JPS61127125A - Method for correcting defect of photomask - Google Patents

Abstract

PURPOSE:To effect the durable correction in a short time by carrying out cleaning of a defect part of a mask and formation of a light screening film continuously in the same container. CONSTITUTION:While holding a mask 7 in the upper part of a correction chamber 8, the air of the chamber is exhausted and the correcting substance (bisbenzene chromium) 10 is evaporated by heating. A focusing point of laser beams 20 is adjusted to the defect by observation by means of an optical system 23. The chamber 8 is kept at 1X10<-3>Torr or under and O2 is introduced into a chamber 34. RF electric field is applied to electrodes 35 and 36 to convert O2 into O+O3 which is supplied to the chamber 8. Ultraviolet rays 32 are focused at the defect part by a mirror 31 and O3 in the optical path is decomposed. The adhering contaminator is eliminated by a pump 13 after decomposition and oxidation and thus the defect part is cleaned and activated chemically. After eliminating the residual O3 and O2, the correcting substance 10 is introduced and under 1X10<-2>Torr, the laser beams 20 are focused and scanned to heat the defect part where the correcting substance 10 is decomposed to deposit Cr which forms a light screening film over the defect part. By this constitution, the correction film having the god wear and chemical resistances can be formed rapidly.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for correcting missing defects in a photomask pattern, and particularly relates to a method for correcting missing patterns in a photomask that allows a repair film with excellent durability to be obtained in a short period of time. It is something.

[Background of the invention]

There are two types of photomask defects: residual defects and missing defects.

These defects affect the yield of semiconductors such as LSI.

Furthermore, since the correction of these defects greatly affects productivity, it is necessary to minimize the number of steps required for correction and to carry out the correction in a short period of time.

Among the defects that occur in photomasks, residual defects can be corrected by laser (Japanese Patent Publication No. 52-9508), which can significantly shorten the process. On the other hand, a lift-off method is used to correct missing defects, such as missing parts of normal patterns.

This lift-off method is performed by the following steps.

(1) Apply a positive photoresist to the entire surface of the photomask having missing defects.

(2) Only the missing defective portion is exposed using a partial exposure method.

(3) A window is opened in the resist at the missing defective part by development processing.

(4) Using vacuum evaporation technology, a metal film is formed on the resist in and around the defective part or on the entire surface of the photomask.

(5) The resist is removed and at the same time the metal film formed on the resist is also removed.

As described above, the lift-off method requires many steps and cannot be said to be sufficient in terms of production for correcting missing defects in photomasks, posing a major technical problem.

Furthermore, recently, a method has been reported in which a metal is deposited from an organometallic solution by laser beam irradiation. (Kaide et al.: Metal Deposition from Organometallic Solutions by Laser Irradiation: Spring 1980, 30th Applied Physics Conference, Proceedings P, 202) As shown in Figure 3, this is a Cr complex or A benzene solution 1 of Mo complex is put into a cell 3 having two glass windows 2, and a laser beam 4 is focused on the inside of one glass window 2a by an objective lens 5 to deposit a metal 6.

The inventors attempted to apply this technique to repairing missing defects in photomasks.

However, the Cr complex or Mo complex used here is very unstable, and when exposed to the atmosphere, it reacts with oxygen in the atmosphere to form an oxide, making it difficult to handle and causing the metal deposits to deteriorate. However, there are technical problems in directly applying this technology to repairing missing defects in photomasks.

By the way, before a photomask is used for exposing a wafer or the like, it is subjected to scrub cleaning using a nylon brush or the like or chemical cleaning using hot concentrated sulfuric acid or the like. Therefore, the portion of the photomask in which missing defects have been corrected is required to have excellent abrasion resistance and chemical resistance so that it can withstand such cleaning during use.

In this respect, the lift-off method described above can be modified to have excellent chemical resistance by appropriately selecting the metal to be deposited. However, regarding abrasion resistance, even if the deposited metal film itself has excellent abrasion resistance, photoresist residue due to variations in exposure and development conditions, moisture, etc. may be generated from the development process to the vacuum deposition process. Contaminants due to adsorption may adhere to the defective parts, reducing the adhesion to the substrate, and may peel off during scrubbing. On the other hand, in the method using an organic metal solution, the deposited metal tends to be in a state of agglomeration of particles, so there is a problem in wear resistance.

