JP2003173017A - Method for correction of mask defect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make pattern defect repair possible with high accuracy without adversely affecting transfer by realizing high-accuracy drift compensation without damaging an observation region including a pattern and marker for drift compensation in correction of a mask defect using an ion beam defect correction device. <P>SOLUTION: While the defect 15 is corrected by ion beams 5 by the apparatus combined with the ion beam defect correction device and an atomic force microscope in contactless type, the continuous high-resolution observation of the characteristic pattern 16 or the marker formed by the ion beam defect correction device is performed by the atomic force microscope 2 of the contactless type in parallel with processing in a place as nearest the correction region as possible where the influence of the ion beams or the charges of the electron beams neutralized by electrification is not received. The quantity of the drift is calculated from the comparison with the atomic force microscope of the previous time and the defect correction is performed while the drift is corrected by applying a feedback to the scanning region of the ion beams 5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask defect correction method.

[0002]

2. Description of the Related Art The miniaturization of Si semiconductor integrated circuits is remarkable, and along with this, the pattern size on a photomask or reticle used for transfer is also becoming fine. Reduction projection exposure systems have responded to this demand by increasing the NA and shortening the wavelength. Nowadays, in order to improve the resolution and the depth of focus, a phase shift mask, which is a kind of super-resolution technology, has come to be used while keeping the reduction projection exposure apparatus as it is. The presence of defects on the photomask or reticle causes defects to be transferred to the wafer and reduces the yield.Therefore, the presence or absence of defects on the photomask or reticle is checked by a defect inspection device before transferring the mask pattern to the wafer. The location is checked, and if there is a defect, the defect repairing device performs a defect repairing process before transferring to the wafer. Due to the above-mentioned technological trend, it is required to deal with small defects even in the defect correction of the photomask or the reticle. Focused ion beam devices that use liquid metal Ga ion sources have become the mainstream of mask repair devices instead of defect repair devices that use lasers due to their fine processing dimensions. In the defect repair system using the above ion beam, when repairing white defects, the raw material gas adsorbed on the surface is decomposed only at the point where it is hit by the ion beam (F
IB-CVD), the high-precision processing is achieved by utilizing the effect of sputtering with a focused ion beam when repairing black defects or the effect of etching only where it is hit by a finely focused ion beam in the presence of an assist gas.

[0003] In order to improve the correction accuracy in the ion beam defect correction device, a black hole or a white defect is formed by making a small hole on the pattern near the defect of the mask by the ion beam that is not exposed by the reduction projection exposure device as a marker. Machining is periodically interrupted during correction machining, the secondary ion image or secondary electron image is observed only on the pattern around the marker, the drift amount is calculated from the comparison with the previously acquired image, and it is fed back to the machining scanning range. Therefore, it has been attempted to prevent the accuracy from decreasing due to drift.

Further, in order to cope with the recent miniaturization of patterns on a mask, an ion beam defect repairing device is also required to have higher resolution and further improve neutralization of electrification. In order to meet the requirements for both high resolution and neutralization by electrification, the probe current of the ion beam has been reduced. If the probe current is lowered, the processing time becomes longer, and in order to prevent the accuracy from decreasing due to drift, it is necessary to increase the frequency of drift correction by observing the above-mentioned small holes and matching patterns and feedback to the ion beam irradiation range. However, because the observation area is ablated by the physical sputtering effect of the ion beam during image observation, the phase changes with a phase shift mask, or when observing small holes, the diameter of the holes gradually increases and the wafer There was a problem that it was exposed above.

[0005] In addition to a method of observing a small hole or a characteristic pattern and calculating a drift amount from comparison with an image acquired last time, a mirror is provided on a side surface of a stage, and a distance is measured by a laser interferometer to measure an ion beam Also widely used is a method of correcting the drift by feeding back the scanning range of. This method has the advantage that it does not damage the mask to be repaired except for the processed part, but when the temperature differs between the mask and the stage or when there is a local heat expansion of the mask when there is a heat source near the mask. There was a problem that it could not be corrected for thermal drift such as. Pattern matching is also a useful method for determining the amount of drift, but Ga ions are implanted into the glass substrate around the pattern each time the secondary ion image or secondary electron image is observed, and the transmittance of the glass substrate decreases. Since it occurs, it is not used for drift correction of ion beam defectors.

