JPH04295851A - Photomask correcting device - Google Patents

Abstract

PURPOSE:To form a metallic film in a rectangular shape with good edging accuracy. CONSTITUTION:A consecutive excitation Q switch Nd:YAG laser (SHG) 10 by which high repetitive pulse output is obtained is used as a laser. A beam expander 9 and a slit mechanism 7 are arranged in a laser optical path, and a rectangular laser beam whose intensity distribution is uniform is projected to a photomask 3 in a chamber 2 by an objective lens 8. Stock gas A flowing on the surface of the photomask 3 is dissociated at a part irradiated with the rectangular laser beam, and the metallic film is formed on the photomask 3. By moving the photomask 3 on an XY stage 6, the metallic film is formed in a belt shape. The width of the metallic film in such a case is changed by varying the distance between the knife edges 7 of the slit mechanism 7.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for repairing white defects on a photomask, and more particularly to a photomask repair apparatus using laser CVD technology.

0002

2. Description of the Related Art FIB (Focus
A method using a focused ion beam (sed ion beam) and a method using a laser beam have been proposed. The latter method uses photolytic chemical vapor deposition (CVD), which uses ultraviolet laser light.
vapor deposition) technology, and thermal CVD (pyrolytic chemical vapor deposition), which uses the heating effect of laser light on the target.
(vaper deposition) technology.

Compared to the latter device using laser light, the former device using FIB has a beam focusing diameter of 0.5 mm.
It can be made as small as about 1 to 0.5 μm. Therefore, highly accurate correction is possible. However, since the device cannot be operated unless the raw material gas is in a dilute state, the deposition rate of the carbon film is slow. , it takes about 1000 seconds. Also, during operation, 1×
It is necessary to maintain a high vacuum of about 10-6 Torr.
The vacuum container cannot be made larger.

[0004] Therefore, it is difficult for the former FIB-based device to handle large substrates, and the photomask repair devices that have been developed so far are limited to 7-inch square substrates. There's a problem. For this reason, general photomasks or LCD (Liquid Crystal d
Currently, this device cannot be applied to large photomasks for use in iPlay (liquid crystal display).

[0005]

[Problems to be Solved by the Invention] On the other hand, among the latter photomask white defect correction devices that use a laser, in the device that uses an ultraviolet laser, lens materials are limited due to the use of ultraviolet light, making it difficult to design the device. There was a problem that. Moreover, the objective lens used for both observation and laser processing in this device must be achromatized between the ultraviolet and visible regions.
There were problems with the configuration of the optical system, such as the difficulty of manufacturing it. In addition, in this latter device, since the photodissociation reaction is the main one, a thin film is deposited by CVD on the window material through which the laser light is introduced, reducing the transmittance of the window and causing so-called window fogging. there were.

[0006] Therefore, a more practical photomask repair apparatus can be constructed by using visible laser light and its heating effect.

By the way, conventional photomask repair equipment that utilizes the heating effect of laser light uses a continuous oscillation argon laser as the laser, and the laser light is simply focused into a spot. . For this reason,
There was a problem in that heat diffusion to the vicinity of the laser beam irradiation area increased, and a thin film was deposited in a width much wider than the condensing diameter of the laser beam. In addition, J. K. Tison a
ndM. G. Cohen, Solid State
Technology, Feb. (1987), “La
Please refer to the photograph shown in Fig. 2 on page 113 of ``Ser in Mask Repair''.

Therefore, an object of the present invention is to provide a photomask that can form a metal film with high edge precision by utilizing visible laser light and its heating effect and by suppressing heat diffusion to the vicinity of the laser light irradiated area as much as possible. The purpose of this invention is to provide a correction device.

