U.S. patent application number 11/594757 was filed with the patent office on 2007-05-10 for wafer inspection data handling and defect review tool.
This patent application is currently assigned to HITACHI HIGH-TECHNOLOGIES CORPORATION. Invention is credited to Fumiaki Endo, Tomohiro Funakoshi, Yuko Kariya, Junko Konishi, Noritsugu Takahashi.
Application Number | 20070105245 11/594757 |
Document ID | / |
Family ID | 38004256 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070105245 |
Kind Code |
A1 |
Funakoshi; Tomohiro ; et
al. |
May 10, 2007 |
Wafer inspection data handling and defect review tool
Abstract
A defect detected by a wafer inspection tool is reliably
captured by a defect review tool. A defect review condition in the
defect review tool is varied depending on defect attributes
provided by the wafer inspection tool so as to optimize the review
process. For example, review magnification is varied depending on
the size of the defect, or the frame addition number is varied
depending on the maximum gray level difference.
Inventors: |
Funakoshi; Tomohiro;
(Hitachinaka, JP) ; Konishi; Junko; (Yokohama,
JP) ; Kariya; Yuko; (Hitachinaka, JP) ;
Takahashi; Noritsugu; (Kokubunji, JP) ; Endo;
Fumiaki; (Hitachinaka, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
HITACHI HIGH-TECHNOLOGIES
CORPORATION
|
Family ID: |
38004256 |
Appl. No.: |
11/594757 |
Filed: |
November 9, 2006 |
Current U.S.
Class: |
438/14 |
Current CPC
Class: |
G03F 1/84 20130101; G01N
21/8851 20130101; G01N 2021/8861 20130101; G03F 7/7065 20130101;
G01N 21/9501 20130101 |
Class at
Publication: |
438/014 |
International
Class: |
H01L 21/66 20060101
H01L021/66 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2005 |
JP |
2005-326123 |
Claims
1. A defect data processing method comprising the steps of:
acquiring from a wafer inspection tool a plurality of pieces of
information about the coordinates and attributes of defects
obtained by inspecting a test subject a plurality of times;
identifying information from said plurality of pieces of
information that is associated with the same defect based on the
coordinates of said defects; outputting information concerning the
coordinates and attributes of a defect to be reviewed to a defect
review tool; and acquiring an image of said defect in said defect
review tool using the information about the coordinates and
attributes of said defect.
2. The defect data processing method according to claim 1, wherein
a review condition of said defect review tool is modified depending
on the attributes of said defect that have been outputted.
3. The defect data processing method according to claim 1, wherein
the plurality of inspections are performed with varying inspection
conditions.
4. The defect data processing method according to claim 2, wherein
the attributes of said defect comprise the absolute value of the
gray level of a defect portion obtained from a subtract image
between an image of the location where said defect has been
identified and a reference image thereof.
5. The defect data processing method according to claim 2, wherein
the attributes of said defect comprise the size of said defect.
6. The defect data processing method according to claim 4, wherein
said review condition comprises the frame addition number upon
acquisition of an image of said defect.
7. The defect data processing method according to claim 5, wherein
said review condition comprises magnification upon acquisition of
an image of said defect.
8. A defect review tool comprising: an input unit for accepting the
entry of information about the coordinates and attributes of a
defect; a sample stage that is movable while carrying a test
subject; an image acquiring unit for acquiring an image of said
test subject; a control unit for controlling said sample stage and
said image acquiring unit; and a table in which a relationship
between the attributes of a defect and a review condition is
stored, wherein said control unit moves said sample stage to the
coordinates of a defect that are entered on said input unit,
determines a review condition by referring to said table, and
acquires an image of said defect while setting the thus determined
review condition in said image acquiring unit.
9. The defect review tool according to claim 8, wherein said table
stores a relationship between the absolute value of the gray level
of a defect portion obtained from a subtract image between an image
of the location where a defect has been identified and a reference
image thereof, and the frame addition number upon acquisition of an
image of the defect.
10. The defect review tool according to claim 8, wherein said table
stores a relationship between the size of a defect and
magnification upon acquisition of a defect image.
