JPH0587679A - Optical system evaluating apparatus and optical system evaluating method - Google Patents

Abstract

PURPOSE:To make alignment while observing an image forming pattern by detecting, magnifying and displaying an image obtained by means of an optical part having an illuminating light source which projects a specific wavelength light, a plurality of mirrors and a moving mechanism for the mirrors. CONSTITUTION:The light from an illuminating light source which projects a light of not larger than 1000Angstrom wavelength is cast to a mask pattern 3 through a spectroscope 2. The reducing ratio of the pattern is determined by a mirror 41. The positional relationship between the mask pattern 3 and an optical part 4 is set so as to obtain a predetermined reducing ratio. The spectral light passing through the mask pattern 3 is brought into the optical part 4. The image of the mask pattern reduced with a predetermined ratio by the optical part 4 is formed on a photoelectric surface of an X-ray zooming tube 50 of a magnifying/photographing part 5. The X-ray pattern image is converted to a photoelectric image and then magnified and electronically multiplied. Thereafter, the fluorescent surface is read by a camera 51 and taken into an image processing device 52, where the quality of the input image is improved. The magnified pattern image is projected to a monitor 53. Accordingly, it is possible to adjust the image and obtain the image forming condition while observing the pattern image by eyes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for evaluating an optical system such as an X-ray exposure apparatus, an X-ray microscope, etc., that is, an optical system used in a wavelength range from vacuum ultraviolet rays to 1000 Å or less in the X-ray region. The present invention relates to an optical system evaluation apparatus and an optical system evaluation method for aligning an optical system and further evaluating a multilayer mirror used in the optical system.

[0002]

2. Description of the Related Art In recent years, an imaging optical system using a mirror in the X-ray region from vacuum ultraviolet rays has been actively applied.
FIG. 6 shows an example of a conventional X-ray microscope. In the figure, 6
1 is a target, 62 is a condenser mirror, 63 is a sample, 64
Is an objective mirror, and 65 is a film. The optical axes of the two condenser mirrors 62 and the objective mirror 64 used in this microscope are projected by projecting a pattern image on an image pickup tube (not shown) with visible light to form an image formation pattern or an image formation signal. I was aligning while watching.

However, the wavelength range actually used in the X-ray microscope is several tens to several hundreds of A, which is significantly different from the wavelength range of visible light, so that it is impossible to confirm a sufficient resolution. Therefore, when high-precision alignment is required,
It is necessary to print the film 65 according to the wavelength actually used to adjust the position of the optical axis.

FIG. 7 shows an example of a Schwarz-Schult optical system used in a conventional X-ray reduction projection exposure apparatus. In the figure, 71 is a radiation light source, 72 is a slit, and 7
3 is a reflection mask which is a pattern, 74 is an optical part, and 75 is a wafer. In the X-ray reduction projection exposure, the pattern of the reflection mask 73 is reduced to a desired size and transferred onto the wafer 77 or the like coated with a photosensitive material. Since the reduction optical system of the optical unit 74 is composed of the two concave-convex mirrors 75 and 76, a good imaging pattern cannot be obtained unless the alignment between the mirrors and the aberration correction are properly performed.

For this reason, alignment between the mirrors and aberration correction are important. Normally, the position adjustment of the optical system is performed by a visible light source. That is, visible light is reflected on a predetermined pattern of the reflection mask 73, and this pattern image is sequentially reflected by the convex mirror 75 and the concave mirror 76 of the Schwarz-Schult optical system, and the mask pattern image is observed by an optical microscope, and the concave-convex mirror 75 , 76 are aligned.

However, since this optical system has resolution in the wavelength band in the soft X-ray region, there is a problem that adjustment with high resolution is impossible with visible light. Also, the mirrors 75, 7
Since a multilayer film mirror with a soft X-ray mirror is used as 6, the matching between the wavelength band used and the wavelength band of the multilayer film of the mirror is important. However, in visible light, the matching adjustment is performed due to the difference in the wavelength band used. Is impossible. Therefore, the pattern is actually transferred and the resolution of the pattern is evaluated.

[0007]

In the conventional X-ray microscope of FIG. 6 described above, adjustment by visible light causes
It is impossible to confirm the resolution sufficiently. Further, the method of printing a film according to the wavelength actually used requires a lot of time.

Furthermore, in the conventional X-ray reduction projection exposure apparatus of FIG. 7, visible light cannot be adjusted with high resolution. Also,
Matching adjustment between the wavelength band used and the wavelength band of the multilayer film of the mirror is impossible with visible light. Therefore, it is necessary to actually transfer the pattern and evaluate the resolution of the pattern. However, in order to use the wavelength band in the soft X-ray region, since it is handled in a high vacuum, an operation time for vacuuming and evacuation is required for each exposure, and thus it takes a long time to align the optical system. It costs.

