U.S. patent application number 11/953777 was filed with the patent office on 2008-05-08 for scanning electron microscope with measurement function.
Invention is credited to Tsuyoshi Morimoto, Yuuki Ojima, Katsuhiro Sasada, Kazuhiro Ueda.
Application Number | 20080109755 11/953777 |
Document ID | / |
Family ID | 32866476 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080109755 |
Kind Code |
A1 |
Ojima; Yuuki ; et
al. |
May 8, 2008 |
Scanning electron microscope with measurement function
Abstract
A scanning electron microscope which efficiently makes
measurements for plural measurement items at a time and allows easy
entry, confirmation and revision of auto measurement parameters.
Parameters for creation of a line profile from an image captured by
the scanning electron microscope are entered as auto measurement
parameters (AMP) to be used as common conditions for all
measurement items. Also, plural combinations of edge detection
methods and measurement calculation methods are entered as auto
measurement parameters to make measurements for plural items.
Inventors: |
Ojima; Yuuki; (Hitachinaka,
JP) ; Sasada; Katsuhiro; (Hitachinaka, JP) ;
Ueda; Kazuhiro; (Hitachinaka, JP) ; Morimoto;
Tsuyoshi; (Hitachinaka, JP) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1177 AVENUE OF THE AMERICAS (6TH AVENUE)
NEW YORK
NY
10036-2714
US
|
Family ID: |
32866476 |
Appl. No.: |
11/953777 |
Filed: |
December 10, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11398522 |
Apr 6, 2006 |
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11953777 |
Dec 10, 2007 |
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10779848 |
Feb 18, 2004 |
7053371 |
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11398522 |
Apr 6, 2006 |
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Current U.S.
Class: |
715/811 |
Current CPC
Class: |
H01J 37/28 20130101;
H01J 2237/2816 20130101; H01J 2237/221 20130101; H01J 2237/2817
20130101; G01N 23/2251 20130101; H01J 37/265 20130101 |
Class at
Publication: |
715/811 |
International
Class: |
G06F 3/048 20060101
G06F003/048 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2003 |
JP |
2003-044290 |
Claims
1. A computer comprising a display unit for displaying a setting
screen for setting a condition for the measurement of the size of a
pattern formed on a sample based on a line profile that is formed
on the basis of electrons emitted upon irradiation of the sample
with an electron beam, wherein, the setting screen displays a first
setting area for setting a condition for the formation of the line
profile, which condition is common to a plurality of measurement
objects, and a second setting area in which a plurality of
measurable objects can be set on the basis of a line profile formed
on the basis of the condition that is set.
2. The computer according to claim 1, wherein the display unit
displays a setting screen for setting a method of measurement of an
object set in the second setting area.
3. The computer according to claim 1, wherein the condition set in
the first setting area concerns the type of the pattern.
4. The computer according to claim 3, wherein the condition set in
the first setting area concerns at least one of: the direction of
measurement of length; the area of creation of a line profile; the
area of edge detection of the pattern; the number of line profiles
created; the area of integration of signals per line profile when
creating a line profile; the distance between box cursors for
length measurement; a line profile smoothing condition; and a line
profile differentiation condition.
5. A computer comprising a display unit for displaying a setting
screen for setting a condition for the measurement of the size of a
pattern formed on a sample based on a line profile that is formed
on the basis of electrons emitted upon irradiation of the sample
with an electron beam wherein, the setting screen displays a
setting area for setting a condition for the formation of the line
profile, which condition is common to a plurality of measurement
objects, and an area for displaying a plurality of measurable
objects based on a line profile formed on the basis of the
condition that is set.
Description
CROSS-REFERENCE TO RELATED CASES
[0001] The present application is a continuation of U.S.
application Ser. No. 11/398,522, filed Apr. 6, 2006, which is a
continuation of U.S. application Ser. No. 10/779,848, filed Feb.
18, 2004, now U.S. Pat. No. 7,053,371, issued May 30, 2006, which
claims the benefit of Japanese Application No. 2003-044290, filed
on Feb. 21, 2003, the disclosures of which are herewith
incorporated by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a scanning electron
microscope with a measurement function and a measurement method
which uses it.
BACKGROUND OF THE INVENTION
[0003] The following patent documents (gazettes) describe
conventional techniques in this field:
[0004] Patent Document 1: JP-A No. 347246/1994
[0005] Patent Document 2: JP-A No. 22794/1996
[0006] Patent Document 3: JP-A No. 237231/1999
[0007] Patent Document 4: JP-A No. 213427/1998
[0008] Patent Document 5: JP-A No. 201919/1999
[0009] A scanning electron microscope with a measurement function
(hereinafter called a measurement SEM) has been used for control of
semiconductor sample dimensions or other similar purposes. There
are two dimensional measurement modes: a manual measurement mode
and an auto measurement mode. In the manual measurement mode, an
operator visually makes a measurement using a measurement cursor.
