Optical position measuring mechanism

Abstract

To provide an optical position measuring mechanism to sense a relative position of at least two scales which are movable relative to each other along two measurement directions even in different planes and disposed so as to cross each other.SOLUTION: Both scales each have at least one measuring graduation. The directions of longitudinal extent of the scales are each oriented parallel to a first or second measurement direction. At the first scale, an illumination beam is split into sub-beams. The sub-beams subsequently impinge on a second scale and are reflected back toward the first scale. The sub-beams strike the first scale again, and recombined, so that a signal beam subsequently propagates toward a detection unit, which makes it possible to generate scanning signals with respect to the relative movement of the scales along the first or second measurement direction. The measuring graduation of the scale is configured as a two-dimensional cross grating which has a filtering effect that suppresses disturbing relatively higher diffraction orders at the cross grating.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical position measurement mechanism suitable for high-precision position measurement of two objects movable relative to one another along at least two measurement directions, whereby both objects are respectively coupled to a scale. [Background technology]

[0002] Optical position measuring mechanisms based on the interference scanning principle are known, in which an illumination light beam is split into different partial light beams by diffraction at the measuring graduations of a scale, which then travel along a scanning light path and encounter one or more further scales in the process. After the appropriate partial light beams are recombined, a regular signal is generated in the detection unit from the interference of both partial light beams when one scale is displaced relative to the other. By counting the signal periods in the detection unit, the magnitude of the displacement of both scales or of an object coupled to these scales can be deduced.

[0003] Such optical position measurement mechanisms are used, for example, for high-precision position measurements in the semiconductor industry, where, for example, exposure masks for photolithography move relative to wafers at speeds of over 1 meter per second while maintaining positioning accuracies in the range of a few nanometers or less. A crucial advantage of grating-based position measurement mechanisms over interferometers is that the interfering partial beams only have to travel very short distances. This makes them less disruptive to environmental effects such as air pressure, temperature, and humidity fluctuations, which can distort measurements, for example, through variations in the refractive index of air.

[0004] WO 2008 / 138501 A1 discloses an optical position measuring mechanism including two intersecting scales, each having a measuring graduation with lines or grating areas regularly arranged across a common measuring direction. The interference scanning principle is used to generate position-dependent signals. Such a position measuring mechanism allows the position of a table movable in two directions along a first measuring direction x to be determined with high precision, regardless of the position of the table along a second measuring direction y. When using two such position measuring mechanisms arranged orthogonally to each other, the position of the table can also be determined with high precision along the second measuring direction y, again regardless of the position of the table along the first measuring direction x.

[0005] Furthermore, a comparable arrangement using an optical position measurement mechanism using interference is known from U.S. Patent Application Publication No. 2009 / 0135388 A1. This arrangement is used to determine the position of a movable table in a semiconductor manufacturing facility relative to an apparatus in a horizontal movement plane. For example, a wafer may be placed on the table, and the apparatus may be an exposure objective. In this regard, in the example of FIG. 6B, a first scale formed as a two-dimensional grating is placed on the movable table, and a second scale also formed as a two-dimensional grating and, unlike the first scale, is stationary. This arrangement allows the movement of the table in the horizontal xy movement plane to be captured.

[0006] Interferometric scanning of the scale generally results in systematic position errors, also known as interpolation errors, which undesirably reduce measurement accuracy. Neither of the cited documents suggests any measures suitable for minimizing such position or interpolation errors in optical position measuring systems with crossed scales. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2008 / 138501A1 [Patent Document 2] U.S. Patent Application Publication No. 2009 / 0135388(A1) [Patent Document 3] EP2857901A1 [Patent Document 4] EP3739300A1 Summary of the Invention [Problem to be solved by the invention]

[0008] The problem underlying the invention is to provide a high-precision optical position measuring mechanism with cross-arranged scales that ensures position measurements with as little position error as possible. [Means for solving the problem]

[0009] This problem is solved according to the invention by an optical position measuring mechanism having the features of claim 1. Advantageous embodiments of the optical position measuring mechanism according to the invention are evident from the measures set forth in the dependent claims.

