WO2013118613A1 - パターン評価方法およびパターン評価装置 - Google Patents
パターン評価方法およびパターン評価装置 Download PDFInfo
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- WO2013118613A1 WO2013118613A1 PCT/JP2013/051945 JP2013051945W WO2013118613A1 WO 2013118613 A1 WO2013118613 A1 WO 2013118613A1 JP 2013051945 W JP2013051945 W JP 2013051945W WO 2013118613 A1 WO2013118613 A1 WO 2013118613A1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/0004—Microscopes specially adapted for specific applications
- G02B21/002—Scanning microscopes
- G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
- G02B21/008—Details of detection or image processing, including general computer control
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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
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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
- G03F7/70633—Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
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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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- 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
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
- H01L21/033—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers
- H01L21/0334—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane
- H01L21/0337—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane characterised by the process involved to create the mask, e.g. lift-off masks, sidewalls, or to modify the mask, e.g. pre-treatment, post-treatment
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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
- a method for efficiently and accurately inspecting a superposition of circuit patterns formed on a wafer in a semiconductor device using a scanning charged particle microscope is provided.
- a coating material called a resist is applied on the semiconductor wafer, and an exposure mask (reticle) for the circuit pattern is superimposed on the resist, and then visible light, ultraviolet light, or electron beam is applied from there.
- a circuit pattern is formed on a semiconductor wafer by irradiating the resist, exposing and developing the resist, and etching the semiconductor wafer using the resist circuit pattern as a mask. Etc. are adopted.
- DP double patterning
- a double exposure technique which is one of the DP techniques will be described.
- a resist is applied on a wafer to form a first resist film, and this is exposed and developed to form a first pattern by the first exposure.
- the first pattern is frozen and processed so as not to be exposed in the second exposure.
- a resist for the second exposure is applied thereon to form a second resist film, and a second pattern is formed in the gap between the first patterns by the second exposure.
- Patent Document 2 Japanese Patent Application Laid-Open No. 2010-177500.
- a method of comparing the layout information with an image obtained by capturing a pattern based on the above information is disclosed.
- the object of the present invention is to use a scanning charged particle microscope to detect the pattern between upper and lower layers in a semiconductor device (between the first pattern formed in the lower layer and the second pattern formed in the upper layer) or different exposures in the DP.
- a scanning charged particle microscope to detect the pattern between upper and lower layers in a semiconductor device (between the first pattern formed in the lower layer and the second pattern formed in the upper layer) or different exposures in the DP.
- the requirements for overlay accuracy have become stricter, mask manufacturing errors, and exposure shots (in the area exposed by one exposure irradiation. One shot to several chips can be achieved. Exposure distortion) cannot be ignored, and not only misalignment of the entire mask for each exposure shot, but also overlay evaluation at a plurality of points in the exposure shot is required.
- the present invention provides a circuit pattern evaluation system and method having the following features. As a result, it is possible to evaluate dense overlay deviation in the wafer surface with high accuracy. By the following processing, it is possible to automatically determine the EP and the measurement point in the EP based on the layout information by the computer. In addition, the following processing enables the user to manually determine the EP or the measurement point in the EP instead of automatically.
- the first pattern generated on the sample by the first manufacturing process and the second pattern on the sample are generated by the second manufacturing process.
- a method of evaluating the overlay position with the second pattern, and estimating an allowable imaging deviation for evaluating the overlay position for one or a plurality of evaluation point candidates based on the layout information of the pattern Determining one or a plurality of evaluation points from evaluation point candidates based on the allowable imaging deviation, determining an imaging sequence for imaging the selected evaluation points, Superimposition of the first pattern and the second pattern from the image obtained by imaging the evaluation point according to the imaging sequence It characterized by having a step of evaluating the allowed positions. Further, in the step of estimating an allowable imaging deviation, the allowable imaging deviation is allowed on condition that the identification of the first pattern and the second pattern included in the evaluation point does not fail even if the imaging deviation occurs. The imaging deviation is estimated.
- the difference between the first pattern and the second pattern may be a difference in layers such as upper and lower layers, or a difference in multiple exposure in DP.
- the number of patterns for evaluating the overlay position may be two or more. For example, when the pattern of 3 layers (upper middle layer and lower layer) is seen in the captured image, the deviation between the first to third patterns can be evaluated, and when performing triple exposure (triple patterning) The deviation between the first to third patterns can be evaluated. In addition, when not all patterns can be observed by one imaging, it is possible to perform overlay evaluation by imaging a plurality of times at different manufacturing process timings.
- the pattern layout information for example, pattern design data described in the GDSII format may be used, or an image obtained by capturing a pattern using a scanning charged particle microscope or an optical microscope may be used.
- imaging deviation may occur. For this reason, it is necessary to set an area including a pattern that does not fail in evaluation even for imaging deviation as an evaluation point (referred to as an EP). It is necessary to estimate an imaging deviation (referred to as an allowable imaging deviation) to be performed and an imaging deviation that may actually occur (referred to as an estimated imaging deviation), and to take into consideration when determining the EP. That is, an EP that satisfies allowable imaging deviation ⁇ estimated imaging deviation is selected. Further, at this time, the deviation of the exposure position of the pattern itself to be evaluated and the shape deformation of the pattern may be taken into consideration, and these pattern variations may be considered together.
- an EP an imaging deviation that satisfies allowable imaging deviation ⁇ estimated imaging deviation
- an EP that does not fail in the evaluation of the overlay position even for the assumed pattern variation is determined.
- the layout information of the pattern is used for the estimation of the allowable imaging deviation. This is because the allowable imaging deviation differs depending on the pattern shape and arrangement included in the EP.
- an estimation condition for the allowable imaging deviation (A) the first pattern with respect to the imaging deviation and the second pattern should not be specified; (B) the first pattern with respect to the imaging deviation; For example, the measurement site of the second pattern is included in the visual field.
- the first pattern and the second pattern may be similar in an image, and the condition (A) is important.
- the imaging sequence In the estimation of the estimated imaging deviation, it is necessary to consider the imaging sequence in the scanning charged particle microscope. A supplementary description of the imaging sequence will be given here.
- a unique pattern called an addressing point (referred to as AP) is once imaged to estimate a stage error or the like, or an autofocus point (referred to as AF) is imaged to detect a charged particle beam. After adjusting the focus, image the EP. Therefore, for example, the imaging deviation changes depending on whether or not an appropriate AP exists.
- AP an addressing point
- AF autofocus point
- the imaging deviation changes depending on whether or not an appropriate AP exists.
- the imaging condition of the EP may be determined together.
- the imaging conditions include the EP field of view (imaging range or magnification), probe current, acceleration voltage, and charged particle beam scanning direction.
- the pattern may not be clearly observed on the image if the acceleration voltage is low. Therefore, when a lower layer pattern is included, it is conceivable to set a high acceleration voltage.
- the edge in the X direction can be sharply imaged by setting the scanning direction of the charged particle beam applied to the soot sample to the Y direction. Therefore, it is effective to set the scanning direction according to the pattern direction in the EP.
- this item (2) is the method of considering the robustness of the overlay evaluation with respect to the pattern deformation. It is. Even if a pattern suitable for measurement is included in the EP as judged from the pattern shape in the design data, in practice, it may be difficult to perform stable overlay evaluation due to pattern deformation. Possible types of pattern deformation include pattern width thickening / thinning, line end retraction, corner rounding, pattern shift (parallel movement), and the like.
- the EP is determined so as to include a part that is difficult to deform so that stable measurement can be performed, or a part that does not fail even if it is deformed. To do.
- the item (B) is an EP determination method in consideration of robustness with respect to pattern width thickening / thinning among the assumed pattern deformations. Assuming that pattern thickening / thinning occurs approximately symmetrically when viewed from the center of the pattern in the first pattern and the second pattern, the shift amount of the central portion of the first pattern and the second pattern is the pattern thickening / thinning. It is thought that it does not depend greatly on thinness. In order to obtain the position of the center of the pattern, the edges on both sides (upper and lower or left and right) of the pattern are required, so it is effective to set an EP that includes the edges on both sides.
- the EP can be determined in consideration of the management of critical patterns with respect to device characteristics. For example, an area including a pattern that is determined to easily cause a pattern shift based on a litho simulation or the like mounted on an EDA tool may be preferentially selected as an EP.
- an EP an area including a pattern that is determined to easily cause a pattern shift based on a litho simulation or the like mounted on an EDA tool may be preferentially selected as an EP.
- the position of the contact hole and the wiring pattern that electrically connect the upper and lower layers of the stacked layer, or the position of the gate wiring and the active layer in the transistor are shifted, this is directly connected to the change in device characteristics. May be preferentially selected as EP.
- the lower layer pattern is hidden from the upper layer pattern from the layout information in the step of determining the evaluation point.
- the estimation point is determined in consideration of the hiding.
- a plurality of EPs can be determined in consideration of the in-plane distribution of the evaluation points on the sample. Specifically, (A) a plurality of regions are set on the sample, and at least one evaluation point is determined from each of the regions. Alternatively, (B) a condition regarding a distance between any two evaluation points is given, and a plurality of evaluation points are determined so as to satisfy the condition.
- a plurality of areas within a certain range where each EP can be arranged are set. Since the EP may be set anywhere in the area, an EP that can be evaluated for overlaying is selected from the viewpoint of the item (1) in the area.
- the regions where the respective EPs can be arranged are arranged in a plane at regular intervals, for example, EPs that can be superposed and evaluated without significant deviation in distribution can be arranged.
- the item (B) is another embodiment that solves the same problem, and gives conditions regarding the distance between any two EPs, for example, the condition that the distance between the EPs falls between Aum and Bum.
- At least one evaluation point is designated in advance, and another evaluation including a pattern similar to the pattern included in the evaluation point based on the designated evaluation point It is determined by searching for points.
- the EP can be selected from various viewpoints depending on the intention of the user who is the evaluator. It also varies depending on the type and process of the semiconductor device. However, since overlay evaluation is performed at a plurality of locations, it is not easy for the user to register a large amount of EPs in a recipe. Therefore, a mechanism is provided that allows a user to input a desired EP, and an EP similar to the input EP is automatically extracted from the layout information as an EP candidate. As a result, the user can save time and effort for selecting a large amount of EPs only by inputting a few EPs, and can quickly respond to different EP selection criteria for each user, product type, and process.
- the user can specify all of a plurality of EPs. In this case, whether or not the user-specified EP is an EP suitable for overlay evaluation is evaluated based on the layout information from the viewpoint of the items (1) to (4) or the item (6) described later. If necessary, processing such as slightly shifting the user-specified EP position to a position more suitable for overlay evaluation or changing the size of the EP a little can be performed. As a result, the user only has to specify the approximate EP position, and the accurate position and size are automatically optimized, so that labor can be saved.
- a measurement point for evaluating the overlay position in the evaluation point is determined based on the pattern layout information.
- the step of determining the evaluation point includes a process of determining, for each evaluation point, a processing method for evaluating the overlay position in the evaluation point based on the layout information of the pattern.
- (Processing method A) A method of evaluating the overlay position by comparing the image obtained by imaging the evaluation point with design data, and (Processing method B) obtained by imaging the evaluation point. And a method of evaluating a superposition position by recognizing a pattern from the obtained image by image processing.
- a processing method for obtaining the distance can be determined for each evaluation pattern.
- the process using design data as in (Processing Method A) and the process of obtaining measurement values directly from an image as in the above item (Processing Method B) may be good or bad depending on the pattern included in the EP. It is effective to determine the processing method for each EP based on the information.
- a processing method for obtaining the distance can be designated in advance by the user, and an area where a measurement value can be obtained by the processing method based on the layout information can be selected as the EP.
- some users may desire to select only an area that can be processed in (Processing Method B) as an EP.
- EP is determined by using design data at the time of recipe generation, but there is an advantage that it is not necessary to handle design data at the time of imaging / measurement using a scanning charged particle microscope.
- the manufacturing process is determined for each pattern edge as attribute information, and the edge generated by the first manufacturing process based on the attribute information And an evaluation point is determined on the condition that the edge generated by the second manufacturing process is included in the field of view.
- manufacturing process information is assigned as attribute information for each edge, and a combination of measurement target edges is determined based on the attribute information. This is effective not only for evaluating the overlay displacement between layers, but also for evaluating the displacement between multiple processes between patterns formed in the same layer by multiple processes such as DP and SADP (Self-Aligned Double Patterning). It is.
- the addition of the attribute information is effective when automatically determining the EP and the measurement point in the EP based on the layout information, but when the user manually determines the measurement point in the EP and the EP instead of automatically. Is also very effective. This is because it may be difficult to predict which edge is generated by which manufacturing process from the layout information of the finally formed pattern. In addition, even if it can be predicted, knowledge of the process and specification of the pattern position are necessary for that purpose. Therefore, by displaying the layout information and the attribute information together to the user in the GUI or the like, it helps the user to determine the EP or the measurement point in the EP.
- the step of determining the evaluation point when evaluating the overlapping position in the x direction, at least either the left or right edge of the first pattern and the left or right edge of the second pattern are included in the first evaluation point. And determining the first and second evaluation points so that the second evaluation point includes either the left or right edge of the first pattern and the left or right edge of the second pattern, The overlay deviation is evaluated using the first and second evaluation points.
- the direction of the pattern included in the first evaluation point and the direction of the pattern edge included in the second evaluation point are opposite to each other in the first and second patterns.
- the first evaluation point when evaluating the overlapping position in the y direction, includes at least one of the upper and lower edges of the first pattern and the upper and lower edges of the second pattern.
- the first and second evaluation points are determined so that either the upper or lower edge of the first pattern and the upper or lower edge of the second pattern are included in the evaluation point, and the first and second evaluation points are determined. It is characterized by evaluating overlay displacement using points.
- the direction of the pattern edge included in the first evaluation point and the direction of the pattern edge included in the second evaluation point are upside down in the first and second patterns, respectively.
- the edge group necessary for measuring the deviation that did not fit in the field of view in one EP can be captured in the first EP and the second EP, so that they can all be contained in the field of view. There is a case.
- the edge group necessary for the measurement is combined with the first as described above. It was found that it is necessary to take an image with the EP of the second and the second EP. In this way, if two EPs are imaged to measure one shift amount, the measurement throughput decreases.
- a two-dimensional (x, y direction) deviation vector at a predetermined coordinate is estimated by interpolating the measurement value based on the measurable direction and the measured deviation amount in each EP. Even if the EP distribution is sparse or uneven, it is possible to estimate an in-plane distribution with a certain degree of deviation. However, since the reliability of the measured value obtained by the interpolation process is not necessarily high, the reliability is calculated for each estimated deviation vector. When correcting the deviation by feeding back the evaluation result of the deviation to a semiconductor manufacturing apparatus or the like, the degree of adding the deviation vector can be controlled according to the reliability.
- Examples of the reliability calculation method include a difference between interpolation / extrapolation of interpolation processing, a distance between EP and an interpolation point, and the like.
- evaluation point candidates are displayed together with the attribute information of the evaluation points.
- the attribute information described here includes not only attribute information related to the manufacturing process described in the item (7) but also attribute information (A) to (G) described later. This feature will be supplemented.
- determining an EP it is effective that a plurality of EP candidates are presented to the user, and the user is allowed to select from among them, rather than being all automatic.
- the position of the EP on the wafer can be plotted and displayed in order to grasp the in-plane distribution of the EP.
- various information determined in (1) to (9) can be displayed as EP candidate attribute information. For example, (A) Allowable imaging deviation / estimated imaging deviation, (B) Imaging sequence / imaging condition / assumed imaging time, (C) Ease of deformation of pattern serving as a standard of evaluation stability, (D) pattern (E) Processing method for evaluating measurement point / overlapping position, (F) Direction of overlapping position that can be evaluated, (G) Each pattern included in EP Manufacturing process in which the edge was generated, etc.
- the overlay position in the X direction or the Y direction can be evaluated as the direction of the overlay position that can be evaluated in the item (F), the overlay position in both the XY directions can be evaluated, and the overlay position in the A ° direction can be evaluated. Etc. For example, if the EP candidate includes only a pattern edge that changes in the X direction, the overlay position in the Y direction cannot be evaluated. This information can be obtained by analyzing the layout information in the EP candidate.
- a recipe that satisfies a measurement request (setting of an evaluation point, an imaging sequence, and a measurement point / processing method) can be automatically and rapidly performed.
- the present invention provides a method for efficiently and accurately inspecting the overlay of circuit patterns formed on a wafer using a scanning charged particle microscope in the design or manufacturing process of a semiconductor device. That is, between the patterns of the upper and lower layers (between the first pattern formed in the lower layer and the second pattern formed in the upper layer), or between the different patterns in DP (the first pattern formed by the first exposure) Provided is a method for closely estimating the misalignment between the pattern and the second pattern formed by the second exposure) within the wafer surface. By feeding back the evaluation result to correction parameters in semiconductor manufacturing apparatuses such as an exposure apparatus, pattern design data, and the like, it is expected that the exposure pattern overlay position accuracy is improved and the process margin is expanded.
- a scanning electron microscope which is one of the scanning charged particle microscopes, as an example.
- the scanning electron microscope include a scanning electron microscope for length measurement (Critical Dimension Scanning Electron Microscope: CD-SEM) and a scanning electron microscope for defect review (Defect Review Scanning Electron Microscope: DR-SEM).
- CD-SEM scanning electron microscope for length measurement
- DR-SEM scanning electron microscope for defect review
- the present invention is not limited to this, and can be applied to a scanning charged particle microscope such as a scanning ion microscope (Scanning Ion Microscope: SIM).
- the present invention is not limited to semiconductor devices, and can be applied to inspection of samples having patterns that require overlay evaluation.
- FIG. 2 shows an embodiment using an SEM as an example of a scanning charged particle microscope for imaging a sample to be evaluated.
- a secondary electron image (Secondary Electron: SE image) or a reflected electron image (Backscattered Electron: BSE image) of the sample.
- SE image Secondary Electron
- BSE image reflected electron image
- SE image and the BSE image are collectively referred to as an SEM image.
- the image acquired here is a top-down image obtained by irradiating the measurement object with an electron beam from the vertical direction, or a part of a tilt image obtained by irradiating the electron beam from an arbitrary tilted direction. Or include everything.
- the electron optical system 202 includes an electron gun 203 therein and generates an electron beam 204.
- the electron beam emitted from the electron gun 203 is narrowed down by the condenser lens 205, and then deflected so that the electron beam is focused and irradiated on the semiconductor wafer 201 which is a sample placed on the stage 221.
- the irradiation position and aperture of the electron beam are controlled by 206 and the objective lens 208.
- Secondary electrons and reflected electrons are emitted from the semiconductor wafer 201 irradiated with the electron beam, and the secondary electrons separated from the orbit of the irradiated electron beam by the ExB deflector 207 are detected by the secondary electron detector 209. .
- the reflected electrons are detected by the reflected electron detectors 210 and 211.
- the backscattered electron detectors 210 and 211 are installed in different directions.
- the secondary electrons and reflected electrons detected by the secondary electron detector 209 and the reflected electron detectors 210 and 211 are converted into digital signals by the A / D converters 212, 213, and 214, and input to the processing / control unit 215.
