JPH01106062A - Photomask white dot defective correcting device - Google Patents

Abstract

PURPOSE:To easily correct a white dot defective of large area of a photomask without increasing the power of laser light by scanning the laser light which enters a slit by a relatively simple mechanism. CONSTITUTION:A glass plate 40 is installed between a beam expander 2 and the slit 4, and this glass plate 40 is varied optionally in angle theta to the optical axis and rotated around the optical axis. When the glass plate makes one rotation around the optical axis, the laser light is scanned within a range shown by an envelope 43 to obtain the same effect with an increase in the diameter of the laser light. The opening size of the slit 4 is therefore increased correspondingly and large-area correction is enabled. Consequently, the white dot defective of large area of the photomask is corrected without increasing the power of the laser light.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a photomask white spot defect correction device.

In particular, the present invention relates to a white spot defect correction apparatus using a laser CVD method.

[Conventional technology]

Photomasks used for manufacturing ICs, LSIs, etc. have two types of defects called black spot defects and white spot defects.

The former is a defect in which a metal film (usually a chromium film) serving as a light-shielding film remains in an unnecessary part, and the latter is a defect in which a metal film in a necessary part is missing. If these defects exist in the photomask, they will cause poor performance of ICs and LSIs.

These defects must be corrected because they cause a decrease in yield.

Currently, a device that uses laser light to evaporate and remove the metal film has been put into practical use to correct sunspot defects, and is being used on actual production lines to improve yields. On the other hand, white spot defects were traditionally corrected using the lift-off method;
This method has the disadvantages that the repair process is complicated, takes a long time, and may cause secondary defects.

Recently, as an alternative method to this, a repair device as shown in FIG. 6 using a so-called laser CVD method has been proposed and is beginning to be put into practical use. In FIG. 6, 21 is a laser light source, and 2 is a beam expander that expands the laser light emitted from the laser light source 1.

4 is a rectangular slit that shapes the expanded laser beam;
10 is an objective lens for condensing the laser beam onto the surface of the photomask 14; 9 is an eyepiece optical system for observing the photomask 14; 15 is an XY stage on which the photomask 14 is placed and is movable; This is a correction substance supply device that supplies a correction substance to the surface of the photomask 14 at a constant flow rate.

The apparatus shown in FIG. 6 introduces Cr (even) 6 (chromium carbonyl) as a correction substance onto the surface of a photomask 14 installed in a chamber 19, and irradiates the white spot defect with laser light to apply the correction substance. By photolysis or thermal decomposition,
Metallic chromium is deposited in the defect area. This is because a high quality metal film cannot be obtained in an atmosphere where air, water vapor, etc. are present.

[Problem that the invention seeks to solve]

In the correction apparatus shown in FIG. 6, the laser beam is expanded by a beam expander 2, and then focused onto a shift mask 14 by an objective lens 10 through a rectangular opening called a slit 4. The positional relationship between the slit 4 and the photomask 14 is such that the image of the slit 4 is reduced and formed on the shift mask 14 by the objective lens 10.

A metal film can be deposited in the same size as this image. The maximum correction size in this device is about 25 μm square, and it is difficult to correct larger sizes in one go. This is due to the following reasons.

In other words, the reduction rate of the slit 4 mentioned above is about the same as in ancient times, and the 25 μm square on the photomask 14 is 2 on the slit surface.
．． The intensity distribution of the laser beam within this range must be uniform in order to deposit a uniform metal film. For this purpose, it is necessary to increase the magnification of the beam expander 2 as much as possible, but this causes the problem that a high-quality metal film cannot be obtained because the A'-kuality decreases. Of course, if the power of the laser light emitted from the laser light source 1 can be increased,
Although it is possible to increase the magnification of the expander 2, the power of the laser beam is currently being used at near the maximum power, and a significant improvement cannot be expected.

For example, if you want to make a correction of 50 μm square.

The area is four times that of a 25 μm square, and therefore the magnification of the expander must also be increased four times. Correspondingly, in order to maintain the same power density, four times as many laser beams and wafers are required. However, this is currently not possible. Therefore, it is currently not possible to significantly increase the maximum modification size.

However, as shown in FIG. 7(a), a white spot defect 31 exceeding 25 μm square sometimes occurs on the photomask 32, but in this case, it is not necessary to correct it as shown in FIG. 7(b). It needs to be applied in several times. The figure shows the case of three times, and 33, 34, and 35 show the deposited films of the first, second, and third times. However, in that case, Fig. 7(c)
As shown in the A-A' cross-sectional view of FIG. 3(b), a step 36 may occur at the portion where the metal films are overlapped, and may be detected as a defect by inspection using a surface inspection machine or the like. Additionally, if small pinholes are concentrated in an area larger than 25 μm square, the correction is currently carried out in several parts.

This makes the correction process troublesome and inefficient, and causes the problem of the difference in level as described above.

The present invention aims to solve these problems of the conventional ones, and is aimed at solving the problems of the conventional ones. An object of the present invention is to provide a photomask white spot defect repairing device capable of repairing a large area white spot defect on a photomask without requiring lifting.

