JPH0878320A - Projection type alignment method and apparatus - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A high-performance projection alignment method that can correct the effect of chromatic aberration due to the difference in wavelength between the exposure light and the alignment illumination light without degrading the alignment speed or accuracy, and its Provide a device. A second light receiving unit receives the light of a target mark 37 on a reference plate 25 provided on the substrate stage and the light of an alignment mark 12 formed on the mask in the light 11 having a wavelength substantially the same as the exposure light. 7-10 receives and detects, the alignment mark 12 on the mask and the target mark 37 are relatively aligned,
The alignment illumination light 31 in the aligned state
Is irradiated to the target mark 37, the reflected light from the target mark is received by the first light receiving means through the projection lens, and the position of the target mark that is detected is extracted as the reference position.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens type alignment method and apparatus for semiconductor exposure, and particularly to the case where alignment illumination light having a wavelength different from the exposure wavelength is used. The present invention relates to a hostile projection type alignment method and apparatus. 2. Description of the Related Art FIG. 1 shows a conventional example of an alignment apparatus for a reduction projection exposure apparatus using a reduction lens which is most often used in projection type semiconductor exposure apparatuses. In the reduction projection exposure apparatus, the pattern of the reticle 1 is exposed on the wafer 3 by 1 to several chips via the projection lens 2, and the exposure of the entire surface of the wafer is completed by step-and-repeat driving the wafer stage 4. However, it is necessary to align the reticle pattern with the wafer pattern. In this example, the reticle alignment optical system 5 sets the reticle to the initial position, and then the wafer alignment detection optical system aligns the reticle pattern and the wafer pattern via the reduction lens 2. The wafer alignment detection optical system includes a mirror 6, a relay lens 7, a magnifying lens 8, a movable slit 9, a photomultiplier tube 10, and an optical fiber 11 for emitting alignment illumination light. A window pattern 12 as shown in FIG. 2 is formed on the reticle 1, and an alignment mark 13 as shown in FIG. 3 is formed on the wafer 3. When these are irradiated with alignment illumination light having the same wavelength as the exposure light. A magnified image of the wafer pattern as shown in FIG. 4 is formed at the position of the movable slit 9. 14 is a window pattern image, 15
Is an image of the alignment mark. When this image is detected by the photomultiplier tube 10 while scanning the movable slit 9, a waveform such as 16 in FIG. 5 is obtained. From this, the center 17 of the window pattern and the center 18 of the alignment mark are obtained,
The amount of deviation Δ is fed back to the reticle or wafer fine movement device to perform alignment. However, with the miniaturization of semiconductor patterns, a change in the line width due to the reflected light in the underlayer and the resolution limit due to the step difference in the underlayer pose problems, and the multilayer resist and the light absorption layer are absorbed. Chemical resists have come to be used. These resists are used for exposure wavelength light (for example, i-line,
Since the h line and the g line do not reach the base, the alignment method cannot detect the alignment mark and changes the wavelength of the alignment illumination light (for example, e
Line, He-Ne line). FIG. 6 shows how the image formation position of the enlarged image of the wafer pattern changes due to chromatic aberration when the wafer side is fixed. Reference numeral 19 is an image forming position at the exposure wavelength, and 20 is an image forming position at the alignment illumination light having a wavelength different from the exposure wavelength. Usually, this difference in image formation position is several to several tens of millimeters, and in order to perform alignment with the conventional alignment detection optical system, the wafer side is lowered to the position 21 as shown in FIG. It is necessary to perform the alignment described above and return the wafer to the position of 22 again to perform exposure, which causes a problem in alignment speed and accuracy. In addition, in order to reduce the influence of chromatic aberration, there is an example in which the mirrors 23 and 24 are inserted to correct the optical path length as shown in FIG. 8, but there is a problem that the mounting accuracy of the mirror directly affects the alignment accuracy. Was there. In order to solve the above-mentioned problems of the prior art, an object of the present invention is to achieve a high performance capable of correcting the influence of chromatic aberration due to the wavelength difference between the exposure light and the alignment illumination light without deteriorating the alignment speed and accuracy. A projection type alignment method and apparatus therefor are provided. In order to achieve the above object, the present invention provides an alignment illumination light having a wavelength different from that of the exposure light formed on the substrate to be exposed installed on the substrate stage. The alignment mark is irradiated in a state of being stationary with respect to the mark, and the substrate stage is finely moved in the X and Y axis directions perpendicular to the optical axis of the projection lens so that the reflected light from the alignment mark