U.S. patent application number 11/244172 was filed with the patent office on 2006-04-13 for wafer grinding method.
This patent application is currently assigned to Disco Corporation. Invention is credited to Satoshi Kobayashi, Masahiro Murata, Masaru Nakamura, Takashi Sanpei, Noboru Takeda, Yosuke Watanabe, Masanori Yoshida.
Application Number | 20060079155 11/244172 |
Document ID | / |
Family ID | 36145955 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060079155 |
Kind Code |
A1 |
Nakamura; Masaru ; et
al. |
April 13, 2006 |
Wafer grinding method
Abstract
A wafer grinding method for grinding the surface to be ground of
a wafer having an arcuatedly chamfered outer peripheral surface,
comprising an outer peripheral portion removal step for removing
the outer peripheral portion of the wafer by applying a laser beam
from one surface side of the wafer along the outer periphery at a
location on the inside of the outer periphery by a predetermined
distance; and a grinding step for grinding the surface to be ground
of the wafer whose outer peripheral portion has been removed, to a
predetermined finish thickness.
Inventors: |
Nakamura; Masaru; (Tokyo,
JP) ; Watanabe; Yosuke; (Tokyo, JP) ;
Kobayashi; Satoshi; (Tokyo, JP) ; Takeda; Noboru;
(Tokyo, JP) ; Yoshida; Masanori; (Tokyo, JP)
; Sanpei; Takashi; (Tokyo, JP) ; Murata;
Masahiro; (Tokyo, JP) |
Correspondence
Address: |
SMITH, GAMBRELL & RUSSELL, LLP
1850 M STREET, N.W., SUITE 800
WASHINGTON
DC
20036
US
|
Assignee: |
Disco Corporation
|
Family ID: |
36145955 |
Appl. No.: |
11/244172 |
Filed: |
October 6, 2005 |
Current U.S.
Class: |
451/41 ;
257/E21.214 |
Current CPC
Class: |
B23K 2101/40 20180801;
B23K 26/40 20130101; H01L 21/302 20130101; B24B 7/228 20130101;
H01L 21/02021 20130101; B23K 2103/50 20180801 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2004 |
JP |
2004-295786 |
Claims
1. A wafer grinding method for grinding a surface to be ground of a
wafer having an arcuatedly chamfered outer peripheral surface,
comprising: an outer peripheral portion removal step for removing
the outer peripheral portion of the wafer by applying a laser beam
from one surface side of the wafer along the outer periphery at a
location on the inside of the outer periphery by a predetermined
distance; and a grinding step for grinding the surface to be ground
of the wafer whose outer peripheral portion has been removed, to a
predetermined finish thickness.
2. The wafer grinding method according to claim 1, wherein a
plurality of function elements are formed on the front surface of
the wafer, and the surface to be ground of the wafer is the back
surface.
3. The wafer grinding method according to claim 1, wherein the
outer peripheral portion removal step comprises applying a laser
beam of a wavelength capable of passing through the wafer along the
outer periphery to form an annular deteriorated layer along the
outer periphery in the inside of the wafer and dividing the wafer
along the deteriorated layer.
4. The wafer grinding method according to claim 1, wherein the
outer peripheral portion removal step is to form an annular groove,
which reaches the other side from one side along the outer
periphery of the wafer by applying a laser beam of a wavelength
having absorptivity for the wafer.
5. A wafer grinding method for grinding the back surface of a wafer
having a plurality of function elements on the front surface
thereof and an arcuatedly chamfered outer peripheral surface,
comprising: a groove forming step for forming an annular groove
deeper than at least the finish thickness of the wafer from the
front surface of the wafer by applying a laser beam of a wavelength
having absorptivity for the wafer from the front surface of the
wafer along the outer periphery at a location on the inside of the
outer periphery by a predetermined distance; and a grinding step
for grinding the back surface of the wafer having the groove formed
thereon, to a predetermined finish thickness.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method of grinding a
wafer such as a semiconductor wafer to a predetermined
thickness.
