JPH079536B2 - Photomask white spot defect repair device - Google Patents

Description

The present invention relates to a photomask white spot defect repairing apparatus, and more particularly to a white spot defect repairing apparatus using a laser CVD method.

[Conventional technology]

Photomasks used in the manufacture of ICs and LSIs have two types of defects called black spot defects and white spot defects. The former is a metal film (usually a chrome film) that serves as a light-shielding film in unnecessary areas.
Is the remaining defect, and the latter is, on the contrary, the defect in which the required portion of the metal film is lacking. The presence of these defects in the photomask causes poor performance of ICs and LSIs,
These defects will need to be repaired as they cause a decrease in yield.

At present, a device for vaporizing and removing a metal film by laser light has been put into practical use to correct black spot defects, and it is being used in an actual production line to improve the yield. On the other hand, the white spot defect was corrected by the lift-off method in the old days.
This method has the drawbacks that the repair process is complicated, it takes a long time, and secondary defects may occur.

Recently, a so-called laser has been used as an alternative method.
A correction device by the CVD method as shown in Fig. 6 was proposed,
It is beginning to be put to practical use. In FIG. 6, 1 is a laser light source, 2 is a beam expander for expanding the laser light emitted from the laser light source 1, 4 is a rectangular slit for shaping the shape of the expanded laser light, and 10 is the laser light. Photo mask 1
4 an objective lens for focusing on the surface, 9 an eyepiece optical system for observing the photomask 14, 15 an XY stage movable with the photomask 14 mounted, 16 a correction substance on the surface of the photomask 14 It is a correction substance supply device that supplies at a constant flow rate.

The apparatus shown in FIG. ₆ introduces Cr (CO) ₆ (chromium carbonyl) as a correction substance on the surface of the photomask 14 installed in the chamber 19 and irradiates the white spot defect portion with a laser beam to remove the correction substance. It is designed to deposit metallic chromium in the defect portion by photolysis or thermal decomposition. Here, it is necessary to carry out the above-mentioned CVD reaction in the chamber because Cr (CO) ₆ , which is a correction substance, is toxic, and a high-quality metal film can be obtained in the presence of air, water vapor, etc. It depends on the reason such as not.

[Problems to be solved by the invention]

In the correction device of FIG. 6, the laser light is expanded by the beam expander 2 and then focused on the photomask 14 by the objective lens 10 through a rectangular opening called a slit 4. And the positional relationship between the slit 4 and the photomask 14 is
The image of the slit 4 is placed in such a relationship that the image is reduced and formed on the photomask 14 by the objective lens 10, and the 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 modify the size larger than this once.
This is for the following reasons.

That is, the reduction ratio of the slit 4 is about 1/100, and the 25 μm square on the photomask 14 is 2.
It corresponds to a 5 mm square, and in order to deposit a uniform metal film, the laser light intensity distribution within this range must be uniform. For this purpose, it is necessary to increase the magnification of the beam expander 2 as much as possible, but this causes a problem that a good quality metal film cannot be obtained because the power density decreases. Of course, if the power of the laser light emitted from the laser light source 1 can be increased, the magnification of the expander 2 can also be increased, but at the present time, the power of the laser light is used near the maximum, which is a significant improvement. I can't expect.

For example, in the case of modifying the square of 50 μm, the area becomes 4 times as large as that of the square of 25 μm, so that it is necessary to increase the magnification of the expander to 4 times. Correspondingly, in order to make the power density the same, the laser power also needs to be four times. However, this is not possible at present. Therefore, at present, the maximum modification size cannot be increased significantly.

However, as shown in FIG. 7 (a), the photomask 32 may sometimes have white spot defects 31 exceeding 25 μm square. In this case, the correction as shown in FIG. 7 (b) should be avoided. It is necessary to apply it in several steps. The figure shows the case of three times
33, 34, and 35 indicate the first, second, and third deposited films.
However, in doing so, FIG. 7 (c) shows A- in FIG. 7 (b).
As shown in the A'cross-sectional view, a step 36 is formed in the portion where the metal films are overlapped, and it may be detected as a defect by the inspection of a surface inspection machine or the like. Also, when small pinholes are concentratedly distributed in a range of 25 μm square or more, at present, the correction process is divided into several times, but this correction process is troublesome.
It is inefficient and causes the problem of steps as described above.

The present invention is intended to solve such a problem of the conventional one, and it is possible to correct a white spot defect of a photomask in a large area of a photomask without increasing the power of laser light. A defect repairing device is provided.

[Means for solving problems]

According to the present invention, a laser light source that emits a laser beam, a laser beam enlargement processing unit that enlarges the emitted laser beam by using a lens mechanism and sends out a laser beam having an enlarged diameter, A slit for shaping a laser beam having an enlarged diameter based on the diameter to set an aperture size, a means for focusing the laser beam having the set aperture size on a photomask surface, and 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 photomask surface at a constant flow rate, and the photomask is obtained by decomposing the correction substance with the laser light. In a photomask white spot defect repairing device for depositing metal on the photomask to repair white spot defects, the laser beam expansion processing means receives the expanded laser beam. It has a scanning means that is decentered from the optical axis of the laser beam and rotates around the optical axis, and emits a laser beam of a further expanded diameter surrounded by an envelope formed by the rotating expanded laser beam. A photomask white spot defect repairing device is obtained, which is a laser beam enlargement processing unit capable of enlarging the opening size.

〔Example〕

 Next, the present invention will be described 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 including the concave lens 21 and the convex lens 22 and the slit 4. As shown in FIGS. 2 (a) and 2 (b), this glass plate can be arbitrarily changed in angle θ with respect to the optical axis and can be rotated around the optical axis.

