U.S. patent application number 14/441768 was filed with the patent office on 2015-10-01 for image processor, method for generating pattern using self- organizing lithographic techniques and computer program.
The applicant listed for this patent is HITACHI HIGH-TECHNOLOGIES CORPORATION. Invention is credited to Miki Isawa, Shunsuke Koshihara, Akiyuki Sugiyama, Takumichi Sutani.
Application Number | 20150277237 14/441768 |
Document ID | / |
Family ID | 50731212 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150277237 |
Kind Code |
A1 |
Sutani; Takumichi ; et
al. |
October 1, 2015 |
IMAGE PROCESSOR, METHOD FOR GENERATING PATTERN USING SELF-
ORGANIZING LITHOGRAPHIC TECHNIQUES AND COMPUTER PROGRAM
Abstract
An image processor, a method for generating a pattern using
self-organizing lithographic techniques, and a computer program are
provided to achieve image processing suitable for addressing a
sample generated by patterning using Directed Self-Assembly (DSA),
and the processor, method, and computer program are characterized
in that a template for addressing is prepared on the basis of guide
pattern data used for patterning by DSA. The above configuration
makes it possible to provide an addressing pattern suitable for
visual field positioning in measuring or inspecting a pattern
formed through the patterning process using DSA.
Inventors: |
Sutani; Takumichi; (Tokyo,
JP) ; Isawa; Miki; (Tokyo, JP) ; Koshihara;
Shunsuke; (Tokyo, JP) ; Sugiyama; Akiyuki;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI HIGH-TECHNOLOGIES CORPORATION |
Minato-ku, Tokyo |
|
JP |
|
|
Family ID: |
50731212 |
Appl. No.: |
14/441768 |
Filed: |
November 14, 2013 |
PCT Filed: |
November 14, 2013 |
PCT NO: |
PCT/JP2013/080753 |
371 Date: |
May 8, 2015 |
Current U.S.
Class: |
355/53 |
Current CPC
Class: |
G03F 7/70491 20130101;
H01L 21/0337 20130101; B82Y 40/00 20130101 |
International
Class: |
G03F 7/20 20060101
G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2012 |
JP |
2012-251770 |
Claims
1. An image processor comprising a matching processing unit that
performs pattern matching on an image using a template created in
advance, wherein said matching processing unit performs the pattern
matching using a template that is formed based on data indicating a
guide pattern used for self-organizing lithography.
2. The image processor according to claim 1 wherein said matching
processing unit performs the pattern matching by using a template
in which a pattern, formed through annealing processing during the
self-organizing lithography, is selectively arranged within the
guide pattern.
3. The image processor according to claim 2 wherein the template
indicates a pattern shape obtained by performing the annealing
processing for a pattern in which, within the guide pattern, a
guide pattern is further formed.
4. The image processor according to claim 1 wherein the template is
an image created by removing an image of a high molecular compound
outside the guide pattern from an image acquired by a charged
particle beam device.
5. The image processor according to claim 1 wherein the template is
created by adding an image of a pattern, formed based on a high
molecular compound formed within the guide pattern, to image data
of the guide pattern.
6. The image processor according to claim 5 wherein the image data
of the guide pattern is graphic data, obtained based on design data
on the guide pattern, or graphic data obtained based on simulation
for the design data.
7. A pattern generation method based on a self-organizing
lithography technology for patterning by applying a polymer block
copolymer on, and performing annealing for, a sample on which on a
guide pattern is formed, wherein the patterning is performed by
applying the polymer block copolymer on, and then performing the
annealing for, a pattern that is created based on an exposure using
a photomask created by forming a guide pattern within a pattern
that will become a template for pattern matching.
8. The pattern generation method based on a self-organizing
lithography technology according to claim 7 wherein the guide
pattern is arranged at equal intervals within the pattern that will
become the template.
9. The pattern generation method based on a self-organizing
lithography technology according to claim 8 wherein a width and a
pitch of the guide is an allowable size and an allowable pitch in
the self-organizing technology and a segment is oriented in one
direction only.
10. A computer program that causes an arithmetic processing device
to execute pattern matching on an image using a template, wherein
said program causes said arithmetic processing device to perform
the pattern matching using a template that is formed based on data
indicating a guide pattern used for self-organizing
lithography.
11. The computer program according to claim 10 wherein said program
causes said arithmetic processing device to perform the pattern
matching by using a template in which a pattern, formed through
annealing processing during the self-organizing lithography, is
selectively arranged within the guide pattern.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image processor that
processes an image obtained by a scanning electron microscope, a
pattern generation method that generates a pattern required for
evaluation using a scanning electron microscope, and a computer
program, and more particularly to an image processor that generates
addressing pattern data for identifying the position of a pattern
that is an evaluation object, a pattern generation method that
generates an addressing pattern, and a computer program.
BACKGROUND ART
[0002] As one of the technologies for forming a minute pattern, DSA
(Directed Self-Assembly; self-organization technique) is known.
