JP4144352B2 - Line width measuring device, line width measuring method, line width variation detecting device, and line width variation displaying method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a line width measuring apparatus, a line width measuring method, and a line width measuring mask for measuring a line width fluctuation of a pattern on a substrate, and in particular, measuring a line width fluctuation of a fine pattern in a manufacturing process of a semiconductor circuit element or the like. Line width measuring apparatus and line width measuring method suitable for, Line width variation detection device and line width variation display methodAbout.
[0002]
[Prior art]
Conventionally, in the manufacturing process of a semiconductor circuit element and a liquid crystal display element, measurement of line width variation of a fine pattern formed on the surface of a semiconductor wafer or a liquid crystal substrate (generally referred to as “substrate”) has been performed. For this measurement, a CD-SEM (Critical Dimension Scanning Electron Microscope) is generally used (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
JP 2001-273865 A
[0004]
[Problems to be solved by the invention]
However, CD-SEM measurement is so-called one-point measurement, and is sequentially performed for each fine pattern on the substrate. Therefore, the required time increases as the number of fine patterns to be measured increases.
[0005]
  An object of the present invention is to provide a line width measuring device capable of measuring line width fluctuations at high speed regardless of the number of fine patterns to be measured, andLine width variation detectorIs to provide.
[0007]
  The line width measuring device of the present invention isImage capturing means for selectively capturing diffraction images of the plurality of types of repetitive patterns from a substrate on which a plurality of types of repetitive patterns are transferred to each of different shot regions, and portions of the different shot regions of the diffraction images And calculating means for calculating line width variation of the repetitive pattern transferred to the different shot areas by comparing luminance information.
  Preferably,The image capturing means selectively captures the diffraction images of the plurality of types of repetitive patterns one by one with the same repetitive direction and different repetitive pitches and design line widths.But it ’s okay.
[0008]
  Also preferably,The image capturing means selectively captures the diffraction images of the plurality of types of repetitive patterns one by one with the same repetitive pitch and design line width and different repetitive directions.But it ’s okay.
  Also preferably,The image capturing unit includes a setting unit that sets an apparatus condition at the time of capturing an image according to the repetition direction and the repetition pitch of the repetitive pattern.May be.
[0009]
  Also preferably,A plurality of the repetitive patterns are arranged in each shot area of the substrate at a pitch smaller than the imaging resolution of the image capturing means.May be.
[0011]
  The line width measuring method of the present invention isA plurality of types of repetitive patterns are transferred to each of different shot regions, and at least two types of repetitive patterns of the plurality of types of repetitive patterns transferred to a certain shot region, a repetitive direction, a repetitive pitch, and a design line A diffraction pattern of a repetitive pattern having the same repetitive direction, repetitive pitch, and design line width of each of the different shot regions is obtained from a substrate on which a repetitive pattern having the same width is also transferred to another shot region. An image capturing step of selectively capturing, and a calculation step of calculating line width variation of the repetitive pattern transferred to the different shot regions by comparing luminance information of the portions of the different shot regions of the diffraction image; It is equipped with.
[0012]
  Preferably,In the image capturing step, the diffraction images of the plurality of types of repetitive patterns having the same repetitive direction and the repetitive pitch and the design line width are selectively captured one by one.But it ’s okay.
  Also preferably,In the image capturing step, the diffraction images of the plurality of types of repeated patterns having the same repetition pitch and the same design line width and different repetition directions are selectively captured one by one.But it ’s okay.
[0013]
  Also preferably,In the image capturing step, apparatus conditions at the time of image capturing are set according to the repetition direction and the repetition pitch of the repetitive pattern.You may do it.
  Also preferably,A plurality of the repetitive patterns are arranged in each shot area of the substrate at a pitch smaller than the imaging resolution of the image capturing means.May be.
[0014]
  The line width variation detection apparatus of the present invention includes an image capturing unit that selectively captures diffraction images of the plurality of types of repetitive patterns from a substrate on which a plurality of types of repetitive patterns are transferred to different shot regions, and Display means for displaying line width variation of the repetitive pattern transferred to the different shot areas by displaying luminance information of the different shot areas of the diffraction image.
  Preferably, an adjustment unit that adjusts a relative positional relationship between the substrate and the image capturing device may be further provided.
[0015]
  According to the line width variation display method of the present invention, a plurality of types of repetitive patterns are transferred to different shot areas, and at least two types of repetitive patterns of the plurality of types of repetitive patterns transferred to a certain shot area are used. From the substrate on which a repeating pattern having the same pattern and repeating direction, repeating pitch and design line width is also transferred to other shot areas, the repeating direction, repeating pitch and design line width of each of the different shot areas The image capturing step of selectively capturing a diffraction image of a repetitive pattern having the same, and displaying the luminance information of the portion of the different shot region of the diffraction image and the luminance information of the certain shot region Luminance information is the line width variation of the repetitive pattern transferred to the shot area. It is obtained by a Shimesuru display step.
