JP4801433B2 - Ultrasonic drive device and driven member used therefor - Google Patents

Description

  The present invention relates to an ultrasonic driving apparatus that drives a driven member such as a positioning stage using an ultrasonic motor, and a driven member used therefor.

  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 the ultrasonic motor is in contact with the drive force transmission member of the driven member to transmit the drive force. For this reason, generation of particles due to wear of the contact member on the ultrasonic motor side and the driving force transmission member on the driven member side is inevitable.

As a countermeasure against particles, a method of using a composite material as a sliding contact member on the driven member side (for example, Patent Document 1) or a method of defining surface roughness (for example, a patent) for the purpose of reducing wear and ensuring a life. Document 2), a method using a thermal spray material (for example, Patent Document 3), and the like have been proposed. Further, alumina (for example, Patent Document 4) and Al ₂ O ₃ / TiC composite material (for example, Patent Document 5) have been proposed as a method of using ceramics for the sliding contact member.

However, in the field where particles are extremely hated, such as semiconductor manufacturing equipment, it is necessary to take thorough countermeasures against particles, and even the proposals in Patent Documents 1 to 5 are still insufficient as particle countermeasures. It was.
JP 2003-264984 A JP 2000-278968 A Japanese Patent Laid-Open No. 10-309085 JP 2002-0277768 A JP 2003-018870 A

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic drive device with little wear and generation of particles and a driven member used therefor.

In order to solve the above problems, a first aspect of the present invention is an ultrasonic motor including an abutting member;
A driving force transmission member that transmits the driving force of the ultrasonic motor by the contact of the contact member, and a driven member that is driven by the ultrasonic motor;
An ultrasonic drive device comprising:
The driving force transmission member is made of alumina ceramic having a purity of 99.5% or more, and an average particle diameter thereof is 7.7 μm or less. The ceramic material has a purity of 99.5% or more as a raw material, and There is provided an ultrasonic driving device characterized in that an aluminum oxide powder having an average particle diameter of 1 μm or less is used and is fired at a firing temperature of 1200 to 1400 ° C.

  In the first aspect, it is preferable that an average particle diameter of alumina ceramics constituting the driving force transmitting member is 2.1 μm or more and 5.6 μm or less.

According to a second aspect of the present invention, there is provided a driven member for an ultrasonic driving device provided with a driving force transmitting member to which the driving force is transmitted by contact of an ultrasonic motor provided with an abutting member,
The driving force transmitting member is composed of a purity of 99.5% or higher alumina ceramics, and Ri der an average particle size 7.7μm or less, the ceramic material is 99.5% pure as a raw material and, A driven member for an ultrasonic drive device, characterized in that it is fired using an aluminum oxide powder having an average particle diameter of 1 μm or less and a firing temperature of 1200 to 1400 ° C.

In the second aspect, it is preferable that an average particle diameter of alumina ceramics constituting the driving force transmitting member is 2.1 μm or more and 5.6 μm or less.

  According to the present invention, the driving force transmitting member that transmits the driving force to the driven member by the contact of the abutting member of the ultrasonic motor has a purity of 99.5% or more and an average particle diameter of 7.7 μm or less. By using alumina ceramics, particles generated by sliding contact between the contact member and the driving force transmission member can be effectively suppressed. Therefore, the ultrasonic drive device of the present invention can be suitably used as a precision positioning device or the like in a field where particles must be suppressed as much as possible, for example, a semiconductor manufacturing 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 apparatus 100 is used for precise alignment of an object to be processed in a processing chamber such as a semiconductor manufacturing apparatus.

  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 13 a, and the abutting portion 13 a is disposed in a state where the abutting portion 13 a can abut against the driving force transmission surface 4 a 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 includes two ultrasonic vibrators 11a and 11b having a Langevin type structure, a holding member 12 that holds the ultrasonic vibrators 11a and 11b at a predetermined angle (90 degrees in FIG. 2), The head 13 has a substantially V-shaped shape that contacts the driving force transmission surface 4 a of the sliding contact plate 4. For example, a pressing mechanism 14 such as an air cylinder, a hydraulic cylinder, or a spring coil is attached to the holding member 12, and the head 13 is pressed against the driving force transmission surface 4 a of the sliding contact plate 4 with a predetermined force.

