JPS5880544A - Detector for foreign matter on reticle of exposure device - Google Patents

Abstract

PURPOSE:To detect foreign matter in a reticle while the reticle is held set in the optical path for exposure by providing a means for generating laser light and an optical conducting means which conducts the laser light in the same direction as that of the exposure light in the optical path before the light for exposure enters a condenser lens. CONSTITUTION:A detector for foreign matter on the reticle of an exposure device is so constituted as to irradiate a reticle 5 having a pattern with the light condensed by condenser lenses 2, 4 and to form the pattern image on the photoresist coated on a wafer 8 or a mask. A means for generating laser light 20 is provided to this device, and an optical conductive means for introducing the laser light 20 in the same direction as exposure light is provided in the optical path before the light for exposure enters the lenses 2, 4. The foreign matter in the reticle 5 is detected while the reticle is held set in the optical path for exposure.

Description

[Detailed description of the invention] 5.

The present invention relates to a reduction projection type exposure apparatus, (e) IJ beater, 1:
1. This invention relates to a method for inspecting foreign matter adhering to a reticle in an exposure device such as an exposure device.

First, as a representative example of an exposure apparatus, the principle of a reduction projection type linear light apparatus will be explained based on FIG. A mercury lamp 1 is used as a light source for exposure illumination light 50 of this exposure apparatus. Mercury lamp 1
The light passes through a condenser lens 2, an interference filter 15, an aperture 16, a mirror 6, and a condenser lens 4, and illuminates a dry plate reticle 5 having an LSI pattern 5at. The image of the pattern 5a is reduced and formed on the upper surface of the wafer 8 by the M small lens 7 (the optical path is shown by a solid line). A photoresist is coated on the wafer 8, and the reduced size of the LSI pattern 5a becomes a latent image in the photoresist. After the exposure of the illumination light 50 for the set exposure time by the shutter 51 is completed,
When wafer 8 is removed and exposed, LS is formed on the photoresist.
A reduced pattern of I pattern 5a is obtained.

Here, if a foreign object 6 exists on the reticle 5, the foreign object 6 forms a wrong image on the photoresist, and the desired LS
After the I-pattern cannot be obtained and the wafer 8 is removed, it is necessary to inspect the photoresist pattern on the wafer 8, but because the inspection is done visually, oversights occur.

Dust in the air in the workplace is detected as a foreign object 6 on the reticle 5.
Since foreign objects may adhere to the reticle 5 after being installed in the apparatus, it is desirable to conduct a foreign matter inspection by observing the reticle 5 with a microscope while the reticle 5 is installed.

However, since the condenser lens 4 and the reticle mounting mechanism are present on the mounted reticle 5, the mounted reticle 5 cannot be visually observed. Therefore, conventionally, the reticle 5 is taken out to the outside and inspected. In this case, there is a problem in that dust generated by the worker during the reticle take-out and take-in operations causes further foreign matter to adhere to the reticle.

When the reduction ratio of the reduction lens 7 is lAo (for example, Z
When using eiaa 5-Planar 50m)
If a foreign object with a size of 10 μm or more adheres to the top surface of the reticle and 5 μm or more to the bottom surface, an erroneous latent image will be formed, so it is necessary to detect these foreign objects while the reticle is attached.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a foreign object detection device on a reticle of an exposure apparatus that can detect foreign objects attached to a reticle while the reticle is set in an exposure optical path. be.

A foreign matter detection device on a reticle of an exposure apparatus according to the present invention includes:
In an apparatus for detecting foreign matter on a reticle in an exposure apparatus that irradiates a reticle having a pattern with light focused by a condenser lens and forms a pattern image on a photoresist coated on a wafer or a mask, (a) means for generating laser light; (b) light guide means for introducing the laser light in the same direction as the exposure light onto an optical path before the light for exposure enters the condenser lens; (d) an optical means for condensing the laser beam onto a patterned surface of a reticle and forming an incident spot on the surface; (d) a scanning means for scanning the entire surface of the reticle; e) a light guide means for guiding the scattered light generated by the laser light reflected by a foreign object on the reticle to the photoelectric conversion element; a photoelectric conversion element that directly receives light; (2) means for determining and displaying the presence or absence of foreign matter based on the output signal of the photoelectric conversion element;
This is a detection device that is characterized by being very versatile.

