Abstract:
In the case of a mounting apparatus, an optical element having an inner mount and an outer mount, in particular a lens in a projection lens system for semiconductor lithography, the inner mount is connected to the outer mount via three circumferentially distributed articulations. Manipulators, whereby said inner mount is displaceable, act on the articulations. The articulations comprise a mechanism which transforms a radial movement into an axial movement.

Description:
TECHNICAL FIELD 
     The invention relates to a mounting apparatus for an optical element and more particularly to a mounting apparatus for mounting a lens. 
     BACKGROUND OF THE INVENTION 
     Optical elements, e.g. lenses, have to be installed and adjusted very precisely in relation to their mechanical reference, in particular, in lens systems for semiconductor lithography. It is thus the case, eg. with lenses, that the optical axis has to be made to coincide as precisely as possible with the ideal mechanical axis. 
     The Applicant&#39;s earlier application P 199 08 554.4 discloses a three-point mounting via solid-state rotary articulations with solid-state transitions which can be adjusted by manipulators. A three-point mounting is also known from U.S. Pat. No. 3,917,385. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to improve the hitherto known installation and adjustment mounting method by an integrated fine-tuning functional unit, in order to achieve higher positioning accuracy. 
     Methods and apparatuses for achieving this object are described. In one embodiment, a mounting apparatus for an optical element includes an inner mount and an outer mount, the inner mount being connected to the outer mount via three circumferentially distributed articulations. An exemplary mounting apparatus is disclosed in U.S. Pat. No. 6,580,570, issued Jun. 17, 2003, to Becker et al., which is incorporated herein by reference. Manipulators act on the articulations wherein said inner mount is displaceable, and wherein the articulations comprise a mechanism which transforms a radial movement into an axial movement. In another embodiment, the mounting apparatus is for mounting a lens in a projection lens system for semiconductor lithography. In another embodiment, the articulations comprise at least one lever for transforming the radial movement into an axial movement, wherein the manipulators act on said at least one lever. In another embodiment, the articulations comprise at least one bell crank lever with attachment points between the inner mount and the outer mount. The outer mount is located in the region of the outer ends of a first lever of the at least one bell crank lever and the manipulators act in the region of the outer end of a second lever of the at least one bell crank lever which is in an angle to the first lever. 
     In another embodiment, the articulations comprise at least one T-shaped lever in cross section, with a T-bar and a T-support, attachment points between the inner mount and the outer mount being located in each case in the region of the outer ends of the T-bar, and the manipulators acting on the T-support in each case, this embodiment being disclosed in U.S. Pat. No. 6,580,570, previously incorporated herein by reference. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the following accompanying drawings. 
     FIG. 1 shows a basic perspective illustration of the three-point mounting with the articulations according to the invention; 
     FIG. 2 shows a basic illustration of a first embodiment of an articulation; and 
     FIG. 3 shows a basic illustration of a second embodiment of an articulation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8). 
     According to the illustration in FIG. 1, an exemplary mounting apparatus  10  is shown. An optical element  20  is mounted in an inner mount  22 , which is connected to an outer mount  24  via a plurality of circumferentially distributed articulations  30 . An exemplary optical element includes a lens  20  for a projection lens system sued in semiconductor lithography processing. The number of exemplary plurality articulations  30  include three as shown. However, it should be understood that one or any number of articulations  30  could be used in the scope of this invention, and oriented circumferentially in any matter along inner mount  22 . For reasons of clarity, the outer mount  24  is only indicated at the attachment points in FIG.  1 . Inner mount  22  has a circular sidewall  26  with an upper edge  27  and lower edge  28 . An exemplary articulation  30  includes a bell crank lever  30  rotatably secured between inner and outer mounts  22  and  24  by pivots or attachment points  32  and  34 . Attachment points  32  and  34  are located between the inner mount  22  and the outer mount  24  and at an outer end of a first lever  35  of the bell crank lever  30 . A second lever  36  of the bell crank lever  30  is located perpendicularly or rectangularly to the first lever  35 . A manipulator  40  (referenced only by direction arrow  40 ) provides a force to the outer end of the second lever  36  and subjects second lever  36  to tensile and/or compressive forces. As a result of the force by manipulator  40  and the kinematics of the bell crank lever  30 , the inner mount  22  is displaced in an upward or a downward direction by transforming a radial movement into an axial movement. Exemplary manipulators include mechanical, electrical, hydraulic and pneumatic actuating members as understood by those skilled in the art, and an exemplary location for such manipulator is in the outer mount  24  (not shown). 
     FIG. 1 further illustrates in principle how position determination can be carried out, for example, by a capacitive sensor  52 , which may be located in a recess  54  between the inner mount  22  and the outer mount  24 . For this purpose, of course, it is necessary to have a plurality of capacitive sensors  52  correspondingly distributed over the circumference of inner mount  22 . 
     FIG. 2 shows a first exemplary embodiment of an articulation illustrated as a bell crank lever  30 . The attachment points  32  and  34  are positioned between the inner mount  22  and the outer mount  24  generally coextensive with the upper edge  27  of circular sidewall  26  of inner mount  22 . In this orientation of bell crank lever  30 , the second lever  36  extends downward from attachment point  34  generally spaced from and along circular sidewall  26 . Manipulator  40  provides a compressive force to the outer end of the second lever  36  and moves the outer end of the second lever  36  radially to drive inner mount  22  and optical element  20  axially upward in direction  42 . Alternatively, manipulator  40  provides a tensile force to the outer end of the second lever  36  and moves the outer end of the second lever  36  radially to drive inner mount  22  and optical element  20  axially in a direction opposite to direction  42 . 
     FIG. 3 shows a second exemplary embodiment of an articulation illustrated as a bell crank lever  30 . The attachment points  32  and  34  are positioned between the inner mount  22  and the outer mount  24  generally coextensive with the lower edge  27  of circular sidewall  26  of inner mount  22 . In this orientation of bell crank lever  30 , the second lever  36  extends upward from attachment point  34  generally spaced from and along circular sidewall  26 . Manipulator  40  provides a tensile force to the outer end of the second lever  36  and moves the outer end of the second lever  36  radially to drive inner mount  22  and optical element  20  axially upward in direction  42 . Alternatively, manipulator  40  provides a compressive force to the outer end of the second lever  36  and moves the outer end of the second lever  36  radially to drive inner mount  22  and optical element  20  axially in a direction opposite to direction  42 . 
     It should be understood that manipulator  30  can be rotatably secured to inner mount  22  by attachment point  34  between upper and lower edges  27  and  28  at any location of circular sidewall  26 . It should be understood that any combination of articulations  30  can be used, for example, all the articulations  30  secured to mounting apparatus  10  could be bell crank levers, or all could be the one T-shaped articulations disclosed in U.S. Pat. No. 6,580,570, previously incorporated herein by reference, or any combination of differently designed articulations. 
     In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.