This is a method for forming a minute pattern using the
characteristics that a polymer is regularly organized by applying
heat treatment to polymer.
[0003] Patent Literature 1 describes an example of observing a
pattern, which is formed with the DSA technology, using a scanning
electron microscope and an example of pattern size measurement.
CITATION LIST
Patent Literature
[0004] PATENT LITERATURE 1: JP-A-2010-269304 (corresponding U.S.
Pat. No. 8,114,306)
SUMMARY OF INVENTION
Technical Problem
[0005] On the other hand, to make a pattern evaluation using a
scanning electron microscope, it is required for the field of view
(Field Of View: FOV) of the scanning electron microscope to be
accurately positioned onto an evaluation object pattern. As a
method for positioning the field of view onto a very minute
evaluation object pattern, there is a method called addressing.
Addressing is a method that finds a unique pattern, which is
present near an evaluation object pattern, through the matching
processing with the use of a pre-set template and, at the same
time, performs field of view positioning onto the evaluation object
pattern that has a known positional relation with the unique
pattern. Patent Literature 1 does not disclose a method for
performing addressing on a sample formed through the DSA
technology. In the future, there will be a need for an addressing
method suitable for a sample created through DSA patterning, a
template creation method for addressing, or the creation of a
pattern suitable for addressing.
[0006] The following describes an image processor the purpose of
which is to implement image processing suitable for addressing on a
sample generated through DSA patterning, a pattern generation
method implemented by the self-organizing lithographic technique,
and a computer program.
Solution to Problem
[0007] In one aspect for achieving the above object, the following
proposes an image processor that creates a template for addressing
based on guide pattern data used for DSA patterning, a pattern
generation method implemented by the self-organizing lithographic
technique, and a computer program.
Advantageous Effects of Invention
[0008] According to the configuration described above, an
addressing pattern can be provided that is suitable for field of
view positioning when a pattern, formed via the DSA patterning
process, is measured or inspected.
[0009] The other objects, features, and advantages of the present
invention will become apparent from the following description taken
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a diagram showing an example of a patterning
process using the DSA technology.
[0011] FIG. 2 is a diagram showing an example of a pattern formed
via the patterning process using the DSA technology.
[0012] FIG. 3 is a diagram showing an example of a patterning
process using the DSA technology (large distance between guide
patterns).
[0013] FIG. 4 is a diagram showing an example of a pattern formed
via the patterning process using the DSA technology (large distance
between guide patterns).
[0014] FIG. 5 is a diagram showing a general configuration of a
scanning electron microscope.
[0015] FIG. 6 is a flowchart showing the creation process of an
addressing pattern.
[0016] FIG. 7 is a diagram showing an example of pattern data used
as the base of an addressing pattern.
[0017] FIG. 8 is a diagram showing an example in which a guide
pattern is arranged in an addressing pattern.
[0018] FIG. 9 is a diagram showing an example in which a pattern is
arranged in an addressing pattern through annealing.
[0019] FIG. 10 is a flowchart showing a process for creating an
addressing pattern by removing a random pattern.
[0020] FIG. 11 is a diagram showing an example of a template for
selectively extracting an aligned part after annealing.
[0021] FIG. 12 is a diagram showing an example of an addressing
pattern after a random pattern is removed.
[0022] FIG. 13 is a flowchart showing the creation process of an
addressing pattern and the measurement process using the created
addressing pattern.
[0023] FIG. 14 is a diagram showing an example of a semiconductor
wafer that has a plurality of chips created under the same
fabrication condition.
[0024] FIG. 15 is a diagram showing an example of addressing
pattern design data and an addressing pattern created based on the
design data.
[0025] FIG. 16 is a diagram showing an example of the arrangement
of a guide pattern.
[0026] FIG. 17 is a diagram showing an example in which a
DSA-formed pattern is changed according to the arrangement
condition of a guide pattern.
[0027] FIG. 18 is a diagram showing an example of a recipe creation
system used to create a recipe for a SEM (Scanning Electron
Microscope).
[0028] FIG. 19 is a diagram showing an example of a table in which
a high molecular compound, a formed pattern pitch, and a width,
which are associated with each other, are stored.
[0029] FIG. 20 is a diagram showing an example of a GUI (Graphical
User Interface) screen for specifying a condition for forming an
addressing pattern for use when a sample created using the DSA
technology is measured.
[0030] FIG. 21 is a diagram showing an example of a measurement or
inspection system that measures or inspects a semiconductor
device.
DESCRIPTION OF EMBODIMENTS
[0031] DSA is a new patterning technology that uses the
self-organization phenomenon of a macromolecule. The shape or the
size of a pattern can be controlled by designing the molecular
structure or the molecular weight of a BPC using a method that uses
the microphase separation phenomenon in which a polymer block
copolymer (Block C-Polymer: BCP) forms a nano-sized, regularly
distributed domain. Because this method does not use a special
device and facilities, the cost can be reduced. Recently, the
semiconductor fabrication process using this method is under
development. FIG. 1 is a diagram showing an example of a patterning
process using DSA.
