JPS5936219A - Fixed slit type photoelectric microscope - Google Patents

Abstract

PURPOSE:To facilitate adjustment by providing a fixedly arranged couple of slits, a couple of polarizers which have polarization directions crossing with each other at right angles, and a mechanism which generates a couple of light beams alternately at a specific periods as a modulating means of luminous flux incident to a photoelectric transducer. CONSTITUTION:Luminous flux from a scale line 42 on a scale 41 is incident to the photoelectric transducer 58 through slits 54a and 54b of a slit plate 54 alternately by the irradiation with alternate polarized light beams P' and Q' from a light irradiating mechanism which are polarized linearly at right angles to each other and the operation of the slits 54a and 54b of the slit plate 54 and polarizing plates 56a and 56b. This when viewed from the side of the photoelectric transducer 58 is equivalent to the effect when one slit is oscillated mechanically corresponding to a detection origin and the displacement of the scale line 42 on the scale is therefore detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fixed slit type photoelectron microscope machine gun that detects the position of a linear pattern on an object.

[Technical background of the invention and its melting point]

Conventionally, various photoelectron microscopes have been proposed for optically detecting the position of a linear pattern, and representative ones of these are shown in FIGS. 1 and 2. The light shown in Figure 1!
In a microscope, a scale 2 having graduation lines (&l-shaped pattern) 1 to be detected is illuminated by transmitted illumination when the scale 2 is a transparent object, and an epi-illumination system 4 for a bright object. The image of the graduation line 1 on the scale 2 is formed on the focusing mirror 8 via the objective lens 6, the half mirror 7, and the slit 9 of the slit plate 9.
The image is formed on a.

The image formed on the focal whale 8 is monitored with the naked eye through an eyepiece 1θ. The plate 9 is attached to an oscillator 12 which is vibrated by the afterflow from the oscillator 11, and is vibrated in the direction of arrow A in the figure. ) is converted into an electrical signal. After this conversion signal is amplified via the preamplifier 14, it is synchronously rectified by the synchronous rectifier circuit 15, and this rectified output is displayed on the indicator 16 as the displacement amount of the scale 1M1 on the scale 2. ing.

In addition to vibrating the slit plate 9 shown in Fig. 2, the vibrator 12 is configured to excite the reflex chain 17 in the direction of arrow B in the figure. It is something. That is, the scale line 10 image on the scale 2 is transmitted to the half mirrors 5, 7 and the reflecting mirror 1 by the objective lens 6.
The image is formed on the slit 9a of the top plate 9 through the slit 7.

In this way, the photoelectric transducer shown in FIGS. 1 and 2 modulates the light beam transmitted through the slit 9& of the slit plate 9 and received by the photoelectric conversion element 13 by vibrating the slit plate 9 or by vibrating the slit plate 9. The only difference is whether the luminous flux is lifted, and the other configurations are the same. And this glazed light'fI
With the L microscope, displacement-output-5 pressure characteristics as shown in FIG. 3 can be obtained. It is also known that since the light beam received by the photoelectric conversion element 13 is modulated, an AC bj°C amplifier can be used and a detection output with a high S'N ratio can be obtained. However, since the principle is to mechanically vibrate the slit 9a or the reflecting mirror 17 and make the vibration center correspond to the detection origin, there is a drawback that detection accuracy higher than the amount of variation in the vibration center cannot be obtained. However, since the slit 9a or the reflecting mirror 17 is mechanically vibrated, it is difficult to accurately align the center of vibration with the detection origin, and detection accuracy may be affected due to fluctuations in the center of vibration. The decline could not be prevented.

On the other hand, the literature (Pr.
International Conte
rsnce onMlcrolithography
, Mierocircult Engineerin
g80, Amsterdam (1980) P2S
5), an alignment signal detection device for an aligner used for mask-to-odd turn printing of integrated circuits has been proposed. This device IT detects the displacement of the alignment mark 22 of the diffraction grating structure on the wafer 2 with respect to the center position of the multi-slits 24IL and 24b on the reticle mask 23, as shown in FIG. The light from the light source 25 is transmitted to the acoustic optical modulator 2
6. The alignment mark 2 on the wafer 21 is deflected through the half mirror 27 and the lens 28.
2. At this time, the light from the sound source quality adjuster 26 is transmitted through the multi-slits 24h and 2 on the reticle mask 23.
4bk is transmitted through the lens 28, so the light beam irradiated to the alignment mark 22 is shaped to be similar to the shape of the multi-slits 24&, 24b. After passing through 24* and 24b, the light is received by the photoelectric conversion element 13 via the half mirror 27, the reflecting mirror 29, and the focusing lens 3Q. And this light! The conversion signal converted into an electric signal by the conversion element 13 is amplified and synchronously rectified via the preamplifier 14 and the synchronous rectification circuit 15, and the displacement amount of the alignment mark 22 is displayed on the indicator 16 in the same way as described above. It has become something that will be done. In addition, 31 in the figure
indicates a driver for providing a reference signal to the acoustic optical modulator 26 and the synchronous rectifier circuit 15.

