JP2019012137A - Evaluation method, evaluation apparatus, exposure system, and method for manufacturing device - Google Patents

Abstract

To efficiently evaluate process conditions with high accuracy when a pattern is formed on a substrate, by using the patterned substrate.SOLUTION: An evaluation method is provided for evaluating process conditions of a repeated pattern based on template information including, as an input value, a signal obtained by irradiating a surface of a wafer (wafer surface) where the repeated pattern is formed on the surface thereof with illumination light and then detecting diffracted light exiting from the wafer surface by the irradiation with the illumination light. The method includes: inputting a varied input value obtained by adding a fixed value as a variation to the above input value; calculating or estimating a variation in the process conditions based on the template information accepting the varied input value; and evaluating stability and the like of the evaluation results of the template information based on the calculated or estimated variation in the process conditions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an evaluation technique for evaluating a processing condition of a pattern formed on a substrate, an exposure technique using the evaluation technique, and a device manufacturing technique using the evaluation technique.

In a lithography process for manufacturing a device (semiconductor device, etc.), a photosensitive resin (so-called resist) is applied to a substrate such as a semiconductor wafer (hereinafter simply referred to as a wafer) by a coater / developer, and the substrate is exposed. The mask pattern image is exposed by the apparatus, and the exposed substrate is developed and etched.
In addition, in order to increase the yield of devices to be finally manufactured, film thickness conditions (such as a set value of the applied film thickness) in the coater / developer, exposure conditions in the exposure apparatus, and / or etching time in the etching apparatus, etc. It is necessary to manage the machining conditions in a desired state with high accuracy. Exposure conditions in the exposure apparatus include an exposure amount (so-called dose), a focus position (a defocus amount of the substrate to be exposed with respect to the image plane of the projection optical system), and the like. In order to manage these processing conditions with high accuracy, it is necessary to evaluate those processing conditions with high accuracy.

  For example, as a conventional method for evaluating the focus position in the exposure conditions of an exposure apparatus, a pattern for mask evaluation is illuminated with illumination light whose chief ray is inclined, and the pattern image is changed while changing the height of the substrate on the stage. Is sequentially exposed to a plurality of shots on the substrate, the lateral shift amount of the resist pattern obtained by development after exposure is measured, and the focus position at the time of exposure of each shot is evaluated from the measurement result. (For example, refer to Patent Document 1).

  In order to further increase the yield of devices manufactured through the lithography process, it is desirable to evaluate the processing conditions such as the exposure conditions with higher accuracy and correct the processing conditions based on the evaluation result. Furthermore, in order to manufacture a device with high throughput (productivity) with high accuracy, it is required to consider that the processing conditions are evaluated with high accuracy and efficiency.

US Patent Application Publication No. 2002/0100012

  According to the first aspect of the present invention, the surface of the substrate on which the pattern is formed is irradiated with light, and based on the evaluation characteristics using the signal based on the detected light from the surface as an input value, In the evaluation method for evaluating the processing conditions of a pattern, the amount of change in the processing condition is estimated based on the input value, the amount of change in the input value, and the evaluation characteristics, and the amount of change in the estimated processing condition is An evaluation method is provided that includes evaluating the evaluation characteristics based on the evaluation characteristics.

  According to the second aspect, in the evaluation apparatus that evaluates the processing conditions of the pattern of the substrate on which the pattern is formed, the illumination unit that irradiates light to the surface of the substrate, and the light irradiation from the surface A detection unit that detects the emitted light, and an evaluation unit that evaluates a processing condition of the pattern based on an evaluation characteristic that uses a signal detected by the detection unit as an input value. An evaluation device is provided that estimates a change amount of the machining condition based on the value, a change amount of the input value and the evaluation characteristic, and evaluates the evaluation characteristic based on the estimated change amount of the machining condition. .

(A) is a figure which shows schematic structure of the evaluation apparatus which concerns on one Embodiment, (b) is a figure which shows the device manufacturing system containing the exposure system which concerns on one Embodiment. (A) is a plan view showing the wafer in FIG. 1 (a), (b) is an enlarged view showing a part of a repetitive pattern in FIG. 2 (a), (c) is an enlarged view showing an example of a mask pattern. , (D) is an enlarged perspective view showing a part of the repetitive pattern. (A) is a flowchart which shows an example of an evaluation method, (b) is a flowchart which shows an example of the method (condition extraction) which calculates | requires apparatus conditions. It is a flowchart which shows an example of the evaluation method of exposure conditions. (A) is a plan view showing an example of a shot arrangement of a conditioned wafer, (b) is an enlarged view showing one shot, and (c) is an enlarged view showing an example of an arrangement of a plurality of measurement regions in the shot. . (A) is a diagram showing a curve (template) showing the relationship between the focus position and the signal intensity under two device conditions, and (b) is a calculation template for obtaining the focus position from the signal intensity. FIG. 10C is a diagram showing an example of a template showing the relationship between exposure amount and signal intensity. (A) is a diagram showing a wafer exposed by gradually changing only the focus position, (b) is a diagram showing a wafer exposed with best dose and best focus, and (c) is a plurality of shots exposed at different focus positions. (D) is an enlarged view showing one shot of an example of the wafer image, (e) is an enlarged view showing a part of the edge portion of the wafer image, and (f) is in FIG. 7 (e). It is a figure which shows an example of the measurement area | region used for evaluation. (A), (b), (c), (d), and (e) are two templates showing the relationship between the focus position and the signal intensity obtained under two device conditions, respectively. It is a figure which shows two templates from which the difference of the focus position of a peak becomes 10 nm, 20 nm, 30 nm, 40 nm, and 50 nm. (A) is a figure which shows the correlation curve of each two template combination of Fig.8 (a)-(e) in signal strength space, (b) is the focus position on the correlation curve of Fig.9 (a). The figure which shows the curve obtained by multiplying the accumulation distance from the 0 position to each focus position by the sign of the focus position, and (c) is obtained by dividing the value of each position of the curve in FIG. 9B by the focus position. The figure which shows a curve, (d) is a flowchart which shows an example of the evaluation method of a template. (A) is a flowchart which shows an example of the selection method of a template and an apparatus condition, (b) is a flowchart which shows the selection method of a modification. (A), (b), (c), (d), and (e) are diagrams each showing a correlation curve of a combination of each of the two templates of FIGS. 8 (a) to (e) in the signal intensity space. (F) is a diagram showing the stability of the focus value calculated using each of the two templates. (A) And (b) is a figure which shows an example of distribution of the signal intensity | strength obtained on the basis of the 1st and 2nd apparatus conditions, respectively, (c) and (d) are respectively Fig.12 (a) and (b) ) Is a diagram showing the rotationally symmetric component of the signal intensity, and FIG. 9E is a diagram showing the signal intensity of the two rotationally symmetric components. (A) is a figure which shows an example of the fluctuation | variation of the focus value resulting from the signal intensity distribution in a wafer surface, (b) is 3 of the standard deviation of the focus value in each focus position resulting from the signal intensity distribution in a wafer surface. The figure which shows an example of double (3 (sigma)), (c) is a figure which shows an example of the correlation curve of change amount (DELTA) F1, (DELTA) F2 of the signal strength resulting from a process error, (d) is the correlation curve resulting from a process error, for example The figure which shows the case where it divides | segments by 10 points | pieces, (e) is a figure which shows an example of the value which converted the process error into the error of a focus position and exposure amount. (A) And (b) is a figure which shows an example of the correction amount of a process error, respectively. (A) is a diagram showing an example of a shot arrangement of a conditionally adjusted wafer, (b) is a diagram showing an example of a shot arrangement of a wafer exposed by shaking only the focus position, and (c) is an exposure at a best dose and a best focus position. FIG. 8D is a diagram showing an example of shot arrangement of a wafer (normal wafer), FIG. 8D is a diagram showing an example of distribution of measurement points of normal wafer signal intensity, and FIG. It is a figure which shows an example of distribution of the measurement point of intensity | strength. (A), (b), and (c) are diagrams showing how the signal strength detected by the change with time changes, and (d) shows an example of the change in the calculated value of the focus position due to the change with time. (E) is a figure which shows an example of the change of CD (critical dimension) by a time-dependent change, (f) is a figure which shows an example of the film thickness reduction of the resist by a time-dependent change, (g) is a signal intensity change by thin film interference. The figure for demonstrating, (f) is a figure for calculating the optical path length difference at the time of thin film interference. (A) is a figure which shows an example of distribution of the measurement area | region of a signal intensity | strength in case there exist a some chip pattern in the shot of a wafer, (b) is an error distribution of the focus value calculated | required in the case of Fig.17 (a). It is a figure which shows an example. In (a), (b), (c), and (d), the peak position is shifted by −15 nm, +15 nm, −25 nm, and +5 nm with respect to the best focus position when the exposure amount is in three stages. It is a figure which shows three templates. (A) is a figure which shows the correlation curve in the signal intensity space at the time of using the template of Fig.18 (a) and (b), (b) is a unit focus position and unit exposure of the correlation curve of Fig.18 (a). The figure which shows the correlation of the change of signal intensity | strength F1 and F2 with respect to the change of quantity, (c) is a figure which shows the angle of change of signal intensity | strength F1, F2 of FIG.19 (b), (d) is FIG.18 (c) and FIG. (D) is a diagram showing a correlation curve in the signal intensity space when using the template of (d), (e) is a graph of the signal intensity F1 and F2 with respect to the change of unit focus position and unit exposure of the correlation curve of FIG. 18 (d). The figure which shows the correlation of a change, (f) is a figure which shows the angle of change of the signal strength F1, F2 of FIG.19 (e). It is a flowchart which shows a semiconductor device manufacturing method.

  One embodiment will be described with reference to FIGS. 1 (a) to 10 (a). FIG. 1A shows an evaluation apparatus 1 according to this embodiment, and FIG. 1B shows a device manufacturing system DMS including an exposure system according to this embodiment. In FIG. 1B, a device manufacturing system DMS includes a thin film forming apparatus (not shown) for forming a thin film on a surface (hereinafter referred to as a wafer surface) of a wafer (semiconductor wafer) as a substrate, and a resist as a photosensitive resin. A coater / developer 200 for coating and developing the wafer surface, an exposure apparatus 100 for exposing an image of a circuit pattern such as a semiconductor device on the wafer surface coated with the resist, and etching the wafer using the developed resist pattern as a mask. An etching apparatus 300 and an evaluation apparatus 1 that evaluates the processing conditions of this pattern using a pattern formed on the wafer surface after exposure and development (or after etching or the like) are provided. Further, the device manufacturing system DMS is a host computer that performs overall control of the evaluation apparatus 1, exposure apparatus 100, coater / developer 200, etching apparatus 300, etc., process management, and mediation of various information between these apparatuses. 600 and a transfer system 500 for transferring a wafer between the evaluation apparatus 1 to the etching apparatus 300 and the like.

  As the exposure apparatus 100, for example, an immersion scanning stepper (scanning projection exposure apparatus) disclosed in, for example, US Patent Application Publication No. 2007/242247 is used. The processing conditions that can be evaluated by the evaluation apparatus 1 include film formation conditions (such as film thickness setting values) in the thin film forming apparatus, resist application conditions (such as resist film thickness setting values) and development conditions in the coater / developer 200, and the like. There are exposure conditions described later in the exposure apparatus 100, etching conditions (such as etching time) in the etching apparatus 300, and the like.

  In FIG. 1A, the evaluation apparatus 1 includes a stage 5 that supports a substantially disk-shaped wafer 10, and the wafer 10 transferred by a transfer system (not shown) is an upper surface (mounting surface) of the stage 5. And fixed and held by, for example, vacuum suction. Hereinafter, in a plane parallel to the upper surface of the stage 5 in an untilted state, the axis along the direction parallel to the paper surface of FIG. 1A is the XE axis, and the direction perpendicular to the paper surface of FIG. The axis along the direction perpendicular to the plane including the XE axis and the YE axis will be described as the ZE axis. The stage 5 passes through a first drive unit (not shown) that controls the rotation angle φ1 with the normal CA at the center of the upper surface of the stage 5 as a rotation axis, and the center of the upper surface of the stage 5, for example, and passes through the center of FIG. A second drive unit (not shown) for controlling a tilt angle φ2 (tilt angle of the wafer 10), which is an inclination angle with an axis TA (tilt axis) perpendicular to the paper surface (parallel to the YE axis) as a rotation axis. Via a base member (not shown).

  The evaluation apparatus 1 further includes an illumination system 20 that irradiates the illumination light ILI as parallel light onto the surface (wafer surface) of the wafer 10 supported by the stage 5 and having a predetermined repetitive pattern formed on the surface (wafer surface). A light receiving system 30 that collects light (regular reflection light, diffracted light, etc.) emitted from the wafer surface upon receiving the illumination light ILI, and forms an image of the wafer surface from the light collected by the light receiving system 30; An image pickup device 35 that picks up the image and outputs an image signal, and an image signal output from the image pickup device 35 is processed to obtain a signal intensity for each pixel of the image on the wafer surface (a signal based on light from the wafer surface). Image processing unit 40 for calculating (strength), and a calculation unit 50 for evaluating the above-described processing conditions using the information of the signal strength thus determined. The imaging device 35 includes an imaging optical system 35a that forms an image on the wafer surface, and a two-dimensional imaging element 35b (device that generates and outputs an image signal of the image on the wafer surface) such as a CCD or a CMOS. For example, the image pickup device 35b picks up an image of the entire surface of the wafer 10 and outputs an image signal. When the pattern to be evaluated for the processing conditions is formed only in a partial region on the entire surface of the wafer 10, the image sensor 35b may capture only an image of the partial region.

  Further, as shown in FIG. 2A, exposure regions having a mask pattern as a unit are formed at predetermined intervals on the wafer surface by exposure of the exposure apparatus 100. Hereinafter, this exposure area is referred to as a shot 11. Some shots 11 have only one mask pattern exposed, while others have a plurality of mask patterns connected and exposed. In the shot 11, an area that finally becomes a single device after the exposure process is referred to as a chip below. There may be a plurality of chips in the shot 11, or one shot 11 may become one chip.