DESCRIPTION OF THE PRIOR ART
[0002] In the production process of a semiconductor device, a large
number of rectangular areas are sectioned by dividing lines called
"streets" formed in a lattice pattern on the front surface of a
substantially disk-like semiconductor wafer, and a circuit is
formed in each of the rectangular areas. Individual semiconductor
chips are manufactured by dividing this semiconductor wafer having
a large number of circuits along the dividing lines. In order to
reduce the size and weight of each semiconductor chip, the back
surface of the semiconductor wafer is generally ground to a
predetermined thickness before the semiconductor wafer is cut along
the dividing lines to separate individual rectangular areas from
one another. To reduce the size and weight of the semiconductor
chip, the semiconductor wafer is nowadays formed as thin as 100
.mu.m or less.
[0003] To prevent inconvenience with that chippings are produced
while the semiconductor wafer is transferred between steps before
it is divided into semiconductor chips, the outer peripheral
surface of the semiconductor wafer is chamfered arcuatedly. When
the back surface of the semiconductor wafer having a chamfered
portion at an outer periphery is ground to reduce the thickness of
the wafer to half or less, a sharp knife-edge is formed in the
arcuatedly chamfered portion. Therefore, there is a problem that
the semiconductor wafer may be cracked during the grinding or
transportation of the semiconductor wafer. Further, another problem
arises that when the back surface of the semiconductor wafer is
polished with a polishing cloth to remove a grinding mark or
micro-cracks formed on the back surface of the semiconductor wafer,
the polishing cloth is caught by the above knife-edge, whereby the
semiconductor wafer is broken during polishing.
[0004] To solve the above problems, JP-A2003-273053 discloses a
technology for cutting the arcuatedly chamfered portion at right
angles to a top surface of the wafer by holding the semiconductor
wafer on the chuck table of a cutting machine, positioning a
cutting blade on the top surface of the outer peripheral portion of
the semiconductor wafer, and turning the chuck table while the
cutting blade is rotated.
[0005] When the wafer is cut along the outer periphery with the
cutting blade, however, there exists a problem that since it is cut
arcuatedly in defiance of the linear movement of the cutting blade,
stress remains at the outer periphery of the wafer, thereby
damaging the wafer during grinding. Further, it takes a long time
to cut the wafer along the outer periphery with the cutting blade.
For instance, when a silicon wafer having a diameter of 200 mm is
cut along the outer periphery, it takes more than 30 minutes,
thereby reducing productivity.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a wafer
grinding method capable of grinding a wafer to a predetermined
thickness without damaging the wafer during grinding and without
forming a sharp knife-edge at the outer periphery.
[0007] To solve the above main technical problems, according to the
present invention, there is provided a wafer grinding method for
grinding the surface to be ground of a wafer having an arcuatedly
chamfered outer peripheral surface, comprising: [0008] an outer
peripheral portion removal step for removing the outer peripheral
portion of the wafer by applying a laser beam from one surface side
of the wafer along the outer periphery at a location on the inside
of the outer periphery by a predetermined distance; and [0009] a
grinding step for grinding the surface to be ground of the wafer
whose outer peripheral portion has been removed, to a predetermined
finish thickness.
[0010] A plurality of function elements are formed on the front
surface of the wafer, and the surface to be ground of the wafer is
the back surface. The above outer peripheral portion removal step
comprises applying a laser beam of a wavelength capable of passing
through the wafer along the outer periphery to form an annular
deteriorated layer along the outer periphery in the inside of the
wafer and dividing the wafer along the deteriorated layer. Further,
the above outer peripheral portion removal step is to form an
annular groove which reaches the other surface side from one
surface side along the outer periphery of the wafer by applying a
laser beam of a wavelength having absorptivity for the wafer.
[0011] Further, according to the present invention, there is also
provided a wafer grinding method for grinding the back surface of a
wafer having a plurality of function elements on the front surface
and an arcuatedly chamfered outer peripheral surface, comprising:
[0012] a groove forming step for forming an annular groove deeper
than at least the finish thickness of the wafer from the front
surface of the wafer by applying a laser beam of a wavelength
having absorptivity for the wafer from the front surface side of
the wafer along the outer periphery at a location on the inside of
the outer periphery by a predetermined distance; and [0013] a
grinding step for grinding the back surface of the wafer having the
groove formed thereon, to a predetermined finish thickness.
