WO2012014520A1 - フォトマスク修正方法およびレーザ加工装置 - Google Patents
フォトマスク修正方法およびレーザ加工装置 Download PDFInfo
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- WO2012014520A1 WO2012014520A1 PCT/JP2011/056242 JP2011056242W WO2012014520A1 WO 2012014520 A1 WO2012014520 A1 WO 2012014520A1 JP 2011056242 W JP2011056242 W JP 2011056242W WO 2012014520 A1 WO2012014520 A1 WO 2012014520A1
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- photomask
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- film
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/50—Mask blanks not covered by G03F1/20 - G03F1/34; Preparation thereof
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
- G03F1/72—Repair or correction of mask defects
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
- B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
- B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
- B23K26/066—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms by using masks
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
- G03F1/54—Absorbers, e.g. of opaque materials
Definitions
- the present invention relates to a photomask correction method and a laser processing apparatus, and more particularly to a photomask correction method and a laser processing apparatus suitable for use in correcting a halftone pattern of a photomask.
- the intensity of the laser beam for example, the irradiation energy density per pulse is 10 to 30 mJ / cm 2
- the concentration of the chromium carbonyl gas that is the source gas can be reduced.
- a CVD film can be deposited while being almost rate-determined by the supply amount.
- the transmittance distribution of the CVD film is hardly affected by the intensity distribution of the laser beam, and a CVD film having a substantially uniform transmittance can be formed. Further, since the film formation rate is low (for example, around 0.5 nm / s), fine adjustment of the transmittance becomes easy.
- the Q switch frequency is set to, for example, 2 to 4 kHz at which the average output of the laser beam becomes maximum.
- the relationship between the transmittance T and the film thickness d of the CVD film is obtained by the following equation (1) using the reflectance R and the absorption coefficient ⁇ of the CVD film (in practice, however, the multiple generated in the CVD film) Because of the influence of interference, the transmittance ⁇ is increased or decreased from the value obtained by the equation (1)).
- the CVD film obtained by the conventional film formation method described above contains chromium oxide III (Cr 2 O 3 ) as a main component.
- the CVD film mainly composed of chromium oxide III has an absorption coefficient for the exposure wavelength (mercury emission line i line (365 nm), h line (405 nm), g line (436 nm)) of a photomask for FPD (Flat Panel Display). ⁇ is low. Therefore, the required film thickness d is increased with respect to the target transmittance T.
- the absorption coefficient with respect to i-line of a CVD film mainly composed of chromium oxide III is about 9 ⁇ 10 3 cm ⁇ 1
- the film thickness necessary for making the transmittance with respect to i-line 40% is about
- the film thickness necessary for 90 nm and 10% is about 250 nm.
- the present invention has been made in view of such a situation, and is intended to enable correction of a halftone pattern of a photomask having a lower transmittance.
- a photomask correction method is a photomask correction method for correcting a photomask, and is for each pulse emitted from a laser oscillator in which a Q switch frequency is set in a range of 1 Hz to 1 kHz. Is applied to the halftone pattern correction portion of the photomask using an ultraviolet laser beam having an irradiation energy density of 40 mJ / cm 2 or more, or an irradiation power density of 1 MW / cm 2 or more, and a source gas made of chromium carbonyl gas. A CVD film is formed.
- a CVD film having a metal chromium film quality is formed on the correction portion of the halftone pattern of the photomask.
- This laser oscillator is composed of, for example, a CW (Continuous Wave) pumped Q-switched Nd: YLF laser.
- This ultraviolet laser beam is, for example, a laser beam of the fourth harmonic (FHG, oscillation wavelength 263 nm) of a Q switch Nd: YLF laser.
- an ultraviolet laser beam having a pulse width of 40 ns or less and an irradiation power density of 1 MW / cm 2 or more, or a pulse width exceeding 40 ns and an irradiation energy density per pulse of 40 mJ UV laser light exceeding / cm 2 can be used.
- a laser processing apparatus is a laser processing apparatus for correcting a photomask, wherein a Q-switch laser oscillation means for oscillating ultraviolet laser light and a source gas composed of chromium carbonyl gas are supplied to a half of the photomask.
