JPH0728228A - Method for correcting protrusion defect part - Google Patents

Abstract

PURPOSE:To cope with a defect pitted by a laser beam and to correct the defective part due to the micronization of a semiconductor integrated circuit by separating the protrusion defect part from a regular pattern part and irradiating the separated and left protrusion defect part with a laser beam. CONSTITUTION:A protrusion defect part 3 is separated from a regular pattern part by the milling of a focused ion beam 5 or gas-assisted etching. The left protrusion defect part 3 is separated and removed by the ion beam 5 of about 0.2mum diameter. The protrusion defect part 3 left after separation is irradiated with a laser beam, and hence the defect is eliminated by the laser beam irradiation performed once or several times without need for not so high precision in the correction with a laser beam 6. Since the irradiation with the ion beam 5 and that with the laser beam 6 are jointly used, the defects such as roughness of the end of the corrected part, stripping and pitting are coped with, and the protrusion defect of the photomask pattern due to the micronization is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of repairing a light-shielding film in a photomask, a light-shielding film in a phase shift photomask, or a convex defect portion of a shifter.

[0002]

2. Description of the Related Art In recent years, with the high integration of semiconductor integrated circuits, further miniaturization has been required for reticles used in the fabrication of these circuits. Currently 1
The line width of the device pattern transferred from the reticle of the 6M DRAM reticle is as small as 0.6 μm. Furthermore, in the case of a 64 M DRAM device pattern, resolution of 0.35 μm line width is required, and the conventional optical exposure method using a stepper has reached its limit. Therefore, in the fabrication of a fine circuit of 64 M DRAM revex or more, the resolution of the device pattern on the wafer transferred from the reticle in light exposure can be increased, and the phase shift of the method that can be used in the current stepper. Masks have attracted attention, and their development has been actively considered. With such a high integration of semiconductor circuits, residual defects of the light-shielding layer in the photomask for transferring and forming the pattern on the wafer only by the conventional light-shielding pattern, the light-shielding layer and the shifter in the phase shift mask using the shifter layer, Regarding residual defects (hereinafter referred to as convex defects), the size of the defect portion that has to be corrected has become smaller and smaller, and the accuracy of the correction has become more and more severe.

Conventionally, YAG (N
A method of evaporating and removing the defective portion using a laser beam such as b) is used. This laser light irradiation correction method is one in which the laser light is expanded to a certain range and the aperture has a predetermined shape (usually rectangular), size, and intensity distribution, which is usually further reduced after passing through the aperture. , It is condensed and irradiated to the part to be corrected, but it is caused by defective alignment position of aperture, misalignment of focus, misalignment of optical axis, instability of laser power, material of shading film, film thickness, etc. The shape of the end of the corrected portion of the end portion of the laser beam that is molded and irradiated is not linear, and the edge is generally rough, and the light-shielding film may be damaged. FIG. 3 shows an example of correcting a convex defect laser in a conventional photomask consisting only of a light shielding film pattern.
(A) is a positioning alignment of the laser beam, which is performed by visually observing the laser beam rectangularly shaped by the aperture at the boundary between the regular light shielding pattern portion and the convex defect portion while looking through the microscope. After aligning, the laser beam is irradiated with a predetermined intensity, but the end portion of the shaped laser beam caused by the above-mentioned poor alignment position adjustment of the aperture, poor focus adjustment, poor optical axis adjustment, etc. Due to the non-uniformity in strength, even if the alignment is successful, the correction boundary becomes rough 13 or blind 14 as shown in (b). If the alignment is not successful, the regular light-shielding pattern portion is removed as shown in FIG. Even if the alignment is successful, if the adjustment of the laser beam is poor, an egre may occur. And finally, the alignment that determines the irradiation position of the laser beam should be made by gradually increasing the magnification of the microscope. However, it is a judgment made by the human eye, and there are mistakes. In this case, it is often a big egre. Due to this correction, even the regular pattern is removed, and the egre has become a big problem due to the miniaturization of the photomask pattern accompanying the high integration of the semiconductor integrated circuit.

