JPS59126630A - Method and device for correcting photomask - Google Patents

Abstract

PURPOSE:To prevent the contamination of a photomask by a method wherein, before the photomask is taken out into the atmospheric air, the organic metal solution adhered to the photomask is removed using a cleaning solvent. CONSTITUTION:The laser beam sent from a laser oscillator 1 is condensed and irradiated on the perforated defective part of a photomask 4 by a condensing lens 3 through the intermediary of a reflecting mirror 2. The illumination light sent from an illumination light source 5 is overlapped on the laser beam through the intermediary of a beam splitter 6, and an observation is performed by the observing optical system 7 of the photomask 4. An organic metal solution is filed in a holder 8 from a raw solution reservoir 9, a laser beam is made to irradiated in a converged form on the defective part of the photomask, and the organic metal which is dissociated from the solution is deposited on the perforated defective part. After the defective part has been corrected, a cleaning solvent such as toluene and the like flows into the holder 8 from a cleaning solvent reservoir 16, and the organic metal solvent is washed away from the surface of the photomask 4, thereby enabling to prevent the contamination of the photomask due to the oxidation of the organic metal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for repairing a photomask that uses a laser beam to deposit metal on a transparent defective portion of a photomask.

With the recent development of integrated circuit technology, the density of integration is becoming higher and higher, as seen in the realization of very large scale integrated circuits. As the density increases, defects in photomasks for integrated circuits have become a serious problem from the viewpoint of improving yield. Defects in photomasks include blind defects (black defects) and hole defects (white defects), and a laser-based repair device is already in use for blind defects. However, in order to correct hole defects, it is necessary to deposit a metal such as chromium, which has good adhesion to the glass substrate and has excellent acid resistance, on minute parts, and such a process technology has been established. Therefore, it was not possible to realize a practical correction device. Up until now, methods for repairing hole defects have been completely inefficient, such as repeating the exact same process as photomask patterning or applying paint to the defect as a temporary measure. Ta.

Recently, a metal deposition method using a laser has been developed, and it has become possible to form minute metal patterns on glass or semiconductors using organic metals such as trimethylaluminum and dimethylcadmium as raw materials. In this method, the inside of a cell with a glass window is evacuated using a pump, and then cold metal vapor at a pressure of several Torr is heated to an appropriate pressure of A.
This method is sealed in a cell with an inert gas such as R, and focused laser light in the ultraviolet or visible range is irradiated onto the inner wall of the glass window to deposit metal using photodissociation and thermal dissociation of organic metal vapor. be.

This was in the early days when metal deposition using lasers was attempted.
．． Application to photomask repair was proposed, but there were several difficulties in putting it into practical use. They are listed below:
One is the one that has been experimentally carried out so far, but it uses a lumber organic metal in a vapor state that reacts explosively with the air. The problem is that it is not possible to realize a typical equipment system. In addition, since the dissociation energy of these organic metals is large, in order to realize metal deposition, methods of photodissociation of organic metals using harmonics of ultraviolet lasers or visible lasers with wavelengths around 200+- are often used. However, in this case, the laser device becomes very complicated and large. On the other hand, even when thermal dissociation is used, it is necessary to heat the area where the metal is deposited to a high temperature of several hundred degrees (by irradiation with high-power visible or infrared laser light) on the order of several watts, and the substrate The problem is that even if there is no damage, the area of metal deposition is much wider than the desired area due to heat diffusion.

In order to eliminate the drawbacks of the conventional methods described above, a method using a complex organic metal such as bisbenzene chromium or bisbenzene molybdenum in a liquid form such as a benzene solution has recently attracted attention. These organic metals exhibit strong absorption of visible light, and
It has the property of dissociating at a relatively low temperature of about 50°C to precipitate metals such as chromium and molybdenum. In addition, it does not undergo an explosive reaction in the atmosphere, but only mildly oxidizes and turns black, and its oxidation is hardly a problem, so it has high utility value from the point of view of safety.

However, these organic metals are solid at room temperature, and even if the temperature is raised to near the dissociation temperature, the vapor pressure is less than 1 Torr.
-1 mole/! The preferred method is to use a solution of benzene, toluene, etc., which can be used at a high concentration. Experiments have actually been conducted in which the inner wall of a glass container containing such a solution is irradiated with focused visible laser light to deposit metal in the form of an irradiation spot.