[Failure to solve the problem]

According to the present invention, a laser light source, a beam expander that expands the laser light emitted from the laser light source, a (rectangular) slit that shapes the expanded laser light, and a laser light source that directs the laser light onto the photomask surface. comprising means for condensing light, means for observing the photomask, a movable XY stage on which the photomask is placed, and means for supplying a correction substance to the surface of the photomask in a constant flow, In a photomask white spot defect repairing device, the white spot defect of the photomask is repaired by decomposing the repairing substance with the laser beam to deposit a metal on the photomask,
A photomask white spot defect correction apparatus is obtained, which is characterized by having a scanning means for scanning a laser beam incident on a rectangular slit over a desired range.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of the present invention. In this example, a glass plate 40 is installed between the beam expander 2 and the slit 4. This glass plate is shown in Figure 2 (,
) As shown in (b), the angle θ with respect to the optical axis can be arbitrarily changed and the optical axis can be rotated.

To measure the eccentricity of the laser beam, use the refractive index of the glass plate as n.

When the plate thickness is d, it is given by D=d cos θ (lsin θ/4 ar; υ−). When the glass plate is in the position shown in Figure 2 (,), the laser beam is directed upwards as shown in Figure 2 (c).
When the position shown in the figure (b) is eccentric, the position shown in the figure (d) is
It is eccentric downward by D as shown in the figure. In this way, when the glass plate makes one rotation of the optical axis, the laser beam can be scanned within the range indicated by the envelope 43, as shown in FIG. You can have the same effect as you did.

Therefore, the opening size of the slit 4 can be increased accordingly, and a large area can be corrected. Since the eccentricity measurement can be changed depending on the inclination angle θ of the glass plate, θ can be changed according to the required correction size.

Note that when there is no need to particularly increase the correction size, θ
It is clear that it is sufficient to set the angle to 90°.

Further, the rotation speed of the glass plate must be optimally set according to the deposition rate of the metal film. This is due to the following reasons. This is because if the rotation speed is too slow, the deposited film at each instant becomes thicker, and the step difference in the film becomes noticeable. On the other hand, if it is too early, the heating effect of the laser beam is small, so the deposition rate of the film may be slow, or the film may not be deposited at all. Furthermore, for rotating the glass plate, it is better to use a continuous drive such as a DC motor rather than a step drive using a pulse motor or the like.

This is because the difference in level of the film at each step position becomes noticeable.

A second embodiment according to the invention is shown in FIG. This is a beam expander 2 equipped with an eccentric and rotation mechanism so that it can scan a laser beam. As shown in FIG. 4, the expander shaft 52 is offset by an amount α from the optical axis 53 so that the expander can rotate in the same direction as the shaft.

in this case.

The eccentricity β of the laser beam is considered to be the product of α and the expander magnification, but since there are also lens aberrations, it is thought that the value will differ somewhat.

In this case, as in the first embodiment, by rotating the expander at an appropriate speed, the laser beam can be scanned, making it possible to correct a large area. However, in this method, care must be taken because if the eccentricity α of the axis is made too large, the distribution of the laser beam may change due to lens aberration. According to the method described above, the fifth
As shown in Figure (, ) and its β-β' cross section (b), even for large-area white spot defects, the metal film 37 can be deposited uniformly and the correction can be performed without any 9-step difference. be able to.

〔Effect of the invention〕

As explained above, the present invention can scan a large area of a photomask without increasing the power of the laser beam by simply scanning the laser beam incident on the slit using a relatively simple mechanism. This has the effect that point defects can be easily corrected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a photomask white spot defect correction apparatus showing a first embodiment of the present invention, FIG. 2 is a diagram showing a beam scanning mechanism of this embodiment, and FIG. FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing a beam scanning mechanism of this embodiment. Fig. 5 is a diagram showing an example of correcting a large-area white spot defect using the apparatus shown in Fig. 4, Fig. 6 is a block diagram showing a conventional photomask white dot defect correction apparatus, and Fig. 7 is a conventional large-area white spot defect correcting apparatus. It is a figure which shows the example of a correction. Explanation of symbols: 1...Laser light source, 2...Beam extractor, 3, 6...Dichroic mirror, 4...
... Slit, 5... Slit illumination light source, 7... Half mirror 98... Reflected illumination light source, 9... Eyepiece optical system, io... Objective lens, 11... Window, 12
... Pressing plate, 13 ... O-ring, 14 ... Photomask, 15 ... XY stage, 16 ... Correction material supply device, 17 ... Trap, 18 ... Exhaust device,
19... Chamber, 20... Transparent illumination light source, 31.
...white spot defect, 32...photomask, 33.34.
35... Deposited film, 40... Glass plate. 50... Eccentric laser beam, 51... Laser i when α or zero, 52... Ext/da axis, 53...
Laser main axis. Figure 2 (Cl) (C) (d)
<e Figure 4 Figure 5 (b) Figure 7 (b) (C) Jb: Danburaya

Claims (1)

[Claims] 1) A laser light source, a beam expander that expands the laser light emitted from the laser light source, a slit that shapes the expanded laser light, and a beam expander that directs the laser light onto the surface of the photomask. a means for condensing light, a means for observing the photomask, an XY stage on which the photomask is placed and movable, and a means for supplying a correction substance to the surface of the photomask at a constant flow rate; In the photomask white spot defect correction device, the white spot defect of the photomask is corrected by decomposing a correction substance by the laser beam to precipitate a metal onto the photomask, in which the laser beam is incident on the rectangular slit as desired. 1. A photomask white spot defect correcting apparatus comprising a scanning means for scanning in a range of . 2) The photomask white spot defect according to claim (1), wherein the scanning means comprises a means for rotating a glass plate installed between a beam expander and a slit. Correction device. 3) The photo camera according to claim 1, wherein the scanning means comprises means for rotating a beam expander whose axis is eccentric in a plane perpendicular to the optical axis. Mask white spot defect correction device.