WO2015159513A1

WO2015159513A1 - Stage control apparatus, processing apparatus, measurement apparatus, and exposure apparatus

Info

Publication number: WO2015159513A1
Application number: PCT/JP2015/001982
Authority: WO
Inventors: Tomohiro Mizuno; Masashi Nakatsugawa; Kouji Takanashi; Yusuke Kuroda; Toshikazu Sakai
Original assignee: Canon Kabushiki Kaisha
Priority date: 2014-04-14
Filing date: 2015-04-08
Publication date: 2015-10-22
Also published as: JP5859156B2; JP2015212932A

Abstract

A stage control apparatus that requires precise moving accuracy and stationary accuracy has a problem that vibration of a stage and a structure is increased by vibration from gas generated from an air conditioner or the like and the moving accuracy and the stationary accuracy are degraded. A stage control apparatus includes a first pressure measurement unit for estimating a force applied to the structure by vibration from gas and a second pressure measurement unit for estimating a force applied to the stage by vibration from gas. A value which is obtained from a value of the first pressure measurement unit and a value of the second pressure measurement unit and which reduces relative acceleration between the structure and the stage is inputted to a driving unit.

Description

STAGE CONTROL APPARATUS, PROCESSING APPARATUS, MEASUREMENT APPARATUS, AND EXPOSURE APPARATUS

The present invention relates to a stage control apparatus used for various apparatuses that require precise moving accuracy and stationary accuracy, specifically, for a semiconductor exposure apparatus, a processing apparatus such as a cutting machine, a grinding machine, and a polishing machine, and a measurement apparatus such as a wave aberration measurement machine and a three-dimensional shape measurement machine.

In a field of semiconductor exposure apparatus, more precise moving accuracy and stationary accuracy are required to cope with miniaturization request of IC pattern line width. Further, highly precise processing accuracy is required for a precision processing machine such as a cutting machine, a grinding machine, and a polishing machine, which manufacture an optical component such as precision lens and mirror and a metal mold of an optical component. In the same manner, improvement of measurement accuracy is required for a precision measurement apparatus such as a wave aberration measurement machine and a three-dimensional shape measurement machine, which evaluate an optical component and a metal mold. Further, in a precision processing apparatus and a precision measurement apparatus, a movement locus of a work, a tool, and a probe largely affects the processing accuracy and the measurement accuracy, so that precise moving accuracy and stationary accuracy are required.

To realize the precise moving accuracy and stationary accuracy, it is necessary to take account of the effects of disturbance factors that count for nothing in a conventional stage control apparatus. One of the disturbance factors is vibration and noise generated from an air-conditioning apparatus, which is an installed machine to acclimatize an apparatus and a work to a certain atmosphere. Wave propagation media of vibration and noise are different from each other. However, the physical phenomena of vibration and noise are the same. The vibration is a vibration in which a vibration of a vibration source propagates through a member such as a structural member, which is used as a propagation medium, and the noise is a vibration from gas, in which a vibration of a vibration source propagates as a compression wave of air.

Conventionally, a method has been employed in which the vibration is detected by a high precision acceleration sensor and a detection result is appropriately processed and fed back to an actuator that applies a driving force to a stage to actively control the vibration. As a specific example, PTL 1 discloses a method in which an accelerator is mounted on a structure and the same acceleration as that received by the structure is applied to the stage in order to suppress vibration when the stage is driven, and thereby a position shift between the structure and the stage is suppressed to realize precise moving accuracy and stationary accuracy.

PTL 2 discloses a method in which the noise is detected by a sound pressure sensor, a detection result is appropriately processed, a compensation signal is inputted to an actuator of an anti-vibration apparatus as feed-forward, and the stationary accuracy of the anti-vibration apparatus is improved.

Japanese Patent No. 3277581 Japanese Patent Laid-Open No. 2001-23881

However, the method described in PTL 1 suppresses vibration generated in the structure when the stage is driven and vibration from gas (for example, vibration by sound) which is directly applied to the stage is not taken account of. Therefore, there is a problem that it is not possible to achieve more precise moving accuracy and stationary accuracy.

On the other hand, the method described in PTL 2 performs control on only the anti-vibration apparatus, so that vibration from gas (for example, vibration by sound), which is directly applied to the stage and the structure, cannot be coped with. Therefore, there is a problem that it is not possible to achieve more precise moving accuracy and stationary accuracy.

The present invention provides a stage control apparatus including a structure, a stage that can move with respect to the structure, and a driving unit that moves the stage to a predetermined position of the structure by an instruction value. The stage control apparatus further includes a first pressure measurement unit that measures pressure in spaces sandwiching the structure and a second pressure measurement unit that measures pressure in spaces sandwiching the stage. A correction value that reduces relative acceleration between the structure and the stage is obtained by using a measurement value of the first pressure measurement unit and a measurement value of the second pressure measurement unit, and the correction value is added to the instruction value.

The processing apparatus of the present invention is characterized by including the stage control apparatus.

The measurement apparatus of the present invention is characterized by including the stage control apparatus.