[0032] In the patterning shown in FIG. 1, a pattern 103 of one type
of polymer A is first created on the substrate, on which SiN 102 is
formed on a Si wafer 101, using the lithography process. In this
example, the size of the pattern 103 is 28 nm, and the pitch to the
neighboring pattern is 168 nm. Next, an intermediate layer 104 is
formed between the pattern 103 of polymer A and the neighboring
pattern 103, and a BCP 105 is applied on the top.
[0033] When heat treatment (annealing) is applied in this state,
the BCP is divided into two layers, a pattern 106 (polymer A) and a
pattern 107 (polymer B), and these are spaced at equal intervals
each with a size of 28 nm. At this time, the pattern 106 is formed
on the pattern 103 and a pattern 108 is formed on the intermediate
layer 104, with both patterns made of the same material. After
that, a line pattern is formed by removing the pattern 107. As
described above, the patterns 106 and 108, which are target
patterns, are formed along the pattern 103 that is a guide pattern.
On this guide pattern, only a pattern of a unique size and a unique
pitch is formed suitably. FIG. 2 shows the pattern observed from
top.
[0034] To correctly evaluate the pattern formed via the process
described above, it is desirable to use a CD-SEM (Critical
Dimension Scanning Electron Microscope) that is suitable for
pattern size measurement. When a pattern is measured using a
CD-SEM, an addressing pattern for correcting the position of an
object pattern is required near the object pattern.
[0035] Addressing uses a template, registered in advance as
described above, to search an image, acquired with a field of view
relatively larger than the field of view at measurement time, to
find the matching degree between each position and the template.
Addressing identifies a position, where the matching degree is
highest or the matching degree satisfies a predetermined condition,
as a matching position and, at the same time, allows the field of
view to be moved to an evaluation object position (area including a
measurement object pattern) that has a known positional relation
with the matching position.
[0036] On the other hand, when the BCP is applied to, and annealing
is performed for, the sample as described above, the pattern is
regularly arranged in the guide pattern and, in the other part, a
random pattern is generated in which there is no directional
regularity. For example, an attempt to perform addressing with a
random pattern remained results in a situation in which the shape
matching degree between an already-registered template including a
random pattern and a particular position determined by the template
varies among the measuring objects and, as a result, the matching
accuracy is decreased. When addressing is performed with a random
pattern removed, an image is generated in which the guide pattern
and the polymers selectively arranged in the guide pattern are
superimposed. It is desired to create such a template that is
similar to the pattern shape.
[0037] An image processor that performs pattern matching using a
template including a guide pattern and a computer program are
described below. In particular, the method for creating a template,
which includes a guide pattern and a pattern, formed based on the
alignment of polymers in the guide pattern, are described in
detail.
[0038] The following describes the outline of a scanning electron
microscope (Scanning Electron Microscope: SEM) that positions the
field of view onto an area, which includes a measurement object
pattern, via addressing. Although a SEM is used as an example of
the image acquisition device in the embodiment below, another
charged particle beam device such as a focused ion beam (Focused
Ion Beam: FIB) device, which forms an image based on the signal
obtained by scanning with the use of a focused ion beam, may also
be used as the image acquisition device. FIG. 5 is a diagram
showing an outline of a SEM. A charged particle beam (electron
beam) 502 emitted from a charged particle source (electron gun) 501
is used for one-dimensional or two-dimensional scanning on a sample
504 by means of scanning coils 503.
[0039] A secondary particle (for example, secondary electron) 505
emitted from the sample 504 through the irradiation of the charged
particle beam 502 is detected by a detector 506 and is input to a
control device 507 (control processor), which has the arithmetic
control function, as image data. Although a detector that directly
detects the secondary electron emitted from the sample is shown as
an example in this embodiment, a detector that detects a secondary
electron, generated when the electron emitted from the sample
collides with a secondary electron conversion electrode, may also
be used. Because the charged particle beam 502 is focused by a
focus lens, not shown, and a probe with an extremely small diameter
is used for scanning, a high-resolution image can be formed.
[0040] The sample 504 can be moved in all three-dimension
directions by an x-y-z stage 508. The control device 507 also
controls the charged particle source (electron gun) 501, lens,
detector 506, x-y-z stage 508, and an image display device 509.
[0041] In this example, the charged particle beam 502 is used to
scan the sample 504 two-dimensionally (x-y direction) with the use
of the scanning coils 503. The signal detected by the detector 506
is amplified by a signal amplifier included in the control device
507 and, then, transferred to the image memory for display on the
image display device 509 as the sample image. The secondary signal
detector may be a device that detects a secondary electron and a
reflection electron or a device that detects a light or an X
ray.
[0042] The address signal corresponding to a memory location in the
image memory is generated in the control device 507 or in a
separately installed computer and, after being converted to an
analog signal, is supplied to the scanning coils. For example, when
the image memory is composed of 512.times.512 pixels, the
x-direction address signal is a digital signal that repeats the
address from 0 to 512, and the y-direction address signal is a
digital signal that is incremented by one when the x-direction
address signal reaches 512 from 0 and then repeats 0 to 512. This
digital signal is converted to an analog signal.
