JP2003195472A - Defect repair method for phase shift mask, phase shift mask and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and surely repair a hardly repairable defect arising in a phase shift section. <P>SOLUTION: In case of the occurrence of a projecting part 5 which is the defect of the same material as the material of a slit groove 4 in this slit groove 4, part of a light shielding film 3 adjacent to the slit groove 4 having the projecting part 5 is removed in accordance with a data table T formed by measuring the sizes of the defects and bringing together the amounts of removal of light shielding films 3 derived from the differences between the pattern widths of the transfer patterns obtained by the transfer experiments of the phase shift mask 1 having the defects and desired pattern widths and the measured sizes of the projecting parts 5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of correcting a defect of a phase shift mask when a defect occurs in a phase shift portion, a phase shift mask in which the defect is corrected, and an exposure method using the phase shift mask. .

[0002]

2. Description of the Related Art In the photolithography technology, there has been conventionally known a phase shift mask capable of transferring a pattern with high resolution by utilizing the phase difference of exposure light passing through a photomask. In this phase shift mask, a Levenson-type phase shift mask that produces a phase difference of light by forming a slit groove in the transparent substrate, or a phase shifter such as a phase shift film is formed on the transparent substrate. There is a phase shift mask that causes a phase difference.

In the Levenson type phase shift mask as described above, one or both sides of a transparent substrate made of a substrate material such as quartz glass (SiO ₂ ) is etched to form a plurality of slit grooves having different depths. However, this slit groove is used as a phase shift portion. In the Levenson-type phase shift mask, the phase difference of the light transmitted through each slit groove can be shifted by setting the difference in the depth of these slit grooves to a predetermined value. Further, in the Levenson-type phase shift mask, a light-shielding film that constitutes a light-shielding portion, for example, chromium (Cr), is formed on a portion other than the slit groove of the mask substrate.

In the Levenson type phase shift mask
Is before or after etching the phase shift
In the inside, S is partially caused by foreign matter adhering to the phase shift part.
iO _TwoSlit groove without etching the substrate material such as
May remain convex at the bottom of the. In addition, the phase shift film
In the phase shift mask that is formed to be the phase shift part
When etching the phase shift film,
The outside is covered with resist, but this resist
If there is a hole, that part will be etched and it will be concave
Will be a defect. Defects due to such unevenness have a high resolution.
Is a hindrance to obtaining the transfer pattern.

Conventionally, the correction of the irregularity defect generated in the photomask is performed by using a focused ion beam device (Focused Ion).
Beam: Hereinafter, it will be described as FIB. ) Is used. In the defect correction by the FIB, the defect portion is irradiated with an ion beam in a predetermined gas atmosphere, and when the beam is irradiated, Cr is blown off and collected in the detector.
The defect is imaged by measuring the number of Si and Si particles, the size of the defect is recognized, and then the defect is removed by etching according to the imaging result.

[0006]

However, since the defect in the phase shift mask as described above is SiO _{2 made} of the same material as the part other than this defective part, an extra light shield made of Cr in the binary type photomask is used. As in the case where the film is removed from the transparent substrate made of SiO _2, the contrast between the two cannot be obtained, and imaging by FIB is difficult. Therefore, the size of the defect cannot be accurately grasped, and the etching end point cannot be determined. In such a case, the shape of most defects is first grasped by an atomic force microscope (hereinafter, referred to as AFM) and the like, and then once etched by FIB, and then again by AFM. When the correction is insufficient, the etching is performed again by measuring and confirming, or by checking the state of the transfer pattern formed by actually performing the transfer experiment. However, since it is difficult to grasp the exact shape of the defect as described above, the correction is often insufficient even by etching again.

Further, when the above-mentioned convex defect occurs in the phase shift portion, there is a repairing method using xenon fluoride or the like, but it is difficult to repair because the etching rate of SiO ₂ is high. . Further, when a concave defect is generated in the phase shift part, there is a method of depositing SiO _{2 on} the defective part, but it is difficult to reproduce the transmittance in the state before the correction and it is practical. is not.

As described above, in the present situation, when the defect portion and the other portion are made of the same material, such as a defect due to etching residue generated in the slit groove of the Levenson type phase shift mask, this defect is eliminated. It is very difficult to fix it completely.

