JPS58152243A - Detector for foreign matter in reticle - Google Patents

Abstract

PURPOSE:To detect the sizes, kinds, etc. of the foreign matters on a reticle, by providing a reflecting mirror, which is movable forward and backward, in the midway of an optical path which projects and exposes reticle patterns on a wafer, magnifying the image reflected by the same and observing the image. CONSTITUTION:This device illuminates a reticle 1, which is a photographic dry plate having circuit patterns, from above with a mercury arc lamp 2 for illumination and a condenser lens 3, projects the patterns of the reticle 1 with a scale- down projecting lens 4 in a reduced size on a wafer 5 and forming chips 6. To detect the foreign matters stuck on the reticle 1, a shutter 23 is closed to shut off the illuminating light of the lamp 2 and a lamp 25 for reflection illumination is lighted. The light from the lamp 25 is reflected by a semitransparent mirror 27 and a reflecting mirror 16, and irradiates the bottom surface of the reticle 1. The images of the patterns and foreign matters on the reticle 1 are observed through a semitransparent mirror 27 with a microscope 20.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reticle foreign matter detection device that detects foreign matter by scanning a spot light on a reticle of a reduction projection exposure apparatus.

First, the concept of a reduction projection exposure apparatus will be explained using Fig. 1.

I will explain. In this device, a reticle 1, which is a photographic plate having one circuit pattern, is illuminated from above by a mercury lamp 2 for illumination and a condenser lens S.

A pattern on a reticle 1 is reduced by a reduction projection lens 4 and projected onto a wafer 5 to form a chip 6.

It is something that At this time, since only the chip 6 is exposed at one time, the wafer 5 is moved in the x and y directions,
Instead of exposing one chip at a time, the entire surface of the sea urchin was exposed.

If a foreign object 7 adheres to the reticle 6 for some reason, the exposure light will be blocked by the foreign object, so that the exposure light will not reach the chip 6 and a pinhole 8 will be created. Since the chips are automatically exposed by driving the wafer in a step-and-repeat manner in the "r!" direction, if there is a foreign object on the reticle, pinholes will appear in all the chips and all products will be defective. Therefore, it is necessary to constantly inspect the reticle for adhering foreign matter, and if object A adheres to the reticle during exposure, it is necessary to immediately issue a warning, stop the exposure, and replace the reticle.

As a conventional reticle foreign object detection method, OCA's automatic reduction projection method! There is a foreign matter detection method adopted by Spherina [DyI]. One reticle is automatically conveyed under the condenser lens 3 as shown in FIG. In this foreign object detection method.

Object A on the reticle is detected during transportation.

For detection, a laser oscillator is placed above the reticle 1, and the laser beam is focused onto the surface of the reticle 1 by a focusing lens 10. Foreign matter 11 adheres to the reticle 1 while it is being transported, and when this foreign matter 11 comes directly below the laser focal point, the laser light is scattered. A lens 12 and a photoelectric conversion element 15 are provided around the focal point.

When the output of the element 15 exceeds a certain value, it is determined that there is an attached foreign substance.

Furthermore, the inventors have already proposed a method in which a reticle is completely sectioned under a condenser lens and then a laser beam is irradiated onto the reticle surface to detect foreign objects. Furthermore, by scanning the laser beam spot on the reticle in the x and y directions, if a foreign object is attached to the top or bottom surface of the reticle, the coordinate position of the foreign object on the reticle in the x and y directions can be detected. can.

According to the above method, Ii can completely detect the foreign object on the reticle and can also detect the Vc: t, y direction coordinate position, but the size and type of the foreign object cannot be determined. I couldn't even tell if it was on the reticle pattern or not.

In the reduction projection exposure apparatus, not all A objects on the reticle become defects in the wafer pattern, and in the pattern 1ljli on the reticle (lower If of Fig. 1), the non-pattern ff1 ([Fig. In the upper WJ), foreign particles larger than about 15 μm can lead to defects in the wafer pattern, so the size of the foreign particles must be detected accurately.

Further, the pattern on the reticle is generally made of Cr. As shown in FIG. 1, when the mercury lamp 2 is turned on and the reticle surface is irradiated.

These Cr patterns function to block irradiation light.

Therefore, even if foreign matter adheres to these Cr patterns, it will not have any adverse effect, so it is necessary to detect foreign matter adhered to areas other than the Cr patterns.

Conventional reticle foreign object inspection devices cannot meet these requirements, that is, detect one type of foreign object size and its position relative to the reticle pattern.

