WO2013051456A1 - 計測方法、データ処理装置及びそれを用いた電子顕微鏡 - Google Patents
計測方法、データ処理装置及びそれを用いた電子顕微鏡 Download PDFInfo
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- WO2013051456A1 WO2013051456A1 PCT/JP2012/074888 JP2012074888W WO2013051456A1 WO 2013051456 A1 WO2013051456 A1 WO 2013051456A1 JP 2012074888 W JP2012074888 W JP 2012074888W WO 2013051456 A1 WO2013051456 A1 WO 2013051456A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
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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
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
- G01B2210/56—Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth
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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
- H01J2237/26—Electron or ion microscopes
- H01J2237/28—Scanning microscopes
- H01J2237/2813—Scanning microscopes characterised by the application
- H01J2237/2817—Pattern inspection
Definitions
- the present invention relates to a fine pattern measurement method, a data processing apparatus, and an electron microscope using the same.
- a lithography technique using an ArF excimer laser as a light source is used for forming a fine pattern in a semiconductor manufacturing process. While the miniaturization of patterns has progressed, the practical use of EUV (Extreme Ultraviolet Lithography), which is a next-generation exposure light source with a shorter wavelength, has been delayed, so that the size of a fraction of the wavelength can be obtained using ArF lithography technology. Lithography is performed in the vicinity of the resolution limit so as to form a fine pattern. For lithography near the resolution limit, OPC (Optical Proximity Correction) technology that corrects the mask pattern shape and the exposure light source shape in consideration of the proximity effect of light is essential.
- OPC Optical Proximity Correction
- a sample having a fine resist pattern (hereinafter referred to as a fine resist sample or a resist sample) created by actually transferring a mask pattern is measured to evaluate a deviation from the design, and a mask or light source It is necessary to correct the shape.
- a scanning electron microscope (SEM) is used for the measurement of the fine resist sample.
- SEM scanning electron microscope
- the resist sample pattern shrinks (shrinks) due to electron beam irradiation, and the dimensions and shape change. Therefore, in order to accurately measure the size and shape of the pattern of the fine resist sample, it is necessary to accurately estimate and correct the shrink amount of the resist pattern.
- the resist sample is usually an insulator, charging may occur on the surface of the sample due to electron beam irradiation. When charging occurs, the trajectory of the incident electron beam changes, or some of the signal electrons generated from the sample are pulled back by the positive charging of the sample surface, and the SEM image becomes locally dark. As a result, an error may occur in the size and shape obtained from the obtained SEM image. Therefore, in order to accurately measure the pattern dimension and shape of the fine resist sample, it is necessary to correct errors caused by charging.
- Patent Document 1 discloses the following method. This is a method of estimating a shrink amount by measuring a resist sample a plurality of times with an SEM and obtaining a relationship (shrink curve) between the number of measurements and the amount of change in the pattern dimension of the resist sample.
- Patent Document 2 discloses the following method. This is because, when measuring the shift of the edge position between the acquired pattern shape and the reference shape, the average value of the shift amount of the edge point is the first time in order to correct the influence of shrinkage when measuring a plurality of times. In this method, a fixed value is added to the amount of deviation of the edge position in the second and subsequent measurements so as to coincide with the measurement.
- Patent Document 3 discloses a method of correcting a contour by collating a database according to a pattern shape of a sample, determining a change in size and shape due to shrinkage, and an error due to charging, and a sample. A method of correcting the change in the sample pattern position by calculating the stress between the pattern portions is shown.
- Patent Document 1 it is possible to estimate the size before shrinking by acquiring the image a plurality of times, approximating the dependence of shrinkage on the number of times of measurement, and storing the approximation function.
- the target pattern is limited to a line pattern or a hole pattern having a constant size, and cannot deal with a complicated two-dimensional shape.
- the shrink amount cannot be estimated correctly for patterns with different base materials.
- the correction target is a shrink amount between the first measurement and the second and subsequent measurements, and a method for deriving the contour before shrink is not described. Also, the pattern shape dependency and background dependency of the shrink amount are not taken into consideration, and the shrink amount cannot be estimated with high accuracy.
- An object of the present invention is to provide a measurement method, a data processing apparatus, and an electronic device using the same, which can obtain a pattern outline and dimensions with high accuracy even when the measurement object is shrunk by irradiation of a charged particle beam such as an electron beam. To provide a microscope.
- a data processing apparatus for processing data including information on the pattern shape of a sample in which a pattern is formed on a base material different from the base material;
- An image storage means, a material parameter storage means, and a shrink operation unit The image storage means stores image data obtained by photographing the sample,
- the material parameter storage means stores the shrink parameter of the pattern portion of the sample and the shrink parameter of the base portion of the sample,
- the shrink calculation unit uses the image data, the shrink parameter of the pattern unit, and the shrink parameter of the base unit, or a pattern shape before irradiating the sample with a charged particle beam, or the sample
- a data processing apparatus is characterized in that a pattern shape after irradiation with a charged particle beam is calculated.
- the data processing device calculates a pattern shape before irradiating the sample with an electron beam or a pattern shape after irradiating the sample with an electron beam.
- a measurement method for measuring a pattern of a sample in which a pattern is formed of a material different from the material of the base above the base Preparing pattern data before charged particle beam irradiation of the sample; Preparing parameters relating to shrinkage of the sample pattern portion; Preparing parameters relating to shrinkage of the sample substrate, Preparing beam conditions for measuring the pattern of the sample using a charged particle beam; Using the pattern data before irradiation with the charged particle beam, the shrink parameter of the pattern part, the shrink parameter of the base part, and the beam condition, the charged particle beam of the beam condition is applied to the sample.
- a data processing apparatus and an electron microscope using the same, which can obtain a pattern outline and dimensions with high accuracy even when a measurement target is shrunk by irradiation of a charged particle beam such as an electron beam. it can.
- FIG. 6 is a schematic diagram of a sample according to Examples 1 to 7, in which an upper part shows a top view of the sample on which a line pattern is formed, and a lower part shows a cross-sectional view.
- FIG. 6 is a schematic diagram of a sample according to Examples 1 to 7, in which an upper part shows a top view of the sample on which a hole pattern is formed, and a lower part shows a cross-sectional view.
- FIG. 6 is a schematic diagram of a sample according to Examples 1 to 7, and shows a top view on which an arbitrary pattern is formed.
- FIG. 5 is a schematic diagram of a sample according to Examples 1 to 7 and shows a cross-sectional view in which an embedded pattern is formed.
- FIG. 1 is an example of a schematic overall configuration diagram of an image processing apparatus according to Embodiment 1.
- 3 is another example of a schematic overall configuration diagram of an image processing apparatus according to Embodiment 1.
- FIG. 3 is another example of a schematic overall configuration diagram of an image processing apparatus according to Embodiment 1.
- FIG. 3 is an example of an input display image in the image processing apparatus according to the first embodiment.
- 7 is another example of a display image for input in the image processing apparatus according to the first embodiment.
- 7 is another example of a display image for input in the image processing apparatus according to the first embodiment.
- FIG. 10 is an example of a schematic overall configuration diagram of an image processing apparatus according to a second embodiment. In Example 3, it is a schematic diagram for demonstrating the relationship between the moving direction of an electron beam irradiation position, and charging, and the case where the moving direction is orthogonal to a pattern outline is shown.