- a source gas supply means for supplying the vicinity of the correction portion of the tone pattern; a laser control means for controlling the Q switch frequency of the Q switch laser oscillation means and the irradiation energy density and irradiation power density per pulse of the ultraviolet laser light;
- the Q switch frequency of the Q switch laser oscillation means is set within the range of 1 Hz to 1 kHz, and the irradiation energy density per pulse of the ultraviolet laser light is 40 mJ / cm 2 or more, or the irradiation power of the ultraviolet laser light set the density of 1 MW / cm 2 or more, and irradiated with ultraviolet laser light to the correction area, before And generating a CVD film on the modified portion.
- a CVD film having a metal chromium film quality is formed on the correction portion of the halftone pattern of the photomask.
- the Q-switch laser oscillation means is constituted by, for example, a CW (Continuous Wave) pumped Q-switch Nd: YLF laser.
- This ultraviolet laser beam is, for example, a laser beam of the fourth harmonic (FHG, oscillation wavelength 263 nm) of a Q switch Nd: YLF laser.
- This source gas supply means is constituted by, for example, a gas unit and a source gas supply / exhaust unit.
- This laser control means is constituted by, for example, a computer or various processors.
- the halftone pattern of the photomask can be corrected.
- Embodiment 2 modes for carrying out the present invention (hereinafter referred to as embodiments) will be described. The description will be given in the following order. 1. Embodiment 2. FIG. Modified example
- FIG. 1 is a block diagram showing an embodiment of a laser processing apparatus 1 to which the present invention is applied.
- the laser processing apparatus 1 is an apparatus that corrects a photomask 2 having a halftone pattern.
- the laser processing apparatus 1 includes a CVD processing laser oscillator 11, a laser irradiation intensity uniformizing optical system 12, a ZAP processing laser oscillator 13, a laser irradiation intensity uniformizing optical system 14, a variable slit 15, an imaging processing optical system 16, a gas.
- Unit 17 source gas supply / exhaust unit 18, mask holder 19, XY stage 20, transmitted illumination 21, transmitted illumination lens 22, observation optical system 23, probe light source 24, transmitted light intensity measuring device 25, and control unit 26 Configured to include.
- the CVD processing laser oscillator 11 is configured by, for example, a CW (Continuous Wave) -excited Q-switched Nd: YLF laser, and a fourth harmonic (FHG, oscillation wavelength 263 nm) laser beam (hereinafter also referred to as a CVD laser beam). Oscillates and emits.
- CW Continuous Wave
- Q-switched Nd YLF laser
- FHG oscillation wavelength 263 nm
- the laser irradiation intensity uniformizing optical system 12 is an optical system for making the intensity distribution of the CVD laser light passing through the variable slit 15 substantially uniform.
- the laser irradiation intensity uniformizing optical system 12 passes through the variable slit 15 by enlarging the beam diameter of the CVD laser beam with a beam expander and causing the central portion of the beam having a small intensity difference to enter the opening of the variable slit 15.
- the intensity distribution of the CVD laser light in the spatial direction is averaged.
- the laser irradiation intensity uniformizing optical system 12 averages the intensity distribution in the time direction of the CVD laser light passing through the variable slit 15 by swaying the laser beam with a galvanometer or the like.
- the laser illumination intensity uniformizing optical system 12 includes an optical attenuator for adjusting the irradiation power density of the CVD laser light.
- the laser oscillator 13 for ZAP processing is constituted by, for example, a pulse-excited Q-switched Nd: YLF laser, and a third harmonic (THG, oscillation wavelength 355 nm) laser light (hereinafter referred to as ZAP laser light) having an oscillation repetition frequency of 50 Hz or less. Oscillate and emit.
- ZAP laser light a third harmonic (THG, oscillation wavelength 355 nm) laser light
- ZAP laser light a third harmonic (THG, oscillation wavelength 355 nm) laser light
- ZAP laser light an oscillation repetition frequency of 50 Hz or less. Oscillate and emit.
- the near-ultraviolet laser beam having a wavelength of around 355 nm has been conventionally used as a laser beam for ZAP processing in a repair apparatus for correcting a photomask.
- the laser irradiation intensity uniformizing optical system 14 has a configuration similar to that of the laser irradiation intensity uniforming optical system 12, and the intensity distribution in the spatial direction and time direction of the ZAP laser light passing through the variable slit 15 is substantially uniform. To do.
