JP4804826B2 - Ultrasonic drive - Google Patents

Description

The present invention relates to ultrasonic driving equipment for driving a driven member such as positioning stage using an ultrasonic motor.

  Precision positioning systems using ultrasonic motors have begun to be used in fields that hate magnetism such as electron beam exposure (EB). Such a precision positioning system employs a friction drive system in which an ultrasonic motor transmits a driving force by coming into contact with a driving force transmission surface of a driven member. For this reason, generation of particles due to wear of the contact member on the ultrasonic motor side and the driving force transmission surface on the driven member side is inevitable. Further, there is a problem that wear is accelerated by the generated particles being caught between the contact member and the driving force transmission surface during repeated driving. Further, there is a problem that the wear power is fluctuated between the contact member and the driving force transmission surface, the driving force fluctuates, the precision positioning control becomes unstable, and the positioning accuracy is lowered.

As countermeasures against these problems, a method of sweeping away abrasion powder on the driving force transmission surface with a brush (for example, Patent Document 1 and Patent Document 2), or a method of scraping dust adhering to the driving force transmission surface with a scraper (for example, Patent Document 3) has been proposed.
JP 2002-142471 A JP 2004-236389 A JP 2005-051836 A

  When the precision positioning system is used in a vacuum environment, for example, in a vacuum chamber of a semiconductor manufacturing apparatus, dust adheres to the driving force transmission surface more firmly than in a normal pressure use environment. In a vacuum environment, a small amount of organic matter present in the atmosphere adheres to the driving force transmission surface. These dusts and organic substances may gradually accumulate on the driving force transmission surface and form deposits. Such deposits cannot be suppressed or removed by the methods of Patent Documents 1 to 3 described above, and the control of precision positioning becomes unstable, or the driven member is driven over a long distance. There was a problem that the sonic motor stopped.

  Accordingly, an object of the present invention is to provide an ultrasonic driving device that has little deposit formation even when used in a vacuum environment and does not deteriorate positioning accuracy and durability in long-distance driving.

To solve the above problems, the present onset Ming, an ultrasonic motor having a contact member,
A driven member that is driven by the ultrasonic motor, and includes a driving force transmission surface that transmits the driving force of the ultrasonic motor when the abutting member comes into contact;
An ultrasonic drive device comprising:
The driving force transmission surface is made of a ceramic material having a center line average roughness (Ra) of 0.5 μm or less and 3 μm or more pores of 10,000 or less per 1 mm ² .
An ultrasonic driving device is provided, comprising a wiping member for wiping off deposits on the driving force transmission surface .

In the first aspect, the ceramic material preferably has 1000 or less pores having a diameter of 3 μm or less per 1 mm ² .

According to the present invention, the driving force transmission surface of the driven member driven by the ultrasonic motor of the ultrasonic driving device has a center line average roughness (Ra) of 0.5 μm or less and a diameter of 3 μm or more. Since the pores are made of a ceramic material having 10,000 or less per 1 mm ² , the formation of deposits on the driving force transmission surface is suppressed even in a vacuum environment, and the driven member is stably driven over a long distance with a small positional error. be able to.

  In particular, it is possible to dramatically improve the driving distance in a vacuum environment by disposing a wiping member for removing deposits on the driving force transmission surface in the ultrasonic driving device.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a positioning apparatus 100 according to an embodiment of an ultrasonic driving apparatus using an ultrasonic motor as a driving source. The positioning device 100 is used for precise positioning of an object to be processed in a processing chamber such as a semiconductor manufacturing apparatus in a vacuum environment.

  As shown in the figure, the positioning device 100 includes, for example, a pair of guide rails 2 on a base 1, and linearly guides a stage 3 that is a movable body by these guide rails 2. A sliding plate 4 having a driving force transmission surface 4 a parallel to the guide rail 2 is fixed to one side surface of the stage 3. A linear scale 5 is provided on the other side surface of the stage 3 in parallel with the sliding contact plate 4. A detector 6 for reading information recorded on the linear scale 5 is provided at a position facing the linear scale 5. The linear scale 5 and the detector 6 function as position detecting means in cooperation.

