JPH08240919A - Light exposing method - Google Patents

Abstract

PURPOSE: To easily form images of each light wavelength on the same spot in the case of detecting a positioning mark on an exposed body by using a light beam with plural wavelengths. CONSTITUTION: In this light exposing method for detecting a reflected light through projecting lens 14, an original image pattern 16 is irradiated with a monochromatic light from a light source 44, the image of the original pattern 16 on an exposed body 10 is projected through an projecting lens 14 which is compensated in aberration for exposure, the exposed body is placed on a movable table 26, and a position aligning mark 12 formed on the exposed body 10 is irradiated with a beam of plural light wavelengths through the projecting lens 14. Relative position between the original pattern 16 and the exposed body 10 is aligned by forming individual image points, which exist on different positions on the reflected light axis in accordance with the wavelengths of the reflected light, on a selected position of the reflected light axis through compensating lenses 68, 70 which are located between the projecting lens 14 and the detectors 56, 58, thus to compensate the position of the formed image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical exposure apparatus, which projects a plurality of original image patterns on a semiconductor wafer through a projection lens so as to superimpose them on a semiconductor wafer as used in the manufacture of large-scale integrated circuits. The present invention relates to an optical exposure method for detecting alignment marks formed on a semiconductor wafer via a projection lens.

[0002]

2. Description of the Related Art In the conventional light exposure method in the manufacturing process of a large-scale integrated circuit, one original image pattern is projected and transferred onto a semiconductor wafer, and then the next original image pattern is transferred onto the previously transferred original image pattern. I am trying to transfer them over again. Then, the detection method of the previous pattern for superimposing the pattern transferred last time and the pattern of the original image transferred this time is such that the detection light is passed through the projection lens provided for transferring the original image pattern onto the semiconductor wafer. A method of irradiating an alignment mark on a semiconductor wafer and observing the reflected light image through a projection lens is used.

Usually, the projection lens requires the ability to transfer the original image pattern onto the semiconductor wafer with high resolution without aberration and is dedicated to monochromatic light in order to exert this performance. Therefore, the detection light for detecting the reflected light image of the alignment mark on the semiconductor wafer also needs to be monochromatic light. However, due to the uneven coating of the photoresist around the alignment mark, the reflected light causes interference, and when the alignment mark is detected,
It is known that the detection signal is greatly disturbed. Therefore,
In order to solve this problem, Japanese Patent Application No. 58-187025 proposes a method of detecting the alignment mark with light of a plurality of wavelengths.

As is well known, the image forming position of light of a plurality of wavelengths differs depending on each wavelength. That is, as shown in FIG. 3, the light reflected from the alignment mark 12 of the semiconductor wafer (object to be exposed) 10 is processed by a reduction plate 14 which is a projection lens to form an original image pattern ( When the light is guided to the reference window 18 of the reticle 16 and imaged on the detection slit 20, for example, the e-line (547n
When the image forming point 22 of m) is set on the detection slit 20,
The image forming point 24 of the line (577 nm) is located above the image forming point 22 of the e line as shown by the broken line in FIG. Therefore, Japanese Patent Application Sho 58
No. 187025 proposes the following method. (1) When detecting the alignment mark using light of a plurality of wavelengths, the semiconductor wafer is set to the best focus position corresponding to each wavelength so that the best focus image of each monochromatic light is formed at a predetermined position. Move up and down. (2) The semiconductor wafer is fixed at a fixed position, and the measuring device is provided at the position where the best focus image of each monochromatic light is formed. However, the method (1) takes time because data is captured at one wavelength and then the wafer is moved to the best focus position corresponding to another wavelength to capture the data. Further, in the method (2), an optical system must be provided for each wavelength, which not only complicates the apparatus but also raises the cost.

[0005]

In the conventional light exposure method, the projection lens usually requires the ability to transfer the original image pattern onto the semiconductor wafer with high resolution without aberration and exerts this performance. It is exclusively for monochromatic light in order to make it. Therefore, the detection light for detecting the reflected light image of the alignment mark on the semiconductor wafer also needs to be monochromatic light. However, there is a problem in that the reflected light causes interference due to the uneven coating of the photoresist around the alignment mark, and the detection signal is greatly disturbed when the alignment mark is detected.

