JP2005175146A - Aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system, capable of reducing astigmatism on the whole surface by bending a lens to a specific direction to control it, when the lens is deformed due to exposure load (heat) in the optical system, and astigmatism is generated on the whole surface, as a result of the deformation. <P>SOLUTION: Holding structure, having a groove formed on the outer peripheral part of an optical element, a 1st support member, engaged with the groove part and capable of fixing a place slightly separated from either one of two fixing points which are of 180° pitch points in the gravity direction, and a 2nd support member for supporting the 1st support member is provided with a driving mechanism, capable of generating 2θ deformation on a face, causing self-weight deformation of the lens and controlling force in the antigravity direction on one or two points to control the astigmatism of the optical element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for supporting an optical member or the like, for example, a lens support device for a projection lens used in a semiconductor exposure apparatus, and further relates to a projection exposure apparatus.

  The semiconductor exposure apparatus is an apparatus for transferring an original plate (reticle) having a circuit pattern onto a substrate (silicon wafer). When transferring, a projection lens is used to form an image of the reticle pattern on the wafer. In order to create a highly integrated circuit, the projection lens is required to have a high resolving power. The projection lens for use must have low aberrations. However, during exposure in the projection lens, lens deformation may occur due to exposure load (heat), and as a result, image displacement on the optical axis, for example, astigmatism may occur. Astigmatism (astigmatism) is an aberration in which light from one off-axis point does not converge on one point after passing through the lens, but becomes two perpendicular lines that are shifted back and forth. When there is aberration, the shape of the hole changes due to defocusing. In order to correct this astigmatism, there is a method of correcting the wavefront aberration by changing the surface shape of the lens.

As a well-known example of correcting wavefront aberration by deforming the lens surface shape, a lens indicating member provided with indicating portions at three equal intervals in the lens circumferential direction as disclosed in Japanese Patent Laid-Open No. 11-149029 It has a structure provided with a second support member that gives instructions while pushing up in the direction of gravity, and an operating member that acts at least substantially perpendicular to the optical axis on the lens arranged in the mount as in JP-A-2002-519843 The actuating member is not rotationally symmetric because the actuating member generates a bend that does not substantially change in thickness, and has a structure that generates a force or moment that deviates from the radial direction on the optical element. is there.
JP-A-11-149029 JP 2002-519843 A

  However, in the projection lens used in a semiconductor exposure apparatus that requires high-precision optical performance, the above-mentioned conventional example, Japanese Patent Application Laid-Open No. 11-149029 is a three-spaced support method and aims to reduce 3θ plane deformation. Therefore, it is not a 2θ-plane deformation control method, and Japanese Patent Laid-Open No. 2002-519843 does not clearly describe the support method for the lens and the support member 1 that supports the lens. Such a structure must be integrated with the support member by bonding around the circumference or mechanical clamping at multiple points. However, since it is very difficult to apply the adhesive uniformly over the entire circumference, lens deformation occurs due to uneven thickness of the adhesive. There is also concern about the influence of contamination due to adhesive outgassing. In addition, even in a multi-point mechanical clamp, a load applied to the lens is increased and lens deformation occurs.

  In order to achieve the above object, an optical element supporting method according to the present invention is a method of holding an optical element in a predetermined place, engaging with a groove formed on an outer peripheral part of the optical element, and the groove part, (1) 180 ° In addition to the two fixed points on the pitch, a place slightly away from either fixed point in the direction of gravity is fixed. (2) Out of the three fixed points, two fixed points with a distance of 120 ° or more and less than 180 ° in the 180 ° pitch direction of one fixed point are fixed. (3) Fix 3 points out of 4 90 ° pitches. A holding structure comprising a first support member and a second support member that supports the support member arranged by any one of the three methods, and at least one or two locations between the support portions, A drive mechanism for applying a force to the optical element is provided, and each drive mechanism includes an airtight chamber whose volume can be changed by an internal pressure, a control unit for controlling the pressure in the airtight chamber, and a change in the internal pressure of the airtight chamber. It is characterized by comprising a lever member capable of receiving a force and applying a force to the lens. According to the above configuration, the optical element can generate 2θ deformation of the surface due to its own weight deformation, and by providing a drive mechanism that can adjust the force in the antigravity direction at one place or two places at the place where its own weight is deformed. It is possible to adjust asphalt actively.

  As described above, according to the invention of the present application, the lens member can be held in a state in which the lens posture is maintained, and asphalt is actively controlled by using the drive mechanism against the lens weight change. Is possible. Therefore, high-precision optical performance can be provided by controlling the lens surface shape.