In the auto measurement mode, a measurement SEM captures an image
of a pattern to be measured (hereinafter called an "SEM image") and
creates, from the image, a line profile which is considered to
reflect the cross section of the pattern; the position of an edge
of the pattern is detected from the line profile and according to
the detected edge, the measurement (length) of the pattern is
calculated. In the auto mode, line profile creation, edge
detection, and measurement calculation are carried out according to
predetermined auto measurement parameters (hereinafter called AMP).
Refer to Patent Document 1.
[0010] Patent Document 2 describes a groove shape measuring method
in which a secondary electron image of a groove is obtained from
observation of its surface by a scanning electron microscope and
the width of the groove or track pitch as a groove shape factor is
measured. This method comprises the following four steps. In the
first step, the secondary electron image of the groove is converted
into image file data in a sequential file form. In the second step,
according to the image file data obtained in the first step, a
profile image of contrast is obtained by successively scanning the
number of "bright" spots existing in a measuring unit area enclosed
by a desired length in the groove direction perpendicular to the
groove width direction and a length in the width direction,
equivalent to one dot as the minimum pixel unit. In the third step,
for the profile image of contrast obtained in the second step, an
edge detecting slice level for measurement of the opening width of
the groove, HLV, and an edge detecting slice level for measurement
of the bottom width of the groove, LLV, are calculated from the
following equations, where AVG represents the average of the number
of "bright" spots existing in each of the measuring unit areas:
HLV=AVG.times.SLU(1<SLU<2)
LLV=AVG.times.SLB(0<SLB<2)
[0011] In the fourth step, the track pitch between neighboring
grooves is calculated using one of the edges of the groove opening
or bottom which is detected according to the slice levels HLV and
LLV calculated in the third step.
[0012] Patent Document 3 describes a method of determining the
position of a pattern edge and Patent Document 4 and Patent
Document 5 each describe a method of obtaining a line profile.
[0013] In recent years, there has been an increasing tendency to
use an auto dimensional measurement method and the accuracy of auto
measurement has been improving year by year. In auto measurement,
there are two operation modes: a semi-auto mode in which movement
to a measuring point or identification of a measuring point is done
by an operator, and a full-auto mode in which measurements are made
fully automatically, or with no operator assistance, by executing a
recipe file which stores wafer surface data, measuring point
position data or other information.
[0014] The recent trend is as follows: as semiconductor samples
become smaller, measurement SEMs are more functional; they measure
not only the line width of a pattern or the diameter of a hole
automatically but also width roughness, edge roughness and so on
for evaluation of the pattern shape.
[0015] In the conventional techniques, a set of auto measurement
parameters (AMP) is needed to make a measurement for an item in the
auto mode. Therefore, in semi-auto measurement, if several types of
measurements are to be made, it is necessary to specify a set of
AMP for each measurement type, which is very troublesome. In
full-auto measurement, if several types of measurements are to be
made, required AMP data is stored in a recipe file and thus
operation is easy, but it is troublesome to revise and check the
stored AMP data. A resulting measurement value is displayed in a
window of the SEM upon execution of measurement; when several types
of measurements are made, it is not easy to check numerical
measurement values so the operator has to wait for completion of
the whole measurement process until a list of measurement results
appears.
SUMMARY OF THE INVENTION
[0016] An object of the present invention is to provide a scanning
electron microscope which efficiently and easily makes measurements
for plural measurement items and a measurement method which use
it.
[0017] Another object of the present invention is to make it easy
to store, check, and revise auto measurement parameters to make
measurements for plural measurement items.
[0018] According to one aspect of the present invention, parameters
for creation of a line profile from an SEM image are specified for
common use for plural measurement items and entered as auto
measurement parameters (AMP entry). Here, "AMP entry" means that
parameters are specified in an AMP window and saved in a storage.
Also, plural edge detection methods and measurement calculation
methods can be entered in the AMP window so that measurements for
plural items can be made easily.
[0019] According to another aspect of the present invention, there
is provided a scanning electron microscope with a measurement
function, where plural measurement items including plural
measurement calculation methods are specified for an edge detected
by at least one edge detection method, or a single edge detection
operation, in an auto measurement parameter (AMP) configuration
window; a line profile is created from an SEM image; an edge is
detected as specified from the line profile; and measurements are
calculated successively from each detected edge according to the
specified plural measurement calculation methods. Also, a
measurement method which uses it is provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention will be more particularly described with
reference to the accompanying drawings, in which:
[0021] FIG. 1 shows an AMP configuration window according to an
embodiment of the present invention;
[0022] FIG. 2 shows a window where edge detection parameters are
specified and measurement calculation methods are selected;
[0023] FIG. 3 shows a window for selection of a measurement
method;
[0024] FIG. 4 shows a window displaying items which can be measured
by a measurement method L/S (Multi);
[0025] FIG. 5 shows a selection window for entry of an edge
detection method;
[0026] FIG. 6 shows a window for viewing an SEM image;
[0027] FIG. 7 illustrates measurement box cursors on an SEM
image;
[0028] FIG. 8 illustrates detected positions and their symbols on
detected signals;
[0029] FIG. 9 illustrates a measurement calculation method on a
line profile;
[0030] FIG. 10 shows an SEM image with detected edge positions;
[0031] FIG. 11 shows measurement results displayed in a window;
[0032] FIG. 12 illustrates one example of a mean width calculation
method;
[0033] FIG. 13 is a flowchart showing a semi-auto measurement
process according to the present invention;
[0034] FIG. 14 is a flowchart showing a semi-auto measurement
process according to the prior art; and
[0035] FIG. 15 is a known block diagram showing the general
structure of a scanning electron microscope with a measurement
function.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Next, preferred embodiments of the present invention will be
described referring to the accompanying drawings.
