Position Detection System Using Laser Interferometry

Abstract

The present invention relates to a position detection system using a laser light interference method for an XYZ coordinate system and for measuring the position and displacement of an object within the XYZ coordinate system. The system includes a frame and a holder including a mounting surface of the object. The mounting surface is oriented within the XY plane of the XYZ coordinate system. The holder is configured to be displaced relative to the frame between at least a first operating position and a second operating position within the XY plane. Such a laser light interference detection system can be implemented, for example, in a manufacturing process of a semiconductor or an integrated circuit.

Description

Technical Field

[0001] The present invention relates to a position detection system using a laser light interference method for measuring the position and displacement of an object with respect to an XYZ coordinate system and within the XYZ coordinate system. The system includes a frame and a holder including a mounting surface of the object, the mounting surface being oriented within the XY plane of the XYZ coordinate system, and the holder having a structure that is displaceable relative to the frame at least between a first operating position and a second operating position within the XY plane. Such a laser light interference detection system can be implemented, for example, in the manufacturing process of semiconductors and integrated circuits.

Background Art

[0002] Applications that require high-precision positioning and displacement, such as a wafer substrate during the semiconductor and integrated circuit manufacturing processes, implement a laser light interference method detection system. A plurality of measurement mirrors and laser light beams directed towards and irradiated from those mirrors are used to determine the position and displacement of an object within an XYZ coordinate system based on the laser light interference method.

[0003] In current laser light interference method detection systems, multi-degree-of-freedom (DOF) measurements within such an XYZ coordinate system are possible, but the accuracy of these measurements is limited, which has an adverse effect on the efficiency of the entire process in which the laser light interference method detection system is implemented.

[0004] For example, for displacement distances or strokes longer than the dimensions of the holder, multiple DOF measurement values may be lost. Furthermore, in currently known applications, additional measurement mirrors arranged within the working space are implemented, occupying the working volume in the immediate vicinity where the semiconductor and integrated circuit manufacturing processes are performed.

[0005] However, in applications where these additional measurement mirrors are placed within the working space to cover a large displacement distance or stroke of the holder through the position detection system, the interferometer sensor is fixed to the frame of the system. Therefore, the measurement area that the interferometer sensor can cover is limited by the size of the mirror attached to the holder that displaces between the first operating position and the second operating position within the working space of the system.

[0006] When the stroke (which means the distance between the first operating position and the second operating position in the system working space) is larger than the size of the mirror attached to the holder, the signal of the interferometer is lost. Losing the signal means that since the IFM is only an incremental measurement, the system needs to find the correct reference again. Therefore, it is necessary to implement multiple interferometer sensors and six DOF zeroing sensors. As a result, a more expensive and complex laser interferometer detection system is obtained. However, implementing multiple sensors requires new calculations to determine the absolute reference point of the holder within the working space of the system, resulting in an even more expensive system. Furthermore, losing the accurate reference point of the holder within the system working space and repeatedly recalculating the reference point reduces the output of the system and poses a continuous risk of accuracy errors.

[0007] This problem typically occurs in laser interferometry applications where there is a measurement station (or first working position) for measuring a sample on the holder and a processing station (or second working position) for processing the sample on the holder. Especially when the stroke of the stage in at least one direction (i.e., the distance between the first operating position and the second operating position) is larger than the size of the mirror (on the holder) while the holder with the sample is displaced from the measurement position towards the processing position, an accurate measurement system is required.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present disclosure aims to provide a solution to the above-specified problem, and presents a position detection system using a laser light interference method having a reduced and simplified optical system, and thus has reduced structural dimensions and improved accuracy regarding the measurement of the position and / or displacement of a holder within an XYZ coordinate system.

Means for Solving the Problem

[0009] A first aspect of the present disclosure is a position detection system using a laser light interference method for measuring the position and displacement of an object with respect to and within an XYZ coordinate system. This system includes a frame, a holder including a mounting surface of the object oriented in the XY plane of the XYZ coordinate system, a plurality of measurement mirrors, and a plurality of optical devices. The holder is configured to be displaced at least between a first operating position and a second operating position with respect to the frame within the XY plane. Each of the optical devices is configured to emit and irradiate each laser light beam of each of the measurement mirrors from each of the measurement mirrors. Further, each of the optical devices is configured to detect at least a part of each laser light beam reflected by each of the measurement mirrors and convert it into an electrical measurement signal. The electrical measurement signal includes information regarding the XYZ position of the holder. To measure the position of the holder with respect to the first coordinate axis of the XY plane, at least one first-axis optical device is configured to be displaced together with the holder between the first operating position and the second operating position along the first coordinate axis of the XY plane. Further, the at least one first-axis optical device is configured to emit each first laser light beam parallel to the XY plane and perpendicular to the first coordinate axis from the first mirror surface of each first-axis measurement mirror extending along the first coordinate axis beyond both the first operating position and the second operating position and to be incident on the first mirror surface of each first-axis measurement mirror.