[Purpose of the invention]

The present invention solves the conventional problems described above, corrects missing defects in mask patterns in a shorter time using a simpler process than conventional methods, and has excellent wear resistance and chemical resistance comparable to conventional lift-off methods. An object of the present invention is to provide a method for repairing missing defects in a photomask.

[Summary of the invention]

In order to achieve the above object, the present invention cleans the missing defective part of a photomask at least in a single container without exposing the missing defective part to the atmosphere, and forms a light shielding film on the missing defective part. The above cleaning process is performed by irradiating ultraviolet light in the 03 atmosphere to oxidize and decompose the contaminants, and the formation of the light shielding film is performed by irradiating the missing defect with a laser beam in the vapor of the correction material. The method is characterized in that the correction substance vapor is decomposed by irradiation and metal is deposited only on the missing defect portion.

[Embodiments of the invention]

FIG. 1 showing an embodiment of the present invention will be described below. In the figure, reference numeral 8 denotes a repair container, which holds a photomask having a missing defect in its upper part with its pattern surface 7' facing downward, and holds a window 16 in its lower part. Further, the correction container 8 is connected between the photomask 7 and the window 16 inside thereof to a vacuum pump 13 via a valve 12, to an inert gas cylinder 15 via a valve 14, and a valve 27. connected to the ozone generation chamber 34 via
It is connected to the oxygen gas cylinder 28 via the ozone generation chamber 34 and the valve 33, and is also connected to the vacuum gauge 29. The ozone generation chamber 34 is formed of an insulator such as a quartz glass tube, and is inserted between two electrodes 35 and 36. One electrode 35 is connected to a high frequency power source (not shown) in the control device 26, and the other electrode 36 is connected to ground 36'. When applied, the oxygen gas cylinder 28
02 supplied into the ozone generation chamber 34 from 0 or 0
I am trying to convert it to 3. Reference numeral 11 designates a sealed correction substance container, the inside of which is filled with vacuum or inert gas, the upper part holds the correction substance 10 such as bis-benzene-chromium or bis-benzene-molybdenum, and the lower part holds the correction substance 10. A heater 17 is provided to heat and vaporize the correction substance 10. The laser beam 2 emitted from the laser oscillator 19a is used as a laser irradiation optical system.
0 is reflected by a dichroic mirror 21 tilted at an angle of 45° via a shutter 19b, and then focused and irradiated onto the defective portion of the photomask by an objective lens 22. U is an observation optical system, and the illumination light from the illumination light source 23a is transmitted through the lens 2.
3b, a half mirror 24° tilted at an angle of 45' irradiates the missing defective portion of the photomask 7 through the dichroic mirror 21 and the objective lens 22; The ocular lens 25 is used to observe the positional relationship between the missing defective portion of the photomask 7 and the laser beam and the missing defective portion through the dichroic mirror 21 and the half mirror 24. Reference numeral 30 denotes an ultraviolet light lamp, which emits ultraviolet light 32 having a strong emission spectrum in the range of 200 to 300 nm, for example. Reference numeral 31 is an elliptical mirror that focuses and irradiates ultraviolet light 32 from the ultraviolet light lamp 30 onto the missing defective part of the photomask 7, and decomposes 03 in the repair container 8 with the ultraviolet light 32. Contaminants (not shown) are converted into 0+o2 and adhere to the missing defective parts of the photomask 7.
At the same time, the chemical bonds of the contaminants are oxidized and decomposed by the ultraviolet light 32, and the contaminants are discharged to the outside of the container 8 by the vacuum pump 13. 26 is a control device for opening and closing the five valves 9, 12, 14, 27, and 33 mentioned above.

