JPH08328239A - Method for removing projecting defect of phase difference mask - Google Patents

Abstract

PURPOSE: To provide a method for removing projecting defects without damaging the mask parts near the projecting defects, on the under side of the projecting defects and in the periphery of the projecting defects or to exactly remove only the projecting defects. CONSTITUTION: A protective film 22 covering the entire surface on the upper side of the phase difference mask 100 in which the projecting defect 14 arises in the recessed region of a mask substrate 10 having ruggedness is formed. The protective film having the removal speed at the time of irradiation with a convergent ion beam approximate to the removal speed of the projecting defect 14 is used as the protective film 22. The convergent ion beam is thereafter radiated toward the region to be irradiated from the protective film side to remove the part of the region 24 to be irradiated with the convergent ion beam. The irradiation with the convergent ion beam is ended at the point of time when the protective film part 22a on the periphery of the projecting defect is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing convex defects on a retardation mask.

[0002]

2. Description of the Related Art Recently, in order to remove a convex defect generated on a phase difference mask (sometimes referred to as a phase shift photomask or a phase shift photomask), a focused ion beam (FIB (Focused Ion) is used. (Beam))) Equipment is beginning to be used. In this case, first, a defect inspection machine is used to detect a convex defect generated in the mask, and data regarding the coordinate position and size on the mask is collected. Then, using a FIB device, a gallium (Ga) ion beam is focused on the convex defect in a gas atmosphere having reactivity with the convex defect, such as XeF ₂ , while scanning the convex defect. The convex defects are removed.
At this time, secondary electrons and / or secondary ions from the convex defect are monitored by a detector to detect the end point of removal of the convex defect. In this way, the convex defect of the phase difference mask is removed (reference: “SPIE, Vol. 1671,
224 (1992) ").

[0003]

However, when the convex defect is removed by using the Ga ion beam, not only the mask portion below the convex defect but also the vicinity thereof is damaged by the Ga ion beam. Suffer. For example, Ga stain is generated on the mask substrate below the convex defect.

Further, when the convex defects are removed by a Ga ion beam in a XeF ₂ gas atmosphere, the masked portion around the convex defects, for example, the mask substrate is also etched by the F ions generated during the removal. Therefore, a phase error may occur.

Further, in general, the convex defect has a variation in film thickness, and it is difficult to accurately set the removal depth by time control. If the mask portion is made of the same material or a similar material, the above method causes a problem. That is,
In such a case, no change occurs in the detection signal in the convex defect and the mask portion below the convex defect. Therefore, it is difficult to remove only the convex defect, and the mask portion below the convex defect may also be removed.

Therefore, in removing the convex defect using the FIB, there are the following first to fifth problems. And at least one of these first to fifth problems
It was desired to develop a method for solving one problem, and in some cases, a plurality of problems.

First, the convex defect is removed without damaging the mask portion near the convex defect.

Secondly, the convex defect is removed without damaging the mask portion below the convex defect. Further, desirably, thirdly, the convex defect is removed without damaging the mask portion around the convex defect.

Fourthly, even if the convex defect and the detection signal in the mask portion below the convex defect do not change, only the convex defect is accurately removed.

Fifthly, preferably, in the case of using a focused ion beam to remove a convex defect generated in contact with the boundary with the convex region in the concave region of the retardation mask having an uneven surface, Remove only convex defects.

[0011]

Therefore, according to the method of removing the convex defect of the phase difference mask of the present invention, in order to solve the first problem, the convex shape generated on the upper surface of the phase difference mask is solved. In removing defects using a focused ion beam, first, a protective film covering the entire upper surface of the mask is formed. Then, the focused ion beam is irradiated toward the region including the convex defect and the periphery thereof from the protective film side to remove the irradiated region portion of the focused ion beam. Then, the irradiation of the focused ion beam is terminated when the convex defect is removed.

Preferably, in addition to the first problem,
Further, in order to solve the fourth problem, it is preferable that the irradiation of the focused ion beam is ended when the protective film portion around the convex defect is removed.

Further, preferably, in order to solve the second and third problems in addition to the first and fourth problems, the irradiation of the focused ion beam causes etching reactivity with respect to the convex defect. Is preferably performed in a gas atmosphere having

Further, in order to solve the fifth problem in addition to the first problem, the convex defect generated in contact with the boundary with the convex region in the concave region of the phase difference mask having the unevenness on the upper surface. In the case of removing by using a focused ion beam, first, a protective film covering the entire upper surface of the mask is formed. afterwards,
The focused ion beam is irradiated toward the region including the convex defect and the periphery thereof from the protective film side to remove the irradiated region portion of the focused ion beam. Then, when the protective film portion on the convex area is removed, the boundary between the convex area and the concave area is detected,
After that, the focused ion beam is irradiated from the protective film side toward the region including the convex defect and the periphery thereof in the concave region with the boundary as a boundary, and the irradiation target region portion of the focused ion beam is removed. Then, when the convex defect or the protective film portion around the convex defect in the concave region is removed, the irradiation of the focused ion beam is terminated.

Further, in addition to the first and fifth problems, the above-mentioned method may be used to solve the fourth or second and third problems.

In order to solve the first problem, the following method may be used. First, a protective film that covers the entire upper surface of the mask is formed. Then, the focused ion beam is irradiated toward the region including the convex defect and the periphery thereof from the protective film side to remove the irradiated region portion of the focused ion beam. Then, the irradiation of the focused ion beam is terminated when the protective film portion on the defect is removed. After that, the convex defects are removed by etching using the protective film after the irradiation of the focused ion beam as a mask.

