JPH027046B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is for use in pattern printing devices that can focus on unevenness on a photosensitive surface in micron units, such as pattern generator devices used for ultra-precision pattern printing, etc. The present invention relates to a focus detection device.

[Conventional technology]

Due to the nature of the internal structure of semiconductor devices, pattern generator equipment used in the process of manufacturing semiconductor devices such as ICs and LSIs prints fine patterns in microns or smaller onto photosensitive objects with alignment accuracy of microns or less. Must be. Therefore, the reduction lens must have an ultra-high resolution, and it is desirable to use a lens with a resolution of about 1600 lines/mm, for example. When such a lens is used, the depth of focus is 0.5 μm or less, and focus detection is required to be more accurate than the above dimensions.

The pattern generator device moves the photosensitive surface within an X-Y plane parallel to the photosensitive surface with an accuracy of less than a micron, and creates dimensions and areas of a micron or less for each portion of a predetermined position coordinate. It is required to print the figure with. Therefore, when it comes to irregularities of less than microns on the photosensitive surface,
have to focus. In commercially available high-resolution dry plates, the unevenness of the photosensitive surface is approximately 12 μm, and the focus detection device must be capable of sufficiently tracking these unevenness. Furthermore, since the area of the printed figure is required to be on the order of microns or less, focus detection must also be performed within the above area.

As mentioned above, the focus detection device that can be implemented in the pattern generator device is required to detect the focus with high precision in extremely small dimensions, and is usually used in cameras, projectors, etc. In this case, it is difficult to detect the focal point with respect to irregularities in the area of the photosensitive surface of microns or less, and implementation is impossible.

[Problem to be solved by the invention]

An example of a focus detection device used in a conventional camera or projector is disclosed in Japanese Patent Publication No. 32-8346. In the focus detection device disclosed in this example, the light passing through the objective lens is imaged onto a moving slit. The light that passes through the moving slit becomes intermittent light and enters the photoelectric device. It is characterized by the fact that it generates a measurement current that is precisely adjusted. In the case of this example device, the photosensitive surface must be set at a different position that is equivalent to the optical path to the photoelectric device, and a fixed image is focused on the moving slit surface to detect the focusing state. Therefore, it is necessary to move the slit within a fixed area of the fixed image on the slit disk.
Therefore, as in a pattern generator device, it is possible to print a large number of different patterns on a portion of the photosensitive surface while moving at high speed in the X-Y plane and detecting the focal point with respect to the unevenness of the photosensitive surface. In addition, it is actually impossible to manufacture a slitting machine with a size and movement area of microns or smaller and to make it move.

[Means to solve the problem]

The purpose of the present invention is to draw a complex LSI circuit diagram on a photosensitive surface having irregularities on the order of microns while sequentially moving the circuit diagram on the photosensitive surface one after another while detecting the focus with accuracy on the order of microns or less. An object of the present invention is to provide a focus detection device that enables printing. Another object of the present invention is to provide a focal point that makes it possible to expose complex LSI circuit diagrams with micron-accurate dimensions, consisting of hundreds of thousands to millions of exposure shots, at a high speed of more than 50 times/second. An object of the present invention is to provide a detection device.

That is, the present invention detects a focal point using light of a first wavelength, reduces a printing pattern using light of a second wavelength different from this, and prints the pattern on a photosensitive surface having unevenness in microns. A focus detection device for a pattern printing device that repeatedly performs focus detection and printing, the focus detection pattern having a striped portion consisting of a plurality of lines, the focus detection pattern being reduced to the photosensitive surface. comprising at least a reduction lens that forms an image with the photosensitive surface, a measuring element that detects the image reflected on the photosensitive surface, and a mechanism that causes the boundary between brightness and darkness of the image of the focus detection pattern to cross over the surface of the measuring element; A focus detection device for a pattern printing apparatus is characterized in that a focus state on the photosensitive surface is detected by detecting a change in light amount based on a measurement signal detected by the measurement element using light of a first wavelength.

