U.S. patent application number 14/771967 was filed with the patent office on 2016-01-14 for template assembly and method of producing template assembly.
This patent application is currently assigned to Shin-Etsu Handotai Co., Ltd.. The applicant listed for this patent is SHIN-ETSU HANDOTAI CO., LTD.. Invention is credited to Michito SATO.
Application Number | 20160008947 14/771967 |
Document ID | / |
Family ID | 51579672 |
Filed Date | 2016-01-14 |
United States Patent
Application |
20160008947 |
Kind Code |
A1 |
SATO; Michito |
January 14, 2016 |
TEMPLATE ASSEMBLY AND METHOD OF PRODUCING TEMPLATE ASSEMBLY
Abstract
The invention is directed to a template assembly configured to
hold a workpiece in polishing of the workpiece, including: a PET
base; an annular template adhering to an outer circumferential
portion of a lower surface of the PET base, the template having an
annular notch formed at an upper portion of an inner surface of the
template; and a discoid backing pad whose peripheral portion is
fitted into the notch, the backing pad adhering to a central
portion of the lower surface of the PET base, wherein a recess
configured to receive and hold the workpiece during polishing is
defined by the inner surface of the template and a lower surface of
the backing pad. This template assembly can reduce in-plane
variation in depth of the recess and thereby improve flatness of a
polished workpiece while inhibiting the occurrence of a scratch and
a defect of the workpiece.
Inventors: |
SATO; Michito;
(Nishigo-mura, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHIN-ETSU HANDOTAI CO., LTD. |
Chiyoda-ku, Tokyo |
|
JP |
|
|
Assignee: |
Shin-Etsu Handotai Co.,
Ltd.
Tokyo
JP
|
Family ID: |
51579672 |
Appl. No.: |
14/771967 |
Filed: |
February 26, 2014 |
PCT Filed: |
February 26, 2014 |
PCT NO: |
PCT/JP2014/000997 |
371 Date: |
September 1, 2015 |
Current U.S.
Class: |
451/442 ;
156/153; 156/303.1 |
Current CPC
Class: |
B24B 31/12 20130101;
B24B 37/30 20130101 |
International
Class: |
B24B 31/12 20060101
B24B031/12; B24B 37/30 20060101 B24B037/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2013 |
JP |
2013-060418 |
Claims
1-7. (canceled)
8. A template assembly configured to hold a workpiece in polishing
of the workpiece, comprising: a polyethylene terephthalate (PET)
base; an annular template adhering to an outer circumferential
portion of a lower surface of the PET base, the template having an
annular notch formed at an upper portion of an inner surface of the
template; and a discoid backing pad whose a peripheral portion is
fitted into the notch, the backing pad adhering to a central
portion of the lower surface of the PET base, wherein a recess
configured to receive and hold the workpiece during polishing is
defined by the inner surface of the template and a lower surface of
the backing pad.
9. The template assembly according to claim 8, wherein the notch
has a thickness equal to or less than a target thickness of the
backing pad.
10. The template assembly according to claim 8, wherein the
template is made of glass epoxy resin.
11. The template assembly according to claim 9, wherein the
template is made of glass epoxy resin.
12. The template assembly according to claim 8, wherein in-plane
variation in depth of the recess is equal to or less than 10
.mu.m.
13. The template assembly according to claim 9, wherein in-plane
variation in depth of the recess is equal to or less than 10
.mu.m.
14. The template assembly according to claim 10, wherein in-plane
variation in depth of the recess is equal to or less than 10
.mu.m.
15. The template assembly according to claim 11, wherein in-plane
variation in depth of the recess is equal to or less than 10
.mu.m.
16. A method of producing a template assembly according to claim 8,
comprising: preparing the annular template having the annular notch
formed at the upper portion of the inner surface of the template;
sticking the discoid backing pad on the central portion of the PET
base; and sticking the template on the outer circumferential
portion of the lower surface of the PET base such that the
peripheral portion of the backing pad is fitted into the notch of
the template.
17. A method of producing a template assembly according to claim
15, comprising: preparing the annular template having the annular
notch formed at the upper portion of the inner surface of the
template; sticking the discoid backing pad on the central portion
of the PET base; and sticking the template on the outer
circumferential portion of the lower surface of the PET base such
that the peripheral portion of the backing pad is fitted into the
notch of the template.