[0037] FIG. 15 shows the general structure of a scanning electron
microscope with a measurement function according to an embodiment
of the present invention (see Patent Document 1). An electron beam
2 emitted from an electron gun 1 is narrowed by an objective lens 6
and thrown on a sample 7. The objective lens 6 is excited by an
objective lens power supply 11. A deflecting signal generator 14
sends a deflecting signal depending on a scanning area or scanning
position of the electron beam 2 as indicated by a computer 21
through a deflecting amplifier 10 to a deflecting coil 5 to excite
it so that the sample 7 is scanned with the electron beam 2
two-dimensionally.
[0038] A secondary signal (secondary electron signal, reflection
electron signal, etc.), which is generated from the sample 7 in
response to irradiation of the electron beam 2, is detected by a
detector 12 and converted into an electric signal before being
converted from an analog signal into a digital signal by an A/D
converter 15 and stored in an image memory 16. The content of the
image memory 16 in the digital form is always reconverted into an
analog signal by a D/A converter 17 and applied to a grid as a
brightness signal for an image display CRT (cathode ray tube) 19.
Here, the A/D converter 15, image memory 16, and D/A converter 17
receive a timing signal from the deflecting signal generator 14 so
as to A/D convert, store, and D/A convert it and display an image.
A deflecting coil 20 for the image display CRT 19 is excited by a
signal obtained by amplifying the deflecting signal generated from
the deflecting signal generator 14 by a deflecting amplifier
18.
[0039] On the other hand, a sample stage 8 on which the sample 7
rests is moved by a stage drive circuit 13 so that the scanning
position of the electron beam 2 on the sample 7 changes and the
field of view moves. The field of view can also be moved by
exciting an image shift coil 3 through a DC amplifier 9 and
shifting the scanning position of the electron beam 2 on the sample
7. Movement of the field of view is controlled by the computer
21.
[0040] A cursor signal generated by a cursor signal generator 22 is
varied by a signal from a trackball 24 or the computer 21 to change
the position of the cursor on the image display CRT 19. The
computer 21 acquires data on the cursor position on the image
display CRT 19 depending on the status of the cursor signal
generator 22. The computer 21 can read some or all image data in
the image memory 16. Thus, using data on some image area around the
cursor position in combination with the cursor position data, image
line integration is done to generate a signal waveform, change a
corresponding position in the image memory 16, and view the signal
waveform (line profile) on the image display CRT 19. Another
approach to viewing a signal waveform on the CRT 19 is that a
special memory for viewing a signal waveform is provided to change
a corresponding position in the special memory and the special
memory is XORed with the image memory 16.
[0041] FIG. 1 shows an AMP configuration window (hereinafter called
the AMP window) 100. Here, the process of specifying AMP in the AMP
window 100 is called "specification of AMP" or "AMP entry."
[0042] The AMP window 100 is mainly composed of three areas: a
window area C, that is a first window area 103, where plural
measurement items are specified; a window area A, that is a second
window area 101, where auto measurement parameters are specified as
common conditions for the specified plural measurement items; and a
window area B, that is a third window area 102, where plural
measurement items are displayed and revisions are made.
[0043] In the window area A (101), the following parameters are
specified as conditions. These will be explained in detail
later.
[0044] Method: L/S (Multi) (selected measurement method) [0045]
Direction: X [0046] Inspect Area: 300 [0047] Search Area: 80 [0048]
MP: 5 [0049] Sum Lines/Point: 60 [0050] Design Value: 0.200 .mu.m
[0051] Smoothing: 5 [0052] Differential for Linear: 5
[0053] In the window area B (102), plural edge detection method
options are specified. TABLE-US-00001 Edge Detect Method B(1)Bottom
Th 1 T(1)Top Th 2
[0054] In the window area C (103), plural measurement items
including plural measurement calculation methods are shown.
TABLE-US-00002 Measurement Data 1 B(1) W1 2 B(1) WR1 3 T(1) W1 4
T(1) WR1
[0055] In the AMP configuration shown in FIG. 1, Multi Point
Measurement for line and space type patterns (L/S (Multi) is
selected as a measurement method and AMP entry (specification and
storage of auto measurement parameters) is made for auto
measurement of a (mean) width of the line pattern bottom and a
width of the roughness (3.sigma.) as well as a (mean) top width and
a width of the roughness (3.sigma.).
