WO2012056638A1 - パターン測定方法,パターン測定装置及びそれを用いたプログラム - Google Patents
パターン測定方法,パターン測定装置及びそれを用いたプログラム Download PDFInfo
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- WO2012056638A1 WO2012056638A1 PCT/JP2011/005747 JP2011005747W WO2012056638A1 WO 2012056638 A1 WO2012056638 A1 WO 2012056638A1 JP 2011005747 W JP2011005747 W JP 2011005747W WO 2012056638 A1 WO2012056638 A1 WO 2012056638A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70605—Workpiece metrology
- G03F7/70616—Monitoring the printed patterns
- G03F7/70625—Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
- G01B15/04—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring contours or curvatures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
- H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
- G06F2218/08—Feature extraction
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24571—Measurements of non-electric or non-magnetic variables
- H01J2237/24578—Spatial variables, e.g. position, distance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24592—Inspection and quality control of devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/26—Electron or ion microscopes
- H01J2237/28—Scanning microscopes
- H01J2237/2813—Scanning microscopes characterised by the application
- H01J2237/2817—Pattern inspection
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Definitions
- the present invention relates to a pattern measuring apparatus, a pattern measuring method, and a pattern measuring program suitable for a semiconductor inspection apparatus.
- pattern matching for performing alignment with a pattern on the recorded data
- pattern measurement a function for performing dimension measurement of a target pattern
- Patent Document 1 is an invention relating to a method for measuring dimensions with high accuracy with respect to a shape error between a pattern on a sample image called a process variation in a pattern manufacturing process and a pattern on a pre-registered sample data. If the pattern measurement result is invalid, it is disclosed that the size or position of the cursor is corrected.
- Patent Document 2 calculates a shape separation between a pattern in an SEM image and a pattern in design data when a target region including an edge of a pattern is set and imaged and image processed to measure a pattern, and based on the calculated information. It is described that an inspection area is designated by a measurement cursor and the position and shape are managed as a measurement recipe. It is disclosed that when the cursor position deviates from the edge, the cursor position is shifted in accordance with the edge position to increase the distance between the cursors.
- Japanese Patent Laid-Open No. 2004-260688 sets a mask area that is not subject to pattern matching in sample image data, and the pattern data registered in advance spans the target area and the mask area in the image data at the stage of scanning.
- a method for setting processing conditions based on the degree of overlap between the target area and at least one of the mask areas is disclosed.
- Patent Document 1 and Patent Document 2 when correcting the size and position of the measurement cursor as a method for dealing with process variations that occur in the manufacturing process of the sample, the measurement object is not around the pattern that is the measurement object. No consideration was given to the case where there was no other pattern or noise such as dust. For this reason, in such a case, the problem of pattern measurement at an incorrect position of the corrected measurement cursor that may be caused by noise cannot be solved. Further, in Patent Document 1, since the measurement cursor is adjusted after determining the validity of the pattern measurement result, the pattern measurement failure due to process variation cannot be prevented in advance. .
- Patent Document 3 does not describe the relevance between setting a mask in an area that is not subject to pattern matching processing and the problem of pattern measurement at an incorrect position using the above-described corrected measurement cursor.
- An object of the present invention is to provide means for accurately measuring a pattern even when another pattern or dust that is not a measurement target exists around the measurement target pattern.
- a measurement region is set in image data obtained by imaging a sample, pattern matching is performed between the image data and pre-stored pattern data, and the image data aligned by the matching is included in the image data.
- a pattern measuring apparatus, method, and program for setting a predetermined area as an area to be excluded from a measurement target, and performing pattern measurement by excluding a signal included in an area where the measurement area and the predetermined area overlap each other I will provide a.
- the predetermined region set as the non-measurement target region overlaps the measurement region. Since the region is not affected by these, pattern measurement can be performed with high accuracy even when process variation occurs between image data obtained by photographing a sample and pattern data stored in advance. Also, the work can be simplified when adjusting the size and position of the measurement cursor.
- the block diagram which shows the pattern measuring apparatus of this invention The block diagram of the scanning electron microscope system carrying the pattern measuring apparatus of this invention.
- region in a circular pattern The figure which shows the example of various conditions setting at the time of the imaging condition input in this invention, and a processing flow.
- FIG. 1 is a block diagram showing a basic configuration of a pattern measuring apparatus 100 of the present invention.
