JPH07120939A - Wafer positioning device - Google Patents

Abstract

PURPOSE:To directly and easily measure an alignment mark by installing a space filter for the alignment mark on a Fourier transform surface and removing the patterns exclusive of the alignment mark. CONSTITUTION:This wafer positioning device has the alignment mark 10 disposed on a wafer 8 to be positioned, a laser beam source 1 for radiating monochromatic light, a beam expander 2 for widening this monochromatic light to illuminating light of a prescribed size and a diaphragm window 3 disposed to irradiate only the prescribed range including the alignment mark 10 with this illuminating light. The device has also a half mirror 4 for irradiating a sample with the illuminating light past this diaphragm window 3 by changing the optical path of the illuminating light, a lens 5 for inspection for condensing and imaging the illuminating light reflected from the wafer 8, a space filter 6 for the alignment mark 10 arranged on the Fourier transform surface of this lens 5 for inspection and an image pickup element 7 existing in the imaging position of the lens 5 for inspection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer positioning device, and more particularly to a wafer positioning device for positioning a positioning mark spatial filter on a Fourier transform plane.

[0002]

2. Description of the Related Art FIG. 5 shows, for example, Japanese Patent Laid-Open No. 4-196307.
It is a block diagram which shows an example of the conventional wafer positioning device shown by the publication. Referring to FIG. 5, the conventional wafer positioning apparatus includes an exposure light source 11, a reticle 12, a reduction lens 13 for reducing and transferring a pattern on the reticle 12, a wafer stage 9 for sucking and moving a wafer 8, and a wafer stage 9. It comprises a length measuring device 15 for measuring the position of the stage 9, an alignment detector 17 for detecting the alignment mark 10 on the wafer 8, and a main control system 18 for controlling the entire apparatus.

First, the alignment detection is corrected. As shown in FIG. 5A, by illuminating the detection pattern 16 on the reticle 12 with exposure light, the detection unit 14 provided on the wafer stage 9 via the reduction lens 13 is illuminated.
Project the pattern on top. This projection image is detected by the detection unit 1
The light amount detector in 4 detects the light amount change signal, and the light amount change signal is taken into the main control system 18 to obtain the center position of the pattern projection image. Next, the alignment detector 17 detects the position of the alignment mark 10 provided on the detection unit 14, and takes the position data into the main control system 18. Here, the main control system 18 obtains the amount of deviation between the center of the inspection pattern projection image and the position of the alignment mark 10.

Next, the wafer stage 9 is moved to the position shown in FIG.
This correction value can be added by detecting the position of 0 with the alignment detector 17, taking it into the main control system 18, and adding the above-mentioned deviation amount as the correction value to the position data of the alignment mark 10 detected by the alignment detector 17. The position data is the position of the projected image of the reticle 12.

[0005]

This conventional wafer positioning apparatus is an indirect alignment mark because it is possible to see the degree of pattern overlap, which is shifted by a small amount, with respect to alignment marks arranged at arbitrary intervals by a light amount detector or the like. Do not catch.

[0006]

A wafer positioning apparatus of the present invention comprises a positioning mark provided on a sample to be positioned, a monochromatic light source for irradiating monochromatic light, and an illumination light of a predetermined size for the monochromatic light. To the sample by changing the optical path of the illumination light that has passed through the aperture window, which is provided to irradiate the illumination light only in a predetermined range including the positioning mark with the first optical system. A second optical system for irradiating, a third optical system for condensing and forming the illumination light reflected by the sample, and a spatial filter for the positioning mark arranged on the Fourier transform surface of the third optical system. And an image pickup unit at the image forming position of the third optical system.

[0007]

The present invention will be described below with reference to the drawings. Referring to FIG. 1 which is a block diagram showing an embodiment of the present invention, a wafer positioning apparatus according to this embodiment includes an alignment mark 1 provided on a wafer 8 to be positioned.
0, a laser light source 1 that emits monochromatic light, and a beam expander 2 that expands the monochromatic light into illumination light of a predetermined size.
A diaphragm window 3 provided for irradiating the illumination light only on a predetermined range including the alignment mark 10, and a half mirror 4 for changing the optical path of the illumination light passing through the diaphragm window 3 and irradiating the sample. The inspection lens 5 that collects and forms an image of the illumination light reflected from the wafer 8, the spatial filter 6 of the alignment mark 10 that is arranged on the Fourier transform surface of the inspection lens 5, and the image formation position of the inspection lens 5 are provided. It is composed of an image sensor 7.

The laser light from the laser light source 1 is emitted by the beam expander 2 with the laser light diameter enlarged. The expanded laser light is narrowed down by the diaphragm window 3. FIG. 2 shows an illumination range 1 narrowed down by the aperture window 3 with respect to the visual field of the image sensor 7.
9 is shown. The shaded area in FIG. 2 is shielded by the aperture window 3. The laser light reflected from the sample wafer 8 forms a Fourier transform image corresponding to the spatial frequency of the sample plane on the Fourier transform surface of the inspection lens 5. When the spatial Fourier transform image of the alignment mark 10 of FIG. 4 is, for example, FIG.
When the image of the image is placed on the Fourier transform plane as the spatial filter 6, the image sensor 7 has an alignment mark 10 in the aperture window 3.
When is positioned, no image appears on the image sensor 7.
When a pattern (mark) other than the alignment mark 10 appears in the window, this image appears on the image sensor 7. Therefore,
If the size of the aperture window 3 is a size including only the alignment mark 10 and is within the range of the positioning accuracy, it means that the positioning is performed when nothing is projected on the image sensor 7.

If the Fourier transform image and the image in which the lightness and darkness are reversed are used as the filter instead of the spatial filter 6 of this embodiment, the alignment mark 10 is displayed on the image pickup element 7 only when the alignment mark 10 is positioned on the aperture window 3. , The surrounding noise component is removed and the alignment mark 1
Only 0 can be cut out.

[0010]

As described above, according to the present invention,
A diaphragm window provided for illuminating only the predetermined range including the positioning mark provided on the sample for positioning the illumination light that spreads the monochromatic light to a predetermined size, and the illumination light reflected from the sample By providing the third optical system for imaging and the spatial filter of the positioning mark arranged on the Fourier transform surface of the third optical system, the pattern other than the positioning mark on the sample can be removed to directly and easily perform the positioning mark. Can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing an illumination range narrowed down by a diaphragm window with respect to the visual field of the image sensor of this embodiment.

FIG. 3 is a diagram showing an example of a spatial filter of this embodiment.

FIG. 4 is a diagram showing an example of an alignment mark of this embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 Laser Light Source 2 Beam Expander 3 Aperture Window 4 Half Mirror 5 Inspection Lens 6 Spatial Filter 7 Imaging Device 8 Wafer 9 Wafer Stage 10 Alignment Mark 19 Illumination Range Constricted by Aperture Window

Claims (2)

[Claims] 1. A positioning mark provided on a sample, a monochromatic light source for irradiating monochromatic light, a first optical system for spreading the monochromatic light into illumination light of a predetermined size, and the illumination light A diaphragm window provided to irradiate only a predetermined range including the positioning mark, a second optical system that irradiates the sample by changing the optical path of the illumination light that has passed through the diaphragm window, and reflects the sample. A third for focusing and forming the illumination light
Wafer positioning system, a third optical system, a spatial filter for the positioning marks arranged on the Fourier transform surface of the third optical system, and an image pickup unit at the image forming position of the third optical system. apparatus. 2. The wafer positioning apparatus according to claim 1, wherein the monochromatic light is laser light.