Position detection system using laser light interferometry

Abstract

In the present disclosure, a position detection system using laser light interferometry is provided for measuring the position and displacement of an object relative to and within an XYZ coordinate system. The position detection system includes a holder. The holder includes an object mounting surface, an X measurement mirror, a Y measurement mirror, a Z measurement mirror, an X optical device, a Y optical device, and a Z optical device. The mounting surface is oriented in the XY plane of the XYZ coordinate system. Each of the X optical device, the Y optical device, and the Z optical device directs and illuminates an X laser light beam, a Y laser light beam, and a Z laser light beam to the respective X measurement mirror, the Y measurement mirror, and the Z measurement mirror, and detects and converts at least a portion of the X laser light beam, the Y laser light beam, or the Z laser light beam reflected by the respective X measurement mirror, the Y measurement mirror, and the Z measurement mirror into an electrical measurement signal. The electrical measurement signal includes information regarding at least the X, Y, and Z positions of the object. To measure the Z position of the object, at least one Y laser light beam is directed parallel to the XY plane and is projected to and from a Y measurement mirror arranged perpendicular to the XY plane, and at least one Z laser light beam is directed downward at an angle α to the XY plane and is projected to and from the Z measurement mirror.

Description

[Technical field]

[0001] The present invention relates to a laser interferometry position detection system for measuring the position and displacement of an object relative to (and within) an XYZ coordinate system. The system uses a holder that includes a mounting surface for the object. The mounting surface is oriented in the XY plane of the XYZ coordinate system. Such a laser interferometry detection system can be applied, for example, in semiconductor and integrated circuit manufacturing processes. [Background technology]

[0002] Applications requiring high precision positioning and displacement, such as wafer substrates in semiconductor and integrated circuit manufacturing, implement laser interferometry detection systems where multiple measurement mirrors and laser light beams directed at and from the mirrors are used to determine the position and displacement of an object in an XYZ coordinate system based on laser interferometry.

[0003] Current laser interferometry detection systems are capable of such multiple degree of freedom (DOF) measurements in an XYZ coordinate system, but the accuracy of these measurements is limited, which negatively impacts the efficiency of the overall process in which the laser interferometry detection system is implemented.

[0004] For example, for displacement distances or strokes longer than the holder dimensions, multiple DOF measurements may be lost. Furthermore, currently known applications implement additional measurement mirrors located within the working space, thus occupying working volume in the direct vicinity where the semiconductor or integrated circuit manufacturing process is performed.

[0005] Moreover, the use of an additional measurement mirror in the working space not only occupies the working volume, but also requires an additional light reflection for each measurement. This therefore requires higher requirements for the surface quality per measurement mirror, more complex adjustment of the measurement mirror, and a smaller angular range of the moving holder. Thus, the dynamics of the Z measurement mirror can limit the overall performance of the laser light interferometer detection system. Summary of the Invention [Problem to be solved by the invention]

[0006] The objective of the present disclosure is to provide a solution to the above identified problems, in particular to present a position detection system using laser light interferometry with reduced and simplified optics and therefore reduced structural dimensions and improved accuracy for measuring the position and / or displacement of a holder in an XYZ coordinate system. [Means for solving the problem]

[0007] According to a first aspect of the present disclosure, a position detection system using laser light interferometry for measuring the position and displacement of an object relative to and within an XYZ coordinate system is provided. The position detection system includes a holder. The holder includes an object mounting surface, an X measurement mirror, a Y measurement mirror, a Z measurement mirror, an X optical device, a Y optical device, and a Z optical device. The mounting surface is oriented in an XY plane of the XYZ coordinate system. Each of the X optical device, the Y optical device, and the Z optical device directs and irradiates an X laser light beam, a Y laser light beam, and a Z laser light beam to the respective X measurement mirror, Y measurement mirror, and Z measurement mirror, and detects and converts at least a portion of the X laser light beam, the Y laser light beam, or the Z laser light beam reflected by the respective X measurement mirror, Y measurement mirror, and Z measurement mirror into an electrical measurement signal. The electrical measurement signal includes information regarding at least the X, Y, and Z positions of the object. To measure the Z position of the object, at least one Y laser light beam is directed parallel to the XY plane and is projected to and from a Y measurement mirror arranged perpendicular to the XY plane, and at least one Z laser light beam is directed downward at an angle α to the XY plane and is projected to and from the Z measurement mirror.

