JP2004287322A - Mask defect correction method - Google Patents

Abstract

A high-precision and high-quality defect correction of a fine isolated pattern and an OPC pattern which are difficult to observe with a photomask defect correction apparatus using an electron beam for charge-up is made possible.
A region including a defect is observed with an atomic force microscope (AFM), and a pattern for defect shape and alignment is extracted from an AFM image. The extracted pattern is converted into a graphic format of a photomask defect correcting apparatus using an electron beam and transferred. The extracted / converted alignment pattern is aligned with the corresponding pattern 6 of the secondary electron image. The same correction as the irradiation area correction for the pattern matching processing from the normal secondary electron image of the photomask defect correction apparatus using the electron beam is performed, and the position is extracted by the AFM, and the position is adjusted by the alignment of the pattern for alignment. While the gas is supplied to the finely adjusted defect area 3b, the defect is corrected by the electron beam 8.
[Selection] Figure 6

Description

[0001]
[Industrial application fields]
The present invention relates to a photomask or reticle defect correcting method using an electron beam.
[0002]
[Prior art]
Focused ion beam devices using a liquid metal Ga ion source have become the mainstream of mask correction devices instead of defect correction devices using lasers due to their fine processing dimensions. In the defect correction apparatus using the above ion beam, when white defects are corrected, a thin film is formed by decomposing only the portion of the source gas adsorbed on the surface that has been squeezed finely (FIB-CVD), and black defects are corrected. In some cases, high processing accuracy is realized by utilizing the sputtering effect by the focused ion beam or the effect of etching only the portion where the narrowly focused ion beam hits in the presence of the assist gas. (See Patent Document 1)
[0003]
In addition, conventionally used photomasks are made by depositing a metal film such as Cr or a halftone material such as MoSiON on a glass such as quartz glass by sputtering to form a light shielding film, and the mask pattern has a difference in light transmittance. It is converted. For this reason, when observing and correcting with a defect correcting apparatus using an ion beam which is a charged particle, there is a problem that the primary ions are bent by charge-up, and the secondary ion image and the secondary electron image become invisible. In order to prevent this, conventionally, electrons have been irradiated to neutralize charges (see, for example, Patent Document 2).
[Patent Document 1]
Japanese Unexamined Patent Publication No. 03-015068 (page 2-3)
[Patent Document 2]
JP 2000-043771 A (for example,
~
0007)
[Problems to be solved by the invention]
In a defect correction apparatus using an ion beam, it is unavoidable to inject a focused ion beam into the glass substrate with Ga ions, and there is a problem in that the transmittance of the glass-injected portion of the glass substrate is lowered. Further progress in shortening the exposure wavelength of the mask in the future, that is, shortening of the exposure wavelength from DUV light such as KrF (wavelength 248 nm) and ArF (wavelength 193 nm) to VUV light of F ₂ (wavelength 157 nm) With the progress, the above-mentioned decrease in transmittance becomes a more serious problem.
Further, in the conventional ion beam defect correction apparatus, when the design rule is not strict, an image practical enough for recognizing the defect region can be obtained by optimizing the charge neutralization condition. However, in isolated patterns due to recent miniaturization of design rules and patterns introduced to correct the optical proximity effect of the exposure apparatus (OPC pattern), even if electrons are neutralized in charge, It is difficult to observe the correct shape, the charge neutralization conditions differ from pattern to pattern, and even small objects cannot be seen. As described above, the fine isolated pattern and the OPC pattern cannot correctly recognize the defect, and therefore cannot be corrected to satisfy the specifications required for the defect correction.
[0004]
Recently, as the defect size to be corrected has been reduced, an atomic force microscope (AFM) with high spatial resolution has been used instead of an optical microscope or a stylus-type film thickness meter. The processing quality of defect correction points is being evaluated. AFM enables high spatial resolution observation even for photomasks or reticles that are easy to charge up due to their structure. In secondary electron image observation of a defect correction device using an ion beam, the fineness that could not be seen due to charge-up was observed. A small isolated pattern and a fine shape of the OPC pattern can be observed.
[0005]
The increasing demand for system LSIs in recent years has promoted the frequent use of fine isolated patterns and OPC patterns, and high-precision and high-quality correction of these defects has become a defect correction device using an ion beam. Is also sought. For that purpose, accurate recognition of the defect shape and position is essential.
[0006]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems and corrects a mask defect, without reducing the transmittance of the glass substrate, and with high accuracy of a fine isolated pattern or OPC pattern that is difficult to observe with a photomask defect correction apparatus. It is also intended to enable high-quality defect correction.
[0007]
[Means for Solving the Problems]