For the miniaturization of patterns, laser light has a limit due to diffraction. This limit is generally set to about 0.5 μm, which is the limit of laser focusing. On the other hand, the line width at the level of 16 MDRAM is 0.60 μm on the device and 0.
The line width accuracy is about 60 μm × 5, but the line width accuracy is 1/5 to 1/10, 3.0 μm × (1/5 to 1/1
0) is required, and those of 0.4-0.5 μm size are
At present, the defect is inspected and corrected as a defect, and the limit of focusing of the laser beam is no longer present. At the 64M DRAM level, the correction beyond the limit is required. Thus, with laser irradiation correction, 16 MDR
It is difficult to repair defects having a line width as fine as the AM level or higher, and another method has been required. In recent years, instead of laser beam irradiation correction, as a method that can respond to miniaturization, a method of removing convex defects due to ion beam irradiation has also been used, and defects can be detected by chromium ion or Si ion monitoring by an ion detector. Some have been equipped with a mechanism for detecting the end point of partial removal,
Many of the defects themselves are indefinite, and the defects around the defects cause damage to the underlying glass substrate of the convex defects.When transferring them to the wafer, those parts are transferred, so it is still in a practical stage. However, the response was required.

[0005]

Under the circumstances described above, the present invention provides a light-shielding pattern of a photomask which can cope with the generation of egress in the correction of the photomask by a laser beam and can also cope with the miniaturization of the photomask pattern. The present invention provides a method for repairing the above-mentioned bump defect, the light-shielding pattern bump defect of the phase shift photomask, and the shifter bump defect.

[0006]

A method of repairing a convex defect portion according to the present invention is a method of repairing a light shielding film in a photomask, a light shielding film in a phase shift photomask, and a convex defective portion of a shifter. The boundary of the convex defect portion is milled by a focused ion beam (FIB), or a predetermined gas is excited by an ion beam for etching, or is separated by gas assisted etching, and then the separated convex defect portion is irradiated with a laser. This is a method of removing by evaporation. Here, the material of the light-shielding pattern member and the material of the shifter member to be removed by the laser beam are those that absorb the energy of the laser beam when they are irradiated, and generally contain chromium as the main component and Examples thereof include films, nitride films, oxynitride films, and molybdenum silicide-based oxide films, nitride films, oxynitride films, and the like. When the laser beam irradiation does not absorb the energy, it is necessary to absorb the energy by some method. The laser beam is generally the second harmonic 530 of a YAG laser.
nm is used. As the focused ion beam (FIB), an ion beam of Ga, Ar or the like having a small diameter of about 0.2 μmφ is generally used, but it irradiates only the boundary between the regular pattern portion and the convex defect portion, and others. Is extremely small, and the portion other than the defective portion is hardly damaged by the ion beam.