  Preferably, a correction step for correcting the non-uniformity of sensitivity inherent to the apparatus may be further provided prior to the display.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
BookAs shown in FIG. 1, the line width measuring apparatus 10 of the embodiment includes a stage 12 that holds a substrate 11, an illumination optical system 13 that irradiates illumination light L <b> 1 to the substrate 11 on the stage 12, and illumination light L <b> 1. The light receiving optical system (14 to 16) for receiving the diffracted light L2 from the substrate 11 and the image processing unit 17 are configured.
[0018]
The line width measuring apparatus 10 is an apparatus for automatically measuring a line width variation of a fine pattern (described later) formed on the surface of the substrate 11 in a manufacturing process of a semiconductor circuit element or the like. The substrate 11 is a test wafer, and is in a state after exposure / development to the resist film formed in the uppermost layer and before etching processing to a predetermined material film adjacent immediately below the resist film.
[0019]
Before specifically describing the line width measuring apparatus 10 of the present embodiment, the substrate 11 will be described. A plurality of shot regions (not shown) are two-dimensionally arranged on the entire surface of the substrate 11 (for example, 300 mmφ). In each shot area, a pattern group for line width measurement (to be described next) is uniformly transferred without a gap.
These pattern groups are transferred using the line width measurement mask 20 shown in FIG. 2 and an exposure apparatus (not shown). FIG. 2 is a diagram showing a configuration of the line width measurement mask 20, FIG. 2 (a) shows an overall image of the line width measurement mask 20, and FIG. 2 (b) is a diagram of FIG. 2 (a). It is the figure which expanded the inside of the broken line frame 20A.
[0020]
As shown in FIG. 2B, the pattern area of the line width measurement mask 20 is composed of a plurality of basic blocks 21 arranged two-dimensionally. The basic block 21 includes 5 basic blocks 21 as shown in FIG. It consists of the types of cells 22, 23, 24, 25, 26. In one basic block 21, two cells 22, 23, 24, 25, and 26 are provided, as shown in FIG.
[0021]
FIG. 3 is a diagram showing a configuration in one cell 22 of the line width measurement mask 20. As shown in FIG. 3, the cell 22 is provided with four types of repeating patterns 31, 32, 33, and 34. Among them, the repeated pattern 31 is composed of five line patterns 41, and these line patterns 41 are arranged at a constant pitch P1 along the short direction B1. The five line patterns 41 have the same design line width D1.
[0022]
Each of the other three types of repeating patterns 32, 33, and 34 is composed of five line patterns 42, 43, and 44, like the above-described repeating pattern 31, and these line patterns 42, 43, and 44 have a constant pitch. It is arranged with. The line patterns 42, 43, and 44 all have the same design line width and pitch as the design line width D1 and pitch P1 of the line pattern 41.
[0023]
Further, the arrangement directions B2, B3, and B4 of the five line patterns 42, 43, and 44 are different from each other, and are also different from the arrangement direction B1 of the line pattern 41. Specifically, the four types of arrangement directions B1, B2, B3, and B4 are different at an angular interval of 45 degrees.
In this specification, the design line width D1, the pitch P1, and the arrangement directions B1 to B4 of the line patterns 41 to 44 are appropriately referred to as “the design line width D1, the repeat pitch P1, and the repeat directions B1 to B4 of the repeat patterns 31 to 34”.
[0024]
As described above, the four types of repeating patterns 31 to 34 provided in one cell 22 have the same design line width D1 and repeating pitch P1, and different repeating directions B1 to B4.
Further, although not shown in the cells 23 to 26 other than the cell 22 (FIG. 2C), as in the case of the cell 22, four types of repeating patterns having the same design line width and repeating pitch and different repeating directions are used. Is provided.
[0025]
However, when the repeated patterns are compared between the cells 23 to 26, the design line width and the repeated pitch are different from each other, and the designed line width D1 and the repeated pitch P1 of the repeated patterns 31 to 34 of the cell 22 are also different. In addition, the repeating direction (four types) of the repeating pattern in each of the cells 23 to 26 is the same as the repeating direction B1 to B4 in the cell 22.
[0026]
As described above, the basic block 21 including the five types of cells 22, 23, 24, 25, and 26 has 20 types of repetitions by combining the design line width, the repetition pitch (5 types), and the repetition direction (4 types). Patterns 31, 32, 33, 34,... Are provided.
[0027]
Further, since two cells 22 to 26 are provided in one basic block 21, two 20 kinds of repeated patterns 31, 32, 33, 34,... Are also provided.