[0008] By directing the Y laser light beam parallel to the XY plane to and from the Y measurement mirror arranged perpendicular to the XY plane, and the Z laser light beam downwards at an angle α to and from the Z measurement mirror, the need for an additional Z measurement mirror is eliminated, thus simplifying the optics of the position detection system. In particular, this results in a smaller occupied work volume in the direct vicinity of the semiconductor or integrated circuit manufacturing process.

[0009] In a particular embodiment of the position detection system according to the present disclosure, at least one Z laser light beam may be directed perpendicularly to the Z measurement mirror and emitted to and from the Z measurement mirror, which further reduces the structural dimensions of the detection system, in particular its Z dimension.

[0010] In a preferred embodiment according to the present disclosure, the X measurement mirror, the Y measurement mirror, and the Z measurement mirror may be mounted only on the holder. In this case, the overall structure is simplified while the measurement accuracy is improved. No additional optical components are mounted in the working space, and all degrees of freedom measurements are performed by a single mirror reflecting surface mounted on the holder. As a result, the stringent surface finish requirements of the mirror surface are reduced, reducing costs. In addition, complex adjustment of the system is not required, since only the orientation of each optical element in XYZ is adjusted. Furthermore, this structure allows the holder to have a large angular range.

[0011] Since the laser interferometer optical system of the embodiment according to the present disclosure shows only one reflection for the Z laser light beam (indeed for all X, Y and Z laser light beams), the reflected laser light beams return to the respective optical device sensor in a more ideal direction (parallel to the emitted laser light beam). This minimal beam distortion allows more or larger angular displacement of the holder to be tolerated without losing the measurement signal. In the prior art application, a second mirror is implemented, which requires two more beam reflections before the laser light beam is detected by the optical device again. Therefore, the initial positioning errors of both mirrors are added, reducing the (angular) margin to rotate the holder without losing the signal. It should be noted that the holder displacement is mainly translational, but always accompanied by a small rotation. If multiple mirrors were used, the holder angular displacement margin would be limited and signal could be lost.

[0012] Depending on the structural dimensions of the holder used and the desired measurement accuracy, the angle α of the Z laser light beam with respect to the XY plane may be greater than or equal to 5° and less than or equal to 45°, specifically greater than or equal to 5° and less than or equal to 25°, more specifically greater than or equal to 5° and less than or equal to 15°, and even more specifically 7°.

[0013] In a particular embodiment of the position detection system according to the present disclosure, the Y measurement mirror and the Z measurement mirror may form a compound YZ measurement mirror comprising a first mirror surface arranged perpendicular to the XY plane and a second mirror surface arranged at an angle α to the first mirror surface, which allows further reducing the structural dimensions of the holder, in particular its thickness or Z dimension.

[0014] More specifically, the compound YZ measurement mirror may include a third mirror surface arranged perpendicular to the XY plane and opposite the first mirror surface and adjacent to the second mirror surface, in which case the third mirror surface can serve as an additional Y measurement mirror for an additional Y laser light beam, which can then be used to measure further degrees of freedom of the holder, in particular its rotation or tilt.

[0015] Optionally, the holder may include two compound YZ measurement mirrors mounted on opposite sides of the holder. In this case, it is also possible to measure the change in the longitudinal dimension of the holder due to thermal expansion. Two Y optics continuously project Y laser beams on opposite sides of the holder to obtain two opposite Y dimension measurements. Based on these two Y measurements, the width of the holder can be continuously measured and thermal expansion can be monitored. Thus, by correcting for such thermal expansion, a higher accuracy can be obtained for the actual XYZ dimensions.

[0016] Advantageous embodiments according to the present disclosure allow for measurement of the X degree of freedom, where at least one X laser light beam may be oriented parallel to the XY plane and projected to and from an X measurement mirror positioned perpendicular to the XY plane.

