JPH06138646A - Correcting method for phase shift mask - Google Patents

Abstract

PURPOSE:To provide a correcting method for a phase shift mask which does not substantially affect a resist pattern even if any defective part exsists in the mask. CONSTITUTION:When the defective part is corrected, the light transmittance in the corrected region is reduced and the light intensity of the transmitted light beam passed through the region is thus reduced. Consequently, when the mask pattern of the phase shift mask is projected on a wafer by using a reduction stepper the distribution of the light intensity at an image-formed position of the projection optical system is smaller than the light intensity corresponding to a region not corrected because the light intensity (at the normal time) at a position corresponding to the corrected region has the defective part. In this case, auxiliary openings 19 and 22 are formed at the defective parts 16 and 20, i.e., at a light shielding pattern 14 in close vicinity to the corrected region. The transmitted light beam passed through the auxiliary openings 19 and 22 compensates for the reduction of the light quantity of the transmitted light beam at the corrected region, thereby raising the light intensity at the corresponding image-formed position toward a light intensity level at the positive normal time. Thus, the formation of a prescribed resist pattern as previously designed is allowable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photolithography technique used for manufacturing an LSI or the like, and more particularly to a method for correcting a phase shift mask.

[0002]

2. Description of the Related Art In recent years, lithography technology has come to introduce a new concept of improving resolution by modifying a mask. This technique is also used in the field of photolithography technique by projection exposure, and has attracted attention as a technique for forming a fine resist pattern corresponding to high integration of semiconductor devices. One of them is the phase shift method.

In this method, in order to increase the optical contrast on the wafer, a shifter for shifting the phase of the exposure light is partially provided on the photomask on the glass substrate which is the mask substrate. A technique for improving the resolution of projection exposure by such a method is a mask correction method by phase shift.

One of the problems in putting this technique to practical use is the mask correction technique. Two methods described below regarding this method are disclosed in Document I and Document II (Document I: “Ga-FI in Phase Shift Mask Modification”).
Study of Removal Method of B-implanted Layer ", Hosono et al., 52nd Academic Lecture of Applied Physics, 12p-ZF-5; Reference II:" P
has Shift Reticles ”, S.H. Ok
azaki, et. al. , Technical Di
best of IEDM, 1991, p55).

The method of Document I is a mask correction method when a shifter defect is missing. As this method, Ga-
The mask is corrected using milling by FIB (Focused Ion Beam).

First, the substrate in the shifter lacking region is milled to a depth of about 360 nm by Ga-FIB (25 KeV). At this time, Ga stain remains in the portion milled by FIB.

Next, a Q-switched pulse Ne-YAG laser (532 nm) is used to remove this residual Ga stain.
Is irradiated to the Ga stain remaining region to evaporate the Ga stain. It is reported that the contrast of the photomask can be enhanced by removing Ga stain and reducing the reflected light by such a method.

On the other hand, in Document II, the defect correction of the shifter is described by taking a two-layer phase shift structure in which a main shifter layer and a sub shifter layer are provided on a base mask as an example.

When there is a defect in the main shifter layer, this defect and the peripheral portion are milled by FIB or etched by lithography, and then the main shifter layer and the sub shifter layer having the defective portion are removed. According to this method, the defect is repaired so that the phases of the lights transmitted through the same transmission region are aligned.

[0010]

However, the FIB
In the milling method according to (1), Ga stain remains on the processed surface as disclosed in Document I, and the light transmittance is reduced. Therefore, there is a problem that the resist pattern transferred cannot be formed into a predetermined shape due to the influence of Ga stain.

On the other hand, the method of forming two shifter layers and then correcting so that the phases are aligned becomes expensive, and the adhesiveness between the main shifter layer and the sub-shifter layer is deteriorated, which easily causes defects. There was a problem of becoming.

The present invention has been made in view of the above-mentioned problems. Therefore, the object of the present invention is to correct the defective portion of the phase shift mask, but the correction affects the shape of the resist pattern. It is an object of the present invention to provide a method for modifying a phase shift mask, which considers the structure of the phase shift mask so as not to give substantially. Another object of the present invention is to provide Ga generated by FIB when the transmissive region is an opening.
It is an object of the present invention to provide a method for correcting a phase shift mask that can form a predetermined resist pattern without being affected by the defect even if there is a hole defect when the stain or the transmission region is a phase shifter. .

