JP2004128307A - Aligner and its adjustment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute the assembly of a device and the adjustment of a mirror group highly accurately in a short time. <P>SOLUTION: Inside a projection optical system lens barrel 20, a preceding stage mirror group (mirrors M1-M3) and a post stage mirror group (mirrors M4-M6) are incorporated in front and at the back of an intermediate image forming position P. The lens barrel 20 is divided into a preceding stage optical lens barrel 21 incorporating and housing the preceding stage mirror group and a post stage optical lens barrel 31 incorporating and housing the post stage mirror group, wave front aberration can be measured at the intermediate image forming position P and a space image can be formed as well. Thus, an optical performance is confirmed/adjusted in each mirror group. At the time, since the number of constituting mirrors of each mirror group is small, the mirror which is the cause of accuracy defect is easily searched. Then, after a sufficient performance is obtained in each mirror group, a projection optical system is assembled and the whole is adjusted. As a result, the device is assembled/adjusted efficiently in a short time. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure apparatus that uses EUV light (Extreme Ultra Violet light: extreme ultraviolet light) and a method of adjusting the same. In particular, the present invention relates to an exposure apparatus that can perform assembly of an apparatus and adjustment of a mirror group in a shorter time and with higher accuracy, and an adjustment method thereof.
[0002]
[Background Art]
In recent years, with the miniaturization of semiconductor integrated circuits, a projection lithography technique using EUV light having a wavelength of about 13 nm has been developed in order to improve the resolution of an optical system limited by the diffraction limit of light. In an exposure apparatus using such EUV light, a reflection optical system combining a reflection mirror is generally used. One example of an optical system includes four or six EUV reflecting mirrors coated with a multilayer film. These reflecting mirrors match the phase of the reflected light at each interface of the multilayer film, and realize a high reflectance by an interference effect.
[0003]
Hereinafter, an example of an EUV exposure apparatus will be described with reference to FIG.
FIG. 3 is a schematic configuration diagram illustrating an example (a four-projection system) of the EUV exposure apparatus.
The EUV exposure apparatus shown in FIG. 3 includes an illumination system IL including a light source. EUV light (generally, a wavelength of 5 to 20 nm is used, and specifically, a wavelength of 13 nm or 11 nm is used) emitted from the illumination system IL is reflected by the turning mirror 1 and irradiated on the reticle 2.
[0004]
The reticle 2 is held on a reticle stage 3. The reticle stage 3 has a stroke of 100 mm or more in the scanning direction (Y axis), has a minute stroke in the direction (X axis) orthogonal to the scanning direction in the reticle plane, and has a minute stroke in the optical axis direction (Z axis). Have a stroke. The position in the XY directions is monitored with high precision by a laser interferometer (not shown), and the position in the Z direction is monitored by a reticle focus sensor including a reticle focus light transmitting system 4 and a reticle focus light receiving system 5.
[0005]
The EUV light reflected by the reticle 2 enters the lower optical barrel 14 in the figure. The EUV light includes information on a circuit pattern drawn on the reticle 2. The reticle 2 is formed with a multilayer film (for example, Mo / Si or Mo / Be) that reflects EUV light, and is patterned with or without an absorption layer (for example, Ni or Al) on the multilayer film.
[0006]
The EUV light that has entered the optical barrel 14 is reflected by the first mirror 6, then sequentially reflected by the second mirror 7, the third mirror 8, and the fourth mirror 9, and finally is perpendicular to the wafer 10. Incident on. The reduction magnification of the projection system is, for example, 1/4 or 1/5. In this figure, there are four mirrors. A. It is effective to increase the number of mirrors to six or eight in order to further increase. An off-axis microscope 15 for alignment is arranged near the lens barrel 14.
[0007]
The wafer 10 is placed on a wafer stage 11. The wafer stage 11 can freely move in a plane (XY plane) orthogonal to the optical axis, and has a stroke of, for example, 300 to 400 mm. The wafer stage 11 can move up and down a minute stroke in the optical axis direction (Z axis), and the position in the Z direction is monitored by a wafer focus sensor including a wafer autofocus light transmitting system 12 and a wafer autofocus light receiving system 13. ing. The position of the wafer stage 11 in the XY directions is monitored with high precision by a laser interferometer (not shown). In the exposure operation, the reticle stage 3 and the wafer stage 11 perform synchronous scanning at the same speed ratio as the reduction ratio of the projection system, that is, at 4: 1 or 5: 1.