Application of a high frequency electric field to the two electrodes 35 and 36, opening and closing of the shutter 19b, and turning on and off the ultraviolet light lamp 30.
It seems to be controlled automatically. With the above configuration, after holding the photomask 7 at the top of the correction container 8 with all the valves 9, 12, 14, 27, and 33 closed,
The valve 12 is opened and the vacuum pump 13 is operated to exhaust gas such as air from the correction container 8. In addition, the heater 17 is operated to heat the correction material 10 on the upper part of the heater 17 to heat the correction material 10.
evaporate. Heating by the heater 17 may be carried out all the time, and sublimation occurs at 100 to 290°C when the correction substance is bis-benzene-chromium, and at 50-100°C when it is bis-benzene-molybdenum. After that, the missing defective part of the photomask 7 is illuminated using the illumination light source 23a, the half mirror 24, the eyepiece lens 25, and the objective lens 22, and the focal point of the laser beam 20 is aligned with the missing defective part. Let's do it. Next, the pressure inside the correction container 8 is measured by the vacuum gauge 29, and when the pressure reaches a predetermined pressure value (for example, L x 10-'' torr) or less, the valve 27.33 is opened to release 02 from the oxygen gas cylinder 28. The ozone is supplied into the ozone generation chamber 34, and the ozone is supplied to the two electrodes 35.
36 is converted into 0+o or o3+o by a high frequency electric field and introduced into the correction container 8. Then ultraviolet light lamp 30
is turned on, and the ultraviolet light 32 is focused and irradiated onto the defective portion of the photomask 7 through the elliptical mirror 31.

0 in the correction container 8 in the optical path of the ultraviolet light 32.
At the same time, the chemical bonds of contaminants adhering to the defective portions of the photomask 7 are broken by irradiation with the ultraviolet light 32.

Contaminants that have not been decomposed by the ultraviolet light 32 are oxidized by strong oxidizing agents 03 and 0 to produce H2O, CO2, etc., which are discharged from the correction container 8 by the vacuum pump 13. After that, after a certain period of time has passed, the valve 27.33 closes and the 2Q electrode 35.3
The application of the high frequency electric field to 6 is stopped, and the ultraviolet light lamp 3
0 becomes OFF. As a result of the above, the missing defective portion of the photomask 7 is in a clean and chemically activated state.

When the vacuum pump 13 is driven for a certain period of time and the discharge of contaminants etc. from the correction container 8 is completed, the valve 12 closes and the valve 14
is opened to supply inert gas into the correction container 8. After that, when the correction container 8 is filled with inert gas to about atmospheric pressure, the valve 14 is closed, and the valve 12 is opened again, and the correction container 8 is filled with the inert gas to about atmospheric pressure.
Exhaust inert gas and remaining trace amounts of o, 02 and 03 from inside. When the pressure inside the correction container 8 reaches a predetermined pressure (for example, I x 10-'torr) or less, the valve 12
, and open valve 9 to release the correction substance 1 in the correction substance container ll.
0 steam is placed in the correction vessel 8 at a constant pressure (for example, I
X 10-” torr).

Next, the valve 9 is closed, the shutter 19b is opened, and the laser beam 20 from the laser oscillator 19a is focused and irradiated on the missing defect part of the photomask 7, and if the missing defect area is larger than the spot diameter of the laser beam 20, teeth.

Correction container 8 or laser irradiation optical system eye, observation optical system η-
or insert two wedge-shaped prisms into the optical path of the laser beam 20 and rotate them in opposite directions, or tilt the dichroic mirror 21 to direct the laser beam 20 to the missing defect in the photomask 7. The shutter 19b is focused and irradiated while scanning the area, and the shutter 19b is closed when a certain period of time has elapsed or when scanning of a certain area is completed. In this way, when the missing defect portion of the photomask 7 is heated by focusing and irradiating the laser beam 20, the repair material 1
0 (more than 300℃ in the case of bis-benzene-chromium,
110℃ or higher for bis-benzene-molybdenum)
is decomposed and chromium or molybdenum is precipitated to form a light-shielding film in the missing defect area. Next, the valve 12 is opened to discharge the vapor of the correction substance 10 in the correction container 8, and then the valve 12 is closed and the valve 14 is opened to supply inert gas from the inert gas cylinder 15 into the correction container 8, and this correction container is 10 to approximately the same pressure as atmospheric pressure.