In this device, an acoustic optical modulator 26 and two fixed diffraction grating structures 24m are used to modulate the light beam incident on the photoelectric conversion element 13.

24b, it is possible to avoid a decrease in the detection accuracy due to the displacement of the vibration centers of the slit 9a, the reflecting mirror 17, etc. described above.

However, since double diffraction is used to detect the alignment mark 22, multiple pick-ups occur.

It is necessary to make the pitch interval of the marks 24m and 24b exactly match the dimension obtained by multiplying the pitch interval of the alignment mark 22 by the magnification of the lens 28, which makes the adjustment of the apparatus complicated. Sarani, Alignment Mark 22 and Multisuri.

There were also some gaps that made the process of forming upper 24*, 24b, etc. complicated.

[Purpose of the invention]

The purpose of the present invention is to be able to detect the position of a line or main turn on an object to be inspected with high precision without causing a decrease in detection accuracy due to mechanical vibrations of slits, reflectors, etc.
The object of the present invention is to provide a fixed slot-type photoelectron microscope that facilitates the adjustment.

[Summary of the invention]

The gist of the present invention is to provide a method for modulating a light flux incident on a photoelectric conversion element, including a pair of fixedly arranged slits, a pair of polarizers having polarization directions perpendicular to each other, and a pair of polarizers polarized in each of the above polarization directions. The purpose is to use a mechanism that generates polarized light alternately at a constant period.

That is, the present invention provides a photoelectric detector for detecting the position of a linear i4 turn on an object to be inspected, in which a pair of slits and slits are arranged in parallel at a position conjugate with the linear i4 turn with respect to the objective lens. , a pair of polarizers having mutually orthogonal polarization directions and disposed in front or behind the slit;
A light irradiation mechanism that alternately irradiates a linear pattern on the object to be inspected with a pair of polarized lights that are polarized in accordance with each of the polarization directions at a constant cycle; a photoelectric conversion element that detects the reflected light or transmitted light of the light through the slit, the polarizer, and the polarizer, and the detection signal of this photoelectric conversion element is rectified in synchronization with the alternating irradiation of the pair of polarized lights by the light irradiation mechanism. This device includes a synchronous rectifier circuit and a display that displays the output signal of the synchronous rectifier circuit.

〔Effect of the invention〕

According to the present invention, it is possible to modulate the light flux that enters the combustion element without mechanically vibrating the slit, the reflecting mirror, or the like. Therefore, it is possible to prevent the detection accuracy from decreasing due to mechanical vibration, and it is possible to significantly improve the detection accuracy. Moreover, it does not utilize double diffraction, and has the advantage of being easy to adjust.

[Embodiments of the invention]

FIG. 5 is a schematic diagram showing a simple embodiment of the present invention. 41 in the figure is a scale of a transparent object, and this scale 41
A scale line (linear-arm turn) 42 is formed on the top. Below the scale 41 is a light source 43 and a half mirror 44.
, 45, reflecting mirrors 46, 47, polarizing plates 48, 49, and a chopper 5°. In this light irradiation mechanism, light from a light source 43 is irradiated via a half mirror 44 to a polarizing plate 48)', and is also irradiated to a polarizing plate 49 via a half mirror 44 and a reflecting mirror 46. .49 are arranged so that their respective polarization directions are perpendicular to each other, and a pair of polarized lights linearly polarized in directions orthogonal to each other by these polarizing plates 48 and 49 are irradiated onto the front and rear 50, respectively. By rotating the brim 5oVi in the direction C in the figure, the brim 5oVi is formed, for example, by cutting out part of the outer circumference of an opaque disc body at regular intervals. As shown in Figure 6, the pair of linearly polarized lights P and Q are alternately 0N with a constant period T.
-Turned off. ) The polarized light selected according to 5θ passes through the half mirror 45 or through the reflecting mirror 47 and the half mirror 45 and reaches the graduation line 42 on the scale 41.
is irradiated. In other words, a pair of polarized lights polarized in directions orthogonal to each other by the light irradiation mechanism are alternately irradiated onto the scale m42 on the scale 41 at a constant period.

An objective lens 51 is disposed above the scale 41, and the objective lens 51 forms an image of the graduation lines 42 on the scale 41 onto a focusing mirror 53 and a slit plate 54 via a half mirror 52. . The image formed on the focusing mirror 53 can be detected with the naked eye through an eyepiece lens 55. The slit plate 54 is provided with a pair of slits 54&, 54b arranged in parallel, and on the top surface of the slit plate 54, a pair of polarizing plates (polarizers) 56* having mutually orthogonal polarization directions, 56b is applied.

