JP2007109957A - Mirror mounting structure, projection optical system, and aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To check the deformation of a mirror fixed to a base plate easily and reliably in a mirror mounting structure for mounting the mirror into a barrel, a projection optical system using the mirror mounting structure, and an aligner. <P>SOLUTION: In the mirror mounting structure for supporting a mirror support arranged at the outer periphery of the mirror to a base material through an elastically deformable support member; a mirror position reference member is arranged at the mirror support, and a base member position reference member is arranged in the base member. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mirror mounting structure for mounting a mirror in a lens barrel, a projection optical system using the mirror mounting structure, and an exposure apparatus.

In general, in an EUV exposure apparatus using EUV light, an extremely high shape accuracy of, for example, 0.1 nm or less is required for a mirror disposed in a lens barrel of a projection optical system. Therefore, it is necessary to minimize the deformation of the mirror when the mirror is held in the lens barrel as well as the processing accuracy of the mirror.
Conventionally, the mirror is mounted in the lens barrel by fixing a support block disposed on the outer periphery of the mirror to a base plate disposed in the lens barrel via a support flexure. And after fixing a mirror to a baseplate, since there exists a possibility that a mirror may deform | transform, checking the shape precision of a mirror is performed.
JP 2004-62091 A

However, in order to check the shape accuracy of the mirror and determine the deformation of the mirror, the shape accuracy required for the mirror is extremely small, and the deformation of the mirror is only allowed to be smaller than the shape accuracy. Even if an accurate measuring machine is used, there is a problem that it is difficult to check the deformation of the mirror with sufficient accuracy.
For example, a laser interferometry, especially a measurement method using a Fizeau interferometer, can be used as a method for measuring the mirror shape accuracy with high accuracy. Even if this measurement method is used, mirror deformation can be checked with sufficient accuracy. It is difficult to do.

  The present invention has been made to solve such a conventional problem. A mirror mounting structure capable of easily and surely checking the deformation of a mirror fixed to a base plate, and a projection optical having the mirror mounting structure are provided. An object is to provide a system and an exposure apparatus.

A mirror mounting structure according to a first aspect of the present invention is the mirror mounting structure in which a mirror support portion disposed on the outer periphery of the mirror is supported on a base member via a support member that can be elastically deformed. A reference member is disposed, and a base member position reference member is disposed on the base member.
The mirror mounting structure according to a second aspect of the invention is the mirror mounting structure according to the first aspect of the invention, wherein the mirror support portion is arranged at three positions with a predetermined angle on the outer periphery of the mirror, and the mirror position is set on each mirror support portion. A reference member is arranged, and the base member position reference member is arranged at a position corresponding to each mirror support portion of the base member.

A mirror mounting structure according to a third aspect of the present invention is the mirror mounting structure in which the mirror support portion disposed on the outer periphery of the mirror is supported by the base member via the elastically deformable support member. A reference member is disposed, and a base member position reference member is disposed on the base member.
The mirror mounting structure according to a fourth aspect of the invention is the mirror mounting structure according to the third aspect of the invention, wherein the mirror support portion is arranged at three positions with a predetermined angle on the outer periphery of the mirror, and each mirror support of the base member is provided. The base member position reference member is arranged at a position corresponding to the portion.

A mirror mounting structure according to a fifth aspect of the present invention is the mirror mounting structure according to the third or fourth aspect, wherein a plurality of the supporting member position reference members are arranged on the supporting member.
A mirror mounting structure according to a sixth aspect of the invention is the mirror mounting structure according to any one of the first to fifth aspects, wherein the mirror is an aspherical mirror.
A projection optical system according to a seventh aspect of the invention is characterized in that a plurality of mirrors supported by a base member by any one of the first to sixth mirror mounting structures are arranged in a lens barrel.

  An exposure apparatus of an eighth invention is characterized by having the projection optical system of the seventh invention.

In the mirror mounting structure of the present invention (first invention), the deformation of the mirror fixed to the base plate can be checked easily and reliably.
In the mirror mounting structure of the present invention (third invention), the deformation of the support member fixed to the base plate can be easily and reliably measured.
With the projection optical system of the present invention, a desired wavefront aberration can be obtained easily and reliably.