Therefore, the present invention uses a defect correcting method of a phase shift mask capable of easily correcting a defect generated in a phase shift portion which is difficult to correct, a phase shift mask in which the defect is corrected, and this phase shift mask. It is an object to provide an exposure method.

[0010]

A method of correcting a defect of a phase shift mask according to the present invention which solves the above-mentioned problems, corrects a defect generated in a phase shift portion of a phase shift mask having a light shielding portion and a phase shift portion. In doing so, the defect generated in the phase shift part is corrected by modifying the light shielding part. Further, in repairing a defect generated in a phase shift portion of a phase shift mask used in a photolithography process in which exposure is performed in at least two steps using a plurality of photomasks, a light shielding portion of a photomask other than the phase shift mask is used. Is corrected to correct the defect generated in the phase shift section.

The above-described method of repairing a defect of a phase shift mask according to the present invention does not repair the defect itself generated in the phase shift portion which is difficult to repair, but repairs the light shielding portion in a simpler manner. Correct the defects that occur in the. Thus, according to the photomask correction method of the present invention,
Even when a defect that is difficult to correct occurs, the defect is corrected by a simpler process, and a simple and reliable formation of a desired transfer pattern is realized.

Further, according to the method of repairing a defect of a phase shift mask according to the present invention, in repairing a defect generated in a phase shift portion of a phase shift mask having a light shielding portion and a phase shift portion, a defect generated in the phase shift portion. Then, the remaining defect is corrected by correcting the light shielding part.

The above-described defect correcting method of the phase shift mask according to the present invention is not completed by the correction of the defect generated in the difficult-to-correct phase shift portion, and the defect is further corrected by further performing the simpler correction of the light shielding portion. to correct. As described above, according to the photomask repairing method of the present invention, the defect is corrected by performing the processing that is easy to process in combination with the processing that is difficult to process, so that the phase shift mask can be corrected more reliably. Will be realized.

Further, the phase shift mask and the exposure method according to the present invention are those in which the defect is corrected by the above-mentioned defect repairing method, and exposure is performed using the mask in which this defect is repaired. According to the phase shift mask and the exposure method of the present invention, even if a difficult-to-correct defect occurs in the phase shift portion at the manufacturing stage of the phase shift mask, this defect is easily corrected and a desired transfer pattern is formed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in detail below with reference to the drawings. In addition,
In this embodiment, the case where the phase shift mask 1 having a defect in the phase shift portion is a Levenson type phase shift mask will be described.

As shown in FIG. 1, the phase shift mask 1 has a transparent phase shift pattern formed by a light shielding film 3 and a slit groove 4 on one surface side of a glass substrate 2 made of, for example, SiO _2. ing. The light-shielding film 3 is, for example, Cr
Is formed by a sputtering method or the like, and the portion where the light shielding film 3 is formed serves as a light shielding portion A that shields exposure light in the photolithography process. The slit groove 4 is a dug portion for forming a phase difference formed on the glass substrate 2 by etching, and the portion where the slit groove 4 is formed causes a phase difference of the exposure light transmitted in the photolithography process. It is a phase shift unit B.

In the phase shift mask 1, a plurality of slit grooves 4 described above are provided with different depths, and the difference between the depths of these slit grooves 4 is set to a predetermined value so that the adjacent slit grooves 4 are formed. It is possible to shift the phase of the exposure light passing through each of the. In the phase shift mask 1, by using the exposure light whose phase is shifted by the slit grooves 4 having different depths in this way, a transfer pattern forming target substrate such as a semiconductor substrate (hereinafter, simply referred to as a target substrate will be described. A fine transfer pattern can be formed on the.

In the phase shift mask 1, when the slit groove 4 is formed on the glass substrate 2 by etching as described above, the convex portion 5 as shown in FIG.
May remain on the bottom 4a of the. In this way the slit groove 4
When a defect occurs on the substrate, this defect, that is, the convex portion 5 influences the exposure light transmitted through the slit groove 4, and the line width of the transfer pattern formed on the target substrate varies. A pattern defect occurs. In order to avoid such a defect in the transfer pattern and obtain a desired transfer pattern, that is, a transfer pattern similar to the case where the slit groove 4 has no defect, the defect of the phase shift mask 1 is corrected. The defect correction performed on the phase shift mask 1 will be described below.