18. The method according to claim 16, wherein the step of preparing
the template includes: preparing a substrate for the template;
cutting the prepared substrate into an annular shape; and then
forming the notch by grinding an upper portion of an inner surface
of the annular substrate.
19. The method according to claim 17, wherein the step of preparing
the template includes: preparing a substrate for the template;
cutting the prepared substrate into an annular shape; and then
forming the notch by grinding an upper portion of an inner surface
of the annular substrate.
20. The method according to claim 16, wherein the step of preparing
the template includes: before forming the notch, lapping and/or
polishing the template such that in-plane variation in thickness of
the template is equal to or less than 10 .mu.m.
21. The method according to claim 17, wherein the step of preparing
the template includes: before forming the notch, lapping and/or
polishing the template such that in-plane variation in thickness of
the template is equal to or less than 10 .mu.m.
22. The method according to claim 18, wherein the step of preparing
the template includes: before forming the notch, lapping and/or
polishing the template such that in-plane variation in thickness of
the template is equal to or less than 10 .mu.m.
23. The method according to claim 19, wherein the step of preparing
the template includes: before forming the notch, lapping and/or
polishing the template such that in-plane variation in thickness of
the template is equal to or less than 10 .mu.m.
Description
TECHNICAL FIELD
[0001] The present invention relates to a template assembly used in
polishing of a surface of workpieces, such as various semiconductor
wafers starting with silicon wafers, to hold the workpiece and a
method of producing the template assembly.
BACKGROUND ART
[0002] The apparatuses that can be mentioned as apparatuses for
polishing surfaces of a workpiece such as a silicon wafer are a
single-side polishing apparatus to polish one surface of the
workpiece at a time and a double-side polishing apparatus to polish
both surfaces of the workpiece simultaneously. A typical
single-side polishing apparatus 200 as shown in FIG. 8 is
constituted of a turn table 203 to which a polishing pad 202 is
attached, a polishing agent supply mechanism 204, a polishing head
201, and so on. The polishing apparatus 200 holds a workpiece W
with the polishing head 201, rotates the turn table 203 and the
polishing head 201 while supplying a polishing agent 205 to the
polishing pad 202 from the polishing agent supply mechanism 204,
and brings a surface of the workpiece W into sliding contact with
the polishing pad 202 to polish the workpiece W.
[0003] A polishing head with a retainer ring or a polishing head
with a template assembly is used as a means of holding a
workpiece.
[0004] This polishing head with a retainer ring serves a function
to press a polishing pad at the periphery of the workpiece by the
retainer ring and thereby to prevent compressive deformation of the
polishing pad due to the workpiece itself, so as to prevent an
outer peripheral sag of the workpiece. The structure of this
polishing head however is complicated and makes its cost high.
[0005] FIG. 9 shows an example of a conventional polishing head
with a template assembly. As shown in FIG. 9, this template
assembly has a backing pad 102 and an annular template 103 adhering
to the outer circumferential portion of the lower surface of the
backing pad. The inner surface of the template and the lower
surface of the backing pad 102 define a recess. During polishing, a
workpiece W is received and held in this recess. The polishing head
101 is configured such that this template assembly is stuck to a
polishing head body 104 by double-stick tape 105. Glass epoxy
resin, for example, is used as the material of the template
103.
[0006] In this polishing head 101 with the template assembly, the
shape of the outer circumference of the wafer W is controlled by a
difference between the depth of the recess of the template assembly
and the thickness of the wafer W. In other words, proper selection
of the thickness of the template 103 enables adjustment of the
pressure of the workpiece outer circumference during polishing, so
the outer peripheral sag can be comparatively readily inhibited
without using a polishing head having a complicated structure.
[0007] However, variation in the depth of the recess of the
template assembly is larger compared with the precision of the
thickness of a wafer. This makes it difficult to stably achieve the
target difference in the thickness.
[0008] Accordingly, the surface of the backing pad is subjected to
a buffing process after the backing pad is formed or the template
is ground or lapped to improve the variation in the depth of the
recess (See Patent Document 1).
[0009] A template assembly with a PET base, as shown in FIG. 10, is
also known (See Patent Document 2). As shown in FIG. 10, in the
template assembly 110, a template 103 subjected to a grinding or
lapping process is stuck directly to a PET base 106 and a backing
pad 102 having a thickness whose variation is reduced by a buffing
process is attached to the inside of the template.