- the laser irradiation intensity uniformizing optical system 14 includes an optical attenuator for adjusting the irradiation power density of the ZAP laser light.
- the variable slit 15 has two sets of two knife edges, and the size of the rectangular opening can be changed by adjusting the interval between the knife edges of each set.
- the variable slit 15 has a mechanism for rotating the whole around the optical axis.
- the imaging processing optical system 16 is an optical system that forms an image of the laser light that has passed through the variable slit 3 on the surface of the photomask 2.
- the imaging processing optical system 16 includes, for example, an objective lens 14a, an imaging lens (not shown), a dichroic mirror (not shown), a mirror (not shown) that forms an optical path of laser light, and laser light after passing through the variable slit 15. It is comprised by the laser output measuring device (not shown) etc. which measure the output of this.
- the imaging processing optical system 16 includes a fine movement stage 16b for finely moving the objective lens 16a in order to scan an irradiation spot, which is an image of the opening of the variable slit 15 by laser light, at a predetermined speed on the photomask 2. .
- the gas unit 17 supplies a carrier gas and a purge gas for conveying the chromium carbonyl gas, which is a source gas, to the source gas supply / exhaust unit 18.
- the gas unit 17 thermally decomposes the source gas contained in the gas sucked from the suction port of the source gas supply / exhaust unit 18 and captures it with a filter.
- the concentration of the source gas supplied to the processing portion of the photomask 2 is adjusted based on the control of the control unit 26 to adjust the concentration of the source gas generated by adjusting the temperature of the source gas container, or the purge gas and the carrier. It is adjusted by adjusting the gas flow rate.
- the raw material gas supply / exhaust unit 18 supplies a carrier gas and a purge gas to the processing portion of the photomask 2.
- the source gas is supplied to the processing portion of the photomask 2 by the carrier gas.
- the purge gas removes air from the processed portion of the photomask 2.
- the source gas supply / exhaust unit 18 includes a suction port for sucking the source gas so that the source gas does not leak outside, and supplies the sucked gas to the gas unit 17. Thereby, the space near the processed part of the photomask 2 is maintained in the source gas atmosphere.
- a CVD film is deposited on the processing portion by irradiating the processing portion with the CVD laser light in a state where the space near the processing portion of the photomask 2 is maintained in the source gas atmosphere.
- the source gas supply / exhaust unit 18 includes a window plate that transmits laser light, observation illumination light, and probe light.
- the purge gas also serves to prevent the window plate from being CVD processed.
- the mask holder 19 is mounted on the XY stage 20 and fixes the position of the photomask 2.
- the XY stage 20 moves the mask holder 19 in the horizontal direction under the control of the control unit 26 and positions the processing position of the photomask 2 held by the mask holder 19.
- the transmission illumination 21 emits observation illumination light for generating a transmission image of the photomask.
- the observation illumination light emitted from the transmission illumination 21 is condensed on the surface of the photomask 2 by the transmission illumination lens 22.
- the observation illumination light transmitted through the photomask 2 is reflected in the direction of the observation optical system 23 by a dichroic mirror (not shown) in the image forming optical system 16.
- the observation optical system 23 forms an image of the surface of the photomask 2 (hereinafter referred to as an observation image) with observation illumination light.
- the user can observe the observed image through an eyepiece (not shown) or the like. It is also possible to display an image obtained by taking an observation image by providing an imaging element in the observation optical system 23.
- the probe light source 24 emits light (probe light) having a wavelength close to or equal to the light source wavelength of an exposure machine that performs exposure of the photomask 2 under the control of the control unit 26.
- the probe light emitted from the probe light source 24 passes through the window plate of the imaging processing optical system 16 and the source gas supply / exhaust unit 18 and is irradiated onto the photomask 2.
- the probe light transmitted through the photomask 2 is collected by the transmission illumination lens 22 and enters the transmitted light intensity measuring device 25.
- the transmitted light intensity measuring device 25 measures the intensity of the probe light transmitted through the photomask 2 and supplies a signal indicating the measurement result to the control unit 26.
- the transmitted illumination 21 and the transmitted light intensity measuring device 25 are moved under the control of the control unit 26, and either the transmitted illumination 21 or the transmitted light intensity measuring device 25 is placed on the optical axis of the transmitted illumination lens 22. It is possible to select and install.
