U.S. patent application number 10/937398 was filed with the patent office on 2005-04-28 for resist reflow measurement key and method of forming a fine pattern of a semiconductor device using the same.
Invention is credited to Cho, Han-ku, Lee, Doo-youl, Lee, Jung-hyeon, Yeo, Gi-sung.
Application Number | 20050089776 10/937398 |
Document ID | / |
Family ID | 34510847 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050089776 |
Kind Code |
A1 |
Lee, Doo-youl ; et
al. |
April 28, 2005 |
Resist reflow measurement key and method of forming a fine pattern
of a semiconductor device using the same
Abstract
In a resist reflow measurement key, and method of fabricating a
fine pattern of a semiconductor device using the same, the resist
reflow measurement key includes a first reflow key including a
plurality of first pattern elements each having a first pattern
with a first radius of curvature located on a first side of a first
center line and a second pattern with a second radius of curvature
located on a second side of the first center line, and a second
reflow key including a plurality of second pattern elements each
having a third pattern with a third radius of curvature located on
a first side of a second center line and a fourth pattern with a
fourth radius of curvature located on a second side of the second
center line, the second reflow key being formed on a same plane of
a substrate as the first reflow key.
Inventors: |
Lee, Doo-youl; (Seoul,
KR) ; Yeo, Gi-sung; (Seoul, KR) ; Cho,
Han-ku; (Seongnam-si, KR) ; Lee, Jung-hyeon;
(Yongin-si, KR) |
Correspondence
Address: |
LEE & STERBA, P.C.
1101 Wilson Boulevard, Suite 2000
Arlington
VA
22209
US
|
Family ID: |
34510847 |
Appl. No.: |
10/937398 |
Filed: |
September 10, 2004 |
Current U.S.
Class: |
430/30 ;
257/E21.026 |
Current CPC
Class: |
H01L 21/0273 20130101;
G03F 7/40 20130101; H01L 22/34 20130101 |
Class at
Publication: |
430/030 |
International
Class: |
G03C 005/00; H01L
021/4763; H01L 021/3205 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2003 |
KR |
03-67434 |
Claims
What is claimed is:
1. A resist reflow measurement key, comprising: a first reflow key
disposed on a substrate around a first center point, the first
reflow key including a plurality of first pattern elements each
having a first pattern with a first radius of curvature located on
a first side of a first center line extending in a lengthwise
direction of each of the plurality of first pattern elements and a
second pattern with a second radius of curvature located on a
second side of the first center line, which is opposite to the
first side of the first center line; and a second reflow key
disposed on the substrate around a second center point, the second
reflow key including a plurality of second pattern elements each
having a third pattern with a third radius of curvature located on
a first side of a second center line extending in a lengthwise
direction of each of the plurality of second pattern elements and a
fourth pattern with a fourth radius of curvature located on a
second side of the second center line, which is opposite to the
first side of the second center line, the second reflow key being
formed on a same plane as the first reflow key.
2. The resist reflow measurement key as claimed in claim 1, wherein
the first reflow key has a rectangular shape and the plurality of
first pattern elements is four first pattern elements, each one of
the four first pattern elements constituting a side of the
rectangular shaped first reflow key.
3. The resist reflow measurement key as claimed in claim 1, wherein
the second reflow key has a rectangular shape and the plurality of
second pattern elements is four second pattern elements, each one
of the four second pattern elements constituting a side of the
rectangular shaped second reflow key.
4. The resist reflow measurement key as claimed in claim 1, wherein
the first pattern of each of the plurality of first pattern
elements is a plurality of first pattern shape portions positioned
at the first side of the first center line and having the first
radius of curvature, and the second pattern of each of the
plurality of first pattern elements is a plurality of second
pattern shape portions positioned at the second side of the first
center line and having the second radius of curvature, which is
larger than the first radius of curvature, and the third pattern of
the plurality of second pattern elements is a plurality of third
pattern shape portions positioned at the first side of the second
center line and having the third radius of curvature, and the
fourth pattern of the plurality of second pattern elements is a
plurality of fourth pattern shape portions positioned at the second
side of the second center line and having the fourth radius of
curvature, which is larger than the third radius of curvature.
5. The resist reflow measurement key as claimed in claim 4, wherein
the plurality of first pattern elements are respectively arranged
such that the plurality of second pattern shape portions is
disposed facing a first direction of a line extending diagonally
through the first center point, and the plurality of second pattern
elements are respectively arranged such that the plurality of
fourth pattern shape portions is disposed facing a second
direction, which is opposite to the first direction, of a line
extending diagonally through the second center point.
