or not used at all.
Accordingly, it is an object of the invention to provide a relatively simple polishing machine for polishing a notch in a wafer.
It is another object of the invention to be able to polish the orientation notch of a silicon wafer in a simple economical manner.
It is another object of the invention to provide a wafer notch polishing machine that can be employed as a stand-alone unit or as a station in a wafering grinding and polishing machine.
Briefly, the invention provides a wafer notch polishing machine which employs a chuck for holding a wafer having a peripheral notch thereon, means for moving the chuck in two mutually perpendicular directions on a common plane, and a polishing unit for moving a polishing medium within the notch along an axis perpendicular to the common plane and angularly within a plane perpendicular to the common plane.
The polishing unit is constructed to move the polishing medium relative to the wafer so that the polishing medium is able to polish the peripheral edge of the wafer within the notch as well as both sides of the wafer within the notch. Depending upon the cross-sectional shape of the wafer within the notch, the polishing unit is programmed to follow the contour of the notch during the polishing operation. In particular, the polishing unit includes a means for oscillating the polishing medium during movement between the two angular positions relative to the wafer. The oscillation of the polishing medium effects a polishing of the exposed surfaces of the wafer within the notch.
In one embodiment, the polishing medium is in the form of a polishing tape mounted on a rounded nose surface of a resilient backing and , in particular, in the form of a length of polishing tape that is supplied to and around the nose surface of the backing by a suitable means so that fresh surfaces of the tape may be used for polishing. For example, this means includes a supply reel disposed on an axis parallel to the common plane of movement of the chuck for feeding the polishing tape to the backing and a take-up reel disposed on an axis parallel to the same plane for winding-up of the polishing tape from the backing. In addition, the rounded nose surface has a forward portion on a radius less than a radiused portion of the notch in the wafer.
In order to move the polishing medium within a notch of a wafer, the polishing unit has a means for pivoting the backing about an axis parallel to the common plane between a first position with the backing disposed angularly of one surface of the wafer and a second position with the backing disposed angularly of the opposite surface of the wafer.
The polishing unit may be constructed to have a plurality of polishing media disposed in spaced apart parallel relation. In this way, polishing media having different grades of grit may be employed from a course grade to a fine grade. To this end, the chuck on which the wafer is mounted is indexed to move laterally from one polishing medium to another in order to conduct a notch polishing operation.
These and other objects of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:
FIG. 1
illustrates a schematic view of a backing holding a polishing tape within a notch of a wafer in accordance with the invention;
FIG. 2
schematically illustrates one angular position of a polishing tape relative to an upper surface of a wafer during a polishing operation in accordance with the invention;
FIG. 3
schematically illustrates a view of a polishing tape held in a different angular position relative to a lower surface of the wafer in accordance with the invention;
FIG. 4
schematically illustrates a view of the polishing tape of
FIG. 1 and a
backing within the notch of a wafer during a polishing operation;
FIG. 5
schematically illustrates a plurality of backings for a plurality of polishing tapes for sequentially polishing a notch in a wafer;
FIG. 6
illustrates a plan view of a wafer notch polishing machine employing four polishing tapes in accordance with the invention;
FIG. 7
illustrates an enlarged plan view of a row of blocks of a polishing unit used for mounting the polishing tapes in the machine of
FIG. 6
;
FIG. 8
illustrates a view taken on line
8
—
8
of
FIG. 7
;
FIG. 9
illustrates a side view of a means for supplying and taking up a polishing tape for a block of a polishing unit in accordance with the invention;
FIG. 10
illustrates a cross-sectional view of a chuck for holding a wafer in position during a polishing operation;
FIG. 11
illustrates a rear view of a mounting arrangement for the tape holding blocks of the polishing unit;
FIG. 12
illustrates a part cross-sectional side view of a means for oscillating a polishing tape:
FIG. 13
illustrates an enlarged view of the oscillating means of
FIG. 12
;
FIG. 14
illustrates a side view of an arrangement for mounting a polishing tape in a block in accordance with the invention; and
FIG. 15
illustrates a view taken on line
15
—
15
of FIG.
14
.