[0056] First of all, the operator opens an SEM image display window
600 (FIG. 6) on the CRT for AMP entry and presses an AMP button 601
in the window 600 to open the AMP window 100 on the CRT. Then, AMP
entry is made as follows. First, a measurement method is selected.
The selection is made as follows. The Edit button for Method in the
window area A (101) of the AMP window 100 is pressed and a
measurement method selection window 300 (FIG. 3) appears. From a
list of measurement methods in the measurement method selection
window 300, a measurement method which matches the pattern shape is
selected; in this case, L/S (Multi) 301 is selected to measure
(mean) top and bottom widths and a width roughness (3.sigma.).
Then, the OK button 302 is pressed. When the Information button 303
is pressed after selection of the measurement method in the window
300, measurement items for which measurement by each measurement
method is possible are viewed as shown in FIG. 4.
[0057] In the Method window (FIG. 3), available measurement methods
are shown as follows: TABLE-US-00003 1. L/S (Multi) Line 2. L/S
(Single) Line 3. Hole (Diameter) Hole 4. Hole (Multi) Hole 5. Hole
(Single) Hole 6. Gap Gap
[0058] When L/S (Multi) is selected as the measurement method,
objects to be measured (Object) are listed in the Information
window (FIG. 4) as follows: TABLE-US-00004 Bottom B Top T Space S
Pitch (Left) Pl Pitch (Right) Pr Slope (Left) Sl Slope (Right)
Sr
[0059] and also measurement items to be calculated (Measurement)
are listed as follows: TABLE-US-00005 Width 1. Mean W1 2. Mean' W2
3. Max W3 4. Min W4
[0060] TABLE-US-00006 Width Roughness 1. 3.sigma. WR1 2. 3.sigma.'
WR2 3. Max-Min WR3
[0061] TABLE-US-00007 Edge Roughness (Left) 1. 3.sigma. E11 2.
3.sigma.' E12 3. Max-Min E13
[0062] TABLE-US-00008 Edge Roughness (Right) 1. 3.sigma. Er1 2.
3.sigma.' Er2 3. Max-Min Er3
[0063] In multi point measurement, plural edge positions are
detected from plural line profiles. From data on plural edge
positions, measurement values are calculated by the method selected
in the AMP entry process. From one edge position, plural
measurement values are calculated.
[0064] An example of a procedure of calculating a measurement from
data on each edge position is explained below. Since different
measurement results can be shown as measurement values, they are
identified by number.
[0065] The terms used here have the following meanings:
When L/S (Multi) is selected and MP=32:
W: Width
[0066] W1: mean of widths at 32 points [0067] W2: mean of widths at
30 points (excluding the maximum and minimum values) [0068] W3:
maximum width among widths at 32 points [0069] W4: minimum width
among widths at 32 points WR: Width Roughness [0070] WR1:
.sigma..times.3 for widths at 32 points [0071] WR2: .sigma..times.3
for widths at 30 points (excluding the maximum and minimum values)
[0072] WR3: Maximum value among widths at 32 points minus the
minimum value E1: Edge Roughness Left Edge (pattern left edge
roughness) [0073] E11: .sigma..times.3 for edge positions (X
coordinate values) at 32 points on the left of the pattern [0074]
E12: .sigma..times.3 for edge positions (X coordinate values) at 30
points on the left of the pattern excluding the maximum and minimum
values [0075] E13: Maximum edge position X coordinate value minus
the minimum value Er: Edge Roughness Right Edge (pattern right edge
roughness)
[0076] Alternatively, edge roughness after compensation for pattern
inclination may be expressed.
[0077] Next, a measuring area and conditions (parameters) for
creation of a line profile are specified in the window area A (101)
of the AMP window 100. The items shown in the window area A (101)
are parameters concerning measuring points and a measuring area. An
explanation is given below with reference to FIG. 1 and FIG. 7.
"Direction" is used to specify the direction of creation of a line
profile and the direction of edge detection. If a vertical line
pattern 701 in an SEM image 700 (FIG. 7) is to be measured, X is
chosen for Direction. Then, "Inspect Area" 703 and "Search Area"
704 are used to specify the area for line profile creation and the
area for edge detection, respectively. For example, the measuring
area is specified by entering 300 for Inspect Area 703 and 80 for
Search Area. "Design Value" 705 represents the distance between the
right and left box cursors. If a larger value (for example, 0.200
.mu.m) is entered for Design Value 705, the distance between the
left edge detection area and right edge detection area is
increased.
[0078] In the area specified by the value for "Search Area" (in
pixels), the peak of the line profile (secondary electron signal
amount or secondary electron signal waveform) is searched. If the
value for "Search Area" is 80, a peak is searched only within the
area specified by the measuring box cursor (80 pixels) to detect an
edge position. The distance between the box cursors can be
increased using the "Design Value" (.mu.m or nm) parameter to limit
the edge used for measurement (or line profile peak).
[0079] Parameters "Search Area" and "Design Value" are needed to
specify in which area an edge position should be searched. A
mistake in determining an edge position can be prevented by
specifying and limiting the area for edge detection.