[0006]

SUMMARY OF THE INVENTION The present invention provides highly accurate drift correction in a mask defect correction using an ion beam defect correction device without damaging an observation region including a drift correction pattern and a marker. By realizing it, it is intended to enable defect correction with high accuracy and without adversely affecting transfer.

[0007]

A non-contact mode atomic force microscope, whose resolution is remarkably improved by improving frequency modulation detection technology in recent years, is combined with an ion beam defect repairing device and used for drift detection. As shown in Fig. 1, while the defect is being repaired by the ion beam, the ion beam and the electron beam for electrification neutralization should be as close to the repair area as possible.
A characteristic of non-contact atomic force microscopes that does not damage the observation area in parallel with processing in a place that is not affected by electric charges (when modifying a material with low conductivity such as a photomask). A marker created by a pattern or ion beam defect repair device is continuously observed at high resolution, a drift amount is calculated from comparison with a previous image, and feedback is applied to the scanning range of the ion beam to correct the drift.

[0008]

Since the observation is performed with the non-contact type atomic force microscope, the mask is not damaged even if the frequency of drift correction is increased. Even when a marker is formed and observed by the ion beam defect correction device, the diameter of the hole is gradually increased and the wafer is not exposed.
The ion beam processing and the drift correction image acquisition can be performed in parallel, and the processing time does not increase even if the frequency of drift correction increases. Since the drift is corrected by the pattern or the marker on the mask and in the vicinity of the defect correction area, it is possible to correct the drift which cannot be dealt with by the length measurement by the laser interferometer. For the above reasons,
Since the drift correction can be performed with high accuracy without reducing the film thickness or the hole diameter in the observation region for drift correction, it is possible to perform defect correction with high accuracy and without adversely affecting transfer.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An example in which the present invention is applied to a defect correction of a photomask will be described below. Photomask with defects (binary mask or phase shift mask)
3 is introduced into the vacuum chamber of the combined apparatus of the ion beam defect correction device 1 and the non-contact type atomic force microscope 2 as shown in FIG. 2, and the XY stage 4 is placed at the defect position detected by the defect inspection device. Moving. A secondary electron detector or secondary ion detector 7 synchronized with the scanning of secondary electrons or secondary ions 6 generated by irradiating the photomask 3 with an ion beam 5
Then, the defective area is recognized from the secondary electron image or secondary ion image. Since the photomask has a conductive light-shielding film pattern 14 deposited on the glass substrate 13 which is an insulator, the secondary electron image or secondary ion image can be seen by charging up due to the accumulation of positive ions of the ion beam 5. Because it disappears, several hundreds with the electron gun 8 for charge neutralization
The electron beam 9 which is accelerated to V and focused is irradiated to observe the state where the charge is neutralized. In parallel with the above-mentioned defect recognition, a defect area to be processed as much as possible in a place not affected by the charges of the ion beam 5 and the electron beam 9 for charge neutralization so that the electrostatic force does not adversely affect the atomic force microscope probe 10. 15
A wide range is observed in the vicinity of with a non-contact type atomic force microscope 2, a pattern 16 used for drift correction is determined, and this pattern is observed at a high magnification sufficient for drift correction in the future.

[0010] Since the atomic force microscope 2 flows a shielding film raw material gas and a gas for enhanced etching during the defect correction processing, the probe 10
In order to avoid the effect of gas adsorption on the gas, the pattern located upstream of the gas flow should be used for drift compensation,
Furthermore, a shielding plate 11 is provided to shield gas molecules.
Atomic force microscope probe 10 is also made of a material that does not easily react with gas, such as platinum, so that the probe and photomask do not have a negative effect on the image of the atomic force microscope even when physically adsorbed, even if the resolution is slightly degraded. Also try to take a wider space.

