Title: Device for polishing outer peripheral edge of semiconductor wafer
Abstract: A polishing machine for a peripheral edge of a semiconductor wafer comprises a rotary mechanism 2 which rotates a stack 1 of semiconductor wafers 4 mounted thereon, and a polishing mechanism 3 which is arranged to be movable in the radial direction of the rotary mechanism 2 and polishes the peripheral edges of the rotating semiconductor wafers 4 by means of contactless polishing. Minute gaps s are formed between the rotary column 10 of the polishing mechanism 3 and the stack 1 of semiconductor wafers 4, and polishing solution is drawn into these minute gaps s. The peripheral edges of the semiconductor wafers 4 are polished by means of contactless polishing, using polishing abrasive particles included in polishing solution.
Patent Number: 6,921,455 Issued on 07/26/2005 to Nakano, et al.
| Inventors:
|
Nakano; Teruyuki (Hiroshima, JP);
Kozawa; Yasuhiro (Hiroshima, JP);
Tambo; Hitoshi (Hiroshima, JP)
|
| Assignee:
|
Kabushiki Kaisha Ishii Hyoki (Hiroshima, JP)
|
| Appl. No.:
|
856402 |
| Filed:
|
October 18, 2000 |
| PCT Filed:
|
October 18, 2000
|
| PCT NO:
|
PCT/JP00/07229
|
| 371 Date:
|
October 12, 2001
|
| 102(e) Date:
|
October 12, 2001
|
| PCT PUB.NO.:
|
WO01/28739 |
| PCT PUB. Date:
|
April 26, 2001 |
Foreign Application Priority Data
| Oct 18, 1999[JP] | 11-295847 |
| Current U.S. Class: |
156/345.11; 156/345.12; 451/66 |
| Intern'l Class: |
C23F 001/00; H01L 021/30.6 |
| Field of Search: |
156/34512,345.13,345.17,345.18,345.23
451/63,66,44,106,93,36,40
43/691,692
134/13,135,902
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Hassanzadeh; P.
Assistant Examiner: Culbert; Roberts
Attorney, Agent or Firm: J.C. Patents
Claims
1. A polishing machine for a peripheral edge of a semiconductor wafer, said machine comprising:
a rotary mechanism for holding a semiconductor wafer while rotating it in a prescribed
direction;
a rotary body which rotates relative to the semiconductor wafer while maintaining
a prescribed gap from a periphery of said semiconductor wafer, having a rotary
axis which is set in the same direction as the rotary axis of said semiconductor
wafer, so that the rotary body and the semiconductor wafer are not in contact with
each other during a complete polishing process;
a polishing solution channel for channeling the flow of polishing solution to
said gap; and
a polishing solution supply portion for supplying the polishing solution to said
polishing solution channel;
wherein said polishing solution is drawn into said gap between the peripheral
edge of said semiconductor wafer and said rotary body, and polishing abrasive particles
in said polishing solution collide with the peripheral edge of said semiconductor
wafer to conduct non-contact polishing of the peripheral edge of said semiconductor
wafer.
2. A polishing machine for a peripheral edge of a semiconductor wafer, said machine comprising:
a rotary mechanism for holding a semiconductor wafer while rotating it in a prescribed
direction;
a rotary body which rotates relative to the semiconductor wafer while maintaining
a prescribed gap from a periphery of said semiconductor wafer, having a rotary
axis which is set in the same direction as the rotary axis of said semiconductor
wafer, so that the rotary body and the semiconductor wafer are not in contact with
each other during a complete polishing process;
a polishing solution tank for immersing said rotary mechanism and said rotary
body in polishing solution; and
a polishing solution circulation portion for circulating the polishing solution
in and out of said polishing solution tank;
wherein said polishing solution is drawn into said gap between the peripheral
edge of said semiconductor wafer and said rotary body, and polishing abrasive particles
in said polishing solution collide with the peripheral edge of said semiconductor
wafer to conduct non-contact polishing of the peripheral edge of said semiconductor
wafer.
3. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 1, wherein said rotary mechanism holds a plurality of semiconductor wafers
in a stacked state.
4. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 1, wherein dynamic pressure generating grooves are formed on the peripheral
surface of said rotary body facing the periphery of said semiconductor wafer.
5. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 1, wherein a magnet is installed in said rotary body and a magnetic polishing
solution is used as said polishing solution.
6. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 1, wherein at least the peripheral surface of said rotary body facing
the periphery of said semiconductor wafer is formed of an elastic material with
a hardness in the range of 7-40 Hs.
7. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 2, wherein said rotary mechanism holds a plurality of semiconductor wafers
in a stacked state.
8. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 2, wherein dynamic pressure generating grooves are formed on the peripheral
surface of said rotary body facing the periphery of said semiconductor wafer.
9. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 2, wherein a magnet is installed in said rotary body and a magnetic polishing
solution is used as said polishing solution.
10. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 2, wherein at least the peripheral surface of said rotary body facing
the periphery of said semiconductor wafer is formed of an elastic material with
a hardness in the range of 7-40 Hs.
11. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 1, wherein the rotary mechanism holds a plurality of semiconductor wafers
forming a cylindrical shaped stack, the rotary body is accommodated in a housing,
the housing has a contact surface conforming to a circumference of the cylindrical
shaped stack of the semiconductor wafers, an aperture is formed in the contact
surface to expose the semiconductor wafers to the rotary body.
12. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 11, wherein the contact surface of the housing is in sealed contact with
the circumference of the cylindrical shaped stack of the semiconductor wafers.
13. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 11, wherein the cylindrical shaped stack comprises disc shaped spacers
to separate each of the semiconductor wafers, the diameter of the disc shaped spacers
is larger than the diameter of the semiconductor wafers.
14. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 1, wherein the rotary mechanism holds a plurality of semiconductor wafers
forming a cylindrical shaped stack, the rotary body has a hollow cylindrical shape
for accommodating the cylindrical shaped stack of the semiconductor wafers, said
prescribed gap is formed between an inner surface of the hollow cylindrical shaped
rotary body and a circumference of the cylindrical shaped stack of the semiconductor wafers.
15. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 14, wherein a dynamic pressure groove is formed on the inner surface of
the hollow cylindrical shaped rotary body, extending in the direction of the rotary
axis of the hollow cylindrical shaped rotary body.
16. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 14, further comprising a fixed hollow cylindrical body for accommodating
the hollow cylindrical shaped rotary body, a passage is formed between an outer
surface of the hollow cylindrical shaped rotary body and an inner surface of the
fixed hollow cylindrical body for providing the polishing solution.
17. The polishing machine for a peripheral edge of a semiconductor wafer according
to claim 14, wherein the hollow cylindrical shaped rotary body comprises n-polar
and s-polar magnets alternatively arranged on its inner surface.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a polishing machine for polishing the peripheral
edge of a semiconductor wafer.
The peripheral edges of semiconductor wafers made from silicon and the like are
chamfered, but in recent years, further polishing of the peripheral edge has come
to be conducted in order to prevent particle formation on the peripheral edge,
imperfections arising during handling, and the like. Edge processing methods are
known, for example, a method for rotating a semiconductor wafer, and pressing a
similarly rotating polishing pad thereto, while supplying polishing solution, as
described in Japanese Patent Laid-Open Publication No. Hei. 11-104942, and a method
for pressing a rotating polishing pad to a plurality of stacked semiconductor wafers,
while supplying polishing solution thereto, as described in Japanese Patent Laid-Open
Publication No. Hei. 05-182939.
Chamfering processes of the peripheral edge of semiconductor wafers have
had the following problems, due to the fact that the chamfering radius is small
and the chamfering corners are steeply inclined: even with a flexible polishing
pad it is unfeasible to obtain uniform contact with the surface of the peripheral
edge, making it difficult to obtain highly precise polishing, and because only
a small part of the surface of the pad is in contact with the edge surface, for
instance a point or a line, the polishing process is inefficient. Additionally,
constant adjustments were required in order to maintain favorable polishing conditions,
including changing the polishing pad at appropriate intervals.
SUMMARY OF THE INVENTION
In light of the above, it is an object of the present invention to provide a
polishing
machine for a peripheral edge of a semiconductor wafer, capable of highly precise,
uniform, highly efficient, and stable polishing.
In order to achieve the above-mentioned object, the present invention provides
a construction comprising: a rotary mechanism for holding a semiconductor wafer
while rotating it in a prescribed direction; a rotary body which rotates relative
to the semiconductor wafer while maintaining a prescribed gap from a periphery
thereof, having a rotary axis which is set in the same direction as the rotary
axis of the semiconductor wafer; a polishing solution channel for channeling the
flow of polishing solution to said gap; and a polishing solution supply portion
for supplying polishing solution to the polishing solution channel.
Additionally, in order to achieve the above-mentioned object, the present
invention provides a construction comprising: a rotary mechanism for holding a
semiconductor wafer while rotating it in a prescribed direction; a rotary body
which rotates relative to the semiconductor wafer while maintaining a prescribed
gap from a periphery thereof, having a rotary axis which is set in the same direction
as the rotary axis of the semiconductor wafer; a polishing solution tank for immersing
the rotary mechanism and rotary body in polishing solution; and a polishing solution
circulation portion for circulating the polishing solution in and out of the polishing
solution tank.