[0014] In the wafer grinding method of the present invention, since
the outer peripheral portion removal step for removing the outer
peripheral portion of the wafer by applying a laser beam along the
outer periphery at a location on the inside of the outer periphery
of the wafer by a predetermined distance is carried out before the
grinding step for grinding the surface to be ground of the wafer, a
sharp knife-edge is not formed at the outer periphery by grinding,
even when the outer peripheral surface of the wafer is chamfered
arcuatedly. Since the outer peripheral portion removal step is
carried out by laser processing, stress, which is generated by
cutting with a cutting blade, does not remain. Therefore, it is
possible to prevent the wafer from being damaged by the residual
stress during grinding. Further, since the outer peripheral portion
removal step in the present invention is carried out by laser
processing, its operation time can be greatly shortened as compared
with the operation of cutting with the cutting blade.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of a semiconductor wafer to be
ground by the wafer grinding method of the present invention;
[0016] FIG. 2 is a perspective view of the principal section of a
laser beam processing machine for carrying out the outer peripheral
portion removal step or the groove forming step in the wafer
grinding method of the present invention;
[0017] FIG. 3 is a block diagram schematically showing the
constitution of a laser beam application means provided in the
laser beam processing machine shown in FIG. 2;
[0018] FIG. 4 is a schematic diagram showing the focusing spot
diameter of a pulse laser beam;
[0019] FIG. 5 is an explanatory diagram showing an embodiment of
the outer peripheral portion removal step in the wafer grinding
method of the present invention;
[0020] FIG. 6 is an explanatory diagram showing another embodiment
of the outer peripheral portion removal step in the wafer grinding
method of the present invention;
[0021] FIG. 7 is an explanatory diagram showing still another
embodiment of the outer peripheral portion removal step in the
wafer grinding method of the present invention;
[0022] FIG. 8 is a perspective view showing a state where a wafer
subjected to the outer peripheral portion removal step in the wafer
grinding method of the present invention has a protective member
affixed to the front surface;
[0023] FIG. 9 is an explanatory diagram showing the step of
grinding the back surface of the wafer that has been subjected to
the outer peripheral portion removal step in the wafer grinding
method of the present invention;
[0024] FIG. 10 is an explanatory diagram showing the groove forming
step in the wafer grinding method of the present invention;
[0025] FIG. 11 is a perspective view showing a state where a wafer
subjected to the groove forming step in the wafer grinding method
of the present invention has a protective member affixed to the
front surface; and
[0026] FIG. 12 is an explanatory diagram showing the step of
grinding the back surface of the wafer that has been subjected to
the groove forming step in the wafer grinding method of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Preferred embodiments of the wafer grinding method of the
present invention will be described in detail hereinunder with
reference to the accompanying drawings.
[0028] FIG. 1 is a perspective view of a semiconductor wafer as a
wafer to be ground according to the present invention. The
semiconductor wafer 2 shown in FIG. 1 is, for example, a silicon
wafer having a diameter of 200 mm and a thickness of 500 .mu.m, and
a plurality of dividing lines 21 are formed in a lattice pattern on
the front surface 2a. And, a circuit 22 as a function element is
formed in a plurality of areas sectioned by a plurality of dividing
lines 21. The outer peripheral surface 2c of the outer peripheral
portion of the semiconductor wafer 2 is chamfered arcuatedly. A
description is subsequently given of a first embodiment of the
method of grinding this semiconductor wafer 2 to a predetermined
thickness.
[0029] In the first embodiment of the wafer grinding method of the
present invention, the step of removing the outer peripheral
portion of the wafer by applying a laser beam from one side of the
wafer along the outer periphery of the wafer at a position on the
inside of the outer periphery by a predetermined distance is first
carried out. This outer peripheral portion removal step is carried
out by using a laser beam processing machine 3 shown in FIGS. 2 to
4. The laser beam processing machine 3 shown in FIGS. 2 to 4
comprises a chuck table 31 for holding a workpiece and a laser beam
application means 32 for applying a laser beam to the workpiece
held on the chuck table 31. The chuck table 31 is so constituted as
to suction-hold the workpiece on the top surface and is designed to
be turned in the direction indicated by an arrow in FIG. 2 by a
turning mechanism that is not shown.
[0030] The above laser beam application means 32 comprises a
cylindrical casing 321 arranged substantially horizontally. In the
casing 321, there are installed a pulse laser beam oscillation
means 322 and a transmission optical system 323 as shown in FIG. 3.