- Example 3 it is a schematic diagram for demonstrating the relationship between the moving direction of an electron beam irradiation position, and charging, and the case where the moving direction is parallel to a pattern outline is shown.
- Example 3 it is a schematic diagram for demonstrating the influence on the profile of the image brightness of charging.
- 10 is an example of a schematic overall configuration diagram of an image processing apparatus according to Embodiment 3.
- FIG. 10 is an example of a schematic diagram of an overall configuration of an SEM according to Example 4.
- FIG. 10 is an example of a flowchart of image processing (post-shrink contour estimation) according to Embodiment 5.
- FIG. 10 is an example of a result display image in an image processing apparatus according to Embodiment 5.
- FIG. 10 is an example of a schematic overall configuration diagram of an image processing apparatus according to a seventh embodiment.
- Example 7 it is a schematic diagram for demonstrating a response
- Example 7 it is a schematic diagram for demonstrating the profile of an image brightness
- 10 is an example of a flowchart of information processing (adjustment / registration of material parameters) according to an eighth embodiment;
- FIG. 10 is an example of a schematic overall configuration diagram of an image processing apparatus according to an eighth embodiment.
- image processing is performed on an SEM image acquired by a scanning electron microscope (SEM), shrink correction in consideration of the influence of the background, and correction of errors caused by charging.
- SEM scanning electron microscope
- the pattern is a convex portion formed on the sample surface
- the base is a portion that is not a pattern when viewed from above the sample. Further, if the base material is also present in the lower part of the pattern, this is also included in the base.
- 1A and 1B show examples of patterns and bases in line-shaped and hole-shaped samples.
- Reference numerals 101 and 103 are schematic views when viewed from above the sample, and reference numerals 102 and 104 are schematic cross-sectional views.
- the regions 105 and 107 are pattern portions and the regions 106 and 108 are ground portions.
- the regions 109 and 111 are pattern portions and the regions 110 and 112 are ground portions.
- the region 113 is a convex portion
- the region 113 is a pattern portion
- the region 114 is a base portion.
- the sample surface is flat, but the sample is made of two or more types of materials.
- a portion 116 having a mark is a base portion
- an embedded portion 115 is a pattern portion.
- the pattern is, for example, various ArF resist patterns
- the base is, for example, an antireflection film, an oxide film, a nitrogen film, a silicon substrate, or the like.
- the influence of the base is the influence of the stress exerted on the pattern part by the base part, and includes the effect that the stress changes due to the shrinkage of the base part and the change in elastic modulus caused by electron beam irradiation.
- image processing for an SEM image will be described as an example. However, the same applies to image data other than an SEM image or data not in an image format as long as the data includes shape information of a sample. Can be processed. Hereinafter, the embodiment will be described in detail.
- the first embodiment according to the present invention is an embodiment for obtaining a pattern outline before shrinking from an SEM image.
- FIG. 2 is an example of a flowchart of image processing (pre-shrink contour estimation) according to the present embodiment.
- FIG. 3 is an example of a schematic overall configuration diagram of an image processing apparatus (data processing apparatus) that is desirable when executing this flowchart.
- This apparatus includes an image storage unit 301, a material parameter storage unit 302, a contour extraction calculation unit 303, and a shrink calculation unit 304.
- the contour extraction calculation unit 303 and the shrink calculation unit 304 include memories 305 and 306 that store data used for calculation, respectively.
- the above-described configuration may be realized as an independent device, or may be realized by one or a plurality of computers.
- symbol shows the same component.
- step S ⁇ b> 201 an SEM image file obtained by photographing a resist sample to be measured is input and stored in the image storage unit 301.
- the SEM image file includes, in addition to the image data detected by the SEM signal electrons, information on the pattern portion of the sample, information on the ground portion, and information on the beam conditions of the SEM at the time of SEM image acquisition. It is desirable to be saved in the file.
- the information on the pattern part and the base part is the type and height of each material.
- a file including the information may be prepared in association with the image file and input together with the image file. Further, as will be described later, the operator may input in a later step. Note that information on the pattern portion and the base portion of the sample is stored in the material parameter storage unit 302.
- step S202 the SEM image data stored in the image storage unit 301 is stored in the memory 305 of the contour extraction calculation unit 303, and the contour of the sample is extracted by the contour extraction calculation unit 303 using this data.
- the extracted contour data is stored in the memory 306 in the shrink calculation unit 304.
- the contour is extracted by extracting pixels with high luminance in the image. Further, as shown in FIG.
- a profile 401 in which the position dependency of luminance in the direction orthogonal to the contour line is extracted is created in the vicinity of the contour extracted by the above-described method, and the maximum luminance value 402 and the background portion
- the average luminance with the minimum luminance value 403 may be obtained, the average luminance may be used as the reference value 404, and the position 405 where the luminance becomes the reference value may be extracted as the contour point.
- the reference value may be a value obtained by distributing the value of the maximum value 402 to the value of the luminance 403 at a predetermined ratio without being limited to the average luminance.
- the lower luminance may be simply used as the background, or separately connected to the apparatus as shown in FIG. 5A.
- the SEM image may be displayed on the monitor 307 to allow the operator to input which part is the base or pattern, or the sample pattern to be measured can be stored in the database 308 separately connected to the apparatus as shown in FIG. 5B. If design data is recorded, the determination may be made with reference to this. Alternatively, when there are a plurality of SEM images acquired for the same pattern, the pattern portion and the background portion can be determined from the moving direction of the contour line.
- the SEM image acquired earlier and the SEM image acquired later are compared with the contours obtained by extracting the pixels whose luminance is increased in the image, and the side on which the contour is moving is compared.
- the pattern portion is determined.
- the accuracy can be improved by determining the pattern portion and the background portion in the moving direction of each contour point, and setting the pattern portion as the side determined as the pattern portion by more contour points.
- the pattern portion is determined by the above method for a combination of a plurality of two SEM images, such as the first and second sheets, the first and third sheets, and the like.
- the accuracy can be further improved by making the portion determined to be the pattern portion by more combinations as the pattern portion.
- pattern matching is performed using any one of the images as a reference image, the pattern misalignment in the SEM image is measured, and the pattern in the image is corrected so as to correct it.
- the error of the image acquisition position that occurs at each imaging location, and to determine the pattern portion and the background portion with higher accuracy.
- any method for extracting a contour from an image and any method for discriminating a pattern and a background portion can be used.
- a pattern material parameter that is, a shrink parameter and a height of the pattern portion are designated.
- the shrink parameter will be described in step S206. If the pattern material and height information are input together with the image data in step S201, the shrinkage parameters of various materials stored in the material parameter storage unit 302 are selected according to the input information.
- the shrink parameter of the material of the pattern portion is stored in the memory 306 in the shrink operation unit 304, and the height is also stored in the memory 306.
- the pattern unit as shown in FIG. 6A is connected to the monitor 307 separately connected to the apparatus as shown in FIG. 5A. It is also possible to display information for the input of the information and allow the operator to input the material and height of the pattern portion.
- the shrink parameter may be directly input by the operator without using the material parameter storage unit 302.
- step S204 the base material parameter, that is, the shrink parameter and height of the base portion are designated.