- the control unit 26 is configured by, for example, a computer or various processors, and controls each unit of the laser processing apparatus 1. For example, the control unit 26 adjusts the Q switch frequency of the laser oscillator 11 for CVD processing, the pulse width of the CVD laser light, and the like. The control unit 26 controls the optical attenuator of the laser irradiation intensity uniformizing optical system 12 to adjust the irradiation power density of the CVD laser light. Further, the control unit 26 adjusts the Q switch frequency of the ZAP processing laser oscillator 13, the pulse width of the ZAP laser light, and the like. Further, the control unit 26 controls the optical attenuator of the laser irradiation intensity uniformizing optical system 14 to adjust the irradiation power density of the ZAP laser light.
- control unit 26 controls the fine movement stage 16b of the imaging processing optical system 16 to adjust the scanning speed of the irradiation spot. Further, the control unit 26 controls the gas unit 17 to adjust the concentration of the source gas and the flow rates of the purge gas and the carrier gas. Further, the control unit 26 controls the XY stage 20 to move the horizontal position of the photomask 2. Further, the control unit 26 sets the positions of the transmitted illumination 21 and the transmitted light intensity measuring device 25. Furthermore, the control unit 26 obtains the transmittance of the photomask 2 such as a halftone pattern based on the measurement result of the probe light intensity by the transmitted light intensity measuring device 25.
- the absorption coefficient for the ZAP laser light which is near-ultraviolet light, is large, and the film thickness is A thin CVD film may be formed.
- the CVD process may be performed under the same conditions as those for correcting white defects in a conventional binary mask. That is, the concentration of the source gas is made higher than that of the conventional halftone pattern correction described above, the intensity of the CVD laser light is increased, and a CVD film having a higher quality of metallic chromium is formed. That's fine.
- the Q switch frequency is 2 kHz (pulse width (full width at half maximum) of about 40 ns)
- the average irradiation power density of CVD laser light is 80 to 200 W / cm 2
- the irradiation energy density per pulse is 40 to 100 mJ / cm 2 .
- CVD with an absorption coefficient of about 3 ⁇ 10 5 cm ⁇ 1 (a film thickness of about 150 nm at which OD3 is about (transmittance of about 0.1%)) is performed under this CVD processing condition. A film is deposited.
- the CVD film mainly composed of chromium oxide III formed under the conventional CVD processing conditions has an absorption coefficient for the exposure wavelength (i-line, h-line, g-line) of the FPD photomask. Since it is low, the transmittance largely changes depending on the exposure wavelength.
- a CVD film formed under these CVD processing conditions has a film quality close to that of metallic chromium, so the absorption coefficients for i-line, h-line, and g-line are almost the same, and the transmittance due to the difference in exposure wavelength. Can be reduced.
- the deposition rate of the CVD film becomes as fast as around 100 nm / s, and it becomes difficult to control the film thickness.
- the absorption coefficient of the CVD film increases not only for ZAP laser light, which is near-ultraviolet light, but also for i-line, h-line, and g-line. Change. Therefore, it is difficult to set the transmittance of the CVD film to a desired value, and the transmittance unevenness due to the non-uniform film thickness in the CVD film becomes large.
- FIG. 2 shows an irradiation spot on a quartz substrate with a CVD laser beam having a pulse width (full width at half maximum) of about 40 ns and an irradiation energy density per pulse of about 40 mJ / cm 2 (irradiation power density is about 1 MW / cm 2 ).
- irradiation power density is about 1 MW / cm 2 .
- FIG. 3 is a graph showing an example of measurement results of average transmittance for i-line and transmittance unevenness in the scanning direction under the same conditions as in FIG. Note that the transmittance unevenness is represented by a difference between the maximum value and the minimum value of the transmittance in the scanning direction. Further, the horizontal axis of FIG. 3 represents average transmittance (unit:%), and the vertical axis represents transmittance unevenness (unit:%).
- FIG. 2 shows that the lower the Q switch frequency, the longer the irradiation time required to lower the average transmittance of the CVD film. That is, the lower the Q switch frequency, the slower the deposition rate of the CVD film.
