JP2006135230A - Electrostrictive actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply a compression load to a piezoelectric element inside an electrostrictive actuator, without reducing the rigidity of the electrostrictive actuator, when an optical element is hung in a vertical downward direction from a fixing portion connecting a barrel by a parallel linkage that uses the electrostrictive actuator. <P>SOLUTION: A mechanism is used for converting a tensile load due to the weight of the optical element into compression load inside the electrostrictive actuator, when then optical element is hung down in the vertical downward direction from the fixing portion connecting the barrel by the parallel linkage by using the electrostrictive actuator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to precise driving, and in particular, manufactures various devices such as semiconductor chips such as IC and LSI, display elements such as liquid crystal panels, detection elements such as magnetic heads, and imaging elements such as CCDs. The present invention relates to a piezoelectric actuator related to positioning of an optical element (lens or mirror, etc.) of an exposure apparatus used in the process. In the present invention, for example, positioning of a plurality of reflective optical elements used in an optical system of an exposure apparatus (hereinafter referred to as “EUV exposure apparatus”) that uses extreme ultraviolet (EUV) light as exposure light. Ideal for mechanism actuators.

  A semiconductor exposure apparatus is an apparatus for transferring an original (reticle) having many different types of patterns onto a silicon wafer (substrate). In order to create a highly integrated circuit, it is essential to improve not only the resolution performance but also the overlay accuracy.

  Overlay errors in a semiconductor exposure apparatus are classified into alignment errors, image distortions, and magnification errors. The alignment error can be reduced by adjusting the relative displacement between the original (reticle) and the substrate (wafer). On the other hand, image distortion and magnification error can be adjusted by moving some optical elements of the optical system. When moving the optical element, it is necessary to prevent the parallel decentering and tilt decentering error components from increasing.

  In recent years, development of an EUV exposure apparatus that uses extreme ultraviolet (EUV) light as exposure light has been started. In such an EUV exposure apparatus, the projection optical system includes only a reflective optical element (mirror).

The positioning of the optical element is performed using a drive mechanism generally called a parallel link mechanism. A method of using a piezoelectric element (piezo element) as an actuator of a parallel link mechanism has been devised.
JP-A-10-169524 Japanese Patent Laid-Open No. 10-173248

  Due to the configuration of the exposure apparatus, the optical element inside the projection optical system PO may be hung vertically downward from a fixed portion connected to the lens barrel. However, the piezoelectric element needs to be compressed by applying a compressive load due to the characteristics of the element.

  Accordingly, an exemplary object of the present invention is to provide a piezoelectric actuator used in an exposure apparatus that is optimal for driving a movable portion including an optical element suspended vertically downward.

  In order to achieve the above object, when the optical element is suspended vertically downward from the fixed part connected to the lens barrel via the parallel link mechanism, the tensile load due to the weight of the movable part is converted into a compressive load, and the piezoelectric element is A load conversion mechanism for applying a compressive load to the element is provided inside the piezoelectric actuator.

  That is, the present invention has a piezoelectric element and a load conversion mechanism that converts a tensile load into a compression load, converts the tensile load applied to the piezoelectric actuator into a compression load using the load conversion mechanism, and compresses the piezoelectric element. It is characterized by applying a load.

  Further objects and other features of the present invention will be made clear by the preferred embodiments described below with reference to the accompanying drawings.

  It is possible to provide a piezoelectric actuator having a higher rigidity than conventional ones.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 6 schematically shows the overall configuration of exposure apparatus 100 according to the present embodiment. The exposure apparatus 100 is a projection exposure apparatus that uses, for example, EUV light as the exposure light EL and performs an exposure operation by a step-and-scan method. In the present embodiment, a projection optical system PO that projects a reflected light beam from a reticle (mask) R as a mask vertically onto a wafer (substrate, photosensitive substrate) W is used. The projection direction of the EUV light EL from the system PO onto the wafer W is referred to as the optical axis direction of the projection optical system PO, and this optical axis direction is the Z-axis direction, and the direction in the drawing in FIG. The Y-axis direction and the direction perpendicular to the paper surface will be described as the X-axis direction.

  The exposure apparatus 100 projects the reticle R and the wafer W while projecting an image of a part of the circuit pattern drawn on the reflective reticle R as a mask onto the wafer W as a substrate via the projection optical system PO. The entire circuit pattern of the reticle R is transferred to each of a plurality of shot areas on the wafer W by a step-and-scan method by scanning relative to the projection optical system PO in a one-dimensional direction (here, the Y-axis direction). Is.

