JP2009104024A - Exposure mask, focus measuring method, and pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and accurately measure the defocusing amount, in an exposure device. <P>SOLUTION: The exposure mask 10 has a focus measuring pattern formed on the mask base plate 11, and this focus measuring pattern has a first pattern group 15a, including at least three first patterns 22a arranged with a first pitch, and a second pattern group 15b, including at least three second patterns 22b arranged with a second pitch different from the first pitch; and the first and second pattern groups 15a, 15b are constituted of plural recessed regions and projecting regions formed on the mask base plate 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exposure mask used in electronic device manufacturing and the like, and a focus measurement method and a pattern formation method using the exposure mask.

  With the recent progress of microfabrication technology in electronic device manufacturing, the focus margin in the lithography process is becoming narrower. Therefore, in order to maintain a stable yield by effectively utilizing a small process margin, more accurate focus management is required.

  As a conventional focus measurement method using a resist pattern, for example, the PSFM method (Phase Shift Focus Monitor method) described in Patent Document 1 can be cited.

  The PSFM method uses a so-called Levenson type phase shift mask (Alternating Phase Shift Mask), and the phase difference is other than 180 ° (optimum value is 90 °) on both sides of the isolated line pattern (isolated line-shaped light shielding pattern). This is a focus measurement method using a phenomenon in which an image of the isolated line pattern moves in a horizontal direction (a direction perpendicular to a direction in which the isolated line pattern extends) when such a pattern is exposed in a defocused state.

According to the PSFM method, the movement distance of the image of the isolated line pattern changes almost linearly in the vicinity of the best focus. Therefore, the defocus amount (the difference from a predetermined focus value with respect to the best focus value) of the code collision is obtained by one exposure. Can be determined.
US Patent No. 5300786 Proceeding of SPIE, Volume 5567, pp. 669-679

  However, the PSFM method described above has the following problems.

  In the PSFM method, a so-called Levenson type phase shift mask must be used in principle. Further, in the PSFM method, a phase shifter of 90 ° or the like (a phase shifter having a value included in a predetermined range not including around 180 °) is used. On the other hand, in general device manufacturing, a phase shifter having a value included in a predetermined range around 180 ° is used. Therefore, when the PSFM method is used, it is difficult to place a focus measurement test pattern on a device manufacturing mask. The “180 ° phase shifter” means a phase shifter in which the phase difference from the light that is not transmitted is 180 ° when the light is transmitted through the phase shifter. Similarly, a “90 ° phase shifter” is a phase shifter that causes a predetermined phase difference with respect to light that is not transmitted by transmitting light.

  In view of the above, the present invention provides an exposure mask for easily and accurately measuring the defocus amount of an exposure apparatus without using a phase shifter outside the range of about 180 ° and a focus measurement method using the same. In addition, an object of the present invention is to provide a device manufacturing method and an exposure apparatus management method to which the focus measurement method is applied.

  To achieve the above object, an exposure mask according to the present invention is provided with a focus measurement pattern on a mask substrate, and the focus measurement pattern includes a first pattern including at least three first patterns arranged at a first pitch. A pattern group and a second pattern group including at least three second patterns arranged at a second pitch different from the first pitch, and both the first pattern group and the second pattern group are: It comprises a plurality of concave areas and a plurality of convex areas provided on the mask substrate.

  According to the exposure mask of the present invention, the first pitch at which the first pattern constituting the first pattern group is arranged is different from the second pitch at which the second pattern constituting the second pattern group is arranged. For this reason, when the mask pattern is transferred using the exposure mask by the exposure apparatus, the first pattern group and the second pattern group have different light propagation states from the inside of the exposure mask to the outside. In particular, in the case of oblique illumination with a large incident angle of incident light on the exposure mask, the best focus position on the substrate onto which the mask pattern is transferred differs between the first pattern group and the second pattern group. Therefore, the defocus amount of the exposure apparatus is easily and accurately obtained based on the dimensional difference between the first transfer pattern having the first pattern transferred to the substrate and the second transfer pattern having the second pattern transferred. be able to.

  The first pattern group and the second pattern group are preferably arranged within a predetermined distance.

  That is, since focus measurement is performed using both the first pattern group and the second pattern group, it is desirable that both pattern groups be arranged close to each other. However, it is also necessary that the two pattern groups are arranged apart from each other to the extent that optical isolation can be maintained.