[0017] Measurement of further degrees of freedom is also possible, such as rotational and tilting movements about the X, Y and Z axes. For example, to measure the rotational position of the holder about the Z axis, the position detection system may comprise at least two Y optical devices arranged at a predetermined distance from each other in the XY plane. Alternatively, to measure the rotational position about the X axis, the position detection system may comprise at least two Y optical devices arranged at a predetermined distance from each other in the YZ plane. Alternatively, to measure the rotational position about the Y axis, the position detection system may comprise at least two Z optical devices arranged at a predetermined distance from each other. [Brief description of the drawings]

[0018] The present invention will now be described with reference to the drawings. [Figure 1A] FIG. 1 is a diagram showing an example of a position detection system using laser light interferometry according to the prior art. [Figure 1B] FIG. 1 is a diagram showing an example of a position detection system using laser light interferometry according to the prior art. [Figure 2A] FIG. 1 is a diagram illustrating an example of a position detection system using laser light interferometry according to the present disclosure. [Figure 2B] FIG. 1 is a diagram illustrating an example of a position detection system using laser light interferometry according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] For a proper understanding of the present disclosure, in the following detailed description, corresponding elements or portions of the present disclosure are designated with the same reference numerals in the drawings.

[0020] (Prior Art) It is known in the art that applications requiring high precision positioning and displacement, such as wafer substrates during semiconductor and integrated circuit manufacturing, can be implemented with laser light interferometer detection systems, in which a number of measurement mirrors and laser light beams directed at and emitted from the mirrors are used to determine the position and displacement of an object in an XYZ coordinate system based on laser light interferometry.

[0021] An example of such a laser light interferometry detection system is shown in Figures 1A and 1B and designated by reference numeral 10. Such a position detection system 10 using laser light interferometry can measure the position and displacement of an object relative to (and within) an XYZ coordinate system. In one example, the object (not shown in Figures 1A, 1B) may be a wafer substrate during a semiconductor and integrated circuit manufacturing process for the production of semiconductor components.

[0022] Typically, the system 10 implements a holder 11 for holding an object (wafer substrate). As shown in Figures 1A and 1B, the holder 11 includes a mounting surface 11a for the object, and preferably such object is accommodated in a mounting space 11b machined (or provided) in the mounting surface 11a. The mounting surface 11a of the holder 11 is oriented, preferably parallel, in the XY plane of an XYZ coordinate system. That orientation is depicted in the corner of Figure 1A.

[0023] The system 10 according to the art further comprises a plurality of X, Y and Z measurement mirrors, indicated by reference numerals 14x, 14y and 14z. The optical devices 13x, 13y (13y-1) and 13z (13z-1) are respectively configured to project and direct laser light beams 13x', 13y-1' and 13z-1' to and from one of the respective XY or Z measurement mirrors 14x, 14y, 14z (14z-1 / 14z-2) for measuring the respective XYZ positions / displacements (degrees of freedom, DOF) of the holder 11 (including the object mounted in the mounting space 11b on the mounting surface 11a) relative to the XYZ coordinate system.

[0024] In particular, each laser light beam is reflected by a respective X measurement mirror 14x, Y measurement mirror 14y and Z measurement mirror 14z (14z-1 / 14z-2). At least a part of the reflected laser light beam is detected by the optical device 13x, 13y (13y-1) and 13z (13z-1). The reflected and detected laser light beam is converted into an electrical measurement signal that contains information about at least the XYZ position of the holder 11 (and the object) in the XYZ coordinate system. The emitted and reflected laser light beams are used to calculate the X-, Y- and Z-positions using laser interferometry with the aid of a suitable signal processing unit (not shown).

[0025] Current laser interferometry detection systems are capable of such multiple degree of freedom (DOF) measurements in an XYZ coordinate system, but the accuracy of these measurements is limited, which negatively impacts the efficiency of the overall process in which the laser interferometry detection system is implemented.