  The exposure apparatus 100 reflects the EUV light EL from the light source device (not shown) that emits the EUV light EL and enters the pattern surface of the reticle R at a predetermined incident angle θ. Projection optical system comprising a reflecting mirror M0 for reflecting, a reticle stage RS for holding the reticle R, and an EUV light EL reflected by the pattern surface of the reticle R perpendicularly to the exposed surface of the wafer W A wafer stage WS for holding PO and wafer W is provided.

  The reflective optical element M1 inside the projection optical system PO is fixed to the back plate 30 via the holding mechanism 40. The back plate 30 is connected to a fixed portion 50 that is a part of the lens barrel T via the parallel link mechanism 20. As shown in FIG. 5, the parallel link mechanism 20 is composed of six legs, and the piezoelectric actuator 10 is attached to each leg. The piezoelectric actuator 10 can be expanded and contracted in the longitudinal direction by expansion and contraction of the piezoelectric element 3 provided inside. When the six piezoelectric actuators 10 expand and contract, the back plate 30 including the optical element M1 can be positioned in the six-axis directions.

  As shown in FIG. 6, the optical element M1 inside the projection optical system PO may be suspended vertically downward from a fixed portion 50 connected to the lens barrel T due to the configuration of the apparatus. However, the piezoelectric element needs to be compressed by applying a compressive load due to the characteristics of the element. Therefore, by using the configuration shown in FIG. 1 as the configuration of the piezoelectric actuator, the weight of the optical element M1 and the back plate 30 can be converted into a compressive load and applied to the piezoelectric element 3.

  The structure of the piezoelectric actuator 10 is shown in FIG. The upper part of the member 1 is connected to the fixed part 50, and the lower part of the member 1 is connected to the lower part of the piezoelectric element 3. The lower part of the member 2 is connected to the back plate 30, and the upper part of the member 2 is connected to the upper part of the piezoelectric element 3. With the piezoelectric actuator 10 having such a structure, the weight of the optical element M1 can be converted into a compressive load and applied to the piezoelectric element 3.

  6 measures the position of the optical element M1 or the back plate 30 from a reference structure, for example, the lens barrel T, in a non-contact manner. Measurement information 71 measured by the measuring means 70 is converted into output information 81 to the piezoelectric actuator 10 by a compensator 80 (here, a PI compensator is used). As a result, the positioning of the optical element M1 or the back plate 30 with respect to the reference structure can be controlled.

  In this embodiment, the number of optical elements is two, but the number of optical elements may be other numbers such as four or six.

  Since the difference between the first embodiment and the second embodiment is that the configuration of the piezoelectric actuator 10 is different, the configuration of the piezoelectric actuator 10 will be mainly described here.

  The configuration of the piezoelectric actuator 10 is shown in FIG. A hole is passed through the piezoelectric element 3. The upper part of the member 1 is connected to the fixing part 50 through the hole through which the piezoelectric element 3 passes, and the lower part of the member 1 is connected to the lower part of the piezoelectric element 3. The lower part of the member 2 is connected to the back plate 30, and the upper part of the member 2 is connected to the upper part of the piezoelectric element 3. With the piezoelectric actuator 10 having such a structure, the weight of the optical element M1 can be applied to the piezoelectric element as a compressive load. Further, since the structure is symmetrical with respect to the Z axis, it is possible to prevent the piezoelectric element 3 from being subjected to an unbalanced load. be able to.

  Since the difference between the first embodiment and the third embodiment is that the configuration of the piezoelectric actuator 10 is different, the configuration of the piezoelectric actuator 10 will be mainly described here.

  The configuration of the piezoelectric actuator 10 is shown in FIG. A hole is passed through the piezoelectric element 3. The upper part of the member 1 is connected to the fixed part 50, and the lower part of the member 1 is connected to the lower part of the piezoelectric element 3. The lower part of the member 2 is connected to the back plate 30, and the upper part of the member 2 is connected to the upper part of the piezoelectric element 3 through a through hole of the piezoelectric element 3. By configuring the piezoelectric actuator 10 in this way, the weight of the optical element M1 can be applied to the piezoelectric element 3 as a compressive load. Further, since the structure is symmetric with respect to the Z axis, the piezoelectric element 3 can be applied with an offset load. Can be prevented.

  Since the difference between the first embodiment and the fourth embodiment is that the configuration of the piezoelectric actuator 10 is different, the configuration of the piezoelectric actuator 10 will be mainly described here.

  The configuration of the piezoelectric actuator is shown in FIG. The piezoelectric actuator 10 shown in FIG. 4 covers the periphery of the piezoelectric element 3 with a jacket 4, whereby the lateral rigidity of the piezoelectric actuator 10 can be increased. A part of the jacket covering the piezoelectric element 3 is provided with a flexure portion 5 for facilitating the expansion and contraction of the jacket.