- the pattern measuring apparatus of the present invention includes image data 105 (hereinafter referred to as SEM image) obtained by photographing a sample with an imaging device such as a scanning electron microscope (hereinafter referred to as SEM), and a sample pattern stored in advance.
- SEM image image data obtained by photographing a sample with an imaging device such as a scanning electron microscope (hereinafter referred to as SEM), and a sample pattern stored in advance.
- the data 106 is input, the measurement area is set for the image data 105 by the measurement area setting unit 101, and the pattern matching unit 103 performs pattern matching between the image data 105 and the pattern data 106.
- the non-matching target area may be set by providing the non-matching target area setting unit 102 as necessary.
- the non-measurement target area setting unit 108 sets a predetermined area used for alignment in the image data 105 as an area to be excluded from the measurement area.
- a pattern measurement unit that extracts a signal included in the measurement region and measures a pattern formed on the sample is configured such that the pattern measurement unit 104 includes the measurement region and the predetermined region in the image data 109 after setting. Pattern measurement is performed by excluding signals included in the overlapping region, and a pattern measurement result 110 is output.
- FIG. 2 is a schematic diagram of a configuration in which the pattern measuring apparatus 100 of the present invention is applied to the image processing apparatus 202 of the scanning electron microscope system 200.
- the scanning electron microscope system 200 includes an SEM 201 that captures an image of a semiconductor device, an image processing apparatus 202 that performs processing for reducing specific noise included in the image data 105, and pattern measurement processing of the present invention, and an SEM 201.
- the display device 203 is configured to display display data 210 for controlling the device 100.
- the control computer 204 controls the entire scanning electron microscope system 200 such as the imaging conditions of the SEM 201, the inspection position of the semiconductor device, and the setting of the image processing function of the image processing apparatus 202, and is represented by a personal computer or the like.
- a memory for storing pre-stored pattern data 106, sample image data 105, a scanning electron microscope (hereinafter referred to as SEM) 201, a program for controlling the image processing apparatus 202, and the like.
- SEM scanning electron microscope
- a CPU that executes the control program, a signal input IF for inputting image processing results 207 such as image data 105 and pattern matching values from the image processing apparatus 202, SEM control data 208 for controlling the SEM 201, and an image processing apparatus 202.
- the input means 205 is for the operator to instruct the control computer 204 of the imaging conditions of the SEM 201, the inspection position of the sample, the position of the design data corresponding to the inspection position, the setting of the image processing function, and the like.
- a mouse or a keyboard connected to the control computer 204.
- the display device 203 displays the image data 105 captured by the SEM 201, the pattern matching value, the information on the inspection position on the semiconductor device, the display data 210 such as the SEM 201, the image processing device 202, the pattern data 106, and the like.
- An image display device such as a CRT (Cathode Ray Tube) or a liquid crystal display connected to the control computer 204.
- the function of the SEM 201 is to irradiate the sample with an electron beam while performing raster scanning on the sample surface, detect and amplify secondary electrons and reflected electrons generated from the sample surface, and convert them into luminance information. Is something to get.
- the image processing apparatus 202 includes a memory for storing image data 105, pattern matching and pattern measurement results and image processing results, a CPU for controlling an image processing program and overall image processing in accordance with instructions from the control computer 204, and high-speed image processing. It includes hardware for execution, image data 105 used for pattern matching and pattern measurement, and signal output IF for transferring image processing data 209 of the image processing function to the control computer 204.
- the pattern measuring apparatus 100 of the present invention can be realized by combining the hardware and software processing using a CPU.
- FIG. 3 shows an example of a general measurement region 302 and measurement position setting method for obtaining the measurement distance 303 for the measurement target pattern 301 on the image data 300.
- a region including the edge position 304 to be measured is set with a measurement cursor such as a rectangle, circle, or short shape.
- a measurement region 302 including each edge is designated by a rectangular length measurement cursor. It is an example.
- FIG. 3 (2) shows an example in which, when measuring the measurement distance 303 of the left and right edge positions 304 of the measurement target pattern 301, it is designated by one rectangular length measuring cursor including both the left and right edges.
- FIG. 3 (6) is an example in which when measuring the measurement distance 303 of the measurement area 302 between two circular patterns, the measurement area 302 including each edge is designated by a sector-shaped length measurement cursor.
- FIG. 3 (7) shows the pattern edge position using the signal information 305 acquired from the measurement target pattern 301 when measuring the measurement distance 303 of the left and right edge positions 304 of the measurement target pattern 301 that is the measurement target.