  In the exposure apparatus of the present invention, high exposure accuracy can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
1 and 2 show a first embodiment of the mirror mounting structure of the present invention.
In this embodiment, the mirror mounting structure of the present invention is applied to a projection optical system of an EUV exposure apparatus that performs exposure with EUV light.

  FIG. 3 schematically shows an example of a projection optical system to which the mirror mounting structure of this embodiment is applied. In this projection optical system, six aspherical mirrors M1, M2, M3, M4, M5, A ring field optical system composed of M6 is used. The EUV light L reflected by the reticle R is sequentially reflected by the first to sixth aspherical mirrors M1 to M6 and projected onto the wafer W. In this ring field optical system, for example, a chip of about 30 mm square cannot be exposed at a time, so that exposure is performed by synchronously scanning the reticle R and the wafer W. The aspherical mirrors M1 to M6 are required to have extremely high shape accuracy of 0.1 nm or less. Accordingly, when the projection optical system is manufactured, not only the processing accuracy of the aspherical mirrors M1 to M6 but also the aspherical mirrors M1 to M6 when the aspherical mirrors M1 to M6 are held in a lens barrel (not shown). It is necessary to suppress the deformation of as much as possible.

  1 and 2, reference numeral 11 indicates a base plate arranged in the lens barrel of the projection optical system. The base plate 11 is incorporated in the lens barrel with high accuracy. A mirror 13 made of an aspherical mirror is fixed to the base plate 11. The mirror 13 is fixed with high accuracy through the support flexure 15 so that the mirror 13 is not deformed.

The mirror 13 has a disk shape, and three mirror support blocks 17 are fixed to the outer periphery at an angle of 120 degrees from the center O of the mirror 13. The mirror support block 17 is made of metal, for example. Each mirror support block 17 is fixed to the disc-shaped base plate 11 via the support flexure 15.
The support flexure 15 is fixed to the mirror support block 17 and the base plate 11 by, for example, screws (not shown). The support flexure 15 is made of an elastic member that elastically deforms relatively easily. The support flexure 15 has a very low rigidity compared to the rigidity of the mirror 13.

In this embodiment, a mirror position reference member 19 is disposed on the side of each mirror support block 17 opposite to the support flexure 15. Each mirror position reference member 19 is arranged on the same circumference centering on the center O of the mirror 13.
Further, on the mirror 13 side of the base plate 11, three base plate position reference members 21 are arranged at positions corresponding to the mirror position reference member 19. More specifically, as shown in FIG. 1, each base plate position reference member 21 is arranged on a straight line passing through the center O of the mirror 13 and the mirror position reference member 19. Further, they are arranged on the same circumference with the center O of the mirror 13 as the center. The mirror position reference member 19 and the base plate position reference member 21 are made of highly accurate metal balls, and half are embedded in the mirror support block 17 and the base plate 11.

Thus, by providing the mirror position reference member 19 in the three mirror support blocks 17 and providing the base plate position reference member 21 in the base plate 11, the three-dimensional positional relationship between the mirror 13 and the base plate 11 can be obtained. Easy and reliable measurement.
FIG. 4 shows an example of the manufacturing process of the projection optical system described above.

First, in step S1, a mirror 13 made of an aspherical mirror that is not coated with a multilayer film is produced. Next, in step S2, the mirror 13 is attached to the lens barrel. This mounting is performed by fixing the mirror 13 to the base plate 11 in the lens barrel via the support flexure 15.
Next, since there is a possibility that the mirror 13 mounted on the lens barrel may be deformed, the deformation of the mirror 13 is checked in step S3. In this embodiment, the relative positional relationship between the mirror position reference member 19 arranged on the mirror support block 17 and the base plate position reference member 21 arranged on the base plate 11 is measured without directly measuring the shape of the mirror 13. This is done by measuring.