Referring to
FIGS. 1
to
4
, in accordance with the method of the invention, a wafer
10
which is provided with an orientation notch
11
is subjected to a polishing operation by means of a polishing medium in the form of a polishing tape
12
disposed about a resilient backing
13
. During a polishing operation, the wafer
10
is held in a fixed plane, for example, a horizontal plane, as indicated in
FIGS. 2 and 3
, and is moved in two mutually perpendicular directions within the plane for reasons as explained below.
As illustrated in
FIGS. 1 and 4
, the polishing tape
12
is moved within the notch
11
of the wafer
10
along an axis perpendicular to the plane of the wafer
10
and angularly, as shown in
FIGS. 2 and 3
, within a plane perpendicular to the plane of the wafer
10
. As also illustrated, the resilient backing
13
has a rounded nose surface
14
about which the tape
12
is mounted. In addition, this rounded nose surface
14
has a forward portion on a radius less than a radiused portion of the notch
11
in the wafer
10
. Thus, during a polishing operation, the wafer
10
may be moved within the plane of the wafer in X and Y directions so that the polishing tape
12
is able to polish all the peripheral surface of the notch
11
.
As indicated in
FIGS. 2 and 3
, the backing and polishing tape are pivoted about an axis parallel to the plane of the wafer
10
between a first position with the polishing tape disposed angularly of one surface of the wafer
10
and a second position with the polishing tape disposed angularly of the opposite surface of the wafer
10
. In this way, not only is the peripheral surface of the notch
11
polished within a plane perpendicular to the plane of the wafer
10
but also any chamfered surfaces on the notch
11
may be polished.
During the polishing operation, the backing
13
is oscillated longitudinally thereof during pivoting between the various positions. In this way, a gentle polishing action is carried out on the exposed surfaces of the notch
11
.
Referring to
FIG. 5
, wherein like characters indicate like parts as above, a plurality of polishing tapes
12
may be employed in the polishing operation with each having a different size of grit from coarse to fine. As indicated, the wafer
10
may be moved from polishing tape to polishing tape
12
in a sequential manner or may be moved to only some of the polishing tapes.
Referring to
FIG. 6
, the wafer notch polishing machine
15
is constructed as a stand-alone unit, or a unit which may be incorporated into an edge grinder or other processing equipment, such as that described in pending patent application U.S. Ser. No. 09/491,812, filed Jan. 28, 2000.
The polishing machine
15
includes a chuck
16
for holding a wafer
10
having a peripheral notch
11
. For example, the chuck
16
is disposed so that the wafer
10
is mounted in a horizontal plane.
Referring to
FIG. 10
, the machine
15
also has a means
17
for moving the chuck
16
in two mutually perpendicular directions in a common plane, i.e. the horizontal plane as viewed. This means
17
will be further described below.
As shown in
FIG. 6
, the machine
15
also employs a polishing unit
18
for moving a selected one of a plurality of polishing media
19
(e.g., four) into the notch
11
of the wafer
10
, for example, as shown in
FIG. 1
, along an axis perpendicular to the plane of the wafer
10
and, as shown in
FIGS. 2 and 3
, angularly within a plane perpendicular to the plane of the wafer
10
.
The polishing unit
18
includes a mounting arrangement
20
for the polishing tapes
19
and a tape supply and removal means
21
for supplying the tapes
19
to the mounting arrangement
20
.
As indicated in
FIGS. 6 and 11
, the mounting arrangement
20
is mounted on a tub
22
in which the chuck
16
for holding the wafer
10
is also mounted. The mounting arrangement
20
includes a main piece
23
which extends across and within the tub
22
and is mounted on opposite ends for pivoting about a horizontal axis
24
(see FIGS.
8
and
11
).
As shown in
FIG. 11
, one end of the main piece
23
is bifurcated and clamped over a pivot shaft
25
by bolts
26
for pivoting therewith. The shaft
25
passes through a bearing support
27
in which the shaft
25
is rotatably mounted via ball bearings
28
or the like. The shaft
25
is coupled to a pivot drive assembly (not shown) so that the shaft may be oscillated back and forth in a programmed manner by a suitable computer drive (not shown). The opposite end of the main piece
23
has a pair of legs
29
each of which is bifurcated and clamped by bolts
26
to a pivot shaft or pin
30
, which is rotatably mounted via suitable bearings
31
in a second bearing support
32
.
The two bearing supports
27
,
32
which pivotally support the main piece
23
are secured in suitable fashion to a main support
33
which extends across the tub
22
and is fixed in a stationary manner to the base of a tub
22
in a manner not shown.