- the measurement region 302 is designated by one rectangular length measuring cursor including the two signal information peaks 306. is there.
- Examples of process fluctuations 4 and 5 show an example of occurrence of process fluctuation between data such as design data regarding a sample such as a semiconductor device and an SEM image obtained by photographing the sample. In this case, a pattern to be measured cannot be detected, or an erroneous position is detected, thereby causing erroneous pattern measurement.
- FIG. 4A shows an example in which the measurement region 402 is correctly set when the measurement target pattern 401 to be measured on the image data 400 is thick and shifted to the right side.
- the correct measurement distance 403 it is necessary to set an area including the left and right edge positions 404 to be measured with respect to the measurement area 402 with a length measurement cursor as shown in the figure.
- FIG. 4 (2) shows an example in which only one of the left and right edge positions is set as the measurement region 402 with respect to the measurement target pattern 401 of (1). In this case, since the edge position 405 of the portion not included in the measurement cursor is not measured, an erroneous measurement for measuring the measurement distance 406 occurs.
- FIG. 4 (3) shows an example in which the measurement region 402 is set with respect to the measurement target pattern 401 of (1) with reference to the center of gravity of the pattern. In this case, both the left and right edge positions 404 are not included in the measurement region 402, and an erroneous measurement for measuring an incorrect measurement distance 406 occurs.
- FIG. 5A shows an example in which the measurement region 502 is correctly set with respect to the central measurement target pattern 501 to be measured on the image data 500.
- the correct measurement distance 503 it is necessary to set an area including the left and right edge positions 504 to be measured with respect to the measurement area 502 with the measurement cursor as shown in the figure.
- FIG. 5B shows an example in which only one of the edge positions 504 is set as the measurement region 502 when the shape of the measurement target pattern 501 in (1) is large and is shifted to the right side. .
- an erroneous measurement for measuring the measurement distance 506 occurs.
- the pattern to be measured in this step or the pattern that is not the target to be measured around it is allowed to have some dimensional variation or contact with neighboring patterns when it is removed in the subsequent steps. In that case, it is expected that more significant process variations will occur.
- Non-measurement area setting A method of setting a region including a pattern 602 that is not used at the time of measurement among the plurality of measurement target patterns 601 and 602 on the image data 600 as a non-measurement target region 606 will be described with reference to FIG.
- the non-measurement target area 606 can be set from various types of data such as pattern data 106 stored in advance, that is, design data, simulation data, reference images, signal information acquired from measurement patterns, and the like. is there.
- the measurement area 603 is set with the measurement cursor for the measurement target pattern 601 used for measurement without setting the non-measurement target area 606 among the plurality of patterns on the image data 600.
- An example of measuring the distance 605 between the left and right edge positions 604 is shown.
- FIG. 6B is an example in which an area including a pattern 602 that is not used for measurement among a plurality of patterns on the data 600 is set as a non-measurement target area 606. It is assumed that the pattern 602 included in the set non-measurement target region 606 is not used for measurement.
- the measurement region 603 is set so that the left and right edge positions 604 of the pattern used for measurement are included. At this time, an area where the measurement target pattern 601 used for measurement is expected to change due to process variation is predicted, and the left and right edge positions 604 used for measurement are included in the measurement region 603 even when process variation occurs. Set widely. As a countermeasure against the process variation shown in FIG. 4, this measure may cause erroneous measurement due to the influence of noise such as patterns and dust that are not used for surrounding measurement even when the size and position of the measurement cursor are corrected. This makes it possible to measure the pattern stably.
- FIG. 7 illustrates a method for setting, as a non-measurement target region 706, a region including a pattern 702 that is not used during measurement among a plurality of circular patterns on the image data 700.
- the measurement region 703 is set with the measurement cursor for the measurement target pattern 701 used for measurement without setting the non-measurement target region 706 among the plurality of circular patterns on the data 700.
- An example of measuring the distance 705 between the left and right edge positions 704 is shown.
- the measurement area is set wide as a countermeasure for the case where the process fluctuation occurs, there is a possibility that an erroneous measurement occurs due to the inclusion of the pattern 702 that is not used for the measurement existing around.
- FIG. 7B is an example in which an area including a pattern 702 that is not used for measurement among a plurality of patterns on the image data 700 is set as a non-measurement target area 706. It is assumed that the pattern 702 included in the set non-measurement target region 706 is not used for measurement.