More specifically, the relative positional relationship between the mirror position reference member 19 and the base plate position reference member 21 is measured using, for example, a three-dimensional coordinate measuring machine. If the mirror 13 is mounted at a predetermined position on the base plate 11, the positional relationship between the mirror position reference member 19 and the base plate position reference member 21 is substantially the same as the design value.
On the other hand, when the positional relationship between the mirror position reference member 19 and the base plate position reference member 21 deviates from the design value, the distortion due to the deformation of the mirror 13 is absorbed by the deformation of the support flexure 15. The relationship between the deformation amount of the support flexure 15 and the deformation amount of the mirror 13 can be estimated with high accuracy by calculation. Therefore, the deformation amount of the mirror 13 can be estimated by indirectly measuring the deformation amount of the support flexure 15.

  In other words, in the present invention, when the mirror 13 is attached to the base plate 11 in the lens barrel via the support flexure 15, the deformation amount of the support flexure 15 becomes very large compared to the deformation amount of the mirror 13. The deformation ratio is determined by the rigidity ratio of the mirror 13 and the support flexure 15, but it is possible to give a difference of at least three orders of magnitude. For example, when the ratio of the deformation amount of the mirror 13 and the deformation amount of the support flexure 15 is set to be greater than 1000 times, the relative position between the mirror position reference member 19 and the base plate position reference member 21 is measured with an accuracy of about 1 μm. As a result, the deformation amount of the mirror 13 can be measured with sufficient accuracy. This is a level that can be sufficiently measured with a three-dimensional coordinate measuring machine. Therefore, the deformation of the mirror 13 can be checked with sufficient accuracy by the three-dimensional coordinate measuring machine.

  If the positional relationship between the mirror position reference member 19 and the base plate position reference member 21 deviates from the design value, the position of the mirror 13 relative to the base plate 11 may be finely adjusted and reattached. In this case, since the positional relationship between the mirror position reference member 19 and the base plate position reference member 21 can be directly known, position adjustment can be easily performed.

  After all the mirrors 13 are mounted on the lens barrel in this way, the wavefront aberration is measured in step S4. Since the projection optical system is a reflection system, the wavefront aberration may be checked at a wavelength other than the exposure light, that is, a wavelength of visible light or the like. After confirming that a desired wavefront aberration can be obtained at this time, the mirror 13 is removed from the lens barrel in step S5. When checking the wavefront aberration, if the shape accuracy of the mirror 13 is insufficient, the shape of the mirror 13 may be corrected as appropriate.

  In step S6, the mirror 13 is coated with a multilayer film. Next, in step S7, the mirror 13 is mounted on the lens barrel again. This mounting is performed in the same manner as in step S2. Next, in step S8, since the mirror 13 may be deformed, the deformation of the mirror 13 is checked. This check is performed in the same manner as in step S3. After all the mirrors 13 are mounted on the lens barrel in this way, wavefront aberration is measured in step S9. This measurement is performed in the same manner as in step S4. After confirming that the desired wavefront aberration can be obtained, the production of the projection optical system is completed.

In the mirror mounting structure described above, the mirror position reference member 19 disposed on the mirror support block 17 of the mirror 13 and the base plate position reference member 21 disposed on the base plate 11 are relatively measured without directly measuring the shape of the mirror 13. By measuring the relative positional relationship, the deformation of the mirror 13 can be checked. Therefore, for example, the deformation of the mirror 13 can be checked by measurement with a three-dimensional coordinate measuring machine, and the deformation of the mirror 13 fixed to the base plate 11 can be easily and reliably checked.
(Second Embodiment)
FIG. 5 shows a main part of a second embodiment of the mirror mounting structure of the present invention.

In this embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
In this embodiment, the support flexure 15 has an attachment portion 15a and an elastic deformation portion 15b. The attachment portion 15a is formed perpendicular to the elastic deformation portion 15b and protrudes on both sides from the upper end of the elastic deformation portion 15b. Then, it is fixed to the mirror support block 17. The lower end of the elastic deformation portion 15 b is fixed to the base plate 11. Similar to the first embodiment, a mirror position reference member 19 and a base plate position reference member 21 are embedded in the upper surface of the mirror support block 17 and the base plate 11.

In this embodiment, support flexure position reference members 23 are arranged on both sides and the center of the attachment portion 15a. The support flexure position reference member 23 is made of a metal sphere, and a half portion is embedded in the attachment portion 15a.
In this embodiment, as in the first embodiment, the relative positional relationship between the mirror position reference member 19 disposed on the mirror support block 17 of the mirror 13 and the base plate position reference member 21 disposed on the base plate 11. It is possible to check the deformation of the mirror 13 by measuring.