- the image data is stored in the image memory 217, and the CPU 216 performs image processing according to the purpose.
- FIG. 2 shows an embodiment having two detectors of reflected electron images, it is possible to eliminate the detector of reflected electron images, to reduce the number, to increase the number, and to change the detection direction. Is also possible.
- FIG. 3 shows a method of imaging the signal amount of electrons emitted from the semiconductor wafer 307 when the semiconductor wafer 307 is scanned and irradiated with an electron beam.
- the electron beam is scanned and irradiated in the x and y directions as 301 to 303 or 304 to 306. It is possible to change the scanning direction by changing the deflection direction of the electron beam.
- the locations on the semiconductor wafer irradiated with the electron beams 301 to 303 scanned in the x direction are denoted by G1 to G3, respectively.
- G4 to G6 locations on the semiconductor wafer irradiated with electron beams 304 to 306 scanned in the y direction are denoted by G4 to G6, respectively.
- the signal amounts of electrons emitted in G1 to G6 are the brightness values of the pixels H1 to H6 in the image 309 shown on the right of FIG. 3 (subscripts 1 to 6 in G and H correspond to each other).
- Reference numeral 308 denotes a coordinate system indicating the x and y directions on the image (referred to as an Ix-Iy coordinate system).
- the image frame 309 can be obtained by scanning the inside of the visual field with the electron beam.
- a high S / N image can be obtained by scanning the inside of the visual field several times with an electron beam in the same manner and averaging the obtained image frames.
- the number of addition frames can be set arbitrarily.
- a processing / control unit 215 in FIG. 2 is a computer system including a CPU 216 and an image memory 217, and images a region including a circuit pattern to be evaluated based on an imaging recipe as an evaluation pattern. Processing and control such as sending a control signal to the deflection control unit 220 or performing various image processing based on a measurement recipe for a captured image of an arbitrary evaluation pattern on the semiconductor wafer 201 is performed.
- the measurement recipe is a file that specifies an image processing algorithm and a processing parameter for performing evaluation such as pattern shape measurement and pattern superposition using a captured SEM image.
- the SEM is based on the measurement recipe.
- An evaluation result is obtained by processing the SEM image.
- the processing / control unit 215 is connected to a processing terminal 218 (provided with input / output means such as a display, a keyboard, and a mouse), and displays a GUI or the like on the GUI (accepts input from the user).
- a processing terminal 218 provided with input / output means such as a display, a keyboard, and a mouse
- GUI or the like displayed on the GUI (accepts input from the user).
- Reference numeral 221 denotes an XY stage, which moves the semiconductor wafer 201 and enables imaging of an arbitrary position of the semiconductor wafer. Changing the imaging position with the XY stage 221 is called stage shift, for example, changing the observation position by deflecting an electron beam with the deflector 206 is called image shift.
- the stage shift has a wide movable range but the positioning accuracy of the imaging position is low.
- the image shift has a property that the movable range is narrow but the imaging position positioning accuracy is high.
- the recipe generation unit 222 is connected to the processing terminal 225 and includes a GUI that displays the generated recipe to the user or receives settings related to imaging and recipe generation from the user.
- the processing / control unit 215 and the recipe generation unit 222 described above can transmit and receive information via the network 228.
- a database server 226 having a storage 227 is connected to the network, and (A) design data (mask design data (without / with optical proximity correction (OPC)), wafer transfer pattern design data ), (B) simulation pattern of actual pattern estimated from litho simulation etc.
- OPC optical proximity correction
- the imaging recipe is a file that specifies an SEM imaging sequence. That is, the coordinates of an imaging area (referred to as an evaluation point (EP)) to be imaged as an evaluation target and an imaging sequence for imaging the EP with high definition without positional deviation are designated. There may be a plurality of EPs on one wafer, and if the entire surface of the wafer is inspected, the EP will fill the wafer.
- FIG. 4A shows a flowchart of a typical imaging sequence for imaging an EP
- FIG. 4B shows imaging locations corresponding to the representative imaging sequence.
- the imaging sequence will be described with reference to FIGS. 4 (a) and 4 (b).
- a sample semiconductor wafer (201 in FIG. 2 and 416 in FIG. 4B) is mounted on the stage 221 of the SEM apparatus.
- a square frame represented by 417 to 420 drawn in the wafer 416 represents a chip
- 421 is an enlarged view of the chip 418.
- Reference numeral 425 is an enlarged view of a part of the chip 421 with the EP 433 as a center.
- step 402 the visual field of the optical microscope (not shown in FIG. 2) attached to the SEM is moved to the alignment pattern on the wafer specified in advance by stage shift, and the alignment pattern on the wafer is imaged with the optical microscope.
- An image (referred to as OM image) is obtained.
- the amount of wafer shift is calculated by matching matching data (template) in the alignment pattern prepared in advance with the OM image.
- FIG. 4B the imaging range of the alignment pattern is indicated by a thick frame 422.
- step 403 an SEM image is captured by irradiation with the electron beam 204, and alignment using the SEM image is performed.
- the field of view of the SEM (referred to as field-of-view (FOV)) is smaller than the FOV of the optical microscope, and depending on the amount of wafer displacement, there is a risk that the pattern to be imaged will be outside the FOV.
- FOV field-of-view
- step 404 the imaging position of the SEM is moved to the alignment pattern imaging autofocus pattern 423 to perform imaging, an autofocus adjustment parameter is obtained, and autofocus adjustment is performed based on the obtained parameter.
- step 405 the SEM imaging position is moved to the alignment pattern 424, and the matching data (template) in the alignment pattern 424 prepared in advance is matched with the SEM image, so that more accurate wafer displacement can be achieved. Calculate the quantity.
- FIG. 4B shows an example of the imaging positions of the optical microscope alignment pattern 422, SEM alignment pattern imaging autofocus pattern 423, and SEM alignment pattern 424. In selecting these imaging positions, it is necessary to consider whether a pattern suitable for alignment or autofocus is included.
- Alignment using the optical microscope and SEM in Steps 402 and 403 is performed at a plurality of locations on the wafer, and a large origin displacement of the wafer and rotation of the wafer are calculated based on the amount of displacement obtained at the plurality of locations (global alignment). .
- FIG. 4A alignment is performed at Na locations (step 406)
- FIG. 4B shows an example where alignment is performed at four locations of chips 417-420. Thereafter, when the visual field is moved to a desired coordinate, the movement is performed so as to cancel the origin deviation / rotation obtained here.
- step 407 more accurate positioning (addressing) and image quality adjustment are performed for each evaluation pattern (EP), and the EP is imaged.
- the addressing is performed to cancel a stage shift error that occurs when the visual field moves to each EP.
- the stage is first shifted to EP433. That is, the stage 221 is moved so that the vertical incident position of the electron beam 204 is the EP center.
- the vertical incident position of the electron beam is called a Move coordinate (hereinafter referred to as MP) and is indicated by a cross mark 426.
- MP Move coordinate
- a range 427 (dotted line frame) in which the visual field can be moved only by image shift without moving the stage is determined.
- the imaging position of the SEM is image-shifted to an addressing pattern imaging autofocus pattern 428 (hereinafter referred to as AF) and imaged to obtain parameters for autofocus adjustment, and autofocus adjustment is performed based on the obtained parameters. I do.
- the SEM imaging position is moved to an addressing pattern 429 (hereinafter referred to as AP), and imaging is performed.
- the stage shift is further performed. Calculate the error. In the subsequent image shift, the visual field is moved so as to cancel the calculated stage shift error.
- the SEM imaging position is image-shifted to the EP imaging AF 430, and an autofocus adjustment parameter is obtained, and autofocus adjustment is performed based on the obtained parameter.
- the SEM imaging position is image-shifted to an auto stigma pattern 431 (hereinafter referred to as AST) and imaged, an auto stigma adjustment parameter is obtained, and auto stigma adjustment is performed based on the obtained parameter.
- AST auto stigma pattern 431
- the auto stigma refers to correcting astigmatism so that the cross-sectional shape of the converged electron beam becomes a spot shape in order to obtain an image without distortion during SEM imaging.
- the SEM imaging position is image-shifted to an auto brightness & contrast pattern 432 (hereinafter referred to as ABCC) and imaged, and auto brightness & contrast adjustment parameters are obtained. Based on the obtained parameters, auto brightness & contrast parameters are obtained. Adjust the contrast.
- the auto-brightness & contrast refers to parameters such as the voltage value of the photomultiplier (photomultiplier tube) in the secondary electron detector 209 in order to obtain a clear image having an appropriate brightness value and contrast during EP imaging.
- the highest part and the lowest part of the image signal have a full contrast or a contrast close thereto. Since the visual field shift to the AP AF and the EP AP, AF, AST, ABCC is performed by image shift, it must be set within the image shiftable range 427.
- step 413 the imaging location is moved to EP by image shift, and imaging is performed.
- the wafer is taken out from the SEM apparatus in step 415.
- the adjustment points are generally set so that there is no overlap between the EP and the imaging area due to the problem of contamination of the sample due to electron beam irradiation (contamination). If the same region is imaged twice, the phenomenon that the image becomes dark or the line width of the pattern changes may appear more strongly in the second image due to contamination. Therefore, in order to maintain the pattern shape accuracy in the EP used for the evaluation of the evaluation pattern, various adjustments are performed using the pattern around the EP, and the EP is imaged with the adjusted parameters to minimize the irradiation of the electron beam to the EP. Keep it down.
- the imaging sequence the coordinates, size (field of view or imaging magnification) of various imaging patterns (EP, AP, AF, AST, ABCC), imaging order (field-of-view moving means (stage shift or image shift) to each imaging pattern )) And imaging conditions (probe current, acceleration voltage, electron beam scanning direction, etc.).
- the imaging sequence is specified by an imaging recipe.
- matching data template used for alignment and addressing is registered in the imaging recipe.
- matching algorithms image processing methods and image processing parameters
- the SEM images the EP based on the imaging recipe.
- Pattern overlay evaluation method 2.1 Overview uses a first pattern generated on a sample by a first manufacturing process and a first pattern generated on the sample by a second manufacturing process using an image obtained by imaging an evaluation point on the sample by an SEM.
- a method for evaluating an overlay position with a second pattern the step of estimating an imaging deviation allowed for evaluating the overlay position for one or a plurality of evaluation point candidates based on the layout information of the pattern; Determining one or a plurality of evaluation points from evaluation point candidates based on the allowable imaging deviation, determining an imaging sequence for imaging the selected evaluation point, and the imaging sequence
- the overlay position of the first pattern and the second pattern is evaluated from the image obtained by imaging the evaluation point according to It characterized by having a that step.
- the allowable imaging deviation is allowed on condition that the identification of the first pattern and the second pattern included in the evaluation point does not fail even if the imaging deviation occurs.
- the imaging deviation is estimated.
- the difference between the first pattern and the second pattern may be a difference in layers such as upper and lower layers, or a difference in multiple exposure in DP.
- the number of patterns for evaluating the overlay position may be two or more. For example, when the pattern of 3 layers (upper middle layer and lower layer) is seen in the captured image, the deviation between the first to third patterns can be evaluated, and when performing multiple exposure (triple patterning) as multiple exposure The deviation between the first to third patterns can be evaluated. Further, when not all patterns can be observed with one imaging, it is possible to perform overlay evaluation by imaging a plurality of times at different manufacturing process timings. In the following description, overlay evaluation between two patterns (first pattern and second pattern) will be described as an example.
- Figure 1 shows the overall processing flow of the present invention.
- process data / process parameters are input.
- pattern layout information for example, pattern design data described in the GDSII format may be used, or an image obtained by capturing a pattern using a scanning charged particle microscope or an optical microscope may be used.
- the design data includes (A) design data for masks (without / with optical proximity correction (Optical Proximity Correction) (OPC)), (B) design data for wafer transfer patterns, and (C) design data for the masks. Any of the simulation shapes of the actual pattern estimated from the design data by litho simulation or the like may be used.
- OPC optical Proximity Correction
- layout information includes the first pattern and the second pattern, and these may be managed by one data file or may be managed separately in different data files.
- EP selection conditions and device conditions can be input as one of the processing parameters (steps 103 and 104, respectively). Details of these inputs will be described later.
- EP candidates that can be evaluated for overlay are extracted.
- an EP candidate extraction range an arbitrary range where dense overlay evaluation is desired can be set, and all EPs for which overlay evaluation can be performed can be extracted from the range. Examples of the arbitrary range include all chips in the surface, a plurality of chips in an arbitrary combination, a partial range in the chip, a range extending between the chips, and the like.
- FIG. 5A shows an EP selection example for performing overlay evaluation.
- the first pattern formed by the first exposure is hatched with a diagonal line (for example, a round pattern of 501 or 513), and the second pattern formed by the second exposure is a white pattern ( For example, a round pattern 502 or 514 (a cross pattern 503) is used. That is, for the round pattern, the first pattern and the second pattern are alternately arranged.
- EP 505 is considered as an evaluation point for imaging using the SEM in order to evaluate the overlay of the first pattern and the second pattern (thick frame indicates the imaging range).
- the superimposed positional relationship 504 can be evaluated based on, for example, the first pattern 501 and the second pattern 502 in the captured image of the EP.
- an imaging deviation occurs. For this reason, it is necessary to set a region including a pattern that does not fail in evaluation even for imaging deviation, and for this purpose, imaging deviation (allowable) that is permitted in order to succeed in evaluating the overlay position in each EP candidate. It is necessary to estimate an imaging shift that can actually occur (referred to as an imaging shift) and to consider it when determining an EP. That is, an EP that satisfies allowable imaging deviation ⁇ estimated imaging deviation is selected. Further, at this time, the deviation of the exposure position of the pattern itself to be evaluated and the shape deformation of the pattern may be taken into consideration, and these pattern variations may be considered together.
- an EP that does not fail in the evaluation of the overlay position even for the assumed pattern variation is determined.
- the layout information of the pattern is used for the estimation of the allowable imaging deviation. This is because the allowable imaging deviation differs depending on the pattern shape and arrangement included in the EP.
- an estimation condition for the allowable imaging deviation (A) the first pattern with respect to the imaging deviation and the second pattern should not be specified; (B) the first pattern with respect to the imaging deviation; For example, the measurement site of the second pattern is included in the visual field.
- the first pattern and the second pattern may be similar in an image, and the condition (A) is important.
- the first pattern and the second pattern are different in appearance from the hatched circle and the white circle on the display, but in the actual SEM image, they may not be distinguished as similar patterns. For this reason, for example, if the pitch between the first pattern and the second pattern (510 in the x direction and 511 in the y direction) is P and an imaging deviation of EP occurs ⁇ P / 2, the first pattern in EP 505 It becomes difficult to specify the second pattern. Further, as shown in the figure, the maximum imaging deviation expected in EP is 508 in the x direction and 509 in the y direction. In this case, with respect to the set EP imaging position 505, the actual imaging position may become a dotted frame 512 due to imaging deviation.
- the patterns 513 and 514 are out of view. Therefore, when imaging deviation is taken into consideration when setting EP 505, it must be taken into consideration that the patterns 513 and 514 may not be used for overlay evaluation. As described above, it is necessary to determine the position and field of view (imaging range or imaging magnification) of the EP in consideration of imaging deviation.
- the imaging sequence In the estimation of the estimated imaging deviation, it is necessary to consider the imaging sequence in the scanning charged particle microscope. A supplementary description of the imaging sequence will be given here.
- a unique pattern called an addressing point (referred to as AP) is once imaged to estimate a stage error or the like, or an autofocus point (referred to as AF) is imaged to detect a charged particle beam. After adjusting the focus, image the EP. Therefore, for example, the imaging deviation changes depending on whether or not an appropriate AP exists.
- AP an addressing point
- AF autofocus point
- the imaging deviation changes depending on whether or not an appropriate AP exists.
- AP506 is set as the imaging sequence of EP505.
- the AP 506 captures the unique second pattern 503 in the field of view, and can estimate the stage shift error when moving to the AP 506 by stage shift. If the distance 507 between the EP 505 and the AP 506 is within the image shift movable range, the visual field shift to the EP can be performed by the image shift, and the visual field shift of the EP can be suppressed within the image shift error. However, if there is no unique pattern such as the pattern 503 in the vicinity of the EP 505, the imaging deviation cannot be reduced. Conversely, if the allowable imaging deviation in EP is larger than the stage shift error, it is not necessary to perform addressing in the imaging sequence (AP506 is not required).
- the imaging condition of the EP may be determined together (step 109 in FIG. 1).
- the imaging conditions include the EP field of view (imaging range or magnification), probe current, acceleration voltage, and charged particle beam scanning direction.
- the pattern may not be clearly observed on the image if the acceleration voltage is low. Therefore, when a lower layer pattern is included, it is conceivable to set a high acceleration voltage.
- the edge in the X direction can be sharply imaged by setting the scanning direction of the charged particle beam applied to the soot sample to the Y direction. Therefore, it is effective to set the scanning direction according to the pattern direction in the EP.
- the measurement points and processing method in EP may be determined together (step 110 in FIG. 1).
- a measurement point is a part of a pattern in which a position is measured by image processing in order to quantitatively evaluate an overlay position in EP
- a processing method is an image processing method that measures a position.
- all the pattern edges in the EP may be used as measurement points, the left and right edges of the patterns 515 and 516 in the EP may be used, An edge may be used, or the right edge of the pattern 515 and the left edge of the pattern 516 may be used. Further, in consideration of the fact that the image may be distorted around the image, an edge only near the center of the image may be used.
- processing methods there are an image processing method and a method of utilizing design data. Details will be described later. Such measurement points and processing methods can be determined for each EP.
- FIG. 5 (b) shows another example of EP selection for overlay evaluation. Similar to FIG. 5A, the first pattern is represented by a hatched pattern (for example, 515), and the second pattern is represented by a white pattern (for example, 516 or 517). In this example, since the first pattern and the second pattern are alternately arranged at a pitch 521, it is considered that 519 is imaged as EP and the positional relationship 518 between the patterns 515 and 516 is evaluated. However, in EP519, since the pattern extends long in the y direction and there is only a pattern edge that changes in the x direction, only overlay displacement in the x direction can be evaluated.
- overlay evaluation in the xy direction can be approximately performed.
- the pattern does not change in the layout data with respect to the y direction in the EP 519 and its surroundings, the overlay evaluation in the x direction in the EP can be performed even if a slight imaging deviation occurs in the y direction. Therefore, AP520 is set as the imaging sequence of EP519. The AP 520 captures the second pattern 517 unique in the x direction and can only estimate the stage shift error in the x direction. Absent.
- the pattern that can be addressed in both xy directions is near the EP, the pattern is It is effective to set the AP included in the field of view.
- an EP is determined from the EP candidates extracted at step 105 in FIG. 1 (step 111 in FIG. 1).
- the EP group determined in step 111 may be the same as the EP candidate group extracted in step 105, or the EP candidate group is presented to the user, and the user selects or finely modifies it. EP may be used.
- the determined EP is registered in the recipe (step 112 in FIG. 1).
- the imaging sequence for the EP (determined in step 107), the imaging condition (determined in step 109), and the measurement point / processing method (step 110) can also be registered in the recipe.