  The first pattern and the second pattern are preferably provided as a plurality of convex regions. The first pattern and the second pattern are also preferably provided as a plurality of concave regions.

  As described above, at least three first patterns constituting the first pattern group and at least three second patterns constituting the second pattern group are each configured as either a convex region or a concave region. Just do it.

  Moreover, it is preferable that the plurality of concave regions are regions that are engraved on the mask substrate, and the plurality of convex regions are regions that are not engraved on the mask substrate.

  In the mask substrate, a plurality of concave regions and a plurality of convex regions may be realized in this way.

  Further, both the first pattern and the second pattern are preferably line patterns.

  The first pattern and the second pattern preferably have the same line width.

  In this way, the defocus amount can be measured more reliably.

  Moreover, it is preferable that at least a part of the convex region is covered with a light-shielding film or a semi-light-shielding film. Moreover, it is preferable that the boundary part with the recessed area | region among convex areas is covered with the light shielding film or the semi-light shielding film. Moreover, it is preferable that the entire surface of the convex region is covered with a light shielding film or a semi-light shielding film.

  In this way, the light transmittance in each convex region can be set, and the local effective light transmittance can be adjusted.

  In order to achieve the above object, a focus measuring method according to the present invention uses any one of the exposure masks according to the present invention, and focuses at the time of transferring the mask pattern using the projection optical system of the projection exposure apparatus. A focus measurement method to be obtained, the step (a) of measuring the dimension of the first transfer pattern in which the first pattern is transferred to the substrate and the dimension of the second transfer pattern in which the second pattern is transferred to the substrate; A step (b) of calculating a dimensional difference between the first transfer pattern and the second transfer pattern, and a step (c) of calculating a focus by comparing the dimensional difference with previously prepared reference data.

  According to the focus measurement method of the present invention, by comparing the dimensional difference between the first transfer pattern and the second transfer pattern corresponding to the first pattern group and the second pattern group having different arrangement pitches with reference data obtained in advance. The defocus amount can be measured.

  In order to achieve the above object, a pattern forming method according to the present invention includes a step of obtaining a focus value by the focus measuring method according to the present invention, feeding back the focus to a projection exposure apparatus, and transferring a mask pattern to another substrate. And performing the process.

  According to the pattern forming method of the present invention, the defocus amount when the mask pattern is transferred to the substrate is obtained by the focus measurement method using the exposure mask of the present invention, and the defocus amount is fed back to the projection exposure apparatus and used. be able to.

  Unlike focus measurement by the PSFM method, in the present invention, it is not necessary to use a phase shifter outside the range of about 180 °. For this reason, the exposure mask of the present invention and the focus measurement method and pattern formation method using the exposure mask are generally advantageous in device manufacturing using a photomask having a phase shifter in the range of about 180 °.

  According to the exposure mask of the present invention and the focus measurement method and pattern formation method using the exposure mask, focus measurement can be performed without using a phase shifter other than 180 °, and it is easy and highly accurate in general device manufacturing. Focus management can be performed.

(First embodiment)
Hereinafter, an exposure mask according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a view showing the structure of the exposure mask 10 of the present embodiment.

  As shown in FIG. 1A, the exposure mask 10 is configured using a mask substrate 11 made of glass, for example. The mask substrate 11 has a shot area 12 which is an arrangement area of a pattern to be exposed in one shot, and a focus measurement area 13 having a focus measurement pattern is provided in the shot area 12.

  In the focus measurement region 13, a pattern group as shown in a plan view in FIG. 1B is formed as a first pattern group 15a and a second pattern group 15b with two different densities (pitch).

  Each of the first pattern group 15a and the second pattern group 15b has a structure as shown in a perspective view in FIG. That is, the pattern 22 is a concave region that is engraved with respect to the mask substrate 11 and that is a bright region 21 that forms a background, and a convex region that is not engraved and that forms a dark image. is there. Here, depending on the presence or absence of engraving, the exposure light transmitted through the bright region 21 that is a concave region and the exposure light transmitted through the pattern 22 that is a convex region have a phase difference of 180 °. However, the phase difference is not limited to 180 °, and may be a phase difference in a predetermined range around 180 °. Although a specific range depends on conditions, for example, it may be about ± 10 ° with respect to 180 °, that is, a range of about 170 ° to 190 °.