[0026] For example, for displacement distances or strokes longer than the holder dimensions, multiple DOF measurements are lost. Furthermore, currently known applications implement additional optics located within the working space, thereby occupying nearby working volumes where semiconductor or integrated circuit manufacturing processes are performed.

[0027] 1A and 1B, such an additional optical component is designated by the reference numeral 12 and is arranged directly above the holder 11 in the Z direction. The additional optical component 12 serves as a measurement mirror support. It obstructs the working volume in the direct vicinity of the holder 11, in which, for example, semiconductor and integrated circuit manufacturing processes are carried out.

[0028] 1B, the Z position of the holder 11 relative to and within the XYZ coordinate system is measured using a first Z measurement mirror 14z-1 mounted on the holder 11 and a second Z measurement mirror 14z-2 mounted on the additional optics (measurement mirror support) 12. The first Z measurement mirror 14z-1 is at an angle of 45° to the holder 11 with respect to the XY plane / mounting surface 11a, while the second Z measurement mirror 14z-2 is parallel to the XY plane / mounting surface 11a and faces the mounting surface 11a of the holder 11.

[0029] The optical device 13z-1 is fixedly mounted in a frame (not shown) of the laser light interferometry detection device 10. It is configured, for example, as a laser emitting device and generates and emits a laser light beam 13z-1'. The laser light beam 13z-1' is emitted towards a first Z measurement mirror 14z-1 with an angle of 45° and is reflected towards a second Z measurement mirror 14z-2 on the optical system 12. The laser light beam 13z-1' is then reflected towards the optical device 13z-1 via the second Z measurement mirror 14z-2 and the first Z measurement mirror 14z-1. Using a laser interferometer, the Z position of the holder 11 relative to the XYZ coordinate system is determined using the emitted laser light beam and (part of) the reflected laser light beam 13z-1'.

[0030] The use of an additional measurement mirror 14z-2 mounted in the additional optics 12 in the working space, in addition to occupying working volume, requires an additional light reflection per measurement. Therefore, a higher surface quality per measurement mirror 14z-1 and 14z-2 is required. Therefore, a more complicated adjustment of the measurement mirror and a smaller angular range of the movement of the holder 11 are required. Therefore, in the current state of the art, the dynamics of the Z measurement mirror may limit the overall performance of the laser light interferometry detection system 10.

[0031] The present disclosure aims to provide a solution to the above identified problems. Figures 2A and 2B show an example of a position detection system 100 using laser light interferometry with reduced and simplified optics and therefore reduced structural dimensions, which provides improved accuracy in terms of measuring the position and / or displacement of a holder in an XYZ coordinate system.

[0032] 2A and 2B, the laser light interferometry position detection system 100 can similarly measure the position and displacement of an object relative to (and within) an XYZ coordinate system. As with the prior art system 10, a holder 110 is also implemented with a mounting surface 110a oriented in the XY plane of the XYZ coordinate system. The mounting surface 110a of the holder 110 is provided with a mounting space 110b for an object (not shown), e.g., a wafer substrate.

[0033] In an example of a position detection system 100 according to the present disclosure, the optical system includes a plurality of X, Y and Z measurement mirrors, respectively indicated as 140x, 140y-1 and 140z. Similarly, a plurality of XYZ optical devices 130x, 130y-1, 130y-2, 130z-1, 130z-2 are fixedly mounted next to and near the holder 110. Each optical device 130x, 130y-1, 130y-2, 130z-1, 130z-2 is structured, for example, as a laser light beam emitting source to irradiate and direct a respective XY or Z laser light beam 130x', 130y-1', 130y-2', 130z-1', 130z-2' to and from a respective X measurement mirror 140x, Y measurement mirror 140y-1 or Z measurement mirror 140z.

[0034] The reflected portions of the X laser light beam 130x', the Y laser light beams 130y-1', 130y-2', and the Z laser light beams 130z-1', 130z-2' are detected by respective optical devices 130x, 130y-1, 130y-2, 130z-1 and 130z-2 and converted into electrical measurement signals. As with prior art laser interferometer techniques, the electrical measurement signals contain at least information regarding the XYZ position of the holder 110 relative to the XYZ coordinate system.