CITATION LIST
Patent Literature
[0010] Patent Document 1: Japanese Unexamined Patent publication
(Kokai) No. 2009-208199 [0011] Patent Document 2: Japanese
Unexamined Patent publication (Kokai) No. 2008-93811 [0012] Patent
Document 3: Japanese Unexamined Patent publication (Kokai) No.
H7-58066
SUMMARY OF INVENTION
Technical Problem
[0013] The above method of buffing the backing pad or grinding and
polishing the template is effective in reducing variation in
thickness of each of the backing pad and the template. It is
however difficult to improve the precision of adhesion between the
template and the backing pad, which is an elastic body. The
precision of the template assembly such as in-plane variation in
depth of the recess cannot greatly be improved.
[0014] The recess of a commercially available template assembly has
the depth with precision of a variation of .+-.20 .mu.m from the
target value. In-plane variation of the depth is about 15
.mu.m.
[0015] Variation in thickness from the target thickness of the
template can be improved to within .+-.3 .mu.m and in-plane
variation in its thickness can be improved to 3 .mu.m or less after
grinding and polishing the template. After the template is stuck to
the backing pad, however, the recess of the template assembly has
the depth with precision of a variation of .+-.10 .mu.m from the
target value and the in-plane variation in the depth is degraded to
about 10 .mu.m.
[0016] In the template assembly 110 shown in FIG. 10, which has the
template and the backing pad directly stuck to the PET base, the
precision of adhesion can comparatively readily be improved because
glass epoxy resin used as the template is hard, so the precision of
the template assembly can be improved. Since the backing pad having
a discoid shape is attached to the inner surface of the template,
however, a space is created between the template and the backing
pad. During polishing, slurry enters this space. This slurry is a
source of generating particles that exerts an adverse effect on the
quality of a polished workpiece such as a fine scratch and a defect
of the workpiece.
[0017] Compared with the template assembly having the template
stuck to the backing pad as shown in FIG. 9, the template assembly
110 having the template with an increased thickness has a smaller
gap between the template and the polishing pad because the template
hardly sinks in during polishing. This results in a shortage of
slurry supply to a workpiece surface and may adversely affect the
workpiece quality. Accordingly, the template cannot be thickened
too much.
[0018] It is also known that an annular groove is formed in the
backing pad along the inner surface of the template so that the
outer peripheral sag of a workpiece is inhibited (See Patent
Document 3). Even this method cannot improve defects on the
workpiece surface because the slurry enters the groove during
polishing and becomes the source of generating particles.
[0019] The present invention was accomplished in view of the
above-described problems. It is an object of the present invention
to provide a template assembly that can reduce the in-plane
variation in depth of the recess and thereby improve flatness of a
polished workpiece while inhibiting the occurrence of a scratch and
a defect of the workpiece.
Solution to Problem
[0020] To achieve this object, the present invention provides a
template assembly configured to hold a workpiece in polishing of
the workpiece, comprising: a polyethylene terephthalate (PET) base;
an annular template adhering to an outer circumferential portion of
a lower surface of the PET base, the template having an annular
notch formed at an upper portion of an inner surface of the
template; and a discoid backing pad whose peripheral portion is
fitted into the notch, the backing pad adhering to a central
portion of the lower surface of the PET base, wherein a recess
configured to receive and hold the workpiece during polishing is
defined by the inner surface of the template and a lower surface of
the backing pad.
[0021] Such a template assembly has no space between the template
and the backing pad and generate no particle during polishing,
thereby enabling inhibition of the occurrence of the scratch and
defect of the workpiece. In addition, since the template and the
backing pad are stuck to the PET base, this template assembly can
reduce in-plane variation in their thickness and hence in-plane
variation in depth of the recess and thereby improve the flatness
of the polished workpiece.
[0022] The notch preferably has a thickness equal to or less than a
target thickness of the backing pad.
[0023] Such a template assembly prevents the formation of a space
between the template and the backing pad. If the notch has a
thickness less than the target thickness of the backing pad, then a
polishing pressure of the outer circumferential portion of the
workpiece can be reduced and the amount of polishing the outer
circumferential portion of the workpiece can thereby be reduced, so
the outer peripheral sag can be inhibited.
[0024] The template is preferably made of glass epoxy resin.
[0025] Such a template has excellent mechanical properties and can
prevent metal contamination and scratch of the workpiece.