[0043] Because there is a correspondence between the addresses in
the image memory and the addresses of the deflection signals used
for electron beam scanning, the two-dimensional image in the
electron beam deflection area, generated by the scanning coils, is
recorded in the image memory. The signals in the image memory can
be read sequentially on a time-series basis by the read-address
generation circuit that operates in synchronization with the read
clock. A signal that is read corresponding to an address is
converted to an analog signal and is used as the brightness
modulation signal in the image display device 509.
[0044] The control device 507, which functions as the image
processor, has an input device, not shown, via which an image
capturing condition (scanning speed, cumulative number of images)
or a field of view correction method can be specified or the output
or saving of an image can be specified.
[0045] The device described in this example has the function to
form a line profile based on the detected secondary electron or the
reflection electron. The line profile is formed based on the amount
of electrons detected when the primary electron beam is used for
one-dimensional or two-dimensional scanning or based on the
brightness information on the sample image. The obtained line
profile is used, for example, for measuring the size of a pattern
formed on a semiconductor wafer.
[0046] Although the scanning electron microscope shown in FIG. 5
has a configuration, in which the control device 507 is integrated
with the main body of the scanning electron microscope, or a
similar configuration, the scanning electron microscope is not of
course limited to that configuration. A control processor, provided
separately from the main body of the scanning electron microscope,
may also be used to perform the processing described below. In that
case, a transmission medium that transmits the detection signal,
detected by the secondary signal detector, to the control processor
or transmits the signal from the control processor to the lens or
the deflector of the scanning electron microscope, as well as an
input/output terminal that sends or receives the signal transmitted
via the transmission medium, is required.
[0047] In addition, the device in this example has the function
that stores a condition, used for observing a plurality of points
on a semiconductor wafer (size measurement positions, optical
conditions for the scanning electron microscope, etc.), as a recipe
in advance and performs size measurement or observation according
to the contents of the recipe.
[0048] Furthermore, the program that performs the processing
described below may be registered in a recording medium to allow
the control processor, which supplies necessary signals to the
scanning electron microscope, to execute the program. That is, the
description of the example below is also the description of the
program that can be used on a charged particle beam device such as
a scanning electron microscope having an image processor or is the
description of the program product.
[0049] In addition, a circuit design data management device 510,
which stores design data on a pattern on a semiconductor wafer and
converts the design data to the data necessary for SEM control, is
connected to the control device 507. The circuit design data
management device 510 has the function that creates a recipe for
controlling the SEM based on the design data on a semiconductor
pattern received from an input device not shown. The circuit design
data management device 510 also has the function to rewrite a
recipe based on the signal transmitted from the control device 507.
Although separate from the control device 507 in the description of
this embodiment, the circuit design data management device 510 is
not limited to this configuration. The control device 507 and the
circuit design data management device 510 may be configured as one
integrated device.
[0050] In this embodiment, the sample 504 is a wafer created using
the self-organizing technology in the semiconductor fabrication
process. As one of the inputs used for creating a recipe used for
evaluating the wafer, the semiconductor circuit design data
corresponding to the pattern is used. The semiconductor circuit
design data used in this case is a pattern shape formed on a
photomask. Although the inspection object is a semiconductor wafer
in the description below, any inspection object may be used as long
as the object is a DSA technology based wafer. The circuit design
data may have any format and type if the software that displays the
circuit design data can display its format form and can treat the
circuit design data as graphic data.
[0051] As a system for creating a measurement recipe from
semiconductor circuit design data, a device is used that can set a
measurement recipe from circuit design data, that can execute the
measurement recipe on the CD-SEM, and that can obtain necessary
measurement data.
[0052] FIG. 18 is a diagram showing an example of a recipe creation
system that includes an image processor (arithmetic processing
device) 1800 and recording media that store data for creating
addressing pattern data. The image processor 1800 is connected to a
SEM not shown and is connected to a design data storage medium
1801, a target pattern data storage medium 1802, and a simulator
1803, which simulates a pattern shape and so on based on design
data, via a network. An input device 1804, from which an addressing
pattern creation condition can be entered, is connected also to the
image processor 1800. The design data storage medium 1801 stores
graphic data on a guide pattern used for the DSA technology. This
graphic data can be read based on selection information received
from the input device 1804. It is also possible to cause the
simulator 1803 to simulate the result of a pattern based on the
graphic data on a guide pattern stored in the design data storage
medium 1801 and to send the graphic data to the image processor
1800 as data on the guide pattern. In addition, the target pattern
data storage medium 1802 stores SEM image data on high molecular
compounds, the pitch width data on high molecular compounds, or
pseudo image data on high molecular compounds. These data can be
read based on an instruction on a high molecular compound, or based
on an input of the pattern width or pitch of a high molecular
compound, received from the input device 1804. FIG. 19 is a diagram
showing a database in which the type of a high molecular compound
and the pitch and width of the high molecular compound, which are
associated with each other, are stored. Based on these data, the
image processor 1800 can form the pseudo image of a polymer formed
with the same line width and pitch.