In the method of repairing a convex defect portion of the present invention, an end using an ion detector or an electron detector when separating only the boundary between the regular pattern portion and the convex defect portion with an ion beam. The point monitor determines the time when the underlying substrate of the convex defect is exposed and stops the separation process.The endpoint is determined by monitoring the increase or decrease of chromium ions, the increase or decrease of Si ions, or the amount of secondary electrons. is doing. As a result, when the boundaries are separated, the ion beam causes almost no damage to the underlying glass substrate under the defect. From the state of FIG. 1A, the thickness of the boundary between the pattern portion and the defect portion is thinned by the ion beam irradiation.
There is no increase or decrease in the amount of ions, and when reaching the underlying substrate material at the boundary between the pattern portion and the defect portion, the chromium ion sharply decreases and the Si ion sharply increases. This point is used as the end point of the boundary removal by the ion beam, and the basic is monitoring by detecting chromium ions from the light shielding pattern or shifter, but below the light shielding pattern or shifter,
If the glass material is used immediately, it can be monitored by detecting Si ions. The more accurate judgment can be made by monitoring both ions. By monitoring the amount of secondary electrons, the endpoint detection is the same as in the case of chromium ion detection.It sharply decreases when the light-shielding pattern is exposed, so this point is the endpoint removal endpoint for ion beams. It is what Practically, both the detection of chromium ions and the detection of the amount of secondary electrons are safe, and if necessary, Si ion detection is also performed. FIG. 2 is a schematic view of a focused ion beam apparatus, in which 17 is an ion beam, 18 is an ion source, and 2
3 is a correction photomass 21 is a stage for driving it in fixed X and Y directions, 19 is an ion detector, 22 is a gas gun, and while vacuum pumping, ion beam irradiation is controlled by the position of the photomask, milling, or gas assist. Etching is performed. In the method of repairing the convex defect portion of the present invention, a photomask, a light-shielding film of a phase shift photomask, or a film having resistance to ion beam milling or gas-assisted etching under a shifter is provided, In some cases, it may not be necessary to monitor changes in the amount of chromium ions, Si ions, or electrons.

[0008]

According to the method of repairing a convex defect portion of the present invention, the boundary between the regular pattern portion and the convex defect portion is corrected in the correction of the convex defective portion of the light shielding film in the photomask or the light shielding film and the shifter in the phase shift photomask. In addition, the removal work by the laser beam of the remaining convex defect portion by the milling by the focused ion beam (FIB) or the gas-assisted etching is performed, the rough alignment accuracy of the aperture image, which is conventionally required, is rough. Moreover, by separating the boundary with an ion beam having a small beam diameter of about ~ μmΦ, there is almost no damage to non-defective parts other than the boundary part, and the edge of the removal part is also less rugged. . After the separation, by irradiating the remaining convex defect portion with a laser, accuracy in laser beam correction is not so required, and at the same time,
The defects can be removed by laser irradiation several times. In this way, by using both ion beam irradiation and laser beam irradiation, it is possible to deal with defects such as the shape of the end of the correction portion due to the laser beam that has been conventionally used, and defects such as blind spots and egre, and miniaturization. This is a method that can sufficiently deal with the correction of convex defects in the photomask pattern due to the above. Then, in the conventional laser beam correction, due to an adjustment error or an error caused by a manual operation, an egglet which is a fatal regular pattern is removed even in a defect of a photomask pattern due to miniaturization of a semiconductor integrated circuit. It enables a method that can eliminate the occurrence. Further, when separating the boundary between the regular pattern portion and the convex defect portion with an ion beam, an endpoint monitor is used, and when the base substrate of the convex defect portion is exposed, the separation process is stopped, The damage to the base under the defect is extremely small, and there is no problem in practical use.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a process of repairing a reticle mask having a convex defect in a light-shielding pattern portion of the present invention.
FIG. 4A is a plan view of a defective portion and a sectional view of the defective portion in each step. First, a reticle mask having convex defects as described in (A) is prepared. The light-shielding pattern portion 2 is made of chromium, and is formed into a film having a thickness of 100 nm by sputtering and patterned using an electron beam drawing apparatus. The base of the light shielding pattern is the silica glass substrate 4. Reference numeral 3 is a convex defect connected to the light-shielding pattern portion 2. In the regular pattern, the chrome film remains in a portion that does not exist for some reason.
Then, using a focused ion beam (FIB) device of Ga ions, the Ga ions are accelerated at a voltage of 20 KV and a current value of 140 PA at the boundary between the regular pattern portion and the convex defect portion of this mask.
Then, the ion beam 5 was milled with a diameter of 0.2 μnΦ. At this time, the chromium ion detector was used to monitor the increase and decrease of chromium ions. A few seconds after the milling was started, the chromium ions rapidly decreased, so it was judged that the glass substrate underlying the chromium light-shielding film was exposed at this point, the milling end point was set, and the milling was stopped to obtain (B). Then, the laser beam projecting defect repair device using the second harmonic 530nm of YAG laser, a laser as as in a plan view, surrounds the residual chromium convex defect portion ^3, which is separated from the normal pattern of (C) By changing the size of the aperture image formed in the rectangular shape of the beam 6, the irradiation area 8 is designated and the entire area is covered at once.
Irradiated. By irradiating several times, the defective portion was completely removed and a corrected photomask 7 was obtained (D), and the correction of the defective portion was completed. The result is that the edge of the pattern formed by separating the boundary between the regular pattern and the convex defect 3 is formed when the light-shielding film is removed by the laser beam alone. It is also good
Ion beam damage to the glass substrate under chromium was also invisible. Next, using this photomask, a device pattern on the wafer was transferred and produced, but there was no problem because the portion corresponding to the portion where the convex defect of chromium was removed was also normally transferred. When a film having resistance to ion beam milling or gas-assisted etching is used under the light-shielding film or the shifter, it may not be necessary to monitor increase or decrease in the amount of chromium ions, Si ions, or electrons. However, it is also possible to monitor depending on the material of the resistant film. Separately, since a master pattern for equal-magnification transfer to a wafer, which is the same size as the semiconductor device pattern, is produced by contact transfer, defects in the sub-master pattern are also corrected and transferred by the above method. I tried it, but it was found that there was no effect of the correction part and it was a correction method that could be put to practical use.