Furthermore, in the pattern area of the line width measurement mask 20 in which a plurality of basic blocks 21 are two-dimensionally arranged, each of the 20 types of repeated patterns 31, 32, 33, 34,._{twenty one}, Y_{twenty one}A large number are arranged at a constant pitch in accordance with (FIG. 2 (c)).
[0028]
In this specification, each of the repeated patterns 31, 32, 33, 34,... Arranged in the pattern area of the line width measuring mask 20 is collectively referred to as “pattern groups (31), (32), (33), ( 34), ... " The repeating patterns 31, 32, 33, 34,... Constituting each of the 20 types of pattern groups (31), (32), (33), (34),... Have the same number density.
[0029]
By using the line width measuring mask 20 (FIGS. 2 and 3) configured as described above and an exposure apparatus (not shown), 20 types of patterns are sequentially formed on the resist film in each shot region of the substrate 11. The group is transferred uniformly without gaps. The 20 types of pattern groups transferred to each shot area correspond to each of the pattern groups (31), (32), (33), (34),.
[0030]
Further, since the shot areas are two-dimensionally arranged on the entire surface of the substrate 11, as a result of transfer using the above-described line width measurement mask 20 (FIGS. 2 and 3), the entire surface of the substrate 11 (a plurality of shot areas). In this case, 20 types of pattern groups are transferred in the mixed state as many as the shot areas.
In the following description, the pattern groups (31), (32) of the line width measurement mask 20 (FIGS. 2 and 3) are respectively used for each of the 20 types of pattern groups transferred to the entire surface (a plurality of shot areas) of the substrate 11. ), (33), (34),..., Are added with a symbol added with a subscript “w”.
[0031]
Here, each of the 20 types of pattern groups (31w), (32w), (33w), (34w),... Transferred onto the entire surface (a plurality of shot areas) of the substrate 11 will be described. For example, the pattern group (31w) includes a large number of repetitive patterns 31w (fine patterns) transferred to different shot regions on the entire surface of the substrate 11, and the repetitive direction, repetitive pitch, and design line width of the repetitive patterns 31w are the same.
[0032]
However, the actual line width of the repetitive pattern 31w varies according to the exposure focus (focus) shift. In general, when the exposure focus is deviated from an appropriate value, the line width becomes thick regardless of the deviation direction (front pin, rear pin). That is, the actual line width of the repeated pattern 31w is the smallest when the exposure focus is an appropriate value. Such line width variation occurs for each shot region of the substrate 11. Note that it is considered that the repeat direction and repeat pitch of the repeat pattern 31w do not vary due to the exposure focus shift.
[0033]
Note that an isolated line pattern having an extremely large space may have the largest line width when the exposure focus is an appropriate value, and may become thinner when the exposure focus is shifted.
In the present embodiment, for example, the pattern group (31w) is a measurement target, and the line width measurement apparatus 10 is used to measure the line width variation of a large number of repetitive patterns 31w transferred to the entire surface of the substrate 11 for each shot region ( Details will be described later). Then, based on the measurement result by the line width measuring device 10, the quality of the transfer performance of the exposure device is determined.
[0034]
The other 19 types of pattern groups (32w), (33w), (34w),... Transferred on the entire surface of the substrate 11 are different shots on the entire surface of the substrate 11, as with the pattern group (31w). It is composed of a large number of repetitive patterns 32w, 33w, 34w,... Transferred to the region, and the repetitive direction, repetitive pitch, and design line width of the repetitive patterns 32w, 33w, 34w,.
[0035]
In addition, when 20 types of pattern groups (31w), (32w), (33w), (34w),... Are compared among the repeated patterns 31w, 32w, 33w, 34w,. At least one of the directions is different from each other. In the present embodiment, five types of design line widths and repetition pitches and four types of repetition directions exist in 20 types of repetition patterns 31w, 32w, 33w, 34w,.
[0036]
In general, the transfer performance of the exposure apparatus varies depending on the design line width of the repetitive pattern. Moreover, even if the design line width is the same, it varies depending on the repetition direction. For this reason, if the exposure focus is deviated from an appropriate value in one shot region, different line width variations occur in each of the 20 types of repetitive patterns 31w, 32w, 33w, 34w,.
[0037]
Therefore, 20 types of pattern groups (31w), (32w), (33w), (34w),... Transferred onto the entire surface of the substrate 11 are measured one by one and shot using the line width measuring device 10. By measuring the line width variation for each region (details will be described later), it is possible to determine whether the transfer performance of the exposure apparatus is good or bad from various angles.
Incidentally, each shot area of the substrate 11 has a maximum of 30 mm to 40 mm square, and a transfer portion (hereinafter referred to as a “basic block 21 w”) corresponding to the basic block 21 (FIG. 2C) on the substrate 11. , Longitudinal dimension (X in FIG. 2 (c)_{twenty one}Is about 60 μm. For this reason, about 100 basic blocks 21w are included in one shot area.