The object of the present invention is to use 1000
Å Provide an optical system evaluation means that can align the imaging means obtained from the optical system while observing the imaging pattern by using a light source with a wavelength of Å or less, and further, a multilayer film mirror used for the optical system. The present invention provides an optical system evaluation means capable of evaluating the performance of.

[0010]

SUMMARY OF THE INVENTION The present invention comprises an illumination light source in the X-ray range from vacuum ultraviolet rays having a wavelength of 1000 Å or less, a plurality of mirrors, and a moving mechanism for spatially determining the position of each mirror. In order to evaluate the optical system of
By observing the image formation state of the mask pattern with high accuracy by enlarging and displaying the pattern image reduced or enlarged by the optical unit by the enlarged image pickup unit, the defocus of the optical system, the aberration, etc. are moved by the optical system. Adjust by mechanism.

Further, the illuminating light from the illuminating light source is continuously scanned by the spectroscope for the wavelength thereof to evaluate the matching degree between the illuminating light and the multilayer mirror used in the optical system.

[0012]

With the above arrangement, the position of the optical system can be adjusted in real time while observing the image formation using the wavelength that is actually used for the evaluation of the optical system. Further, since the imaging pattern can be magnified and observed, high-resolution position setting is possible. Furthermore, since the matching degree and matching width of the multilayer mirror can be measured by continuously scanning the wavelength with a spectroscope, the performance of the multilayer mirror can be evaluated.

[0013]

【Example】

[First Embodiment] An example in which the present invention is applied to an X-ray reduction projection exposure apparatus will be described as a first embodiment with reference to FIGS.
1 is a block diagram showing the whole of this example, FIG. 2 is a block diagram of the optical system in FIG. 1, FIG. 3 is a block diagram showing the position coordinates of the optical system, and FIG. It is a flow chart for explaining.

In FIG. 1, 1 is an illumination light source, 2 is a spectroscope, 3 is a mask pattern, 4 is an optical section, 41 is a mirror of the optical section, 42 is a mirror adjusting mechanism, and 6 is a mask pattern 3 and an optical section 4. The mounted base stage, 5 is an enlarged image pickup unit, 5
Reference numeral 0 is an X-ray zooming tube, 51 is a CCD camera, 52 is an image processing device, and 53 is a CRT monitor.

The irradiation light emitted from the illumination light source 1 is projected on the mask pattern 3 through the spectroscope 2. Mask pattern 3
For this, either a transmissive mask or a reflective mask can be used, but in this example, a transmissive mask is used. Since the reduction ratio of the pattern is uniquely determined by the mirror 41, the position between the mask pattern 3 and the optical section 4 is determined in order to set the predetermined reduction ratio. Mask pattern 3
The spectroscopic light transmitted through is incident on the optical unit 4. The mask pattern image reduced by the optical unit 4 at a predetermined magnification is formed on the photoelectric surface of the X-ray zooming tube 50 of the magnifying image pickup unit 5.

The X-ray zooming tube 50 converts the X-ray pattern image into a photoelectron image, the electron lens magnifies the electron image, and the electron image is multiplied by the MCP (multi-channel plate), and then the fluorescent screen is changed. The light is emitted and the fluorescent screen is read by the CCD camera 51, and the image processing device 52
, The image quality of the input image is improved, and the enlarged pattern image is displayed on the CRT monitor 53. By visually observing the magnified mask pattern image, it is possible to adjust the pattern reduction rate, the blurring of the pattern image, the aberration, etc., and obtain the optimum imaging condition of the optical system in real time.

Next, the position adjusting mechanism of the optical section 4 will be described.

FIG. 2 shows an example of a position adjusting mechanism when a Schwarz-Schult reduction optical system is used as the optical unit 4. This optical system is composed of two concave and convex spherical mirrors 411 and 412. The spectral light that has passed through the mask pattern 3 is sequentially reflected by the convex mirror 411 and the concave mirror 412 to guide the reduced pattern to the enlarged image pickup unit 5. .. These mirrors 411, 412
Is composed of a multilayer mirror. The evaluation method of this multilayer mirror will be described later. The coordinate system of the position adjusting mechanism of the optical unit 4 has the optical axis in the Z-axis direction as shown in FIG.
The vertical direction is the Y axis and the Z axis is the direction orthogonal to the Y axis.

The position adjusting mechanism of the optical unit includes a mask pattern 3, a base stage 6 having the optical unit 4, a mask pattern driving stage 31 for setting the position between the mask pattern 3 and the optical unit 4, and an uneven mirror. Gap adjustment stage 421 between four and aberration correction X stage 42
2. The Y stage 423 for aberration correction.