[0010] When the holder moves along the coordinate axes of the XY plane between the first operating position and the second operating position, and the optical device is displaced accordingly, even if the displacement stroke of the holder between the first operating position and the second operating position is larger than the size of the holder itself (and further the size of the mirror thereon), the accurate reference point of the holder within the system working space is not lost.

[0011] In one example, at least one first-axis optical device is attached to the holder.

[0012] In a preferred alternative embodiment, at least one first-axis optical device is attached to the mount. This mount is configured to be displaced between a first operating position and a second operating position along the first coordinate axis with respect to the frame. Therefore, in any of the embodiments, the accurate reference point of the holder within the system working space (XYZ coordinate system) is not lost because the position of the holder is measured in real time.

[0013] In one embodiment, the first-axis measurement mirror is attached to the frame. In another embodiment, the first-axis measurement mirror is composed of at least two first-axis measurement sub-mirrors. In the latter case, the accuracy regarding the position measurement of the holder with respect to the first coordinate axis within the system working space is improved.

[0014] In a more advantageous embodiment, the mount is provided with a recess for receiving the first-axis measurement mirror. In this case, if a Michelson interferometer type sensor is used, each direction can be measured with a single light source and detector within the sensor.

[0015] Furthermore, in order to measure the position of the holder with respect to the first coordinate axis of the XY plane, the holder may be provided with a first-axis holder measurement mirror having at least a first mirror surface arranged perpendicular to the XY plane.

[0016] In a preferred embodiment, the cooperative displacement of both the holder and the first-axis optical device is a synchronous displacement.

[0017] Next, in a further advantageous embodiment, to measure the Z position of the holder with respect to the XY plane, the at least one first-axis optical device is configured to emit and irradiate respective further laser light beams from a further mirror surface of the first-axis measurement mirror and at an angle α with respect to the XY plane with respect to the further mirror surface of the first-axis measurement mirror.

[0018] Similarly, to measure the Z position of the holder with respect to the XY plane, the at least one first-axis optical device is configured to emit and irradiate respective further laser light beams from a further mirror surface of the first-axis measurement mirror and at an angle α with respect to the XY plane with respect to the further mirror surface of the first-axis holder measurement mirror.

[0019] In the above two examples, the further mirror surface of the first-axis measurement mirror or the first-axis holder measurement mirror is oriented at an angle α with respect to the first mirror surface of the first-axis measurement mirror or the first-axis holder measurement mirror.

[0020] Thus, by implementing a composite (holder) measurement mirror composed of a laser light beam with an additional angle, a first mirror surface arranged perpendicular to the XY plane, and a further mirror surface oriented at an angle α with respect to the first mirror surface, an additional Z measurement mirror becomes unnecessary. For this reason, the optical system of the position detection system can be significantly simplified. In particular, as a result, the occupied working volume in the immediate vicinity of the manufacturing process of semiconductors and integrated circuits is reduced.

[0021] Depending on the structural dimensions of the holder used and the desired measurement accuracy, the angle α of the at least one angled Z laser light beam with respect to the XY plane is in the range of 5° to 45°, specifically in the range of 5° to 25°, more specifically in the range of 5° to 15°, and even more specifically the angle α = 7°.

[0022] More specifically, the first-axis holder measurement mirror includes a third mirror surface. This third mirror surface is arranged perpendicular to the XY plane and is adjacent to a further mirror surface facing the first mirror surface. The third mirror surface can function as an additional first-axis measurement mirror for an additional first-axis laser beam, and accordingly, can be used to measure a further six degrees of freedom of the holder, particularly rotation or inclination around the XY or Z axes.

[0023] In a further embodiment of the present disclosure, a second-axis optical device is provided to measure the position of the holder with respect to the second coordinate axis in the XY plane. This second-axis optical device is configured to emit respective laser beams parallel to the XY plane and parallel to the first coordinate axis from at least one second measurement mirror and to irradiate the second measurement mirror. The second measurement mirror is arranged perpendicular to the first coordinate axis in the XY plane and is arranged beyond the first operating position or the second operating position.

[0024] In particular, the second measurement mirror may be arranged perpendicular to the first coordinate axis in the XY plane and may be arranged between the first operating position and the second operating position. This further second measurement mirror can be effectively used as a reference mirror for each degree of freedom to be measured.

Brief Description of the Drawings

[0025] Next, the present invention will be described with reference to the drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0026] To properly understand the present invention, in the following detailed description, corresponding elements or parts of the present invention are denoted by the same reference numerals in the drawings.

[0027] It has been known in the prior art that applications requiring high-precision positioning and displacement, such as a wafer substrate during semiconductor and integrated circuit manufacturing processes, may implement a laser interferometer detection system. A plurality of measurement mirrors and laser light beams directed at those mirrors are used to determine the position and displacement of an object within an XYZ coordinate system based on the laser light interference method.

[0028] In current laser light interference method detection systems, although multi-degree-of-freedom (DOF) measurements within such an XYZ coordinate system are possible, there are some limitations.

[0029] For example, for displacement distances or strokes longer than the dimensions of the holder, multiple degree-of-freedom measurements may be lost. Further, in currently known applications, additional measurement mirrors are implemented within the working space, occupying the working volume in the immediate vicinity where the semiconductor or integrated circuit manufacturing process is performed.