[0010] The optical position measuring mechanism according to the present invention is used to acquire the relative position of at least two scales that are movable relative to each other along two measurement directions, also in different planes, and that are arranged crosswise relative to each other. Each of the scales has at least one measuring graduation with grating regions with different optical properties regularly arranged along at least one measurement direction, and the longitudinal extension of the scales is oriented parallel to the first or second measurement direction, respectively. The first scale splits an illumination ray bundle emitted by a light source into at least two partial ray bundles. The partial ray bundles then strike the second scale and are reflected back toward the first scale. The reflected partial ray bundles then strike the first scale again and are recombined there, resulting in at least one signal ray bundle that propagates toward a detection unit, via which one or more position-dependent scanning signals related to the relative movement of the scales along the first or second measurement direction can be generated. The measuring graduation of at least one scale is configured as a two-dimensional cross grating, which has a filtering effect such that disturbing relatively high diffraction orders are suppressed at the cross grating.

[0011] The cross grating may have first and second extensive measuring graduation areas with different optical properties arranged in a checkerboard pattern, the first and second extensive measuring graduation areas being arranged in a checkerboard pattern with a first area periodicity along the longitudinal direction of the cross grating and with a second area periodicity along a transverse direction oriented perpendicular to the longitudinal direction, and the first and second extensive measuring graduation areas being overlaid with a one- or two-dimensional regular line grating.

[0012] The line grating may have respective line grating regions within each of the large measuring graduation regions, and the line grating regions may have: - at least one first pair of straight grating lines extending over the entire length of the extensive measuring graduation area, parallel to a first direction of extension and spaced a first distance apart from one another; - in the case of a two-dimensional line grating, it further comprises a second pair of straight grating lines extending over the entire length of the extensive measuring graduation area and arranged at a second distance from one another along a second direction of extension, which is oriented perpendicular to the first direction of extension, - the line grating area has the same periodicity along the first extension direction as the extensive measuring graduation area of ​​the cross grating; In the case of a two-dimensional line grating, the line grating areas have the same periodicity along the second direction of extension as the long measuring graduation areas of the cross grating.

[0013] Preferably, it is provided that within the extensive measuring graduation area there are at least three areas along the first extension direction and / or along the second extension direction, respectively, which are separated from one another by grating lines.

[0014] The different optical properties of the cross grating are: - different transmission characteristics and / or - different reflective properties and / or - Different phase shifts may also be intended.

[0015] In one possible embodiment, the cross grating can be configured as a binary grating with two different optical properties, each of the grating lines of the line grating having an optical property that is different from the optical property of the first and second large measuring graduation areas.

[0016] Furthermore, the cross grating may have a spacing region between the first and second extensive measuring graduation regions, the spacing region having a third optical property different from the optical property of the first and second extensive measuring graduation regions.

[0017] In this regard, the spacing area between the first and second extensive measuring graduation areas may have the same width along the longitudinal and transverse directions, respectively. Furthermore, the spacing regions may be structured.

[0018] Additionally, the measuring graduation of the second scale can be configured as a reflective linear grating, which has measuring graduation areas that are regularly arranged along the longitudinal direction of the second scale and have different phase-shifting effects on the light beams reflected thereby.

[0019] In this regard, the linear grating of the second scale may have a filtering effect such that certain diffraction orders n>1 are suppressed. Additionally, it may be further contemplated that at least one of the measuring graduations is shaped such that the resulting diffraction orders each retain a defined polarization.

[0020] Advantageously, at least one of the scales is arranged tilted about its longitudinal extension. In a configuration with a table, a plurality of optical position measuring mechanisms according to the present invention may be provided, - the table is arranged to be movable along two perpendicular measurement directions in a horizontal movement plane; - Two primary scales are placed on opposite sides of the table, - at least one second scale is disposed in a plane spaced apart from the horizontal plane of motion along a direction that intersects both first scales at an angle of 90° in a stationary state, the direction being oriented orthogonal to the plane of motion; - A plurality of scanning units are stationarily positioned adjacent to opposite sides of the table with the first scale, each of the scanning units including a light source and a detection unit.

[0021] In this regard, - both first scales each have a reflective measuring graduation in the form of a two-dimensional cross grating and are arranged inclined relative to the horizontal movement plane about their longitudinal extension, It may also be provided that the second scale has at least two reflective measuring graduations in two parallel tracks extending parallel to the longitudinal direction, the measuring graduations each being formed as a reflective linear grating with graduation fields regularly arranged along the respective longitudinal direction, the grating plane of the reflective measuring graduations being oriented parallel to the horizontal movement plane.