  Since the focus measurement is performed in a predetermined area (in this embodiment, the focus measurement area 13) using both the first pattern group 15a and the second pattern group 15b, these two pattern groups are sufficiently close to each other. Must be arranged side by side. However, since it is necessary to maintain the optical isolation of both pattern groups, it is inconvenient to be too close, and it is also necessary to arrange them apart to some extent. Specifically, it is desirable that at least 0.5 μm is disposed with a gap, and more desirably, it is disposed with a gap of 1 μm or more.

  As a specific example, in the case of the present embodiment, the first pattern group 15a and the second pattern group 15b are arranged with an interval of about 1.5 μm.

  FIGS. 2B and 2C sequentially show cross sections of a first pattern group and a second pattern group having the same line width and different pitches. In the first pattern group shown in FIG. 2B, the line width A of the first pattern 22a as a linear pattern for forming a dark image is 80 nm, and the arrangement pitch B is 220 nm across the first bright region 21a. It is. In the second pattern group shown in FIG. 2C, the line width C of the second pattern 22b as a linear pattern for forming a dark image is 80 nm, which is the same as the first pattern 22a, but the second bright region 21b. The arrangement pitch D is 420 nm, which is larger than that of the first pattern group. Note that there are five first patterns 22a and two second patterns 22b. In addition, all of the above dimensions indicate converted values on the wafer that are reduced to, for example, one fifth of the mask.

  Next, FIG. 3 shows line dimensions when the first pattern group 22a and the second pattern group 22b provided on the exposure mask 10 of the present embodiment are transferred onto the wafer using the projection optical system of the projection exposure apparatus. Shows the result of simulation with respect to the focus position.

  Here, a case is shown in which four-eye illumination is used through a projection optical system of NA (Numerical Aperture) 0.75. In addition to the first pattern group 22a and the second pattern group 22b having a pitch of 220 nm and 420 nm, cases where the pitch is 180, 260, 300, 340, and 380 nm are also shown. It should be noted that annular illumination, two-lens illumination, or the like may be used instead of four-eye illumination, but oblique incidence illumination is desirable.

  As shown in FIG. 3, the line dimension to which the linear patterns arranged with the respective pitches are transferred tends to be maximal at a predetermined focus position, and tends to become smaller (the line becomes thinner) as the focus moves away from that position. Furthermore, the best focus position for each pattern, that is, the focus position at which the line dimension is maximized differs depending on the pitch. This is because the state of propagation of light from the inside of the exposure mask 10 to the outside differs depending on the pitch of the exposure mask 10 and oblique incidence illumination with a large incident angle of the incident light with respect to the exposure mask 10 is used. Is caused by fluctuations.

  FIG. 4 shows the difference between the post-transfer line dimension corresponding to the first pattern group having a pitch of 220 nm and the post-transfer line dimension corresponding to the second pattern group having a pitch of 420 nm shown in FIG. (Line width difference) is plotted against the focus position during transfer. As shown in FIG. 4, the line width difference regarding the first pattern group and the second pattern group tends to monotonously increase with respect to the focus position during transfer. For this reason, it is possible to estimate the defocus amount by measuring the dimensional difference between two different pattern groups.

  In the above description, the first pattern group and the second pattern group having the same pattern line width and different pitches have been described. However, the pattern line width should be different between the first pattern group and the second pattern group. You can also.

  In the present embodiment, the number of first patterns 22a and the number of second patterns 22b is five. However, the present invention is not limited to this.

  Further, when the exposure mask 10 of the present embodiment is used, unlike the case of performing focus measurement by the PSFM method, it is not necessary to use a phase shifter outside the range of around 180 ° (particularly 90 °). For this reason, it is easy to apply to a mask for manufacturing a device using a phase shifter generally in the range of about 180 °.

  In the present embodiment, the line width A of the first pattern 22a is equal to the line width C of the second pattern 22b, but this is not essential.

(Modification 1 of the first embodiment)
Next, an exposure mask according to Modification 1 of the first embodiment will be described. FIG. 5 shows a focus measurement pattern in the exposure mask of this modification. In the structure shown in FIG. 5, the concave area engraved with respect to the mask substrate 11 is a pattern 22c that forms a dark image, and the convex area that is not engraved between them forms a background. This is a region 21c. Compared with the exposure mask 10 of the first embodiment shown in FIGS. 2A to 2C, this can be said to be a configuration in which the concave region and the convex region are reversed. Therefore, for example, the line width of the pattern 22c may be 80 nm and the pitch may be 220 nm and 420 nm.