Since according to the present invention, contactless polishing is conducted
by drawing polishing solution into the gap between the peripheral edge of semiconductor
wafer and the rotary body, the peripheral edge of semiconductor wafer can be polished
in a highly precise and uniform manner. Additionally, because the polishing pad
of existing methods is not needed, polishing pad changing and adjustments are not
necessary, allowing for a stable polishing process.
In the above-mentioned construction, the rotary mechanism holds one semiconductor
wafer, or a plurality thereof in a stacked state. In the first case, the single
semiconductor wafer held in the rotary mechanism is polished (the so-called single-wafer
method), and in the second case, the plurality of semiconductor wafers held in
the rotary mechanism are polished in turn (the so-called batch method).
Additionally, in the above-mentioned construction, a dynamic pressure
generating grooves can be formed on the peripheral surface of the rotary body,
facing the periphery of the semiconductor wafer. Because, according to this construction,
the flow speed of polishing solution is increased through the dynamic pressure
effect of the dynamic pressure generating grooves, the polishing efficiency is increased.
Additionally, in the above-mentioned construction, a magnet may be
installed in the rotary body, and a magnetic polishing solution may be used as
the polishing solution. Because, according to this construction, the magnetic polishing
solution is confined by the magnet of the rotary body, the polishing efficiency
is increased.
Additionally, in the above-mentioned construction, at least the peripheral
surface of the rotary body facing the periphery of the semiconductor wafer may
be formed of an elastic material with a hardness in the range of 7-40 Hs. The entire
rotary body may be formed of an elastic material having a hardness of 7-40 Hs,
and only the outer surface layer of the rotary body, including the peripheral surface,
may be formed of an elastic material having a hardness of 7-40 Hs. The elastic
material having a hardness of 7-40 Hs may be, for example, a rubber such as chloroprene
rubber, or alternatively a synthetic resin formed into a porous (spongy) state
by such means as expansion molding. The term "Hs" used here refers to hardness
as measured by a JIS-standard Type A spring hardness tester (used to measure the
hardness of rubber). This is widely used to express the hardness of a material
in order to evaluate the elasticity of such elastic materials as rubber.
In the polishing machine of the present invention, the polishing efficiency and
coarseness of the polished surface are influenced by such factors as polishing
speed (the relative rotating speed of the semiconductor wafer and the rotary body),
the flow speed and pressure of polishing solution in the above-mentioned gaps,
the viscosity of the polishing solution, and the concentration and diameter of
abrasive particles in the polishing solution. However, by forming at least the
peripheral surface of the rotary body from an elastic material with a hardness
of 7-40 Hs, variations in the values of the above-mentioned factors are absorbed
by the appropriate elasticity of the rotary body peripheral surface, making it
possible to constantly obtain a stable polishing efficiency and level of polished
surface coarseness. Additionally, during the polishing process, the polishing speed
may be changed (for example, polishing with a relatively high polishing speed for
a prescribed length of time from the start of the polishing process, then polishing
at a relatively lower polishing speed for the remainder of the polishing process)
without changing the semiconductor wafer holding status, the polishing solution,
or the like, enabling highly precise, highly efficient polishing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a polishing machine for a peripheral edge of
a semiconductor wafer according to a first embodiment of the present invention.
FIG. 2 shows the polishing surface of the polishing mechanism according to the
first embodiment of the present invention.
FIG. 3 shows the operational states of the polishing mechanism according to
the first embodiment of the present invention.
FIG. 4 shows an example of the polishing machine according to the first embodiment
of the present invention, using differently shaped spacers.
FIG. 5 is a perspective view of a polishing machine for a peripheral edge of
a semiconductor wafer according to a second embodiment of the present invention.
FIG. 6 is a perspective view of a polishing machine for a peripheral edge of
a semiconductor wafer according to a third embodiment of the present invention.
FIG. 7 shows a magnetic polishing mechanism of a polishing machine for a peripheral
edge of a semiconductor wafer according to a fourth embodiment of the present invention.
FIG. 8 is a perspective view of a polishing machine for a peripheral edge of
a semiconductor wafer according to a fifth embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the current invention will be described in detail
below, making reference to the drawings.
As shown in FIG. 1, the polishing machine for a peripheral edge of a semiconductor
wafer according to the first embodiment of the present invention comprises a rotary
mechanism
2 on which is mounted and rotated a stack
1 of semiconductor
wafers
4, and a polishing mechanism
3 which can be moved as desired
along the radial direction of the rotary mechanism
2, and which polishes
the peripheral edges of the rotating semiconductor wafers
4 via a contactless
polishing process.