[0017]

According to the method of removing the convex defect of the retardation mask of the present invention described above, when the convex defect generated on the upper surface of the retardation mask is removed by using the focused ion beam,
A protective film covering the entire upper surface of the retardation mask is used. Since this protective film is also formed around the convex defects, when the convex defects are removed by irradiation with the focused ion beam in the subsequent steps, the mask portion near the convex defects is Protected from irradiation.

When the irradiation target area is removed by irradiation with the focused ion beam in a gas atmosphere having etching reactivity with the convex defect, the focused ion beam is below the convex defect. Damage to the mask part of
This gas reacts with the damaged part and is removed. Further, since this protective film is also formed around the convex defect, the mask portion around the convex defect is not damaged by this gas.

Further, when the irradiation of the focused ion beam is ended when the protective film portion around the convex defect is removed, the boundary between the protective film portion and the mask portion can be easily detected. Therefore, even when the detection signal in the convex defect and the mask portion below the convex defect does not change, only the convex defect can be accurately removed.
That is, even if it is difficult to accurately set the processing depth by controlling the time because the film thickness of the convex defect varies, the convergent ions are removed when the protective film portion around the convex defect is removed. The convex defect can be removed by ending the irradiation of the beam.

Further, in removing the convex defect generated in contact with the boundary with the convex region in the concave region of the retardation mask having the unevenness on the upper surface by using the focused ion beam, the protection on the convex region is performed. The boundary between the convex region and the concave region is detected when the film portion is removed, and then the focused ion beam is irradiated toward the region including the convex defect in the concave region and its periphery with the boundary as a boundary. . In this way, the boundary between the convex area and the concave area can be easily detected, and then, when the focused ion beam is irradiated toward the area including the defect in the concave area and its periphery with this boundary as a boundary, the convex area is formed. Even if the convex defect is formed in contact with the boundary between and, only the convex defect can be removed.

In another method for removing the convex defect generated on the upper surface of the phase difference mask, irradiation of the focused ion beam is terminated when the protective film portion on the convex defect is removed. After that, the convex defects are removed by etching using the protective film as a mask. In this way, since the convex defects are removed by etching, the convex defects can be easily removed.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the drawings used for the description merely schematically show the shapes, sizes, and arrangement relationships of the respective constituent components to the extent that the present invention can be understood. Further, in each of the drawings used for the description, the same components are denoted by the same reference numerals. Further, the materials used, the forming method and the numerical conditions described in the following description are merely preferred examples of the present invention. Therefore, it should be understood that the present invention is not limited to only these conditions.

1. First Embodiment FIG. 1 shows a phase difference mask used in the first embodiment.
1A is a cross-sectional view taken along the line I-I in FIG. 1B, and FIG. 1B is a plan view thereof.

As shown in FIGS. 1A and 1B, the retardation mask 100 used in the first embodiment is a substrate digging type retardation mask, which is a mask substrate 10 and a light shielding pattern 1.
2 and. As a material of the mask substrate 10, a material that transmits light, for example, quartz (quart).
z: quartz) is used, and chromium (Cr) is used as the material of the light shielding pattern 12. Then, the convex defect 14
Are generated in the concave region 16 of the mask substrate 10 having irregularities. Further, the light-shielding pattern 12 is in contact with the concave region 16 on the convex region 18 on the upper surface of the mask substrate having the irregularities,
It is provided with a certain width. The concave region 16 of the phase difference mask 100 having such a structure is a phase shifter region, and the convex region 18 is divided into a light-shielding pattern region 18a provided with a light-shielding pattern and a light-transmitting region 18b exposing the mask substrate 10. . Therefore, the convex defect 14 is generated in the phase shifter region. The light-shielding pattern 12 and the convex defect 14 in FIG. 1B are not sectional views,
It is shown with hatching.

Next, a general method of manufacturing a mask having such a structure will be briefly described. First, a plate having a flat surface to be a mask substrate is prepared. After that, a light-shielding pattern is formed on one surface of this flat plate by using a usual mask manufacturing method. Then, using a resist pattern having an opening in a portion to be a phase shifter area, a concave area to be a phase shifter area is formed by etching.
Then, the resist pattern is removed. The mask is manufactured as described above. Then, for example, when the resist pattern used for forming the phase shifter region is not accurately formed, or when dust is present in the opening portion of the resist pattern, there are convex defects in the phase shifter region. Occurs. The convex defect generated in this case is the same material as the mask substrate. Since the retardation mask 100 used in the first embodiment is also manufactured by using such a method, the convex defect 14 is made of the quartz material which is the material of the mask substrate 12. Then, such a convex defect 1
There are variations in the film thickness of No. 2.

Next, a method of removing the convex defect 14 generated on the upper surface of the phase difference mask 100 by using a focused ion beam will be described below. 2 (A) to (C)
FIG. 4 is a process diagram of removing the convex defect 14 shown by a cross-sectional view corresponding to a cross section taken along line I-I in FIG. Further, FIGS. 3A and 3B are similar to FIG.
9A and 9B respectively correspond to (A) and (B) and are process diagrams (shown in plan views) for removing the convex defect 14 when viewed from the upper surface of the phase difference mask 100.

First, using the defect detector, the convex defect 14
To obtain coordinate data. Then, based on the obtained coordinate data, the irradiation area of the ion beam at the time of irradiation of the focused ion beam in the subsequent step is determined. Note that the method of determining the coordinate position on the phase difference mask 100 may be performed by a method generally used in the past, and the present invention is not characterized by this method of determining the coordinate position. Omit it.