[0008]
[Problems to be solved by the invention]
The EUV exposure apparatus shown in FIG. 3 includes a four-projection system composed of four mirrors. A. It is known that it is effective to increase the number of mirrors to 6 or 8 in order to further increase the (numerical aperture). More specifically, the N.I. A. Is 0.18 to 0.20, and N.I. A. Is set to 0.25 or more.
[0009]
In the projection optical system of EUV exposure equipment, it is necessary to secure a wide exposure field while minimizing the wavefront aberration and minimizing the number of reflecting mirrors in order to accurately transfer a fine circuit pattern. Is done. As an example, numerical values are required for the wavefront aberration of the projection optical system of the EUV exposure apparatus to be 1 nm or less in rms or 0.5 nm or less. However, it is very difficult to assemble and adjust a projection optical system having six or eight mirrors to satisfy such ultra-high precision wavefront aberration.
[0010]
At present, a method has been considered in which six or eight mirrors are held in an optical barrel while illuminating the outer shape or reference mark using a three-dimensional coordinate measuring device or the like. However, according to this method, when the wavefront aberration of the entire projection optical system is poor, it is difficult to specify which of the plurality of mirrors causes the deterioration of the wavefront aberration. In addition, when an interferometer having a narrow capture range (measurable range) such as a PDI (Point Difference Interferometer) is used, it may be impossible to measure the wavefront itself.
[0011]
The present invention has been made in view of such a problem, and an object of the present invention is to provide an exposure apparatus capable of performing assembly of an apparatus and adjustment of a mirror group in a shorter time and with higher accuracy, and an adjustment method thereof. Aim.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, an exposure apparatus according to the present invention includes a light source that emits EUV light, an illumination optical system that adjusts and shapes the EUV light emitted from the light source and applies the adjusted light to a reticle, and mounts the reticle. A reticle stage for moving and positioning the same; a projection optical system for projecting EUV light reflected from the reticle onto a sensitive substrate; a sensitive substrate stage for mounting and moving and positioning the sensitive substrate; An optical lens barrel that houses a plurality of mirror groups (a front mirror group and a rear mirror group) arranged before and after an intermediate imaging position, respectively. The optical lens barrel is characterized in that the optical lens barrel is divided into a front optical lens barrel and a rear optical lens barrel that incorporate and house the front mirror group or the rear mirror group.
[0013]
According to the present invention, the front mirror group and the rear mirror group before and after the intermediate imaging position are accommodated in the divided front optical barrel and the rear optical barrel, respectively, so that the wavefront aberration is reduced at the intermediate imaging position. It can measure and form an aerial image. Therefore, the confirmation and adjustment of the optical performance can be performed in each mirror group. At this time, since the number of constituent mirrors in each mirror group is small, it is easy to search for a mirror that causes the accuracy failure. Then, after sufficient performance is obtained in each mirror group, the entire adjustment is performed by assembling the projection optical system. As a result, the apparatus can be efficiently assembled and adjusted in a short time.
[0014]
In the exposure apparatus of the present invention, each of the mirror groups is adjusted independently after incorporating the front-stage mirror group into the front-stage optical barrel and incorporating the rear-stage mirror group into the rear-stage optical barrel. Comprehensive adjustment may be performed after the optical barrel is integrated.
[0015]
An adjustment method of an exposure apparatus according to the present invention includes a light source that emits EUV light, an illumination optical system that adjusts and shapes the EUV light emitted from the light source and applies the adjusted light to a reticle, and is disposed before and after an intermediate imaging position. A projection optical system having a plurality of mirror groups (a front mirror group and a rear mirror group) for projecting EUV light reflected from the reticle onto a sensitive substrate; and the front mirror group or the rear mirror of the projection optical system. A method for adjusting an exposure apparatus, comprising: a first-stage optical barrel and a second-stage optical barrel divided into a first-stage optical barrel, wherein the first-stage mirror group is incorporated in the first-stage optical barrel, and It is characterized in that after the mirror groups are assembled in the rear optical barrel, each mirror group is adjusted independently, and then the overall adjustment is performed after integrating the two optical barrels.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating a configuration example of an optical barrel of an EUV exposure apparatus according to a first embodiment of the present invention.