- a specific method is the same as that in step S203.
- FIG. 6B is an example of display when the operator uses the monitor 307 to input.
- step S205 SEM beam conditions at the time of SEM image acquisition are designated.
- the beam conditions are, for example, the acceleration voltage of incident electrons, the probe current, the magnification of the SEM image, the number of repeated scans (frame integration number), and the like. If necessary, the scanning speed (moving speed of the electron beam irradiation position when acquiring the SEM image), the number of pixels of the SEM image, or the like, or the electron beam irradiation amount per unit area may be used.
- the beam condition is input together with the image data in step S201, it is read into the memory 306 in the shrink calculation unit 304.
- the SEM image is considered to be observing the sample being irradiated with the electron beam, not the sample after the electron beam irradiation, all the scans used in the image acquisition were performed as the number of scans to the sample and the electron beam irradiation amount. It is desirable to read not a number of times or an electron beam irradiation amount but a smaller value, for example, a half value.
- the beam condition input as shown in FIG. 6C is connected to the monitor 307 separately connected to the apparatus as shown in FIG. 5A. May be displayed and input by the operator.
- step S206 the contour data stored in the memory 306 in the shrink calculation unit 304, the shrink parameter of the pattern unit, the height of the pattern unit, the shrink parameter of the base unit, the height of the base unit, and the beam condition are used. Calculate and output the contour before shrinking.
- any algorithm can be used as long as it is an algorithm for estimating the contour before shrinkage in consideration of the influence of the base material. A desirable example will be described below.
- One example is a method using elastic body simulation.
- the volume change rate and the elastic modulus with respect to the electron beam irradiation dose are used as the shrink parameters of the pattern part and the base part.
- mesh data of the sample shape including the ground is created from the contour data, the pattern and the ground height data.
- the electron beam irradiation amount for each mesh is calculated from the beam condition data, and the volume change due to shrink is obtained using the volume change rate with respect to the electron beam irradiation amount per unit volume.
- the elastic energy generated in each mesh is calculated using the elastic modulus.
- each mesh position is optimized so that the total sum of the elastic energy is minimized.
- the optimized pattern contour is the pre-shrink contour.
- Another example is a method using a rigid model.
- the volume change rate with respect to the electron beam irradiation amount and the integration range of the shrink amount are used as material parameters. Similar to the above example, first, mesh data of the sample shape including the ground is created. Next, the volume change due to shrink is calculated for each mesh, and the change amount of the mesh size is obtained. Thereafter, the dimensional change amount of the mesh included in the integration range of the shrink amount is integrated to obtain an estimated shrink amount at each location of the pattern, and the estimated shrink amount is added to the contour data to obtain the pre-shrink contour.
- the volume change rate with respect to the electron beam irradiation amount may be corrected according to the light intensity in each mesh used in the above example.
- the pre-shrink outline 701 may be displayed together with the post-shrink outline 702. Or you may display together with a SEM image.
- a shrink correction amount that is a difference from the contour data after shrinking that is, an amount obtained by reversing the shrink amount, may be obtained and displayed on the vector together with the contour data as shown in FIG. 7B.
- the amount of shrink correction is small, it is desirable that the length of the arrow is stretched at a certain rate so that it can be displayed easily.
- FIG. 7A shows that the amount of shrink correction is small, it is desirable that the length of the arrow is stretched at a certain rate so that it can be displayed easily.
- the distance from the end of the contour line of a certain contour point may be plotted on the horizontal axis, and the shrink amount at the contour point may be plotted on the vertical axis.
- the vertical axis may be an absolute value of the shrink amount, or only a component in a certain direction such as a normal component of a contour line may be displayed.
- a warning may be displayed on the monitor 307.
- the above method is an example of a method for estimating the outline before shrinking from the SEM image with high accuracy.
- the outline data is obtained from the SEM image in step S201 and step S202.
- the contour data output by another device may be replaced with a step of storing it in the memory 306 in the shrink operation unit 304.
- the contour extraction calculation unit 303 shown in the device configuration diagram of FIG. 3 is not necessary.
- the above method can be applied to a single SEM image.
- a plurality of SEM images obtained by imaging the same portion or patterns with similar shapes are used.
- an image obtained by averaging the images may be created, and the method of this embodiment may be applied to the average image.
- the luminance of each pixel may be simply averaged, but pattern matching is performed using any image as a reference image, and the positional deviation of the pattern in the SEM image is measured. After moving the pattern in the image so as to correct this, the luminance of each pixel is averaged to correct the error in the image acquisition position that occurs at each imaging location, and to create a more accurate contour. Can be obtained.
- the second embodiment according to the present invention is an embodiment for obtaining a pattern size before shrinking from an SEM image. Note that the matters described in the first embodiment but not described in the present embodiment can be applied to the present embodiment as long as there is no particular circumstance.
- FIG. 8 is an example of a flowchart of image processing according to the present embodiment.
- FIG. 9 is an example of a schematic overall configuration diagram of an image processing apparatus (data processing apparatus) that is desirable when implementing this embodiment.
- this apparatus includes a dimension measurement calculation unit 309 including a memory 310.
- Steps S801 to S805 are the same as steps S201 to S205.
- step S806 the pre-shrink contour is calculated in the same manner as in step S206, but instead of outputting it, it is stored in the memory 310 in the dimension measurement calculation unit 309.
- step S807 the dimension measurement calculation unit 309 uses the pre-shrink contour stored in the memory 310 to determine the distance between the contour lines of a predetermined portion of the pattern, and performs statistical processing such as averaging as necessary. This is output as a dimension.
- step S806 and step S807 may be replaced with the method described below.
- step S806 the pre-shrink contour is calculated in the same manner as in step S206. Instead of outputting this, the shrink amount of each contour point, that is, the difference between the pre-shrink contour and the post-shrink contour is obtained, and the dimension measurement calculation unit The data is stored in the memory 310 in 309.
- step S807 the image data is read from the image storage unit 301 and stored in the memory 310 in the dimension measurement calculation unit 309.
- the dimension measurement calculation unit 309 obtains a dimension value for a predetermined pattern portion in the image data.
- a known algorithm may be used for obtaining a dimension from the SEM image.
- the shrink amount of the pattern whose dimension is to be obtained is obtained from the shrink amount of each contour point stored in the memory 310. For example, when the sample has a line shape as shown in FIG. 1A, the average value of the shrinkage amount at the contour line constituting the line may be obtained, and when the sample has a hole shape as shown in FIG. 1B, the hole is formed.
- the dimension value before shrinking is obtained by subtracting the shrink amount from the dimension value obtained from the SEM image, and output.
- the dimension to be obtained is the size of the base portion, for example, in the case of the hole shape diameter in FIG. 1B
- the dimension value before shrinking is obtained by adding the shrink amount to the dimension value obtained from the SEM image. Is output.
- a third embodiment according to the present invention is an embodiment in which a pattern contour line of a sample is obtained from an SEM image by correcting an error caused by charging. Note that matters described in the first or second embodiment but not described in the present embodiment can also be applied to the present embodiment unless there are special circumstances.
- FIG. 10A and 10B schematically show the moving direction of the electron beam irradiation position in each case for the contour line 1002 of the line-shaped pattern portion 1001 by arrows 1003 and 1004.