In the present invention, a photomask defect is corrected by an electron beam in order to prevent a decrease in the transmittance of the glass substrate due to the implantation of Ga ions. Even in a mask defect correction apparatus using an electron beam, an accurate shape of the defect may not be obtained due to the effect of charge-up, so that the atomic force microscope has high spatial resolution and is insulated. Utilizing the ability to perform high-resolution observations on objects. First, an area including a defect is observed with an atomic force microscope (AFM), and a pattern for defect shape and alignment is extracted from the AFM image. The extracted pattern is converted into a graphic format of a correction device using an electron beam and stored. At this time, an alignment pattern that can be observed by a correction device using an electron beam is selected. The mask that has recognized the defect by AFM is transferred to a device using an electron beam, the pattern including the defect extracted and converted from the above AFM image is read, and the alignment pattern of the extracted pattern is read in the region including the defect. Align with the corresponding pattern of the secondary electron image. Defects that have been adjusted in the same way as the adjustment of the irradiation area for pattern matching processing from the normal secondary electron image of the correction device using the electron beam, extracted by AFM, and finely adjusted by aligning the pattern for alignment The region is corrected by an electron beam while supplying an etching gas in the case of correcting black defects and supplying a light shielding film material in the case of correcting white defects.
[0008]
[Action]
The AFM is used to recognize defects with high resolution even for insulating materials, and the alignment is matched to a pattern that is not affected by charge-up. Therefore, the defect correction device using an electron beam is affected by charge-up. Even high-quality defects can be corrected with high accuracy. Also, if the electron beam irradiation amount is controlled by utilizing the height information obtained during AFM observation, the problem of end point detection can be solved without using the material contrast difference between the pattern and glass secondary electrons, and black defects can be corrected. High-quality defect correction can be performed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example in which the present invention is applied to a case where the shape of a black defect cannot be correctly recognized by charge-up will be described.
The stage is moved to the place where the defect is found by the defect inspection apparatus, and the region including the defect is observed by the atomic force microscope (AFM). A defect area 1 and a pattern 2 for alignment are extracted from the AFM image as shown in FIG. 1 as shown in FIG. The extracted pattern is converted into a graphic format unique to a photomask defect correction apparatus using an electron beam and stored. At this time, as the alignment pattern 2, a photomask defect correcting device using an electron beam is selected which is not easily affected by charge-up. The defect area 3a extracted and converted from the AFM image and the pattern 4 data for alignment are transferred to a photomask defect correcting apparatus using an electron beam.
[0010]
The mask whose defect area has been recognized by the AFM is moved to a photomask defect correction apparatus using an electron beam, and the stage is moved to a place where a defect is found by the defect inspection apparatus. A secondary electron image of a region including a defect is observed with a photomask defect correcting apparatus using an electron beam. Observation is performed while irradiating Ar ⁺ ions with a low acceleration voltage of 700 V to 1500 V in which incident electrons and secondary electrons are balanced so as not to cause charge-up or with an Ar ion gun to neutralize charges. The alignment pattern 4 extracted from the AFM image is aligned with the corresponding pattern of the secondary electron image 6 in the region including the defect as shown in FIG. 3 as shown in FIG. After the pattern alignment as shown in FIG. 5 is completed, the irradiation area is corrected in consideration of the shape of the electron beam for the pattern matching processing from the normal secondary electron image of the photomask defect correcting apparatus using the electron beam. A similar correction is performed. Instead of the defect region 5 visible in the secondary electron image, the defect region 3b obtained by performing the above-described alignment and correction on the defect region 3a extracted by AFM is supplied from the etching gas gun 9 as shown in FIG. Removal and correction are performed using an electron beam while supplying an etching gas 10 such as.
[0011]
If the end point detection using the contrast difference due to the secondary electron material is not successful, the height information of the defect area is also collected at the time of defect recognition by AFM as shown in FIG. The amount of electron beam irradiation at the time of black defect correction in the photomask defect correction apparatus is determined so that uncut material and damage to the underlying glass surface 7 are reduced.
[0012]
Next, a description will be given of an example in which the present invention is applied to a case where a black defect becomes invisible by a photomask defect correcting apparatus using an electron beam due to charge-up.
The defect area and the alignment pattern are extracted from the AFM image by the same method as when the defect shape cannot be correctly recognized by the charge-up, and the converted data is transferred to the defect correction apparatus using the electron beam. While neutralizing charges by irradiating Ar ⁺ ions with a low acceleration voltage of 700 V to 1500 V or an Ar ion gun in which incident electrons and secondary electrons are balanced so that charge-up does not occur in a defect correction apparatus using an electron beam. The secondary electron image of the region including the defect is observed, and the alignment pattern 4 extracted by the AFM is aligned with the alignment pattern 6 obtained from the secondary electron image as shown in FIG. Although no defects are visible in the secondary electron image, only an area 3b extracted by AFM and subjected to alignment and irradiation position correction is subjected to etching gas 10 such as xenon fluoride from an etching gas gun 9 as shown in FIG. Irradiate an electron beam while supplying to remove and correct black defects.