[0035] For example, at least one X optical device 130x is implemented for measuring the X degree of freedom or X position (e.g., in mm) of holder 110 in an XYZ coordinate system. This optical device generates and emits an X laser light beam 130x' parallel to the XY plane and directs it towards an X measurement mirror 140x. X measurement mirror 140x is mounted on holder 110 and positioned perpendicular to the XY plane, which plane is formed by mounting surface 110a. Thus, X laser light beam 130x' is perpendicularly incident on X measurement mirror 140x and is reflected back in the opposite direction to at least one X optical device 130x.

[0036] Advantageous embodiments according to the present disclosure can measure the Z position (e.g., in mm) of the holder 110 with reduced and simplified optics that are less complex than prior art optics, as shown in FIGS. 1A and 1B. To measure the Z position of the holder 110 and the object mounted thereon, at least one Y optics 130y-1 is used. This Y optics 130y-1 emits and directs at least one Y laser light beam 130y-1' parallel to the XY plane towards a Y measurement mirror 140y-1 mounted on the holder 110 and positioned perpendicular to the XY plane formed by the mounting surface 110a. Furthermore, at least one Z optics 130z-1 generates and emits a corresponding Z laser light beam 130z-1'. This Z laser light beam 130z-1' is directed downward to and from the Z measurement mirror 140z at an angle α with respect to the XY plane.

[0037] Thus, instead of being directed parallel to the Y laser light beam 130y-1', the angled Z laser light beam 130z-1' is tilted downwards by the same angle α relative to the Y laser light beam 130y-1', see FIG. 2B for details.

[0038] Both the Y laser light beam 130y-1' and the angled Z laser light beam 130z-1' are reflected off the respective Y optics 130y-1 and Z optics 130z-1. The Z measurement (Z position, e.g., in mm) of the holder 110 relative to the XYZ coordinate system is determined by a differential measurement of the laser interference signals generated by both the Y optics 130y-1 and the Z optics 130z-1. Z=Y1 / (sin(α)cos(α))-Z1 / sin(α)+Z0 or ΔZ=Z-Z0=Y1 / (sin(α)cos(α))-Z1 / sin(α) Z0 is the initial Z position of the holder 110 in the XYZ coordinate system (eg, in mm).

[0039] By irradiating the Y laser light beam 130y-1 parallel to the XY plane (mounting surface 110a of the holder) to the Y measurement mirror 140y-1 arranged perpendicular to the XY plane / mounting surface 110a, and irradiating the Z laser light beam 130z-1' to and from the Z measurement mirror 140z at an angle α downward with respect to the XY plane / mounting surface 110a, the additional Z measurement mirror as in Figures 1A and 1B can be omitted. As a result, the optical system of the position detection system 100 can be simplified. In particular, the occupied working volume in the vicinity of the semiconductor and integrated circuit manufacturing process can be reduced.

[0040] 2B, at least one angled Z laser light beam 130z-1′ is directed perpendicular to and away from the Z measurement mirror 140z, which allows for further reduction in the structural dimensions of the detection system 100, particularly the Z dimension.

[0041] One advantage of the system 100 according to the present disclosure is that all the X, Y and Z measurement mirrors are mounted only on the holder 110. This simplifies the overall structure and improves the measurement accuracy. No additional optical components mounted in the workspace are required, as in the prior art shown in, for example, FIG. 1A and FIG. 1B. Also, all degrees of freedom measurements can be performed by a single mirror reflective surface (indicated by reference numeral 150) mounted on the holder 110, which reduces the stringent surface finish requirements of the mirror surfaces 140y-1 and 140z, resulting in significant cost savings. Also, fewer complex adjustments are required for the system 100, since only the orientation of some XYZ optical devices needs to be adjusted. Furthermore, this structure allows a larger angular range for the holder 110.

[0042] 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 130z-1' relative to the XY plane / mounting surface 110a is greater than or equal to 5° and less than or equal to 45°, specifically greater than or equal to 5° and less than or equal to 25°, more specifically greater than or equal to 5° and less than or equal to 15°, and even more specifically greater than or equal to 7°.

