JPH01288647A - Active damping base for precise instrument - Google Patents

Abstract

PURPOSE:To cut off the vibration transmission onto a high precision instrument by arranging an elastic support body having a low spring constant in the horizontal direction and high spring constant in the vertical direction and controlling the vibration of the additional mass so that its phase may reverse against a harmful vibration. CONSTITUTION:An elastic support body 2 is that which laminates a metal sheet 12 and rubber sheet 13 alternately. Pressure containers 4a, 4b are mutually communicated via the conduit 14 having an orifice 5 and communicated respectively to air springs 6a, 6b as well. A compressed air source 7 is connected via a vibration control valve 9 to one part of the pressure containers 4a, 4b and the whole body of this part becomes the actuator A for active control offsetting a harmful vibration by sensing the harmful vibration vibrating an upper part foundation 1a and applying the reaction force for control reversing its phase to the upper part foundation 1a. Consequently the upper part foundation 1a can maintain its still state despite of the input of the harmful vibration.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is applicable to ultra-precision processing and measuring equipment including semiconductor manufacturing equipment such as steppers, mask aligners, electron beam exposure equipment, STM, and laser equipment. Concerning the basics of active vibration damping for precision equipment.

(Conventional technology and its problems) Conventionally, in precision facilities such as semiconductor factories where vibrations are averse, highly rigid foundations that are separated from other areas have been used as spaces for installing particularly precise equipment.

However, if we take semiconductor equipment as an example, as the grade of microfabrication becomes higher and higher due to the development of ultra-LSIs, the vibration characteristics of these fundamentals have become a problem.

Normally, a grating floor structure is used in semiconductor factories, and where ultra-precision equipment is installed, a foundation is provided independent of the floor to prevent the transmission of vibrations, and the height of the foundation is 1.
It was necessary to raise the height by ~3111. Therefore, although the rigidity in the vertical direction can be maintained relatively sufficiently, it is extremely difficult to maintain the rigidity in the horizontal direction. Even in foundations for such ultra-precision equipment, amplification of vibrations in the horizontal direction is likely to occur, and countermeasures have been required.However, with conventional vibration-proof foundations, vibrations are always amplified near the resonance point. ,
Furthermore, there was also the problem of vibration achieved with the ultra-precision equipment on board, which was extremely difficult to solve.

In addition, vibration isolators are built into the ultra-precision equipment itself, and many eigenmodes converge in similar frequency bands, making it difficult to provide effective vibration isolation effects.

(Object of the invention) The present invention was made in view of the drawbacks of the conventional example, and
The purpose is to provide an innovative active vibration damping foundation for precision equipment that can solve such complex vibration environments at once and cut off vibration transmission to ultra-precision equipment.

(Means for Solving the Problems) The present invention provides the first method for solving the problems of the prior art.
In section: ■An elastic support with a low spring constant in the horizontal direction and a high spring constant in the vertical direction (2) is placed on the lower foundation (1b) to support the upper foundation (1a), and ■The upper foundation ( 1a) is installed in the active control actuator that senses the harmful vibration that vibrates and controls the control vibration of the additional mass (8) so that its phase is inverted with respect to the harmful vibration to offset the harmful vibration. do.

The following technical measures have been adopted, and in Section 2: ■ An elastic support (2) with a low spring constant in the horizontal direction and a high spring constant in the vertical direction is placed on the lower foundation (1b). The upper foundation (1a) is supported by an additional mass (1a) that can swing freely in the horizontal direction.
8) to set the horizontal natural frequency of the added mass (8) to be approximately equal to the natural frequency of the water first mode of the upper foundation (1a), thereby reducing the harmful vibrations of the upper foundation (la). The harmful vibration is canceled by sensing the vibration and controlling the controlled vibration of the added mass (8) so that its phase is inverted with respect to the harmful vibration.

In Section 3, we have adopted the following technical means: The horizontal natural frequency of the mass (8) is set approximately equal to the natural frequency of the horizontal primary mode of the base body (1), and the harmful vibrations that cause the base body (1) to vibrate are sensed to reduce the vibration of the additional mass (8). The control vibration is controlled so that its phase is inverted with respect to the harmful vibration, thereby canceling out the harmful vibration.

: We have adopted the technical means of

(Function) Hereinafter, the function of the active vibration damping foundation for precision equipment according to the present invention will be explained.

