JP2006139049A - Method and device for correcting photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a mask so that the transmittance of a glass substrate is not reduced; to provide an optimal correction method depending on the kind of material or defect; and to correct the mask in a shorter time. <P>SOLUTION: A device 300 for correcting a photomask is equipped with an electron beam correction unit 200 for correcting a defect by irradiating the position where the defect is formed with an electron beam 112 when the defect is formed on the photomask and an atomic force microscope 200 having a probe 210 for removing the defect by bringing the probe 210 into contact with the defect when the defect is formed on the photomask. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photomask correction method and a photomask correction apparatus, and more particularly to correction of a white defect or a black defect in a photomask for exposure patterning when manufacturing a semiconductor device such as an LSI.

  In conventional photomask defect correction, processing using a focused ion beam using gallium (Ga) ions is generally used. However, the photomask pattern is miniaturized and a three-dimensional structure such as a phase shift mask is used. Along with this trend, a correction device that combines an atomic force microscope and a focused ion beam has been proposed.

  Here, as a method of using the atomic force microscope, a defect portion is extracted by taking advantage of the feature that an insulator can be measured with high accuracy. In this method, an area including a defect is observed with an atomic force microscope (AFM), and a pattern for alignment and alignment of the defect is extracted from the AFM image. Then, the extracted pattern is converted into a graphic format of the ion beam defect correcting apparatus and transferred. At this time, an alignment pattern that can be observed with an ion beam defect correcting apparatus is selected. The extracted / converted alignment pattern is aligned with the corresponding pattern of the secondary electron image or secondary ion image. Performs the same correction as the irradiation area correction for the pattern matching processing from the normal secondary ion image or secondary electron image of the ion beam defect correction device, extracts by AFM, and fine-tunes by aligning the pattern for alignment The defect area thus formed is corrected with an ion beam (see, for example, Patent Document 1).

  The atomic force microscope is also used for drift correction at the time of correction. The technique is an apparatus that combines an ion beam defect correcting apparatus and a non-contact atomic force microscope. While correcting defects with the ion beam 5, the ion beam or neutralization of electricity is performed as close as possible to the correction area. In a place not affected by the charge of the electron beam, in parallel with processing, a non-contact atomic force microscope is used to perform continuous high-resolution observation of characteristic patterns or markers created with an ion beam defect correction device. The drift amount is calculated from a comparison with the previous atomic force microscope image, and the defect is corrected while feedback is applied to the scanning range of the ion beam to correct the drift (see, for example, Patent Document 2).

  A correction method using a focused ion beam and an atomic force microscope has been proposed. In order to realize black defect correction without glass digging (river bed), the technique prevents the tail component of the ion beam and the ion beam scattered at a small angle from hitting the surrounding glass part in the first stage. Irradiate only the inside of the recognized defect area, perform etching to leave the edge of the defect, and physically use an AFM hard probe in which only the edge of the defect left in the second stage is fixed at the height of the glass surface. The black defect is corrected by following a two-step correction procedure of sharpening. In this way, by combining a defect correction apparatus using an ion beam and an atomic force microscope (AFM), it is possible to correct a black defect without a river bed with a practical throughput (for example, (See Patent Document 3).

Hereinafter, an example of general pattern correction using a conventional focused ion beam will be described.
FIG. 11 is a view showing a part of a photomask in which a composite defect of a white defect and a black defect exists.
Here, the photomask 400 shows a case where a chromium (Cr) film 402 serving as a light-shielding film is formed on a glass substrate 401. The photomask 400 is the same even if it is a substrate digging phase shift mask. First, a defect region generated on the photomask 400 is observed with an ion beam using an ion beam correction device such as Ga ions, and correction data is created. Next, the white defect portion 403 and the black defect portion 404 are corrected using an ion beam. Next, the pattern of the correction portion is observed using an atomic microscope of a mechanical correction device, and detailed information including the three-dimensional structure of the defect pattern is extracted to generate correction data. If there is a defect area, the defect area is scraped off and corrected by mechanical correction.
JP 2002-214758 A JP 2003-173017 A JP 2002-214760 A

  By the way, in recent semiconductor lithography, along with miniaturization and shortening of the exposure light source wavelength, when metal ions by an ion beam such as Ga ions are implanted into a glass substrate of a photomask, the transmittance of the glass substrate is lowered. There was a problem that transfer characteristics deteriorated. In addition, the optimal correction method differs depending on the type of material and defect, such as glass correction of a phase shift mask and halftone film correction, and there is a problem that it takes time to perform correction with a plurality of apparatuses.

  The present invention overcomes the above-described problems and corrects the mask so that the transmittance of the glass substrate does not decrease, and provides an optimal correction method depending on the material and the type of defect, and corrects the mask in a shorter time. For the purpose.