  In such a structure, similarly to the structures of FIGS. 2A to 2C, the exposure light that passes through the pattern 22c that forms the dark image, and the exposure light that passes through the bright area 21c that forms the background. A phase difference can be generated in the pattern 22c, and the pattern 22c can be transferred as a dark image.

  In the exposure mask, both the first pattern group and the second pattern group may have the structure of this modification shown in FIG. 5, or only one of them may have the structure of FIG.

(Modification 2 of the first embodiment)
Next, an exposure mask according to Modification 2 of the first embodiment will be described. FIG. 6 shows a focus measurement pattern in the exposure mask of this modification. In the structure shown in FIG. 6, similarly to the exposure mask 10 of the first embodiment shown in FIGS. 2A to 2C, the engraved recessed area is a bright area 21 d that forms the background, In the meantime, a pattern 22d in which the convex region forms a dark image is arranged. However, in the case of the exposure mask of this modification shown in FIG. 6, the pattern 22d is covered with the light shielding film or the semi-light shielding film 23. In this way, the light transmittance can be arbitrarily set for the pattern 22d, which is a linear region forming a dark image. The light shielding film is a film that can be regarded as not transmitting light at all, and the semi-light shielding film is a film that transmits light with a predetermined transmittance.

  Further, in the exposure mask, both the first pattern group and the second pattern group may have the structure of the present modification shown in FIG. 6, or only one of them may have the structure of FIG.

  As described above, when an exposure mask having a light-shielding film or a semi-light-shielding film is used, the size control of the dark image can be performed more favorably. For example, to obtain a wide dark image using a mask that does not have a light-shielding film or a semi-light-shielding film, it is necessary to increase the mask size. However, if the mask dimension is increased to a certain extent, the area itself is no longer a dark image. On the other hand, when the transmittance is controlled using a light-shielding film or a semi-light-shielding film, a dark image can be formed even when the mask dimension is large.

(Modification 3 of the first embodiment)
Next, an exposure mask according to Modification 3 of the first embodiment will be described. FIG. 7 shows a focus measurement pattern in the exposure mask of this modification. The structure shown in FIG. 7 is provided with a pattern 22e, which is a convex region that forms a dark image, in the bright region 21e provided as a concave region, as in the second modification of the first embodiment shown in FIG. A light shielding film or semi-light shielding film 23 is formed on the pattern 22e. However, in the second modification, the light-shielding film or the semi-light-shielding film 23 is formed so as to cover the entire surface of the convex area, whereas in the present modification, the pattern is a linear area that forms a dark image. A light shielding film or semi-light shielding film 23 is formed so as to cover a part on 22e.

  Thereby, the light transmittance in the pattern 22e can be arbitrarily set, and the local effective transmittance on the same exposure mask can be adjusted.

  Thereby, similarly to the case of the modified example 2, the size control of the dark image can be performed better.

  In the case of FIG. 7, the light shielding film or semi-light shielding film 23 is formed so as to cover the boundary portion (both end portions) with the bright region 21 e in the pattern 22 e, but is not limited thereto. For example, the light shielding film or semi-light shielding film 23 may be formed in a horizontal stripe pattern on the pattern 22e.

  In the exposure mask, both the first pattern group and the second pattern group may have the structure of this modification shown in FIG. 7, or only one of them may have the structure of FIG.

(Second Embodiment)
Next, a focus measurement method according to a second embodiment of the present invention will be described with reference to the drawings. The focus measurement method uses a focus measurement mask to which the exposure mask described in the first embodiment and each modification thereof is applied, and performs focus measurement to measure the focus amount of an exposure apparatus when exposing the substrate. Is the method.

  FIG. 8 is a diagram showing an example of a focus measurement mask used in the focus measurement method of the present embodiment. The focus measurement mask 30 shown in FIG. 8 is configured using a mask substrate 31 made of glass or the like. The mask substrate 31 has a shot area 32 which is an arrangement area of a pattern to be exposed in one shot, and a plurality of chip areas 33 which are arrangement areas of a pattern to be transferred to a microchip are formed in a matrix in the shot area 32. Is provided. A reticle alignment pattern arrangement region 34 is provided in the vicinity of the shot region 32 on the mask substrate 31.