  An ultrasonic motor 10 is provided at a position facing the sliding plate 4. The ultrasonic motor 10 includes an abutting portion 10 a, and the abutting portion 10 a is disposed in a state where the abutting portion 10 a abuts against the driving force transmission surface 4 a of the sliding contact plate 4. Further, wiping members 13 and 14 for cleaning the driving force transmission surface 4a of the sliding contact plate 4 are disposed on both sides of the ultrasonic motor 10 so as to sandwich the contact portion 10a therebetween. The tips of the wiping members 13 and 14 are also arranged in contact with the driving force transmission surface 4a of the sliding contact plate 4. Note that reference numeral 9 in FIG. 1 denotes a housing that houses the ultrasonic motor 10.

  Further, the positioning device 100 outputs a control unit 7 for controlling the driving conditions of the stage 3 according to the position information measured by the linear scale 5 and the detector 6 as position detecting means, and the control unit 7 outputs the position information. A driver 8 that outputs a command signal for driving the ultrasonic motor 10 based on the signal is provided, and these are electrically connected.

  FIG. 2 shows a schematic configuration of the ultrasonic motor 10. The ultrasonic motor 10 has a structure in which the piezoelectric elements 11a or the piezoelectric elements 11b and the metal plates 12 are alternately stacked, and the driving force transmission surface 4a of the sliding contact plate 4 is provided at the most distal portion of the stacked body. A ceramic plate 15 having a contact portion 10a for contacting and pressing the ceramic plate 15 is provided. The contact portion 10 a is a convex portion formed on the ceramic plate 15.

  The piezoelectric element 11a has driving electrodes (not shown) formed on both surfaces of a thin plate-like piezoelectric body, and a 33 mode element in which the piezoelectric body is displaced in the thickness direction when a predetermined voltage is applied between the driving electrodes. It is. On the other hand, the piezoelectric element 11b is a 15-mode element in which driving electrodes (not shown) are formed on both surfaces of a thin plate-like piezoelectric body, and the piezoelectric body is displaced in the shearing direction when a predetermined voltage is applied between the driving electrodes. It is.

  The 33-mode element 11a is prepared by, for example, preparing a piezoelectric body having a predetermined thickness, printing electrodes on both surfaces by a screen printing method or the like using a silver paste or the like, firing, and then forming a predetermined gap between the formed electrodes. It can be produced by applying a voltage of The 15-mode element 11b is prepared by preparing a piezoelectric body having a predetermined thickness, and applying a predetermined high voltage between electrodes formed using a silver paste or the like on a pair of opposing side surfaces to perform polarization processing. Thereafter, the electrode can be removed, and a drive electrode can be newly formed on both surfaces of the piezoelectric body using a conductive resin or the like so that the polarization cannot be released.

  The 33-mode element 11a and the metal plate 12 and the 15-mode element 11b and the metal plate 12 are bonded with a resin adhesive, respectively. The adhesive layer formed by the resin adhesive is thin, and the driving electrodes formed on the 33 mode element 11 a and the 15 mode element 11 b are in partial contact with the metal plate 12. In this way, the metal plate 12 is connected to every other layer to form a positive electrode and a negative electrode, and a drive voltage is applied thereto, whereby a drive voltage is applied to the drive electrodes formed in the 33 mode element 11a and the 15 mode element 11b. The result is the same as applying.

  As shown in FIG. 2, when the 33 mode element 11a is used to extend when a voltage is applied, the electric field generated by the drive voltage is in the same direction as the polarization direction (arrow S1) of the piezoelectric body of the 33 mode element 11a. Arrange so that (arrow S2) is applied. On the other hand, when the 33-mode element 11a is used to contract when a voltage is applied, the electric field (arrow S2) by the drive voltage and the direction of polarization of the piezoelectric body (arrow S1) are reversed.

  Further, the 15-mode element 11b is arranged so that the direction of shear deformation is the same and the displacement amount is totaled. For example, in the two 15-mode elements 11b positioned above and below the single metal plate 12, the direction in which the electric field is applied (arrow S2) is opposite, so the direction of polarization (arrow S3) is also perpendicular to the thickness direction. Arrange so that the direction is opposite. In FIG. 2, a state in which the four-layer 15-mode element 11b is shear-deformed is indicated by a broken line.

  In the ultrasonic motor 10, the lower four layers are configured by 33 mode elements 11a, and the upper four layers are configured by 15 mode elements 11b. The number of layers of the 33 mode element 11a and the 15 mode element 11b can be arbitrarily set in order to obtain a desired amount of displacement. The metal plate 12 located at the boundary between the 33-mode element 11a and the 15-mode element 11b is set so as to always be ground (GRD) when a drive voltage is applied to the 33-mode element 11a or the 15-mode element 11b. . The voltage applied to the 33-mode element 11a (33-mode element drive signal) and the voltage applied to the 15-mode element 11b (15-mode element drive signal) are set to appropriate values in order to obtain a predetermined amount of displacement. Is done.

  When driving the ultrasonic motor 10, for example, first, the 33-mode element 11a of the ultrasonic motor 10 fixed in the housing 9 is contracted, and then the 15-mode element 11b is shear-deformed, and then the 33-mode element is operated. The element 11a is extended, and then the shear deformation of the 15-mode element 11b is released. When the 33-mode element 11a and the 15-mode element 11b are driven in this way, the abutting portion 10a makes a circular motion in a direction perpendicular to the driving force transmission surface 4a of the sliding contact plate 4, and can be driven by one cycle. The stage 3 can be moved by the amount of shear deformation of the 15-mode element 11b. In addition, the stage 3 can be finely positioned by controlling the voltage value for applying the displacement amount of the 15-mode element 11b to a predetermined value.

  The sliding contact plate 4 fixed to the stage 3 that is a movable body functions as a driving force transmission member that transmits the driving force of the ultrasonic motor 10 to the stage 3. Therefore, the stage 3 and the sliding contact plate 4 constitute a driven member in the positioning device 100.

Examples of the ceramic material constituting the sliding contact plate 4 include alumina, Al ₂ O ₃ —TiC, SiC, Si ₃ N _{4 and the} like. In the present embodiment, the driving force transmission surface 4a of the slidable contact plate 4 has a center line average roughness (Ra) of 0.5 μm or less, preferably 0.05 to 0.2 μm (processing costs are sharp for 0.1 μm or less). And the pores having a diameter of 3 μm or more are formed of alumina having 10,000 or less, preferably 1000 or less, per 1 mm ² .

  For the wear of the tip (contact portion 10a) of the ultrasonic motor 10 and the sliding member (sliding contact plate 4), the initial wear having a fast wear speed called "familiar" in the initial stage and the wear after "familiar". There is a state of low speed. When the center line average roughness (Ra) of the driving force transmission surface 4a of the sliding contact plate 4 exceeds 0.5 μm, the initial wear and the wear rate after “familiarity” do not change so much and a lot of wear powder is generated. Therefore, regardless of the number of pores and the presence or absence of the wiping members 13 and 14, deposits are formed on the driving force transmission surface 4 a at an early stage, which causes a position error in the stage 3, which is not preferable.

Further, if there are more than 10000 pores with a diameter of 3 μm or more on the surface of the sliding contact plate 4 (driving force transmission surface 4 a) per 1 mm ² , the wiping members 13 and 14 are positioned at an early stage when the wiping members 13 and 14 are not provided. An error occurs. When a large number of pores having a diameter of 3 μm or more exist on the driving force transmission surface 4a, the interaction between the deposit and the sliding contact plate 4 is strong, and the tip of the ultrasonic motor 10 (the contact portion 10a) hits. Depending on the detachment or wiping with the wiping members 13, 14, the deposits are not completely removed, so that the formation of deposits easily proceeds. On the other hand, when the number of pores having a diameter of 3 μm or more is 10,000 or less, preferably 1000 or less per 1 mm ² on the driving force transmission surface 4a of the sliding contact plate 4, formation of deposits is suppressed, and the stage 3 It is possible to dramatically improve the travel distance until the position error exceeds the allowable range.

  For example, the sliding contact plate 4 is formed into a plate shape or a sheet shape by using various methods such as a press molding method, an extrusion molding method, and an injection molding method, and fired at a predetermined temperature, and then ground as necessary. -It can be produced by cutting or the like. Hereinafter, the manufacturing method will be described by taking the case of using alumina as the ceramic material of the sliding contact plate 4 as an example.

As the aluminum oxide powder used as a raw material, it is preferable to use a powder having a high purity of 99% or more. If the purity is less than 99%, it is difficult to obtain the driving force transmission surface 4a having a pore number of 3 μm diameter or more and 10000 / mm ² or less. The average particle diameter of the aluminum oxide powder is preferably 1 μm or less. If the average particle diameter of the raw material aluminum oxide powder exceeds 1 μm, it is difficult to obtain the driving force transmission surface 4a having a pore number of 3 μm or more and 10000 / mm ² or less.

  When the purity of the raw material is less than 99% or when the average particle diameter is coarser than 1 μm, the low-temperature easy-sintering property is lost and the sintering density is not sufficiently increased. On the other hand, if sintering is performed at a high temperature to increase the sintering density, grain growth may occur and the pores may become coarse. Therefore, as the aluminum oxide powder used as a raw material, it is preferable to use a powder having an average particle diameter of 1 μm or less with a purity of 99% or more, and an average particle diameter of 0.5 μm or less with a purity of 99.8% or more. It is more preferable to use those.

In order to produce the sliding contact plate 4, a powder obtained by mixing a raw material aluminum oxide powder and a binder is molded, subjected to CIP treatment, and then fired while controlling firing conditions. The firing temperature condition can be set to 1200 to 1400 ° C., for example. When the firing temperature is less than 1200 ° C., the sintering itself does not proceed easily, and it becomes difficult to obtain a sintered body. On the other hand, a firing temperature exceeding 1400 ° C. is not preferable because it is difficult to obtain the driving force transmission surface 4a having a pore number of 3 μm or more and 10000 / mm ² or less.

  The reason for firing at 1200 to 1400 ° C., which is lower than the firing temperature normally used for alumina ceramics (1500 to 1600 ° C.), is that grain growth (crystal growth) at temperatures exceeding 1400 ° C. (in the case of an aluminum oxide substrate). This is because the pores move to the grain boundary phase and the pores become coarse due to grain growth. In addition, in order to facilitate such low-temperature sintering (that is, to exhibit low-temperature easy-sinterability), the above-described aluminum oxide having a high purity of 99% or more and an average particle diameter of 1 μm or less is used. Powder is used as a raw material. As the firing atmosphere, for example, firing can be performed in air, inert atmosphere (for example, argon atmosphere), or reducing atmosphere (for example, nitrogen atmosphere by using a carbon heater or the like).

Further, in order to reduce the pores on the surface of the sliding contact plate 4 (the driving force transmission surface 4a), the aluminum oxide sintered body obtained under the above firing conditions is further subjected to HIP treatment (for example, in a HIP furnace having a carbon heater). It is preferable to apply a treatment. The HIP treatment is preferably performed at a temperature somewhat lower than the firing temperature, for example, less than 1000 to 1400 ° C. from the viewpoint of not causing pore coarsening due to grain growth, and is preferably performed at a pressure of about 1800 kg / cm ^2. .

  As described above, the positioning device 100 is provided with the wiping members 13 and 14 for the purpose of removing the deposits on the driving force transmission surface 4a. As shown in FIG. 1, the wiping members 13 and 14 are preferably provided on both sides of the contact portion 10 a of the ultrasonic motor 10. The wiping members 13 and 14 can be cleaned by physically scraping off dust or the like adhering to the driving force transmission surface 4a of the sliding contact plate 4 in a vacuum environment. Further, in a vacuum environment, a slight amount of organic matter present in the atmosphere is fixed to the driving force transmission surface 4a little by little and it becomes easy to form a deposit. However, by providing the wiping members 13 and 14, examples described later As shown in the figure, it is possible to suppress the formation of deposits and to significantly improve the travel distance of the stage 3.

Next, test results for confirming the effects of the present invention will be described.
A continuous driving experiment was performed by changing the material of the sliding contact plate 4 of the stage 3 as a driven member. Four types of samples A to D shown in Table 1 were prepared as the sliding contact plate 4. Samples A to D are all alumina and have the following physical properties in addition to those shown in Table 1.

<Physical properties of sample>
Purity:> 99.9%
Vickers hardness = 20 GPa
Fracture toughness value = 3 MPa√m
Young's modulus = 400 GPa
Thermal conductivity = 35 W / m · K

Each sample A to D was previously mirror-polished, and the number of pores having a diameter of 3 μm or more (per 1 mm ² ) was measured by observation with a scanning electron microscope (SEM). In addition, the number of pores of each sample is as shown in Table 1.

The ultrasonic motor 10 uses a “Spider” (product name) manufactured by Tech Concierge Kumamoto Co., Ltd. having the same structure as that shown in FIG. 2, and this is applied to the stage 3 having a moving part weight of 1.2 kg and a stroke of 100 mm. It attached and installed in the vacuum chamber of 1x10 <^-4> Pa. Further, alumina having a purity of 99.99% was used as the material of the contact portion 10a of the ultrasonic motor 10. The stage 3 was driven continuously at a speed of 50 mm / sec and an acceleration of 80 mm / sec ² .