In a preferred embodiment of the foreign object detection device according to the present invention,
The light guiding means for the scattered light is configured using a light guiding means for introducing the laser beam, an optical means for condensing light, and a scanning means, and the scattered light is reversed in the incident optical path of the laser beam. After advancing, the mirror separates the specularly reflected light from the optical path and takes it out, and guides the light to a photoelectric conversion element.

In a further preferred embodiment of the foreign object detection device according to the present invention, the light guiding means for the scattered light is arranged in parallel with a condenser lens of the optical means for the laser source, and the condenser lens It has a full set of auxiliary lenses that direct the light toward the optical axis.

In another preferred embodiment of the foreign object detection device according to the present invention, the photoelectric conversion element is provided at the end of the light guide path of the light guide means for the scattered light, and at the upper and lower sides of the periphery of the reticle. , are provided in plurality toward the reticle.

First, FIG. 2 schematically shows how scattered light 210 is generated from the foreign object 6 when the laser beam 20 is irradiated onto the reticle 5. The circuit pattern 5a is formed on the lower surface of the reticle 5, and the laser beam 20 forms a spot on the lower surface of the reticle 5. Therefore, the irradiation intensity of the laser beam 20 on the lower surface of the reticle 5 is υ larger than that on the upper surface.

In other words, the intensity of the reflected and scattered light from the foreign object 6 is greater when the intensity is the same for the foreign object on the lower surface layer, and in order to have the same intensity, the foreign object attached to the upper surface must be large, and its size The ratio of diameter) is approximately 1:2. Therefore, the upper surface 10 μm and the lower surface 5 μm form the erroneous latent image as described above.
Since the scattered light from the foreign object has the same intensity, by appropriately selecting the intensity of the irradiated laser beam, it is possible to simultaneously detect foreign objects of the above-mentioned size or larger on the upper and lower surfaces by forming one laser spot.

The intensity of the main component 22 of the scattered light at the edge of the LSI pattern 5a is also extremely weak. Further, the laser beam irradiated onto the back surface of the LSI pattern 5a is specularly reflected in the same manner as on the reticle 5 surface.

Next, an embodiment of the apparatus of the present invention shown in FIG. 6 will be described. This apparatus is attached to the reduction projection type exposure apparatus shown in FIG. However, the reflecting mirror 6 that reflects the illumination light 50 from the mercury lamp 1 is a dichroic mirror 6a to allow the laser 20 to pass through.

A laser beam 20 is oscillated by the laser oscillator 9, transmitted through the laser beam conversion lens 10, and deflected by the deflector 11a111b.
It is reflected by the dichroic mirror 5a, transmitted by the dichroic mirror 5a, and a laser spot 2 is formed on the lower surface of the reticle 5 by the condenser lens 4.
Form 0a k. (Laser beam on the bottom surface of reticle 5)
20a scans the entire surface of the reticle 5 as shown in FIG. 4 by synchronized deflection of the deflectors 10a and 10b. The scanning interval P needs to be the same diameter as the laser beam 21a or smaller. □Figure 3 (e
), reflected and scattered light 21 is generated by the laser 20 irradiated onto the foreign object 6. The scattered light 21 is transmitted through a condenser lens 4, a dichroic mirror 5a, and a polarizer 1.
1m and 11b, passes through the lens 10, is reflected by the reflection plate 12', and is guided to the photoelectric conversion element 15.

As shown in FIG. 5(b), the reflection chamber 12 has an annular shape, and has a central opening through which the incident laser 20 and the incident light are irradiated onto the reticle 5 and the pattern 5a, and the reflected specularly reflected light is allowed to pass through. , only the scattered light 21 that is generated by diffuse reflection from a foreign object and deviates from the original axis of the incident light is reflected by the annular bowl portion.

In FIG. 6(a), the reflected light that travels through the shaded area is not guided to the photoelectric conversion element 13.

When the photoelectric conversion element 15 receives light, it outputs an electric signal. FIG. 5 shows a processing circuit for output signals from the photoelectric conversion element. The output current from the photoelectric conversion element 15 is converted into a voltage by a resistor R, amplified by a gain circuit 50, and then converted to a voltage by a binarization circuit 51.
A comparison is made between the input voltage value and a preset voltage value VO, and when the input voltage value is greater than VO, the foreign object display circuit 62 displays a foreign object.