The details of these position adjusting mechanisms will be described. First, the gap adjusting stage 421 between the concave and convex mirrors.
Determines the gap between the concave and convex mirrors so that the predetermined reduction ratio is obtained. As a driving unit of the gap adjusting stage 421, a DC motor or the like capable of fine step movement is used.

The position between the mask pattern 3 and the optical section 4 is determined in order to set the mask pattern drive stage 31 in the optical axis direction to a predetermined reduction magnification. The stage section is operated by a DC motor, and the position is detected by a potentiometer or the like.

The base stage 6 is for adjusting the focus between the mask pattern 3, the optical section 4, and the photocathode of the X-ray zooming tube 50 of the magnifying image pickup section 5. The depth of focus of the Schwarzschild reduction optical system is about several μm. The drive unit of the base stage 6 uses a DC motor or the like to ensure the position stop accuracy of the sub-Miglon. The position is detected by a laser interferometer, a linear scale, or the like.

Aberration correction X stage 42 between concave and convex mirrors
2. As the aberration correction Y stage 423, a DC motor or the like is used for the X and Y axis drive units on the concave mirror side, and the position is detected by a potentiometer or the like.

Next, the position adjustment procedure will be described.

FIG. 4 shows a processing flow of the position adjustment procedure.
First, in order to set the reduction ratio, the position between the concave and convex mirrors is operated by the gap adjusting stage 421. Next, in order to perform positioning between the mask pattern 3 and the optical section 4, the mask pattern drive stage 31 is operated to set it at a predetermined reduction magnification position (step 401).

After the reduction magnification is set, the mask pattern 3 and the base stage 6 having the optical unit 4 are mounted in order to form the reduction pattern on the photocathode of the X-ray zooming tube 50.
To focus. Focusing is performed by bringing the base stage 6 closer to the X-ray zooming tube 50 and using the imaging pattern enlarged by the X-ray zooming tube 50. As for the image formation pattern, after obtaining a good pattern image by the image processing device 52 such as cumulative addition, the brightness of the pattern image is obtained, and the base stage 6 is moved so that the brightness becomes maximum. In this operation, the maximum position can be obtained by visually observing the luminance signal, but automatic focusing is also possible by applying the feedback signal obtained from the luminance signal to the drive unit of the base stage 6 (step 402). ).

Next, the reduction ratio of the pattern is adjusted in the in-focus state. As for the pattern reduction rate, data calibrated with the mesh size on the CRT monitor 53 is collected in advance by a standard mesh pattern or the like. Based on this calibration data and the mask pattern image, it is checked whether the magnification is a predetermined magnification. If the reduction ratio is different, the gap adjusting stage 421 between the concave and convex mirrors of the reduction optical system is operated to set the predetermined reduction magnification (step 403). If defocus occurs during the reduction ratio adjustment, the above-described focus adjustment processing is performed everywhere (step 404).

After the reduction ratio and the focusing are completed, the aberration of the image forming pattern is corrected. The aberration correction is performed by the aberration correction stages 422 and 423 of the reduction optical system.
The aberration correction stages 422 and 423 move and adjust the concave mirror 412 in the X- and Y-axis directions with respect to the optical axis.
The aberration between 12 and the convex mirror 411 is minimized (step 405). When the focus and the reduction magnification change during the aberration correction, the above processing is repeated, and when the focus, the reduction magnification, and the aberration are all good, the processing ends (step 406).

When the concave-convex mirrors 411 and 412 are spherical, aberration correction can be performed by the X and Y2 axes as in this example, but when the concave-convex mirrors are aspherical,
In addition to the X and Y axes, it is necessary to adjust the tilt and tilt between the concave and convex mirrors. At this time, α and β axes for tilt correction are provided to match the parallelism between the mirrors.

As described above, the position of the aberration-free optical system can be adjusted at a predetermined reduction ratio while directly observing the imaging pattern. Since it is not necessary to transfer the pattern once to check the pattern as in the conventional case, the adjustment time of the optical system can be greatly shortened.

Next, the convex mirror 411 and the concave mirror 4 described above.
The performance evaluation of the multilayer film mirror used as No. 12 will be described.