[0030] When the stroke (the distance between the first operating position and the second operating position in the system workspace) is required to be large for the holder compared to the size of the mirror attached thereto, the interferometer signal is lost. Losing the signal means that since the IFM is only an incremental measurement, the system needs to find the correct reference again. Therefore, it is necessary to implement a plurality of interferometer sensors and six 6-DOF zeroing sensors, resulting in a more expensive and complex laser interferometer detection system. However, implementing a plurality of sensors requires new calculations to determine the absolute reference point of the holder within the working space of the system, making the system even more expensive. Furthermore, losing the accurate reference point of the holder within the system working space and repeatedly recalculating the reference point reduces the output of the system and poses a continuous risk of accuracy errors.

[0031] An example of such a laser interferometer detection system is depicted in FIGS. 1A - 1C and is designated by reference numeral 10. Such a position detection system 10 using laser interferometry can measure the position and displacement of an object with respect to and within an XYZ coordinate system. In one example, the object 14 may be a wafer substrate during semiconductor and integrated circuit manufacturing processes for semiconductor component fabrication.

[0032] Typically, the system 10 includes a frame 11 in which a holder 12 is movably accommodated. The displacement of the holder 12 is achieved using suitable holder displacement means 13, which displace the holder 12 within the frame 11 of the system 10 / along the ground plane (solid world). The holder 12 can hold an object (wafer substrate) 14. As shown in FIGS. 1A - 1C, the holder 12 includes an attachment surface 12a for the object 14, and preferably, such an object 14 is accommodated within an attachment space 12b machined or provided on the attachment surface 12a. The attachment surface 12a of the holder 12 is preferably oriented parallel within the XY plane of the XYZ coordinate system, and its orientation is depicted on the left side of FIG. 1A.

[0033] The XYZ coordinate system depicted on the left side of FIG. 1A is composed of three coordinate axes XYZ and defines the coordinate orientation of the holder 12 within the working space of the system 10.

[0034] The above-specified problem of losing the exact reference point of the holder 12 within the working space of the system typically occurs in laser interferometry applications where the holder 12 (with the sample object 14) is displaced between the measurement station I (or the first operating position) where the sample object 14 on the holder 12 is measured and the processing station II (or the second operating position) where the sample object 14 on the holder 12 is processed. In particular, when the stroke of the stage in at least one direction (i.e., the distance between the first operating position and the second operating position) is larger than the size of the mirror (on the holder), an accurate measurement system is required while the holder 12 with the sample object 14 mounted thereon is displaced from its measurement position I towards its processing position II.

[0035] In the example of FIGS. 1A - 1C, the stroke of the stage (the displacement of the holder 12 from position I to position II) is depicted as a displacement along the X coordinate axis of the XY plane with respect to the frame 11.

[0036] To monitor the displacement, and more particularly, to monitor the exact position of the holder 12 passing through the system working space (and thus within the XYZ coordinate system) of the system 10 according to the state of the art, a plurality of optical devices are implemented. Each optical device is configured to irradiate a laser beam onto its respective laser interferometry mirror and direct the laser beam therefrom. The reflected laser beam is converted into an electrical measurement signal, and the electrical measurement signal contains information regarding the actual XYZ position of the holder 12 (including the object 14 mounted in the mounting space 12b on the mounting surface 12a) within the system working space (XYZ coordinate system).

[0037] Using a suitable signal processing unit (not shown), the emitted and reflected laser beam is used to calculate the XY and Z positions using a laser interferometer.

[0038] As an example, the second-axis optical device 21x (attached to the frame 11) emits a laser beam 23x parallel to the first (X) coordinate axis, and this beam 23x is reflected back and forth by a corresponding measurement mirror 22x attached to the frame 11 and a mirror 12x attached to the holder 12. The reflected beam 23x provides information about the actual X position of the holder 12 with respect to the Y coordinate axis. In the XY plane, the second-axis optical device 21x determines the X position or distance of the holder with respect to the Y coordinate axis.

[0039] Similarly, as shown in FIGS. 1A - 1C, two or more optical devices 21y-a and 21y-b are attached to the frame 11 along the X coordinate axis and irradiate a laser beam 23y (not shown, but the propagation direction of the laser beam 23y is considered to be out of the plane of FIGS. 1A - 1C) towards the holder 12 (parallel to the Y axis). The holder 12 includes a measurement mirror on its side surface, which reflects the laser beam 23y back to the respective optical devices 21y-a and 21y-b. The reflected beam 23y provides information about the actual Y position of the holder 12 in the XY plane with respect to the X coordinate axis. Thereby, any (minimum) Y displacement of the holder 12 in the direction of the Y coordinate axis (and thus with respect to the X coordinate axis) can be effectively measured.

[0040] However, in the application of FIGS. 1A - 1C, the measurement area covered by the optical devices (interferometer sensors) 21y-a and 21y-b is limited by the size of the mirror attached to the holder 12. In FIG. 1A, the holder 12 is in the first operating position I and is within the detection range of the first optical device 21y-a. However, while displacing from the first operating position I to the second operating position II (FIGS. 1B and 1C), the holder 12 moves out of the detection area of the first optical device 21y-a but does not enter the detection area of the second optical device 21y-b.