[0038]
Further, 20 types of pattern groups (31w), (32w), (33w), (34w),... Transferred onto the substrate 11 have a design line width (5 types) of, for example, about 100 nm to 300 nm and a repetitive pitch (5 For example, the angle is about 200 nm to 600 nm, and the repeat direction (four types) is 45 degrees.
[0039]
Next, a specific configuration of the line width measuring apparatus 10 (FIG. 1) will be described.
The stage 12 can be tilted within a predetermined angle range about an axis parallel to the surface of the substrate 11 (perpendicular to the paper surface) by a tilt mechanism (not shown). Further, it can be rotated around the normal direction of the substrate 11 by a rotation mechanism (not shown). In this stage 12, the substrate 11 transported by a transport device (not shown) is placed on the upper surface and fixed and held by vacuum suction.
[0040]
Here, a direction parallel to the tilt axis of the stage 12 is defined as an “X direction”. Further, a direction parallel to a normal line (reference normal line) in a state where the stage 12 (substrate 11) is kept horizontal is referred to as a “Z direction”. Further, a direction perpendicular to the X direction and the Z direction is defined as a “Y direction”.
The illumination optical system 13 is disposed obliquely above the stage 12. That is, the optical axis O1 of the illumination optical system 13 is inclined by a predetermined angle with respect to the reference normal line (Z direction). The illumination optical system 13 is disposed so that the optical axis O1 is orthogonal to the tilt axis (X direction) of the stage 12. Further, the illumination optical system 13 is arranged so that the rear focal position substantially coincides with the substrate 11, and is an optical system telecentric with respect to the substrate 11 side.
[0041]
The light receiving optical system (14 to 16) is a decentered optical system including the concave reflecting mirror 14, the imaging lens 15, and the imaging device 16. The concave reflecting mirror 14 is disposed above the stage 12. That is, the optical axis O2 on the stage 12 side of the concave reflecting mirror 14 is arranged so as to be parallel to the Z direction. Further, the concave reflecting mirror 14 is arranged so that the front focal position substantially coincides with the substrate 11. Therefore, the light receiving optical systems (14 to 16) are telecentric optical systems with respect to the substrate 11 side.
[0042]
The imaging lens 15 is disposed in the vicinity of the pupil position of the light receiving optical system (14 to 16) so as to substantially coincide with the rear focal position of the concave reflecting mirror 14. The image pickup device 16 is a CCD image sensor in which a plurality of pixels are two-dimensionally arranged, and is arranged in a state where its image pickup surface is substantially coincident with the rear focal position of the imaging lens 15. For this reason, the light receiving optical system (14 to 16) is also a telecentric optical system for the image sensor 16 side. Note that the imaging surface of the imaging device 16 is conjugate to the surface of the substrate 11.
[0043]
The illumination light L1 (wavelength λ) emitted from the illumination optical system 13 having the above configuration is substantially parallel light, and is irradiated on the entire surface (a plurality of shot regions) of the substrate 11 on the stage 12. Since the substrate 11 side of the illumination optical system 13 is a telecentric system, the incident angle θi of the illumination light L1 is uniform over the entire surface of the substrate 11.
Of the 20 types of pattern groups (31w), (32w), (33w), (34w),... Formed on the entire surface of the substrate 11, the repeating direction of the repeated patterns 31w, 32w, 33w, 34w,. Diffracted light is generated in various directions from those parallel to the tilt axis of the stage 12 (five types).
[0044]
The diffracted light L2 shown in FIG. 1 is a part of the diffracted light (for example, the first order diffracted light of the pattern group (31w)) generated in the direction of the optical axis O2 of the light receiving optical system (14-16). By changing the setting of the tilt angle θt of the stage 12, diffracted light generated from a pattern group having a different repetitive pitch (the design line width is different in this embodiment) can be guided to the light receiving optical system (14 to 16). .
[0045]
  Here, in the shot area where the exposure focus is deviated from the appropriate value in the entire surface (a plurality of shot areas) of the substrate 11, the line width of the repetitive pattern is thick (the repetitive direction and repetitive pitch are unchanged). Due to this line width variation, the diffraction efficiency is lowered, and as a result, the intensity of the diffracted light is reduced.
  The diffracted light L 2 guided from the substrate 11 to the light receiving optical system (14 to 16) is condensed by the action of the concave reflecting mirror 14 and the imaging lens 15 and reaches the imaging surface of the imaging element 16. The image sensor 16 captures a diffraction image formed on the imaging surface and outputs an image signal to the image processing device 18..
