WO2012007527A2 - Methods and systems for detecting, setting, monitoring, determining, storing and compensating the spatial situation of a mobile unit - Google Patents

Methods and systems for detecting, setting, monitoring, determining, storing and compensating the spatial situation of a mobile unit Download PDF

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Publication number
WO2012007527A2
WO2012007527A2 PCT/EP2011/061997 EP2011061997W WO2012007527A2 WO 2012007527 A2 WO2012007527 A2 WO 2012007527A2 EP 2011061997 W EP2011061997 W EP 2011061997W WO 2012007527 A2 WO2012007527 A2 WO 2012007527A2
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WO
WIPO (PCT)
Prior art keywords
mobile unit
setting
error
air
respect
Prior art date
Application number
PCT/EP2011/061997
Other languages
French (fr)
Other versions
WO2012007527A3 (en
Inventor
Gilbert Cavazza
Stefan Svensson
Tomas UTTERBÄCK
Nicolas Raynaud
Patrik MÖLLER
Aurélien DETRY
Eric Cunningham
Original Assignee
Replisaurus Group Sas
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Replisaurus Group Sas filed Critical Replisaurus Group Sas
Priority to EP11745504.8A priority Critical patent/EP2593841A2/en
Publication of WO2012007527A2 publication Critical patent/WO2012007527A2/en
Publication of WO2012007527A3 publication Critical patent/WO2012007527A3/en

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/70808—Construction details, e.g. housing, load-lock, seals or windows for passing light in or out of apparatus
    • G03F7/70816—Bearings
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0002—Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping

Definitions

  • the present invention relates to a method and a system for setting the spatial situation of a mobile unit moving with respect to a movement surface.
  • an X-Y movement table generally comprises a fixed base, provided with a movement surface on its upper part, and with a mobile carriage having a reception face for receiving one or more parts.
  • the mobile carriage is brought on the movement surface through precision bearings, such as air bearings, for instance planar or cylindrical air bearings and is adapted to hold a plurality of distinct positions on said surface.
  • a planar air bearing may be created by having an air pad arranged on the movement surface, the air pad being supplied with air in the interface between the proximal surface of the air pad and the movement surface making the air pad float with a certain height above the movement surface.
  • air pads for simplicity different possible geometrical arrangements of air bearings will hereby jointly be referred to as air pads, implying a planar air bearing, though the invention is by no means limited to this specific geometrical arrangement.
  • the movement surface of the fixed base presents, in some of said distinct positions, flatness imperfections at the origin of a parallelism error between the reception face of the mobile carriage and a reference plan (corresponding for instance to the movement surface with no flatness error) .
  • a parallelism error does generally not allow to meet the required precision requirements, so that the operation quality (for instance measuring, exposing or mask replication) attached to these applications is reduced.
  • positioning tables comprising at least one longitudinal guiding rail along which a mobile carriage is able to move so as to hold a plurality of distinct longitudinal positions.
  • the guiding rail being defined by two parallel longitudinal surfaces, air pads mounted on the mobile carriage cooperate with the two side movement surfaces of said guiding rail.
  • a predefined side positioning of the mobile carriage with respect to the guiding rail is furthermore associated.
  • the flatness in the side surfaces of the rail being also not perfect, for some of the distinct longitudinal positions, the side positioning of the mobile carriage with respect to the guiding rail may differ from the corresponding predefined side positioning. Such inaccuracy can among others lower the quality of the operations being performed subsequently on the parts placed on the mobile carriage .
  • the present invention aims to overcome at least on or all of these drawbacks and, among others, to set the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support as well as providing methods to measure errors with respect to calibration points and correct or compensate for such errors.
  • the method for setting the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support, said mobile unit being able to hold a plurality of distinct positions with respect to said movement surface, this latter presenting flatness errors in at least some of said positions, is remarkable in that it comprises the following steps consisting in:
  • the air pad (s) and/or actuator (s) arranged between the mobile unit and the movement surface is or are used in order to be able to correct a possible error of spatial situation of the mobile unit with respect to a predefined reference spatial situation, for a given distinct position.
  • the position thereof can be precisely adjusted, so as to reach a reference spatial situation.
  • step C) can be performed in an iterative form, and that in step C) the information about current spatial situation can be used either to actively correct the spatial situation of the unit, or to keep the current spatial situation and instead compensate for the difference compared to a predefined reference spatial situation from a calibration point by providing a correction parameter used by an algorithm in a computer based control system.
  • the present invention relates to a method and a system for setting the spatial situation of a mobile unit moving with respect to a movement surface by means of precision bearings, such as air bearings and motorized adjustable support structures, for setting the height, pitch and roll of the system with respect to said movement surface.
  • precision bearings such as air bearings and motorized adjustable support structures
  • the present invention is particularly well adapted, yet not exclusively, to the X-Y positioning tables dedicated to the movement of parts (for instance a measurement system, an electronic circuit, a silicon disc, ... ) according to two orthogonal directions X and Y.
  • the present invention aims to overcome those drawbacks and, among others, to set the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support as well as providing methods to measure errors with respect to calibration points and correct or compensate for such errors.
  • the method for setting the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support, said mobile unit being able to hold a plurality of distinct positions with respect to said movement surface, this latter presenting flatness errors in at least some of said positions, is remarkable in that it comprises the following steps consisting in:
  • the air pad(s) and/or actuator (s) arranged between the mobile unit and the movement surface is/are used in order to be able to correct a possible error of spatial situation of the mobile unit with respect to a predefined reference spatial situation, for a given distinct position.
  • the position thereof can be precisely adjusted, so as to reach a reference spatial situation.
  • steps A) , B) and C) can be performed in an iterative form, and that in step C) the information about current spatial situation can be used either to actively correct the spatial situation of the unit, or to keep the current spatial situation and instead compensate for the difference compared to a predefined reference spatial situation from a calibration point by providing a correction parameter used by an algorithm in a computer based control system.
  • the information about current spatial situation can be used either to actively correct the spatial situation of the unit, or to keep the current spatial situation and instead compensate for the difference compared to a predefined reference spatial situation from a calibration point by providing a correction parameter used by an algorithm in a computer based control system.
  • step B) in case of detection of parallelism error, a setting piece of information allowing to correct or compensate it is determined;
  • step C) when said mobile unit holds one of said distinct positions for which a parallelism error has been detected, from the corresponding setting piece of information, at least one bearing feeding and/or motor parameter of at least one such air bearing or motorized support structure is set, or a correction factor associated with said position is obtained from a calibration/mapping matrix, in order to compensate the error in spatial situation by calculating the difference in spatial situation compared to the spatial position from a previous calibration point in order to obtain a parallelism between said reference plan and the face of said mobile unit.
  • the thickness of the air pad and/or height of the motorized support structure can be adjusted and thus, and for a stage unit with multiple air pads and/or motorized support structures arranged to support the stage unit against the movement plane the parallelism between the reference plan and said mobile unit face performed, for a given position of the mobile unit on the movement surface.
  • the mobile unit is thus checked at least in height, roll and/or pitch.
  • said mobile unit being hold by said movement surface by means of three air pads with at least one motorized support structure, at step C) , at least one air feeding parameter and or motor parameter of at least one of said air pads and/or motor is set.