The photomask correction method of the present invention includes:
In a photomask correction method for correcting defects on a photomask,
When black defects are formed on the photomask, the black defects are removed by using an electron beam and an atomic force microscope probe at a position where the black defects are formed. .

  By removing the black defects using an electron beam, it is possible to eliminate implantation of metal ions into the glass substrate. Further, by removing the black defects using the electron beam and an atomic force microscope probe, the electron beam and the atomic force microscope probe can be used properly depending on the type of material and defect. it can.

  Furthermore, in the photomask correction method of the present invention, when a white defect is formed on the photomask, a predetermined thin film is formed at the position where the white defect is formed using the electron beam. It is characterized by that.

  By forming a predetermined thin film using the electron beam, it is possible to eliminate implantation of metal ions into the glass substrate even when correcting white defects.

  Further, in the case of removing the black defect in the present invention, if the black defect is a chromium (Cr) film, the black defect of the Cr film is removed using a probe of the atomic force microscope, When the black defect is a halftone film, the electron beam is used to remove the black defect of the halftone film.

  By removing the black defect of the Cr film, which is difficult with an electron beam, using the probe of the atomic force microscope, and removing the halftone film possible with the electron beam using the electron beam, an optimal correction method Can be performed. Further, by removing the halftone film using an electron beam, it is possible to prevent generation of shavings that are generated when the probe of the atomic force microscope is used.

The photomask correction device of the present invention is
In a photomask correction apparatus for correcting a photomask,
When a defect is formed on the photomask, an electron beam correction unit that corrects the defect by irradiating an electron beam to the position where the defect is formed;
When a defect is formed on the photomask, an atomic force microscope having a probe that contacts the defect and removes the defect;
It is provided with.

  By providing an electron beam correction unit and an atomic force microscope having a probe in one apparatus, an optimal correction method that differs depending on the type of material and defect can be performed with one apparatus.

  As described above, according to the present invention, since the implantation of metal ions into the glass substrate can be eliminated, it is possible to suppress a decrease in the transmittance of the glass substrate. Furthermore, since the electron beam and the probe of the atomic force microscope can be used properly depending on the type of material and defect, the mask can be corrected by an optimal correction method. Furthermore, since the mask can be corrected by such an optimal correction method with a single device, the mask can be corrected in a shorter time.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram showing the configuration of the photomask correction apparatus in the first embodiment.
In FIG. 1, a photomask correcting device 300 includes an electron beam correcting device 100 serving as an electron beam correcting unit that corrects a defect by irradiating an electron beam 112, and a probe 210 that scrapes and removes the defect in contact with the defect. And an atomic force microscope 200. By providing the electron beam correction device 100 and the atomic force microscope 200 as a mechanical correction device, the electron beam and the probe of the atomic force microscope can be used properly depending on the type of material and defect.

  The electron beam correction apparatus 100 emits electrons from the electron gun 110, passes through an optical system 120 such as an electron lens, and focuses and accelerates the electrons into a beam. The focused and accelerated electron beam 112 is deflected by a deflector and irradiates a predetermined region of the mask 340 disposed on the mask stage 150 as a focused electron beam. The position on the mask 340 to be irradiated can be grasped by detecting secondary electrons generated by irradiation of the electron beam 112 with a secondary electron detector (SED) 130. Secondary electrons generated on the surface of the mask 340 disposed on the mask stage 150 are detected by the secondary electron detector 130 to obtain a surface image. A defect can be detected by displaying such a surface image on a monitor (not shown). The electron beam 112 irradiates a predetermined area where such a defect has occurred. When forming a deposition film for correcting white defects, a deposition gas is injected from the gas gun 140 to form a film in the predetermined region by chemical vapor deposition (CVD). Next, a deflector is deflected so that the electron beam 112 irradiates the adjacent region, and similarly, a deposition film is grown to the adjacent region. When correcting a black defect, an etching gas is injected from the gas gun 140 and the black defect existing in the predetermined region is etched by a gas assist etching method.

  On the other hand, the atomic force microscope 200 irradiates the laser 250 from the laser oscillator 230 while moving the cantilever 220 on which the probe 210 is disposed on the mask 340, and the detector 240 detects the reflected laser 250 and the mask shape is detected. To figure out. In the atomic force microscope 200, black defects can be corrected. When correcting a black defect, the hard defect 210 is used to physically or mechanically remove the black defect.

FIG. 2 is a diagram for explaining a technique for removing black defects on the mask.
In a photomask in which a Cr film 403 serving as a light-shielding film is formed on a glass substrate 401, when a black defect 152 occurs on the glass substrate 101, the electron beam correction apparatus 100 irradiates the black defect 152 with the electron beam 112. Then, an etching gas is injected from the gas gun 140 of FIG. 1 to etch the black defect 152 by a gas assist etching method. In the atomic force microscope 200, the tip of the probe 210 is moved to the same height as the surface of the glass substrate 101, and the cantilever 220 is moved to move the probe 210 in parallel with the surface of the glass substrate 101. Then, the probe 210 is brought into contact with the black defect 152, and the black defect 152 is removed physically or mechanically.

