JPS6124232A - Pattern inspecting method - Google Patents

Abstract

PURPOSE:To remove the foreign matter adhered to the material to be inspected as well as to improve the reliability of inspection by a method wherein a clean and dried fluid is blown against the circuit forming surface of a pattern. CONSTITUTION:Nozzles 16a and 16b are formed on the holder 15 of an objective lens 10. A piping tube 17 is connected to the entrances of the nozzles 16a and 16b, and the air sent from the source of air is supplied to the nozzle 16a or the nozzle 16b after passing through a filter 19 and a direction switching valve 18. When a mark 3 is moving in the direction of an arrow A and an inspection is performed, the air passed through the filter 19 and a drier 20 is supplied to the nozzle 16a by a direction switching valve 18. The emitting end of the nozzle 16a is opposing to the mask 3, and air is blown upon the part in forward direction of the part to be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for inspecting patterns of LSI patterns and printed circuit boards.

[Background of the invention]

The prior art will be explained with reference to FIG. 1, taking an LSI photomazu appearance inspection device as an example.

An X-Y stage 2 is provided above the pace 1, and a transport device 4 is installed that moves in the front, rear, right and left directions in the figure, and loads or unloads a mask 5 having a circuit pattern on the X-Y stage 2. has been done. In order to supply the mask 3 to the transport device 4 (or to store the mask 6 from the transport device 4), a cartridge 5 is provided next to the transport device, and it is possible to automatically supply or store the mask 3. It has become.

A mask stand 6 that holds a mask 6 is fixed to the XY stage 2, and the mask 6 is illuminated from below by an illumination lens 7. An inspection microscope 8 is installed on the base 1 by a column 9 above the mask 5, and the pattern of the mask 3 is enlarged and projected by an objective lens 10 above the illumination section, and is transmitted through a sensor 11 in the inspection microscope 8 to a defect determination section 12. electrically input.

On the other hand, the defect determination unit 1 also uses the quick tape 13 that stores the design data of the circuit pattern of the photomask 3 as an image signal.
2.

When the mask 5 housed in the cartridge 5 in the apparatus configured as described above is loaded onto the mask stand 6 on the XY stage 2 by the transport device 4, the entire surface of the photomask is inspected in the order of the arrows in FIG. While the X-Y stage 2 is being scanned for inspection, the output signals of the pattern sensor 10 and the magnetic tape 11 are compared in the defect determination section 15, and if there is a difference, it is determined that the defect portion is abnormal.

This inspection equipment detects defects of % 1 to 21 Irn, so the objective lens must have high resolution, and a high-magnification objective lens (50 to 100 times) is used, and the time it takes to inspect the entire mask surface is 1 to 21 Irn. It takes 60 to 90 minutes to detect 2 capes of defects. During this inspection, if a foreign substance of the same size (1 to 2 μm) is found on the mask pattern, it may naturally be determined to be a defect. However, with this device, 5 to 10 masks are automatically inspected continuously, so the masks are stored in the cartridge for 5 to 10 hours, and the mask pattern surface is exposed to the surface during inspection or while waiting for inspection. Foreign matter adheres.

As a countermeasure, we take precautions to prevent dust, such as putting the equipment itself in a clean room or surrounding it with a clean bench. Furthermore, the masks supplied to this type of inspection equipment are washed several times to remove potential defects such as dirt and foreign matter with great care. The reason for these dust removals is
This is because even if there is a defect as described above at one location on the mask (reticle), the yield of LSI will be greatly reduced.

Moreover, in recent years, as patterns have become finer, the target size of defects has become even smaller, and even defects of 1 μm or less are becoming a problem.

For this reason, the above-mentioned dust prevention measures have become insufficient.

For example, even if the above inspection equipment is inspected in a clean bench with extremely high cleanliness of class 100, the clean bench is filled with foreign matter of 1 μm or less, and the X-Y stage simply moves during the inspection. There is a risk that foreign matter may adhere to the mask pattern.

Furthermore, it is natural that foreign matter from the subsiphon may adhere when a cleaned mask is set in an inspection device or during transportation. from these things.

If a conventionally used inspection method is used to inspect a mask to which fine foreign matter of one strand or less is attached, it is natural that the foreign matter will also be determined to be a defect and the number of defects will increase.

That is, even if there are 2 to 6 true defects in one mask, it is determined that there are several tens to hundreds of defects.

With traditional methods, if there were too many defects, the mask would be discarded. However, when such problems occur, it is necessary to distinguish between defects and foreign objects. In this method, after the inspection is completed, the above-mentioned pseudo defect position is reproduced and determined by visual observation using an 8-microscope or by observation on a TV monitor. As the number of pseudo defect candidates increases, the inspection time increases and the inspection throughput decreases. Furthermore, when the number of defect candidates increases, there is a risk that even true defects may be determined to be foreign substances.