  • said mobile unit being able to move with respect to at least one guiding rail defined by two longitudinal side movement surfaces being parallel between them, said mobile unit comprising at least two air pads which cooperate respectively with said longitudinal side surfaces, said mobile unit being able to hold a plurality of distinct longitudinal positions along said guiding rail, with each one of said distinct longitudinal position being associated with a predefined side positioning of said mobile unit with respect to said guiding rail:
  • step A) for each one of said distinct longitudinal positions, a possible error of side positioning of said mobile unit with respect to said guiding rail is detected;
  • - at step B) in case of detection of such side positioning error, a setting piece of information allowing to correct or compensate it is determined; and - at step C) , when said mobile unit holds one of said distinct longitudinal positions for which a side positioning error has been detected, from the corresponding setting piece of information, at least one air feeding or motor setting parameter of at least one of said air pads or support structure motors, is set in order to obtain said predefined side positioning associated with said longitudinal position or a correction factor associated with said position is obtained from a calibration/mapping matrix, in order to compensate the error in spatial situation by calculating the difference in spatial situation compared to the spatial position from a previous calibration point.
  • the side positioning of the mobile unit can be modified with respect to the guiding rail and the predefined side positioning associated with this longitudinal position can be obtained.
  • the detected error spatial situation can be kept, and instead compensated for by providing a correction parameter used by an algorithm in a computer based control system.
  • the mobile unit is at least checked in yaw.
  • setting said feeding or motor parameter can be:
  • the thickness measured is compared with a predetermined reference thickness obtained from said setting piece of information, in order to check the quality of the setting performed at step C) ;
  • the setting of the air feeding parameter of at least said air pad is adjusted so that the thickness of said air pad is at least approximately equal to said reference thickness.
  • the measured distance is compared with a predetermined reference distance
  • At least one air feeding parameter of at least one air pad or at least one motor parameter of one motorized support structure is set, so that the measured distance is at least approximately equal to the reference distance. Furthermore, in case of a plurality of air pads, the setting is performed simultaneously on all the air pads .
  • the present invention relates to a system for setting the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one air pad, said mobile unit being able to hold a plurality of distinct positions with respect to said movement surface, this latter showing flatness errors in at least some of said positions.
  • said system comprises:
  • said detection means are formed to detect, for each one of said distinct positions, a possible parallelism error between the reference plan and the face of said mobile unit;
  • said determining means are formed to determine, in case of detection of a parallelism error, a setting piece of information allowing to correct or compensate it;
  • said setting means are formed to set, when said mobile unit holds one of said distinct positions for which a parallelism error has been detected, at least one air feeding parameter of at least one such air pad or at least one position parameter for at least one motorized support structure, from the corresponding setting piece of information.
  • said mobile unit being able to move with respect to at least one guiding rail defined by two longitudinal side movement surfaces being parallel between them, said mobile unit comprising at least two air pads which cooperate respectively with said longitudinal side surfaces, said mobile unit being able to hold a plurality of distinct longitudinal positions along said guiding rail, with each one of said distinct longitudinal position being associated a predefined side positioning of said mobile unit with respect to said guiding rail:
  • said detection means are formed to detect, for each one of said longitudinal positions, a possible side positioning error of said mobile unit with respect to said guiding rail;
  • said determining means are formed to determine, in case of detection of such a side positioning error, a setting piece of information allowing to correct or compensate this latter;
  • said setting means are formed to set, when said mobile unit holds one of said distinct longitudinal positions for which a side positioning error has been detected, at least one air feeding parameter of at least one of said air pads or at least one position parameter for at least one motorized support structure, from the corresponding setting piece of information.
  • a reference system comprising fixed reference targets that may be used as a reference point for a certain spatial situation that is long term stable with respect to a global coordinate system is used together with a mobile unit that has a measurement system capable of measuring the position of said fixed reference targets.
  • a spatial reference position can be detected by acquiring the position of at least one marker, such as two markers positioned with respect to the movement surface so that at least one spatial situations, such as pitch or roll, can for instance be calculated by subtracting the position value of a second marker from the position value of a first marker.
  • any difference in spatial situation compared to this reference position can be calculated.
  • This fixed target reference structure and described method can be used as a mean for detecting variations in spatial situation over time, such as drift in angular (pitch, yaw or roll) or linear directions along or perpendicular to a movement surface.
  • the material of choice for the base, reference frame and measurement frame are materials which are rigid and stiff and have low thermal expansion, such that varying temperature, vibrations, bending, twisting or any other cause of deformation will only marginally affect measurements.
  • Said fixed reference target structure may be designed and fabricated to minimize the effect of thermal deformations or other longer term movements, such as internal relaxation effects in the materials used to form the structures, giving rise to structural deformation or surface errors.
  • One way of reducing the effect of thermal expansion is to first of all manufacture the reference structure in symmetrical highly stable construction with a high eigenfrequency and second of all attaching it to the base of a larger system, such as a semiconductor manufacturing or measurement tool, in a thermally insensitive manner using symmetrical attachment points that can allow the material to thermally expand or contract substantially without deforming the reference frame.
  • the structure of the mobile unit itself that is providing the structural integrity of the mobile unit, by connecting the air pads that are supported by the movement surface of a base, providing a stable connection to a measurement device attached on either side of the mobile unit.
  • this structure and its connections to other parts can be designed and manufactured in materials that allow thermal expansions or other disturbances of any of the mechanical parts in the whole tolerance chain to be done in a way that does not deform or expand the mobile unit itself.
  • the fixed reference target structure and the mobile unit structure can be manufactured in low thermal expansion materials such as Invar, carbon fibre reinforced materials, Zerodur or other types low CTE materials commonly used.
  • the opposite ends may be positioned substantially symmetrically relatively the measurement point of the mobile unit as well as the base structure of a larger system, such a base structure of a semiconductor manufacturing or measurement tool, where the fixed reference targets serve as a global reference, so that any movements of said ends due to thermal expansion are substantially equally large.
  • an external measurement system in order to measure the spatial position of a mobile unit moving along a movement surface, by use of the external measurement system the spatial situation for a plurality of distinct positions along the movement surface can be determined.
  • the spatial situation for an array of multiple positions along said movement surface By storing the spatial situation for an array of multiple positions along said movement surface the difference between a spatial situation of a first reference position and a second position can be calculated.
  • the differential spatial situation information between multiple distinct positions along the movement surface may then be used to provide a correction value for setting at least one air feeding or motor setting parameter of at least one of said air pads or support structure motors, in order to obtain the same spatial situation of a second position as for a first reference position, or a correction factor associated with a second position compared to a reference position to be used to compensate for the difference in spatial position in a computer based control system.
  • the external measurement system used to determine the spatial situation of the mobile unit in a plurality of distinct positions along the movement surface may be:
  • Optical intersubstrate measurement microscopes attached to the mobile unit, arranged to measure position markers on calibration reticules placed within the field of view on both sides of dual- beam measurement microscope, the calibration reticules having arrays of position markers being substantially aligned to each other so that a differential measurement between two reticules placed on opposite sides of the intersubstrate measurement microscope can be used to determine the spatial situation of the intersubstrate microscope in a plurality of distinct positions of the mobile unit.
  • 2D encoder heads attached to a reference frame
  • 2D encoders attached on a measurement system or the holding member of the mobile unit, arranged to measure 2D positions on 2D encoders, the 2D encoders being arranged so that a differential measurement between two encoders placed on opposite sides of a holding member or other structure of the mobile unit can be used to determine the spatial situation of the mobile unit in a plurality of distinct positions, either during a mapping sequence or continuously as an integrated part of the mobile unit .
  • 3-beam interferometers or digital autocollimators arranged to measure the spatial situation of a stage unit, either during a mapping sequence or continuously as an integrated part of the mobile unit.
  • FIG. 1 shows a block diagram of a setting system according to the present invention.
  • FIG. 2 is a schematic view of the top of an X-Y movement table associated with the system of FIG. 1 to set the parallelism according to a first embodiment of the invention.
  • FIG. 3 shows, in a profile view, an X-Y movement table of FIG. 2.