[0046]
In the present embodiment, the optical magnification by the concave reflecting mirror 14 and the imaging lens 15 is set so that a diffraction image of the entire surface of the substrate 11 is formed on the imaging surface of the imaging device 16. In consideration of this optical magnification, the area (imaging resolution) on the substrate 11 corresponding to one pixel of the imaging element 16 is about 250 μm square.
With respect to the imaging resolution (about 250 μm square) of the line width measuring apparatus 10, the size of the basic block 21w (the transfer portion of the basic block 21 to the substrate 11 in FIG. 2C) is about 60 μm × 25 μm. is there. That is, the basic block 21w is sufficiently smaller than the imaging resolution. In other words, a large number of repeating patterns 32w, 33w, 34w,... Are arranged on the substrate 11 at a pitch smaller than the imaging resolution.
[0047]
The imaging resolution includes about 40 (4 × 10) basic blocks 21w (that is, each of eight repetitive patterns 32w, 33w, 34w,...). In this case, the image signal from the imaging device 16 includes the total intensity of the diffracted light L2 generated from about 40 basic blocks 21w as information of one pixel. Further, since the substrate 11 side of the light receiving optical system (14-16) is a telecentric system, the traveling direction of the diffracted light L2 is uniform over the entire surface of the substrate 11, and the intensity of the diffracted light L2 incident on the image sensor 16 is also as follows. It becomes uniform for each state (line width variation) of the repeated pattern of the substrate 11. Therefore, only the state of the repetitive pattern (line width fluctuation amount) is reflected in the strength of the image signal from the image sensor 16.
[0048]
The image processing unit 17 captures a diffraction image corresponding to the entire surface of the substrate 11 based on an image signal from the image sensor 16 during line width measurement. This diffraction image relates to one of 20 types of pattern groups (31w), (32w), (33w), (34w),... Transferred onto the entire surface of the substrate 11.
Selection of the diffraction image captured by the image processing unit 17 is performed using the tilt mechanism and the rotation mechanism of the stage 12. That is, by tilting the substrate 11 with the tilt mechanism, any one of the pattern groups having different repetitive pitches (the design line widths are different in this embodiment) can be selected. In addition, by rotating the substrate 11 by the rotation mechanism, it is possible to select any one of the pattern groups having different repetition directions.
[0049]
The apparatus conditions (tilt angle θt, rotation angle) by the tilt mechanism and rotation mechanism of the stage 12 may be set based on a recipe created in advance. The recipe is various setting conditions necessary for optimally measuring the line width variation of 20 types of pattern groups (31w), (32w), (33w), (34w),. Pre-stored in the memory.
[0050]
Here, a recipe regarding the tilt angle θt of the stage 12 will be described. In general, the tilt angle θt is calculated from the design value of the repetitive pitch p of the pattern group to be measured using a well-known diffraction conditional expression (the following expression (1)), and this calculation result is registered in the recipe. Yes.
sin (θi−θt) −sin (θd + θt) = mλ / p (1)
Expression (1) represents the relationship among the tilt angle θt of the stage 12, the repetition pitch p of the pattern group, the wavelength λ and the incident angle θi of the illumination light L1, and the diffraction angle θd and the diffraction order m of the diffracted light L2. It is a formula. The reference for the tilt angle θt is the horizontal plane. The reference for the incident angle θi and the diffraction angle θd is the reference normal line (Z direction) of the substrate 11.
[0051]
With reference to a recipe created and registered in advance, the apparatus conditions are determined by the tilt mechanism and the rotation mechanism of the stage 12 based on the tilt angle θt corresponding to the repetition pitch p of the pattern group to be measured and the rotation angle corresponding to the repetition direction. By setting, the diffraction image of the pattern group to be measured can be selectively captured.
In this way, when a diffraction image relating to one of 20 types of pattern groups (31w), (32w), (33w), (34w),... First, the unit 17 corrects the non-uniformity of sensitivity inherent in the line width measuring apparatus 10 (for example, brightness unevenness of the illumination optical system 13). Hereinafter, a case where the pattern group (31w) is a measurement target will be described as an example.
[0052]
As a result of the above correction process, a diffraction image reflecting only the line width variation of a large number of repetitive patterns 31w constituting the pattern group (31w) is obtained (see FIG. 4). That is, the line width variation of the repetitive pattern 31w appears as a local luminance change in the corrected diffraction image. However, since the line width variation occurs for each shot region, a luminance change corresponding to the line width variation also appears for each shot region.
[0053]
In addition, the line width variation in the shot area where the exposure focus has deviated from the appropriate value is “a variation in which the line width becomes thicker”, and the diffraction efficiency decreases due to this line width variation. Is a “change in which luminance decreases”.
