U.S. patent application number 12/247314 was filed with the patent office on 2009-04-23 for grinding apparatus and method of grinding wafer.
Invention is credited to Setsuo YAMAMOTO.
Application Number | 20090104858 12/247314 |
Document ID | / |
Family ID | 40563939 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090104858 |
Kind Code |
A1 |
YAMAMOTO; Setsuo |
April 23, 2009 |
GRINDING APPARATUS AND METHOD OF GRINDING WAFER
Abstract
In order not to transmit an impact when grinding is started, or
micro-vibrations of a grinding wheel during grinding to a wafer, a
grinding apparatus at least includes: a chuck table that holds a
wafer; a grinding unit having a grinding wheel configured to
include a grinding wheel part that is fixed to a wheel base and
grinds a wafer held on the chuck table and having a wheel mount
that supports the wheel base; and a grinding unit feeding unit that
brings the grinding unit dose to and away from the chuck table,
wherein a vibration damping rubber having a rebound resilience of
2% to 4% standardized by ISO 4662 is provided between the wheel
base and the wheel mount, whereby an impact when grinding is
started, or micro-vibrations of a grinding wheel during grinding
are absorbed.
Inventors: |
YAMAMOTO; Setsuo; (Tokyo,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
40563939 |
Appl. No.: |
12/247314 |
Filed: |
October 8, 2008 |
Current U.S.
Class: |
451/259 |
Current CPC
Class: |
B24B 37/042 20130101;
B24B 37/04 20130101; B24B 41/007 20130101 |
Class at
Publication: |
451/259 |
International
Class: |
B24B 7/00 20060101
B24B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2007 |
JP |
2007-271123 |
Claims
1. A grinding apparatus at least comprising: a chuck table that
holds a wafer; a grinding unit having a grinding wheel configured
to include a grinding wheel part that is fixed to a wheel base and
grinds a wafer held on the chuck table and having a wheel mount
that supports the wheel base; and a grinding unit feeding unit that
brings the grinding unit close to and away from the chuck table,
wherein a vibration damping rubber having a rebound resilience of
2% to 4% standardized by ISO 4662 is provided between the wheel
base and the wheel mount.
2. A method of grinding a wafer in which the grinding apparatus
according to claim 1 is used to grind a wafer, the method
comprising the steps of: holding a wafer on the chuck table as a
back surface of the wafer is exposed; rotating the chuck table; and
feeding the grinding unit for grinding by the grinding unit feeding
unit while the grinding wheel is rotated, and bringing the grinding
wheel into contact with the back surface of the wafer to grind the
back surface.
3. The method of grinding a wafer according to claim 2, wherein a
feed speed of the grinding unit by the grinding unit feeding unit
is 0.1 mm/sec. to 15 mm/sec., a rotating speed of the chuck table
is 10 rpm to 400 rpm, and a rotating speed of the grinding wheel is
1000 rpm to 7200 rpm.
4. The method of grinding a wafer according to claim 2, wherein on
a front surface of the wafer, a plurality of devices is formed as
the devices are defined by streets, and a protective member is
bonded to on the front surface, and the protective member is held
on the chuck table.
5. The method of grinding a wafer according to claim 2, wherein the
wafer is a silicon wafer.
6. The method of grinding a wafer according to claim 3, wherein the
wafer is a silicon wafer.
7. The method of grinding a wafer according to claim 4, wherein the
wafer is a silicon wafer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a grinding apparatus that
grinds a wafer and a method of grinding a wafer using the grinding
apparatus.
[0003] 2. Prior Art
[0004] A wafer having a plurality of devices such as an integrated
circuit formed on the front surface thereof is divided into
individual devices by a dicing apparatus, and the devices are used
for various electronic appliances.
[0005] Before the wafer is divided into individual devices, its
back surface is ground to smooth the back surface, and the wafer is
finished to have a desired thickness. For grinding the back surface
of the wafer, the front surface side of the wafer is held on a
chuck table of the grinding apparatus, and a rotating grinding
wheel is brought into contact with the back surface of the wafer to
apply a predetermined pressing force for grinding (for example, see
JP-A-2007-222986).
[0006] However, when the rotating grinding wheel is fed for
grinding and brought into contact with the wafer and the strength
reaches a predetermined pressing force to start grinding, a strong
impact is transmitted to the wafer at the moment of the start. In
addition, during grinding, microvibrations are generated in the
grinding wheel because of grinding resistance, and the wafer is
finely beaten correspondingly. Therefore, due to these phenomena, a
problem arises that grinding distortion such as cracks occurs in
the grinding surface of the wafer to deteriorate die strength of
the devices configuring the wafer.