In other words, the polarizing plates 56*, 56b as shown in FIG. 7(a)
The pickpocket board 54 as shown in FIG.
) are laminated as shown. Here, the polarizing plate 56m
, 56b, and E are determined to match the respective polarization directions of the light beams alternately irradiated onto the graduation lines 42 on the scale 41 by the light irradiation mechanism. In other words, the polarization direction of the polarized light P/ obtained by passing the polarized light P through the half mirror 45 matches the polarization direction of the polarizing plate 56m, and the polarized light obtained by passing the polarized light Qf through the reflecting mirror 47. The polarization direction of the light Q' and the polarization direction E of the polarizing plate 56b are made to match. As a result, the polarized light P' is not blocked by the polarizing plate 56b, and the polarized light P' is not blocked.

The light passes through the front plate 54 and the polarizing plate 56a, is heated by the focusing lens 57, and enters the photoelectric conversion element 58. Similarly, the polarized light Q/ is not blocked by the polarizing plate 5611, but passes through the slit 54b of the top plate 54 and the polarizing plate 56b, and enters the photoelectric conversion element 58. .

The signal detected by the photoelectric conversion element 58 and converted into an electric signal is amplified via a preamplifier 59 and then supplied to a synchronous current circuit 60 . In the synchronous rectification circuit 60, the input signal is rectified in synchronization with the alternating irradiation of a pair of polarized lights by the light irradiation mechanism. And this synchronous rectification circuit 6
An output signal of 0 is displayed by the indicator 61 as a displacement of the graduation line 42 on the scale 41. In addition, 62 in the figure is the above-mentioned Cho/4'5
The photointerrupter 62 is attached to the photointerrupter 17 and detects the timing of alternate irradiation of the polarized lights P and Q by f50.A reference signal is supplied from the photointerrupter 62 to the synchronous rectifier circuit 60. .

With such a configuration, a pair of polarized lights p/, Q linearly polarized in mutually orthogonal directions by the light irradiation mechanism
Alternate irradiation of /, pickpocket, to plate 54th slit vto 54*-54
b and the polarizing plates 56m and 56b, the light flux (positional information) from the graduation line 42 on the scale 4 is incident on the photoelectric conversion element 58 through the slits 54h and 54b of the top plate 54 alternately. become. When viewed from the photoelectric conversion element 58 side, this is equivalent to the case where a single slit is mechanically vibrated in correspondence with the detection origin. Therefore, the displacement of the graduation line 42 on the scale 41 can be detected in the same way as the photoelectron microscope shown in FIGS. 1 and 2.

In this case, the luminous flux incident on the photoelectric conversion element 58 is f
There is no need to use a mechanical vibrator for tuning, and fluctuations in the vibration center due to mechanical vibration can be completely eliminated. Therefore, the position of the graduation line 42 on the scale 4 can be detected with extremely high accuracy. According to experiments conducted by the present inventors, it has been confirmed that an extremely high position detection axis of 0.01 [: μm] can be obtained. In addition, the scale line 42
0 width and the width and spacing of the slits 54 and 54b are:
It is necessary to optimally set the magnification of the objective lens 51, but as with the case where double diffraction is used, the manufacturing method limitations are not as strict as shown on the left. There are no complications during production. Furthermore, compared to those using double diffraction, there are also advantages such as extremely easy adjustment.

FIG. 8 is a schematic configuration diagram showing another embodiment.

Note that the same parts as in FIG. 5 are given the same reference numerals, and detailed description thereof will be omitted. This embodiment differs from the previously described embodiments in that an electro-optic modulator 6 is used as the light irradiation mechanism.
The reason is that 3f was used.

In an electro-optic modulator made of a crystal such as KDP (mFR2 potassium hydrogen), the polarization state of transmitted light differs between a state in which a constant voltage determined by the characteristics of the crystal is applied and a state in which no voltage is applied.

Then, it is possible to extract polarized light whose polarization directions are perpendicular to each other. By applying a rectangular wave alternating current voltage with a duty ratio of 5oc* as shown in FIG. It is taken out. These polarized lights are then irradiated onto the graduation lines 42 on the scale 41 via the reflecting mirror 64. Note that the scale 41 is
A pair of polarized lights irradiated to the polarizing plates 56 & , 56
This corresponds to each polarization direction of b.