6. The resist reflow measurement key as claimed in claim 4, wherein
the first and second reflow keys are respectively arranged such
that at least one of the plurality of first pattern shape portions
of the plurality of first pattern elements faces a corresponding
one of the plurality of third pattern shape portions of the
plurality of second pattern elements.
7. The resist reflow measurement key as claimed in claim 4, wherein
the first reflow key and the second reflow key are respectively
arranged such that at least one of the plurality of second pattern
shape portions of the plurality of first pattern elements faces a
corresponding one of the plurality of fourth pattern shape portions
of the plurality of second pattern elements.
8. The resist reflow measurement key as claimed in claim 6, wherein
the first reflow key and the second reflow key are respectively
arranged such that at least one of the plurality of first pattern
shape portions of the plurality of first pattern elements faces a
corresponding one of the plurality of third pattern shape portions
of the plurality of second pattern elements and at least one of the
plurality of second pattern shape portions of the plurality of
first pattern elements faces a corresponding one of the plurality
of fourth pattern shape portions of the plurality of second pattern
elements concurrently.
9. The resist reflow measurement key as claimed in claim 4, wherein
the first radius of curvature and the third radius of curvature are
the same.
10. The resist reflow measurement key as claimed in claim 4,
wherein the second radius of curvature and the fourth radius of
curvature are the same.
11. The resist reflow measurement key as claimed in claim 1,
wherein the second reflow key has a size smaller than a size of the
first reflow key.
12. The resist reflow measurement key as claimed in claim 11,
wherein the second reflow key is formed in a region defined by the
first reflow key.
13. The resist reflow measurement key as claimed in claim 1,
wherein the first and second reflow keys are each of a trench type
pattern.
14. The resist reflow measurement key as claimed in claim 1,
wherein the first and second reflow keys are each of a mesa type
pattern.
15. The resist reflow measurement key as claimed in claim 1,
wherein the first reflow key and the second reflow key are formed
of a material selected from positive photoresist and negative
photoresist.
16. A method of forming a fine pattern of a semiconductor device,
the method comprising: forming a resist pattern on a semiconductor
substrate to form a pattern having a predetermined shape; forming a
resist reflow measurement key on the semiconductor substrate while
forming the resist pattern; reflowing the resist pattern and the
resist reflow measurement key at the same time; measuring a
variation in a position of a first center point of the reflowed
resist reflow measurement key and a variation in a position of a
second center point of the reflowed resist reflow measurement key
by using an optical overlay measurement apparatus; and determining
a critical dimension of the reflowed resist pattern from
measurement values of the variation in the position of the first
center point and the variation in the position of the second center
point.
17. The method as claimed in claim 16, wherein the pattern having
the predetermined shape is a contact hole pattern or a line and
space pattern.
18. The method as claimed in claim 16, wherein the optical overlay
measurement apparatus is a laser scan alignment (LSA) type overlay
measurement apparatus or a field image alignment (FIA) type overlay
measurement apparatus.
19. The method as claimed in claim 16, wherein the resist pattern
and the resist reflow measurement key are formed of an identical
material.
20. The method as claimed in claim 16, wherein the semiconductor
substrate comprises a device region where an actual device is
formed, and a test element group (TEG) region where a test device
for measuring an electrical property of the actual device is
formed, the resist pattern being formed in the device region, and
the resist reflow measurement key being formed in the TEG region.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a measurement key used in
semiconductor device fabrication and a method of fabricating a
semiconductor device using the same. More particularly, the present
invention relates to a resist reflow measurement key used for
measuring the flow of resist and a method of forming a fine pattern
of a semiconductor device using the same.
[0003] 2. Description of the Related Art
[0004] Due to widespread demand for semiconductor devices having an
increased processing speed and highly integrated memory devices for
use in a wide range of electronic devices, there is a need to
develop a circuitry product having a sub-micron size. To satisfy
this need in highly integrated devices, efforts to develop an
improved photoresist composition have been accelerated. Moreover,
efforts to obtain a pattern having more precise dimensions to
obtain, in particular, a pattern suitable for a structure having a
minimum feature size have been accelerated. To fabricate highly
integrated semiconductor devices successfully, it is necessary to
form more precisely and finely a photoresist pattern widely used in
etch and ion implantation processes. To realize these products, a
sensitive photoresist is required. However, use of a sensitive
photoresist is necessarily accompanied by an additional process,
which is complicated.