The peripheral edges of semiconductor wafers
4, having for example the
shapes of circular plates, are chamfered as necessary, and notches (omitted from
the drawing) are formed on the periphery at prescribed locations. The stack
1
of the semiconductor wafers
4 is aligned with the notches, and formed by
placing spacers
5 between each semiconductor wafer
4. Note that the
stack
1 of semiconductor wafers
4 is preferably provided with spacers
5 on the top and the bottom thereof, in order to keep from marking the surface
of the wafers
4 when the stack
1 is locked into the rotary mechanism
2.
Rotary mechanism
2 comprises a turntable
6 on which is mounted
the stack
1 of semiconductor wafers
4, and a locking piece
7
for pressing the stack
1 of semiconductor wafers
4 onto the turntable
6.
Polishing mechanism
3 has as the chief elements of its construction
a housing
11, and a rotary body freely rotating and accommodated in the
housing
11, for example a rotary column
10. This polishing mechanism
3 is mounted on a slide rail
8 installed in the radial direction
of the rotary mechanism
2, and can move freely along the slide. Additionally,
the elasticity means not shown in the drawing constantly presses the polishing
mechanism
3 against the rotary mechanism
2 in the direction of the
rotary mechanism
2 center through a prescribed level of elastic pressure.
As shown in FIG. 2, the housing
11 is provided with a contact surface
13,
for example an approximately rectangular parallelepiped member on the side facing
the rotary mechanism
2. The contact surface
13 contacts the periphery
of the stack
1 along the contour of the outer surface thereof. The contact
surface
13 has a curved inner side shape in order to conform to the outer
shape of the stack
1 of semiconductor wafers
4. An aperture
12
is formed on the contact surface
13 in order to expose the rotary column
10 inside the housing
11. The periphery of the aperture
12
is sealed in order to keep the polishing solution from leaking.
The rotary column
10, for example a cylindrical member formed from metal
or other materials having necessary rigidity, is accommodated within the housing
11 so that it can rotate freely, rotating on the vertical axis under the
power of freely chosen rotary drive means. The outer surface
10a of
the rotary column
10 is exposed at the aperture
12, and the polishing
solution flow channel
9 narrows at the aperture
12. As shown in FIG.
3, the rotary column
10 faces the stack
1 at the aperture
12
via a minute gap s, and rotates in the opposite direction relative thereto.
As shown in FIG. 3, the housing
11 is equipped with the polishing solution
flow channel
9 which channels polishing solution via the gap s of the aperture
12. The polishing solution flow channel
9 runs through the gap s
of the aperture
12 at either side, and has a supply channel
14 and
a drain channel
15 shown on the right and left sides of the drawing.
The polishing solution, for example an aqueous solution including polishing abrasive
particles, is pressure-fed down the supply channel
14 using prescribed levels
of pressure and heat, by means of an external pump and heat exchanger (omitted
from the drawing). The polishing solution then flows from the supply channel
14
to the drain channel
15 by way of the gap s, forming in its totality the
polishing solution flow channel
9.
A spring mounted on the slide rail
8 (omitted from the drawing) presses
the polishing mechanism
3 against the stack
1 of semiconductor wafers
4. This absorbs differences in the diameters of the stack
1 and rotary
column
10 and rotary vibration when the polishing machine for a peripheral
edge is operated, ensuring contact between the contact surface
13 and stack
1, maintaining the appropriate size of the above-mentioned minute gap s,
and preventing the leakage of polishing solution from the contact surface
13.
Then, because the polishing solution flow channel
9 narrows at the minute
gap s, the flow speed and pressure of polishing solution passing therethrough increases,
and the polishing abrasive particles collide with the peripheral edges of the semiconductor
wafers
4 at a nearly flat angle. This enables the polishing mechanism
3
to polish the peripheral edges of the semiconductor wafers
4 with a high
level of precision by destroying minute quantities thereof. Additionally, since
this polishing machine polishes by causing polishing abrasive particles to collide
with the edges during the flow of polishing solution, it is possible to uniformly
polish the peripheral edges.
The above has described the first embodiment of the polishing machine for a peripheral
edge, but this embodiment may be modified in a number of ways.