[0053] FIG. 20 is a diagram showing an example of the GUI
(Graphical User Interface) screen displayed on the display device
of the input device 1804. Based on a pattern name or a location
entered from a pattern name input window 2001 and a pattern
location input window 2002, the graphic data on an area, which
includes a guide pattern, is read from the design data storage
medium 1801 and the simulator 1803. The field of view size for
addressing may be selected by selecting a field of view size from a
field of view size setting window 2003 for setting the field of
view size. Where in the field of view to locate the pattern for
addressing may be selected by entering location information in a
location in field of view selection window 2004.
[0054] The information on the type of a high molecular compound can
be selected in an additional pattern selection window 2005. For
example, based on a material selected in this window, the SEM image
data, high molecular compound pitch and width data, or pseudo image
data, which are stored in association with the material, can be
read. In addition, using the image processor 1800, the pseudo image
of a high molecular compound can be formed based on the numeric
values entered in a pitch information input window 2006 and a
pattern width input window 2007. The pseudo image of a high
molecular compound may be formed by reading the brightness
information allocated in advance to each high molecular compound
and by arranging the brightness information according to the size
of the address pattern to be created and the pitch information and
pattern information that are set.
[0055] The image processor 1800 can store an addressing pattern,
created based on the setting information, in a recipe storage
medium 1808 as the SEM measurement recipe information.
[0056] FIG. 21 is a diagram showing the detail of a measurement or
inspection system that includes a SEM. This system includes a SEM
main body 2101, a control device 2102 of the SEM main body, and an
image processor 2103 that performs template matching and
measurement processing. A recipe storage unit 2104, included in the
image processor 2103, is for registering a recipe, created by the
image processor 1800 shown in FIG. 18.
[0057] The image processor 2103 includes a matching processing unit
2105 that performs matching processing using a template in the
image signals obtained via the control device 2102 and a
measurement processing execution unit 2106 that locates the field
of view onto the measurement position identified by the matching
processing unit 2105, obtains the detection signal, creates a line
profile based on the detection signal, and measures the size
between peaks in the profile. A recipe, an operation program for
automatically operating the SEM, is stored in a memory 208
described above or in an external storage medium for each type of a
sample to be measured, and is read as necessary. In addition,
though not shown, image processing hardware, such as the CPU
(Central Processing Unit), ASIC (Application Specific Integrated
Circuit), and FPGA (Field Programmable Gate Array) included in the
image processor 2103, is used to perform image processing according
to the purpose. An image processing unit 207 has the function.
[0058] It is also possible to allocate the whole or a part of the
control and processing performed in an arithmetic processing device
205 to an electronic computer, which has the CPU and a memory in
which an image can be accumulated, for performing the processing
and control. Template matching is a method for identifying a
position, where a captured image to be located and a template
match, based on the matching degree determination using normalized
correlation. The matching processing unit 2105 identifies a desired
position in a captured image based on the matching degree
determination. Although the degree of matching between a template
and an image is represented by the term "matching degree" or
"similarity degree" in this embodiment, these two terms are
equivalent in that they mean an index indicating a coincidence
between the two. A mismatching degree or dissimilarity degree is
one mode of a matching degree or similarity degree.
First Embodiment
[0059] The method for generating an addressing pattern based on a
guide pattern, used for DSA, is described below. In this
embodiment, an addressing pattern is created using a photomask that
is created by arranging a guide pattern with the same size and
pitch as those of a target pattern as shown in FIG. 1. More
specifically, exposure is performed using a photomask created by
arranging the pattern 103, which will become the guide pattern, at
the same pitch in a pattern (for example, cross pattern) that will
become an addressing pattern and, in addition, the BCP is applied
and annealing is performed to form the pattern.
[0060] In addition, from an image generated by capturing the
addressing pattern created as described above, a random pattern,
which is present outside the addressing pattern, is removed to
generate template image data for addressing.
[0061] The reason for generating an addressing pattern by preparing
a guide pattern arranged at a pitch smaller than the whole size of
the addressing pattern is as follows. Because an addressing pattern
must capture an image with magnification lower (larger field of
view) than that of a measurement object pattern for correcting the
position of a radiated electron beam, the addressing pattern is
usually formed in a size larger than that of the target
pattern.
[0062] On the other hand, when a guide pattern used for DSA is
formed in a large size, DSA-based pattern formation is not
performed properly on a guide pattern as shown in FIG. 3. FIG. 4 is
a top view of a pattern created using the process shown in FIG. 3.
A guide pattern 401 is present in the lower layer of a target
pattern 402. Although the size and the pitch of the pattern of the
target pattern 402 are created as intended, its direction cannot be
controlled with the result that the pattern is formed in random
directions. Because the guide pattern 401 is present in the lower
layer of the target pattern 402 and the target pattern 402 in the
upper layer is formed in random directions, the contrast is
decreased and it is sometimes difficult to use the pattern as an
addressing pattern.