Next, a protective film 22 is formed so as to cover the entire upper surface of the mask 100 (FIGS. 2A and 3).
(A)). As the protective film 22, in this first embodiment, a novolac-based positive resist, for example, PFI-15 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) was used. Then, before the focused ion beam irradiation, the protective film 22 was heated to about 80 ° C., and the removal rate of the protective film 22 during the Ga ion beam irradiation was brought close to the removal rate of the convex defects 14. Protective film 2
2 is not limited to this, and other organic films can be used. However, as in the first embodiment, it is preferable to use the protective film 22 having plasma resistance rather than the convex defect 14. In this case, by controlling the heating temperature of the protective film 22 before the irradiation of the focused ion beam, not only the removal rate of the convex defects 14 and the removal rate of the protective film 22 can be made closer but also the protection rate can be improved. There is an advantage that the removal rate of the film 22 can be slower than the removal rate for the convex defect 14. Moreover, not only can the removal rate of the convex defect 14 and the removal rate of the protective film 22 be close to each other, but the removal rate of the protective film 22 is slower than the removal rate of the convex defect 14. There is a merit that you can also do it.

When the removal rate of the protective film 22 is close to the removal rate of the convex defects 14, even when the Ga ion beam irradiation is performed on both the convex defects 14 and the protective film 22, the convex defects are formed. The defects 14 and the protective film 22 are removed at a uniform rate. Therefore, if the Ga ion beam irradiation is terminated at the time when the protective film 22a around the convex defect is removed, only the convex defect 14 can be accurately removed. The protective film 22 is made of the same material as that of the convex defect 14 and the mask portion (the mask substrate in the first embodiment) below the convex defect 14, that is, the FIB. When the detector for detecting secondary electrons and / or secondary ions installed in the apparatus (not shown) cannot distinguish between the convex defect 14 and the mask portion below the convex defect 14. Is effective for.

Further, the removal rate of the protective film 22 is higher than that of the convex defect 1
If the removal speed is slower than that for No. 4, the irradiation of the focused ion beam is terminated when the convex defect 14 is removed.
The protective film 22 as described above includes the convex defects 14 and the convex defects 14.
It is recommended to use it when the material of the lower mask part is different.

After that, the sample covered with the protective film 22 was FI.
Set to a predetermined position of the B device (sometimes referred to as loading). Then, the focused ion beam (FIB) is irradiated from the side of the protective film 22 toward a region including the convex defect 14 and its periphery (hereinafter, also referred to as irradiation target region 24), and the focused ion beam (FIB) is irradiated. The portion of the irradiated region 24 in () is removed. The irradiation area 24 of the focused ion beam (FIB) is obtained from the coordinate data of the convex defect 14. Then, when the convex defect 14 and the protective film portion 22a around the convex defect 14 are removed, the irradiation of the focused ion beam (FIB) is finished (FIG. 2).
(B), FIG. 3 (B)).

In the first embodiment, a gallium (Ga) ion beam was used as the focused ion beam, and the Ga ion beam was irradiated in a xenon fluoride (XeF ₂ ) atmosphere. In this case, the Ga ion beam irradiation is Xe.
F ₂ gas pressure, accelerating voltage, current, beam spot size, etc. were set to predetermined conditions. Then, a Ga ion beam was irradiated while scanning a predetermined region, and during scanning irradiation, secondary ion signals and secondary electron signals from the irradiated region 24 were detected at any time. In this way, when the convex defects are removed by irradiating the Ga ion beam, the protective film 2
2 protects the mask portion near the convex defect 14, that is, the surface of the mask substrate from Ga ion beam irradiation. Therefore, it is considered that the generation of Ga stain in the portion of the mask substrate near the convex defect 14 is alleviated. In this case, the vicinity of the convex defect 14 is within the concave region 16 where the convex defect 14 occurs, and in some cases, the convex region 18 is also included. Also, XeF ₂ gas is
It has etching reactivity with the quartz material which is the material of the convex defect 14 of the first embodiment. For this reason,
When the Ga ion beam irradiation is performed in the XeF ₂ gas, generation of Ga stain in the mask portion below the convex defect 14 can be relaxed. Further, the protective film 22 also protects the etching of the mask portion around the convex defect due to the fluorine ions generated during the Ga ion beam irradiation. In this case, the entire surface of the mask substrate 10 on which the light shielding film pattern 12 is not provided is protected by the fluorine ions. In addition, when the generation of Ga stain does not adversely affect the retardation mask, the Ga ion beam irradiation does not necessarily have to be performed in the XeF ₂ gas atmosphere. Further, in the first embodiment, the surface of the protective film 22 in the irradiated region 24 is removed by the Ga ion beam, and finally the protective film portion 22 around the convex defect is formed.
Irradiation of the focused ion beam was completed when a was removed to the bottom surface of the concave region 16. The reason why the protective film portion 22a around the convex defect is removed is that the protective film portion 22a around the convex defect disappears and the signal from the protective film portion 22a disappears so that the Ga ion beam irradiation is changed. This is for the purpose of determining the end time, and how far away the protective film portion from the convex defect 14 is to be removed by the Ga ion beam may be arbitrarily determined according to the design. And
Since the removal rate at the time of irradiation of the focused ion beam is close to the removal rate of the convex defect 14 as the protective film 22,
The convex defect 14 and the protective film 22 are removed at a uniform rate. Therefore, only the convex defect 14 could be removed accurately. It should be noted that the protective film portion 22a around the convex defect in FIG. 3A is shown by hatching although it is not a cross-sectional view. In addition, in FIG. 2 (B) and FIG. 3 (B),
Reference numeral 221 denotes the FIB after the Ga ion beam irradiation is completed.
The irradiated protective film is shown.