[0013]

In order to achieve this object, according to the method of forming a phase shift mask of the present invention,
A masked substrate is provided with a light-shielding pattern and a phase shifter, and an opening portion where the light-shielding pattern and the phase shifter are not provided and the phase shifter respectively form a light-transmitting region. In doing so, (a) a step of repairing a defective portion existing in the transmissive region, and (b) a step of removing a part of the light shielding pattern adjacent to the defective portion to form an auxiliary opening portion, To do.

Preferably, in the method of correcting a phase shift mask, the steps (a) and (b) may be carried out at the same time, or preferably, after the step (a), the step (a) is performed. The step b) may be carried out.

When the transmission area is an opening and the defective portion is a shifter residual defective portion, (a)
It is preferable to correct the process by using FIB to remove the shifter residual defect portion.

Further, preferably, when the transmission region is a phase shifter and the defective portion is a shifter hole defective portion, the correction in the step (a) is performed by filling the shifter hole defective portion with a light shielding material. Is good.

Further, preferably, when the transmission region is an opening and the defect is a shifter residual defect, the step (a) is modified by providing a light shielding film for covering the shifter residual defect. Good to do.

Further, preferably, after filling the hole defect portion with a light shielding material, the correction in the step (b) is performed on the side opposite to the auxiliary opening portion where a part of the light shielding pattern adjacent to the shifter hole defect portion is removed. It is preferable that the light-shielding pattern has a second auxiliary opening.

Further, preferably, the correction of the step (b) is performed by using lithography to remove a part of the light shielding pattern close to the defective portion.

Further, it is preferable to use carbon compound-based hexane as a light-shielding material for filling the shifter hole defect portion.

Also, preferably, the modification of the above (b) is
It is preferable that the removal area of a part of the light shielding pattern adjacent to the shifter defect be equal to the area of the light shielding film filled in the shifter hole defect.

[0022]

As described above, according to the method of forming a phase shift mask of the present invention, when roughly classified, a step of repairing a defective portion existing in a transmissive region and a portion of a light shielding pattern adjacent to this defective portion are removed to assist. And forming an opening. When the defective portion is repaired, the light transmittance of the repaired area is lowered, so that the light intensity of the transmitted light passing through this area is lowered. Therefore, when the mask pattern of the phase shift mask is projected onto the wafer by the reduction projection exposure apparatus, the light intensity distribution at the image forming position of the projection optical system has a defect in the light intensity at the position corresponding to the corrected region. Therefore, the light intensity is smaller than the light intensity corresponding to the uncorrected region (the light intensity under normal conditions).

However, according to the present invention, since the auxiliary opening is formed in the light-shielding pattern which is close to the defective portion and thus the corrected area, the transmitted light passing through the auxiliary opening is transmitted through the corrected area. In order to compensate for the decrease in the amount of light, the light intensity at the corresponding image forming position is increased to the light intensity in the square direction at all times, so that it is possible to form a predetermined resist pattern as designed.

The correction method when the transmission region is an opening and the defect is a shifter residual defect is as follows.
The defective portion is removed by using. At this time, the Ga stain due to the FIB milling remains in the removed portion, so that the light transmittance decreases. In order to improve this, a part of the light shielding pattern adjacent to the shifter residual defect portion is removed by FIB. At this time, the phase shifter under the light shielding pattern may be removed simultaneously or separately. By this method, it is possible to supplement the transmitted light by providing an auxiliary opening for the decrease in the transmittance in the Ga stain region. Further, a light-shielding film that covers the shifter residual defect portion in the same opening may be provided. At this time, the transmittance of the opening portion is affected by the defective portion and decreases. Therefore, in order to compensate the transmittance, a part of the light shielding pattern adjacent to the shifter residual defect portion is removed.
In the method of covering this defective portion with the light-shielding film, there remains no Ga stain residue due to FIB. Therefore, a part of the light shielding pattern can be removed by using lithography.

Further, when the defective portion is removed by using FIB, the mask substrate may be excessively milled to the extent that a concave portion is formed, and then a light shielding film may be provided to cover the milled mask substrate.

Next, when the transmission region is a phase shifter and the defective portion is a shifter hole defective portion, after filling the shifter hole defective portion with a light shielding material, a part of the light shielding pattern adjacent to the hole defective portion is FIB or , Using lithography. At this time, it is preferable that the area of the light shielding film filled with the light shielding material and the area of a part of the light shielding pattern to be removed be equal. By such modification, it is possible to compensate for the decrease in the transmittance of the phase shift portion in the transmissive region. As described above, a predetermined transmittance can be ensured by removing a part of the light-shielding pattern for the decrease in the transmittance of the defective portion and providing the auxiliary opening.
In addition, carbon (C) is formed by decomposing using a carbon compound-based hexane as a light-shielding material for filling the defective portion. This is because the adhesion to the substrate is good.

