JPS6361613B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reduction projection exposure apparatus, a photorepeater,
The present invention relates to a device for detecting foreign matter adhering to a reticle in an exposure device such as a 1:1 exposure device.

First, as a representative example of an exposure apparatus, the principle of a reduction projection type exposure 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. Light from the mercury lamp 1 passes through a condenser lens 2, an interference filter 15, an aperture 16, a mirror 3, and a condenser lens 4, and illuminates a dry plate reticle 5 having an LSI pattern 5a. pattern 5a
The image is reduced and formed on the upper surface of the wafer 8 by the reduction lens 7 (the optical path is shown by a solid line). A photoresist is coated on the wafer 8, and a reduced image of the LSI pattern 5a becomes a latent image in the photoresist. Illumination light 5 of set exposure time by shutter 51
After the completion of the 0 exposure, the wafer 8 is taken out and developed to obtain a reduced pattern of the LSI pattern 5a on the photoresist.

Here, if a foreign object 6 is present on the reticle 5, the foreign object 6 forms an erroneous image on the photoresist, a desired LSI pattern cannot be obtained, and the wafer 8 becomes a defective product. For this reason, it is necessary to inspect the photoresist pattern on the wafer 8 after the exposure and phenomenon using this apparatus, but since it is a visual inspection, oversights may occur.

Dust in the air in the workplace may adhere to the reticle 5 as foreign matter 6 after the reticle 5 is installed in the device, so when the reticle 5 is installed,
It is desirable to perform a foreign matter inspection by observing the top of the reticle 5 with a microscope as appropriate.

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 foreign matter adheres to the reticle due to the dust generated by the worker during the reticle take-out and take-in operations.

When the reduction ratio of reduction lens 7 is set to 1/10 (for example, when using Zeiss S-Planar 50mm),
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 with the reticle attached.

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

A foreign object detection device on a reticle of an exposure apparatus according to the present invention reflects light from an exposure illumination light source with a mirror and illuminates the reticle through a condenser lens, and projects a circuit pattern on the reticle onto a wafer using a projection lens. An exposure apparatus that performs exposure includes a laser oscillator, a plurality of polarizers that two-dimensionally scans laser light from the laser oscillator, and a laser light scanned by the polarizers that passes through the mirror and condenser lens to the reticle. an optical system that focuses and illuminates the lower surface; a photoelectric conversion element that receives scattered light obtained from the reticle; and a detection means that detects a foreign object on the reticle based on the magnitude of a signal obtained from the photoelectric conversion element. It is characterized by having the following.

In a preferred embodiment of the foreign object detection device according to the present invention, the photoelectric conversion element described above is installed between the polarizer and the laser light source.

In a further preferred embodiment of the foreign object detection device according to the present invention, a plurality of the photoelectric conversion elements described above are installed around the reticle.

First, FIG. 2 schematically shows how the scattered light 21 from the foreign object 6 is generated when the reticle 5 is irradiated with the laser beam 20. The circuit pattern 5a is the reticle 5
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 greater than that on the upper surface. That is,
Regarding the intensity of the reflected and scattered light from the foreign object 6, for the same size, the intensity of the foreign object attached to the bottom surface is greater, and in order to have the same intensity, the foreign object attached to the upper surface must be large, and its size (diameter) The ratio is approximately 1:2. Therefore, since the scattered light from the foreign matter of 10 μm on the top surface and 5 μm on the bottom surface, which form the erroneous latent image as mentioned above, has the same intensity, by appropriately selecting the intensity of the irradiated laser beam, it is possible to form one laser spot. Foreign objects on the upper and lower surfaces having the above-mentioned size or larger can be detected at the same time. The angle θ ₁ of the main component 22 of the scattered light at the edge of the LSI pattern 5a is smaller than the angle θ ₂ of the scattered light from the foreign object, and its intensity is also significantly weaker. 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. 3 will be described. This apparatus is attached to the reduction projection type exposure apparatus shown in FIG. However, the reflective mirror 3 that reflects the illumination light 50 from the mercury lamp 1 is replaced by the laser 2.
It is set as dichroic mirror 3a in order to pass 0.