The exposure apparatus of the present invention is characterized by including the stage control apparatus.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Fig. 1 is a diagram showing a stage control apparatus according to a first embodiment of the present invention. Fig. 2 is a diagram summarizing a relationship between calculation formulas according to the first embodiment of the present invention. Fig. 3A is a diagram of another calculation example of a case in which cross-sectional areas are the same. Fig. 3B is a diagram of another calculation example of a case in which cross-sectional areas are the same. Fig. 4A is a diagram of a case in which a differential pressure detection unit is used as a pressure measurement unit. Fig. 4B is a diagram of a case in which a differential pressure detection unit is used as a pressure measurement unit. Fig. 5 is a diagram showing a stage control apparatus according to a second embodiment of the present invention. Fig. 6 is a diagram of a calculation example of a structure force disturbance estimation unit according to the second embodiment of the present invention. Fig. 7 is a diagram in which a part of the pressure measurement units is omitted. Fig. 8 is a diagram in which a part of the pressure measurement units is omitted. Fig. 9 is a diagram showing a calculation example of a case in which vibration is transmitted to only a structure. Fig. 10 is a diagram showing a calculation example according to a third embodiment of the present invention. Fig. 11 is a diagram showing a calculation example according to a fourth embodiment of the present invention. Fig. 12 is a flowchart of determining a parameter according to the fourth embodiment of the present invention. Fig. 13 is a diagram showing a calculation example according to a fifth embodiment of the present invention. Fig. 14 is a diagram showing a calculation example according to a sixth embodiment of the present invention. Fig. 15 is a flowchart of determining a parameter according to the sixth embodiment of the present invention.

Fig. 1 is a diagram showing a processing apparatus including a stage control apparatus according to a first embodiment of the present invention. The processing apparatus includes a structure, a stage movable with respect to the structure, and a driving unit for moving the stage with respect to the structure. In Fig. 1, reference numeral 1 denotes an anti-vibration apparatus top plate to be mounted in an apparatus. Reference numeral 2 denotes an anti-vibration apparatus mount for supporting the anti-vibration apparatus top plate 1 and blocking external vibration. Reference numeral 3 denotes a structure provided on the anti-vibration apparatus top plate 1. Reference numeral 4z denotes a Z stage that is contactlessly supported movably in the vertical direction of the page with respect to the structure 3. Reference numeral 5z denotes a Z linear motor that is a driving unit for driving the Z stage 4z in the vertical direction of the page and moving the Z stage 4z to a predetermined position. Reference numeral 25 denotes a balance cylinder for supporting the weight of the Z stage 4z. Reference numeral 29 denotes a work. Reference numeral 4y denotes a Y stage that is contactlessly supported to be able to move the structure 3 in the horizontal direction of the page. Reference numeral 5y denotes a Y linear motor that is a driving unit for driving the Y stage 4y in the horizontal direction of the page. Reference numeral 28 denotes a tool. Reference numeral 30 denotes a main shaft that rotates the tool 28. The work 29 is processed by relatively moving the tool 28 and the work 29 while rotating the tool 28. The Z stage 4z may include a mechanism that rotates the work 29. A configuration is possible in which a work is attached to the Y stage 4y and a tool is attached to the Z stage 4z.

Although the processing apparatus will be described in the present embodiment, the embodiment is not limited to the processing embodiment. When a measurement unit such as a probe is attached to instead of the tool, the embodiment can be preferably used as a measurement apparatus.

Although a linear motor is used as a driving unit here, the driving unit is not limited to the linear motor, but a voice coil motor or the like may be used as the driving unit. When the voice coil motor is used, responsiveness is further improved, so that it is possible to reduce time error with respect to a driving signal.

Further, a Z reflecting mirror 23z and a Z interferometer 24z are provided to measure a relative distance between the Z stage 4z and the structure 3 in the vertical direction of the page. In the same manner, a Y reflecting mirror 23y and a Y interferometer 24y are provided to measure a relative distance between the Y stage 4y and the structure 3 in the horizontal direction of the page. The present apparatus is required to maintain a temperature stability over a long time to realize a precise processing accuracy. Therefore, air of a constant temperature is supplied from an air conditioner (not shown in the drawings). Reference numeral 22 denotes an air conditioner outlet. Reference numeral 21 denotes an apparatus area. Reference numeral 27 denotes a filter. Reference numeral 20 denotes a processing area. Temperature-adjusted air is supplied to the processing area 20 from the apparatus area 21 through the filter 27 and a structure is employed in which oil mist in the processing area 20 does not flow into the apparatus area 21.

Further, to improve processing shape accuracy, temperature adjustment accuracy needs to be improved, and to improve the temperature adjustment accuracy, a large flow rate of temperature-adjusted air needs to be supplied to the processing area 20 and the apparatus area 21. However, when the flow rate is increased, the vibration from gas generated from the air conditioner also increases. When the vibration from the gas increases, vibration of the Z stage 4z, Y stage 4y, and the structure 3 are increased by the vibration from the gas, so that there is a problem that the processing accuracy is degraded. Therefore, in the present invention, to prevent the degradation of the moving accuracy and the stationary accuracy due to the vibration from the gas, pressure measurement units 6a to 6d, a force disturbance estimation unit 7, and a compensation force calculation unit 8 are provided and compensation is performed on the vibration from the gas.

Here, only a case in the vertical direction of the page will be described. In Fig. 1, the vertical direction of the page is the gravitational direction. However, the vertical direction is not limited to the gravitational direction, and present invention is also established in the horizontal direction of the page in which there is no influence of gravity. In Fig. 1, the weight of the Z stage 4z is supported by using a balance cylinder 25. However, the present invention is also established for a stage where the balance cylinder 25 does not exist.

First, a principle of improving the moving accuracy and the stationary accuracy will be described. To improve the moving accuracy and the stationary accuracy, relative positions of the work 29 and the tool 28 may be positioned as instructed. For example, even when the structure 3 vibrates, if the relative positions are set as instructed, in principle, the moving accuracy and the stationary accuracy are improved. Here, when assuming that the Y stage 4y that holds the tool 28 and the structure 3 are one object because the rigidity of the Y stage 4y and the structure 3 in the vertical direction of the page is sufficiently high, improving the moving accuracy and the stationary accuracy is assumed to be a problem to set the relative positions of the Z stage 4z that holds the work 29 and the structure 3 as instructed. First, a method is considered in which the relative positions are set as instructed when the stage is stopped at a certain position. In this case, the relative acceleration may be zero. In the present invention, a force disturbance given by the vibration from the gas to the structure 3 and the Z stage 4z is estimated by the force disturbance estimation unit 7, a compensation force for reducing (decreasing) the relative acceleration is calculated from the estimated force disturbance by the compensation force calculation unit 8, and the compensation force is added to the Z linear motor 5z. Thereby, the relative acceleration between the Z stage 4z and the structure 3 is reduced (decreased) and improvement of the stationary accuracy is achieved. Next, a method is considered in which the relative positions are set as instructed when the stage is moved. In this case, the relative acceleration needs to be controlled so that the relative acceleration becomes a value of relative acceleration obtained by solving an equation of motion from a movement instruction of the stage. However, the operation in which the force disturbance due to the vibration from the gas is estimated by the force disturbance estimation unit 7, the compensation force is obtained by the compensation force calculation unit 8 from the estimated force disturbance, and the compensation force is added to the Z linear motor 5z is an operation to cancel only the disturbance generated by the vibration from the gas. Thereby, it is possible to achieve improvement of the moving accuracy by the same algorism as that used when the stage is stopped at a certain position.

A detailed operation of the present invention will be described.

First, the pressure measurement units 6a to 6d are arranged in the apparatus to measure the force disturbance due to the vibration from the gas in the vertical direction of the page to the structure 3 and the Z stage 4z. The arrangement positions are a position (6a) above the structure 3, a position (6b) below the structure 3, a position (6c) above the Z stage in the processing area 20, and a position (6d) below the Z stage 4z in the apparatus area 21. In other words, the pressure measurement units are arranged at positions where the pressure in spaces sandwiching the structure can be measured. Further, the pressure measurement units are arranged at positions where the pressure in spaces sandwiching the Z stage can be measured. Here, an example is described in which the vibration in the vertical direction of the page is measured. However, when the vibration in the horizontal direction of the page is measured, the pressure measurement units may be arranged in the horizontal direction of the page so that the pressure measurement units sandwich the structure and the stage. For example, pressure gauges and microphones can be used as the pressure measurement units 6a to 6d. Here, the pressure measurement units are arranged at four positions. However, when there are arrangement positions which are close to each other and at which substantially the same measurement values are obtained, the redundant positions may be excluded and the number of measurement positions may be smaller than four.

When microphones are used, although a direct current (DC) component of the pressure cannot be measured, it is often practically sufficient to perform the present invention.

Fig. 2 shows a process to outputting a relative force disturbance 33 by using values measured by the pressure measurement units 6a to 6d as inputs. Here, the relative force disturbance 33 indicates a relative force disturbance applied to the Z stage 4z by gas vibration in a coordinate system based on the structure 3.

A force applied to the structure 3 by the vibration from the gas is defined as a structure force disturbance 9. A structure force disturbance estimation unit 12 estimates the structure force disturbance 9. The structure force disturbance 9 can be obtained from forces applied from above the structure and from below the structure. The force applied from above the structure is obtained by multiplying a measurement value of the pressure measurement unit 6a by a structure upper portion cross-sectional area A_a. In the same manner, the force applied from below the structure is obtained by multiplying a measurement value of the pressure measurement unit 6b by a structure lower portion cross-sectional area A_b. Therefore, the structure force disturbance 9 is obtained by subtracting the force applied from below the structure from the force applied from above the structure. This calculation can be represented by Formula (1).

The pressure measurement units may be arranged at any positions sandwiching the structure as long as the pressure above the structure and the pressure below the structure can be measured. Fig. 1 shows an example in which the pressure measurement units are arranged above the structure (6a) and below the structure (6b). In the present specification, the

pressure measurement units

6a and 6b that measure the pressure above the structure and the pressure below the structure are collectively referred to as a first pressure measurement unit. Alternatively, when the vibration in the horizontal direction of the page is measured, the pressure measurement units which sandwich the structure and which measure the pressure to the left side of the structure and the pressure to the right side of the structure are collectively referred to as a first pressure measurement unit. In other words, the pressure measurement units that measure the pressure in spaces sandwiching the structure are referred to as the first pressure measurement unit.

In the same manner, a force applied to the Z stage 4z by the vibration from the gas is defined as a stage force disturbance 10. A stage force disturbance estimation unit 13 estimates the stage force disturbance 10. The stage force disturbance 10 can be obtained from forces applied from above the stage and from below the stage. The force applied from above the stage is obtained by multiplying a measurement value of the pressure measurement unit 6c by a stage upper portion cross-sectional area A_c. In the same manner, the force applied from below the stage is obtained by multiplying a measurement value of the pressure measurement unit 6d by a stage lower portion cross-sectional area A_d. Therefore, the stage force disturbance 10 is obtained by subtracting the force applied from below the stage from the force applied from above the stage. This calculation can be represented by Formula (2).

The pressure measurement units may be arranged at any positions sandwiching the stage as long as the pressure above the stage and the pressure below the stage can be measured. Fig. 1 shows an example in which the pressure measurement units are arranged at a position (6c) above the Z stage 4z in the processing area 20 and at a position (6d) below the Z stage 4z in the apparatus area 21. In the present specification, the

pressure measurement units

6c and 6d which sandwich the stage and which measure the pressure above the stage and the pressure below the stage are collectively referred to as a second pressure measurement unit. Alternatively, when the vibration in the horizontal direction of the page is measured, the pressure measurement units which sandwich the stage and which measure the pressure to the left side of the stage and the pressure to the right side of the stage are collectively referred to as a second pressure measurement unit. In other words, the pressure measurement units that measure the pressure in spaces sandwiching the stage are referred to as the second pressure measurement unit.

An acceleration disturbance which is generated by the structure force disturbance 9 and which is applied to the structure 3 is defined as a structure acceleration disturbance 31. In the same manner, an acceleration disturbance which is generated by the stage force disturbance 10 and which is applied to the Z stage 4z is defined as a stage acceleration disturbance 32. The structure acceleration disturbance 31 is obtained by dividing the structure force disturbance 9 by the mass of the structure. In the same manner, the stage acceleration disturbance 32 is obtained by dividing the stage force disturbance 10 by the mass of the stage. This calculation can be represented by Formula (3).

Next, a relative force disturbance applied to the Z stage 4z by the gas vibration in the coordinate system based on the structure 3 is defined as a relative force disturbance 33. The relative force disturbance 33 can be obtained by multiplying a value obtained by subtracting the structure acceleration disturbance 31 from the stage acceleration disturbance 32 by the mass of the Z stage. This calculation can be represented as Formula (4). The calculations of Formula (3) and Formula (4) are performed by, for example, the calculation unit 14.

With reference to Fig. 1 again, the description below will be described. The relative force disturbance 33, which is an output of the calculation unit 14, is inputted into a sign inversion unit 16. In the sign inversion unit 16, a sign of an input signal is inverted and the input signal becomes a force that cancels the gas vibration. Here, the force that cancels the vibration from the gas described here is a force that cancels a disturbance that prevents the relative acceleration between the structure 3 and the Z stage 4z from being controlled to a desired value. Specifically, the force that cancels the vibration from the gas does not compensate for a state in which the structure 3 and the Z stage 4z are vibrated by a force disturbance due to the vibration from the gas but the structure 3 and the Z stage 4z vibrate at the same acceleration and in the same phase, and the force that cancels the vibration from the gas cancels only a component that disturbs the relative positional relationship. The output of the sign inversion unit 16 is a compensation force (correction value) 11. The above operation is an operation of the force disturbance estimation unit 7 and the compensation force calculation unit 8 which calculate the compensation force (correction value) 11 from the pressure measurement units 6a to 6d.

Finally, the compensation force (correction value) 11 is added to an output of a position control unit 19 as feed-forward and a thrust force instruction (instruction value) 38, which is a signal after the addition, is obtained. The Z linear motor 5z, which is a driving unit, is driven by the thrust force instruction (instruction value) 38. Although the correction value may be subtracted depending on the direction, this subtraction is also referred to as addition in the present specification. Thereby, it is possible to apply the same acceleration (force) as the relative acceleration disturbance (relative force disturbance) of the structure 3 and the stage generated by the vibration from the gas to the Z stage 4z by driving of the Z linear motor 5z and cancel the disturbance due to the vibration from the gas. Here, the relative acceleration between the structure 3 and the Z stage 4z is a difference between the acceleration of the structure 3 and the acceleration of the Z stage 4z. Therefore, it is possible to achieve improvement of the moving accuracy and the stationary accuracy, so that the processing accuracy of the apparatus improves.

The position control unit 19 calculates and outputs a value that is a base of the thrust force instruction 38 applied to the Z linear motor 5z by performing feedback control calculation by using a position deviation, which is a difference between a position instruction 26 and a current position 37. Regarding the current position 37, the distance between the structure 3 and the Z stage 4z is measured by using a laser length measuring machine (not shown in the drawings), the Z interferometer 24z, and the reflecting mirror 23z.

In the present embodiment, the areas of the upper surface and the lower surface of the structure 3 are separately calculated. However, when the areas of the surfaces to which pressure is applied are the same, that is, when the structure upper portion cross-sectional area A_a and the structure lower portion cross-sectional area A_b are the same, it is possible to calculate as shown in Fig. 3A. Specifically, the structure force disturbance 9 is obtained by multiplying a result obtained by subtracting the value of the pressure measurement unit 6b from the measurement value of the pressure measurement unit 6a by the structure upper portion cross-sectional area A_a. This calculation can be represented by Formula (5).

In the same manner, in the present embodiment, the areas of the upper surface and the lower surface of the Z stage 4z are separately calculated. However, when the areas of the surfaces to which pressure is applied are the same, that is, when the stage upper portion cross-sectional area A_c and the stage lower portion cross-sectional area A_d are the same, it is possible to calculate as shown in Fig. 3B. Specifically, the stage force disturbance 10 is obtained by multiplying a result obtained by subtracting the value of the pressure measurement unit 6d from the measurement value of the pressure measurement unit 6c by the stage upper portion cross-sectional area A_c. This calculation can be represented by Formula (6).

When the structure upper portion cross-sectional area A_a and the structure lower portion cross-sectional area A_b are the same, as shown in Fig. 4A, a pair of the pressure measurement unit 6a and the pressure measurement unit 6b can be replaced with a differential pressure gauge (differential pressure measurement unit) 6i. This calculation in this case can be represented by Formula (7). As two measurement points which will be inputs of the differential pressure gauge, the positions at which the pressure measurement unit 6a and the pressure measurement unit 6b are arranged can be used without change.

In the same manner, when the stage upper portion cross-sectional area A_c and the stage lower portion cross-sectional area A_d are the same, as shown in Fig. 4B, a pair of the pressure measurement unit 6c and the pressure measurement unit 6d can be replaced with a differential pressure gauge (differential pressure measurement unit) 6j. This calculation in this case can be represented by Formula (8). Two measurement points which will be inputs of the differential pressure gauge may be the positions at which the pressure measurement unit 6c and the pressure measurement unit 6d are arranged.

Although four

pressure measurement units

6a, 6b, 6c, and 6d are arranged in the present embodiment, four pressure measurement units are not necessarily required to be arranged. For example, the pressure measurement units 6 at the position (6b) below the structure 3 and at the position (6d) below the stage are arranged in the same apparatus area 21 and the measurement positions thereof are close to each other. Therefore, the measurement values indicate substantially the same value. Therefore, the measurement value of the pressure measurement unit 6b can be used instead of the value measured by the pressure measurement unit 6d. In this case, three pressure measurement units may be arranged. As described above, some measurement values indicate substantially the same value depending on the arrangement positions of the pressure measurement units 6. In this case, it is possible to reduce the number of the pressure measurement units 6 by arranging a pressure measurement unit 6 that represents a value of a plurality of pressure measurement units 6 that indicate substantially the same value instead of the plurality of pressure measurement units 6.

In the present embodiment, calculation is performed in a simplified manner by using the mass of the structure and the mass of the stage. However, actually, objects vibrated by the gas vibration are not only the structure 3 and the Z stage 4z. The mass of objects that are vibrated together as a rigid body should be used. Therefore, to be exact, the mass of the structure is the mass of all portions that move together with the structure 3 when a force is applied in the vertical direction of the page. Specifically, the mass of the structure is the sum of the masses of the anti-vibration apparatus top plate 1, the structure 3, the Y stage 4y, the main shaft 30, and the tool 28. The mass of the stage is the sum of the masses of the Z stage 4z and the work 29.

It is effective to add a force necessary to move the stage by feed-forward to improve the moving accuracy of the stage, and it is easy to use the force in the present invention. In this case, the position instruction 26 is multiplied by inverse transmission characteristic of the stage, and an output of the multiplication may be added to the output of the position control unit 19.

Fig. 5 is a diagram showing a processing apparatus including a stage control apparatus according to a second embodiment of the present invention. The same reference numerals as those in Fig. 1 denote the same components. The processing apparatus includes a structure, a stage movable with respect to the structure, and a driving unit for moving the stage with respect to the structure. A difference from Fig. 1 is that the structure 3 and the Z stage 4z are mounted on separate anti-vibration apparatuses. Specifically, the structure 3 is mounted on a first anti-vibration apparatus top plate 1a, and the first anti-vibration apparatus top plate 1a is connected to the anti-vibration apparatus mount 2. On the other hand, the Z stage 4z is mounted on an X stage 4x, the X stage 4x is mounted on the Y stage 4y, the Y stage 4y is mounted on a second anti-vibration apparatus top plate 1b, and the second anti-vibration apparatus top plate 1b is connected to the anti-vibration apparatus mount 2. A reflecting mirror 23 is mounted on the X stage 4x to measure the position of the stage, and the relative distance between the X stage 4x and the structure 3 is measured for three axes of X, Y, and Z. A linear scale 39 is arranged to measure the distance between the X stage 4x and the Z stage 4z. The relative distance between the structure 3 and the Z stage 4z is obtained from a difference between the distance measured by the Z interferometer 24z and the reflecting mirror 23 and the distance measured by the linear scale 39, and the relative distance between the structure 3 and the Z stage 4z is the current position 37. The apparatus also includes an air conditioner (not shown in the drawings) and the air conditioner supplies temperature-adjusted air to a first apparatus area 21a from an air conditioner outlet 22. The first apparatus area 21a and the processing area 20 are connected through the filer 27, and the temperature-adjusted air is supplied from the first apparatus area 21a to the processing area 20. The first apparatus area 21a and a second apparatus area 21b are also connected to each other, and the temperature-adjusted air is also supplied from the first apparatus area 21a to the second apparatus area 21b.

In the present example, the pressure measurement units 6a to 6e are arranged to measure the force disturbance due to the vibration from the gas in the vertical direction of the page to the structure 3 and the Z stage 4z. The arrangement positions are a position (6a) above the structure 3 in the apparatus area 21a, a position (6b) below the structure 3 in the apparatus area 21b, a position (6e) below the structure 3 in the processing area 20, a position (6c) above the Z stage in the processing area 20, and a position (6d) below the Z stage 4z in the apparatus area 21b. Most of calculations for obtaining the relative force disturbance 33 from the measurement values of the pressure measurement units are the same as those in the first embodiment. In other words, the calculations are as shown in Fig. 2. However, the structure 3 is in contact with three spaces, which are the first apparatus area 21a, the second apparatus area 21b, and the processing area 20. Therefore, forces received from these spaces have to be calculated for the structure force disturbance 9 which is a force applied to the structure 3 by the vibration from the gas. Therefore, the structure force disturbance estimation unit 12 that estimates the structure force disturbance 9 is as shown in Fig. 6. Thus, the calculation is as follows. There is only one space above the structure, so that the force applied from above the structure is obtained by multiplying the measurement value of the pressure measurement unit 6a by the structure upper portion cross-sectional area A_a. On the other hand, there are two spaces below the structure, so that calculation is required for each space. Specifically, the force applied from below the structure is the sum of a value obtained by multiplying the measurement value of the pressure measurement unit 6b by a first structure lower portion cross-sectional area A_b and a value obtained by multiplying the measurement value of the pressure measurement unit 6e by a second structure lower portion cross-sectional area A_e. The structure force disturbance 9 is obtained by subtracting the force applied from below the structure from the force applied from above the structure. This calculation can be represented by Formula (9). The first structure lower portion cross-sectional area A_b indicates the area where the structure 3 is in contact with the apparatus area 21b in the vertical direction of the page. In the same manner, the second structure lower portion cross-sectional area A_e indicates the area where the structure 3 is in contact with the processing area 21b in the vertical direction of the page.

The calculation for obtaining the compensation force (correction value) 11 from the relative force disturbance 33 is the same as that of the first embodiment.

In the case of the present embodiment, the pressure measurement units 6 at the position (6e) below the structure 3 in the processing area 20 and at the position (6c) above the Z stage in the processing area 20 are arranged in the same space, so that the measurement values are substantially the same. Therefore, one pressure measurement unit 6 can be omitted. Fig. 7 shows a diagram in which a part of the pressure measurement units 6 is omitted. In Fig. 7, the value of the pressure measurement unit 6e is used instead of the value of the pressure measurement unit 6c.

Further, a pressure measurement unit may be omitted depending on the arrangement and the situation. For example, the space below the Z stage 4z is isolated and the gas vibration from the air conditioner outlet 22 is difficult to be transmitted to the space. In this case, the measurement value of the pressure measurement unit at the position (6d) below the Z stage 4z is substantially constant. Therefore, as shown in Fig. 8, it is possible to artificially create the measurement value of the position (6d) below the Z stage 4z by causing the measurement value of the position (6c) above the Z stage to pass through a low-pass filter (LPF). In this case, the pressure measurement unit 6 at the position (6d) below the Z stage 4z is unnecessary and can be omitted.

In the same manner of thinking, it can be considered that the gas vibration from the air conditioner outlet 22 mainly affects only the structure 3. In this case, although the measurement value of the position (6a) above the structure 3 in the apparatus area 21a varies largely, it can be considered that the measurement values of four pressure measurement units at the position (6b) below the structure 3 in the apparatus area 21b, the position (6e) below the structure 3 in the processing area 20, the position (6c) above the Z stage in the processing area 20, and the position (6d) below the Z stage 4z in the apparatus area 21b are substantially constant. When the disturbance is constant, it is possible to compensate sufficiently by feedback control of a position control system, so that the compensation calculation can be largely simplified. Fig. 9 shows a simplified compensation calculation. The stage is not affected by the gas vibration, so that the gas vibration need not be considered and the stage force disturbance estimation unit 13 can be omitted. Therefore, the relative force disturbance 33 can be obtained by the following procedure. First, a measurement value P_a of the pressure measurement unit 6a is passed through the low-pass filter (LPF) and a measurement value P_b of the pressure measurement unit 6b is artificially generated. The measurement value P_b can be used as a pseudo measurement value P_e of the pressure measurement unit 6e. Next, the measurement value P_a is multiplied by the structure upper portion cross-sectional area A_a to obtain a force applied from above the structure. In the same manner, a value obtained by multiplying the measurement value P_b by the first structure lower portion cross-sectional area A_b and a value obtained by multiplying the measurement value P_e by the second structure lower portion cross-sectional area A_e are added together to obtain a force applied from below the structure. Next, the structure force disturbance 9 is obtained by subtracting the force applied from below the structure from the force applied from above the structure. The structure acceleration disturbance 31 is obtained by dividing the obtained structure force disturbance 9 by a structure mass M_base. The relative force disturbance 33 can be obtained by multiplying the structure acceleration disturbance 31 by (-1) and multiplying the multiplication result by the stage mass M_stage.

Although an example is described in which the low-pass filter (LPF) is used to obtain a pseudo measurement value of a pressure measurement unit, the low-pass filter (LPF) may be omitted by defining that the measurement value of the pressure measurement unit that is not affected by the gas vibration is zero. This is because although a large error occurs in a direct current (DC) component in this case, the direct current (DC) component can be compensated by feedback control of a position control system, so that the error can be ignored even when the error of the direct current (DC) component occurs in the compensation force (correction value) 11. When the measurement value is defined as zero and omitted, there is an advantage that the amount of calculation is reduced and the calculation is performed at high speed.

Fig. 10 is a diagram showing a calculation example according to a third embodiment of the present invention. The same reference numerals as those in Figs. 1 and 5 denote the same components. The present embodiment includes a filter unit 15, a delay calculation unit 17, and a gain calculation unit 18. In the present embodiment, the relative force disturbance 33, which is an output of the calculation unit 14, is inputted into the filter unit 15. The filter unit 15 removes sensor noise superimposed on the measurement values measured by the pressure measurement units 6. Next, the output of the filter unit 15 is inputted into the sign inversion unit 16. In the sign inversion unit 16, the sign of the input signal is inverted and the input signal becomes a force that cancels the gas vibration. Next, the output of the sign inversion unit 16 is inputted into the delay calculation unit 17. The delay calculation unit 17 delays a signal by a predetermined time. This is because the time when the Z stage 4z and the structure 3 begin to vibrate may delay with respect to the time when the pressure measurement units 6a to 6d measure the pressure, so that the timing of compensation of the delay needs to be adjusted. Next, the output of the delay calculation unit 17 is inputted into the gain calculation unit 18. The gain calculation unit 18 multiplies the input signal by a predetermined amplification ratio and outputs the compensation force (correction value) 11. The purpose of the gain calculation unit 18 is to enable fine tuning of the magnitude of the compensation force and adjust the moving accuracy and the stationary accuracy of the stage to an optimal state.

Although an IIR filter is mounted as a secondary low-pass filter in the filter unit 15 in the present embodiment, an FIR filter and a moving average may be used instead of the IIR filter. In the same manner, the type of the filter is not limited to the secondary low-pass filter, but a high-pass filter of any order and a band-pass filter of any order may be used. When the pressure measurement units 6a to 6d have resonance characteristics, a notch filter may be used to cancel the characteristics. The filter unit 15, the delay calculation unit 17, and the gain calculation unit 18 are not necessarily required and some of them may be omitted. The order of the calculations may be changed.

According to the present embodiment, it is possible to remove the sensor noise in the filter unit 15, adjust the phase of the signal in the delay calculation unit 17, and adjust the magnitude of the signal in the gain calculation unit 18. Thereby, it is possible to suppress deterioration of the moving accuracy and the stationary accuracy generated by the force (disturbance) due to vibration from the gas such as sound that directly affects the stage as compared with the first embodiment and the second embodiment.

Fig. 11 is a diagram showing a calculation example according to a fourth embodiment of the present invention. The same reference numerals as those in Figs. 1, 5 and 10 denote the same components. The present embodiment includes a deviation evaluation unit 34. The deviation evaluation unit 34 has a function to perform setting for obtaining a combination of parameters that most suppress deterioration of the moving accuracy and the stationary accuracy from among a combination of parameters of the delay calculation unit 17 and the gain calculation unit 18, which are prepared in advance. For example, the combination of parameters are created as shown in Table 1 when there are three types of delay time parameters that are set in the delay calculation unit 17 and three types of gain parameters that are set in the gain calculation unit 18.

The combination of parameters that most suppress deterioration of the moving accuracy and the stationary accuracy is obtained by sequentially setting the combinations of the delay time parameter and the gain parameter in the delay calculation unit 17 and the gain calculation unit 18. A table such as Table 1 that holds combinations of the delay time parameter and the gain parameter is referred to as a delay time & gain parameter table.

Fig. 12 is a flowchart showing a procedure for obtaining the combination of parameters. First, in 34a, one set is read from the delay time & gain parameter table. Next, in 34b, the read parameters are set in the delay calculation unit 17 and the gain calculation unit 18. Next, in 34c, deviation data is cleared. Next, in 34d, it is waited until deviation data is accumulated. Here, the deviation data is a difference between the position instruction 26 and the current position 37. When sufficient deviation data is accumulated, the standard deviation is obtained from the deviation data accumulated in 34e and the obtained standard deviation is stored. In 34f, conditional branching occurs depending on whether or not all the combinations of parameters have been evaluated. When all the combinations of parameters have not yet been evaluated, the process returns to processing for reading one set from the delay time & gain parameter table to evaluate the next combination of parameters. When all the combinations of parameters have been evaluated, a combination of parameters having the smallest standard deviation is identified from among all the combinations of parameters. In 34h, the identified parameters are set in the delay calculation unit 17 and the gain calculation unit 18. Thereby, the combination of parameters that most suppress deterioration of the moving accuracy and the stationary accuracy is obtained from the delay time & gain parameter table and the parameters are set.

It is preferable that the series of processing shown in Fig. 12 is performed before a work is processed. While the difference between the position instruction 26 and the current position 37 is used as the deviation data without change, a value obtained by causing the difference to be passed through a filer may be used as the deviation data. As the filter, for example, a low-pass filter may be used to remove sensor noise and to remove a signal of a frequency band that cannot drive the Z stage 4z.

According to the present embodiment, even when the force disturbance generated by the vibration from the gas such as sound that directly affects the stage varies due to aged deterioration of the air conditioner, it is possible to suppress deterioration of the moving accuracy and the stationary accuracy due to noise and the like.

Fig. 13 is a diagram showing a calculation example according to a fifth embodiment of the present invention. The same reference numerals as those in Figs. 1, 5 and 10 denote the same components. The present embodiment includes a frequency dividing unit 35 and is configured so that the compensation force (correction value) 11 is calculated for each frequency component and the calculated compensation forces (correction values) 11 are added together and outputted. As a detailed operation, the output of the sign inversion unit 16 is inputted into the frequency dividing unit 35. The frequency dividing unit 35 divides a signal into different frequency components. A low-pass filter, a high-pass filter, a band-pass filter, a notch filter, and the like are used to divide the signal. Thereby, each signal having a different frequency component can be extracted. The divided signals are inputted into the delay calculation unit 17. In the case of the present embodiment, the delay calculation units 17, the number of which corresponds to the number of the divided signals, are prepared to apply processing to each of the divided signals. Thereby, the delay calculation units 17 delay each of the divided signals by a predetermined time. Next, the outputs of the delay calculation units 17 are inputted into the gain calculation units 18. The gain calculation units 18, the number of which corresponds to the number of the divided signals, are prepared to apply processing to each of the divided signals. Thereby, processing is performed in which each of a plurality of input singles from the delay calculation units 17 is multiplied by a predetermined amplification ratio. Finally, outputs of the gain calculation units 18 are combined again by addition to form the compensation force (correction value) 11. The delay time that is set in the delay calculation units 17 and the gain that is set in the gain calculation units 18 can be individually set corresponding to each of the divided signals.

While the frequency is divided and combined by the division by the filter and the combining by the addition, the frequency may be divided and combined by using Fourier transformation and inverse Fourier transformation.

In the present embodiment, the processing after the frequency dividing unit 35 is only the delay calculation units 17 and the gain calculation units 18. However, the gain and the phase of the signal may be adjusted by further providing a filter unit. The processing order of the added filter unit, the delay calculation units 17, and the gain calculation units 18 may be changed to any desired order.

According to the present embodiment, the delay time and the gain are adjusted for each frequency band, so that it is possible to suppress deterioration of the moving accuracy and the stationary accuracy generated by the force disturbance due to the vibration from the gas such as sound that directly affects the stage as compared with the first, the second, and the third embodiments.

Fig. 14 is a diagram showing a calculation example according to a sixth embodiment of the present invention. The same reference numerals as those in Figs. 1, 5, 11, and 13 denote the same components. The present embodiment includes a deviation evaluation unit 34 and a second frequency dividing unit 36 that generates input signals to the deviation evaluation unit 34 so as to optimize parameters of a plurality of delay calculation units 17 and a plurality of gain calculation units 18. Thereby, it is possible to set the parameters of the delay calculation units 17 and the gain calculation units 18 so as to most suppress deterioration of the moving accuracy and the stationary accuracy.

Fig. 15 is a flowchart showing a parameter determination procedure in Fig. 14. In this flow, the delay calculation units 17 and the gain calculation units 18, the numbers of which correspond to the number of signals divided by the first frequency dividing unit 35 and the second frequency dividing unit 36, are sequentially adjusted for each frequency band. When there is a frequency band table in which indexes of divided frequency bands are stored, the flow is as follows. First, in 34i, one frequency band is read from the frequency band table. Next, in 34j, the sequence of Fig. 12 is performed for the frequency band read from the frequency band table. Next, in 34k, conditional branching occurs depending on whether or not all the frequency bands have been processed. When all the frequency bands have not yet been processed, the process returns to processing for reading one frequency band from the frequency band table to process the next frequency band. When all the frequency bands have been processed, the process ends. The deviation data in the sequence of Fig. 12 of the present embodiment is deviation data of a frequency band corresponding to a selected frequency band among the output data of the second frequency dividing unit 36 in Fig. 14.