- the measurement region 703 is set so that the left and right edge positions 704 of the pattern used for measurement are included. At this time, a region where the measurement target pattern 701 used for measurement is expected to change due to process variation is predicted, and the left and right edge positions 704 used for measurement are included in the measurement region 703 even when process variation occurs. Set widely.
- This operation may be performed at the time of setting measurement conditions at the time of pattern registration / detection, or may be performed at the stage of actual pattern measurement.
- this correspondence makes it possible to perform pattern measurement stably without causing erroneous measurement due to the influence of noise such as patterns not used in surrounding measurement and dust.
- FIG. 8 shows a setting example and processing flow of various conditions at the time of pattern registration / detection in the present invention.
- This process is an example in which a non-measurement target region is set as information to be input from a pattern on data on a sample such as a semiconductor device such as design data in advance before performing actual pattern matching or pattern measurement. That is, in the pattern measurement apparatus shown in FIG. 1, this is a processing example in which the setting of the non-measurement target area performed after pattern matching is performed in advance when setting the conditions.
- various conditions related to pattern matching and pattern measurement are set.
- processing such as setting of image conditions, focusing, and alignment is repeated from low magnification to high magnification, and adjustment is performed so that the pattern to be measured falls within the field of view.
- it is easier to set measurement conditions if there is information such as the location of large and small process variations around the position to be measured, or how much the pattern changes due to process variations. .
- the surrounding pattern 802 it is assumed that there is almost no variation in the size and shape of the pattern 802, and there is little process variation.
- the central measurement target pattern 801 having a large process variation is a measurement target
- measurement is performed by masking a peripheral pattern 802 having a small process variation and a small measurement variation. Not applicable.
- a measurement region and measurement conditions in this example, the line width is measured
- the measurement area is set to be large so that the pattern falls within the measurement area even if process variation occurs.
- the size of the measurement area may be set larger so that the non-measurement target area is superimposed on the measurement area as long as the non-measurement target area is appropriately set.
- a pattern used for pattern matching is set.
- the central measurement target with a large process variation is used by using the entire screen so as not to be affected by the process variation of the central measurement target pattern 801 not used for pattern matching. Only the region including the pattern 801 may be set as the non-measurement target region 803.
- Measure information, measurement conditions, information used for measurement, mask information, etc. are all stored in association with each other.
- FIG. 9 shows an example of a processing flow in the case of actually performing pattern matching and pattern measurement based on the conditions registered in the procedures described above with reference to FIGS. As processing, the following sequence is assumed. (1) Positioning under low magnification conditions (2) Moving to measurement position under high magnification conditions (3) Brightness / focus adjustment (4) Pattern matching under high magnification conditions (5) Non-measurement target area processing (6) Pattern Measurement
- pattern matching and pattern measurement are performed on a sample such as a semiconductor device to be measured based on the above-described condition setting at the time of pattern detection / registration.
- a sample such as a semiconductor device to be measured based on the above-described condition setting at the time of pattern detection / registration.
- alignment is performed at a magnification lower than the measurement magnification.
- the measurement target pattern 901 at the center of the screen with a large process variation is the measurement target.
- a pattern 902 having a small process variation existing in the measurement region at a magnification of about 1 ⁇ 2 at the time of measurement is set as an alignment target.
- (2) move to the measurement position under the high magnification condition the region surrounded by the dotted line 903 in FIG. 9 (1)
- (4) pattern matching under high magnification conditions is performed.
- alignment is performed using a region including a peripheral pattern 902 surrounded by a dotted line and having a small process variation.
- an area including the central measurement target pattern 901 having a large process variation may be set as the non-matching target area 905 as necessary.
- processing is performed using the non-measurement target region 906 registered in advance by the above-described method.
- the peripheral pattern 902 used for pattern matching corresponds to the non-measurement target region 906 here.
- the center line pattern is set by setting the measurement region 909 wider as shown in FIG. 9 (5). For the distance 908 between the left and right edge positions 907, stable measurement corresponding to process variation can be performed.
- pattern matching and pattern measurement with the same magnification and the same field of view, and it is possible to use information with a wide field of view by performing pattern matching at a lower magnification. It is recommended that pattern matching be performed at a low magnification when the position accuracy of the apparatus is poor or when measurement is performed at a higher magnification.