11. A defect review tool comprising: an input unit for accepting
the entry of information concerning the coordinates and attributes
of a defect from a wafer inspection tool; a sample stage that is
movable while carrying a test subject; an image acquiring unit for
acquiring an image of said test subject; a control unit for
controlling said sample stage and said image acquiring unit; a
table in which a relationship between the attributes of a defect
and a review condition is stored; and a display unit for displaying
information about a defect and accepting an entry regarding the
selection of a defect to be reviewed, wherein said control unit
accepts the entry of a plurality of pieces of information regarding
the coordinates and attributes of a defect from a wafer inspection
tool, which information is obtained by inspecting said test subject
a plurality of times, identifies information from said plurality of
pieces of information that is associated with the same defect based
on the coordinates of said defect, and causes the pieces of
information concerning the same defect to be displayed on said
display unit at once, and wherein said control unit moves the
sample stage to the coordinates of a defect selected on said
display unit, determines a review condition by referring to said
table based on the attributes of said defect, and acquires an image
of said defect while setting the thus determined review condition
in said image acquiring unit.
12. The defect review tool according to claim 11, wherein said
table stores a relationship between the absolute value of the gray
level of a defect portion obtained from a subtract image between an
image of the location where the defect has been identified and a
reference image thereof, and the frame addition number upon
acquisition of a defect image.
13. The defect review tool according to claim 11, wherein said
table stores a relationship between the size of a defect and
magnification upon acquisition of a defect image.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese
application JP 2005-326123 filed on Nov. 10, 2005, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a defect review operation
concerning products or components being manufactured. Particularly,
the invention relates to a system for improving the efficiency of
the process of determining conditions in a tool for detecting
particles or pattern defects on the surface of a semiconductor
wafer, photo mask, magnetic disc, or liquid crystal display
substrate, for example.
[0004] 2. Background Art
[0005] In semiconductor production, particles or pattern defects on
the surface of a wafer during the production process may lead to
defective products. Therefore, it is necessary to quantify such
particles or pattern defects (to be hereafter referred to as
defects) and constantly monitor the manufacturing equipment or
environment for possible problems. It is also necessary to observe
the shape of such a defect so as to determine if it could have a
fatal impact on the final product.
[0006] Conventionally, such observation of shapes has often been
conducted manually by an operator. This has resulted in problems
such as the presence of a bias in the position of a defect in the
observed object depending on the operator, or the lack of
uniformity in the defects to be observed. In order to solve these
problems, technologies are being introduced such as automatic
defect review (ADR) and automatic defect classification (ADC). For
example, a system has been proposed for reducing the burden on the
operator and facilitating an efficient operation when observing or
reviewing a part (such as a pattern formed on a wafer) that has
been inspected by a wafer inspection tool using an SEM (Scanning
Electron Microscopy) defect review tool (see JP Patent Publication
(Kokai) No. 10-135288 A, for example). A means has also been
proposed for arranging the enormous amount of information including
the defect ID (identification number) and coordinates information
provided by the wafer inspection tool and the ADR and ADC
information provided by the defect review tool, thereby
facilitating defect analysis (see JP Patent Publication (Kokai) No.
2001-156141 A, for example). According to this proposal, the
information provided by the wafer inspection tool consists of the
name of product and wafer identification numbers, such as the lot
number and wafer number, the name of the process step under
investigation, and the coordinates information about a detected
defect, for example. [0007] Patent Document 1: JP Patent
Publication (Kokai) No. 10-135288 A [0008] Patent Document 2: JP
Patent Publication (Kokai) No. 2001-156141 A
SUMMARY OF THE INVENTION
[0009] In response to the shrinkage in defect size, the modem
inspection of the state-of-the-art devices may involve assigning a
plurality of inspection conditions and obtaining a single result as
an output. Further, as a result of the increase in the sensitivity
of wafer inspection tools, the influence of noise has also
increased, resulting in the total number of defects that are
detected sometimes exceeding several tens of thousands or more. In
order to eliminate such noise, a technique is employed whereby
defects are classified by the RDC (Real-Time Defect Classification)
function on the wafer inspection tool during inspection. However,
in order to determine the defect detection condition and the RDC
condition for the elimination of noise accurately on the part of
the wafer inspection tool, it is necessary to collate as much
information provided by the wafer inspection tool with as much
information provided by the defect review tool (observing device)
as possible.