SUMMARY OF THE INVENTION
[0007] An object to be solved by the invention is that in the case
in which a grinding wheel is brought into contact with a wafer for
grinding, an impact at the time of starting grinding caused by a
grinding wheel, or microvibrations of a grinding wheel during
grinding is prevented from being transmitted to the wafer.
[0008] A first aspect of the invention is a grinding apparatus at
least including: a chuck table that holds a wafer, a grinding unit
having a grinding wheel configured to include a grinding wheel part
that is fixed to a wheel base and grinds a wafer held on the chuck
table and having a wheel mount that supports the wheel base; and a
grinding unit feeding unit that brings the grinding unit dose to
and away from the chuck table, wherein a vibration damping rubber
having a rebound resilience of 2% to 4% standardized by ISO 4662 is
provided between the wheel base and the wheel mount.
[0009] A second aspect of the invention is a method of grinding a
wafer in which the grinding apparatus according to the first aspect
is used to grind a wafer, the method including the steps of holding
a wafer on the chuck table as a back surface of the wafer is
exposed; rotating the chuck table; and feeding the grinding unit
for grinding by the grinding unit feeding unit while the grinding
wheel is rotated, and bringing the grinding wheel into contact with
the back surface of the wafer to grind the back surface.
[0010] In the method of grinding a wafer, preferably, a feed speed
of the grinding unit by the grinding unit feeding unit is 0.1
.mu.m/sec. to 15 .mu.m/sec., a rotating speed of the chuck table is
10 rpm to 400 rpm, and a rotating speed of the grinding wheel is
1000 rpm to 7200 rpm. In the case in which on a front surface of
the wafer, a plurality of devices is formed as the devices are
defined by streets as dividing lines, a protective member is bonded
to on the front surface and the protective member is held on the
chuck table. As an exemplary wafer, a silicon wafer is named.
[0011] According to the invention, because a vibration damping
rubber having a rebound resilience of 2% to 4% standardized by ISO
4662 is provided between the wheel base and the wheel mount of the
grinding wheel, even though the grinding unit is fed for grinding
to apply a predetermined pressing force to the wafer, the impact at
this time is absorbed through the vibration damping rubber to
prevent the impact from being transmitted to the wafer. In
addition, because micro-vibrations caused by grinding resistance
during grinding are also absorbed by the vibration damping rubber,
finely beating the wafer is softened. Therefore, stripes are hardly
formed on the grinding surface of the wafer to prevent die strength
of the device from being deteriorated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view showing an exemplary grinding
apparatus;
[0013] FIG. 2 is an exploded perspective view showing a wheel
mount, a vibration damping rubber and a grinding wheel configuring
a grinding unit;
[0014] FIG. 3 is a perspective view showing the state in which the
wheel mount, the vibration damping rubber and the grinding wheel
are fixed to each other;
[0015] FIG. 4 is a perspective view showing an exemplary wafer of a
grinding subject;
[0016] FIG. 5 is a front view showing the state in which a
protective member is bonded to the front surface of the wafer;
and
[0017] FIG. 6 is a cross section schematically showing the state
before grinding the back surface of the wafer is started.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] In a grinding apparatus 1 shown in FIG. 1, a wafer cassette
100a that accommodates therein a wafer to be ground and a wafer
cassette 100b that accommodates therein a wafer after ground are
mounted, respectively on cassette mounting areas 10a and 10b.
[0019] Near the cassette mounting areas 10a and 10b, a carrying
unit 11 that brings a wafer in and out of the wafer cassettes 100a
and 100b is arranged. The wafer brought out of the wafer cassette
100a by the carrying unit 11 is placed on a positioning table 12,
and the wafer is positioned at a fixed position here.
[0020] Near the positioning table 12, a first carrying unit 13a is
arranged. The first carrying unit 13a carries the wafer positioned
on the positioning table 12 to any one of three chuck tables 14a,
14b, and 14c that hold the wafer. Each of the chuck tables is
configured of a holding part 140 that holds the wafer, and a
holding part base 141 that rotatably supports the holding part 140.
In addition, these three chuck tables 14a, 14b, and 14c are rotated
in association with the rotation of a turntable 15.