- FIG. 10B shows a case where the electron beam irradiation position is moved in a direction close to the direction and perpendicular to the direction.
- FIG. 11 is a schematic diagram showing an example of a profile obtained by extracting the position dependency of the luminance in the direction orthogonal to the contour line at the same position of the SEM image acquired by the method shown in FIGS. 10A and 10B.
- 10A and FIG. 10B correspond to the dotted line 1101 and the solid line 1102, respectively.
- the solid line 1102 when the electron beam irradiation position is moved in a direction that is nearly parallel to the direction of the contour line, a decrease in luminance occurs.
- the reference value 1105 is determined from the maximum value 1103 of the image luminance profile and the minimum value 1104 in the background portion with respect to the profile 1102 in FIG.
- the position 1106 of the contour point obtained by the method for determining the position of the position is different from the original position obtained from the profile 1101. This is an error caused by charging.
- FIG. 12 is an example of a schematic overall configuration diagram of an image processing apparatus (data processing apparatus) desirable for carrying out this embodiment.
- This apparatus includes a charge correction data storage unit 311 in addition to the components shown in FIG.
- an index A indicating the profile asymmetry is used as an index indicating the change in profile due to charging.
- a profile is obtained from a plurality of SEM images acquired under different conditions of the movement of the electron beam irradiation position with respect to the contour line, and caused by charging. What is necessary is just to obtain
- the position of the original contour point may be determined using other means such as design data, a cross-section SEM, a cross-section TEM (Transmission Electron Microscope), and the deviation from this may be regarded as an error caused by charging.
- design data design data
- a cross-section SEM cross-section SEM
- a cross-section TEM Transmission Electron Microscope
- the relationship between the index A stored in the charging correction data storage unit 311 and the error due to charging may be the one obtained by storing the relationship obtained by the above-described method in a table format, or a linear function or a quadratic function. An approximation function obtained by approximation may be used.
- step S202 when determining the pattern dimensions from the SEM image, it is possible to correct the error due to charging and estimate the pattern contour with high accuracy. It becomes possible.
- a fourth embodiment according to the present invention is an SEM incorporating the image processing apparatus shown in the first embodiment. Note that the matters described in any of the first to third embodiments but not described in the present embodiment can be applied to the present embodiment as long as there are no special circumstances.
- FIG. 13 is an example of a schematic diagram of the overall configuration of the SEM in this embodiment.
- An electron beam 1302 emitted from an electron source 1301 is deflected by a deflector 1303, converged by an objective lens 1304, and placed on a stage 1305.
- the surface of the held sample 1306 is irradiated.
- Secondary electrons 1307 emitted from the sample surface by the irradiation of the electron beam are detected by a detector 1308.
- These parts are controlled by the apparatus control unit 1309, and the SEM image is generated by expressing the signal intensity from the detector as the luminance of the pixel at the position corresponding to the deflection amount of the deflector on the image.
- Contour correction is performed on the SEM image using the contour correction calculation unit 1310.
- the contour correction calculation unit 1310 is the image processing apparatus shown in FIG.
- the shrinkage is calculated from the pattern design data instead of the SEM image, and the contour obtained from the SEM image when the SEM image is acquired by the SEM image after the shrinkage is obtained.
- This is an example of estimation. Note that matters described in any of the first to fourth embodiments but not described in the present embodiment can also be applied to the present embodiment unless there are special circumstances.
- FIG. 14 is an example of a flowchart of image processing (post-shrink contour estimation) according to the present embodiment.
- step S ⁇ b> 1401 the pre-shrink contour of the resist sample whose contour after shrinking is to be obtained is input and stored in the memory 306 in the shrink computing unit 304.
- the contour before shrinking may be contour data of a designed pattern portion, or may be contour data of a pattern portion obtained from an exposure prediction result output from a lithography simulator or the like.
- steps S1402, S1403, and S1404 similarly to steps S203, S204, and S205, the shrink parameter and height of the pattern unit, the shrink parameter and height of the base unit, and the beam condition are designated, and the memory in the shrink calculation unit 304 is specified. It stores in 306. However, since the SEM observation of the sample is not actually performed, the input is the assumed sample conditions and beam irradiation conditions. It is desirable to input these pieces of information together by using a data format in which the design data file at the time of inputting the design data in step S1401 includes information on the material and height of the pattern portion and the base portion. Further, a file having information on the material and height of the pattern portion and the base portion may be input along with the design data. Further, as described in the first embodiment, the operator may input. Further, instead of designating the beam irradiation condition in step S1404, standard conditions may be designated.
- step S1405 using the contour data stored in the memory 306 in the shrink calculation unit 304, the shrink parameter of the pattern unit, the height of the pattern unit, the shrink parameter of the base unit, the height of the base unit, and the beam condition, Calculate and output the contour after shrinking.
- an algorithm used in this calculation an arbitrary algorithm can be used as long as it is an algorithm for estimating the contour after shrinkage in consideration of the influence of the base material. An example similar to the algorithm illustrated in the first embodiment will be described below.
- One example is a method using elastic body simulation.
- the volume change rate and the elastic modulus with respect to the electron beam irradiation dose are used as the shrink parameters of the pattern part and the base part.
- mesh data of the sample shape including the ground is created from the contour data, the pattern and the ground height data.
- the electron beam irradiation amount for each mesh is calculated from the beam condition data, and the volume change due to shrink is obtained using the volume change rate with respect to the electron beam irradiation amount per unit volume.
- the elastic energy generated in each mesh is calculated using the elastic modulus.
- each mesh position is optimized so that the total sum of the elastic energy is minimized.
- the pattern outline after optimization is the outline after shrinking.
- Another example is a method using a rigid model.
- the volume change rate with respect to the electron beam irradiation amount and the integration range of the shrink amount are used as material parameters. Similar to the above example, first, mesh data of the sample shape including the ground is created. Next, the volume change due to shrink is calculated for each mesh, and the change amount of the mesh size is obtained. Thereafter, the dimensional change amount of the mesh included in the integration range of the shrink amount is integrated to obtain an estimated shrink amount at each location of the pattern, and the estimated shrink amount is subtracted from the contour data to obtain the contour after shrink.
- a pattern contour 1501 obtained from the design pattern contour or the output result of the lithography simulator and the calculated contour 1502 after shrinking may be displayed together.
- a shrink amount which is a difference from the contour data after shrinking may be obtained and displayed on the vector together with the contour data as shown in FIG. 15B.
- the amount of shrink correction is small, it is desirable that the length of the arrow is stretched at a certain rate so that it can be displayed easily.
- the distance from the end of the contour line of a certain contour point may be plotted on the horizontal axis, and the shrink amount at the contour point may be plotted on the vertical axis.
- the vertical axis may be an absolute value of the shrink amount, or only a component in a certain direction such as a normal component of a contour line may be displayed.
- a warning may be displayed on the monitor 307. Further, a beam condition in which the shrink amount is less than the allowable value may be searched and output.
- a sixth embodiment according to the present invention is an embodiment that estimates and corrects a change in cross-sectional shape due to shrinkage. Note that the matters described in any of the first to fifth embodiments but not described in the present embodiment can be applied to the present embodiment as long as there are no special circumstances.