For example, as shown in FIG. 4, the diameter of the spacer
5 may be slightly
made larger than that of the semiconductor wafer
4, to form a prescribed
minute gap s between the peripheral edges of the semiconductor wafers
4
and the rotary column
10 by causing the spacers
5 to contact the
rotary column
10. Additionally, grooves
16 may be formed around the
circumference of the spacers
5 in conformity with the edges of the chamfered
portions of the semiconductor wafers
4, in order to uniformly draw polishing
solution in around the entire edges of the semiconductor wafers
4. Additionally,
in the above mentioned embodiment, the rotary axis of the rotary mechanism
2
which rotates the stack of semiconductor wafers
4 is set up along the vertical
axis. However, the rotary axis of the rotary mechanism (the rotary axis of the
semiconductor wafers
4) may be set up along the horizontal axis, and the
related apparatuses may be arranged to correspond thereto.
Additionally, the polishing mechanism
3 does not only move along
the radial direction of the stack
1 of semiconductor wafers
4, but
is also provided with a mechanism which can move along the periphery of the stack
1 of semiconductor wafers
4. Moreover, the polishing solution may
include surfactants and viscosity modifiers, and it is also permissible to modify
the diameter of the polishing abrasive particles in a stepwise or continuous manner,
in accordance with the process in question to perform sequentially coarse processing
to finishing without removing a work. In addition, it is possible to use a polishing
solution having mechanochemical polishing effects which includes chemically active
solid particles or chemical solutions, or to use a polishing solution whose polishing
abrasive particles themselves have mechanochemical polishing effects. It is also
possible to form grooves on the surface of the rotary column
10, parallel
to the rotary axis or in a spiral configuration, as dynamic pressure generating
grooves in order to increase the flow speed of polishing solution at the gap between
the rotary column
10 and semiconductor wafers
4, to form a textured
surface, to form a hydrophilic membrane on the surface of the rotary column
10,
or to construct the rotary column
10 from a porous material. Alternatively,
it is possible to take a replica of the peripheral edge of a wafer using a softened
polymer material, and use this as the rotary column
10.
Next, a polishing machine for a peripheral edge of a semiconductor wafer according
to the second embodiment of the present invention will be described.
As shown in FIG. 5, the polishing machine for a peripheral edge of a semiconductor
wafer according to this embodiment is made up of the entire polishing machine for
a peripheral edge of the first embodiment, immersed in a polishing solution tank
21 filled with polishing solution.
The polishing solution tank
21 is equipped with a polishing solution circulation
apparatus
25. The polishing solution circulation apparatus
25 has
two communicating pipes: a supply pipe
22 installed in the upper portion
of the polishing solution tank
21, and a drain pipe
23 installed
in the lower portion thereof, and circulates polishing solution in and out of the
polishing solution tank
21. The polishing solution is collected from the
lower portion of the polishing solution tank
21 by the polishing solution
circulation apparatus
25, and after its temperature is regulated inside
the heat exchanger
26, it is again supplied to the upper portion of the
polishing solution tank
21.
The semiconductor wafers
4 are stacked, sandwiched by spacers
5
in the same manner as the first embodiment. In the approximate center of the polishing
solution tank
21 is installed a rotary mechanism
2, which rotates
the stack
1 of semiconductor wafers
4 mounted thereon. As in the
first embodiment, the rotary mechanism
2 is equipped with a turntable
6
on which is mounted the stack
1 of semiconductor wafers
4, and a
locking piece
7 which presses the stack
1 of semiconductor wafers
4 against the turntable
6, and fixes it in place. A slide rail
8
is installed in the radial direction of the rotary mechanism
2. The slide
rail
8 axially supports a rotary column
10 which is freely movable.
The rotary column
10 is constructed so as to rotate with the stack
1
of semiconductor wafers
4, mediated by a minute gap s.
In this polishing machine for a peripheral edge, the rotary mechanism
2
upon which is mounted the stack
1 of semiconductor wafers
4 and the
rotary column
10 rotate in the opposite direction relative to each other,
in a state in which polishing solution has penetrated therebetween. The polishing
solution is drawn into the space between the relatively rotating stack
1
of semiconductor wafers
4 and rotary column
10 by means of viscosity.
Fluid mechanics cause the speed of the polishing solution to increase as it is
drawn into the minute gap s, due to the narrowing thereof. Then, when the polishing
abrasive particles in the polishing solution pass through the minute gap s, they
collide with the peripheral surfaces of the semiconductor wafers
4 at a
nearly flat angle, polishing the peripheral edges thereof.
In other words, in the same manner as the polishing machine for a peripheral
edge
of the first embodiment, this polishing machine for a peripheral edge is able to
polish the peripheral edges of the semiconductor wafers
4 with a high level
of precision by destroying minute quantities thereof.