[0010] As mentioned above, the operation for detecting defects is
very important for achieving higher yields. On the other hand, as
semiconductor devices shrink in size, wafer inspection tools are
being required to provide better capability and performance for
defect detection. Wafer inspection tools have actually appeared
that are capable of detecting defects with higher sensitivity. Such
enhanced sensitivity has also enabled the detection of very small
defects, resulting in very large numbers of defects that are
detected in which increasingly noise is also detected. This has led
to a very large number of defects whose shapes need to be confirmed
using a defect review tool in a review operation. It has also led
to an increase in the number of cases where no defects can be found
by the review operation, resulting in a decrease in operational
efficiency. In addition, there has been an explosive increase in
the volume of information that needs to be fed back for the purpose
of inspection and RDC condition determination in order to reduce
such noise, making it ever more difficult to determine inspection
conditions accurately.
[0011] Because the conventional operation of collating the
information from the wafer inspection tool with the information
from the defect review tool is often done manually by the operator,
the collating method may vary from one operator to another, or
variations could be introduced in the inspection conditions
finalized in accordance with the result of such collation. It has
also been difficult to set sensitivity to such a level that no
noise that does not need to be detected in actual defect detection
would be detected.
[0012] Even if the inspection conditions can be optimized, defects
that can be detected become smaller and smaller as the wafer
inspection tool achieves higher sensitivity, resulting in a need
for a high-performance defect review tool for identifying such
defects. However, defects having low signal levels upon defect
detection are so small that their review is difficult. Thus, there
are many defects of which identification is difficult and which
cause a decrease in yield. It is becoming increasingly difficult to
review such defects and to distinguish noise from defects
accurately.
[0013] It is therefore an object of the invention to achieve higher
efficiency in defect extraction while reducing the time it takes
for the determination of an inspection condition that is set in a
wafer inspection tool for detecting defects. For this purpose, the
invention allows a defect detected by a wafer inspection tool to be
captured by a defect review tool reliably.
[0014] In accordance with the invention, a review image in which a
defect is reliably captured is easily obtained as information
guiding the determination of such a defect inspection condition
that a DOI (Defect of Interest) can be detected while reducing
noise and improving the average defect capture ratio. For this
purpose, the defect review condition in the defect review tool is
varied depending on the defect attributes provided by the wafer
inspection tool so as to optimize the reviewing process. In this
way, a detected defect can be surely captured in the review image
provided by the defect review tool, and the reliability of defect
inspection condition determination can be improved.
[0015] Specifically, based on a setting such that RDC attributes
can be outputted by the wafer inspection tool, a data handling tool
is prepared that is connected to both the wafer inspection tool and
the defect review tool via a network. The data handling tool
processes the data provided by the wafer inspection tool and the
defect review tool, and causes the defect ID of the result of
inspection, which is performed a plurality of times with the same
or varying inspection condition, a corresponding image data, and
RDC attributes to be displayed and arranged. Data concerning the
same defect is grouped by collating the coordinates, and such
defect information (coordinates and attributes) is outputted to the
defect review tool. Based on the information, the defect review
tool modifies the review condition either manually or
automatically, and acquires an image using such a review condition
under which even a defect that is particularly difficult to observe
can be captured in the image. The thus obtained image is then fed
back to the data handling tool and displayed alongside the
information provided by the wafer inspection tool. In this way, an
optimum wafer inspection condition can be determined in a short
time. The data handling tool may be integrally constructed with the
defect review tool.
[0016] In accordance with the invention, defect attributes, such as
the signal level of a defect, for example, are outputted to the
defect review tool, and the review conditions of the defect review
tool are optimized on the basis of that information. This allows
the capture of an image of a very small defect that has been
heretofore difficult to obtain. The image is then displayed
alongside the information outputted by the wafer inspection tool,
whereby the time it takes for the optimization of the inspection
conditions for DOI detection can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows an overall structure of a defect review assist
system including a data handling tool according to the
invention.
[0018] FIG. 2 shows how information is exchanged between various
units.
[0019] FIG. 3 shows an example of defect information exchanged
between a wafer inspection tool and a defect review tool.