- FIG. 16 is a schematic diagram of a cross-sectional shape before and after shrinking, in which 1601 is a cross-sectional shape after shrinking, and 1602 is a cross-sectional shape before shrinking.
- cross-sectional shape data an actual measurement result by a cross-section TEM, a cross-section STEM (Scanning Transmission Electron Microscope), a cross-section SEM, an AFM (Atomic Force Microscope), or a calculation result of a lithography simulator or the like may be used.
- the amount of shrinkage can be calculated by taking into account how much damage has been caused by the electron beam in which part of the sample using a simulation of scattering of incident electron beams in the sample. In addition, more accurate estimation is possible.
- the contour extraction algorithm when extracting a contour from an SEM image, the contour extraction algorithm is corrected in consideration of a change in cross-sectional shape due to shrinkage. Note that matters described in any of Examples 1 to 6 but not described in this example can be applied to this example as long as there is no particular circumstance.
- FIG. 17 is a flowchart of information processing according to the present embodiment.
- FIG. 18 is an example of a schematic overall configuration diagram of an image processing apparatus (data processing apparatus) that is desirable when executing this flowchart.
- the same components as those shown in FIG. 3 are denoted by the same reference numerals and the description thereof is omitted.
- this apparatus includes an optimum contour extraction condition calculation unit 312 including a memory 313.
- pre-shrink 3D shape data of a sample to be measured is input and stored in the memory 306 in the shrink operation unit 304.
- the three-dimensional shape data needs to be three-dimensional shape data of a sample to be observed by SEM, and it is desirable to use a shape predicted by a lithography simulator.
- a three-dimensional shape measured using an AFM, a cross-section TEM, a cross-section SEM, or a three-dimensional shape estimated by combining calculation and measurement results may be used.
- Steps S1702, S1703, and S1704 are the same as steps S203, S204, and S205 described in the first embodiment, or S1402, S1403, and S1404 described in the fifth embodiment.
- the heights of the pattern part and the background part are included in the solid shape data read in step S1701, and need not be specified in these steps.
- step S1705 the post-shrink solid shape is calculated using the pre-shrink solid shape data, the pattern portion shrink parameter, the ground portion shrink parameter, and the beam condition stored in the memory 306 in the shrink calculation unit 304. It is stored in the memory 313 in the optimum contour extraction condition calculation unit 312.
- any algorithm can be used as long as it is an algorithm that estimates the three-dimensional shape after shrinking in consideration of the influence of the base material, but is similar to the algorithm exemplified in the first and fifth embodiments. An example of this is described below.
- One example is a method using elastic body simulation.
- the volume change rate and the elastic modulus with respect to the electron beam irradiation dose are used as the shrink parameters of the pattern part and the base part.
- sample shape mesh data including the ground is created from the solid shape data.
- the electron beam irradiation amount for each mesh is calculated from the beam condition data, and the volume change due to shrink is obtained using the volume change rate with respect to the electron beam irradiation amount per unit volume.
- the elastic energy generated in each mesh is calculated using the elastic modulus.
- each mesh position is optimized so that the total sum of the elastic energy is minimized.
- the three-dimensional shape of the pattern after optimization is the three-dimensional shape after shrinking.
- Another example is a method using a rigid model.
- the volume change rate with respect to the electron beam irradiation amount and the integration range of the shrink amount are used as material parameters. Similar to the above example, first, mesh data of the sample shape including the ground is created. Next, the volume change due to shrink is calculated for each mesh, and the change amount of the mesh size is obtained. After that, the dimensional change amount of the mesh included in the integration range of the shrink amount is integrated to obtain the estimated shrink amount at each place of the pattern, and the estimated shrink amount is subtracted from the three-dimensional shape data to obtain the three-dimensional shape after shrinking. .
- step S 1706 the optimum contour extraction condition calculation unit 312 determines the optimum parameters at the time of contour extraction using the post-shrink solid shape stored in the memory 313, and stores it in the memory 305 in the contour extraction calculation unit 303. .
- the cross-sectional shape 1901 of the location where the contour point is extracted is obtained from the three-dimensional shape after shrinking stored in the memory 313, and the SEM image is acquired for the cross-sectional shape.
- the intensity distribution of the signal electrons is calculated using an electron beam scattering simulation or the like, and a luminance profile 1902 in the image is estimated.
- the position 1904 on the luminance profile corresponding to the position 1903 at the height at which the contour line is desired to be measured in the actual pattern can be found.
- the distribution ratio of the minimum value and the maximum value of the luminance of the background portion, in which the luminance at this position becomes the reference value, is the optimum contour extraction condition.
- Such optimum contour extraction conditions are determined for each location where the contour is measured.
- step S1707 SEM image data obtained by photographing a sample to be measured is input and stored in the memory 305 of the contour extraction calculation unit 303.
- step S1708 using the optimum contour extraction condition and SEM image data stored in the memory 305, the contour extraction calculation unit 303 extracts the contour of the sample and outputs it.
- FIG. 20 shows the case where the optimum contour extraction condition is 20:80, that is, the distribution ratio between the maximum value 2002 value in the luminance profile 2001 and the minimum luminance value 2003 of the background portion is 20:80 as the reference value.
- the position 2005 that is the luminance reference value 2004 is detected as the position of the contour point.
- contour extraction considering cross-sectional deformation due to shrinkage can be performed, and a contour line at a desired pattern height can be obtained.
- the contour line obtained by this method is a contour line after shrinking, and the contour line before shrinking can be obtained with high accuracy by subsequently carrying out the first and second embodiments.
- the eighth embodiment according to the present invention is an embodiment for obtaining material parameters used in the first to seventh embodiments.
- the shrinkage amount is actually measured for a plurality of patterns, and the material parameter is adjusted so that a value matching the actual measurement is obtained in the shrinkage amount estimation. Note that the matters described in any of Examples 1 to 7 but not described in this example can be applied to this example as long as there is no particular circumstance.
- a line shape or hole shape with different line widths, or a line shape or hole shape pattern arranged with a different period is desirable for accurate parameter determination.
- This pattern can also be applied.
- FIG. 21 is a flowchart of information processing (material parameter adjustment / registration) according to the present embodiment.
- FIG. 22 is an example of a schematic overall configuration diagram of an image processing apparatus (data processing apparatus) that is desirable when executing this flowchart.
- the same components as those shown in FIG. 3 are denoted by the same reference numerals and the description thereof is omitted.
- the apparatus includes a shrink measurement calculation unit 314 including a memory 315 and a shrink comparison calculation unit 316 including a memory 317.
- step S2101 a plurality of SEM images captured continuously for the same part of the pattern made of the material whose material parameter is to be determined are read, stored in the image storage unit 301, and stored in the memory 315 of the shrink measurement calculation unit 314. Store.
- the accuracy can be further improved by picking up an image of different portions having patterns of similar shapes and using an averaged SEM image.
- the shrink measurement calculation unit 314 compares the SEM images stored in the memory 315, measures the shrink amount, and stores the obtained shrink measurement value in the memory 317 of the shrink comparison calculation unit 316.
- Any method can be applied to the shrink measurement method as long as it is an algorithm that compares the measurement data before and after the shrink and calculates the shrink amount of the pattern. For example, there is a method described below. There are a method of extracting a contour line and measuring an interval between contour lines before and after shrinking for each contour point, and a method of obtaining a change amount of a dimension value in the case of a line pattern or a hole pattern. When three or more SEM images are used, a method of approximating the relationship between the number of image capturing times and the amount of beam irradiation and the amount of change in shrink amount may be used.