(First embodiment)
An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a part of a projection optical system unit of a semiconductor exposure apparatus to which the present invention is applied. In FIG. 1, 1 is a lens barrel including a projection optical system in the semiconductor exposure apparatus of the present embodiment, 2 is a main body platen that supports the lens barrel, 3 is a wafer that is a transfer substrate, and 4 is a wafer that supports the wafer and moves to a desired position. The wafer stage 5 to be driven is a part of the unit of the illumination system optical system. Reference numeral 6 denotes a reticle on which a pattern to be transferred to a wafer is depicted, and reference numeral 7 denotes a reticle stage that supports the reticle. The reticle 6 is exposed by the unit of the illumination optical system, and the pattern of the reticle 6 is transferred to the wafer 3 through the lens barrel 1 including the projection optical system.

  FIG. 2 is a projection optical system diagram to which an embodiment of the optical element support mechanism belonging to the lens barrel is applied. FIG. 3 shows the contact portion of the second holding member 23 with the optical member 21 except for the optical member 21. It is the figure shown as follows. The direction of gravity coincides with the optical axis and is the −Z direction in the figure. 2 and 3, 21 is an optical member (lens), 22 is a first support member that supports the optical member, and a second support member 23 whose tip is a spherical member is provided on the outer periphery of the first support member. Are arranged at locations slightly apart from one of the fixed points in the direction of gravity in addition to the two fixed points at a 180 ° pitch, and the optical member 21 is fixed. The spherical members arranged at a position slightly separated in the direction of gravity are for restricting the rotation of the lens, and it is calculated that this constrained arrangement is smaller than the upper spherical member and the lens inclination amount is smaller. It has become clearer. The 90 ° pitch of the second support member 23 is provided with a drive mechanism 24 that deforms the lens in the direction of the optical axis at two positions with a 180 ° pitch on the outer periphery of the lens. Details of the drive mechanism 24 will be described later. A groove having a V-shaped cross section (hereinafter referred to as “V groove”) or a cone-shaped groove (hereinafter referred to as “cone groove”) is processed in the edge portion of the optical member 21. The second support member 23 is in contact with the upper and lower surfaces of the V-groove or cone groove, and is positioned so as not to apply pressure in the radial direction of the optical member 21.

  Next, a detailed portion of the drive mechanism 24 will be described with reference to FIG. The drive mechanism 24 has two airtight chambers 25 which communicate with each other. Each of the airtight chambers can be changed in volume by an internal pressure, such as a bellows, and a control unit for controlling the pressure in the airtight chamber and an airtight chamber. The lever member 26 is configured to receive a force due to a change in the internal pressure of the closed chamber and apply a force to the lens. With this configuration, a desired load is applied to the lens outer peripheral portion in the antigravity direction by controlling the pressure in the hermetic chamber. At this time, the force transmitted to the lens is determined by the pressure in the hermetic chamber, the effective area, and the lever point of the action point, fulcrum, and force point of the lever member. For example, in this example, when the pressure adjustment amount of the hermetic chamber is 0.08 MPa, the effective area is 1.54 cm2, and the lever ratio is 0.39 with respect to the lens load of 18.1 N, the force applied to the lens can be adjusted to 4.53 N. It is possible to control the 2θ plane deformation by the self-weight deformation amount to almost zero. The force in the antigravity direction corrects the deformation caused by the lens's own weight deflection, whereby the wavefront aberration of the lens can be deformed, and the exposure aberration can be corrected. The insulator member has two support points that are not on the straight line connecting the point of action (lens contact point) and the force point (bellows contact part) or parallel to the straight line, and the direction of the force from the hermetic chamber is Even if the direction is not strictly anti-gravity, the lever member does not rotate. In this configuration, the hermetic chamber is in communication, and it is possible to generate force equally to the two drive units with one pressure control, but it is also possible to individually control the respective hermetic chamber pressure, In that case, it is possible to control not only the deformation amount of the lens but also the tilt amount. In this embodiment, the maximum deformation adjustment amount of the lens is the deformation amount due to its own weight deflection, but by applying a certain pressure from the opposite side of the gravity point of the action point of the lever, the deformation amount exceeding its own weight deformation amount. Control can be performed. That is, if the force by the pressurizing mechanism is -F and the force from the lever member is f (p), the force N for changing the lens shape is N = -F + f (p), which is the minimum (0) Even at this time, the lens deformation is larger than the self-weight deformation. The pressurizing member is preferably, for example, a one-sided beam-like spring member or a ball plunger with a built-in coil spring, but may be any member that can apply a constant pressure in the direction of gravity of the lens. According to these configurations, the optical member 21 hardly receives a moment as an external force at three support points. In addition, by arranging the second support member 23 at the support position, the optical member 1 mainly undergoes its own weight deformation of 2θ, and the adjusted lens surface can be actively adjusted by lifting the deformed lens surface with the drive mechanism 24. it can. Furthermore, since no adhesive is used, it is not affected by outgassing contamination.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIG.