- alignment is performed at a low magnification before measurement, and alignment is performed again at a magnification that is close to the pattern measurement based on the information, so that the inspection pattern enters the field of view at the measurement / inspection magnification.
- a setting may be performed.
- a region including the left and right edge positions 1004 of the measurement target pattern 1001 predicted to have a large process variation on the image data 1000 is defined as a measurement region 1003.
- a place where a shape change due to a process change is generated is distinguished from a place where it does not occur from the foresight information. For example, it can be predicted from the process formation state or existing inspection results.
- the measurement target pattern 1001 located in the center of the screen is a measurement target, but there is a high possibility of process variation, and the line pattern 1002 around the screen is not a measurement target, but the possibility of process variation occurs.
- the line pattern 1002 around the screen is not a measurement target, but the possibility of process variation occurs.
- there is foresight information that is low.
- a region having a high process variation occurrence probability as distinguished by a double line and a region having a low process variation occurrence probability as enclosed by a dotted line are distinguished.
- pattern matching is performed using only this information.
- pattern matching may be performed by setting the measurement target pattern 1001 as the non-matching target area 1009 and executing the entire screen as a template, or by setting a part of the screen as a template and setting the entire screen as a non-matching target area ( It is also possible to execute after executing (not shown).
- the setting of the non-matching target area is not necessarily a process that must be performed, it is desirable that the non-matching target area is executed as necessary in consideration of the influence of process variations.
- the measurement target pattern 1001 having a large process variation is the measurement target, when pattern measurement is performed after the pattern matching is completed, as shown in FIG.
- a surrounding pattern 1002 having a small process variation is set as the non-measurement target region 1010, and pattern measurement is performed in the measurement region 1008.
- FIG. 10 (5) it is possible to set all parts other than the measurement cursor as the non-measurement target area 1010.
- the non-matching target region, the non-measurement target region, and the measurement region are set for a plurality of patterns on the data according to the size of the process variation, and only the region including the pattern with a small process variation. It is also possible to perform pattern matching using, and perform pattern measurement using only a region including a pattern having a large process variation. If a pattern with small process variation is to be measured, each of pattern matching and pattern measurement may be performed using only an area including a pattern with small process variation.
- FIG. 11 shows an example of pattern matching and pattern measurement using a plurality of templates for a plurality of patterns on the image data 1100. A specific method will be described below.
- Fig. 11 (1) shows a setting example of a pattern to be measured and a measurement region.
- the measurement cursors 1106 and 1107 including the pattern measurement reference position are set as (rml) and (rmr), respectively.
- the distance 1108 (rdm) between rml and rmr is stored as information at the time of registration.
- a non-measurement target area that is not used for pattern measurement may be set. This procedure does not have to be set, but it is desirable to execute it as necessary in consideration of the influence of process variations.
- a measurement target pattern 1101 whose size has changed due to process variation is set as a measurement target.
- FIG. 11 (6) more detailed pattern matching is performed on the pattern whose size has changed using the measurement cursors 1110 (trml) and 1111 (trml) as templates. Since the approximate position is predicted by the condition setting at the time of pattern registration in FIGS. 11 (1) to 11 (3) in the previous stage, at this stage, only the measurement cursor 1110 (trml) and the measurement cursor 1111 (trml) and the vicinity Detection may be performed.
- Pattern matching is executed in the process of FIG. 11 (6), and the pattern measurement is performed with the detected new measurement cursor positions as 1114 (rml ′) and 1115 (rmr ′) and the distance as 1118 (rdm ′).
- the index value of the process variation between the pattern data stored in advance and the image data of the sample is shown by the following formula.
- This index value can be expressed as follows when the measurement target is two-dimensional.
- ⁇ It is also possible to correct the position and size of the measurement cursors rmrx 'and rmry' based on this index value.
- FIG. 12 shows an example of a procedure for automatically setting a non-matching target area corresponding to various process variations when an actual image is used.
- a reference image is used as data relating to the sample is shown, but this method can also be applied to various types of data such as design data, simulation images, and signal information corresponding to measurement pattern information.
- image sets In order to set the non-matching target region, a plurality of sample image sets (hereinafter referred to as image sets) that are considered suitable for application to various process variations are prepared. Although it is desirable that a plurality of image sets covering the range of the assumed process variation can be prepared because the shape has actually changed, it is also possible to set it by taking into account the user's foresight information.