[0080] In full auto measurement which uses a recipe, a measuring
point is searched based on the recognition of a previously entered
reference image and the box cursors are automatically positioned to
perform auto measurement.
[0081] Next, values for "MP" and "Sum Lines/Point" 706 are entered.
MP represents the number of line profiles to be created in the
Inspect Area 703. For instance, if the value for MP is 5, five line
profiles are created in a way that the Inspect Area 703 is divided
into five equal parts. Sum Lines/Point 706 represents an area for
secondary electron signal integration of each line profile. In this
case, 60 is entered for Sum Lines/Point 706. When the
abovementioned values are set in the AMP window, the conditions for
creation of line profiles from an image and the area where an edge
is detected can be specified.
[0082] Here, an area for integration to make one line profile is
expressed in pixels. When the value for Sum Lines/Point is 60,
signals equivalent to 60 pixels in the Y direction are integrated
to create line profiles. As the value for Sum Lines/Point (the
number of pixels) becomes larger, the amount of signals increases
and signals are averaged, resulting in noise reduction.
[0083] "Inspect Area" represents an area in the Y direction where
measurement is to be made; it is used to specify which area in the
image is used for measurement.
[0084] The "Smoothing" parameter in the window area A (101) is used
to specify the degree of smoothing for a line profile created from
the image. If the value for Smoothing is 5, noise will be smaller
than when no smoothing is done on the line profile. A smoothed line
profile is used for edge detection in auto measurement. When linear
approximation is also used for edge detection, a line profile
created from the differential (inclination) of a smoothed line
profile is used, so the "Differential" parameter in the window area
A (101) is used to specify the differential. When the above
parameters are specified in the window area A (101), all necessary
conditions to create line profiles for edge detection are
established. The parameters thus specified in the window area A
(101) are common conditions for all auto measurement items which
are entered in the AMP window. Therefore, measurement conditions
for all measurement items can be easily revised just by altering
relevant parameters in the window area A (101).
[0085] Next, in the window area B (102) of the AMP window 100, for
example, a bottom edge detection method is specified. A window 200
shown in FIG. 2 and a window 500 shown in FIG. 5 are also used
here.
[0086] The window 200 in FIG. 2 appears when Bottom (B1) is chosen
for Edge Detect Method and Threshold is chosen for Method. In this
window, for example, the following parameters appear under "Edge
Detect Parameter": TABLE-US-00009 Left Right Threshold 50% 50% Edge
Number .sup. 1 .sup. 1 Base Line Start Point -- -- Base Line Area
-- -- Edge Search Direction Normal Normal
[0087] and the following measurement item options appear under
"Measurement Select": TABLE-US-00010 Width Mean W1 Width Mean' W2
Width Max W3 Width Min W4 Width Roughness 3.sigma. WR1 Width
Roughness 3.sigma.' WR2 Width Roughness Max-Min WR3 Edge Roughness
Left 3.sigma. E11 Edge Roughness Left 3.sigma.' E12 Edge Roughness
Left Max-Min E13 Edge Roughness Right 3.sigma. Er1 Edge Roughness
Right 3.sigma.' Er2 Edge Roughness Right Max-Min Er3
[0088] From these measurement items, two or more items are selected
and entered in the AMP window 100 (AMP entry) in FIG. 1.
[0089] The procedure for entry of the edge detection method is as
follows. First the Add button in the window area B (102) is pressed
and a window 500 showing a list of edge detection object options
appears as shown in FIG. 5. For example, "Bottom B (1)" 501 is
selected from the list in order to make a bottom measurement and
the OK button 502 is pressed. Upon press of the OK button 502, the
window 200 in FIG. 2 appears in which edge detection parameters can
be specified and measurement calculation and representation methods
can be selected.
[0090] In the window area D (201) of the window 200, an edge
detection method is selected. To use threshold data, "Threshold" is
selected. When the threshold method is selected for edge detection,
for example, 50% is entered as the value for Threshold. When
"Normal" is selected for "Edge Search Direction" and plural edges
are detected in the area specified by the parameter "Search Area,"
if 1 is entered for Edge Number, the edge first detected is
selected. The edge detection method is thus established with the
above procedure.
[0091] Next, the method of calculating a measurement from data on
the edge detected by the above method is specified by selection
among options under Measurement Select in a window area E (202) of
the window 200. For example, in the window area E (202), W1 (Width,
mean) 203 and WR1 (Width Roughness, 3.sigma.) 204 are selected from
a list of calculation/representation methods.
[0092] After the edge detection method and the measurement
calculation/representation method are selected with the above
procedure, the OK button 205 in the window 200 is pressed to close
the window 200. Upon press of the OK button 205, B (1) appears
under Edge Detect Method in the window area B (102) of the AMP
window and for measurement items, W1 and WR1, each combined with B
(1), appear in the window area C (103), where B (1) expresses the
selected edge detection method and W1 and WR1 respectively express
(mean) bottom width and width roughness (3.sigma.) for measurement
calculation.