That is, in the diffracted image of FIG. 4, the black portion where the brightness is greatly reduced corresponds to the shot region where the exposure focus is greatly deviated from the appropriate value, and the gray portion where the brightness is slightly lowered corresponds to the exposure focus from the appropriate value. Corresponding to a shot area that is slightly deviated, the white part where the luminance is not lowered corresponds to the shot area where the exposure focus is an appropriate value.
[0054]
The image processing unit 17 compares the luminance information of the portion corresponding to each shot area (hereinafter referred to as “shot image”) in the corrected diffraction image (see FIG. 4), and is transferred to a different shot area. The line width variation of the repeated pattern 31w is calculated (calculation means).
The luminance information of the shot image is, for example, the average luminance of 3 × 3 pixels located in the center of the shot image, and is considered as luminance information of a portion corresponding to a large number of repetitive patterns 31w transferred to the shot area. Can do. Note that the average luminance of all the pixels of the shot image may be used as “shot image luminance information”.
[0055]
The comparison of brightness information of shot images is, for example, selecting a shot image having the highest average brightness and calculating a reduction amount of the average brightness of other shot images based on the average brightness of the shot image. Is done.
At this time, if the amount of decrease in average luminance is “0”, the shot area on the substrate 11 corresponding to the shot image is considered to have an appropriate exposure focus, and the repetitive pattern transferred to the shot area The line width variation of 31w is considered to be “0”.
[0056]
Then, it is considered that as the amount of decrease in average luminance is “large”, the exposure focus of the shot area is greatly deviated from the appropriate value, and the line width variation of the repetitive pattern 31w transferred to the shot area is considered “large”. That is, the amount of decrease in the average luminance of the shot image represents a relative line width variation.
Here, with respect to a case where exposure focus shift amounts (offset amounts) in several shot regions are known, a diffraction image relating to the entire surface of the substrate 11 is captured and the average luminance of the shot image is calculated (FIG. 5). explain.
[0057]
The horizontal axis of FIG. 5 represents the offset amount (μm) of exposure focus, and “offset amount = 0” represents an appropriate value. The vertical axis on the right is the average luminance (gradation) of the shot image, and the lower the figure is, the higher the luminance is. Moreover, the measurement result (micrometer) by CD-SEM is also shown on the left vertical axis | shaft of FIG. 5 for the comparison.
As can be seen from FIG. 5, the average luminance (■) of the shot image calculated by the line width measuring apparatus 10 of the present embodiment shows a line width variation that has a very good correlation with the measurement result (▲) by the CD-SEM. ing. When “offset amount = 0”, the average luminance (■) of the shot image is the highest, and the measurement result (結果) by the CD-SEM has the smallest line width.
[0058]
It can also be seen that the change in the average luminance (■) of the shot image is proportional to the line width variation. For example, in the example of FIG. 5, the correlation coefficient between the line width variation and the luminance change is about 20 nm / 100 gradations. In this case, the line width variation can be measured with an accuracy of several nanometers or less with respect to 10 gradations of the change amount of the average luminance (■) of the shot image.
Therefore, by measuring the correlation coefficient (for example, 20 nm / 100 gradation) between the line width variation and the luminance change in advance, other than the highest average luminance (reference) among the above-described diffraction images (see FIG. 4). The absolute value of the line width variation can be calculated based on the amount of decrease in the average brightness of the shot image.
[0059]
In the line width measuring apparatus 10 of the present embodiment, the diffraction image of the entire surface of the substrate 11 is captured in a collective field of view, and the luminance information of each shot image in the diffraction image is compared to measure the line width variation. Regardless of the number of target repeating patterns (number of shot areas), line width variation can be measured at high speed.
In this embodiment, the basic block 21w of the pattern group (31w), (32w), (33w), (34w),... For line width measurement is made sufficiently smaller than the imaging resolution (about 250 μm square). Generation of moire fringes in an image can be reliably suppressed. That is, generation of pseudo contrast other than the contrast related to the actual pattern structure can be avoided. As a result, the measurement accuracy of line width variation is improved.
[0060]
Furthermore, a single substrate 11 (test wafer) is used, and a plurality (20 in this embodiment) of line width variations can be obtained simply by changing the setting of the apparatus conditions (tilt angle θt, rotation angle) when capturing a diffraction image. Can be measured easily. For this reason, the quality of the transfer performance of the exposure apparatus can be easily determined from various angles.
For example, when a plurality of types of pattern groups having the same repetition direction but different repetition pitches and design line widths are to be measured, the tilt angle θt of the apparatus conditions is changed according to the repetition pitch (the rotation angle is fixed). In other words, each diffraction image can be selectively captured one by one, and the measurement of the line width variation (determination of the transfer performance of the exposure apparatus) when the repeat direction is the same can be easily performed.