Only the region 15 recognized as a white defect or a black defect by the ion beam defect correction device is selectively supplied while flowing a shielding film material gas (at the time of white defect) or a gas for accelerated etching (at the time of black defect) from the gas gun 12. To scan the defective area 15. The pattern 16 selected by the non-contact type atomic force microscope 2 is continuously observed in parallel with the processing, and the position of the pattern 16 is compared with the previous atomic force microscope image to calculate the drift amount. The processing of the ion beam defect repairing device is interrupted, the drift amount calculated from the atomic force microscope image is fed back to the scanning range of the ion beam 5 to correct the drift, and the processing for defect repairing is restarted again. Observation of a specific pattern on the photomask by the non-contact type atomic force microscope 2, calculation of the amount of drift, and feedback to the scanning range of the ion beam 5 of the ion beam defect repairing apparatus 1 are repeated,
The defect region 15 is processed while correcting the drift.

[0012] Since the drift correction is observed with a non-contact type atomic force microscope, the probe does not come into contact with the photomask. Therefore, even if the drift correction frequency is increased, the mask pattern 13 and the glass substrate 14 are not changed. Does no damage. The ion beam processing and the drift correction image acquisition can be performed in parallel, and the processing time does not increase even if the frequency of drift correction increases. Since the drift is corrected in the pattern on the photomask and in the vicinity of the defect correction area, it is possible to correct the drift that cannot be dealt with by the length measurement with the laser interferometer. For the above reasons, highly accurate drift correction can be realized without damaging the observation region including the drift correction pattern, and defect correction that is highly accurate and does not adversely affect transfer can be performed.

[0013] Instead of observing the pattern in the above correction procedure, the pattern is not exposed by the reduction projection exposure device on the pattern by the ion beam defect repair device at a place not affected by the charges of the ion beam 5 and the electron beam 9 for charge neutralization. A small hole is opened as the marker 17, and the area including the marker 17 is continuously observed in parallel with the defect correction processing, and the drift amount is calculated from the comparison with the previous atomic force microscope image, Even if the feedback is applied to the scanning range of the beam, the drift correction can be performed with high accuracy, so that the defect can be corrected with high accuracy. Since the region including the marker 17 for drift correction is observed by the non-contact type atomic force microscope, the film thickness in the observation region and the diameter of the hole are increased and the transfer is not adversely affected.

When a mask other than the photomask is repaired, when a material having low conductivity is included, the repair is performed by the same method as described above. When modifying a conductive mask,
Of the above procedures, the procedure for charge neutralization may be omitted and the defect may be repaired in the same manner.

[0015]

As described above, according to the present invention, highly accurate drift correction can be performed without film loss in the observation area for drift correction or transfer of markers, and therefore, high accuracy and adverse effect on transfer. The defect can be corrected without giving

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view that best represents the features of the present invention.

FIG. 2 is a diagram illustrating a case where the present invention is applied to defect correction of a photomask.

FIG. 3 is a schematic cross-sectional view of observing a marker created by an ion beam defect repairing device with a non-contact type atomic force microscope in parallel with processing.

[Explanation of symbols] 1 Ion beam defect repair device 2 Non-contact atomic force microscope 3 Photomask 4 XY stage 5 Ion beam 6 Secondary electron or secondary ion 7 Secondary electron detector or secondary ion detector 8 Electron gun for charge neutralization 9 Electron beam 10 Atomic force microscope probe 11 Shielding plate 12 Shielding film Gas or gas gun for accelerated etching 13 Glass substrate 14 Shielding film pattern 15 Defect area 16 Shielding film used for drift correction Pattern 17 Marker for drift correction created with the ion beam defect repair system

Claims (2)

[Claims] 1. In a mask defect repairing method using a combined device of an ion beam defect repairing device and a non-contact type atomic force microscope, black defect removal and white defect repairing are performed by an ion beam defect repairing device, and drift correction is processed. It is characterized in that the field of view is fixed with a non-contact type atomic force microscope, the characteristic pattern is repeatedly observed, and the amount of drift is fed back to the scanning range of the ion beam from the comparison of observed images. Photomask defect repair method. 2. The photomask defect repairing method according to claim 1, wherein the marker formed by the ion beam defect repairing device is repeatedly observed while the field of view is fixed by a non-contact type atomic force microscope during processing. The method of correcting a defect in a photomask, wherein the drift amount is corrected by feeding back the drift amount to the scanning range of the ion beam.