- This process can be performed manually when the number of image sets is small, but it is recommended to automate considering the case where the number of image sets increases.
- Fig. 12 (1) shows an example of the assumed process variation with reference image.
- the line width is thick (FIG. 12 (2-1)), thin (FIG. 12 (2-2)), or when the white band is thick with respect to the measurement target pattern 1201 of the reference image (FIG. 12 (2-3)).
- FIG. 12 (2-4) it is assumed that there is another pattern such as dust around the measurement pattern.
- FIG. Pattern matching may be performed without setting the non-matching target region 1208.
- the matching is performed by receiving a lot of influence of the portion. Therefore, it is more preferable to set the non-matching target area 1208. Since this processing requires manual processing, it is necessary to uniformly extract images with various process variations in the image set.
- pattern matching is performed in a region including a peripheral pattern 1202 with small process variation, and the positional deviation amount of each image in the image set can be calculated.
- the appearance probability of the pattern at each position in the image is calculated.
- noise removal processing and binarization processing are executed on the image sets shown in FIGS. 13 (1-1) to (1-4). Extract the pattern.
- known Otsu binarization processing or the like may be performed, or noise removal processing using a Gaussian filter or the like may be applied in consideration of image noise.
- Each binarized image is subjected to an addition process in consideration of the above-described positional deviation amount.
- a pattern appearance probability map is created as shown in FIG. First, regarding the image set, the amount of positional deviation between sample images is calculated. An existing alignment method may be used or may be performed visually.
- a binarized average image is created based on the binarized image created by the above-described method and information on the amount of positional deviation between the calculated images. Let this image be a pattern appearance probability map. In FIG. 13 (3), it is assumed that the measurement target pattern 1301 has a low pattern appearance probability, and the surrounding pattern 1302 has a high pattern appearance probability.
- the non-matching target region 1304 is set from the pattern appearance probability map created by the above method, manually or automatically, as shown in FIG.
- FIG. 14 is an example of the processing flow described above with reference to FIG.
- a threshold is set for the appearance probability of the pattern.
- the measurement area can be specified by setting a portion smaller than the threshold as a non-measurement target area. it can.
- you want to stably detect patterns with small process fluctuations you can set the area where the process fluctuations are larger than the threshold as the non-matching target area (or match areas containing patterns with small process fluctuations). Specified in the area).
- the threshold value may be set from the outside, or may be automatically set by using Otsu's binarization process.
- Otsu's binarization process As a simple method, there is a method of creating a histogram of a binarized average image and setting a threshold value from the information.
- the above method has distinguished the high and low pattern appearance probability.
- the magnitude of the process variation may be distinguished from the user's foresight information without using the above-described method.
- Fig. 16 (1) shows the pattern to be measured and the measurement area.
- the measurement target pattern 1601 and the upper right pattern 1602 are set as measurement targets, and a region including the right edge 1604 of the center line pattern and the left edge 1605 of the upper right line pattern is defined as a measurement region 1606.
- the portions used for pattern measurement are set as measurement cursors 1607 (rml) and 1608 (rmr), respectively, and a measurement distance 1609 (rdm) between them is measured.
- a pattern appearance probability map of this example is shown in FIG. In this case, the measurement target pattern 1601 at the center of the screen has a high process variation occurrence probability and a low pattern appearance probability.
- FIG. 16 (3) shows an example of an actual measurement image.
- the measurement target pattern 1601 near the center of the screen is shifted to the left of the screen as the positional relationship with the surroundings.
- the line width is assumed to be almost the same.
- the information of the set measurement area is stored as templates 1610 (trml) and 1611 (trml) from the information of the reference image.
- templates 1610 (trml) and 1611 (trml) from the information of the reference image.
- an area not used for pattern measurement may be set as a non-measurement target area by the above-described method.
- pattern matching is performed.
- This may be a normal method, but it is desirable to set a non-matching target region as shown in FIG. 16 (7) and perform pattern detection using peripheral patterns 1602 and 1603 with small process variations as templates.
- the central measurement target pattern 1601 having a large process variation may be used as a template, but both the central measurement target pattern 1601 and the pattern 1602 at the upper right of the screen, which are finally measured, need to appear in the screen. Therefore, the former method should be used in consideration of the effect of process variations.
- the measurement cursor 1607 (rml) exists in a region including the central measurement target pattern 1601 having a large process variation, and the measurement cursor 1608 (rmr) exists in a region including a peripheral pattern 1602 having a small process variation. Therefore, the measurement cursor 1608 (rmr) can be easily detected.