[0021] In the grinding apparatus 1 shown in FIG. 1, a first
grinding unit feeding unit 17 and a second grinding unit feeding
unit 18 are arranged on a wall 16 erected from one end of the
apparatus. The first grinding unit feeding unit 17 is configured of
a pair of guide rails 170 vertically arranged, a ball screw 171
arranged in parallel with the guide rails 170, a motor 172 joined
to the tip end of the ball screw 171, and an elevating part 173
that is slidably engaged with the guide rails 170 and has an
internal nut screwed to the ball screw 171, in which the elevating
part 173 moves up and down as guided by the guide rails 170 in
association with the rotation of the ball screw 171 driven by the
motor 172.
[0022] The second grinding unit feeding unit 18 is configured of a
pair of guide rails 180 vertically arranged, a ball screw 181
arranged in parallel with the guide rails 180, a motor 182 joined
to the tip end of the ball screw 181, and an elevating part 183
that is slidably engaged with the guide rails 180 and has an
internal nut screwed to the ball screw 181, in which the elevating
part 183 moves up and down as guided by the guide rails 180 in
association with the rotation of the ball screw 181 driven by the
motor 182.
[0023] The elevating part 173 configuring the first grinding unit
feeding unit 17 supports a first grinding unit 19. The first
grinding unit 19 includes a spindle 200 having a vertical shaft, a
spindle housing 190 that rotatably supports the spindle 200, a
wheel mount 210 formed at the tip end of the spindle 200, a
grinding wheel 230 supported by the wheel mount 210, and a motor
200a that is joined to the spindle 200 to rotate the spindle 200,
in which the grinding wheel 230 is also rotated as the spindle 200
is driven by the motor 200a for rotation. The first grinding unit
19 is driven by the first grinding unit feeding unit 17, and
brought close to and away from the chuck table.
[0024] The elevating part 183 configuring the second grinding unit
feeding unit 18 supports a second grinding unit 20. The second
grinding unit 20 includes a spindle 201 having a vertical shaft, a
spindle housing 191 that rotatably supports the spindle 201, a
wheel mount 211 formed at the tip end of the spindle 201, a
grinding wheel 231 supported by the wheel mount 211, and a motor
201a that is joined to the spindle 201 to rotate the spindle 201,
in which the grinding wheel 231 is also rotated as the spindle 201
is driven by the motor 201a for rotation. The second grinding unit
20 is driven by the second grinding unit feeding unit 18, and
brought close to and away from the chuck table.
[0025] As shown in FIG. 2, in the first grinding unit 19 and the
second grinding unit 20, the grinding wheel 230 (231) is configured
in which grinding wheel parts 230b (231b) that grind a wafer is
fixed in an arc shape to the bottom surface of a ring-shaped wheel
base 230a (231a), and a plurality of screw holes 230c (231c) is
formed in the wheel base 230a (231a). In addition, the grinding
wheel part 230b is a grinding wheel of diamond abrasive grain
having a grain size of about 10 .mu.m fixed with a resin bond and
the grinding wheel part 231b is a grinding wheel having a grain
size of 1 .mu.m or below of diamond abrasive grain fixed with a
vitrified bond.
[0026] For example, as shown in FIG. 2, in the wheel mount 210
(211), a plurality of through holes 210a (211a) is formed. On the
wheel mount 210 (211), the grinding wheel 230 (231) is fixed and
supported through a vibration damping rubber 220 (221). For
example, for the vibration damping rubber 220 (221), "HANENITE"
(registered trademark) provided by Kayo Corporation can be
used.
[0027] As shown in FIG. 2, a screw 240 (241) is inserted into the
through hole 210a (211a) of the wheel mount 210 (211) and the
through hole 220a (221a) of the vibration damping rubber 220 (221),
and screwed to the screw hole 230c (231c) of the wheel base 230a
(231a). Then, as shown in FIG. 3, the grinding wheel 230 (231) is
fixed to the wheel mount 210 (211) through the vibration damping
rubber 220 (221), and the wheel mount 210 (211) supports the wheel
base 230a (231a) through the vibration damping rubber 220 (221). In
addition, the vibration damping rubber 220 (221) may be fixed to
the surface of the wheel base 230a (231a) on which the wheel mount
210 (211) is mounted and formed in one piece with the grinding
wheel 230 (231) in advance.
[0028] Next, a method of grinding a wafer will be described. For
example, as shown in FIG. 4, in the case of grinding a back surface
W2 of a wafer W having a plurality of devices D formed on a front
surface W1 as defined by streets S, as shown in FIG. 5, a
protective member P is bonded to the front surface W1 to protect
the devices, the wafer W is accommodated in the wafer cassette 100a
shown in FIG. 1 upside down, and the carrying unit 11 brings the
wafer W out of the wafer cassette 100a to place it on the
positioning table 12. Then, after the wafer W is positioned at a
fixed position, the first carrying unit 13a carries the wafer W to
the chuck table 14a, for example. On the chuck table 14a, the
surface having the protective member P bonded to the wafer W is
held, and the back surface W2 is exposed.