Defect correction for the phase shift mask 1 is performed by
As shown in FIG. 3, first, it is detected whether or not the convex portion 5 is formed in the slit groove 4 (step 1-1). When the defective convex portion 5 is detected in the slit groove 4,
The size of the convex portion 5, specifically, the height and shape of the convex portion 5,
The size and the like or the line width of the transfer pattern formed under the influence of the convex portion 5 is measured (step 1-
2).

When measuring the size of the convex portion 5 described above, the size such as the height of the convex portion 5 is measured by using, for example, an AFM. Further, when the line width of the transfer pattern is measured, a transfer experiment for forming the transfer pattern on the target substrate using the uncorrected phase shift mask 1 was performed, and the transfer pattern was actually formed in the transfer experiment. The line width of the transfer pattern is measured.

Then, as described above, the size of the convex portion 5,
Alternatively, after measuring the line width of the transfer pattern formed using the unshifted phase shift mask 1, the light-shielding film 3 (3a shown in FIG. 2) adjacent to the slit groove 4 having the convex portion 5 is measured according to these measurement results. 3b) is partially removed by etching (step 1-3), and the region of the phase shift portion B is enlarged.

The removal amount of the light-shielding film 3 in step 1-3 is determined based on the data obtained in advance as follows. That is, first, a transfer experiment was actually performed using the phase shift mask 1 having a defect, the line width of the obtained transfer pattern was compared with the line width of the desired transfer pattern, and the removal amount of the light shielding film 3 was determined from these differences. To calculate. And
The height and shape of the defect subjected to the transfer experiment, for example, the cross-sectional area is measured by the AFM, and the data obtained by associating the measurement result with the removal amount of the light shielding film 3 is shown in a data table as shown in FIG.
In T, for example, the amount of removal X of the light-shielding film 3 when the height of the measured defect is c (nm) and the cross-sectional area is D (nm ² ) is summarized, and based on this data table T Thus, the light shielding film 3 is removed. In addition, step 1-2
When the line width of the transfer pattern is measured in, the data table that can derive the removal amount of the light shielding film 3 from the relationship between the line width of the transfer pattern and the measured value of the height of the defect of the phase shift mask 1, that is, , A light-shielding film based on a table that summarizes data on the removal amount of the light-shielding film 3 obtained by comparing a line width obtained in a transfer experiment performed with a phase shift mask having a defect of a certain height and a desired line width 3 is removed.

After the removal of the light-shielding film 3, cleaning of the phase shift mask 1 and a transfer experiment are performed (step 1-
4) Check the line width of the transfer pattern actually formed after the correction.

In the correction of the phase shift mask 1 described above, the defect was explained as the convex portion 5 formed on the bottom portion 4a of the slit groove 4. However, when the defect formed on the bottom portion 4a is a concave step. Of course, it can also be applied to. Even if the defect generated in the shift portion is concave, the light-shielding film is obtained from the line width of the transfer pattern and the desired line width obtained in the transfer experiment using the phase shift mask 1 with the defect still formed. The removal amount of 3 is obtained, a data table is created in which the measured values of the depth and opening area of this defect are associated with the removal amount of the light blocking film 3, and the removal amount of the light blocking film based on the data in this table is created. Etch 3.

In the defect correction of the phase shift mask 1 described above, the defect is corrected without correcting the convex portion 5 generated in the slit groove 4. However, the defect correction method according to the present invention is first performed. The defect may be corrected by modifying the convex portion 5 in general, then further modifying the light-shielding film 3, and combining these modifications. Hereinafter, a defect correction method including a step of once correcting the convex portion 5 will be described. As shown in FIG. 5, this defect correction is performed by first detecting defects (step 2-1) and measuring the size of the defect or the line width of the transfer pattern (step 2-2) as in the above-described defect correction.