The pulse laser beam oscillation means 322 is constituted by a
pulse laser beam oscillator 322a composed of a YAG laser oscillator
or YVO4 laser oscillator and a repetition frequency setting means
322b connected to the pulse laser beam oscillator 322a. The
transmission optical system 323 has suitable optical elements such
as a beam splitter, etc. A condenser 324 housing condensing lenses
(not shown) constituted by a combination of lenses that may be
formation known per se is attached to the end of the above casing
321. A laser beam oscillated from the above pulse laser beam
oscillation means 322 reaches the condenser 324 through the
transmission optical system 323 and is applied from the condenser
324 to the workpiece held on the above chuck table 31 at a
predetermined focusing spot diameter D. This focusing spot diameter
D is defined by the expression D
(.mu.m)=4.times..lamda..times.f/(.pi..times.W) (wherein .lamda. is
the wavelength (.mu.m) of the pulse laser beam, W is the diameter
(mm) of the pulse laser beam applied to an objective lens 324a, and
f is the focusing distance (mm) of the objective lens 324a) when
the pulse laser beam showing a Gaussian distribution is applied
through the objective lens 324a of the condenser 324, as shown in
FIG. 4.
[0031] The outer peripheral portion removal step that is carried
out by using the above laser beam processing machine 3 will be
described with reference to FIG. 5.
[0032] In this outer peripheral portion removal step, the
semiconductor wafer 2 is first placed on the chuck table 31 of the
above laser beam processing machine 3 in such a manner that the
front surface 2a faces up, and suction-held on the chuck table 31.
The chuck table 31 suction-holding the semiconductor wafer 2 is
moved to a processing area where the condenser 324 is located, by a
moving mechanism (not shown) to bring a location on the inside of
the outer periphery of the semiconductor wafer 2 by a predetermined
distance to a position right below the condenser 324, as shown in
FIG. 5. Then, the chuck table 31, that is, the semiconductor wafer
2 is turned in the direction indicated by the arrow in FIG. 5 while
a pulse laser beam of a wavelength capable of passing through the
semiconductor wafer 2 is applied from the condenser 324. At this
point, the focusing point P of the pulse laser beam applied from
the condenser 324 is set to a position near the back surface 2b
(undersurface) of the semiconductor wafer 2. As a result, an
annular deteriorated layer 210 is exposed to the back surface 2b
(undersurface) at the location on the inside of the outer periphery
by a predetermined distance and formed from the back surface 2b
(undersurface) toward the inside of the semiconductor wafer 2. This
deteriorated layer 210 is formed as a molten and re-solidified
layer (that is, as a layer that has been molten when the pulse
laser beam is converged and then, re-solidified after the
convergence of the pulse laser beam) and has greatly reduced
strength. Therefore, by exerting external force to the outer
peripheral portion of the semiconductor wafer 2, the outer
peripheral portion of the semiconductor wafer 2 is fractured along
the deteriorated layer 210 to be removed. Stress, which is
generated when the outer peripheral portion is cut with a cutting
blade, does not remain in the semiconductor wafer 2 whose outer
peripheral portion has been thus removed by laser processing.
Although the deteriorated layer 210 may be formed only in the
inside without being exposed to the front surface 2a and the back
surface 2b of the semiconductor wafer 2, it is desirable that a
plurality of deteriorated layers 210 are formed by carrying out the
above laser processing a plurality of times by changing the above
focusing point P stepwise so that they extend from the front
surface 2a to the back surface 2b of the semiconductor wafer 2.
[0033] The processing conditions in the above outer peripheral
portion removal step are set as follows, for example. [0034] Light
source: LD excited Q switch Nd:YVO4 laser [0035] Wavelength: pulse
laser beam having a wavelength of 1,064 nm [0036] Pulse output: 10
.mu.J [0037] Focusing spot diameter: 1.0 .mu.m [0038] Repetition
frequency: 100 kHz [0039] Revolution of chuck table: 1 rpm
[0040] Since the deteriorated layer which is formed at a time under
the above processing conditions is as thick as about 50 .mu.m, when
the semiconductor wafer 2 has a thickness of 500 .mu.m, ten
deteriorated layers are formed in the inside of the semiconductor
wafer 2 so that they can extend from the front surface 2a up to the
back surface 2b of the semiconductor wafer 2. As the revolution of
the chuck table under the above processing conditions is 1 rpm, one
deteriorated layer can be formed in minute, and therefore, even
when 10 deteriorated layers are formed in the inside of the
semiconductor wafer 2 from the front surface 2a up to the back
surface 2b, the operation time of the outer peripheral portion
removal step is 10 minutes which is much shorter than the operation
time of cutting with the cutting blade.