Referring to
FIG. 11
, a guide plate
34
is secured by a plurality of bolts
35
to the underside of the main piece
23
and is also coupled to the respective pivot shafts
25
,
30
by a bifurcated section and clamping screws
36
. The guide plate
34
carries a pair of bars
37
, one on each side, which are secured thereto via suitable bolts
38
. Each bar
37
includes a plurality of recesses
39
in the upper surface, each of which receive a spring
40
for purposes as described below.
The guide plate
34
has four vertical slots within an intermediate area for receiving four blocks
41
in a vertically slidable manner. Referring to
FIGS. 14 and 15
, each block
41
is formed of two substantially U-shaped half-blocks
42
which are secured in back-to-back fashion by a pair of clamping screws
43
. Each half-block
42
has a rectangular recess
44
on the outside to receive the guide plate
34
as indicated in FIG.
12
.
As indicated in
FIGS. 14 and 15
, a pair of keys
45
are provided in slots at the top and bottom of each half-block
42
for keying the half blocks
42
together and for guiding a polishing tape
19
therebetween. Each half-block
42
also includes a recess
46
facing the other half-block
42
in order to receive a length of an elastomeric pneumatic tube
47
which is folded over on itself and which is connected to a suitable source of air pressure or the like (not shown). As indicated in
FIG. 14
, the pneumatic tube
47
extends to near the top of the block
41
before being folded over on itself to extend downwardly. The terminal end of the tube
47
is sealed in any suitable fashion, for example, by means of a plug (not shown).
Each block
41
also has a pair of end-caps
48
, one of which envelopes the tops of the half-blocks
42
and the other of which envelopes the bottoms of the half-blocks
42
. As indicated in
FIG. 14
, the lower end-cap
48
is provided with a slot
49
through which the elastomeric pneumatic tube
47
passes. Each end-cap
48
is secured as by a pair of screws
50
to the respective half-blocks
42
, as indicated in FIG.
15
. Each end-cap
48
is also provided with a notch
51
on an inside wall for receiving a soft resilient tube
52
. Typically, the tube
52
, or an equivalent roller, is mounted to be freely rollable within the notches
51
of the end-caps
48
.
Each block
42
is constructed so that a polishing tape
19
is looped over the outside of the soft resilient tube
52
with the two ends of the tape
19
disposed between the two lengths of pneumatic tubing
47
and between the two half-blocks
42
. The mounting is such that the tape
19
may be readily pulled in either direction so as to dispose a fresh section of polishing tape
19
over the soft resilient tube
52
. However, upon inflation of the elastomeric pneumatic tubing
47
under an internal pressure, as from a source of pressure, the two ends of the polishing tape
19
are clamped between the two sections of tubing
47
so that further motion of the tape
19
is not permitted.
As schematically illustrated in
FIGS. 7 and 12
, the soft resilient tube
52
in a block
41
is positioned to move into the notch
11
of the wafer
10
when the wafer
10
is brought into position for polishing of the notch
11
.
Referring to
FIGS. 11
,
12
and
13
, the polishing unit
18
is also provided with a means
54
for oscillating the blocks
41
during a polishing operation.
As shown in
FIG. 11
, the means
54
for oscillating the blocks
41
includes a motor
55
which is mounted via a mounting block
56
on the main piece
23
via suitable screws. In this way, the motor
55
moves with the main piece
23
during pivoting of the main piece
23
. The motor
55
includes a cam shaft
57
which extends through the main piece
23
over the positions of the four blocks
41
. This cam shaft
57
is provided with recesses
58
(see
FIG. 13
) coincident with the positions of the blocks
41
. In addition, each consecutive recess
58
is disposed on an opposite side of the cam shaft
57
from the next. That is to say, the cam shaft
57
has a pair of recesses
58
on one side and a pair of recesses 180° apart on the opposite side. Each recess
58
, as indicated in
FIG. 13
, receives a ball bearing
59
and, particularly, the inner race ring
60
of the ball bearing
59
. The outer race ring
61
of each bearing
59
is disposed in contact with the upper end-cap
48
of a respective block
41
.