In item 1, the elastic support (2) passively insulates vibration amplification and transmission.
) has a high spring constant in the vertical direction, so vibrations and rocking in the vertical direction are placed in a high frequency range.

On the other hand, since this elastic support 2) has a small spring constant in the horizontal direction, active control is possible in the horizontal direction.

Therefore, in the horizontal direction, the harmful vibration that vibrates the upper foundation (1a) is sensed, and a control reaction force whose phase is inverted is added to the additional mass (1a) to vibrate the additional mass (1a). Cancel harmful vibrations. As a result, the upper foundation (1a) maintains a stationary state regardless of the input of harmful vibrations.

The second term also exhibits the same effect, but in this case, the following points are added to the above. That is, among the miscellaneous frequencies input to the foundation, there is a frequency that causes the foundation to resonate, but by making the horizontal natural frequency of the additional mass (8) approximately equal to this frequency, the upper foundation (1a) is made to vibrate. The most efficient way to cancel the harmful vibrations is to sense the harmful vibrations, invert the vibrations, vibrate the additional mass (8), and superimpose the control vibrations created by this on the harmful vibrations to cancel out the harmful vibrations. It is possible.

In the third term, a horizontally vibrating basic body (1) is used instead of the elastic support (2) in the second term, and active control is performed using the addition fit (8) as in the second term. It is something.

(Example) Examples of ultra-precision equipment (10) to which the active vibration damping basis for precision equipment of the present invention is applied include semiconductor manufacturing equipment such as steppers, mask aligners, electron beam exposure equipment, STM, and laser equipment. These include ultra-precision machining and measuring equipment.

Examples of vibrations that adversely affect ultra-precision equipment (10) include: - Disturbance vibrations such as constant microtremors, traffic vibrations, and construction vibrations;
■Internal vibration with a vibration source inside the building;■Vibration that is also input from outside the building, but with natural external forces that depend on natural forces.Disturbance vibration is a vibration source! ! ! Internal disturbance vibrations are transmitted via a path such as to the board building) to the free access floor <11) to the equipment in the mount, and the internal vibration is transmitted to the equipment) to the mount)
It is transmitted through a route such as a free access floor, a pedestal, a device, or a person walking (such as a trolley) Q to a free access floor) to a pedestal) to a device.

Although vibration isolation may be performed at any point during this period, in the present invention it is performed at the foundation on which the equipment (10) is mounted.

The vibration damping basics will be explained below. The damping foundation according to item 1 of the present invention has a lower foundation (1b
) and an upper foundation (1a), and a lower foundation (
1b) The upper foundation (1
a) is supported. The elastic support (2) is a metal plate (1
2) and rubber plates (13) are alternately laminated, and has some resistance in the vertical direction, but little resistance in the horizontal direction.

Two fixed pressure vessels (4a) (one pair) are installed on the upper foundation (1a).
4b) horizontally and fixed pressure vessels (4a) (4b)
), an additional mass (8) suspended from the upper foundation (1a) by something like an elastic spring is arranged between the fixed pressure vessels (4a
) (4b) and the additional mass (8).
) (6b) are interposed respectively, and air springs (6b) are interposed respectively.
a> The additional mass (8) is held and elastically contacted at (6b). The pressure vessels (4a) (4b) communicate with each other via a conduit (14) with an orifice (5), and the pressure vessels (4a) (4b) and the air spring (6u
) (6b), and one pressure vessel (4a) (4b) is connected to a compressed air source (l) via a vibration control valve (9), and this entire part is connected to the upper part. Acudep control actuator () that senses the harmful vibration that vibrates the foundation (1a) and applies a control reaction force whose phase is reversed to the upper foundation (1a) to offset the harmful vibration.
^).

The vibration control valve (9) is one of various control valves, such as a servo valve or a proportional control valve, and its opening/closing degree is precisely controlled by the drive circuit (15). The drive circuit 15) includes a vibration sensor (16) such as an acceleration sensor that detects vibrations transmitted from the outside or vibrations generated from the device itself, and a second low-pass filter that receives high frequency components. , an arithmetic circuit that calculates the vibration signal, a phase inverter that inverts the phase of the signal output from the arithmetic circuit by 180 degrees, and a drive circuit that controls the vibration control valve (9) based on the phase-inverted signal. (15) etc.