[0026] Moreover, in-plane variation in depth of the recess is
preferably equal to or less than 10 .mu.m.
[0027] Such a template assembly can reliably improve the flatness
of the polished workpiece.
[0028] Furthermore, the present invention provides a method of
producing the inventive template assembly, comprising: preparing
the annular template having the annular notch formed at the upper
portion of the inner surface of the template; sticking the discoid
backing pad on the central portion of the PET base; and sticking
the template on the outer circumferential portion of the lower
surface of the PET base such that the peripheral portion of the
backing pad is fitted into the notch of the template.
[0029] This method can produce the inventive template assembly that
can reduce the in-plane variation in the thickness of the template
and the backing pad and improve the flatness of the polished
workpiece while inhibiting the occurrence of the scratch and defect
of the workpiece.
[0030] The step of preparing the template may include: preparing a
substrate for the template; cutting the prepared substrate into an
annular shape; and then forming the notch by grinding an upper
portion of an inner surface of the annular substrate.
[0031] In this manner, the annular template having the notch can
readily be prepared.
[0032] The step of preparing the template preferably includes:
before forming the notch, lapping and/or polishing the template
such that in-plane variation in thickness of the template is equal
to or less than 10 .mu.m.
[0033] In this manner, the in-plane variation in depth of the
recess that is defined by the inner surface of the template and the
lower surface of the backing pad can reliably be reduced.
Advantageous Effects of Invention
[0034] The inventive template assembly includes a PET base, an
annular template adhering to the outer circumferential portion of
the lower surface of the PET base, and a discoid backing pad
adhering to the central portion of the lower surface of the PET
base; an annular notch is formed at an upper portion of the inner
surface of the template; a peripheral portion of the backing pad is
fitted into the notch. This template assembly can inhibit the
occurrence of the scratch and defect of a workpiece without
generating particles during polishing, and reduce the in-plane
variation in thickness of the template and the backing pad and
hence the in-plane variation in depth of the recess, thereby
enabling improvement in flatness of a polished workpiece.
BRIEF DESCRIPTION OF DRAWINGS
[0035] FIG. 1 is a schematic diagram of an example of the inventive
template assembly;
[0036] FIG. 2 is an enlarged view around the notch having the same
thickness as the target thickness of the backing pad of the
inventive template assembly;
[0037] FIG. 3 is an enlarged view around the notch having a smaller
thickness than the target thickness of the backing pad of the
inventive template assembly;
[0038] FIG. 4 is a diagram of the relationship of roll off to
variation in depth of the recess from the target value in examples
1 and 2 and comparative examples 1 and 2;
[0039] FIG. 5 is a diagram showing the average, the maximum, and
the minimum of roll off in examples 1 and 2 and comparative
examples 1 and 2;
[0040] FIG. 6 is a radar chart of a difference in position of roll
off at eight points in a plane in examples 1 and 2 and comparative
examples 1 and 2;
[0041] FIG. 7 is a diagram showing the number of defects of wafers
in examples 1 and 2 and comparative examples 1 and 3;
[0042] FIG. 8 is a schematic diagram of an example of a common
polishing apparatus;
[0043] FIG. 9 is a schematic diagram of an example of a
conventional template assembly;
[0044] FIG. 10 is a schematic diagram of another example of a
conventional template assembly; and
[0045] FIG. 11 is an explanatory view of a method of measuring the
depth of the recess in examples 1 and 2 and comparative examples 1
to 3.
DESCRIPTION OF EMBODIMENTS
[0046] An embodiment of the present invention will be hereinafter
described, but the present invention is not limited to this
embodiment.
[0047] First, the inventive template assembly will be described
with reference to FIGS. 1 and 2.
[0048] As shown in FIG. 1, the inventive template assembly 1 has a
polyethylene terephthalate (PET) base 2, an annular template 3, and
a discoid backing pad 4. The thickness and the shape of the PET
base 2 are not particularly limited; for example, the shape may be
discoid.
[0049] The backing pad 4 holds a workpiece W by attaching the
workpiece W on its lower surface containing water. The backing pad
4 may be made of, for example, foamed polyurethane. This backing
pad 4 containing water can reliably hold the workpiece W by surface
tension of the wafer contained in the backing pad 4.
[0050] The template 3 is stuck on an outer circumferential portion
of the lower surface of the PET base 2. The backing pad 4 is stuck
on a central portion of the lower surface of the PET base 2.