  • FIG. 4 is a schematic view of the top of a movement table according to a sole longitudinal axis associated with the system of FIG. 1 to set a side positioning, according to a second embodiment of the invention .
  • FIG. 5 is a profile view, according to the arrow V, of the movement table of FIG. 4.
  • FIG. 6, similar to FIG. 5, represents an alternative to the guiding rail of the movement table of FIG. 4.
  • FIG. 7 shows, in a profile schematic view, a crossed movement table entirely guided on air pads implementing various setting systems according to the invention .
  • FIG. 8 shows a side view of a mobile unit with two air pads and two motorized support structures, a movement surface as well as a fixed target system used as an external reference point for detecting the spatial situation of a mobile unit by means of optical measurement of position markers arranged on opposite sides of an intersubstrate measurement microscope.
  • FIG. 9 shows systems and methods to determine the spatial situation of a mobile unit during the movement between a plurality of distinct positions along a movement surface.
  • a system 1A, IB is shown according to the present invention for setting the spatial situation of a mobile unit 2 moving with respect to at least one movement surface 3, 4 by means of air pads 5, 6 (also see FIGS . 2 and 4) .
  • the mobile unit 2 is able to hold a plurality of distinct positions with respect to such a movement surface 3, 4, this latter presenting flatness errors in at least some of said positions.
  • the mobile unit 2 movement is performed by means of at least one motor M controlled by control means 7.
  • system 1A, IB comprises:
  • the detection means 8 can thus perform a recording of the whole flatness errors of a movement surface 3, 4. For this, they can for instance implement one or more reference marks;
  • controlling means 10 comprise:
  • the means 12 are able to receive the mobile unit position 2 with respect to a movement surface by control means 7 (link L3) and a setting piece of information associated with the position being considered (link L2) . Once determined, the setting orders are addressed to the electropneumatic components 11 by a link L4.
  • the system 1A, IB also comprises:
  • the distance sensors 13 can implement any known technology type (for instance laser, acoustic, capacitive, inductive, optical etc.); and
  • the means 10 adjust the setting of the air feeding parameter of at least one of the three air pads 5, 6, in order to reach said reference thickness.
  • this latter can also comprise : - a distance sensor 15 associated with the mobile unit 2 and formed to measure the distance between a reference point of the mobile unit 2 and a movement surface 3, 4, for a sole predetermined origin position Po of the movement surface 3, 4; and
  • the means 10 set at least one air feeding parameter of the three air pads 5, 6, simultaneously so that the measured distance is at least approximately equal to the reference distance.
  • the system 1A is adapted for setting the parallelism between a reference plan (corresponding for instance to an horizontal movement surface 3 with no flatness imperfections) and a face 17 of a mobile unit 2 which moves on the horizontal movement surface 3 by means of three air pads 5 equiangularly distributed around a centre 0 of the mobile unit 2.
  • the setting system 1A can be associated, but not exclusively, with an X-Y movement table T.
  • the X-Y movement table T comprises a fixed basis 18, the upper part of which forms the movement surface 3, and the mobile unit 2 (in a carriage form), the upper part of which serving for receiving one or more parts to be processed (not represented) defines the face 17.
  • the X-Y movement table T also comprises usual guiding means 19 that force the mobile unit 2 to move according to the two orthogonal directions X-X and Y-Y. It should be noticed that the movement of the mobile unit 2 is performed without friction on the horizontal movement surface 3. With these guiding means 19 there are associated electric motors M for putting the mobile unit 2 in movement with a very high moving dynamics and a high positioning precision. The motors M are controlled by said control means 7.
  • the detection means 8 are formed for detecting, for each one of the distinct positions, a possible parallelism error between the reference plan and the face 17 of the mobile unit 2 ;
  • the determining means 9 are formed for determining, in case of detection of a parallelism error, a setting piece of information allowing to correct it;
  • the setting means 10 are formed so as to set, when said mobile unit 2 holds one of the distinct positions for which a parallelism error has been detected, at least one air feeding parameter of at least one of the three air pads, from the corresponding setting piece of information.
  • the respective thickness e of the corresponding air pad 5 can be modified.
  • the parallelism between the face 17 of the mobile unit 2 and the reference plan can be obtained for a given distinct position for which a parallelism error is observed.
  • the mobile unit 2 can be checked in roll and/or pitch.
  • a mobile unit 2 is from now on forced to move on the movement table T according to a longitudinal guiding rail 20 in rib shape, protruding with respect to an horizontal movement surface 3.
  • the mobile unit 2 is hold by the movement surface 3 by means of three air pads 5, which are driven according to the first embodiment by the setting system 1A (not illustrated on FIG. 4 for clarity's sake) .
  • the guiding rail 20 is defined by two longitudinal and vertical side movement surfaces 4, which are mutually parallel.
  • the mobile unit 2 comprises three auxiliary air pads 6, two of which cooperate with one of said side movement surfaces 4 and the other one with the other surface 4.
  • the mobile unit 2 is able to hold a plurality of distinct longitudinal positions along said guiding rail 20. Furthermore, with each one of said distinct longitudinal positions is associated a predefined side positioning of the mobile unit 2 with respect to said guiding rail 20.
  • the mobile unit 2 movement along the guiding rail 20 is performed by an electrical motor M controlled by said control means 7.
  • the detecting means 8 are formed to detect, for each one of the distinct longitudinal positions, a possible side positioning error of the mobile unit 2 with respect to said guiding rail 20; - the determining means 9 are formed to determine, in case of detection of such a side positioning error, a setting piece of information allowing to correct this latter; and
  • the setting means 10 are formed so as to set, when said mobile unit 2 holds one of said distinct longitudinal positions for which a side positioning error has been detected, at least one air feeding parameter of at least one of the three auxiliary air pads, from the corresponding setting piece of information received from the determining means .
  • the side positioning of the mobile unit 2 can be modified with respect to the guiding rail 20 and the predefined side positioning associated with this longitudinal position can be obtained .
  • said mobile unit 2 can be checked in roll and/or pitch (by the air pads 5) , as well as in yaw (by the air pads 6) .
  • the guiding rail 20 can have the shape of a groove arranged in the upper part of the fixed base 18.
  • the mobile unit 2 of a crossed movement table T comprises a first and a second mobile element PI and P2.
  • the element PI is hold by the horizontal movement surface 3A of the element P2, by means of three air pads 5A, and is able to move with respect to this one according to a first longitudinal, rectilinear first guiding rail 20A (defining the X direction) protruding with respect to the movement surface 3A.
  • the three air pads are driven by a first regulating system 1A (not illustrated on FIG. 7), previously described and according to the invention .
  • the guiding rail 20A is defined by two longitudinal side movement surfaces 4A parallel there between. These two surfaces 4A are vertical.
  • the element PI comprises more than three auxiliary air pads 6A, two of which cooperate with one of said movement surfaces 4A and the other with the other surface 4A. These three air pads 6A are checked by a first setting system IB (not illustrated on FIG. 7) of the type described hereinabove.
  • the mobile element P2 is hold by an horizontal movement surface 3B in the upper part of a fixed base 18, by means of the three air pads 5B, and is able to move with respect to this one according to a second longitudinal rectilinear guiding rail 20B (defining the Y direction) , orthogonal to the rail 20A and protruding with respect to the movement surface 3B.
  • the three air pads 5B are driven by a second setting system 1A (not illustrated on FIG. 7) .
  • the guiding rail 20B is also defined by two longitudinal side movement surfaces 4B parallel therebetween. These two surfaces are vertical.