Hereinafter, the case where the photomask in which the composite defect of the white defect and the black defect described in FIG. 11 exists is corrected will be described.
A photomask 400 illustrated in FIG. 11 illustrates a case where a chromium (Cr) film 402 serving as a light-shielding film is formed over a glass substrate 401. The photomask 400 is the same even if it is a substrate digging phase shift mask. In the photomask 400, a white defect portion 403 in which the Cr film 402 is missing and a black defect portion 404 in which the Cr film 402 is excessively formed are generated on the glass substrate 101. Further, a glass convex defect 405 is generated on the glass substrate 401.

FIG. 3 is a diagram showing a part of the photomask after correcting the white defect of the composite defect.
First, a defect region generated on the photomask 400 is observed with the electron beam 112 or the atomic force microscope 200, and detailed information including the three-dimensional structure of the defect pattern is extracted to create correction data.
Next, as shown in FIG. 3, the white defect portion 403 is subjected to deposition correction by the electron beam 112 to form a deposition film 260. By using an electron beam, the deposition film 260 can be formed even with a small pattern.

FIG. 4 is a diagram for explaining a method of forming a deposition film.
The deposition film 260 is formed by irradiating the region where the deposition film is to be formed with the electron beam 112, spraying the deposition gas 142 which is a deposition reaction gas, and performing chemical vapor deposition (CVD). In FIG. 4, an electron beam 112 is used as a focused beam instead of a Ga ion beam. When irradiated with a Ga ion beam, Ga ions enter the glass substrate 401. When Ga ions enter, the transmittance of the glass substrate is changed. In Embodiment 1, since the electron beam 112 is used, metal ions such as Ga do not enter the glass substrate 401 and the transmittance of the glass substrate can be prevented from changing.
The deposition film 260 is preferably composed of a carbon-based material. The deposition gas 142 is necessarily preferably composed mainly of a carbon-based material. For example, diamond-like carbon (DLC) or the like can be used as the deposition film 260. An aromatic gas such as phenanthrene can be used as the film forming gas 142.

FIG. 5 is a view showing a part of the photomask after correcting the black defect of the composite defect.
Mechanical correction is carried out by scraping the black defect portion 404 shown in FIG. 3 with the probe 210 of the atomic force microscope 200. Then, as shown in the mechanical correction region 407 in FIG. 5, the black defect portion 404 is removed. Here, when the black defect portion 404 is formed of a Cr film serving as a light shielding film, it is difficult to etch using the electron beam 112. Therefore, here, the atomic force microscope 200 is used without using the electron beam correction apparatus 100. Correction can be performed in a shorter time by using an optimum method according to the material.

FIG. 6 is a diagram showing a part of the photomask after correcting the glass convex defect of the composite defect.
Finally, the glass convex defect 405 shown in FIG. 3 is corrected by mechanical correction by scraping with the probe 210 of the atomic force microscope 200. Then, as shown in FIG. 6, the glass convex defect 405 is removed.

Next, as another example, a case of correcting a composite defect in a tritone halftone mask will be described.
FIG. 7 is a plan view showing a part of a sample showing a composite defect in a tritone type halftone mask.
In FIG. 7, in the tritone halftone mask 500, a Cr film 506 serving as a light shielding film is formed on a glass substrate 508, and a halftone film 507 is formed on the glass substrate 508 in a region surrounded by the Cr film 506. Is done. Then, a glass substrate 508 which is a light-transmitting region that becomes an original hole pattern is left in the region surrounded by the halftone film 507. As a material for the halftone film, molybdenum silicide (MoSi) may be used. Here, a black defect 510 of the Cr film is generated on the halftone film 507. Further, a black defect portion 509 is generated on the central glass substrate 508. Hereinafter, the case of correcting the composite defect in the tritone halftone mask 500 will be described.

First, a defect region generated on a halftone mask 500 which is a photomask is observed with an electron beam or an atomic force microscope, and detailed information including the three-dimensional structure of the defect pattern is extracted to create correction data.
FIG. 8 is a diagram showing a part of the tritone halftone shift mask after correcting the hole of the composite defect.
Etching correction is performed on the hole black defect portion 509 shown in FIG. 7 with an electron beam. Then, as shown in FIG. 8, the black defect portion 509 is removed.