- the measurement cursor 1607 (rml) is present on the left side of the measurement cursor 1608 (rmr), and within the region set as the non-matching target region 1612 when performing pattern matching as shown in FIG. Since it is known to exist in the vicinity, detection processing may be performed by matching using normal correlation or the like.
- the information on the distance of rml / rmr here can be calculated as the process variation index value by the above formulas (1) to (4) and used as an index value for process management.
- FIG. 17 shows various setting examples of the non-measurement target region.
- the data 1700 includes a plurality of patterns.
- FIG. 17 (2-1) only the upper two of the surrounding patterns 1702 are to be measured, and a plurality of non-measurement target areas are set for the line pattern of the other stocks and the center line pattern 1701.
- FIG. 17 (2-2) shows an example in which all areas other than the measurement area are set as non-measurement target areas.
- a pattern existing at the upper right of a part of the central measurement target pattern 1701 and the peripheral pattern 1702 is set as a measurement target, and the rest are explicitly selected and set as a non-measurement target region.
- FIG. 17 (2-3) is an example in which a measurement area is set in a non-measurement target area.
- a part of the central measurement target pattern 1701 is a measurement target.
- the operation can be simplified by selecting and setting both the non-measurement target region and the measurement region.
- FIG. 17 (2-4) shows an example in which all areas other than the non-measurement target area are set as measurement areas.
- FIG. 17 (2-2) and FIG. 17 (2-4) are the same as a result, but the operation can be simplified by explicitly designating either the non-measurement target region or the measurement region. For example, even if the non-measurement target area is wide, it is easier to specify only the non-measurement target area if it can be set with one rectangle. It is desirable to select by a simple method from the number and shape of non-measurement target areas and measurement areas.
- Pattern measuring apparatus 101 Measurement area
- Pattern measurement result 200 Scanning electron microscope system 201
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Abstract
Description
図3は、画像データ300上の測定対象パターン301に対して、測定距離303を求めるための一般的な測定領域302及び測定位置の設定方法の例を示す。測定領域302に関しては、例えば測定するエッジ位置304を含む領域を長方形や円,短形などの測定カーソルにて設定する。
図4及び図5は、半導体デバイス等の試料に関する設計データ等のデータと、試料を撮影することにより得られるSEM画像の間のプロセス変動の発生例を示す。この場合、測定すべきパターンを検出できない、あるいは誤った位置を検出してしまうことにより、パターンの誤測定が発生する原因となる。
図6を用いて、画像データ600上の複数の測定対象パターン601とパターン602のうち、測定時に使用しないパターン602を含んだ領域を非測定対象領域606として設定する方法について説明する。ここで、非測定対象領域606は、予め記憶されたパターンデータ106、すなわち設計データ,シュミレーションデータ,参照画像,測定パターンから取得される信号情報等、様々な種類のデータから設定することが可能である。