  • the element P2 comprises three auxiliary air pads 6B, two of which cooperate with one of said movement surfaces 4B and the other with the other surface 4B. These three air pads 6B are checked by a second setting system IB (not illustrated on FIG. 7) of the type described hereinabove.
  • the first and second setting systems 1A are independent from each other, as well as the first and second setting systems IB.
  • the mobile unit 2 is checkable in pitch and/or roll (by the air pads 5A and 5B) , as well as in yaw along the X direction (by the air pads 6A) and/or along the Y direction (by the air pads 6B) .

Abstract

A method and system for setting the spatial situation of a mobile unit is provided. The mobile unit is moving with respect to a movement surface by means of at least one air pad (5, 6) and/or a motorized support structure, and the system (1A, 1B) comprises means (8, 9, 10) for setting an air feeding parameter of at least one such air pad (5, 6) or at least on position parameter for a motorized support structure, when the mobile unit (2) holds a position for which a spatial situation error is detected with respect to a predefined reference spatial situation.

Description

Methods and systems for detecting, setting, toring, determining, storing and compensating the spatial situation of a mobile unit Field of the invention
The present invention relates to a method and a system for setting the spatial situation of a mobile unit moving with respect to a movement surface. Background
It is known that such an X-Y movement table generally comprises a fixed base, provided with a movement surface on its upper part, and with a mobile carriage having a reception face for receiving one or more parts. The mobile carriage is brought on the movement surface through precision bearings, such as air bearings, for instance planar or cylindrical air bearings and is adapted to hold a plurality of distinct positions on said surface. A planar air bearing may be created by having an air pad arranged on the movement surface, the air pad being supplied with air in the interface between the proximal surface of the air pad and the movement surface making the air pad float with a certain height above the movement surface. For simplicity different possible geometrical arrangements of air bearings will hereby jointly be referred to as air pads, implying a planar air bearing, though the invention is by no means limited to this specific geometrical arrangement.
On the movement surface there can then slide, with minimal or no friction, the mobile carriage with which guiding means are associated forcing it to move according to the two orthogonal directions X and Y. Electric motors are usually provided to put the carriage in movement with a very high movement dynamics and a high positioning precision .
However, the movement surface of the fixed base presents, in some of said distinct positions, flatness imperfections at the origin of a parallelism error between the reception face of the mobile carriage and a reference plan (corresponding for instance to the movement surface with no flatness error) .
In some applications (for instance microelectronic circuit manufacturing tools) for which the parallelism between the carriage face and the reference plan is essential, a parallelism error does generally not allow to meet the required precision requirements, so that the operation quality (for instance measuring, exposing or mask replication) attached to these applications is reduced.
Furthermore, positioning tables according to at least one longitudinal direction are generally known, comprising at least one longitudinal guiding rail along which a mobile carriage is able to move so as to hold a plurality of distinct longitudinal positions. The guiding rail being defined by two parallel longitudinal surfaces, air pads mounted on the mobile carriage cooperate with the two side movement surfaces of said guiding rail. At each one of said distinct longitudinal positions a predefined side positioning of the mobile carriage with respect to the guiding rail is furthermore associated.
However, the flatness in the side surfaces of the rail being also not perfect, for some of the distinct longitudinal positions, the side positioning of the mobile carriage with respect to the guiding rail may differ from the corresponding predefined side positioning. Such inaccuracy can among others lower the quality of the operations being performed subsequently on the parts placed on the mobile carriage .
Yet another problem with prior art related to movable units set up to hold a specific spatial situation, such as height, pitch, yaw or roll, with respect to a plane is that relaxation effects in the material used in the mobile unit and/or support surfaces as well as temperature variations or other external disturbances may give deformation of parts or surfaces creating variations in spatial situation over time, such as drift in angular (pitch, yaw or roll) or linear directions along or perpendicular to said plane . The Invention
The present invention aims to overcome at least on or all of these drawbacks and, among others, to set the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support as well as providing methods to measure errors with respect to calibration points and correct or compensate for such errors.
To this end, according to one embodiment of the invention, the method for setting the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support, said mobile unit being able to hold a plurality of distinct positions with respect to said movement surface, this latter presenting flatness errors in at least some of said positions, is remarkable in that it comprises the following steps consisting in:
A) for each one of said distinct positions, detecting a possible error of spatial situation of said mobile unit with respect to a predefined reference spatial situation associated with the said position;
B) in case of detection of such an error, determining a setting piece of information allowing to correct or compensate said error; and
C) when said mobile unit holds one of said positions for which an error of spatial situation is detected, setting from the corresponding setting piece of information at least one air bearing feeding or motor parameter of at least one such air bearing or motorized support structure , in order to obtain the reference spatial situation of said mobile unit associated with said position or from a calibration/mapping matrix obtain a correction factor associated with said position, in order to compensate the error in spatial situation by calculating the difference in spatial situation compared to the spatial position from a previous calibration point.
Thus, thanks to at least one embodiment of the invention, the air pad (s) and/or actuator (s) arranged between the mobile unit and the movement surface is or are used in order to be able to correct a possible error of spatial situation of the mobile unit with respect to a predefined reference spatial situation, for a given distinct position. Indeed, by setting at least one air feeding or motor parameter of at least one air pad or motorized support structure, the position thereof can be precisely adjusted, so as to reach a reference spatial situation.
It should be noticed that steps A) , B) and
C) can be performed in an iterative form, and that in step C) the information about current spatial situation can be used either to actively correct the spatial situation of the unit, or to keep the current spatial situation and instead compensate for the difference compared to a predefined reference spatial situation from a calibration point by providing a correction parameter used by an algorithm in a computer based control system.
The present invention relates to a method and a system for setting the spatial situation of a mobile unit moving with respect to a movement surface by means of precision bearings, such as air bearings and motorized adjustable support structures, for setting the height, pitch and roll of the system with respect to said movement surface.
In the following, it is meant by "spatial situation" :
- the parallelism and height between a reference plane and a mobile unit face moving on a movement surface. The spatial situation is then checked in height, pitch and/or roll;
- and/or, when one a mobile unit moves along at least one guiding rail, the side positioning of said unit with respect to said rail. The spatial situation is then checked in height and/or yaw.
The present invention is particularly well adapted, yet not exclusively, to the X-Y positioning tables dedicated to the movement of parts (for instance a measurement system, an electronic circuit, a silicon disc, ... ) according to two orthogonal directions X and Y.
The present invention aims to overcome those drawbacks and, among others, to set the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support as well as providing methods to measure errors with respect to calibration points and correct or compensate for such errors.
To this end, according to the invention, the method for setting the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one precision bearing, air pad and/or motorized support, said mobile unit being able to hold a plurality of distinct positions with respect to said movement surface, this latter presenting flatness errors in at least some of said positions, is remarkable in that it comprises the following steps consisting in:
A) for each one of said distinct positions, detecting a possible error of spatial situation of said mobile unit with respect to a predefined reference spatial situation associated with the said position;
B) in case of detection of such an error, determining a setting piece of information allowing to correct or compensate said error; and
C) when said mobile unit holds one of said positions for which an error of spatial situation is detected, setting from the corresponding setting piece of information at least one air bearing feeding or motor parameter of at least one such air bearing or motorized support structure , in order to obtain the reference spatial situation of said mobile unit associated with said position or from a calibration/mapping matrix obtain a correction factor associated with said position, in order to compensate the error in spatial situation by calculating the difference in spatial situation compared to the spatial position from a previous calibration point.
Thus, thanks to the invention, the air pad(s) and/or actuator (s) arranged between the mobile unit and the movement surface is/are used in order to be able to correct a possible error of spatial situation of the mobile unit with respect to a predefined reference spatial situation, for a given distinct position. Indeed, by setting at least one air feeding or motor parameter of at least one air pad or motorized support structure, the position thereof can be precisely adjusted, so as to reach a reference spatial situation.
It should be noticed that steps A) , B) and C) can be performed in an iterative form, and that in step C) the information about current spatial situation can be used either to actively correct the spatial situation of the unit, or to keep the current spatial situation and instead compensate for the difference compared to a predefined reference spatial situation from a calibration point by providing a correction parameter used by an algorithm in a computer based control system. In a first embodiment according to the present invention for setting the parallelism between a reference plan and a face of said mobile unit moving on said movement surface by means of at least one such air pad:
- at step A) , for each one of said distinct positions, a possible parallelism error between said reference plan and the face of said mobile is detected;
- at step B) , in case of detection of parallelism error, a setting piece of information allowing to correct or compensate it is determined; and
- at step C) , when said mobile unit holds one of said distinct positions for which a parallelism error has been detected, from the corresponding setting piece of information, at least one bearing feeding and/or motor parameter of at least one such air bearing or motorized support structure is set, or a correction factor associated with said position is obtained from a calibration/mapping matrix, in order to compensate the error in spatial situation by calculating the difference in spatial situation compared to the spatial position from a previous calibration point in order to obtain a parallelism between said reference plan and the face of said mobile unit.
Thus, by setting an air feeding parameter of at least one air pad and/or an motor setting parameter of at least one motorized support structure, the thickness of the air pad and/or height of the motorized support structure can be adjusted and thus, and for a stage unit with multiple air pads and/or motorized support structures arranged to support the stage unit against the movement plane the parallelism between the reference plan and said mobile unit face performed, for a given position of the mobile unit on the movement surface. The mobile unit is thus checked at least in height, roll and/or pitch.
In a particular embodiment of the first embodiment, said mobile unit being hold by said movement surface by means of three air pads with at least one motorized support structure, at step C) , at least one air feeding parameter and or motor parameter of at least one of said air pads and/or motor is set.
Furthermore, alternatively or in addition, in a second embodiment according to the present invention, said mobile unit being able to move with respect to at least one guiding rail defined by two longitudinal side movement surfaces being parallel between them, said mobile unit comprising at least two air pads which cooperate respectively with said longitudinal side surfaces, said mobile unit being able to hold a plurality of distinct longitudinal positions along said guiding rail, with each one of said distinct longitudinal position being associated with a predefined side positioning of said mobile unit with respect to said guiding rail:
- at step A) , for each one of said distinct longitudinal positions, a possible error of side positioning of said mobile unit with respect to said guiding rail is detected;
- at step B) , in case of detection of such side positioning error, a setting piece of information allowing to correct or compensate it is determined; and - at step C) , when said mobile unit holds one of said distinct longitudinal positions for which a side positioning error has been detected, from the corresponding setting piece of information, at least one air feeding or motor setting parameter of at least one of said air pads or support structure motors, is set in order to obtain said predefined side positioning associated with said longitudinal position or a correction factor associated with said position is obtained from a calibration/mapping matrix, in order to compensate the error in spatial situation by calculating the difference in spatial situation compared to the spatial position from a previous calibration point.
Thus, for a given longitudinal position, by setting the thickness of at least one of the air pads or support structure motors, the side positioning of the mobile unit can be modified with respect to the guiding rail and the predefined side positioning associated with this longitudinal position can be obtained. Alternatively the detected error spatial situation can be kept, and instead compensated for by providing a correction parameter used by an algorithm in a computer based control system.
The mobile unit is at least checked in yaw.
Furthermore, whatever the embodiment of the invention being considered, setting said feeding or motor parameter can be:
- the air feeding pressure for an air pad; - the air feeding rate for an air pad;
- the longitudinal position of an electrical linear motor having a linear position encoder for measuring its position. - the rotational position of an electrical rotational motor, such as a stepper motor, having a rotational encoder for measuring its rotational position
Additionally, for setting check purposes, the following steps can be performed:
- for each one of said positions for which a spatial situation error is detected, the thickness of at least one air pad is measured;
- the thickness measured is compared with a predetermined reference thickness obtained from said setting piece of information, in order to check the quality of the setting performed at step C) ; and
- in case the measured thickness is not equal to the reference thickness, the setting of the air feeding parameter of at least said air pad is adjusted so that the thickness of said air pad is at least approximately equal to said reference thickness.
Alternatively or additionally, for calibrating purposes, the following steps can furthermore been performed:
- for one sole position of predefined origin of said movement surface, the distance between a reference point of said mobile unit and said movement surface is measured;
- the measured distance is compared with a predetermined reference distance; and
- in the case where the measured distance is not equal to the reference distance, at least one air feeding parameter of at least one air pad or at least one motor parameter of one motorized support structure is set, so that the measured distance is at least approximately equal to the reference distance. Furthermore, in case of a plurality of air pads, the setting is performed simultaneously on all the air pads .
Moreover, the present invention relates to a system for setting the spatial situation of a mobile unit moving with respect to at least one movement surface by means of at least one air pad, said mobile unit being able to hold a plurality of distinct positions with respect to said movement surface, this latter showing flatness errors in at least some of said positions. According to the invention, said system comprises:
- means for detecting, for each one of said distinct positions, a possible spatial situation error of said mobile unit with respect to a predefined reference spatial situation associated with said position;
- means for determining, in case of detection of such an error, a setting piece of information allowing to correct or compensate said error; and
- means for setting, when said mobile unit holds one of said positions for which a spatial situation error is detected, at least one air feeding or motor parameter of at least one such air pad or motorized support structure, from the corresponding setting piece of information.
In the first embodiment of the invention for setting the parallelism between a reference plan and a face of said mobile unit moving on said movement surface by means of at least one such air pad or motorized support structure: - said detection means are formed to detect, for each one of said distinct positions, a possible parallelism error between the reference plan and the face of said mobile unit;
- said determining means are formed to determine, in case of detection of a parallelism error, a setting piece of information allowing to correct or compensate it; and
- said setting means are formed to set, when said mobile unit holds one of said distinct positions for which a parallelism error has been detected, at least one air feeding parameter of at least one such air pad or at least one position parameter for at least one motorized support structure, from the corresponding setting piece of information.
In the second embodiment of the invention, said mobile unit being able to move with respect to at least one guiding rail defined by two longitudinal side movement surfaces being parallel between them, said mobile unit comprising at least two air pads which cooperate respectively with said longitudinal side surfaces, said mobile unit being able to hold a plurality of distinct longitudinal positions along said guiding rail, with each one of said distinct longitudinal position being associated a predefined side positioning of said mobile unit with respect to said guiding rail:
- said detection means are formed to detect, for each one of said longitudinal positions, a possible side positioning error of said mobile unit with respect to said guiding rail;
- said determining means are formed to determine, in case of detection of such a side positioning error, a setting piece of information allowing to correct or compensate this latter; and
- said setting means are formed to set, when said mobile unit holds one of said distinct longitudinal positions for which a side positioning error has been detected, at least one air feeding parameter of at least one of said air pads or at least one position parameter for at least one motorized support structure, from the corresponding setting piece of information.