  In each chip region 33, a pattern group similar to the first pattern group and the second pattern group arranged in the exposure mask according to the first embodiment and each of the modifications thereof is a test pattern for focus monitor. It is provided as. As described above, by arranging the focus monitor test patterns including a plurality of pattern groups having different pitches, it is possible to accurately obtain the focus in the area where the patterns are arranged. This will be further described below.

  In the focus measurement method of the present embodiment, first, after applying a photosensitive agent on a device substrate for manufacturing a semiconductor device or the like, the projection optical system of the projection exposure apparatus is used by using the focus measurement mask 30 shown in FIG. The mask pattern is transferred to the photosensitive agent on the device substrate.

  Thereafter, when the photosensitive agent is developed, a transfer chip area to which the chip area 33 is transferred is formed on the device substrate, and a focus monitor test pattern provided in the chip area 33 is also transferred onto the device substrate. Formed as.

  Since the focus monitor test pattern in each chip area 33 includes the first pattern group and the second pattern group, the transfer chip area includes the corresponding first transfer test pattern and second transfer test pattern.

  At this time, the dimensional difference between the first transfer test pattern and the second transfer test pattern in one transfer chip region varies depending on the defocus amount of the exposure apparatus. The defocus amount differs for each pattern due to unevenness on the device substrate (wafer).

  Therefore, the pattern dimensions in the first transfer pattern group and the second transfer pattern group in the same transfer chip region transferred onto the device substrate are measured by a measuring means (for example, a length measuring SEM (scanning electron microscope)), It is calculated by a dimension difference data calculation unit or the like. The focus in the transfer chip region can be obtained by comparing the dimensional difference calculated in this way with reference data created in advance and stored in the reference data storage unit. More specifically, the reference data includes reference dimension difference data corresponding to each line width and pitch under different focus conditions, and the focus calculation unit compares the calculated dimension difference with the calculated dimension difference to obtain the focus. be able to. Note that the data calculation unit, the reference data storage unit, and the focus calculation unit (further, a data calculation unit described later) are realized in a computer or the like provided in a focus measurement apparatus including a length measurement SEM.

  Since a plurality of chip areas 33 are provided in the shot area 32 of the focus measurement mask 30, the defocus amount can be obtained for each chip area 33. The defocus amount of the point can be acquired with high accuracy.

  In the focus measurement method of the present embodiment, it is necessary to obtain reference data in advance as described above. The reference data is data indicating the correlation between the pattern dimensional difference in the first transfer pattern group and the second transfer pattern group in the same transfer chip region and the defocus amount of the exposure apparatus. Such reference data is created as follows.

  That is, using the focus measurement mask 30 of FIG. 8, while changing the focus offset value of the exposure apparatus at a predetermined interval (that is, performing a focus swing at a constant interval), for each shot corresponding to each focus offset value. Measure the dimensional difference of the pattern. Thereby, the fluctuation amount of the dimensional difference of the pattern accompanying the defocus of the exposure apparatus can be obtained.

  At this time, in order to suppress the influence of variations in the flatness of the substrate, the focus reproducibility of the exposure apparatus, and other process factors, the above correlation is measured a plurality of times, and the average value of the measurement results is used as the dimensional difference data. It is preferable.

  The dimension difference data thus obtained is stored as reference data in a reference data storage unit such as a length measurement SEM main body or a computer connected to the length measurement SEM. The defocus amount is calculated by reading this out as necessary and comparing the measured dimension difference calculated by the data calculation unit with the focus calculation unit.

(Third embodiment)
The exposure apparatus management method according to the third embodiment of the present invention will be described below with reference to the drawings. The exposure apparatus management method of the present embodiment measures the defocus amount of the exposure apparatus using the focus measurement method according to the second embodiment, and sets the focus offset value of the exposure apparatus based on the defocus amount. Thus, image plane management of the exposure apparatus is performed.

  Specifically, first, defocus amounts (that is, focus values) corresponding to a large number of points in the shot region 32 are obtained by the focus measurement method according to the second embodiment. The focus measurement mask 30 (FIG. 8) used in the second embodiment is provided with a number of chip regions 33, and each chip region 33 includes a first pattern group and a second pattern group. Is provided. Therefore, the in-shot focus distribution can be obtained with very high accuracy by the focus measurement method of the second embodiment.