From the above, it is clear that in order to accurately and quickly inspect pattern defects of 1 μm or less, foreign matter that adheres during the inspection becomes a problem, and the reduction in reliability of the inspection apparatus due to foreign matter is also a problem.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable inspection method that eliminates the above-mentioned drawbacks caused by foreign substances adhering to circuit forming surfaces of masks, wafers, etc. that are being inspected or are waiting to be inspected.

[Summary of the invention]

In order to achieve the above object, the present invention employs a method of removing foreign matter on the circuit forming surface immediately before inspecting the pattern.

That is, a configuration is provided in which a foreign object removing means is provided to remove foreign objects immediately before the inspection point that is imaged and detected by the objective lens of the inspection device. As a specific example of the foreign matter removing means, a method was used in which a means for spraying clean and dry fluid onto the circuit forming surface of the pattern was provided around the objective lens to remove foreign matter.

[Embodiments of the Invention] Examples of the present invention will be described with reference to FIGS.

FIG. 6 shows an embodiment of the LSI photomask inspection apparatus of the present invention. A foreign matter removing section 14 is arranged around the objective lens 10. The rest of the structure and operation are similar to the conventional embodiment shown in FIG. FIG. 4 shows a specific example of the method for removing foreign matter. A nozzle 16a, 1 is attached to the holder 15 of the objective lens 10.
Form 6k.

A piping tube 17 is installed at the inlet of the nozzle/l/16a, 164.
is connected so that the air from the air source is supplied to the nozzle 16a or 1μ after passing through the filter 19° and the directional valve. Now, when the mask 3 is moving in the direction of the arrow and an inspection is being performed, the directional control valve 1
8, the filter 19. Air that has passed through the dryer 20 is supplied to the nozzle 16H.

The output end of the nozzle 16H faces the mask 3 and blows air in front of the inspection area.

Next, when the inspection direction becomes the B direction, the direction switching valve 18
to supply air to the nozzle 167.

By blowing clean, dry air in front of the inspection area in this way, the inspection can be performed while blowing away foreign matter adhering to the mask.

FIG. 5 shows the method shown in FIG. 4 except that a foreign matter suction section is provided, and foreign matter exhaust ports 21a, 214. It is a diagram in which a vacuum piping tube 22 is added. By vacuum suctioning the blown foreign matter explained in FIG. 4 from the foreign matter exhaust port, it is possible to reduce the amount of dispersion of the foreign matter. Photomasks supplied to the semiconductor photomask inspection process are subjected to extensive cleaning (for example, chemical cleaning with chemicals, heating cleaning with chemicals, scrub cleaning with a brush, etc., and high-pressure water cleaning) beforehand.

According to the present invention, even if the above-described cleaning is performed, foreign matter adhering to the mask can be removed before the start of the inspection or during the inspection, so that erroneous detection of defects due to foreign matter can be reduced. or.

The working environment of semiconductor manufacturing is extremely clean, and the number of problematic foreign particles is about 1 μm, but at printed circuit board manufacturing sites, etc., the environment does not need to be so clean. but,
Even in the process of inspecting printed circuit board patterns, the density of pattern packaging is increasing, and the number of pattern defects is 10 to 2.
0 μm is becoming a problem.

As described above, according to the present invention, it is possible to eliminate the negative influence of defect detection caused by these 10 to 20 μm foreign particles.

Additionally, this type of device has conventionally been used in clean benches, etc., but by applying the present invention.

This eliminates the need for a clean bench and reduces equipment costs.

According to this embodiment, air is used as a means for removing foreign matter, but other dry and clean fluids may be used.

〔Effect of the invention〕

According to the present invention, since the inspection is performed while removing foreign matter attached to the object to be inspected, the number of erroneous detections in which foreign matter is determined to be a defect is reduced, and the reliability of the inspection is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional LSI photomask inspection apparatus, FIG. 2 is an explanatory diagram showing an L8I photomask inspection method and inspection order, FIG. 3 is a block diagram of an LSI photomask inspection apparatus of the present invention, and FIG. FIG. 5 is an explanatory diagram showing a method for removing foreign matter according to an embodiment of the present invention, and FIG. 5 is an explanatory diagram showing another method for removing foreign matter. 3...Mask, 8...Inspection microscope, 10...Objective lens, 11...Sensor, 12...Defect determination unit, 13 ······Magnetic tape. 14...Foreign matter removal unit, 15...Holder, 16a...Nozzle, 164...Nozzle, 17...Tube, 18... ... Directional switching valve, 19 ... Filter, 20 ... Dryer. 21a... Foreign matter exhaust port, 21k... Foreign matter exhaust port, 22... Vacuum piping tube.

Claims (1)

[Claims] 1. A pattern inspection method for inspecting defects in circuit patterns of semiconductor photomasks, wafers, printed circuit boards, etc., characterized in that the inspection is performed while removing foreign substances on the circuit patterns.