U.S. patent application number 14/722222 was filed with the patent office on 2015-09-24 for method for producing polished-article.
The applicant listed for this patent is NGK Insulators, Ltd.. Invention is credited to Kazumasa KITAMURA, Tomoki NAGAE.
Application Number | 20150266155 14/722222 |
Document ID | / |
Family ID | 52778802 |
Filed Date | 2015-09-24 |
United States Patent
Application |
20150266155 |
Kind Code |
A1 |
KITAMURA; Kazumasa ; et
al. |
September 24, 2015 |
METHOD FOR PRODUCING POLISHED-ARTICLE
Abstract
A grinding apparatus 10 includes a controller 11 for controlling
the entire apparatus, a grinding motor 14, a base metal 15 to be
rotated by the grinding motor 14, and a grinding wheel 16 fixed to
the base metal 15. In a grinding step, the grinding apparatus 10 is
used and a surface 19 of an object to be polished 18 is ground with
the grinding wheel 16 rotating at a peripheral speed of 10 m/s or
less. In the grinding step, the surface 19 of the object to be
polished 18 is preferably ground with the grinding wheel 16
rotating at a peripheral speed of 0.5 m/s or more. In the grinding
step, a surface of alumina, sapphire, silicon carbide, or gallium
nitride is ground as the object to be polished.
Inventors: |
KITAMURA; Kazumasa;
(Ichinomiya-City, JP) ; NAGAE; Tomoki;
(Nagoya-City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NGK Insulators, Ltd. |
Nagoya-City |
|
JP |
|
|
Family ID: |
52778802 |
Appl. No.: |
14/722222 |
Filed: |
May 27, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2014/076433 |
Oct 2, 2014 |
|
|
|
14722222 |
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Current U.S.
Class: |
451/41 |
Current CPC
Class: |
H01L 21/02013 20130101;
B24B 7/228 20130101; B24B 37/044 20130101; C30B 33/00 20130101;
B24B 37/08 20130101; B24B 9/065 20130101; B24B 37/105 20130101 |
International
Class: |
B24B 9/06 20060101
B24B009/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2013 |
JP |
2013-206888 |
Claims
1. A method for producing a polished-article that produces a
polished article by polishing an object to be polished, the method
for producing a polished-article comprising a grinding step of
grinding a surface of the object to be polished with a grinding
wheel rotating at a peripheral speed of 10 m/s or less.
2. The method for producing a polished-article according to claim
1, wherein the surface of the object to be polished is ground with
the grinding wheel rotating at a peripheral speed of 0.5 m/s or
more in the grinding step.
3. The method for producing a polished-article according to claim
1, wherein a surface of alumina, sapphire, silicon carbide, or
gallium nitride is ground as the object to be polished in the
grinding step.
4. The method for producing a polished-article according to claim
1, further comprising a lapping step of polishing the object to be
polished with abrasive grains after the grinding step.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for producing a
polished-article.
[0003] 2. Description of the Related Art
[0004] As a grinding method for a substrate, there has hitherto
been proposed a method in which a semiconductor substrate is given
a desired thickness by grinding front and back surfaces of the
semiconductor substrate with a surface grinding wheel including a
base metal and a balance wall projecting from a surface of an outer
peripheral portion of the base metal opposite from a surface from
which an annular outer peripheral wall projects, in a direction
opposite from the annular outer peripheral wall (see, for example,
Patent Literature 1). It is described that this method can provide
a surface grinding wheel in which deformation of the base metal is
suppressed and grinding quality and grinding accuracy are
maintained even when the surface grinding wheel is rotated at high
speed.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Unexamined Patent Application Publication
No. 2005-271160
SUMMARY OF INVENTION
[0006] For example, in the grinding method described in Patent
Literature 1, grinding is performed for as short a time as possible
with high rotation at 1500 to 10000 rpm, and smoothness is further
increased by a later polishing step. In such a grinding step,
strain, a damaged layer, a microcrack, or the like is caused in the
surface, and the obtained substrate has a high surface roughness.
It is possible to deal with this problem by removing strain, a
damaged layer, a microcrack, or the like in the later polishing
step. However, the polishing step takes much time, and a long
processing time is required until the completion of the grinding
and polishing steps.
[0007] The present invention has been made in view of these
problems, and an object of the invention is to provide a method for
producing a polished-article that can further improve machining
quality in a grinding step. Another object of the invention is to
provide a producing method for polished-article that can further
shorten the processing time.