[0027]

Embodiments of the present invention will now be described with reference to the drawings. It should be noted that each of the drawings merely schematically shows the dimensions, shapes, and positional relationships of the respective constituent components to the extent that these inventions can be understood. Further, in the following description, specific materials and conditions are used for description, but these materials and conditions are merely preferable examples, and thus the present invention is not limited thereto.

First, in order to predict the effects of the present invention in advance, a mask pattern for simulation is formed.
A typical example of the structure of the phase mask pattern used at this time will be described with reference to the plan view of FIG. Note that, in FIG. 1, hatching and the like do not represent a cross-sectional portion, but emphasize a specific region when seen in a plan view.

A phase shifter 12 and a light shielding pattern 14 are provided on a mask substrate. The opening 10 and the phase shifter 12 where the light shielding pattern 14 and the phase shifter 12 are not provided respectively form a light transmitting region. FIG. 1A shows a case where a shifter residual defect portion remains on the inner opening 10.

In order to remove the shifter residual defect 16,
The FIB method is used to remove a part of the light shielding pattern close to the residual defect. At this time, the Ga stain remaining region 18 is formed in the portion milled by the FIB. continue,
A part of the light shielding pattern 14 near the residual defect is
And then removed by etching. This removed portion is called an auxiliary opening 19.

At this time, the phase shifter 12 below the light shielding pattern 14 is also removed at the same time. As a method of removing the phase shifter under the light shielding pattern 14,
This may be performed at the same time as the defective portion is removed by FIB, or may be performed after the defective portion is removed.

Next, FIG. 1 shows a case where the transmission region is used as a phase shifter and the phase shifter has a shifter hole defect portion 20.
This will be described with reference to (C) and (D).

A phase shifter 12, a light shielding pattern 14 and an opening 10 are formed on the mask substrate. At the center of the phase shifter 12, there is a defect such as a pinhole or a hole (referred to as a shifter hole defect 20) ((C) in FIG. 1).

In order to correct this shifter hole defect portion 20,
After the defective portion is filled with the light shielding material, a part of the light shielding pattern 14 adjacent to the defective portion is removed by using a method such as FIB or lithography. Incidentally, this light shielding pattern removal portion is shown by an auxiliary opening portion 22 ((D) of FIG. 1).

Next, a method of correcting the phase shift mask used in the simulation of the present invention will be described in detail with reference to FIGS.

First, in the case of the shifter residual defect portion, there are three methods of correcting the mask. The first of these is a method of removing the residual defect and then removing a part of the light-shielding pattern adjacent to this defect, and the second is the method of covering the defect portion with the light-shielding film while leaving the residual defect. After that, it is a method of removing a part of the light-shielding pattern close to this defect. And the third is a method of removing the residual defect, further scraping the substrate under the defective portion, covering the defective portion with the light shielding film, and then removing a part of the light shielding pattern adjacent to the defect. is there.

FIG. 2 is a plan view showing a forming process for explaining the first embodiment of the present invention. Here, hatching or the like does not represent a cross section, but emphasizes a specific region when viewed two-dimensionally.

First, the glass substrate 31 is used as a substrate. The phase shifter 34 is formed on the glass substrate 31 by using any appropriate method. Furthermore, this phase shifter 34
A light-shielding pattern, for example, chrome (Cr) or the like is formed on the upper surface by using a vapor deposition method. In addition, an opening 30 that forms a part of the transmissive region is provided on the substrate 31. This opening 30
The pattern is designed so that a shifter residual defect portion 36 of 0.2 μm square is generated on the substrate surface of (2) (A of FIG. 2 and (A) of FIG. 3).

Next, the shifter residual defect portion 36 of the opening 30 is milled by FIB. The FIB milling conditions at this time were as follows: acceleration voltage 20 kV, ion current 120 p
Milling removal is performed with A and Ga ions. A Ga stain residual region 38 is formed in this removed portion (FIG. 2).
(B) and FIG. 3 (B)).

Then, a part of the light shielding pattern 40 adjacent to the Ga stain remaining region 38 is removed by using FIB. The portion removed at this time is called the auxiliary opening 40.
At this time, the phase shifter exposed below the light shielding pattern 40 is also removed. At this time, the removal dimension of the auxiliary opening is 0.09 μm × 0.8 μm ((C) of FIG. 2 and (C) of FIG. 3).

Next, FIG. 4 shows the results of measuring the light intensity distributions of the simulation masks thus formed. This simulation was performed assuming that a mask was attached to the reduction projection exposure apparatus.

The simulation conditions at this time are i
A line, NA (aperture) 0.42, and σ (coherence factor) are 0.5.

In the figures, (A), (C) and (E) are represented by the position on the horizontal axis and the contour line of the light intensity on the vertical axis. Further, (B), (D), and (F) are shown with the position on the horizontal axis and the relative light intensity on the vertical axis. Further, the light intensity waveform curve of FIG. 4B is drawn corresponding to the light intensity contour line of the center line (II cross section) of FIG. 4A.

Further, all the mask patterns (here, the light-shielding pattern width, the opening width, and the line pattern width of the phase shift region) for forming 0.4 μmL / S (line & space) on the substrate are 0. It is calculated as 0.4 μm.

The results of measuring the light intensity distribution in the case where the shifter forming thin film corresponding to 0.2 μm square remained on the substrate as a residual defect are shown in FIGS. 4 (A) and 4 (B).

As is clear from this result, the light intensity distribution is lowered by the influence of the shifter residual defect portion in the central portion.

Next, the light intensity distribution in the case where there is a Ga stain remaining region formed by FIB is shown in FIGS. 4C and 4D. At this time, it is a value obtained by performing a simulation assuming that the transmittance decreased to 56% due to the remaining Ga stain. In addition, the region where the transmittance is lowered is 0.
4 μm × 0.8 μm, and Ga stain remains in this region.

As is apparent from FIG. 4, the Ga stain region from which the defective portion has been removed has a reduced transmittance ((D) of FIG. 4).

Next, FIGS. 4 (E) and 4 (F) show the light intensity distribution when a part of the light-shielding pattern adjacent to the region from which the defect has been removed is removed by FIB. At this time, the area of the removed portion of the light shielding pattern is 0.09 μm × 0.8 μ
m. At this time, a part of the light shielding pattern is removed and an auxiliary opening 40 is provided. The conditions are set so that the transmittance of the auxiliary opening is 100% with the Ga stain remaining region left. However, in reality, it is considered that the transmittance decreases because Ga stain remains. Therefore, it is possible to compensate for the decrease by slightly widening the width of the auxiliary opening. For example, if the transmittance is set to 56%, the width of the auxiliary opening may be expanded to about 0.15 μm. The length of this auxiliary opening is 0.8 μm. To increase the transmittance in this way, the width of the auxiliary opening may be increased. As is clear from FIGS. 4E and 4F, when the opening of the light shielding pattern is provided, the same light intensity distribution as when there is no defect can be obtained.

Next, in order to confirm the effect of the simulation, a mask having a shifter residual defect portion is intentionally prepared and the mask is corrected. As the mask used at this time, a mask called a shifter lower type as shown in FIGS. 2 and 3 is formed.

A line & space pattern of 4 μm (corresponding to 0.4 μm on a wafer with a 10: 1 stepper) is formed on the reticle. This corresponds to the case where the same shifter residual defect as the pattern used in the simulation is formed on the reticle. The size of the shifter residual defect portion is 2 μm □.

Next, the pattern of this residual defect portion is FIB.
The shifter residual defect is removed by using a mask correction device. The FIB conditions at this time are an acceleration voltage of 20 KV and an ion current of 120 pA.

The scanning range of the ion beam is 2 μm.
Since it is □, the part where the transmittance is reduced becomes 2 μm □.

Next, portions on both sides of the portion close to the defect are removed by FIB. At this time, the auxiliary opening to be milled has a width of 1 μm and a length of 4 μm. The phase shifter under the light shielding pattern is also removed at the same time.

This mask is set on the i-line stepper, and
A line resist (ip-1800, manufactured by Tokyo Ohka) is patterned.

Next, after development, this pattern is observed using, for example, an SEM length measuring device. As a result, the modified auxiliary opening did not show any change compared to the defect-free portion. Further, even if the exposure amount and the focus position are changed, no change is observed.

In the case where the pseudo shifter residual defects having the same defect pattern are still milled by FIB, the line portion transferred to the resist pattern becomes thick under the influence of Ga stain when the proper exposure amount is 160 mj / cm ^2. Become. However, I could not reach the bridge between the lines. Next, when the exposure amount is 140 mj / cm ² or less, a bridge is generated between the lines. Further, it has been confirmed that a bridge is generated at an exposure dose of 160 mj / cm ² in the pattern in which the shifter residual defect remains.

Next, the method of repairing the mask when the shifter residual defects are not removed is the same as the method of repairing when there is a shifter hole defect portion, which will be described below, and will be described later.

Next, a second embodiment of the present invention, which is a method of repairing a mask in the case where the phase shifter region has a shifter hole defect portion, will be described with reference to FIGS. 5 and 6.

First, the glass substrate 41 is used as the substrate. A phase shifter 42 is formed on the substrate 41, and a light shielding pattern 44 is formed on the phase shifter 42. At this time, the method for forming each thin film is the same as the method for the shifter residual defect, and thus the description thereof is omitted. After that, each film is patterned by any appropriate method to form the opening 46. A shifter hole defect portion 48 is provided at the center of the region of the phase shift 42. The size of this hole defect is set to 0.2 μm □ ((A) of FIG. 5 and (A) of FIG. 6).

Next, a light shielding material is embedded in the shifter hole defect portion 48 to form a light shielding film 50. This light-shielding material is decomposed using, for example, a carbon compound-based hexane (CH ₃ (CH ₂ ) ₄ CH ₃ ) to form carbon. In addition, this light-shielding film 5
The thickness of 0 is about 300 nm. At this time, the film may be formed regardless of the thickness of the film (FIG. 5B and FIG. 6B).

Next, a part of the light shielding pattern adjacent to the hole defect portion 48 is removed by the FIB method or the lithography method. The removed portion is referred to as an auxiliary opening 47. In this case, the phase shifter 4 below the light-shielding pattern
2 is left (FIG. 5 (C) and FIG. 6 (C)).

The light intensity distribution is measured using the defective mask thus formed. The simulation conditions at this time are exactly the same as those for the residual defect portion. The results are shown in FIGS. 7 (A), (B), (C),
Shown in (D), (E) and (F).

From this figure, if there is a shifter hole defect portion, the contour line 104 of the light intensity is disturbed and the light intensity waveform 106 is also lowered ((A) and (B) of FIG. 7).

Next, FIGS. 7C and 7D show the case where the light shielding film is formed. As a result, the light intensity is slightly improved as compared with the case where there are hole defects. It is considered that this is because the phase shifter improves the phases in the same direction.

Next, FIGS. 4E and 4F show the case where the auxiliary opening 47 is provided in the light shielding pattern.
At this time, the size of the auxiliary opening is 0.1 μm × on the substrate.
The thickness is set to 0.3 μm, and both sides of the light shielding pattern are opened. With such a correction, the light intensity distribution is restored to a defect-free state.

Next, referring to FIGS. 8 and 9, a third embodiment of the present invention which is a mask repairing method in the case where the shifter hole defect portion 48 in the phase shifter 42 is large enough to be adjacent to the light shielding pattern. This will be described with reference to FIGS. 8 and 9.

A glass substrate is used as the substrate. The phase shifter 42 and the light shielding pattern 44 are formed on this substrate. Further, an opening 46 is formed in a predetermined area. Further, a shifter hole defect portion 48 is generated in the area of the phase shifter 42 ((A) of FIG. 8).

Next, a light shielding material is embedded in the shifter hole defect portion 48 to form a light shielding film 50. Further, a part of the light-shielding film pattern is removed from the adjacent part of the hole defect part by using the FIB method or the lithography method. At this time, the lower phase shifter is left. The portion obtained by removing a part of the light shielding film pattern is referred to as an auxiliary opening 47 ((B) of FIG. 8).

Next, a second auxiliary opening 52 is provided on the opposite side of the auxiliary opening 47 and the light shielding pattern. The removal method at this time is performed by milling by FIB, a lithography method, or the like ((C) of FIG. 8).

FIG. 9 shows the result of measuring the light intensity distribution of the mask pattern thus formed. In the figure,
(A) and (B) show the light intensity distribution when the auxiliary opening 47 is provided in the hole defect portion. When this is seen, the distortion portion 108 is observed in the dotted line portion on the right side when viewed from the center of the contour line, and the light transmitting portion is slightly widened ((A) in FIG. 9).

Next, FIGS. 9C and 9D show the case where the light-shielding pattern is provided with the second auxiliary opening. According to this, the distortion portion 108 is corrected. This modified distortion section becomes 110. As a result, a light intensity distribution equivalent to that without defects can be obtained.

In order to confirm the effect of this simulation, a mask intentionally having a shifter hole defect portion is prepared and the mask is corrected. This mask correction method is performed using a method similar to that used for the residual defect portion. Therefore, the description of the correction method is omitted here.

As a result, in the case where the mask is corrected by providing the auxiliary opening, no difference occurs when the resist pattern is examined as compared with the case where there is no defect.

In the case where the light-shielding material having the same defective portion is buried, the line portion of the resist pattern becomes thick when the exposure amount is 160 mj / cm ² . However, it did not reach the bridge. Further, when a part of the light shielding pattern is removed and an auxiliary opening is provided, the line portion of the resist pattern becomes thick when the exposure amount is 160 mj / cm ² . However, it did not reach the bridge.

For those having hole defects, the exposure amount is 16
At 0 mj / cm ² , a bridge is generated between the lines.
When the exposure amount is increased to 230 mj / cm ² , the bridge between the lines disappears, but the exposure amount of other pattern regions is overexposed, so that the line portion becomes thin and some of them collapse.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 10 and 11 which is a method of correcting a light-shielding film after forming a light-shielding film in a shifter residual defect portion and then providing an auxiliary opening portion in the light-shielding pattern.

The method of forming the phase shifter 34, the light shielding pattern 32 and the opening 30 using a glass substrate as the mask substrate is the same as in the case of FIG. 2 and FIG. Therefore, the forming method will be described with reference to FIG. The shifter residual defect portion 36 is filled with a light shielding material. It is preferable to form the light-shielding film 38 by using carbon compound-based hexane ((B) of FIG. 10).

Next, a part of the light shielding pattern adjacent to the defective portion is removed to form the auxiliary opening 40. As the removing method, for example, the FIB method or the lithography method is used. The results of forming a resist pattern using the mask thus formed are shown in FIGS. 10B and 10D.
Shown in.

10A and 10B show the light shielding film 3
When there is 6, the resist pattern formed using this mask has a pestle pattern. But,
When the auxiliary opening is provided, the same resist pattern as when there is no defect is formed ((C) and (D) in FIG. 11).

Next, a fifth embodiment of the present invention, which is a correction method in the case where the light-shielding pattern is below the phase shifter in the opening as the transmissive region, will be described with reference to FIG.

A glass substrate 60 is used as the mask substrate, and a light-shielding pattern 62 is formed on the substrate 60.
A phase shifter 64 is provided. The method of forming each film is the same as in FIG.

Next, the shifter residual defect portion 68 is removed by FIB. At this time, Ga stain remains. This area is defined as a Ga stain remaining area 70.

Next, a part of the light shielding pattern adjacent to the defective portion is removed. This removed portion is used as the auxiliary opening 72 ((C) of FIG. 12). Even if the mask thus formed is used, a resist pattern similar to that obtained when there is no defect can be obtained.

Next, when removing the shifter residual defect portion,
FIG. 13 shows a sixth embodiment of the present invention, which is a mask correction method in which the mask substrate is milled excessively to the extent that recesses are formed.
And it demonstrates using FIG. This correction method solves the problem that minute irregularities are generated on the lower glass substrate when milling the shifter residual defect portion. In the figure, the same components as those in FIGS. 2 and 3 are designated by the same reference numerals.

FIG. 13 is a plan view for explaining the mask correcting method of the present invention, and FIG. 14 is a sectional view thereof.

13 (A) and 14 (A), a phase shifter 34 and a light shielding pattern 32 made of chromium (Cr) or the like are used on a glass substrate 31. The light-shielding pattern 32 is a repeating pattern having a width of 3 μm and a pitch of 6 μm, and has a line and space of 0.3 μm on the wafer when a 10: 1 stepper is used. The space existing between the light shielding patterns 32 is the opening 30 forming a part of the transmissive region.

The mask having the above-mentioned defective portion is corrected as follows.

First, the shifter residual defect portion 36 exists 2
The shifter residual defect portion 36 and the glass substrate 31 located in the 2.4 μm square region, which is wider than the μm square region, are continuously milled using the FIB mask repairing device. At this time, the shifter residual defect portion 36 is completely removed, and at the same time, the surface of the glass substrate 31 is shaved by about 50 nm and the surface roughness of the glass substrate 31 caused by milling is removed.
(FIGS. 13 (B), 14 (B) and (C)) The FIB conditions at this time are as follows: acceleration voltage 120 kV, ion current 12
It is set to 0 pA.

Next, by irradiation with C ₆ H ₁₀ gas and Ga ions in a 2.6 μm square area wider than the milled 2.4 μm square area by using a FIB mask repair device, as shown in FIG.
The light shielding film 50 as described with reference to FIG. 6 is formed. (Fig. 13
(D) and FIG. 14 (D)) Next, using the FIB mask repair device, the light shielding film pattern 32 adjacent to the light shielding film 50 is formed.
And the phase shifter 34 located thereunder,
The auxiliary opening 40 is formed. The size of the light-shielding pattern 32 to be cut at this time is about 1.6 μm in width and 3.0 μm in length. (FIG. 13 (E) and FIG. 14 (E)) Above, the correction of the defective mask was completed.

Next, this mask was set on an i-line stepper, and the i-line resist was patterned.

Then, this resist was developed, and the patterned pattern was evaluated using a SEM length measuring device.

As a result, the corrected auxiliary opening did not show any change as compared with the defect-free portion.

The shifter residual defect portion 3 having the same pattern is also used.
In the case where only the glass substrate 6 was removed and the lower glass substrate 31 was not shaved, the resist pattern was thick around the defective portion when the proper exposure amount was 160 mj / cm ² .

At an exposure dose of 140 mj / cm ² , a bridge was generated between the lines.

When the focus is shifted, the exposure amount 16
Even at 0 mj / cm ² , a bridge was generated between the lines.

Next, the size of the shifter residual defect 36 is set to 0.
The same evaluation as above was performed by changing from 5 μm □ to 3.0 μm □. The area where the light shielding film 50 is formed is 3.0 μm.
The size of the light-shielding pattern 32 fixed to □ and scraped off was fixed to a width of 1.6 μm and a length of 3.0 μm.

As a result, the resist pattern was good with no bridges.

As described above, according to the present invention, since the glass substrate is also ground so as to absorb the surface roughness generated when removing the shifter residual defect, it is possible to prevent the peeling of the light shielding film. .

Therefore, according to the present invention, it is possible to form a resist pattern with higher accuracy than the correction method described with reference to FIGS.

[0101]

As is apparent from the above description, according to the method of repairing the phase shift mask of the present invention, when the defective portion is repaired, the light transmittance of the repaired area is lowered. The light intensity of the transmitted light that has passed through this region is reduced. Therefore, when the mask pattern of the phase shift mask is projected onto the wafer by the reduction projection exposure apparatus, the light intensity distribution at the image forming position of the projection optical system has a defect in the light intensity at the position corresponding to the corrected region. Therefore, the light intensity is smaller than the light intensity corresponding to the uncorrected region (the light intensity under normal conditions).

However, according to the present invention, since the auxiliary opening is formed in the light-shielding pattern adjacent to the defective portion, that is, the corrected area, the transmitted light passing through the auxiliary opening is transmitted through the corrected area. In order to compensate for the decrease in the light amount of the light, the light intensity at the corresponding image forming position is increased to the square light intensity at all times, so that it is possible to form a predetermined resist pattern as designed.

Further, after the shifter residual defective portion existing in the transmission region of the opening is removed by using FIB, a part of the light shielding pattern adjacent to this defective portion is removed. By such mask correction, the Ga stain remaining region remains in the transmissive region of the opening. Therefore, the transmittance of this region is lowered. In order to improve this, a part of the light shielding pattern near the shifter residual defect portion is removed by using FIB. At this time, the phase shifter under the light shielding pattern is removed. By such a correction method, the amount of decrease in the transmittance in the Ga stain remaining region can be compensated for by the auxiliary opening, so patterning equivalent to that of a defect-free mask is possible.

Further, since this mask correction can be performed only by FIB milling, low cost and high throughput correction can be performed. Further, even if the shifter residual defect portion is covered with the light shielding material and a part of the light shielding pattern adjacent to the defect portion is removed, the same effect as the above-described result can be obtained.

Next, when the transmission region is a phase shifter and the defective portion is a shifter hole defective portion, the shifter hole defective portion is filled with a light shielding material, and then a part of the light shielding pattern close to the hole defective portion is subjected to FIB or lithography. To remove. At this time, the phase shifter under the light shielding pattern is left as it is. Further, it is preferable that the area of the light-shielding film filled with the light-shielding material is equal to the area of removal of a part of the light-shielding pattern. Since the decrease in the transmittance of the defective portion can be compensated by such mask correction, patterning equivalent to that of a defect-free mask can be obtained. Further, unlike the conventional case, since two shifter layers are not required, the cost can be reduced, and the problem of adhesion between the main shift layer and the sub shifter layer can be solved. Further, there is an advantage that the existing correction device can be used for this correction.

[Brief description of drawings]

1A to 1D are plan views for explaining a basic process of an embodiment of the present invention.

2A to 2C are plan views showing a forming process for explaining the first embodiment of the present invention.

3 (A) to 3 (C) are cross-sectional views showing a forming process for explaining the first embodiment of the present invention.

FIGS. 4A to 4F are light intensity distribution curve diagrams simulating the steps of the first embodiment of the present invention.

5 (A) to 5 (C) are plan views showing a forming process for explaining a second embodiment of the present invention.

6A to 6C are cross-sectional views showing a forming process for explaining a second embodiment of the present invention.

7 (A) to (F) are light intensity distribution curve diagrams simulating the steps of the second embodiment of the present invention.

FIG. 8A to FIG. 8C are plan views showing a forming process for explaining a third embodiment of the present invention.

9A to 9D are light intensity distribution curve diagrams simulating steps (B) and (C) of the third embodiment of the present invention.

10A to 10C are plan views showing a forming process for explaining a fourth embodiment of the present invention.

11A to 11D are diagrams in which the masks in the steps (B) and (C) of the fourth embodiment of the present invention are formed into resist patterns.

12A to 12C are cross-sectional views showing a forming process for explaining a fifth embodiment of the present invention.

13A to 13D are plan views showing a forming process for explaining a sixth embodiment of the present invention.

14 (A) to (E) are cross-sectional views showing a forming process for explaining a sixth embodiment of the present invention.

[Explanation of symbols]

 10 Openings 12 Phase Shifter 14 Light-shielding Pattern 16 Shifter Residual Defects 18 Ga Stain Remaining Region 19 Auxiliary Opening 20 Shifter Hole Defects 22 Auxiliary Opening 24 Light-shielding Film 30, 66 Opening 31, 41, 60 Glass Substrate 32, 44 , 62 light-shielding pattern 34, 42, 64 phase shifter 36, 68 shifter residual defect portion 37 light-shielding film 38, 70 Ga stain residual region 40, 47, 72 auxiliary opening 48 shifter hole defect portion 50 light-shielding film 52 second auxiliary opening Part 100, 104 Light intensity contour line 102, 106 Light intensity waveform 108 Distortion part 110 Distortion correction part

Claims (7)

[Claims] 1. A phase shift mask comprising a mask substrate and a light-shielding pattern and a phase shifter, and an opening where the light-shielding pattern and the phase shifter are not provided and the phase shifter respectively form a light transmission region. In repairing the defective portion of (1), (a) the step of repairing the defective portion existing in the transmissive region, and (b) the step of removing a part of the light shielding pattern adjacent to the defective portion to form the auxiliary opening portion. A method of modifying a phase shift mask, comprising: 2. The method of repairing a phase shift mask according to claim 1, wherein when the transmission region is an opening and the defect is a shifter residual defect, the correction in the step (a) is FIB.
A method of repairing a phase shift mask, characterized in that the shifter residual defect portion is removed by using. 3. The method of correcting a phase shift mask according to claim 1, wherein when the transmission region is a phase shifter and the defective portion is a shifter hole defective portion, the correction in the step (a) includes A method of repairing a phase shift mask, which comprises filling a defect portion of a shifter hole with a light shielding material. 4. The method of repairing a phase shift mask according to claim 1, wherein when the transmission region is an opening and the defect is a shifter residual defect, the repair in the step (a) is A method for repairing a phase shift mask, which is performed by providing a light-shielding film that covers the shifter residual defect portion. 5. The method of repairing a phase shift mask according to claim 5, wherein after the hole defect portion is filled with a light-shielding material, the step (b) is performed by modifying the light-shielding pattern close to the shifter hole defect portion. A method of repairing a phase shift mask, comprising: providing a second auxiliary opening in a part of the light-shielding pattern on the side opposite to the auxiliary opening from which a part has been removed. 6. The method of repairing a phase shift mask according to claim 5, wherein carbon compound-based hexane is used as a light shielding material for filling the shifter hole defect portion. 7. The method of repairing a phase shift mask according to claim 1, wherein the repairing of (b) is performed by using a light-shielding film in which a removal area of a part of the light-shielding pattern adjacent to the shifter defect is filled with a shifter hole defect. A method of correcting a phase shift mask, which is performed by making it equal to the area.