- the deposition rate of the CVD film is about 1 ⁇ 2
- the deposition rate of the CVD film is Becomes about 1/4. Thereby, the control of the film thickness becomes easy, and a CVD film closer to the desired transmittance can be obtained.
- FIG. 3 shows that the lower the Q switch frequency is, the less uneven transmission in the scanning direction and the more uniform the film thickness in the scanning direction.
- the lower the Q switch frequency the slower the deposition rate of the CVD film, and the longer the irradiation time of the CVD laser light necessary to obtain a CVD film having a desired transmittance.
- the vibration of the CVD laser light, the fluctuation of the scanning speed, and the fluctuation of the output intensity within the time shorter than the irradiation time are averaged, and the film thickness in the CVD film is made uniform, thereby improving the transmittance unevenness.
- the Q switch frequency is lowered and the time interval for performing the irradiation with the CVD laser light (the rest period of the CVD laser light) is increased, the surface adsorption amount of the source gas molecules at the tip portion of the CVD film is saturated during that time, The stable formation of growth nuclei and the stable deposition rate of the CVD film are another factor in improving the transmittance unevenness.
- the range of the average transmittance where the transmittance unevenness is 4% or less is 20% or less when the Q switch frequency is 2.0 kHz, whereas the Q switch frequency is 1.0 kHz. In the case of 0.5 kHz, they are about 40% or less and 49% or less, respectively. Therefore, assuming that the allowable level of transmittance unevenness is 4% ( ⁇ 2%), if the Q switch frequency is set to 1.0 kHz or less, a halftone pattern with a transmittance of less than 40% that could not be corrected conventionally is corrected. A sufficient CVD film can be deposited.
- the film thickness at which the average transmittance for i-line was 40% was 40 nm or less, and the film thickness at which the average transmittance for i-line was 10% was 100 nm or less. This indicates that the absorption coefficient of the CVD film with respect to i-line is about 2.3 ⁇ 10 5 cm ⁇ 1 or more.
- the Q switch frequency is set higher than 1 kHz, it is possible to reduce the deposition rate of the CVD film and extend the irradiation time of the CVD laser light by reducing the source gas concentration or the irradiation power density of the CVD laser light. Is possible.
- the Q switch frequency is increased, the formation of growth nuclei at the tip of the CVD film becomes unstable, and the transmittance unevenness deteriorates.
- the measurement results in FIGS. 2 and 3 are obtained when the pulse width of the CVD laser light is about 40 ns. Further, when the pulse width is other than 40 ns, for example, the pulse width is within a range of several ns to 100 ns. Consider different cases.
- ⁇ T is the amount of increase in the surface temperature of the quartz substrate per pulse of the CVD laser beam necessary for obtaining a CVD film having a metallic film quality.
- the thermal diffusion length ( ⁇ CVD ⁇ ⁇ ) 1/2 ( ⁇ CVD is the heat transfer coefficient of the CVD film, ⁇ is the pulse width of the CVD laser light) is sufficiently larger than the film thickness. It is assumed that the temperature of the film changes uniformly.
- heat transfer to the quartz substrate is expressed as C g ⁇ ⁇ g ⁇ ( ⁇ g ⁇ ⁇ ) 1/2 ⁇ ⁇ T (C g is the specific heat of the quartz substrate, ⁇ g is the density of the quartz substrate, and ⁇ g is the quartz It approximates the heat transfer coefficient of the substrate.
- C g is the specific heat of the quartz substrate
- ⁇ g is the density of the quartz substrate
- ⁇ g is the quartz It approximates the heat transfer coefficient of the substrate.
- ⁇ T is expressed by the following equation.
- ⁇ T P ⁇ ⁇ / (C CVD ⁇ ⁇ CVD ⁇ d + C g ⁇ ⁇ g ⁇ ( ⁇ g ⁇ ⁇ ) 1/2 ) (2)
- P represents the irradiation power density of the CVD laser light
- C CVD represents the specific heat of the CVD film
- ⁇ CVD represents the density of the CVD film
- d represents the film thickness of the CVD film.
- the irradiation power density P and the irradiation energy density P ⁇ ⁇ at which the same surface temperature increase ⁇ T can be obtained are as follows.
- the irradiation energy density per pulse was about 25 mJ / cm 2 (the irradiation power density was about 3.5 MW / cm 2).