As indicated in
FIGS. 11
,
12
and
13
, an elongated key
62
is disposed within the inner race ring
60
of each bearing
59
and is secured to the cam shaft
57
by a pair of lock screws
63
. The key
62
and screws
63
serve to lock the bearing
59
to the cam shaft
57
in an offset or eccentric manner. Thus, as the cam shaft
57
rotates, the inner race
60
ring of the bearing
59
rotates with the cam shaft
57
in an eccentric manner about the axis of the cam shaft
57
. As a result, the bearing
59
causes the block
41
with which the bearing
59
is in contact to move down within the guide plate
34
against the biasing force of the springs
40
which bear against the lower end-cap
48
of the block
41
as well as allowing the block
41
to move up within the guide plate
34
under the force of the springs
40
in an oscillating manner.
As shown in
FIG. 11
, the cam shaft
57
is rotatably mounted within bearings
64
which are held in mounting blocks
65
secured to the main piece
23
.
Upon actuation of the motor
55
, the cam shaft
57
rotates causing the four bearings
59
to act as cams to move the blocks
41
up and down within the guide plate
23
. The arrangement of the bearings
59
is such that two blocks
41
are moved downwardly while two other blocks are moved upwardly via the resilient mounting afforded by the springs
40
.
Referring to
FIG. 12
, each resilient tube
52
of a block
41
serves as a rounded nose surface to fit within the notch
11
of the wafer
10
. Further, the resiliency of the tube
52
allows for small deviations in pressure during contact between the wafer
10
and the polishing tape
19
. To this end, the resilient tube
52
is of a radius which is less than the radius of the notch
11
.
Referring to
FIG. 10
, the mounting arrangement
20
is pivotal on the axis of the pivot shafts
25
,
30
(see
FIGS. 8 and 11
) so as to move between a first position, as shown in dotted line, with a block
41
disposed angularly of the top surface of the wafer
10
and a second position, also as shown in dotted line, with the block
41
disposed angularly of the opposite bottom surface of the wafer
10
. Typically, each end position of a block
41
defines an included angle of 10° with the plane of the wafer
10
.
Referring to
FIG. 6
, the means
21
for delivering the polishing tapes
19
to the respective blocks
41
includes a plurality of supply reels
66
, i.e., four reels, for supplying the polishing tapes
19
to the respective blocks
41
and four take-up reels
67
. As indicated, the four supply reels
66
are mounted on a common axis which is parallel to the plane of the wafer. Likewise, the four take-up reels
67
are mounted on a common axis parallel to the plane of the wafer
10
. Thus, each tape
19
is initially played off a supply reel
66
in a horizontal plane and is then twisted into a vertical plane for passage through a respective block
41
. Likewise, each tape
19
is again twisted into a horizontal plane when fed back to a take-up reel
67
.
Referring to
FIG. 9
, the supply reels
66
and take-up reels
67
are mounted on a common carriage
68
which, in turn, is mounted on a slide bearing
69
to move along bearing rails
70
for movement in a horizontal plane towards and away from the tub
22
. Movement of the carriage
68
is effected via a pneumatic cylinder actuator arrangement
71
.
The purpose of the movement of the carriage
68
from a fixed “home” position is to accommodate and provide the slack necessary in the tapes
19
to allow movement of the blocks
41
between the angular polishing positions relative to the top and bottom surfaces of a wafer
10
being polished. That is to say, as a block
41
is moved from a position perpendicular to the plane of the wafer
10
to an angular position relative to the plane of the wafer
10
, the carriage
68
is moved to advance from the “home” position towards the tub
22
to prevent stretching of the tapes
19
. Conversely, as a block is moved back to the “home” position perpendicular to the plane of the wafer, the carriage
68
moves backwardly away from the tub
22
.
The carriage
68
is held in the fixed “home” position while the block
41
is positioned stationary and perpendicular to the plane of the wafer
10
when a fresh section of polishing tape from the tape supply reel
66
is fed to a block
41
. Should there be slack in the tapes, the carriage
68
would be moved in a direction away from the tub
22
to take up the slack in the tapes and assure uniform positioning of the fresh section of each tape.