[0051] The inner surface of the template 3 and the lower surface of
the backing pad 4 define a recess 6. During polishing of the
workpiece W, the workpiece W is received in this recess 6, and the
edge and the upper surface of the workpiece W are held on the inner
surface of the template 3 and the lower surface of the backing pad
4, respectively.
[0052] The template assembly having the template 3 and backing pad
4 that both adhere directly to the PET base 2 in this manner can
reduce the difference between the actual depth and the target depth
of the recess 6 and the in-plane variation of the depth of the
recess 6. Accordingly, the flatness of the workpiece W polished
with the inventive template assembly can be improved especially by
reducing the outer peripheral sag of the workpiece W. In
particular, when the in-plane variation in depth of the recess is
10 .mu.m or less, the flatness of the workpiece W can reliably be
improved.
[0053] The template 3 is preferably made of a material that is
softer than the workpiece W and has high abrasion resistance that
makes it hard to wear when being brought into sliding contact with
a polishing pad during polishing, for such a material avoids
contamination, a scratch, and an impression of the workpiece W.
From this viewpoint, an exemplary material of the template 3 may be
glass epoxy resin.
[0054] As shown in FIG. 1, an annular notch 5 is formed at an upper
portion of the inner surface of the template 3. The backing pad 4
is stuck on the central portion of the lower surface of the PET
base 2 such that a peripheral portion of the backing pad 4 is
fitted into the notch 5. This configuration allows the template
assembly to use the template 3 and the backing pad 4 that are
directly stuck on the PET base 2 and have no space between the
template 3 and the backing pad 4. This template assembly can
thereby prevent the generation of particles due to slurry entering
a space during polishing and inhibit the occurrence of a fine
scratch and defect of the workpiece, which are problems of a
conventional template assembly.
[0055] As shown in FIG. 2, the notch 5 preferably has a thickness d
that is equal to or less than the target thickness of the backing
pad 4 so that no space is defined between the backing pad 4 and the
template.
[0056] As shown in FIG. 3, the notch 5 may have a thickness d less
than the target thickness of the backing pad 4 so that the outer
peripheral sag of the workpiece is more effectively inhibited. In
this manner, the peripheral portion of the backing pad 4 that is
held by the template 3 is compressed annularly, resulting in
reduction in polishing pressure of the outer circumferential
portion of the workpiece. This reduction reduces the amount of
polishing the outer circumferential portion of the workpiece and
thereby enables the inhibition of the outer peripheral sag of the
workpiece.
[0057] The inventive template assembly with the notch 5 can adjust
the polishing pressure of the outer circumferential portion of the
workpiece by adjusting the thickness of the notch 5 without
changing the thickness of the template 3. The template assembly can
therefore inhibit a shortage of slurry supply due to a decreased
space between the template 3 and the polishing pad, thereby
enabling the inhibition of the occurrence of surface defects of the
workpiece.
[0058] This configuration also allows for the combination with the
method of forming an annular groove in the backing pad 4.
[0059] Next, the method of producing the inventive template
assembly will be described.
[0060] As shown in FIG. 1, the annular template 3 having the
annular notch 5 formed at the upper portion of its inner surface is
first prepared. This step may be performed for example as
follows:
[0061] A substrate for the template such as a glass epoxy resin
substrate is prepared. This substrate is lapped and/or polished so
as to have the target thickness.
[0062] At this time, the in-plane variation in thickness of the
template 3 is preferably reduced to 10 .mu.m or less. In this
manner, the surface shape of the outer circumferential portion of
the workpiece can be inhibited from partially degrading during
polishing of the workpiece.
[0063] If lapping is performed at this time, then exemplary
abrasive grains that can be used are alumina or SiC abrasive
grains. If polishing is performed at this time, then an alkali
solution containing colloidal silica, for example, can be used.
[0064] The substrate is then cleaned to remove the abrasive grains
and/or alkali solution attached in the lapping and/or
polishing.
[0065] The substrate is next cut into the annular template 3, for
example, by a numerical control. The notch 5 is then formed by
grinding the upper portion of the inner surface of the annular
template 3. In this grinding, the thickness of the notch 5 is
adjusted to a prescribed thickness that is equal to or less than
the target thickness of the backing pad 4, as described above.