[0008] As a result of earnest study to achieve the above main
objects, the present inventors found that the machining quality in
the grinding step could be further improved and the total
processing time in the grinding and polishing steps could be
further shortened by considering the processing time in total and
reviewing working in the grinding step, and achieved the present
invention.
[0009] A method for producing a polished-article of the present
invention is a method that produces a polished article by polishing
an object to be polished, the method for producing a
polished-article including a grinding step of grinding a surface of
the object to be polished with a grinding wheel rotating at a
peripheral speed of 10 m/s or less.
[0010] The producing method for the polished-article according to
the present invention can further improve machining quality in the
grinding step and can further shorten the processing time in the
grinding and polishing steps. This is because, in the grinding
step, the occurrence of strain, a damaged layer, a microcrack, or
the like due to machining can be further suppressed by performing
low-speed grinding that was not performed before. As a result, the
processing time in the grinding step is lengthened, but the time
required for the polishing step after the grinding step can be
greatly shortened. Thus, the processing time in the grinding and
polishing steps can be shortened.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a flowchart showing an example of a substrate
machining process.
[0012] FIG. 2 is a schematic structural view illustrating an
example of a configuration of a grinding apparatus 10 according to
an embodiment.
[0013] FIG. 3 is a schematic structural view illustrating an
example of a structure of a lapping device 20 according to the
embodiment.
[0014] FIG. 4 is a schematic structural view illustrating an
example of a structure of a CMP device 30 according to the
embodiment.
[0015] FIG. 5 shows images of surfaces after grinding in Example 1
and Comparative Example 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Next, an embodiment of the present invention will be
described with reference to the drawings. FIG. 1 is a flowchart
showing an example of a substrate machining process according to an
embodiment of the present invention. FIG. 2 is a schematic
structural view illustrating an example of a configuration of a
grinding apparatus 10 according to the embodiment. FIG. 3 is a
schematic structural view illustrating an example of a structure of
a lapping device 20 according to the embodiment. FIG. 4 is a
schematic structural view illustrating an example of a structure of
a CMP (chemical mechanical polishing) device 30 according to the
present invention.
[0017] A method for producing a polished-article according to the
embodiment includes a cutting step of obtaining a disc-shaped
object to be polished by cutting a columnar ingot (Step S100), a
grinding step of grinding the object to be polished obtained by
cutting (Step S110), a lapping step of polishing the ground object
to be polished (Step S120), a CMP step of further performing in
tandem with chemical treatment (Step S130), and a cleaning step of
performing surface cleaning (Step S140), and obtains a polished
article subjected to polishing. Herein, the grinding step, the
lapping step, and the CMP step will be described mainly. For
example, the lapping step and the CMP step may be omitted, or a
step other than these steps, such as a polishing step, may be added
appropriately.
[0018] For example, an object to be polished 18 includes various
kinds of semiconductor wafers and single crystal wafers, and
contains silicon, silicon oxide, alumina, sapphire, or silicon
carbide, or a compound semiconductor such as gallium nitride,
gallium phosphate, gallium arsenide, indium phosphide, lithium
niobate, or lithium tantalate.
[0019] (Grinding Step)
[0020] In the grinding step, an object to be polished 18
(substrate) is ground with a grinding apparatus 10 illustrated in
FIG. 2. The grinding apparatus 10 includes a controller 11 for
controlling the entire apparatus, a grinding motor 14, a base metal
15 to be rotated by the grinding motor 14, and a grinding wheel 16
fixed to the base metal 15. A grinding mechanism 12 of the grinding
apparatus 10 is configured as a mechanism that carries out infeed
machining for grinding the object to be polished 18 with the
grinding wheel 16 while axially rotating the grinding wheel 16 and
axially rotating the object to be polished 18 fixed to an
unillustrated fixing plate. The grinding apparatus 10 is provided
with the grinding motor 14 that can output sufficient torque when
the grinding wheel 16 rotates in a low-speed rotation range, for
example, a rotation speed range higher than or equal to 10 rpm and
less than 2000 rpm. The controller 11 controls driving of the
grinding motor 14 so that the grinding motor 14 rotates at a
predetermined number of rotations.