  In FIG. 1A, the image processing unit 40 is configured to generate a digital image of the wafer 10 based on the image signal of the wafer 10 input from the imaging device 35 (signal intensity for each pixel, signal intensity averaged for each shot, Alternatively, information on a plurality of measurement regions 16 smaller than the shot (for example, the signal intensity averaged for each of the measurement areas 16 (see FIG. 5C)) is generated, and this information is output to the calculation unit 50. In addition, the calculation unit 50 is obtained by an inspection unit 60 that processes the information, a control unit 80 that controls operations of the image processing unit 40 and the inspection unit 60, and a storage unit 85 that stores information about the image. The evaluation results of the processing conditions are respectively sent to the control unit (not shown) of the coater / developer 200, the control unit (not shown) of the exposure apparatus 100, and the control unit (not shown) of the etching apparatus 300 via the host computer 600 of FIG. And a signal output unit 90 for outputting to a non-illustrated). In FIG. 1A, only the exposure apparatus 100 is shown for convenience of explanation. The image processing unit 40 and the calculation unit 50 may be configured as a whole by a computer, and the image processing unit 40, the inspection unit 60, the control unit 80, and the like may be functions on the computer software.

  In the evaluation apparatus 1, the illumination system 20 includes an illumination unit 21 that emits illumination light, and an illumination-side concave mirror 25 that reflects illumination light emitted from the illumination unit 21 toward the wafer surface as parallel light. The illumination unit 21 emits light having a predetermined wavelength (for example, different wavelengths λ1, λ2, λ3, etc.) out of light from the light source unit 22 according to a command from the control unit 80 and a light source unit 22 such as a metal halide lamp or a mercury lamp. The light adjusting unit 23 selects and adjusts the intensity thereof, and the light guide fiber 24 that emits the light selected by the light adjusting unit 23 and adjusted in intensity from the predetermined emission surface to the illumination-side concave mirror 25. As an example, the wavelength λ1 is 248 nm, λ2 is 265 nm, and λ3 is 313 nm. In this case, since the exit surface of the light guide fiber 24 is disposed at the focal point of the illumination-side concave mirror 25, the illumination light ILI reflected by the illumination-side concave mirror 25 is irradiated as a parallel light beam onto the wafer surface. The incident angle θ1 of the illumination light ILI with respect to the wafer 10 (the angle formed by the principal ray of the illumination light and the normal of the wafer surface) is determined by the command of the control unit 80 via the drive mechanism (not shown). Adjustment is possible by controlling the position of the emitting portion and the position and angle of the illumination-side concave mirror 25. In the present embodiment, the normal line of the wafer surface is parallel to the normal line CA of the stage 5.

  In this embodiment, the position and angle of the illumination-side concave mirror 25 are controlled by tilting the illumination-side concave mirror 25 about the tilt axis TA of the stage 5, and thereby the illumination light ILI incident on the wafer 10 (wafer surface). Is adjusted. In the present embodiment, as an example, it is composed of diffracted light ILD of a predetermined order m (m is a positive or negative integer other than 0) generated from the repeated pattern 12 (see FIG. 2A) formed on the wafer surface. The parallel light is received by the light receiving system 30.

  In this case, it is assumed that the incident direction of the illumination light ILI on the wafer surface (the direction of the line of intersection between the incident surface of the illumination light ILI and the wafer surface) is parallel to a certain periodic direction (repetition direction) of the repeating pattern 12 (FIG. 2 ( b)), assuming that the period (pitch) in the periodic direction of the repetitive pattern 12 is P1, and the wavelength of the illumination light ILI is λ, the incident angle θ1 of the illumination light ILI and the diffraction angle θ2 of the diffracted light ILD of order m ( The following relationship exists between the angle between the principal ray of the diffracted light and the normal of the wafer surface.

sin (θ1) −sin (θ2) = m · λ / P1 (1)
For this reason, when changing the incident angle θ1, the position of the exit portion of the light guide fiber 24 and the position and angle of the illumination-side concave mirror 25 are controlled, and the diffracted light emitted from the wafer 10 and incident on the light receiving system 30 The tilt angle φ2 of the stage 5 is controlled so that the diffraction angle θ2 of the ILD satisfies the relationship of the expression (1).

  The light receiving system 30 includes a light receiving side concave mirror 31 disposed to face the stage 5 (wafer 10), and the front focal point of the imaging optical system 35 a of the imaging device 35 is disposed at the focal point of the light receiving side concave mirror 31. . The diffracted light ILD (parallel light) emitted from the wafer surface is collected by the light receiving side concave mirror 31 and the imaging optical system 35a of the imaging device 35, and an image of the wafer surface is formed on the imaging surface of the imaging element 35b. .

  Further, an oxide film is formed on the surface of the wafer 10 by a thermal oxidation apparatus or a plasma CVD apparatus according to a process, or a conductive film is formed by a vacuum evaporation apparatus, a sputtering apparatus, a CVD apparatus, or the like. A resist is applied by the coater / developer 200. Then, a predetermined pattern is projected and exposed by the exposure apparatus 100 through a mask with respect to the uppermost resist. After the development of the resist by the coater / developer 200, the wafer 10 is transferred onto the stage 5 of the evaluation apparatus 1. Here, a repetitive pattern 12 (see FIG. 2A) is formed on the upper surface of the wafer 10 transferred onto the stage 5 through exposure and development processes by the exposure apparatus 100 and the coater / developer 200.

  Then, the wafer 10 is transferred by a not-shown alignment mechanism in the course of conveyance, a pattern in a shot of the wafer 10, a mark on the wafer surface (for example, a search alignment mark), or an outer edge (notch, orientation flat, uneven mark on the back surface, etc.) Is transferred onto the stage 5 in a state where alignment is performed with reference to. In the present embodiment, as shown in FIG. 2A, a plurality of shots 11 are arranged in two directions orthogonal to each other at predetermined intervals on the wafer surface, and a circuit pattern of a semiconductor device is included in each shot 11. As an example, a repetitive pattern 12 composed of a line and space pattern (hereinafter referred to as an L & S pattern) is formed. In the following, on a plane parallel to the wafer surface, the X axis and the Y axis are taken along two orthogonal arrangement directions of the plurality of shots 11, and the axis perpendicular to the plane including the X axis and the Y axis is the Z axis. Will be described. In the present embodiment, the periodic direction (repeating direction) of the repeated pattern 12 on the wafer surface is a direction (X direction) parallel to the X axis.

As an example, as shown in an enlarged view in FIG. 2B, the repetitive pattern 12 is a pattern in which line portions 2A and space portions 2B are alternately arranged in the X direction with a period P1. The period P1 is, for example, about 170 to 300 nm (for example, about 200 nm).
If a general period Px is substituted instead of the period P1 on the right side of Expression (1), the value on the left side of Expression (1) is 2 or less, and therefore the condition for generating at least the first-order diffracted light (m = 1) is The wavelength λ of the incident light is smaller than twice the period Px (the period Px is larger than λ / 2) as follows.
λ / Px <2 That is, λ <2 · Px (2)
For this reason, when the wavelength of the illumination light ILI is the above-mentioned λ1 to λ3 (248 to 313 nm), diffracted light is not generated from the L & S pattern having the period P1 of about 40 to 80 nm, but the L & S having the period P1 of about 170 nm or more. Diffracted light is generated from the repeated pattern 12 which is a pattern.

  Further, when the repeated pattern 12 is formed on the wafer 10, as an example, as shown in FIG. 2 (c), a dark portion MP1 and a bright portion MP2 extending in the Y direction, respectively, have a predetermined period P2 (period) in the X direction. A mask pattern having a shape arranged by multiplying P1 by the reciprocal of the projection magnification is exposed on the resist of the wafer. By developing the resist after the exposure, it is possible to form a repeated pattern 12 as an uneven resist pattern. Further, by performing etching using a resist pattern formed after the development, a repeated pattern having the same shape as the repeated pattern 12 can be formed on the base of the resist (a thin film such as an insulating film).

The repeating pattern 12 may be a pattern made of metal, for example. Furthermore, the repeating pattern may be a hole pattern or a plurality of hole pattern groups. A single shot 11 often includes a plurality of chip areas, but in FIG. 2A, it is assumed that there is one chip area in one shot for simplicity.
In the present embodiment, as an example, a case will be described in which the inspection unit 60 processes an image on the wafer surface as described later and evaluates (inspects) the exposure conditions of the exposure apparatus 100 as processing conditions.
Here, the exposure conditions are the focus position of the exposure apparatus 100 that has exposed the wafer 10 (the position of the image plane of the mask pattern in the optical axis direction of the projection optical system in the exposure apparatus), the exposure amount (so-called dose such as exposure energy), An exposure apparatus for exposure using an immersion method such as a defocus amount of the image surface of the mask pattern in the optical axis direction of the projection optical system of the exposure apparatus with respect to the wafer to be exposed, and an immersion method. The temperature of the liquid between the projection optical system and the wafer. As an example, the evaluation result of the exposure condition is output to a control unit (not shown) in the exposure apparatus 100 via the host computer 600, and the exposure apparatus 100 corrects the exposure condition (for example, offset) according to the evaluation result. Correction of variations and the like).

An example of a method for performing evaluation or inspection based on the reflected light from the wafer surface using the evaluation apparatus 1 configured as described above will be described. In this case, the repetitive pattern 12 on the wafer surface in FIG. 2A is a pattern in which the line portions 2A and the space portions 2B are arranged in the resist at a period P1 in the X direction, as shown in FIG. 2D.
Here, the design value of the line width D _A of the line portion 2A in the repeated pattern 12 is set to ½ of the pitch P1. Appropriate exposure conditions (i.e., exposure dose and focus position) if the repetitive pattern 12 is formed by, together with the line width D _B of the line width D _A and the space portion 2B of the line portion 2A are equal, side walls of the line portion 2A The part 2Aa is formed substantially perpendicular to the surface of the wafer 10, and the volume ratio of the line part 2A and the space part 2B is about 1: 1. Further, the shape of the XZ cross section of the line portion 2A at that time is a square or a rectangle. On the other hand, if the focus position in the exposure apparatus 100 when forming the repeated pattern 12 deviates from the proper focus position, the pitch P1 does not change, but the side wall portion 2Aa of the line portion 2A is relative to the surface of the wafer 10. The shape of the XZ cross section of the line portion 2A is not a right angle but a trapezoid. Accordingly, the line widths D _A and D _B of the line portion 2A and the space portion 2B are different from the design values, and the volume ratio of the line portion 2A and the space portion 2B deviates from about 1: 1. On the other hand, when the exposure amount in the exposure apparatus 100 is changed, the pitch P1 and the line width D _A changes, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: deviates from 1.

Using the change in the signal intensity of the reflected light (diffracted light) accompanying the change in the volume ratio between the line part 2A and the space part 2B in the repeated pattern 12 as described above, the state of the repeated pattern 12 (good or bad) is inspected. It can be performed.
The change in the volume ratio and / or the change in the cross-sectional shape of the line portion 2A is caused by a deviation from the appropriate value of the focus position and the exposure amount. Appears for each region, and evaluates exposure conditions from the change in the signal intensity of the diffracted light caused by the change in the volume ratio. Compare the value).

In order to evaluate the exposure condition from the change in the signal intensity of the diffracted light from the wafer surface using the evaluation apparatus 1 of the present embodiment, the control unit 80 stores recipe information stored in the storage unit 85 (apparatus conditions described later). And an evaluation procedure such as the procedure shown in the flowcharts of FIGS.
First, the wafer 10 on which the repeated pattern 12 to be inspected is formed on the stage 5 through the steps of resist application in the coater / developer 200, resist exposure in the exposure apparatus 100, and resist development in the coater / developer 200. Is placed at a predetermined position. As an example, the rotation angle of the stage 5 is such that the periodic direction A1 (X direction of the wafer surface) of the repeated pattern 12 on the wafer surface is in the incident direction of the illumination light ILI on the wafer surface as shown in FIG. Set to be parallel.

The tilt angle φ2 of the stage 5 is such that the light receiving system 30 can receive the m-order diffracted light ILD from the wafer 10, that is, the light received by the light receiving system 30 with respect to the incident angle θ1 of the incident illumination light ILI. The diffraction angle θ2 with respect to the wafer surface is set so as to be an angle determined by the above-described equation (1). For this reason, the diffraction angle θ <b> 2 is also a light receiving angle by the light receiving system 30.
The diffracted light ILD of the detection target m-order parallel light diffracted on the wafer surface is condensed by the light receiving side concave mirror 31 of the light receiving system 30 and reaches the image pickup surface of the image pickup device 35. As a result, an image of the wafer surface by the diffracted light ILD is formed on the imaging surface of the imaging device 35. The image signal of the imaging device 35 is supplied to the image processing unit 40.

  The image processing unit 40 outputs the obtained signal intensity information for each pixel of the imaging device 35 to the inspection unit 60. The inspection unit 60 evaluates the exposure conditions in the exposure apparatus 100 used when forming the repeated pattern 12 of the wafer 10 using the information. As described above, when the signal intensity for each pixel of the image on the wafer surface is obtained, the angle of incidence θ1 of the illumination light ILI on the wafer surface in the evaluation apparatus 1 (or the diffraction angle obtained from the equation (1) according to the incident angle θ1). A combination of θ2), the wavelength λ of the illumination light ILI (λ1 to λ3, etc.), the order m of the diffracted light ILD to be detected, the rotation angle of the stage 5 (azimuth of the wafer 10), etc. is called one apparatus condition. The apparatus conditions can also be called evaluation conditions. A plurality of apparatus conditions (for example, the first apparatus condition is an angle θa having an incident angle θ1, the wavelength is λ1, the order m of the diffracted light to be detected is 1, the second apparatus condition is an incident angle θ1 is the angle θa, and the wavelength Λ2, the order m of the diffracted light to be detected is 1), and the like are included in the recipe information of the evaluation apparatus 1 stored in the storage unit 85.

  In the present embodiment, an apparatus condition suitable for evaluating the exposure condition of the pattern formed on the wafer is selected from the plurality of apparatus conditions. In addition, as apparatus conditions, at least one of wavelength (lambda) and incident angle (theta) 1 may be used, and the other arbitrary conditions which can be adjusted in the evaluation apparatus 1 may be used. For example, as an apparatus condition, an apparatus condition suitable for evaluating the exposure condition may be selected from a plurality of apparatus conditions (for example, the wavelength λ is a set value) in which only the incident angle θ1 gradually changes. In the apparatus conditions, the wavelength λ of the illumination light ILI and the incident angle θ1 of the illumination light ILI with respect to the wafer surface can be called an example of the illumination condition, and the diffraction angle θ2 (light reception) of the diffracted light ILD from the wafer surface. The light reception angle by the system 30) can be called an example of detection conditions of the light reception system 30 and the imaging device 35. The rotation angle of the stage 5 (azimuth of the wafer 10) and the tilt angle φ2 of the stage 5 (tilt angle of the wafer surface). ) Can be called an example of stage posture conditions.