Therefore, in the past, it was unavoidable to print the pattern on the reticle onto the Unino 1, visualize the Unino, and then carefully inspect the pattern on it with a microscope to ensure that there were no defects at all in the pattern. After confirming the above, the actual exposure work began, which took 2 to 5 hours to prepare.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide a reticle foreign object detection device for a reduction projection exposure apparatus that can detect the size, type, and position of foreign objects on a reticle in relation to the reticle pattern. There is something to do.

A reticle foreign matter detection device according to the present invention is a reticle foreign matter detection device that detects foreign matter by scanning a spot light on a reticle of a reduction projection exposure device. A mirror is provided, and the actual image of the reticle pattern is formed outside the projection exposure optical path by the reflecting mirror, and the actual image is further magnified for visual observation or automatic recognition means. This device is characterized by being capable of detecting the type and position relative to the reticle pattern.

In a preferred embodiment of the reticle foreign object detection apparatus according to the present invention, the illumination light itself for projecting and exposing the reticle pattern onto the wafer is used as the illumination light for forming an image of the reticle pattern outside the projection exposure optical path.

Other preferred Jl of the reticle foreign object detection device according to the present invention
In case i1, the image of the reticle pattern #* projected outside the projection exposure optical path is obtained by using at least one of the transmitted light of the reticle and the reflected light of the illumination light projected onto the bottom surface of the reticle. can get.

An actual example of the apparatus of the present invention will be explained below with reference to FIG. 5. The implementation of the reduction projection exposure apparatus provided with this reticle foreign object detection device is the same as the apparatus described in FIG. That is, the illumination light from the mercury lamps 2 to 1 is condensed by the condenser lens 5 and illuminates the reticle 1. The pattern on the reticle 1 is reduced in size by a small projection lens 4 and projected onto a wafer 5 to form a chip 6.

This foreign object detection device I is not shown in FIG.

It has means for detecting foreign matter by scanning a spot light on the reticle. A typical example of this means is a means for detecting the position of a foreign object.1 The position detecting means scans a laser spot light over the reticle (upper surface and lower surface) over the entire WJ in the x and y directions, and detects the presence of the foreign object. For example, there is a method for determining the coordinate position of a foreign object based on the laser scattered light that is generated. Of course.

Other position detection means may also be used. Furthermore, it may be possible to use means that cannot determine the coordinate position of a foreign object and can simply detect the presence or absence of a foreign object.

In this foreign object detection device, the cylinder 17 rotates the foreign object in the middle of the optical path for projecting and exposing the reticle pattern onto the wafer 5, and advances and retreats into the optical path.

A reflecting mirror 16 is provided which forms an angle of 45[degrees] in the optical path when the light enters. Therefore, the light transmitted through the reticle from the mercury lamp 2 is reflected at right angles by the reflecting mirror 16), and the imaging lens 18 forms a real image of the reticle 1 at a position 19 outside the optical path of the reduction projection exposure apparatus. 20 is a microscope for magnifying and detecting this foreign object, and when the above-mentioned foreign object position detection means is provided, the same coordinates (
:vO,y・)K is positioned. 21 is a close-up lens for visual observation, and 22 is a camera for taking a reticle image.

Further, a shutter 25 is provided for blocking illumination light from the mercury lamp 2 to the reticle 1.

In addition, 45 in the optical path between 1 reflection m16 and la's lens 18
A semi-transparent mirror 27 is provided at an angle of inclination, and the light from one reflective illumination lamp 25 is focused by a condenser lens 26, reflected by the semi-transparent mirror 27 and the reflecting mirror 16, and illuminates the lower surface of the reticle 1. be. The reflected light from the bottom surface of the reticle 1 is reflected by the reflecting mirror 16, passes through the semi-transparent part 11i27,
1 as well as the transmitted light of the reticle 1.
Make an image of the reticle pattern at position 9.

To detect a foreign object with this device, first open the shutter 25 and illuminate the reticle 1 from above.

The silhouette of the pattern is projected onto 19 and then projected onto the shell 424 of foreign object 15. Next, when the shutter 2S is closed to cut off the illumination light from the mercury lamp 2 and the second knob 25 for reflected illumination is turned on, the image of the pattern and foreign matter on the reticle 1 is It is formed at position 19.

The size and type of the foreign object can be determined by observing the reticle pattern and the image of the foreign object formed at the position 19 by the transmitted light or reflected light of the reticle 1 using the microscope 20. Furthermore, it is possible to determine whether the foreign matter adheres to the reticle pattern and does not have an adverse effect, or whether the foreign matter adheres to the reticle pattern and interferes with exposure.