- a plurality of EPs are sequentially imaged and measured, and overlay deviation is evaluated (step 113). In the measurement, the positional relationship between the first pattern and the second pattern can be measured, and for example, the amount of deviation from the design value can be evaluated.
- the present invention makes it easy to deform each part of a pattern from layout information as an evaluation point selection criterion in the step of determining an evaluation point (step 105 or step 111 in FIG. 1).
- the evaluation point is determined based on the ease of deformation of each part.
- the robustness of overlay evaluation with respect to pattern deformation can be considered. Even if a pattern suitable for measurement is included in the EP as judged from the pattern shape in the design data, in practice, it may be difficult to perform stable overlay evaluation due to pattern deformation. Possible types of pattern deformation include pattern width thickening / thinning, line end retraction, corner rounding, pattern shift (parallel movement), and the like. Therefore, based on the ease of deformation of each part of the pattern, the EP is determined so as to include a part that is difficult to be deformed so that stable measurement can be performed, or a part that does not fail even if it is deformed.
- FIG. 6A and 6B show the shape divergence between the design data, which is one of the layout information, and the pattern actually generated on the wafer.
- FIG. 6A shows design data
- EP 601 includes a lower layer pattern 602 and an upper layer pattern 603.
- FIG. 6B is a captured image of an actual pattern corresponding to FIG. 6A, and an actual pattern 606 corresponding to the lower layer pattern 602 and an actual pattern corresponding to the upper layer pattern 603 in EP 605 obtained by imaging a location corresponding to EP 601.
- a pattern 607 is included. In actual patterns, the corners of the pattern are rounded, making measurement at the same location difficult.
- the layout information by using the simulation pattern of the actual pattern estimated from the mask design data by litho simulation or the like, it is possible to determine the EP using a pattern closer to the actual pattern shape 606,607. Conceivable. However, even in such a case, a prediction error of the simulation may occur, so it is effective to consider the shape deformation amount expected as described above.
- FIGS. 6C and 6D are other examples showing the shape divergence between the design data and the actual pattern.
- FIG. 6C depicts design data
- EP 609 includes a lower layer pattern 610 and an upper layer pattern 611.
- FIG. 6D is a captured image of an actual pattern corresponding to FIG. 6C, and an actual pattern 613 corresponding to the lower layer pattern 610 and an actual pattern corresponding to the upper layer pattern 611 in the EP 612 where the location corresponding to the EP 609 is captured.
- a pattern 614 is included.
- the upper layer pattern 614 is largely deformed in the actual pattern.
- the part bent in the crank shape in the design data is dull in the actual pattern due to the optical proximity effect at the time of exposure.
- the end of the pattern is rounded in the actual pattern, and the position is also retracted. For this reason, there is no long linear pattern suitable for measurement, so it is not suitable for stable measurement.
- Such deformation can be predicted based on the design data, and the region 609 can not be extracted as an EP candidate or can be an EP candidate with a low evaluation value.
- both the left and right edges of the pattern are evaluated when evaluating the overlapping position in the x direction as an evaluation reference for selecting an evaluation point in the step of determining the evaluation point (step 105 or step 111 in FIG. 1).
- both the upper and lower edges of the pattern are included in the evaluation point for the first pattern and the second pattern, respectively.
- FIG. 7A shows an example in which an area 703 is set as an EP for performing overlay evaluation of the lower layer pattern 701 and the upper layer pattern 702 (the patterns 701 and 702 have a pattern shape on the captured image).
- the left end of the lower layer pattern 701 is called a left edge (edge surrounded by a dotted frame 721), and the right end is called a right edge (edge surrounded by a dotted frame 722).
- the left end is called a left edge (edge surrounded by a dotted frame 723), and the right end is called a right edge (edge surrounded by a dotted frame 724).
- the overlay of the upper and lower layers can be evaluated by measuring the distance 704 between the left edge of the lower layer pattern and the left edge of the upper layer pattern.
- FIG. 7B shows an example in which an area 707 is set as an EP for performing overlay evaluation of the lower layer pattern 705 and the upper layer pattern 706 (the patterns 705 and 706 are pattern shapes on the captured image).
- the pattern setting data and the set EP position are the same.
- the upper layer pattern 706 is thinner than the upper layer pattern 702 due to a change in exposure conditions or the like.
- FIG. 7D is the same pattern as FIG. 7B, and the upper layer pattern is thin.
- the EP is arranged at the same position 715 as EP 709 in FIG. 7C and the upper and lower layer pattern widths 718 and 716, their midpoints 719 and 717, and the distance 720 between the midpoints are obtained, the midpoint is obtained.
- the distance 720 between is not different from the distance 714. That is, by setting the EP and the measurement point as shown in FIGS. 7C and 7D, the positional relationship between the upper and lower layers can be obtained separately from the pattern thickening / thinning.
- FIG. 7D is the same pattern as FIG. 7B, and the upper layer pattern is thin.
- the effect of including the opposite edge in the EP with reference to FIG. 7 is a processing method for detecting the pattern edge by image processing and evaluating the overlay error (this processing method belongs to (Processing Method B) described later).
- this processing method belongs to (Processing Method B) described later.
- the same effect can be expected in a processing method (a processing method belonging to (Processing Method A), which will be described later) that evaluates the overlay displacement by comparing the eyelid design data with the captured image.
- the position due to the pattern thickening / thinning is obtained by aligning the design data and the captured image so that the centers of the opposite edges of the two match.
- the alignment error can be reduced.
- the upper and lower layer patterns have been described as examples of the first and second patterns. However, it is effective to consider the pattern shape deformation in the first and second patterns formed by DP as well. is there.
- FIGS. 5C and 5D can be considered.
- the figure drawn on the left and right of FIG. 5 (c) uses the EP 505 selected in FIG. 5 (a) to evaluate the overlay deviation between the first pattern and the second pattern using the patterns 501 and 502. Two types of measurement methods are shown.
- the overlay deviation is evaluated by measuring the width 522 between the pattern edges of the patterns 501 and 502. As described above, the width 522 corresponds to the pattern thickness / thinning. However, the value changes greatly.
- the overlay deviation is evaluated by measuring the width 525 between the center 523 of the first pattern 501 and the center 524 of the second pattern 502.
- the width 525 changes little with respect to the pattern thickness.
- a pattern center detection method it is conceivable to detect the edge of the pattern by image processing and obtain the pattern center from the edge. However, the edge is not clear in the captured image, and it may be difficult to detect the edge. In that case, the pattern center may be directly obtained without edge detection by calculating the center of gravity of the brightness value near the pattern.
- the diagram drawn on the left and right of FIG. 5 (d) uses EP 519 selected in FIG. 5 (b) to evaluate the misalignment between the first pattern and the second pattern using patterns 515 and 516. Two types of measurement methods are shown.
- the misalignment is attempted to be evaluated by measuring the width 528 between the edges of the patterns 515 and 516.
- the misalignment is evaluated by measuring the width 533 between the center 530 of the width 529 of the first pattern 515 and the center 532 of the width 531 of the second pattern 516.
- the width 533 changes little with respect to the pattern thickness.
- the EP can be determined in consideration of the management of critical patterns with respect to device characteristics. For example, an area including a pattern that is determined to easily cause a pattern shift based on a litho simulation or the like mounted on an EDA tool may be preferentially selected as an EP.
- an EP an area including a pattern that is determined to easily cause a pattern shift based on a litho simulation or the like mounted on an EDA tool may be preferentially selected as an EP.
- the position of the contact hole and the wiring pattern that electrically connect the upper and lower layers of the stacked layer, or the position of the gate wiring and the active layer in the transistor are shifted, this is directly connected to the change in device characteristics. May be preferentially selected as EP.
- the present invention is a step of determining an evaluation point when the first pattern is a lower layer pattern and the second pattern is an upper layer pattern with respect to the laminated layer on the wafer ( In step 105 or step 111) in FIG. 1, hiding of the lower layer pattern by the upper layer pattern is estimated from the layout information, and the evaluation point is determined in consideration of the hiding.
- pattern hiding is estimated based on the layout information and taken into consideration in EP selection.
- FIGS. 8A to 8C show patterns at the same location on the wafer drawn by layering or by superposing upper and lower layers.
- FIG. 8A shows lower layer patterns 802, 803 and FIG. 8 (b) shows an upper layer pattern 805, and FIG. 8 (c) shows upper and lower layer patterns superimposed on each other.
- FIG. 8A there are four pattern edges extending in the vertical direction in the dotted frame 804, but the pattern in the captured image is actually a dotted frame as shown in FIG. Edges corresponding to the edges in 804 are not observed and cannot be used for overlay evaluation. Thus, it is necessary to determine EP, measurement point, imaging sequence, etc. in consideration of hiding the lower layer pattern by the upper layer pattern.
- the actual pattern may overlap the upper layer pattern due to the displacement of the pattern transfer position. Therefore, it is effective to evaluate the easiness of hiding the pattern by considering the distance between the upper layer pattern and the lower layer pattern, and to consider it in EP selection.
- FIG. 8D shows design data in EP 806 arranged at a certain coordinate, and an upper layer pattern 807 and a lower layer pattern 808 exist.
- FIG. 8E shows an actual pattern at the same location as FIG. 8D, and there is an actual pattern 810 corresponding to the upper layer pattern 807 in the design data and an actual pattern 811 corresponding to the lower layer pattern 808 in the design data.
- the left edge of the lower layer pattern (edge surrounded by a dotted frame 809) that can be observed on the design data is shown in FIG. In e), it is hidden in the upper layer pattern and cannot be observed.
- Such a situation is not limited to the expansion of the pattern, but can also occur due to a shift or deformation of the pattern.
- EP 806 is selected on the assumption that an edge surrounded by a dotted line frame 809 is used for measurement, it is highly likely that overlay evaluation using the EP will fail. In this way, it is possible to determine the EP with high accuracy by simply determining whether the pattern can be observed in consideration of the pattern deformation as well as whether the pattern can be observed on the design data.
- the pattern observability depends on the degree of pattern deformation, and the degree of pattern deformation may change, it may be difficult to determine whether the pattern is observable from only design data.
- the easiness of hiding a pattern based on the distance between patterns can be calculated as EP attribute information and used for prioritizing EP selection.
- a plurality of evaluation points are considered in consideration of the in-plane distribution of the evaluation point on the sample.
- EP can be determined. Specifically, (A) a plurality of regions are set on the sample, and at least one evaluation point is determined from each of the regions. Alternatively, (B) a condition regarding a distance between any two evaluation points is given, and a plurality of evaluation points are determined so as to satisfy the condition.
- FIG. 9A is an enlarged view of a part of the wafer surface.
- the chips are arranged in a lattice shape, and the chip 901 is arranged in the center.
- four dedicated patterns for overlay evaluation are arranged in a scribe area near the four corners of the chip (for example, a cross mark 902).
- the arrangement of the chip and the dedicated pattern is common in FIGS. 9A to 9D (chips 901, 905, 914, 919, dedicated patterns 902, 906, 915, 920).
- the estimated amount of deviation is sparse, and an accurate in-plane tendency cannot be captured. Therefore, in this example, overlay evaluation is performed closely even in the chip.
- a plurality of regions within a certain range where each EP can be arranged are set.
- the EP may be set anywhere in the area, each EP that can be evaluated for overlaying is selected from each area in view of the above EP candidate extraction method.
- the selected EP is displayed with a thick frame.
- the EP 904 is selected from the area 903.
- the regions where the respective EPs can be arranged are arranged in a plane at regular intervals, for example, EPs that can be superposed and evaluated without significant deviation in distribution can be arranged.
- the number of EPs extracted from the area is one, but a plurality of EPs can be extracted from one area.
- 4 ⁇ 4 16 areas where EPs can be arranged are arranged, but the number of areas, the width of the areas, and the width between the areas can be arbitrarily set. For example, when it is desired to perform a more precise overlay evaluation, the width of the area may be reduced and the number of areas may be increased. Further, the arrangement of the regions is not limited to the lattice shape, and the arrangement can be performed with other arbitrary degrees of freedom. Further, in this example, the range in which the area is arranged is in the chip 901. However, it is possible to set an arbitrary range where dense overlay evaluation is desired and arrange the area in the range.
- Examples of the arbitrary range include all chips in the surface, a plurality of chips in an arbitrary combination, a partial range in the chip, a range extending between the chips, and the like.
- the range in which the overlay evaluation is to be performed for one chip it is conceivable to set the range in which the overlay evaluation is to be performed for one chip to several chips in one shot within the region exposed by one exposure irradiation.
- a combination of an overlay deviation between the first pattern and the second pattern that can be evaluated in both xy directions, an evaluation that can be evaluated only in the x direction, and a combination that can be evaluated only in the y direction is combined.
- 4 ⁇ 4 16 regions (for example, dotted line frames 907, 909, 912) where EPs can be arranged are arranged in a lattice pattern, and EPs are arranged from the respective regions. Is an example of determining.
- EPs determined from within each area are indicated by a thick frame, but EPs represented by white squares (for example, 908) indicate that they can evaluate overlay displacement in both xy directions (referred to as EPXY).
- An EP for example, 910, 913) in which “x” is written in the square indicates that it is an EP that can evaluate only the overlay displacement in the x direction (referred to as EPX. For example, EP 519 in FIG. 5B).
- EPX for example, EP 519 in FIG. 5B.
- An EP (for example, 911) in which “y” is written in a square indicates that it is an EP that can evaluate only the overlay deviation in the y direction (referred to as EPY).
- EPX and EPY can be added as EP options.
- EPX 910 and EPY 911 are selected close to each other as in the region 909 and the deviation amounts estimated from both EPs are merged, the overlay deviation in the xy direction can be evaluated approximately. Even when only the EPX 913 can be selected as in the area 912, the overlay evaluation is helpful.
- EPXY, EPX, and EPY are shown here as EP variations, other EPs that allow evaluation of an overlay position in an oblique direction, EP that can evaluate pattern rotation, and variations in pattern size ( Variations such as EP that can evaluate (transfer magnification) can be mentioned.
- FIG. 9C is another embodiment of the EP determination method considering the in-plane distribution of EP, and the condition regarding the distance between any two EPs, for example, the distance between the EPs falls within Aum to Bum.
- an EP candidate that satisfies the same condition and that can be subjected to overlay evaluation, it is possible to eliminate both distribution bias and overlay evaluation accuracy.
- a thick frame indicates EP.
- a distance between EP 916 and EP 917 is given by 918.
- An arbitrary range where dense overlay evaluation is desired is set (chip 914 in the figure), and the EP is determined so that the distance between arbitrary EPs satisfies the above condition.
- FIG. 9D shows an embodiment in which variations of EPXY, EPX, and EPY are considered with respect to FIG. 9C (the notation in EPXY, EPX, and EPY is the same as FIG. 9B). Is).
- FIG. 9B there is a case where EPXY does not exist in a region where an EP is to be arranged.
- FIG. 9D considering the distance from surrounding EPs (for example, the distance 924 from EP 923), it is assumed that one EP is set per dotted frame 926, but there is no EPXY in the dotted frame. In this case, if EPX or EPY exists, it may be selected as EP, or if both EPX and EPY exist, both may be selected.
- the figure shows an example in which both EPX921 and EPY922 can be selected.
- the overlay displacement in the xy direction can be estimated approximately, so both may be arranged nearby. Therefore, as a condition regarding the distance between EPs, a condition regarding a distance between EPX and EPY (for example, 925) and a condition regarding a distance between normal EPs (for example, 924) can be given separately (distance 925 ⁇ distance 924 in this example). .
- step 105 or step 111 in FIG. 1 at least one evaluation point is specified in advance and the specified evaluation is performed. It is determined by searching another evaluation point including a pattern similar to the pattern included in the evaluation point based on the point.
- the EP can be selected from various viewpoints depending on the intention of the user who is the evaluator. It also varies depending on the type and process of the semiconductor device. However, since overlay evaluation is performed at a plurality of locations, it is not easy for the user to register a large amount of EPs in a recipe. Therefore, a mechanism is provided that allows a user to input a desired EP, and an EP similar to the input EP is automatically extracted from the layout information as an EP candidate. As a result, the user can save time and effort for selecting a large amount of EPs only by inputting a few EPs, and can quickly respond to different EP selection criteria for each user, product type, and process.
- FIG. 10A shows an EP 1001 which is an example of designation of an EP by the user.
- the EP there is a pattern in which the first pattern formed by the first exposure is hatched (for example, 1002), and a second pattern formed by the second exposure is in the form of a white pattern (for example, 1003).
- This designation may be performed on the layout data or may be designated by an image.
- FIG. 10B shows the result of extracting EP candidates similar to the designated EP from the layout data with EP 1001 as an input.
- the first pattern is displayed as a hatched pattern (for example, 1004, 1012)
- the second pattern is displayed as a white pattern (for example, 1005, 1006, 1013).
- the range for extracting similar EP candidates can be arbitrarily set.
- EPs 1007 and 1008 similar to the designated EP 1001 are extracted.
- the similar EP 1007 can be excluded from extraction candidates, and the EP extraction accuracy can be improved.
- the number of similar EPs finally extracted is 1008, but in the present invention, a plurality of similar EPs existing within the range for extracting EP candidates are all extracted. , Can be presented to the user.
- the user can specify all of a plurality of EPs.
- whether or not the user-specified EP is an EP suitable for overlay evaluation is the viewpoint of the EP selection criterion described with reference to FIGS. 5 to 9 and the viewpoint of the measurement point / processing method described later with reference to FIG.
- processing such as slightly shifting the user-specified EP position to a position more suitable for overlay evaluation or changing the size of the EP a little can be performed.
- the user only has to specify the approximate EP position, and the accurate position and size are automatically optimized, so that labor can be saved.
- EP 703 in FIG. 7A when EP 703 in FIG. 7A is given as the user-specified EP position, the EP can be moved to the position of EP 709 in FIG. 7C where higher overlay accuracy can be expected.
- step 105 or step 111 in FIG. 1 the present invention obtains as an attribute information which manufacturing process is used for each pattern edge, based on the attribute information.
- An evaluation point is determined on the condition that the edge generated by the first manufacturing process and the edge generated by the second manufacturing process are included in the field of view. This feature will be supplemented.
- the first pattern formed on the lower layer by the first exposure is a hatched pattern (1901, 1902), and the second exposure (second manufacturing process).
- the second pattern formed on the upper layer is drawn as a white pattern (1903a to 1905a, 1903b to 1905b) (however, as will be described later, the patterns 1903a to 1905a and 1903b to 1905b are strictly Produced by manufacturing process and cutting process).
- the pattern generation process is shown in FIGS. 19 (a) to 19 (c).
- first patterns 1901 and 1902 are generated by the first exposure.
- FIG. 19B second patterns 1903 to 1905 are generated by the second exposure.
- FIG. 19A first patterns 1901 and 1902 are generated by the first exposure.
- the second pattern existing in the region 1906 is removed by a process called a cutting process.
- the cutting process may remove the second pattern in the region 1906 by exposing the region 1906 as an exposure pattern, or irradiate the region 1906 with an electron beam by direct drawing of the electron beam.
- the second pattern may be removed.