It is also permissible to form grooves on the surface of the rotary column
10
of this polishing machine for a peripheral edge, parallel with the rotary axis
or in a spiral configuration, or process it to give it a textured surface. Additionally,
it is possible to form a hydrophilic membrane on the surface of the rotary column
10, or to construct the rotary column
10 from a porous material.
The shapes of the flow channel cover and/or polishing solution tank
21 may
be changed in order to minimize the flow of polishing solution circulating therein.
Additionally, in the present embodiment the diameter of the spacer
5 may be slightly made larger than that of the semiconductor wafer
4
to form a prescribed minute gap s between the peripheries of the semiconductor
wafers
4 and the periphery of the rotary column
10 by causing the
spacers
5 to contact the rotary column
10.
Next, a polishing machine for a peripheral edge of a semiconductor wafer according
to the third embodiment of the present invention will be described.
As shown in FIG. 6, in this polishing machine for a peripheral edge, a rotary
mechanism
2 upon which is mounted a stack
1 of semiconductor wafers
4, and an interior pipe body
32 mounted on the periphery of the stack
1 of semiconductor wafers
4, are accommodated inside an approximately
cylindrical exterior pipe body
31 installed on the base thereof. Polishing
solution is drawn into the minute gap between the stack
1 of semiconductor
wafers
4 and interior pipe body
32, polishing the peripheral edges
of the semiconductor wafers
4.
As in the first embodiment, the rotary mechanism
2 is equipped with a
turntable
6 upon which is mounted the stack
1 of semiconductor wafers
4,
and a locking piece
7 which presses the stack
1 of semiconductor
wafers
4 onto the turntable
6, and fixes it thereto.
The exterior pipe body
31 serving as a polishing solution supply portion
is affixed to the base so as to be on the same axis as the rotary mechanism
2.
The exterior pipe body
31 is equipped with a storage portion
33 in
order to create a space between it and the interior pipe body
32, and store
polishing solution. In the interior of the exterior pipe body
31, the upper
end
33a and lower end
33b are sealed in order to prevent
leakage of the polishing solution from the storage portion
33. The side
of the exterior pipe body
31 is equipped with a supply pipe
34 for
supplying polishing solution, and a drain pipe
35 for draining the polishing
solution. Polishing solution of a prescribed pressure is supplied to the storage
portion
33 via the supply pipe
34 from a polishing solution supply
apparatus (omitted from the drawing).
The interior pipe body
32, serving as a rotary column, is accommodated
between the exterior pipe body
31 and the stack
1 of semiconductor
wafers
4, and rotated by a rotary mechanism not shown in the drawing. The
inner surface
35 of the interior pipe body
32 faces the peripheral
surface of the stack
1 of semiconductor wafers
4 mediated by a minute
gap. Vertically aligned dynamic pressure grooves
36 formed on the inner
surface
35 of the interior pipe body
32 are distributed around the
periphery at prescribed intervals. The dynamic pressure grooves
36 are equipped
ith a plurality of polishing solution supply apertures
37 which are linked
to the storage portion
33 of the exterior pipe body
31, in order
to supply polishing solution to the interior of the interior pipe body
32.
This polishing machine for a peripheral edge rotates the stack
1 of semiconductor
wafers
4 by means of the rotary mechanism
2 and rotates the interior
pipe body
32 in the opposite direction relative to the stack
1 of
semiconductor wafers
4, while supplying polishing solution at a prescribed
pressure to the exterior pipe body
31. At this time, dynamic pressure generated
between the stack
1 of semiconductor wafers
4 and interior pipe body
32 draws polishing solution between the inner surface
35 of the interior
pipe body
32 and the stack
1 of semiconductor wafers
4 from
the dynamic pressure grooves
36 of the interior pipe body
32.
The flow speed and pressure of the polishing solution drawn between the inner
surface
35 of the interior pipe body
32 and the stack
1 of
semiconductor wafers
4 is accelerated due to the narrowing of the flow channel
therebetween. Additionally, due to the fact that the polishing solution flows around
the peripheries of the semiconductor wafers
4, the polishing abrasive particles
in the polishing solution pass collide with the peripheral surfaces of the semiconductor
wafers
4 at a nearly flat angle, polishing the peripheral edges thereof.
In other words, in the same manner as the polishing machine for a peripheral edge
of the first embodiment, this polishing machine for a peripheral edge is able to
polish the peripheral edges of the semiconductor wafers
4 with a high level
of precision by destroying minute quantities thereof.