The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a partial diagram showing an embodiment of an ultra-precision pattern generator device to which the focus detection device of the present invention is applied.

This is a case where the light source 1 for focus detection shown in FIG. 1 is separately provided and used, and has a first half mirror 4 and a second half mirror 7.

A white lamp, a mercury lamp, a light emitting diode, etc. are used as the light source 1 for focus detection. The light emitted from the light source 1 passes through the filter 2 and becomes light of a first wavelength outside the photosensitive area of the photosensitive surface 9. This first wavelength light passes through the focus detection pattern 3, projects the pattern, enters the first half mirror 4, is reflected and refracted by 90 degrees, and is transmitted through the second half mirror 7. The image passes through a reduction lens 8 and is reduced to form an image on a photosensitive surface 9. A part of the light is reflected by the photosensitive surface 9, passes through the reduction lens 8 again, and is passed through the second half mirror 7.
The incident light is reflected and refracted at 90 degrees, and is condensed by a condenser lens 6. In this case, if the condenser lens 6 is not used, the distance to the measuring element will be longer than the second half mirror 7. The focused projection pattern is
The beam enters the measuring element 5 and detects the focal point. After focus detection, a printing pattern is printed on the photosensitive surface using light of a second wavelength, which is different from the first wavelength, within the photosensitive area of the photosensitive surface 9, and focus detection at the next location within the photosensitive surface is performed. This is done using light of the first wavelength.

The focus detection light source 1, filter 2, and focus detection pattern 3 shown in FIG. 1 can also serve as the same, as long as their respective purposes can be achieved. For example, if a light emitting diode or the like is used, a wavelength that is difficult to be sensitive to the photosensitive material is used as the emission wavelength of the light wave for focusing, and if the emission pattern itself is used as the focus detection pattern 3,
The filter 2 and the focus detection pattern 3 become unnecessary.

In addition, adjusting the location of the half mirror, such as placing the half mirror only in the center, can cause the burning rays to pass through the filter when the location where the burning rays entering the lens pass and the location where the focusing rays pass through are different. Even if you don't put it in, you can avoid it and the accuracy of focusing will not decrease.

Focus detection in the measuring element 5 is shown in Figure 2a.
As shown in the example, by making the light-receiving element 10 and the projected pattern 11 cross the boundary between brightness and darkness of the image of the pattern, if the focus is off, the gradient of brightness will be gentle as shown in a, and the focus will be As the slopes come together, the slope becomes steeper as shown in b. Therefore, by detecting the gradient of blur, that is, the differential value, the degree of focus can be detected. In other words, since the boundary between light and dark of the pattern projected onto the measuring element 5 becomes clearer as it approaches the focal position, the rate of change in the amount of light detected by the measuring element configured to cross this boundary between bright and dark increases. , reaches its maximum at the focal point.

The detection pattern may be a striped pattern to increase the detection sensitivity as shown in FIG. 2b, or a square-like pattern to detect rough focusing and precise focusing. As shown in Fig. 2c, rough focus detection is performed by wide spacing, and precise focus detection is performed by swinging the detection patterns with narrow spacing by changing the direction in the direction of the arrow shown in the figure. , coarse focus detection and fine focus detection may be performed. Further, by arranging a pattern as shown in FIG. 2d and vibrating in the direction of the arrow, rough focus detection and precise focus detection can be performed without changing the vibration direction. For example, the brightness on the reduction lens 8 is F=
1.2, a focal length of 28.6 mm, and a reduction magnification of 1/25 using a lens with a resolution of 1600 lines/mm.

In this case, the depth of focus is 0.5μ.

For example, in the case of FIG. 1 when the photosensitive surface is shifted by 0.5 μ from the focal point, the blur of the focusing pattern on the measuring element surface is about 10 μ since the blur on the photosensitive surface 9 is magnified by the reduction lens 8. Therefore, if the distance is within 10 μ, the photosensitive surface 9 will be within the depth of focus of the reduction lens 8.