passes through the projection lens. The position of the alignment mark received and detected by the first light receiving unit is aligned with the reference position, and the circuit pattern formed on the mask by the exposure light on the aligned substrate to be exposed is projected by the projection lens. In the projection type alignment method of exposing, the substrate in an image forming relationship by the projection lens with respect to light having substantially the same wavelength as the exposure light The light of the target mark on the reference plate provided on the stage and the light of the alignment mark formed on the mask are received and detected by the second light receiving means, and the substrate stage or the mask stage on which the mask is mounted. Is finely moved in the X and Y axis directions perpendicular to the optical axis of the projection lens to relatively align the alignment mark on the mask detected by the second light receiving means with the target mark, and The alignment illumination light, which is stationary with respect to the target mark in the aligned state, is applied to the target mark, and the reflected light from the target mark is received by the first light receiving means through the projection lens and detected. In the projection type alignment method, the position of the target mark is extracted as the reference position. Further, according to the present invention, alignment illumination light having a wavelength different from that of the exposure light is applied to the alignment mark formed on the substrate to be exposed mounted on the substrate stage in a stationary state. The position of the alignment mark, which is detected by slightly moving the substrate stage in the X and Y axis directions perpendicular to the optical axis of the projection lens and receiving the reflected light from the alignment mark through the projection lens by the first light receiving means, is determined. A projection type alignment apparatus that aligns a reference position and exposes a circuit pattern formed on the mask by the exposure light on the aligned substrate to be exposed by the projection lens, is provided on the substrate stage, In addition, the reference plate on which the target mark is formed and the projection lens are exposed to the light having the same wavelength as the exposure light. A second light receiving means for receiving and detecting the light of the target mark and the light of the alignment mark formed on the mask in an image forming relationship; and the substrate stage or the mask stage on which the mask is mounted. The alignment mark on the mask detected by the second light receiving means and the target mark are relatively aligned by finely moving in the X and Y axis directions perpendicular to the optical axis of the projection lens, and the alignment is performed. The target that is detected by irradiating the target mark with the alignment illumination light that is stationary with respect to the target mark, and receiving the reflected light from the target mark through the projection lens by the first light receiving means. A projection type alignment apparatus comprising: a reference position extracting unit that extracts a mark position as the reference position. That. Further, the invention is characterized in that, in the projection type alignment apparatus, the first light receiving means and the second light receiving means are constituted by different photoelectric conversion means arranged in an image forming relationship at a wavelength of each illumination light. And Further, the present invention, in the projection type alignment apparatus, has optical path length changing means for arranging the first light receiving means and the second light receiving means in an image forming relationship at a wavelength of each illumination light, and the same photoelectric conversion means is provided. It is characterized in that it is constituted by a conversion means. With the above structure, the reference position between the mask and the exposure light is extracted by using the target mark formed on the reference plate provided on the substrate stage on which the resist is not applied. Therefore, the alignment illumination light (wavelength different from the exposure wavelength (eg, g-line, h-line, i-line)) can be used to cope with the multilayer resist and the resist containing a light absorber which have been used due to the miniaturization of semiconductor patterns. For example, e-line, He-Ne line) is illuminated on an alignment mark formed on a substrate to be exposed such as a wafer,
Detecting the alignment mark through a projection lens to realize alignment of the substrate to be exposed with the reference position, and achieving alignment of the substrate to be exposed through the projection lens at extremely high speed and with high accuracy. You can Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 9 is an embodiment showing the basic configuration of the present invention. A wavelength selection mirror 26 that reflects only the light of the wavelength of the alignment illumination light (e.g., e-line, He-Ne line) is provided in the middle of the detection system, and the same wavelength as the exposure light from the fiber 11 (e.g., g-line, h-line). Line, i line), the pattern of the reticle 1 and the pattern of the reference plate 25 on the wafer stage 4 are mirror 6, relay lens 7, magnifying lens 8, and movable slit 9 which is reciprocally scanned as shown by an arrow. The detection optical system including the photomultiplier tube 10 obtains a detection waveform as shown in FIG. In this state, the reticle stage (not shown) on which the reticle 1 is mounted or the wafer stage 4 is finely moved to move the window pattern 12 on the reticle.