[0061]
In addition, when a plurality of types of pattern groups having the same repetition pitch and the same design line width but different repetition directions are to be measured, the rotation angle of the apparatus conditions is changed according to the repetition direction (tilt angle θt is fixed). In other words, each diffraction image can be selectively captured one by one, and the measurement of the line width variation due to the repetition direction (determination of the transfer performance of the exposure apparatus) can be easily performed.
[0062]
(Modification)
In the above-described embodiment, the line width variation is measured based on the diffraction image after correcting the non-uniformity of sensitivity inherent in the line width measuring apparatus 10 (for example, brightness unevenness of the illumination optical system 13). However, the present invention is not limited to this. For example, when a change in luminance over a wide range due to uneven thickness of the resist film on the substrate 11 or a change in luminance over a wide range due to warpage of the substrate 11 appears in the diffraction image, It is preferable to measure the line width variation by selecting only shot images outside the range.
[0063]
Further, in the above-described embodiment, the measurement of the line width of the repetitive pattern at the resist stage has been described as an example, but the present invention is not limited to this. For example, it is possible to measure the line width of the repetitive pattern transferred to the underlayer in a state after etching the material film adjacent to the resist film.
In the above-described embodiment, line width measurement is performed by capturing a diffraction image of the entire surface of the substrate 11 in a collective field of view, but the present invention is not limited to this. For example, line width measurement may be performed by designating an arbitrary area (including one or more shot areas) that requires line width measurement in the substrate 11 and capturing the diffraction image in a collective field of view. .
[0064]
Furthermore, in the above-described embodiment, the apparatus conditions (tilt angle θt, rotation angle) are set and changed by the tilt mechanism and the rotation mechanism of the stage 12, but the present invention is not limited to this. Instead of the tilt mechanism and rotation mechanism of the stage 12, a tilt mechanism and a rotation mechanism are provided in the illumination optical system 13 and the light receiving optical system (14 to 16), and the apparatus conditions (tilt angle θt, rotation angle) are similarly changed. May be.
[0065]
In the above-described embodiment, 20 types of pattern groups (31w), (32w), (33w), (34w),... Transferred using the line width measuring mask 20 shown in FIG. Although the line width variation is measured, the present invention is not limited to this. For example, a plurality of pattern groups transferred by a line width measurement mask provided with the cell 50 shown in FIG. 6 and one or more other cells (not shown) may be measured one by one.
[0066]
The cell 50 in FIG. 6 will be described. The cell 50 is provided with two types of repeating patterns 51 and 52. Each of the repeated patterns 51 and 52 is composed of 11 line patterns 53 and 54, and these line patterns 53 and 54 are arranged at a constant pitch along the short direction. Further, the repeated patterns 51 and 52 have the same design line width and repeated pitch, and have different repeated directions (90-degree angle interval).
[0067]
Furthermore, the repeated patterns 51 and 52 are designed so that the outer shape thereof is a square shape. That is, when the length of the line patterns 53 and 54 is L, the number is n (= 11), the repetition pitch is P2, and the design line width is D2, it is designed to satisfy L = n × (P2 + D2). Yes. The repeated patterns 51 and 52 are staggered in the vertical and horizontal directions.
[0068]
In this way, by designing the outer shapes of the repeated patterns 51 and 52 to be square and making the occupied areas of the repeated patterns 51 and 52 equal, the diffraction efficiencies of the repeated patterns 51 and 52 are equalized. As a result, comparative measurement can be performed for each repetition direction of the repeated patterns 51 and 52.
Further, the interval Δ between the repeating patterns 51 and 52 is, for example, three times or more of the repeating pitch (P2). By laying out the repeated patterns 51 and 52 while ensuring the interval Δ at least larger than 1 times the repeating pitch (P2), it is possible to prevent the occurrence of pseudo-diffraction caused by interference between the repeated patterns 51 and 52. The interval Δ may be set based on the order to be excluded from the high-order diffraction condition.
[0069]
A plurality of pattern groups transferred by a line width measuring mask having the cell 50 shown in FIG. 6 and one or more other cells (cells having different repetition pitch and design line width) are lined one by one. Even when a width variation measurement target is selected, a diffraction image of the entire surface of the substrate 11 is captured in a collective field of view, and brightness information of each shot image in the diffraction image is compared to measure line width variation at high speed. Can do.
[0070]
【The invention's effect】
As described above, according to the present invention, line width variation can be measured at high speed regardless of the number of fine patterns to be measured.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the overall configuration of a line width measuring apparatus 10;
FIG. 2 is a schematic diagram showing a configuration of a line width measuring mask 20;
FIG. 3 is a schematic diagram showing a configuration of one cell 22 of a line width measuring mask 20;
4 is a diagram showing an example of an entire diffraction image of a substrate 11. FIG.
FIG. 5 is a diagram illustrating an example of a measurement result when an exposure focus shift amount (offset amount) is known;
FIG. 6 is a schematic diagram showing a configuration of a cell 50 according to a modified example.