- the distance between the upper and lower layer patterns is evaluated by subtracting the design value of the distance (widths 1911 and 1910 correspond to the widths 712 and 710, respectively, in the measurement example of FIG.
- the shift obtained from the widths 1911 and 1910 is not the overlay shift between the first and second patterns.
- the first pattern and the cutting process pattern will be misaligned.
- manufacturing process information is given as attribute information for each edge, and a combination of measurement target edges is determined based on the attribute information.
- FIG. 19E shows an edge displayed for each attribute information.
- Edges represented by dotted lines typified by edge 1907 are edges generated by the first manufacturing process
- edges represented by thin solid lines typified by edge 1908 are edges and edges generated by the second manufacturing process.
- An edge indicated by a thick solid line represented by 1909 indicates an edge generated by the cutting process.
- the attribute information is characterized in that it is given in units of edges (line segments), not in units of closed figures of the pattern. Based on the attribute information, it can be determined whether or not an edge used for measurement is an edge generated by the process to be evaluated.
- the measurement shown in FIG. 19G may be performed in order to evaluate the overlay deviation between the first and second patterns.
- the left edge of the upper layer pattern 1904a (having attribute information generated by the second manufacturing process according to FIG. 19E) and the right edge of the upper layer pattern 1904b (second according to FIG. 19E).
- the left edge of the lower layer pattern 1901 (having attribute information generated by the first manufacturing process according to FIG. 19 (e)).
- the right edge of the lower layer pattern 1902 (having attribute information generated by the second manufacturing process according to FIG. 19E), the distance between the middle point of the width 1912 and the distance between the first and second patterns Deviation can be evaluated.
- the deviation between the second pattern and the cutting process pattern it is understood from the attribute information that, for example, the measurement shown in FIG.
- the left edge of the upper layer pattern 1904a (having attribute information generated by the second manufacturing process according to FIG. 19E) and the right edge of the upper layer pattern 1904b (second according to FIG. 19E).
- the attribute information generated by the manufacturing process and the right edge of the upper layer pattern 1904a (having attribute information generated by the Cutting process according to FIG. 19E) and the upper layer pattern
- the deviation between the second pattern and the cutting process pattern can be evaluated from the distance between the left edge of 1904b (having attribute information generated by the cutting process according to FIG. 19 (e)) and the midpoint of the width 1914.
- the intent design data is generated based on the design data for each process shown in c) and the layer information for each process and information on whether or not it is a cutting process. Attribute information is obtained from the intent design data, and an EP or a measurement point in the EP is determined based on the intent design data and the attribute information. Conversely, if intent design data exists, but design data for each process cannot be obtained, attribute information is assigned to the intent design data based on layer information and cutting process information for each process. It is characterized by determining an EP or a measurement point in the EP.
- the determination of the EP and the measurement point in the EP using the attribute information is not limited to the evaluation of the overlay error between layers described with reference to FIG. 19, but by a plurality of processes such as DP and SADP (Self-Aligned Double Patterning). This is also effective when evaluating the deviation between the plurality of processes between patterns formed in the same layer.
- DP and SADP Self-Aligned Double Patterning
- This is also effective when evaluating the deviation between the plurality of processes between patterns formed in the same layer.
- determination of an EP using attribute information in SADP and measurement points in the EP will be described with reference to FIG.
- FIG. 20A patterns 2001 to 2004 are formed by DP in the manner described in the background art on the upper surface of the base 2006 and the hard mask layer 2005.
- first patterns 2001 and 2003 represented by hatched patterns are first generated, and then second patterns 2002 and 2004 represented by white patterns are generated in the gaps of the first pattern.
- etching is performed as shown in FIG. 20 (c) so that the sidewalls of the patterns 2001 to 2004 are called side wall spacers. Patterns 2007a to 2007h are formed.
- the hard mask layer 2005 is etched using the sidewall spacers 2007a to 2007h as a mask, thereby forming the patterns 2005a to 2005h as shown in FIG. 20 (e).
- FIGS. 20A and 20E Drawings of FIGS. 20A and 20E from the top surface direction (z direction) of the wafer are the upper and lower views in FIG. Below FIG. 20 (f), there is drawn a state in which eight patterns 2005a to 2005h corresponding to FIG. 20 (e) are arranged side by side. I do not know which pattern distance to measure in order to measure the deviation between the first and second patterns. Therefore, the attribute information regarding the manufacturing process described with reference to FIG. 19 is also considered in this example. On FIG.
- the first pattern 2001, 2003 and the second pattern 2002, 2004 are drawn so that the positions in the x direction correspond to the patterns 2005a to 2005h.
- the pattern 2005a is a pattern that shifts depending on the left edge position of the first pattern 2001. Therefore, the pattern 2005a is not a pattern directly generated by the manufacturing process in which the left edge of the first pattern 2001 is generated, but is a pattern whose generation position depends on the manufacturing process in which the first pattern 2001 is generated.
- the pattern 2005b is a pattern whose generation position depends on the manufacturing process in which the right edge of the first pattern 2001 is generated.
- the pattern 2005c is a pattern whose generation position depends on the manufacturing process in which the second pattern 2002 is generated, and the pattern 2005d has a generation position depending on the manufacturing process in which the right edge of the second pattern 2002 is generated.
- Pattern. Taking such attribute information into account, for example, the midpoint of the width 2008 between the right edge of the pattern 2005b and the left edge of the pattern 2005e (indicated by an x on the arrow indicating the width 2008), the left edge of the pattern 2005c, and the pattern It can be seen that the deviation in the x direction between the first and second patterns can be evaluated from the distance from the midpoint of the width 2009 to the right edge of 2005d (indicated by an x on the arrow indicating the width 2009).
- the midpoint of the width 2009 is also shifted to the right with respect to the midpoint of the width 2008.
- the amount of deviation can be obtained by subtracting the design value of the distance between the midpoints from the distance between the midpoints on the image.
- the distance between the midpoint of the width 2011 and the midpoint of the width 2010 shown in FIG. 20 (f) the distance between the midpoint of the width 2012 and the midpoint of the width 2013, or the midpoint and the width of the width 2014
- FIG. 20 (g) shows attribute information of each edge of the patterns 2005a to 2005h.
- the ID of the attribute information is indicated by an alphabet in a circle drawn on each edge (in this example, there are eight types of attributes A to D and a to d).
- the attribute of the left edge of the sidewall spacer generated on the side wall of the left edge of the pattern generated by the first manufacturing process represented by 2016 is generated by the first manufacturing process represented by A and 2017.
- the attribute of the right edge of the sidewall spacer generated on the side wall of the left edge of the pattern is B, and the attribute of the sidewall spacer generated on the side wall of the right edge of the pattern generated by the first manufacturing process represented by B, 2018 is shown.
- the attribute of the right edge is a
- the attribute of the left edge of the sidewall spacer generated on the side wall of the right edge of the pattern generated by the first manufacturing process represented by 2019 is b.
- the attributes of the side wall spacer generated on the side wall of the pattern generated by the second manufacturing process are set to C, D, c, and d according to the positions as shown in the figure.
- the attribute information of each edge is not only information on the manufacturing process that directly generates the edge, but also information on other manufacturing processes that affect the position of the edge, and patterns generated by the manufacturing process with the edge. (The left edge of the sidewall spacer generated to the left of the second pattern, etc.). From such attribute information, the following rule can be derived for a combination of edges capable of evaluating the deviation between the first and second patterns. First, pair edges with the same alphabet and uppercase and lowercase attributes, and consider the midpoint. For example, the midpoint of the width between the edge of attribute A and the edge of attribute a is called midpoint Aa. The deviation between the first and second patterns can be obtained from the distance between the midpoint Aa or midpoint BB and the midpoint Cc or midpoint Dd.
- (overlapping deviation of the second pattern with respect to the first pattern) (coordinate of the midpoint Cc or the coordinate of the midpoint Dd) ⁇ (coordinate of the midpoint Aa or midpoint B -b coordinate)-(design value of distance between midpoints).
- All the measurement points shown in FIG. 20 (f) satisfy this condition. For example, when measuring the deviation from the distance between the midpoint of the width 2008 and the midpoint of the width 2009, the midpoint Aa and the midpoint are measured. The deviation is measured from the distance from the point C-c. In this way, all combinations of edges that can be measured for deviation can be obtained by using attribute information.
- design data is used as layout information
- design data (intent design data) of final patterns 2005a to 2005h generated at the time of imaging depicted in FIG. Generate intent design data based on the patterns 2001-2004, which are the design data of the previous process drawn on FIG. 20 (f), and the manufacturing process information drawn on FIGS. 20 (a)-(e). It is characterized by doing. Attribute information is obtained from the intent design data, and an EP or a measurement point in the EP is determined based on the intent design data and the attribute information. Conversely, if intent design data exists, but design data for each process cannot be obtained, attribute information is added to the intent design data based on the information of each manufacturing process, and measurement points in EP and EP It is characterized by determining.
- step 105 or step 111 in FIG. 1 when evaluating the overlapping position in the x direction, at least one of the left and right edges of the first pattern and the first pattern are included in the first evaluation point.
- the first and second edges include a left or right edge of the second pattern, and a second evaluation point includes the left or right edge of the first pattern and the left or right edge of the second pattern.
- the evaluation point is determined, and overlay deviation is evaluated using the first and second evaluation points.
- the direction of the pattern included in the first evaluation point and the direction of the pattern edge included in the second evaluation point are opposite to each other in the first and second patterns.
- the first evaluation point includes at least one of the upper and lower edges of the first pattern and the upper and lower edges of the second pattern, and the second evaluation point.
- the first and second evaluation points are determined so that either the upper or lower edge of the first pattern and the upper or lower edge of the second pattern are included in the point, and the first and second evaluation points are determined. Is used to evaluate the overlay deviation.
- the direction of the pattern edge included in the first evaluation point and the direction of the pattern edge included in the second evaluation point are upside down in the first and second patterns, respectively.
- This feature will be supplemented.
- overlay evaluation is performed using a normal circuit pattern instead of a dedicated pattern for overlay evaluation, whether or not there is an EP including a pattern suitable for overlay evaluation depends on the pattern layout and is always desired. Does not necessarily exist. Therefore, when evaluating the in-plane distribution of overlay deviation using an actual pattern, it becomes a problem how many EPs can be extracted without deviation, and this processing is effective for the above problem. As described above with reference to FIG.
- An EP in which “y” is written in a square represents an EP (referred to as EPY, which corresponds to EP 911 in FIG. 9B) that can evaluate only the overlay deviation in the y direction.
- FIG.21 shows the enlarged view of the area
- EPa and EPb can be set as two EPs that do not exist in the figure or can evaluate the overlay deviation in the Y direction as two EPs that can evaluate the overlay deviation in the Y direction as well.
- the edge group necessary for the measurement is combined with the first as described above. It was found that it is necessary to take an image with the EP of the second and the second EP.
- first and second EP examples satisfying the above-described combinations.
- the first patterns 2109 and 2111 (displayed as hatched patterns) existing in the lower layer and the second patterns 2110 and 2112 (displayed as white patterns) existing in the upper layer
- the left edge of the first pattern 2109 and the second edge of the second pattern The left edge of the pattern 2110 is included.
- the second EP must include either the left or right edge of the first pattern and the left or right edge of the second pattern.
- the right edge of the first pattern 2111 and the second edge The right edge of the pattern 2112 is included.
- the direction of the pattern included in the first EP and the direction of the pattern included in the second EP need to be reversed in the first and second patterns. If the direction of the pattern is defined as the direction from the inside to the outside of the pattern, in this example, the left edge of the first pattern 2109 and the left edge of the second pattern 2110 that are measurement target edges of the first EP are both in the right direction, The right edge of the first pattern 2111 and the right edge of the second pattern 2112 that are the measurement target edges of the second EP are both in the right direction, and satisfy the condition that the directions are opposite for the first and second patterns, respectively. Yes.
- the difference between the first and second patterns can be evaluated by subtracting the design value of the distance between the midpoints from the distance between the first and second patterns. In this example, the design value of the distance between the midpoints is 0.
- FIG. 21 (c) shows an example of actual imaging positions, but the actual imaging positions of EPXa and EPXb displayed in dotted line frames with respect to the imaging positions 2106 and 2107 at the time of setting of EPXa and EPXb displayed in bold line frames. 2119, 2120 are misaligned.
- the imaging position deviation does not directly affect the measurement value of overlay deviation.
- the overlay deviation can be obtained correctly. Further, the overlay deviation obtained in this way is hardly affected by the increase / decrease of the pattern width for the same reason as described with reference to FIG. However, this is a case where the deformations of the patterns 2110 and 2112 (or the deformations of the patterns 2109 and 2111) occur to the same extent (these patterns including the edges to be measured are called measurement target patterns). For example, even if the overlay deviation does not occur, if the measurement target pattern 2110 is thicker than the measurement target pattern 2112, the overlay deviation occurs in the calculation.
- the shape of the measurement target pattern and the shape of the surrounding pattern of each measurement target pattern Must be similar between the paired target patterns, and must be taken into account when setting the EP.
- the reason why the similarity of the shape of the surrounding pattern is also considered is that the shape of the surrounding pattern may affect the shape of the measurement target pattern due to the optical proximity effect at the time of pattern exposure.
- the manufacturing conditions and the like must be similar between the pair of measurement target patterns.
- the overlay deviation generated in the paired measurement target pattern must be approximately the same. Considering this point, it is necessary that the measurement target patterns to be paired are arranged close to some extent, and for that purpose, the first and second EPs need to be arranged close to each other.
- a constraint condition can be set for the distance between EPs (distance 2108 in FIG. 21). In this way, if two EPs are imaged to measure one shift amount, the measurement throughput decreases.
- the measurement point for evaluating the overlay position in the evaluation point based on the layout information of the pattern is determined. It is characterized by determining.
- the step of determining the evaluation point includes a process of determining, for each evaluation point, a processing method for evaluating the overlay position in the evaluation point based on the layout information of the pattern.
- the method includes at least (processing method A) a method of evaluating an overlay position by comparing an image obtained by imaging the evaluation point and design data, and (processing method B) obtained by imaging the evaluation point. And a method of evaluating a superposition position by recognizing a pattern from the obtained image by image processing.
- a processing method for obtaining the distance can be determined for each evaluation pattern.
- the processing using design data as in (Processing Method A) and the processing for obtaining measurement values directly from an image as in (Processing Method B) may be good or bad depending on the pattern included in the EP. It is effective to determine the processing method for each EP based on the above.
- the measurement point / processing method will be described by taking two types of EPs shown in FIG. 11 as an example.
- a first pattern formed by the first exposure is hatched with a hatched pattern (for example, 1102), and a second pattern formed by the second exposure is a white pattern ( For example, 1103).
- a white pattern for example, 1103.
- two locations indicated by arrows 1104 and 1105 are set as measurement points, the same location is recognized by image processing, and the first location at the same location is determined. It is conceivable to measure the distance between the pattern and the second pattern. This belongs to the aforementioned (Processing Method B).
- the pattern in EP 1101 is complicated, and advanced image processing is required to recognize and measure the locations of arrows 1104 and 1105.
- the above-mentioned (Processing Method A) is suitable for evaluation in EP1101. That is, design data for the first exposure (referred to as first design data) and design data for the second exposure (referred to as second design data) are matched with the pattern in the captured image.
- the overlay shift can be evaluated by the shift between the matching position of the first design data and the matching position of the second design data.
- the first pattern in the captured image is recognized by matching the first design data
- the second pattern in the captured image is similarly recognized by matching the second design data.
- the overlay deviation can be evaluated from the positional relationship between the first pattern and the second pattern.
- EP 1106 in FIG. 11B only the first pattern 1107 and the second pattern 1108 are arranged side by side.
- two edges are detected by detecting left and right edges (edges included in a dotted frame 1110) in the first and second patterns. It is conceivable to measure the distance 1109 as an evaluation point.
- a brightness profile 1111 obtained by integrating the brightness values of the captured image in the y direction may be created to detect a location where the brightness value changes greatly (more at the edge portion of the pattern). Electrons are emitted and become brighter on the image).
- the overlay evaluation can be performed by simple image processing without using design data, the above-described (Processing Method B) is suitable.
- the user designates in advance a processing method (for example, (processing method A) or (processing method B)) for obtaining the distance, and the measured value is obtained by the processing method based on the layout information.
- the region that can be obtained can also be selected as EP.
- some users since it is not necessary to use design data in the processing of (Processing Method B), some users may desire to select only an area that can be processed in (Processing Method B) as an EP.
- EP is determined by using design data at the time of recipe generation, but there is an advantage that it is not necessary to handle design data at the time of imaging / measurement using a scanning charged particle microscope.
- step 105 or step 111 in FIG. 1 a plurality of evaluation points in which directions in which the superposition position can be evaluated are determined for each evaluation point are determined, and the superposition is performed.
- step 113 in FIG. 1 an overlay deviation vector at a predetermined coordinate is calculated based on the overlay deviation with respect to the direction in which the overlay position measured at each of the plurality of evaluation points can be evaluated. It is characterized by calculating. This feature will be supplemented.
- overlay evaluation is performed using a normal circuit pattern instead of a dedicated pattern for overlay evaluation, whether or not there is an EP including a pattern suitable for overlay evaluation depends on the pattern layout and is always desired.
- FIG. 16A shows an example in which an EP is extracted from the chip 1601.
- a dotted line frame represented by an area 1602 is an area from which an EP is extracted (corresponding to an area 907 in FIG. 9B), and 1605 is representative.
- EPX that can evaluate only the overlay displacement in the x direction
- EPX which corresponds to EP910 in FIG. 9B
- An EP written as “y” represents an EP (referred to as EPY, which corresponds to EP911 in FIG. 9B) that can evaluate only the overlay deviation in the y direction.
- the region such as 1602 where EP extraction should be performed should be centered on the coordinates from which EP is to be extracted. For example, when EP is extracted without deviation at a certain interval and the distribution tendency of overlay deviation with high reliability is to be known. As shown in the figure, the EP extraction areas should be set in a grid pattern at certain intervals. However, even if an EP search is performed within the grid-arranged region, the EP does not exist near the center of the region 1602 as in the region 1602, but is extracted toward the end of the region 1602 as in the EP 1605.
- FIG. 16B shows a result obtained by imaging each extracted EP and calculating a registration error with respect to such a biased EP extraction result.
- the amount of overlay deviation calculated from an image obtained by capturing each EP is represented by an arrow extending from each EP, and the direction of the arrow indicates the direction of overlay deviation that can be measured in each EP. ing.
- an arrow 1607 representing a deviation in the x direction extends from EP 1605 capable of measuring an overlay deviation in the x direction.
- an arrow 1608 representing a deviation in the y direction extends from EP 1606 which can measure the overlay deviation in the y direction.
- the measurement values are interpolated based on the direction-specific overlap misalignment arrows (1607, 1608, etc.) shown in FIG. 16 (b) to obtain a desired value as shown in FIG. 16 (c). It is characterized by estimating a two-dimensional (x, y direction) shift vector (1611, etc.) in coordinates. Even if the EP distribution is sparse or biased, any in-plane distribution that is dense and biased to some extent can be estimated. In FIG.
