WO2014104055A1 - パターン形状評価方法、半導体装置の製造方法及びパターン形状評価装置 - Google Patents
パターン形状評価方法、半導体装置の製造方法及びパターン形状評価装置 Download PDFInfo
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- H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
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- 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
- 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
- H01J37/02—Details
- H01J37/22—Optical or photographic arrangements associated with the tube
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- 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
- H01J37/261—Details
- H01J37/265—Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
- H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
- G01B15/04—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring contours or curvatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
- G01B2210/56—Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/22—Treatment of data
- H01J2237/221—Image processing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24571—Measurements of non-electric or non-magnetic variables
- H01J2237/24578—Spatial variables, e.g. position, distance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24592—Inspection and quality control of devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Definitions
- the present invention relates to a detailed shape evaluation method by non-destructive observation and image processing using, for example, a scanning microscope, an apparatus therefor, and a semiconductor device manufacturing method employing the technology.
- Non-Patent Document 1 describes a field emission electron microscope (CD-SEM: “Critical Dimension” SEM) dedicated to circuit dimension measurement for observing a wafer from above.
- the CD-SEM is used for measuring various feature quantities in addition to measuring the line width of a semiconductor circuit.
- the edge of the circuit pattern has irregularities called line edge roughness (LER), which adversely affects circuit performance.
- LER line edge roughness
- Patent Document 1 describes the measurement method.
- AFM is a method for measuring the uneven shape of the sample surface by scanning with a probe having a fine tip so that the atomic force between the tip of the probe and the sample surface is constant. The details are described in Patent Document 2, for example.
- Scatterometry measures the wavelength or diffraction angle dependence of the reflected diffracted light by making light incident on a pattern having a periodic three-dimensional structure, and this is the diffraction angle dependence obtained by calculation for various cross-sectional shapes in advance. By comparing, the cross-sectional shape of the three-dimensional structure is estimated. Scatterometry is described in Non-Patent Document 2, for example.
- MBL model-based library
- tilt-SEM is a method for measuring the three-dimensional structure using SEM.
- a three-dimensional shape is estimated based on the principle of a stereo image from a plurality of images obtained by making an electron beam incident on the wafer from different angles.
- tilt-SEM it describes in the patent document 4, for example.
- LSI semiconductor integrated circuit
- CD-SEM can measure the dimensions of minute circuit patterns of any shape in a non-destructive, high-precision and simple manner, but it is difficult to estimate the cross-sectional shape because the planar shape of the circuit is observed from above the wafer. It has a technical problem.
- the AFM method has a problem that, as the size of the circuit pattern is reduced, the probe cannot enter between the patterns and the shape measurement becomes difficult.
- the method using tilt-SEM requires a special electron optical system for changing the incident angle of the convergent electron beam, and generally has problems such as deterioration in performance such as resolution.
- problems such as deterioration in performance such as resolution.
- problems there are a problem that the apparatus becomes large in order to tilt the stage, a problem that the measurement takes time, and the like.
- the present invention can estimate the cross-sectional shape of an arbitrary structure formed on the upper surface of the substrate with high accuracy while using only the observation image from the upper surface of the substrate acquired using the charged particle beam apparatus. Provide technology.
- the invention as an example includes: (a) irradiating a convergent energy beam from a direction substantially perpendicular to the main surface of the substrate on which the three-dimensional structure is formed, and scanning the upper surface of the substrate, so that the substrate and the structure A process of detecting and / or measuring the intensity of secondary energy rays generated from a body or energy rays reflected or scattered by the substrate and the structure, and obtaining an upper surface observation image of the structure; A process for obtaining uncertainty information of scattering intensity due to the uneven shape of the surface of the structure from the focused energy beam irradiation position in the upper surface observation image and the measured intensity, and (c) the structure based on the obtained uncertainty information.
- FIG. 5 is a characteristic diagram for illustrating the estimation result of the cross-sectional shape for each sample illustrated in FIG. 4. It is a flowchart explaining the process sequence in 1st Embodiment. It is a schematic diagram which shows the structural example of the apparatus used by 1st Example.
- a substantially cubic structure for example, a semiconductor or a resist pattern
- the substrate surface is defined as the xy plane
- the direction in which the edge of the structure extends is defined as the y direction.
- An electron beam converged sufficiently narrower than the characteristic dimension of the structure is irradiated onto the substrate from a direction (z direction) substantially perpendicular to the substrate surface, and the direction on the substrate is substantially perpendicular to the edge direction (x Direction).
- Electrons incident on the substrate or structure are scattered inside the substrate or structure to emit secondary electrons, or directly reflected (or backscattered), and part of the electrons are emitted to the outside of the substrate or structure. To do.
- the amount of secondary electrons or reflected electrons (hereinafter referred to as “secondary electrons”) is increased when an electron beam is incident on a convex portion (or an upper portion of a corner).
- a detection signal intensity distribution of secondary electrons or the like is obtained.
- a pattern based on the position when the detection signal intensity distribution is cut at a predetermined threshold level when the detection signal intensity distribution is normalized by the maximum value of the detection signal, or the position where the inclination of the detection signal intensity distribution is maximum Determine non-pattern boundaries.
- the pattern dimension is measured from the distance between the two pattern boundary positions.
- the edge shape of the pattern is obtained by connecting the obtained pattern / non-pattern boundary.
- the edge shape obtained in this way exhibits an uneven shape along the edge direction.
- the size of this unevenness is called line edge roughness.
- substrate surface including a direction parallel to the pattern edge and a direction perpendicular to the pattern edge
- the above-described line edge roughness is generally considered to be caused by variations in the edge position of the structure as shown in the upper diagram (a) of FIG.
- the actual structure is not a cube, and its side wall is inclined as shown in the upper diagram (a) of FIG. 2, or the surface is uneven (surface roughness) as shown in the middle diagram (b) of FIG.
- Have The detection signal intensity distribution is considered to be affected by changes in the tilt angle and surface irregularities.
- the secondary electron detection signal intensity When the secondary electron detection signal intensity is measured by scanning the electron beam in the x direction from the start point defined at a constant sampling interval in the y direction, the secondary electron detection signal as shown in the lower diagram (c) of FIG. A two-dimensional distribution of intensity is obtained.
- the two-dimensional distribution of the secondary electron detection signal intensity includes (1) intensity change caused by the three-dimensional shape and material characteristics of the structure, and (2) intensity distribution due to the x-direction position fluctuation of the structure along the edge direction. And (3) the influence of three factors of the intensity distribution due to the unevenness of the structure surface.