After that, the remaining protective film 221 is entirely removed by using a known etching technique. The state after the entire surface is removed is shown in FIGS. 2 (C) and 3 (C). Note that FIG.
The light-shielding pattern 12 in (C) is not a cross-sectional view,
It is shown with hatching.

As described above, the convex defect 14 formed on the upper surface of the retardation mask 100 was removed by using the focused ion beam.

2. Second Example In the second example, the pressure of a gas having an etching reactivity with the convex defects 14, that is, XeF ₂ is used to remove the protective film 22 against the removal rate of the convex defects 14 in the second example. The speed ratio was controlled to be 0.7 to 1.3.
Otherwise, the retardation mask 1 is similar to the first embodiment.
The convex defect 14 generated on the upper surface of 00 was removed by using a focused ion beam. In the case of the second embodiment, as the protective film 22, one having more plasma resistance than the convex defects 14 such as PFI-15 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) was used. And before irradiation of the focused ion beam,
The protective film 22 was heated at a predetermined temperature. However, the removal rate of the protective film 22 does not necessarily have to approach the removal rate of the convex defect 14.

Empirically, in the phase shifter area of the phase difference mask 100, the allowable range of the phase error is π / maximum.
3 or less (reference: “Jpn. J. Appl. Phy
s. , Vol. 31 (1992), pp. 4143-4
149 ”and the literature:“ Jpn. J. Appl. Phy.
s. , Vol. 32 (1993), pp. 5892-5
899 ”). Then, when the film thickness of the convex defect 14 is equal to the depth of the concave region, the ratio of the removal rate of the protective film 22 to the removal rate of the convex defect 14 as described above, that is, (removal rate of the convex defect 14 / protection When the removal rate of the film 22) is in the range of 0.7 to 1.3, the phase error can be π / 3 or less.

For example, if the refractive index of the mask substrate 10 is 1.4
2, and the wavelength of light used for exposure is assumed to be 365 nm. In this case, the phase difference for light with a wavelength of 365 nm is π
Since the thickness is 4350Å, the depth of the concave area is 4
At 350Å, the phase error is zero. However, when the Ga ion beam irradiation is terminated at the time when the protective film 22a around the convex defect is removed, when the removal rate of the convex defect 14 is 70% of the removal rate of the protective film 22, about 1300.
The convex defect 14 remains with a thickness of Å. On the other hand, convex defect 1
When the removal rate of No. 4 is 130% of the removal rate of the protective film 22, the mask substrate 10 is excessively removed with a thickness of about 1300Å. Then, when the thickness at which the phase error with respect to the light having a wavelength of 365 nm is π / 3 is calculated from the equation (1), it is about
Since it is 50Å, the phase error can be π / 3 or less.

D = λ / (2 (n−1) × 3) ... (1) However, in (1), d is the thickness at which the phase error is π / 3,
λ is the exposure light wavelength, and n is the refractive index of the mask substrate.

3. Third Example In a third example, a novolac-based positive resist, such as PFI-15 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) was used as the protective film 22. Then, before the irradiation of the focused ion beam, the protective film 22 is heated to about 120 to 200 ° C., and G
The removal rate of the protective film 22 during the irradiation with the a-ion beam was set slower than the removal rate of the convex defects 14. Then, the Ga ion beam irradiation is performed by using XeF ₂ gas, which is a gas having etching reactivity with the convex defects 14, and O ₂ which is a gas having etching reactivity with the protective film 22.
It was carried out in a gas atmosphere. Other than that, the convex defect 14 generated on the upper surface of the retardation mask 100 was removed by using a focused ion beam in the same manner as in the first embodiment. Even when the protective film 22 whose removal rate is slower than the removal rate for the convex defects 14 is used, the Ga ion beam is applied in an atmosphere in which O ₂ gas, which is a gas having etching reactivity with the protective film 22, is present. Therefore, if the Ga ion beam irradiation is terminated when the protective film 22a around the convex defect 14 is removed, only the convex defect 14 can be accurately removed.

Also in the case of the third embodiment, when the film thickness of the convex defect 14 is equal to the depth of the concave region 16, the pressure of the O ₂ gas, which is a gas having etching reactivity with the protective film 22, is applied. Is controlled so that the ratio of the removal rate of the protective film 22 to the removal rate of the convex defects 14, that is, (removal rate of the protective film 22 / removal rate of the protective film 22) is 0.7 to 1.3, The same effect as the second embodiment can be obtained.

4. Fourth Example In the first example, the Ga ion beam irradiation was performed uniformly on the entire region 24 to be irradiated. On the other hand, in the fourth embodiment, the removal of the irradiated area 24 is
The ion beam irradiation amount was increased at the portion where the removal rate was relatively slow. For example, as the protective film 22, a novolac-based positive resist such as PFI-15 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) was used. Then, the protective film 22 is heated to about 120 to 200 ° C. before the irradiation of the focused ion beam, and the protective film 2 during the irradiation of the Ga ion beam is performed.
When the removal speed of the convex defect 14 is set to be slower when the removal speed of 2 is slower, the scan speed is slowed when the portion of the protective film 22a around the convex defect 14 is scan-irradiated. The boundary between the convex defect 14 and the protective film 22a around the convex defect is a secondary ion signal and / or a secondary electron when the convex defect 14 and the protective film 22a around the convex defect 14 are scan-irradiated. Judging from changes in signals, etc. In this way, the dose of ion beam irradiation can be increased. In addition, the beam current may be increased or the number of scans may be increased in order to increase the ion beam irradiation amount in the portion of the protective film 22a around the convex defect. as a result,
The convex defect 14 was able to remove the scale accurately.