  Further, by measuring the relative positional relationship between the support flexure position reference member 23 and the base plate position reference member 21, the deformation of the support flexure 15 due to the displacement of the fixed position of the mirror 13 is measured, and the support flexure 15. The deformation mode can be captured. Then, by finely adjusting the position of the mirror 13 with respect to the base plate 11 based on the deformation mode of the support flexure 15, the position of the mirror 13 can be adjusted more easily.

For example, as shown in FIG. 6, when the mounting portion 15 a of the support flexure 15 is inclined, the relative positional relationship between the three support flexure position reference members 23 and the base plate position reference member 21 is measured. This makes it possible to know the direction of inclination of the mounting portion 15a. Then, by finely adjusting the position of the mirror 13 relative to the base plate 11 based on this inclination, the position of the mirror 13 can be adjusted more easily.
(Embodiment of exposure apparatus)
FIG. 7 schematically shows an EUV exposure apparatus provided with a projection optical system 101 to which the mirror mounting structure of the present invention is applied.

In this embodiment, EUV light is used as illumination light for exposure. EUV light has a wavelength of 0.1 to 100 nm, and in this embodiment, a wavelength of about 1 to 50 nm is particularly preferable. The projection optical system 101 uses a ring field optical system, and forms a reduced image of the pattern by the reticle 19 on the wafer 121.
The pattern irradiated on the wafer 121 is determined by a reflective reticle 103 disposed on the reticle stage 102 via an electrostatic chuck 104. The wafer 121 is disposed on the wafer stage 123 via the electrostatic chuck 127. Typically, exposure is done by step scanning.

  Since EUV light used as illumination light at the time of exposure has low permeability to the atmosphere, the light path through which the EUV light passes is surrounded by a vacuum chamber 106 that is kept in a vacuum using a suitable vacuum pump 107. EUV light is generated by a laser plasma X-ray source. The laser plasma X-ray source includes a laser source 108 (acting as an excitation light source) and a xenon gas supply device 109. The laser plasma X-ray source is surrounded by a vacuum chamber 110. EUV light generated by the laser plasma X-ray source passes through the window 111 of the vacuum chamber 110.

  The parabolic mirror 113 is disposed in the vicinity of the xenon gas discharge portion. The parabolic mirror 113 collects EUV light generated by the plasma. The parabolic mirror 113 constitutes a condensing optical system, and is arranged so that the focal position comes near the position where the xenon gas from the nozzle 112 is emitted. The EUV light is reflected by the multilayer film of the parabolic mirror 113 and reaches the condensing mirror 114 through the window 111 of the vacuum chamber 110. The condensing mirror 114 condenses and reflects EUV light to the reflective reticle 103. The EUV light is reflected by the condensing mirror 114 and illuminates a predetermined portion of the reticle 103. That is, the parabolic mirror 113 and the condensing mirror 114 constitute an illumination system of this apparatus.

The reticle 103 has a multilayer film that reflects EUV light and an absorber pattern layer for forming a pattern. The EUV light is “patterned” by being reflected by the reticle 103. The patterned EUV light reaches the wafer 121 through the image optical system 101.
The projection optical system 101 of this embodiment includes four reflecting mirrors: a concave first mirror 115a, a convex second mirror 115b, a convex third mirror 115c, and a concave fourth mirror 115d. Each of the mirrors 115a to 115d is provided with a multilayer film that reflects EUV light. Each of the mirrors 115a to 115d is attached to the base plate by the mirror mounting structure of the present invention.

The EUV light reflected by the reticle 103 is sequentially reflected from the first mirror 115a to the fourth mirror 115d to form a reduced image (for example, 1/4, 1/5, 1/6) of the reticle 103 pattern. . The projection optical system 101 is telecentric on the image side (wafer 121 side).
The reticle 103 is supported at least in the XY plane by a movable reticle stage 102. The wafer 121 is preferably supported by a wafer stage 123 that is movable in the X, Y, and Z directions. When exposing the die on the wafer 121, EUV light is irradiated to a predetermined region of the reticle 103 by the illumination system, and the reticle 103 and the wafer 121 are predetermined with respect to the projection optical system 101 according to the reduction ratio of the projection optical system 101. It moves at the speed of In this way, the reticle pattern is exposed to a predetermined exposure range (with respect to the die) on the wafer 121.