- a grid pattern 1609 indicated by a bold line is drawn, and bold circles (1610 and the like) existing at the intersections of the grids indicate coordinates on the chip for which overlay deviation is to be obtained.
- a thick arrow extending from the bold circle is a vector (1611 or the like) representing an overlay error in the bold circle.
- the amount of misalignment in the y direction at each bold circle is obtained by interpolation from a group of arrows of misalignment in the y direction such as 1608. If the amount of deviation in the x and y directions in each bold circle is obtained, a two-dimensional deviation vector (1611 etc.) in the bold circle having these as components is given.
- the coordinates for which the overlay deviation indicated by the bold circles in FIG. 16C can be obtained can be arbitrarily set by the user. For example, the interval between the grids 1609 may be set more finely to obtain a dense deviation distribution. , The intervals of the grids may be changed non-uniformly depending on the location, or bold circles may be arbitrarily arranged instead of the lattice shape.
- the EP extracted in the example shown in FIG. 16 is only an EP that can evaluate the misalignment for each direction from one EP, but the superposition for each direction from the two EPs described with reference to FIG. EP which can evaluate deviation may be included.
- the EP extracted in the example shown in FIG. 16 is of two types: EPX that can evaluate only the overlay deviation in the x direction and EPY that can evaluate only the overlay deviation in the y direction.
- Other types of EP related to can be processed in the same manner and used for estimation of a two-dimensional deviation vector.
- FIG. 17 shows variations of the EP regarding the measurable direction.
- the hatched patterns 1701, 1706, 1711, 1721, 1723 represent the first pattern
- the white patterns 1702, 1707, 1712, 1720, 1722 represent the second pattern
- the thick frames 1703, 1708, 1713, 1718 Indicates EP. From the first pattern widths 1704, 1709, 1714, 1716, 1725 and the second pattern widths 1705, 1710, 1715, 1717, 1724, EP1703 is in the x direction
- EP1708 is in the y direction
- EP1713 is in both the x and y directions
- EP1718 Can evaluate misalignment in the direction of angle 1726.
- EP1718 there is an oblique wiring inclined at an angle of 1726, and the overlay displacement in the direction of angle 1726 can be evaluated, but EPX when angle 1726 is 0 ° and EPY when angle 1726 is 90 °. It becomes.
- the pattern shown in FIG. 17D is imaged by SEM, the pattern edge can be clearly imaged so that the scanning direction of the electron beam can be set to be perpendicular to the edge.
- the dotted line frame 1719 rotated left by 1726 minutes may be set as EP.
- a coordinate system 1728 (referred to as an Ix-Iy coordinate system) indicating the x and y directions on the image has an angle of 1726 minutes with respect to a wafer or shot or chip coordinate system 1727 (referred to as an xy coordinate system). Will only rotate. Therefore, the registration displacement in the Ix direction obtained on the image is the registration displacement in the angle 1726 direction in the xy coordinate system.
- the information on the overlay shift in an arbitrary direction in each EP can be used for estimation of a two-dimensional shift vector. However, since the reliability of the measurement value obtained by the interpolation process is not always high, the reliability of the estimation is calculated for each estimated deviation vector.
- the reliability calculation method includes a difference between interpolation / extrapolation of interpolation processing, a distance between an EP to be interpolated and an interpolation point, and the like.
- FIG. 18 (a) shows an example of deviation interpolation treatment.
- an overlay deviation 1811 in the x direction in the bold circle 1810 and an overlay deviation 1813 in the x direction in the bold circle 1812 are estimated by interpolation from the overlay deviations 1804 to 1806 in the x direction measured in the three EPXs 1801 to 1803. is doing.
- the bold circles 1810 and 1812 are the coordinates on the chip for which the overlay deviation specified by the user is to be obtained in the same manner as the bold circle 1610.
- Examples of the interpolation processing include linear interpolation and curved surface interpolation. Since the bold circle 1810 exists inside the area surrounded by the dotted lines 1807 to 1809 connecting the EPs 1801 to 1803 which are the interpolation points, the vector 1811 can be estimated by interpolation processing, and the estimation reliability is generally high. On the other hand, since the bold circle 1812 exists outside the region surrounded by the dotted lines 1807 to 1809, the vector 1813 is estimated by extrapolation processing, and the reliability of estimation is generally low.
- a perpendicular line from the bold circles 1814, 1817, 1820 to the straight line 1809 connecting the interpolated points EP1801 and EP1803 is considered, and the lengths of the perpendicular lines 1816, 1819, 1922 are assumed. Comparing the lengths 1816 and 1819 of the perpendiculars, 1816 is shorter. Therefore, it is considered that the estimation vector 1815 has higher estimation reliability than the estimation vector 1818 in terms of the distance from the region surrounded by the interpolated points. On the other hand, when the lengths 1816 and 1822 of the vertical lines are compared, 1822 is shorter, but the estimated vector 1821 does not necessarily have higher estimation reliability than the estimated vector 1815.
- the estimation vector 1815 is considered to have higher estimation reliability than the estimation vector 1821.
- the above-described reliability calculation method is an example, and the present invention is not limited to this. For example, it is also conceivable to find an interpolated point closest to the interpolation point and use the distance between the interpolated point and the closest interpolated point for reliability calculation.
- a bold circle (1827, etc.) present at the intersection of the grid pattern 1826 indicates the coordinates on the chip for which overlay deviation is to be obtained, and an arrow extending from the bold circle represents the overlay deviation in the bold circle estimated by interpolation. It is a vector (1828-1831 etc.).
- a solid line vector (1828, 1829, etc.) indicates a vector obtained by interpolation processing, and a dotted line vector (1830, 1831, etc.) indicates a vector obtained by extrapolation processing.
- the brightness of the vector represents the reliability.
- the gray vector 1829 indicates that the estimation reliability is lower than the black vector 1828.
- a gray vector 1831 indicates that the estimation reliability is low with respect to a black vector 1830.
- GUI FIG. 12 shows a GUI example for inputting various information, setting or displaying recipe generation / output, and controlling the SEM apparatus in the present invention.
- Various information drawn in the window 1201 in FIG. 12 can be displayed on a display or the like in one screen or divided.
- the layout data input method (step 102) will be described.
- a chip array can be input by pressing a button 1202.
- layout data can be input by pressing a button 1203.
- the layout data of the first pattern and the second pattern can be input as separate files, or merged data can be input.
- information on multiple layers may be included. Therefore, the first pattern and the second pattern to be subjected to overlay evaluation in the window 1204 can be designated by ID or the like.
- ID is specified in the pull-down menu 1205 for the layer ID
- an exposure ID is specified for the DP overlay evaluation.
- the number of patterns to be subjected to overlay evaluation may be three or more.
- EP selection condition input step 103
- a description will be given of a distribution designation of EP arrangement or a method of EP designation.
- the check box of “Specify by area where EP can be arranged” is turned ON, the EP determination described with reference to FIGS. 9A and 9B can be performed.
- the setting method of the area where the EP can be arranged can be selected from “arrange areas in a grid pattern”, “manually set areas”, and the like using radio buttons in the window 1207.
- a grid interval for arranging areas in a box 1208 can be designated.
- the EP determination described with reference to FIGS. 9C and 9D can be performed.
- the distance between the EPs can be specified in the box 1209.
- an EP search is performed so that an EP (EPY) whose overlay can be evaluated only in the y direction is arranged as close as possible. (Conversely, EPX is placed near EPY). At that time, a distance between EPX and EPY can be designated in a box 1211.
- the EP designation described with reference to FIG. 10 can be performed.
- the radio button in the window 1212 can be used to select “search for an EP similar to the specified EP” or “fine correction with the specified EP as an initial value”.
- the designation of EP may be designated with a mouse or the like in displays 1226, 1228, and 1231 described later, or a list file may be read and designated by pressing a button 1213.
- a list of designated EPs is displayed in a list 1214, and an EP actually used as a designated EP can be redesignated on the list.
- a method of specifying a processing method at the time of measurement will be described as one of EP selection condition input (step 103).
- the processing method for evaluating the overlapping position described with reference to FIG. 11 (the above-mentioned (processing method A) or (processing method B)) is designated by a radio button or the like, and an EP satisfying the designated condition is selected. Can be determined. Examples of the designation method include “no designation”, “measurement by comparison of design data in all EPs”, “measurement by comparison of design data as much as possible”, “measurement by only image processing in all EPs”, “measurement by only image processing as much as possible”, etc. .
- a method of inputting device conditions as device condition input (step 104) will be described.
- an assumed stage shift accuracy, image shift accuracy, matching error in AP, and the like can be input and used for estimation of estimated imaging deviation at the time of EP determination.
- each check box is turned on, so that when the EP is determined, “considering imaging deviation (explained in FIG. 5)”, “considering pattern deformation (explained in FIG. 6)”, “facing an opposing edge in the EP. It can be included (explained in FIG. 7), “search only for EP that can evaluate the overlap in both xy directions (explained in FIG. 9)”, and the like. Although not shown, it is also possible to specify “considering hiding of the lower layer pattern by the upper layer pattern” described with reference to FIG.
- an EP candidate is searched based on the input of the layout data, processing parameters, etc., and the result can be displayed.
- EP candidates can be displayed together with the EP attribute information. It supplements about this display.
- it is effective not to be all automatic, but to indicate a plurality of EP candidates to the user and allow the user to select from them.
- the position of the EP on the wafer can be plotted and displayed in order to grasp the in-plane distribution of the EP.
- EP candidate attribute information can be displayed.
- the attribute information includes (A) allowable imaging deviation / estimated imaging deviation, (B) imaging sequence / imaging condition / assumed imaging time, and (C) evaluation.
- Ease of pattern deformation that is a measure of stability
- D Pattern hiding or hiding by pattern deformation
- E Processing method for evaluating measurement point / overlapping position
- F Evaluable The direction of the superposition position, etc.
- the direction of the overlay position that can be evaluated in (F) can be evaluated only for the overlay position in the X or Y direction, the overlay position in both the XY directions can be evaluated, the overlay position in the A ° direction can be evaluated, etc.
- This information can be obtained by analyzing the layout information in the EP candidate. These pieces of information can be displayed as numerical values or figures.
- EP candidates can be listed in a list 1220.
- various attribute information can be displayed in addition to the EP coordinates, the imaging magnification, the imaging conditions, and the direction in which overlay evaluation is possible (separate from EPXY, EPX, and EPY).
- the position of the EP and the attribute information related to each EP can be displayed on the displays 1226, 1228, and 1231. Although all of the attribute information is not shown in the displays 1226, 1228, and 1231, arbitrary attribute information can be displayed numerically or graphically.
- a display 1226 indicates a wafer.
- the range can be enlarged and displayed on the display 1228.
- the position of the EP candidate is displayed in a thick frame on the display 1228 (for example, the thick frame 1229), and after the overlay displacement amount is measured, the displacement amount can also be displayed as a vector (for example, extending from the thick frame 1229). Arrow).
- the range 1230 By designating the range 1230 using a mouse or the like in the display 1228, the range can be enlarged and displayed on the display 1231.
- the display 1231 displays the first pattern as a hatched pattern (for example, 1232) and the second pattern as a white pattern (for example, 1233) as pattern layout information, and further images the same EP as the EP 1236.
- An imaging sequence for displaying is displayed.
- auto-focusing is performed with the AF 1235
- an imaging sequence for imaging the EP 1236 is set.
- the imaging order is indicated by numbers (1) to (3) written before AP, AF, EP.
- the EP position is not displayed on the display 1226, but this is a display example.
- the layout information, the EP position, the imaging sequence, the imaging condition, the measurement point / processing method, the overlay evaluation result, and the like are displayed on the display 1226. Any one of 1228 and 1231 can be displayed.
- the EP, imaging sequence, imaging conditions, measurement point / processing method, etc. determined by pressing the button 1221 can be registered in the recipe.
- the EP that is actually registered in the recipe as an EP can be redesignated from among the EP candidates.
- a recipe to be used is designated by pressing a button 1222 (a previously registered recipe can be used, or a recipe created in the past can also be used).
- a button 1223 By pressing a button 1223, imaging / overlay evaluation using SEM is executed based on the recipe.
- the overlay evaluation result can be arbitrarily displayed in the list 1225 or the displays 1226, 1228, and 1231 as described above.
- the EP is obtained for each direction in which the overlay evaluation can be performed.
- An EP (for example, 1300) represented by a white square is an EP (EPXY) in which the overlay deviation in both xy directions can be evaluated.
- EP (for example, 1302) that can be evaluated only for overlay deviation in the x direction, and EP for which “y” is written in the square (for example, 1303) can only be for overlay displacement in the y direction.
- Indicates that the EP (EPY) can be evaluated.
- the deviation amount can be displayed as a vector.
- the vector obtained in the EPX 1302 is only the deviation amount in the x direction (an arrow extending from the thick frame 1302 in the x direction).
- a displacement vector in the xy direction can be approximately calculated from the amount of displacement between the two and displayed.
- a display 1305 is an enlarged display of the range 1304.
- the first pattern is displayed as a hatched pattern (for example, 1311)
- the second pattern is displayed as a white pattern (for example, 1312)
- An imaging sequence for imaging EP2 (1309, corresponding to 1303) and the two EPs is displayed.
- the vertical incident position of the electron beam is moved to the Move coordinate 1310 by the stage shift, and then the visual field is moved and addressed to the AP 1306 by the image shift, and then the visual field is moved and the autofocus is performed to the AF 1307 by the image shift.
- the field of view is moved to EP1 (1308) by image shift and imaged, and then the field of view is moved to EP2 (1309) by image shift and imaged.
- the imaging order is indicated by numbers (1) to (4) written before AP, AF, EP1, and EP2.
- the imaging time can be shortened by collectively performing one address without performing addressing or autofocus for each EP.
- the imaging time can also be one of judgment materials for EP determination. Note that such imaging sequence optimization between EPs can be performed in step 107 in FIG. 1, but in addition, the imaging sequence can be optimized between step 111 and step 112. The reason for this is that the EP candidate group assumed in step 107 may be subject to addition / deletion of EPs in the final EP decision in step 111, and between EPs such as performing addressing once. This is because the setting of the imaging sequence over the range may change.
- FIG. 14 shows the result of overlay evaluation between three or more layers.
- the in-plane distribution of the overlay vector of the second pattern and the third pattern generated in the third layer is set to 1402, and the third pattern and the fourth pattern generated in the fourth layer are generated.
- An in-plane distribution of the overlay deviation vector with the pattern is displayed at 1403.
- the evaluation result on the display 1401 is based on an image obtained by imaging the wafer immediately after the second pattern is generated
- the evaluation result on the display 1402 is an image obtained by imaging the wafer immediately after the third pattern is generated
- the evaluation result of the display 1403 is based on an image obtained by imaging the wafer immediately after the fourth pattern is generated.
- the displays 1401 to 1403 can be displayed simultaneously with the coordinates adjusted.
- the EP setting locations may be the same or different between the displays 1401 to 1403.
- the EPs that can be subjected to overlay evaluation are in the same location regardless of the layer. It is good also as one of the judgment criteria of EP selection that the place of EP is similar between layers.
- a wafer 2201 is displayed, and a plurality of chips are arranged therein (for example, chips 2202 to 2210). In all of these chips, the misalignment in the chips may be evaluated, or from the viewpoint of inspection throughput, for example, only the chips 2202 to 2210 displayed by oblique lines may be sampled and evaluated.
- the right diagram of FIG. 22 displays the distribution of deviation vectors in the chip measured in the chips 2202 to 2210.
- the displays 2211 to 2219 correspond to the display of the shift vector distribution in the chips 2202 to 2210, and the shift distribution can be displayed side by side in this way.
- reference numeral 1501 denotes a mask pattern design apparatus
- 1502 denotes a mask drawing apparatus
- 1503 denotes an exposure / development apparatus for a mask pattern on a wafer
- 1504 denotes a wafer etching apparatus
- 1505 and 1507 denote SEM apparatuses
- 1506 and 1508 Is an SEM control device for controlling the SEM device
- 1509 is an EDA (Electronic Design Automation) tool server
- 1510 is a database server
- 1511 is a storage for storing the database
- 1512 is an imaging / measurement recipe creation device
- 1513 is an imaging / measurement.
- a recipe server 1514 is an image processing server that performs pattern shape measurement / evaluation, and these can transmit and receive information via a network 1515.
- a storage 1511 is attached to the database server 1510, and (A) design data (design data for a mask (with / without optical proximity effect correction (Optical-Proximity-Correction: OPC), wafer transfer pattern design data)), ( B) Simulation pattern of actual pattern estimated by lithography simulation from the mask design data, (C) Generated imaging / measurement recipe, (D) Captured image (OM image, SEM image), (E) Evaluation results (pattern shape length measurement value for each part of the evaluation pattern, pattern outline, pattern deformation amount, overlay displacement amount and displacement direction between patterns, normality or abnormality level of overlay position, etc.) ( F) Some or all of the rules for determining imaging / measurement recipes are linked to the product type, manufacturing process, date / time, data acquisition device, etc.
- an imaging / measurement recipe is stored in the database server 1510 or the imaging / measurement recipe in any of a plurality of SEM apparatuses. It can be shared by the recipe server 1513, and the plurality of SEM devices can be operated by one imaging / measurement recipe creation. In addition, by sharing the database among multiple SEM devices, the success or failure of past imaging or measurement and the accumulation of failure causes can be accelerated. By referring to this, it is possible to help generate a good imaging / measurement recipe. it can.
- FIG. 15B shows an example in which 1506, 1508, 1509, 1510, and 1512 to 1514 in FIG. 15A are integrated into one device 1516. As in this example, it is possible to divide or integrate arbitrary functions into arbitrary plural devices.
- a dense in-plane distribution of overlapping positions in a semiconductor device or the like can be grasped using the scanning charged particle microscope by the above means.
- a recipe that satisfies a measurement request (evaluation point, imaging sequence, measurement point / processing method setting) can be automatically and rapidly performed, and inspection preparation time (recipe creation time) can be shortened. , Operator skills can be expected to be unnecessary.
- an embodiment in which an EP is selected from within a chip has been described (for example, chips 1601, 2101, 2202 to 2210), but the chip may be replaced with a shot (ie, Considered shots 1601, 2101, 2202 to 2210).
- a shot ie, Considered shots 1601, 2101, 2202 to 2210).
- one shot includes several chips.
- a shot is an area exposed by one exposure irradiation, and it is effective to evaluate the distribution of overlay deviation in the shot when analyzing the characteristics of the exposure apparatus.
- 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.
- each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit.
- each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor.
- Information such as programs, tables, and files for realizing each function can be stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.
- control lines and information lines indicate what is considered necessary for explanation, and not all control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.
- imaging recipe creation device 224 ... measurement recipe creation device, 226 ... database server, 227 ... Database (storage), 301 to 306 ... Incident direction of convergent electron beam, 307 ... Sample surface, 308 ... Ix-Iy coordinate system (image coordinate system), 309 ... Image, 416 ... Wafer, 417 to 420 ... Chip for alignment , 421 ... Chip, 422 ... OM alignment pattern imaging range, 423 ... SEM array ,..., SEM alignment pattern imaging range, 425... Partially expanded range of design data, 426... MP, 427... Image shift movable range from MP, 428. 430 ... AF, 431 ... AST, 432 ... ABCC, 433 ...