- step S2103 it is determined whether or not the shrinkage measurement has been completed for all SEM images obtained by capturing patterns of various shapes set in advance. If not, the process returns to step S2101.
- step S2104 initial parameters are stored in the memory 306 in the shrink operation unit 304 as the shrink parameters for the material and the base.
- the initial parameter may be a fixed value set in advance, or when a monitor 307 is connected as shown in FIG. 5A, an input screen may be displayed on this and input by the operator. Alternatively, if it can be estimated from the shrink amount obtained in step S2102, the estimated value may be used.
- step S2105 the shrink amount is estimated for one of the SEM images stored in the image storage unit 301, and the shrink estimated value is stored in the memory 317 of the shrink comparison operation unit 316.
- a specific method for estimating the shrinkage will be described below.
- step S202 of the first embodiment is performed on the target SEM image, contour data is calculated, and stored in the memory 306 in the shrink operation unit 304. Further, the height of the pattern portion and the base portion and the beam condition are designated and stored in the memory 306. This may be performed by a method similar to the method described in steps S203, S204, and S205 of the first embodiment. However, for the beam condition, the difference in the beam condition of the SEM image compared in step S2102 is designated. For example, when the compared images are the first SEM image and the second SEM image obtained by continuously capturing the same place, the difference, that is, the beam condition for acquiring one SEM image is designated.
- the shrink parameter of the pattern unit the height of the pattern unit, the shrink parameter of the base unit, the height of the base unit, and the beam condition.
- the contour amount is calculated, and the shrink amount at each contour point is obtained from the difference from the contour data after shrinking.
- the dimension value is calculated for each of the calculated pre-shrink contour and post-shrink contour using the method described in step S807 of the second embodiment. And the difference is taken as the shrink amount.
- step S2106 it is determined whether or not the estimation of the shrinkage amount has been completed for all SEM images obtained by capturing patterns of various shapes set in advance. If not, the process returns to step S2105.
- step S2107 the shrink comparison calculation unit 316 is used to compare the shrink measured value and the shrink estimated value stored in the memory 317 with all the patterns of various shapes set in advance, and an error is determined in advance. If it is equal to or smaller than the threshold, the process proceeds to step S2109, and if it exceeds the threshold, the process proceeds to step S2108.
- the error an average value of errors at each contour point of each pattern may be used, or a value obtained by other statistical processing may be used.
- step S2108 the shrink parameter is corrected.
- the correction algorithm an existing method such as Newton's method may be used.
- the obtained shrink parameter is recorded in the material parameter storage unit 302.
- the material parameters used in Examples 1 to 7 can be determined by the above method. Note that the parameters of both the pattern material and the base material may be determined by the above-described method, or one parameter that has already been registered for one parameter may be newly determined. .
- this invention is not limited to the above-mentioned Example, Various modifications are included.
- the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
- a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment.
- Movement direction of electron beam irradiation position, 1004 ... Movement direction of electron beam irradiation position, 1101 ... Luminance profile when there is no influence of charging 1102 ... Luminance profile when there is an influence of charging, 1103 ... Maximum value of luminance, 1104 ... Minimum value of luminance of base portion, 1105 ... Reference value of luminance, 1106 ... Contour detection position, 1107 ... Minimum value of luminance of pattern portion, 1301 ... Electron source, 1302 ... Electron beam, 1303 ... Deflector, 1304 ... Objective Lens, 1305 ... Stage, 1306 ... Sample, 1307 ... Secondary electron, 1308 ... Detector, 1309 ... Device control unit, 1310 ...