  FIG. 5 is a projection optical system diagram to which an embodiment of the optical element support mechanism belonging to the lens barrel is applied as in FIG. 2, and FIG. 6 is an optical member 21 of the second holding member 23 except for the optical member 21. It is the figure shown so that a contact part might be understood. The direction of gravity coincides with the optical axis and is the −Z direction in the figure. The explanation of the symbols in this embodiment is omitted because it is the same member as in the first embodiment. In the present embodiment, the second support member 23 is arranged so as to fix two fixed points of which the distance between the two points is 120 ° or more and less than 180 ° in the 180 ° pitch direction of one fixed point. Has been. A driving mechanism 24 for deforming the lens in the direction of the optical axis is provided at two positions at a 180 ° pitch on the outer periphery of the lens at a 90 ° pitch of one fixed point. By adopting this arrangement method, the posture position of the lens can be maintained, and surface deformation mainly having 2θ can be generated. Note that the amount of components other than 2θ decreases by bringing the distance between two points in the 180 ° pitch direction of one fixed point closer, so the distance between the two points can be narrowed to such an extent that the lens posture fixing force is maintained. desirable.

  As in the present embodiment, the second support member 23 is disposed at the support position, so that the optical member 21 mainly undergoes its own weight deformation of 2θ, and the deformed lens surface is driven by the drive mechanism 24, as in the first embodiment. You can actively adjust the asses by lifting in. Furthermore, since no adhesive is used, it is not affected by outgassing contamination.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG.

  6 is a projection optical system diagram to which an embodiment of the optical element support mechanism belonging to the lens barrel is applied as in FIG. 2. FIG. 6 is an optical member 21 of the second holding member 23 except for the optical member 21. It is the figure shown so that a contact part might be understood. The direction of gravity coincides with the optical axis and is the −Z direction in the figure. The explanation of the symbols in this embodiment is omitted because it is the same member as in the first embodiment. In the present embodiment, the second support member 23 is arranged to fix three of the four 90 ° pitch points, and the drive mechanism 24 is arranged at the remaining one 90 ° pitch. By adopting this arrangement method, the posture position of the lens can be maintained, and surface deformation mainly having 2θ can be generated.

  As in the present embodiment, the second support member 23 is disposed at the support position, so that the optical member 21 mainly undergoes its own weight deformation of 2θ, and the deformed lens surface is driven by the drive mechanism 24, as in the first embodiment. You can actively adjust the asses by lifting in. Furthermore, since no adhesive is used, it is not affected by outgassing contamination.

FIG. 3 is a view for explaining a projection optical system unit of the semiconductor exposure apparatus according to the first embodiment of the present invention. 1 is a lens holding device showing a first embodiment of the present invention. 1 is a lens holding device showing a first embodiment of the present invention. 1 is a drive mechanism device showing a first embodiment of the present invention; 6 is a lens holding device showing a second embodiment of the present invention. 6 is a lens holding device showing a second embodiment of the present invention. 4 is a lens holding device showing a third embodiment of the present invention. 4 is a lens holding device showing a third embodiment of the present invention.

Explanation of symbols

1 Lens tube
2 Main body surface plate
3 Wafer
4 Wafer stage
5 Part of the illumination optics unit
6 Reticle
7 Reticle stage
21 Optical elements (lenses)
22 First support member (cell)
23 Second support member
24 Drive mechanism
25 Airtight room
26 Insulator material

Claims (5)

  In the method of holding the optical element in place, in addition to the groove formed on the outer periphery of the optical element and the two support points with a pitch of 180 °, gravity is applied from either one of the support points. An optical element holding method comprising: a holding structure including a first support member disposed at a position slightly apart in a direction and a second support member supporting the support member.   In the method of holding the optical element in a predetermined place, a groove formed on the outer periphery of the optical element, and the two engaging points between two points in the 180 pitch direction of the supporting point among the three supporting points. A holding structure comprising a first support member disposed at two points with a distance of 120 ° or more and less than 180 ° and a second support member that supports the support member. Element holding method.   In a method of holding an optical element in a predetermined place, a groove formed on the outer periphery of the optical element, and a first support member that engages with the groove and is disposed at three of four 90 ° pitches. And a second support member that supports the support member.   In the optical element holding method recited in any one of claims 1 to 3, a driving mechanism that applies a force to the optical element in the antigravity direction is provided in two locations at a pitch of 180 degrees on the outer periphery of the lens in claims 1 and 2. The optical element holding method according to claim 3, wherein the optical element holding method is provided at one remaining portion of the 90 ° pitch. The optical element holding method according to any one of claims 1 to 3, wherein the driving mechanism that applies force to the optical element includes an airtight chamber whose volume can be changed by an internal pressure, a control unit that controls the pressure in the airtight chamber, An optical element holding method comprising: a lever member capable of receiving a force due to a change in internal pressure and applying a force to a lens.

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