[0041] A description will be subsequently given of another
embodiment of the outer peripheral portion removal step with
reference to FIG. 6.
[0042] In the embodiment shown in FIG. 6, a pulse laser beam of a
wavelength having absorptivity for the semiconductor wafer 2 is
applied from the condenser 324 to remove the outer peripheral
portion of the wafer. That is, as shown in FIG. 6, the location on
the inside of the outer periphery by a predetermined distance of
the semiconductor wafer 2 held on the chuck table 31 is so brought
as to be a position right below the condenser 324. The chuck table
31, that is, the semiconductor wafer 2 is turned in the direction
indicated by the arrow in FIG. 6 while a pulse laser beam of a
wavelength having absorptivity for the semiconductor wafer 2 is
applied from the condenser 324. At this point, the focusing point P
of the pulse laser beam applied from the condenser 324 is set to a
position near the front surface 2a (top surface) of the
semiconductor wafer 2. As a result, an annular groove 220 reaching
the back surface 2b from the front surface 2a is formed at the
location on the inside of the outer periphery by a predetermined
distance of the semiconductor wafer 2 as shown in FIG. 6, whereby
the outer peripheral portion of the semiconductor wafer 2 is
removed.
[0043] The processing conditions in the above outer peripheral
portion removal step are set as follows, for example. [0044] Light
source: LD excited Q switch Nd:YVO4 laser [0045] Wavelength: pulse
laser beam having a wavelength of 355 nm [0046] Average output:
1.35 W [0047] Focusing spot diameter: 13 .mu.m [0048] Repetition
frequency: 100 kHz [0049] Revolution of chuck table: 0.1 rpm
[0050] Since the revolution of the chuck table under the above
processing conditions is 0.1 rpm, the operation time of the outer
peripheral portion removal step is 10 minutes, which is much
shorter than the operation time of cutting with the above cutting
blade.
[0051] A description will be subsequently given of still another
embodiment of the outer peripheral portion removal step with
reference to FIG. 7.
[0052] In the embodiment shown in FIG. 7, the outer peripheral
portion of one of the wafers of an SOI wafer 20 having a
double-layer structure manufactured by joining two wafers 20A and
20B through an oxide film is removed. That is, as shown in FIG. 7,
the SOI wafer 20 is first placed on the chuck table 31 in such a
manner that the wafer 20A, which is one of the two wafers, faces
up, and suction-held on the chuck table 31. Laser processing is
then carried out in the same manner as in the embodiment shown in
FIG. 6 to form an annular groove 220 in the wafer 20A at the
location on the inside of the outer periphery by a predetermined
distance, whereby the outer peripheral portion of the wafer 20A is
removed. In the outer peripheral portion removal step for removing
the outer peripheral portion of one wafer of the two wafers
constituting the SOI wafer 20, a deteriorated layer may be formed
in the inside of the wafer 20A along the outer periphery at the
location on the inside of the outer periphery by a predetermined
distance, in the same manner as the above embodiment in FIG. 5.
[0053] After the above outer peripheral portion removal step is
carried out as described above, a protective member 4 is affixed to
the front surface 2a of the semiconductor wafer 2 whose outer
peripheral portion has been removed, as shown in FIG. 8 (protective
member affixing step). Since the other wafer 20B functions as a
protective member in the case of the above SOI wafer 20, the
protective member may not be affixed to the undersurface of the
wafer 20B.
[0054] After the protective member 4 is affixed to the front
surface 2a of the semiconductor wafer 2 by carrying out the
protective member affixing step, next comes the grinding step for
grinding the back surface to be ground of the wafer whose outer
peripheral portion has been removed, to a predetermined finish
thickness. This grinding step is carried out by using a grinding
machine 5 in the embodiment shown in FIG. 9. That is, in the
grinding step, the protective member 4 side of the semiconductor
wafer 2 is first placed on the chuck table 51 of the grinding
machine 5 (therefore, the back surface 2b of the semiconductor
wafer 2 faces up), and the semiconductor wafer 2 is suction-held on
the chuck table 51 by a suction means that is not shown. A grinding
wheel 53 having a grindstone 52 is rotated at 6,000 rpm and brought
into contact with the back surface 2b of the semiconductor wafer 2
while the chuck table 51 is turned at 300 rpm, for example, to
grind the back surface 2b until its thickness becomes a
predetermined finish thickness, for example, 100 .mu.m. Even when
the semiconductor wafer 2 is thus ground until it becomes thin, as
the outer peripheral portion of the semiconductor wafer 2 has been
removed and the outer peripheral surface of the semiconductor wafer
2 is not arcuate, a sharp knife-edge is not formed. Further, since
stress does not remain in the outer peripheral portion of the
semiconductor wafer 2 whose outer peripheral portion has been
removed as described above, the semiconductor wafer 2 is not
damaged during grinding.