[Explanation of symbols]
10 Line width measuring device
11 Substrate
12 stages
13 Illumination optics
14 Concave reflector
15 Imaging lens
16 Image sensor
17 Image processing section
20 Line width measurement mask
21 basic blocks
22, 23, 24, 25, 26, 50 cells
31, 32, 33, 34, 51, 52 Repeat pattern
41, 42, 43, 44, 53, 54 Line pattern

Claims (14)

Image capturing means for selectively capturing diffraction images of the plurality of types of repetitive patterns from a substrate on which a plurality of types of repetitive patterns are transferred to each of different shot regions;
A line width comprising: a calculating means for calculating line width variation of the repetitive pattern transferred to the different shot areas by comparing luminance information of the different shot areas of the diffraction image Measuring device. In the line | wire width measuring apparatus of Claim 1 ,
The line width measuring apparatus, wherein the image capturing means selectively captures the diffraction images of the plurality of types of repetitive patterns one by one having the same repetitive direction and different repetitive pitches and design line widths. In the line | wire width measuring apparatus of Claim 1 ,
The line width measuring apparatus, wherein the image capturing means selectively captures the diffraction images of the plurality of types of repeated patterns having the same repetition pitch and design line width and different repetition directions one by one. In the line | wire width measuring apparatus of any one of Claims 1-3 ,
The line width measuring apparatus, wherein the image capturing unit includes a setting unit that sets an apparatus condition at the time of capturing an image according to the repetition direction and the repetition pitch of the repetitive pattern. In the line width measuring device according to any one of claims 1 to 4 ,
The line width measuring apparatus according to claim 1, wherein a plurality of the repeated patterns are arranged in each shot area of the substrate at a pitch smaller than an imaging resolution of the image capturing means. A plurality of types of repetitive patterns are transferred to each of different shot regions, and at least two types of repetitive patterns of the plurality of types of repetitive patterns transferred to a certain shot region, a repetitive direction, a repetitive pitch, and a design line A diffraction pattern of a repetitive pattern having the same repetitive direction, repetitive pitch, and design line width of each of the different shot regions is obtained from a substrate on which a repetitive pattern having the same width is also transferred to another shot region. An image capture process for selectively capturing;
A calculation step of calculating line width variation of the repetitive pattern transferred to the different shot areas by comparing luminance information of the different shot areas of the diffraction image. Measurement method. The line width measuring method according to claim 6 ,
In the image capturing step, the line width measurement, wherein the diffraction images of the plurality of types of repetitive patterns having the same repetitive direction and the repetitive pitch and the different design line width are selectively captured one by one. Method. The line width measuring method according to claim 6 ,
In the image capturing process, the diffraction image of the plurality of types of repetitive patterns having the same repetition pitch and the same design line width and different repetition directions are selectively captured one by one. Method. In the line width measuring method according to any one of claims 6 to 8 ,
In the image capturing step, apparatus conditions at the time of capturing an image are set according to the repetition direction and the repetition pitch of the repetitive pattern. In the line width measuring method according to any one of claims 6 to 9 ,
The line width measuring method, wherein a plurality of the repetitive patterns are arranged at a pitch smaller than the imaging resolution of the image capturing means in each shot area of the substrate. Image capturing means for selectively capturing diffraction images of the plurality of types of repetitive patterns from a substrate on which a plurality of types of repetitive patterns are transferred to each of different shot regions;
Display means for displaying line width variation of the repetitive pattern transferred to the different shot areas by displaying luminance information of the different shot areas of the diffraction image;
A line width variation detecting device comprising: In the line | wire width fluctuation | variation detection apparatus of Claim 11,
An adjustment unit that adjusts a relative positional relationship between the substrate and the image capturing device is further provided.
A line width variation detecting device characterized by the above. A plurality of types of repetitive patterns are transferred to each of different shot regions, and at least two types of repetitive patterns of the plurality of types of repetitive patterns transferred to a certain shot region, a repetitive direction, a repetitive pitch, and a design line A diffraction pattern of a repetitive pattern having the same repetitive direction, repetitive pitch, and design line width of each of the different shot regions is obtained from a substrate on which a repetitive pattern having the same width is also transferred to another shot region. An image capture process for selectively capturing;
Display that displays the luminance information of the portion of the different shot area of the diffraction image and the luminance information of the certain shot area, thereby displaying the line width variation of the repetitive pattern transferred to the different shot area as luminance information Process and
A line width variation display method characterized by comprising: The line width variation display method according to claim 13,
Prior to the display, the image processing apparatus further includes a correction step for correcting the non-uniformity of sensitivity inherent in the apparatus.
A line width variation display method characterized by the above.

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