[0009]

[Means for Solving the Problems] The invention as claimed in claim 1 is a method for irradiating laser light onto the surface of a photomask that is in contact with an atmosphere containing a compound gas that enables the deposition of metal through a dissociation reaction, and mainly thermally decomposing the compound gas. A metal thin film selectively formed on the laser beam irradiated area by laser beam irradiation, or a metal thin film deposited in a band shape on the photomask by scanning the laser beam relative to the photomask, eliminates white defects on the photomask. A photomask repairing device configured to correct a photomask includes: a laser capable of outputting a laser pulse at a frequency higher than a predetermined frequency, such as 1 KHz; and a shaping means for shaping the laser beam irradiated onto the photomask into a rectangular shape. The structure includes a uniformizing means for uniformizing the intensity distribution of the rectangularly shaped laser beam.

[0010] According to the second aspect of the invention, a slit mechanism having a knife edge portion at the peripheral edge and a variable opening is used as the shaping means for shaping the laser beam into a rectangular shape.

[0011] According to the third aspect of the invention, an attenuator is arranged in the optical path of the laser beam.

0012

[Operation] According to the present invention, since the laser beam shaped into a rectangular shape is image-transferred onto the photomask surface, a metal film of any size with good edge precision can be formed along the pattern on the photomask. becomes possible.

[0013]

EXAMPLES The present invention will be explained in detail with reference to Examples below.

FIG. 1 is a schematic diagram showing an embodiment of a photomask repair apparatus according to the present invention. In the apparatus of this embodiment, molybdenum carbonyl (Mo) is used as a raw material for CVD.
(CO)6) and the second harmonic (SHG: wavelength 0.53 μm) of a continuously pumped Q-switched Nd:YAG laser (hereinafter referred to as CW-YAG laser) as a laser.
are using.

Metal carbonyls such as Mo(CO)6 are solid or liquid at room temperature, so they are heated and vaporized before use. In this example, it is vaporized at 50° C. in the reservoir 1 and used. The saturated vapor pressure at this time is given by the Encyclopedia of Chemistry (
Kyoritsu Shuppan, Tokyo), P294, as shown in "Molybdenum Carbonyl", it is 1.4 Torr. Argon gas is used as carrier gas, flow rate 250cc
Use at a rate of 500 cc/min to 500 cc/min.

As shown in FIG. 1, raw material gas A is guided into a chamber 2 which is kept airtight together with carrier gas B taken out from a reservoir 1. Raw material gas A is in chamber 2
It flows on the surface of the photomask 3 inside. A glass window 4 is provided on the upper surface of the chamber 2, through which the laser beam is focused onto the photomask 3. A Mo film is deposited by CVD at the condensing portion of this laser beam. The photomask 3 in the chamber 2 maintains a temperature balance with the source gas A so that Mo(CO)6 does not precipitate on the photomask 3, and also controls the amount of adsorption onto the surface to reduce the deposition rate of the Mo film. For control purposes, it is heated to about 50°C by a heater 5. After the raw material gas A flows on the surface of the photomask 3, it is led to the exhaust gas processing section 14, where it is treated and then discharged as exhaust gas C.

This photomask repairing apparatus employs a method in which the optical system for introducing laser light is fixed and the photomask 3 is moved on an XY stage 6 to form a strip-shaped Mo film.

By the way, in this photomask repairing device, in order to shape the laser beam irradiated onto the photomask 3 into a rectangular shape, a knife whose spacing can be changed on both axes is provided on the end side where the opening 7A is formed. It has a slit mechanism 7 having an edge. Opening 7 of this slit mechanism 7
The image of A is transferred onto the photomask 3 by the objective lens 8. Opening 7 of this slit mechanism 7
In order to make the intensity of the laser beam uniform after passing through A,
A beam expander 9 is arranged on the output side of the CW-YAG laser 10. The beam expander 9 is configured to expand the beam diameter of the laser beam so that only the central portion where the change in intensity distribution is small can pass through the opening 7A of the slit mechanism 7.

In the photomask repair apparatus of this embodiment, by changing the width dimension of the opening 7A of the slit mechanism 7, it is possible to form a Mo film with an appropriate width depending on the size of the defect. Furthermore, since a high-frequency laser pulse from the CW-YAG laser 10 is used, heat diffusion to areas other than the laser irradiated area can be slightly suppressed, making it possible to form a Mo film with good edge precision.