Then, based on the measurement of the size of the defect or the line width of the transfer pattern in the above step 2-2,
The convex portion 5 is etched by using, for example, FIB (step 2-3). Then, the phase shift mask 1 is washed, and the size of the convex portion 5 after etching in step 2-3 or the line width of the transfer pattern obtained by the phase shift mask 1 after etching is measured again (step 2- 4) Then, a part of the light-shielding film 3 is removed by etching according to the size of the convex portion 5 or the line width of the transfer pattern by this remeasurement (step 2-5). The second measurement in step 2-4 is performed to confirm whether the convex portion 5 is left uncorrected by etching or whether there is a concave portion due to excessive cutting, and is performed by the same method as the measurement performed in step 2-2. . Further, the removal of the light-shielding film 3 by the etching in step 2-5 is removed based on the data of the data table T obtained in the defect correction described above. Then, the phase shift mask 1 is washed again, and a transfer experiment is performed (step 2-6) to confirm the line width of the transfer pattern actually formed after the correction.

After the defect correction as described above, the phase shift mask 1 as shown in FIG. 6 is formed. In the phase shift mask 1, as shown in the figure, a part of the light shielding film 3 is removed and the light shielding portion A is narrowed, so that the region of the phase shift portion B formed by the slit groove 4 having the convex portion 5 is formed. Has been expanded. In such a phase shift mask 1,
The exposure light transmitted from the portion where the light-shielding film 3 is removed adjusts the exposure light of the entire phase shift portion B having the convex portion 5 so that the same exposure light as that in the defect-free state is irradiated on the target substrate. Is corrected to. In the phase shift mask 1 in which the defect is corrected in this way, a transfer pattern having a desired line width can be formed on the target substrate even when the convex portion 5 remains in the slit groove 4.

Although the Levenson type phase shift mask has been described as an example in the above-mentioned embodiment, the present invention is not limited to this. In the present invention, for example, instead of the slit groove 4, in a phase shift mask that forms a phase shifter such as a phase shift film on a glass substrate, when a concave defect occurs in the phase shift film made of SiO ₂ , It can also be applied when correcting defects.

In the defect correction of the phase shift mask 1 described above, the defect is corrected by etching a part of the light shielding film 3. However, instead of partially removing the light shielding film 3 as described above. The exposure light may be adjusted by depositing a light-shielding film such as a carbon film on the bottom portion 4a of the shift portion 4 by a method such as sputtering to narrow the light transmission region of the slit groove 4.

Next, using the Levenson-type phase shift mask 1 and another photomask 11 shown in FIG. 7, a two-step photolithography process is performed to obtain a desired transfer pattern 20. A method for correcting the above will be described. The photo mask 1 used here
Reference numeral 1 is a binary type photomask having a light shielding portion 12 and a light transmitting portion 13.

In the phase shift mask 1, as shown in the figure, the convex portion 5 as a defect is formed in the slit groove 4. When exposure is performed using such a phase shift mask 1, a transfer pattern having a line width different from that of a desired pattern is formed on the target substrate by the exposure light affected by the convex portion 5. In such a case, the transfer pattern having a desired line width can be obtained by correcting the defect as follows.

First, as shown in FIG. 8, the presence or absence of a convex portion 5 which is a defect occurring in the phase shift mask 1 is detected (step 3-1), and when the convex portion 5 which is a defect is detected. The size of the convex portion 5 or the line width of the transfer pattern formed by the phase shift mask 1 having the convex portion 5 is measured (step 3-2).

When the convex portion 5 is thus measured, the size such as the height of the convex portion 5 is measured by using, for example, an AFM. When measuring the line width of the transfer pattern,
A transfer experiment in which a transfer pattern is actually formed on the target substrate using the uncorrected phase shift mask 1 is performed, and the line width of the transfer pattern formed in the transfer experiment is measured.

Then, after measuring the size of the convex portion 5 or the line width of the transfer pattern described above, a part of the light-shielding film forming the light-shielding portion 12 of the photomask 11 is removed in accordance with the measurement result to form a notch. 14 is formed (step 3-3). In the photomask 11, the glass substrate is exposed and the region of the light transmitting portion 13 is enlarged by forming the notch 14 as described above. In this way, after the exposure of the different stage where the exposure light affected by the convex portion 5 is applied, the exposure is performed by the photomask 1 in which the notch 14 is formed in the light shielding portion 12 in the exposure of the second stage. The exposure light in the entire photolithography process is adjusted. This step 3
The size of the notch 14 formed in -3, that is, the amount of the light shielding film removed from the light shielding portion 12 has data obtained in the same manner as the defect correction of the phase shift mask 1 described above, that is, has a defect. The removal amount of the light shielding film 3 calculated from the difference between the line width obtained by the transfer experiment of the phase shift mask 1 and the desired line width is performed based on the data table created in correspondence with the measured defect size.