[0005] In a semiconductor fabrication process using a single layer
resist and a 0.13 .mu.m process, ArF lithography technology is
used. It is forecast, however, that greater precision and dimension
control will be required for a process below 0.10 .mu.m, which will
be used in the future.
[0006] The wavelength of a light source for exposure directly
influences the minimum resolution that can be obtained in an
exposure apparatus. For instance, in forming a fine line and space
(L/S) pattern, a g-line exposure apparatus has a resolution limit
of about 0.5 .mu.m and an i-line exposure apparatus has a
resolution limit of about 0.3 .mu.m. The recent trend, however,
shows that the device design rule is approaching an US measurement
value below about 0.2 .mu.m. It is forecast that the allowable
minimum feature size in a next generation device design rule will
continue to decrease. In particular, in fabricating a highly
integrated device that requires a small contact hole having a high
aspect ratio in an US pattern having a fine critical dimension
(CD), or a cell array region of a device, various processes to
overcome the resolution limit of exposure apparatuses have been
developed. A reflow process using heat is one example of such a
process.
[0007] In a reflow process using heat, an initial photoresist
pattern having formed therein a contact hole, which has a size
larger than the CD of a final L/S pattern or the size of a contact
hole to be formed, is first formed. Then, the formed photoresist
pattern is heated to a temperature above the glass transition
temperature (Tg) of the photoresist and is reflowed to form a fine
pattern. The heating reduces the viscosity of the linked
photoresist to reflow the photoresist. Thus, the CD of the US
pattern or the size of the contact hole is reduced, thereby
obtaining a desired fine pattern.
[0008] In the reflow process, the CD of the reflowed resist pattern
is monitored at the after flow inspection (AFI) stage. The exposure
dose is controlled on the basis of the CD value measured in the AFI
stage. In the process of controlling the CD of the resist pattern
in the aforementioned manner, the amount of time required to
monitor the CD of the reflowed resist pattern in the AFI stage is
very important because it influences the throughput of the whole
exposure process.
[0009] Until recently, monitoring the CD of the reflowed resist
pattern involved measuring the CD of the reflowed resist pattern
using a scanning electron microscope (SEM) in the AFI stage. In
other words, in applying the present reflow process using heat, the
resist pattern, which is reflowed in the AFI stage, is monitored by
an SEM and an exposure dose is controlled on the basis of the
monitored result. Thus, it takes a significant amount of time to
perform a process that can satisfy a desired CD size since the
monitoring in the post-development baking (PDB) step, i.e., in the
reflow step of the resist, depends only on the CD measurement using
the SEM. As a result, performing the CD monitoring on the entire
region of a wafer takes too long, thereby significantly reducing
throughput as a size of the wafer increases.
SUMMARY OF THE INVENTION
[0010] The present invention is therefore directed to a resist
reflow measurement key and a method of forming a fine pattern of a
semiconductor device using the same, which substantially overcome
one or more of the problems due to the limitations and
disadvantages of the related art.
[0011] It is a feature of an embodiment of the present invention to
provide a resist reflow measurement key that enables the flow of a
reflowed resist pattern to be quantitatively monitored within a
very short time in forming a fine pattern to overcome the
resolution limit of an exposure apparatus by a reflow process using
heat.
[0012] It is another feature of an embodiment of the present
invention to provide a method of forming a fine pattern to overcome
the resolution limit of an exposure apparatus by a process set to
quantitatively monitor the flow of a reflowed resist pattern within
a very short time in forming a fine pattern of a semiconductor
device by a reflow process using heat.
[0013] It is still another feature of an embodiment of the present
invention to provide a resist reflow measurement key and a method
of forming a fine pattern of a semiconductor device using the same
that is able to monitor the flow of the resist pattern on the wafer
in an AFI step within a very short time to improve throughput when
the process is performed on wafers having a relatively large
size.
[0014] It is yet another feature of an embodiment of the present
invention to provide a resist reflow measurement key and a method
of forming a fine pattern of a semiconductor device using the same
that is able to obtain feedback rapidly in the reflow process of
the resist pattern, decrease AFI monitoring turn around time (TAT),
and enhance pattern uniformity according to the position on the
wafer.