[0066] The discoid backing pad 4 is stuck on the central portion of
the PET base 2. The diameter of the backing pad 4 is adjusted such
that the backing pad can be fitted into the annular notch 5 formed
as above. The template 3 is stuck on the outer circumferential
portion of the lower surface of the PET base 2 such that the
peripheral portion of the backing pad 4 is fitted into the notch 5
of the template 3.
[0067] This inventive method can produce the inventive template
assembly.
EXAMPLE
[0068] The present invention will be more specifically described
with reference to examples and comparative examples, but the
present invention is not limited to these examples.
Example 1
[0069] The inventive template assembly as shown in FIG. 1 was
produced according to the inventive producing method to evaluate
the precision of the depth of the recess. The precision of the
depth of the recess was evaluated by the difference in depth from
the target depth and the in-plane variation in depth.
[0070] A glass epoxy resin substrate was lapped so as to have a
thickness close to the target thickness. The substrate was then
polished with a slurry containing about 1 .mu.m of cerium oxide
powder and cut into an annular shape with a prescribed size. The
notch having the same thickness as the backing pad was then formed
by annularly grinding the substrate up to a position of 5 mm away
from the inner circumference with a lathe.
[0071] The template thus produced was stuck to the PET base on
which the backing pad was stuck on its central portion to complete
the production of the template assembly.
[0072] The depth of the recess of this template assembly was
measured. As shown in Table 1, the difference from the target depth
was an average (Ave) of -0.51 .mu.m, and a maximum of 4.8 .mu.m on
the plus side (Max) and 6.5 .mu.m on the minus side (Min). As shown
in Table 2, the in-plane variation in depth was an average (Ave) of
5.3 .mu.m and a maximum (Max) of 7 .mu.m in terms of the range of
eight measurement points. It was revealed from these results that
the precision of the depth of the recess was greatly improved
compared with the results in comparative examples 1 and 2 as
described later.
[0073] At that time, the depth of the recess was measured in the
following manner. As shown in FIG. 11, the workpiece was marked at
eight points in its plane within 1 to 2 mm away from its outer
circumference. The thickness of the marked portions was measured
(this measured thickness is referred to as workpiece thickness).
This workpiece was put into the recess of the template assembly.
The thickness of the marked portions of the workpiece was measured
while a load of 100 g/cm.sup.2 was applied to the workpiece (this
measured thickness is referred to as workpiece-portion thickness).
The thickness of the template was also measured at a position of 1
to 2 mm away from the inner circumference of the template toward
the outer circumference (this measured thickness is referred to as
template thickness). These measured values were used to calculate
the depth of the recess by using the following expression. The
average of the eight points and its range were used as the central
value of the recess depth.
Recess depth=template thickness-(workpiece-portion
thickness-workpiece thickness)
[0074] These thicknesses were measured with a height gage HDF-300N
made by Mitutoyo Corp.
[0075] Then, 300-mm-diameter silicon wafers were polished with a
polishing apparatus, as shown in FIG. 8, having the template
assembly produced in example 1 to evaluate flatness and surface
defects of the wafers. The flatness was evaluated by roll off
measurement with an edge roll off measuring system LER-310M made by
Kobelco Research Institute.
[0076] The portion of 3 to 6 mm away from the outer circumference
was regarded as a reference surface to calculate the value of roll
off. The roll off was measured on four wafers at 0.5 mm, 0.7 mm,
1.0 mm, and 2.0 mm away from their outer circumference.
[0077] Table 3 shows the average of roll off values at these
points. Table 4 shows the relationship between the difference in
the recess depth from the target depth shown in Table 1 and the
roll off shown in Table 3. As shown in FIG. 4, the difference in
the recess depth from the target depth was a minus value (the
recess depth was shallower). As the absolute value of this
difference increased, the template was more difficult to reduce the
polishing pressure of the outer circumferential portion of the
workpiece. In particular, the roll off was significantly changed at
0.5 mm away from the outer circumference, which is easy to be
affected by the recess depth.
[0078] FIG. 5 shows the average (Ave), the maximum (Max), and the
minimum (Min) of the roll off at 0.5 mm away from the outer
circumference of each wafer. FIG. 6 shows radar charts that
demonstrate how the positions of the roll off were changed at the
measured eight points in the plane.
[0079] As shown in FIGS. 5 and 6, example 1 carried out a further
improvement in the roll off and a greater improvement in the
in-plane variation compared with comparative examples 1 and 2 as
described later, because example 1 achieved substantially the same
recess depth as the target depth.