5. Fifth Embodiment FIG. 4 shows a phase difference mask used in the fifth embodiment.
4A is a cross-sectional view taken along the line I-I in FIG. 4B, and FIG. 4B is a plan view thereof.

As shown in FIGS. 4A and 4B, the retardation mask 500 used in the fifth embodiment includes the mask substrate 10 and the light shielding pattern 12 as in the first embodiment. A material that transmits light, for example, a quartz (quartz) material, is used as the material of the mask substrate 10, and Cr is used as the material of the light shielding pattern 12. Then, the convex defect 14 is generated in the concave region of the upper surface of the mask substrate 10 having irregularities. However, in the case of the fifth embodiment, the light-shielding pattern region 18a provided in a constant width in the convex region 18 on the upper surface of the mask substrate 10 having the irregularities is in contact with the concave region 16.
The convex defect 14 is formed in contact with the boundary of the. The upper layer 14a of such a convex defect is made of the same material as the light shielding pattern 12, and the lower layer 14b is made of the quartz material which is the material of the mask substrate 10. Further, as in the case of the first embodiment, the retardation mask 50 having such a configuration is used.
The 0 concave region 16 is a phase shifter region, and the convex region 18 is a light shielding pattern region 1 in which the light shielding pattern 12 is provided.
8a and a light transmitting region 18b where the mask substrate 10 is exposed. Therefore, the convex defect 14 is generated in the phase shifter region. Note that the light-shielding patterns and the convex defects in FIG. 4B are shown by hatching although they are not sectional views.

The convex defect 14 as described above, that is, the concave region 16 of the retardation mask 500 having irregularities on the upper surface thereof.
In which the convex defect 14 generated in contact with the boundary with the convex region 18
A method of removing the beam using a focused ion beam will be described below. 5A to 5D show I of FIG. 4B.
It is a process of removing the convex defect 14 shown by a cross-sectional view corresponding to a cross section taken along line -I. Further, FIGS. 6A to 6D are plan views corresponding to FIGS. 5A to 5D, respectively, and the removal process of the convex defect 14 when viewed from the upper surface of the phase difference mask 500. It is a figure (it has shown by the top view).

First, the protective film 22 covering the entire upper surface of the mask 500 is formed through the same steps as those in the first embodiment (FIGS. 5A and 6A). In the fifth embodiment, the protective film 22 is a novolac-based positive resist, such as PFI-15 (trade name, manufactured by Sumitomo Chemical Co., Ltd.).
Was used. Then, before the focused ion beam irradiation, the protective film 22 was heated to about 80 ° C. to make the removal rate of the protective film 22 during Ga ion beam irradiation close to the removal rate of the convex defects 14.

After that, the focused ion beam (FIB) is directed toward the region including the convex defect 14 and its periphery to form the protective film 2.
Irradiation from the 2nd side, the first of the focused ion beam (FIB)
The portion of the irradiated area 26 is removed. Then, the convex region 18
When the upper protective film portion is removed, the convex area 18 and the concave area 1
The boundary with 6 is detected (FIG. 5 (B), FIG. 6 (B)).

In the fifth embodiment, as in the case of the first embodiment, a Ga ion beam is used as the focused ion beam, and the Ga ion beam is irradiated in the XeF ₂ gas atmosphere. Then, a predetermined region is irradiated with a Ga ion beam, and the secondary ion signal and / or the secondary electron signal from the first irradiated region 26 is detected at any time during scan irradiation to detect the boundary between the convex region 18 and the concave region 16. Was detected. In addition, in FIG. 5B and FIG. 6B, the arrow indicates the scanning direction of the Ga ion beam. In this case, the Ga ion beam was scanned in a direction orthogonal to the light shielding pattern 12 to irradiate the inside of the first irradiation region 26 with the Ga ion beam. In this way, the protective film portion in the first irradiated area 26 is gradually removed, and the light shielding pattern in the convex area 18 at the time when the convex area 18, that is, the protective film portion 22b on the light shielding pattern 12 is removed. The boundary between 12 and the phase shifter area which is the concave area 16 is detected. In this case, this boundary is determined by the signal change caused by the disappearance of the protective film portion 22b on the light shielding pattern 12 and the disappearance of the signal from the protective film portion 22b. More specifically, in the case of the fifth embodiment, the upper layer 14a of the convex defect 14 is made of the same material as that of the light-shielding pattern 12, and the boundary between the convex defect 14 and the light-shielding pattern 12 is separated from the protective film portion 22b. It cannot be directly determined from the signal change due to the disappearance of the signal. Therefore, the boundary between the light shielding pattern 12 and the phase shifter region in the convex defect nonexisting region 26a where the convex defect 14 does not exist is detected at the time of scanning a plurality of Ga ion beams, and the boundary is connected to form the light shielding pattern. The boundary between 12 and the phase shifter region 16 is determined. Note that FIG.
The protective film portion 22b on the light-shielding pattern 12 in (A) is shown by hatching although it is not a cross-sectional view. Further, in FIGS. 5B and 6B, the reference numeral 222 indicates the first
The first FIB-irradiated protective film after the Ga ion beam irradiation on the irradiated region 26 is completed is shown.