An object of the present invention is to provide an optical exposure capable of easily forming an image of each wavelength at the same position when detecting an alignment mark on an object to be exposed using light of a plurality of wavelengths. To provide a method.

[0007]

In order to achieve the above-mentioned object, a light exposure method according to the present invention is a method in which an original image pattern is irradiated with monochromatic light from a light source, and an image of the original image pattern is projected with aberration correction for exposure. Project onto the object to be exposed through a lens, place the object to be exposed on a moving table, irradiate the alignment marks formed on the object with light of multiple wavelengths, and reflect the reflected light through the projection lens. In the light exposure method of detecting with a detector,
Each image point existing at a different position on the reflected light axis according to each wavelength of the reflected light is passed through a correction lens that corrects the image formation position of the reflected light provided between the projection lens and the detector. , A configuration in which an image is formed at a selected position on the reflected light axis, the movable table is positioned based on the signal of the detector corresponding to each wavelength of the reflected light, and the relative alignment between the original image pattern and the exposed object is performed. And

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the movable table 26 on which the semiconductor wafer (object to be exposed) 10 is mounted is driven by the drive motor 2
8 and 30 and can be moved in the X and Y directions indicated by the arrows in the figure by so-called step and repeat. The position of the moving table 26 is the laser measuring unit 32.
Is detected by The laser length measuring unit 32 guides the laser light emitted from the laser light source 34 to the interferometers 38 and 40 by, for example, a half mirror 36, and guides the laser light to the interferometers 38 and 40 by a calculator (not shown).
The positions of the X direction and the Y direction are calculated. The computer controls the drive motors 28 and 30 to move the movable table 26 to 0.05.
Positioning and control with accuracy of μm.

A reduction lens 14 which is a projection lens is disposed above the semiconductor wafer 10, and an original plate mounting table 42 is positioned above the reduction lens 14. The reticle (original image pattern) 16 can be fixedly arranged on the original plate mounting table 42. Then, the reticle 16 is irradiated with the light from the exposure illumination unit (light source) 44 via the condenser lens 46. The reticle 16 has reference windows 48, 5
0 is provided so that the irradiation light of the pattern detecting portions 52 and 54 can be irradiated to the alignment marks 12X and 12Y formed on the semiconductor wafer 10 through the reference windows 48 and 50. The pattern detection units 52 and 54 are
Pattern detectors 56 and 58, slits 60 and 6, respectively
2, collimators 64 and 66, correction lenses 68 and 70 for chromatic aberration correction, half mirrors 72 and 74, mirrors 76 and 7.
8 and the illuminators 80 and 82, and a detection slit (not shown) at the focal point of the collimator.

The operation of this embodiment is as follows. First, the semiconductor wafer 10 is placed on a predetermined position on the moving table 26, and the first reticle 16 is set on the original plate placing table 42. Then, the light emitted from the exposure illumination unit 44 is condensed by the condenser lens 46 and is applied to the reticle 16. The light transmitted through the reticle 16 is projected onto the semiconductor wafer 10 by the reduction lens 14, and the pattern of the reticle 16 is transferred onto the semiconductor wafer 10. After the first pattern of the reticle 16 is transferred onto the semiconductor wafer 10, the next reticle 16 is set on the original plate mounting table 42, and a new pattern is transferred onto the previous pattern transferred onto the semiconductor wafer 10. Are overlaid and transferred. When a new pattern is superposed and transferred onto the pattern ahead of this, the semiconductor wafer 10 and the reticle 16 are aligned in the following manner in order to align each pattern and to superimpose them accurately.