- the amount of secondary electron emission increases when the electron beam is incident on the convex portion, and conversely decreases when the electron beam is incident on the concave portion. Therefore, when looking at the macro structure of the entire pattern, the upper surface corner of the pattern is convex, so that the signal intensity increases toward the upper surface corner (right side of the upper diagram (a) in FIG. 3). On the other hand, when looking at the micro structure, the signal intensity increases when entering the convex and concave portions existing on the pattern surface (right side of the middle diagram (b) in FIG. 3). Accordingly, the secondary electron signal intensity distribution corresponding to this has a large peak distribution corresponding to the macro pattern structure (on the right side of the upper diagram (a) in FIG.
- the x coordinate obtained when the obtained secondary electron signal intensity distribution is cut by a certain threshold value is usually detected as an edge coordinate.
- the threshold value when the threshold value is changed, a plurality of edges corresponding to different height positions z of the structure are detected.
- the edge coordinates fluctuate with uncertainty, and the feature of the fluctuation amount ⁇ is a function of a threshold value. That is, it is a function of different height positions z (or positions x perpendicular to the edges) of the structure.
- a top surface observation image of a structure having the three types of cross-sectional profiles is acquired by CD-SEM, and an edge portion of the structure is designated as an analysis region.
- a designed straight line portion is selected, and the direction along the straight line is defined as the y direction.
- the deviation ⁇ 2 (T) ⁇ [xi (T) ⁇ ⁇ x (T)>] 2 from the average edge position ⁇ x (T)> of the point sequence was calculated.
- ⁇ (T) is plotted against the threshold value T, an upper diagram (a), a middle diagram (b), and a lower diagram (c) in FIG. 5 are obtained.
- the point sequence shown in each stage corresponds to the structure having the cross-sectional profile of the same stage in FIG.
- the x-direction distribution I (x) of the detection signal intensity has a peak near the edge of the structure.
- a so-called line pattern having a convex structure with a certain width W such as a resist line pattern
- two intensity peaks appear corresponding to the left and right edges of each pattern shown in FIG. That is, when one edge is observed, two edge detection points are obtained on both sides of the distribution peak of the detection signal intensity with respect to the same threshold value T. Therefore, ⁇ (T) is obtained separately for each of the inside and outside of the peak structure.
- the x coordinate of the point where the intensity gradually increases from the outside and reaches a predetermined threshold value is defined as the edge position.
- the x coordinate of the point where the intensity gradually increases from the inner side and reaches a predetermined threshold is set as the edge position, and ⁇ (T) is obtained from these values.
- the threshold value and the x coordinate correspond to each other one to one.
- the deviation ⁇ (T) as a function of the threshold value T is converted into a deviation ⁇ (x) as a function of x.
- the deviation ⁇ (T) of the peak with respect to the outside / inside x of the structure is made to correspond to the outside / inside x of each structure.
- the characteristic diagrams shown in the upper diagram (a), the middle diagram (b), and the lower diagram (c) of FIG. 6 all correspond to the structures having the same cross-sectional profile of FIG.
- Each figure of FIG. 6 represents the detected edge fluctuation at the average edge position obtained for the electron beam incident on the position x.
- the deviation ⁇ (x) is large on the flat surface at the outer bottom of the structure, and the incident electron beam is at the edge.
- it rapidly decreases and reaches a minimum value, then gradually increases toward the center of the structure, and reaches a maximum near the flat surface at the top of the structure.
- the deviation ⁇ (x) takes a minimum value, then increases rapidly to take a plateau-like peak, decreases once, gradually increases toward the center of the structure, and near the flat surface at the top of the structure. It becomes maximum.
- the height of the peak is slightly larger in the sample C having the reverse tapered side wall. Such a difference in distribution shape is considered to reflect a difference in cross-sectional profile.
- the average cross-sectional profile ⁇ Z> (x) is considered for convenience, corresponding to the average detection signal intensity distribution ⁇ I> (x), and the three-dimensional shape Z (x, y) is expressed by the following equation.
- the actual three-dimensional shape Z (x, y) shifts the average cross-sectional profile ⁇ Z> (x) by ⁇ x (y) in the x direction according to the edge point position y, and further changes the cross-sectional profile by ⁇ Z (x , y).
- ⁇ x (y) is determined for each y so that, for example,
- the three-dimensional distribution of the actually observed detection signal intensity can also be expressed as follows.
- ⁇ I (x, y) is a term generated by a deviation from the average of the cross-sectional profile corresponding to ⁇ Z (x, y).
- ⁇ noise (x, y) is a random detection noise superimposed on an actual detection image, and its amplitude does not depend on the position / image.
- ⁇ x (y) is determined for each y so that, for example,
- the deviation ⁇ (x) from the average of the detected edge point sequence can also be divided into the components due to the respective terms.
- ⁇ _measured is the measurement result.
- ⁇ _y is a component resulting from variations in edge positions of the structure when the cross section is optimally fitted with an average cross section profile for each y.
- ⁇ _xz is a component resulting from a change in the cross-sectional shape of the structure.
- ⁇ _noise is a component caused by an edge detection error caused by detection (image) noise.
- ⁇ _y is considered as a component having a 1 / f characteristic with respect to the spatial frequency f in the y direction (referred to as “true LER” for convenience).
- Patent Document 1 describes a method of decomposing variation in the x-direction edge point detection position measured along the edge into a component having 1 / f characteristics and other components.
- the decomposition of the LER component may be performed for each threshold value, or may be performed for a certain representative threshold value T.
- True LER is a fluctuation in the y direction of the edge position of the structure itself. Therefore, it can be considered that the measurement results obtained by changing the threshold T are almost common. For this reason, the latter idea is also reasonable.
- ⁇ _noise depends on the slope of the signal intensity distribution.
- FIG. 7 shows the result obtained by adding the intensity gradient in the one-dimensional (x) direction to the image obtained on the smooth flat surface and obtaining the fluctuation of the edge point obtained with respect to the average level threshold value. As shown in FIG. 7, as the intensity gradient of the detection signal increases, ⁇ _noise decreases.
- ⁇ _noise (x) can be calculated by obtaining ⁇ _noise with respect to the gradient at the position x of the average detected intensity distribution from FIG.
- ⁇ _xz can be obtained.