[0021] In the grinding step, a surface 19 of the object to be
polished 18 is ground with the grinding wheel 16 that rotates at a
peripheral speed of 10 m/s or less. This can further improve
machining quality in the grinding step and can further shorten the
processing time in the grinding and polishing steps. In this
grinding step, the surface 19 of the object to be polished 18 is
preferably ground with the grinding wheel 16 that rotates at a
peripheral speed of 0.5 m/s or more. This is preferable because
lengthening of the time in the grinding step can be further
suppressed and the processing time in the grinding and polishing
steps can be further shortened. In the grinding step, for example,
the number of rotations of the grinding wheel 16 is preferably 1000
rpm or less, and more preferably 800 rpm or less. The cut amount in
the grinding step can be appropriately set according to the
peripheral speed of the grinding wheel 16, and for example, the cut
amount is preferably within the range of 0.1 to 50 .mu.m/min, more
preferably within the range of 0.5 to 40 .mu.m/min, and further
preferably within the range of 1 to 30 .mu.m/min.
[0022] Here, the grinding step will be described. The grinding step
is generally performed while the grain cut depth is smaller than a
critical cut depth Dc. This critical cut depth Dc refers to the cut
amount at a transition point in a deformation process from a
brittle mode to a ductile mode in ductile mode machining of a hard
brittle material. The grain cut depth is inversely proportional to
the peripheral speed (that is, number of rotations) of the grinding
wheel. To decrease the grain cut depth, it is necessary to increase
the peripheral speed of the grinding wheel. However, when the
peripheral speed of the grinding wheel is increased, the load on
the abrasive grains decreases, and the abrasive grains become
susceptible to abrasion and wear. Although abrasion and wear of the
abrasive grains are so small that they cause no problem for general
materials, they become heavy particularly for a high-hardness
material. This sometimes deteriorates the machining quality. In the
present invention, abrasion and wear of the abrasive grains are
further suppressed by further decreasing the peripheral speed of
the grinding wheel.
[0023] For example, the grinding wheel 16 used in the grinding step
can be formed by compacting abrasive grains of oxide, carbide,
nitride, and diamond. Examples of the grinding wheel 16 are a
vitrified bonded wheel to be fired at high temperature by using
clay, such as feldspar, as the binder, a metal bonded wheel fixed
by metal, and a resin bonded wheel to be fired at low temperature
by using a synthetic resin of phenol, formalin, or the like. Since
the grinding wheel 16 is rotated at low peripheral speed, which was
not adopted before, in the grinding apparatus 10, the hardness,
porosity, and so on thereof are appropriately adjusted. For
example, the grinding wheel 16 may be an electrodeposited grain
wheel in which abrasive grains are fixed by a plating layer.
[0024] (Lapping Step)
[0025] In the lapping step, the object to be polished 18 is lapped
with a lapping device 20 illustrated in FIG. 3. As illustrated in
FIG. 3, the lapping device includes an upper surface plate 22, a
rotatable lower surface plate 23 disposed opposed to the upper
surface plate 22, and disc-shaped carriers 24 to be clamped between
these laps. The object to be polished 18 is placed on lower
surfaces of the carriers 24. The object to be polished 18 is
clamped by the upper surface plate 22 and the lower surface plate
23, and is polished with abrasive grains to increase flatness.
[0026] (CMP Step)
[0027] In the CMP step, the object to be polished 18 is chemically
and mechanically polished with a CMP device 30 illustrated in FIG.
4. As illustrated in FIG. 4, the CMP device 30 includes a surface
plate 32, a polishing head 33, and a slurry supply device 34. A
polishing pad 40 is attached to the surface plate 32. Slurry is
supplied from the slurry supply device 34 onto the polishing pad
40, and the surface plate 32 rotates. Also, the polishing head 33
rotates in the same direction as the surface plate 32 while
pressing the object to be polished 18 placed on the polishing pad
40 against the polishing pad 40, and thereby chemically and
mechanically polishes the surface 19 of the object to be polished
18. The slurry is supplied from the slurry supply device 34 of the
CMP device 30 onto a surface of the polishing pad 40. The slurry
contains an abrasive material, an acid, an oxidant, a surfactant,
and water. As the abrasive material, for example, colloidal silica,
fumed silica, alumina, titania, zirconia, diamond, and a mixture of
these materials can be used. As the oxidant, for example, peroxide
and nitrate can be used. The slurry may further contain a pH
adjuster. The pH adjuster appropriately uses an acid substance or a
basic substance in order to adjust the pH value of the slurry to a
desired value.
[0028] According to the above-described method for producing a
polished-article of the embodiment, the machining quality in the
grinding step can be further improved, and the processing time in
the grinding and polishing steps can be further shortened. This is
because the occurrence of strain, a damaged layer, and a microcrack
due to machining can be further suppressed by performing
lower-speed grinding, which was not performed before, in the
grinding step. As a result, the processing time in the grinding
step is lengthened, but the time required for the polishing step
after the grinding step can be greatly shortened. Thus, the
processing time in the grinding and polishing steps can be
shortened.