Further, the shaking speed may be faster than the speed at which the photosensitive surface or the reduction lens is moved.

By the above, the printing pattern is reduced to 1/25,
Moreover, it can be exposed with a resolution of 1600 lines/mm. It is impossible to describe all combinations of patterns and vibration directions, and the patterns are not limited to those shown here.

Next, we will discuss how the measuring element relatively crosses the bright/dark boundary of the projected pattern. Electrostriction, magnetostriction, or electromagnets are used to move the projected pattern in a direction parallel to the light-receiving surface of the measuring element. Just configure it. For this purpose, the pattern may be fixed and the measuring element moved, or conversely, the measuring element may be fixed and the pattern moved by moving and rotating a half mirror or the like.

As a light receiving element, a photoelectric conversion element such as a photodiode, a phototransistor, or a photoconverter can be used for detection. At this time, when a multi-line pattern is used, the vibration is usually sinusoidal, but the moving speed changes every moment, and it is slowest when it is oscillating, so the output is large at the center and small at both ends. Become. In order to avoid this error, it is possible to install a correction circuit synchronized with vibration, but the simplest method is to increase the number of multi-filaments sufficiently so that the border of the wires is almost at the center position. The easiest way is to set the amplitude to 1 and then detect the maximum value of the amplitude.

〔Example〕

3a and 3b show an embodiment of an ultra-precision pattern generator device to which the focus detection device of the present invention is applied, and FIG. The case where the light source 1 and the focus detection pattern 3 are used is shown. This is because the circuit pattern of an LSI usually includes a striped pattern made up of a large number of lines, so the striped pattern can be used as it is as a pattern for focus detection. Using a direct printing light source 13, it passes through a filter 14 and a printing pattern 15, becomes a focus detection light with a wavelength different from the printing light wavelength, passes through a zoom lens 16, and is transmitted through a half mirror 17 to produce a reduced image. Photosensitive surface 9 from lens 8
The image is formed on the upper surface, reflected, passes through the reduction lens 8 again, enters the half mirror 17, is reflected and refracted by 90 degrees, and the projected pattern is transferred to the measuring element 5 by the condensing lens 6.
The focus is detected by entering the beam into the beam.

In the method shown in FIG. 3A, the light source 1 for focus detection and the pattern 3 for focus detection are not particularly provided, and the light source 10 for printing and the pattern 15 for printing can be used as they are. In the case of printing, the filter 14 is naturally removed and the light of the printing wavelength is exposed. In addition, 18 in the figure is a condenser lens,
19 indicates a variable aperture, and 20 indicates a filter.

Further, FIG. 3b shows a case where the focus detection device is incorporated within the optical axis for printing.

Similarly to FIG. 3A, the light is directly emitted from the printing light source 13, passes through the filter 14, the printing pattern 15, the zoom lens 16, and enters the reduction lens 8, where it forms an image on the upper surface of the photosensitive surface 9. The projected pattern is then reflected, passes through the reduction lens 8 again, is condensed by the condenser lens 22, and enters the measurement element 21, where the focal point is detected.

Alternatively, as shown by the two-dot chain line, the condenser lens 6 and the measuring element 5 may be placed in front of the zoom lens 16, and the reflected projection pattern may be incident on the measuring element 5 using the half mirror 17 to detect the focal point. Alternatively, the condenser lenses 6, 22 and the measuring elements 5, 21 can be used as the printing light source 1.
It may be provided near 3 for detection. This method has the advantage of correcting focal shifts when changing the zoom ratio, etc. For other methods, zoom lens 1
It is effective to anticipate in advance the focus shift caused by No. 6 and correct it somewhere.

As described above, several focus detection devices are used. The present invention is not limited to the above description, but it is sufficient to detect whether or not the focus is in focus by making the blur appear to be moving and reading the differential value of the blur.