  Next, the focus distribution thus obtained, that is, the image plane, is analyzed and separated into an average value, a tilt component, and a curved component.

  Here, the average value is an average value of focus values in a shot. If this value is different from the focus value set during exposure, the difference between the measured average value and the set focus value is set as the focus offset value of the exposure apparatus.

  Further, the tilt component is a value reflecting both the tilt component resulting from the lens aberration and the stage accuracy of the exposure apparatus. If this value exceeds a certain value, the inverted value is set as the focus sensor offset value of the exposure apparatus or as the offset value of the stage tilt.

  The curved component is a value mainly attributable to the lens. If this becomes a specified value abnormality (when it is far from the specified value), it is highly likely that there is some abnormality in the projection optical system. Therefore, the necessity of device improvement such as lens correction is examined.

  According to the exposure apparatus management method of the third embodiment, after obtaining defocus amounts at a large number of points in a shot to obtain an in-shot focus distribution with high accuracy, the focus of the exposure apparatus is based on the in-shot focus distribution. By setting the offset value, exposure apparatus management such as image plane management can be performed with high accuracy.

  The focus sensor offset value is an offset value between focus sensors provided in a plurality of exposure apparatuses, and adjusts a relative value between the focus sensors. The focus offset value is an offset value of the focus itself.

(Fourth embodiment)
Next, a method for manufacturing an electronic device according to a fourth embodiment of the present invention will be described with reference to the drawings. The electronic device manufacturing method according to the present embodiment feeds back data related to processing of one lot in the photolithography process to processing of other lots, thereby making it possible to manufacture a device due to variations in manufacturing apparatus or processes. The effect is suppressed. Here, in the lithography process, as one of the inspection processes after pattern formation, the defocus amount of the exposure apparatus is measured by the focus measurement method according to the second embodiment.

  FIG. 9 is a diagram illustrating an example of a device manufacturing mask used in the electronic device manufacturing method of the present embodiment. The device manufacturing mask 40 of FIG. 9 is configured using a mask substrate 41 made of glass or the like. The mask substrate 41 is provided with a shot area 42 that is an arrangement area of a pattern to be exposed in one shot, and a plurality of device pattern areas 45 that are device pattern arrangement areas are formed in the shot area 42 (in the present embodiment). In the case of 4) provided in a matrix. Each device pattern area 45 is partitioned from each other by a scribe lane area 46.

  In addition, focus measurement regions 43 are provided at a plurality of locations (9 locations in the present embodiment) in the scribe lane region 46. In the focus measurement region 43, the first pattern group and the second pattern group similar to those in the first embodiment or any modification thereof are provided as test patterns for focus monitoring.

  A reticle alignment pattern arrangement region 44 is provided in the vicinity of the shot region 42 in the mask substrate 41.

  As an inspection process after pattern formation in the photolithography process, dimension measurement and overlay measurement by a length measurement SEM are performed. The dimension measurement process is a process for confirming whether the pattern is formed according to the desired dimension. If there is a difference between the desired dimension and the actual pattern dimension, the exposure amount is changed. To do. Further, based on the value obtained in the overlay measurement process, that is, based on the overlay measurement value, the offset, magnification and rotation for the shot, and the magnification and rotation value for the wafer are used as exposure parameters of the exposure apparatus. To reflect.

  Here, as a feedback method of the inspection data (diffusion data) obtained in the dimension measurement process or the overlaying process, for example, inspection data is acquired using a pilot lot, and the inspection data is reflected in the processing of the main body lot. There is a way to make it. There is also a method of reflecting the inspection data of the lot processed last time in the processing of the lot processed next time.

  In the electronic device manufacturing method of the present embodiment, nine focus measurement regions are measured by the focus measurement method according to the third embodiment using the device manufacturing mask shown in FIG. The focus value at 43 is measured, and the focus distribution within the shot is obtained with high accuracy.

  Thereby, the average value, the inclination component of the image plane, and the curvature component of the image plane can be grasped based on the focus distribution in the shot. For this reason, in addition to feedback of dimensions and overlay accuracy, the focus value can be fed back with high accuracy. As a result, the focus correction at the time of lot processing is conventionally performed by the autofocus function of the exposure apparatus, but in the case of the present embodiment, feedback regarding focus can be performed with higher accuracy.