After the position adjustment of the above optical system is completed,
The illumination light 1 is continuously wavelength-split by the spectroscope 2 in a predetermined wavelength band and extracted. As the spectral light, the optimum wavelength band is determined by the constituent material of the multilayer mirror used in the optical section. Now, when the reduction optical system is configured by the concave-convex mirror using the Mo / Si multilayer film as the optical portion, the reflectance with respect to X-ray becomes high in the wavelength band around 130Å. By changing the wavelength selected by the spectroscope, calculating the brightness of the imaging pattern at that time by the image processing device, and determining the wavelength at which the brightness becomes maximum and the brightness of each wavelength The degree of matching with the multilayer film and the matching width are obtained, and the performance of the multilayer film mirror can be evaluated.

[Embodiment 2] An embodiment in which the optical system evaluation apparatus of the present invention and the X-ray reduction projection exposure apparatus are combined and integrated will be described as Embodiment 2 with reference to FIG. In FIG. 5, components having the same functions as those of the first embodiment described above are designated by the same reference numerals, and repeated description will be omitted.

In the figure, 7 is a wafer, 8 is a switching stage, 9 is a slit, and 10 is a mask pattern. In this example, the magnified image pickup unit 5 and the wafer 7 are mounted together on the switching stage 8, and the movement of the changeover stage 8 causes the magnified image pickup unit 5 and the wafer 7 to alternate at the imaging position of the optical unit 4. Is located in.

Explaining the operation of this example, the switching stage 8 is moved in the direction of arrow A before the reduction pattern is transferred to the wafer 7 by X-rays, and the magnified image pickup section 5 is placed at the image forming position of the optical section 4. Set to the state shown in the figure. Thereafter, the reduction magnification, focus, aberration correction, etc. of the reduction optical system are optimally adjusted by the pattern of the X-ray zooming tube according to the procedure described in the first embodiment. After the adjustment is completed, the switching stage 8 is moved in the direction of the arrow B to retract the enlarged image pickup unit 5, and the wafer 7 to be transferred is set at the image forming position of the optical unit 4. In this way, since pattern transfer can be performed immediately after the optimum adjustment of the optical system, the transfer performance can be improved and the efficiency can be improved.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

In the above description, the field of application of the invention is mainly applied to the X-ray reduction projection exposure apparatus, but the present invention is not limited to this and can be applied to, for example, an X-ray microscope. The present invention has at least one wavelength
It is applicable to an optical system using a light source of 000Å or less.

[0038]

The present invention monitors the optical system such as the optical axis of the optical system used from the far ultraviolet ray to the soft X-ray region, the position adjustment such as aberration correction, and the performance evaluation of the multilayer film mirror in a predetermined wavelength band. By doing so, it is possible to make direct adjustment while viewing the pattern image, and it is possible to perform highly accurate evaluation in a short time.

[Brief description of drawings]

FIG. 1 is a device configuration diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of the optical system of FIG.

FIG. 3 is a diagram showing position coordinates of the optical system of FIG.

FIG. 4 is a flowchart of a position adjustment procedure.

FIG. 5 is a device configuration diagram of a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional X-ray microscope.

FIG. 7 is a configuration diagram of a conventional X-ray reduction projection exposure apparatus.

[Explanation of symbols]

1 ... Illumination light source, 2 ... Spectrometer, 3 ... Mask pattern, 31 ...
Mask pattern drive stage, 4 ... Optical unit, 41 ... Mirror, 411 ... Convex mirror, 412 ... Concave mirror, 42 ... Mirror adjusting mechanism, 421 ... Gap adjustment stage between concave and convex mirrors, 422 ... Aberration correction X stage, 423 ... Aberration correction Y stage, 5 ... Enlarging image pickup unit, 50 ... X-ray zooming tube, 51 ... CCD camera, 52 ... Image processing device, 53 ...
CRT monitor, 6 ... Base stage, 7 ... Wafer, 8
… Switching stage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Mizoda 1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Tsuneyuki Haga 1-6 Uchiyukicho, Chiyoda-ku, Tokyo No. Japan Nippon Telegraph and Telephone Corporation (72) Inventor Yasuhiro Torii 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Nippon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. An optical unit having a pattern, an illumination light source for projecting the pattern with light having a wavelength of 1000 Å or less, a plurality of mirrors, and a moving mechanism for spatially determining the position of each mirror; An optical system evaluation apparatus comprising: a magnifying image pickup unit that detects and magnifies an image obtained by the unit and displays the image. 2. The optical system evaluation apparatus according to claim 1, wherein the mirror of the optical section is formed of a multilayer film mirror, and a spectroscope for continuously scanning the wavelength of the illumination light from the illumination light source is provided. .. 3. The pattern is magnified and projected on a magnifying and imaging section through an optical section, the moving mechanism of a plurality of mirrors is operated by the pattern image to perform optical axis alignment, and then the projected illumination light is wavelength-spectroscopic by a spectroscope. Then, an optical system evaluation method for evaluating the performance of the multilayer film mirror.