[0015] At least one of the above and other features and advantages
of the present invention may be realized by providing a resist
reflow measurement key including a first reflow key disposed on a
substrate around a first center point, the first reflow key
including a plurality of first pattern elements each having a first
pattern with a first radius of curvature located on a first side of
a first center line extending in a lengthwise direction of each of
the plurality of first pattern elements and a second pattern with a
second radius of curvature located on a second side of the first
center line, which is opposite to the first side of the first
center line, and a second reflow key disposed on the substrate
around a second center point, the second reflow key including a
plurality of second pattern elements each having a third pattern
with a third radius of curvature located on a first side of a
second center line extending in a lengthwise direction of each of
the plurality of second pattern elements and a fourth pattern with
a fourth radius of curvature located on a second side of the second
center line, which is opposite to the first side of the second
center line, the second reflow key being formed on a same plane as
the first reflow key.
[0016] The first reflow key may have a rectangular shape and the
plurality of first pattern elements may be four first pattern
elements, each one of the four first pattern elements constituting
a side of the rectangular shaped first reflow key.
[0017] The second reflow key may have a rectangular shape and the
plurality of second pattern elements may be four second pattern
elements, each one of the four second pattern elements constituting
a side of the rectangular shaped second reflow key.
[0018] The first pattern of each of the plurality of first pattern
elements may be a plurality of first pattern shape portions
positioned at the first side of the first center line and having
the first radius of curvature, and the second pattern of each of
the plurality of first pattern elements may be a plurality of
second pattern shape portions positioned at the second side of the
first center line and having the second radius of curvature, which
is larger than the first radius of curvature, and the third pattern
of the plurality of second pattern elements may be a plurality of
third pattern shape portions positioned at the first side of the
second center line and having the third radius of curvature, and
the fourth pattern of the plurality of second pattern elements may
be a plurality of fourth pattern shape portions positioned at the
second side of the second center line and having the fourth radius
of curvature, which is larger than the third radius of
curvature.
[0019] The plurality of first pattern elements may be respectively
arranged such that the plurality of second pattern shape portions
is disposed facing a first direction of a line extending diagonally
through the first center point, and the plurality of second pattern
elements may be respectively arranged such that the plurality of
fourth pattern shape portions is disposed facing a second
direction, which is opposite to the first direction, of a line
extending diagonally through the second center point.
[0020] The first and second reflow keys may be respectively
arranged such that at least one of the plurality of first pattern
shape portions of the plurality of first pattern elements faces a
corresponding one of the plurality of third pattern shape portions
of the plurality of second pattern elements.
[0021] The first reflow key and the second reflow key may be
respectively arranged such that at least one of the plurality of
second pattern shape portions of the plurality of first pattern
elements faces a corresponding one of the plurality of fourth
pattern shape portions of the plurality of second pattern
elements.
[0022] The first reflow key and the second reflow key may be
respectively arranged such that at least one of the plurality of
first pattern shape portions of the plurality of first pattern
elements faces a corresponding one of the plurality of third
pattern shape portions of the plurality of second pattern elements
and at least one of the plurality of second pattern shape portions
of the plurality of first pattern elements faces a corresponding
one of the plurality of fourth pattern shape portions of the
plurality of second pattern elements concurrently.
[0023] The first radius of curvature and the third radius of
curvature may be the same. The second radius of curvature and the
fourth radius of curvature may be the same.
[0024] The second reflow key may have a size smaller than a size of
the first reflow key. The second reflow key may be formed in a
region defined by the first reflow key.
[0025] The first and second reflow keys may each be of a trench
type pattern. The first and second reflow keys may each be of a
mesa type pattern.
[0026] The first reflow key and the second reflow key are formed of
a material selected from positive photoresist and negative
photoresist.
[0027] At least one of the above and other features and advantages
of the present invention may be realized by providing a method of
forming a fine pattern of a semiconductor device including forming
a resist pattern on a semiconductor substrate to form a pattern
having a predetermined shape, forming a resist reflow measurement
key on the semiconductor substrate while forming the resist
pattern, reflowing the resist pattern and the resist reflow
measurement key at the same time, measuring a variation in a
position of a first center point of the reflowed resist reflow
measurement key and a variation in a position of a second center
point of the reflowed resist reflow measurement key by using an
optical overlay measurement apparatus, and determining a critical
dimension of the reflowed resist pattern from measurement values of
the variation in the position of the first center point and the
variation in the position of the second center point.
[0028] The pattern having the predetermined shape may be a contact
hole pattern or a line and space pattern.