However, in photomask modification, major problems arise when using organometallic solutions such as N. That is, the organometallic bath i in contact with the photomask must not be oxidized. If the organic gold J/14 solution in contact with the photomask is oxidized by oxygen in the atmosphere, the shift mask will be contaminated by the oxidation of the organic metal and adhesion of the proboscis. This oxide cannot be easily removed even by organic solvents or enemies. On the other hand, attaching a photomask to the correction equipment,
It is practical to prepare and prepare sushi in the atmosphere, and therefore, during these operations, it is necessary to ensure that the organic metal solution does not adhere to the photomask. Of course, it goes without saying that oxidation of the organometallic solution must be prevented even during photomask repair work.

Conventionally, no measures have been taken to prevent the photomask from being contaminated by the above-mentioned organometallic oxides, so a practical photomask repair method has not yet been realized.

An object of the present invention is to solve the problem of organic metal oxide adhesion to a photomask as described above.

An object of the present invention is to provide a highly reliable photomask repair method and apparatus.

According to the present invention, metal is deposited on the holed defect portion of a photomask that is brought into contact with an organometallic solution that is shielded from the atmosphere by condensed laser beam irradiation to repair the holed defect portion. In the method, the organic metal solution adhering to the photomask is first removed using a cleaning solvent before the photomask is taken out into the atmosphere, and the photomask made of an organic metal oxide is removed. can prevent contamination.

Furthermore, the present invention provides a laser oscillator, a focusing optical system for condensing and irradiating a laser beam emitted from the laser oscillator onto a perforated defect in a photomask, a holder for the photomask, and a laser beam emitted from the laser oscillator. A photomask repair apparatus comprising a raw material supply system that flows into the holder an organic metal solution, which is a raw material for depositing metal on the perforated defect portion of the photomask, by irradiation with light, the photomask and The present invention is characterized in that a cleaning liquid supply system is provided for flowing a cleaning solution into the holder to remove the organometallic solution from the holder.

Next, the present invention will be explained in detail with reference to the drawings.

The figure shows a schematic configuration of an embodiment of the present invention. Laser oscillator 1.1:pThe emitted laser light is condensed and irradiated onto the perforated defect portion of photomask 4 by condensing lens 3 via reflecting mirror 2.

At this time, the white illumination light emitted from the illumination light source 5 is also superimposed on the laser light via the beam splitter 6, which has a characteristic of extremely little reflection of the laser light. Reflector 2 has a laser beam and a number 107 close to the laser beam.
Although light with a wavelength within the IJ range is almost completely reflected, light with other wavelengths has a large transmission characteristic, and the state of the photomask 4 can be observed by the observation optical system 7. can. The photomask 4 is placed on the holder 8 with the mask side facing down, and the cap 1 is placed on top of it.
9 into the holder 8 and fix it. Here, the holder 8 and the cap 19 are made of Teflon resin with excellent chemical resistance, and the filter 12 fitted into the bottom of the holder 8 and the fixed photomask 4 and the holder 8 provide an airtight seal. It is designed to consist of scattered cells with good properties.

Next, nitrogen gas or an inert gas that does not react with the organic metal is filled into the raw material liquid reservoir 9 containing the organic metal solution through the gas filling port 10 for feeding the raw material liquid, and the organic metal is placed in the holder 8. By filling the organometallic bath with a metal solution, the organometallic solution and the mask surface of the photomask 4 come into contact.

After this, while observing the pattern on the mask surface using the observation optical system 7, the holder 8 is slightly moved A using the drive device fll to position the holed defect portion to be focused and irradiated with the laser beam. . Next, by irradiating the holed defect with a focused laser beam emitted from the laser oscillator 1, the organic metal solution near the holed defect is heated, the organic metal dissociates, and the holed defect is heated. Metal is deposited on the parts. During metal deposition, a certain amount of the organometallic solution is allowed to flow in order to remove air bubbles generated when the organometallic dissociates. In addition, since the filter 12 has good transmission characteristics only for light having a wavelength near the laser beam, by monitoring the intensity of the laser beam that has passed through the photodetector 13, it is possible to detect the perforation defect. The degree of metal deposition can be detected. filter 1
When the intensity of the laser beam transmitted through the hole defect is very weak, and it is no longer detected by the photodetector 13, it is assumed that the hole has been repaired by depositing sufficient metal on the hole defect.
4, the oscillation of the laser beam from the laser oscillator 1 is stopped.