[0029] Subsequently, the turntable 15 is rotated to position the
wafer W directly below the grinding wheel 230 (the position of the
chuck table 14c in FIG. 1). Then, as shown in FIG. 6, the chuck
table 14a is rotated as well as the first grinding unit 19 is fed
for grinding by the first grinding unit feeding unit 17 (see FIG.
1) while the grinding wheel part 230b is rotating in association
with the rotation of the spindle 200, and the grinding wheel part
230b is descended. The rotating grinding wheel part 230b is brought
into contact with the back surface W2 of the wafer W to grind the
back surface W2. Here, for example, rough grinding is
conducted.
[0030] After rough grinding is finished, the turntable 15 is
rotated to position the wafer W directly below the grinding wheel
231 (the position of the chuck table 14b in FIG. 1). Then, as shown
in FIG. 6, the chuck table 14a is rotated as well as the wheel
mount 211 is fed for grinding by the second grinding unit feeding
unit 18 (see FIG. 1) while the grinding wheel part 231b is rotating
in association with the rotation of the spindle 201, and the
grinding wheel part 231b is descended. The rotating grinding wheel
part 231b is brought into contact with the back surface W2 of the
wafer W to grind the back surface W2. Here, finish grinding is
conducted.
[0031] Because the vibration damping rubber 220 (221) is provided
between the grinding wheel 230 (231) and the wheel mount 210 (211),
in starting rough grinding and finish grinding, an impact when the
grinding wheel part 230b (231b) is brought into contact with the
back surface W2 of the wafer W is absorbed by the effect of the
vibration damping rubber 220 (221), whereby the impact is not
transmitted to the wafer W. In addition, the grinding wheel part
230b (231b) is brought into contact with the wafer W to generate
grinding resistance to cause micro-vibrations in the grinding wheel
parts 230b (231b). However, the microvibrations are also absorbed
in the vibration damping rubber 220 (221), and hardly transmitted
to the wafer W, and thus it is softened to beat the wafer W.
Therefore, grinding distortion such as cracks hardly occurs in the
grinding surface of the wafer W (the back surface W2), and the
deterioration of the die strength of the individual devices D
configuring the wafer W and the breakage can be prevented.
[0032] The wafer W thus ground is positioned near the second
carrying unit 13b by the rotation of the turntable 15 shown in FIG.
1, and carried to a cleaning unit 25 by the second carrying unit
13b. Grinding wastes are removed here, and then the wafer W is
accommodated in the wafer cassette 100b by the carrying unit
11.
[0033] In addition, in the embodiment above, the vibration damping
rubber is provided to both of the first grinding unit 19 and the
second grinding unit 20. However, it may be configured to provide
the vibration damping rubber to only one of them, for example, the
second grinding unit 20. In addition, the grinding apparatus 1
having two grinding wheels are taken and described as an example.
However, the invention can be also adapted to such apparatuses
having a single grinding wheel or three or more. Moreover, the
number of chuck tables may be any numbers.
EXAMPLE
[0034] As the vibration damping rubbers 220 and 221 shown in FIG.
2, a vibration damping rubber having a rebound resilience of 2%,
4%, 6%, 8%, 10%, and 12% standardized by ISO 4662 was provided
between the wheel bases 230 and 231 and the wheel mounts 210 and
211 to grind the back surface of a silicon wafer.
[0035] In grinding, the speeds were varied in the following ranges,
where the feed speed of the first grinding unit 19 and the second
grinding unit 20 was in the range of 0.1 .mu.m/sec. to 15
.mu.m/sec., the rotating speed of the chuck table was in the range
of 10 rpm to 400 rpm, and the rotating speed of the grinding wheels
230 and 231 was in the range of 1000 rpm to 7200 rpm.
[0036] In the case in which the vibration damping rubbers having
rebound resilience of 6% or above were used, stripes were observed
on the grinding surface of the wafer. These stripes are grinding
distortion, which become the factor that deteriorates the die
strength of the devices configuring the wafer. On the other hand,
in the case in which the vibration damping rubbers having a rebound
resilience of 2% and 4% were used, stripes were not observed
particularly on the grinding surface of the wafer after ground
which were caused by the second grinding unit 20. Therefore, when
the rebound resilience is set from 2% to 4%, the deterioration in
the transverse strength of the device can be prevented.
* * * * *