Thereafter, the photomask 11 is washed and a transfer experiment is performed (step 3-4) to confirm the line width of the transfer pattern actually formed after the correction.

Incidentally, in the defect repair of the mask in the case of performing the two-step photolithography process, the repair method shown in FIGS. 3 and 5 is carried out instead of repairing the photomask 11 as described above. Thus, the Levenson type phase shift mask 1 may be modified and the photomask 1 side may not be modified. In addition, as described above, the phase shift mask 1 and the photomask 11 are used as embodiments.
Although the case where the two-step photolithography process is performed is described by using and, the present invention is not limited to this and is also applicable to the case where the mask used in the three or more steps photolithography process is modified. You can

In the photolithography process using the phase shift mask 1 and the photomask 11 in which the defects are corrected as described above, as shown in FIG. 7, first, the Levenson type phase shift is performed on the portion that needs to be finely processed. A first photolithography process is performed using the mask 1 and then a second photolithography process is performed using the binary photomask 11.
Photolithography process is performed. By performing the photolithography process in two or more steps using the photomask 11 as described above, a defect occurs in the slit groove 4 which is the phase shift part of the Levenson type phase shift mask 1 which is one of the masks used. Even in such a case, the transfer pattern 20 having a desired line width can be obtained.

[0038]

As described in detail above, according to the method of repairing a defect of a photomask according to the present invention, a defect which is difficult to repair, for example, a defect generated in a slit groove which is a phase shift portion, can be repaired. Of the photomask for forming a transfer pattern having a desired line width can be easily performed by correcting the easily repaired portion of the photomask or by further correcting the easily repaired portion in combination with the correction of the defect that is difficult to repair. And it can be done reliably.

Further, according to the photomask and the exposure method of the present invention, even if a defect which is difficult to correct occurs in the photomask manufacturing stage, it is possible to easily form a transfer pattern having a desired line width.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a Levenson-type photomask.

FIG. 2 is a vertical cross-sectional view of a main part of the same photomask in which a shift portion has a defect.

FIG. 3 is a flowchart of a defect correction method to which the present invention is applied.

FIG. 4 is a diagram showing an example of a data table relating to a removal amount of a light shielding film.

FIG. 5 is a flowchart of another defect repairing method to which the present invention is applied.

FIG. 6 is a vertical cross-sectional view of a main part of a photomask according to the present invention, which has been modified.

FIG. 7 is a diagram for explaining a mask shape and a transfer pattern shape in the case of performing two-step exposure.

FIG. 8 is a flowchart of a defect repairing method according to the present invention in the case of performing two-step exposure.

[Explanation of reference numerals] 1 photomask, 2 glass substrate, 3 light shielding film, 4
Shift part, 5 convex part

Claims (30)