[0029] The optical overlay measurement apparatus may be a laser
scan alignment (LSA) type overlay measurement apparatus or a field
image alignment (FIA) type overlay measurement apparatus.
[0030] The resist pattern and the resist reflow measurement key may
be formed of an identical material.
[0031] The semiconductor substrate may include a device region
where an actual device is formed and a test element group (TEG)
region where a test device for measuring an electrical property of
the actual device is formed, the resist pattern being formed in the
device region, and the resist reflow measurement key being formed
in the TEG region.
[0032] According to an embodiment of the present invention, after
the reflow process of the resist pattern formed on the device
region of the wafer is performed, a variation in a position of a
center point due to the flow in the resist reflow measurement key
reflowed concurrently with the resist pattern is measured in the
AFI step using an overlay measurement apparatus to monitor the CD
of the resist pattern. Accordingly, the flow of the resist pattern
on the wafer in AFI step can be monitored within a very short time,
thereby improving throughput when the process is performed on
wafers having a relatively large sized. Also, in the reflow process
of the resist pattern, feedback can be rapidly obtained, AFI
monitoring turn around time (TAT) can be shortened, and pattern
uniformity according to the position on the wafer can be
enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above and other features and advantages of the present
invention will become more apparent to those of ordinary skill in
the art by describing in detail exemplary embodiments thereof with
reference to the attached drawings in which:
[0034] FIG. 1 illustrates a plan view of a resist reflow
measurement key according to an embodiment of the present
invention;
[0035] FIG. 2 shows a series of SEM photographs observed through
after development inspection (ADI) before flowing a photoresist
material and SEM photographs observed through after flow inspection
(AFI) after flowing the photoresist material;
[0036] FIG. 3 illustrates a sectional view of a resist reflow
measurement key according to an embodiment of the present invention
and taken along line II-II' of FIG. 1;
[0037] FIG. 4 illustrates a sectional view of a resist reflow
measurement key according to another embodiment of the present
invention and taken along line II-II of FIG. 1; and
[0038] FIG. 5 is a flow chart of a method for forming a fine
pattern of a semiconductor device according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Korean Patent Application No. 2003-67434, filed on Sep. 29,
2003, in the Korean Intellectual Property Office, and entitled:
"Resist Reflow Measurement Key and Method of Forming a Fine Pattern
of a Semiconductor Device Using the Same," is incorporated by
reference herein in its entirety.
[0040] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown. The invention
may, however, be embodied in different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. In the figures, the
dimensions of layers and regions are exaggerated for clarity of
illustration. It will also be understood that when a layer is
referred to as being "on" another layer or substrate, it can be
directly on the other layer or substrate, or intervening layers may
also be present. Like reference numerals refer to like elements
throughout.
[0041] FIG. 1 illustrates a plan view of a resist reflow
measurement key 50 according to an embodiment of the present
invention.
[0042] Referring to FIG. 1, a resist reflow measurement key 50
according to an embodiment of the present invention includes a
first reflow key 100 including a plurality of first pattern
elements 110, 120, 130, 140 and a second reflow key 200 including a
plurality of second pattern elements 210, 220, 230, 240.
[0043] The plurality of first pattern elements 110, 120, 130, and
140 constituting the first reflow key are arranged around on a
first center point C, on a semiconductor substrate. The plurality
of first pattern elements 110, 120, 130, and 140 have pattern
shapes having different radii of curvature at opposite sides of a
first center line 100c extending in a lengthwise direction of each
of the plurality of first pattern elements 110, 120, 130, and 140.
In other words, each of the plurality of first pattern elements
110, 120, 130, and 140 includes a first pattern shape portion 102
positioned at a first side of and extending in the lengthwise
direction of the first center line 100c. The first pattern shape
portion 102 has a first curvature radius. Each of the plurality of
first pattern elements 110, 120, 130, and 140 further includes a
second pattern shape portion 104 positioned at a second side of the
first center line 100c, which is opposite to the first side. The
second pattern shape portion 104 has a second radius of curvature,
which is larger than the first radius of curvature. In FIG. 1, the
second pattern shape portion 104 is shaped as a substantially
straight line and thus has an infinite radius of curvature.