[0080] In addition, as shown in FIG. 6, the radar chart exhibits
substantially concentric circles, which means that the in-plane
variation in the roll off was inhibited.
[0081] FIG. 7 shows the result of the surface defects of the
wafers. As shown in FIG. 7, the occurrence of the surface defects
of the wafers was inhibited compared with the result in comparative
example 3 as described later.
[0082] The surface defects were evaluated with Magics 350 made by
Lasertec Corporation as values converted such that the total number
of defects in comparative example 1 was regarded as 1.0.
Example 2
[0083] The inventive template assembly was produced in the same
manner as example 1 except that the thickness of the template was
10 .mu.m thinner than the thickness in example 1 and the thickness
of the notch was 20 .mu.m thinner than the thickness of the backing
pad. The same evaluation as example 1 was conducted. It is to be
noted that the thickness of this notch was adjusted such that
although the used template was 10 .mu.m thinner than the thickness
in example 1, the depth of the recess when a load of 100 g/cm.sup.2
was applied to the workpiece became substantially the same as in
example 1 by pressing the peripheral portion of the backing pad
with the template.
[0084] The depth of the recess of this template assembly was
measured. As shown in Table 1, the difference from the target depth
was an average of -0.43 .mu.m, and a maximum of 2.0 .mu.m on the
plus side and 2.8 .mu.m on the minus side. As shown in Table 2, the
in-plane variation in depth was an average of 5.8 .mu.m and a
maximum of 7 .mu.m in terms of the range of eight measurement
points. It was revealed from these results that the precision of
the depth of the recess was greatly improved compared with the
results in comparative examples 1 and 2 as described later.
[0085] Then, 300-mm-diameter silicon wafers were polished with a
polishing apparatus, as shown in FIG. 8, having the template
assembly produced in example 2 to evaluate flatness and surface
defects of the wafers as in example 1.
[0086] Although example 2 used the template having the different
thickness from the thickness in example 1 as above, since the
recess depth was substantially the same as example 1, the same
result of the roll off of the polished wafers was obtained. It was
revealed from the radar chart shown in FIG. 6 that the in-plane
variation in roll off was inhibited as in example 1.
[0087] FIG. 7 shows the result of the surface defects of the
wafers. As shown in FIG. 7, the occurrence of the surface defects
of the wafers was inhibited compared with the result in comparative
example 3 as described later.
[0088] The roll off values of the polished wafers in examples 1 and
2 were on the same level. The in-plane variations of the roll off
were also on the same level. More specifically, even when the
template is thinned like example 2, the recess having the target
depth can be formed by adjusting the thickness of the notch. This
allows the template to have a thinner thickness than the
conventionally required thickness, even when a deep recess, which
may reduce slurry supply to the wafer surface during polishing, is
chosen, for example, in consideration for the effect of the
compressibility of a polishing pad to be used. The roll off and the
surface defects of the wafers can thereby be improved while the
reduction in slurry supply to the workpiece surface is inhibited
during polishing.
Comparative Example 1
[0089] The same evaluation as example 1 was conducted by using a
conventional template assembly, which is commercially available,
having a template stuck on the outer circumferential portion of the
lower surface of a baking pad as shown in FIG. 9 without performing
lapping and polishing on the template.
[0090] The depth of the recess of this template assembly was
measured. As shown in Table 1, the difference from the target depth
was an average of -4.46 .mu.m, and a maximum of 11.0 .mu.m on the
plus side and 16.9 .mu.m on the minus side. As shown in Table 2,
the in-plane variation in depth was an average of 15.63 .mu.m and a
maximum of 26 .mu.m in terms of the range of eight measurement
points. It was revealed from these results that the precision of
the depth of the recess was considerably worse compared with the
results in examples 1 and 2.
[0091] Then, 300-mm-diameter silicon wafers were polished with a
polishing apparatus, as shown in FIG. 8, having the template
assembly in comparative example 1 to conduct the same evaluation as
example 1.
[0092] As shown in Tables 1 and 2, since the difference in the
recess depth from the target depth in comparative example 1 was
larger than those in examples 1 and 2, the roll off and the
in-plane variation were also larger. It was revealed from the radar
chart shown in FIG. 6 that some wafers had a deviation in roll off
in its plane.
