JPS5922372B2 - Photomask modification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photomask repair method for repairing missing defects in a photomask used in LSI manufacturing.

Defects existing in the photomask include defects in which extra mask material (e.g. chromium, chromium oxide, iron oxide, silicon, etc.) remains on the substrate 1 other than the pattern 2 (black spot defect), as shown in Figure 1. There are two types of defects: 3. and 4. defects where mask material is missing (white spot defects).

Among these, black spot defects can be corrected extremely well by laser.

On the other hand, regarding white spot defects, as shown in FIG. A high-energy beam 8 is irradiated to the part 6 of the metal film for deposition facing the defect 4, and the vapor of the metal for deposition heated and evaporated by this energy adheres to the white spot defect 4, forming a film and repairing it. is completed. However, in this method, metal vapor is attached to white spot defects in the atmosphere, so the adhesion strength is extremely low and a sufficient film thickness cannot be obtained.
In addition, the wraparound to the periphery is large, causing black spot defects in the periphery, and an additional process of removing them is also required. SUMMARY OF THE INVENTION An object of the present invention is to provide a photomask repair method that eliminates the above-mentioned drawbacks of the prior art and allows white spot defects to be repaired easily and accurately.

That is, in the present invention, a complex salt containing a metal atom, particularly a metal chelate compound, is applied to the white spot defect area and its surrounding area, and the white spot defect area is irradiated with an energy beam to be thermally decomposed to precipitate the metal. Correct white spot defects by attaching precipitated metal to the surface. Embodiments of the present invention will be specifically described below with reference to the drawings.

As shown in FIG. 3, a metal chelate polymer dissolved in a solvent is coated on a substrate 1 and then dried to form a film 11 of the metal chelate polymer. When the metal chelate polymer film is heated here, the metal chelate polymer in the heated portion is decomposed and metal is precipitated, forming a metal film 13 on the substrate 1. Thereafter, by washing with a solvent, the undecomposed metal chelate polymer is dissolved and only the metal film 13 remains on the substrate 1. By using a high-energy beam, such as a laser beam or an electron beam, as a heating source, it is possible to heat only a very limited area of V1. By forming a metal chelate polymer film on the defect and its surroundings, and irradiating and heating only the white spot defect area with an energy beam, the decomposed and precipitated metal is removed.
White spot defects can be corrected.

Although the metal chelate polymer has been described here, a film having a uniform thickness can be obtained by using a metal complex salt, particularly a metal chelate compound. The metal chelate polymer used here is, for example, one obtained by polymerizing a metal chelate of ethyleneimine (that is, a chelate containing Cr, .Cu, .Pd, etc. as the metal).

Next, FIG. 4 shows a correction device using a laser beam as a heating source.

The real image plane of the objective lens 13 is provided with a slit 14 (only one direction is shown in the figure) that is movable in two directions of X and Y and can form a rectangle of any size. The light having the wavelength transmitted through the dichroic mirror 16 is shaped into a rectangle of arbitrary size by the slit 14.
The image is projected by the objective lens 13 onto the metal chelate polymer coated on the white spot defect portion 4 on the substrate 1 .

This projected rectangle can be created by installing a characteristic filter 17 immediately after the illumination device that transmits only a specific visible wavelength when using a YAG laser as a laser source, or by installing a characteristic filter 17 that transmits only a specific visible wavelength as a laser source, or by installing a characteristic filter 17 that transmits only a specific visible wavelength as a laser source. If a laser with a different wavelength is used, a characteristic filter 17 that transmits visible wavelengths different from the laser wavelength may be used.
Under the illumination of white light by the half mirror 18, the reflection half mirror 19 and the eyepiece lens 20 can be clearly distinguished.
The size of the white spot defect 4 and the size of the rectangle can be matched or aligned while observing as follows.