[0020] FIG. 4 shows an example of the screen on which defect
attributes provided by the wafer inspection tool are shown.
[0021] FIG. 5 shows an example of the screen displayed on the data
handling tool.
[0022] FIG. 6 shows an example of the defect information outputted
by the data handling tool to the defect review tool.
[0023] FIG. 7 shows an example of the operation screen of the
defect review tool.
[0024] FIG. 8 shows an example of a frame addition optimizer
window.
[0025] FIG. 9 shows an example of a graph window for the
confirmation of the setting of the frame addition optimizer.
[0026] FIG. 10 shows an example of a magnification optimizer
window.
[0027] FIG. 11 shows an example of a graph window for the
confirmation of the setting of the magnification optimizer.
[0028] FIG. 12 shows a schematic diagram of an SEM defect review
tool.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
[0029] In the following, an embodiment of the invention will be
described with reference to the drawings, where the invention is
applied to a semiconductor production line.
[0030] An example of the defect review assist system of the
invention will be described with reference to FIGS. 1, 2, and 3.
FIG. 1 shows an example of the overall structure of the system.
FIG. 2 shows how the defect attributes and ADR image information
provided by the wafer inspection tool and the ADR/ADC information
provided by the defect review tool are exchanged. FIG. 3 shows an
example of the defect information exchanged between the wafer
inspection tool and the defect review tool. While in the example
shown in FIGS. 1 and 2 the data handling tool is shown
independently provided, alternatively the data handling tool may be
integrally constructed with the wafer inspection tool or the defect
review tool.
[0031] Semiconductor production steps 11 are normally implemented
in a clean room 10 in which a clean environment is maintained. The
clean room 10 houses a wafer inspection tool 1 for detecting a
defect in a product wafer, and a defect review tool 2 for
reviewing, i.e., observing the defect based on the data provided by
the wafer inspection tool 1. The wafer inspection tool 1 and the
defect review tool 2 are connected with a data handling tool 3 for
the exchange of inspection/image data, via a communications line 4.
The product wafers flow through the semiconductor production steps
11 on a lot-unit basis. Wafer inspection is performed after the
completion of the production step that requires wafer inspection,
at the wafer inspection tool 1 to which the wafer is transferred by
the operator or a transferring robot. After the wafers are
processed through the production steps 11 and by the wafer
inspection tool 1 and the defect review tool 2, each chip on the
wafer is finally checked by a probe machine to make sure that there
is no problem in its electric characteristics.
[0032] Defect information 21 obtained by wafer inspection is
managed by the data handling tool 3 with respect to the lot number,
wafer number, inspection step, and date of inspection. FIG. 3 shows
an example of the defect information 21, which consists of the lot
number, wafer ID, die layout, defect ID of a defect that has been
detected during inspection, and its coordinate information, for
example. The defect information 21 may also contain a defect ADR
image, defect attributes information (RDC information), and so
on.
[0033] An example of defect attributes information is shown in FIG.
4. This data is transmitted in the form of text data in a
predetermined format, together with other defect information.
Conventionally, the defect information provided by the wafer
inspection tool has consisted only of defect ID, its coordinates,
and size, for example.
[0034] In order to optimize the inspection sensitivity of this
wafer inspection, it is conventional to repeat inspection a
plurality of times while varying threshold conditions and optical
conditions such as focus offset and inspection magnification. As
the inspection conditions are optimized during such multiple
inspections, more and more DOIs may be detected, making it
increasingly difficult to not only detect but also review them. As
a result, there have been cases where, even though a DOI is
detected, the review provides nuisance, i.e., it concludes that no
defect image has been found, thus introducing an error in the
setting of optimum inspection conditions. In accordance with the
invention, such erroneous judgment is prevented by making the
review conditions in the defect review tool variable using the
defect attributes information provided by the wafer inspection
tool. Thus, the invention provides a means for determining optimum
inspection conditions in the wafer inspection tool based on the
result of a plurality of inspections.
[0035] Hereafter the parameters shown by way of example in FIG. 4
are described. The maximum gray level difference refers to the
absolute value of the gray level of a defect portion in a subtract
image, which is obtained by processing the image of a location
determined to include a defect and a corresponding reference image.