[0093] In this way, a parameter configuration for measurement of
(mean) bottom width and width roughness (3.sigma.) is made. In
order to make a parameter configuration for measurement of (mean)
top width and width roughness (3.sigma.), the Add button in the
window area B (102) of the AMP window is pressed to display a list
of available edge detection object options 500 and Top (T (1)) 503
is selected. Then, a procedure similar to that for bottom is
carried out to make a parameter configuration for measurement of
(mean) top width and width roughness (3.sigma.).
[0094] After all the abovementioned procedures are carried out, all
the entered measurement conditions appear in the AMP window 100 as
shown in FIG. 1. After completion of entry of all required
measurement items, the OK button 104 or the Apply button 105 of the
AMP window 100 is pressed to apply the entered parameters and
finish the AMP entry process.
[0095] The parameter configuration data in the AMP window 100 can
be saved under a file name using a Save button 106 and the saved
AMP data file can be loaded using a Load button 107. Also, an AMP
data file for measurement of plural items including plural
measurement calculation methods for one edge detection method can
be easily generated by loading the saved AMP data file and revising
the AMP configuration data and reentering it.
[0096] Given below is a procedure of confirming AMP configuration
data and revising it. The parameters for creation of line profiles
which are used for measurement can be easily confirmed or revised
in the window area A (101) of the AMP window 100. The selected edge
detection methods can also be checked in the window area B (102).
Similarly, the selected edge detection method for measurement used
can be confirmed from the specified measurement items in the window
area C (103). When in the window area B (102) of the AMP window
100, the specified edge detection parameters are confirmed, an edge
detection method which the operator wishes to revise is selected
and the Edit button is pressed, or when in the window area C (103)
of the AMP window a measurement item which uses the edge detection
method to be revised is selected and the Edit button is pressed, an
edge detection parameter configuration window appears for
confirmation and revision. With this procedure for AMP entry, it is
very easy to confirm and revise parameters for plural
measurements.
[0097] The above embodiment concerns a case of multi point
measurement of a line and space pattern. However, even when the
object to be measured is, for example, a hole pattern, line
profiles can be creased in a similar way though some parameters may
differ; if line profile creation and edge detection are to be done,
a similar AMP entry process can be used.
[0098] Plural measurement values and roughness are shown as
follows. FIG. 8 shows edge positions and their symbols for
measurement of Bottom, Top, Slope (Left), and Slope (Right) of a
line profile.
[0099] As illustrated in FIG. 9 and FIG. 10, edge positions are
shown with a pointing device on an SEM image and measurement is
made on a measurement result representation sheet (window) or SEM
image.
[0100] In this case, an edge detection method (edge symbol) and an
edge position (pointing device) are shown on the SEM image
simultaneously, so the edge position can be confirmed on the SEM
image.
[0101] As illustrated, on a measurement result representation
sheet, measurement items are each represented by a combination of a
symbol for an edge detection method and a symbol for a measurement
calculation/representation method. If measurement items are not
known from symbols, detailed information on measurement items can
be displayed by clicking or a similar method.
[0102] On the measurement result representation sheet, data is
shown in a way that the order of representation of edge positions
is clear. Actual measurements are shown in a way that measured
parts and unmeasured parts can be distinguished.
[0103] Although a measurement result representation sheet, which
typically consists of an image showing measurement results, is easy
to check, it may consist of two or more images showing all
measurement results.
[0104] FIG. 12 illustrates a method of calculating the mean value
of W1 width as an example.
[0105] This sheet displays an image showing measurement results in
real time.
[0106] Detected edges and calculated (measured) parts are indicated
in different fonts: for example, bold letters or a different
color.
[0107] When an edge position appears in an image in real time, the
edge detection method used to detect it is also indicated. For
example, a rectangular frame or enclosure is used.
[0108] An image and a data sheet can be saved together as a set of
data.
[0109] The saved data can be read to confirm measurement
conditions, etc. in the Information window.
[0110] As mentioned so far, there is provided a scanning electron
microscope with a measurement function in which plural measurement
items including plural measurement calculation methods for an edge
detected by an edge detection are specified in an auto measurement
parameter configuration window; a line profile is created from an
SEM image and edges are detected from the line profile as
specified; for each detected edge, successive measurement
calculations are repeated for the specified measurement items; and
measurement values calculated for measurement items including
plural calculation methods for an edge detection method are
displayed in a display window. Also there is provided a measurement
method which uses the microscope.
[0111] Furthermore, there is provided a scanning electron
microscope with a measurement function in which plural measurement
items including plural measurement calculation methods for an edge
detected by an edge detection are specified in an auto measurement
parameter configuration window; a line profile is created from an
SEM image and an edge is detected from the line profile as
specified; for the specified measurement items, measurements are
calculated from detected edges; after plural measurements are
calculated for each edge detection method, edge detection from the
line profile is done for a next edge detection method; plural
measurements are calculated from an edge detected for another
measurement item; and measurement values calculated on plural
measurement items are displayed in a display window. Also there is
provided a measurement method which uses the microscope.