After alignment and size matching are completed, the laser oscillator 21 is made to oscillate, or if necessary, the shutter 22 is opened for a certain period of time to allow the laser beam 23 to pass through, and the same area as the rectangular area formed by the illumination lamp 15a is created. The metal chelate polymer is irradiated with laser light to decompose only the white spot defects and metal is precipitated to correct the white spot defects.

Further, in FIG. 4, the coated metal chelate polymer 11 is irradiated with laser light 23, but even if the metal chelate polymer 11 is irradiated from the substrate 1 side through the substrate as shown in FIG. It's exactly the same.

Further, FIG. 6 shows another example in which a laser beam is similarly used as a heating source.

This is a mechanism that rotates two prisms with the same apex angle in opposite directions at the same speed, and scans the laser beam passing through the prisms in a straight line.The scanning device consists of the two prisms. 25a, 25b1 and motors 26a, 26b1 for rotating these, rotary encoders 27a, 27b for detecting the rotation angle of the prism 25 or the motor 26, and the laser beam 23 oscillated from the oscillator 21. is focused and irradiated by the objective lens 28 onto the metal chelate polymer 11 coated on the mask including the white spot defect 4 on the substrate 1.

It also includes an observation optical system 30 for observing the laser beam irradiation area. Laser oscillation is controlled by a control device 29 as follows. That is, depending on the size of the white spot defect 4, the laser irradiation position is detected only in a set area using a signal from the rotary encoder 27a, and the laser beam 23 is oscillated, or the shutter 22 provided as necessary is opened to allow the laser beam 23 to pass. The metal chelate polymer 11 is irradiated while being scanned by the scanning device 26a. When one effective scan is completed, the laser oscillation is stopped or the shutter 22 is closed, and at the same time another set of scanning devices 26 is adjusted so that the scanning directions are perpendicular to each other.
By repeating this by shifting by a certain distance as shown in b), the white spot defect area is scanned two-dimensionally, metal is deposited, and the white spot defect is repaired. FIG. 7 shows the movement of the laser beam at this time. The dashed line indicates the scannable locus of the laser spot 31, and the thick solid line indicates the locus of the center of the laser spot 31 that is actually irradiated. At this time, it is necessary to select a shift amount so that the spots overlap sufficiently. Further, as shown in FIG. 5, the same effect can be obtained by irradiating light through the substrate from the substrate 1 side. As a laser source, it has enough power to not damage pattern 2 in the irradiated area! Since it is necessary to heat the metal chelate to a temperature of several hundred degrees Celsius or higher, continuous wave or pulsed laser light with a sufficiently long pulse width (for example, 1 μs or more) is desirable.

Also, when an electron beam is used as a heating source, the electron beam may be scanned over a set area as shown in FIG.

However, the method shown in FIG. 5 cannot be used. As explained above, according to the present invention, a sufficiently thick metal film can be easily and accurately attached to a defect where mask material is missing (white spot defect) to completely repair it, and a photomask that can withstand practical use can be obtained. It has the effect of being

[Brief explanation of drawings]

Fig. 1 is a diagram explaining various defects, Fig. 2 is a diagram showing a conventional photomask repair method, Fig. 3 is a diagram showing a photomask repair method of the present invention, and Fig. 4 is a diagram showing a photomask repair method according to the present invention. Fig. 5 is a schematic diagram showing an embodiment of the device for irradiating the substrate.
This figure is a schematic diagram showing an embodiment of the photomask correction device different from that shown in FIG. 4, and FIG. 7 is a diagram illustrating the movement of a laser spot scanned by the device shown in FIG. 6.

Claims (1)

[Claims] 1. For white spot defects where the photomask pattern is missing, a film of metal chelate compound is applied to the entire surface of the photomask or the defective area and its surroundings, and a high-energy beam is irradiated only to the defective area to remove the metal chelate compound. A method for repairing a photomask, comprising heating the film to decompose the metal chelate compound, precipitating the metal, and filling the white spots with the precipitated metal.