- Contour correction calculation unit 1501 ... Design pattern contour, etc. 1502 ... Contour after shrinking, 1601 ... Cross-sectional shape after shrinking, 1602 ... Cross-sectional shape before shrinking, 1901 ... Cross-sectional shape, 1902 ... Estimated luminance profile, 1903 ... Position corresponding to the contour measurement height in the cross-sectional shape, 1904 ... Contour measurement height in the luminance profile , 2001 ... luminance profile, 2002 ... maximum luminance value, 2 03 ... minimum value of the luminance of the base portion, the reference value of 2004 ... brightness, 2005 ... contour detection position.
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Abstract
Description
前記試料に対して前記荷電粒子線を照射中に、あるいは照射した後に取得した、前記試料のパターン形状を含むデータを準備するステップと、
前記試料のパターン部のシュリンクに関するパラメータを準備するステップと、
前記試料の下地部のシュリンクに関するパラメータを準備するステップと、
前記荷電粒子線を前記試料に照射する際のビーム条件を準備するステップと、
前記パターン形状を含むデータと、前記パターン部のシュリンクに関するパラメータと、前記下地部のシュリンクに関するパラメータと、前記ビーム条件とを用いて、前記試料に対して前記荷電粒子線を照射する前の前記試料のパターン形状、あるいは寸法を算出するステップと、
を有することを特徴とする計測方法とする。
画像保存手段と、材料パラメータ保存手段と、シュリンク演算部とを備え、
前記画像保存手段は、前記試料を撮影した画像データを保存するものであり、
前記材料パラメータ保存手段は、前記試料のパターン部のシュリンクパラメータおよび前記試料の下地部のシュリンクパラメータを保存するものであり、
前記シュリンク演算部は、前記画像データと、前記パターン部のシュリンクパラメータと、前記下地部のシュリンクパラメータとを用いて、前記試料に対して荷電粒子線を照射する前のパターン形状、あるいは、前記試料に対して荷電粒子線を照射した後のパターン形状を算出するものであることを特徴とするデータ処理装置とする。
電子源と、前記電子源から放出された電子を前記試料に照射するための光学系と、前記試料から放出される電子を検出する検出器と、これらを制御する装置制御部と、を備え、
前記データ処理装置は、前記試料に対して電子線を照射する前のパターン形状、あるいは、前記試料に対して電子線を照射した後のパターン形状を算出するものであることを特徴とする電子顕微鏡とする。
前記試料の荷電粒子線照射前のパターンデータを準備するステップと、
前記試料パターン部のシュリンクに関するパラメータを準備するステップと、
前記試料下地部のシュリンクに関するパラメータを準備するステップと、
前記試料を荷電粒子線を用いて前記パターンを計測する際のビーム条件を準備するステップと、
前記荷電粒子線照射前のパターンデータと、前記パターン部のシュリンクに関するパラメータと、前記下地部のシュリンクに関するパラメータと、前記ビーム条件とを用いて、前記試料に対して前記ビーム条件の荷電粒子線を照射して計測する際に得られるパターン形状、あるいは寸法を算出するステップと、
を有することを特徴とする計測方法とする。
以下、実施例により詳細に説明する。
図2は、本実施例に係る画像処理(シュリンク前輪郭推定)のフローチャートの一例である。
図3は、このフローチャートを実施する際に望ましい、画像処理装置(データ処理装置)の概略全体構成図の一例である。本装置は、画像保存部301、材料パラメータ保存部302、輪郭抽出演算部303、シュリンク演算部304から構成される。輪郭抽出演算部303、シュリンク演算部304には、それぞれ、演算に用いるデータを保存するメモリ305、306が備わっている。前記の構成は、それぞれ独立した装置として構成して実現しても良いし、1台、あるいは複数の計算機で実現しても良い。なお、同一符号は同一構成要素を示す。
ステップS201では、計測したいレジスト試料を撮影したSEM画像ファイルを入力し、画像保存部301に保存する。SEM画像ファイルは、SEMの信号電子検出された画像データの他に、試料のパターン部の情報と、下地部の情報と、SEM画像取得時のSEMのビーム条件の情報とがあわせて含まれる形式のファイルで保存されていることが望ましい。パターン部、及び下地部の情報とは、それぞれの材料の種類と高さである。
その他、画像から輪郭を抽出する任意の方法、及びパターンと下地部を判別する任意の方法を用いることができる。
図8は、本実施例に係る画像処理のフローチャートの一例である。
図9は、この本実施例を実施する際に望ましい、画像処理装置(データ処理装置)の概略全体構成図の一例である。実施例1にて、図3に示した装置と重複する構成要素については、同じ番号を用いて示しており説明は省略する。本装置には、図3の構成要素に加えて、メモリ310を備えた寸法計測演算部309から構成される。
ステップS801からS805は、ステップS201からS205と同様である。
まず、図10を用いて、帯電に起因する誤差を説明する。
SEM画像を取得するために試料に電子線を照射する際輪郭線の向きと直交に近い向に電子線照射位置を移動させて取得したSEM画像に比べて、輪郭線の向きと平行に近い方向に電子線照射位置を移動させて取得したSEM画像では、輪郭線の近傍で画像輝度が低下することがある。図10A、図10Bは、ライン形状のパターン部1001の輪郭線1002について、それぞれの場合の電子線照射位置の移動方向を矢印1003、1004で模式的に示したもので、図10Aは輪郭線の向きと垂直に近い方向で、図10Bは平行に近い方向で、電子線照射位置を移動させる場合である。
本実施例のフローチャートは、図2と同じであるが、ステップS202の輪郭抽出のアルゴリズムについて、以下に説明するものを用いる。また、図12は、本実施例を実施するのに望ましい画像処理装置(データ処理装置)の概略全体構成図の一例である。実施例1にて、図3に示した装置と重複する構成要素については、同じ番号を用いて示しており説明は省略する。本装置には、図3の構成要素に加えて、帯電補正データ保存部311から構成される。
A=L/(L+R)
あらかじめ、指標Aと、帯電に起因する誤差との関係を帯電補正データ保存部311に保存しておけば、プロファイル1102から輪郭点を求める際に、図4にて説明した方法で輪郭点を求めるとともに、指標Aを求めて前述の関係を参照して帯電に起因する誤差を求め、これを補正することで正確な輪郭点を決定できる。
図13は、本実施例におけるSEMの全体構成外略図の一例であり、電子源1301より発せられた電子ビーム1302は、偏向器1303によって偏向され、対物レンズ1304によって収束され、ステージ1305の上に保持された試料1306の表面に照射される。電子ビームの照射によって試料表面から発せられた二次電子1307は、検出器1308によって検出される。これらの部分は、装置制御部1309によって制御され、検出器からの信号強度を、画像上の偏向器にする偏向量に応じた位置の画素の輝度として表すことで、SEM画像を生成する。このSEM画像に対して、輪郭補正演算部1310を用いて輪郭補正を行う。この輪郭補正演算部1310が、図3に示した画像処理装置である。
また、実施例に2に示した装置を輪郭補正演算部1310として用いることで、シュリンク前の寸法を取得できるようにしても良い。
あるいは、実施例3に示した装置を輪郭補正演算部1310として用いることで、帯電に起因する誤差を補正した輪郭を取得できるようにしても良い。
本実施例を実施する際に望ましい、画像処理装置の概略全体構成図の一例は、図3と同様である。
図14は、本実施例に係る画像処理(シュリンク後輪郭推定)のフローチャートの一例である。
ステップS1401では、シュリンク後の輪郭を求めたいレジスト試料のシュリンク前の輪郭を入力し、シュリンク演算部304内のメモリ306に格納する。シュリンク前の輪郭とは、設計上のパターン部の輪郭データであっても良いし、あるいは、リソグラフィーシミュレータなどが出力する露光予想結果から得られるパターン部の輪郭データであっても良い。
この実施例は、実施例1、5にて用いた図1の符号101、103に示したようなパターン輪郭データの代わりに、図1の符号102、104に示したような断面形状データを用いる。これにより、シュリンク後の断面形状データからのシュリンク前断面形状の復元や、シュリンク前断面形状データからシュリンク後の断面形状の予測が可能となる。図16は、シュリンク前後の断面形状の模式図であり、1601がシュリンク後断面形状、1602がシュリンク前断面形状である。
図17は、本実施例に係る情報処理のフローチャートである。