[0022] By the measures according to the invention, the position errors can be significantly reduced in the case of optical position measuring mechanisms with crossed scales, and highly precise position measurements can be guaranteed. A corresponding position measuring mechanism is particularly suitable for capturing the movement of a table, for example, in a horizontal movement plane, so that the translational movement of the table along two linear measurement directions in the movement plane and the rotational movement of the table about a rotation axis perpendicular to the movement plane can be determined with high precision by the measurement technique.

[0023] Further details and advantages of the invention are explained on the basis of the following description of an exemplary embodiment of the device according to the invention in connection with the drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 1 illustrates the unfolded scanning ray path of one exemplary embodiment of an optical position measurement mechanism according to this invention. [Figure 2] Figure 2a shows a partial view of a position measuring mechanism according to the invention with cross-arranged scales utilizing the scanning principle according to Figure 1. Figure 2b shows a partial view of a position measuring mechanism according to the invention with cross-arranged scales utilizing the scanning principle according to Figure 1. [Figure 3]Figure 3a shows a plan view of an arrangement with an optical position measuring mechanism according to the invention based on the four figures 2a and 2b, and Figure 3b shows a side cross-sectional view of an arrangement with an optical position measuring mechanism according to the invention based on the four figures 2a and 2b. [Figure 4] 1 is a plan view of a suitable second measuring graduation of an optical position measuring mechanism according to the present invention; [Figure 5a] 1 is a plan view of a first variant of a suitable cross grating for an optical position measurement mechanism according to the invention; FIG. [Figure 5b] FIG. 5b is a partial cross-sectional view of a first variant of the cross grid from FIG. 5a. [Figure 5c] FIG. 5b is a partial cross-sectional view of a variant of the first variant of the cross grid from FIG. 5a. [Figure 5d] FIG. 5b is a partial cross-sectional view of a variant of the first variant of the cross grid from FIG. 5a. [Figure 5e] FIG. 5b is a partial cross-sectional view of a variant of the first variant of the cross grid from FIG. 5a. [Figure 6] Figures 6a and 6b are plan and partial cross-sectional views of a second variant of a cross grating suitable for an optical position measurement mechanism according to the invention. [Figure 7] Figures 7a and 7b are plan and partial cross-sectional views of a third variant of a cross grating suitable for an optical position measurement mechanism according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Before describing in detail below one exemplary embodiment of a position measuring mechanism according to the invention and some variants of suitable measuring graduations, an exemplary scanning beam path for such a position measuring mechanism will first be described on the basis of Figure 1. In this regard, the figure shows the scanning beam path in an exploded view.

[0026] The illumination ray bundle S emitted by the light source LQ first strikes a first scale with a first grating-type measuring graduation G1. At the first scale or its measuring graduation G1, the illumination ray bundle S is split into two partial ray bundles S1, S2 at the impact point P1.1. Both partial ray bundles S1, S2 then strike a second scale with a second grating-type measuring graduation G2 at the impact points P2a.1 and P2b.2. There, the partial ray bundles S1, S2 are each diffracted back towards the central symmetry axis A of the entire system as shown. Then, at the impact point P3.1, both partial ray bundles S1, S2 strike a third scale with a third measuring graduation G3 and are recombined there. Then, at the impact point P3.2, the partial ray bundles S1, S2 strike a third scale with a third measuring graduation G3 and are recombined there. G3 Due to the diffraction of both partial ray bundles S1, S2 occurring at the above collision point P3.1, at least one resulting signal ray bundle SB containing interfering diffraction orders of the two partial ray bundles S1, S2 propagates in the direction of the detection unit DET. If the second measuring graduation G2 is moved relative to both measuring graduations G1, G3 along the measuring direction y, one or more position-dependent scanning signals can be generated via the detection unit DET, which characterize the change in the position of the measuring graduation G2 relative to the measuring graduations G1, G3.

[0027] In this regard, the unfolded scanning beam path shown in FIG. 1 with different first and third scales or measuring graduations G1, G3 corresponds to a transmitted light scan in which all measuring graduations G1, G2, G3 are formed as transmission gratings. Alternatively, such a scanning beam path can also be implemented as an incident light scan with the second measuring graduation G2 formed as a reflective grating. In this case, the first and third scales or first and third measuring graduations G1, G3 are formed identically, i.e., G1=G3, so that after being reflected by the second measuring graduation G2, the beam strikes the first measuring graduation G1 again. In this regard, the first and third measuring graduations G1, G3 can be formed as reflective or transmission gratings.

[0028] A specific implementation of such an optical scanning principle in one exemplary embodiment of a position measuring mechanism according to the invention with scales arranged crosswise relative to one another is explained below with reference to Figures 2a and 2b, in which case an incident light scan is carried out with identically shaped first and third measuring graduations.

[0029] The corresponding position measuring mechanism comprises a first scale 30 arranged on a first object 10. The object 10 is arranged to be movable along two measuring directions x, y oriented orthogonally to one another in a plane, the direction orthogonal to this plane being referred to below as direction z. In this regard, the longitudinal extension R of the first scale 30 L1 is oriented parallel to the measurement direction y. 30 A reflective measuring graduation 31 is arranged thereon, which has grating regions with different optical properties along at least one measuring direction x, y. In this example, the first measuring graduation is embodied as a two-dimensional cross grating. This cross grating has a filtering effect, such that disturbing higher diffraction orders are suppressed at the cross grating. In this regard, the various grating regions of the first measuring graduation 31 have different phase-shifting effects on the ray bundles reflected thereby, i.e., the cross grating is embodied as a reflective phase grating. A detailed description of the cross grating in the position measuring system according to the invention, which is important for the desired reduction of position errors, will be provided further in this description.

[0030] A second scale 40 is arranged on the stationary second object 20 in a plane that is stationary and intersects the first scale 30 and spaced apart along the z direction. L2 is oriented parallel to the measuring direction x. A reflective measuring graduation 41 is also arranged on the second scale 40, which has grating areas with different optical properties along at least one measuring direction x, y. In the illustrated example, the second measuring graduation 41 consists of a linear grating, which is aligned parallel to the longitudinal extension R of the second scale 40. L2, which have rectangular measuring graduation areas with different phase-shift characteristics for the light beams reflected thereby, so that the second measuring graduation 41 is configured as a reflective phase grating in this exemplary embodiment.

[0031] The illustrated exemplary embodiment of the position measuring mechanism according to the invention also includes a scanning unit 50, which is also stationary with respect to the first scale 30, and in which a light source and a detection unit are arranged, the latter not being shown in detail in FIGS. 2a and 2b. In this regard, the light source and the detection unit do not necessarily have to be arranged directly in the scanning unit 50. It is also possible to arrange these components spatially separate from the scanning unit 50, and for the corresponding light beams of the light source to be transmitted to the scanning unit 50 via an optical waveguide, or from the scanning unit 50 to the detection unit via an optical waveguide. In such an embodiment, the scanning unit 50 therefore contains only the corresponding optical waveguide as a purely passive building block, whose decoupling and coupling surfaces function as the light source or detection unit.

[0032] Based on the scanning beam path, which is only very schematically indicated in FIGS. 2a and 2b, the impact point of the first measuring graduation 31 P1.1 In the second measuring graduation, the beam S coming from the light source or from the scanning unit 50 is split into two partial beams of + / -1 diffraction orders symmetrically in the z direction. 41 The light impinges on the first impingement point P2a.1 and P2b.1 and is diffracted from there in such a way that it propagates antiparallel to the incoming partial ray bundle in the direction of the first graduation 31. As mentioned above, in this incident light system the third impinging graduation is identical to the first graduation 31. In this case, the first impingement point P2a.1 and P2b.1 are diffracted from there in such a way that they propagate back in the direction of the first graduation 31, antiparallel to the incoming partial ray bundle. P1.1 This results in a recombination of the partial ray bundles at the collision point P3.1, which is identical to the point P3.1. The resulting signal ray bundle SB with at least one pair of interfering partial ray bundles then propagates back towards the detection unit arranged in the scanning unit 50.

[0033] 3a and 3b show, very diagrammatically, an arrangement including four position measurement mechanisms according to the present invention and according to FIGS. 2a and 2b, which are used to determine the position of a movable object in the xy plane. The movable object may be, for example, a table 110 of a semiconductor fabrication or inspection facility, which is positioned relative to a stationary object in the form of a machine frame 120 on which an instrument 160 is arranged. A wafer 111 is placed on the table 110 and processed or inspected by the instrument 160, which is formed, for example, as an exposure objective or a microscope. In this arrangement, the four position measurement mechanisms according to the present invention enable measurement techniques to capture translational movements of the table 110 along measurement directions x and y, as well as rotational movements of the table 110 about the perpendicular z-direction.