- EP 501, 513, 515, 527 ... first pattern, 502, 503, 514, 516, 517, 526 ... second pattern, 504, 518, 522, 528, 529, 531, 534, 535 ... measurement points, 505, 519 ... EP, 506,520 ... AP, 507 ... EP-AP distance, 508,509 ... maximum expected imaging deviation, 510, 511, 521: Distance between first and second patterns, 512: Actual EP imaging position, 523, 524, 530, 532: Pattern center, 525, 533: Distance between pattern centers, 602, 606, 610, 613 ... First pattern, 603, 607, 611, 614 ... Second pattern, 601, 605, 609, 612 ...
- Overlapping evaluation dedicated pattern, 904, 908, 910, 911, 913, 916, 917, 921, 922, 923 ... EP, 900, 903, 907, 909, 912 ... EP can be placed in the area, 918 , 924, 925 ... EP distance, 926 ... EP area, 1002,1004,1012 ... first pattern, 1003,1005,1006,1013 ... second pattern, 1001,1007,1008 ... EP , 1009 ... AP, 1010, 1011 ... EP-AP distance, 1102, 1107 ... First pattern, 1103, 1108 ... Second pattern, 1101, 1106 ... EP, 1104, 1105, 1109 ... Measurement point, 1110 ... edge position, 1111 ...
- 1604 Area where EP can be arranged, 1605, 1606 ... EP, 1607, 1608 ... Overlay deviation amount by direction, 1609 ... Grid, 1610 ... Desired overlay deviation measurement location, 1611 ... Overlay deviation vector, 1701, 1706, 1711, 1721, 1723 ... first pattern, 1702, 1707, 1712, 1720, 1722 ... second pattern, 1703, 1708, 1713, 1718, 1719 ... EP, 1704, 1705, 1709, 1710, 1714-1717, 1724, 1725 ...
- Measurement points 172 6... Inclination angle of diagonal wiring pattern, 1727... XY coordinate system (wafer or shot or chip coordinate system), 1728... Ix-Iy coordinate system (image coordinate system), 1801 to 1803... EP, 1804 to 1806, 1811, 1813, 1815, 1818, 1821 ... Overlay deviation amount by direction, 1807 to 1809 ... Straight lines connecting EP, 1810, 1812, 1814, 1817, 1820, 1827 ... Overlay deviation measurement desired location, 1816, 1819 , 1822 ... distance between the desired overlay deviation measurement points 1814, 1817, 1820 and the straight line 1809, 1823-1825 ...
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Abstract
Description
本特徴について補足する。重ね合わせ評価用の専用パターンではなく,通常の回路パターンを用いて重ね合わせ評価を行う場合,重ね合わせ評価に適したパターンを含むEPが存在するか否かはパターンレイアウトに依存し,常に望むEPが存在するとは限らない。そのため,実パターンを用いて重ね合わせずれの面内分布を評価する際には,(課題1)いかに偏りなく多くのEPを抽出できるか,(課題2)抽出できたEPが少ない場合であってもいかに重ね合わせずれの面内分布の推定に有効な情報を算出できるかが課題となる。本項目は前記(課題1)に対し有効な処理である。前記項目(2)において,EP選択の評価基準の例として,「(B)x方向の重ね合わせ位置を評価する際はパターンの左と右の両方のエッジを,y方向の重ね合わせ位置を評価する際はパターンの上と下の両方のエッジを,第一パターンと第二のパターンについてそれぞれ前記評価ポイント内に含む」を挙げたが,パターンレイアウトによっては,このような計測に必要なエッジ群を全て視野内に含むEPがほとんど存在しない場合がある。これに対して,EPの撮像倍率を下げてEPの視野を大きくすることによって,より多くのパターンを視野内に含ませて前記基準を満たすようなEPが存在する可能性を高めることが考えられる。ただし,撮像倍率と計測精度はトレードオフの関係にあるため,視野の拡大には限界がある。そこで,1つのEPからずれ量を推定するのではなく,2つのEPからずれ量を推定することを考える。すなわち,1つのEPでは視野内におさまらなかったずれの計測に必要なエッジ群が,第一のEP,第二のEP内に分けて撮像することで,全て視野内におさめることが可能になる場合がある。ただし,パターン幅の太り/細りや2つのEPの撮像ずれに対してずれの計測値が影響を受けないようにするためには,計測に必要なエッジ群を前述のような組合せで前記第一のEP,第二のEPで撮像する必要があることを見出した。このように1つのずれ量を計測するために2つのEPを撮像すれば計測のスループットは低下するが,計測のための基準を満たすEPの選択肢が増え,偏りなく密なずれの面内分布を推定できる可能性が高くなる。
本特徴について補足する。本項目は前記項目(7)において述べた「(課題2)抽出できたEPが少ない場合であってもいかに重ね合わせずれの面内分布の推定に有効な情報を算出できるか」に対し有効であり,各EPにおける計測可能な方向と計測したずれ量とを基に計測値を補間処理することで所定の座標における二次元(x,y方向)のずれベクトルを推定することを特徴とする。前記EPの分布が疎であったり偏りがあったとしても,ある程度,ずれの密な面内分布を推定することが可能となる。ただし,補間処理によって求めた計測値の信頼性は必ずしも高くない場合があるため,推定したずれベクトル毎に信頼度を算出することを特徴とする。ずれの評価結果を半導体製造装置等へフィードバックしてずれを補正する際には,前記信頼度に応じてずれベクトルを加味する度合いを制御することができる。前記信頼度の算出方法としては,補間処理の内挿/外挿の違いや,EPと補間点との距離等が挙げられる。
(10)評価ポイントを決定するステップにおいては,評価ポイントの候補を前記評価ポイントの属性情報と合わせて表示することを特徴とする。ここで述べる属性情報には前記項目(7)で述べた製造プロセスに関する属性情報のみならず,後述する属性情報(A)~(G)が含まれる。
本特徴について補足する。EPの決定においては,全て自動ではなく,複数のEP候補をユーザに示し,その中からユーザに選択させることが有効である。ユーザにEP選択の判断材料を与えるための表示方法として,EPの面内分布を把握するためにウェーハ上におけるEPの位置をプロットして表示することができる。
また,(1)~(9)で決定した各種情報をEP候補の属性情報として表示することができる。例えば,(A)許容撮像ずれ/推定撮像ずれ,(B)撮像シーケンス/撮像条件/想定される撮像時間,(C)評価の安定性の目安となるパターンの変形し易さ,(D)パターンの隠れあるいはパターンの変形による隠れ易さ,(E)計測ポイント/重ね合わせ位置を評価するための処理方法,(F)評価可能な重ね合わせ位置の方向,(G)EP内に含まれる各パターンエッジが生成された製造プロセス,等である。前記項目(F)の評価可能な重ね合わせ位置の方向とは,X方向もしくはY方向の重ね合わせ位置のみ評価可能,XY両方向の重ね合わせ位置を評価可能,A゜方向の重ね合わせ位置を評価可能等の情報である。例えばEP候補内にX方向に変化するパターンエッジしか含まれない場合,Y方向の重ね合わせ位置を評価することはできない。この情報はEP候補内のレイアウト情報を解析することにより求めることができる。
1.1 SEM構成要素
本発明における評価システムの一例を図2に示す。図2は評価を行う試料を撮像する走査荷電粒子顕微鏡の例としてSEMを用いた実施例であり,試料の二次電子像(Secondary Electron:SE像)あるいは反射電子像(Backscattered Electron:BSE像)を取得するSEMの構成概要のブロック図を示す。また,SE像とBSE像を総称してSEM画像と呼ぶ。また,ここで取得される画像は測定対象を垂直方向から電子ビームを照射して得られたトップダウン画像,あるいは任意の傾斜させた方向から電子ビームを照射して得られたチルト像の一部または全てを含む。
撮像レシピとは,SEMの撮像シーケンスを指定するファイルである。すなわち,評価対象として撮像すべき撮像領域(評価ポイント(EP)と呼ぶ)の座標や,前記EPを位置ずれなく,かつ高精細に撮像するための撮像シーケンスを指定する。EPは1ウェーハ上に複数存在する場合もあるし,ウェーハの全面検査であればEPがウェーハを埋め尽くすということになる。図4(a)にEPを撮像するための代表的な撮像シーケンスのフロー図,図4(b)に前記代表的な撮像シーケンスに対応する撮像箇所を示す。以後,図4(a)(b)を対応させながら,撮像シーケンスについて説明する。
2.1 概要
本発明は,SEMにより試料上の評価ポイントを撮像した画像を用いて,第一の製造プロセスにより試料上に生成された第一のパターンと第二の製造プロセスにより前記試料上に生成された第二のパターンとの重ね合わせ位置を評価する方法であって,パターンのレイアウト情報を基に一つあるいは複数の評価ポイント候補について重ね合わせ位置を評価するために許容される撮像ずれを推定するステップと,前記許容される撮像ずれを基に評価ポイント候補の中から一つあるいは複数の評価ポイントを決定するステップと,前記選択した評価ポイントを撮像するための撮像シーケンスを決定するステップと,前記撮像シーケンスに従って前記評価ポイントを撮像して得られた画像から第一のパターンと第二のパターンとの重ね合わせ位置を評価するステップを有することを特徴とする。
ここで第一のパターンと第二のパターンとの違いは,上下層といったレイヤの違いであってもよいし,DPにおける多重露光の違いであっても良い。また,重ね合せ位置を評価するパターン数は2つ以上であってもよい。例えば撮像画像において3レイヤ(上中下層)のパターンが見える場合は第一~第三のパターン間のずれを評価することができるし,多重露光として三回の露光(triple patterning)を行う場合は第一~第三のパターン間のずれを評価することができる。また,一回の撮像で全てのパターンが観察できない場合は,異なる製造工程のタイミングで複数回の撮像を行い重ね合わせ評価を行うこともできる。以降の説明では2つのパターン(第一のパターンと第二のパターン)間の重ね合わせ評価を例に説明する。
2.2.1 パターン変形を考慮したEP決定
本発明は,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)における評価ポイント選択の評価基準として,レイアウト情報からパターンの各部位の変形し易さを評価し,前記各部位の変形し易さを基に評価ポイントを決定することを特徴とする。
図5(d)の左右に描かれた図は,図5(b)で選択されたEP519を用いて 第一のパターンと第二のパターン間の重ね合せずれをパターン515,516を用いて評価する際の二種類の計測方法を示している。図5(c)の例と同様,図5(d)の左図ではパターン515,516のエッジ間の幅528を計測することによって重ね合せずれを評価しようとしているが,図5(d)の右図では
第一のパターン515の幅529の中心530と,第二のパターン516の幅531の中心532との間の幅533を計測することによって重ね合せずれを評価している。前記幅533はパターンの太り/細りに対して変化が少ない。パターン515の左右のエッジのx座標をx1,x2,パターン516の左右のエッジのx座標をx3,x4とすると,この重ね合わせずれは次式で書くことができる。
(第一のパターンに対する第二のパターンの重ね合せずれ)
= (幅531の中点)-(幅529の中点) = (x3+x4)/2-(x1+x2)/2
= ((x4-x2)-(x1-x3))/2 = ((幅535)-(幅534))/2
すなわち,重ね合わせずれを計測するためには,幅531の中点と幅529の中点を計測してその差分をとってもよいし,幅535,幅534を計測してその差分をとってもよい。ただし,幅535,幅534はエッジの位置関係によってプラスの値やマイナスの値となることに注意が必要である。
本発明は,ウェーハ上の積層レイヤに関して第一のパターンが下層パターンであり,第二のパターンが上層パターンである場合,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,レイアウト情報から前記上層パターンによる下層パターンの隠れを推定し,前記隠れを考慮して評価ポイントを決定することを特徴とする。
本発明は,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,評価ポイントの試料上の面内分布を考慮して複数のEPを決定することができる。具体的には,(A)試料上に複数の領域を設定し,それぞれの前記領域内から評価ポイントを少なくとも一つ決定することを特徴とする。あるいは(B)任意の二つの評価ポイント間の距離に関する条件を与え,前記条件を満たすように複数の評価ポイントを決定することを特徴とする。
本発明は,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,事前に少なくとも一つ以上の評価ポイントを指定し,前記指定した評価ポイントを基に前記評価ポイント内に含まれるパターンと類似したパターンを含む別の評価ポイントを探索することによって決定することを特徴とする。
2.2.5 製造プロセスに関する属性情報を考慮したEP決定
本発明は,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,パターンエッジ毎にどの製造プロセスで生成されたエッジであるかを属性情報として求め,前記属性情報を基に前記第一の製造プロセスにより生成されたエッジと前記第二の製造プロセスにより生成されたエッジが視野内に含まれることを条件に評価ポイントを決定することを特徴とする。
本特徴について補足する。例として図19(d)に示す上下層パターン間の重ね合せずれを評価することを考える。同図において,1回目の露光(第一の製造プロセス)により下層レイヤに形成された第一のパターンを斜線でハッチングされたパターン(1901,1902),2回目の露光(第二の製造プロセス)により上層レイヤに形成された第二のパターンを白いパターン(1903a~1905a,1903b~1905b)として描画している(ただし,後述するように厳密にはパターン1903a~1905a,1903b~1905bは第二の製造プロセスとCutting processによって生成されている)。同パターン生成のプロセスを図19(a)~(c)に示す。まず,図19(a)に示すように1回目の露光により第一のパターン1901,1902を生成する。次に図19(b)に示すように2回目の露光により第二のパターン1903~1905を生成する。最後に図19(c)に示すようにCutting processと呼ばれる処理により領域1906内に存在する前記第二のパターンを除去する。Cutting processは領域1906を露光パターンとして露光することにより領域1906内の第二のパターンを除去することもあるし,電子線の直描によって領域1906に電子線を照射することにより領域1906内の第二のパターンを除去することもある。
このようなパターンに対して前記第一,第二のパターン間の重ね合せずれを評価する際,単に下層に存在する第一のパターンのエッジと上層に存在する第二のパターンのエッジ間の距離を計測しても前記ずれを評価できないケースがある。その例を図19(f)に示す。同図においては上層パターン1904aの右エッジ(太線で表示)と上層パターン1904bの左エッジ(太線で表示)との幅1911の中点(幅1911を表す矢印上に×印で表示)と,下層パターン1901の右エッジ(太線で表示)と下層パターン1902の左エッジ(太線で表示)との幅1910の中点(幅1910を表す矢印上に×印で表示)との距離から前記中点間の距離の設計値を差し引くことによって上下層パターン間のずれを評価しようとしている(幅1911,1910は図7(c)の計測例においてはそれぞれ幅712,710に相当する)。しかしながら,上層パターン1904aの右エッジと上層パターン1904bの左エッジはCutting processによって生成されたエッジであるため,幅1911,1910から求められるずれは第一,第二のパターン間の重ね合わせずれではなく,第一のパターンとCutting processのパターンとの重ね合わせずれになる。このように,所望の2つのレイヤ間の重ね合わせずれを評価する際には,単に前記2つのレイヤに存在するパターンのエッジをそれぞれ選択してその距離を計測するのでなく,エッジがどの製造プロセスによって生成されたかも加味して計測に用いるエッジを選択する必要がある。そのため,エッジ毎に製造プロセス情報を属性情報として付与し,前記属性情報を基に計測対象エッジの組合せを決定することを特徴とする。図19(e)は前記属性情報別にエッジを表示したものである。エッジ1907に代表される点線で表示されたエッジは第一の製造プロセスにより生成されたエッジ,エッジ1908に代表される細い実線で表示されたエッジは第二の製造プロセスにより生成されたエッジ,エッジ1909に代表される太い実線で表示されたエッジはCutting processにより生成されたエッジであることを示す。エッジの方向に加え,エッジの製造プロセスに関する属性情報を加味することによって評価したいプロセス間のずれを求めるために認識すべきエッジを適切に選択することができる。このように,属性情報はパターンの閉図形の単位ではなく,エッジ(線分)単位で与えることが特徴である。前記属性情報によって,計測に用いるエッジが前記評価したいプロセスによって生成されたエッジであるか否かを判断することができる。
前記属性情報によれば,第一,第二のパターン間の重ね合わせずれを評価するためには,例えば図19(g)に示す計測を行えばよいことが分かる。本例では上層パターン1904aの左エッジ(図19(e)によれば第二の製造プロセスにより生成された属性情報をもつ)と上層パターン1904bの右エッジ(図19(e)によれば第二の製造プロセスにより生成された属性情報をもつ)との幅1913の中点と,下層パターン1901の左エッジ(図19(e)によれば第一の製造プロセスにより生成された属性情報をもつ)と下層パターン1902の右エッジ(図19(e)によれば第二の製造プロセスにより生成された属性情報をもつ)との幅1912の中点との距離から第一,第二のパターン間のずれを評価できる。
同様に,もし第二のパターンとCutting processのパターンとのずれを評価したいのであれば,前記属性情報より例えば図19(h)に示される計測を行えばよいことが分かる。本例では上層パターン1904aの左エッジ(図19(e)によれば第二の製造プロセスにより生成された属性情報をもつ)と上層パターン1904bの右エッジ(図19(e)によれば第二の製造プロセスにより生成された属性情報をもつ)との幅1915の中点と,上層パターン1904aの右エッジ(図19(e)によればCutting processにより生成された属性情報をもつ)と上層パターン1904bの左エッジ(図19(e)によればCutting processにより生成された属性情報をもつ)との幅1914の中点との距離から第二のパターンとCutting processのパターン間のずれを評価できる。