[0041] This situation is shown in Figure 1B, where the interferometer signal is lost. The loss of the signal means that since the interferometry is only an incremental measurement, the system 10 needs to find the correct reference again. In this case, multiple interferometer sensors (optical devices) are required, resulting in a more expensive and complex laser interferometer detection system.

[0042] The present disclosure aims to provide a solution to the above - identified problems, presenting a position - detection system using laser - light interferometry with a reduced and simplified optical system, and thus having reduced structural dimensions and improved accuracy with respect to the measurement of the position and / or displacement of a holder within an XYZ coordinate system.

[0043] An example of such a position - detection system using laser - light interferometry according to the present disclosure is depicted in Figures 2A - 2C, and further details are shown in Figures 3, 4A - 4C, and 5A - 5D. In the figures, the position - detection system is denoted by reference numeral 100, and it is also possible to measure the position and displacement of an object 12 with respect to and within an XYZ coordinate system.

[0044] The position - detection system 100 includes a frame 110 in which a holder 120 is movably accommodated. The displacement of the holder 120 is achieved using appropriate holder - displacement means 130 that displace the holder 120 along the ground surface (solid world) / within the frame 110 of the system 100 in a manner similar to the position - detection system 10 shown in Figures 1A - 1C. The holder 120 can hold an object (wafer substrate) 140. Similarly, the holder 120 includes a mounting surface 120a for the object 140, and preferably, such an object 140 is accommodated within a mounting space 120b machined or provided on the mounting surface 120a. The mounting surface 120a of the holder 120 is oriented within the XY plane of the XYZ coordinate system, preferably parallel, and its orientation is depicted on the left side of Figure 2A.

[0045] The position of the holder 120 within the XYZ coordinate system is measured using a laser interferometry method that uses a measurement mirror, similar to the optical device. Each optical device irradiates its respective laser light beam onto its respective measurement mirror and is structured to lead from there. At least a part of each laser light beam reflected by each measurement mirror is converted into an electrical measurement signal that contains at least representative information regarding the XYZ position of the holder 120.

[0046] To avoid the problem of losing the interferometer signal as shown in FIG. 1B, in the system 100 according to the present disclosure, the holder according to the prior art is no longer within the measurement area of any optical device. To measure the Y position of the holder 120 with respect to the first coordinate axis (denoted as the X axis) in the XY plane, at least one first-axis optical device 210y is structured to be displaced together with the holder 120 between a first operating position I and a second operating position II along the first (X) coordinate axis in the XY plane.

[0047] At least one first-axis optical device 210y uses a laser device 215 with reference to FIG. 3 to direct respective first laser light beams 230y (230y-1 and / or 230y-2) that are parallel to the XY plane (parallel to the Y coordinate axis) and perpendicular to the first coordinate axis X onto the first mirror surface 220y-1 of respective first-axis measurement mirrors 220y and to emit and direct them from the first mirror surface 220y-1. The first-axis measurement mirror 220y has an important longitudinal dimension and extends along the first coordinate axis X beyond both the first operating position I and the second operating position II (see FIG. 2B).

[0048] While the holder 120 moves from the first operating position I and the second operating position II along the first coordinate axis (here the X axis) in the XY plane, the displacement of the optical device 210y together with the holder 120 ensures that even if the displacement stroke of the holder 120 between the first operating position and the second operating position is larger than the size of the holder 120 itself (on the mirror), the exact reference point of the holder 120 within the system working space is not lost.

[0049] In one embodiment, at least one first-axis optical device 210y is attached to the holder 120 and thus displaced together with the holder 120 by the holder displacement means 130.

[0050] In a preferred alternative, shown in more detail alternatively by FIGS. 3 and 5A-5C, at least one first-axis optical device 210y (210y') is attached to a mount or housing 212y which houses a laser device 215. The mount 212y is also structured to be displaceable between a first operating position I and a second operating position II along a first coordinate axis X relative to the frame 110 using suitable device displacement means 211y. Thus, in any embodiment, since the Y position of the holder 120 is measured in real time relative to the first coordinate axis X, there is no risk of losing the exact reference point of the holder 120 within the system working space (XYZ coordinate system).

[0051] In another advantageous embodiment, depicted in FIGS. 4A-4B, 6A-6C and 7A-7B, the frame 110 comprises a guide part 110y to which a guide rail 111 is attached. The guide rail 111 houses the mount or housing 212y of the first-axis optical device 210y.

[0052] In a particular embodiment as shown in the figures, the first-axis measurement mirror 220y is attached to the frame 110 as shown in FIGS. 3 and 5A-5C and is attached directly or alternatively to the guide part 110y as shown in FIGS. 4A-4B, 6A-6C and 7A-7B. Alternatively, the first-axis measurement mirror 220y may consist of at least two first-axis measurement sub-mirrors indicated by reference numerals 230y-1 and 230y-2 in FIG. 5A, the latter providing improved accuracy with respect to the Y position measurement of the holder 120 relative to the first coordinate axis X within the system working space (in particular, any oblique or rotated orientation).