Further, 65 in the figure indicates a driver for applying a rectangular wave alternating current voltage with a duty ratio of 50C% described in the MTI to the electro-optic modulator 63, and the output voltage of this driver 650 is used as a reference signal to the synchronous rectifier circuit 60. It is to be given to

With such a configuration, the light source 43 and the electro-optic modulator 6
As in the previous embodiment, a light irradiator sK consisting of a mirror 3 and a reflecting mirror 64 sends a pair of polarized lights polarized in mutually orthogonal directions alternately at regular intervals to the graduation line 42 on the scale 41.
can be irradiated. Therefore, the same effects as in the previous embodiment can be achieved. Further, there are also advantages such as no need for mechanically rotating parts such as the above-mentioned Chocno 950, and the structure thereof can be simplified.

It should be noted that the present invention is not limited to the embodiments described above. For example, the light irradiation mechanism is not limited to being placed below the object to be inspected, but may be placed above the original inspection object and the light irradiation mechanism may be used as a reflective illumination thread.

Further, as the light irradiation mechanism, it is possible to use a magneto-optic modulator that changes the polarization direction by applying a magnetic field. Further, as means for tracing the pair of polarized lights, The present invention is not limited to optical modulators, electro-optic modulators, magneto-optic modulators, etc., but uses two light sources (semiconductor light source) corresponding to a pair of single light beams, and these light sources are turned on alternately. It's okay. Further, as the polarizer, a polarizing prism or any other element that converts natural light into linearly polarized light may be used instead of a polarizing plate. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic diagrams showing a conventional photoelectron microscope, respectively. FIG. 3 is a schematic diagram showing the displacement-output voltage characteristics of the above-mentioned -i turtle microscope, and FIG. 4 is a diagram showing a conventional alignment signal detection device. 5 is a schematic diagram showing a fixed slit optical microscope according to an embodiment of the present invention, and FIG. 6 is a signal waveform showing temporal changes in polarized illumination light in the above embodiment. 7(a) to (c) are plan views showing the caslit and polarizing plate used in the above embodiment, FIG. 8 is a schematic configuration diagram showing another embodiment, and FIG. 9 is a plan view showing the other embodiment. FIG. 3 is a signal waveform diagram showing a extraction signal applied to an electro-optic modulator used in an example. 41...Scale (object to be inspected), 42...Graduation line (linear, flat turn), 43...Light source, 44.46...
・Half mirror 145, 47, 64...Reflector, 48
．． 49...Polarizing plate, 50...Chopper, 5...
Objective lens, 54... pickpocket, top plate, 54h, 54b.
...Slit, 56m, 56b...Polarizing plate (polarizer)
, 57... Focusing lens, 58... Photoelectric conversion element, 6
0...Synchronous rectifier circuit, 61...Indication meter (indicator), 62...Photointerrupter, 63...Electro-optic modulator, 65...Driver. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (5)

[Claims] (1) With respect to the objective lens, a pair of slits are arranged parallel to each other in the same position as the linear projection on the object to be inspected, and the slits have mutually orthogonal polarization directions, and are arranged in front or behind the slits, respectively. a pair of polarizers, and a light irradiation mechanism that alternately irradiates nine linear turns of the object to be inspected with polarized light that is polarized in accordance with each polarization direction of the polarizer at a constant cycle; A photoelectric conversion element that detects reflected light or transmitted light from the object to be inspected by the light irradiation mechanism via the slit and a polarizer; A fixed slot, G-type photoelectric collapsing microscope characterized by comprising a synchronous rectifier circuit that rectifies in synchronization with alternating irradiation, and a display that displays an output signal of the synchronous rectifier circuit. (2) The light irradiation mechanism includes a pair of polarizers that polarize light from a light source in mutually orthogonal directions, and a polarizer that polarizes the polarized light obtained through these polarizers. The fixing device according to claim 1, further comprising an optical system that irradiates the linear main turn of the object to be inspected with selected polarized light. Slit type generator, #b4 micromirror. (3) The light irradiation mechanism includes an electro-optic modulation element that alternately polarizes light from the light source in orthogonal directions by applying an electric field, and polarized light obtained through the electro-optic modulation element onto the object to be inspected. A fixed slit type original electron microscope microaccurate according to claim 1, characterized in that it comprises an optical system that irradiates a linear pattern. (4) The light irradiation mechanism is a magneto-optical mechanism that polarizes light from multiple light sources alternately in orthogonal directions by applying a magnetic field.
1, and an optical system that irradiates polarized light 1 obtained through the magneto-optical modulation element to four linear turns on the object to be inspected. The fixed slit photoelectron microscope according to item 1. (5) The light irradiation mechanism includes a pair of semiconductor light emitting devices that are turned on alternately, a pair of polarizers that polarize the light from these semiconductor light emitting devices in directions perpendicular to each other, and a pair of light emitting devices that emit light through these polarizers. 2. The fixed slit mold microsharpening device according to claim 1, further comprising an optical system that irradiates the obtained polarized light onto a linear pattern on the object to be inspected.