Illuminator 80 of pattern detectors 52 and 54,
The light emitted by 82 is guided to the reference windows 48, 50 through the half mirrors 72, 74 and the mirrors 76, 78. The light passing through the reference windows 48, 50 is formed on the semiconductor wafer 10 via the reduction lens 14. The aligned alignment marks 12X and 12Y are illuminated. Then, the light reflected by the alignment marks 12X and 12Y is guided again to the reticle 16 via the reduction lens 14 and forms an image on the reticle 16. The alignment marks 12X and 12Y formed on the reticle 16 are magnified to form mirrors 76 and 7.
8 and half mirrors 72 and 74 to correct lens 6
8 and 70, and forms an image on a detection slit (not shown).

As shown in FIG. 2, the images of the alignment marks formed through the correction lenses 68 and 70 are, for example, an e-line image shown by a solid line and a d-line image shown by a broken line. Form an image at the same position, that is, on the detection slit 20. The light forming the image of the alignment mark on the detection slit 20 is collimated by the collimators 64 and 66 and then formed into parallel rays on the slits 60 and 62, and detected by the pattern detectors 56 and 58. To be done. Then, the laser measuring unit 32 obtains the X and Y coordinates of the positions of the alignment marks 12X and 12Y on the semiconductor wafer 10.
The X and Y coordinates of the alignment marks 12X and 12Y are obtained for the two chips on the semiconductor wafer 10,
The relative error between the positions of the semiconductor wafer 10 and the reticle 16 is known, and the relative error is controlled by controlling the moving table 26.

As described above, in this embodiment, the correction lenses 68 and 70 are used to change the wavelengths, for example, the d line and the e line.
Since the reflected light image of the line alignment mark is formed at the same position, the influence of the reflected light due to the uneven coating of the photoresist on the semiconductor wafer 10 is reduced, and the position between the semiconductor wafer 10 and the reticle 16 is reduced. The matching can be performed quickly and easily. Moreover, in this embodiment, since the correction lenses 68 and 70 are simply inserted in the optical paths of the reflected light of the alignment marks 12X and 12Y, it is not necessary to provide a plurality of complicated optical systems, and the apparatus is simplified. Can be achieved.

In the above embodiment, the case where the d-line and the e-line are used as the detection rays for detecting the alignment marks 12X and 12Y has been described, but the detection rays are not limited to this. It is also possible to use monochromatic light having three or more different wavelengths. In the above embodiment, the case where the correction lenses 68 and 70 are placed immediately before the collimator has been described. However, the correction lenses 68 and 70 may be inserted anywhere between the collimators 64 and 66 and the reduction lens 14. May be.

[0015]

According to the present invention, the image of the alignment mark on the object to be exposed, which is obtained by light of a plurality of wavelengths, can be easily formed at a selected position. The influence of the interference of the reflected light due to the uneven coating of the photoresist can be reduced, and the position of the exposed body and the exposed body can be quickly and easily adjusted.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a light exposure apparatus according to the present invention.

FIG. 2 is an explanatory diagram of an image forming position of an alignment mark by a plurality of monochromatic lights having different wavelengths.

FIG. 3 is an explanatory diagram of a conventional image forming position of an alignment mark by a plurality of monochromatic lights having different wavelengths.

[Explanation of symbols]

 10 semiconductor wafer 12, 12X, 12Y alignment mark 14 reduction lens 16 reticle 26 moving table 32 laser measuring unit 44 exposure illumination unit 46 condenser lens 52, 54 pattern detection unit 56, 58 pattern detector 64, 66 collimator 68, 70 Correction lens 80, 82 Illuminator

Claims (1)

[Claims] 1. An original pattern is irradiated with monochromatic light from a light source, an image of the original pattern is projected onto an object to be exposed through a projection lens whose aberration is corrected for exposure, and the object to be exposed is mounted on a movable table. In the light exposure method of irradiating a plurality of wavelengths of light to the alignment mark formed on the exposed object, and detecting the reflected light with a detector via the projection lens, each wavelength of the reflected light The image points existing at different positions on the reflected light axis are reflected by the correction lens provided between the projection lens and the detector for correcting the image formation position of the reflected light. An image is formed at a selected position on the optical axis, the movable table is positioned based on the signal of the detector according to each wavelength of the reflected light, and the relative alignment between the original image pattern and the exposed object Light exposure method characterized by performing Law.