The eccentricity D of the laser light is given by assuming that the refractive index of the glass plate is n and the plate thickness is d. Given in. When the glass plate is at the position shown in FIG. 2 (a), the laser light is eccentric by D upward as shown in FIG. 2 (c), and when it is at the position shown in FIG. As in d), eccentric by D downward. In this way, when the glass plate makes one revolution around the optical axis, the envelope curve is
The laser beam can be scanned within the range indicated by 43, and the same effect as increasing the diameter of the laser beam can be provided.

Therefore, the opening size of the slit 4 can be increased correspondingly, and a large area can be corrected. Since the amount of eccentricity D can be changed by the inclination angle θ of the glass plate, θ may be changed according to the required correction size. If it is not necessary to increase the correction size, it is clear that θ should be 90 °.

In addition, the rotation speed of the glass plate must be optimally set according to the deposition rate of the metal film. This is for the following reasons. This is because, if the rotation speed is too slow, the deposited film becomes thicker at each moment, and the steps of the film become noticeable. On the other hand, if it is too fast, the heating effect of the laser beam is small, so that the deposition rate of the film may be slow, or the deposition may not occur at all. Furthermore, it is better to use a continuous drive like a DC motor to rotate the glass plate instead of stepping with a pulse motor. This is because the step difference of the film at each step position becomes remarkable in the case of step driving.

A second embodiment according to the present invention is shown in FIG. In this system, the beam expander 2 is provided with an eccentric and rotating mechanism so that the laser beam can be scanned. As shown in FIG. 4, the shaft 52 of the expander is eccentric from the optical axis 53 by α so that it can rotate around the shaft. In this case, the eccentricity amount β of the laser light is considered to be a product of approximately α and the expander magnification, but it is considered to be somewhat different from that value due to lens aberration and the like. Also in this case, as in the first embodiment, by rotating the expander at an appropriate speed, the laser light can be scanned and a large area can be corrected. However, in this method, if the eccentricity α of the axis is made too large, the distribution of the laser light may change due to the aberration of the lens, so care must be taken. According to the method described above, the metal film 37 is uniformly deposited even on a large area white spot defect as shown in FIG. It is possible to make a correction without steps.

〔The invention's effect〕

As described above, according to the present invention, by scanning the laser light incident on the slit with a relatively simple mechanism, it is possible to remove the white spot defect of a large area of the photomask without the need to increase the power of the laser light. There is an effect that can be easily corrected.

[Brief description of drawings]

FIG. 1 is a block diagram of a photomask white spot defect repairing apparatus showing a first embodiment of the present invention, FIG. 2 is a view showing a beam scanning mechanism of this embodiment, and FIG. 3 is a second view of the present invention. FIG. 4 is a block diagram showing the embodiment of the present invention, FIG. 4 is a view showing the beam scanning mechanism of this embodiment, and FIG. 5 is an example of correcting a large area white spot defect by the apparatus of FIG. 4, FIG. Is a block diagram showing a conventional photomask white spot defect repairing apparatus, and FIG. 7 is a view showing an example of conventional large area repairing. Explanation of symbols: 1 …… Laser light source, 2 …… Beam expander, 3,6 …… Dichroic mirror, 4 …… Slit, 5 ……
Slit illumination light source, 7 …… Half mirror, 8 …… Reflection illumination light source, 9 …… Eyepiece optical system, 10 …… Objective lens, 11 …… Window, 12 …… Holding plate, 13 …… O-ring, 14 …… Photo Mask,
15 …… XY stage, 16 …… Correcting substance supply device, 17 …… Trap, 18 …… Exhaust device, 19 …… Chamber, 20 …… Transparent illumination light source, 21 …… Concave lens, 22 …… Convex lens, 31 …… White Spot Defect,
32 …… photomask, 33,34,35 …… deposited film, 40 …… glass plate, 50 …… eccentric laser light, 51 …… laser light when α or zero, 52 …… expander axis, 53 …… Laser optical axis.

Claims (3)

[Claims] 1. A laser light source that emits a laser beam, a laser beam enlargement processing unit that enlarges the emitted laser beam by using a lens mechanism and sends out a laser beam having an enlarged diameter, A slit for shaping a laser beam having an enlarged diameter based on the diameter to set an aperture size, a means for focusing the laser beam having the set aperture size on a photomask surface, and a means for observing the photomask An XY stage on which the photomask is placed and movable, and means for supplying a correction substance to the surface of the photomask at a constant flow rate,
In a photomask white spot defect repairing device for decomposing the repair substance by the laser light to deposit a metal on the photomask and repairing a white spot defect of the photomask, the laser light enlargement processing means: Enlarging the expanded laser beam with an envelope formed by the rotating expanded laser beam, further comprising scanning means for eccentricizing the expanded laser beam from the optical axis of the received laser beam and rotating it about the optical axis. A photomask white-spot defect correction device, which is a laser beam enlargement processing unit that emits a laser beam of a specified diameter to enlarge the opening size. 2. The scanning means is capable of rotating, around the optical axis, a glass plate in which the angle of the laser light with respect to the optical axis can be arbitrarily changed in the laser light expanded using the lens mechanism. The photomask white spot defect correction device according to claim 1, wherein the photomask white spot defect correction device is a scanning means provided in the. 3. The scanning means, wherein the scanning means is provided with a lens mechanism for emitting the enlarged laser light, which is eccentric to the optical axis of the received laser light and is rotatable about the optical axis. The photomask white spot defect repairing apparatus according to claim 1, wherein