As also shown in
FIG. 9
, a tape containment and locking mechanism
69
′ is mounted on the carriage
68
in order to contain and hold the lengths of tape
19
in proper position relative to the reels
66
at times when the tapes are slackened. As illustrated, the locking mechanism
69
′ employs a pneumatic cylinder actuator
70
′ which moves a set of four rollers
72
into contact with a like set of stationary rollers
72
′ so that a tape
19
is firmly held between each pair of rollers
72
,
72
′. In addition, a plurality of fixed partitions
72
″ are positioned between the tapes
19
and along the outer edge of the outbound tapes to contain the tapes
19
laterally, i.e. the rollers
72
,
72
′ contain and clamp the tapes
19
vertically while the partitions
72
″ keep the tapes
19
separated and aligned horizontally. In this way, the containment and locking mechanism
69
′ serves to prevent a tape
19
from being inadvertently pulled off a supply reel
66
or slipping out of position relative to the reels
66
when the tapes
19
are slackened.
The containment and locking mechanism
69
′ is actuated after the tapes
19
have been locked in the blocks
41
via the pneumatic tubes
47
and prior to moving the carriage
68
to slacken the tapes
19
.
Referring to
FIG. 10
, the chuck
16
is constructed in a suitable manner so as to hold a wafer
10
in place under vacuum. In addition, the chuck
16
is mounted to move via the means
17
in two directions in the plane of the wafer
10
, for example, in an X direction towards a block
41
of the polishing unit
18
and a Y direction perpendicular to the X direction. Movement of the chuck
16
is controlled by a suitable central processing unit and is coordinated with the movements of a polishing block
41
so as to carry out a polishing operation.
The chuck
16
is also provided with a sensing means
73
to sense the point at which a wafer
10
is first brought into contact with a polishing tape
19
on a block
41
. In this regard, the sensing means
73
is mounted on the chuck
16
at a point opposite a point at which the wafer
10
contacts the polishing unit
18
to sense an increase in resistance to further movement of the chuck
16
towards the polishing unit
18
.
As illustrated, the sensing means
73
includes a bracket
74
which is secured to the means
17
for moving the chuck
16
on a side opposite the polishing unit
18
. This bracket
74
is bifurcated to form two legs
75
,
76
, each of which has a set screw
77
,
78
threaded therein in facing relation. A mounting plate
79
is also secured to the chuck
16
and carries a pair of load cells
80
thereon. Each load cell
80
is positioned to an opposite side of the bracket
74
(see FIG.
7
). In addition, a strike bar
81
is secured to and connects the pair of load cells
80
and passes between the two legs
75
,
76
of the bracket
74
. In use, the internally disposed set screw
77
is permanently located in place while the exposed set screw
78
is used to lightly clamp the strike bar
81
between the set screws
77
,
78
.
The chuck
16
is mounted to the x-y moving means
17
via linear roller slide bearings
82
. This assures maximum support of the chuck
16
with minimal frictional influence from the bearings on the contact force as detected by the load cells
80
.
When the means
17
moves the chuck
16
to move a wafer
10
against a polishing tape
19
on a block
41
, the adjustable set screw
78
biases the against the strike bar
81
. When the wafer
10
contacts the polishing tape
19
, the contact force is routed back through the load cells
80
which, in turn, emit a corresponding signal to the central processing unit.
Sensing the contact of the wafer
10
against the tape
19
is important not only for controlling the tape pressure to optimize the polishing operation but also as a preliminary calibration tool to locate the centerline positions of the four blocks
41
relative to the “home” positions of the means
17
for the x-y movements of the chuck
16
. This calibration would necessarily be done any time the blocks
41
are replaced or repaired for maintenance, at the very least. Calibration may also be required to center the notch
11
on the first block
41
with each wafer processed.
The central processing unit of the machine
15
serves to control and coordinate the motions of the carriage
68
for the tape delivering means
21
, the chuck
16
holding the wafer
10
and the pivot drive assembly for pivoting the blocks
41
about the wafer
10
. This central processing unit may also control the motor
55
for rotating the cam shaft
57
which oscillates the blocks
41
within the guide plate
34
.
In operation, the polishing unit
18
is first set up with the polishing tapes
19
positioned in the blocks
41
ready for a polishing operation to commence. A wafer
10
is then placed on the chuck
16
automatically by a suitable delivery device or by hand and then the chuck
16
is moved towards the polishing unit
18
(FIG.
6
). Typically, the wafer
10
is moved towards the polishing unit
18
to position the notch
11
of the wafer
10
against the first polishing block
41
of the polishing unit
18
.
As the wafer
10
comes into contact with a tape
19
on the first polishing block
41
, the sensing means
73
(
FIG. 10
) senses the contact and emits a corresponding signal to the central processing unit (not shown). Depending on the signal the chuck
16
may be stopped or moved towards or away from the wafer lO in order to position the wafer
10
relative to the tape
19
under the desired contact force for a polishing operation. At the time that the wafer
10
abuts a tape
19
, the resilient tube
52
behind the tape
19
absorbs any shock.
Thereafter, the central processing unit (not shown) effects an oscillating movement of the block
41
in contact with the wafer
10
to begin a polishing operation. In addition, the central processing unit effects small movements of the wafer
10
in each of the x and y directions relative to the block
41
so that the tape
19
is able to polish the contour of the notch
11
in the wafer
10
(FIG.
4
).
The central processing unit also effects a pivoting movement of the block
41
, for example, into the upper dotted line position shown in FIG.
10
. During this motion, the block
41
continues to oscillate under the influence of the cam shaft
57
so that the upper surface of the notch
11
of the wafer is polished. Again, the wafer
10
may be moved in small x and y directions relative to the block
41
to enhance the polishing operation.In addition, the carriage
68
is moved toward the tub
22
and the polishing unit
18
to avoid stretching of the polishing tapes
19
.
The block
41
is then pivoted into the lower dotted line position shown in
FIG. 10
to complete the polishing operation. At this time the carriage
68
is moved away from the polishing unit
18
to avoid slack from being introduced in the tapes
19
and then moved toward the polishing unit
18
as the block
41
pivots below the plane of the wafer
10
.
Thereafter, the chuck
16
is moved away from the polishing unit
18
and indexed to align the notch
11
of the wafer
10
with the next block
41
(FIG.
6
). Similar motions of the machine components are then repeated to perform another polishing operation but with the different size grit of the second polishing tape
19
. Indexing of the wafer
10
is repeated until the desired polishing effect has been obtained. The chuck
16
is then moved away from the polishing unit
18
and the wafer
10
moved to another processing operation.
Thereafter, if the sections of the tapes
19
are not reuseable, fresh sections of the tapes
19
are moved into the blocks
41
. At this time, the locking mechanism
69
′ (
FIG. 9
) is actuated to release the tapes
19
so that the tapes
19
may be incremented off the supply rolls
66
an amount sufficient to present fresh surfaces. Next, the compressed air supply to the pneumatic tube
47
of each block
41
is terminated to unclamp the tape
19
therein (FIG.
15
). The take-up reels
67
are then indexed via a suitable motor (not shown) by the central processing unit for each to take-up a determined amount of tape
19
. During this time each tape
19
slides through a respective block
41
to present a fresh polishing surface over the resilient tube
52
. Thereafter, the pneumatic tubes
47
are again inflated to clamp the tapes
19
in place and the locking mechanism
69
′ actuated to again clamp the tapes
19
.
The invention thus provides a relative simple machine which can be used to polish the notch in a wafer in an economic manner. Further, the invention provides a machine which can be used in a stand-alone manner to polish a notch in a wafer or which can be incorporated into a more complex machine for polishing the entire periphery of a wafer.
The machine may also be adapted for other types of uses than polishing a notch in a wafer. For example, the machine may be used to polish the entire periphery of a wafer or the machine may be used to remove a bead of material from a peripheral edge of a wafer. For example where a wafer has been processed and has one of more layers of material thereon, the edge of such a wafer may be placed in the machine so that any bead of material at the edge of the wafer may be ground off.
Also, the machine may be used to grind or polish two opposite surfaces at the edge of any substrate due to the ability to pivot the polishing tapes from one side of a substrate to the opposite side while the tapes are oscillated. In a similar sense, depending on the shape of the substrate, a plurality of tapes may be brought into contact with the substrate rather than only one tape. For example, where the substrate has a straight or contoured edge two or more tapes may be brought into contact with the edge to effect a polishing or grinding operation.
Claims
- 1. A wafer notch polishing machine comprisinga chuck for holding a wafer having a peripheral notch thereon; means for moving said chuck in two mutually perpendicular directions in a common plane; a polishing unit for moving a polishing medium within the notch along an axis perpendicular to said common plane and angularly within a plane perpendicular to said common plane.
- 2. A wafer notch polishing machine as set forth in claim 1 wherein said common plane is a horizontal plane.
- 3. A wafer notch polishing machine as set forth in claim 1 wherein said polishing unit includesat least one block having a rounded nose surface with said polishing medium thereon for fitting into a notch of a wafer held on said chuck; and means for pivoting said block about an axis parallel to said common plane between a first position with said block disposed angularly of one surface of a wafer on said chuck and a second position with said block disposed angularly of an opposite surface of the wafer on said chuck.
- 4. A wafer notch polishing machine as set forth in claim 3 wherein each said position of said block defines an included angle of 10° with said common plane.
- 5. A wafer notch polishing machine as set forth in claim 3 wherein said polishing unit further comprises means for oscillating said block longitudinally thereof during pivoting of said block between said positions.
- 6. A wafer notch polishing machine as set forth in claim 3 wherein said rounded nose surface has a forward portion on a radius less than a radiused portion of a notch in a wafer on said chuck.
- 7. A wafer notch polishing machine as set forth in claim 3 wherein said polishing unit further comprises a plurality of said blocks disposed in spaced-apart parallel relation.
- 8. A wafer notch polishing machine as set forth in claim 3 wherein said polishing medium is a polishing tape disposed on said rounded nose surface.
- 9. A wafer notch polishing machine as set forth in claim 8 wherein said polishing unit further comprises means for delivering said polishing tape to said block.
- 10. A wafer notch polishing machine as set forth in claim 9 wherein said means for delivering a polishing tape includes a supply reel disposed on an axis parallel to said common plane for feeding the polishing tape to said block, and a take-up reel disposed on an axis parallel to said common plane for winding-up of the polishing tape from said block.
- 11. A wafer notch polishing machine as set forth in claim 10 which further comprises a clamping means between said reels and said block for clamping said tape thereat.
- 12. A machine comprisingat least one block having a nose surface for receiving a polishing medium thereon for polishing an edge of a workpiece; means for pivoting said block about a plane of the workpiece between a first position with said block disposed angularly of said plane on one side of the workpiece and a second position with said block disposed angularly of said plane on an opposite side of the workpiece; and means for oscillating said block longitudinally thereof during pivoting of said block between said positions.
- 13. A machine as set forth in claim 12 wherein said means for pivoting said block includes a main piece disposed for pivoting about a fixed axis and having said block slidably mounted thereon for movement longitudinally thereof.
- 14. A machine as set forth in claim 13 wherein said means for oscillating said block includes at least one spring disposed between said block and said main piece, a rotatable cam shaft parallel to and mounted on said main piece and a cam on said cam shaft in contact with said block on a side opposite said spring.
- 15. A machine as set forth in claim 14 wherein said means for oscillating said block further includes a motor mounted on said main piece and drivingly connected to said cam shaft for rotating said cam shaft.
- 16. A machine as set forth in claim 13 having a plurality of said blocks mounted on said main piece.
- 17. A machine as set forth in claim 12 wherein said block includes a pair of half blocks for guiding a folded over polishing tape having the polishing medium thereon therebetween and a tube rotatably disposed between said half blocks for looping of the polishing tape thereover.
- 18. A machine as set forth in claim 17 wherein said tube is resilient.
- 19. A machine as set forth in claim 17 which further comprises an elastomeric pneumatic tube disposed in folded over relation between said half blocks for passage of the folded over tape therebetween, said pneumatic tube being inflatable to clamp the tape therebetween.
- 20. method of polishing an orientation notch in a wafer, said method comprising the steps ofholding a wafer having a peripheral notch therein on a fixed plane; moving the wafer in two mutually perpendicular directions in said plane; moving a polishing medium within the notch along an axis perpendicular to said fixed plane and angularly within a plane perpendicular to said fixed plane during movement of the wafer in said fixed plane.
- 21. A method as set forth in claim 20 which further comprises the step of pivoting the polishing medium about an axis parallel to said fixed plane between a first position with the polishing medium disposed angularly of one surface of the wafer and a second position with the polishing medium disposed angularly of an opposite surface of the wafer.
- 22. A method as set forth in claim 21 wherein each said position defines an included angle of 10° with said fixed plane.
- 23. A method as set forth in claim 21 which further comprises the step of oscillating the polishing medium longitudinally thereof during pivoting between said positions.
US Referenced Citations (5)