Another embodiment of the device of the invention is shown in FIG. This device is the same as the device shown in FIG. 6 except that it is provided with an auxiliary lens 60 that can be removed alongside the condenser lens. As shown in the figure, the auxiliary lens 60 is attached to the exposure apparatus (IN) only when foreign matter is detected, and is removed (OUT) during exposure. In this device, the incident angle to the condenser lens 4 is large, and the scattered light 21 that cannot be collected by the condenser lens 4
The auxiliary lens 60 directs a toward the original axis, and the photoelectric conversion element 16
It is possible to receive light. This makes it possible to improve the ability to detect foreign objects. When the auxiliary lens 60 is installed between the dichroic mirror 6a and the reticle 50 as shown in FIG.
Although it is necessary to remove the lens when forming the pattern j1, there is no need to remove it when the auxiliary lens 60 is provided between the dichroic mirror 5a and the mirror 12. However, as the distance between the auxiliary lens 60 and the reticle 5 increases by 9, it is necessary to increase the light receiving surface of the member between the reticle 5 and the auxiliary lens 60, and the effect of the auxiliary lens 60 also decreases.

Another embodiment of the installation of photoelectric conversion elements in the apparatus of the present invention will be described based on FIG. 7.

In the apparatus of the present invention, a photoelectric conversion element is provided at the end of the light guide path of the light guide means for scattered light as described above, and a plurality of other photoelectric conversion elements are further provided above and below the periphery of the reticle toward the reticle. When the element is provided, the ability to detect foreign matter can be further improved.

FIG. 7 shows an example of the arrangement of the plurality of photoelectric conversion elements. In FIG. 7, 14μ is a photoelectric conversion element (14μ, 1
5d and 8 pieces each).

As is clear from FIGS. 6(a) and (e), the scattered light 21
What can be guided by the light guide means is limited to some things.

Others are scattered between the condenser lens 4 and the reticle 50 or from below the reticle 5 to the surrounding area. In this example, these scattered lights are converted to a photoelectric conversion element 1゛4μ.
Or 14d can receive light.

The outputs from the photoelectric conversion elements 14μ and 14d are converted to voltage by a resistor R, as shown in FIG.
and is compared with V in the binarization circuit 51, and when it is greater than vo, a signal is sent to the display circuit.

This is a diagram showing the state where the original reticle 5 for signal processing from the photoelectric conversion elements 15, 14μ, and 14d is scanned in the X direction. FIG. 2 is a diagram of original signal values and binarized signal values from a photoelectric conversion element in which t (time) = X (distance) of FIG.

A pattern 5a is formed on the lower surface of the reticle 5.

Foreign matter attached to the reticle 5 is shown at 6.6a. As mentioned above, since the laser beam is focused on the lower surface of the reticle 5 (shown as spot f: 20a), the output due to the scattered light from the foreign object received by the photoelectric conversion element is not attached to the upper surface. The result is the same for the 10 μm foreign matter attached to the bottom surface and the 5 μm foreign matter attached to the bottom surface. 6 is attached to the top surface and 1
Foreign matter 'k' is 0 μm or more, 5 pm or more when attached to the bottom surface, and 6m is a foreign matter of 10 μm or less when attached to the top surface and 5 μm or less when attached to the bottom surface.

20a f As you move as shown in the upper diagram, foreign objects will be scattered at the locations of 6.6& and pattern 5&.
) Scattered light is generated, the photoelectric conversion element receives it, and outputs it (voltage conversion vk) as shown in the middle diagram. The output value is indicated by V. Therefore, when setting the output Vo of the photoelectric conversion element when receiving scattered light from a foreign object with a length of 10 μm on the upper surface and 5 μm on the lower surface as a set value, the binarization circuit 51 uses a foreign object of 6 m,
The output of the photoelectric conversion element due to the scattered light from the edges of the pattern 5a is not binarized, but only the output due to the scattered light from the foreign object 6 is binarized, and the presence of the foreign object is displayed on the display circuit 52.

When the auxiliary lens 60 shown in FIG. 6 and the photoelectric conversion elements 14N and 14d on the upper and lower sides of the reticle 5 shown in FIG. 7 are used together, the detection sensitivity of the apparatus of the present invention can be further improved. Of course you can. Above, we have explained the case where the apparatus of the present invention is installed in a reduction projection type exposure apparatus, but 1:
It goes without saying that the present invention can be similarly applied to other exposure apparatuses such as a single exposure apparatus and a photorepeater.