A laser 20 is oscillated by a laser oscillator 9,
It passes through the laser beam conversion lens 10, is reflected by the deflectors 11a and 11b, and is reflected by the dichroic mirror 3.
a, and a laser spot 20a is formed on the lower surface of the reticle 5 by the condenser lens 4. The laser spot 20a on the lower surface of the reticle 5 is located on the deflector 1.
By synchronous deflection of 0a and 10b, the entire surface of the reticle 5 is scanned as shown in FIG. The scanning interval P needs to be the same diameter as the laser spot 21a or smaller.

As shown in FIG. 3c, reflected and scattered light 21 is generated by the laser 20 irradiated onto the foreign object 6. The scattered light 21 passes through the condenser lens 4 and the dichroic mirror 3a, is reflected by the deflectors 11a and 11b, passes through the lens 10, is reflected by the reflection mirror 12, and is guided to the photoelectric conversion element 13. reflection mirror 1
2 has an annular shape as shown in FIG. 3b, and the incident laser 20 and the incident light are irradiated onto the reticle 5 and the turn 5a through the central opening, allowing the specularly reflected light to pass through and being diffusely reflected by foreign objects. Only the scattered light 21 that is generated and deviates from the optical axis of the incident light is reflected by the annular mirror portion. The reflected light that travels through the shaded area in FIG. 3a is not guided to the photoelectric conversion element 13.

When the photoelectric conversion element 13 receives light, it outputs an electrical signal. FIG. 5 shows a processing circuit for the output signal from the photoelectric conversion element. The output current from the photoelectric conversion element 13 is converted into a voltage by a resistor R, and the gain circuit 30
A binarization circuit 31 compares the magnitude of a preset voltage value V ₀ , and when the input voltage value is greater than V ₀ , a foreign object display circuit 32 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. 3 except that it is provided with an auxiliary lens 60 that can be removed alongside the condenser lens. The auxiliary lens 60 is attached to the exposure device (IN) only when detecting foreign objects as shown in the figure.
and exits (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 the light a towards the optical axis, allowing the photoelectric conversion element 13 to receive the light. This makes it possible to improve the ability to detect foreign objects. When the auxiliary lens 60 is provided between the dichroic mirror 3a and the reticle 5 as shown in FIG. 6, it must be removed during pattern exposure; however, the auxiliary lens 60 is provided between the dichroic mirror 3a and the mirror 12. There is no need to evacuate at that time. However, as the distance between the auxiliary lens 60 and the reticle 5 increases, 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 and 14d are photoelectric conversion elements (8 each of 14μ and 15d) arranged above and below the periphery of the reticle 5, respectively.

As is clear from Figure 3 a and c, the scattered light 21
What can be guided by the light guide means is limited to some things. Others are scattered around the area between the condenser lens 4 and the reticle 5 or from below the reticle 5. In this embodiment, the photoelectric conversion element 14μ or 14d can receive these scattered lights.

The output from the photoelectric conversion elements 14μ and 14d is
As shown in Figure 8, it is converted into voltage by a resistor R,
It is added by the gain circuit 40, and V ₀ is added by the binarization circuit 31.
When it is greater than V ₀ , a signal is sent to the display circuit.

The principle of signal processing from the photoelectric conversion elements 13, 14μ, and 14d will be explained based on FIG. 9. The upper part of FIG. 9 is a diagram showing the state in which the laser spot 20a is scanned on the reticle 5 in the x direction.
The middle and lower diagrams are the upper diagram and the horizontal axis t (time).
FIG. 3 is a diagram of the original signal value and the binarized signal value from the photoelectric conversion element shown with =x (distance) matched.

A pattern 5a is formed on the lower surface of the reticle 5. Foreign matter attached to the reticle 5 is indicated by 6, 6a. As mentioned above, the output from the scattered light from the foreign matter received by the photoelectric conversion element is generated by focusing the laser light on the lower surface of the reticle 5 (the spot is indicated by 20a).
The result is the same for a 10 μm foreign object and a 5 μm foreign object attached to the bottom surface. 6 is 10μm attached to the top surface
Above, 6a indicates a foreign substance of 5 μm or more attached to the bottom surface, 10 μm or less if attached to the top surface, and 5 μm or less of a particle attached to the bottom surface.