After that, as in the case of the first embodiment, the focused ion beam (FIB) is used as a boundary between the light-shielding pattern 12 in the convex region 18 and the phase shifter region in the concave region 16 as a boundary. Irradiation from a side of the protective film 12 toward a region (hereinafter, also referred to as a second irradiation region 28) inside the convex defect 14 and its periphery in 16 to generate a focused ion beam (FIB) 2 A part of the irradiated area 28 is removed. Then, the irradiation of the focused ion beam (FIB) is terminated when the convex defect 14 and the protective film portion 22a around the convex defect 14 are removed (FIG. 5C and FIG. 6).
(C)). The protective film portion 22a around the convex defect in FIG. 6B is shown by hatching although it is not a cross-sectional view. 5C and 6C, reference numeral 223 indicates the second FIB-irradiated protective film after the irradiation of the Ga ion beam onto the second irradiation region 28 is completed.

After that, the remaining protective film 223 is entirely removed by using a known etching technique. The state after the entire surface is removed is shown in FIGS. Note that FIG.
The light-shielding pattern 12 in (D) is not a cross-sectional view,
It is shown with hatching.

As described above, the convex defect 14 generated in contact with the boundary with the convex region in the concave region of the retardation mask 500 having the irregularities on the upper surface was removed by using the focused ion beam. In this case, even if the convex defect 14 is formed in contact with the boundary with the convex region 18, only the convex defect 14 can be easily removed.

6. Sixth Embodiment FIG. 7 shows a retardation mask 600 used in the sixth embodiment, and FIG. 7 (A) is a sectional view taken along the line I-I in FIG. 7 (B). 7B is a plan view thereof.

In the fifth embodiment, the case where the convex defect 14 is in contact with one light-shielding pattern 12 has been described, but in the sixth embodiment, the convex defect 14 has two light-shielding patterns 12.
7A and 7B in contact with is described.

In this case, when the protective film portion on the light shielding pattern 12 is removed, two boundaries between the light shielding pattern 12 in the convex region 18 and the phase shifter region 16 which is a concave region are detected. The light shielding pattern 12 and the phase shifter region 16
The boundary between and is detected in the same manner as in the fifth embodiment.
After that, as in the case of the fifth embodiment, the Ga ion beam is projected in the concave region 16 with the light-shielding pattern 12 in the convex region and the phase shifter region being the concave region 16 as the boundary. Irradiation is performed from the protective film 12 side toward the region including the defect 14 and its periphery, and the portion of the irradiation target region of the focused ion beam is removed. Then, when the convex defect 14 or the protective film portion around the convex defect 14 is removed, the irradiation of the focused ion beam is terminated. Therefore, the convex defect 1
Even when 4 is in contact with the two light shielding patterns 12,
Only the convex defect 14 can be easily removed.

When the two light-shielding patterns in contact with the convex defect 14 are parallel to each other, one of the boundaries between the light-shielding pattern 12 and the phase shifter region 16 and one boundary to the other boundary. The irradiation area of the ion beam after that may be set by detecting and obtaining the distance W of the above when detecting the Ga ion beam in the area where the convex defect 14 does not exist and in which the convex defect does not exist.

7. Seventh Embodiment FIG. 8 shows a phase difference mask used in the seventh embodiment.
8A is a cross-sectional view taken along the line I-I in FIG. 8B, and FIG. 8B is a plan view thereof.

As shown in FIGS. 8A and 8B, the retardation mask 700 used in the seventh embodiment is composed of the mask substrate 10 and the light shielding pattern 12 as in the case of the first embodiment. As a material of the mask substrate 10, a region that transmits light, for example, a quartz (quartz) material is used as a material of the mask substrate 10, and Cr is used as a material of the light shielding pattern 12. Then, the convex defect 14 is generated in the concave region 16 on the upper surface of the mask substrate 10 having irregularities. The upper layer 14a of the convex defect 14 is the light shielding pattern 12.
The lower layer 14b is made of the same material as the above, and is made of the quartz material which is the material of the mask substrate 10. Further, as in the case of the first embodiment, the concave region 16 of the phase difference mask 700 having such a structure is the phase shifter region, and the convex region 18 is the light shielding pattern region 18a in which the light shielding pattern 12 is provided. Then, the mask substrate 10 is divided into a light transmitting region 18b which is exposed. Therefore, the convex defect 14 is generated in the phase shifter region. It should be noted that the light shielding pattern 12 and the convex defect 14 in FIG. 8B are shown by hatching although they are not sectional views.

Next, a method of removing the convex defect 14 generated on the upper surface of the phase difference mask 700 by using a focused ion beam will be described below. FIG. 9 (A)-
8D is a process diagram of removing the convex defect 14 shown by a cross-sectional view corresponding to a cross section taken along line I-I in FIG. 8B. In addition, FIGS.
FIG. 9 is a process diagram (shown in plan view) of removing the convex defect 14 when viewed from the upper surface of the phase difference mask 700, corresponding to FIGS.

First, through the same steps as in the first embodiment, a protective film 22 having a flat upper surface is formed to cover the entire upper surface of the mask 700 (FIGS. 9A and 10A). .
As the protective film 22, in this seventh embodiment, a novolac-based positive resist, such as PFI-15 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) was used. Then, before the focused ion beam irradiation, the protective film 22 was heated to about 80 ° C. to make the removal rate of the protective film 22 during Ga ion beam irradiation close to the removal rate of the convex defects 14.