- the irradiation power density is increased from 1 MW / cm 2 to 3.5MW / cm 2
- irradiation energy density is reduced from 40 mJ / cm 2 to 25 mJ / cm 2 is doing.
- the irradiation power density of the CVD laser light is set to 1.0 MW / cm 2 or more (irradiation energy density per pulse is 40 mJ / cm 2 or less), and the pulse width exceeds 40 ns.
- a CVD film having a metallic film quality is formed by setting the irradiation power density of the CVD laser light to less than 1.0 MW / cm 2 (the irradiation energy density per pulse is more than 40 mJ / cm 2 ). Can be said to be possible.
- the irradiation energy density or irradiation power density of the CVD laser light needs to be set lower than a value that damages the deposited CVD film and the light shielding film of the photomask.
- the above values are the CVD processing conditions (for example, the irradiation time of the CVD laser light, the concentration of the source gas, the size of the irradiation spot, the size of the CVD processing, etc.), the material of the photomask substrate, the configuration of the light shielding film (for example, Single layer film, two-layer film, three-layer film, etc.), material and film thickness, etc.
- the CVD processing conditions for example, the irradiation time of the CVD laser light, the concentration of the source gas, the size of the irradiation spot, the size of the CVD processing, etc.
- the material of the photomask substrate for example, the configuration of the light shielding film (for example, Single layer film, two-layer film, three-layer film, etc.), material and film thickness, etc.
- the source gas conditions are appropriately set so that a CVD film having a metallic film quality can be obtained, there is no need to set a lower limit for the Q switch frequency.
- the Q switch frequency is lowered, improvement in the halftone pattern correction quality (for example, transmittance unevenness) can be expected, but the time required for correction becomes longer. Therefore, it is desirable to set the Q switch frequency to an appropriate value in consideration of the economics of photomask correction, for example, the correction time and correction quality, the product price of the photomask, and the delivery date.
- the conventional halftone pattern correction method requires an irradiation time of about 3 minutes, which corresponds to the irradiation time when the Q switch frequency is set to about 1 Hz in the present embodiment. Therefore, if the correction time is set to be equal to or higher than the conventional level, the lower limit value of the Q switch frequency is 1 Hz.
- the Q switch frequency it is desirable to set the Q switch frequency to 0.5 kHz or less in order to more reliably reduce the transmittance unevenness to an allowable level or less.
- step S1 the laser processing apparatus 1 shapes the defect pattern. For example, the laser processing apparatus 1 irradiates the halftone film 51 with ZAP laser light, and removes the halftone film 51 by ZAP processing.
- the photomask 2 may be cleaned in order to prevent a uniform defect of the CVD film due to ZAP processing residue or scattering.
- the laser processing apparatus 1 sets a target transmittance range. Specifically, the laser processing apparatus 1 uses the halftone pattern on the photomask 2 that has the same shape and transmittance as the halftone pattern to be corrected and has no defect as a reference pattern, and measures the probe light and transmitted light intensity. Using the instrument 25, the transmittance of the reference pattern at the actual exposure wavelength is measured. And the control part 26 sets the predetermined range centering on the transmittance
- the laser processing apparatus 1 sets CVD processing conditions.
- the control unit 26 sets the CVD processing conditions of the laser processing apparatus 1 to the CVD processing conditions described above with reference to FIGS. That is, the control unit 26 sets the Q switch frequency of the CVD processing laser oscillator 11 within the range of 1 Hz to 1.0 kHz, and more preferably within the range of 1 Hz to 0.5 kHz.
- the control part 26 controls the gas unit 17, and sets the density
- control unit 26 controls the optical attenuator of the laser irradiation intensity uniformizing optical system 12 to set the average irradiation power density of the CVD laser light to a predetermined value.
- the pulse width of the CVD laser beam is 40 nm or less
- the irradiation power density of the CVD laser beam is 1.0 MW / cm 2 or more
- the irradiation energy density per pulse is 40 mJ / cm 2 or less.
- the irradiation power density of the CVD laser light is less than 1.0 MW / cm 2 , and the average is such that the irradiation energy density per pulse exceeds 40 mJ / cm 2.
- An irradiation power density is set.