The dynamic pressure grooves
36 formed on the interior pipe body
32
may be wedge-shaped, in order to obtain a greater fluid-mechanical effect. Additionally,
it is permissible to form a hydrophilic membrane on the surface of the interior
pipe body
32, process it to give it a textured surface, or construct the
interior pipe body
32 from a porous material. Moreover, as in the second
embodiment, a construction in which the entire apparatus is immersed in polishing
solution may be employed. Moreover, the rotary axis of the stack
1 of semiconductor
wafers
4 may be given a horizontal construction and the related apparatuses
may be arranged to correspond thereto. It is also permissible to employ a construction
which locks the exterior pipe body
31 and interior pipe body
32 in
place, and rotates the stack
1 of semiconductor wafers
4, and in
this case, it is also permissible if the interior and exterior pipes do not completely
enclose the wafers, or if they are notched.
It is also possible for the components adjacent to the semiconductor wafers
4
of the polishing machine for a peripheral edge of the above-mentioned embodiments
1-3 to be formed from high-purity silicon or high-purity quartz. Additionally,
the rotary column
10 and/or interior pipe body
32 may be made of,
for example, polyurethane.
With the above-mentioned construction, the components of the polyurethane rotary
column
10 or interior pipe body
32 that are adjacent to the stack
1 of semiconductor wafers
4 are deformed in conformity with the peripheral
shape of the stack
1, and form a minute gap s together with the semiconductor
wafers
4 within the polishing solution. Then, polishing solution is drawn
between it and the stack
1 of semiconductor wafers
4, generating
a high-speed fluid bearing-type flow. At this time, the polishing abrasive particles
included in the fluid collide with the surface of the semiconductor wafers
4,
achieving high-precision polishing by destroying minute quantities thereof.
For example, in an embodiment in which the rotary column
10 is made of
polyurethane, if the rotary column
10 is pressed against the periphery of
the stack
1 of semiconductor wafers
4, then it is easy to establish
a minute gap s, since the shape thereof is freely changed to conform to the shape
of the periphery of the stack
1 of semiconductor wafers
4 and a minute
gap is formed between it and the semiconductor wafers
4.
Alternatively, it is possible to form the rotary column
10
in its entirety, or the surface portion including the peripheral surface
10a
thereof, of a rubber such as chloroprene rubber, or alternatively a synthetic
resin formed into a porous (spongy) state, using an elastic material with a hardness
of 7-40 Hs. Even if there are fluctuations in polishing speed (the relative rotary
speed of the semiconductor wafer and rotary body), the flow speed and pressure
of the polishing solution inside the minute gap s, viscosity of the polishing solution,
and the concentration and diameters of the abrasive particles included in the polishing
solution, it is possible to constantly obtain a stable polishing efficiency and
polishing surface grain, since these fluctuations are absorbed by the appropriate
elasticity of the peripheral surface
10a of the rotary column
10.
Additionally, during the polishing process, the polishing speed may be changed
(for example, polishing with a relatively high polishing speed for a prescribed
length of time from the start of the polishing process, then polishing at a relatively
lower polishing speed for the remainder of the polishing process) without changing
the semiconductor wafer holding status, the polishing solution, or the like, enabling
highly precise, highly efficient polishing.
Next, a polishing machine for a peripheral edge of a semiconductor wafer according
to a fourth embodiment of the present invention will be described.
AS shown in FIG. 7, although the basic construction of the polishing machine
for
a peripheral edge of this embodiment is the same as that of the polishing machine
for a peripheral edge of the first embodiment, unlike the polishing machine for
a peripheral edge of the first embodiment, this embodiment is equipped with a magnetic
polishing mechanism
41 having n-polar
44 and s-polar
45 magnets
arrayed in alternation around the periphery of the outer surface of the rotary
column
42, and using magnetic polishing solution including polishing abrasive
particles in the magnetic fluid.
Since magnets
44 and
45 are installed in the outer surface of
the rotary column
42, the magnetically charged magnetic polishing solution
is drawn by the magnetic fields of the magnets
44 and
45 of the rotary
column
42. Then, by rotating the stack
1 of semiconductor wafers
4 and the rotary column
42 in opposite directions relative to each
other, the magnetic polishing solution is drawn into the minute gap s of the polishing
solution flow channel
46 along the surface of the rotary column
42.
This enables high-precision polishing of the peripheral edges of the semiconductor
wafers
4 by destroying minute quantities thereof, in the same manner as
the polishing machine for a peripheral edge of the first embodiment.