  The ultrasonic transducer 11a includes a bolt 21 having both ends threaded, a cap nut 22 having a screw hole that fits into a screw groove of the bolt 21, and two ring-shaped piezoelectric plates through which the bolt 21 can pass. 23a and 23b, and ring-shaped electrode plates 24a to 24c through which the bolts 21 can pass.

  Similar to the ultrasonic transducer 11a, the ultrasonic transducer 11b includes a bolt 21 ', a cap nut 22', two ring-shaped piezoelectric plates 23a 'and 23b', and ring-shaped electrode plates 24a 'to 24a'. 24c '. Electrodes (not shown) are formed on the front and back surfaces of the piezoelectric plates 23a, 23b, 23a ', and 23b'. The number of piezoelectric plates provided in one ultrasonic transducer is arbitrary and is not limited to two.

  The holding member 12 is provided with a hole for allowing the bolt 21 to pass therethrough. The head 13 includes a contact portion 13a that is in contact with the driving force transmission surface 4a of the sliding contact plate 4, connection portions 13b and 13b ′ that are connected to the ultrasonic transducers 11a and 11b, contact portions 13a and connection portions 13b, and the like. It is comprised from neck parts 13c and 13c 'which connect 13b'.

  The connecting portions 13b and 13b 'of the head 13 are formed with screw holes that fit into the screw grooves of the bolts 21 and 21', respectively. The head 13 is made of a material having excellent wear resistance, for example, a metal material such as stainless steel or cemented carbide, or a ceramic such as alumina, silicon nitride, or silicon carbide. If the head 13 is made of metal, it is easy to form screw grooves for connecting the bolts 21 and 21 ′ to the head 13. It is also preferable that the head 13 is made of a metal material, and the surface of the contact portion 13a is coated with silicon nitride or the like.

  As shown in FIG. 2, the piezoelectric plates 23 a and 23 b are arranged so as to be sandwiched between the electrode plates 24 a to 24 c, and bolts 21 are inserted into the holes of the piezoelectric plates 23 a and 23 b, the electrode plates 24 a to 24 c and the holding member 12. The head 13 and the cap nut 22 are attached to the end portions of the bolts 21, respectively. As a result, the piezoelectric plates 23a and 23b are fastened with a predetermined force to form the ultrasonic transducer 11a. Thus, in the ultrasonic motor 10, the head 13 not only gives thrust to the stage 3 via the driving force transmission surface 4 a of the sliding contact plate 4, but also plays a role as a member constituting the Langevin type vibrator. ing. In the same manner, the ultrasonic transducer 11b is configured.

  Normally, a metal material is used for the bolt 21, the cap nut 22, and the holding member 12. In this case, the electrode plates 24 a and 24 c are electrically connected to the cap nut 22 through the holding member 12. Therefore, the holding member 12 or the cap nut 22 of the ultrasonic transducer 11a can be used as a ground electrode for driving the piezoelectric bodies 23a and 23b. At this time, the piezoelectric plate 23a ′ included in the ultrasonic transducer 11b. , 23b 'can be grounded simultaneously.

  When the head 13 is made of metal, the head 13 is electrically connected to the electrode plate 24a via the bolt 21 and the cap nut 22, so that the cap nuts 22 and 22 'of the holding member 12 or the ultrasonic transducers 11a and 11b are connected. If either one is grounded, the head 13 can also be held in the grounded state.

  For the piezoelectric plates 23a and 23b, piezoelectric ceramics such as PZT are preferably used. The directions of polarization of the piezoelectric plates 23a and 23b are symmetric with respect to the electrode plate 24b sandwiched between the piezoelectric plates 23a and 23b. The electrode plates 24a and 24c are electrically connected to each other. Therefore, when a voltage is applied between the electrode plate 24b and the electrode plate 24c, the piezoelectric plates 23a and 23b are displaced (vibrated) in the same phase. That is, the piezoelectric plates 23a and 23b extend or shrink together in the thickness direction.

  Therefore, by applying a voltage signal having a resonance frequency to the piezoelectric plates 23a and 23b to vibrate the ultrasonic transducer 11a, this vibration is magnified by the neck portion 13c and transmitted to the contact portion 13a. At the same time, when a voltage signal having a predetermined resonance frequency is input to the piezoelectric plates 23a ′ and 23b ′ to vibrate the ultrasonic vibrator 11b, the vibration is expanded by the neck portion 13c ′ and transmitted to the contact portion 13a. It is done. In this way, a displacement motion is generated in the contact portion 13a in which the vibrations transmitted from the two ultrasonic transducers 11a and 11b via the neck portions 13c and 13c 'are combined.

  Referring to FIG. 1 again, the slidable contact plate 4 fixed to the stage 3, which is a movable body, functions as a driving force transmission member that transmits the driving force from 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.

  As the ceramic material constituting the sliding contact plate 4, alumina whose purity, that is, the alumina content is 99.5% by weight (hereinafter, simply referred to as “%”) or more, preferably 99.9% or more is used. When the alumina content is less than 99.5%, the generation of particles increases as shown in the test examples described later. The average particle diameter of alumina is 7.7 μm or less, preferably 2.1 μm to 5.6 μm or less. When the average particle diameter of alumina exceeds 7.7 μm, the effect of suppressing particles becomes insufficient and the number of particles increases. The reason for this is considered to be that when the average particle diameter of alumina exceeds 7.7 μm, relatively low-strength grain boundary portions are gathered and become larger and easily fall off.

  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, a method for manufacturing the sliding contact plate 4 will be described.

As the aluminum oxide powder used as a raw material, a high purity powder of 99.5% or more is used.
Moreover, as an average particle diameter of the said aluminum oxide powder, it is preferable to use that whose D50 is 1 micrometer or less.

  When the purity of the raw material is less than 99.5% or when the average particle diameter exceeds 1 μm (for example, when it is 2 μm or more), the low-temperature easy-sintering property is lost, and the sintering density is sufficient. Does not go up. 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.

  In order to produce the sliding contact plate 4 having the average particle diameter, a powder obtained by mixing a raw material aluminum oxide powder and a binder is molded, and after CIP treatment, firing is performed 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 grain growth occurs and the pores may become coarse.

  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. Further, in order to facilitate the sintering at such a low temperature (that is, to exhibit the low temperature easy sintering property), the above-described high purity of 99.5% or more and an average particle diameter of 1 μm or less. Aluminum oxide 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).

Moreover, it is preferable to further subject the aluminum oxide sintered body obtained under the above firing conditions to HIP treatment (for example, treatment in a HIP furnace having a carbon heater). 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. .

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 mounted on the stage 3 as a driven member. As the sliding contact plate 4, eight types of samples A to H shown in Table 1 were prepared. Samples A to H are all alumina and have the following physical properties in addition to those shown in Table 1.

<Physical properties of sample>
Vickers hardness = 18-20GPa
Fracture toughness value = 3-4 MPa√m
Young's modulus = 390 to 400 GPa
Thermal conductivity = 30 to 35 W / m · K

Moreover, about each sample AH, mirror surface grinding | polishing was performed beforehand and the pore number (per 1 mm < ² >) and average particle diameter of 3 micrometers diameter or more were measured by observation with a scanning electron microscope (SEM). Here, the average particle diameter was calculated by calculating a value obtained by drawing a line on the SEM photograph and dividing the length of the line by the number of particles crossing the line. In addition, the number of pores of each sample is as shown in Table 1.

  As the ultrasonic motor, an ultrasonic motor 10 having a Langevin type vibrator having the same structure as that shown in FIG. 2 was used, and this was attached to the stage 3 having a movable part weight of 10 kg and a stroke of 250 mm.

At the tip of the ultrasonic motor, alumina having a purity of 99.99% and having a pore number of 3 μm or more (per 1 mm ² ) of 1000 or less was used. These samples were mirror-polished, and the number of pores of 3 μm or more and the average particle diameter were measured by SEM observation.

The test was performed by continuously driving the stage 3 at a speed of 100 mm / sec and an acceleration of 1 m / sec ² and measuring the generated abrasion powder with a particle counter. The particle counter sucks 28.3 liters per minute and simultaneously counts the number of 7-level particles of 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, 1 μm or more. In the mode, measurement was performed continuously for 12 hours from the start of driving for 12 hours, and an average of 1 hour was taken as a measured value. The results are shown in Table 1. FIG. 3 shows the relationship between the average particle diameter of alumina having a purity of 99.5% or more and the amount of particles measured (number).

  From Table 1, Sample A had an extremely large amount of particle measurement compared to the others. This is mainly due to the fact that there is a correlation between the average particle diameter and the amount of generated particles except for sample A, and the number of pores does not change between sample A and sample D, so the purity of sample A is low. It is done. When the purity of the alumina ceramics constituting the sliding contact plate 4 is 99.5% or more, if the average particle diameter is 1.4 to 7.7 μm or less, the amount of particles having a diameter of 0.2 μm regardless of the number of pores Was found to be 200 or less. It was also found that when the average particle size is 2.1 to 5.6 μm, the amount of particles is further reduced, and the amount of particles measured with a diameter of 0.3 μm or more is at a level that is not different from the background. From this test result, it was shown that the generation of particles can be suppressed and the number of particles can be reduced as much as possible by setting the purity of alumina to 99.5% or more and the average particle diameter to 7.7 μm or less.

  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.

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

The perspective view which shows schematic structure of a positioning device. Sectional drawing which shows schematic structure of an ultrasonic motor. The graph which shows the measurement result of the number of particles.

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; Ultrasonic vibrator 12; holding member 13; head 13a; abutting portions 13b and 13b '; connecting portions 13c and 13c'; neck portion 14; pressing mechanism 15; driven bodies 21 and 21 '; Cap nuts 23a, 23b, 23a ', 23b'; piezoelectric plates 24a-24c; 24a'-24c '; electrode plates

Claims (4)

An ultrasonic motor provided with a contact member;
A driving force transmission member that transmits the driving force of the ultrasonic motor by the contact of the contact member, and a driven member that is driven by the ultrasonic motor;
An ultrasonic drive device comprising:
The driving force transmission member is made of alumina ceramic having a purity of 99.5% or more, and an average particle diameter thereof is 7.7 μm or less,
The ceramic material is fired at a firing temperature of 1200 to 1400 ° C. using an aluminum oxide powder having a purity of 99.5% or more as a raw material and an average particle diameter of 1 μm or less, Ultrasonic drive device. 2. The ultrasonic driving device according to claim 1, wherein an average particle diameter of alumina ceramics constituting the driving force transmitting member is 2.1 μm or more and 5.6 μm or less. A driven member for an ultrasonic driving device provided with a driving force transmitting member that transmits a driving force by contacting an ultrasonic motor provided with an abutting member,
The driving force transmission member is made of alumina ceramic having a purity of 99.5% or more, and an average particle diameter thereof is 7.7 μm or less,
The ceramic material is fired at a firing temperature of 1200 to 1400 ° C. using an aluminum oxide powder having a purity of 99.5% or more as a raw material and an average particle diameter of 1 μm or less, A driven member for an ultrasonic driving device. The driven member for an ultrasonic driving device according to claim 3, wherein an average particle diameter of alumina ceramics constituting the driving force transmitting member is 2.1 μm or more and 5.6 μm or less.

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