[0044] The plurality of second pattern elements 210, 220, 230, and
240 constituting the second reflow key 200 are arranged on a same
plane as the plurality of first pattern elements 110, 120, 130, and
140 and are arranged around a second center point C.sub.2 on the
semiconductor substrate. The plurality of second pattern elements
210, 220, 230, and 240 have pattern shapes having different radii
of curvature at opposite sides of a second center line 200c
extending in a lengthwise direction of each of the plurality of
second pattern elements 210, 220, 230, and 240. In other words,
each of the plurality of second pattern elements 210, 220, 230, and
240 includes a third pattern shape portion 202 positioned at a
first side of and extending in the lengthwise direction of the
second center line 200c. The third pattern shape portion 202 has a
third radius of curvature. Each of the plurality of second pattern
elements 210, 220, 230, and 240 further includes a fourth pattern
shape portion 204 positioned at a second side of the second center
line 200c, which is opposite to the first side. The fourth pattern
shape portion 204 has a fourth radius of curvature, which is larger
than the third radius of curvature. In FIG. 1, the fourth pattern
shape portion 204 is shaped as a substantially straight line and
thus has an infinite radius of curvature.
[0045] Although in the embodiment illustrated in FIG. 1 the first
center point C.sub.1 of the first reflow key 100 and the second
center point C.sub.2 of the second reflow key 200 are shown as
positioned at the same site, the first center point C, and the
second center point C.sub.2 may be positioned at different sites.
In particular, a position of the first center point C.sub.1 of the
first reflow key 100 and a position of the second center point
C.sub.2 of the second reflow key 200 may be moved according to a
reflow tendency of the first and second reflow keys 100 and 200
after the respective reflow processes, which will be described
later.
[0046] The first reflow key 100 and the second reflow key 200 are
formed of a photoresist material. Positive photoresist or negative
photoresist may be selectively used as the photoresist material of
the first and second reflow keys 100 and 200. The first reflow key
100 and the second reflow key 200 may be formed in a test element
group (TEG) region where a test device for measuring an electrical
property of the actual device formed on a device region of the
semiconductor substrate is formed. Also, the first reflow key 100
and the second reflow key 200 may be formed of the same material as
a resist pattern formed as a mask pattern for forming a desired
pattern on the device region.
[0047] In the exemplary embodiment shown in FIG. 1, the plurality
of first pattern elements 110, 120, 130 and 140 is four first
pattern elements 110, 120, 130 and 140, each constituting a side of
the first reflow key 100, which is shown having a rectangular
shape. Similarly, the plurality of second pattern elements 210,
220, 230 and 240 is four second pattern elements 210, 220, 230 and
240, each constituting a side of the second reflow key 200, which
also has a rectangular shape. Although FIG. 1 illustrates the first
reflow key 100 and the second reflow key 200 having a rectangular
shape, the first reflow key 100 and the second reflow key 200 are
not limited to that shape and may be have various other shapes.
[0048] By way of further alternative, although FIG. 1 illustrates
the second reflow key 200 having a size smaller than the first
reflow key 100 and being formed within a region defined by the
first reflow key 100, the present invention is not limited to this
particular arrangement.
[0049] The first pattern elements 110, 120, 130, and 140 of the
first reflow key 100 may be arranged such that the portion having a
larger radius of curvature, i.e., the second pattern shape portion
104, is disposed on a side facing a first predetermined direction,
e.g., a direction indicated by an arrow "A", of a line extending
diagonally through the first center point C.sub.1. In addition, the
second pattern elements 210, 220, 230, and 240 of the second reflow
key 200 may be arranged such that the portion having a larger
radius of curvature, i.e., the fourth pattern shape portion 204, is
disposed on a side facing a second predetermined direction, which
is opposite to the first direction, e.g., a direction indicated by
an arrow "B," which is opposite to the arrow "A" direction, of a
line extending diagonally through the second center point
C.sub.2.
[0050] In the exemplary construction of the first and second reflow
keys 100 and 200 shown in FIG. 1, the first and second reflow keys
100 and 200 are arranged such that two of the plurality of first
pattern shape portions 102 of the first pattern elements 110 and
120 face a corresponding two of the plurality of third pattern
shape portions 202 of the second pattern elements 210 and 220.
Concurrently, the first reflow key 100 and the second reflow key
200 are arranged such that two of the plurality of second pattern
shape portions 104 of the first pattern elements 130 and 140 face a
corresponding two of the plurality of fourth pattern shape portions
204 of the second pattern elements 230 and 240.