FIG. 1 shows a projection optical system lens barrel 20 of the EUV exposure apparatus. A reflection reticle (reference numeral 2 in FIG. 3) and an illumination optical system (reference numeral IL in FIG. 3) are arranged upstream (upper side in the figure) of the lens barrel 20. On the other hand, a wafer (sensitive substrate, reference numeral 10 in FIG. 3) is disposed downstream (downward in the figure) of the lens barrel 20. EUV light emitted from the light source (see the dashed line in FIG. 1) is adjusted and shaped by the illumination optical system, hits the reticle on the reticle stage, is introduced into the lens barrel 20, and is projected on the sensitive substrate. .
[0017]
In the projection optical system lens barrel 20 of FIG. 1, a total of six mirrors M1 to M6 are incorporated. The EUV light guided into the lens barrel 20 sequentially impinges on the mirrors M1 to M6, is reflected, and reaches the downstream sensitive substrate. These mirrors M1 to M6 are four mirrors M1 to M4 (front mirror group) on the upstream side (upstream side) and two mirrors M5 on the downstream side (downstream side) with the intermediate imaging position P as a boundary. , M6 (post-mirror group). The projection optical system barrel 20 is divided into a front optical barrel 21 and a rear optical barrel 31 around the vicinity of the intermediate imaging position P. These lens barrels 21 and 31 are cylindrical bodies formed to have the same inner and outer diameters. Four mirrors M <b> 1 to M <b> 4 forming a front mirror group are arranged in the front optical barrel 21. On the other hand, in the rear optical barrel 31, two mirrors M5 and M6 forming a rear mirror group are arranged.
[0018]
The front mirror group will be described in detail.
The mirror M1 is an asymmetric concave mirror. The mirror M1 is attached to the lower member 22 of the front optical barrel 21 with the reflection surface facing upward. The mirror M1 is provided with a fine adjustment mechanism C1.
The mirror M2 is also an asymmetric concave mirror. The mirror M2 is attached to the upper member 23 of the front optical barrel 21 with the reflection surface facing downward. The mirror M2 is provided with a fine adjustment mechanism C2.
[0019]
The mirror M3 is a symmetric convex mirror. The mirror M3 is attached to the intermediate member 24 of the front optical barrel 21 with the reflection surface facing upward. The mirror M3 is provided with a fine adjustment mechanism C3.
The mirror M4 is an asymmetric concave mirror. The mirror M4 is attached to the upper member 23 of the front optical barrel 21 with the reflection surface facing downward, and is arranged on the left side of the mirror M2 in the drawing. The mirror M4 is provided with a fine adjustment mechanism C4.
[0020]
In the front optical barrel 21, an opening 23a for introducing EUV light is formed on the right side of the upper member 23 in the figure (on the right side of the mirror M2). Further, an opening 25a is also formed in the intermediate member 24 of the front optical barrel 21. In the intermediate member 24, openings 24a and 24b through which EUV light passes are formed on the right side of the mirror M3. Further, an opening 22a for introducing EUV light to the rear optical column 31 is formed on the left side of the lower member 22 of the front optical column 21 in the figure (left side of the mirror M1).
[0021]
The rear mirror group will be described in detail.
The mirror M5 is a symmetric convex mirror. The mirror M5 is attached to the lower member 32 of the rear optical barrel 31 with the reflection surface facing upward. The mirror M5 is provided with a fine adjustment mechanism C5. An opening 32a for guiding EUV light to the downstream sensitive substrate is formed in the lower member 32 on the right side of the mirror M5 in the drawing.
[0022]
Mirror M6 is a symmetric concave mirror. The mirror M6 is attached to the upper member 33 of the rear optical barrel 31 with the reflection surface facing downward. The mirror M6 is provided with a fine adjustment mechanism C6. An opening 33a for introducing EUV light from the front optical barrel 21 is formed in the upper member 33 on the left side of the mirror M6 in the drawing.