When the laser spot 20a is moved as shown in the upper diagram, scattered light is generated at the foreign objects 6, 6a and the pattern 5a, which is received by the photoelectric conversion element and output (as shown in the middle diagram). (after voltage conversion). The output value is indicated by V. Therefore, the top surface is 10μm,
When setting the output V ₀ of the photoelectric conversion element when receiving scattered light from a foreign object with a diameter of 5 μm on the bottom surface as the set value,
In the binarization circuit 31, the output of the photoelectric conversion element due to the scattered light from the foreign object 6a and the edge of the pattern 5a is not binarized, but only the output due to the scattered light from the foreign object 6 is binarized. presence is displayed.

The auxiliary lens 60 shown in FIG. 6 and the photoelectric conversion elements 14 on the upper and lower sides of the reticle 5 shown in FIG.
Of course, when μ and 14d are used together, the detection sensitivity of the device of the present invention is further improved.
Above, the case where the apparatus of the present invention is installed in a reduction projection type exposure apparatus has been described, but a 1:1 exposure apparatus,
It goes without saying that the present invention can be similarly applied to other exposure apparatuses such as 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. Furthermore, since it uses a powerful laser beam and has an appropriate configuration, it can exhibit excellent foreign object detection ability. Therefore, by applying the apparatus of the present invention, the production of defective wafers or defective masks can be significantly reduced.

[Brief explanation of drawings]

Figure 1a is a principle diagram of a reduction projection type exposure device;
Figure b is an enlarged view of part A in Figure 1 a, Figure 2 is a schematic diagram showing the generation of scattered light from the reticle, Figure 3 is an embodiment of the device of the present invention, and Figure a is the overall view. FIG. 4 is a plan view showing an example of the scanning state of the laser spot on the reticle in the apparatus of FIG. 3, FIG. 5 is a signal processing circuit diagram of the photoelectric conversion element of the device of FIG. 3, FIG. 6 is a block diagram of another embodiment of the device of the present invention, and FIG. 7 is a diagram of still another embodiment of the device of the present invention. A plan view (Figure A) and a side view (Figure B) showing the arrangement of the photoelectric conversion elements on the upper and lower sides of the reticle, Figure 8 is a signal processing circuit diagram of the photoelectric conversion element in Figure 7, and Figure 9 is the photoelectric conversion element. FIG. 2 is a state diagram and a diagram showing the principle of signal processing of FIG. 1...Mercury lamp, 2, 4...Condenser lens, 3...
Mira, 3a...Dichroic mirror, 5...Reticle, 5a...Circuit pattern, 6, 6a...Foreign object, 7...
Reduction lens, 8... Wafer, 10... Laser beam conversion lens, 11a, 11b... Polarizer, 12... Reflection mirror, 13, 14μ, 14d... Photoelectric conversion element,
15... Interference filter, 16... Aperture, 20... Laser light, 20a... Laser focusing spot, 21, 21a
...Laser reflected and scattered light, 60...Auxiliary lens.

Claims (1)

[Scope of Claims] 1. An exposure apparatus that reflects light from an exposure illumination light source with a mirror and illuminates a reticle through a condenser lens, and projects and exposes a circuit pattern on the reticle onto a wafer using a projection lens. An oscillator, a plurality of polarizers that scan the laser light from the laser oscillator two-dimensionally, and the laser light scanned by the polarizers is focused on the lower surface of the reticle through the mirror and the condenser lens for illumination. a photoelectric conversion element that receives scattered light obtained from the reticle; and a detection means that detects a foreign object on the reticle based on the magnitude of a signal obtained from the photoelectric conversion element. Foreign matter detection device on the reticle in exposure equipment. 2. A foreign object detection device on a reticle in an exposure apparatus according to claim 1, wherein the photoelectric conversion element is installed between the polarizer and the laser light source. 3. Claim 1, characterized in that a plurality of the photoelectric conversion elements are installed around the reticle.
A foreign matter detection device on a reticle in the exposure apparatus according to section 1.