At this time, it is also possible to supply inert gas into the correction container 8 for a certain period of time and discharge it, then close the valve 12 and continue to fill the correction container 8 with inert gas to a pressure approximately equal to atmospheric pressure. However, the laser irradiation may be performed without opening the valves 9 and 12 to allow the vapor of the correction substance 10 to flow into the correction container 8. At this time, a flow controller or the like is required to keep the pressure inside the correction container 8 constant. Next, when the photomask 7 is removed with all the valves 9, 12, 14, 27, and 33 closed, the correction of the missing defective portion of the photomask 7 is completed. In the above embodiment, the laser irradiation optical system (1) and the observation optical system (2) are located above, and the ultraviolet light lamp 30 and elliptical mirror 31 are located below, but the present invention is not limited to this.

There is no problem even if these are placed in reverse positions. Next, FIG. 2 is an explanatory diagram of a laser irradiation optical system and an observation optical system showing another embodiment of the present invention. Components having the same configuration as in FIG. 1 are designated by the same reference numerals as in FIG. 1. As shown in the figure, a laser beam 20 oscillated from a laser oscillator 19a has its beam diameter expanded by a beam expander 40, and a reference light source 41. The reference light 43 of a specific wavelength from the interference filter 42 is coupled to the same optical axis by the coupling optical system 44, and is irradiated onto the rectangular aperture slit 45. With the shutter 20 closed, the operator uses the objective lens 22. Dichroic ink mirror 21° half mirror 46, illumination optical system 37. Laser light cut filter 38. Prism 39. Eyepiece lens 25
While observing the photomask 7 attached to the correction container 8 through the rectangular opening slit 45 by the reference beam 43.
The image is adjusted to the position and size of the missing defect. At this time, the rectangular aperture slit 45° objective lens 22. The photomask 7 is arranged in a positional relationship such that when the magnification of the objective lens 22 is M, an image of the rectangular aperture slit 45 is formed on the photomask 7 in a size of 1/M.

In this state, by opening the shutter 19b for a certain period of time, the reference beam 43 is adjusted to the size of the missing defect.
The laser beam 20 is irradiated to exactly the same size and position as the rectangular aperture slit 45 image. Here, the reference light 43 is selected by the interference filter 42 so that the wavelength of the laser light 20 is different from the wavelength of the laser light 20 to such an extent that chromatic aberration due to the objective lens 22 does not occur and the light can be combined by the coupling optical system 44 . In addition, the dichroic mirror 21 has a sufficiently high reflectance for the wavelength of the laser beam 20, a reflectance of about 50% for the reference beam 43, and a sufficiently high reflectance for other wavelengths. A material with high transmittance is desirable.

Alternatively, if the laser beam 20 is linearly polarized, a polarizing beam splitter is used as the coupling optical system 44, and the combined laser beam 20 and reference beam 43 have exactly the same wavelength and are used with only the polarization directions perpendicular to each other. You can also. In this case, as the dichroic mirror 21, the laser beam 2
A filter that reflects the light in the polarization direction of 0 sufficiently highly and has a reflectance of nearly 50% for the polarization component orthogonal thereto is used as the laser beam cut filter 38 to reflect or absorb the light in the polarization direction of the laser beam 20. By using those with the characteristics of

Correction can be performed completely ignoring the chromatic aberration between the laser beam 20 and the reference beam 43. In addition, the optical system mentioned above.

The arrangement with the ultraviolet light irradiation optical system may be reversed in the vertical direction as in the above embodiment.

In the optical system described above, a portion where the power distribution of the laser beam 20 is approximately uniform is extracted and irradiated (the optical system shown in FIG. 1 uses a laser beam 20 with a Gaussian distribution).