[0051] In the above-described arrangement for the second pattern
shape portion 104 of the first pattern elements 110, 120, 130, 140
to exist at the side facing the arrow "A" direction and for the
fourth pattern shape portion 204 in the second pattern elements
210, 220, 230, 240 to face the direction indicated by the arrow
"B", the first reflow key 100 and the second reflow key 200 may be
arranged such that an area where the first pattern shape portion
102 of the first pattern elements 110 and 120 faces the third
pattern shape portion 202 of the second pattern elements 210 and
220 and an area where the second pattern shape portion 104 of the
first pattern elements 130 and 140 faces the fourth pattern shape
portion 204 of the second pattern elements 230 and 240 coexist.
[0052] As shown in FIG. 1, in the arrangement that the second
pattern shape portion 104 having the relatively larger radius of
curvature in the first pattern elements 110, 120, 130, 140 faces in
the "A" direction and the fourth pattern shape portion 204 having
the relatively larger radius of curvature in the second pattern
elements 210, 220, 230, 240 faces in the "B" direction, after the
reflow process for the photoresist pattern formed on the device
region is performed, the resist reflow measurement key 50 including
the first reflow key 100 and the second reflow key 200 is also
reflowed concurrently with the reflow of the resist pattern. At
this time, the resist of the first pattern shape portion 102 and
the third pattern shape portion 202, which have the relatively
smaller radius of curvature, flows more than the resist of the
second pattern shape portion 104 and the fourth pattern shape
portion 204, which have the relatively larger radius of
curvature.
[0053] A relationship between the radius of curvature of the resist
pattern and an amount of flow will now be described in detail.
[0054] Generally, when a photoresist material flows, flow behavior
of the photoresist material is influenced by the pattern shape.
Especially, as the curvature radius is reduced, more much
photoresist material flows.
[0055] FIG. 2 shows a series of SEM photographs observed through
after development inspection (ADI) before a photoresist material
flows and SEM photographs observed through after flow inspection
(AFI) after the photoresist material flows.
[0056] As shown in FIG. 2, in a case of the line and space (US)
patterns, pattern asymmetry is observed at a dummy line located at
the outermost portion (i.e., the rightmost line) in the case of AFI
in contrast to the case of ADI. When comparing ADI with AFI in an
island contact type pattern, more much flow is generated at an
upper portion and a lower portion having a smaller radius of
curvature in the respective patterns. Thus, as shown in FIG. 2, it
is known that a reduction in a length in a longitudinal vertical
axis direction of each pattern is larger than a reduction amount in
CD of each pattern in the horizontal direction. From the above
result, it is known that a portion having a smaller radius of
curvature flows more than a portion having a larger radius of
curvature when the resist pattern flows.
[0057] As described above, since the first pattern shape portion
102 and the third pattern shape portion 202 having a relatively
smaller radius of curvature flow more than the second pattern shape
portion 104 and the fourth pattern shape portion 204, each first
center line 100c of the plurality of first pattern elements 110,
120, 130 and 140 is shifted toward the second pattern shape portion
104 having the relatively larger radius of curvature. Similarly,
the second center line 200c of the plurality of second pattern
elements 210, 220, 230 and 240 of the second reflow key 200 is
shifted toward the fourth pattern shape portion 204 having the
relatively larger radius of curvature. As a result, the first
center point C.sub.1 of the first reflow key 100 moves toward in
the "A" direction and the second center point C.sub.2 of the second
reflow key 200 moves in the "B" direction. Thus, it is possible to
control the flow of the resist pattern arranged on the device
region of the semiconductor substrate based on the amount of
variation in the position of the first center point C.sub.1 of the
first reflow key 100 and the amount of variation in the position of
the second center point C.sub.2 of the second reflow key 200. If
necessary, a relationship between the amounts of variation in the
positions of the first and second center points C, and C.sub.2 and
the flow of the resist pattern can be quantified through a
simulation.
[0058] The first pattern shape portion 102 of the first pattern
elements 110, 120, 130 and 140 and the third pattern shape portion
202 of the second pattern elements 210, 220, 230 and 240 may be
formed to have the same radius of curvature. In addition, the
second pattern shape portion 104 of the first pattern elements 110,
120, 130 and 140 and the fourth pattern shape portion 204 of the
second pattern elements 210, 220, 230 and 240 may be formed to have
the same radius of curvature.
[0059] FIG. 3 illustrates a sectional view of the resist reflow
measurement key 50 taken along line II-II' of FIG. 1 and shows the
first reflow key 100 and the second reflow key 200 being designed
in a trench type pattern formed in a resist layer 20 on a
semiconductor substrate 10.