The amount of external vibration and other harmful vibration transmitted from the floor surface is detected by the vibration sensor (16) as a corresponding vibration signal voltage. At this stage, a high frequency component is superimposed on the vibration signal voltage, and the next low-pass filter filters out the high frequency component and outputs a relatively smooth vibration signal voltage consisting only of low frequency components. The filtered vibration signal voltage is then input to an arithmetic circuit and output as a fluctuation detection signal. This fluctuation detection signal is then input to a phase inverter, and an inverted signal with a 180° phase inversion is output.
The signal is input to the next drive circuit (15), and based on this inverted signal, the drive circuit (15) precisely controls the opening degree of the vibration control valve (9) and controls the air pressure in one pressure vessel (4a). The additional mass (8) is caused to vibrate, and the harmful vibration input from the outside is offset by this controlled vibration. This pressure vessel (4a)
Let the air pressure be P. If the air pressure of the other pressure vessel (4b) connected at the orifice (5) is P2, then since both are in communication with each other, it becomes approximately P, = P2.

However, since the orifice (5) is inserted between them, the vibration (alternating current) component of Pl is almost blocked, and only the static pressure (direct current) component is transmitted to P2. This results in
The pressure vessel (4a) connected to the vibration control valve (9) simply sets the required level of air pressure to the vibration control valve (9).
The static pressure components of the other pressure vessel (4b) facing this are automatically balanced. In other words, the opposing forces of both pressure vessels (4a) (4b) automatically become equal.

As a result, it is sufficient to control one pressure vessel (4a);
Not only does the differential characteristic improve, but the structure can also be made at low cost.

Further, the elastic support (2) used in the present invention is a metal plate (12
) and a laminate of elastic plates such as rubber plates (13), so even if equipment with a high center of gravity is placed on the upper foundation (1a), it has no effect against vertical movement and rocking. Therefore, locking due to horizontal vibration does not occur.

In addition to the first term, the second term is the one in which the horizontal natural frequency of the additional mass (8) is set approximately equal to the natural frequency of the horizontal first mode of the upper foundation (1a), and the upper foundation (1a) If the harmful vibrations that vibrate are sensed and the controlled vibration of the additional mass (8) is controlled so that its phase is inverted with respect to the harmful vibrations, the harmful vibrations will be canceled out with maximum efficiency.

In other words, the horizontal natural frequency of the additional mass (8) is the upper foundation (1
Since it is set approximately equal to the natural frequency of the horizontal first mode in a), it is possible to cancel harmful vibrations in the resonant frequency region, and as a result, the vibration damping effect can be exhibited most effectively.

The third term is a simplified version of the second term, and is based on the upper foundation (1a).
The lower foundation (1b) and the base body (1) are combined into a base body (1), and the base body (1) itself can vibrate in the horizontal direction instead of the elastic support (2). Other points such as providing the actuator (Δ) having an additional mass (8) on the base body (1) and their functions are the same as in the second term.

Although not shown, a pipe with resistance may be used instead of the orifice (5), or a compressed air source may be connected to one pressure vessel via a vibration control valve, and a regulator may be used instead of the orifice. A provided conduit may be connected directly from the compressed air source to the other compressed vessel. However, in this case, it is necessary to balance the pressures in both pressure vessels using a regulator. In addition, it is necessary to balance the opposing force of one air spring, but it is also possible to change the other air spring to a compression spring.

Incidentally, the actuators (^) are normally arranged on four sides of the upper foundation (1a) to the foundation body (1) as shown in FIG.

Although the above embodiment has been explained with reference to a control mechanism using air springs (6a) (6b), it is of course not limited to this, and various types such as an actuator (8) using the magnetic force of an electromagnet may be used. Needless to say, it can be done.

(Effects) In the first and second aspects of the present invention, an elastic support body having a low spring constant in the horizontal direction and a high spring constant in the vertical direction is disposed on the lower foundation to support the upper foundation. Things related to vibration and rocking are placed in a high frequency range, so even if a device with a high center of gravity is installed, rocking will not occur and cause coupling. In addition, in the first term, since the spring constant in the horizontal direction is small, active control is possible in the horizontal direction, and harmful vibrations that vibrate the upper foundation are sensed and a control reaction force with the phase reversed is added to the mass. In addition to this, the additional mass is vibrated, and the controlled vibration can effectively cancel out harmful vibrations. As a result, the upper foundation remains stationary despite the input of harmful vibrations.

In addition to the above, the second aspect of the present invention is to set the horizontal natural frequency of the additional mass that is horizontally swingably disposed in the upper foundation to be approximately equal to the natural frequency of the horizontal primary mode of the upper foundation, and The harmful vibration that causes the foundation to vibrate is sensed and the control vibration of the additional mass is controlled so that its phase is inverted with respect to the harmful vibration, so it is possible to most effectively prevent the upper foundation from resonating due to harmful vibration. This can be offset and significantly enhances the static effect of the upper foundation.

In addition, the third aspect of the present invention is the same as the second aspect, except that a horizontally vibrating basic body is used instead of the elastic support in the second aspect.

To summarize the second point, the elastic support or the basic body that can vibrate in the horizontal direction gives anisotropy in the spring characteristics in the vertical and horizontal directions, and the on-board equipment... ! ! It can guarantee high stability against volume and imbalance, and since there is no locking, there are no problems with rapid formation with the loaded object.
There is no interference from accu-dip control. In addition, the second
．． In term 3, since the natural frequency of the additional pawnshop system is matched to the natural frequency of the system to be controlled, the force efficiency of active control is the highest, and the feedback system is also stable.

Note that when an actuator using an air spring is used, it does not generate a magnetic field compared to actuators such as a linear meter, and can be applied to precision equipment that dislikes magnetic fields such as electron beam exposure equipment.

Finally, in general, when a building or structure has a large height-to-area ratio, it tends to be more rigid in the vertical direction, but conversely, it tends to be more flexible in the horizontal direction. Therefore, the influence of the mode of the structure tends to appear in the horizontal direction, and the amplitude is also amplified and transmitted. For this reason, buildings in precision facilities had low-rise designs, and the foundations needed to be large in area. However, from the point of view of the total cost of effective use of space, a multi-story small space is advantageous. Therefore, the usefulness of the basis of the present invention, which can reduce horizontal vibrations in all frequency bands, is obvious.

[Brief explanation of the drawing]

Fig. 1 - Schematic plan view of the configuration of the first embodiment of the present invention Fig. 2 -
Schematic front view of the structure of the first embodiment of the present invention FIG. 3 Schematic front view of the structure of the second embodiment of the invention FIG. 4 Schematic front view of the structure of the third embodiment of the invention FIG. 5 ...Graph showing the vibration damping performance during control of the present invention Figure 6...Graph (8) showing the damping performance of the conventional example with the vibration damping performance during non-control of the present invention Actuator (1)・・Foundation body (1a)・−Upper foundation Ob
)...Lower foundation <2)...Elastic support (4a)
(4b)...Pressure vessel (5)...Orifice (6a
) (6b)・Air spring (7)・Compressed air source (8)・
Additional mass (9)...Vibration control valve (10)...Equipment (11)...Free access floor (12)...
・Metal plate (13)...Gono＼board〈14)...
Conduit (15)...Drive circuit (16)...Vibration sensor

Claims (3)

[Claims] (1) An elastic support with a low spring constant in the horizontal direction and a high spring constant in the vertical direction is placed on the lower foundation to support the upper foundation, and the harmful vibrations that vibrate the upper foundation are sensed and the additional mass is reduced. An active vibration damping foundation for precision equipment, characterized in that it is equipped with an active control actuator that cancels harmful vibrations by controlling controlled vibrations so that the phase thereof is reversed with respect to harmful vibrations. (2) An elastic support with a low spring constant in the horizontal direction and a high spring constant in the vertical direction is placed on the lower foundation to support the upper foundation, and an additional mass that can swing freely in the horizontal direction is placed on the upper foundation. The horizontal natural frequency of the additional mass is set approximately equal to the natural frequency of the horizontal first mode of the upper foundation, and the control vibration of the additional mass is controlled against the harmful vibration by sensing the harmful vibration that vibrates the upper foundation. An active vibration damping foundation for precision equipment that cancels out harmful vibrations by controlling the phase to be reversed. (3) An additional mass that can swing horizontally is placed on the foundation body that can vibrate in the horizontal direction, and the horizontal natural frequency of the additional mass is set approximately equal to the natural frequency of the horizontal primary mode of the foundation body. , an active vibration damping foundation for precision equipment, which is characterized in that it senses the harmful vibration that vibrates the basic body and controls the controlled vibration of the additional mass so that its phase is reversed with respect to the harmful vibration, thereby canceling out the harmful vibration. .