This polishing mechanism
41 may be constructed in such a manner that
it does not only move in the radial direction of the stack
1 of semiconductor
wafers
4, but also moves in the peripheral direction along the circular
periphery thereof. Moreover, the magnetic polishing solution may contain surfactants
and viscosity modifiers. In addition, a polishing solution having mechanochemical
polishing effects which includes chemically active solid particles or chemical
solutions, or a polishing solution whose polishing abrasive particles themselves
have mechanochemical polishing effects may be used. It is also possible to form
grooves on the surface of the rotary column
42, parallel to the axis or
in a spiral configuration, as dynamic pressure grooves in order to increase the
flow speed of magnetic polishing solution through the minute gap s by means of
a fluid-mechanical effect. It is also possible to form a hydrophilic membrane on
the surface of the rotary column
42.
In the embodiment shown in FIG. 7, the outer diameter of the spacer
5
is
slightly made larger than that of the semiconductor wafer
4 to contact the
rotary column
42 with the peripheries of the spacers
5, forming a
minute gap between the rotary column
42 and semiconductor wafers
4.
Additionally, grooves
47 are provided in the peripheral direction of the
spacers
5, so that the magnetic polishing solution flows uniformly along
the edges of the semiconductor wafers
4.
Note that in FIG. 7, although the rotary axis of the rotary mechanism is set
up along the vertical axis, the rotary axis of the rotary mechanism may be set
along the horizontal axis, and the related apparatuses may be arranged to correspond
thereto. Moreover, it is also possible to employ a construction immersing the entire
apparatus in magnetic polishing solution, in the same manner as the second embodiment.
Next, a polishing machine for a peripheral edge of a semiconductor wafer according
to the fifth embodiment of the present invention will be described.
As shown in FIG. 8, in the polishing machine for a peripheral edge of this embodiment,
a rotary mechanism
2 upon which is mounted a stack
1 of semiconductor
wafers
4 and an interior pipe body
52 surrounding the stack
1
of semiconductor wafers
4 are accommodated within a generally cylindrical
exterior pipe body
51 installed on the base thereof. Note, however, that
in the present embodiment, an interior pipe body
52 is used which has n-polar
54 and s-polar
55 magnets arrayed in alternation around the periphery
of the inner surface thereof, and a magnetic polishing solution is used including
polishing abrasive particles in magnetic fluid.
The exterior pipe body
51, in the same manner as the exterior pipe body
31 according to the third embodiment, is equipped with an internal storage
portion
56, a supply pipe
57 that supplies magnetic polishing solution
at a prescribed pressure to a storage portion
56 from a magnetic polishing
solution supply apparatus not shown in the drawing, and a drain pipe
58
that drains magnetic polishing solution from the storage portion
56.
This polishing machine for a peripheral edge rotates a stack
1 of semiconductor
wafers
4 by means of a rotary mechanism
2, and rotates an interior
pipe body
52 by means of the rotary mechanism
2 not shown in the
drawing in the direction opposite to that of the stack
1 of semiconductor
wafers
4, while supplying the magnetic polishing solution with a predetermined
pressure into the exterior pipe body
51.
Magnetic polishing solution is supplied to the gap between the interior
pipe body
52 and the stack
1 of semiconductor wafers
4 from
a plurality of supply apertures
59 in the interior pipe body
52.
Then, the magnetic polishing solution is drawn by the magnets
54 and
55
installed in the inner surface of the interior pipe body
52, and drawn into
the gap between the interior pipe body
52 and stack
1 of semiconductor
wafers
4 which are rotating opposite relative one another.
At this time, since the polishing abrasive particles in the magnetic polishing
solution collide with the peripheral edges of the semiconductor wafers
4
at a nearly flat angle, it is possible to conduct high-precision polishing of the
peripheral edges of the semiconductor wafers
4 by means of a minute-quantity
destruction effect.
Note that in order to increase the speed of the magnetic polishing solution
flow at the gap between the interior pipe body
52 and the semiconductor
wafers
4 through a fluid-mechanical effect, it is possible to form grooves
on the inner surface of the interior pipe body
52 parallel to the rotary
axis thereof or in a spiral configuration, as dynamic pressure grooves, and it
is also possible to make these grooves wedge-shaped in order to obtain a greater
fluid-mechanical effect.
The above has described embodiments of the present invention, but the present
invention is not limited to these embodiments. For example, in the stack of semiconductor
wafers, wafers are stacked sandwiched by spacers, but the form is not limited to
a stack of semiconductor wafers. Additionally, the constructions of embodiments
1 to 6 may be combined as desired. Furthermore, although in the embodiments described
above a plurality of semiconductor wafers are simultaneously polished using the
so-called batch method, it is also possible to use a construction in which the
rotary mechanism holds and rotates a single semiconductor wafer, polishing a single
semiconductor wafer at a time (the so-called single-wafer method).
*