[0060] FIG. 4 illustrates a sectional view of an alternate resist
reflow measurement key 50' taken along line II-II' of FIG. 1 and
shows the first reflow key 100' and the second reflow key 200'
being designed in a mesa type pattern on a semiconductor substrate
10.
[0061] As shown in FIGS. 3 and 4, in a resist reflow measurement
key according to an embodiment of the present invention, the first
reflow key 100 and the second reflow key 200 may be designed in a
trench type pattern or a mesa type pattern.
[0062] FIG. 5 is a flow chart of a method of forming a fine pattern
of a semiconductor device according to an embodiment of the present
invention.
[0063] Referring to FIG. 5, in step 310, a resist pattern is first
formed on a semiconductor substrate to form a pattern having a
predetermined shape. The resist pattern can be made in any desired
pattern, e.g., in a contact hole pattern or in a line and space
pattern. Additionally, a resist reflow measurement key 50 according
to an embodiment of the present invention as described in
connection with FIGS. 1, 3 and 4 is concurrently formed on the
semiconductor substrate during the formation of the resist pattern.
As described previously, the resist pattern and the resist reflow
measurement key 50 may be formed of an identical material. The
resist pattern may be formed on a device region of the
semiconductor substrate where an actual device is formed. The
resist reflow measurement key 50 may be formed at a test element
group (TEG) region where a test device for measuring an electrical
property of the actual device is formed.
[0064] In step 320, the resist pattern and the resist reflow
measurement key 50 are reflowed at the same time. At this time, so
as to reflow the resist pattern and the resist reflow measurement
key 50, the same reaction condition is applied. The reflowing of
the resist pattern and the resist reflow measurement key 50 is not
limited only to a method using heat, but any reflow method known to
those skilled to the art is applicable.
[0065] In step 330, a variation in position of the first center
point C.sub.1 and a variation in position of the second center
point C.sub.2 of the reflowed resist reflow measurement key 50 are
measured by using an optical overlay measurement apparatus, which
is generally used for measuring overlay in a semiconductor device
fabrication process. This measurement is performed in the general
AFI step. Any optical overlay measurement apparatus that is well
known to those skilled in the art can be used. For example, in a
laser scan alignment (LSA) type overlay measurement apparatus, the
resist reflow measurement key 50 is scanned using a short
wavelength of laser or a broad band wavelength to read out the
center point value of the resist reflow measurement key 50.
Alternatively, in a field image alignment (FIA) type overlay
measurement apparatus, the shape of the resist reflow measurement
key 50 is inputted into a charged coupled display (CCD) like a
camera measurement, is read out by signal processing, and a shadow
thereof is discriminated to read out the center point value of the
resist reflow measurement key 50.
[0066] In step 340, a critical dimension (CD) of the reflowed
resist pattern is determined from measurement values of the
variation in the position of the first center point C.sub.1 and the
variation in the position of the second center point C.sub.2.
[0067] The reflow process is controlled such that the flow of the
resist pattern is monitored on the basis of the CD value indirectly
determined through the resist reflow measurement key 50 in the AFI
step according to the aforementioned sequence. This control allows
a finally desired CD value of the resist pattern to be
obtained.
[0068] The resist reflow measurement key according to an embodiment
of the present invention includes a first reflow key and a second
reflow key each including a plurality of pattern elements having
different radii of curvature. The resist reflow measurement key
according to an embodiment of the present invention is formed on
the same plane as the resist pattern formed on the device region of
a semiconductor substrate, and may be formed of an identical
material to the resist pattern. Accordingly, after the reflow
process of the resist pattern formed on the device region of the
wafer is performed, a variation in the positions of the center
points on the basis of the flow amount of the resist reflow
measurement key reflowed concurrently with the resist pattern is
measured in the AFI step using a general overlay measurement
apparatus to thereby monitor the CD of the resist pattern.
[0069] According to the present invention, it is possible to
quantify the flow of the resist pattern placed on the device region
by measuring only the resist reflow measurement key in an AFI step.
Accordingly, the flow of the resist pattern on the wafer in AFI
step can be monitored within a very short time, thereby increasing
throughput when performing a process on a large-sized wafer. Also,
in the reflow process of the resist pattern, feedback can be
rapidly performed, AFI monitoring turn around time (TAT) can be
shortened, and the pattern uniformity according to the position on
the wafer can be enhanced.
[0070] Exemplary embodiments of the present invention have been
disclosed herein and, although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. Accordingly, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
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