[0013]
While the above description has been given for black defects, as shown in FIG. 9, while supplying a light source film 12 for a white defect correction film such as phenanthrene or naphthalene from a deposition gas gun 11 arranged in the vicinity of the mask. When the region 3a extracted by AFM and subjected to alignment and irradiation position correction is irradiated with an electron beam, the white defect correction film 13 is deposited, and the white defect can be corrected in the same procedure as the black defect.
FIG. 10 shows a flow of defect correction according to the present invention.
When correcting the defect of the photomask by the electron beam, the white defect is corrected by forming a light shielding film by electron beam CVD using, for example, phenanthrene or naphthalene as a source gas. As for black defects, for example, an electron beam is selectively irradiated only on the defect portion while flowing xenon fluoride to remove the black defect portion of Cr or MoSi. As for glass, an electron beam is selectively irradiated only on the defective portion while flowing xenon fluoride and removed.
[0014]
【The invention's effect】
As described above, according to the present invention, a mask defect is corrected with an electron beam, so that high-quality mask correction can be performed, and an insulating material such as a mask can be used to recognize a defect that is easily charged up. Since the AFM that enables high-resolution observation is used, the exact shape and position of the defect can be grasped, and when correcting the defect using the electron beam, the alignment is processed with a pattern that is not affected by charge-up. In a defect correction apparatus using an electron beam, it is possible to perform high-precision and high-quality correction even for defects affected by charge-up due to electrons.
[Brief description of the drawings]
FIG. 1 is a diagram showing a defect region and an alignment pattern when observed with an AFM.
FIG. 2 is a diagram showing a defect area and an alignment pattern extracted by AFM converted into a graphic format for a photomask defect correction apparatus using an electron beam.
FIG. 3 is a diagram showing a defect region and an alignment pattern when observed with a photomask defect correction apparatus using an electron beam.
FIG. 4 is a diagram illustrating alignment of an alignment pattern extracted by AFM with an alignment pattern observed by a photomask defect correction apparatus using an electron beam.
FIG. 5 is a diagram showing a region actually processed by an electron beam after pattern matching.
FIG. 6 is a schematic cross-sectional view showing that a defect region recognized by an AFM that best shows the features of the present invention is combined and processed by an electron beam.
FIG. 7 is a diagram showing a region actually processed with an electron beam after pattern matching when a defect is not visible with a photomask defect correcting apparatus using an electron beam.
FIG. 8 is a schematic cross-sectional view of a region to be processed with an electron beam when a black defect is not visible with a photomask defect correcting apparatus using an electron beam.
FIG. 9 is a schematic cross-sectional view illustrating a case where a white defect is corrected using the present invention.
FIG. 10 is a flowchart showing a defect correction procedure according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Defect area | region recognized by AFM observation 2 ... Pattern 3a for the alignment recognized by AFM observation ... Defect area | region 3b converted into the figure format of the photomask defect correction apparatus using an electron beam ... Pattern superposition Irradiation area corrected defect area 4 ... pattern for alignment converted into a graphic format of a photomask defect correction apparatus using an electron beam 5 ... defect area 6 observed by a photomask defect correction apparatus using an electron beam ... Pattern 7 for alignment observed with photomask defect correction device using electron beam ... Base glass surface 8 ... Electron beam 9 ... Etching gas gun 10 ... Black defect correction etching gas (xenon fluoride)
11 ... deposition gas gun 12 ... light source gas for the light-shielding film of the white defect correction film (phenanthrene, naphthalene, etc.)
13 ... White defect correction film

Claims (4)

Extract the black defect area and alignment pattern of the mask with an atomic force microscope, and convert the extracted black defect area shape and alignment pattern into the figure format of the mask defect correction device using an electron beam. The extracted alignment pattern is aligned with the alignment pattern of the secondary electron image by the mask defect correcting device using the electron beam in the region including the black defect, and an etching gas is applied to the extracted black defect region. A defect correction method for a mask, wherein the defect is corrected by irradiating with the electron beam while supplying. 2. The mask defect correcting method according to claim 1, wherein the etching gas is a fluorine compound. Extract the white defect area and alignment pattern of the mask with an atomic force microscope, and convert the extracted white defect area shape and alignment pattern into a graphic format for a mask defect correction device using an electron beam. The extracted alignment pattern is aligned with the alignment pattern of the secondary electron image by the mask defect correcting device using the electron beam in the region including the white defect, and a light shielding film is applied to the extracted white defect region. A mask defect correcting method comprising forming a light-shielding film and correcting it by irradiating an electron beam while supplying a source gas. 4. The mask defect correcting method according to claim 3, wherein the light shielding film source gas is phenanthrene or naphthalene.

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