The reference image average gray level refers to an average value
of the gray levels of a pixel portion on the reference image that
has been determined to be the defect portion. The defect image
average gray level refers to an average value of the gray levels of
a pixel portion on the defect image that has been determined to be
the defect portion. The polarity indicates whether the defect
portion is brighter or darker than the reference image; "+"
designates a brighter defect, and "-" designates a darker defect.
The inspection mode refers to the image comparison method used when
a particular defect was found. It includes the die-to-die method,
the cell-to-cell method, and their hybrid method. The defect size,
defect pixel number, and the width/height ratio of the defect show
the size of the detected defect, where the defect size and the
width/height ratio are in units of micrometers and the defect pixel
number is in units of pixels. The defect size ratio is a parameter
representing the width-to-height ratio of the defect size. If the
width and height were the same, the parameter would be 1; if the
width were twice the height, the parameter would be 2, and so on.
The defect pixel differential value represents a differential value
of the pixel portion on the defect image or the reference image
that has been determined to be a defect. The value indicates the
rate of change of gray value in the pixel portion. The value in the
defect image portion is referred to as a defect-pixel differential
value on defect image, while the corresponding value in the
reference image portion is referred to as a defect-pixel
differential value on reference image.
[0036] The wafer of which wafer inspection has been completed is
transferred to the defect review tool 2 for defect review.
Specifically, a predetermined wafer is picked out of the lot and
reviewed. Upon review, defect information 22b and 23b is acquired
from the data handling tool 3, using the information about the
wafer to be reviewed, i.e., the lot number, wafer number, and
inspection step, as key information. The defect information
includes not only the defect ID and coordinates data but also
defect attributes obtained upon inspection. Conventionally, the
defect information 22b and 23b has not included the defect
attributes provided by the wafer inspection tool.
[0037] Because the defect information 21 provided by the wafer
inspection tool 1 consists of a huge volume of data, the defect
information 22b or 23b, which is extracted by the data handling
tool 3 using multiple filter functions, is sent to the optical
defect review tool 24 or an SEM defect review tool 25 via the
communications line 4. The defect information 22b and 23b is
generally in the same format as the defect information 21.
[0038] Based on the extracted defect information 22b or 23b, the
optical defect review tool 24 or SEM defect review tool 25 acquires
an image of the defect detected portion. Defect classification is
then carried out based on the image by the ADC function installed
on each defect review tool. Specifically, the wafer of which wafer
inspection has been completed is retained on the sample stage of
the optical defect review tool 24 or SEM defect review tool 25. The
stage is moved to the coordinates position of the defect contained
in the defect information 22b or 23b, where a defect image is
acquired. The defect is then classified according to the features
of the thus acquired defect image. The resultant information is
sent to the data handling tool 3 as ADR/ADC information 22a or 23a
via the communications line 4.
[0039] With reference to FIG. 5, it is described in the following
how the inspection defect attributes and image data provided by the
wafer inspection tool and the ADR/ADC information provided by the
defect review tool are displayed and processed by the data handling
tool according to the invention.
[0040] The large volume of inspection/image data provided by the
wafer inspection tool, and also the large volume of ADR/ADC
information provided by the defect review tool are displayed side
by side. For this purpose, a screen 30 shown in FIG. 5 is prepared
on the data handling tool.
[0041] The screen 30 includes a table 31 showing the defect ID 34
and ADR image 35 provided by the wafer inspection tool, the defect
attributes 38, and the ADR image 36 and ADC classification
information 37 provided by the defect review tool, each under a
heading 39. Any location of the table can be designated using
scroll bars 47. The screen 30 also includes buttons 48 for directly
selecting the defect information to be displayed. The headings 39
show the defect ID, image by wafer inspection tool, image by defect
review tool, review category, and the maximum gray level
difference, which are the parameters shown in FIG. 4 indicating
defect attributes. Concerning those defects that are determined to
be identical and have the same coordinates based on a collation of
the coordinates of the defects that have been detected in a
plurality of inspections with the same or varying inspection
conditions, the table 31 shows the information about such defects
on the same line. The table shown concerns an example in which
inspection was conducted four times with the same inspection
conditions or with varying inspection conditions in terms of focus
offset, inspection threshold, and inspection magnification, for
example, so that a maximum of four kinds of information are shown
for a single defect. For example, with regard to the defect shown
at the top in FIG. 5, four images from the wafer inspection tool
are displayed. As to the ADR image 35 from the wafer inspection
tool and the ADR image 36 from the defect review tool, the
corresponding columns are empty if there is no such images for a
particular defect ID. A button 49 is provided for outputting the
result of coordinates collation and the defect attributes 38 in the
format of FIG. 3. As a means for displaying a desired location, the
screen includes the scroll bars 47.