[0112] In the scanning electron microscope with a measurement
function and the measurement method which uses it, a measurement
calculation method includes such items as width and width edge
roughness of a line profile.
[0113] In the scanning electron microscope with a measurement
function and the measurement method which uses it, the AMP window
mainly consists of three window areas: a first window area where
plural measurement items are specified; a second window area where
a measurement method is specified and common auto measurement
parameters for all measurements are specified; and a third window
area where measurement items are displayed and revised.
[0114] Next, how semi-auto measurement is made using the AMP window
will be explained referring to the relevant drawings. FIG. 13 is a
flowchart showing a measurement sequence in a semi-auto mode
according to an embodiment of the present invention. FIG. 14 is a
flowchart showing a conventional measurement sequence in a
semi-auto mode. First, an explanation of the measurement sequence
according to the present invention is given below.
[0115] At step 1301, an SEM image of an object to be measured,
namely a line pattern image, is displayed in the SEM image display
window 600 shown in FIG. 6. An SEM image 700 is made to appear by
pressing an Integ button 603 in the window 600 to irradiate the
sample with an electron beam. At step 1302, measurement item data
for auto measurement is entered in the AMP window and the entry is
applied.
[0116] At this time, an AMP data file which has been created and
saved may be loaded to make the AMP entry process easier. At step
1303, an auto measurement start button (AMS button 602) is once
pressed and a box cursor appears on the SEM image. The box cursor
for auto measurement is moved to a measuring point at step 1304;
and the auto measurement start AMS button 602 is pressed at step
1305 to start auto measurement. In the semi-auto mode, the
procedure up to this step is manually carried out. As the auto
measurement start button is pressed, step 1306 and subsequent steps
are all done automatically.
[0117] At step 1306, a line profile is created from the SEM image
under the conditions determined by the AMP entry process. The
created line profile is smoothed and differentiated at step 1307 to
create a line profile for edge detection. At step 1308, using the
created line profile for edge detection, edge detection is carried
out by a first edge detection method specified in the AMP entry
process. At step 1309, the edge detected at step 1308 is displayed
on the SEM image by a point marker or the like so that it can be
confirmed. According to the data on the edge detected at step 1308,
measurement values are calculated by calculation methods specified
in the AMP entry process at step 1310, and the calculated values
are displayed in a measurement result display window or on a
datasheet at step 1311.
[0118] At step 1312, if the AMP entry includes another edge
detection method, edge detection method revision is made at step
1313 and using the line profile created at step 1308, another cycle
of edge detection, detected edge display and measurement
calculation is performed. Finally, all measurement results are
saved in a storage and displayed in a measurement result display
window or on a datasheet. For example, a (mean) width of the line
pattern and/or width roughness will be graphically shown in the
window.
[0119] Next, the conventional measurement sequence in the semi-auto
mode is explained below referring to FIG. 14. At step 1401, an SEM
image is displayed in an SEM image display window; at step 1402,
the AMP entry process is performed. Then, a box cursor is displayed
on the SEM image at step 1403 and moved to a measuring point at
step 1404. As auto measurement is started at step 1405, a line
profile is created from the image at step 1406 and the line profile
is smoothed and differentiated at step 1407. Using the line profile
thus created, edge detection is done at step 1408 and a measurement
value is calculated from the detected edge at step 1409, and a
marker for confirmation of the edge and a measurement result are
displayed on the SEM image at step 1410. In this way, measurement
for an item is made. If it is found at step 1411 that there is
another measurement item, the sequence goes back to step 1402 for
AMP entry and the subsequent steps must be done again.
[0120] The conventional sequence is troublesome because it is
necessary to revise AMP data and start auto measurement operation
for each item manually. Besides, it takes time because a line
profile must be created from the image for each item. In addition,
detection and display of edges are done for each item, which means
that detection and display of edges have to be done many times,
resulting in a long overall measurement time.
[0121] On the other hand, according to the present invention, an
AMP entry process may be manually done for plural measurement items
and thus once auto measurement operation is started, measurement
operation for plural items is done automatically; as a consequence,
it is less frequent that the operator has to revise AMP data and
take the operation start procedure for auto measurement.
[0122] In terms of time required for auto measurement, a single
cycle of line profile creation can be used for plural measurement
items so the overall time for line profile creation can be reduced,
leading to a shorter overall measurement time. Also, a single edge
detection can be used for plural measurement items and therefore,
in making measurement using common edge data, the number of times
of edge detection and display can be decreased, leading to a
shorter overall measurement time. When an image for edge
confirmation is to be saved, the required number of times of save
operation is equal to that of edge detection, so the number of
saved images can be decreased.