- ⁇ _y and ⁇ _noise are calculated for samples A, B, and C having cross-sectional profiles as shown in the upper diagram (a), middle diagram (b), and lower diagram (c) of FIG. 8 are shown in the upper diagram (a), the middle diagram (b), and the lower diagram (c) of FIG.
- FIG. 8 when the cross-sectional profile is an inversely tapered shape, a significant peak appears in ⁇ _xz.
- the electron beam is considered to be incident on a relatively flat surface at the top of the structure away from the edge point.
- a part of the electrons scattered inside the structure escapes from the side surface or reverse tapered surface of the structure to the outside of the structure and is detected.
- electrons that escape to the outside are affected by the uneven pattern on the side surface.
- the absolute number of electrons that escape to the outside from a surface different from the incident surface is small.
- the number of electrons detected by surface scattering is relatively small, it is considered that the influence of the electrons affected by the uneven pattern on the side surface on the detection result for the forward tapered surface cannot be ignored.
- This effect depends on the area of the vertical or reverse taper surface within the range of the electron beam penetration length inside the structure, and is greater as the vertical or reverse taper surface height is larger.
- the influence extends to an electron beam incident on a relatively wide area closer to the inside from the edge of the structure.
- the peak of ⁇ _xz seen in the upper diagram (a), the middle diagram (b) and the lower diagram (c) of FIG. 8 indicates that the electron beam is on the upper flat surface of the structure in a structure having a vertical or reverse tapered side surface. Seen when incident. From this, the peak of ⁇ _xz that appears on the upper flat surface of the structure is considered to be due to classification 2.
- ⁇ _xz is represented by the following two components (formula 4) (1) Influence of uneven pattern on the forward tapered surface near the electron beam incident point: ⁇ _xz_near (2) Influence of uneven pattern on a substantially vertical or reverse tapered surface relatively far from the electron beam incident point: ⁇ _xz_far
- the detection position when the beam is incident on the center of the concave portion, the detection position has a maximum deviation in the positive direction of the phase, and when the beam is incident on the center of the convex portion, the detection position has the largest deviation in the negative direction of the phase. .
- the shift amount of the edge detection position due to the unevenness is determined by the x coordinate position of the convex center, and the fluctuation amplitude ⁇ x is the x-direction distance between the convex centers in the above two cases. Accordingly, assuming that the concave-convex period on the side wall surface is L (that is, the distance in the x direction is L / 2) and the detection position is determined by the middle diagram (b) of FIG. ⁇ X can be estimated by the following equation using the uneven period L and the angle (tilt angle) ⁇ of the side wall inclined surface.
- the fluctuation range ⁇ X of the edge detection position is expressed by the following equation depending on the height H and the angle (inclination angle) ⁇ of the side wall inclined surface. Can be estimated.
- Formula 5 is dominant in a region where the tilt angle ⁇ is relatively small
- Formula 6 is dominant in a region where the tilt angle ⁇ is relatively large.
- the inclination angle ⁇ depends on both the concave and convex period and the height of the side surface. Therefore, the fluctuation range ⁇ X of the edge detection position can be estimated by the following equation obtained by adding both equations.
- the relationship between the variation width ⁇ X of the edge detection position and the inclination angle ⁇ of the inclined surface can be obtained by using the characteristic that the intensity fluctuation amount of the electron beam signal due to the surface unevenness depends on the incident angle of the electron beam to the surface. it can.
- the detection signal intensity distribution is calculated by simulation when an electron beam with various incident angles is irradiated and scanned on a flat surface (upper figure (a1) in FIG. 10) having irregularities with an appropriate period L or height H on the surface. (Upper diagram (a2) in FIG. 10).
- the fluctuation range ⁇ I of the detected intensity is a function of the incident angle ⁇ (middle diagram (b) in FIG. 10).
- the relationship between the intensity fluctuation range ⁇ I ( ⁇ ), the edge detection position fluctuation range ⁇ X, and the average signal intensity distribution I (x) is expressed by the following equation as shown in the lower diagram (c) of FIG. Can do.
- Equation 8 diverges when the gradient becomes 0 (zero) at the peak of the intensity distribution of the detection signal. For this reason, it should be noted that Equation 8 cannot be used when the gradient is 0 (zero) at the peak of the intensity distribution of the detection signal.
- the amplitude ⁇ X of the edge shift amount is a statistical amount estimated from the measurement variation of the edge detection position due to the unevenness on the side wall surface, and ⁇ _xz_near corresponds to this.
- a statistical representative value is also used for the period L and the height H.
- the flat surface may be selected so that the inclination angle ⁇ is 0 (zero).
- the component (2) influence of the uneven pattern at the surface position away from the incident position of the beam
- the detection intensity when the electron beam is incident on the point Q in the upper diagram (a) of FIG. 11 is IQ with respect to the average side wall surface, the side wall surface as shown by curves A and B in FIG.
- the detected intensity changes by ⁇ IA and ⁇ IB with respect to the detected intensity IQ, and the detected edges are shifted by ⁇ x A and ⁇ x B , respectively.
- the height of the trapezoid depends on the height and angle of the side wall, but for example, according to Equation 4, the distribution of ⁇ _xz_near after subtracting ⁇ _xz_far from ⁇ _xz is almost linear from 0 (zero) on the structure side from the minimum value of ⁇ _xz It is conceivable to set the height so as to increase.
- the result of decomposing ⁇ _xz into the above two components is shown in the upper diagram (a) and middle diagram ( It is shown in b) and lower figure (c).
- the cross-sectional shape of the actual structure is considered to have various shapes, such as rounded shapes and hems. That is, generally, the side wall angle ⁇ is not constant with respect to the height direction of the structure or the position in the x direction. If the method according to the present embodiment is used, the cross-sectional shape of such a structure can be estimated appropriately.
- the cross-sectional estimation method based on the two approaches of the analytical shape estimation method and the model-based shape estimation method will be described.
- the local angle of the structure surface at the corresponding height of the structure is calculated by using Equation 5, Equation 6, Equation 7, Equation 8, etc. with respect to the threshold value or the position in the x direction. It is obtained and integrated in the x direction to obtain the cross-sectional shape of the structure. That is, the cross-sectional shape is obtained by the following equation. However, in the following equation, the integration range is from 0 (zero) to x.
- Equations 5 and 8 the distribution of ⁇ (x) estimated from ⁇ _xz_near in FIG. 12 and the estimated cross-sectional shape Z (x) are shown in the upper diagram (a) and middle diagram (b) of FIG. And the lower diagram (c) respectively.
- the estimated cross-sectional shape (the shape indicated by the solid line) is in good agreement with the shape obtained from cross-sectional observation (the shapes in the upper (a), middle (b), and lower (c) of FIG. 4).
- the distribution of detected signal intensity when the surface irregularities (for example, the phase) are changed for various cross-sectional shapes, and the edge positions detected for each are obtained.
- a variation (uncertainty) between them is obtained in advance as a function of a threshold value or a position in the x direction.
- this variation (uncertainty) is matched with an actual measurement result, and the closest cross-sectional shape is obtained or the cross-sectional shape is estimated by interpolation / extrapolation.
- the conventional MBL method that estimates the cross-sectional shape by finding the matching between the calculation result library of the detection signal intensity distribution itself and the measurement result has the problem that the measurement result is affected by the detection system and detection intensity fluctuation In contrast, the method is less susceptible to these effects.
- the present method and the conventional MBL method can be used in combination. Further, a maximum likelihood method or the like may be used for matching.
- FIG. 14 shows a flowchart of a method for estimating the three-dimensional shape of the structure corresponding to the first embodiment. Note that a series of processes described later is realized based on a program executed by a computer.
- a two-dimensional image is acquired with an electron microscope, and an analysis region is designated (step 1401). Thereafter, an average signal intensity distribution I (x) in the designated analysis region is calculated (step 1402).
- the signal strength is normalized by the maximum strength in the specified range. At this time, it is desirable to adjust the image so that the average edge direction in the above range is the y direction.
- a threshold value is set at a predetermined interval from a specified minimum value to a maximum value (for example, every 5% from 5% to 100%), a pattern edge is detected for each threshold value, and the threshold value T LER is obtained as a function of (steps S1403 to 1408).
- the side wall angle ⁇ is obtained according to Equation 5, Equation 6, Equation 7, Equation 8, etc. (Steps S1409, 1410), and the side wall angle ⁇ is integrated in the x direction to obtain a cross-sectional shape (Step S1411).
- FIG. 15 shows a schematic diagram of the hardware configuration of the CD-SEM used in this example.
- the CD-SEM of this example is mainly composed of a scanning electron beam microscope casing 1801 composed of an electron optical column (SEM column) and a sample chamber, a scanning electron microscope control system 1811, and an information processing device 1812. Is done.
- the data processing device 1812 is connected to a data storage device 1813 for storing the obtained scanned electronic image and CAD data necessary for analysis.
- the data storage device 1813 may be stored in the information processing device 1812.
- the information processing apparatus 1812 displays an information input terminal for the CD-SEM operator to input information necessary for data processing to the apparatus and the acquired scanning electronic image.
- Image display means is provided. Specific examples of the information input terminal include a keyboard, a mouse, and a GUI screen displayed on the image display means.
- the electron optical column includes an electron gun 1802, a converging lens 1804, a deflector 1805, an objective lens 1806, a detector 1810, and the like.
- the sample chamber includes a stage 1808 on which an observation wafer 1807 to be inspected is placed. Secondary electrons 1809 generated by the electron beam 1803 irradiated to the observation wafer 1807 from the electron gun 1802 are detected by the detector 1810, converted into digital data by the control system 1811, and then transferred to the information processing device 1812. Image data used for analysis is generated.
- pattern observation was performed using a scanning electron microscope provided in a CD-SEM, and image data to be inspected was acquired.
- the obtained image data was stored in the data storage device 1813.
- the image data analysis was performed by operating the information input terminal, and the roughness index and the cross-sectional structure estimation were analyzed.
- the analysis process is executed by the information processing apparatus 1812.
- the control system 1811 (information processing device 1812) averages the secondary electron signal intensity obtained by scanning the ArF resist line pattern 32 times from the upper left to the lower right of the field of view to obtain the secondary electrons.
- a two-dimensional distribution image of signal intensity is acquired.
- the information processing apparatus 1812 displays the acquired image on the CD-SEM monitor screen as necessary.
- the number of pixels of the observation image is 1500 pixels in the vertical and horizontal directions, one side of each pixel is 1 nm (nanometer), and the length of the observation image in the field of view is 1.5 ⁇ m (micrometer) in the vertical and horizontal directions.
- the information processing apparatus 1812 sets a rectangular inspection region of 1024 pixels vertically and 50 pixels horizontally in a region including an edge to be analyzed in the two-dimensional distribution image of the secondary electron signal intensity. Further, the minimum value Tmin, the maximum value Tmax, the increment value ⁇ T of the threshold value T for edge extraction, the sampling interval ⁇ y in the y direction for data extraction, the noise reduction parameter in the x direction, the averaging parameter S in the y direction, etc. Set the information required for data series extraction. It is also possible to set the number of detection points instead of the sampling interval in the y direction in data extraction. These inspection regions and data series extraction conditions are preferably set in advance through, for example, a GUI screen of a CD-SEM.
- the information processing apparatus 1812 executes a task of extracting the edge roughness data series in the region. That is, the information processing device 1812 calculates a signal intensity distribution corresponding to the y coordinate at the sampling position from the pixel data in the inspection region according to the set extraction start point and sampling interval, and further, from the minimum value Tmin to the maximum value
- the x coordinate data of the edge point is calculated from the signal intensity distribution according to the threshold value T set for each increment value ⁇ T up to Tmax.
- the information processing apparatus 1812 sets the y coordinate corresponding to the lower side of the inspection area as the y coordinate of the data extraction start point, sets 1 nm (nanometer) as the sampling interval in the y direction, and performs the inspection. 1024 point positions (x1 (T), y1 (T)), ... (xi (T), yi (T)), ... (x1024 (T) as edge points in the region every 1nm (nanometer) Therefore, y1024 (T)) was extracted.
- the information processing apparatus 1812 approximates the extracted points with the following straight lines, and obtains values of ⁇ and ⁇ as fitting parameters.
- the method described in Patent Document 1 can be used as a method for obtaining the measurement variation ⁇ _y due to the true LER and the measurement variation ⁇ _xz due to the surface unevenness from the edge roughness series. Is as follows.
- a component whose power spectral density is inversely proportional to the square of the spatial frequency f and other high-frequency components (noise) are superimposed on the measured LER. If the measured LER is averaged, the latter component is reduced. For this reason, as the parameter value representing the degree of the averaging process is increased, the power spectral density distribution in the high frequency region becomes inversely proportional to the square of f. Specifically, considering that one-dimensional signal intensity distributions in the x direction at different y coordinates are averaged in the y direction, the random noise intensity is reduced to 1 / S by averaging. That is, as the averaging parameter S increases, the frequency dependence of the power spectral density approaches 1 / f 2 . The density of the power spectrum obtained at this time becomes true LER.
- ⁇ m (1) is a line edge roughness measurement value obtained from the data before the averaging process
- ⁇ y is the y direction extraction interval of the edge points
- A is a fitting parameter. It is desirable that the extraction interval ⁇ y between S and the edge point satisfies 2S ⁇ y ⁇ 1 / f 0 [nm (nanometer)].
- f 0 is often 0.008 nm ⁇ 1 or less at the inflection point of the spectrum.
- ⁇ 0 ⁇ obtained with respect to the smallest S among S that well explains the experimental results is defined as a true LER.
- the measurement variation component ⁇ b independent of the spatial frequency is obtained by the following equation.
- the information processing apparatus 1812 obtains a measurement error ⁇ _noise from the measured LER and removes it from ⁇ b (T), thereby measuring variation due to projection of the uneven pattern on the sidewall surface on the xy plane (uncertainty). ) ⁇ _xz (T) indicating).
- the side wall angle ⁇ at the height corresponding to the threshold value T of the structure is obtained by the following equation.
- ⁇ s is a representative value of the spatial period of the surface irregularities.
- the average ⁇ I> (x) of the signal intensity distribution in the x direction was calculated for the measurement range in the y direction.
- ⁇ I> ⁇ 1 is an inverse function of ⁇ I>.
- the cross-sectional shape thus obtained was compared with the cross-sectional shape observed by SEM after cutting the pattern portion of the wafer, and it was confirmed that they were in good agreement. In addition, a comparison with the measurement result by AFM was also made, and it was confirmed that this also coincided well.
- ⁇ s and ⁇ _noise are measured and obtained independently as values having physical meanings, but these amounts may be considered as fitting parameters. That is, ⁇ s and ⁇ _noise may be used so that the cross-sectional shape observed by another method and the cross-sectional shape estimated by the present invention are in good agreement.
- Example 2 In this embodiment, an example of a method capable of estimating a three-dimensional structure not only for a cross-sectional structure of a one-dimensional mask pattern but also for a two-dimensional mask pattern will be described. Since the configuration of the scanning electron microscope used in the present embodiment is the same as that of the first embodiment, the description thereof is omitted.
- the following two methods can be considered as a method of extending the method of the first embodiment to a two-dimensional mask pattern.
- First method In this method, the relationship between the threshold value and the pattern height is obtained for the one-dimensional pattern by the method of the first embodiment, and this relationship is applied to the two-dimensional pattern as it is.
- the information processing device 1812 converts T in the upper middle diagram of FIG. 16 into z in accordance with the relationship between the height z of the structure and the threshold value T, and a two-dimensional pattern as shown in the upper right diagram of FIG. Get height information. Note that the relationship shown in the lower part of FIG. 16 is established between T and z. Data giving this relationship is stored in advance in the data storage device 1813, for example.
- the second method will be described. This method can be applied when the same design pattern exists at a plurality of different positions on the same mask.
- the information processing apparatus 1812 observes a plurality of two-dimensional patterns on the wafer formed on a plurality of the same two-dimensional patterns on the mask under the same conditions, and obtains a plurality of SEM images (signal intensity distributions).
- the information processing apparatus 1812 obtains an edge coordinate sequence when it is cut at a certain threshold value T, and considers contour lines connecting the coordinate points. At this time, in order to ensure measurement accuracy, it is desirable to extract the edge by obtaining a signal intensity distribution along a direction substantially perpendicular to the contour line and applying a threshold value thereto.
- the information processing apparatus 1812 shifts each image in the parallel direction so that the sum of the distance deviations between contour lines obtained for the plurality of images is minimized.
- the reference for the shift position may be set as appropriate.
- the information processing apparatus 1812 calculates an average shape for the contour lines of each image after the parallel shift, and calculates a difference (distance) between the contour lines of each image and the average shape in a direction perpendicular to the tangent line of the contour lines. .
- the information processing apparatus 1812 obtains the standard deviation of the difference distribution for each edge point, and assumes this to be a value corresponding to ⁇ b (T) in the first embodiment.
- the inclination angle ⁇ obtained using Equation 5, Equation 6, Equation 7, Equation 8, and the like is set as the sidewall angle ⁇ of the height corresponding to the threshold value T at the position.
- a vertical structure along the direction can be obtained by performing integration similar to Equation 9 along the direction in which the threshold T is changed and the edge is extracted.
- ⁇ b (T) obtained by the second method includes a component corresponding to a true LER, but the edge shift caused by a relatively long period of LER cancels out by performing a parallel shift. Expected to be able to. Further, it is desirable that the true LER short period component and the measurement miscalculation component are appropriately removed from the ⁇ b (T).
- ⁇ s and ⁇ e may be obtained by measuring each independently as values having physical meanings, or may be considered as fitting parameters. .
- the inventor has confirmed that the cross-sectional shape of the structure estimated by such a technique is in good agreement with the cross-sectional shape observed as an SEM image by cutting the same structure.
- Example 3 In this embodiment, the present invention is applied to a resist pattern formation process by photolithography used for manufacturing a semiconductor integrated circuit or the like, or a three-dimensional structure quality evaluation of a semiconductor integrated circuit formed using the resist pattern forming process, and the process monitor. An example will be described.
- the quality index of the formed pattern a value obtained by integrating the absolute value of the deviation between the estimated pattern height and the design pattern height over the entire evaluation area, or the root mean square of the values A value is used (amount corresponding to the area of the hatched portion in the right diagram of FIG. 17A).
- the cross-sectional area Sp of the cross-sectional shape estimated by applying the method of the above-described embodiment for example, the lower portion of the curve in the left diagram of FIG. 17A
- the ideal design shape for example, FIG. 17.
- the ratio Vp / Vi of the shape volume Vi may be used as a pattern quality index.
- the ideal design shape for a two-dimensional mask pattern includes a circuit pattern design shape, optical simulation results for a mask pattern obtained by performing optical proximity effect correction on the circuit design shape, and various actual exposure results.
- the maximum value of the volume estimated by applying the method described in the above embodiment can be used.
- the resist pattern for the same pattern on the mask is CD-SEM for each exposure shot.
- the pattern size was measured for each shot from the observed image, the pattern cross-sectional shape was estimated by the method described in Example 1, and the pattern quality index was obtained.
- the pattern dimension monotonously decreased with respect to the exposure amount, but the pattern dimension change with respect to the focus setting value is small, and the focus setting value is estimated from the pattern dimension change. was difficult.
- the pattern quality index changes almost monotonously with respect to both the exposure amount and the set value of the focus, and can be applied as a monitor of the focus set value. .
- the pattern quality index also changes with respect to the exposure amount. Therefore, it is desirable to first estimate the exposure amount from the pattern dimension change, and estimate the focus setting value for the exposure amount using a pattern quality index.
- the estimated cross-sectional shape when used as a quality index of the formed pattern, it is possible to determine optimum manufacturing conditions easily and at high speed, or to detect quality degradation. Further, if the determination result or the like is fed back to the manufacturing process, the quality deterioration of the formed pattern can be suppressed, and the performance of various elements including the semiconductor device can be improved.
- Example 4 As another method for obtaining ⁇ x and ⁇ s, a method for frequency analysis of a two-dimensional signal intensity distribution in the xy direction will be described. That is, the secondary source solid shape estimation method according to the second embodiment will be described.
- the inclination angle ⁇ is obtained by the following equation.
- the observed two-dimensional intensity distribution of the secondary electron signal is firstly a macroscopic intensity distribution in the x direction, secondly an intensity fluctuation due to a true LER in the y direction, and thirdly a local unevenness due to surface irregularities. Including three fluctuation factors, intensity fluctuation. Therefore, by removing the first and second variation factors from the observed image, only the third surface unevenness information can be extracted. An example of a specific procedure will be described with reference to FIG.
- the information processing apparatus 1812 designates an analysis region and acquires a two-dimensional intensity distribution in the region (step S1901).
- the information processing apparatus 1812 applies two-dimensional spatial frequency filtering to the acquired two-dimensional intensity distribution, and sums the portion resulting from the first variation component and the portion excluding the high-frequency component from the second variation component. And the sum of the high-frequency component of the second variation component and the portion due to the third variation factor (step S1902).
- the latter includes high frequency components of fluctuation due to true LER and fluctuation due to surface irregularities.
- the x direction spatial period of the intensity distribution change changes in the x direction. Therefore, it is desirable to evaluate the spatial period locally with respect to the x direction.
- a wavelet analysis As a general method for performing such an analysis, for example, there is a wavelet analysis.
- the information processing apparatus 1812 detects a change in spatial frequency characteristics along the x direction by performing wavelet analysis in the x direction (step S1903).
- FIG. 20 shows an example of x dependence of the spatial frequency characteristic (spatial frequency dependence of power spectral density PSD) obtained by this method.
- the spatial frequency characteristic changes depending on x.
- the frequency at the peak position is set as the representative spatial frequency, and when the peak is not clear, the spatial frequency distribution spread (for example, half width) is increased.
- the spatial frequency ⁇ x in the x direction is obtained by using the representative spatial frequency and the reciprocal thereof.
- the information processing apparatus 1812 obtains ⁇ y from the representative spatial frequency obtained by performing spatial frequency analysis in the y direction.
- the information processing apparatus 1812 may perform a two-dimensional wavelet analysis in both xy directions. In this process, the information processing apparatus 1812 estimates the high-frequency component of the second fluctuation component and removes it from the latter as necessary. In this way, the information processing apparatus 1812 obtains a two-dimensional distribution of ⁇ x and ⁇ y.
- the information processing apparatus 1812 obtains the two-dimensional distribution ⁇ (x, y) of the sidewall angle from the following equation (step S1904).
- the information processing apparatus 1812 estimates a two-dimensional solid shape by integrating the above expression at the position (x, y) (step S1905).
- Example 5 In this embodiment, a case where the uneven pattern formed on the surface of the structure is not necessarily isotropic will be described.
- the sidewall shape of the resist structure may be affected by standing waves due to exposure light interference in the resist film.
- the secondary electron signal intensity distribution is observed as a plurality of edges parallel to one edge of the structure as shown in FIG.
- the side wall inclination angle between a plurality of edges is expressed by the following equation, where the edge interval is ⁇ Lx.
- ⁇ is the wavelength of the light used for the exposure of the resist pattern
- n is the refractive index of the resist material with respect to the light of the wavelength.
- the period in the edge direction (y direction) of the unevenness is not changed, but the dimension in the vertical direction is changed.
- the vertical dimension of the unevenness is approximately Retch times. Conceivable.
- L in Expression 5 may be multiplied by Retch.
- the etching also proceeds (etching) in a direction (x direction) perpendicular to the edge direction.
- the aspect ratio of the unevenness is not necessarily equal to Retch. Therefore, for example, it is preferable to optimize L in Formula 5 as a fitting parameter so that the cross-sectional shape observed by another method and the cross-sectional shape estimated by the above-described method agree well.
- the most general concept of the present invention is to estimate the three-dimensional shape of a structure from information on local variations in the signal intensity distribution of a two-dimensional image obtained by observing the structure from the top. Therefore, the estimation algorithm is not limited to the method shown above.
- each of the above-described configurations, functions, processing units, processing means, and the like may be partly or entirely realized as, for example, an integrated circuit or other hardware.
- Each of the above-described configurations, functions, and the like may be realized by the processor interpreting and executing a program that realizes each function. That is, it may be realized as software.
- Information such as programs, tables, and files for realizing each function can be stored in a memory, a hard disk, a storage device such as an SSD (Solid State Drive), or a storage 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 do not represent all control lines and information lines necessary for the product. In practice, it can be considered that almost all components are connected to each other.
Abstract
Description
例えばAFMによる方法では、回路パターンの寸法が縮小するのに伴い、探針がパターン間に入り込むことができず、形状測定が困難になるという課題がある。
まず、本発明で用いる電子顕微鏡による観察像の形成過程を、図1を用いて説明する。単純化のため、基板面上に形成された略立方体状の構造体(例えば半導体やレジストパターン等)を考える。基板面をx-y平面、構造体のエッジの延びる方向(エッジ方向)をy方向とする。上記構造体の特徴寸法より十分に細く収束された電子線を、上記基板面と略垂直な方向(z方向)から基板上に照射すると共に、基板上を上記エッジ方向と略垂直な方向(x方向)に走査する。上記基板又は構造体に入射した電子は、基板又は構造体内部で散乱を受けて2次電子を放出し、又は直接反射(又は後方散乱)され、その一部を基板又は構造体の外部へ放出する。上記2次電子又は反射電子(以下、「2次電子等」という)の放出量は、電子線が凸形状の凸部(又は角の上部)に入射した場合に増大する。
以下、本発明の第1の実施形態による構造体の立体(断面)形状推定方法の詳細について説明する。以下では、図4の上段図(a)、中段図(b)及び下段図(c)に示す断面プロファイルを有する3種類の試料A、B及びCを解析対象とする。
このような分布形状の差異は、断面プロファイルの違いを反映したものと考えられる。
まず、解析領域内部において、平均検出信号強度分布<I>(x)に対応して、便宜的に平均断面プロファイル<Z>(x)を考え、実際の構造体の3次元形状Z(x,y)を次式で表わす。
次に、計測されたエッジ変動値σ_measuredを、上述した4つの成分に分解する方法について説明する。以下、各成分について説明する。
ここで、図4の上段図(a)、中段図(b)及び下段図(c)に示すような断面プロファイルを有する試料A、B及びCに対してσ_y及びσ_noiseを計算し、想定結果σ_measuredを、σ_y、σ_noise、σ_xzに分解した結果を図8の上段図(a)、中段図(b)及び下段図(c)に示す。図8から分かるように、断面プロファイルが逆テーパ形状である場合、σ_xzに顕著なピークが現れる。
この分類では、電子線は、最初に順テーパ面に入射すると考える。このとき、構造体内部で散乱された後、再び構造体外に出て検出される電子の数は、順テーパ面上の入射位置のごく近傍の凹凸パターンの影響を受けると考えられる。
この分類では、電子線は、エッジ点から離れた構造体上部における比較的平坦な面に入射すると考える。このとき、構造体内部で散乱された電子の一部が構造体の側面又は逆テーパ面から構造体の外部へ抜け出し、検出される。このとき、外部に抜け出す電子は、側面の凹凸パターンの影響を受ける。このように入射面とは異なる面から外部に抜け出す電子は、その絶対数が少ない。しかし、表面散乱により検出される電子数も比較的少ないので、側面の凹凸パターンの影響を受けた電子が順テーパ面に対する検出結果に及ぼす影響は無視できないと考えられる。
(1)電子線入射点近傍の順テーパ面上の凹凸パターンの影響
:σ_xz_near
(2)電子線入射点から比較的離れた略垂直又は逆テーパ面上の凹凸パターンの影響
:σ_xz_far
まず、凹凸パターンを有する順テーパ面に入射した電子線の散乱に及ぼす凹凸の影響(上記(1)の成分)について考える。ある一定角度の傾斜面に正弦波状の凹凸が存在し、凹部又は凸部の中心(図9の上段図(a)の点P)にビームが入射したとする。ビームの入射位置に対して凹凸の位相を180度変化させると、検出位置が、位相の±方向に1周期分変動する。例えば、ビームが凹部の中心に入射した場合、検出位置は位相の+方向に最大のずれが生じ、ビームが凸部の中心に入射した場合、検出位置は位相の-方向に最大のずれが生じる。
平均的な側壁面に対し、図11の上段図(a)のQ点に電子線が入射したときの検出強度をIQとする場合に、同図内の曲線A及びBに示すように側壁面のパターンが変動した場合を考える。このとき、図11の下段図(b)に示すように、検出強度は検出強度IQに対してΔIA及びΔIBだけ変化し、検出エッジはそれぞれΔxA、ΔxBだけずれる。
次に、不確かさを表す偏差σを分解した結果から、構造体の断面形状を推定する方法について説明する。
(解析的推定法)
解析的推定法では、しきい値又はx方向の位置に対し、式5、式6、式7、式8等を用いて、構造体の対応する高さにおける構造体表面の局所的な角度を求め、これをx方向に積分することにより構造体の断面形状を求める。すなわち、次式により、断面形状を求める。ただし、次式において積分範囲は0(zero)からxまでである。
図14に、第1の実施形態に対応する、構造体の立体形状を推定するための方法のフローチャートを示す。なお、後述する一連の処理は、計算機で実行されるプログラムに基づいて実現される。
本実施例では、前述した推定手法をCD-SEMに適用した実施例について説明する。
(装置構成)
図15に、本実施例で用いたCD-SEMのハードウェア構成の模式図を示す。本実施例のCD-SEMは、主として電子光学カラム(SEMカラム)と試料室からなる走査型電子線顕微鏡の筐体1801と、走査型電子線顕微鏡の制御系1811と、情報処理装置1812により構成される。
まず、制御系1811(情報処理装置1812)は、ArFレジストのラインパターンに対し、視野の左上から右下までの走査を32回行って得られた二次電子信号強度を平均化し、2次電子信号強度の2次元分布画像を取得する。必要に応じ、情報処理装置1812は、取得した画像をCD-SEMのモニタ画面上に表示する。ここで、観察画像の画素数は、縦・横方向に1500画素、1画素の1辺を1nm(ナノメートル)、視野内の観察画像の長さを縦横1.5μm(マイクロメートル)とする。
次に、情報処理装置1812は、エッジラフネス系列X(T)={Δxi(T)}からしきい値毎にLERを求め、求めたLERを真のLERによる測定ばらつきσ_yと、表面凹凸による計測ばらつきσ_xzとに分解する。エッジラフネス系列から、真のLERによる測定ばらつきσ_yと表面凹凸による計測ばらつきσ_xzを求める方法については、例えば特許文献1に記載されている方法を用いることができるが、その代表的な手段について述べるならば以下の通りである。
本実施例においては、1次元マスクパターンの断面構造だけでなく、2次元マスクパターンに対しても立体的構造を推定できる方法の一例を説明する。本実施例で用いる走査形電子顕微鏡の構成は、実施例1と同様なので説明を省略する。
[第1の方法]
この方法では、実施例1の方法により1次元パターンに対してしきい値とパターン高さの関係を求め、この関係をそのまま2次元パターンに対して適用する。
この方法では、実施例1の方法を2次元エッジ情報に対して拡張する。
まず、第1の方法について説明する。情報処理装置1812は、実施例1の方法と同様に取得した2次元画像(図16の上段左図)に対し、その1次元パターン部分に実施例1の方法を適用して断面形状z=Z(x)を求める(推定する)。
本実施例では、本発明を、半導体集積回路等の製造に用いられる光リソグラフィによるレジストパターン形成プロセス、又はそれを用いて形成した半導体集積回路の立体的構造の品質評価、並びに上記プロセスモニターに適用する例について説明する。
本実施例では、σx、σsを求める別の方法として、xy方向の2次元信号強度分布を周波数分析する方法について説明する。すなわち、第2の実施形態による2次源立体形状の推定方法について説明する。
本実施例では、構造体の表面に形成された凹凸パターンが必ずしも等方的でない場合について説明する。構造体表面の凹凸パターンが等方的であるという前提が成り立たないケースには、例えばレジスト構造体の側壁形状が、レジスト膜内における露光光の干渉による定在波の影響を受ける場合がある。この場合、2次電子信号強度分布は、図21に示すように、構造体の1本のエッジに対して、平行する複数のエッジとして観察される。この場合、複数エッジ間の側壁傾斜角度は、エッジ間隔をΔLxとして、次式で表される。
なお、本発明は上述した実施例に限定されるものでなく、様々な変形例を含んでいる。例えば上述した実施例は、本発明を分かりやすく説明するために、一部の実施例について詳細に説明したものであり、必ずしも説明した全ての構成を備える必要は無い。また、ある実施例の一部を他の実施例の構成に置き換えることが可能であり、ある実施例の構成に他の実施例の構成を加えることも可能である。また、各実施例の構成の一部について、他の構成を追加、削除又は置換することも可能である。
1802…電子銃
1803…電子線
1804…収束レンズ
1805…偏向器
1806…対物レンズ
1807…観察ウエハ
1808…ステージ
1809…二次電子
1810…検出器
1811…制御系
1812…情報処理装置
1813…データ記憶装置
Claims (10)
- 計算機に、
立体的な構造体が上面に形成された基板の主面に略垂直な方向から収束エネルギー線を照射するとともに上記基板の上面を走査させ、上記基板及び上記構造体から発生した2次エネルギー線又は上記基板及び上記構造体により反射若しくは散乱されたエネルギー線の強度を検出及び/又は測定し、上記構造体の上面観察像を取得する処理と、
上記上面観察像における収束エネルギー線の照射位置と測定された上記強度から上記構造体の表面の凹凸形状による散乱強度の不確かさ情報を求める処理と、
求めた上記不確かさ情報に基づいて上記構造体の表面の傾斜角度θを求める処理と、
求めた傾斜角度θに基づいて上記構造体の立体形状を推定する処理と
を実行させるパターン形状評価方法。 - 請求項1に記載のパターン形状評価方法において、
上記収束エネルギー線は収束電子線であり、上記2次エネルギー線は2次電子である
ことを特徴とするパターン形状評価方法。 - 請求項1に記載のパターン形状評価方法において、
上記不確かさ情報を求める処理は、
上記2次エネルギー線の強度の異なる複数のレベルに対応して複数のエッジ点列を抽出し、上記複数のエッジ点列の各座標の設計座標からのずれを算出してエッジ点の変動値を算出するサブ処理と、
上記変動値に基づいて、上記異なる複数のレベルに対応する上記上面観察像上の各位置における前記構造体の表面の傾斜角度を求めるサブ処理と
を有することを特徴とするパターン形状評価方法。 - 請求項3に記載のパターン形状評価方法において、
上記エッジ点の変動値を算出するサブ処理は、
上記複数のエッジ点列の空間周波数に依存しない成分を求める工程、
上記エッジ点列からそのパワースペクトルが空間周波数の2乗に反比例する成分を除去する工程、又は、
検出されたノイズ成分を除去する工程
を有することを特徴とするパターン形状評価方法。 - 請求項1に記載のパターン形状評価方法において、
上記傾斜角度θを求める処理は、
上記上面観察像のある所定の領域内において、上記不確かさ情報σxの関数として、上記領域の前記基板の主面に対する傾斜角度θを求める
ことを特徴とするパターン形状評価方法。 - 請求項1に記載のパターン形状評価方法において、
上記傾斜角度θを求める処理は、
上記上面観察像の上記強度の分布に対して異なる複数のしきい値を設定し、各しきい値に対して複数のエッジ点列を抽出することにより求めた傾斜角度θを、上記複数のエッジ点列の各エッジ位置における傾斜角度θとし、
上記立体形状を推定する処理は、
上記上面観察像の各点における傾き角度分布を求め、上記傾き角度の分布を積分することにより立体形状を推定する
ことを特徴とするパターン形状評価方法。 - 請求項1に記載のパターン形状評価方法において、
上記不確かさ情報を求める処理は、
前記上面観察像内の局所領域における2次エネルギー線の強度変動のエッジに垂直及び平行な方向に対する空間周波数特性の差に基づいて、上記局所領域における前記構造体の表面の傾斜角度を求めるサブ処理を含む
ことを特徴とするパターン形状評価方法。 - 請求項3に記載のパターン形状評価方法において、
上記エッジ点列は曲線である
ことを特徴とするパターン形状評価方法。 - 計算機に、
半導体装置を含む立体的な構造体が上面に形成された基板の主面に略垂直な方向から収束エネルギー線を照射するとともに上記基板の上面上を走査させ、上記基板及び上記構造体から発生した2次エネルギー線又は上記基板及び上記構造体により反射若しくは散乱されたエネルギー線の強度を検出及び/又は測定し、上記構造体の上面観察像を取得する処理と、
上記上面観察像における収束エネルギー線の照射位置と測定された上記強度から上記構造体の表面の凹凸形状による散乱強度の不確かさ情報を求める処理と、
求めた上記不確かさ情報に基づいて上記構造体の表面の傾斜角度θを求める処理と、
求めた傾斜角度θに基づいて上記構造体の立体形状を推定する処理と
推定された上記立体形状の特徴に基づいて上記半導体装置の製造工程における製造条件を推定する処理と
を実行させる半導体装置の製造方法。 - 立体的な構造体が上面に形成された基板の主面に略垂直な方向から収束エネルギー線を照射するとともに上記基板の上面上を走査させ、上記基板及び上記構造体から発生した2次エネルギー線又は上記基板及び上記構造体により反射若しくは散乱されたエネルギー線の強度を検出及び/又は測定し、上記構造体の上面観察像を取得するデータ処理部と、
上記上面観察像における収束エネルギー線の照射位置と測定された上記強度から上記構造体の表面の凹凸形状による散乱強度の不確かさ情報を求めるデータ処理部と、
求めた上記不確かさ情報に基づいて上記構造体の表面の傾斜角度θを求めるデータ処理部と、
求めた傾斜角度θに基づいて上記構造体の立体形状を推定するデータ処理部と
を有するパターン形状評価装置。
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