  In the following description, as an example, the exposure conditions to be evaluated by the exposure apparatus 100 are the focus position and the exposure amount. At this time, if the focus position changes, the cross-sectional shape of the pattern changes as described above. Therefore, when illumination light is incident on the wafer surface, the focus position during exposure of the pattern is lower than the optimum value. When an optimum value (so-called best focus position) is passed and the state changes to a state higher than the optimum value, the pattern shape changes, and the signal intensity of the diffracted light from the pattern changes.

  On the other hand, when the exposure amount changes, the line width of the line portion of the repetitive pattern 12 changes (the width of the cross section changes) as described above. Therefore, when illumination light is incident on the wafer surface, the pattern is exposed. When the exposure amount of light changes from a low state to an optimal value through an optimal value (so-called best dose) and then changes to a high state with respect to the optimal value, the pattern shape changes and the signal intensity of the diffracted light from the pattern changes. To do. Thus, by utilizing the fact that the signal intensity varies depending on the exposure condition, it becomes possible to evaluate individual exposure conditions from the detected signal intensity.

Next, in the present embodiment, the evaluation apparatus 1 is used to detect light from the repetitive pattern on the wafer surface, and the exposure conditions (here, the focus position and the exposure amount) of the exposure apparatus 100 used when forming the pattern. ) Will be described with reference to the flowchart of FIG. Since it is necessary to obtain an apparatus condition (evaluation condition) in advance for the evaluation, first, refer to the flowcharts of FIGS. 3A and 3B for an example of a method for obtaining the apparatus condition (hereinafter also referred to as “conditioning”). To explain. These operations are controlled by the control unit 80.
First, as a basic operation, in step 130 of FIG. 3A, the stage 5 of the evaluation apparatus 1 is changed to each shot while changing the exposure conditions so that the focus position and the exposure amount gradually change between shots. A wafer 10a (details will be described later) in FIG. 5A on which a pattern of a mask (not shown) for a device that is actually a product is exposed and developed is placed, and an illumination system 20, a stage 5, and a light receiving system 30 are used. Then, the apparatus conditions on the stage 5 are set, and in the next step 132, the illumination light is irradiated from the illumination system 20 to the wafer 10a, the image of the wafer surface is picked up by the image pickup device 35, and the image signal is output by the image processing unit 40. Then, the signal strength of each pixel is obtained, and the obtained signal strength is output to the inspection unit 60 of the calculation unit 50. In step 134, the inspection unit 60 uses the signal intensity to obtain a characteristic curve (details will be described later) indicating a change in the signal intensity with respect to the focus position. When the signal intensity is input to this characteristic curve, the focus position is calculated. When the fluctuation amount due to disturbance or the like is mixed in the signal supplied from the image processing unit 40, the characteristic curve and the apparatus conditions set in step 130 are evaluated from the fluctuation amount of the focus position obtained from the characteristic curve. To do.

  Next, detailed operation will be described with reference to FIG. First, in order to determine conditions, a wafer 10a (see FIG. 5A) coated with a resist is prepared in the coater / developer 200 in step 102 of FIG. 3B. As shown in FIG. 5A, on the surface of the wafer 10a, N shots 11 (N is an integer of about several 10 to 100, for example) are arranged with the scribe line region SL as an example. Hereinafter, the nth shot 11 on the surface of the wafer 10a is also referred to as a shot SAn (n = 1 to N). Then, the resist-coated wafer 10a is transported to the exposure apparatus 100 in FIG. 1B, and the exposure apparatus 100 scans the wafer 10a, for example, in the scanning direction during scanning exposure (the direction along the Y axis in FIG. 5A). The exposure amount gradually changes between shots arranged in a), and the focus position gradually changes between shots arranged in a non-scanning direction (direction along the X axis in FIG. 5A) orthogonal to the scanning direction. As described above, a pattern of a mask (not shown) for a device that is actually a product is exposed on each shot SAn while changing the exposure conditions.

Thereafter, by developing the exposed wafer 10a, one wafer (hereinafter referred to as a "conditional wafer") 10a in which the repeated pattern 12 is formed on each shot SAn under different exposure conditions is created. .
In the following, it is assumed that a defocus amount with respect to the best focus position Zbe (herein referred to as a focus value) is used as the focus position. With respect to the focus position, as an example, the focus value is set in seven steps from −60 nm to 0 nm to +60 nm in increments of 20 nm. The focus value FV (nm) on the horizontal axis in FIG. 6B and the like to be described later indicates a range of −40 to 40 nm. Note that the focus value can be set in an arbitrary increment and at an arbitrary stage. For example, the focus value can be set at multiple stages in increments of 10 nm or 30 nm. For example, the focus value can be set to 17 levels from −200 nm to +200 nm in increments of 25 nm.

  As an example, the exposure amount is 7 steps (11.5 mJ, 13.0 mJ, 14.5 mJ, 16.0 mJ, 17.5 mJ, 19.0 mJ, 20. 5 mJ). Numbers 1 to 7 of the value DV of the exposure amount D on the horizontal axis in FIG. 6C described later correspond to the seven steps of exposure amounts. The exposure amount can also be set at an arbitrary step amount and at an arbitrary stage (for example, 9 stages).

  The conditionally adjusted wafer 10a of the present embodiment is a so-called FEM wafer (Focus Exposure Matrix wafer) that is exposed and developed by changing the exposure amount and the focus position in a matrix. If the number of shots with different combinations of exposure conditions obtained by the product of the number of focus value stages and the number of exposure dose stages is greater than the number of shots on the entire surface of one conditioned wafer 10a, a plurality of shots It is also possible to create a conditionally adjusted wafer.

  Conversely, for example, when the number of arrangements of shots SAn in the non-scanning direction is larger than the number of stages of change in focus value and / or when the number of arrangements in the scanning direction is larger than the number of stages of change in exposure amount, A plurality of shots having the same value and exposure amount may be formed, and the measurement values obtained for the shots having the same focus value and exposure amount may be averaged. Further, for example, the influence of subtle application unevenness of the resist between the central portion and the peripheral portion of the wafer, the influence of the difference in the scanning direction of the wafer (+ Y direction or -Y direction in FIG. 5A) at the time of scanning exposure, etc. In order to reduce, a plurality of shots having different focus values and exposure amounts may be arranged at random.

  Next, the created conditioned wafer 10 a is transferred onto the stage 5 of the evaluation apparatus 1. Then, the control unit 80 reads out a plurality of device conditions from the recipe information in the storage unit 85. As a plurality of apparatus conditions, for example, the wavelength λ of the illumination light ILI is any one of the above λ1, λ2, and λ3, and the incident angle θ1 of the illumination light ILI is 10 °, 15 °, 30 °, 45 °, and 60 °. , 85 ° is assumed. Hereinafter, it is assumed that the diffracted light ILD received by the light receiving system 30 is + 1st order diffracted light (m = + 1) as an example. However, -1st order diffracted light or other 2nd order or higher order diffracted light may be received. Here, an apparatus condition in which the wavelength λ is λn (n = 1 to 3) and the incident angle θ1 is αm (m = 1 to 6) is represented by a condition ε (nm). When the incident angle θ1 is set to a certain angle, the tilt axis TA of the illumination-side concave mirror 25 is centered so that the diffracted light ILD having the diffraction angle θ2 obtained by the above equation (1) is received by the light receiving system 30. The tilt angle φ2 of the stage 5 and / or the stage 5 is adjusted.

Further, the incident angle θ1 may be an arbitrary settable angle, and may be set at an interval of about 5 ° so as to be any one of 10 ° to 85 °, for example.
Then, in the evaluation apparatus 1, with the conditioned wafer 10a placed on the stage 5, the wavelength of the illumination light ILI is set to λ1 (step 104), and the incident angle θ1 is set to α1 (together with the stage 5). And the light receiving angle of the light receiving system 30 is set (step 106).

Then, under this apparatus condition, the illumination light ILI is irradiated onto the surface of the conditioned wafer 10a, and the imaging device 35 captures an image of the conditioned wafer 10a based on the diffracted light ILD from the conditioned wafer 10a. The image signal is output to the image processing unit 40 (step 108).
Thereafter, in step 110, the image processing unit 40 obtains a signal intensity for each pixel of the image sensor 35b, obtains an average value of the signal intensity for each shot (hereinafter referred to as a shot average value), and obtains the signal intensity and the shot. The average value is the apparatus condition ε (nm) that was set when the signal intensity was obtained and the exposure condition (focus position and exposure amount) that was set for the shot of the condition-controlled wafer 10a that obtained the signal intensity. Are output to the inspection unit 60 and the storage unit 85.

  Thereafter, the process proceeds to step 112 to determine whether or not the incident angle θ1 of the illumination light ILI is set to all angles, that is, whether the incident angle θ1 is set to all angles αm (m = 1 to 6). If not all angles are set, the illumination system 20 and the stage 5 are driven, the incident angle θ1 is set to α2, and the diffraction angle θ2 is set to a corresponding angle (step 114). ), And returns to Step 108. Then, calculation of the signal intensity for each pixel of the image on the wafer surface, calculation of the shot average value, and the like (steps 108 and 110) are executed.

  Thereafter, when the incident angles θ1 are set to all the angles αm (m = 1 to 6), the process proceeds from step 112 to step 116 to determine whether or not the wavelengths λ of the illumination light ILI are set to all the wavelengths. If the wavelength is not set to all wavelengths, the illumination unit 21 changes the wavelength λ to λ2 (step 118) and returns to step 106. Then, calculation of the signal intensity for each pixel of the image on the wafer surface, calculation of the shot average value, and the like (steps 106 to 110) are executed. Thereafter, when the wavelengths λ are set to all the wavelengths λn (n = 1 to 3), the operation shifts from step 116 to step 120.

  In step 120, the inspection unit 60 uses the information on the signal intensity measured for each shot of the conditioned wafer 10a under all the apparatus conditions described above to change the focus value for the signal intensity measured under all the apparatus conditions. Sensitivity (hereinafter also referred to as focus sensitivity) that is the ratio of the change in the measured value with respect to, and sensitivity (hereinafter also referred to as dose sensitivity) that is the ratio of the change in the measured value relative to the change in exposure amount.

In the next step 120, the inspection unit 60 includes a plurality of sets of conditions in which the focus sensitivity is high and the dose sensitivity is lower than the focus sensitivity with respect to the signal intensity among all the apparatus conditions ε (nm). Is determined as the first group apparatus condition (or first group evaluation condition) A. For example, one of the device conditions in the first group of device conditions A is that the wavelength of the illumination light is λ1 and the incident angle θ1 of the illumination light with respect to the wafer surface is 45 °.
The plurality of sets of conditions in the first group of device conditions are, for example, a plurality of device conditions in which the characteristic of change with respect to the change in the focus position of the signal intensity obtained from the captured image has a certain symmetry. Including. In the following, the two sets of apparatus conditions are such that the characteristics of the change of the signal intensity obtained from the captured images with respect to the change of the focus position are substantially symmetric with respect to a certain focus position (for example, the best focus position). Shall be included. The plurality of sets of conditions may each include three or more device conditions, and each of the plurality of sets of device conditions may be one device condition.

  Under one set of device conditions (here, two) in the first group, the signal intensity SI for each pixel has a convex solid curve in FIG. 6A with respect to the focus value FV (nm) of the conditionally adjusted wafer 10a. It changes like a dot row along F41 and a convex dotted curve F42. For example, in the first device condition of the two device conditions, a dot row along the solid curve F41 is obtained, and in the second device condition, a dot row along the dotted curve F42 is obtained. In the following, a solid curve F41 or a dotted curve F42 obtained by approximating these dot rows with, for example, a quadratic curve or a higher-order curve related to the focus value FV (or exposure amount) on the horizontal axis will be referred to as a characteristic curve (hereinafter referred to as a template). F41 and F42. In the following, the templates F41, F42, etc. are standardized so that the peak value is 100. Furthermore, for convenience of explanation, it is assumed that the two templates F41 and F42 in FIG. 6A are substantially symmetrical with respect to the best focus position (FV = 0). The templates F41 and F42 have peaks at positions of +20 nm and −20 nm with respect to the focus value FV, respectively, and the peak interval is 40 nm. Actually, the two templates F41 and F42 may be substantially symmetric with respect to a certain focus position other than the best focus position, and may not be substantially symmetric with respect to any focus position.

  In this example, when the difference between the templates F41 and F42 is taken, a curve (hereinafter referred to as a calculation template) F43 of FIG. 6B is obtained. In the calculation template F43, the signal strength difference ΔF4 on the vertical axis changes monotonously with respect to the focus value FV on the horizontal axis. For this reason, by applying the difference between the signal intensities SI41 and SI42 (ΔF41) obtained at a certain measurement point on the wafer surface to the calculation template F43, in other words, as an input value of the template information including the calculation template F43, The focus value FV of the measurement point can be uniquely calculated as FV1. Hereinafter, a value calculated from the template information by inputting a value in the input value of the template information is also referred to as a calculated value or an estimated value. Note that the method for creating the calculation template is arbitrary. For example, when there is a template in which two peak positions, convex and concave, are shifted with respect to two focus values, the calculation template may be obtained from the sum of the two templates. it can. Hereinafter, the templates F41 and F42 and the calculation template F43 are collectively referred to as one template information.

  A set of templates F41 and F42 in FIG. 6A is the same as the two templates in FIG. Actually, like a set of templates F41 and F42 in FIG. 6A, a set of templates (or a set of apparatus conditions corresponding thereto) that are substantially symmetrical with respect to a certain focus position is shown in FIG. ) Templates F11 and F12, templates F21 and F22 in FIG. 8B, templates F31 and F32 in FIG. 8C, and templates F51 and F52 in FIG. . In the two templates of FIGS. 8A, 8B, 8C, 8D, and 8E, the peak position intervals D are 10 nm, 20 nm, 30 nm, 40 nm, and 50 nm, respectively.

Similarly, in the next step 122, in the inspection unit 60, among all the apparatus conditions ε (nm), a plurality of sets of signal sensitivities are high in terms of signal intensity and focus sensitivity is lower than the dose sensitivity. The condition is determined as the second group apparatus condition (or the second group evaluation condition) B. As one example of the device condition B in the second group of device conditions B, the wavelength of the illumination light is λ2, and the incident angle θ1 of the illumination light with respect to the wafer surface is 60 °.
It should be noted that the plurality of sets of conditions in the second group of device conditions include, for example, a plurality of device conditions in which the characteristic of change with respect to a change in exposure amount of signal intensity obtained from a captured image has a certain symmetry. Including. In the following, the two sets of conditions are such that the characteristics of the change of the signal intensity obtained from each captured image with respect to changes in the exposure amount are substantially symmetrical with respect to a certain exposure amount (for example, best dose). Shall be included. The plurality of sets of conditions may each include three or more device conditions, and each of the plurality of sets of device conditions may be one device condition.