), and a wide area can be irradiated all at once, making it possible to obtain a deposited film of good quality. Note that if the oscillation wavelength of the laser oscillator 19a is in the ultraviolet region of 200 to 300 na+, the ultraviolet light irradiation device and the ON/OFF control section for the ultraviolet light lamp 30 in the control device 26 shown in FIG. 1 are unnecessary. In this case, the cleaning procedure for the cleaning part of the missing defective part is the same as the procedure shown in FIG.
The ultraviolet light irradiation at 1 is replaced by the ultraviolet laser light 19 irradiation by simply opening the shutter 20. Furthermore, although bis-benzene-chromium and bis-benzene-molybdenum have been described as correction substances, the present invention is not limited thereto, and for example, chromium carbonyl, tungsten carbonyl, etc. may be used. As the inert gas, gases that do not react with the correction substance, such as NZ, He, Ar, etc., are used.

The laser light source (oscillator 19a) may also be of any type as long as it can transmit through the photomask substrate or the window material 16;
Fundamental waves and harmonics of r lasers and YAG lasers.

A Kr laser or a dye laser using various excitation methods can be used.

Furthermore, the correction container 8 may be provided with electrodes 35, 36, and the correction container 8 itself may be used as an ozone generation chamber. In that case, as a matter of course, the ozone generation chamber 34 and the valves 27 and 33
Either one becomes unnecessary. Note that if metal is precipitated beyond the missing defect by the repair according to the present invention, it can be repaired by repairing the remaining defect using a conventional laser.

〔Effect of the invention〕

As described in detail above, according to the method for repairing photomask defects according to the present invention, the cleaning process and the formation of a light-shielding film are successively performed on the missing defect portion in one container without exposing it to the atmosphere. and by forming the light-shielding film using a vapor phase growth method, it is possible to obtain a light-shielding film with superior wear resistance compared to conventional methods such as the lift-off method or methods using organometallic solutions. I can do it. Further, by using a chemically stable metal (Cr M or W ), a light shielding film with excellent chemical resistance can be formed.

Furthermore, since the cleaning process and the formation of the light-shielding film are performed continuously in one container, the only process required for correction is to align the focal point of the laser beam with the missing defect. By drastically reducing the number of processes, the time required for correction can be drastically reduced and productivity can be greatly improved. Since the light-shielding film is obtained by vapor phase growth in a vacuum, missing defects can be corrected with high accuracy, and the yield of products can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a photomask missing defect correction apparatus showing one embodiment of the present invention, FIG. 2 is an explanatory diagram of an optical system showing another embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional optical system. FIG. 2 is an explanatory diagram of a device for correcting missing defects in a photomask. DESCRIPTION OF SYMBOLS 1... Benzene solution, 2... Glass window, 3... Cell, 4... Laser light, 5, 22... Objective lens, 6
···metal. 7... Photomask, 8... Correction container, 9, 1
2.14°27, 33... Valve, 10... Correction substance, 11... Correction substance container. 13... Vacuum pump, 15... Inert gas cylinder,
16... Window, 17... Heater, U... Laser irradiation optical system, 19a... Laser oscillator, 19b... Shutter, 20... Laser light, 21... Dichroic mirror, U... ...ms optical system, 24.46...half mirror 125...eyepiece, 26...control device, 28...oxygen gas cylinder, 29...vacuum gauge, 30...
...ultraviolet light lamp, 31...elliptical mirror, 32.
...Ultraviolet light, 34...Ozone generation chamber, 35.36...
- Electrode, 37... Illumination optical system, 38... Laser light cut filter, 39... Prism, 40... Beam...
Expander, 41... Reference light source, 42... Interference filter, 43... Reference light, 44... Coupling optical system, 4
5... Slit Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. The method is characterized in that the missing defect of the photomask is corrected by continuously performing a cleaning process for the missing defective part of the photomask and forming a light shielding film on the defective part in the same container. A method for repairing photomask defects. 2. The inside of the container is made into an ozone atmosphere, and in this ozone atmosphere, the missing defective portion of the photomask is irradiated with ultraviolet light to clean the missing defective portion. The photomask defect repair method described. 3. A photomask is provided in the container and a correction material container is connected to the container to heat and evaporate the correction material, and after introducing the vapor of the correction material into the container from the correction material container, A laser beam is irradiated to the missing defect portion of the photomask to decompose the heated and sublimated repair material, and a light-shielding film is formed by depositing the decomposed metal from the repair material onto the missing defect irradiated with the laser light. A photomask defect repair method according to claim 1, characterized in that: