JP2677294B2 - Piezoelectric actuator and stage device using the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator that generates a driving force and a stage device that is driven by the actuator.
In particular, the present invention relates to a highly accurate actuator using a piezoelectric element and a stage device using the actuator.

In the X-ray exposure apparatus, which is drawing attention as an exposure apparatus for next-generation VLSI, the final superposition accuracy of the mask and the wafer is required to reach a level of 0.05 μm or less.

[Prior Art] An XY stage of a conventional stepper type exposure apparatus mainly uses a combination of a DC motor and a ball screw. The positioning accuracy was on the order of about 0.1 μm. It is difficult to completely eliminate backlash and backlash with this method combining the DC motor and ball screw.
It is considered extremely difficult to achieve a positioning accuracy of 01 μm or less.

An actuator using a piezoelectric element has been proposed as an actuator that enables high-precision positioning. However, some are less flexible and some are less responsive.

[Problems to be Solved by the Invention] As described above, the required high-precision positioning is extremely difficult depending on the conventional actuator using the DC motor and the ball screw.

The piezoelectric element is capable of highly precise micro-displacement and has the possibility of performing highly accurate positioning, but it cannot be said that a structure that fully exhibits its capability has been developed.

An object of the present invention is to provide a piezoelectric actuator that uses a piezoelectric element, enables highly accurate positioning, and is easy to operate.

Another object of the present invention is to provide a stage device using a piezoelectric actuator as described above.

[Means for Solving the Problems] According to the present invention, there is provided a piezoelectric actuator using a piezoelectric element that expands and contracts in a first direction in response to an applied electric signal, the part in the first direction and the first part. A fixed support portion having a portion in the second direction that intersects with the first direction, a piezoelectric element having an expansion / contraction direction in the first direction, and a piezoelectric element coupled to the portion of the fixed support portion in the first direction. A first elastic hinge portion that allows the piezoelectric element to move in the first direction to generate an elastic force according to the amount of movement and substantially prohibits the movement in the other direction; Of the piezoelectric element
A piezoelectric actuator having a wedge member inserted between the ends and controlling a distance therebetween is provided.

[Operation] In order to drive the piezoelectric element with high accuracy, it is desirable to apply a certain amount of preload. The piezoelectric element that expands and contracts in the first direction is supported by the first elastic hinge portion that allows the movement in the first direction to generate an elastic force according to the movement amount and substantially prohibits the movement in the other direction. This makes it possible to drive the piezoelectric element only in the first direction with high accuracy.

Also, by inserting a wedge member between the piezoelectric element and the fixed support portion, a desired preload can be easily applied.

[Embodiment] FIG. 1 is a perspective view showing a piezoelectric actuator according to an embodiment of the present invention. Base structure 1 is 1 in the Y direction in the figure
It is composed of a pair of fixed arm portions 1a, a pair of pillar members 1b, and a beam member 1c. Two pairs of elastic members 4a and 4b for guiding in the Z direction are connected in the base structure. That is, the fixed arm 1
The a, the pillar member 1b, and the beam member 1c form a substantially U-shaped structure as one rigid body. Secure any part of this U-shaped structure on the base. The laminated piezoelectric element 2 is arranged in the middle of the pair of pillar members 1b of the U-shaped base structure. When viewed with the piezoelectric element 2 as the center, it is preferable that the pair of pillar members 1b be symmetrically arranged. A strain gauge 3 is attached to this laminated piezoelectric element to monitor the displacement of the laminated piezoelectric element 2. Two pairs of leaf spring members 4a, 4b, which are arranged symmetrically between the piezoelectric element 2 and the pair of pillar members 1b,
Are joined by In the illustrated configuration, the upper end of the piezoelectric element 2 is formed by two pairs of leaf spring members 4a and 4b.
The lower end of the piezoelectric element 2 is connected to the upper end of b and the lower end of the piezoelectric element 2 is connected to the lower side of the column member 1b by a pair of leaf spring members 4c. The lower end of the laminated piezoelectric element 2 also has a gap with the beam member 1c, and the wedge member 6 is inserted and coupled thereto. That is, when the wedge member 6 is driven to the left side in the drawing, the thick portion of the wedge member is inserted between the laminated piezoelectric element 2 and the beam member 1c, and a large preload is applied to the laminated piezoelectric element 2. On the contrary, if the wedge member 6 is driven rightward in the figure,
The margin between the lower end of the piezoelectric element and the beam member 1c becomes large, and the preload applied to the laminated piezoelectric element 2 decreases. The wedge member 6 can be driven by rotating the screw member 8, for example. That is, by rotating the screw member 8, the preload applied to the laminated piezoelectric element 2 can be adjusted. In the above configuration, the laminated piezoelectric element is placed in the U-shaped rigid portion under a preload, and the upper end thereof is displaced by being driven by a voltage. The second elastic hinge portion 5 is coupled to the upper end of the laminated piezoelectric element 2. In the structure shown in the figure, the upper end of the laminated piezoelectric element 2 is coupled to the intermediate holding portion 9 for fixing the leaf spring members 4a, 4b, and the lower surface of the second elastic hinge portion 5 is bonded and fixed to the intermediate holding portion 9. There is. The upper surface of the second elastic hinge portion 5 is a driven body 7
Is fixed with an adhesive containing alumina, for example. Alumina serves to impart rigidity to the adhesive.

The second elastic hinge portion moves in the moving direction of the laminated piezoelectric element (in the drawing,
Along the Z direction), and exhibits low elasticity against a force in an XY plane orthogonal to the Z direction.
In the illustrated configuration, the cross-sectional shape is constituted by a spherical hinge whose outer periphery of a cylinder is scraped off in an arc shape.

That is, the spherical hinge member 5 has a smaller diameter toward the center thereof. When the laminated piezoelectric element 2 extends, the second elastic hinge portion 5 is driven in the Z direction, and the driven body 7 fixed to the upper end of the second elastic hinge portion 5 is driven in the Z direction. When the force acting on the driven body 7 is unbalanced and its surface is tilted, the driven body 7 moves to the second elastic hinge portion 5
Force in the XY plane acts on the second elastic hinge portion 5
Has a weak elasticity in the XY plane direction, and easily elastically deforms in accordance with the force in the XY plane direction. Therefore, no excessive strain stress is generated in the driven body 7 itself.

A piezoelectric element generally has hysteresis. Piezoelectric element 2
A strain gauge 3 is attached to the device to feed back the displacement of the piezoelectric element 2. A closed loop is formed by forming a feed bag system by integral compensation. Specific 1 of this configuration
In the example, the open loop hysteresis was about 15% and the closed loop feedbag was about 0.1%.

According to the piezoelectric actuator shown in FIG. 1, a desired preload is applied to the piezoelectric element, and a desired piezoelectric displacement is generated according to the electric signal. The displacement of the laminated piezoelectric element 2 is guided by the first elastic hinge portion 4 (4a, 4b) which allows only the displacement in the Z direction, and is transmitted to the second elastic hinge portion 5 as the displacement in the Z direction. Since the second elastic hinge portion has a high rigidity in the Z direction, the Z direction displacement transmitted from the laminated piezoelectric element 2 is transmitted to the driven body 7. On the contrary, the driven body 7
The second elastic hinge portion 5 absorbs the force transmitted from the second elastic hinge portion 5 due to the displacement.

FIG. 2 is a perspective view showing a stage device using the three piezoelectric actuators shown in FIG.

In the figure, a main stage 15 has a wafer chuck 16 on which a semiconductor wafer is placed, and an L-type mirror 17 for position monitoring in the X and Y2 directions at the end. Laser light from a laser (not shown) is incident on the L-shaped mirror 17, and the position in the XY plane is monitored by interference. The main stage 15 includes three coupling members 18a, 18b, 18c and three piezoelectric actuators 10a, 10b, 10c shown in FIG.
Combined with one. Piezoelectric actuators 10a, 10b, 10c
Are driven by the laminated piezoelectric elements 3a, 3b, 3c, respectively, and exert a driving force in the Z direction. The driving force in the Z direction is the second elastic hinge portions 5a, 5b, 5c represented by the spherical hinge members.
Is transmitted to the coupling members 18a, 18b, 18c via the and drives the main stage 15. The coupling members 18a, 18b, 18c are, for example, adhesives filled with alumina powder. Of course, a mechanical coupling member such as a screw can also be used.

When the three laminated piezoelectric members 3a, 3b, 3c are driven by the same amount, the main stage 15 makes a translational motion in the Z direction. 3
By changing the driving amount of the one laminated piezoelectric element 3a, 3b, 3c, a combination of translation in the Z direction, rotation θx about the X axis, and rotation θy about the y axis can be generated.

The points of action of the three piezoelectric actuators 10a, 10b, 10c are preferably selected at the vertices of an equilateral triangle. By choosing the points of action to be equilateral triangles, each of the three piezoelectric actuators is equivalent.

When the drive amounts of the three piezoelectric actuators 3a, 3b, 3c are different, strictly speaking, the inclination of the surface of the main stage 15 changes, and a force corresponding to the inclination is applied to each laminated piezoelectric element.
Here, since the second elastic hinge portions 5a, 5b, 5c each have weak rigidity in the XY plane perpendicular to the Z direction,
Such a force is absorbed by the deformation of the second elastic hinge portion 5.

Thus, by supporting the stage device with three or more piezoelectric actuators, driving in three degrees of freedom in the Z direction, θx rotation, and θy rotation can be performed with high accuracy.

By combining the piezoelectric element, hinge member, and wedge member organically, a compact and lightweight structure
A highly accurate actuator and stage device are realized.

Further, by realizing a driving device having a high degree of freedom for directly driving the driven object, a compact structure and high responsiveness can be obtained.

Even when the driving amount of the laminated piezoelectric element is different, the reaction force received by the main stage is small, and therefore the stress generated inside is also small. As a result, the deformation caused in the main stage can be reduced.

Since the driving force of the piezoelectric element to which the preload is applied is transmitted to the object to be driven by elastic deformation, it is possible to perform highly accurate driving without backlash and backlash.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited thereto. For example, various changes,
It will be apparent to those skilled in the art that modifications, combinations and the like are possible.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a highly accurate and highly responsive actuator using a piezoelectric element, and a stage device using the same.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a piezoelectric actuator according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a stage device using the piezoelectric actuator shown in FIG. In the figure, 1 base structure 1a fixed arm 1b column member 1c beam member 2 laminated piezoelectric element 3 strain gauge 4 first elastic hinge 5 second elastic Hinge part 6 …… Wedge member 7 …… Driven object 10 …… Piezoelectric actuator 11 …… Base structure 15 …… Main stage 16 …… Wafer chuck 17 …… L-shaped mirror 18 …… Coupling member

Claims (4)

(57) [Claims] 1. A piezoelectric actuator using a piezoelectric element that expands and contracts in a first direction in response to an applied electric signal, wherein a portion in the first direction and a second direction intersecting the first direction. And a piezoelectric element having an expansion and contraction direction in a first direction, and a piezoelectric element coupled to a portion of the fixed support section in the first direction,
A first elastic hinge portion that allows the piezoelectric element to move in a first direction to generate an elastic force according to the amount of movement and substantially prohibits a movement in another direction; and a second elastic hinge portion of the fixed support portion. And a wedge member that is inserted between the directional portion and one end of the piezoelectric element and controls the distance therebetween. 2. A pair of pillar members in which the fixed supporting portions are symmetrically arranged on both sides of a piezoelectric element along a first direction, and
It has a substantially U-shape including one beam member that connects each one end of a pair of pillar members, and the first elastic hinge portion connects an even number of pillar members and the piezoelectric element at symmetrical positions. The piezoelectric actuator according to claim 1, further comprising a leaf spring member. 3. The first end coupled to the other end of the piezoelectric element,
3. The piezoelectric actuator according to claim 1, further comprising a second elastic hinge portion having high rigidity in the direction of and the elasticity in a direction orthogonal to the first direction. 4. A fixed support surface defining a plane orthogonal to the first direction, a stage surface spaced from the fixed support surface in the first direction, and the fixed support surface on the fixed support surface. The stage device having three or more piezoelectric actuators according to claim (3), wherein a fixed support portion is fixed, and the second elastic hinge portion is fixed to the stage surface.