  Under this second set of apparatus conditions, the signal intensity SI for each pixel is changed to a convex solid curve D11 and a convex dotted curve D12 in FIG. It changes like a line of dots. In the following, a solid curve D11 or a dotted curve D12 obtained by approximating these dot rows with, for example, a quadratic curve or higher-order curve related to the exposure amount DV (relative value) on the horizontal axis will be a characteristic curve (hereinafter referred to as a template). These are referred to as D11 and D12. The two templates D11 and D12 are substantially symmetric with respect to the base dose. Further, the templates D11 and D12 have peaks at positions of +4 and −4 with respect to the exposure amount DV, respectively.

  In this example, when the difference between the templates D11 and D12 is taken, a curve (hereinafter referred to as a calculation template) D13 is obtained. In the calculation template D13, the signal strength difference ΔD1 on the vertical axis changes monotonously with respect to the focus value FV on the horizontal axis. Therefore, by applying the difference (denoted as ΔD11) between the signal intensities SI11 and SI12 relating to the templates D11 and D12 obtained at a measurement point on the wafer surface to the calculation template D13, the exposure dose DV at that measurement point is unique as DV1. Can be obtained. Other plural sets of apparatus conditions and templates (not shown) that change in the same manner as the one set of templates D11 and D12 in FIG. 6C and have different peak position intervals, for example, are also obtained.

Next, in step 124, the inspection unit 60 evaluates the stability of the calculated value by the template when, for example, noise is mixed with the input value of the template from the plurality of sets of apparatus conditions and templates obtained in step 120 ( A set of two (here, two) devices having the highest stability of the calculated value and high focus sensitivity based on the evaluation result. A condition and a template are selected (details will be described later). The one set of device conditions selected at this time is set as the first set of device conditions for focus position evaluation. The first set of device conditions includes, for example, a first device condition set when obtaining the template F41 in FIG. 6A and a second device condition set when obtaining the template F42. Then, the selected apparatus condition and template are stored in the storage unit 85 as a first set of apparatus condition and template with high focus sensitivity used for evaluation of actual exposure conditions.
In the next step 126, the inspection unit 60 uses the template in the case where noise or the like is mixed with the input value of the template from the plurality of sets of apparatus conditions and templates obtained in step 122, as in step 124. The stability of the calculated value is evaluated, and from the evaluation result, one set (two in this case) of apparatus conditions and templates having the highest stability of the calculated value and high exposure sensitivity are selected (details will be described later). . One set of apparatus conditions selected at this time is set as a second set of apparatus conditions for exposure dose evaluation. The second set of device conditions includes, for example, a first device condition set when obtaining the template D11 in FIG. 6C and a second device condition set when obtaining the template D12. Then, the selected apparatus conditions and template are stored in the storage unit 85 as a second set of apparatus conditions and templates having a high exposure sensitivity used for evaluation of actual exposure conditions.

With the above operation, the apparatus condition used for evaluating the wafer exposure condition and the condition determination for obtaining the corresponding template are completed.
Next, in the actual device manufacturing process, the above conditions are applied by the evaluation apparatus 1 to the wafer on which a repeated pattern is formed by applying a resist by the coater / developer 200, exposing by the exposure apparatus 100, and developing by the coater / developer 200. By measuring the signal intensity of the diffracted light from the wafer surface using the two sets of apparatus conditions and template obtained in the process, the focus position and exposure amount in the exposure conditions of the exposure apparatus 100 are evaluated as follows. . First, a wafer 10 having the same shot arrangement as that in FIG. 5A and serving as an actual product (device) coated with a resist is transferred to the coater / developer 200 in FIG. 1A and coated with the resist. 10 is transferred to the exposure apparatus 100, and the exposure apparatus 100 exposes a mask (not shown) pattern for an actual product (device) to each shot SAn (n = 1 to N) of the wafer 10. The wafer 10 is transferred to the coater / developer 200 and the wafer 10 is developed. The exposure conditions set in the exposure apparatus 100 at this time are optimum values (best focus position and best dose) for all shots, and the exposure amount is the sum of the best doses determined according to the mask. .

  However, in actuality, in the exposure apparatus 100, for example, the wafer 10 is affected by, for example, slight illuminance unevenness in the slit-shaped illumination area at the time of scanning exposure, for example, slight illuminance unevenness and stage vibration (including vibration due to disturbance). Variations in focus position and exposure amount may occur for each shot SAn (each repeated pattern for each shot SAn), and unintended exposure amount change (change from the best dose amount) and unintentional focus position change ( Since the change from the best focus value may occur, the focus position and the exposure amount are individually evaluated.

  In step 150 of FIG. 4, the resist-coated, exposed and developed wafer 10 is loaded onto the stage 5 of the evaluation apparatus 1 of FIG. 1A via an alignment mechanism (not shown). Then, the control unit 80 reads out the first set and the second set of apparatus conditions determined by the above-described condition determination from the recipe information in the storage unit 85. The apparatus conditions are first set to a first set of first apparatus conditions with high focus sensitivity and low dose sensitivity (step 152). Then, the illumination light ILI is irradiated onto the wafer surface, the imaging device 35 captures an image obtained by the diffracted light on the wafer surface, and outputs an image signal of the image to the image processing unit 40 (step 108A).

  Thereafter, in step 110 </ b> A, the image processing unit 40 obtains the signal intensity for each pixel of the imaging device 35 and outputs the obtained information to the inspection unit 60 and the storage unit 85. As an example, the inspection unit 60 obtains a shot average value of the signal intensity and outputs it to the storage unit 85. Then, it is determined whether or not the inspection is performed under all the apparatus conditions (step 154). If all the apparatus conditions for inspection are not set, the second apparatus condition is set at step 156 and then step 108A. Migrate to Then, after the acquisition of the signal strength under the second device condition and the second set of two device conditions is completed, the operation proceeds to step 158.

In step 158, the inspection unit 60 performs the signal intensity SIi1 (i is an integer indicating the order) for each shot of the wafer 10 obtained under the first set of first apparatus conditions and the first set of second apparatus conditions. A focus value (for example, FV1) is obtained by using the difference ΔF4 of the signal intensity SIi2 for each shot of the wafer 10 as an input value of the calculation template F43 in FIG. 6B.
Then, the inspection unit 60 outputs information on the focus value FV for each shot of the wafer 10 to the control unit 80. The control unit 80 stores the focus value FV for each shot in the storage unit 85 and displays it on a display device (not shown). The inspection unit 60 may obtain a distribution (error distribution) of a difference (error) from the best focus position of the focus value FV for each shot of the wafer 10 and output this to the control unit 80. This error distribution may include information on whether or not the focus value FV of each shot is within a predetermined non-defective range. Further, the control unit 80 may not display the focus value FV on the display device.

In step 160, the inspection unit 60 performs the signal intensity SIj1 (j is an integer indicating the order) for each shot of the wafer 10 obtained under the second set of first apparatus conditions, and the second set of second apparatus conditions. The exposure amount DV (for example, DV1) is obtained using the difference ΔD1 of the obtained signal intensity SIj2 for each shot of the wafer 10 as the input value of the calculation template D13 in FIG.
Then, the inspection unit 60 outputs information on the obtained exposure amount DV for each shot to the control unit 80. The control unit 80 stores the exposure amount DV for each shot in the storage unit 85 and displays it on a display device (not shown). The inspection unit 60 may obtain a distribution (error distribution) of a difference (error) from the best dose of the exposure dose DV for each shot, and may output this to the control unit 80. This error distribution may include information on whether or not the exposure amount DV of each shot is within a predetermined non-defective range. The control unit 80 may not display the exposure amount DV on the display device.

  Thereafter, under the control of the control unit 80 of the evaluation apparatus 1, the distribution of the focus position for each shot of the wafer 10 and the control unit (not shown) of the exposure apparatus 100 via the host computer 600 from the signal output unit 90. Information on the distribution of exposure dose is provided (step 162). In response to this, a control unit (not shown) of the exposure apparatus 100 obtains a difference (error) distribution (defocus amount distribution) from the best focus position of the focus position distribution for each shot, for example, and exposes for each shot. The distribution (exposure unevenness) of the difference (error) from the best dose of the amount distribution is obtained, and when the defocus amount distribution and / or the exposure unevenness exceeds a predetermined allowable range, the focus position and In order to correct the exposure amount, for example, the offset of the height of the wafer surface, the adjustment of the focus target value at each position in the wafer surface, and / or the distribution of the width in the scanning direction of the illumination area at the time of scanning exposure Make corrections such as adjustments. This reduces errors in the defocus amount and exposure amount during subsequent exposure. Thereafter, in step 164, the exposure apparatus 100 exposes the wafer under the corrected exposure conditions.

  According to this embodiment, signal intensity is detected under two sets of apparatus conditions using the wafer 10 on which a pattern for a device that is actually a product is formed. By using the detected signal intensity as the input value of the calculation templates F43 and D13 obtained in the condition setting step, the focus position and exposure in the exposure conditions of the exposure apparatus 100 used at the time of pattern formation are used. The amount can be obtained (evaluated) efficiently and with high accuracy. By correcting the exposure conditions in the exposure apparatus 100 based on this evaluation result, the exposure conditions for subsequent wafers can be brought closer to an appropriate range, and the device can be manufactured with high accuracy and high yield.

  In this embodiment, when the focus position of each shot SAn on the wafer 10 is evaluated, the entire surface of each shot SAn is used as a measurement region, or a circuit pattern in the shot SAn as shown in FIG. Rather than uniformly setting a certain portion or the like as the measurement region 16, a narrow region (high focus sensitivity) in which the change in the signal intensity of the diffracted light is large with respect to the change in the focus position in the shot region SAn is set as the measurement region. Can shorten the measurement time. Thus, an example of a method that can efficiently determine a measurement region with high focus sensitivity will be described. In this method, the exposure amount shown in FIG. 7A is the best dose, and each shot SAn is exposed and developed so that the focus position gradually changes in the X direction. The normal wafer 10 is prepared by performing exposure to all shots SAn at the best dose and best focus positions shown in FIG. The wafer 10b is a so-called FM wafer (Focus Matrix wafer).

  Then, in the evaluation apparatus 1 of the present embodiment, images of the entire surface of the wafer 10b and the wafer 10 are sequentially captured under the apparatus conditions that increase the signal intensity of the diffracted light, and are arranged in the X direction at the center of the wafers 10b and 10. In the shots SAm1 to SAm2 in the region 10m, a signal intensity difference ΔSI is obtained for each pixel. As a result, only the signal intensity component due to focus fluctuation can be extracted. Then, virtually as shown in FIG. 7C, all the shots SAm1 to SAm2 in the region 10m are arranged in the focus direction (Z direction), and the pixel 16a at the same position in all the shots SAm1 to SAm2 is described above. The standard deviation ΔFVσ of the difference ΔSI is obtained. Among the pixels 16a, a pixel having a large standard deviation ΔFVσ is a pixel having a large change in luminance with respect to a change in focus position (a pixel that is preferable as a measurement target). Small pixels are not preferable as a measurement target. FIG. 7D shows an example in which the distribution of the standard deviation ΔFVσ for each pixel in the shot SAn calculated as described above is expressed as a luminance (density) distribution.

In order to automatically select the measurement area from the luminance distribution indicating the standard deviation ΔFVσ, as an example, as shown by the partial area SAna in the shot of FIG. The edge portion is detected using. Further, among the detected edge portions, an area having a luminance of 70% or more (or other arbitrary ratio or more) with respect to the maximum value is cut out as an edge portion of the measurement area and displayed on a display device (not shown). . Further, for example, as shown in FIG. 7 (f), the measurement areas B11, B12, and B13 including the area surrounded by the edge portion of the measurement area are automatically and efficiently measured areas with high focus sensitivity. Can be selected or set.
Even when the wafer 10 exposed at the best focus position and the best dose cannot be prepared, the standard deviation ΔFMσ of the signal intensity for each pixel of the shots SAm1 to SAm2 is obtained from the detection result of the image of only the wafer 10b (FM wafer). The distribution of the standard deviation ΔFMσ similar to that shown in FIG. 7D may be obtained. Even using this distribution, it is possible to automatically set a measurement region in which the change in luminance of the signal is large with respect to the change in focus position.
Further, in order to set a measurement region with high dose sensitivity, instead of using an FM wafer, a wafer (Dose Matrix wafer: DM wafer) exposed by gradually changing only the exposure amount or a conditionally adjusted wafer 10a is used. The above setting direction may be used.

  Next, in the present embodiment, a method in which the inspection unit 60 of the calculation unit 50 evaluates and selects a template to be used for evaluating an actual wafer exposure condition from a plurality of sets of templates is shown in FIG. This will be described with reference to a flowchart. As an example, when selecting a template, an apparatus condition when the template is created is also selected, and a calculation template is obtained from the selected template, that is, template information is selected. The template is selected. In the following description, the exposure condition to be evaluated is the focus position, and the template used from five sets of templates F11, F12 to F51, and F52 whose peak position interval D shown in FIGS. The case of selecting will be described. Further, among the signal intensities SI, the signal intensity when the templates F11 to F51 having peaks in the positive direction (having the right-side peak in FIGS. 8A to 8E) are obtained as the signal intensity F1 and the peak. Is the signal strength F2 when the templates F12 to F52 having the left side in FIGS. 8 (a) to 8 (e) are obtained.

  First, as an example, in step 190 of FIG. 9D, the inspection unit 60 in a signal intensity space or F1-F2 plane in which the horizontal axis of FIG. 9A is the signal intensity F1 and the vertical axis is the signal intensity F2. FIG. 8A plots each point of the set of templates F11 and F12 to virtually create a trajectory (hereinafter referred to as a correlation curve indicating the correlation between the signal intensity F1 and the signal intensity F2) F14. . The correlation curve F14 is a signal of two templates F11 and F12 corresponding to each focus value obtained by dividing the range of the focus value FV of −40 nm to +40 nm into, for example, 15 in FIG. The intensities F1 and F2 are sequentially plotted, and the dot row obtained by plotting is approximated by a curve. The end points F14a and F14b in the + direction and − direction of the correlation curve F14 correspond to the focus values of +40 nm and −40 nm, respectively, and the focus value at the center of the correlation curve F14 is 0 nm. Similarly, correlation curves F24, F34, F44, and F54 of templates F21, F22 to F51, and F52 of FIGS. 8B to 8E are as shown in FIG.