図18は、このフローチャートを実施する際に望ましい、画像処理装置(データ処理装置)の概略全体構成図の一例である。実施例1にて、図3に示した装置と重複する構成要素については、同じ番号を用いて示しており説明は省略する。本装置には、図3の構成要素の他に、メモリ313を備えた最適輪郭抽出条件演算部312から構成される。
ステップS1701では、計測したい試料のシュリンク前立体形状データを入力し、シュリンク演算部304内のメモリ306に格納する。立体形状データは、SEM観察したい試料の3次元形状データである必要があり、リソグラフィーシミュレータによって予測される形状を用いるのが望ましい。あるいは、AFM、断面TEM、断面SEMなどを用いて計測した立体形状や、計算、実測結果を組み合わせて推定した立体形状でも良い。
図4にて説明したような、通常用いられる輪郭点抽出方法では、画素の輝度が基準値の輝度404となる位置405が輪郭点位置として検出されるが、パターンの断面形状が異なると、この方法で検出した輪郭点位置の実際のパターンにおける高さは異なる。つまり、一定のパターン高さの等高線を輪郭線として求めたい場合には、前述の方法では正しい輪郭線が求められない。
ステップS1708では、メモリ305に格納された、最適輪郭抽出条件とSEM画像データとを用いて、輪郭抽出演算部303により試料の輪郭を抽出し、出力する。図20は、最適輪郭抽出条件が20:80、つまり輝度プロファイル2001における最大値2002の値と下地部の輝度の最小値2003の値との配分割合が20:80の値が基準値となる場合の例であり、この場合、輝度基準値2004となる位置2005を輪郭点の位置として検出する。各計測箇所にて、同様の方法を用いることにより、求めたいパターン高さ位置の輪郭を抽出できる。
なお、この方法で得られる輪郭線は、シュリンク後の輪郭線であり、引き続いて実施例1、2を実施することで、シュリンク前の輪郭線を高精度に求めることが可能となる。
図21は、本実施例に係る情報処理(材料パラメータの調整・登録)のフローチャートである。
図22は、このフローチャートを実施する際に望ましい、画像処理装置(データ処理装置)の概略全体構成図の一例である。実施例1にて、図3に示した装置と重複する構成要素については、同じ番号を用いて示しており説明は省略する。本装置には、図3の構成要素の他に、メモリ315を備えたシュリンク計測演算部314、及び、メモリ317を備えたシュリンク比較演算部316から構成される。
ステップS2101では、材料パラメータを決定したい材料からなるパターンの同じ箇所について、連続して撮像した複数枚のSEM画像を読み込み、画像保存部301に保存し、また、シュリンク計測演算部314のメモリ315に格納する。なお、より精度の良いパラメータ決定のためには、1枚のSEM画像を取得する際の電子線照射量を小さくすることが望ましい。また、類似した形状のパターンのある異なる箇所を撮像し、平均化したSEM画像を用いることで、さらに精度を向上できる。
ステップS2109では、得られたシュリンクパラメータを材料パラメータ保存部302に記録する。
なお、上記の方法でパターン材料、下地材料の両方のパラメータを決定しても良いし、一方のパラメータについては既に登録されているものを用いて、残る一方のパラメータを新たに決定しても良い。
Claims (18)
- 下地の上方に前記下地の材料とは異なる材料でパターンが形成された試料に荷電粒子線を照射して前記パターンを計測する計測方法であって、
前記試料に対して前記荷電粒子線を照射中に、あるいは照射した後に取得した、前記試料のパターン形状を含むデータを準備するステップと、
前記試料のパターン部のシュリンクに関するパラメータを準備するステップと、
前記試料の下地部のシュリンクに関するパラメータを準備するステップと、
前記荷電粒子線を前記試料に照射する際のビーム条件を準備するステップと、
前記パターン形状を含むデータと、前記パターン部のシュリンクに関するパラメータと、前記下地部のシュリンクに関するパラメータと、前記ビーム条件とを用いて、前記試料に対して前記荷電粒子線を照射する前の前記試料のパターン形状、あるいは寸法を算出するステップと、
を有することを特徴とする計測方法。 - 請求項1に記載の計測方法において、
前記パターンは、レジストによって形成されているパターンであり、
前記試料に対して前記荷電粒子線を照射する前の前記試料のパターン形状、あるいは寸法は、前記パターンのシュリンク前の形状、あるいは寸法であることを特徴とする計測方法。 - 請求項2に記載の計測方法において、
前記パターンのシュリンク量を表示するステップを更に有することを特徴とする計測方法。 - 請求項3に記載の計測方法において、
前記パターンのシュリンク量が、規定の値を超えるかどうかを判定するステップを更に有することを特徴とする計測方法 - 請求項1に記載の計測方法において、
前記パターン部や前記下地部のシュリンクに関するパラメータを準備するステップは、複数の材料についてのシュリンクパラメータを保存したデータベースを利用することを特徴とする計測方法。 - 請求項1に記載の計測方法において、
前記試料に対して前記荷電粒子線を照射中に、あるいは照射した後に取得した、試料のパターン形状を含むデータは、前記試料に対して電子顕微鏡を用いて取得した電子顕微鏡画像、あるいは、前記電子顕微鏡画像から抽出した輪郭線データであることを特徴とする計測方法。 - 請求項1に記載の計測方法において、
前記パターン形状は、前記パターンの断面形状であることを特徴とする計測方法。 - 請求項1に記載の計測方法において、
前記試料のパターン形状を含むデータを準備するステップは、前記試料の帯電に起因する前記パターン形状、あるいは寸法の誤差を補正するステップを含むことを特徴とする計測方法。 - 請求項8に記載の計測方法において、
前記試料の帯電に起因する形状、あるいは寸法の誤差を補正するステップにおいて、画像輝度のプロファイルの非対称性を利用するアルゴリズムを用いることを特徴とする計測方法。 - 請求項1に記載の方法において、
前記パターン部のシュリンクに関するパラメータと前記下地部のシュリンクに関するパラメータは、複数の線幅の異なるラインパターンにおけるシュリンク量から決定されるパラメータであることを特徴とする計測方法。 - 下地の上方に前記下地の材料とは異なる材料でパターンが形成された試料の前記パターン形状の情報を含むデータを処理するデータ処理装置であって、
画像保存手段と、材料パラメータ保存手段と、シュリンク演算部とを備え、
前記画像保存手段は、前記試料を撮影した画像データを保存するものであり、
前記材料パラメータ保存手段は、前記試料のパターン部のシュリンクパラメータおよび前記試料の下地部のシュリンクパラメータを保存するものであり、
前記シュリンク演算部は、前記画像データと、前記パターン部のシュリンクパラメータと、前記下地部のシュリンクパラメータとを用いて、前記試料に対して荷電粒子線を照射する前のパターン形状、あるいは、前記試料に対して荷電粒子線を照射した後のパターン形状を算出するものであることを特徴とするデータ処理装置。 - 請求項11に記載のデータ処理装置と、
電子源と、前記電子源から放出された電子を前記試料に照射するための光学系と、前記試料から放出される電子を検出する検出器と、これらを制御する装置制御部と、を備え、
前記データ処理装置は、前記試料に対して電子線を照射する前のパターン形状、あるいは、前記試料に対して電子線を照射した後のパターン形状を算出するものであることを特徴とする電子顕微鏡。 - 請求項12記載の電子顕微鏡において、
前記画像データは、前記試料を電子線顕微鏡によって観察することで取得した電子顕微鏡の画像データであり、
前記データ処理装置は、前記電子顕微鏡の画像データから輪郭データを抽出する手段を更に有し、
前記シュリンク演算部は、前記画像データに代えて前記輪郭データを用いて前記電子顕微鏡による観察の前のパターン形状を算出するものであることを特徴とする電子顕微鏡。 - 下地の上方に前記下地の材料とは異なる材料でパターンが形成された試料のパターンを計測する計測方法であって、
前記試料の荷電粒子線照射前のパターンデータを準備するステップと、
前記試料パターン部のシュリンクに関するパラメータを準備するステップと、
前記試料下地部のシュリンクに関するパラメータを準備するステップと、
前記試料を荷電粒子線を用いて前記パターンを計測する際のビーム条件を準備するステップと、
前記荷電粒子線照射前のパターンデータと、前記パターン部のシュリンクに関するパラメータと、前記下地部のシュリンクに関するパラメータと、前記ビーム条件とを用いて、前記試料に対して前記ビーム条件の荷電粒子線を照射して計測する際に得られるパターン形状、あるいは寸法を算出するステップと、
を有することを特徴とする計測方法。 - 請求項14に記載の計測方法であって、
前記試料に対して前記ビーム条件の荷電粒子線を照射して計測する際に発生する前記パターンのシュリンク量を表示するステップを更に有することを特徴とする計測方法。 - 請求項14に記載の計測方法であって、
前記試料に対して前記ビーム条件の荷電粒子線を照射して計測する際に発生するパターンのシュリンク量が、規定の値以下となるようなビーム条件を探索するステップを更に有することを特徴とする計測方法。 - 請求項14に記載の計測方法であって、
前記パターンデータは、前記パターンの断面形状のデータであることを特徴とする計測方法。 - 請求項14に記載の方法であって、
前記試料に対して前記ビーム条件の荷電粒子線を照射して計測する際に得られるパターン形状とは、前記パターンの立体形状であり、
前記試料に対して電子顕微鏡を用いて取得した電子顕微鏡画像を入力するステップと、
前記パターンの立体形状を利用して、前記電子顕微鏡画像から前記パターンの形状を抽出するステップと、を有することを特徴とする計測方法。
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