JP2004228215A - Aligner, alignment method, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner for attaining highly precise alignment by contriving improvement of superposition precision, and also to provide an alignment method and a semiconductor device. <P>SOLUTION: In a constant temperature chamber 10, a lighting system 11 is provided as well, and a reticle stage 13 which holds a reticle 12 that is a photo mask for alignment, a projection optical system 14, an alignment system 15 and a shutter 16 that is interlocked with it, a wafer stage 17 for holding a semiconductor substrate Waf, and a stage position measuring system 18 are provided. The alignment system 15 uses the alignment light whose wavelength is identical with an exposure light. With a TTL method that uses the projection optical system 14, a mark MK for alignment that is directly provided on the semiconductor substrate Waf is detected. The alignment mark MK is deployed in the region other than actual element, for example, in a scribe region between chips. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to semiconductor device manufacturing, and more particularly to an exposure apparatus and an exposure control method in a manufacturing line that repeatedly and sequentially exposes a pattern of an integrated circuit on a semiconductor substrate.
[0002]
[Prior art]
Circuit patterns required for LSI manufacturing are sequentially exposed on a semiconductor wafer by a plurality of photomask (reticle) patterns. For example, a reduction projection exposure apparatus (not shown) in which a predetermined reticle is set projects and exposes a pattern repeatedly while shifting the projection target area on the wafer one after another (step-and-repeat method). Alternatively, the reticle and the wafer are synchronously scanned with respect to the projection optical system, and the pattern is repeatedly projected and exposed (step-and-scan method). As a result, a predetermined number of integrated circuit chip areas are obtained in the semiconductor wafer.
[0003]
A plurality of pattern exposures are performed on one area of the integrated circuit chip area. Therefore, the overlay accuracy of the exposure processing greatly depends on the alignment accuracy. For example, three alignment techniques are described below.
FIG. 3A shows a TTL (Through the Lens) system in which alignment light having a wavelength different from the exposure wavelength passes through a projection lens. As the alignment light, a light source to which the photoresist is not exposed, such as a He-Ne laser, is used. Thus, alignment (alignment) is performed according to the alignment marks existing in the scribe line area of the wafer.
FIG. 3B shows the TTL method, but alignment is performed at the same wavelength as the exposure wavelength. Therefore, the alignment detection with the reference mark on the wafer stage is performed so as not to expose the photoresist on the wafer. After that, the wafer is moved to the exposure position depending on the stage accuracy. The amount of movement to the wafer is called a baseline, and greatly depends on the overlay accuracy.
FIG. 3C shows an off-axis system. The alignment light does not pass through the projection lens, but uses an alignment microscope provided separately from the projection lens to position the wafer, and moves the wafer to the exposure position depending on the stage accuracy.
[0004]
In the configuration shown in FIG. 3A, the alignment light has a different wavelength from the exposure light. Therefore, when higher-precision alignment is required, there is a concern about an alignment shift due to a wavelength difference.
The configuration shown in FIG. 2B has a problem that the degree of alignment shift varies depending on the accuracy of the relative position due to a large base line, a stage movement error, an alignment error of each chip area in the wafer, and the like.
In the configuration shown in FIG. 3C, the exposure light does not pass through the projection lens, so that the baseline fluctuation due to the fluctuation of the projection lens cannot be absorbed. Therefore, when higher-precision alignment is required, there is a concern about misalignment during actual exposure.
[0005]
[Problems to be solved by the invention]
As described above, in the conventional alignment, when higher-precision alignment is required, there is a possibility that the misalignment cannot be ignored.
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to provide an exposure apparatus, an alignment method, and a semiconductor device that improve overlay accuracy and realize high-accuracy alignment.
[0006]
[Means for Solving the Problems]
An exposure apparatus according to the present invention includes a projection optical system that irradiates exposure light and projects a pattern image of a photomask onto a photosensitive coating layer on a substrate, and the photosensitive optical system in a plane perpendicular to an optical axis of the projection optical system. A stage mechanism for moving the substrate provided with the coating layer, a stage position measuring system for measuring the amount of movement of the stage mechanism, and a mark for alignment provided in a predetermined area on the substrate, the same as the exposure light. An alignment system that irradiates an alignment light having a wavelength, and a shutter that is close to the upper part of the photomask, opens at the time of alignment at least in accordance with control of the alignment system, allows the alignment light to pass therethrough, and closes otherwise. Features.
[0007]
According to the exposure apparatus of the present invention, the alignment light has the same wavelength as the exposure light, and the problem of misalignment due to the wavelength difference is eliminated. Further, since the alignment is performed directly using the alignment marks provided on the substrate, the relative position of the stage mechanism can be easily grasped, and the misalignment is greatly reduced.