[0055] Next, a description will be given of a second embodiment of
the wafer grinding method of the present invention.
[0056] In this grinding method, the step of forming an annular
groove deeper than at least the finish thickness of the wafer from
the front surface by applying a laser beam of a wavelength having
absorptivity for the wafer along the outer periphery at a location
on the inside of the outer periphery of the wafer by a
predetermined distance, from the front surface side of the wafer is
first carried out. In this groove forming step, the laser beam
processing machine 3 shown in FIG. 2 is used, and a pulse laser
beam having absorptivity for the semiconductor wafer 2 is applied
from the condenser 324 as in the embodiment shown in FIG. 6 to form
an annular groove deeper than the finish thickness of the wafer
from the front surface in the outer peripheral portion of the
wafer. In this embodiment, the focusing point of the laser beam is
set at a position higher than the focusing point in the embodiment
shown in FIG. 6. And, as shown in FIG. 10, the location on the
inside of the outer periphery by a predetermined distance of the
semiconductor wafer 2 held on the chuck table 31 is brought to a
position right below the condenser 324. Then, the chuck table 31,
that is, the semiconductor wafer 2 is turned in the direction
indicated by the arrow in FIG. 10 while a pulse laser beam having
absorptivity for the semiconductor wafer 2 is applied from the
condenser 324. At this point, the focusing point P of the pulse
laser beam applied from the condenser 324 is set to a position
slightly higher than that of the embodiment shown in FIG. 6 near
the front surface 2a (top surface) of the semiconductor wafer 2. As
a result, an annular groove 230 having a predetermined depth from
the front surface 2a is formed in the semiconductor wafer 2 at the
location on the inside of the outer periphery by a predetermined
distance, as shown in FIG. 10. Stress, which is generated by
cutting with the cutting blade does not remain in the semiconductor
wafer 2 having the groove 230 that has been thus formed in the
outer peripheral portion by this laser processing.
[0057] The processing conditions in the above groove forming step
are set as follows, for example. [0058] Light source: LD excited Q
switch Nd:YVO4 laser [0059] Wavelength: pulse laser beam having a
wavelength of 355 nm [0060] Average output: 1.35 W [0061] Focusing
spot diameter: 13 .mu.m [0062] Repetition frequency: 100 kHz [0063]
Revolution of chuck table: 0.1 rpm
[0064] Since the revolution of the chuck table is 0.1 rpm in this
groove forming step, the operation time of the groove forming step
is 10 minutes, which is much shorter than the operation time of
cutting with the cutting blade.
[0065] After the above groove forming step is carried out as
described above, the protective member 4 is affixed to the front
surface 2a of the semiconductor wafer 2 having the groove 230
formed in the outer peripheral portion, as shown in FIG. 11
(protective member affixing step).
[0066] After the protective member 3 is affixed to the front
surface 2a of the semiconductor wafer 2 by carrying out the
protective member affixing step, next comes the grinding step for
grinding the back surface of the wafer having the groove in the
outer peripheral portion to a predetermined finish thickness. This
grinding step is carried out by using the grinding machine 5 shown
in FIG. 9 in accordance with the above-described procedure. When
the semiconductor wafer 2 is ground until its thickness becomes a
predetermined finish thickness, for example, 100 .mu.m, as shown in
FIG. 12, the groove 230 formed in the outer peripheral portion of
the semiconductor wafer 2 is exposed to the back surface 2b (top
surface). As a result, the outer peripheral portion having an
arcuate outer peripheral surface of the semiconductor wafer 2 is
removed. Therefore, the outer peripheral portion of the
semiconductor wafer becomes not knife-edged. Since the
above-mentioned stress does not remain in the outer peripheral
portion of the semiconductor wafer 2 having the groove 230 in the
outer peripheral portion, the semiconductor wafer 2 is not damaged
during grinding.
* * * * *