The center of the image of the target mark 37 on the reference plate 25 is aligned with the center of the image of the target mark 37 as shown in FIG. Here, the illumination light is switched to the original alignment illumination light (for example, e line, He-Ne line), and the fiber 31
More irradiation. The detection system of the relay lens 27, the magnifying lens 28, the movable slit 29, and the photomultiplier tube 30 via the wavelength selection mirror 26, the exposure wavelength (for example, g line, h line,
Since the image of the target mark 37 is formed on the movable slit 29 in accordance with the original optical path length of the alignment illumination light different from the i-line), the detection waveform of the photomultiplier tube 30 is the window pattern of the reticle. However, it is defocused due to chromatic aberration and is not detected, and only the target mark 37 is detected, resulting in the signal 32 shown in FIG. Reference numeral 32 is a detection waveform of the target mark 37, and 33 is a superposition of the detection waveform 16 from the window pattern 12 of the reticle shown in FIG. Reference numeral 34 is the center position (virtual origin) of the target mark 37. The center position 34 of the target mark 37 is set as the virtual origin, and the center position of the detected waveform detected from the alignment pattern of the wafer during the actual exposure thereafter is set as the virtual origin X, Y.
This is done by aligning with the reference position in the axial direction. Figure 11
Is a reference plate 25 provided on the wafer stage 4.
FIG. A transparent glass 36 having a target mark 37 made by etching chrome or aluminum is placed on a black light-absorbing plate 35. Light is reflected only at the target mark and light is absorbed at other portions. It is like this. The center of the detected waveform is obtained by the symmetric pattern matching method (Japanese Patent Laid-Open No. 53-69063), the peak detection method, the binarization center method, or the like. In the embodiment shown in FIG. 9, the apparatus becomes very large, so it is necessary to integrate the two detection optical systems. 12 to 14 show an embodiment in which a means having an optical path length difference correction function for each wavelength is provided in the optical path of the detection optical system. In FIG. 12, fiber 1
The target mark 37 of the reference plate 25 on the wafer stage 4 is imaged at the same 40 position as the window pattern on the reticle 1 with the illumination light having the same wavelength as the exposure light emitted through the half mirror 39 by 1. The image of the window pattern and the target mark is passed through the mirror 6 and the relay lens 7, and then passed through the optical path 47 for the exposure wavelength including the wavelength selection mirror 44, the mirror 45, and the wavelength selection mirror 46, and imaged again at the point 42. Then, an image is formed at a point 43 of the movable slit 9 through the magnifying lens 8 and the mirror 38, and is detected by the photomultiplier tube, the signal waveform shown in FIG. 5 is obtained. In addition,
The wavelength selection mirror 44 totally reflects only the original wavelength of the illumination light for alignment, while the wavelength selection mirror 46 totally reflects only the wavelength of the exposure light. Now, the reticle window pattern 12 is formed in this manner.
When the target mark 37 on the reference plate 25 is aligned, the original alignment illumination light is reflected by the fiber 11. Due to the chromatic aberration of the projection lens (reduction projection lens), the image formation position of the target mark moves from point 40 to point 41. Therefore, since the image formation position by the relay lens 7 is also displaced, after being branched by the wavelength selection mirror 44, the optical path length difference is corrected by the mirror 48 and the optical path 50 via the filter 49 that absorbs the light of the exposure wavelength. When it is returned to the original position by the wavelength selection mirror 46, an image is formed at the point 42, and it becomes possible to detect with the same detection optical system. FIG.