[0023]
Outside the boundary between the front optical barrel 21 and the rear optical barrel 31, a connecting mechanism 30 for connecting the two optical barrels is provided. In the connection state of the two lens barrels 21 and 31 shown in FIG. 1, a point indicated by P in the figure is an intermediate imaging position of EUV light. When the two lens barrels 21 and 31 are connected, the wavefront aberration can be measured at the intermediate imaging position P and an aerial image can be formed, so that the apparatus can be efficiently assembled and adjusted in a shorter time.
As a method of measuring the wavefront aberration, for example, a method described in US Pat. No. 6,307,635B1 (Goldberg) can be used.
[0024]
In such a projection optical system lens barrel 20, a front mirror group and a rear mirror group before and after the intermediate imaging position P are incorporated and accommodated in the divided front optical barrel 21 and rear optical barrel 31, respectively. Therefore, the wavefront aberration can be measured at the intermediate imaging position P, and an aerial image can be formed. Therefore, the confirmation and adjustment of the optical performance can be performed in each mirror group. At this time, since the number of constituent mirrors in each mirror group is four and two, it is easy to search for the mirror that is causing the poor accuracy. Then, after sufficient performance is obtained in each mirror group, the entire adjustment is performed by assembling the projection optical system. As a result, the apparatus can be efficiently assembled and adjusted in a short time.
[0025]
Next, a second embodiment of the present invention will be described.
FIG. 2 is a cross-sectional view illustrating a configuration example of an optical lens barrel of an EUV exposure apparatus according to a second embodiment of the present invention.
The projection optical system barrel 50 shown in FIG. 2 is different from the projection optical barrel 20 shown in FIG. 1 in the following point. That is, in the lens barrel 20 of FIG. 1, the front mirror group includes four mirrors M1 to M4, and the rear mirror group includes two mirrors M5 and M6, whereas the lens barrel 50 in FIG. Each of the front mirror group and the rear mirror group before and after the image forming position P includes three mirrors M1 to M3 and M4 to M6.
[0026]
The projection optical system barrel 50 in FIG. 2 is divided into a front optical barrel 51 and a rear optical barrel 61 around the vicinity of the intermediate imaging position P. The front optical barrel 51 is a tubular body having a lower end 52 protruding in a mountain shape. The rear optical barrel 61 is a tubular body in which an upper left portion in the drawing is cut out to form an opening 61a. The lower part of the front optical barrel 51 is assembled so as to close the opening 61 a of the rear optical barrel 61. In this assembled state, the lower end 52 of the front optical barrel 51 is located inside the rear optical barrel 61. In the front optical barrel 51, three mirrors M1 to M3 forming a front mirror group are arranged. On the other hand, in the rear optical barrel 61, three mirrors M4 to M6 forming a rear mirror group are arranged.
[0027]
The front mirror group will be described in detail.
The mirror M1 is an asymmetric concave mirror. The mirror M1 is attached to the intermediate member 54 of the front optical barrel 51 with the reflection surface facing upward. The mirror M1 is provided with a fine adjustment mechanism C1. An opening 54a through which EUV light passes is formed in the intermediate member 54 on the right side of the mirror M1 in the drawing.
[0028]
Mirror M2 is a symmetric concave mirror. The mirror M2 is attached to the upper member 53 of the front optical barrel 51 with the reflection surface facing downward. The mirror M2 is provided with a fine adjustment mechanism C2. An opening 53a for introducing EUV light from the upstream side is formed in the upper member 53 on the left side of the mirror M2 in the drawing.
[0029]
The mirror M3 is a symmetric convex mirror. The mirror M3 is attached to the lower end 52 of the front optical barrel 21 with the reflection surface facing upward. The mirror M3 is provided with a fine adjustment mechanism C3. Above the mirror M3, an opening 52a for introducing EUV light into the rear optical barrel 61 is formed on the lower side surface of the front optical barrel 21.
[0030]
The rear mirror group will be described in detail.