[0029] The present invention is not limited to the above-described
embodiment, and can be carried out by various modes as long as they
belong to the technical scope of the invention.
EXAMPLES
[0030] Cases in which a polished article was concretely produced
will be described below as examples. The present invention is not
limited to the following examples, and can be carried out by
various modes as long as they belong to the technical scope of the
invention.
[0031] [Production of Grinding Apparatus]
[0032] Since there has been no demand for the grinding apparatus
including the grinding motor 14 that rotates at low speed and the
apparatus did not exist, the above-described grinding apparatus was
produced. The grinding apparatus was produced by using a grinding
motor that generated sufficient torque (for example 20 to 60 Nm)
when a grinding wheel was rotated at a peripheral speed of 10 m/s
or less and using a controller that rotated the grinding motor at
the peripheral speed of 10 m/s or less.
Example 1
[0033] A single crystal wafer of high-purity alumina was prepared,
and a grinding step was performed by the grinding apparatus
illustrated in FIG. 2. In the grinding step, a grinding wheel
having a diameter of 150 cm was used and rotated at a peripheral
speed of 10 m/s (number of rotations of 1000 rpm) to grind the
alumina wafer serving as an object to be polished. At this time,
the cut amount was 30 .mu.m/min. As the grinding wheel, a vitrified
bonded wheel mainly composed of glass was used.
[0034] (Lapping Step)
[0035] The above-described ground wafer was subjected to lapping.
Lapping was performed for three hours by using the lapping device
20 illustrated in FIG. 3 while the number of rotations of the upper
surface plate was set at 60 rpm, the number of rotations of the
lower surface plate was set at 60 rpm, and abrasive grains of
diamond were used.
Comparative Example 1
[0036] In Comparative Example 1, an operation similar to that of
Example 1 was performed except that the grinding wheel was rotated
at a peripheral speed of 15 m/s (number of rotations of 1500 rpm),
the cut amount was 60 .mu.m/min, and the lapping time was nine
hours.
Examples 2 and 3
[0037] In Examples 2 and 3, operations similar to that of Example 1
were performed except that an object to be polished was a sapphire
wafer and a GaN wafer, respectively.
Comparative Examples 2 and 3
[0038] In Comparative Examples 2 and 3, operations similar to that
of Comparative Example 1 were performed except that an object to be
polished was a sapphire wafer and a GaN wafer, respectively.
[0039] (Measurement of Surface Roughness Ra)
[0040] The surface roughnesses Ra in Examples 1 to 3 and
Comparative Example 1 were measured. The measurement was taken in
conformity with JIS-B0601-2001.
[0041] (Result and Study)
[0042] FIG. 5 shows images of surfaces after grinding in Example 1
and Comparative Example 1. As shown in FIG. 5, the surface
roughness Ra after grinding was 0.5 .mu.m in Comparative Example 1,
whereas it was 0.1 .mu.m in Example 1. Thus, the surface roughness
was improved. Further, it was found that the occurrence of strain,
a damaged layer, and a microcrack due to machining was suppressed.
For this reason, the total time required until the completion of
the grinding and lapping steps was 9.5 hours in Comparative Example
1, whereas it was 4.0 hours in Example 1. Thus, it was revealed
that the total processing time was shortened in Example 1. This is
the same for Examples 2 and 3, in which the surface roughness Ra
was 0.1 .mu.m and 0.1 .mu.m, respectively, and was improved,
compared with the surface roughnesses Ra of 0.1 .mu.m and 0.2 .mu.m
in Comparative Examples 2 and 3. Further, in Examples 2 and 3, the
total processing time in the grinding step and the lapping step was
four hours and seven hours, respectively. Thus, the total
processing time was shortened, compared with eight hours and
fifteen hours in Comparative Examples 2 and 3. In this way, the
occurrence of strain, a damaged layer, and a microcrack due to
machining can be further suppressed by performing lower-speed
grinding, which was not performed before, in the grinding step. As
a result, it is found that the processing time in the grinding step
is lengthened, but the time required for the lapping step after the
grinding step can be greatly shortened and the processing time in
the grinding and polishing steps can be shortened.
[0043] The present application claims priority from Japanese Patent
Application No. 2013-206888 filed on Oct. 2, 2013, the entire
contents of which are incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0044] The polishing method for the object to be polished according
to the present invention can be used to polish a surface of an
object to be polished such as a semiconductor wafer.
* * * * *