  In addition, the case where the wipers 13 and 14 are installed on both sides of the abutting portion 10a of the ultrasonic motor 10 and the case where the wipers 13 and 14 are not installed are compared by performing continuous driving under the same conditions.

  The test was stopped when the position error of the stage 3 in the constant speed region during the feedback control driving became 0.1 μm or more, and the shape measurement of the surface of the sliding contact plate 4 (the driving force transmission surface 4a) was performed. It was done with a vessel.

From the experimental results, it was found that the position error increases as the rising height of the driving force transmission surface 4a due to the adhering material increases, and the position error during constant speed traveling exceeds 0.1 μm when the height reaches approximately 200 nm. . In addition, comparison between sample A and sample B confirms that there is a large difference in deposit formation speed depending on the number of pores of 3 μm diameter or more (per 1 mm ² ) present on the driving force transmission surface 4a. It was found that 10000 or less is preferable.

In addition, when the number of pores having a diameter of 3 μm or more existing per 1 mm ^{2 of} the driving force transmission surface 4a is 10,000 or less (sample B), the position of the stage 3 during constant speed traveling by attaching the wiping members 13 and 14 It was found that the travel distance until the error became 0.1 μm increased dramatically. Further, when the number of pores having a diameter of 3 μm or more existing per 1 mm ^{2 of} the driving force transmission surface 4a is 1000 or less (sample C), if the wiping members 13 and 14 are used, the position error of the stage 3 even when traveling 200 km or more. Gave a good result of less than 0.1 μm.

On the other hand, when the center line surface roughness (Ra) of the driving force transmission surface 4a is 1.0 μm or more (sample D), the wiping member 13 is provided even if the number of pores having a diameter of 3 μm or more (per 1 mm ² ) is 1000 or less. No difference in the effect due to the presence or absence of 14 and 14 was observed, and the travel distance until the position error of the stage 3 reached 0.1 μm was as short as 100 to 300 m.
Further, in the test in which the wiping members 13 and 14 were provided, when the wiping members 13 and 14 were observed after the test, the wear powder was filled in the wiping members 13 and 14 and the function as a wiper was not achieved.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.
For example, in the above embodiment, alumina is used as the ceramic material constituting the sliding contact plate 4, but the center line average roughness (Ra) is 0.5 μm or less, and pores having a diameter of 3 μm or more are 10,000 per 1 mm ^2. As long as the ceramic material is less than or equal to the number, materials other than alumina can be used similarly.

  The ultrasonic drive device of the present invention can be suitably used as a precision positioning device provided in, for example, a vacuum chamber in a semiconductor manufacturing apparatus.

The perspective view which shows schematic structure of a positioning device. Sectional drawing which shows one Embodiment of an ultrasonic motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Base 2; Guide rail 3; Stage 4; Sliding contact plate 4a; Driving force transmission surface 5; Linear scale 6; Detector 7; Control part 8; Driver 9; Element 11b; 15-mode element 12; Metal plate 13, 14; Wiping member

Claims (4)

An ultrasonic motor provided with a contact member;
A driven member that is driven by the ultrasonic motor, and includes a driving force transmission surface that transmits the driving force of the ultrasonic motor when the abutting member comes into contact;
An ultrasonic drive device comprising:
The driving force transmission surface is made of a ceramic material having a center line average roughness (Ra) of 0.5 μm or less and 3 μm or more pores of 10,000 or less per 1 mm ² .
An ultrasonic drive device comprising a wiping member for wiping off deposits on the drive force transmission surface . ^{2. The} ultrasonic drive device according to claim 1, wherein the number of pores having a diameter of 3 μm or more in the ceramic material is 1000 or less per 1 mm ² . The ceramic material is a material fired at a firing temperature of 1200 to 1400 ° C. using an aluminum oxide powder having a purity of 99% or more as a raw material and an average particle diameter of 1 μm or less. Or the ultrasonic drive device of Claim 2. 4. The ultrasonic drive according to claim 1, wherein the ultrasonic drive device is used for alignment of an object to be processed in a processing chamber in a vacuum environment. 5. apparatus.

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