  In this embodiment, the reference for selecting a template to be used is, for example, a focus value calculated using a template when a change amount such as fluctuation of an image signal due to disturbance light is added to the signal intensity detected from the wafer. The amount of change from the target value of the calculated value (for example, the focus position when the conditionally adjusted wafer 10a is exposed) is small, that is, the amount of change in the calculated value (evaluation result) with respect to the change in signal intensity is small. This means that the so-called robustness is good with respect to the amount of change such as signal fluctuation. Therefore, in step 192, the inspection unit 60 relates to the correlation curves F14 to F54 in FIG. 9A, as shown in FIG. 9B, respectively, from the position where the focus value of each correlation curve is 0 to each focus value. Cumulative distance curves F15, F25, F35, F45, and F55, which are curves indicating values obtained by multiplying the cumulative distance of the trajectory up to FV by the sign of the focus value FV, are obtained. The cumulative distance curves of the correlation curves F14, F24, F34, F44, and F54 are cumulative distance curves F15, F25, F35, F45, and F55, respectively. Further, in step 194, the inspection unit 60 divides the values (cumulative distances) of the cumulative distance curves F15 to F55 by the focus value FV at each focus value FV, as shown in FIG. Sensitivity curves F16, F26, F36, F46, and F56 indicating the change sensitivity of the distance with respect to the focus position (the amount of change in the cumulative distance on the cumulative distance curves F15 to F55 with respect to the change in the unit amount of the focus position) are expressed as the focus value FV (nm). As a function of When the change sensitivity is large, the amount of change in the signal strengths F1 and F2 on the correlation curves F14 to F54 with respect to the change in the unit amount at the focus position is large, which means that the stability against the change in the signal strength is high. In FIG. 9C, only the sensitivity curve related to the focus value in the + direction is shown, but a similar sensitivity curve is also obtained for the focus value in the − direction.

  Further, in step 196, the inspection unit 60 sets the allowable value of the change sensitivity as 0.5 as shown by a dotted line in FIG. 9C as an example of the template corresponding to the sensitivity curves F16, F26, F36, F46, and F56. Evaluate. In this example, the sensitivity curves F26 and F16 (sensitivity curves created using the signal intensities obtained using the templates in FIGS. 8D and 8E) have regions where the change sensitivity is smaller than the allowable range. The sensitivity curves F26 and F16 are evaluated as having high change sensitivity. Furthermore, as an example, the inspection unit 60 may evaluate that it is not preferable to use the templates of FIGS. 8D and 8E corresponding to the sensitivity curves F26 and F16. In this case, templates that can be used among the templates in FIGS. 8A to 8E are three sets of templates F31, F32 to F51 having a wide peak position interval D in FIGS. 8C to 8E. F52.

Next, an example of a template selection method according to the present embodiment will be described with reference to the flowcharts of FIGS. First, the basic method will be described with reference to the flowchart of FIG. In step 140 of FIG. 10A, a value obtained by adding a predetermined fixed value (details will be described later) to the input value of the template to be evaluated is input. In step 142, the focus value is calculated using the template. In the next step 144, the template is evaluated from the calculated focus value.
Next, a detailed method will be described with reference to the flowchart of FIG. First, in step 170 in FIG. 10B, by executing the operations in steps 102 to 120 in FIG. 3B, a plurality of sets, here, five sets of templates in FIGS. 8A to 8E are obtained. . In the next step 172, the inspection unit 60 of the evaluation apparatus 1 divides the focus value range of, for example, −35 nm to +35 nm into seven regions having a width of, for example, 10 nm. Then, with respect to the five sets of templates Fi1 and Fi2 (i = 1 to 5), the values of the signal intensities F1 and F2 corresponding to the respective focus values with a step width of, for example, 1 nm in seven regions (hereinafter referred to as template values). F1i and F2i are obtained. For example, regarding the template F41 in FIG. 6A, the template values when the focus values are FV1a and FV1b are SI1a and SI1b.

  In step 172, the focus value FV1i is calculated using the obtained template values (F1i, F2i) as input values for the corresponding calculation templates F43 and the like. Further, in step 174, the focus value FV2i is calculated using the template value (F1i + 2, F2i) obtained by adding 2 as a predetermined fixed value to only the template value F1i as an input value for the corresponding calculation template F43 or the like. The fixed value is a value determined on the basis of, for example, a fluctuation amount assumed by disturbance light or the like with respect to an image signal regardless of a process at the time of manufacturing the wafer 10a or a measurement position on the wafer 10a. For example, regarding the calculation template F43 in FIG. 6B, if the difference between the template values (F1i, F2i) is ΔF41 and the difference between the template values (F1i + 2, F2i) is ΔF42, the focus values corresponding to the differences ΔF41, ΔF42 are FV1. , FV2 and FV1 is substantially close to the target value, the deviation of FV2 from the target value is approximately δ1. Similarly, the focus value FV3i is calculated using template values (F1i-2, F2i) obtained by subtracting 2 as a predetermined fixed value from only the template value F1i as input values of the corresponding calculation template F43 and the like. Similarly, the focus values FV4i and FV5i are calculated by using the template values (F1i2, F2i + 2) and (F1i2, F2i-2) as input values of the corresponding calculation templates F43 and the like.

  In the next step 178, the inspection unit 60 calculates the focus value calculation results FV1i to FV5i described above from the target values (for example, the values on the horizontal axis in FIG. 6A) for each of the seven areas of the focus value. FVσ that is three times the standard deviation of the difference is calculated. Further, in step 180, the inspection unit 60 evaluates all sets of templates. In the present embodiment, the template evaluation is set by a calculated value obtained by inputting a value (for example, a value obtained by adding a fixed value to the input value) as a template input value and a conditionally adjusted wafer as a target value. This means that the degree of deviation (here, FVσ) from the value of the exposure condition (focus position or the like) is compared with a predetermined allowable value. Then, as a result of the evaluation, a set of templates in which the calculated value FVσ is less than or equal to an allowable value in the entire region of the focus position, that is, a set of templates having a high stability of the calculated value with respect to mixing of image signal fluctuations and the like is used. To select as a template.

  Here, the correlation curves F18, F28, F38, F48, and F58 in the signal intensity space of FIGS. 11A to 11E are the templates F11, F12 to F51, and F52 of FIGS. 8A to 8E, respectively. Is a correlation curve corresponding to. 11A to 11E, the horizontal axis and the vertical axis represent signal intensities F1 and F2 (values in the range of 40 to 120) relating to templates having peaks on the + side and the − side, respectively. ) Contour lines D1, E1, etc. represent changes in focus position from −40 nm to +40 nm at intervals of approximately 4.5 nm. Similar contour lines are shown in the other FIGS. 11 (b) to 11 (e). Therefore, the focus values of the end points C1, C2, C3, C4, and C5 of the correlation curves F18, F28, F38, F48, and F58 are −40 nm, and the focus values of the end points A1, A2, A3, A4, and A5 are +40 nm. The focus values of the central points B1, B2, B3, B4, and B5 are 0 nm. Instead of using the calculation template F43 or the like, the focus value is calculated or estimated using the contour lines from the position of the signal intensity (F1, F2) in the signal intensity space of FIGS. You can also The boundary lines F1, F5, etc. passing through the middle between the end points A1, A5, etc. and the end points C1, C5, etc. and passing through the central templates B5, B1, etc. are lines where the measured focus value changes by about 80 nm to 10 nm. In other words, this is a line in which a so-called jump (large change) occurs in a calculated value calculated using a template.

  A correlation curve F18 in FIG. 11A represents the correlation between the templates F11 and F12 having the narrowest peak position D in FIG. 8A with the narrowest 10 nm, and the positions of the end points A1 and C1 are closest. . For this reason, for example, if the fluctuations indicated by the arrow G1 are mixed in the signal intensities F1 and F2, the calculated value changes greatly. On the other hand, the correlation curve F58 in FIG. 11 (e) represents the correlation between the templates F51 and F52 having the widest peak distance D in FIG. 8 (e) and the positions of the end points A5 and C5. The farthest. For this reason, for example, even if fluctuations indicated by the arrow G1 are mixed in the signal intensities F1 and F2, since the change in the calculated value is small, the influence of the fluctuation in the input value is small, and the stability of the calculated value is good. Moreover, the robustness of the template is good. As described above, from the correlation curves F18 to F58 in FIGS. 11A to 11E, it is qualitatively understood that the template having the widest peak position interval D has higher stability of the calculated value against the mixing of fluctuations.

  Three times the standard deviation (FVσ) obtained in step 178 of FIG. 10A can be regarded as a quantitative indicator of the stability of such a calculated value. The bar graphs F17, F27, F37, F47, and F57 in FIG. 11F represent FVσ (nm) obtained in step 178 for each of the seven regions of the focus value FV. Bar graphs F17 to F57 are FVσ when the templates F11, F12 to F51, and F52 of FIGS. 8A to 8E are used, respectively. From FIG. 11 (f), it can be seen that as the template having a narrower peak position interval D is used and the focus value is closer to 0 nm, FVσ increases and the stability of the calculated value is worse. As an example, if the allowable value of FVσ is 2.5 nm, the FVσ is equal to or smaller than the allowable value in all the regions. The bar graphs F37 and F47 corresponding to the templates having the peak value intervals D of 30 nm, 40 nm, and 50 nm. , F57 only. For this reason, the stability of the calculated value is high, and three templates shown in FIGS. 8C, 8D, and 8E can be selected as usable templates. Further, in FIG. 11F, since the height of the bar graph F57 is the lowest in all regions, the template shown in FIG. 8E may be selected as the template to be used. Similarly, a template in which the stability of the calculated value of the exposure amount with respect to fluctuation can be selected from a plurality of sets of templates (and apparatus conditions) with high sensitivity regarding the exposure amount. Note that the number of divisions in the focus position range may be any number other than 7, and the allowable value of FVσ may be any value.

  As described above, the evaluation method of the present embodiment irradiates the illumination light IL1 on the surface (wafer surface) of the wafer 10 on which the repetitive pattern 12 is formed, and the diffraction emitted from the wafer surface by the illumination light IL1 irradiation. An evaluation method for evaluating processing conditions of a repetitive pattern 12 based on template information (hereinafter also referred to as evaluation characteristics) having an intensity of a signal obtained by detecting an optical ILD as an input value. Steps 174 and 176 for inputting a change input value to which a fixed value is assigned to the template information, and a step of calculating a change amount (FVσ, etc.) of the machining condition based on the template information to which the change input value is input Based on 178 and the calculated change amount of the machining condition, the stability of the calculated value against the variation of the input value of the template information is evaluated. , In which a step 180 of selecting the template information to be used from the evaluation results.

  The evaluation apparatus 1 is an evaluation apparatus that evaluates the processing conditions of the repeated pattern 12 of the wafer 10 on which the repeated pattern 12 is formed. The illumination system 20 irradiates the surface (wafer surface) of the wafer 10 with the illumination light IL1. (Hereinafter also referred to as an illumination unit), a light receiving system 30, an imaging device 35, and an image processing unit 40 (hereinafter collectively referred to as a detection unit) that detect diffracted light ILD emitted from the wafer surface by irradiation with illumination light IL1. An arithmetic unit 50 (evaluating the processing conditions of the repetitive pattern 12 based on template information (evaluation characteristics) that uses the intensity of the signal detected by the image processing unit 40 as an input value as a signal based on light from the wafer surface. The calculation unit 50 inputs a change input value obtained by adding a change amount to the input value to the template information, and changes the change. Based on the template information to which the force value is input, the change amount of the machining condition is calculated, and on the basis of the calculated change amount of the machining condition (FVσ, etc.), the calculated value for the change in the input value of the template information is calculated. The stability or the like is evaluated, and template information to be used is selected from the evaluation result.

  According to the present embodiment, for example, a plurality of template information (evaluation characteristics) for evaluating the exposure conditions when the pattern is formed is obtained by using the detection result of the diffracted light as an input value under a plurality of apparatus conditions. By applying a predetermined amount of change to the input values of the plurality of template information and calculating the amount of change in the evaluation result of the exposure condition, it is possible to stabilize the variation of the input values of the calculated values due to the plurality of template information. Sexuality etc. can be evaluated quantitatively. For this reason, it is possible to efficiently select actually usable template information with high stability of calculation values (good robustness) with respect to mixing of fluctuations using the evaluation result. Then, using the selected template or the like, the exposure conditions when the repeated pattern 12 is formed using the wafer 10 on which the repeated pattern 12 is formed can be evaluated with high accuracy and efficiency.

  Further, according to the exposure system or the lithography system DMS including the evaluation apparatus 1 and the exposure apparatus 100 of the present embodiment, the exposure apparatus 100 performs exposure according to the evaluation result of the exposure condition supplied from the evaluation apparatus 1 to the exposure apparatus 100. By correcting the conditions, the yield of devices that are finally manufactured can be improved.

In the above-described embodiment, the following modifications are possible.
First, in the above-described embodiment, a change input value obtained by assigning a fixed value as a change amount to the input value is input to the template information (evaluation characteristics), and the processing condition changes based on the template information input with the change input value. The amount is calculated, and the template information is evaluated based on the amount of change. However, a value obtained by adding a change amount to the input value does not need to be input to the template information. For example, a predetermined table (so-called lookup table or the like) is used from the input value, the change amount, and the template information. A change amount of the processing condition may be obtained, and the template information may be evaluated from the change amount. In this case, as an example, a change amount of the processing condition is obtained using a table based on the template information (that is, a table relating to at least one of the focus position, the exposure amount, and the input value) and the input value and the change amount of the input value. Template information may be evaluated. The same applies to the modified examples described below.
Further, in the above-described embodiment, the stability or the like against the inclusion of fluctuations in the calculated values of a plurality of template information is evaluated, and one that can be used under actual exposure conditions in which the calculated values are highly stable based on the evaluation results. Or, a plurality of template information is selected, but the stability of the calculated value based on the plurality of template information is evaluated without selecting the template information (for example, the degree of deviation between the calculated value and the actually measured value and the allowable value). Or the like). In other words, it is only necessary to evaluate the robustness of the template information.
Further, in the above-described embodiment, a value obtained by adding a change amount to the input values of the templates F41, F42, etc. is input without using the calculation template F43, etc., and the processing conditions change using the templates F41, F42, etc. The amount may be calculated or estimated, and the templates F41, F42, etc. may be evaluated from the amount of change.