[0123] An embodiment of the present invention has the following
features. [0124] 1. The same number of detected edges as the number
of edge detections are displayed by a pointing device on an SEM
image (conventionally, an edge is indicated for each measurement
item). This reduces the number of times of edge display, thereby
shortening the overall measurement time. [0125] 2. A measurement
item is represented by a combination of a symbol for an edge
detection method (Object) and a symbol for a measurement
calculation method (Measurement) (a name may be shown at the place
where a symbol is indicated). Therefore, it is easy to confirm a
measurement item. Whether or not common edge position data is used
for measurement can be easily checked. [0126] 3. Edge detection
parameters can be specified as desired and plural such parameters
can be entered for an edge detection method in the AMP window.
Therefore, it is possible to detect plural edges from one line
profile. [0127] 4. There is a window area where parameters which
are commonly used for all measurements can be specified. Therefore,
all parameters can be revised at a time for plural measurement
items. There is no need to revise parameters for each item. [0128]
5. Plural measurement calculation methods can be selected and
entered in the AMP window. This makes the AMP entry process for
plural measurement items easier. [0129] 6. Plural measurements are
made by a single operation start procedure for auto measurement.
Therefore, the number of AMP data revisions or the number of times
of auto measurement start operation is decreased. [0130] 7.
Measurement items (represented by symbols, etc) and measurement
results can be displayed in a single window (on a single sheet).
Therefore, it is easier to confirm measurement results. [0131] 8.
In the above window, different fonts (in letter color, size,
thickness, etc.) are used to distinguish between items for which
measurement has been finished and items for which measurement has
not been finished, so that the entered edge detection methods and
the progress of measurement can be checked. Therefore, how
measurement operation is progressing can be checked in real time.
[0132] 9. As auto measurement operation is started, the
above-mentioned measurement result display window appears.
Therefore, it is easier to confirm measurement results.
[0133] According to the above embodiment, a device and a method
which are described below will be realized.
[0134] A scanning electron microscope has a measurement function
which uses a means to create a line profile from an image, a means
to detect an edge from a line profile automatically, and a means to
calculate a measurement from a detected edge to make measurements
automatically according to specified auto measurement parameters
(AMP), where AMP data can be entered for plural measurement
items.
[0135] A scanning electron microscope may have a measurement
function to enable an operator to specify auto measurement
conditions for plural measurement items in a window for AMP
entry.
[0136] A scanning electron microscope may have a measurement
function to make measurements automatically for plural items using
a common line profile.
[0137] A scanning electron microscope may have a measurement
function to make measurements for plural items in an auto mode
simultaneously using plural edge detection methods.
[0138] A scanning electron microscope may have a measurement
function by which plural measurement values are calculated and
displayed simultaneously according to plural calculation methods
using data on plural detected edges.
[0139] A scanning electron microscope may have a measurement
function by which the number of edge detection methods usable for
plural measurement items can be increased by entering desired
parameters for an edge detection method and adding it to a list of
edge detection methods.
[0140] A scanning electron microscope may have a measurement
function by which plural measurement values are calculated and
displayed by a single operation start procedure for auto
measurement.
[0141] A scanning electron microscope may have a measurement
function by which measurements can be made for plural items
automatically by entering plural combinations of edge detection
methods and measurement calculation methods.
[0142] A scanning electron microscope may have a measurement
function by which edge detection methods and measurement
calculation methods are represented by symbols, letters, numerical
characters and the like in a window for AMP entry.
[0143] A scanning electron microscope may have a measurement
function by which a window which can display plural measurement
results at a time is opened by starting auto measurement
operation.
[0144] A scanning electron microscope may have a measurement
function by which measurement values are displayed in a window
where measurement items can be checked.
[0145] A scanning electron microscope has a measurement function
which uses a means to display a line pattern image, a means to
create a line profile from the image, a means to detect an edge
from a line profile automatically, and a means to calculate a
measurement from a detected edge to make measurements automatically
according to specified auto measurement parameters. In this
microscope, plural measurement items are specified in a window; for
the specified plural measurement items, common parameters as auto
measurement conditions are specified to create the line profile; an
edge is detected from the line profile; and measurements are made
automatically for plural measurement items according to data on the
detected edge.
[0146] A scanning electron microscope has a measurement function
which uses a means to display a line pattern image, a means to
create a line profile from the image, a means to detect an edge
from a line profile automatically, and a means to calculate a
measurement from a detected edge to make measurements automatically
according to specified auto measurement parameters. This microscope
has a window which consists of three window areas: a first window
area where plural measurement items are specified; a second window
area where a common measurement method is specified for specified
plural measurement items; and a third window area where a method of
edge detection from a line profile is displayed. Here, for plural
measurement items, parameters as auto measurement conditions are
specified in the window.
[0147] A scanning electron microscope has a measurement function
which uses a means to display a line pattern image, a means to
create a line profile from the image, a means to detect an edge
from a line profile automatically, and a means to calculate a
measurement from a detected edge to make measurements automatically
according to specified auto measurement parameters. In this
microscope, plural measurement items are specified in a window; an
edge is detected from the created line profile; and edge detection
and measurement calculation methods are revised and auto
measurements are made repeatedly and calculated measurement values
are saved in a storage and, according to measurement values, a line
pattern width and/or width roughness are graphically shown in the
window.
* * * * *