Mirror M4 is a symmetric concave mirror. The mirror M4 is attached to the upper member 63 of the rear optical barrel 61 with the reflection surface facing downward. The mirror M4 is provided with a fine adjustment mechanism C4.
[0031]
Mirror M5 is an asymmetric concave mirror. The mirror M5 is attached to the lower member 62 of the rear optical barrel 61 with the reflection surface facing upward. The mirror M5 is provided with a fine adjustment mechanism C5. An opening 62a for guiding EUV light to the downstream side is formed in the lower member 62 on the left side of the mirror M5 in the figure.
[0032]
Mirror M6 is a symmetric concave mirror. The mirror M6 is cantilevered on the lower surface of the lower end 52 of the front optical barrel 51 with the reflection surface facing downward. In this attached state, the mirror M6 is located in the rear optical barrel 61. The mirror M6 is provided with a fine adjustment mechanism C6.
[0033]
At the boundary between the front optical barrel 51 and the rear optical barrel 61, connecting mechanisms 60 and 70 for connecting these two barrels are provided. In the connection state of the two lens barrels 51 and 61 shown in FIG. 2, a point indicated by P in the figure is an intermediate imaging position of EUV light.
[0034]
Also in such a projection optical system barrel 50, similarly to the projection optical system barrel 20 in FIG. 1, the mirrors M1 to M3 of the front mirror group can be assembled and adjusted in the front optical barrel 51, and the rear mirror can be adjusted. The mirrors M4 to M6 of the group can be assembled and adjusted in the rear optical barrel 61. Therefore, after the lens barrels are integrated, fine adjustment of the fine adjustment mechanisms C1 to C6 attached to the mirrors M1 to M6 allows smooth and precise mirror adjustment in a short time.
[0035]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an exposure apparatus and an adjustment method thereof that can perform assembly of an apparatus and adjustment of a mirror group in a shorter time and with higher accuracy.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration example of an optical barrel of an EUV exposure apparatus according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a configuration example of an optical barrel of an EUV exposure apparatus according to a second embodiment of the present invention.
FIG. 3 is a schematic configuration diagram illustrating an example of an EUV exposure apparatus (four-projection system).
[Explanation of symbols]
20, 50 Projection optical system barrel 21, 51 Front optical barrel 31, 61 Rear optical barrel M1 to M6 Mirror C1 to C6 Fine adjustment mechanism P Intermediate imaging position

Claims (3)

A light source for emitting EUV light,
An illumination optical system for adjusting and shaping the EUV light emitted from the light source and applying the adjusted light to a reticle;
A reticle stage for mounting and moving / positioning the reticle;
A projection optical system for projecting EUV light reflected from the reticle onto a sensitive substrate;
A sensitive substrate stage for mounting and moving and positioning the sensitive substrate,
An optical column housing the projection optical system,
An exposure apparatus comprising:
The projection optical system includes a plurality of mirror groups (a front mirror group and a rear mirror group) arranged before and after the intermediate imaging position, respectively.
An exposure apparatus, wherein the optical lens barrel is divided into a front optical lens barrel and a rear optical lens barrel in which the front mirror group or the rear mirror group is incorporated and accommodated. After incorporating the front mirror group into the front optical barrel, and incorporating the rear mirror group into the rear optical barrel, each mirror group is adjusted independently, and then both optical barrels are integrated. 2. The exposure apparatus according to claim 1, wherein comprehensive adjustment is performed later. A light source for emitting EUV light,
An illumination optical system for adjusting and shaping the EUV light emitted from the light source and applying the adjusted light to a reticle;
A projection optical system having a plurality of mirror groups (a front mirror group and a rear mirror group) arranged before and after the intermediate imaging position, and projecting EUV light reflected from the reticle onto a sensitive substrate;
An optical barrel divided into a front optical barrel and a rear optical barrel, which accommodates the front mirror group or the rear mirror group of the projection optical system,
An adjustment method of an exposure apparatus comprising:
After incorporating the front-stage mirror group into the front-stage optical barrel, and incorporating the rear-stage mirror group into the rear-stage optical barrel, each mirror group is adjusted independently, and then after integrating both optical barrels, A method for adjusting an exposure apparatus, comprising:

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