By repeating the process of repairing the hole defects described above, when all the hole defects in one photomask have been repaired, the filling of gas into the gas filling port 10 for feeding the raw material liquid is stopped, Instead, there is a gas filling inlet 15 for supplying cleaning liquid.
Fill with nitrogen gas or inert gas. Then, a cleaning solvent such as high-purity toluene flows into the holder 8 from the cleaning liquid reservoir 1617'3, and the organometallic solution is delivered to the waste liquid reservoir 17. Subsequently, the cleaning solvent continues to flow until the organic metal solution is sufficiently washed away from the inside of the holder 8 and the mask surface of the photomask 4.

When the cleaning is completed in this way, the photomask 4 can be removed from the holder 8 without worrying about contamination by organic metal oxides. Further, since no organic metal or organic metal oxide exists inside the holder 8, another photomask to be corrected can be attached without fear of contamination.

In addition, when repairing the photomask next time, in order to remove the air taken in when replacing the photomask from inside the holder 8, it is necessary to pour a small amount of cleaning solvent before introducing the organometallic solution. good. In order to avoid backflow of the organometallic solution and cleaning solvent, a backflow prevention valve 18 is installed in the 6TFI liquid path.

In this example, bisbenzene chromium is selected as the organic metal and used as a benzene solution with a concentration of about 10-2 mol/no, and as the laser oscillator 1, an argon laser with a wavelength of 488 nm, which has strong absorption in this solution, is used. Using. Further, the controller 14 employs a current control method in which when the signal intensity from the photodetector 13 becomes smaller than a preset reference level of the comparator, the current flowing through the laser discharge tube is made smaller than the laser oscillation threshold. When a hole defect with a diameter of about 5 pm was repaired using an argon laser output of 50 mW, the repair was completed in about 5 seconds of laser light irradiation time. After all hole defects have been corrected, remove the photomask according to the procedure described above, and
When the mask surface was observed using an inspection device with a resolution of , there were no defects due to contamination that were larger than the resolution and would pose a practical problem.

As described above, according to the present invention, it is possible to realize an Tenkawa-like and extremely reliable photomask repair method and a photomask repair apparatus using the same.

In addition, in the above example, bisbenzene chromium was used as the organometallic, but the same structure can be used when using other complex organometallics such as bisbenzenemolybdenum or phthalocyanine, or carbonyl organometallics. Applicable. In that case, a solution may be prepared using a solvent suitable for the organic metal used, and a suitable cleaning solvent may be selected correspondingly. At this time, it goes without saying that for metal deposition, a laser oscillator capable of generating laser light at a wavelength that is strongly absorbed by the organometallic solution is used, and optical components are also replaced with appropriate ones.

In this example, a current control method was used to check for metal deposition and stop laser oscillation, but it is also possible to use a method in which a loss modulator or the like is placed inside the resonator of the laser oscillator. Of course.

[Brief explanation of drawings]

The figure shows a schematic configuration of an embodiment of the present invention. In the figure, 1...Laser oscillator 2...Reflector 3...Condenser lens 4...Photomask 5...Illumination light source 6...Beam splitter 7...Observation optical system 8- ...Holder 9...Raw material liquid reservoir 10...Gas filling port for feeding raw material liquid 11...Drive device 12...Filter 13...Photodetector 14...Controller 15... Gas filling inlet for cleaning liquid delivery 16...Cleaning liquid reservoir 17...Waste liquid reservoir 18...Backflow prevention valve 1
9... It is a cap.

Claims (2)

[Claims] (1) Polymetal deposition is performed on the hole-defected portion of the photomask that is in contact with the organometallic solution that is shielded from the atmosphere by condensed laser beam irradiation to repair the hole-defected portion. A method for repairing a photomask, characterized in that, before the photomask is taken out into the atmosphere, an organic metal solution adhering to the photomask is removed using a cleaning solvent. (2) A laser oscillator, a focusing optical system for condensing and irradiating the laser beam emitted from the laser oscillator onto the perforated defect portion of the photomask, a holder for the photomask, and a focusing optical system for irradiating the laser beam emitted from the laser oscillator. In a photomask repairing apparatus having a raw material supply system for flowing into the holder an organometallic m solution, which is a raw material for depositing metal on the perforated defects of the photomask, from the photomask and the holder. A photomask repairing apparatus comprising a cleaning liquid supply system for flowing a cleaning solvent into the holder circle to remove the organic metal solution.