After that, the focused ion beam (FIB) is irradiated from the protective film 22 side toward a region including the convex defect 14 and its periphery (hereinafter, may be referred to as an irradiated region 30), and the irradiated region is irradiated. The 30 part is removed. And
Irradiation of the focused ion beam (FIB) is terminated when the protective film portion 22c on the convex defect 14 is removed (FIG. 9).
(B), FIG. 10 (B)). In the seventh embodiment, as in the first embodiment, a Ga ion beam is used as the focused ion beam, and the Ga ion beam is irradiated with oxygen (O 2).
₂ ) It was performed in a mixed gas atmosphere of gas and fluorine (F ₂ ) gas. In such a gas atmosphere, the protective film 22
It is possible to reduce the etching rate for the convex defect 14 by causing an etching reaction to the. Then, the Ga ion beam was irradiated while scanning a predetermined region, and the secondary ion signal and / or the secondary electron signal from the irradiated region 30 was detected at any time during the scanning irradiation. In this way, the protective film 12 portion of the irradiated region 30 is gradually removed, and the protective film portion 2 on the convex defect 14 is removed.
When 2c was removed, Ga ion beam irradiation was terminated. In this case, the protective film portion 22c on the convex defect 14 disappeared, and the signal change caused by the disappearance of the signal from the protective film portion 22c was used to determine the end point of Ga ion beam irradiation. The protective film portion 22c on the convex defect 14 in FIG. 10A is shown by hatching although it is not a cross-sectional view. Further, in FIGS. 9 and 10, reference numeral 224
Indicates the FIB-irradiated protective film after the Ga ion beam irradiation is completed.

After that, the convex defects 14 are removed by etching using the protective film 224 after the irradiation of the focused ion beam as a mask (FIGS. 9C and 10C). In the seventh embodiment, for example, the upper layer 14a of the convex defect 14 is
It was removed by wet etching using cerium ammonium nitrate and the upper layer 14b of the convex defect 14 was removed using hydrofluoric acid.

As described above, the convex defect 14 generated on the upper surface of the phase difference mask 700 was removed by using the focused ion beam. In this case, since the convex defect 14 is removed by etching, the convex defect 14 can be easily removed without damaging the mask portion near the convex defect.

Obviously, the invention is not limited to the embodiments described above. For example, in this embodiment, the phase difference mask having the configuration shown in FIGS. 1, 4, 7, and 8 is used as the phase difference mask, but the phase difference mask is not limited to this case. Further, as the convex defects, those generated when the quartz material to be the mask substrate is etched have been described, but the present invention is not limited to this, and the shifter material forming the phase shifter region, for example, spin-on-glass (SO.
The present invention can be applied to the convex defect made of G) and silicon nitride (SiN).

[0063]

As is apparent from the above description, according to the method of removing the convex defect of the phase difference mask of the present invention, the convex defect generated on the upper surface of the phase difference mask is focused by using the focused ion beam. A protective film covering the entire upper surface of the retardation mask is used for the removal. Since this protective film is also formed around the convex defects, when the convex defects are removed by irradiation with the focused ion beam in the subsequent steps, the mask portion near the convex defects is Protected from irradiation. Therefore, the convex defect can be removed without damaging the mask portion near the convex defect.

When the irradiation target area is removed by irradiation with the focused ion beam in a gas atmosphere having etching reactivity with the convex defect, the focused ion beam is below the convex defect. Damage to the mask part of
This gas reacts with the damaged part and is removed. Further, since this protective film is also formed around the convex defect, the mask portion around the convex defect is not damaged by this gas.

Further, when the irradiation of the focused ion beam is terminated when the protective film portion around the convex defect is removed, the boundary between the protective film portion and the mask portion can be easily detected. Therefore, even when the detection signal in the convex defect and the mask portion below the convex defect does not change, only the convex defect can be accurately removed.
That is, even if it is difficult to accurately set the processing depth by controlling the time because the film thickness of the convex defect varies, the convergent ions are removed when the protective film portion around the convex defect is removed. The convex defect can be removed by ending the irradiation of the beam.

Further, in removing the convex defect generated in contact with the boundary with the convex region in the concave region of the retardation mask having the unevenness on the upper surface by using the focused ion beam, the protection on the convex region is performed. The boundary between the convex region and the concave region is detected when the film portion is removed, and then the focused ion beam is irradiated toward the region including the convex defect in the concave region and its periphery with the boundary as a boundary. . In this way, the boundary between the convex area and the concave area can be easily detected, and then, when the focused ion beam is irradiated toward the area including the defect in the concave area and its periphery with this boundary as a boundary, the convex area is formed. Even if the convex defect is formed in contact with the boundary between and, only the convex defect can be removed.

In another method of removing the convex defect generated on the upper surface of the phase difference mask, the irradiation of the focused ion beam is terminated when the protective film portion on the convex defect is removed. After that, the convex defects are removed by etching using the protective film as a mask. In this way, since the convex defects are removed by etching, the convex defects can be easily removed.

[Brief description of drawings]

FIG. 1A is a sectional view of a retardation mask, and FIG.
[FIG. 3] is a plan view of a retardation mask.

2A to 2C are process diagrams for removing a convex defect shown by a cross-sectional view.

FIG. 3A to FIG. 3C are process diagrams for removing the convex defect shown by the top view.

FIG. 4A is a sectional view of a phase difference mask, and FIG.
[FIG. 3] is a plan view of a retardation mask.