In another embodiment of the invention, a reference system comprising fixed reference targets that may be used as a reference point for a certain spatial situation that is long term stable with respect to a global coordinate system is used together with a mobile unit that has a measurement system capable of measuring the position of said fixed reference targets. By arranging two fixed target at opposite sides of a measurement device being firmly connected to the mobile unit, a spatial reference position can be detected by acquiring the position of at least one marker, such as two markers positioned with respect to the movement surface so that at least one spatial situations, such as pitch or roll, can for instance be calculated by subtracting the position value of a second marker from the position value of a first marker. By storing the spatial position of the mobile unit at a certain time, for instance at the time of performing calibration of the mobile unit, any difference in spatial situation compared to this reference position can be calculated. This fixed target reference structure and described method can be used as a mean for detecting variations in spatial situation over time, such as drift in angular (pitch, yaw or roll) or linear directions along or perpendicular to a movement surface. Preferably, the material of choice for the base, reference frame and measurement frame are materials which are rigid and stiff and have low thermal expansion, such that varying temperature, vibrations, bending, twisting or any other cause of deformation will only marginally affect measurements. Said fixed reference target structure may be designed and fabricated to minimize the effect of thermal deformations or other longer term movements, such as internal relaxation effects in the materials used to form the structures, giving rise to structural deformation or surface errors. One way of reducing the effect of thermal expansion is to first of all manufacture the reference structure in symmetrical highly stable construction with a high eigenfrequency and second of all attaching it to the base of a larger system, such as a semiconductor manufacturing or measurement tool, in a thermally insensitive manner using symmetrical attachment points that can allow the material to thermally expand or contract substantially without deforming the reference frame. The same applies to the structure of the mobile unit itself that is providing the structural integrity of the mobile unit, by connecting the air pads that are supported by the movement surface of a base, providing a stable connection to a measurement device attached on either side of the mobile unit. Also this structure and its connections to other parts can be designed and manufactured in materials that allow thermal expansions or other disturbances of any of the mechanical parts in the whole tolerance chain to be done in a way that does not deform or expand the mobile unit itself. The fixed reference target structure and the mobile unit structure can be manufactured in low thermal expansion materials such as Invar, carbon fibre reinforced materials, Zerodur or other types low CTE materials commonly used.
In order to further lower temperature impact on measurements due to thermal expansion of the various parts of the fixed reference target structure, the opposite ends may be positioned substantially symmetrically relatively the measurement point of the mobile unit as well as the base structure of a larger system, such a base structure of a semiconductor manufacturing or measurement tool, where the fixed reference targets serve as a global reference, so that any movements of said ends due to thermal expansion are substantially equally large.
In another embodiment of the invention an external measurement system is provided, in order to measure the spatial position of a mobile unit moving along a movement surface, by use of the external measurement system the spatial situation for a plurality of distinct positions along the movement surface can be determined. By storing the spatial situation for an array of multiple positions along said movement surface the difference between a spatial situation of a first reference position and a second position can be calculated. The differential spatial situation information between multiple distinct positions along the movement surface, may then be used to provide a correction value for setting at least one air feeding or motor setting parameter of at least one of said air pads or support structure motors, in order to obtain the same spatial situation of a second position as for a first reference position, or a correction factor associated with a second position compared to a reference position to be used to compensate for the difference in spatial position in a computer based control system.
In different embodiments of the invention the external measurement system used to determine the spatial situation of the mobile unit in a plurality of distinct positions along the movement surface, may be:
Optical intersubstrate measurement microscopes attached to the mobile unit, arranged to measure position markers on calibration reticules placed within the field of view on both sides of dual- beam measurement microscope, the calibration reticules having arrays of position markers being substantially aligned to each other so that a differential measurement between two reticules placed on opposite sides of the intersubstrate measurement microscope can be used to determine the spatial situation of the intersubstrate microscope in a plurality of distinct positions of the mobile unit.
- 2D encoder heads attached to a reference frame, and 2D encoders attached on a measurement system or the holding member of the mobile unit, arranged to measure 2D positions on 2D encoders, the 2D encoders being arranged so that a differential measurement between two encoders placed on opposite sides of a holding member or other structure of the mobile unit can be used to determine the spatial situation of the mobile unit in a plurality of distinct positions, either during a mapping sequence or continuously as an integrated part of the mobile unit .
3-beam interferometers or digital autocollimators arranged to measure the spatial situation of a stage unit, either during a mapping sequence or continuously as an integrated part of the mobile unit. By attaching a mirror on the holding member or other structure of the mobile unit that reflects the light from an autocollimator or a 3-beam interferometer the spatial situation of the mobile unit can be determined in a plurality of distinct positions .
The figures of the appended drawing will make it possible to understand how this invention could be implemented. In the figures, identical reference numerals relate to similar components.
FIG. 1 shows a block diagram of a setting system according to the present invention.
FIG. 2 is a schematic view of the top of an X-Y movement table associated with the system of FIG. 1 to set the parallelism according to a first embodiment of the invention.
FIG. 3 shows, in a profile view, an X-Y movement table of FIG. 2.
FIG. 4 is a schematic view of the top of a movement table according to a sole longitudinal axis associated with the system of FIG. 1 to set a side positioning, according to a second embodiment of the invention .
FIG. 5 is a profile view, according to the arrow V, of the movement table of FIG. 4. FIG. 6, similar to FIG. 5, represents an alternative to the guiding rail of the movement table of FIG. 4.
FIG. 7 shows, in a profile schematic view, a crossed movement table entirely guided on air pads implementing various setting systems according to the invention .
FIG. 8 shows a side view of a mobile unit with two air pads and two motorized support structures, a movement surface as well as a fixed target system used as an external reference point for detecting the spatial situation of a mobile unit by means of optical measurement of position markers arranged on opposite sides of an intersubstrate measurement microscope.
FIG. 9 shows systems and methods to determine the spatial situation of a mobile unit during the movement between a plurality of distinct positions along a movement surface. On FIG. 1, a system 1A, IB is shown according to the present invention for setting the spatial situation of a mobile unit 2 moving with respect to at least one movement surface 3, 4 by means of air pads 5, 6 (also see FIGS . 2 and 4) .
The mobile unit 2 is able to hold a plurality of distinct positions with respect to such a movement surface 3, 4, this latter presenting flatness errors in at least some of said positions. The mobile unit 2 movement is performed by means of at least one motor M controlled by control means 7.
The air feeding the three air pads 5, 6 is conveyed by lines C linked, upstream, to a single air source S. Of course, alternatively, it can be contemplated to independently provide each one of the air pads with air by independent air sources.
According to the invention, the system 1A, IB comprises:
- means 8 to detect, for each one of the distinct positions, a possible error of spatial situation of the mobile unit 2 with respect to a predefined reference spatial situation associated with said position. The detection means 8 can thus perform a recording of the whole flatness errors of a movement surface 3, 4. For this, they can for instance implement one or more reference marks;
- means 9 for determining, in case of detection of such an error by means 8 to which they are linked (link LI), a setting piece of information allowing to correct this error; and
- means 10 for setting, when the mobile unit 2 holds one of the positions for which an error of spatial situation is detected, at least one air feeding parameter (namely the air feeding pressure and/or rate flow) of at least one of the air pads 5, 6, from the setting piece of information received from the means 9 through a link L2.
Moreover, within the scope of the present invention, the controlling means 10 comprise:
- electropneumatic components 11, for instance, proportional valves, respectively mounted on the lines C; and
- means 12 for determining the setting orders for the electropneumatic components 11 when for a given position of the mobile unit 2, at least one movement surface 3, 4 presents a flatness error. The means 12 are able to receive the mobile unit position 2 with respect to a movement surface by control means 7 (link L3) and a setting piece of information associated with the position being considered (link L2) . Once determined, the setting orders are addressed to the electropneumatic components 11 by a link L4.
Furthermore, for checking the setting performed by the setting means 10, the system 1A, IB also comprises:
- distance sensors 13 associated with said air pads 5, 6, which are able to measure the thickness e of an air bearing gap 5, 6, for a given position of the mobile unit 2 with respect to a movement surface 3, 4 for which the mobile unit 2 presents a spatial situation error. The distance sensors 13 can implement any known technology type (for instance laser, acoustic, capacitive, inductive, optical etc.); and
- means 14 for comparing the measured thickness e of each one of the air pads 5, 6 with a corresponding predetermined reference thickness obtained from the setting piece of information, in order to check the quality of a setting performed by the setting means 10. These comparison means 14 are linked to the setting means 10 through a link L5.
In case the measured thickness e is not equal to the reference thickness, the means 10 adjust the setting of the air feeding parameter of at least one of the three air pads 5, 6, in order to reach said reference thickness.
Alternatively or additionally, for calibrating the system 1A, IB, this latter can also comprise : - a distance sensor 15 associated with the mobile unit 2 and formed to measure the distance between a reference point of the mobile unit 2 and a movement surface 3, 4, for a sole predetermined origin position Po of the movement surface 3, 4; and
- means 16 for comparing the measured distance with a predetermined reference distance. These means 16 are linked to the setting means 10 through a link L6.
In case the measured distance is not equal to the reference distance, the means 10 set at least one air feeding parameter of the three air pads 5, 6, simultaneously so that the measured distance is at least approximately equal to the reference distance.
In the first embodiment of the present invention, shown on FIGS. 2 and 3, the system 1A is adapted for setting the parallelism between a reference plan (corresponding for instance to an horizontal movement surface 3 with no flatness imperfections) and a face 17 of a mobile unit 2 which moves on the horizontal movement surface 3 by means of three air pads 5 equiangularly distributed around a centre 0 of the mobile unit 2.
Particularly, the setting system 1A can be associated, but not exclusively, with an X-Y movement table T. Thus, as shown on FIGS. 2 and 3, the X-Y movement table T comprises a fixed basis 18, the upper part of which forms the movement surface 3, and the mobile unit 2 (in a carriage form), the upper part of which serving for receiving one or more parts to be processed (not represented) defines the face 17.
Moreover, as shown on FIG. 2, the X-Y movement table T also comprises usual guiding means 19 that force the mobile unit 2 to move according to the two orthogonal directions X-X and Y-Y. It should be noticed that the movement of the mobile unit 2 is performed without friction on the horizontal movement surface 3. With these guiding means 19 there are associated electric motors M for putting the mobile unit 2 in movement with a very high moving dynamics and a high positioning precision. The motors M are controlled by said control means 7.
Furthermore, according to this first embodiment :
- the detection means 8 are formed for detecting, for each one of the distinct positions, a possible parallelism error between the reference plan and the face 17 of the mobile unit 2 ;
- the determining means 9 are formed for determining, in case of detection of a parallelism error, a setting piece of information allowing to correct it; and
- the setting means 10 are formed so as to set, when said mobile unit 2 holds one of the distinct positions for which a parallelism error has been detected, at least one air feeding parameter of at least one of the three air pads, from the corresponding setting piece of information.
Thus, by setting the compressed air feeding pressure and/or rate flow 5, the respective thickness e of the corresponding air pad 5 can be modified. In this way, the parallelism between the face 17 of the mobile unit 2 and the reference plan can be obtained for a given distinct position for which a parallelism error is observed. In this case, the mobile unit 2 can be checked in roll and/or pitch. In the second embodiment according to the present invention, illustrated on FIGS. 4 and 5, a mobile unit 2 is from now on forced to move on the movement table T according to a longitudinal guiding rail 20 in rib shape, protruding with respect to an horizontal movement surface 3.
In the same way as for the first embodiment, the mobile unit 2 is hold by the movement surface 3 by means of three air pads 5, which are driven according to the first embodiment by the setting system 1A (not illustrated on FIG. 4 for clarity's sake) .
Furthermore, the guiding rail 20 is defined by two longitudinal and vertical side movement surfaces 4, which are mutually parallel. The mobile unit 2 comprises three auxiliary air pads 6, two of which cooperate with one of said side movement surfaces 4 and the other one with the other surface 4.
Thus, the mobile unit 2 is able to hold a plurality of distinct longitudinal positions along said guiding rail 20. Furthermore, with each one of said distinct longitudinal positions is associated a predefined side positioning of the mobile unit 2 with respect to said guiding rail 20.
It should be noticed that the mobile unit 2 movement along the guiding rail 20 is performed by an electrical motor M controlled by said control means 7.
Furthermore, according to this second embodiment :
- the detecting means 8 are formed to detect, for each one of the distinct longitudinal positions, a possible side positioning error of the mobile unit 2 with respect to said guiding rail 20; - the determining means 9 are formed to determine, in case of detection of such a side positioning error, a setting piece of information allowing to correct this latter; and
- the setting means 10 are formed so as to set, when said mobile unit 2 holds one of said distinct longitudinal positions for which a side positioning error has been detected, at least one air feeding parameter of at least one of the three auxiliary air pads, from the corresponding setting piece of information received from the determining means .
Thus, for a given longitudinal position, by setting the thickness of at least one of the three auxiliary air pads 6, the side positioning of the mobile unit 2 can be modified with respect to the guiding rail 20 and the predefined side positioning associated with this longitudinal position can be obtained .
In this second embodiment, thanks to the setting systems 1A and IB, said mobile unit 2 can be checked in roll and/or pitch (by the air pads 5) , as well as in yaw (by the air pads 6) .
In an alternative of the second embodiment illustrated on FIG. 6, the guiding rail 20 can have the shape of a groove arranged in the upper part of the fixed base 18.
In another alternative of the second embodiment illustrated on FIG 7, the mobile unit 2 of a crossed movement table T comprises a first and a second mobile element PI and P2. The element PI is hold by the horizontal movement surface 3A of the element P2, by means of three air pads 5A, and is able to move with respect to this one according to a first longitudinal, rectilinear first guiding rail 20A (defining the X direction) protruding with respect to the movement surface 3A. The three air pads are driven by a first regulating system 1A (not illustrated on FIG. 7), previously described and according to the invention .
Furthermore, the guiding rail 20A is defined by two longitudinal side movement surfaces 4A parallel there between. These two surfaces 4A are vertical. The element PI comprises more than three auxiliary air pads 6A, two of which cooperate with one of said movement surfaces 4A and the other with the other surface 4A. These three air pads 6A are checked by a first setting system IB (not illustrated on FIG. 7) of the type described hereinabove.
Moreover, the mobile element P2 is hold by an horizontal movement surface 3B in the upper part of a fixed base 18, by means of the three air pads 5B, and is able to move with respect to this one according to a second longitudinal rectilinear guiding rail 20B (defining the Y direction) , orthogonal to the rail 20A and protruding with respect to the movement surface 3B. The three air pads 5B are driven by a second setting system 1A (not illustrated on FIG. 7) .
The guiding rail 20B is also defined by two longitudinal side movement surfaces 4B parallel therebetween. These two surfaces are vertical. The element P2 comprises three auxiliary air pads 6B, two of which cooperate with one of said movement surfaces 4B and the other with the other surface 4B. These three air pads 6B are checked by a second setting system IB (not illustrated on FIG. 7) of the type described hereinabove.
The first and second setting systems 1A are independent from each other, as well as the first and second setting systems IB.
In this other alternative, the mobile unit 2 is checkable in pitch and/or roll (by the air pads 5A and 5B) , as well as in yaw along the X direction (by the air pads 6A) and/or along the Y direction (by the air pads 6B) .