[0053] As shown in FIG. 5C, the mount 212y of an alternative second embodiment of the optical device 210y' includes a recess 213y in which a first axial measurement mirror 220y is received. In this embodiment, the first axial measurement mirror 220y is attached to the support 110' of the frame / solid world 110. When implementing a Michelson interferometer, the differential mirrors should be measured in the same direction (as shown in FIG. 5A). The advantage of the example of FIG. 5C compared to the example of FIG. 5A is that since both laser beams are in a straight line, the measurement (error) is much less affected by the rotation (Rx) of the optical device 210y'.

[0054] As shown in FIGS. 3, 4A-4B, 5A-5C, 6A-6C, and 7A-7B, in order to obtain a differential position measurement of the Y position of the holder 120 with respect to the first coordinate axis (X) of the XY plane, the holder 120 may be composed of a first axial holder measurement mirror 120y having a first mirror surface 120y-1 disposed perpendicular to the XY plane, and this plane is formed by the mounting surface 120a. Thus, a laser light beam 230y-1, such as emitted by the laser device 215 of at least one first axial optical device 210y, is incident perpendicularly (perpendicular to the X axis / parallel to the Y axis) on the holder measurement mirror 120y and is reflected back in the opposite direction to the first axial optical device 210y.

[0055] It should be noted that the displacement of the optical device 210y, together with the displacement of the holder 120 along the coordinate axis (here the X axis) of the XY plane, should be adjusted so that the optical device 210y is maintained within the "optical field of view" of the first axial holder measurement mirror 120y of the holder 120 and the elongated first axial measurement mirror 220y on the frame 110. Thus, a first laser light beam 230y (230y-1 and / or 230y-2), such as emitted by the laser device 215 of the optical device 210y, is continuously reflected during the coordinated displacement of both the holder 120 and the optical device 210y along the X coordinate axis, providing certain information regarding the actual differential position measurement of the Y position of the holder 120 with respect to the first coordinate axis (X) of the XY plane.

[0056] In a preferred embodiment, the cooperative displacement of both the holder 120 and the optical device 210y is a synchronous displacement.

[0057] The Z position of the holder 120 can be measured simultaneously with the same laser interferometer system. In this embodiment, at least one first-axis optical device 210y emits and irradiates respective additional laser light beams 230z generated by the same or different laser devices 215 within the mount 212y. The additional laser light beams 230z are emitted and irradiated from an additional mirror surface 220z-1 of the first-axis measurement mirror 220y and at an angle α with respect to the additional mirror surface 220z-1 of the first-axis measurement mirror 220y relative to the XY plane (mounting surface 120a).

[0058] The first-axis measurement mirror 220y accordingly exhibits a dual optical function since its composite mirror surface 220y-1 / 220z-1 can be used for laser interferometric measurement of both the Y position and the Z position of the holder 120 within the system working space (XYZ coordinate system). Thus, due to this dual optical function, the first-axis measurement mirror is also denoted by the reference numeral 220y / 220z.

[0059] At least one first-axis optical device 210y emits and irradiates respective additional laser light beams 230z from an additional mirror surface 120z-1 of the first-axis holder measurement mirror 120y and at an angle α with respect to the additional mirror surface 120z-1 of the first-axis holder measurement mirror 120y relative to the XY plane (mounting surface 120a). Thereby, the measurement of the Z position of the holder 120 is improved. The first-axis holder measurement mirror 120y accordingly exhibits a dual optical function since its composite mirror surface 120y-1 / 120z-1 can be used for laser interferometric measurement of both the Y position and the Z position of the holder 120 within the system working space (XYZ coordinate system). Thus, due to this dual optical function, the first-axis holder measurement mirror is also denoted by the reference numeral 120y / 120z.

[0060] The additional mirror surface 220z-1 / 120z-1 of the first-axis measurement mirror 210y / 210z or the first-axis holder measurement mirror 120y / 120z is oriented at an angle α with respect to the first mirror surface 220y-1 / 120y-1 of the first-axis measurement mirror 210y or the first-axis holder measurement mirror 120y.

[0061] By virtue of the advantage of using a single mirror reflecting surface attached to the holder 120, it becomes possible to measure all degrees of freedom, particularly the degrees of freedom in Y and Z (both in units of mm for example). As shown in FIGS. 3, 4A-4B, and 5A-5C, a single composite YZ measurement mirror 120y / 120z (220y / 220z) is used for both the holder 120 and the frame 110. Both composite mirrors are formed by a first-axis measurement mirror 120y (220y) with the first mirror surface 120y-1 (220y-1) arranged perpendicular to the XY plane / mounting surface 120a of the holder 120, and a Z measurement mirror 120z (220z) having an angled additional mirror surface 120z-1 (220z-1). Thereby, it is possible to further reduce the structural dimensions of the holder 120, particularly its thickness or Z dimension. The same applies to the dimensions of the measurement mirror 220y / 220z attached to the frame 110.