  The upper part of the member 1 is connected to the fixing part 50, and the lower part of the member 1 is connected to the lower part of the jacket 4 that covers the piezoelectric element 3. The lower part of the member 2 is connected to the back plate 30, and the upper part of the member 2 is connected to the upper part of the jacket 4 that covers the piezoelectric element 3.

  4, when it is necessary to dispose the back plate 50 and the optical element M1 on the upper portion of the piezoelectric actuator 10 during assembly work, the weight of the pack plate 30 and the optical element M1 is changed from the member 2 to the member 1. It plays a role in preventing the piezoelectric element 3 from being broken by applying a tensile load to the piezoelectric element 3 directly. In this embodiment, the pin 6 is used, but a plunger or the like may be used.

  Also in the configurations of the piezoelectric actuators 10 of the second and third embodiments, the piezoelectric element 3 may be covered with a jacket.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

Diagram showing the configuration of the piezoelectric actuator Diagram showing the configuration of the piezoelectric actuator Diagram showing the configuration of the piezoelectric actuator Diagram showing the configuration of the piezoelectric actuator Diagram showing parallel link mechanism The figure which shows the outline of the exposure equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Member 2 Member 3 Piezoelectric element 4 Jacket 5 Flexure part 6 Pin 10 Piezoelectric actuator 20 Parallel link mechanism 30 Back plate 40 Holding mechanism 50 Fixed part 60 Movable part 70 Non-contact measurement means 71 Measurement information 80 Compensator 81 Output information 100 Exposure apparatus EL Exposure light R Reticle RS Reticle stage M0 Bounce mirror M1 Optical element M2 Optical element W Wafer WS Wafer stage PO Projection optical system T Lens barrel

Claims (13)

  It has a piezoelectric element and a load conversion mechanism that converts a tensile load into a compression load, converts the tensile load applied to the piezoelectric actuator into a compression load using the load conversion mechanism, and applies the compression load to the piezoelectric element. A characteristic piezoelectric actuator.   2. The piezoelectric actuator according to claim 1, wherein the object to be controlled is suspended from the fixed portion via the piezoelectric actuator to position the object to be controlled.   2. The piezoelectric actuator according to claim 1, wherein the object to be controlled is suspended from the fixed portion via a plurality of piezoelectric actuators, and the object to be controlled is positioned with at least one degree of freedom.   4. The piezoelectric actuator according to claim 2, wherein the object to be controlled is an optical element.   5. The piezoelectric actuator according to claim 4, wherein the optical element is a reflective mirror.   6. The piezoelectric actuator according to claim 1, wherein the first member of the piezoelectric actuator connected to the fixed portion is connected to the lower portion of the piezoelectric element, and the second member of the piezoelectric actuator connected to the control target is connected to the upper portion of the piezoelectric element. A piezoelectric actuator characterized by that.   6. The piezoelectric actuator according to any one of claims 2 to 5, wherein the piezoelectric element is connected to a control target through the hole penetrating the piezoelectric element and connected to the lower portion of the piezoelectric element through the hole through which the first member of the piezoelectric actuator connected to the fixed portion passes. A piezoelectric actuator, wherein the second member is connected to an upper portion of the piezoelectric element.   The second member of the piezoelectric actuator according to any one of claims 2 to 5, wherein the first member of the piezoelectric actuator that passes through the hole in the piezoelectric element and is connected to the fixed portion is connected to the lower portion of the piezoelectric element and is connected to the controlled object. Is connected to the upper part of the piezoelectric element through a through-hole.   9. The piezoelectric actuator according to claim 1, wherein the piezoelectric element is covered with a jacket, the first member of the piezoelectric actuator connected to the fixed portion is connected to a lower part of the jacket covering the piezoelectric element, and the piezoelectric actuator connected to the control target is connected. A piezoelectric actuator characterized in that two members are connected to an upper part of a jacket covering a piezoelectric element.   10. The piezoelectric actuator according to claim 9, wherein a flexure part for facilitating expansion and contraction of the jacket is provided on at least a part of the jacket covering the piezoelectric element.   The piezoelectric actuator according to claim 9 or 10, wherein a pin or a plunger is attached to either the member 1 or the member 2 to prevent a tensile load from being applied to the piezoelectric element.   12. The piezoelectric actuator according to claim 2, wherein the optical element of the exposure apparatus is positioned.   13. The piezoelectric actuator according to claim 12, wherein the exposure apparatus uses extreme ultraviolet (EUV) light as exposure light.

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