In the above-described embodiment, two templates F41, F42, etc. are obtained under a set of two device conditions, and a calculation template F43, etc. is obtained from these templates. Originally, it is possible to obtain one template (characteristic) whose signal intensity changes monotonously with respect to the exposure condition (for example, focus value), and use this template as it is as a template for calculation to calculate the exposure condition from the signal intensity. It is. It is also possible to obtain a plurality of templates under three or more apparatus conditions, and to calculate the exposure condition from the signal intensity by combining these templates.
In the above-described embodiment, one or a plurality of template information with high stability of the calculated value is selected from a plurality of template information, but the number of template information to be evaluated may be one. In this case, the stability of the calculated value of one template information may be evaluated. Further, whether or not the template information can be used may be determined from the evaluation result.

In the above-described embodiment, unpolarized light (randomly polarized light) is used as the illumination light irradiated on the wafer 10, but partially polarized light or linearly polarized light (polarized light) is used as the illumination light. May be. In the case of using polarized light, a polarizer and an analyzer are added to the optical system of the evaluation apparatus 1 in FIG. 1A, and the direction of the polarizer and the analyzer is set to an optimum value in determining the conditions. An operation is added, and in the evaluation process, the directions of the polarizer and the analyzer are set to directions determined by the respective apparatus conditions.
When polarized light is used as illumination light, the apparatus conditions (evaluation conditions) of the above-described embodiment are applied to the surface of the wafer 10a in addition to the wavelength of the illumination light, the incident angle, and the order of the diffracted light to be detected. Of the polarization direction of the polarized light and the periodic direction of the repeating pattern 12 on the wafer surface (first relative angle), the polarization direction of the polarized light irradiated on the wafer surface, and the diffracted light emitted from the wafer surface You may make it include at least 1 value among the angles (2nd relative angle) with the polarization direction of the object polarization component.

In the above-described embodiment, the wafer 10b (FM wafer) in FIG. 7A is used to set a measurement region with high focus sensitivity on the wafer surface. Instead, it is also possible to set a measurement region from an image of only the conditionally adjusted wafer 10a (FEM wafer) in FIG. In this case, as an example, an image of a shot exposed at the best focus position and the best dose of the conditioned wafer 10a is taken as a shot of a row exposed at the best dose within another focus evaluation range (for example, the center of FIG. 7A). Subtract from the image of a plurality of shots in the same area as the area 10m. As a result, it is possible to subtract the influence of common fluctuation components (such as exposure mask drawing error, synchronization error during scanning of the exposure apparatus) in the shot. Further, a standard deviation σ of signal intensity of each pixel of a plurality of shots within the focus evaluation range is obtained. At this time, a pixel (measurement region) with a large standard deviation σ has a large luminance change with respect to a change in the focus position, and thus can be easily distinguished from a region including other pixels with a small luminance change with respect to the change in the focus position. The measurement region having a large luminance change can be automatically and efficiently obtained by the method described with reference to FIGS. 8A and 8B.
In addition, an image (standard deviation image) representing the standard deviation σ for each pixel in terms of density is displayed in the order of the period (pitch) of the pattern to be evaluated, and an image obtained by adding the standard deviation image is also displayed as a representative image. May be. The representative image may be displayed on a screen of a display device for setting a measurement region.

  In the above-described embodiment, a fixed value is given as an amount of change to the input of a template for evaluating processing conditions (hereinafter, including a calculation template), but the amount of change to be given is arbitrary. For example, as shown in the flowchart of FIG. 10C of the first modification, the degree of variation in the signal intensity detected from the actual image on the wafer surface may be used as the amount of change. In this modified example, in step 182 of FIG. 10C, as shown in FIG. 7B, the exposure amount and the focus position are set to the best dose and the best focus position in the exposure apparatus 100, respectively. All shots of (normal wafer) are exposed and developed. Then, in step 184, the evaluation apparatus 1 uses a plurality of sets of templates to be evaluated (the five sets of templates in FIGS. 8A to 8E) under the conditions of each set of apparatuses. An image of the wafer 10 is taken. At this time, as an example, it is assumed that a plurality of measurement regions 16 are set in each shot SAn on the wafer surface as shown in FIG. The measurement region 16 is a region in which, for example, a pattern for which a machining process is evaluated is formed among patterns formed in each shot SAn. In step 186, the standard deviation σi of the signal intensity of the i-th (i is an integer of 1 or more) measurement area 16 of all shots of the wafer 10 is calculated and stored. In this case, as an example, a substrate having better flatness than the wafer 10 may be used as the conditionally adjusted wafer 10a.

  Further, in step 188, templates F41 and F42 are input in the i-th measurement region 16 of each shot of the conditioned wafer 10a as an input for the k-th (here, k = 1 to 5) calculation template F43 to be evaluated. The focus value FVki is calculated using a value obtained by adding the standard deviation σi as a change amount to the template values F1i and F2i, which are values of the signal intensity SI (F1, F2) obtained when creating the above. In step 178A, as in step 178, the standard deviation of the difference from the set value (target value) of the calculated focus value FVki on the conditionally adjusted wafer 10a in the form shown in the graph of FIG. Find σ. In step 180A, as in step 180, a set of templates whose standard deviation σ is equal to or smaller than an allowable value is selected as a template to be used for evaluation. According to this modification, the distribution of variation in signal intensity obtained from the normal wafer 10 is used as the amount of change, so that a template with a stable calculation value can be obtained when actually calculating or estimating the exposure conditions of the wafer 10. You can choose.

  In this modification, as shown in FIG. 7A, the wafer 10b (FM wafer) exposed by gradually changing only the focus position in the X direction is also developed in step 182. The standard deviation σf of the difference between the signal intensity obtained from the wafer 10 and the signal intensity obtained from the wafer 10b is obtained, and in step 188, the standard deviation is added to the template input to calculate the focus value. The standard deviation of the focus value may be obtained. In this way, by using the signal intensity of the FM wafer 10b, the stability of the calculated value related to the focus value can be evaluated with higher accuracy.

  Next, as the amount of change in the input when evaluating the template, unevenness in polishing with a process (film formation with a film forming apparatus or chemical mechanical polishing (CMP) apparatus) such as a film thickness distribution of the base film ) May be used. In this modified example, as shown in FIGS. 12A and 12B, in the evaluation apparatus 1, two templates having peaks on the + side and the − side (for example, templates F11 and F12) are obtained. The normal wafer 10 is imaged under the apparatus conditions, and the inspection unit 60 detects the distribution of the signal intensities F1 and F2 detected under the two apparatus conditions (image of the entire surface of the wafer). Light quantity distribution). FIG. 12A shows the distribution of the signal strength F1, and FIG. 12B shows the distribution of the signal strength F2. 12A to 12D, the density of the area in the wafer 10 represents the strength (magnitude) of the signal intensities F1 and F2 detected in the area. Further, a rotationally symmetric component with respect to the center of the wafer 10 is obtained from the distributions of FIGS. 12A and 12B as shown in FIGS. 12C and 12D. Such a rotationally symmetric component is caused by, for example, the rotationally symmetric film thickness distribution of the base film, that is, a process-induced change amount (a change amount when the film thickness distribution is constant). When the rotationally symmetric components of the signal intensities F1 and F2 in FIGS. 12C and 12D are expressed as a function of the distance (mm) from the center of the wafer 10 in the radial direction, FIG. 12E is obtained. . In FIG. 12E, the deviations of the signal intensities F1 and F2 from the intensity 100 are denoted by ΔF1 and ΔF2.

  In this modification, the template intensity (F1i, F2i), which is the signal intensity corresponding to each focus value of the template shown in FIGS. The focus value is calculated by adding the deviations ΔF1 and ΔF2 of the signal intensities F1 and F2 at the position (1). As the amount of change, the added deviations ΔF1 and ΔF2 may be adjusted so that the ratio of the amount of change to the signal intensity at each focus position is constant.

  Curves F110, F210, F310, F410, and F510 in FIG. 13 (a) show the focus value FV calculated using the templates in FIGS. 8 (a) to 8 (e) as shown in FIG. 13 (b). The bar graphs F19, F29, F39, F49, and F59 are three times the standard deviation (FV3σ) of the focus value FV calculated using the templates of FIGS. 8A to 8E for each of the seven areas of the focus value. ). As shown in FIGS. 13A and 13B, the FV3σ becomes smaller in the entire region as the template having a smaller peak position interval D is used, and the exposure condition is increased in a state where the change in the focus value due to process variations is reduced. It can be seen that the evaluation can be performed accurately and efficiently.

  If the distribution of deviations (ΔF1, ΔF2) in FIG. 12E is reproducible, the distribution of deviations (ΔF1, ΔF2) in the wafer surface may be stored in the storage unit 85. In this case, when the signal intensity (F1, F2) (signal intensity obtained under two apparatus conditions) is calculated for each pixel from the image of the wafer 10 in step 118A of FIG. 4, the signal intensity (F1, F2) is calculated. The above-described deviation (ΔF1, ΔF2) detected at the pixel position may be corrected, and the focus value may be calculated by inputting the corrected signal intensity into the template information. Thereby, errors caused by the process can be reduced.

  Further, for example, the distribution of a plurality of sets of deviations (ΔF1, ΔF2) of FIG. 12E for each position on the wafer surface with respect to the plurality of wafers 10 is obtained and stored, and the signal for each pixel obtained in step 118A. A focus value is calculated by inputting the signal intensity obtained by correcting the intensity (F1, F2) with a plurality of sets of deviations (ΔF1, ΔF2) into the template information, and using a fitting error (pre-correction and post-correction signal intensity). A calculation result using a set of deviations (ΔF1, ΔF2) that minimizes the standard deviation of the calculated focus value difference may be adopted as the evaluation result.

  Further, when the process-induced deviations (ΔF1, ΔF2) in FIG. 12E are plotted on the horizontal axis and the vertical axis, as shown in FIG. 13C, the start point B6 corresponding to the value at the center of the wafer is obtained. To the end point A6 corresponding to the value at the outermost periphery, a correlation curve C6 is obtained. Further, as shown in FIG. 13D, deviations (ΔF1, ΔF2) obtained when the exposure amount (relative value) is changed to −1, 0, +1, +2 with respect to the optimum value 0 are represented. When the curve and the dot row representing the deviation (ΔF1, ΔF2) when the focus value (nm) changes to −5 and +5 with respect to the optimum value 0 are displayed in an overlapping manner, the correlation curve of FIG. The end point of C6 is at the position where the exposure amount is +0.5 and the focus value is approximately −5, and the start point of the correlation curve C6 is at the position where the exposure amount is 0 and the focus value is approximately 0. Therefore, when a plurality of (for example, 10) evaluation points P0, P1, P2,..., P9 are taken from the start point to the end point on the correlation curve C6, the deviation (ΔF1) at each evaluation point Pi (i = 0 to 9). , ΔF2) can be divided into an exposure amount and a focus position. In addition, at each evaluation point Pi, a set of deviations (ΔF1, ΔF2) that minimizes the standard deviation is assigned from the plurality of sets of deviations (ΔF1, ΔF2), and the measurement corresponding to each evaluation point Pi is performed. The signal intensity detected in the area may be corrected by the deviation (ΔF1, ΔF2). A numerical value (for example, a numerical value from 1 to 6) indicating which set of deviations (ΔF1, ΔF2) is used is referred to as a process index PI. The process index PI is, for example, the number of the wafer on which the deviation (ΔF1, ΔF2) of the set to be used is measured.

  In FIG. 13D, when the deviations (ΔF1, ΔF2) for the process are observed, the point P3 is obtained even though the wafer 10 is exposed at the best dose (D = 0) and the best focus position (F = 0). Is substantially equal to the case where the exposure amount is +2 and the focus value is +2, and the point P5 is substantially equal to the case where the exposure amount is 0 and the focus value is +4. For this reason, it is preferable to distribute the error caused by the process to the exposure amount, the focus value, and the pure process cause. This distribution is performed using the fact that the error due to the process is rotationally symmetric and the high frequency component is small, and that the error due to the exposure amount is also basically low in the high frequency component.

  First, as a method of obtaining a correction amount for an error caused by a process, a method of obtaining by referring to a signal intensity detected in a region adjacent to a measurement target point on the wafer surface can be considered. In this case, since the high-frequency component of the error caused by the process is small, as shown in FIG. 14A, the measured value (distribution of many dots) of the distribution of the process index PI at the position in the radial direction from the center of the wafer is For example, a function C8 having a second or higher order (for example, sixth order) and an odd-order coefficient of 0 is determined by the method of least squares or the like. Then, at each measurement point on the wafer, as shown in FIG. 14B, a process index PI (for example, a number from 1 to 6) at a position closest to the function C8 is selected according to the distance from the center. To do. Then, the focus value (or exposure amount) may be obtained by correcting the signal intensity using the above-described deviation (ΔF1, ΔF2) determined by the process index.

  Next, as another method, the signal intensity detected from a plurality of shots of the wafer 10b (FM wafer) exposed in advance by gradually changing only the focus value shown in FIG. A difference ΔSI from the signal intensity detected from the shot in the same region may be obtained, and the signal intensity detected from the wafer 10 may be corrected using the difference ΔSI. FIG. 15A shows a conditioned wafer 10a (FEM wafer). In FIGS. 15A to 15C and FIGS. 15D and 15B, Di (i = 1 to 9) and Fi. Is the set value of the exposure amount and the focus position, D0 is the best dose, and F0 is the best focus position. In this case, the distance r (i) (see FIG. 15 (e)) from the center c at the i-th (i is an integer of 1 or more) measurement point of the wafer 10b and the set value of the focus value are associated with each other. The deviation of the signal strengths F1 and F2 can be obtained. In addition, from the signal intensity difference ΔSI, whether the change amount of the signal intensity due to the process can be expressed as an offset (a constant value on the entire wafer surface) or can be expressed using a magnification according to the distance from the wafer center, Or it can confirm whether it can express as the two linear combination.

  Further, as shown in FIG. 15D, in the normal wafer 10, there are many measurement points at a distance r (i) from the center c, and it is necessary to detect the signal intensity at all these measurement points. On the other hand, as shown in FIG. 15E, in the wafer 10b (FM wafer), since the focus position is changed in the horizontal direction, the signal intensity detected at a certain focus position is one column in the vertical direction. It is sufficient to use only the signal intensity detected in the shot. For this reason, the number of measurement points in the wafer 10 b can be reduced as compared with the wafer 10.