FIG. 9 is a diagram for explaining a technique for etching.
The etching gas 144 is sprayed onto the black defect portion 509 to cause the etching gas molecules 146 to be adsorbed on the surface of the black defect portion 509 and irradiated with the electron beam 112, whereby the excess black defect portion 509 is etched by the gas assist etching method. . Since the apparatus described with reference to FIG. 1 is used, description of the apparatus configuration and operation is omitted.
In FIG. 9, the electron beam 112 is used as the focused beam instead of the Ga ion beam. When irradiated with a Ga ion beam, Ga ions enter the glass substrate 508. When Ga ions enter, the transmittance of the glass substrate is changed. In Embodiment 1, since the electron beam 112 is used, metal ions such as Ga do not enter the glass substrate 508 and the transmittance of the glass substrate can be prevented from changing. The etching gas 144 is preferably a halogen-containing material gas. For example, Xe ₂ F, CF ₄ , CHF ₃ , Cl ₂ , CHCl ₃ , I ₂ or the like may be used.
Here, it is difficult to remove the black defect existing in the hole shape by the film with the atomic force microscope 200. This is because the probe 210 cannot be moved to scrape the black defect portion 509 while being surrounded by a film in a hole shape. Alternatively, even if the black defect portion 509 can be shaved by moving the probe 210, shavings cannot be eliminated while being surrounded by a hole. Therefore, here, the electron beam correction apparatus 100 is used instead of the atomic force microscope 200 to perform etching with an electron beam that can irradiate a focused beam even in a small region. Correction can be performed in a shorter time by using an optimum method according to the state of the defect. Further, by etching with the electron beam, the etched black defect portion 509 is gasified and fly away, so that it is possible to prevent generation of shavings as in the case of cutting with the atomic force microscope 200.

FIG. 10 is a diagram showing a part of a tritone type halftone shift mask after correcting a black defect on the halftone film.
The black defect portion 510 on the halftone film 507 shown in FIG. 7 is corrected by mechanical correction that scrapes with the probe 210 of the atomic force microscope 200. Then, as shown in FIG. 10, the black defect portion 510 on the halftone film 507 is removed.
Here, when different materials are formed on the MoSi halftone film 507 so that the black defect portion 510 of the Cr film is formed, it is difficult to perform material selective etching with an electron beam. Therefore, here, the atomic force microscope 200 is used without using the electron beam correction apparatus 100. Even when different materials are laminated, correction can be performed in a shorter time by using an optimum method.

  As described above, by extracting and correcting a defect pattern using an apparatus that uses both an electron beam and an atomic force microscope, the photomask can be corrected with high accuracy and without any substrate damage.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  In addition, all mask correction methods that include elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

1 is a conceptual diagram showing a configuration of a photomask correction device in Embodiment 1. FIG. It is a figure for demonstrating the method of removing the black defect on a mask. It is a figure which shows a part of photomask after white defect correction of a composite defect. It is a figure for demonstrating the method of forming a deposition film. It is a figure which shows a part of photomask after the black defect correction of a composite defect. It is a figure which shows a part of photomask after glass convex defect correction of a composite defect. It is a top view which shows a part of sample which shows the composite defect in a tritone type halftone mask. It is a figure which shows a part of tritone type | mold halftone shift mask after hole correction of a composite defect. It is a figure for demonstrating the method to etch. It is a figure which shows a part of tritone type | mold halftone shift mask after the correction of the black defect on a halftone film. It is a figure which shows a part of photomask in which the composite defect of a white defect and a black defect exists.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Electron beam correction apparatus 110 Electron gun 112 Electron beam 120 Optical system 130 Secondary electron detector 140 Gas gun 142 Deposition gas 144 Etching gas 146 Etching gas molecule 150 Mask stage 152 Black defect 200 Atomic force microscope 210 Probe 220 Cantilever 230 Laser oscillator 240 Detector 250 Laser 260 Deposition film 300 Photomask correction device 340 Mask 400 Photomask 401, 508 Glass substrate 402, 506 Cr film 403 White defect portion 404, 509, 510 Black defect portion 405 Glass convex defect 407 Mechanical correction region 500 Halftone mask 507 Halftone film

Claims (4)

In a photomask correction method for correcting defects on a photomask,
When black defects are formed on the photomask, the black defects are removed by using an electron beam and an atomic force microscope probe at a position where the black defects are formed. Photomask correction method.   In the photomask correction method, when a white defect is formed on the photomask, a predetermined thin film is formed using the electron beam at a position where the white defect is formed. The photomask correction method according to claim 1.   In the case of removing the black defect, when the black defect is a chromium (Cr) film, the black defect of the Cr film is removed using a probe of the atomic force microscope, and the black defect is half 3. The method of correcting a photomask according to claim 1 or 2, wherein in the case of a tone film, black defects in the halftone film are removed using the electron beam. In a photomask correction apparatus for correcting a photomask,
When a defect is formed on the photomask, an electron beam correction unit that corrects the defect by irradiating an electron beam to the position where the defect is formed;
When a defect is formed on the photomask, an atomic force microscope having a probe that contacts the defect and removes the defect;
An apparatus for correcting a photomask, comprising:

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