Also, similar to the focus shift caused by a zoom lens,
The difference in focal length due to the difference between the wavelength of the light for focus detection and the wavelength of the light for printing can be eliminated by correcting the positions of the focus detection pattern 3 or the measuring elements 5 and 21 in advance. Further, the half mirror used here can transmit 100% of the light wavelength for printing by using a dielectric multilayer vapor deposition film, etc., and can be made into a half mirror for the light wavelength for focus detection. Furthermore, it goes without saying that this apparatus can automatically move the photosensitive surface 9, the reduction lens 8, etc. and perform automatic focusing based on the focus detection results from the measuring elements 5 and 21.

FIG. 4 shows an embodiment of an ultra-precision pattern generator device incorporating the focus detection device of the present invention explained in FIG.

The light emitted from the printing light source 13 first passes through a filter 2 such as an H-ray interference filter (404.7 mμ).
Pass through 0. This filter 20 has h-line (404.7mμ), e-line (546.1mμ), and g-line (435.8mμ).
A zoom lens 16 with a coating for
By using filters for H, E, and G lines in the reduction lens 8, the resolution is increased.
By using H-rays, it is also possible to directly bake onto a Si wafer or the like coated with photoresist.

The light that has passed through the filter 20 becomes light with a wavelength of 404.7 mμ and projects the printing pattern 15.
The light enters the zoom lens 16. It is also possible to use slits, spots, etc. created by the variable aperture 19 or the master library as the printing pattern. The pattern projected onto the zoom lens 16 is variably reduced by the zoom ratio, is once formed into an image, and then becomes diffused light. A part of this diffused light enters the entrance pupil of the reduction lens 8,
The photosensitive surface 9 placed in the second imaging section, for example, a high-resolution dry plate, and a projection pattern of Si coated with photoresist, are printed in a reduced size, and the focus detection is performed as explained in Fig. 1. Light source 1 for focus detection
The light is transmitted through the focus detection pattern 3, the filter 2, the first half mirror 4, and the second half mirror 7, and the projection pattern is incident on the photosensitive surface 9 by the reduction lens 8, and the reflected light is reduced. It is reflected and refracted by the second half mirror 7 through the lens 8, and the image of the focus detection pattern 3 is focused on the measurement element 5 by the condenser lens 6 to detect the focus.

During printing, for example, the photosensitive surface 9 is brought into the correct focus by swinging the photosensitive surface 9 relative to the original image (e.g., printing pattern, variable aperture, master reticle, circuit library, etc.). For example, the output of the focus detection light receiving element 5 shows the maximum value. If the photosensitive surface 9 is set so as to vibrate relatively around such a point, it will be in focus when the vibration stops, making focusing easy. and,
When the maximum value is reached, the Xe flash of the light source for short-time printing is activated while the photosensitive surface 9 is shaken, or
Alternatively, the pattern can be printed by operating the shutter. Further, when the vibration of the photosensitive surface 9 is at least approached to the flashing position, the vibration of the photosensitive surface 9 may be stopped, or at least when the vibration has been damped to such an extent that there is no problem, the vibration may be synchronized and the flashing may be performed or the shutter may be operated.

Furthermore, even if the light source or detection device were to vibrate in the direction in which the light travels in order to shift the focus position of a part of the lens system instead of vibrating the photosensitive surface 9, if there is a spot that is exactly in focus, Since it has the maximum amplitude, you can detect that it is in focus in the same way. As mentioned above, in a pattern generator, it is necessary to move the photosensitive surface and print a figure with a size and area of microns or less on a predetermined portion of the photosensitive surface. It is necessary to move the light with ultra-precise precision of less than a micron on the X-Y plane perpendicular to the traveling direction (optical axis) of the light, and instead of vibrating the photosensitive surface, the optical system is vibrated. The configuration of the device becomes simpler.