If this device has a foreign object position detecting means and the coordinate position of the adhered foreign object is known in advance, it is easy to find the adhered foreign object using a mold mirror.

Detection can be performed quickly and reliably. In addition, when detecting foreign objects using MINK using both transmitted light and reflected light, the properties of the foreign objects can be completely determined, and it is possible to determine whether it is okay to use the reticle for exposure work. Judgments can be made easily. Of course, only one of the transmitted light and the reflected light can be used for the purpose. In the embodiment, another lamp 25 is used for one reflected illumination, but the illumination light from the exposure lamp 2 can also be guided and used for reflected illumination.

In the embodiment, *The case was described using a visual observation means using a mold mirror, but instead of this, pattern recognition technology is used to automatically detect the size, type, and position of the foreign object in relation to the reticle pattern. A device for determining this can be used.

Conventionally, foreign matter inspection on a reticle involves printing the pattern on the reticle onto a wafer, then developing the wafer, and then
It took a long time (2 to 5 hours) to carefully inspect the pattern on the reticle (K), as it was inspecting for foreign objects on the reticle, as mentioned above.

In the apparatus of the present invention, when the adhesion of foreign matter is confirmed by spot light scanning, the reticle pattern is printed onto the wafer, and without being amperated, the reticle pattern is directly projected outside the exposure optical path and observed under magnification with a microscope. Therefore, the inspection time for foreign substances can be significantly shortened. Further, when this foreign object detection device has a means for detecting the x and y coordinate position of the foreign object, first, the coordinate position of the foreign object (the upper and lower surfaces of the reticle) is detected by the armpit means.

The time is usually within 1 minute. Further, the number of foreign objects is usually about 10. Next, at least one of the transmitted light and reflected light of the reticle is used.

The reticle pattern is imaged outside the projection exposure optical path, magnified with a microscope, and visually observed. In this case, the coordinate position of object A has already been detected.

Since the number of S objects is about 10, it is necessary to quickly and reliably determine whether or not the foreign objects are interfering with exposure (depending on the size, type, and position of the foreign objects in relation to the reticle pattern). I can do it. The time required for this is 2 to 5 minutes. Therefore, a complete inspection can be completed in a total of 5 to 4 minutes.

Detection of foreign matter on a reticle by the apparatus of the present invention.

Even in the middle of exposure work, you can do it without removing the reticle.
It is possible to automatically inspect by illuminating under the same conditions as during exposure.
Since it is possible to completely check for foreign substances that have adhered during S light work, excellent effects can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of main parts of a typical example showing the concept of a reduction projection lens to which the device of the present invention is attached, Fig. 1m2 is a schematic vertical sectional view showing the configuration of an example of a conventional foreign object detection device, and Fig. FIG. 3 is a related perspective view of each member showing the configuration of an embodiment of the device. 1... Reticle, 2... Mercury lamp, S, 26
... Condenser lens, 4... Reduction projection lens, 5... Wafer. 6... Chip, 7, 11, 15... Foreign matter. 16...Reflector, 17...Cylinder, 18
...Imaging lens, 19...m scratch position on reticle pattern. 20... Microscope, 21... Eyepiece, 22...
Turtle 2.25...Shutter. 24...Foreign object, 25...Rung for reflective lighting. 27...Semi-transparent mirror. First offender/? 2 prisoner 3

Claims (1)

[Scope of Claims] (1) In a reticle foreign matter detection device that detects foreign matter by scanning the top or bottom surface of a reticle with spot light in a reduction projection exposure device, a reticle foreign matter detection device detects foreign matter by scanning the top or bottom surface of a reticle with spot light, in the middle of the optical path for projection exposure onto a reticle pattern or evaporator. A reflector that can move forward and backward is installed,
Using the reflector, the real image of the reticle pattern is projected outside the projection exposure optical path, and the actual image of the reticle pattern is further enlarged to determine the size of the foreign object, the size of the foreign object, and the reticle pattern by visual inspection or automatic means. 1. A reticle foreign object detection device, characterized in that it is capable of detecting the relative position, etc. of a reticle. (2) The reticle foreign matter detection apparatus according to claim 311, wherein the illumination light that projects and exposes the reticle pattern onto the wafer is used as the illumination light that directs the reticle pattern out of the projection exposure optical path. (5) The real image of the reticle pattern formed outside the projection exposure optical path is either the transmitted light from the reticle or the illumination light projected through the semi-transparent, retractable reflector ET1 below the axillary tickle. A reticle foreign object detection device according to claim 1, wherein the reflected light is obtained by using at least one of them.