[0010]

EFFECTS OF THE INVENTION The present invention, which has the above-described structure, can cope with the egre defect which is conventionally difficult when a laser beam is used, and can be applied to miniaturization of a semiconductor integrated circuit. Accordingly, it is possible to provide a method that can sufficiently deal with the correction of the defective portion. In particular, the present invention provides a method that can be carried out relatively easily using a laser repair apparatus using a laser beam and an existing focused ion beam apparatus that are currently used.

[Brief description of drawings]

FIG. 1 is a process diagram of a method for correcting a convex defect of a chromium light-shielding film pattern of the present invention.

FIG. 2 is a schematic view of an FIB device for correcting a convex defect.

FIG. 3 is a view for correcting a convex defect of a conventional chrome light-shielding film pattern.

[Explanation of symbols]

The reticle mask 2 chromium light-shielding film pattern 3 opaque chromium film raised defects third ^pattern, the convex defect 4 glass substrate 5 ion beams 6 laser beam 7 reticle mask 9 convex after laser irradiation region 8 modified after ion beam modification having first convex defects Reticle mask with defects 10 Chromium light-shielding film pattern 11 Convex defects of chromium light-shielding film pattern 12 Laser irradiation region 13 Luster 14 Mekure 15 Egure 16 Focused ion beam device (FI)
B) 17 ion beam 18 ion source 19 ion detector 20 chromium ion 21 XY stage 22 gas gun 23 photomask for correction

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[Procedure amendment]