[0008]
In the above-described exposure apparatus according to the present invention, the shutter controls irradiation / shielding of a predetermined alignment mark with alignment light in a region having an alignment mark outside the actual element pattern region of the photomask. If the position of the predetermined alignment mark changes, the area where the shutter opens needs to be changed accordingly.
[0009]
In the above-described exposure apparatus according to the present invention, the illumination of the exposure light and the alignment light share a light source, and the illumination of the exposure light is limited to a predetermined area during alignment. Alternatively, in the above-described exposure apparatus according to the present invention, the illumination of the exposure light and the alignment light have different light sources.
[0010]
An alignment method in an exposure apparatus according to the present invention relates to an alignment for projecting a pattern image of a photomask irradiated with exposure light onto a predetermined region of a photosensitive coating layer on a substrate, and outside the actual element region on the substrate. A mark for positioning is provided, and the mark for positioning is irradiated with alignment light having the same wavelength as the exposure light.
[0011]
According to the alignment method in the exposure apparatus according to the present invention, the alignment is performed using the alignment light having the same wavelength as the alignment exposure light immediately before the exposure processing. Since alignment light having the same wavelength as the alignment exposure light is used, a mark for positioning is provided outside the actual element region on the substrate, and the mark is aligned with the mark.
[0012]
A semiconductor device according to the present invention is manufactured using the exposure apparatus according to any of the above-described aspects of the present invention or the alignment method in the exposure apparatus.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic view showing a main configuration of an exposure apparatus according to the first embodiment of the present invention. In the constant temperature chamber 10, an illuminating system 11 is provided in parallel, and holds a reticle stage 13, which holds and positions a reticle 12, which is a photomask, a projection optical system 14, an alignment system 15, a shutter 16 interlocked therewith, and a semiconductor substrate Waf. A wafer stage 17 and a stage position measuring system 18 are provided. With such a configuration, the resist applied on the semiconductor substrate Waf can be sequentially subjected to exposure processing according to the reticle pattern for each chip region. The display unit 19 is installed at a place where the operator can operate, and can perform various input / output operations such as recipes and various monitors.
[0014]
The alignment system 15 according to this embodiment and the shutter 16 interlocked with the alignment system 15 will be described. The alignment system 15 uses alignment light having the same wavelength as the exposure light. Further, the alignment mark MK provided directly on the semiconductor substrate Waf is detected by the TTL method via the projection optical system 14. The alignment mark MK is arranged, for example, outside the actual element area, for example, in a scribe area between chips.
[0015]
The shutter 16 is close to the upper part of the reticle 12, a necessary area is opened only at the time of alignment according to the control of the alignment system 15, an alignment light is transmitted, and the other parts are closed. At the time of exposure, a necessary area for transferring another alignment mark on the reticle 12 may be opened. That is, the shutter 16 controls irradiation / shielding of alignment light on predetermined alignment marks in an area having alignment marks outside the actual element pattern area of the reticle 12.
[0016]
Here, the alignment light shares the light source of the exposure light in the exposure illumination. The exposure light may be a mercury lamp bright line (i-line (wavelength: 365 nm), g-line (436 nm), KrF excimer laser light (248 nm), or ArF excimer laser light (189 nm). The exposure light is limited to a predetermined alignment region by controlling a blind or the like (not shown) inside the system 11. Further, the shutter 16 may be configured to cover the actual element pattern of the reticle 12 (broken line 161). In the case of actual exposure, the shutter 161 retreats to the position above the light-shielding band 121 of the reticle 12, and does not hinder the exposure of the actual element pattern of the reticle 12. Needless to say, a necessary area of the shutter 16 is opened for transferring a predetermined alignment mark. You may.
[0017]
According to the exposure apparatus of the above embodiment, at the stage immediately before projecting the pattern image of the reticle 12 illuminated with the exposure light onto a predetermined region of the photoresist layer on the semiconductor substrate Waf, the alignment light having the same wavelength as the alignment exposure light is used. Alignment is performed using. As a result, the concern of misalignment due to the wavelength difference is eliminated. In addition, since the alignment is performed directly using the alignment marks provided on the substrate, the baseline is small, and the relative position in the stage position measurement system 18 can be easily grasped. As a result, misalignment is greatly reduced.
[0018]
FIG. 2 is a schematic view showing a main configuration of an exposure apparatus according to a second embodiment of the present invention. The same parts as those in the first embodiment will be described with the same reference numerals. In the constant temperature chamber 10, an illumination system 11 is provided in parallel, and holds a reticle stage 13, which holds and positions a reticle 12, which is a photomask, a projection optical system 14, an alignment system 25, a shutter 26 interlocked therewith, and a semiconductor substrate Waf. A wafer stage 17 and a stage position measuring system 18 are provided. With such a configuration, the resist applied on the semiconductor substrate Waf can be sequentially subjected to exposure processing according to the reticle pattern for each chip region. The display unit 19 is installed at a place where the operator can operate, and can perform various input / output operations such as recipes and various monitors.