5A to 5D are process diagrams for removing the convex defects shown by the cross-sectional views.

6A to 6D are process diagrams for removing the convex defect shown by the top view.

FIG. 7A is a cross-sectional view of a phase difference mask, and FIG.
[FIG. 3] is a plan view of a retardation mask.

FIG. 8A is a sectional view of a retardation mask, and FIG.
[FIG. 3] is a plan view of a retardation mask.

9A to 9D are process diagrams for removing a convex defect shown by the cross-sectional views.

10A to 10D are process diagrams for removing the convex defects shown in the top view.

[Explanation of symbols]

 10: Mask substrate 12: Light shielding pattern 14: Convex defect 14a: Upper layer of convex defect 14b: Lower layer of convex defect 16: Concave region 18: Convex region 18a: Light shielding pattern region 18b: Light transmitting region 22: Protective film 22a : Protective film around convex defect 22b: Protective film on light-shielding pattern 22c: Protective film on convex defect 24, 30: Irradiated region 26: First irradiated region 26a: Convex defect nonexistent region 100, 500, 700: Phase difference mask

Claims (11)

[Claims] 1. A step of forming a protective film covering the entire upper surface of the mask when removing a convex defect generated on the upper surface of the retardation mask by using a focused ion beam, and thereafter, A step of irradiating an ion beam toward a region including the defect and its periphery from the protective film side to remove an irradiation target region portion of the focused ion beam; and a step of removing the focused ion beam when the defect is removed. And a step of terminating the irradiation, the method for removing convex defects of a retardation mask. 2. A step of forming a protective film covering the entire upper surface of the mask in removing the convex defect generated on the upper surface of the phase difference mask by using a focused ion beam, and thereafter, Irradiating an ion beam toward the region including the defect and its periphery from the protective film side to remove the irradiated region portion of the focused ion beam, and the time when the protective film portion around the defect is removed And a step of terminating the irradiation of the focused ion beam with the method of removing a convex defect of a retardation mask. 3. When removing a convex defect generated in contact with a boundary with a convex region in a concave region of a retardation mask having irregularities on the upper surface by using a focused ion beam, Forming a protective film covering the entire surface, and then irradiating the focused ion beam toward the region including the defect and its periphery from the protective film side to remove the irradiated region portion of the focused ion beam. A step of detecting a boundary between the convex area and the concave area at the time of removing the protective film portion on the convex area, and then a focused ion beam within the concave area with the boundary as a boundary. There is a step of irradiating a region including the defect and its periphery from the protective film side, and removing the irradiation target region portion of the focused ion beam, and when the defect is removed, the focused ion beam Teru Method for removing the convex defect of the retardation mask which comprises a step of terminating the. 4. When removing a convex defect generated in contact with a boundary with a convex region in a concave region of a retardation mask having irregularities on the upper surface by using a focused ion beam, Forming a protective film covering the entire surface, and then irradiating the focused ion beam toward the region including the defect and its periphery from the protective film side to remove the irradiated region portion of the focused ion beam. A step of detecting a boundary between the convex area and the concave area at the time of removing the protective film portion on the convex area, and then a focused ion beam within the concave area with the boundary as a boundary. There is a step of irradiating from the protective film side toward a region including the defect and its periphery, and removing the irradiated region portion of the focused ion beam, in the concave region, around the defect. The protective film part Method for removing the convex defect of the retardation mask, characterized in that when it is removed by a step of terminating the irradiation of the focused ion beam. 5. The method for removing convex defects of a retardation mask according to claim 2, wherein a protective film having plasma resistance higher than that of the convex defects is used as the protective film. Method for removing convex defect of mask. 6. The method of removing a convex defect of a retardation mask according to claim 2 or 4, wherein the irradiation area of the focused ion beam is removed by etching reactivity with respect to the convex defect. A method for removing a convex defect of a retardation mask, which is performed in a gas atmosphere. 7. The method of removing a convex defect of a retardation mask according to claim 6, wherein the pressure of a gas having an etching reactivity with the convex defect is set to the protective film with respect to a removal rate of the convex defect. The method for removing convex defects of a retardation mask, wherein the removal speed ratio is controlled to 0.7 to 1.3. 8. The method of removing a convex defect of a retardation mask according to claim 2 or 4, wherein the irradiation target region of the focused ion beam is removed by etching reactivity with respect to the convex defect. A method of removing a convex defect of a retardation mask, which is performed in an atmosphere of a gas having the same and a gas having an etching reactivity with the protective film. 9. The method of removing a convex defect of a retardation mask according to claim 8, wherein the pressure of the gas having an etching reactivity with the protective film is set to a value corresponding to the removal rate of the convex defect of the protective film. A method for removing a convex defect of a retardation mask, characterized in that the removal speed ratio is controlled to be 0.7 to 1.3. 10. The method for removing a convex defect of a retardation mask according to claim 1, wherein the removal of the irradiated region portion of the focused ion beam is performed at a relatively high removal rate. A method of removing a convex defect of a retardation mask, which is performed by increasing an ion beam irradiation amount in a slow portion. 11. A step of forming a protective film covering the entire upper surface of the mask in removing the convex defect generated on the upper surface of the phase difference mask, and thereafter, applying a focused ion beam to the defect and Irradiating an area including the periphery thereof from the protective film side to remove the irradiation target area portion of the focused ion beam; and irradiation of the focused ion beam when the protective film portion on the defect is removed And a step of removing the defects by etching using the protective film after the irradiation of the focused ion beam as a mask, the method for removing the convex defects of the retardation mask.