[Claims] 1. When correcting a defect generated in the phase shift part of a phase shift mask having a light shielding part and a phase shift part, the defect generated in the phase shift part is corrected by correcting the light shielding part. A method of correcting a defect of a phase shift mask, which is characterized by the above. 2. The defect repairing method for a phase shift mask according to claim 1, wherein the size of the defect generated in the phase shift portion is measured, and the light shielding portion is repaired based on the measurement result. 3. The defect correction method for a phase shift mask according to claim 2, wherein the defect size generated in the phase shift portion is measured by using an atomic force microscope. 4. A transfer experiment is performed using a phase shift mask having a defect in the phase shift section, and the correction amount of the light shielding section is grasped based on the result of the transfer experiment and the measurement result of the defect size. 3. The method of correcting a defect of a phase shift mask according to claim 2, wherein. 5. The method of repairing a defect in a phase shift mask according to claim 1, wherein the phase shift mask is a Levenson type phase shift mask. 6. The method of repairing a defect in a phase shift mask according to claim 5, wherein the phase shift portion is formed as a slit groove of a transparent substrate. 7. The defect of the phase shift portion is a concave portion or a convex portion in the slit groove.
A method for repairing a defect of a phase shift mask according to [4]. 8. The method of repairing a defect in a phase shift mask according to claim 7, wherein the light-shielding portion is repaired by partially removing the light-shielding portion adjacent to the slit groove in which the defect has occurred. . 9. The method of repairing a defect of a phase shift mask according to claim 7, wherein the light-shielding portion is repaired by depositing a light-shielding film on a part of the slit groove where the defect has occurred. 10. When correcting a defect generated in the phase shift portion of a phase shift mask having a light shielding portion and a phase shift portion, after correcting the defect generated in the phase shift portion, the remaining defect is shielded by the light shielding. A method of correcting a defect of a phase shift mask, which comprises correcting by correcting a portion. 11. The method of repairing a defect of a phase shift mask according to claim 10, wherein the defect generated in the phase shift portion is repaired by using a focused ion beam device. 12. The defect correction method for a phase shift mask according to claim 10, wherein the size of the defect remaining in the phase shift portion is measured, and the light shielding portion is corrected based on the measurement result. 13. The method of repairing a defect in a phase shift mask according to claim 12, wherein the size of the defect remaining in the phase shift portion is measured by using an atomic force microscope. 14. A transfer experiment is performed using a phase shift mask in which a defect remains in the phase shift section, and the correction amount of the light shielding section is grasped based on the result of the transfer experiment and the measurement result of the defect size. 13. The method of repairing a defect of a phase shift mask according to claim 12, wherein. 15. The phase shift mask is a Levenson-type phase shift mask.
0. A method of correcting a defect of a phase shift mask according to 0. 16. The method according to claim 15, wherein the phase shift portion is formed as a slit groove of a transparent substrate. 17. The defect correcting method for a phase shift mask according to claim 16, wherein the defect in the phase shift portion is a concave portion or a convex portion in the slit groove. 18. The method of repairing a defect in a phase shift mask according to claim 17, wherein the light-shielding portion is repaired by partially removing the light-shielding portion adjacent to the slit groove in which the defect has occurred. . 19. The method of repairing a defect of a phase shift mask according to claim 17, wherein the light-shielding portion is repaired by depositing a light-shielding film on a part of the slit groove where the defect has occurred. 20. When correcting a defect generated in a phase shift portion of a phase shift mask used in a photolithography process in which exposure is performed in at least two steps using a plurality of photo masks, A defect correcting method for a phase shift mask, characterized in that a defect generated in the phase shift portion is corrected by correcting a light shielding portion of the photomask. 21. The method according to claim 20, wherein the photomasks other than the phase shift mask are binary photomasks. 22. The phase shift according to claim 21, wherein the size of a defect generated in the phase shift portion is measured, and the light shielding portion of the binary type photomask is corrected based on the measurement result. Mask defect repair method. 23. The defect repairing method for a phase shift mask according to claim 22, wherein the defect size generated in the phase shift portion is measured by using an atomic force microscope. 24. A transfer experiment is performed by using a phase shift mask having a defect in the phase shift section, and the light shielding section of the binary type photomask is determined based on the result of the transfer experiment and the measurement result of the defect size. 23. The method of correcting a defect of a phase shift mask according to claim 22, wherein the correction amount is grasped. 25. The phase shift mask is a Levenson type phase shift mask.
0. A method of correcting a defect of a phase shift mask according to 0. 26. The method according to claim 25, wherein the phase shift portion is formed as a slit groove of a transparent substrate. 27. The defect correcting method for a phase shift mask according to claim 26, wherein the defect in the phase shift portion is a concave portion or a convex portion in the slit groove. 28. A phase shift mask comprising a light-shielding portion and a phase-shifting portion, and a defect caused in the phase-shifting portion is corrected by correcting the light-shielding portion. 29. An exposure method comprising a light-shielding portion and a phase-shifting portion, wherein a defect caused in the phase-shifting portion is corrected by correcting the light-shielding portion to perform exposure with a phase-shift mask. . 30. An exposure method of performing exposure in at least two stages using a plurality of photomasks including a phase shift mask having a defect in the phase shift portion, wherein the phase shift mask having the defect in the phase shift portion is used. When used, an exposure method is characterized in that a light-shielding portion of a photomask other than the phase shift mask is corrected to correct a defect in the phase shift mask and then exposure is performed.