Claims

1. A method for setting the spatial situation of a mobile unit (2) moving with respect to at least one movement surface (3, 4) by means of at least one air pad (5, 6), said mobile unit (2) being able to hold a plurality of distinct positions with respect to said movement surface (3, 4), characterized in that said method comprises the steps: A) detecting a possible error of spatial situation of said mobile unit (2) for at least one of said distinct positions with respect to a predefined reference spatial situation associated with said position;
B) determining a setting piece of information allowing to correct or compensate a potential error; and C) setting from the corresponding setting piece of information, when said mobile unit (2) holds one of said positions for which an error of spatial situation is detected, at least one air feeding parameter of at least one such air pad (5, 6) and/or at least one motor position parameter of at least one motorized support structure, in order to obtain the reference spatial situation of said mobile unit associated with said position or from a calibration matrix obtain a correction factor associated with said position, in order to compensate the error in spatial situation in a computer based control system.
2. The method according to claim 1, for setting the parallelism between a reference plan and a face (17) of said mobile unit (2) moving on said movement surface (3) by means of at least one such air pad ( 5 ) ,
characterised in that it further comprises the steps:
- at step A) , detecting a possible parallelism error between said reference plan and the face (17) of said mobile unit (2) for each one of said distinct positions ;
- at step B) , determining a setting piece of information allowing to correct a potential parallelism error, ; and
- at step C) , setting from the corresponding setting piece of information at least one air feeding parameter of at least one such air pad (5) when said mobile unit (2) holds one of said distinct positions for which a parallelism error has been detected, in order to obtain a parallelism between said reference plan and the face (17) of said mobile unit ( 2 ) .
3. The method according to claim 2,
characterized in that said mobile unit (2) being held by said movement surface (3) by means of three air pads (5), at step C) , at least one air feeding parameter of at least one of said air pads (5) is set .
4. The method according to one of claims 1 to 3, said mobile unit (2) being able to move with respect to at least one guiding rail (20) defined by two parallel longitudinal side movement surfaces (4) between them, said mobile unit (2) comprising at least two air pads (6) which cooperate respectively with said longitudinal side surfaces (4), said mobile unit (2) being able to hold a plurality of distinct longitudinal positions along said guiding rail (20), with each one of said distinct longitudinal position being associated a predefined side positioning of said mobile unit with respect to said guiding rail (20),
characterised in that it further comprises the steps:
- at step A) , for each one of said distinct longitudinal positions, detecting a possible error of side positioning of said mobile unit (2) with respect to said guiding rail (20) ;
- at step B) , in case of side positioning error detection, determining a setting piece of information allowing to correct it; and
- at step C) , when said mobile unit (2) holds one of said distinct longitudinal positions for which a side positioning error has been detected, setting from the corresponding setting piece of information at least one air feeding parameter of at least one of said air pads (6), in order to obtain said predefined side positioning associated with said longitudinal position.
5. The method according to one of claims 1 to 4, characterised in that said feeding parameter is the air feeding pressure.
6. The method according to one of claims 1 to 5, characterised in that said feeding parameter is the air feeding flow rate.
7. The method according to one of claims 1 to 6, characterised in that, moreover, for setting checking purposes, it further comprises the steps: - for each one of said positions for which a spatial situation error is detected, measuring the thickness (e) of at least one air pad (5, 6) ;
- comparing the thickness measured to the predetermined reference thickness obtained from said setting piece of information, in order to check the quality of the setting performed at step C) ; and
- adjusting, in case the measured thickness is not equal to the reference thickness, the setting of the air feeding parameter of at least said air pad (5, 6) so that the thickness of said air pad is at least approximately equal to said reference thickness .
8. The method according to one of claims 1 to 7, characterised in that, moreover, for calibrating purposes it comprises the steps:
- for one single position of predefined origin of said movement surface (Po) , measuring the distance between a reference point of said mobile unit (2) and said movement surface (3, 4) ;
- comparing the distance measured with a predetermined reference distance; and
- in case the measured distance is not equal to the reference distance, setting at least one air feeding parameter of at least one air pad (5, 6) , so that the measured distance is at least approximately equal to the reference distance.
9. The method according to one of claims 1 to 8, characterized in that steps A) , B) and C) are performed in an iterative manner.
10. A system for setting the spatial situation of a mobile unit (2) moving with respect to at least one movement surface (3, 4) by means of at least one air pad (5, 6), said mobile unit (2) being able to hold a plurality of distinct positions with respect to said movement surface, ,
characterized in that it comprises:
- means (8) for detecting, for each one of said distinct positions, a possible error of spatial situation of said mobile unit (2) with respect to a predefined reference spatial situation associated with said position;
- means (9) for determining, in case of detection of such an error, a setting piece of information allowing to correct said error; and
- means (10) for setting, when said mobile unit (2) holds one of said positions for which an error of spatial situation is detected, at least one air feeding parameter of at least one such air pad (5, 6) , from the corresponding setting piece of information .
11. The system according to claim 10, for setting the parallelism between a reference plan and a face (17) of said mobile unit (2) moving on said movement surface (3) by means of at least one such air pad ( 5 ) ,
characterised in that:
- said detection means (8) is configured to detect, for each one of said distinct positions, a possible parallelism error between the reference plan and the face (17) of said mobile unit (2) ; - said determining means (9) is configured to determine, in case of detection of a parallelism error, a setting piece of information allowing to correct it; and - said setting means (10) is configured to set, when said mobile unit (2) holds one of said distinct positions for which a parallelism error has been detected, at least one air feeding parameter of at least one such air pad (5), from the corresponding setting piece of information.
12. The system according to claim 10, said mobile unit (2) being able to move with respect to at least one guiding rail (20) defined by two longitudinal side movement surfaces (4) parallel between them, said mobile unit (2) comprising at least two air pads (6) which cooperate respectively with said longitudinal side surfaces (4), said mobile unit (2) being able to hold a plurality of distinct longitudinal positions along said guiding rail (20), with each one of said distinct longitudinal position being associated a predefined side positioning of said mobile unit with respect to said guiding rail (20),
characterised in that:
- said detection means (8) is configured to detect, for each one of said longitudinal positions, a possible side positioning error of said mobile unit (2) with respect to said guiding rail (20) ;
- said determining means (9) is configured to determine, in case of detection of such a side positioning error, a setting piece of information allowing to correct this latter; and
- said setting means (10) is configured to set, when said mobile unit (2) holds one of said distinct longitudinal positions for which a side positioning error has been detected, at least one air feeding parameter of at least one of said air pads (6), from the corresponding setting piece of information .13. A reference system comprising fixed reference targets that may be used as a reference point for a certain spatial situation that is long term stable with respect to a global coordinate system is used together with a mobile unit that has a measurement system capable of measuring the position of said fixed reference targets. By arranging two fixed target at opposite sides of a measurement device being firmly connected to the mobile unit, a spatial reference position can be detected by acquiring the position of at least one marker, such as two markers positioned with respect to the movement surface so that at least one spatial situations, such as pitch or roll, can for instance be calculated by subtracting the position value of a second marker from the position value of a first marker.
A system with an external measurement system used in order to measure the spatial position of a mobile unit moving along a movement surface, by use of the external measurement system the spatial situation for a plurality of distinct positions along the movement surface can be determined.
PCT/EP2011/061997 2010-07-15 2011-07-13 Methods and systems for detecting, setting, monitoring, determining, storing and compensating the spatial situation of a mobile unit WO2012007527A2 (en)

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JPS58116735A (en) * 1981-12-29 1983-07-12 Canon Inc Projection printing apparatus
US5121256A (en) * 1991-03-14 1992-06-09 The Board Of Trustees Of The Leland Stanford Junior University Lithography system employing a solid immersion lens
US6151100A (en) * 1996-12-12 2000-11-21 Canon Kabushiki Kaisha Positioning system
JPH10223519A (en) * 1997-02-04 1998-08-21 Nikon Corp Projection aligner
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