As yet another method, the signal intensity F1 and F2 changes (d1, d2) due to the unit exposure change when the exposure amount and the focus position are the reference values, and the signal intensity due to the unit focus position change. Using the changes (f1, f2) of F1 and F2, the signal intensity deviation (ΔF1, ΔF2) caused by the process is changed to the exposure error (error due to change in exposure) ΔD and the focus error (change in focus position). It is also possible to convert the error to ΔF.
The following equation can be used to convert the exposure amount error ΔD.
ΔD = (d1 × ΔF1 + d2 × ΔF2) / (d1 ² + d2 ² ) (3)
To convert to the focus error ΔF, the following equation can be used.
ΔF = (f1 × ΔF1 + f2 × ΔF2) / (f1 ² + f2 ² ) (4)

These formulas represent the inner product of the signal intensity deviation vector due to process error and the exposure error or focus error vector, with each signal intensity change as a vector in the signal intensity space (or signal intensity plane). It is standardized by the square of the length of the vector of quantity or focus error.
From the calculation result of the above equation, as shown in FIG. 13E, the process error at each position determined according to the distance from the center on the wafer is converted into a focus error and a curve C7F, respectively, and an exposure error. Can be represented as a curved line C7D.

  Next, a modified example for evaluating the stability of the evaluation result of the exposure condition against the change with time will be described. In this modified example, after evaluating the exposure condition (for example, the focus value) of the wafer 10 by the evaluation method of FIG. 5, after a predetermined time, for example, several hours to several days have elapsed, the process of FIG. The focus value of the wafer 10 is evaluated by the evaluation method. In that case, the change in signal intensity detected from the image of the wafer 10 is different for each of the five sets of templates (apparatus conditions) shown in FIGS.

  FIGS. 16A, 16B, and 16C show the predetermined conditions using the apparatus conditions for obtaining the templates F31, F32, F41, F42, and F51, F52 in FIGS. 8C to 8E. An example of a change in signal strength SI detected after a lapse of time is shown. The increase / decrease in the detection signals related to the templates F31 and F32 in FIG. 16A is (−5, +10), the increase / decrease in the detection signals related to the templates F41 and F42 in FIG. 16B is (+5, +10), and FIG. The increase / decrease in the detection signal for the templates F51 and F52 is (+10, +10). In this case, the amount of change in the focus value calculated using the template information varies depending on the sign and magnitude of the signal intensity change.

  As an example, when templates F31, F32, F41, F42, and F51, F52 are used, the time from the exposure and measurement to the second measurement (reservation time) (the unit is days) and two times The relationship between the measurement values and the amount of change (nm) is as shown in FIG. In FIG. 16D, dot rows D13, D14, D15 are focus value changes calculated using templates F31, F32, F41, F42, and F51, F52, respectively. From this result, it is understood that the change with time is the smallest when the templates F51 and F52 having the widest peak interval D are used. For this reason, the templates F51 and F52 are selected as templates to be used in that the stability of the calculated values with respect to changes with time is good.

  As a factor that changes the signal intensity due to the above-described change with time, a decrease in resist volume due to degassing from the resist can be considered. The decrease in the resist volume is divided into a change in CD (critical dimension) of the pattern in the resist Re applied to the substrate P shown in FIG. 16E and a film reduction of the resist Re shown in FIG. . Regarding the influence of CD change, the diffraction efficiency generally increases as the resist film ratio approaches 50%. Therefore, the signal intensity of diffracted light increases with time in the hole-based layer, and the line-based layer has a low resist film ratio. Then, the signal intensity of the diffracted light becomes weaker with time.

  Next, if the refractive index n of the resist and the film thickness t after exposure (or change with time) are known, the change in signal intensity due to the above-mentioned film reduction is the pattern pitch P to be measured and the inclination of the wafer 10. The angle can be calculated using the theory of thin film interference from the incident angle θ1 of the illumination light on the wafer 10, the exit angle θ2 of the diffracted light from the wafer 10, and the incident angle θ1 ′ and exit angle θ2 ′ in the resist. In FIG. 16G, the phase and magnitude of the combined wave of the surface reflection wave and the bottom surface reflection wave of the resist Re before and after film reduction change depending on the optical path length difference D of the two waves.

As shown in FIG. 16F, when the film thickness of the resist Re is t and the refractive index is n, the optical path length of the incident wave is nt / cos (θ1 ′), and the optical path length of the bottom reflected wave is nt / cos ( θ2 ′), and the angles θ1 ′ and θ2 ′ are as follows.
sin θ1 = n · sin θ1 ′, sin θ2 = n · sin θ2 ′ (5)
For this reason, the optical path length difference D between the surface reflected wave and the bottom reflected wave is as follows.

レジスト表面、底面の境界面での屈折率の大小による反射光の位相反転の関係が同じであれば、表面反射波と底面反射波との位相差φは次のようになり、例えばｓｉｎφを信号変化の指標として用いることができる。

If the relationship of phase inversion of the reflected light due to the refractive index at the boundary between the resist surface and the bottom surface is the same, the phase difference φ between the surface reflected wave and the bottom reflected wave is as follows. It can be used as an indicator of change.

φ = D / λ (7)
When a change in CD causes an increase in signal intensity as in a hole pattern, the closer the sin φ is to 1, the stronger the change in film thickness. For example, when sin φ is 0.6 or more, the calculated value of the change in film thickness is given. It may be determined that the influence is large.
Next, a modification example in which one shot of the wafer 10 is formed from a plurality of chip patterns will be described. In this case, the same pattern is exposed by the number of chips on the same shot. Further, even when a plurality of the same functional blocks are formed in one chip, the same pattern is formed in each shot and the number of functional blocks in the chip. Here, for the sake of simplicity, a case will be described in which there are a plurality of (9 in this case) chip patterns in the shot SAn as shown in FIG. At this time, since different mask patterns are used for different chips, the influence of the mask line width error is also different, and an error occurs in the signal intensity detected between shots. This signal strength error varies from mask to mask.

  In this case, a chain of variation in mask line width, variation in signal intensity between chips, and variation in focus position between chips occurs. In this modification, the influence of the mask line width variation on the image plane (the variation of the focus position in the shot) can be obtained by giving the variation in the signal intensity between the chips as the amount of change in the input of the template information. it can. An example of the variation in signal intensity (F1 (horizontal axis), F2 (vertical axis)) with respect to the input when using two templates (for example, templates F41 and F42) between each chip is as shown in FIG. Become. In FIG. 17A, the change amounts of the signal intensities F1 and F2 in the chip pattern SAn1 are +1 and −1, respectively.

  Changes in the focus value at the position of each chip pattern when the variation in signal intensity in FIG. 17A is given to the input of five sets of template information in FIGS. 8A to 8E and the focus value is calculated. Is as shown in FIG. 17B as an example. In FIG. 17B, the table in which the distance D between the peak positions is 10 nm to 50 nm is the result calculated using the templates F11, F12 to F51, and F52 of FIGS. 8A to 8E, respectively. The calculation was performed when the focus positions were -20 nm, 0 nm, and +20 nm.

  FIG. 17B shows that when a set of templates having a wide interval D is used, even if the same mask line width variation is given, the amount of change in the focus value measured on the image plane is small. Further, the signal strengths F1 and F2 whose variation is dominant differ depending on the focus position. When the focus position is −20 nm, F1 is dominant, and when the focus position is +20 nm, F2 is dominant, and the image plane may change depending on the focus position. However, the difference in image plane due to the change in the focus position due to the mask error is smaller in the template set with a wide interval D. The influence of this mask error is that the signal intensity after correction is performed using the correction table in FIG. 17A after correcting the signal intensity at the position of each chip pattern in the shot before performing signal processing. It is possible to remove it by calculating the focus value.

Next, a modification for separating the influence of the change in exposure amount and the influence of the change in focus position will be described.
In this modification, as shown in FIGS. 18A, 18B, 18C, and 18D, a plurality of sets of templates D21, which have different characteristics of changes in signal intensity SI depending on the focus position for each exposure amount. D22, D23, D31, D32, D33, D41, D42, D43, D51, D52, D53 are used. The peak positions (focus positions) of the templates in FIGS. 18A to 18D are −15 nm, +15 nm, −25 nm, and +5 nm, respectively, and the exposure amounts are high for the templates D21 to D51 and low for the templates D23 to D53. Templates D22 to D52 are cases of appropriate exposure amounts.

  As an example, a comparison is made when using templates D21 to D23 and D31 to D33 (symmetric templates) and using templates D41 to D43 and D51 to D53 (asymmetric templates). When the templates D21 to D23 and D31 to D33 are used, the correlation curve in the space of the signal intensities F1 and F2 is the correlation curve D61. D62. When the templates D41 to D43 and D51 to D53 are used, the correlation curve in the space of the signal strengths F1 and F2 is the correlation curve D71.D of FIG. D72. D73. FIGS. 19B and 19E show signal intensities F1 and F2 with respect to changes in unit exposure and unit focus positions at the optimum exposure and best focus positions in the correlation curves of FIGS. 19A and 19D. Represents changes. The straight lines Da and Fa in FIGS. 19B and 19E are changes with respect to changes in the exposure amount and the focus position. FIGS. 19C and 19F show the angle of the change direction of the signal intensities F1 and F2 with respect to the change of the unit exposure amount and the unit focus position in the correlation curves of FIGS. 19A and 19D. . In FIG. 19 (a), the direction of change in signal intensity due to the change in focus position and exposure amount is orthogonal and the two changes are completely separated, whereas in FIG. 19 (d), the focus position and It can be seen that the separation of changes in signal intensity due to changes in exposure dose is not perfect.

  Next, n indexes are used as indicators of the orthogonality of the change in the focus position and the change in the signal intensity due to the change in the exposure amount in each combination of the focus position and the exposure amount (closeness of the angle difference Δθ to the absolute value 0 of cos Δθ). The signal intensity of the diffracted light may be detected under the condition (n is an integer of 2 or more), and the change in the signal intensity due to the change in the focus position and the exposure amount may be represented as a vector in the n-dimensional signal intensity space. At this time, the vector of the change in the signal intensity due to the change in the focus position and the exposure amount is set as F and D, respectively, and the inner product of the focus vector F and the exposure vector D is the length of the focus vector F and the exposure vector D. The value divided by the product is defined as cos θ with respect to the angle θ formed by the two vectors as follows, and the closeness of this value to 0 is used as the evaluation amount.

例えば、４種類の信号強度を用いて、露光量及びフォーカス位置を計測する場合、ある露光量及びフォーカス位置の組み合わせでの露光量ベクトルＤを（ｄ１，ｄ２，ｄ３，ｄ４）として、フォーカスベクトルＦを（ｆ１，ｆ２，ｆ３，ｆ４）とすると、ｃｏｓθは次のようになる。

For example, when the exposure amount and the focus position are measured using four types of signal intensities, the exposure vector D at a combination of a certain exposure amount and focus position is (d1, d2, d3, d4), and the focus vector F Is (f1, f2, f3, f4), cos θ is as follows.

また、上記の実施形態では、図８（ａ）のテンプレートＦ１１，Ｆ１２等を評価装置１の演算部５０で求めているが、そのテンプレートの情報を評価装置１とは別の演算装置としての例えばホストコンピュータ６００で求めてもよい。この場合、ホストコンピュータ６００からそのテンプレートの情報を評価装置１の演算部５０の制御部８０に供給し、制御部８０ではそのテンプレートの情報を記憶部８５に記憶しておく。そして、図５に示すように露光条件を求める際には、その記憶部８５に記憶したテンプレート情報を使用すればよい。

Further, in the above embodiment, the templates F11, F12, etc. in FIG. 8A are obtained by the computing unit 50 of the evaluation device 1, but the information on the template is used as a computing device different from the evaluation device 1, for example. You may obtain | require with the host computer 600. FIG. In this case, the template information is supplied from the host computer 600 to the control unit 80 of the calculation unit 50 of the evaluation apparatus 1, and the control unit 80 stores the template information in the storage unit 85. As shown in FIG. 5, when obtaining the exposure conditions, the template information stored in the storage unit 85 may be used.

In the above embodiment, the pattern to be evaluated is an L & S pattern. However, the pattern to be evaluated is, for example, a plurality of hole patterns arranged in a predetermined direction periodically arranged in a direction orthogonal to the predetermined direction. A hole pattern group may be used.
Moreover, in said embodiment, incident angle (theta) 1 (diffraction angle (theta) 2) of illumination light controls the position of the injection | emission part of the light guide fiber 24, and the position and angle of the illumination side concave mirror 25 via a drive mechanism not shown. And adjusting the tilt angle φ2 of the wafer 10 through the second driving unit. In addition to this adjustment method, the diffraction angle θ2 of the diffracted light ILD detected by the light receiving system 30 is adjusted by controlling the position and angle of the imaging device 35 while tilting the light receiving concave mirror 31 about the tilt axis TA. May be.

In the above embodiment, both the exposure amount and the focus position in the exposure conditions are evaluated. However, at least one of the exposure amount and the focus position may be evaluated.
In the above embodiment, the exposure amount and the focus position are evaluated as the exposure conditions. As the exposure conditions, the exposure light wavelength, the illumination conditions (for example, the coherence factor (σ value), and the projection optical system in the exposure apparatus 100 are evaluated. In order to evaluate the numerical aperture of the liquid or the temperature of the liquid during the immersion exposure, the evaluation of the above embodiment may be used.

In the above embodiment, the exposure condition is evaluated as the processing condition. However, the film thickness condition in the coater / developer 200 as the processing condition is evaluated together with the exposure condition or separately from the exposure condition. May be. The film thickness condition includes a set value of the film thickness of the resist applied to the wafer, variations in the film thickness, and the like.
When evaluating the film thickness condition using the evaluation apparatus 1, as an example, a plurality of sheets coated with resists with different film thicknesses by the coater / developer 200 in the process corresponding to the condition determination of FIG. The wafers are prepared, and each shot of these wafers is exposed by the exposure apparatus 100, and then the wafers are developed to form the pattern 12 repeatedly. Thereafter, the signal intensity of the diffracted light from those wafers is detected under a plurality of apparatus conditions, and an apparatus condition for increasing the signal intensity value with respect to the change in the resist film thickness is obtained. A template showing the relationship with the film thickness is obtained. Thereafter, in a step corresponding to the evaluation method of FIG. 5, the signal intensity detected under the apparatus conditions is applied to the input of the template, whereby the resist film thickness of the wafer 10 on which the repeated pattern 12 is formed. The average value and the variation for each shot can be obtained.

Furthermore, film thickness conditions and exposure conditions can also be evaluated by using a plurality of wafers having different film thicknesses as the above-described FEM wafers.
In addition, when an oxide film or a conductive film is formed as a resist base in the substrate exposed by the exposure apparatus, a pattern such as an oxide film or a conductive film is formed by a process such as etching after developing the resist. The In order to form this pattern with high accuracy, it is preferable to evaluate the film thickness conditions of the oxide film or the conductive film. In this case, a wafer on which a pattern such as an oxide film or a conductive film is formed is placed on the stage 5 in FIG. 1A, and the signal intensity of the diffracted light from the wafer is obtained, whereby the resist film thickness is reduced. As in the case of the evaluation, the film thickness condition of the oxide film or the conductive film can be evaluated.