[0063] In this embodiment, the contrast of the addressing pattern
can be maintained to fulfill its role by forming an addressing
pattern using the guide of the same rule as that of a target
pattern. Performing image processing for the pattern, formed in
this way, eliminates the effect of a part uncontrollable by DSA,
giving high position correction accuracy in addressing in the
measurement sequence.
[0064] The following describes an example in which a template image
for addressing is created using a cross shaped pattern such as that
shown in FIG. 7. FIG. 6 is a flowchart showing a part of the
process. In this embodiment, as an object pattern for creating a
template image, the circuit design data, configured by a
cross-shaped pattern and two straight lines shown in FIG. 7, is
used as an example. The pattern to be created is a pattern that is
larger than the cross target pattern in size and is used as an
addressing pattern in a CD-SEM measurement recipe. The actual sizes
of the cross pattern are shown in the figure. In the DSA technology
used in this example, the target size is 28 nm and the guide
pattern is arranged at a pitch of 168 nm. The line width of each of
the two straight lines is 28 nm that is the target size of the DSA
and the two straight lines are arranged at a pitch of 168 nm. In
this case, it is determined in step 601 that the cross pattern does
not satisfy the DSA allowable size and that the two straight lines
satisfy the DSA allowable size and therefore they are accepted.
[0065] Next, in step 602, the pattern is arranged in such a way
that the cross pattern is configured only by the straight pattern.
Although the straight line is a vertical line, a horizontal line
may also be used. FIG. 8 is a diagram showing an actual example in
which the 28 nm patterns are arranged in the cross pattern in FIG.
7 at a pitch of 168 nm.
[0066] In this case, the guide pattern is arranged at the right end
of the cross pattern and, in such a case, the guide pattern is not
arranged at the pattern ends other than the right end. When
arranging the guide pattern, the guide pattern is not arranged
outside the original pattern area. The reason is that there is a
need to avoid the possibility of overlapping that may occur when
the guide patterns of the patterns, adjacent to each other at a
suitable interval, are arranged. Each of the two straight lines,
originally created according to the DSA allowable size, is used
directly as a guide pattern 802.
[0067] In general, a DSA pattern in a part, where there is no guide
pattern, has a fingerprint-like pattern the direction of which is
uncontrollable. Therefore, when a DSA pattern is formed in the
state in which there is no guide pattern, for example, at the end
of the pattern in FIG. 8, a fingerprint-like random pattern 902 is
formed in the area outside the guide pattern at the ends of the
cross pattern on the wafer, as shown in FIG. 9.
[0068] To use the pattern, created in this way, as an addressing
pattern in the measurement recipe of a CD-SEM, it is necessary to
perform image processing for the captured SEM image and, after
that, to save the image in the measurement recipe as an image
template with the surrounding fingerprint-like pattern removed as
an image.
[0069] FIG. 10 shows the image template registration flow for
registering the image template. In step 1001, the field of view is
moved to the pattern used for addressing and, with the SEM image
displayed, the magnification (field of view area), the accelerating
voltage of electron beam (attainment energy of electron beam), the
probe current, and number of frames condition are selected. In this
example, the magnification is set so that the field of view is a
square area having the side length of 450 nm, and the accelerating
voltage is set to 800V, the probe current is set to 8 pA, and the
cumulative number of frame is set to 16.
[0070] Next, in step 1002, an area including a pattern, which will
be used as the addressing pattern, is specified, and the image of
the area is registered as the base image. This base image becomes a
template image through the processing that will be described later.
In step 1003, annealing is performed to remove a random pattern
positioned in an area other than the self-organizing area. The
reason for removing a random pattern is as follows.
[0071] The CD-SEM is used to perform fixed-point measurement of a
particular pattern of a plurality of samples created under the same
fabrication condition, especially, in the mass production process
of semiconductor devices. However, even under the same fabrication
condition, the shape of a random pattern varies according to the
sample. That is, if a template is created with a random pattern
included, the degree of matching between the template and a
particular area, for which template matching is performed, is
decreased. This embodiment, in which a template is created by
removing a random pattern that will result in a decrease in the
matching degree, can reduce the possibility of matching error
generation.
[0072] Another possible method for removing a random pattern is to
selectively extract a pattern part that is aligned through
self-organization and then to remove a part that is not extracted.
A coordination part extraction unit 1805 of the image processor
1800 shown in FIG. 18 identifies an aligned part and a non-aligned
part using the template of an aligned part that is registered in
advance. To perform this processing, the base image (template) and
an image to be evaluated are required and, in this example of the
cross pattern, the shortest segment in the vertical direction, in
which a straight line is formed, is used. In the pattern shown in
FIG. 7, the segment with a length of 450 nm is used. The line width
of the straight line is 28 nm that is the target size in the DSA
technology used in this example. In addition, because the pitch
used in the guide pattern of the self-organizing technology in this
example is 168 nm, three periods, each composed of the 28 nm line
part and the 28 nm space part, are selected as one unit at image
registration time. FIG. 11 is a diagram showing an example of a
template for extracting an aligned pattern. The correlation value
arithmetic processing, which uses a template such as that shown in
FIG. 11, is performed for the SEM image such as that shown in FIG.