[0042] By clicking any of the headings 39, the information
contained in the table can be sorted in the ascending or descending
order based on the information about the heading clicked. For
example, by clicking AVG GL Def, 1, the entire information is
sorted in the ascending or descending order of the AVG GL Def. Such
sorting allows for an easy understanding of what kind of defect has
what attributes. Furthermore, by referring to the defect pictured
in the image provided by the wafer inspection tool or the defect
review tool, it can be easily confirmed what appearance the defect
of real concern should have, and whether or not it is a nuisance
defect. In the example of table 31, information about each defect
ID is displayed side by side horizontally; it goes without saying,
however, that the same information may be arranged vertically.
[0043] With reference now to FIGS. 2, 3, and 6-8, the function of
the review data creating button 49 included in the screen 30 of
FIG. 5, and the defect review method of the invention, which is
implemented by the defect review tool using that function are
described. It should be obvious that the following descriptions do
not limit the invention.
[0044] First, on the screen 30 shown in FIG. 5, the results of a
plurality of inspections that need to be subjected to data
processing are displayed. As the review data creating button 49 is
depressed, review data is created (22b and 23b of FIG. 2) as shown
in FIG. 6. Such review data includes the defect ID, defect size,
and attributes that have been displayed on the screen 30 of FIG. 5
when depressing the review data creating button 49. This review
data is sent to the optical defect review tool 24 or the SEM defect
review tool 25 of FIG. 2 via the network 4 of FIG. 2.
[0045] FIG. 7 shows an operation screen 60 of the optical defect
review tool 24 or the SEM defect review tool 25. This screen shows
a defect map 61 showing the distribution of defects as dots on a
wafer map, based on the information 22b and 23b acquired from the
wafer inspection tool. The screen also shows a defect list 70
showing IDs 62 of the defects shown on the defect map, the X
coordinate 63 of the die, Y coordinate 64 of the die, intra-die X
coordinate 65, intra-die Y coordinate 66, X-direction size 67 of
the defect, Y-direction size 68 of the defect, and the defect
maximum gray level difference 69, for example. In addition, the
screen shows a defect review image 71, a defect review condition
table 72, a frame addition optimizer button 73, and a magnification
optimizer button 74. By clicking a desired point on the map 61
indicating a defect, or any given defect information in the list
70, any defect that is to be reviewed can be shown in the defect
review image 71.
[0046] In conventional defect review tools, the information
provided by the wafer inspection tool has consisted only of the
defect ID, coordinates, and size. As a result, regardless of the
features of a given defect, a defect image has been acquired merely
with the same electron beam acceleration voltage, probe current,
and frame addition number under the same review conditions in, for
example, the SEM defect review tool.
[0047] In accordance with the invention, using a window 80 shown in
FIG. 8 that appears upon pressing the frame addition optimizer
button 73 on the operation screen 60, or by using a window 100
shown in FIG. 10 that appears upon pressing of the magnification
optimizer button 74, the frame addition number or the magnification
of the defect to be reviewed can be varied depending on the maximum
gray level difference or the size of the subtract image upon
detection by the wafer inspection tool. In this way, the invention
aims to make it possible to reliably capture an image of even those
defects having a small maximum gray level difference, i.e., defects
that have been difficult to detect using the wafer inspection tool
and of which review by the defect review tool has also been
difficult.
[0048] The window 80 of FIG. 8 that appears upon pressing of the
button 73 shows a table 81 for the setting of a frame addition
number and for the setting of a range of maximum gray level
difference (Max GL_Diff) for the application of that value, and a
graph button 82 for the confirmation of those settings on a graph.