In the photomask repair apparatus shown in FIG.
In the diagram of the slit mechanism 7, on the left side is the dichroic mirror 1.
1 is arranged to reflect the laser beam toward the objective lens 8 side. Further, above the dichroic mirror 11, an eyepiece 12A for observing through the dichroic mirror 11 and a CCD camera 12B are arranged so that the light beam split by the half mirror 12C is incident thereon. The image read by the CCD camera 12B can also be observed on the monitor TV 13.

FIG. 2 shows a Mo film formed on a photomask using the photomask repair apparatus of this embodiment. On the mask 3, a Mo film 15 is formed in a strip shape. The right part in this figure represents the glass surface 17.

FIG. 3 shows a procedure for forming such a Mo film. 5 μm as shown in this figure
By scanning a rectangular laser beam 16 of x10 μm in the direction of arrow D, a Mo film 15 was formed so as to completely fill the pseudo defects. In this embodiment, the intensity of the rectangular laser beam 16 is
The power was about 5 mW on the surface of the photomask 3, and the repetition frequency of the Q switch was 10 KHz. Further, the moving speed of the photomask 3 was 3 μm/s.

FIG. 4 shows a modification of the photomask repair apparatus according to the present invention. Components that are the same as those in FIG. 1 are designated by the same reference numerals, and their descriptions will be omitted. In this modification, an attenuator 18 is disposed between the slit mechanism 7 and the dichroic mirror 11 in the optical path of the laser beam. The attenuator 18 is used to reduce the intensity of the laser beam at the start of Mo film formation in order to prevent excessive heating of the substrate due to less heat absorbed by the CVD reaction. This attenuator 18 allows the intensity of the laser beam to be changed with good responsiveness.

[0024]

As explained above, according to the photomask repair device of the present invention, a laser capable of repeatedly outputting laser pulses at a frequency of 1 KHz or more is used, and the laser beam irradiated onto the photomask is shaped into a rectangular shape. As well as making the intensity distribution of this laser beam uniform,
Although this is a photomask repair device using laser CVD technology that utilizes the heating effect of a laser, it is possible to deposit a metal film with good edge straightness. Furthermore, since it is possible to correct a large area at once compared to a device using FIB technology, it has a much higher processing capacity and has the excellent effect of providing a highly practical device.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a photomask repair apparatus according to the present invention.

FIG. 2 is a plan view showing a Mo film formed on a photomask using the apparatus of this example.

FIG. 3 is an explanatory diagram showing the procedure for forming a Mo film using the apparatus of this example.

FIG. 4 is a schematic configuration diagram of a photomask repair apparatus in a modified example of the present invention.

[Explanation of symbols]

3 Photomask 7 Slit mechanism 7A Opening 9 Beam expander 10 CW-YAG laser 15 Mo film 16 Rectangular laser beam 18 Attenuator

Claims (3)

[Claims] [Claim 1] Laser light is irradiated onto the surface of the photomask that is in contact with an atmosphere containing a compound gas that enables metal deposition through a dissociation reaction, and a layer is selectively formed in the laser light irradiated area mainly by thermal decomposition of the compound gas. In a photomask repairing device that corrects white defects on a photomask with a metal thin film or a metal thin film deposited in a band shape on the photomask by scanning a laser beam relative to the photomask, a laser capable of outputting a laser pulse at a frequency higher than the frequency of , a shaping means for shaping the laser beam irradiated onto the photomask into a rectangular shape, and a uniformizer for uniformizing the intensity distribution of the rectangularly shaped laser beam. A photomask repair device comprising: means. 2. The photomask repairing apparatus according to claim 1, wherein the shaping means includes a slit mechanism having a knife edge portion at a peripheral edge and a variable opening. 3. The photomask repair apparatus according to claim 1, further comprising an attenuator disposed in the optical path of the laser beam.