- control unit 26 sets the scan speed or the number of scans based on a comparison table of the target transmittance prepared in advance and the scan speed or the number of scans of the irradiation spot. At this time, considering the variation range of the transmittance of the CVD film, the scanning speed or the number of scans is set so that the transmittance at the exposure wavelength of the CVD film does not fall below the target transmittance range.
- step S4 the laser processing apparatus 1 performs a CVD process under the CVD process conditions set in the process of step S3. Thereby, for example, as shown in FIG. 7, a CVD film 61 is formed on the trace from which the halftone film 51 is removed (that is, the corrected portion of the halftone pattern).
- the processing portion of the photomask 2 is irradiated with CVD laser light at an irradiation power density at the time of processing or higher. You may do it.
- step S5 the laser processing apparatus 1 measures the transmittance of the processed part. That is, the transmittance of the newly formed CVD film 61 is measured in the same manner as the process of step S2.
- step S6 the laser processing apparatus 1 determines whether or not the transmittance is within the range of the target transmittance. That is, the laser processing apparatus 1 determines whether or not the transmittance of the CVD film 61 measured in the process of step S5 is within the range of the target transmittance set in the process of step S2. When it determines with it being outside, a process progresses to step S7.
- step S7 the laser processing apparatus 1 determines whether or not the transmittance is higher than the target transmittance range. That is, the laser processing apparatus 1 determines whether or not the transmittance of the CVD film 61 measured in the process of step S5 is higher than the target transmittance range set in the process of step S2, and from the target transmittance range. If it is determined that the value is high, the process proceeds to step S8.
- step S8 the laser processing apparatus 1 adjusts the CVD processing conditions. Specifically, the laser processing apparatus 1 changes the Q switch frequency, the raw material gas concentration, and the average irradiation power density to predetermined values. Further, the laser processing apparatus 1 sets the scan speed based on a comparison table prepared in advance for the difference between the measurement result of the transmittance and the target transmittance and the scan speed of the irradiation spot.
- the Q switch frequency, the source gas concentration, and the average irradiation power density are set so that the film forming speed of the CVD film is as slow as possible. It is desirable to do. However, even if the CVD processing conditions similar to those used in the conventional halftone pattern correction are set, the thickness of the CVD film 61 that increases in the subsequent step S9 is small. It is very unlikely to occur.
- step S9 the laser processing apparatus 1 performs CVD processing for fine adjustment of transmittance. That is, the laser processing apparatus 1 finely adjusts the transmittance of the CVD film 61 by performing CVD processing under the CVD processing conditions set in the process of step S7 and slightly increasing the film thickness of the CVD film 61.
- step S5 the transmittance is within the range of the target transmittance, or until it is determined in step S7 that the transmittance is lower than the range of the target transmittance.
- steps S5 to S9 are repeatedly executed, and fine adjustment of the transmittance of the CVD film 61 is performed.
- step S7 if it is determined in step S7 that the transmittance is lower than the target transmittance range, that is, if the film thickness of the CVD film 61 is too thick, the process returns to step S1, and the processes after step S1 are performed. Executed. That is, the newly generated CVD film 61 is removed by ZAP processing, and the CVD film is formed again.
- step S6 when it is determined in step S6 that the transmittance is within the range of the target transmittance, the process proceeds to step S10.
- step S10 the laser processing apparatus 1 shapes the CVD film. For example, as shown in FIG. 8, the laser processing apparatus 1 removes the CVD films 61A and 61B protruding from a predetermined pattern from the formed CVD film 61 by ZAP processing, and leaves only the CVD film 61C. At this time, since the CVD film 61 is formed under the CVD processing conditions described above with reference to FIGS. 2 and 3, no cracks are generated even if the ZAP processing is performed on the CVD film 61.