Upon clicking of the button 82, a graph 90 is displayed in which
the gray level difference is shown on the horizontal axis and the
number of image addition frames is shown on the vertical axis. Use
of these tables makes it possible to make settings such as shown in
FIG. 8, for example, where the frame addition number of 128 is
allocated to the gray level difference of 100 or less, 64 to the
difference of 100 or more and 180 or less, and 32 to 180 or more.
In this way, it becomes possible to obtain a defect image having
lower noise levels and better image quality by increasing the frame
addition for those defects with small signal levels. Thus, the
number of cases where determination of noise is difficult can be
reduced. Also, the number of cases where, after a defect image is
acquired by the defect review tool, the wafer has to be transferred
to the defect review tool for a repeated review due to failure to
make a determination can be dramatically reduced. While the values
in the table 81 displayed in the window 80 of FIG. 8 are default
values determined through experience or otherwise, the user may
alternatively modify them as needed.
[0049] The window 100 of FIG. 10 that appears upon pressing of the
button 74 shows a table 101 for the setting of magnification and a
range of defect size in which the relevant value should be applied,
and a graph button 102 for the confirmation of those settings on a
graph. Upon clicking of the button 102, a graph 110 is displayed in
which the defect size is shown on the horizontal axis and the
magnification on the vertical axis. Using those settings, it
becomes possible to obtain an image with magnification of
.times.50,000 for defect size of 4 .mu.m or less, .times.25,000 for
defect size of 4 .mu.m or more and 6 .mu.m or less, and
.times.10,000 for greater sizes, as shown in FIG. 10, for example.
Because lower magnification can be used for larger defects, it also
becomes possible to reliably capture an overall image of a large
defect. While the values in the table 101 displayed in the window
100 of FIG. 10 are default values that are determined in advance
through experience or otherwise, the user may alternatively modify
those values as needed.
[0050] While the foregoing examples of graphs displayed in the
windows 90 and 110 were line graphs 91 and 111, other forms of
graph may be employed, such as a bar graph, a radar chart, and so
on.
[0051] Thus, by modifying the review conditions such as the frame
addition number and magnification depending on the attributes of
the defect to be reviewed, an image of a defect can be reliably
obtained in the defect review tool.
[0052] FIG. 12 shows a schematic diagram of the SEM defect review
tool according to the invention. The defect review tool includes a
sample stage 1202 for retaining and moving a test subject 1201, an
electron beam column 1203 for scanning the test subject by
irradiating it with an electron beam, and a secondary electron
detector 1204 for detecting secondary electrons emitted by the test
subject upon electron beam irradiation. The sample stage 1201 is
driven to a desired stage coordinates position by a stage drive
unit 1206, which is controlled by a control unit 1205. An electron
beam image of the test subject, which is obtained by capturing a
signal from the secondary electron detector 1204 in synchronism
with the electron bean scan, is displayed on the display unit 1207.
The defect information from the wafer inspection tool and the data
handling tool is fed to the tool via a data input unit 1208. The
display unit 1207 displays not only the defect image of the test
subject, but also the screen 30 shown in FIG. 5, the operation
screen shown in FIG. 7, and the windows shown in FIGS. 8-11 as
needed. The scrolling operation on the screen shown in FIG. 5, and
the operation of the defect selection button 48 for the selection
of a defect to be displayed or the like, are carried out using an
input device 1209, such as a keyboard or a mouse. The memory 1210
stores a table defining the relationship between a range of maximum
gray level difference (Max GL_Diff) and the frame addition number,
and a table defining the relationship between a defect size range
and magnification. The control unit 1205 processes data that is
input or performs image processing as well as controls the stage
drive unit 1206, the electron beam column 1203, and the display
unit 1207. Alternatively, the control unit 1205 may also provide
the function of the data handling tool shown in FIGS. 1 and 2.
[0053] While the foregoing description has been made with reference
to an SEM defect review tool, the structure of the SEM defect
review tool shown in FIG. 12 will basically remain the same in the
case of an optical defect review tool, with the only difference
being that the electron beam column and the detector would be
replaced with an optical microscope column and an imaging device,
respectively.
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