なお,レイアウト情報として設計データを用いる際,図19(d)に示される撮像時に生成されている最終的なパターンの設計データ(インテント設計データ)が入手できない場合,図19(a)~(c)に示される各プロセス毎の設計データ,及び前記各プロセス毎のレイヤ情報やCutting processか否かの情報を基にインテント設計データを生成することを特徴とする。前記インテント設計データから属性情報を求め,前記インテント設計データと前記属性情報を基にEPやEP内の計測ポイントを決定することを特徴とする。逆にインテント設計データは存在するが,各プロセス毎の設計データが入手できない場合は,各プロセス毎のレイヤ情報やCutting processの情報を基に,前記インテント設計データに属性情報を付与し,EPやEP内の計測ポイントを決定することを特徴とする。
前記属性情報を用いたEPやEP内の計測ポイントの決定は,図19を用いて説明した層間の重ね合わせずれの評価に限らず,DPやSADP(Self-Aligned Double Patterning)等の複数プロセスによって同層に形成されたパターン間の前記複数プロセス間のずれを評価する際にも有効である。ここでは例としてSADPにおける属性情報を利用したEPやEP内の計測ポイントの決定について図20を用いて説明する。最初に図20(a)~(e)に示したウェーハの断面図を用いてSADPの製造プロセス例を簡単に説明する。まず,図20(a)に示すように,下地2006,ハードマスク層2005の上面に背景技術において述べた要領でDPによりパターン2001~2004を形成する。すなわち,まず斜線でハッチングされたパターンで表した第一のパターン2001,2003を生成し,その後,白いパターンで表した第二のパターン2002,2004を前記第一のパターンの隙間に生成する。次に,図20(b)に示すようにウェーハ表面にレジスト膜2007をデポ(堆積)した後,図20(c)に示すようにエッチングすることによりパターン2001~2004の側壁にSidewall spacerと呼ばれるパターン2007a~2007hを形成する。次に図20(d)に示すようにパターン2001~2004を除去した後にSidewall spacer2007a~2007hをマスクとしてハードマスク層2005をエッチングすることにより,図20(e)に示すようにパターン2005a~2005hを形成する。
ここで,最初にDPで生成した第一のパターン2001,2003と第二のパターン2002,2004のずれをパターン2005a~2005hが生成された時点で計測することを考える。図20(a)(e)をウェーハの上面方向(z方向)からそれぞれ描画したものが図20(f)における上下の図である。図20(f)の下には同図(e)に対応する8つのパターン2005a~2005hが並んで配置されている様子が描かれているが,見た目にはどのパターンも同じであるため,前記第一,第二のパターン間のずれを計測するためにどのパターン間の距離を計測したらよいか分からない。そこで,図19を用いて説明した製造プロセスに関する属性情報を本例でも考える。図20(f)の上に,第一のパターン2001,2003と第二のパターン2002,2004をx方向の位置がパターン2005a~2005hに対応するように描画している。この対応関係から,例えばパターン2005aは第一のパターン2001の左エッジ位置に依存してシフトするパターンである。そのため,パターン2005aは第一のパターン2001の左エッジが生成される製造プロセスによって直接生成されるパターンではないが,第一のパターン2001が生成される製造プロセスに生成位置が依存するパターンである。また,パターン2005bは第一のパターン2001の右エッジが生成される製造プロセスに生成位置が依存するパターンである。同様に,例えばパターン2005cは第二のパターン2002が生成される製造プロセスに生成位置が依存するパターンであり,パターン2005dは第二のパターン2002の右エッジが生成される製造プロセスに生成位置が依存するパターンである。このような属性情報を加味すると,例えばパターン2005bの右エッジとパターン2005eの左エッジとの幅2008の中点(幅2008を表す矢印上に×印で表示)と,パターン2005cの左エッジとパターン2005dの右エッジとの幅2009の中点(幅2009を表す矢印上に×印で表示)との距離から前記第一,第二のパターン間のx方向のずれを評価できることが分かる。すなわち例えば第二のパターンが第一のパターンに対して右(xのプラス方向)にシフトした場合,幅2009の中点も幅2008の中点に対して右にシフトすることになるので,前記中点間の画像上での距離から前記中点間の距離の設計値を差し引くことによってずれ量を求めることができる。
同様に,例えば図20(f)に示す幅2011の中点と幅2010の中点との距離や,幅2012の中点と幅2013の中点との距離や,幅2014の中点と幅2015の中点との距離から前記第一,第二のパターン間のx方向のずれが評価できることも分かる。これらの複数の計測ポイントのいずれかを用いてずれを計測してもよいし,複数の計測ポイントを用いて複数の計測値を得て,それらの平均やメディアンをとることで安定したずれ量を推定することもできる。
図20(g)はパターン2005a~2005hの各エッジの属性情報を示したものである。属性情報のIDを各エッジ上に描かれた丸の中のアルファベットで示す(本例ではA~D,a~dの8種類の属性が存在)。2016に代表される第一の製造プロセスにより生成されたパターンの左側のエッジの側壁に生成されたSidewall spacerの左側のエッジの属性をA,2017に代表される第一の製造プロセスにより生成されたパターンの左側のエッジの側壁に生成されたSidewall spacerの右側のエッジの属性をB,2018に代表される第一の製造プロセスにより生成されたパターンの右側のエッジの側壁に生成されたSidewall spacerの右側のエッジの属性をa,2019に代表される第一の製造プロセスにより生成されたパターンの右側のエッジの側壁に生成されたSidewall spacerの左側のエッジの属性をbとする。同様に第二の製造プロセスにより生成されたパターンの側壁に生成されたSidewall spacerのエッジについても図示するようにその位置に応じて属性をC,D,c,dとする。このように各エッジの属性情報は前記エッジを直接生成した製造プロセスの情報のみならず,前記エッジの位置に影響を与える他の製造プロセスの情報や,前記エッジとある製造プロセスによって生成されたパターンとの位置関係によって定めるように拡張することができる(第二のパターンの左に生成されたSidewall spacerの左エッジである等)。このような属性情報から前記第一,第二のパターン間のずれを評価することが可能なエッジの組合せについて次のルールを導くことができる。まず,同じアルファベットで大文字,小文字の属性をもつエッジをペアとし,その中点を考える。例えば,属性Aのエッジと属性aのエッジ間の幅の中点を中点A-aと呼ぶ。第一,第二のパターン間のずれは,中点A-aまたは中点B-bと,中点C-cまたは中点D-dとの距離から求めることができる。すなわち,(第一のパターンに対する第二のパターンの重ね合せずれ)=(中点C-cの座標,または中点D-dの座標)-(中点A-aの座標,または中点B-bの座標)-(中点間の距離の設計値)である。図20(f)に図示した計測ポイントは全てこの条件を満たしており,例えば幅2008の中点と,幅2009の中点との距離からずれを計測する場合は,中点A-aと中点C-cとの距離からずれを計測している。このように属性情報を用いることでずれ計測可能なエッジの組合せを全て求めることができる。
なお,レイアウト情報として設計データを用いる際,図20(f)の下に描かれた撮像時に生成されている最終的なパターン2005a~2005hの設計データ(インテント設計データ)が入手できない場合,例えば図20(f)の上に描かれた前プロセスの設計データであるパターン2001~2004や,図20(a)~(e)に描かれた製造プロセスの情報を基にインテント設計データを生成することを特徴とする。前記インテント設計データから属性情報を求め,前記インテント設計データと前記属性情報を基にEPやEP内の計測ポイントを決定することを特徴とする。逆にインテント設計データは存在するが,各プロセス毎の設計データが入手できない場合は,各製造プロセスの情報を基に前記インテント設計データに属性情報を付与し,EPやEP内の計測ポイントを決定することを特徴とする。
図19,20を用いて本明細書では特に層間やSADPを例に属性情報を加味した重ね合わせ評価について実施例を述べたが,本発明はこれに限定されず,SAMP(Self-Aligned Multi Patterning)やDSA(Directed Self-Assembly)やGrid Design等を用いたデバイスにおける重ね合わせ評価等の他のプロセスにおいても利用できる。また,前記属性情報の加味はレイアウト情報を基に計算機によってEPやEP内の計測ポイントを自動で決定する際に有効であるが,自動ではなくユーザが手動でEPやEP内の計測ポイントを決定する際も大変有効である。なぜならば,最終的に形成されるパターンのレイアウト情報から,どのエッジがどの製造プロセスによって生成されたか予想することが困難な場合があるからである。また,予想できる場合であっても,そのためにはプロセスに関する知識やパターン位置の特定が必要となる。そのため,レイアウト情報と前記属性情報を併せてGUI等においてユーザに示すことによって,ユーザがEPやEP内の計測ポイントを決定する際の助けとなり,作業効率を大幅に改善することができる。
2.2.6 分割撮像に基づくEP決定
評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,x方向の重ね合わせ位置を評価する際は,第一の評価ポイント内に少なくとも第一のパターンの左右どちらかのエッジと第二のパターンの左右どちらかのエッジを含み,第二の評価ポイント内に第一のパターンの左右どちらかのエッジと第二のパターンの左右どちらかのエッジを含むように前記第一と第二の評価ポイントを決定し,前記第一と第二の評価ポイントを用いて重ね合わせずれを評価することを特徴とする。ここで,前記第一の評価ポイント内に含まれるパターンの方向と前記第二の評価ポイント内に含まれるパターンエッジの方向は前記第一と第二のパターンそれぞれにおいて左右が逆であることを特徴とする。
同様にy方向の重ね合わせ位置を評価する際は,第一の評価ポイント内に少なくとも第一のパターンの上下どちらかのエッジと第二のパターンの上下どちらかのエッジを含み,第二の評価ポイント内に第一のパターンの上下どちらかのエッジと第二のパターンの上下どちらかのエッジを含むように前記第一と第二の評価ポイントを決定し,前記第一と第二の評価ポイントを用いて重ね合わせずれを評価することを特徴とする。ここで,前記第一の評価ポイント内に含まれるパターンエッジの方向と前記第二の評価ポイント内に含まれるパターンエッジの方向は前記第一と第二のパターンそれぞれにおいて上下が逆であることを特徴とする。
本特徴について補足する。重ね合わせ評価用の専用パターンではなく,通常の回路パターンを用いて重ね合わせ評価を行う場合,重ね合わせ評価に適したパターンを含むEPが存在するか否かはパターンレイアウトに依存し,常に望むEPが存在するとは限らない。そのため,実パターンを用いて重ね合わせずれの面内分布を評価する際には,いかに偏りなく多くのEPを抽出できるかが課題となり,本処理は前記課題に対し有効である。先に図7を用いて説明した通り,EP選択の評価基準の例として,「(B)x方向の重ね合わせ位置を評価する際はパターンの左と右の両方のエッジを,y方向の重ね合わせ位置を評価する際はパターンの上と下の両方のエッジを,第一パターンと第二のパターンについてそれぞれ前記評価ポイント内に含む」を挙げたが,パターンレイアウトによっては,このような計測に必要なエッジ群を全て視野内に含むEPがほとんど存在しない場合がある。図21(a)の左図はチップ2101内からEPを抽出した例を示しており,領域2102に代表される点線枠がEPを抽出する領域(図9(b)の領域907に相当),2103に代表される四角の中に「x」と書かれたEPはx方向の重ね合わせずれのみ評価可能なEP(EPXと呼ぶ。図9(b)のEP910に相当),2104に代表される四角の中に「y」と書かれたEPはy方向の重ね合わせずれのみ評価可能なEP(EPYと呼ぶ。図9(b)のEP911に相当)を表す。点線枠の中にはEPが全く存在しないものや,存在はするが,EPXのみ,あるいはEPYのみという場合がある。これに対して,EPの撮像倍率を下げてEPの視野を大きくすることによって,より多くのパターンを視野内に含ませて前記基準を満たすようなEPが存在する可能性を高めることが考えられる。ただし,撮像倍率と計測精度はトレードオフの関係にあるため,視野の拡大には限界がある。そこで,1つのEPから重ね合せずれを推定するのではなく,2つのEPからずれ量を推定することを考える。すなわち,1つのEPでは視野内におさまらなかった重ね合せずれの評価に必要なエッジ群が,第一のEP,第二のEP内に分けて撮像することで,全て視野内におさめることが可能になる場合がある。例えば図21(a)における点線枠2105内には1つのEPで重ね合せずれを評価可能なEPは存在しなかったが,分割撮像を許すことによって,図示するようにEPが設定できる場合がある。同図においてはX方向に変化するパターンエッジを含む第一のEP2106(EPXaと呼ぶ)と第二のEP2107(EPXbと呼ぶ)を設定することができ,両EPの撮像画像から従来評価困難であったX方向の重ね合わせずれを評価することができようになる。図21(a)の右図はEPXa,EPXbを設定できた領域2105の拡大図を示す。また,図には存在しないか同様にY方向の重ね合わせずれを評価可能な2つのEPとしてEPYa,EPYbやXY両方向の重ね合わせずれを評価可能な2つのEPとしてEPa,EPbを設定可能な場合もありうる。
ただし,パターン幅の太り/細りや2つのEPの撮像ずれに対してずれの計測値が影響を受けないようにするためには,計測に必要なエッジ群を前述のような組合せで前記第一のEP,第二のEPで撮像する必要があることを見出した。図21(b)に前述の組合せを満たす第一,第二のEP例を示す。下層に存在する第一のパターン2109,2111(ハッチングされたパターンで表示)と上層に存在する第二のパターン2110,2112(白いパターンで表示)間のx方向の重ね合わせずれを評価するためには,第一のEP内に少なくとも第一のパターンの左右どちらかのエッジと第二のパターンの左右どちらかのエッジを含む必要があり,本例では第一のパターン2109の左エッジと第二のパターン2110の左エッジを含んでいる。また,第二のEP内に第一のパターンの左右どちらかのエッジと第二のパターンの左右どちらかのエッジを含む必要があり,本例では第一のパターン2111の右エッジと第二のパターン2112の右エッジを含んでいる。さらに第一のEP内に含まれるパターンの方向と前記第二のEP内に含まれるパターンの方向は前記第一と第二のパターンそれぞれにおいて左右が逆である必要がある。パターンの方向をパターン内部から外部の方向と定義すると,本例では第一のEPの計測対象エッジである第一のパターン2109の左エッジと第二のパターン2110の左エッジは共に右方向,第二のEPの計測対象エッジである第一のパターン2111の右エッジと第二のパターン2112の右エッジは共に右方向であり,第一,第二のパターンそれぞれに関して方向が逆という条件を満たしている。本例においては第一のパターン2109の左エッジ(エッジ位置のx座標をx1とする)と第一のパターン2111の右エッジ(エッジ位置のx座標をx4とする)との幅2113の中点2117と,第二のパターン2110の左エッジ(エッジ位置のx座標をx2とする)と第二のパターン2112の右エッジ(エッジ位置のx座標をx3とする)との幅2114の中点2118との距離から前記中点間の距離の設計値を差し引くことによって第一,第二のパターン間のずれを評価することができる。本例では前記中点間の距離の設計値は0とする。この重ね合わせずれを式で書き,変形すると次式が得られる。
(第一のパターンに対する第二のパターンの重ね合せずれ)
= (幅2114の中点)-(幅2113の中点) = (x2+x3)/2-(x1+x4)/2
= ((x2-x1)-(x4-x3))/2 = ((幅2115)-(幅2116))/2
すなわち,重ね合わせずれは第一のEP内のパターン2109の左エッジとパターン2110の左エッジとの幅2115と,第二のEP内のパターン2111の右エッジとパターン2112の右エッジとの幅2116との差によって求められるため,計測対象エッジが各EPの視野内におさまっていれば各EPの撮像位置が多少ずれても正しい計測値を得ることができる。図21(c)に実際の撮像位置の例を示すが,太線枠で表示したEPXaとEPXbの設定時の撮像位置2106,2107に対して,点線枠で表示したEPXaとEPXbの実際の撮像位置2119,2120がずれている。このように二回撮像を行うと,EPXaとEPXbの相対撮像位置がずれる可能性が高いが,前述の通り,前記撮像位置のずれは重ね合わせずれの計測値に直接影響を与えないため,それぞれの画像から幅2115,幅2116が正しく計測できれば重ね合わせずれを正しく求めることができる。
また,このように求めた重ね合わせずれは図7を用いて説明した内容と同様の理由によりパターン幅の太り/細りの影響を受けにくい。ただし,そのためにはパターン2110と2112の形状変形(あるいはパターン2109と2111の形状変形)が同程度に発生した場合である(計測するエッジを含むこれらのパターンを計測対象パターンと呼ぶ)。例えば重ね合わせずれが発生していなくても,計測対象パターン2110が計測対象パターン2112と比べて大きく太った場合,計算上は重ね合わせずれが発生してしまう。対となる計測対象パターン2110,2112(あるいは対となる計測対象パターン2109,2111)間の形状変形が同程度であるためには,計測対象パターンの形状や前記各計測対象パターンの周囲パターンの形状が対となる対象パターン間で類似している必要があり,EP設定時に考慮する必要がある。前記周囲パターンの形状の類似性も考慮する理由は,パターン露光時の光近接効果等により,周囲パターンの形状が計測対象パターンの形状に影響を与える場合があるためである。また,各計測対象パターンの形状変形が同程度であるためには,対となる計測対象パターン間において製造条件等が類似している必要がある。さらに,対となる計測対象パターンを用いて重ね合せずれを算出するのであるから,そもそも対となる計測対象パターンにおいて発生している重ね合わせずれが同程度でなければならない。その点を考慮すると,対となる計測対象パターンはある程度近くに配置されている必要があり,そのためには前記第一,第二のEPを近くに配置する必要がある。EP決定時においてはEP間の距離(図21中の距離2108)に制約条件を設定することができる。
このように1つのずれ量を計測するために2つのEPを撮像すれば計測のスループットは低下するが,計測のための基準を満たすEPの選択肢が増え,偏りなく密なずれの面内分布を推定できる可能性は高くなる。
本発明は,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,パターンのレイアウト情報を基に前記評価ポイント内において重ね合わせ位置を評価する計測ポイントを決定することを特徴とする。また,同じく評価ポイントを決定するステップにおいては,パターンのレイアウト情報を基に前記評価ポイント内において重ね合わせ位置を評価するための処理方法を評価ポイント毎に決定する処理を含み,前記処理方法の選択肢には少なくとも,(処理方法A)前記評価ポイントを撮像して得られた画像と設計データとの比較により重ね合わせ位置を評価する方法と,(処理方法B)前記評価ポイントを撮像して得られた画像から画像処理によりパターンを認識して重ね合わせ位置を評価する方法を含むことを特徴とする。
2.4 重ね合わせずれベクトル算出
本発明は,評価ポイントを決定するステップ(図1中ステップ105あるいはステップ111)において,評価ポイント毎に重ね合わせ位置の評価が可能な方向が定められた複数の評価ポイントを決定し,前記重ね合わせ位置を評価するステップ(図1中ステップ113)においては前記複数の評価ポイントにおいてそれぞれ計測された重ね合わせ位置の評価が可能な方向に対する重ね合わせずれを基に所定の座標における重ね合わせのずれベクトルを算出することを特徴とする。