  At the time of exposure, the wafer 121 is desirably disposed behind the partition 116 so that the gas generated from the resist on the wafer 121 does not affect the mirrors 115a to 115d of the projection optical system 101. The partition 116 has an opening 116 a through which EUV light is irradiated from the mirror 115 d onto the wafer 121. The space in the partition 116 is evacuated by a vacuum pump 117. In this manner, gaseous dust generated by irradiating the resist is prevented from adhering to the mirrors 115a to 115d or the reticle 103. Therefore, deterioration of these optical performances is prevented.

In the exposure apparatus of this embodiment, since the mirror mounting structure of the present invention is used for the projection optical system 101, high exposure accuracy can be obtained.
(Supplementary items of the embodiment)
As mentioned above, although this invention was demonstrated by embodiment mentioned above, the technical scope of this invention is not limited to embodiment mentioned above, For example, the following forms may be sufficient.

(1) In the above-described embodiment, the example in which the present invention is applied to the projection optical system has been described. However, the present invention can be widely applied to a mirror mounting structure in which the mirror 13 is attached to the base plate 11.
(2) In the above-described embodiment, the example in which the mirror mounting structure of the present invention is applied to the projection optical system of the EUV exposure apparatus has been described. However, the energy rays for transferring the pattern are not particularly limited, and light, ultraviolet rays, X-rays (Soft X-ray etc.) etc. may be sufficient.

It is a top view which shows 1st Embodiment of the mirror attachment structure of this invention. It is a side view which shows the mirror attachment structure of FIG. It is explanatory drawing which shows the projection optical system with which the mirror attachment structure of FIG. 1 is applied. It is explanatory drawing which shows the production process of the projection optical system of FIG. It is explanatory drawing which shows the principal part of 2nd Embodiment of the mirror attachment structure of this invention. It is explanatory drawing which shows a deformation | transformation of the support flexure of FIG. It is explanatory drawing which shows the exposure apparatus with which the mirror attachment structure of this invention is applied.

Explanation of symbols

11: Base plate, 13: Mirror, 15: Support flexure, 17: Mirror support block, 19: Mirror position reference member, 21: Base plate position reference member, 23: Support flexure position reference member.

Claims (8)

In a mirror mounting structure in which a mirror support portion disposed on the outer periphery of a mirror is supported on a base member via a support member capable of elastic deformation,
A mirror mounting structure comprising: a mirror position reference member disposed on the mirror support portion; and a base member position reference member disposed on the base member. In the mirror mounting structure according to claim 1,
The mirror support portions are arranged at three positions with a predetermined angle on the outer periphery of the mirror, the mirror position reference members are arranged on the mirror support portions, and the base members are located at positions corresponding to the mirror support portions. A mirror mounting structure in which the base member position reference member is arranged. In a mirror mounting structure in which a mirror support portion disposed on the outer periphery of a mirror is supported on a base member via a support member capable of elastic deformation,
A mirror mounting structure comprising a support member position reference member disposed on the support member and a base member position reference member disposed on the base member. In the mirror mounting structure according to claim 3,
The mirror support portions are arranged at three positions with a predetermined angle on the outer periphery of the mirror, and the base member position reference member is arranged at a position corresponding to each mirror support portion of the base member. Mirror mounting structure. In the mirror mounting structure according to claim 3 or 4,
A mirror mounting structure comprising a plurality of the support member position reference members arranged on the support member. In the mirror mounting structure according to any one of claims 1 to 5,
The mirror mounting structure, wherein the mirror is an aspherical mirror.   7. A projection optical system comprising a plurality of mirrors supported by a base member by the mirror mounting structure according to claim 1, wherein a plurality of mirrors are arranged in a lens barrel. An exposure apparatus comprising the projection optical system according to claim 7.

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