In the pattern generator to which the present invention is applied, the flash time is
Focus automatically using 10μsec Xe lamp
By keeping the focus within 0.05μ and repeating focusing and printing while moving to a predetermined portion of the photosensitive surface at a speed of 50 times/sec or more, it is possible to draw a complex pattern of LSI.

By using the light reflected from the photosensitive surface 9, the current position of the photosensitive surface 9 can also be detected from the state of the photosensitive surface 9, for example, existing patterns such as an oxide film pattern and a photosensitive material pattern. In other words, the spectrum and intensity of the light reflected from the oxide film are different from those reflected from silicon, so by measuring the spectrum and intensity of the reflected light, it is possible to determine the boundary between the oxide film and the silicon. Can be detected. Therefore, alignment and focus detection of the existing pattern and the pattern to be printed next can be performed simultaneously.

The present invention has been described above regarding the case where it is incorporated into an ultra-precision pattern generator device.
It goes without saying that the present invention can be used not only for pattern generator devices, but also for focus detection in other semiconductor exposure (printing) devices such as steppers (successive reduction exposure devices) and DSWs (direct writing devices). Not even.

I believe that the gist of the present invention has been made clear through the explanations so far, but it is impossible to describe detailed applications at all, so it is possible to apply them as appropriate as long as the idea of the present invention is not impaired. Needless to say.

〔Effect of the invention〕

As explained above, the focus detection device of the present invention can always accurately and quickly detect the focus, and can sensitize the photosensitive material etc. by using light with a wavelength different from that of the exposure light to detect the focus. without any distortion,
There is no need to worry about scratches, etc., and focus detection is easy regardless of the depth of focus of the lens.

Further, according to the present invention, since focus detection and exposure can be performed in an extremely short time, an LSI circuit pattern consisting of several hundred thousand to several million exposure shots or more can be exposed and drawn in an extremely short time. According to the present invention, focus detection and focus adjustment can be performed with extremely high precision.
Even if the mask dry plate has irregularities of about 12 μm, highly accurate LSI circuit patterns can be drawn, making the mask dry plate manufacturing process cheaper and of high industrial value. According to the present invention, since unevenness on the exposure surface is not a problem, it is extremely easy to perform DSW (direct writing without using a mask) on a complex uneven surface on the semiconductor surface of a three-dimensionally structured LSI.

[Brief explanation of drawings]

FIGS. 1 and 3 a and 3 b are partial views of an embodiment of the focus detection device of the present invention, FIGS. 2 a to d are views showing an example of focus detection in a measuring element, and FIG. 1A and 1B each show an embodiment of an ultra-precision pattern generator device incorporating the focus detection device of the present invention described in . 1...Light source, 2,14,20...Filter,
3... Focus detection pattern, 4... First half mirror, 5, 21... Measuring element, 6, 22... Condensing lens, 7... Second half mirror, 8... Reduction lens, 9 ...Photosensitive surface, 10... Light receiving element, 1
1...Pattern, 13...Light source for printing, 15...
Printing pattern, 16...Zoom lens, 17...
...Half mirror, 18...Condenser lens,
19...Variable aperture.

Claims (1)

[Claims] 1. The focus is detected using light of a first wavelength, and the printing pattern is reduced and printed using light of a second wavelength, which is a different wavelength, onto a photosensitive surface having unevenness in microns. A focus detection device for a pattern printing device that repeatedly performs printing, wherein a focus detection pattern has a striped portion made up of a plurality of lines, and a reduction image is formed by reducing the focus detection pattern on the photosensitive surface. It comprises at least a lens, a measuring element for detecting the image reflected on the photosensitive surface, and a mechanism for making the boundary between brightness and darkness of the image of the focus detection pattern cross over the surface of the measuring element, and A focus detection device for a pattern printing apparatus, characterized in that a focus state on the photosensitive surface is detected by detecting a change in light amount using a measurement signal detected by the measurement element.