3 is also similar to FIG. 12, instead of the wavelength selection mirror,
The prisms 51 and 52 are used. 12 and 1
3, since the optical path length is corrected after the relay lens 7, the magnification of the detection optical system varies depending on the wavelength, but there is no problem if the zero loop closed loop control is performed until the alignment is adjusted to the virtual origin. . In the embodiments shown in FIGS. 9 to 14, the original alignment illumination is also performed from the reticle side. However, when the wavelength of the alignment illumination light and the exposure wavelength are different, reticle illumination is not necessary. An oblique illumination method such as 15 may be used. Reference numeral 53 is a fiber, and 54 is a condenser lens. In this case, since scattered light from the edge of the pattern is detected, the detected waveform is as shown by 55 in FIG. 33 is a superposition of the detection waveforms of FIG. As an alignment system, a system in which an alignment device is placed under a reticle is also considered. FIG. 17 shows an example of this system. On the reticle, as shown at 59 in FIG. 18, a light shielding pattern opposite to the window pattern is provided. Light from the wafer or the reference plate on the wafer stage 4 is reflected by the light shielding pattern. Reference pattern 5 on wafer stage 4
The structure of No. 8 is shown in FIG. The reference plate is transparent glass 3
6 and a target mark 37 formed by etching chromium or aluminum. In the determination of the virtual origin at the exposure wavelength, the reflectance of the light blocking pattern 59 of the reticle is low,
In order to obtain a sufficient amount of light, as shown in FIG. 19, transmission illumination is performed from below the reference plate by the fiber 56 and the lens 57. Since only the light that hits the light shielding pattern 59 is reflected and enters the detection optical system, the detection waveform is as shown in FIG.
It becomes like 61 shown in. In FIG. 17, 6 is a mirror, 7 is a relay lens, 8 is a magnifying lens, and 60 is a linear sensor provided in place of the movable slit and the photomultiplier tube. Reference numerals 51 and 52 are prisms for correcting the optical path length difference. After obtaining the virtual origin in this way, the original alignment illumination is performed by the fiber 53 and the condenser lens 54. According to the present invention, the reference position with respect to the mask by the exposure light is set by using the target mark formed on the reference plate provided on the substrate stage on which the resist is not applied. Since the extraction is performed, the alignment of the wavelength different from the exposure wavelength (for example, g-line, h-line, i-line) can be applied so that it can be applied to the multi-layer resist and the resist containing the light absorber which are used due to the miniaturization of the semiconductor pattern. Illumination light (for example, e-line or He-Ne line) is made to stand on a substrate to be exposed such as a wafer to illuminate the alignment mark formed on the substrate to be exposed, and the alignment mark is passed through the projection lens. It is possible to detect and align the substrate to be exposed to the reference position, and to align the substrate to be exposed at a very high speed and with high accuracy. The effect of being able to realize the component through the projection lens is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a conventional alignment system. FIG. 2 is a diagram showing an alignment pattern of a reticle. FIG. 3 is a diagram showing alignment marks on a wafer. FIG. 4 is a diagram showing an imaging pattern at a movable slit position. 5 is a diagram showing a detection signal detected from the pattern shown in FIG. FIG. 6 is a side view showing an optical system including an alignment system. FIG. 7 is a side view showing an optical system including an alignment system. FIG. 8 is a side view showing an optical system including an alignment system. FIG. 9 is a perspective view showing an alignment system according to the present invention. FIG. 10 is a diagram showing a detection signal waveform according to the present invention. FIG. 11 is a perspective view showing a reference plate. FIG. 12 is a side view showing an optical system including an alignment system according to the present invention. FIG. 13 is a side view showing an optical system including an alignment system according to the present invention. FIG. 14 is a side view showing an optical system including an alignment system according to the present invention. FIG. 15 is a side view showing an optical system including an alignment system according to the present invention. 16 is a diagram showing a detection signal waveform when illuminated by the method shown in FIG. FIG. 17 is a side view showing an optical system including another alignment system according to the present invention. FIG. 18 is a diagram showing an alignment pattern on a reticle according to the present invention. FIG. 19 is a diagram showing a reference plate and its optical system. 20 is a diagram showing a detection signal waveform when illuminated as shown in FIG. [Explanation of Codes] 1 ... Reticle, 2 ... Projection lens, 3 ... Wafer, 4 ... Wafer stage 4 ... Mirror, 7 ... Relay lens, 8 ... Magnifying lens, 9,
29 ... Movable slits 10, 30 ... Photomultiplier tubes, 11, 31 ... Illumination fiber, 12 ... Window pattern 13 ... Alignment pattern, 25 ... Reference plate, 3
6 ... Glass substrate 37 ... Target mark

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G03F 9/00 H (72) Inventor Toshihiko Nakata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Manufacturing Technology In-house (72) Inventor Yukio Utsu 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock Company, Hitachi Ltd.