[0043] As defined above, an advantage of the system 100 according to the present disclosure is the use of a single mirror reflective surface mounted on the holder 110 for all degree of freedom measurements, in particular the Y and Z degrees of freedom (both in mm, for example). As shown in the example of Fig. 2A and Fig. 2B, the reference numeral 150 denotes a single compound YZ measurement mirror formed by both the first Y measurement mirror 140y-1 and the Z measurement mirror 140z. The first Y measurement mirror 140y-1 forms a first mirror surface of the compound YZ measurement mirror 150. This first mirror surface 140y-1 is arranged perpendicular to the XY plane / mounting surface 110a of the holder 110. The second mirror surface forms the Z measurement mirror 140z and is oriented at an angle α to the first mirror surface 140y-1. This allows the structural dimensions of the holder 110, in particular its thickness or Z dimension, to be further reduced.

[0044] In the illustrated example, first Y measurement mirror / first mirror surface 140y-1 is positioned closer to mounting surface 110a than adjacent angled Z measurement mirror / second mirror surface 140z.

[0045] The Z position or orientation of holder 110 relative to the XYZ coordinate system is determined or measured by differential measurements of a combination of laser interferometry on angled mirror surface 140z and laser interferometry on straight mirror surface 140y-1.

[0046] The X degree of freedom (e.g., in mm) is measured using optics 130x and X measurement mirror 140x, while the Y and Z degrees of freedom are measured using single optics 130y-1 and 130z-1 and a single compound YZ measurement mirror 150 consisting of straight mirror surface 140y-1 and angled mirror surface 140z, with both Y laser light beam 130y-1' and angled Z laser light beam 130z-1' perpendicularly incident on their respective mirror surfaces 140y-1 and 140z.

[0047] Three additional degrees of freedom, such as rotation or tilting motion around the X, Y or Z axes (e.g., denoted by ψ, θ, and φ), can be measured using a single compound YZ measurement mirror 150. For example, to measure the rotational position of the holder 110 around the Z axis, the position detection system 100 includes at least two Y optical devices 130y-1 and 130y-2, thus an additional Y optical device 130y-2 next to the already mounted Y optical device 130y-1. Both Y optical devices 130y-1 and 130y-2 are arranged at a distance from each other in the same XY plane parallel to the mounting surface 110a. Both Y optical devices 130y-1 and 130y-2 direct their respective Y laser light beams 130y-1' and 130y-2' towards the linear first measurement mirror 140y-1. Any rotation about the Z axis can be determined or measured by a differential measurement between a laser interferometric measurement on the reflected Y laser light beam 130y-1' and a laser interferometric measurement on the other reflected Y laser light beam 130y-2'.

[0048] To measure the rotational position of the holder 110 around the X-axis, the position detection system 100 includes at least two Y optical devices, indicated as 130y-1 (or 130y-2) and 130y-3. Thus, next to the already mounted Y optical device 130y-1 (130y-2), there is an additional third Y optical device 130y-3. Both Y optical devices 130y-1 and 130y-3 are arranged at a distance from each other in a YZ plane perpendicular to the mounting surface 110a. Both Y optical devices 130y-1 and 130y-3 direct their respective Y laser light beams 130y-1' and 130y-3' towards the respective linear first measurement mirror 140y-1 and also linear third measurement mirror 140y-2.

[0049] In this advantageous embodiment of the present disclosure, the compound YZ measurement mirror 150 includes a third mirror surface, designated by reference numeral 140y-2. The third mirror surface 140y-2 is oriented perpendicular to the XY plane / mounting surface 110a and is disposed parallel to the first Y measurement mirror / first mirror surface 140y-1. In this embodiment of the present disclosure, the third mirror surface 140y-2 is adjacent to the second mirror surface 140z, which faces the first mirror surface 140y-1. The third mirror surface 140y-2 is disposed furthest from the mounting surface 110a and functions as the additional Y measurement mirror 140y-2.