  In the above embodiment, the exposure condition and the like are obtained by using the obtained signal intensity value as a template input. However, there are a plurality of apparatus conditions in the step corresponding to the condition setting step in FIG. The simultaneous equations (characteristics) for calculating a plurality of machining conditions to be evaluated may be obtained from a plurality of signal intensities obtained under the conditions. In this case, in the process corresponding to the evaluation process of FIG. 4, the value of the machining condition to be evaluated can be obtained only by substituting the value of the signal intensity detected under the plurality of apparatus conditions into the simultaneous equations. it can.

In addition, the wavelength λ and the incident angle θ1 included in the above apparatus conditions are merely examples, and the apparatus conditions can include other arbitrary conditions that can be changed by the evaluation apparatus 1.
Further, in step 110, all shots SAn (see FIG. 5B) except for the scribe line region SL of the condition-controlled wafer 10a (region serving as a boundary when the chips are separated in the device dicing process) are supported. The signal intensity of the pixel to be calculated may be calculated, and the calculation result may be averaged to obtain the shot average value. The reason why the shot average value is calculated in this way is to suppress the influence of the aberration of the projection optical system of the exposure apparatus 100 and the like. In order to further suppress the influence of the aberration and the like, for example, a value obtained by averaging the signal intensities of the corresponding pixels in the partial area CAn in the central portion of the shot SAn in FIG. 5B may be calculated.

Further, in step 162 of FIG. 4, information on the exposure amount error distribution (dose unevenness) and the focus position error distribution (defocus amount distribution) on the entire surface of the wafer 10 may be obtained. In this case, the error distribution information may be directly output from the signal output unit 90 to the control unit (not shown) of the exposure apparatus 100 without going through the host computer 600.
Further, the wafer on which the pattern is formed by the exposure apparatus 100 is evaluated as in steps 158 to 160 in FIG. 4 described above, and even if an exposure apparatus different from the exposure apparatus 100 is corrected in step 162 from the evaluation result. Good. Further, the inspection unit 60 may not only determine the exposure conditions (processing conditions) but also determine the quality of the determined exposure conditions. In this case, the signal output unit 90 may provide a warning to the exposure apparatus 100 or the host computer 600 that the exposure conditions are not appropriate based on the quality determination result. This pass / fail judgment may be performed, for example, by comparing the obtained exposure condition with a predetermined threshold value.

Further, in the above-described embodiment, as the pattern processing conditions by the device manufacturing system DMS, the film thickness (thin film deposition amount) by the thin film forming apparatus (not shown) and the etching (etching amount) by the etching apparatus 300 are evaluated. Can also be evaluated.
In the above embodiment, the illumination system 20 of the evaluation apparatus 1 in FIG. 1A collectively illuminates the entire surface of the wafer 10 with the illumination light ILI (unpolarized light), and the imaging device 35 (detection). Part) has an image pickup element 35b for picking up an image of the entire surface of the wafer 10. For this reason, the processing conditions of the repetitive pattern formed on each shot on the entire surface of the wafer 10 can be efficiently evaluated. Note that partially polarized light may be used as the illumination light IL1.

  In contrast, an illumination system that illuminates a part of the surface of the wafer 10 (test substrate) with non-polarized light (or polarized light or partially polarized light), and imaging that captures an image of a part of the surface of the wafer 10. An evaluation apparatus (not shown) including an element and a stage movable in the X direction and the Y direction parallel to the surface of the wafer 10 may be used. In the evaluation apparatus of this modification, the wafer 10 is moved by the stage so that the illumination light from the illumination system is sequentially irradiated onto the entire surface of the wafer 10. In this modification, the surface of the wafer 10 is divided into a plurality of parts, and the processing conditions of the repeated pattern formed in each part are sequentially evaluated. Since the evaluation apparatus of this modification can be reduced in size, for example, it can be incorporated in the exposure apparatus 100 on-body. In this case, since the stage of the evaluation apparatus can also be used as the wafer stage (not shown) of the exposure apparatus 100, the configuration of the evaluation apparatus can be further simplified.

  In each of the above embodiments, the exposure apparatus 100 may be a scanning stepper that uses an immersion exposure method, or may be a dry scanning stepper or a stepper. Further, when the exposure apparatus uses an EUV exposure apparatus that uses EUV light (Extreme Ultraviolet Light) having a wavelength of about 15 nm or less as exposure light, or an electron beam exposure apparatus that uses an electron beam as an exposure beam, the above-described implementation is performed. Form can be applied.

In each of the above embodiments, the non-polarized light from the light source unit 22 is illuminated onto the wafer. However, the light that illuminates the wafer may be linearly polarized light, circularly polarized light, or the like.
In each of the above embodiments, the evaluation apparatus 1 is a part of the device manufacturing system DMS. However, the evaluation apparatus 1 may be used alone to evaluate the processing conditions from, for example, a pattern formed on a wafer. Good.

  Further, as shown in FIG. 20, a semiconductor device (not shown) includes a design process (step 221) for designing the function / performance of the device, and a mask manufacturing process (mask) for manufacturing a mask (reticle) based on the design process (step 221). Step 222), a substrate manufacturing process (Step 223) for manufacturing a wafer substrate from a silicon material or the like, a substrate processing process for forming a pattern on the wafer by a device manufacturing system DMS (exposure system) or a pattern forming method using the same (Step 223) Step 224), a dicing process for assembling the device, a bonding process, an assembly process including a packaging process, and the like (step 225), an inspection process for inspecting the device (step 226), and the like. In the substrate processing step (step 224), a coater / developer 200 applies a resist to the wafer, an exposure apparatus 100 exposes the mask pattern onto the wafer, and a coater / developer 200 develops the wafer. And an evaluation process (inspection process) for evaluating processing conditions such as film thickness conditions and / or exposure conditions using light from the wafer by the evaluation apparatus 1.

In such a device manufacturing method, the processing conditions are evaluated using the evaluation apparatus 1 described above, and the processing conditions are corrected based on the evaluation results, thereby improving the yield of the finally manufactured semiconductor. And throughput (productivity) can be improved.
In the device manufacturing method of the present embodiment, the method of manufacturing a semiconductor device has been particularly described. However, the device manufacturing method of the present embodiment can be applied to a semiconductor material such as a liquid crystal panel or a magnetic disk in addition to a device using a semiconductor material. The present invention can also be applied to the manufacture of devices using other materials.

  DMS: Device manufacturing system, 1 ... Evaluation apparatus, 5 ... Stage, 10 ... Wafer, 10a ... Conditional wafer, 12 ... Repeat pattern, 20 ... Illumination system, 30 ... Light receiving system, 35 ... Imaging unit, 40 ... Image processing unit , 50 ... arithmetic unit, 60 ... inspection unit, 85 ... storage unit, 100 ... exposure apparatus, 200 ... coater / developer

Claims (24)

In an evaluation method for evaluating the processing conditions of the pattern based on evaluation characteristics in which a signal based on the detected light from the surface is irradiated with light on the surface of the substrate on which the pattern is formed,
Estimating the amount of change in the machining condition based on the input value, the amount of change in the input value, and the evaluation characteristics;
Evaluating the evaluation characteristics based on the estimated amount of change in the machining conditions;
Evaluation method including   The evaluation method according to claim 1, wherein the change amount includes a fixed value. The processing conditions include an exposure amount and a focus state in an exposure apparatus,
The amount of change is a signal based on light from a pattern formed in the plurality of regions after exposure by an exposure apparatus in which at least one of an exposure amount and a focus state on the plurality of regions on the surface of the substrate is set to be the same. The evaluation method according to claim 1, wherein the evaluation method includes a degree of variation.   The evaluation method according to claim 3, wherein the amount of change includes a degree of rotationally symmetric variation in the substrate. The processing conditions include an exposure amount and a focus state in an exposure apparatus,
The amount of change is the light from the pattern formed in the plurality of regions through exposure by an exposure apparatus set so that one of the exposure amount and the focus state on the surface of the substrate gradually changes. The evaluation method according to claim 1, wherein the evaluation method includes a degree of variation of the signal based thereon.   The amount of change is an amount due to a difference between a signal based on light from the pattern irradiated with light at a first time and a signal based on light from the pattern irradiated at a second time different from the first time. The evaluation method as described in any one of Claims 1-5 containing these. The pattern formed on the surface of the substrate is formed through a lithography process including thin film formation by a thin film forming apparatus, exposure by an exposure apparatus, and etching by an etching apparatus,
The processing condition includes at least one of a film forming condition of the thin film by the thin film forming apparatus, a focus state and an exposure amount in the exposure apparatus, and an etching condition in the etching apparatus. The evaluation method according to one item. The evaluation characteristics are:
It is a characteristic obtained based on a signal obtained by irradiating the surface of the substrate with light under a predetermined evaluation condition and detecting light from the surface,
The predetermined evaluation condition is:
8. The method according to claim 1, comprising at least one condition of an incident angle of light applied to the surface of the substrate, a wavelength of the light, and an order of diffracted light to be detected emitted from the surface. The evaluation method described. The evaluation characteristics are:
It is a characteristic obtained based on a signal obtained by irradiating the surface of the substrate with light under a predetermined evaluation condition and detecting light from the surface,
The light applied to the substrate is polarized light,
The predetermined evaluation condition is:
The first relative angle between the polarization direction of the polarized light irradiated to the surface of the substrate and the periodic direction of the pattern, the polarization direction of the polarized light irradiated to the surface, and the light emitted from the surface The evaluation method as described in any one of Claims 1-8 including at least 1 conditions among the 2nd relative angles with the polarization direction of the polarization component of this detection target.   The evaluation method according to claim 8 or 9, wherein the evaluation characteristics include a plurality of evaluation characteristics obtained under a plurality of different evaluation conditions. The evaluation characteristics include a plurality of different evaluation characteristics,
Based on the result of evaluating the evaluation characteristics, selecting an evaluation characteristic used for evaluating the processing conditions of the pattern to be evaluated;
Irradiating light on the surface of the substrate on which the pattern to be evaluated is formed;
Detecting light from the surface;
Evaluating a processing condition of the pattern to be evaluated based on the signal based on the detected light and the selected evaluation characteristic;
The evaluation method according to any one of claims 1 to 10, further comprising: Forming a pattern on the surface of the substrate;
Evaluating the processing conditions when the pattern is formed using the evaluation method according to any one of claims 1 to 11,
Correcting the processing conditions for forming the pattern according to the evaluation result of the evaluation method. In the evaluation apparatus for evaluating the processing conditions of the pattern of the substrate on which the pattern is formed,
An illumination unit for irradiating light on the surface of the substrate;
A detection unit for detecting light emitted from the surface by irradiation of the light;
An evaluation unit that evaluates a processing condition of the pattern based on an evaluation characteristic using a signal detected by the detection unit as an input value,
The evaluation unit is
Based on the input value, the change amount of the input value, and the evaluation characteristics, the change amount of the machining condition is estimated,
An evaluation device that evaluates the evaluation characteristics based on the estimated amount of change in the machining conditions.   The evaluation apparatus according to claim 13, wherein the change amount includes a fixed value. The processing conditions include an exposure amount and a focus state in an exposure apparatus,
The amount of change is a signal based on light from a pattern formed in the plurality of regions after exposure by an exposure apparatus in which at least one of an exposure amount and a focus state on the plurality of regions on the surface of the substrate is set to be the same. The evaluation apparatus according to claim 13, wherein the evaluation apparatus includes a degree of variation.   The evaluation apparatus according to claim 13, wherein the change amount includes a degree of rotationally symmetric variation in the substrate. The processing conditions include an exposure amount and a focus state in an exposure apparatus,
The amount of change is the light from the pattern formed in the plurality of regions through exposure by an exposure apparatus set so that one of the exposure amount and the focus state on the surface of the substrate gradually changes. The evaluation apparatus according to claim 13, wherein the evaluation apparatus includes a degree of variation of the signal based thereon.   The amount of change is an amount due to a difference between a signal based on light from the pattern irradiated with light at a first time and a signal based on light from the pattern irradiated at a second time different from the first time. The evaluation apparatus as described in any one of Claims 13-17 containing this. The pattern formed on the surface of the substrate is formed through a lithography process including thin film formation by a thin film forming apparatus, exposure by an exposure apparatus, and etching by an etching apparatus,
The processing condition includes at least one of a film forming condition of the thin film by the thin film forming apparatus, a focus state and an exposure amount in the exposure apparatus, and an etching condition in the etching apparatus. The evaluation apparatus according to one item. The evaluation characteristics are:
It is a characteristic obtained based on a signal obtained by irradiating the surface of the substrate with light under a predetermined evaluation condition and detecting light from the surface,
The predetermined evaluation condition is:
20. The method according to claim 13, comprising at least one condition of an incident angle of light applied to the surface of the substrate, a wavelength of the light, and an order of diffracted light to be detected emitted from the surface. The evaluation device described. The evaluation characteristics are:
It is a characteristic obtained based on a signal obtained by irradiating the surface of the substrate with light under a predetermined evaluation condition and detecting light from the surface,
The illumination unit irradiates the substrate with polarized light,
The predetermined evaluation condition is:
The first relative angle between the polarization direction of the polarized light irradiated to the surface of the substrate and the periodic direction of the pattern, the polarization direction of the polarized light irradiated to the surface, and the light emitted from the surface The evaluation apparatus according to any one of claims 13 to 20, including at least one condition of a second relative angle with a polarization direction of a polarization component to be detected.   The evaluation apparatus according to claim 20 or 21, wherein the evaluation characteristics include a plurality of evaluation characteristics obtained under a plurality of different evaluation conditions. The evaluation characteristics include a plurality of different evaluation characteristics,
The evaluation unit is
Based on the evaluation results of the evaluation characteristics, select the evaluation characteristics used for the evaluation of the processing conditions of the pattern to be evaluated,
Light is emitted from the illumination unit to the surface of the substrate on which the pattern to be evaluated is formed, and a signal obtained by detecting the light from the surface by the detection unit is obtained with the selected evaluation characteristic. Evaluating the processing conditions of the pattern to be evaluated as the input value,
The evaluation apparatus according to any one of claims 13 to 22. A processing apparatus for forming a pattern on the surface of the substrate;
An evaluation apparatus according to any one of claims 13 to 23,
An exposure system that adjusts the processing apparatus in accordance with an evaluation result of the evaluation apparatus.

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