本特徴について補足する。重ね合わせ評価用の専用パターンではなく,通常の回路パターンを用いて重ね合わせ評価を行う場合,重ね合わせ評価に適したパターンを含むEPが存在するか否かはパターンレイアウトに依存し,常に望むEPが存在するとは限らない。そのため,実パターンを用いて重ね合わせずれの面内分布を評価する際には,抽出できたEPが少ない場合であってもいかに重ね合わせずれの面内分布の推定に有効な情報を算出できるかが課題となる。図16(a)はチップ1601内からEPを抽出した例を示しており,領域1602に代表される点線枠がEPを抽出する領域(図9(b)の領域907に相当),1605に代表される四角の中に「x」と書かれたEPはx方向の重ね合わせずれのみ評価可能なEP(EPXと呼ぶ。図9(b)のEP910に相当),1606に代表される四角の中に「y」と書かれたEPはy方向の重ね合わせずれのみ評価可能なEP(EPYと呼ぶ。図9(b)のEP911に相当)を表す。EP抽出を行う1602等の領域はEPを抽出したい座標を中心に配置すべきであり,例えばEPをある間隔で偏りなく抽出して信頼性の高い重ね合わせずれの分布傾向を知りたい場合には,図示するようにある間隔で格子状にEP抽出領域を設定すべきである。ところが,前記格子状に配置した領域内でEP探索を行っても,領域1602のようにEPが領域1602の中心付近には存在せず,EP1605のように領域1602の端の方で抽出される場合や,領域1604のようにEPが全く存在しない場合や,領域1603のように存在はするが,EPXのみという場合がある。このような偏りのあるEP抽出結果に対して,抽出した各EPを撮像して重ね合せずれを算出した結果が図16(b)である。同図では各EPを撮像した画像から算出された重ね合わせずれ量の大きさを前記各EPからのびる矢印で表しており,矢印の方向は前記各EPにおいて計測可能な重ね合わせずれの方向を示している。例えばx方向の重ね合わせずれを計測可能なEP1605からはx方向のずれを表す矢印1607がのびている。同様にy方向の重ね合わせずれを計測可能なEP1606からはy方向のずれを表す矢印1608がのびている。しかし,図16(b)における偏りのある方向別重ね合せずれの矢印群をみてもずれの分布傾向はつかみにくい。そこで本発明では,図16(b)に示した方向別重ね合せずれの矢印群(1607,1608等)を基に計測値を補間処理することで,図16(c)に示すように所望の座標における二次元(x,y方向)のずれベクトル(1611等)を推定することを特徴とする。前記EPの分布が疎であったり偏りがあったとしても,ある程度,密で偏りのないずれの面内分布を推定することが可能となる。図16(c)には太線で表示したグリッドパターン1609が描かれており,グリッドの交点に存在する太丸(1610等)は重ね合わせずれを求めたいチップ上の座標を示している。前記太丸からのびる太矢印は前記太丸における重ね合わせずれを表すベクトル(1611等)である。前記方向別重ね合せずれの矢印群から太丸における重ね合わせずれを表すベクトルを求める方法として,例えば,1607等のx方向の重ね合せずれの矢印群から各太丸におけるx方向のずれ量を補間により求め(補間方法の具体例は図18を用いて後述する),同様に1608等のy方向の重ね合せずれの矢印群から各太丸におけるy方向のずれ量を補間により求める。各太丸におけるx,y方向のずれ量が求まれば,これらを成分とする前記太丸における二次元のずれベクトル(1611等)が与えられる。
図16(c)に太丸で示した重ね合せずれを求めたい座標はユーザが任意に設定することができ,例えばグリッド1609の間隔をもっと細かく設定して密なずれ分布を求めてもよいし,グリッドの間隔を場所によって不均一に変えてもよいし,格子状ではなく任意に太丸を配置してもよい。
また,図16に示した例において抽出されたEPは,一つのEPから方向別重ね合せずれを評価可能なEPのみであったが,図21を用いて説明した2つのEPから方向別重ね合せずれを評価可能なEPが含まれていてもよい。さらに,図16に示した例において抽出されたEPは,x方向の重ね合わせずれのみ評価可能なEPXとy方向の重ね合わせずれのみ評価可能なEPYの2種類であったが,計測可能な方向に関するその他の種類のEPにおいても同様に処理し,二次元のずれベクトルの推定に利用することができる。図17に計測可能な方向に関するEPのバリエーションを示す。斜線でハッチングされたパターン1701,1706,1711,1721,1723は第一のパターンを,白いパターン1702,1707,1712,1720,1722は第二のパターンを表し,太枠1703,1708,1713,1718はEPを示す。第一のパターンの幅1704,1709,1714,1716,1725と第二のパターンの幅1705,1710,1715,1717,1724からEP1703はx方向,EP1708はy方向,EP1713はx,y両方向,EP1718は角度1726方向の重ね合わせずれを評価することができる。EP1718の視野内には角度1726だけ傾いた斜め配線が存在しており,角度1726方向の重ね合わせずれが評価できるが,角度1726が0゜のときはEPX,角度1726が90゜のときはEPYとなる。また,図17(d)に示したパターンをSEM撮像する際にはパターンエッジを鮮明に撮像するため,電子ビームの走査方向がエッジに対して垂直になるよう設定することができ,EP1718を角度1726分だけ左回転させた点線枠1719をEPとすることもできる。その場合,画像上のx,y方向を示す座標系1728(Ix-Iy座標系と呼ぶ)は,ウェーハあるいはショットあるいはチップの座標系1727(x-y座標系と呼ぶ)に対して角度1726分だけ回転することになる。そのため画像上で求めたIx方向の重ね合せずれはx-y座標系では角度1726方向の重ね合せずれである。このように各EPにおける任意の方向に対する重ね合わせずれの情報を二次元のずれベクトルの推定に利用することができる。
ただし,補間処理によって求めた計測値の信頼性は必ずしも高くない場合があるため,推定したずれベクトル毎に推定の信頼度を算出することを特徴とする。ずれの評価結果を半導体製造装置等へフィードバックしてずれを補正する際には,前記信頼度に応じてずれベクトルを加味する度合いを制御することができる。前記信頼度の算出方法としては,補間処理の内挿/外挿の違いや,被補間点であるEPと補間点との距離等が挙げられる。図18(a)にずれの補間処置の例を示す。本例では3つのEPX1801~1803において計測されたx方向の重ね合わせずれ1804~1806から補間処理により太丸1810におけるx方向の重ね合わせずれ1811や太丸1812におけるx方向の重ね合わせずれ1813を推測している。太丸1810,1812は太丸1610と同様,ユーザにより指定された重ね合わせずれを求めたいチップ上の座標である。前記補間処理の例として線形補間や曲面補間が挙げられる。太丸1810は被補間点であるEP1801~1803を結ぶ点線1807~1809によって囲まれる領域の内部に存在するので,内挿処理によってベクトル1811を推定することができ,一般に推定の信頼度は高い。一方,太丸1812は点線1807~1809によって囲まれる領域の外部に存在するので,外挿処理によってベクトル1813を推定することになり,一般に推定の信頼度は低い。また,単に内挿/外挿の二通りではなく,推定の信頼度を連続的に評価することもできる。例えば図18(b)に示すように,図18(a)と同じ被補間点1801~1803に対して,太丸1814,1817,1820におけるx方向の重ね合わせずれ1815,1818,1821を推定することを考える。これらの太丸におけるずれベクトルの推定は点線1807~1809によって囲まれる領域の外部に存在するという観点から全て外挿処理となるが,推定の信頼度は同じではない。例えば太丸1814,1817,1820から被補間点であるEP1801とEP1803を結ぶ直線1809への垂線を考え,その垂線の長さ1816,1819,1922とする。垂線の長さ1816,1819を比較すると1816の方が短い。そのため被補間点により囲まれる領域からの距離という観点では,推定ベクトル1815の方が,推定ベクトル1818よりも推定の信頼度が高いと考えられる。一方,垂線の長さ1816,1822を比較すると1822の方が短いが,推定ベクトル1821の方が,推定ベクトル1815よりも推定の信頼度が高いとは限らない。各垂線と直線1809との交点1823,1825を比較すると交点1823は被補間点1801と1803の間に存在するが,交点1825は被補間点1801と1803の間の外に存在する。そのため直線1809の方向に関して補間点が被補間点の間に存在するという観点では,推定ベクトル1815の方が,推定ベクトル1821よりも推定の信頼度が高いと考えられる。前述の信頼度の算出方法は実施例であり,これに限定されるものではない。例えば,補間点に一番近い被補間点を見つけ,前記補間点と前記一番近い被補間点との距離を信頼度算出に用いることも考えられる。
図18(c)に推定ベクトルの内挿/外挿の別や推定の信頼度を表示する方法の一例を示す。グリッドパターン1826の交点に存在する太丸(1827等)は重ね合わせずれを求めたいチップ上の座標を示しており,前記太丸からのびる矢印は補間により推定した前記太丸における重ね合わせずれを表すベクトル(1828~1831等)である。実線のベクトル(1828,1829等)は内挿処理により求められたベクトルであることを示し,点線のベクトル(1830,1831等)は外挿処理により求められたベクトルであることを示す。またベクトルの明るさは信頼度を表しており,例えば内挿処理によって推定されたベクトルについて,黒のベクトル1828に対して灰色のベクトル1829は推定の信頼度が低いことを表す。同様に外挿処理によって推定されたベクトルについて,黒のベクトル1830に対して灰色のベクトル1831は推定の信頼度が低いことを表す。信頼性に関する明るさのレベルはいくつあっても構わないし,定量化された信頼度を数値として各ベクトルの横に表示してもよい。
本発明における各種情報の入力,レシピ生成・出力の設定あるいは表示,SEM装置の制御を行うGUI例を図12に示す。図12中のウィンドウ1201内に描画された各種情報は一画面中,あるいは分割してディスプレイ等に表示することができる。
本発明におけるシステム構成の実施例を図15を用いて説明する。
802,803,808,811…第一のパターン,805,807,810…第二のパターン,801,806…EP,804,809…エッジ位置,901,905,914,919…チップ,902,906,915,920…重ね合せ評価専用パターン,904,908,910,911,913,916,917,921,922,923…EP,900,903,907,909,912…EPを配置できる領域,918,924,925…EP間の距離,926…EPを配置すべき領域,1002,1004,1012…第一のパターン,1003,1005,1006,1013…第二のパターン,1001,1007,1008…EP,1009…AP,1010,1011…EP-AP間の距離,1102,1107…第一のパターン,1103,1108…第二のパターン,1101,1106…EP,1104,1105,1109…計測ポイント,1110…エッジ位置,1111…明度プロファイル,1501…マスクパターン設計装置,1502…マスク描画装置,1503…露光・現像装置,1504…エッチング装置,1505,1507…SEM装置,1506,1508…SEM制御装置,1509…EDAツールサーバ,1510…データベースサーバ,1511…データベース,1512…撮像・計測レシピ作成演算装置,1513…撮像・計測レシピサーバ,1514…画像処理サーバ(形状計測・評価)1515…ネットワーク,1516…EDAツール,データベース管理,撮像・計測レシピ作成,画像処理(形状計測・評価),撮像・計測レシピ管理,SEM制御用統合サーバ&演算装置,1601…チップ,1602~1604…EPを配置できる領域,1605,1606…EP,1607,1608…方向別の重ね合せずれ量,1609…グリッド,1610…重ね合わせずれ計測希望箇所,1611…重ね合わせずれベクトル,1701,1706,1711,1721,1723…第一のパターン,1702,1707,1712,1720,1722…第二のパターン,1703,1708,1713,1718,1719…EP,1704,1705,1709,1710,1714~1717,1724,1725…計測ポイント,1726…斜め配線パターンの傾斜角,1727…x-y座標系(ウェーハあるいはショットあるいはチップの座標系),1728…Ix-Iy座標系(画像座標系),1801~1803…EP,1804~1806,1811,1813,1815,1818,1821…方向別の重ね合せずれ量,1807~1809…EP間を結ぶ直線,1810,1812,1814,1817,1820,1827…重ね合わせずれ計測希望箇所,1816,1819,1822…重ね合わせずれ計測希望箇所1814,1817,1820と直線1809との距離,1823~1825……重ね合わせずれ計測希望箇所1814,1817,1820から直線1809への垂線と直線1809との交点,1826…グリッド,1828~1831…重ね合わせずれベクトル,1901,1902…第一のパターン,1903~1905…第二のパターン,1903a~1905c,1903b~1905b…Cutting process後の第二のパターン,1906…Cutting processのパターン,1907…第一の製造プロセスにより生成されたエッジ,1908…第二の製造プロセスにより生成されたエッジ,1909…Cutting processにより生成されたエッジ,1910~1915…計測ポイント,2001,2003…第一のパターン,2002,2004…第二のパターン,2005…ハードマスク層,2005a~2005h…Sidewall spacerによってマスクされたパターン,2006…下地,2007…デポ層,2007a~2007h…Sidewall spacer,2008~2015…計測ポイント,2016~2019…パターンエッジ,2101…チップ,2102,2105…EPを配置できる領域,2103,2104,2106,2107…EP,2119,2120…実際のEP撮像位置,2108…EP間の距離,2109,2111…第一のパターン,2110,2112…第二のパターン,2113~2116…計測ポイント,2117,2118…パターン中心,2201…ウェーハ,2202~2219…チップ,2211~2219…チップ2202~2219内の重ね合わせずれベクトルの分布
Claims (16)
- 走査荷電粒子顕微鏡により試料上の評価ポイントを撮像した画像を用いて,第一の製造プロセスにより試料上に生成された第一のパターンと第二の製造プロセスにより前記試料上に生成された第二のパターンとの重ね合わせ位置を評価する方法であって,
パターンのレイアウト情報と製造プロセス情報を入力するステップと,
前記レイアウト情報と製造プロセス情報を基に,前記レイアウト情報におけるパターンエッジ毎にどの製造プロセスで生成されたエッジであるかを属性情報として付与するステップと,
前記属性情報を基に前記第一の製造プロセスにより生成されたエッジと前記第二の製造プロセスにより生成されたエッジが視野内に含まれることを条件に一つあるいは複数の評価ポイントを決定するステップと、
を備えるパターン評価方法。 - 前記製造プロセスにはCutting processが含まれることを特徴とする請求項1記載のパターン評価方法。
- 前記製造プロセスにはSidewall spacerを生成するプロセスが含まれることを特徴とする請求項1記載のパターン評価方法。
- パターンのレイアウト情報を基に評価ポイント候補について重ね合わせ位置を評価するために許容される撮像ずれを推定し,前記許容される撮像ずれを基に評価ポイント候補の中から評価ポイントと前記評価ポイントを撮像するための撮像シーケンスを決定し,
前記許容される撮像ずれは前記撮像ずれが発生しても前記評価ポイント内に含まれる第一のパターンと第二のパターンの特定に失敗しないことを条件に推定することを特徴とする請求項1記載のパターン評価方法。 - 評価ポイントを決定するステップにおいては,レイアウト情報からパターンの各部位の変形し易さを評価し,前記各部位の変形し易さを基に評価ポイントを決定することを特徴とする請求項1記載のパターン評価方法。
- 評価ポイントを決定するステップにおいては,x方向の重ね合わせ位置を評価する際はパターンの左と右の両方のエッジを,y方向の重ね合わせ位置を評価する際はパターンの上と下の両方のエッジを第一パターンと第二のパターンについてそれぞれ前記評価ポイント内に含むことを特徴とする請求項1記載のパターン評価方法。
- ウェーハ上の積層レイヤに関して第一のパターンが下層パターンであり,第二のパターンが上層パターンである場合,評価ポイントを決定するステップにおいて,レイアウト情報から前記上層パターンによる下層パターンの隠れを推定し,前記隠れを考慮して評価ポイントを決定し,
前記隠れの推定においてはパターンの変形に伴い下層パターンが隠れる場合の推定を含むことを特徴とする請求項1記載のパターン評価方法。 - 評価ポイントを決定するステップにおいては,試料上に複数の領域を設定し,それぞれの前記領域内から評価ポイントを少なくとも一つ決定することを特徴とする請求項1記載のパターン評価方法。
- 評価ポイントを決定するステップにおいては,任意の二つの評価ポイント間の距離に関する条件を与え,前記条件を満たすように複数の評価ポイントを決定することを特徴とする請求項1記載のパターン評価方法。
- 評価ポイントを決定するステップにおいては,事前に少なくとも一つ以上の評価ポイントを指定し,前記指定した評価ポイントを基に前記評価ポイント内に含まれるパターンと類似したパターンを含む別の評価ポイントを探索することによって決定することを特徴とする請求項1記載のパターン評価方法。
- 評価ポイントを決定するステップにおいては,パターンのレイアウト情報を基に前記評価ポイント内において重ね合わせ位置を評価する計測ポイントを決定することを特徴とする請求項1記載のパターン評価方法。
- 評価ポイントを決定するステップにおいては,パターンのレイアウト情報を基に前記評価ポイント内において重ね合わせ位置を評価するための処理方法を評価ポイント毎に決定する処理を含み,前記処理方法の選択肢には少なくとも,前記評価ポイントを撮像して得られた画像と設計データとの比較により重ね合わせ位置を評価する方法と,
前記評価ポイントを撮像して得られた画像から画像処理によりパターンを認識して重ね合わせ位置を評価する方法を含むことを特徴とする請求項1記載のパターン評価方法。 - 評価ポイントを決定するステップにおいては,評価ポイントの候補を前記評価ポイントの属性情報と合わせて表示することを特徴とする請求項1記載のパターン評価方法であって,前記属性情報には評価可能な重ね合わせ位置の方向を含むことを特徴とする請求項1記載のパターン評価方法。
- x方向の重ね合わせ位置を評価する際は,第一の評価ポイント内に少なくとも第一のパターンの左右どちらかのエッジと第二のパターンの左右どちらかのエッジを含み,第二の評価ポイント内に第一のパターンの左右どちらかのエッジと第二のパターンの左右どちらかのエッジを含むように前記第一と第二の評価ポイントを決定し,前記第一と第二の評価ポイントを用いて重ね合わせずれを評価し,
前記第一の評価ポイント内に含まれるパターンの方向と前記第二の評価ポイント内に含まれるパターンエッジの方向は前記第一と第二のパターンそれぞれにおいて左右が逆であり、
y方向の重ね合わせ位置を評価する際は,第一の評価ポイント内に少なくとも第一のパターンの上下どちらかのエッジと第二のパターンの上下どちらかのエッジを含み,第二の評価ポイント内に第一のパターンの上下どちらかのエッジと第二のパターンの上下どちらかのエッジを含むように前記第一と第二の評価ポイントを決定し,前記第一と第二の評価ポイントを用いて重ね合わせずれを評価し、
前記第一の評価ポイント内に含まれるパターンの方向と前記第二の評価ポイント内に含まれるパターンエッジの方向は前記第一と第二のパターンそれぞれにおいて上下が逆であることを特徴とする請求項1記載のパターン評価方法。 - 前記評価ポイントを決定するステップにおいては,評価ポイント毎に重ね合わせ位置の評価が可能な方向が定められた複数の評価ポイントを決定し,前記重ね合わせ位置を評価するステップにおいては前記複数の評価ポイントにおいてそれぞれ計測された重ね合わせ位置の評価が可能な方向に対する重ね合わせずれを基に所定の座標における重ね合わせのずれベクトルを算出することを特徴とする請求項1のパターン評価方法。
- 走査荷電粒子顕微鏡により試料上の評価ポイントを撮像した画像を用いて,第一の製造プロセスにより試料上に生成された第一のパターンと第二の製造プロセスにより前記試料上に生成された第二のパターンとの重ね合わせ位置を評価する装置であって,
パターンのレイアウト情報と製造プロセス情報を入力する手段と,
前記レイアウト情報と製造プロセス情報を基に,前記レイアウト情報におけるパターンエッジ毎にどの製造プロセスで生成されたエッジであるかを属性情報として付与する手段と,
前記属性情報を基に前記第一の製造プロセスにより生成されたエッジと前記第二の製造プロセスにより生成されたエッジが視野内に含まれることを条件に一つあるいは複数の評価ポイントを決定する手段と、
を有することを特徴とするパターン評価装置。
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JPWO2013118613A1 (ja) | 2015-05-11 |
TWI475597B (zh) | 2015-03-01 |
TW201346983A (zh) | 2013-11-16 |
US20140320627A1 (en) | 2014-10-30 |
TWI517210B (zh) | 2016-01-11 |
KR101828124B1 (ko) | 2018-02-09 |
JP6038053B2 (ja) | 2016-12-07 |
TW201334029A (zh) | 2013-08-16 |
KR20140101420A (ko) | 2014-08-19 |
US9488815B2 (en) | 2016-11-08 |
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