[0062] In the illustrated example, the first-axis measurement mirror / first mirror surface 120y / 120y-1 is arranged at the closest / nearer position to the mounting surface 120a than the adjacent angled Z measurement mirror / additional mirror surface 120z / 120z-1.

[0063] The Z position or direction of the holder 120 with respect to the XYZ coordinate system is determined or measured by the differential measurement of the laser interferometry on the angled mirror surface 120z-1 combined with the laser interferometry on the straight mirror surface 120y-1 and the laser interferometry on the angled mirror surface 220z-1 combined with the laser interferometry on the straight mirror surface 220y-1.

[0064] Depending on the structural dimensions of the holder 120 and the desired accuracy of the measurement, the angle α of at least one angled Z laser beam 230z with respect to the XY plane is in the range of 5° to 45°, specifically in the range of 5° to 25°, more specifically in the range of 5° to 15°, and even more specifically the angle α = 7°.

[0065] As shown in FIGS. 3A and 4A - 4B, and FIGS. 5A - 5C, more specifically, the first axis holder measurement mirrors 120y - 120z are arranged perpendicular to the XY plane and include a third mirror surface 120y - 2 adjacent to a further mirror surface 120z - 1 facing the first mirror surface 120y - 1. The third mirror surface 120y - 2 functions as an additional first axis measurement mirror 120y for an additional first axis laser beam 230y - 2 and is used to measure a further degree of freedom of the holder 120, particularly the rotation or tilt Rx around the first coordinate axis X.

[0066] Any rotation Rx around the X - axis can be determined or measured by differential measurement between a laser interferometry measurement for the reflected laser beam 230y - 1 through the first mirror surface 120y - 1 and a laser interferometry measurement for the reflected laser beam 230y - 2 through the third mirror surface 120y - 2. Note that both the first mirror surface 120y - 1 and the third mirror surface 120y - 2 have an orientation perpendicular to the XY plane / mounting surface 120a, are parallel to each other, and the further angled mirror surface 120z - 1 is arranged between the two mirror surfaces 120y - 1 and 120y - 2.

[0067] To make the measurement less affected by the rotation of the optical device 210y, the most preferred solution for accurate measurement is to ensure that the laser beam 230y - 1(230y - 2) directed towards the holder 120 / the first axis holder measurement mirror 120y and the laser beam 230y - 1(230y - 2) directed towards the measurement mirror 220y are in a straight line (coincide) with each other.

[0068] In an alternative example of the first-axis holder measurement mirror 120y to 120z, the functions of the Y mirror surface 120y-1 (the first mirror surface) and the Y mirror surface 120y-2 (the third mirror surface) can be reversed. The third mirror surface 120y-2 (for measuring rotation around the X axis) is arranged at the position closest to the mounting surface 120a, and the first mirror surface 120y-1 (for measuring rotation around the X axis together with the third mirror surface, measuring the Y position / displacement, and measuring the Z position / displacement together with a further mirror surface 120z-1) is arranged at the position farthest from the mounting surface 120a.

[0069] Furthermore, in FIG. 3, the thickness of the further mirror surface 120z-1 (for example, the angled holder measurement mirror 120z) decreases (becomes smaller or thinner) in the direction away from the mounting surface 120a, or the thickness progresses towards the mounting surface 120a. However, in another embodiment of the holder measurement mirror 120-y / 120z, the angled mirror surface 120z-1 can be reversed such that its thickness decreases (becomes smaller or thinner) in the direction towards the mounting surface 120a.

[0070] To measure the position of the holder 120 with respect to the second coordinate axis Y in the XY plane, and thus to determine the X position with respect to the Y axis, the system 100 comprises a laser beam 230x parallel to the XY plane and parallel to the first coordinate axis X, which is irradiated onto and directed towards at least one measurement mirror 220x arranged perpendicular to the first coordinate axis X in the XY plane and beyond the first operating position I or the second operating position II, and a second-axis optical device 210x. Optionally, a further second measurement mirror 220x is arranged perpendicular to the first coordinate axis X in the XY plane and between the first operating position I and the second operating position II. This further second measurement mirror 220x can be effectively used as a reference mirror for each degree of freedom to be measured.

[0071] Figures 6A and 6B show the situation of the holder 120 while it moves from the first operating position I (Figure 6A) and the second operating position II (Figure 6B) along the YX plane and the X coordinate axis. On the other hand, Figure 6C shows the situation where the holder 120 is displaced towards a further third operating position III which can be a load / unload position for loading / unloading the object 140 from / to the holder 120. During the movement between the operating positions I, II, and III, the optical device 210y is displaced in cooperation with the holder 120 along the first coordinate axis X of the XY plane for a constant real-time measurement of the Y position of the holder 120. Similarly, the cooperative displacement of both the holder 120 and the optical device 210y can be a synchronous displacement.

[0072] Figures 8A - 8D disclose several examples according to the present disclosure of the optical system used in the optical device 210y. The optical system of the optical device implements a so-called "Michelson" interferometer optical system. In Figure 8A, the optical device 210y'' incorporates a laser light device 215b. The laser light device 215b emits a laser light beam 230y which is split by a beam splitter 216 and reflected towards a first-axis holder measurement mirror 120y attached to the holder 120 (Figure 8A) via a mirror 217. The reflected portion of the laser light 230y is reflected towards the "Michelson" interference optical system and detected by a photodetector 215a.