In the present embodiment, the flow shown in Fig. 15 is used to obtain optimal parameters. However, a genetic algorithm and another optimization algorithm may be applied.

In the present embodiment, parameters of a plurality of delay calculation units 17 and a plurality of gain calculation units 18, which are prepared to adjust the delay time and the gain for each frequency band, are determined in ascending order of the frequency. However, the degree of influence varies for each frequency band, so that the adjustment may be performed in descending order of the degree of influence of the frequency band.

When the adjustment is performed in descending order of the degree of influence of the frequency band, it is possible to reduce the processing time by not performing processing of frequency bands whose degree of influence is small. When there is an interaction in which, for example, when parameters of the delay calculation unit 17 and the gain calculation unit 18 of a certain frequency band are changed, another frequency band is affected, a good result is obtained by performing processing in descending order of the degree of influence of the frequency band. As a method of performing processing in descending order of the degree of influence of the frequency band, there is the following method. An appropriate initial value is given to the delay calculation units 17 and the gain calculation units18, the numbers of which correspond to the number of divided frequency bands. In a state in which the initial value is given, the standard deviation of the deviation is obtained for each frequency band by the deviation evaluation unit 34. The processing is performed in descending order of the obtained standard deviation of the frequency band.
According to the present embodiment, it is possible to set the parameters of a plurality of delay calculation units 17 and a plurality of gain calculation units 18, which are prepared to adjust the delay time and the gain for each frequency band, so as to most suppress deterioration of the moving accuracy and the stationary accuracy.

The present invention can cancel the force (disturbance) due to the vibration from the gas such as sound that directly affects the stage and can suppress deterioration of the moving accuracy and the stationary accuracy due to noise and the like.

The present invention can be used for stage control of various apparatuses that require precise moving accuracy and stationary accuracy, specifically, for a semiconductor exposure apparatus, a precision processing apparatus such as a cutting machine, a grinding machine, and a polishing machine, and a precision measurement apparatus such as a wave aberration measurement machine and a three-dimensional shape measurement machine. In particular, the present invention suppresses deterioration of the moving accuracy and the stationary accuracy due to noise generated by an air conditioner and the like. Therefore, the industrial applicability is high.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2014-083135, filed April 14, 2014 and No. 2015-065248 filed March 26, 2015, which are hereby incorporated by reference herein in their entirety.

Claims

A stage control apparatus including a structure, a stage that can move with respect to the structure, and a driving unit that moves the stage to a predetermined position of the structure by an instruction value, the stage control apparatus comprising:
a first pressure measurement unit that measures pressure in spaces sandwiching the structure; and
a second pressure measurement unit that measures pressure in spaces sandwiching the stage;
wherein a correction value that reduces relative acceleration between the structure and the stage is obtained by using a measurement value of the first pressure measurement unit and a measurement value of the second pressure measurement unit, and
the correction value is added to the instruction value.
The stage control apparatus according to Claim 1, wherein the correction value is obtained from a structure force disturbance which is applied to the structure by vibration from gas and which is obtained from the measurement value of the first pressure measurement unit and a stage force disturbance which is applied to the stage by vibration from gas and which is obtained from the measurement value of the second pressure measurement unit.
The stage control apparatus according to Claim 2, wherein the correction value is obtained by multiplying a difference between a structure acceleration disturbance generated by the structure force disturbance and a stage acceleration disturbance generated by the stage force disturbance by a mass of the stage.
The stage control apparatus according to Claim 3, wherein the structure acceleration disturbance is obtained by dividing the structure force disturbance by a mass of the structure and the stage acceleration disturbance is obtained by dividing the stage force disturbance by the mass of the stage.
The stage control apparatus according to any one of Claims 1 to 4, wherein the first pressure measurement unit is at least two microphones or pressure gauges, which are arranged respectively in the spaces sandwiching the structure.
The stage control apparatus according to any one of Claims 1 to 4, wherein the second pressure measurement unit is at least two microphones or pressure gauges, which are arranged respectively in the spaces sandwiching the stage.
The stage control apparatus according to any one of Claims 1 to 4, wherein the first pressure measurement unit is a differential pressure gauge whose measurement points are arranged respectively in the spaces sandwiching the structure.
The stage control apparatus according to any one of Claims 1 to 4, wherein the second pressure measurement unit is a differential pressure gauge whose measurement points are arranged respectively in the spaces sandwiching the stage.
The stage control apparatus according to Claim 5, wherein the structure force disturbance is a difference between a value obtained by multiplying pressure measured by one of the at least two microphones or pressure gauges and an area of a surface of the structure to which the pressure is applied and a value obtained by multiplying pressure measured by the other of the at least two microphones or pressure gauges and an area of a surface to which the pressure is applied.
The stage control apparatus according to Claim 6, wherein the stage force disturbance is a difference between a value obtained by multiplying pressure measured by one of the at least two microphones or pressure gauges and an area of a surface of the stage to which the pressure is applied and a value obtained by multiplying pressure measured by the other of the at least two microphones or pressure gauges and an area of a surface to which the pressure is applied.
The stage control apparatus according to Claim 7, wherein the structure force disturbance is obtained by multiplying a measurement value of the differential pressure gauge by a cross-sectional area of the structure.
The stage control apparatus according to Claim 8, wherein the stage force disturbance is obtained by multiplying a measurement value of the differential pressure gauge by a cross-sectional area of the stage.
A processing apparatus comprising the stage control apparatus according to any one of Claims 1 to 12.
A measurement apparatus comprising the stage control apparatus according to any one of Claims 1 to 12.
An exposure apparatus comprising the stage control apparatus according to any one of Claims 1 to 12.