Claims (1)

[Claims] 1. The alignment illumination light having a wavelength different from that of the exposure light is applied to the alignment mark formed on the substrate to be exposed installed on the substrate stage in a stationary state, and the alignment mark is irradiated to the substrate stage of the projection lens. The position of the alignment mark detected by receiving the reflected light from the alignment mark by the first light receiving means through the projection lens by finely moving it in the X and Y axis directions perpendicular to the optical axis is aligned with the reference position, In a projection type alignment method of exposing a circuit pattern formed on a mask by the exposure light on the aligned substrate to be exposed by the projection lens, an image is formed by the projection lens on light having substantially the same wavelength as the exposure light. Formed on the mask and the light of the target mark on the reference plate provided on the related substrate stage The light of the formed alignment mark is received and detected by the second light receiving means, and the substrate stage or the mask stage on which the mask is mounted is finely moved in the X and Y axis directions perpendicular to the optical axis of the projection lens. The alignment mark on the mask detected by the second light receiving means and the target mark are relatively aligned,
The alignment illumination light, which is stationary with respect to the target mark in the aligned state, is applied to the target mark, and reflected light from the target mark is received by the first light receiving means through the projection lens and detected. The projection alignment method, wherein the position of the target mark to be extracted is extracted as the reference position. 2. The alignment illumination light having a wavelength different from that of the exposure light is applied to the alignment mark formed on the substrate to be exposed installed on the substrate stage in a stationary state, and the alignment mark is irradiated to the substrate stage of the projection lens. The position of the alignment mark detected by receiving the reflected light from the alignment mark by the first light receiving means through the projection lens by finely moving it in the X and Y axis directions perpendicular to the optical axis is aligned with the reference position, In a projection type alignment apparatus that exposes a circuit pattern formed on a mask by the exposure light on an aligned substrate to be exposed by the projection lens, a reference plate provided on the substrate stage and having a target mark formed thereon And the target which is in an image-forming relationship by the projection lens with respect to the light having substantially the same wavelength as the exposure light. Second light receiving means for receiving and detecting the light of the dot mark and the light of the alignment mark formed on the mask, and the substrate stage or the mask stage on which the mask is mounted are perpendicular to the optical axis of the projection lens. The alignment mark on the mask detected by the second light receiving means and the target mark are relatively aligned by finely moving in the X and Y axis directions, and in the aligned state, with respect to the target mark. The target mark is irradiated with the stationary alignment illumination light and the reflected light from the target mark is received by the first light receiving means through the projection lens, and the target mark position is detected as the reference position. A projection type alignment apparatus comprising: a reference position extracting means for extracting. 3. The projection according to claim 2, characterized in that the first light receiving means and the second light receiving means are constituted by different photoelectric conversion means arranged in an image forming relationship at each wavelength of the illumination light. Type alignment device. 4. The first light receiving means and the second light receiving means have an optical path length changing means for arranging in an image forming relationship at the wavelength of each illumination light, and are configured by the same photoelectric conversion means. The projection type alignment apparatus according to the second item.