9 to selectively extract a part where the correlation value is
equal to or larger than the predetermined value (or to remove the
other part). To increase the extraction accuracy, not only the
value of correlation between the template and the image but also
the determination of whether a part, where the correlation value
exceeds the predetermined value, forms a predetermined shape may
also be included.
[0073] At this time, the size of the cross pattern itself becomes
smaller than the original size that is set in FIG. 7. However,
because the purpose of the addressing pattern is to match
positions, the relative position remains the same and therefore no
problem is generated if both the size of the template image and the
size of the pattern on the wafer change in the same manner.
[0074] In step 1004, whether the fingerprint-like pattern
surrounding the addressing pattern is successfully removed is
confirmed either visually or using a determination algorithm for
automatically determining the pattern shape. If the removal cannot
be confirmed successfully, the surrounding pattern can be removed
successfully in some cases by changing the specification of the
base pattern area specified in step 1002.
[0075] The processing described above allows the template, in which
the aligned part is selectively extracted as shown in FIG. 12, to
be created. The image data extracted by the coordination part
extraction unit 1805, to which the predetermined information
required to register a condition as a recipe is added by an
addressing pattern data generation unit 1807, is registered in the
recipe data storage medium 1808. The template shown in FIG. 12 has
the shape of a cross-shaped guide pattern, and this image data is
stored as the template.
[0076] Next, with reference to the flowchart shown in FIG. 13, the
following describes the process of measurement on the SEM that is
performed by the image processor 2103, shown in FIG. 21, by
executing a recipe stored in the recipe data storage medium
1808.
[0077] A measurement object pattern is created using the
self-organizing technology, and there is a pattern with a size
larger than the target size. This pattern is configured only by an
allowable pattern created through the process such as that
described above. When a CD-SEM measurement recipe is executed, a
wafer is loaded into the device, the condition to be used is set
and, after that, wafer alignment is performed first to position the
wafer. This wafer alignment is performed in two stages: one is
alignment by means of an optical microscope image (step 1301) and
the other by means of a SEM image (step 1302).
[0078] Alignment by means of an optical microscope image is not
affected much by the presence of a random pattern. On the other
hand, alignment by means of a SEM image requires the usual
procedure as well as the procedure for removing a fingerprint-like
pattern generated by the DDA technology. The reason is that
alignment by means of a SEM image requires that the similar
position correction be performed at different exposure positions on
a wafer 1401 as shown by a chip 1403 (FIG. 14).
[0079] However, when creating a pattern using the DSA technology,
there is no problem with a pattern the direction of which is
controlled by a guide pattern. However, in an area where there is
no guide pattern and the direction cannot be controlled, the
so-called fingerprint-like pattern is randomly formed with the
result that not all three images used for SEM image alignment are
the similar. To address this problem, the surrounding
fingerprint-like, randomly shaped pattern is removed when SEM
alignment is performed (step 1303) to select a pattern intended for
use in SEM alignment. This makes the three SEM images similar to
that shown in FIG. 12, allowing positioning to be performed using
these images (step 1304).
[0080] After wafer alignment is performed, the field of view is
moved to a position registered as the length measurement point
(step 1305) and addressing is performed. Also when this addressing
is performed, the fingerprint-like pattern around the pattern must
be removed (step 1306) before performing addressing. The reason is
that the exposure shot, used at measurement recipe registration
time, and the exposure shot, used for actual measurement, are
sometimes different shots and, in that case, the patterns are not
exactly similar because the pattern, for which addressing is
performed, is a pattern around which there is a fingerprint-like
pattern the direction of which is random.
[0081] The subsequent sequence includes the step for performing
position correction using the registered template (step 1307), the
step for setting the brightness and contrast of the length
measurement point (step 1308), the step for performing auto-focus
(step 1309), and the step for moving the field of view to the
length measurement point, for acquiring the SEM image, and for
performing measurement (step 1310).
[0082] After measurement, the processing moves to the next length
measurement point to perform length measurement using the same
sequence. Using this method allows addressing to be performed
suitably even for a pattern formed based on DSA, thus enabling
length measurement to be performed using a measurement recipe.
Second Embodiment
[0083] When creating a measurement recipe in the first embodiment,
an image template to be saved in the measurement recipe is
registered by observing an accrual wafer, while, when creating a
measurement recipe in this embodiment, an image template to be
registered is created based on circuit design data. Although the
circuit design data used at this time is data used when the
photomask is created, the size of the whole data is reduced to 1/4
in order to establish correspondence with the pattern on the wafer.
This is because a 1/4 reduction projection type exposure device is
used in this embodiment when exposure is performed for the guide
pattern.
[0084] The circuit design data used this time does not include a
pattern that is formed using a size other than the target size of
the DSA technology. As shown in FIG. 8, the line pattern with the
target size is arranged at a specified periodic interval.