[0050] Any rotation about the X-axis can be determined or measured by a differential laser interferometric measurement of the reflected Y laser light beam 130y-1' via the first Y measurement mirror 140y-1 and the reflected Y laser light beam 130y-3' via the additional further Y measurement mirror 140y-2. Both the first Y measurement mirror 140y-1 and the further Y measurement mirror 140y-2 have a perpendicular orientation to the XY plane / mounting surface 110a and are parallel to each other. The angled mirror surface 140z is disposed between the two Y measurement mirrors 140y-1 and 140y-2.

[0051] In an alternative embodiment of the YZ measurement mirror 150, the functions of the Y measurement mirror 140y-1 (first mirror surface) and the Y measurement mirror 140y-2 (third mirror surface) can be reversed. The third mirror surface 140y-2 is positioned closest to the mounting surface 110a to measure rotation about the X axis. The first mirror surface 140y-1 is positioned furthest from the mounting surface 110a to measure rotation about the X axis together with the third mirror surface, measure Y position / displacement, and measure Z position / displacement together with the second mirror surface 140z.

[0052] For accurate measurement of rotation about the X axis, the first Y optical device 130y-1 and the third Y optical device 130y-3 are preferably placed at a distance from each other. The same is true for the distance between the first mirror surface 140y-1 and the third mirror surface 140y-2, where the second mirror surface 140z is preferably placed between both mirror surfaces 140y-1 and 140y-2.

[0053] 2B, the thickness of second mirror surface 140z (e.g., angled Z measurement mirror 140z) may decrease (become smaller or thinner) away from mounting surface 110a or may increase (i.e., become larger or thicker) in thickness toward mounting surface 110a. However, in another embodiment of YZ measurement mirror 150, angled second mirror surface 140z may instead decrease (i.e., become smaller or thinner) in thickness toward mounting surface 110a. The reverse may be possible.

[0054] Finally, to measure the rotational position of the holder 110 about the Y axis, the position detection system 100 includes at least two Z optical devices 130z-1 and 130z-2, which are arranged at a distance from each other but at the same angle relative to the XY plane / mounting surface 110a. The two Z optical devices 130z-1 and 130z-2 direct their respective Z laser light beams 130z-1' and 130z-2' to the angled measurement mirror 140z. The rotation about the Y axis is measured by a differential laser interferometric measurement of the reflected Z laser light beam 130z-1' and the other reflected Z laser light beam 130z-2'.

[0055] A single compound YZ measurement mirror 150 is sufficient to measure five degrees of freedom (Y, Z, and three-axis rotation ψ, θ, φ). Meanwhile, the X measurement mirror 140x measures the remaining sixth degree of freedom (X), so the holder 110 may include two compound YZ measurement mirrors 150, 150', each compound YZ measurement mirror 150, 150' mounted on opposite sides of the holder 110. This feature also allows for measuring changes in the longitudinal dimensions of the holder 110 due to thermal expansion. Two opposing Y dimension measurements are obtained by sequentially directing a Y laser light beam 130y-1' (or 130y-2' or 130y-3') towards the two compound YZ measurement mirrors 150, 150' on opposite sides of the holder 110 by two corresponding but opposing Y optical devices 130y-1 (or 130y-2 or 130y-3). Based on these two Y dimension measurements, the width of the holder 110 can be measured at any time, and thus thermal expansion can be monitored, thus compensating for such thermal expansion to provide additional accuracy with respect to the actual XYZ measurements. [Explanation of symbols]