[0093] FIG. 7 shows the result of the surface defects of the
wafers. As shown in FIG. 7, since the template assembly used in
comparative example 1 had no space between the template and the
backing pad unlike FIG. 10, the occurrence of the surface defects
of the wafers was inhibited compared with comparative example
3.
Comparative Example 2
[0094] The same evaluation as comparative example 1 was conducted
by using the same template assembly as comparative example 1 except
that the template was lapped.
[0095] The depth of the recess of this template assembly was
measured. As shown in Table 1, the difference from the target depth
was an average of -3.04 .mu.m, and a maximum of 8.9 .mu.m on the
plus side and 10.9 .mu.m on the minus side. As shown in Table 2,
the in-plane variation in depth was an average of 9.77 .mu.m and a
maximum of 16 .mu.m in terms of the range of eight measurement
points.
[0096] It was revealed that although the precision of depth of the
recess was improved by performing lapping on the template compared
with comparative example 1, this precision of depth was
considerably worse compared with the results in examples 1 and
2.
[0097] Then, 300-mm-diameter silicon wafers were polished with a
polishing apparatus, as shown in FIG. 8, having the template
assembly in comparative example 2 to evaluate the flatness as in
example 1.
[0098] As shown in Tables 1 and 2, since the difference in the
recess depth from the target depth in comparative example 2 was
smaller than that in comparative example 1, the roll off and
in-plane variation were improved compared with comparative example
1, but significantly worse than those in examples 1 and 2. It was
revealed from the radar chart shown in FIG. 6 that some wafers had
a deviation in roll off in its plane like comparative example 1 and
the variation in the roll off at the outer circumference was not
inhibited.
[0099] Since the difference in the recess depth from the target
depth can be reduced by an adjustment of the thickness of
components to be used or an improvement of sticking method, the
average of roll off can be improved to some degree as demonstrated
in comparative example 2. The in-plane variation in roll off,
however, cannot be improved. In contrast, the inventive template
assembly can also improve this in-plane variation as above.
[0100] Table 1 shows summarized results of the difference in the
recess depth from the target depth in examples 1 and 2 and
comparative examples 1 and 2. Table 2 shows summarized results of
the in-plane variation in the recess depth in examples 1 and 2 and
comparative examples 1 and 2.
TABLE-US-00001 TABLE 1 COMPARATIVE COMPARATIVE EXAMPLE EXAMPLE
EXAMPLE 1 EXAMPLE 2 1 2 N 40 26 10 5 Ave -4.46 -3.04 -0.51 -0.43 S
7.37 6.00 3.53 2.03 Max 11.0 8.9 4.8 2.0 Min -16.9 -10.9 -6.5
-2.8
TABLE-US-00002 TABLE 2 COMPARATIVE COMPARATIVE EXAMPLE 1 EXAMPLE 2
EXAMPLE 1 EXAMPLE 2 N 40 26 10 5 Ave 15.63 9.77 5.30 5.80 S 4.91
2.67 1.64 1.30 Max 26.0 16.0 7.0 7.0 Min 8.0 6.0 2.0 4.0
TABLE-US-00003 TABLE 3 DIFFERENCE IN RECESS DEPTH FROM ROLL OFF
TARGET DEPTH 0.5 mm 0.7 mm 1.0 mm 2.0 mm comparative -4.46 0.27
0.10 0.05 0.01 example 1 comparative -3.04 0.23 0.08 0.04 0.01
example 2 example 1 -0.51 0.13 0.07 0.03 0.00 example 2 -0.43 0.12
0.08 0.03 0.00
Comparative Example 3
[0101] With a polishing apparatus, as shown in FIG. 8, having a
conventional template assembly with a template having no notch as
shown in FIG. 10, 300-mm-diameter silicon wafers were polished to
evaluate the in-plane variation in the recess depth and surface
defects of the wafers as in example 1.
[0102] The result was that although the same level of the in-plane
variation in the recess depth as examples 1 and 2 was obtained, the
surface defects of the wafers were degraded compared with examples
1 and 2 and comparative example 1. It can be understood that these
surface defects were due to particles generated by slurry entering
the space between the template and the backing pad during
polishing.
[0103] It is to be noted that the present invention is not limited
to the foregoing embodiment. The embodiment is just an
exemplification, and any examples that have substantially the same
feature and demonstrate the same functions and effects as those in
the technical concept described in claims of the present invention
are included in the technical scope of the present invention.
* * * * *