[Submission date] August 6, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

Conventionally, YAG (N
A method of evaporating and removing the defective portion using a laser beam such as b) is used. This laser light irradiation correction method is one in which the laser light is expanded to a certain range and the aperture has a predetermined shape (usually rectangular), size, and intensity distribution, which is usually further reduced after passing through the aperture. , It is condensed and irradiated to the part to be corrected, but it is caused by defective alignment position of aperture, misalignment of focus, misalignment of optical axis, instability of laser power, material of shading film, film thickness, etc. The shape of the end of the modified portion of the end of the laser beam that is shaped and irradiated is not linear, and the edge is generally rough, and the light-shielding film may be damaged. FIG. 3 shows an example of correcting a convex defect laser in a conventional photomask consisting only of a light shielding film pattern.
(A) is a positioning alignment of the laser beam, which is performed by visually observing the laser beam rectangularly shaped by the aperture at the boundary between the regular light shielding pattern portion and the convex defect portion while looking through the microscope. After aligning, the laser beam is irradiated with a predetermined intensity, but the end portion of the shaped laser beam caused by the above-mentioned poor alignment position adjustment of the aperture, poor focus adjustment, poor optical axis adjustment, etc. Due to the non-uniformity in strength, even if the alignment is successful, the correction boundary becomes rough 13 or blind 14 as shown in (b). If the alignment is not successful, the regular light-shielding pattern portion is removed as shown in FIG. Even if the alignment is successful, if the adjustment of the laser beam is bad, an egress may occur.Finally, the alignment that determines the irradiation position of the laser beam should be made by gradually increasing the magnification of the microscope. However, it is a judgment made by the human eye, and there are mistakes. In this case, it is often a big egre. Due to this correction, even the regular pattern is removed, and the egre has become a big problem due to the miniaturization of the photomask pattern accompanying the high integration of the semiconductor integrated circuit.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

According to the method of repairing a convex defect portion of the present invention, the boundary between the regular pattern portion and the convex defect portion is corrected in the correction of the convex defective portion of the light shielding film in the photomask or the light shielding film and the shifter in the phase shift photomask. In addition, the removal work by the laser beam of the remaining convex defect portion by the milling by the focused ion beam (FIB) or the gas-assisted etching is performed, the rough alignment accuracy of the aperture image, which is conventionally required, is rough. In addition, by separating the boundary with an ion beam with a small beam diameter of about 0.2 μmΦ, there is almost no damage to non-defective parts other than the boundary part, and the edge of the removal part is less rugged. There is. By irradiating the remaining convex defect portion with laser after separation, the defect can be removed all at once or by several times of laser irradiation without requiring so much accuracy in laser beam correction. In this way, by using both ion beam irradiation and laser beam irradiation, it is possible to deal with defects such as the shape of the end of the correction portion due to the laser beam that has been conventionally used, and defects such as blind spots and egre, and miniaturization. This is a method that can sufficiently deal with the correction of convex defects in the photomask pattern due to the above. Then, in the conventional laser beam correction, due to an adjustment error or an error caused by a manual operation, an egglet which is a fatal regular pattern is removed even in a defect of a photomask pattern due to miniaturization of a semiconductor integrated circuit. It enables a method that can eliminate the occurrence. Also, when separating the boundary between the regular pattern portion and the convex defect portion with an ion beam, an endpoint monitor is used, and when the base substrate of the convex defect portion is exposed,
By stopping the separation process, damage to the base under the defective portion is made extremely small, and there is no problem in practical use.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location 7352-4M H01L 21/30 528 (72) Inventor Kenichi Harusawa 1-1-1, Tanikaga-cho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Inventor Yutaka Suzuki 1-1-1 Ichigaya-Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd.

Claims (3)

[Claims] 1. A method of repairing a light-shielding film in a photomask, a light-shielding film in a phase shift photomask, and a bump defect portion of a shifter, wherein a boundary between a regular pattern portion and a bump defect portion is formed.
A method for repairing a convex defect portion, which comprises separating the residual convex defect portion by milling or gas-assisted etching using a focused ion beam (FIB), and then irradiating a laser beam to the separated convex defect portion to remove by evaporation. 2. The base substrate of the convex defect portion is exposed by an endpoint monitor using an ion detector or an electron detector when separating the boundary between the regular pattern portion and the convex defect portion according to claim 1. The method for repairing a convex defect portion, characterized in that the separation process is stopped and the separation process is stopped. 3. A light-shielding film for a photomask or a film and a shifter for light-shielding a phase shift photomask according to claim 1, wherein the material of the film and the shifter is an oxide film, a nitride film, or an oxynitride containing chromium or molybdenum silicide as a main component. A method of repairing a convex defect portion, characterized in that the energy of the film or the like is absorbed by the irradiation of the laser beam.