(1)低倍率条件における位置合わせ
(2)高倍率条件にて測定位置に移動
(3)明るさ・焦点調整
(4)高倍率条件におけるパターンマッチング
(5)非測定対象領域処理
(6)パターン測定
図17は、非測定対象領域の種々の設定例を示す。図17(1)に示すように、データ1700上には複数のパターンを含んでいるものとする。図17(2-1)は、周辺のパターン1702のうち上部の2つのみを測定対象とし、それ以外の株のラインパターン及び中央のラインパターン1701に対しては非測定対象領域として複数設定する例を示す。図17(2-2)は、測定領域以外全てを非測定対象領域として設定する例である。ここでは中央の測定対象パターン1701の一部と周辺のパターン1702のうち右上に存在するパターンのみを測定対象とし、それ以外は明示的に非測定対象領域として選択し、設定する。
101 測定領域設定部
102 非マッチング対象領域設定部
103 パターンマッチング部
104 パターン測定部
105,109,300,400,500,600,700,800,900,1000,1100,1200,1300,1600,1700 画像データ
106 パターンデータ
107 パターンマッチング結果
108 非測定対象領域設定部
110 パターン測定結果
200 走査型電子顕微鏡システム
201 SEM
202 画像処理装置
203 表示装置
204 制御用計算機
205 入力手段
207 画像処理結果
208 SEM制御データ
209 画像処理用データ
210 表示用データ
211 制御データ
301,401,501,601,701,801,901,1001,1101,1201,1301,1601,1603,1701 測定対象パターン
302,402,502,603,703,803,909,1003,1103,1206,1606 測定領域
303,403,406,503,506,605,705,805,908,1005,1105,1205,1609,1116 測定距離
304,404,405,504,505,604,704,804,907,1004,1104,1204,1604,1605 エッジ
305 信号情報
306 ピーク
307 エッジ位置に対応した複数ピーク間の距離
602,702,802,902,1002,1102,1202,1302,1602,1702 パターン
606,706,806,906,1010,1703 非測定対象領域
807,905,1109,1208,1304 非マッチング対象領域
903,904 マッチング領域
1006 プロセス変動の発生する可能性が高い領域
1007 プロセス変動の発生する可能性が低い領域
1106,1107,1110,1111,1607,1608 測定カーソル
1108 距離
1112,1113 新たに設定した測定カーソル
1207 ゴミ等のノイズ成分
1704 非測定領域中に設定した測定領域
Claims (9)
- 試料を撮像することにより得られる画像データ中に測定領域を設定する測定領域設定部と、
前記画像データと、予め記憶されたパターンデータとの間でパターンマッチングを行うマッチング部と、
当該マッチング部によって、位置合わせされた前記画像データ中の所定領域を、測定対象から除外する領域として設定する非測定対象領域設定部と、
当該測定領域に含まれる信号を抽出して、前記試料上に形成されたパターンの測定を行うパターン測定部を備え、
前記パターン測定部は、前記測定領域と前記所定領域が重畳する領域に含まれる信号を除外してパターン測定を行うことを特徴とするパターン測定装置。 - 請求項1に記載のパターン測定装置において、
前記パターンデータは、前記試料の設計データ,シュミレーションデータ,参照画像,測定パターンから取得される信号情報のいずれかであることを特徴とするパターン測定装置。 - 請求項1または請求項2に記載のパターン測定装置において、
前記所定領域は、前記パターンデータを用いて設定されることを特徴とするパターン測定装置。 - 請求項3に記載のパターン測定装置において、
前記所定領域は、前記試料の設計データ,シュミレーションデータ,参照画像,測定パターンから取得される信号情報のいずれかを用いて設定されることを特徴とするパターン測定装置。 - 請求項1~請求項4のいずれかに記載のパターン測定装置において、
前記画像データ中の所定領域に含まれるパターンは、前記測定領域中の前記所定領域を除く領域に含まれるパターンよりも前記パターンデータとの間の形状誤差が相対的に小さいことを特徴とするパターン測定装置。 - 請求項5に記載のパターン測定装置において、
前記画像データ中の所定領域に含まれるパターンは、前記パターンデータとの間の形徐誤差が所定の閾値以下であることを特徴とするパターン測定装置。 - 請求項1~請求項6のいずれかに記載のパターン測定装置を備えた画像処理装置と、
走査型電子顕微鏡と画像処理装置を制御する制御用計算機と、
走査型電子顕微鏡や、パターンマッチング及びパターン測定を行うためのパラメータ等を入力する入力手段と、
走査型電子顕微鏡からの画像データ,パターンマッチング及びパターン測定結果を表示する表示装置を備えたことを特徴とする走査型電子顕微鏡システム。 - 試料を撮像することにより得られる画像データ中に測定領域を設定する測定領域設定工程と、
前記画像データと、予め記憶されたパターンデータとの間でパターンマッチングを行うマッチング工程と、
当該マッチング工程によって、位置合わせされた前記画像データ中の所定領域を、測定対象から除外する領域として設定する非測定対象領域設定工程と、
当該測定領域に含まれる信号を抽出して、前記試料上に形成されたパターンの測定を行うパターン測定工程を備え、
前記パターン測定工程は、前記測定領域と前記所定領域が重畳する領域に含まれる信号を除外してパターン測定を行うことを特徴とするパターン測定方法。 - ネットワーク経由、もしくは外部接続型のメモリ経由で、走査型電子顕微鏡の画像データや、予め記憶されたパターンデータを受信可能な計算機と、パターンマッチング及びパターン測定を行うためのパラメータ等を入力する入力手段と、走査型電子顕微鏡からの画像データや、パターンマッチング及びパターン測定結果を表示する表示装置を備え、請求項1に記載のパターン測定装置の機能をソフトウェア処理で行うことを特徴としたプログラム。
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