[0034] The table 110 has first scales 130.1, 130.2 arranged on two opposite sides, respectively, with reflective first measuring graduations 1131.1, 1131.2, which are aligned in their respective longitudinal directions R L1 In this respect, the tilting of both first scales 130.1, 130.2 is performed in such a way that it results in a deflection of the partial ray bundles diffracted therefrom that is symmetrical with respect to the z direction.

[0035] Furthermore, with regard to the arrangement of the first scales 130.1, 130.2 or the first measuring graduations 1131.1, 1131.2 along the z-direction, care must be taken to arrange the first scales 130.1, 130.2 or the first measuring graduations 1131.1, 1131.2 on the table 110 so that the first impact points of the different scans of the four inventive position measuring mechanisms are at the height of the wafer 111 on the table 110. In this way, position measurements with respect to the wafer 111 are possible without resulting in Abbe errors.

[0036] In contrast, two second scales 140.1, 140.2, each having two reflective second measuring graduations, and four scanning units 150.1 to 150.4 of the position measuring mechanism according to the invention are arranged on the stationary object in the form of a machine frame 120.

[0037] On both second scales 140.1, 140.2, the reflective second measuring graduations arranged in two parallel tracks are each formed as a linear grating, which are aligned in the respective longitudinal direction R L2 The grating plane of the linear grating is arranged parallel to the plane of horizontal movement of the table in the xy plane. A generally indicated instrument 160 is also coupled to the stationary object or machine frame 120.

[0038] The plan view of one of the two second scales 140.1 is shown in Fig. 4 with the second measuring graduations 1141.1, 1141.2 formed as linear gratings 141.1 arranged on it in two parallel tracks. As can be seen from Fig. 4, in both tracks the longitudinal extension R of the second scale L2 1141.1a, 1141.1b or 1141.2a, 1141.2b are regularly arranged along the longitudinal direction R of the second scale. L2 is the measurement direction x Furthermore, as is clear from FIG. 4, the scale areas 1141.1a, 1141.1b or 1141.2a, 1141.2 b are arranged in a V-shape relative to one another in both tracks, i.e., the opposing graduation fields 1141.1a, 1141.2a or 1141.1b, 1141.2b from both tracks are aligned in the longitudinal direction R L2The graduation fields 1141.1a, 1141.1b and 1141.2a, 1141.2b of the second graduations 1141.1, 1141.2 have different phase shifts, i.e. both second graduations 1141.1, 1141.2 are formed as reflective phase gratings.

[0039] In the illustrated configuration, the four position measuring mechanisms according to the present invention each have a sensitivity vector E1-E4 in the xy plane, which is indicated by the corresponding arrows in FIG. 3a. Each sensitivity vector indicates the direction of movement in which the position signal in the respective measuring direction x, y increases most rapidly per unit of length traveled. By processing both obtained regular scanning signals for each scanning unit, the actual movement in the desired measuring direction x, y can be obtained. For the concept of sensitivity vectors in optical position measuring mechanisms, see, for example, document EP 2 857 901 A1.

[0040] In this regard, in the illustrated configuration, the first position measuring mechanism comprises a first scanning unit 150.1, a first scale 130.1 with a first measuring graduation 1131.1 on the left side of the table 110, and a second scale 140.1 with a second measuring graduation 1141.1 on the left side of the table, with an associated sensitivity vector denoted E1 in FIG. 3a. The second position measuring mechanism comprises a second scanning unit 150.2, a first scale 130.1 with a first measuring graduation 1131.1 on the left side of the table 110, and a second scale 140.1 with a second measuring graduation 1141.2, with an associated sensitivity vector denoted E2. The first and second position measuring mechanisms thus utilize the same first measuring graduation 1131.1 on the first scale 130.1.

[0041] The third position measuring mechanism is constituted by a third scanning unit 150.3, a first scale 130.2 with a first measuring graduation 1131.2 on the right side of the table 110, and a second scale 140.2 with a second measuring graduation 1141.3, with an associated sensitivity vector indicated by E3 in this figure. The fourth position measuring mechanism includes a fourth scanning unit 150.4, a first scale 130.2 with a first measuring graduation 1131.2 on the right side of the table 110, and a second scale 140.2 with a further second measuring graduation 1141.4, with an associated sensitivity vector indicated by E4. Accordingly, the third and fourth position measuring mechanisms utilize the same first measuring graduation 1131.2 on the first scale 130.2.