  According to the exposure mask of the present invention, and the focus measurement method and pattern formation method using the exposure mask, the focus distribution in the shot can be measured with high accuracy, which is also useful for manufacturing electronic devices. .

FIG. 1A shows an exposure mask 10 according to the first embodiment of the present invention, and FIG. 1B shows a first pattern group 15a and a second pattern group provided on the exposure mask 10. FIG. It is a figure which shows 15b. FIG. 2A is a schematic perspective view of patterns provided on the exposure mask 10, and FIGS. 2B and 2C show first pattern groups and first patterns arranged at different pitches, respectively. It is a figure which shows 2 pattern groups. FIG. 3 shows the result of simulating the line dimensions when the first pattern group and the second pattern group are transferred to the device substrate with respect to the focus position. FIG. 4 is a diagram showing a result of plotting a difference in line size after transfer between the first pattern group and the second pattern group provided on the exposure mask 10 with respect to the focus position. FIG. 5 is a view showing the structure of a focus measurement pattern in the exposure mask according to the first modification of the first embodiment of the present invention. FIG. 6 is a view showing the structure of a focus measurement pattern in the exposure mask according to the second modification of the first embodiment of the present invention. FIG. 7 is a view showing the structure of a focus measurement pattern in an exposure mask according to Modification 3 of the first embodiment of the present invention. FIG. 8 is a diagram showing a focus measurement mask 30 used in the focus measurement method according to the second embodiment of the present invention. FIG. 9 is a diagram showing a device manufacturing mask 40 used in the electronic device manufacturing method according to the fourth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exposure mask 11, 31, 41 Mask substrate 12, 32, 42 Shot area | region 13, 43 Focus measurement area | region 15a 1st pattern group 15b 2nd pattern group 21 Bright area 21a 1st bright area 21b 2nd bright area 21c, 21d, 21e Bright area 22 Pattern 22a First pattern 22b Second pattern 22c, 22d, 22e Pattern 23 Semi-shield film 30 Focus measurement mask 33 Chip area 34, 44 Reticle alignment pattern arrangement area 40 Device manufacturing mask 45 Device pattern area 46 Scribe Lane Area

Claims (12)

A focus measurement pattern is provided on the mask substrate,
The focus measurement pattern includes a first pattern group including at least three first patterns arranged at a first pitch, and at least three second patterns arranged at a second pitch different from the first pitch. A second pattern group including two patterns,
Both the first pattern group and the second pattern group are constituted by a plurality of concave regions and a plurality of convex regions provided on the mask substrate. In claim 1,
The exposure mask according to claim 1, wherein the first pattern group and the second pattern group are arranged within a predetermined distance. In claim 1 or 2,
The exposure mask, wherein the first pattern and the second pattern are provided as the plurality of convex regions. In claim 1 or 2,
The exposure mask according to claim 1, wherein the first pattern and the second pattern are provided as the plurality of concave regions. In any one of Claims 1-4,
The plurality of concave regions are regions engraved with respect to the mask substrate,
The plurality of convex regions are regions that are not engraved on the mask substrate. In any one of Claims 1-5,
Both the first pattern and the second pattern are line patterns. In claim 6,
An exposure mask, wherein the first pattern and the second pattern have the same line width. In any one of Claims 1-7,
An exposure mask, wherein at least a part of the convex region is covered with a light shielding film or a semi-light shielding film. In any one of Claims 1-7,
An exposure mask, wherein a boundary portion of the convex region with the concave region is covered with a light shielding film or a semi-light shielding film. In any one of Claims 1-7,
An exposure mask characterized in that the entire surface of the convex region is covered with a light shielding film or a semi-light shielding film. A focus measurement method for obtaining a focus when performing mask pattern transfer using a projection optical system of a projection exposure apparatus using the exposure mask according to any one of claims 1 to 10,
A step (a) of measuring a dimension of the first transfer pattern in which the first pattern is transferred to the substrate and a dimension of the second transfer pattern in which the second pattern is transferred to the substrate;
Calculating a dimensional difference between the first transfer pattern and the second transfer pattern (b);
A focus measurement method comprising the step (c) of calculating the focus by comparing the dimensional difference with reference data prepared in advance. Obtaining the focus by the focus measuring method according to claim 11;
Feeding back the focus value to the projection exposure apparatus and transferring the mask pattern to another substrate.

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