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Abstract
Description
こうすることで、CVD膜の透過率分布がレーザ光の強度分布の影響を受けにくくなり、透過率がほぼ均一なCVD膜を成膜することができる。また、成膜速度が低い(例えば、0.5nm/s前後)ため、透過率の微調整が容易になる。
1.実施の形態
2.変形例
[レーザ加工装置の構成例]
図1は、本発明を適用したレーザ加工装置1の一実施の形態を示すブロック図である。
レーザ加工装置1は、ハーフトーンパターンを有するフォトマスク2の修正を行う装置である。レーザ加工装置1は、CVD加工用レーザ発振器11、レーザ照射強度均一化光学系12、ZAP加工用レーザ発振器13、レーザ照射強度均一化光学系14、可変スリット15、結像加工光学系16、ガスユニット17、原料ガス供給・排気ユニット18、マスクホルダ19、XYステージ20、透過照明21、透過照明レンズ22、観察光学系23、プローブ光源24、透過光強度測定器25、および、制御部26を含むように構成される。
ここで、レーザ加工装置1において、フォトマスク2のハーフトーンパターンの欠陥部を修正するときのCVD加工条件について検討する。
ただし、PはCVDレーザ光の照射パワー密度、CCVDはCVD膜の比熱、ρCVDはCVD膜の密度、dはCVD膜の膜厚を表す。
P×τ=ΔT×(CCVD×ρCVD×d+Cg×ρg×(κg×τ)1/2) ・・・(4)
次に、図4のフローチャートを参照して、レーザ加工装置1により実行されるフォトマスク修正処理について説明する。なお、以下、図5のフォトマスク2上に形成されたハーフトーンパターンのハーフトーン膜51ににより形成されるハーフトーンパターンに欠陥52が生じており、そのハーフトーンパターンの修正を行う場合を例に挙げて説明する。
なお、以上の説明では、ハーフトーン膜51を全て除去してから、ハーフトーンパターンを修正する例を示したが、欠陥52の周辺のハーフトーン膜51のみを除去してからハーフトーンパターンを修正するようにしてもよい。
2 フォトマスク
11 CVD加工用レーザ発振器
12 レーザ照射強度均一化光学系
13 ZAP加工用レーザ発振器
14 レーザ照射強度均一化光学系
15 可変スリット
16 結像加工光学系
16a 対物レンズ
16b 微動ステージ
17 ガスユニット
18 原料ガス供給・排気ユニット
24 プローブ光源
25 透過光強度測定器
26 制御部
Claims (3)
- フォトマスクの修正を行うフォトマスク修正方法において、
Qスイッチ周波数が1Hzから1kHzの範囲内に設定されたレーザ発振器から出射される、1パルス当りの照射エネルギ密度が40mJ/cm2以上、もしくは、照射パワー密度が1MW/cm2以上の紫外レーザ光、および、クロムカルボニルガスからなる原料ガスを用いて前記フォトマスクのハーフトーンパターンの修正部分にCVD膜を成膜する
ことを特徴とするフォトマスク修正方法。 - パルス幅が40ns以下、かつ、照射パワー密度が1MW/cm2以上の紫外レーザ光、または、パルス幅が40nsを超え、かつ、1パルス当りの照射エネルギ密度が40mJ/cm2を超える紫外レーザ光を用いる
ことを特徴とする請求項1に記載のフォトマスク修正方法。 - フォトマスクの修正を行うレーザ加工装置において、
紫外レーザ光を発振するQスイッチレーザ発振手段と、
クロムカルボニルガスからなる原料ガスを前記フォトマスクのハーフトーンパターンの修正部分近傍に供給する原料ガス供給手段と、
前記Qスイッチレーザ発振手段のQスイッチ周波数、並びに、紫外レーザ光の1パルス当りの照射エネルギ密度および照射パワー密度を制御するレーザ制御手段と
を備え、
前記Qスイッチレーザ発振手段のQスイッチ周波数を1Hzから1kHzの範囲内に設定し、紫外レーザ光の1パルス当りの照射エネルギ密度を40mJ/cm2以上、または、紫外レーザ光の照射パワー密度を1MW/cm2以上に設定して、紫外レーザ光を前記修正部分に照射し、前記修正部分にCVD膜を生成する
ことを特徴とするレーザ加工装置。
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CN104746041B (zh) * | 2015-03-04 | 2018-02-13 | 深圳清溢光电股份有限公司 | 激光气相沉积方式修补白缺陷的方法 |
TWI691608B (zh) * | 2017-09-12 | 2020-04-21 | 日商Hoya股份有限公司 | 光罩之修正方法、光罩之製造方法、光罩及顯示裝置之製造方法 |
JP2018133591A (ja) * | 2018-05-18 | 2018-08-23 | 大日本印刷株式会社 | テンプレートの製造方法 |
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