[0085] This circuit design data is stored in the design data
storage medium 1801 and is captured into the image processor 1800
based on selection information entered from the input device 1804.
The information not included in the design data is acquired by
capturing the information other than the usual design data stored
in the target pattern data storage medium 1802 or by capturing the
input information entered from the input device 1804. For example,
the information not included in the design data is information on
the target pattern size, guide pattern pitch, target pattern pitch,
and base pattern period. These information is received as addition
information. In this embodiment, to create a template equivalent to
the template created in the first embodiment, the target pattern
size is set to 28 nm, the guide pattern pitch is set to 168 nm, the
target pattern pitch is set to 1:1, and the base pattern period is
set to 1. FIG. 15 is a diagram showing design data 1501 in which
the guide pattern is formed in the cross-shaped addressing pattern
data and superimposition data 1502 obtained by adding additional
information to the design data 1501.
[0086] As described above, in the pattering according to DSA, a new
pattern is arranged between the guide patterns arranged in advance.
In this case, the target pattern with the size of 28 nm is formed
at a pitch of 168 nm with the ratio between the line part and the
space part being 1:1. The base pattern period is the same as the
period in the template that is used for removing a fingerprint-like
pattern before performing addressing when the measurement recipe,
which is set, is executed on the CD-SEM.
[0087] Because the base pattern period is set to 1 in this
embodiment, the base area has the size equivalent to one period,
that is, 168 nm, in the direction perpendicular to the line pattern
and the size equal to that of the shortest part of the cross
pattern as in FIG. 11, that is 450 nm, in the direction of the line
pattern. That is, the line and the space, each in 28 nm in width,
are formed at a ratio of 1:1, and the area surrounded by the lines,
168 nm and 450 nm in size, is the base area in this embodiment.
This embodiment is different from the first embodiment in that the
area shown in FIG. 11 is an area selected by the user from an
actual pattern on a wafer while the area in this embodiment is set
automatically by the system based on the parameters.
[0088] When the lengths of neighboring guide patterns differ from
each other, the areas are classified into types, one is an area in
which a pattern is arranged and the other is an area in which a
pattern is not arranged, according to whether there is a
neighboring guide pattern. In the case of FIG. 16(a), guide
patterns 1601, different in length, are arranged at the guide
pattern pitch of 168 nm. Because there is a guide pattern at both
ends of the area of a guide pattern pitch 1602, a pattern is
arranged in this area. On the other hand, because there is a guide
pattern only at one end of an area 1603, a pattern is not formed in
this area. In the case of FIG. 16(b), because there is a guide
pattern at both ends of an area 1604 but the interval is not equal
to the guide pattern pitch that is set by the parameters described
above, a pattern is not formed in this area. A pattern is formed
when there is a guide pattern at both ends of an area and its
interval is equal to the guide pitch. The figure is a figure
showing the pattern shape obtained by performing annealing for the
sample shown in FIG. 16 and is a figure showing the figure in which
a pattern 1702 is arranged in an area where there is a guide
pattern 1701 at both ends. As shown in FIG. 17(b), when the
distance between the guide patterns is large, a pattern is not
arranged.
[0089] As described above, the information different from circuit
design data, composed only of guide patterns, is stored in the
target pattern data storage medium 1802 and is read as necessary,
or such information is set via the input device 1804, to enable an
addressing pattern, similar to the actual image, to be
generated.
[0090] The addressing pattern data generation unit 1807 creates a
measurement recipe by adding information, necessary for automatic
measurement such as the information on an addressing point, auto
focus point, and brightness and contrast algorithm for use in the
sequence of the measurement recipe, to the superimposition data
formed by adding additional information to the design data
(simulation data) that is formed as described above. Then, the
addressing pattern data generation unit 1807 stores the created
measurement recipe in the recipe data storage medium 1808.
[0091] It is desirable that the data shown in FIG. 7 be used as the
circuit design data rather than the pattern shown in FIG. 17 where
a DSA target pattern is arranged or the pattern 1501 shown in FIG.
15 where a guide pattern is arranged. The reason is that a
large-sized pattern must be arranged as a large pattern when the
method used for automatic setting is directly used.
[0092] The GUI screen shown in FIG. 20 has a display area 2008 in
which a template image being created is displayed and a display are
2009 in which a low-magnification image for addressing is
displayed. These display areas allows a recipe creator to confirm
the suitability of an addressing pattern while visually confirming
these display areas.
[0093] Although the present invention has been described with
reference to embodiments thereof, it will be obvious to those
skilled in the art that various changes and modifications may be
made without departing from the spirit or scope of the present
invention.
REFERENCE SIGNS LIST
[0094] 501 Charged particle source [0095] 502 Charged particle beam
[0096] 503 Scanning coil [0097] 504 Sample [0098] 505 Secondary
particle [0099] 506 Detector [0100] 507 Control device [0101] 508
Stage [0102] 509 Image display device [0103] 510 Circuit design
data management unit
* * * * *