[0019]
An alignment system 25 according to this embodiment and a shutter 26 interlocked with the alignment system 25 will be described. The alignment system 25 detects alignment marks MK directly provided on the semiconductor substrate Waf by the TTL method using alignment light having the same wavelength as the exposure light, as in the first embodiment. The alignment mark MK is arranged, for example, outside the actual element area, for example, in a scribe area between chips. The shutter 26 controls the alignment light from the alignment light source 251 which is close to the upper part of the reticle 12 and is provided separately from the exposure light source.
[0020]
The shutter 26 opens at a necessary area only at the time of alignment according to the control of the alignment system 25 and allows the alignment light to pass therethrough, and closes the other areas. At the time of exposure, a necessary area for transferring another alignment mark on the reticle 12 may be opened. Further, the shutter 26 may be configured to cover the actual element pattern of the reticle 12 (broken line 261). In this case, at the time of actual exposure, the shutter 261 is retracted to the position above the light-shielding band 121 of the reticle 12, and does not hinder exposure of the reticle 12 to the actual element pattern. Needless to say, a necessary area of the shutter 26 may be opened for transfer of a predetermined alignment mark. That is, the shutter 26 controls irradiation / shielding of alignment light to a predetermined alignment mark in a region having the alignment mark outside the actual element pattern region of the reticle 12. When the alignment light source 251 is small, the accuracy is further improved if the alignment light source 251 is moved according to the opening of the shutter 26.
[0021]
In the exposure apparatus according to the above-described embodiment, the alignment light having the same wavelength as the alignment exposure light is emitted immediately before projecting the pattern image of the reticle 12 illuminated with the exposure light onto a predetermined region of the photoresist layer on the semiconductor substrate Waf. Alignment is performed using As a result, the concern of misalignment due to the wavelength difference is eliminated. In addition, since the alignment is performed directly using the alignment marks provided on the substrate, the baseline is small, and the relative position in the stage position measurement system 18 can be easily grasped. As a result, misalignment is greatly reduced.
[0022]
As described above, according to the present invention, the alignment light has the same wavelength as that of the exposure light, and the problem of misalignment due to the wavelength difference is eliminated. Further, since the alignment is performed directly using the alignment marks provided on the substrate, the relative position of the stage mechanism can be easily grasped, and the misalignment is greatly reduced. As a result, it is possible to provide an exposure apparatus, an alignment method, and a semiconductor device which realize high-accuracy alignment by improving the overlay accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a main part of an exposure apparatus according to a first embodiment.
FIG. 2 is an outline view showing a configuration of a main part of an exposure apparatus according to a second embodiment.
FIGS. 3A and 3B are conceptual views showing alignment techniques of a conventional exposure apparatus.
[Explanation of symbols]
Reference Signs List 10: constant temperature chamber, 11: illumination system, 12: reticle, 13: reticle stage, 14: projection optical system, 15, 25: alignment system, 16, 26: shutter, 17: wafer stage, 18: stage position measurement system, 19: display unit, MK: alignment mark, Waf: substrate.

Claims (7)

A projection optical system that illuminates the exposure light and projects a pattern image of the photomask onto a photosensitive coating layer on the substrate,
A stage mechanism for moving the substrate provided with the photosensitive coating layer in a plane perpendicular to the optical axis of the projection optical system,
A stage position measuring system for measuring a movement amount in the stage mechanism,
An alignment system that irradiates alignment light having the same wavelength as the exposure light to a positioning mark provided in a predetermined region on the substrate,
A shutter that is close to the upper portion of the photomask, opens only at the time of alignment according to the control of the alignment system, passes alignment light, and otherwise closes;
An exposure apparatus comprising: 2. The exposure apparatus according to claim 1, wherein the shutter controls irradiation / shielding of a predetermined alignment mark with alignment light in an area having an alignment mark outside the actual element pattern area of the photomask. 3. 3. The exposure apparatus according to claim 1, wherein a light source is shared between the illumination of the exposure light and the alignment light, and the illumination of the exposure light is limited to a predetermined area during alignment. 3. The exposure apparatus according to claim 1, wherein the illumination light of the exposure light and the alignment light have different light sources. Regarding alignment for projecting a pattern image of a photomask illuminated with exposure light onto a predetermined region of a photosensitive coating layer on a substrate, alignment marks are provided outside the actual element region on the substrate, and the alignment mark is provided. An alignment method in an exposure apparatus, wherein alignment marks are irradiated with alignment light having the same wavelength as the exposure light. A semiconductor device manufactured using the exposure apparatus according to claim 1. A semiconductor device manufactured by using the alignment method in the exposure apparatus according to claim 5.

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