As described above, when the apparatus of the present invention is used, foreign objects on a reticle can be automatically detected while the apparatus is attached to an exposure apparatus. In addition, since the powerful laser beam 111-1 is used and has an appropriate configuration, it is possible to exhibit excellent foreign object detection ability. Therefore, by applying the defective device, the production of defective wafers or defective masks can be significantly reduced.

[Brief explanation of drawings]

Figure 1(a) is a principle diagram of a reduction projection type exposure apparatus;
b) is an enlarged view of part A in FIG. 1(a), FIG. 2 is a schematic diagram showing the generation of scattered light from the reticle, and FIG. ) Figure is the overall configuration diagram, Figure (b) is a perspective view of the reflecting mirror, Figure (C) is the (a)
), Figure 4 is a plan view showing an example of the scanning state of the laser spot on the reticle in the apparatus shown in Figure 6, and Figure 5 is a signal processing circuit of the photoelectric conversion element of the apparatus shown in Figure 5. 6 is a block diagram of another embodiment of the apparatus of the present invention, and FIG. 7 is a plan view (a
), side view (b), and WJs diagram are signal processing circuit diagrams of the photoelectric conversion element in FIG. 7, and FIG. 9 is a state diagram and line diagram showing the principle of signal processing of the photoelectric conversion element. 1...Mercury lamp, 2.4...Condenser lens, 6.
・, Mira, 5a... Dichroic mirror, 5... Reticle, 5a... Circuit pattern, 6.6a... Foreign object, 7... Reduction lens, 8... Wafer, 10... Laser Beam conversion lens, 118111b...Polarizer, 12...Reflection mirror, 16.14μ, 14d...Photoelectric conversion element, 15...Interference filter, 16...Aperture, 20...Laser light , 20a... Laser focused spot, 21.21a... Laser reflected scattered light, 60...
Auxiliary lens. Agent Patent Attorney Tadashi Akimoto Actual 1st cause (a) 1 1st cause (b) Figure 2 Taku 3 (a) Figure 3A81 (b) Figure 3 (C) Figure 4C Figure 5 Figure 6 Fig. 7 (a) also convex σ Fig. 8 Section 9-1,

Claims (1)

[Scope of Claims] 1. A reticle having a pattern is irradiated with light condensed by a condenser lens, and a pattern is formed on the photoresist coated on a photoresist or a mask in an exposure device. In a foreign object detection device,
(a) means for generating laser light; (b) light guiding means for introducing the laser light into an optical path before the light for exposure enters the condenser lens in the same direction as the exposure source;
(C) an optical means for condensing the laser beam onto a patterned surface of the reticle to form a condensed spot on the surface; (d) a scanning means for scanning the condensed laser beam spot over the entire surface of the reticle; e) a light guide means for guiding scattered light generated when the cough laser light is reflected by a foreign object on the reticle to a photoelectric conversion element;
(f) A photoelectric conversion element that receives light from a cough scattering source through a light guiding means or directly through a light guiding means; A device for detecting foreign matter on a reticle of an exposure apparatus, characterized in that it serves as a means for displaying and, more particularly, a device for detecting foreign matter on a reticle of an exposure apparatus. 2. The light guiding means for the scattered light is configured using a light guiding means for introducing the laser beam, an optical means for focusing the light, and a scanning means, and the scattered light is guided along the incident optical path of the laser beam. 2. The foreign object detection device according to claim 1, wherein the foreign object detection device is configured such that after the light travels in the opposite direction, the light is separated from the specularly reflected light from the original path by a mirror and is emitted and guided to a photoelectric conversion element. (5) A patent claim in which the light guiding means for the scattered light is arranged in parallel with the condenser lens of the optical means for concentrating the laser beam, and the condenser lens has an auxiliary lens that directs the scattered light that cannot be focused toward the optical axis. The range of all! ! Foreign object detection device in Section 2. 4. The photoelectric conversion element is provided at the end of the light guide path of the light guide means for the scattered light, and a plurality of photoelectric conversion elements are provided on the upper and lower sides of the periphery of the reticle toward the reticle. A foreign matter removal device according to claim 2 or 6.