[0056] 10 Prior Art Location Detection Systems 11 Holder 11a XY mounting surface of holder 11 11b Mounting space for holder 11 12 Additional optics with second Z measurement mirror 14z-2 (mirror support) (prior art) 13x X optics 13y-1 / 2 1st / 2nd Y optical device (prior art) 13z-1 / 2 1st / 2nd Z optical device (prior art) 13x' X-laser light beam (prior art) 13y-1' / 2' 1st / 2nd Y laser light beams (prior art) 13z-1' / 2' 1st / 2nd Z laser light beam (prior art) 14x X-Measuring Mirror (Conventional Technology) 14y Y measurement mirror (conventional technology) 14z-1' / 2' 1st / 2nd Z measurement mirror (prior art) 100 Position detection system according to the present disclosure 110 Holder 110a XY mounting surface of holder 110 110b Mounting space for holder 110 130x X optics 130y-1 / 2 / 3 1st / 2nd / 3rd Y optical device (related to the present disclosure) 130z-1 / 2 1st / 2nd Z optical device (related to the present disclosure) 130x' X laser light beam (pertaining to the present disclosure) 130y-1' / 2' / 3' 1st / 2nd / 3rd Y laser light beams (according to the present disclosure) 130z-1' / 2' 1st / 2nd Z laser light beam (according to the present disclosure) 140x X-Measuring Mirror (pertaining to this disclosure) 140y-1 / 2 1st / 2nd Y measurement mirror surface (pertaining to the present disclosure) 140z Z measurement mirror surface (pertaining to the present disclosure) 150 / 150' 1st / 2nd further combined YZ measuring mirror

Claims

1. 1. A position detection system using laser light interferometry for measuring the position and displacement of an object relative to and within an XYZ coordinate system, comprising: the position detection system includes a holder; the holder includes an object mounting surface, an X measurement mirror, a Y measurement mirror, a Z measurement mirror, an X optical assembly, a Y optical assembly, and a Z optical assembly; the mounting surface is oriented in an XY plane of an XYZ coordinate system; each of the X, Y and Z optical devices directs an X, Y and Z laser light beam onto the respective X, Y and Z measurement mirror; detects and converts at least a portion of the X, Y or Z laser light beam reflected by the respective X, Y and Z measurement mirror into an electrical measurement signal; the electrical measurement signals contain information about at least the X-, Y- and Z-positions of the object, To measure the Z position of the object, at least one of the Y laser light beams is directed parallel to the XY plane and is projected to and from the Y measurement mirror disposed perpendicular to the XY plane; 11. A position detection system, comprising: at least one of said Z laser light beams directed downward at an angle α with respect to an XY plane and projected to and from said Z measurement mirror.

2. 2. The position detection system of claim 1, wherein at least one of the Z laser light beams is directed perpendicular to the Z measurement mirror and is projected to and from the Z measurement mirror.

3. 3. The position detection system according to claim 1, wherein the X measurement mirror, the Y measurement mirror and the Z measurement mirror are attached only to the holder.

4. 4. A position detection system according to claim 1, wherein the angle α is greater than or equal to 5° and less than or equal to 45°, specifically greater than or equal to 5° and less than or equal to 25°, more specifically greater than or equal to 5° and less than or equal to 15°, and even more specifically greater than or equal to 7°.

5. 5. The position detection system according to claim 1, wherein the Y measurement mirror and the Z measurement mirror form a compound YZ measurement mirror including a first mirror surface arranged perpendicular to the XY plane and a second mirror surface arranged at an angle α with respect to the first mirror surface.

6. 6. The position detection system of claim 5, wherein the compound YZ measurement mirror includes a third mirror surface disposed perpendicular to the XY plane and opposite the first mirror surface and adjacent to the second mirror surface.

7. 7. A position detection system according to claim 5 or 6, wherein the holder includes two compound YZ measurement mirrors mounted on opposite sides of the holder.

8. 8. A position detection system according to claim 1, wherein at least one of the X laser light beams is directed parallel to an XY plane and is projected to and from an X measurement mirror arranged perpendicular to the XY plane in order to measure the X position of the holder.

9. 9. A position detection system as described in any one of claims 1 to 8, characterized in that it comprises at least two Y optical devices arranged at a predetermined distance from each other in the XY plane to measure the rotational position of the holder about the Z axis.

10. 10. A position detection system as described in any one of claims 1 to 9, characterized in that it includes at least two Y optical devices arranged at a predetermined distance from each other in the YZ plane to measure the rotational position of the holder about the X axis.

11. 11. A position detection system as described in any one of claims 1 to 10, comprising at least two Z optical devices arranged at a predetermined distance from each other to measure the rotational position of the holder about the Y axis.

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