[0073] Similarly, as shown in an alternative example of the optical device 210y'' in Figure 8B, the laser light device 215b emits a laser light 230y which is also split by the beam splitter 216 and reflected towards both the first-axis holder measurement mirror 120y attached to the holder 120 and a measurement mirror 220y attached to the frame 110 via a mirror 217. A part of the laser beam light 230y from both mirrors 120y, 220y is reflected towards the "Michelson" interference optical system and detected by the photodetector 215a.

[0074] The example of FIG. 8C shows an optical device 210y'' having the same configuration as the optical device 210y' of FIG. 5C. Also, this example implements a "Michelson" interference optical system and emits a laser beam 230y with a laser light device 215b. The beam splitter 216 and the plurality of mirrors 217 irradiate the laser beam 230y toward both the first-axis holder measurement mirror 120y attached to the holder 120 and the measurement mirror 220y attached to the support portion 110' of the frame 110. This measurement mirror 220y reaches the recess 213y of the mount 212y of the optical device 210y''. The reflected portion of the laser beam light 230y is reflected toward the "Michelson" interference optical system and detected by the photodetector 215a.

[0075] The example of FIG. 8D should be considered together with the example of FIG. 9. In both examples, two optical devices 210y''-a and 210y''-b are displaceably attached to the frame 110 via, for example, separate guide components 110y - 110y' and guide rails 111 - 111'. Both of them implement a laser light device 215b, a beam splitter 216, and a mirror 217, and direct the laser beam 230y toward either the first-axis holder measurement mirror 120y attached to a separate holder 120 - 120' or the measurement mirror 220y / 220z - 220y' / 220z' attached to the frame 110. The reflected portions of the reflected laser light 230y (in FIG. 9, three laser lights 230y-1, 230y-2, 230z) are detected by the respective photodetectors 215a of the two optical devices 210y''-a and 210y''-b.

[0076] Figure 9 shows a position measurement system 100' that enables monitoring of the positions of two holders 120-120 within the XYZ coordinate system during independent displacements within the system working space between a first operating position I and a second operating position II. To accurately monitor the positions of both holders 120-120', the frame 110 comprises two measurement mirrors 220y / 220z-220y' / 220z' that are alternatively attached to their respective guide components 110y-110y' at positions opposing the first coordinate axis (X) within the frame 110. The two first-axis optical devices 210y''-a and 210y''-b are, as previously clarified, equally displaceable along the first coordinate axis X and their respective measurement mirrors 220y / 220z-220y' / 220z' by means of the guide rails 111-111'. The first-axis optical devices 210y''-a and 210y''-b measure the Y and Z positions and any tilt position Rx of their respective holders 120-120 within the XYZ coordinate system (system working space).

[0077] Similarly, to measure the X position of each holder 120-120', second-axis optical devices 210x-210x' are implemented that emit corresponding laser light beams 230x towards the corresponding second-axis (X) measurement mirrors 220x-220x'.

[0078] In all of the illustrated embodiments, the electrical laser interferometry signals generated by the first-axis optical devices 210y and the second-axis optical devices 210x and containing at least information regarding the XY and Z positions of the holders 120 / 120' within the XYZ coordinate system are processed via appropriate signal wiring 218 (see, for example, FIGS. 4A-4B, 7A-7B, and 9).

[0079] In all embodiments of FIGS. 8A - 8D, when using a laser interferometer, the appropriate Y position of the holder 120 with respect to the first coordinate axis X can be determined based on the reflected laser light 230y. With one laser light device 215b and a photodetector 215a, a differential detection device is obtained, where the measurement mirror 220y should be irradiated from the same side as the first - axis holder measurement mirror 120y on the holder 120 because it is insensitive to the (Y) displacement of the optical device.

Explanation of Signs

[0080] I / II / III First / Second / Third operating positions 10 Position - detection system according to the prior art 11 Frame / Solid world 12 Holder 12a XY mounting surface of the holder 12 13 Holder displacement means of the holder 12 14 Object 21x Second - axis (X) optical device (state of the art) 21y - a / b First / Second first - axis (Y) optical devices (state of the art) 22x - a / b First / Second second - axis (X) measurement mirrors (state of the art) 23x Second - axis (X) laser light beam (state of the art) 100 - 100' Position - detection system (first / second embodiments according to the present disclosure) 110 Frame / Solid world 110' Support part of the frame 110 110y Guide part of the frame 110 111 Guide rail of the guide part of the frame 110 120 Holder 120a XY mounting surface of the holder 120 120b Mounting space of the holder 120 120y Measurement mirror of the holder 120 regarding the first axis (Y) 120y - 1 / 2 (First / Second) mirror surface of the first - axis (Y) holder measurement mirror 120z Third (Z) - axis holder measurement mirror of the holder 120 120z-1 Third axis (Z) holder measurement mirror and further mirror surface 130 Holder displacement means of holder 120 140 Object 210x Second axis (X) optical device 210y (’’-’’’) First axis (Y) optical device (first, second, third examples) 211y Device displacement means of first axis (Y) optical device 210y 212y Mount or housing of first axis (Y) optical device 210y 213y Recess of mount 212y 215-a / b (First / Second) laser device 216 Interferometer optical system 217 Reflective mirror 218 Signal wiring 220x Second axis (X) measurement mirror (according to the present disclosure) 220y First axis (Y) measurement mirror (according to the present disclosure) 220y-1 Mirror surface of first axis (Y) measurement mirror 220z Third axis (Z) measurement mirror (according to the present disclosure) 220z-1 Mirror surface of third axis (Y) measurement mirror 230x X laser beam (according to the present disclosure) 230y-1 / 2 (First / Second) Y laser beam (according to the present disclosure) 230z Z laser light (according to the present disclosure)

Claims

1. A position detection system using a laser light interference method for measuring the position and displacement of an object with respect to an XYZ coordinate system and within the XYZ coordinate system, comprising: a frame; a holder including a mounting surface of the object oriented in the XY plane of the XYZ coordinate system; a plurality of measurement mirrors and a plurality of optical devices; wherein: the holder is configured to be displaced within the XY plane between at least a first operating position and a second operating position with respect to the frame; each of the optical devices is configured to emit and irradiate a laser light beam of each of the measurement mirrors from each of the measurement mirrors; furthermore, each of the optical devices is configured to detect at least a part of each laser light beam reflected by each of the measurement mirrors and convert it into an electrical measurement signal; the electrical measurement signal includes information regarding the XYZ position of the holder; to measure the position of the holder with respect to the first coordinate axis in the XY plane, at least one first-axis optical device is configured to be displaced together with the holder between the first operating position and the second operating position along the first coordinate axis in the XY plane; furthermore, the at least one first-axis optical device is configured to emit a respective first laser light beam parallel to the XY plane and perpendicular to the first coordinate axis from a first mirror surface of each first-axis measurement mirror extending along the first coordinate axis beyond both the first operating position and the second operating position and to be incident on the first mirror surface of each first-axis measurement mirror, a position detection system characterized by this.

2. The position detection system according to claim 1, characterized in that the at least one first-axis optical device is attached to the holder.

3. The position detection system according to claim 1, characterized in that the at least one first-axis optical device is attached to a mount displaceable between the first operating position and the second operating position along the first coordinate axis with respect to the frame.

4. The position detection system according to any one of claims 1 to 3, characterized in that the first-axis measurement mirror is attached to the frame.

5. The position detection system according to claim 4, characterized in that the first-axis measurement mirror is composed of at least two first-axis sub-mirrors for measurement.

6. The position detection system according to any one of claims 3 to 5, wherein the mount includes a recess for receiving the first-axis measurement mirror.

7. The position detection system according to any one of claims 3 to 4, wherein the holder includes a first-axis holder measurement mirror having at least a first mirror surface disposed perpendicular to the XY plane for measuring the position of the holder with respect to the first coordinate axis in the XY plane.

8. The position detection system according to any one of claims 1 to 7, wherein, in order to measure the Z position of the holder with respect to the XY plane, the at least one first-axis optical device is configured to emit and irradiate respective additional laser light beams from an additional mirror surface of the first-axis measurement mirror and at an angle α with respect to the XY plane with respect to the additional mirror surface of the first-axis measurement mirror.

9. The position detection system according to claim 8, wherein, in order to measure the Z position of the holder with respect to the XY plane, the at least one first-axis optical device is configured to emit and irradiate respective additional laser light beams from an additional mirror surface of the first-axis measurement mirror and at an angle α with respect to the XY plane with respect to the additional mirror surface of the first-axis holder measurement mirror.

10. The position detection system according to claim 8 or 9, wherein the additional mirror surface of the first-axis measurement mirror or the first-axis holder measurement mirror is oriented at an angle α with respect to the first mirror surface of the first-axis measurement mirror or the first-axis holder measurement mirror.

11. The position detection system according to any one of claims 8 to 10, wherein the angle α is in the range of 5° to 45°, specifically in the range of 5° to 25°, more specifically in the range of 5° to 15°, and even more specifically the angle α = 7°.

12. The first-axis holder measurement mirror includes a third mirror surface, The position detection system according to any one of claims 8 to 11, wherein the third mirror surface is disposed perpendicular to the XY plane and adjacent to an additional mirror surface facing the first mirror surface.

13. A second-axis optical device is provided for measuring the position of the holder with respect to the second coordinate axis in the XY plane, The second-axis optical device is configured to emit respective laser light beams parallel to the XY plane and parallel to the first coordinate axis from at least one second measurement mirror and to irradiate the second measurement mirror. The position detection system according to any one of claims 1 to 12, wherein the second measurement mirror is disposed perpendicular to the first coordinate axis in the XY plane and is disposed beyond the first operating position or the second operating position. **Claim 14** The position detection system according to claim 13, wherein the second measurement mirror is disposed perpendicular to the first coordinate axis in the XY plane and is disposed between the first operating position and the second operating position.

Images