[0042] According to Figure 3a, the sensitivity vectors E1, E2 of the first and second position measuring mechanisms, as well as the sensitivity vectors E3, E4 of the third and fourth position measuring mechanisms, are oriented orthogonal to each other. The sensitivity vectors E1 to E4 of the four position measuring mechanisms are angled at 45° with respect to the measurement directions x and y, respectively, in the xy plane.

[0043] As already mentioned above, the design of the respective first measuring graduation in the corresponding optical position measuring mechanism according to the invention is crucial for avoiding undesired measurement errors in the individual position measuring mechanisms. As also already mentioned, the first measuring graduation in the exemplary embodiment of FIGS. 2a and 2b or 3a and 3b 31、1131.1、1131.2 are each implemented as a reflective cross grating in the form of a reflective phase grating with specific filter characteristics.

[0044] A first variant 131.1 of a suitable cross grating for a first measuring graduation is shown partially in the plan view of Figure 5a and in the partial cross-section of Figure 5b. First, the underlying grating design is explained based on the plan view of Figure 5a, and then possible grating structures of the first cross grating variant are explained by means of the partial cross-sections. Thereafter, further variations of the grating structure of the first cross grating variant are explained based on the partial cross-sections of Figures 5c to 5e.

[0045] As can be seen from Fig. 5a, the cross grating 131.1 used as the first measuring graduation has first and second large measuring graduation areas M11, M12 with different optical properties arranged in a checkerboard pattern. The first and second large measuring graduation areas M11, M12 are aligned in the longitudinal direction R of the cross grating 131.1. L1 The first region periodicity P along B1 and in the longitudinal direction R of the cross grid 131.1 L1 The horizontal direction R is oriented perpendicular to Q1 The second region periodicity P along B2 In this regard, the first measuring field M11, which is shown light in the figure, exerts a different phase shift on the reflected light beam than the second measuring field M12, which is shown hatched, i.e., the measuring field M11 or M12 has a different phase shift Δ1 or Δ2. Different phase shifts are therefore intended here as different optical properties of the first and second large measuring fields M11, M12 of the cross grating 131.1.

[0046] In this variant, the first and second extensive graduation fields M11, M12 of the cross grating 131.1 are overlaid with a two-dimensional regular line grating. The corresponding line grating also has a line grating region in each extensive graduation field M11, M12, which comprises a first and a second pair of straight grating lines L11, L12 or L21, L22, respectively. In this respect, the first pair of straight grating lines L11, L12 extends over the entire length of the extensive graduation field M11, M12 and is aligned in the longitudinal direction R. L1 The grating lines L11, L12 are arranged parallel to the horizontal direction R, with a first distance d1 between them. A second pair of straight grating lines L21, L22 also extend over the entire length of the extended measuring graduation areas M11, M12 and are arranged parallel to the horizontal direction R. Q1 The grating lines L21, L22 are arranged parallel to the longitudinal extension direction R with a second spacing d2 between them. Therefore, the first pair of grating lines L11, L12 are arranged perpendicular to the second pair of grating lines L21, L22. The line grating region is L1 and the horizontal extension direction RQ1 along the same periodicity P as the broad measuring graduation areas M11, M12 of the cross grating 131.1, respectively. B1 , P B2 In this type of cross grating configuration, therefore, the longitudinal direction R L1 and the horizontal extension direction R Q1 There are at least three regions along the grid lines L11, L12 or L21, L22, respectively, separated from each other.

[0047] The line gratings superimposed on the large graduation fields M11, M12 of the cross grating 131.1 serving as the first graduation are so-called superstructures that are important for the desired suppression of disturbing higher diffraction orders. In this regard, the following disturbing diffraction orders (mx, my) are suppressed, among others: (+ / -2, + / -1), (+ / -1, +2), (+ / -3, 0), (0, + / -3). In contrast, a cross grating consisting solely of the large graduation fields M11, M12 arranged in a checkerboard pattern would result in many more higher diffraction orders, which would cause errors in the position determination.

[0048] In the exemplary embodiment of Fig. 5a, the cross grating 131.1 used as the first measuring scale is formed as a binary grating. This means that the cross grating 131.1 has only two distinct regions with different optical properties, which in the illustrated example are the hatched and light regions in the cross grating 131.1, which have different phase-shifting effects on the bundle of rays reflected by it. Such a binary grating can be produced using only one lithographic process and is therefore relatively cheap and easy to manufacture.

[0049] As can be seen from the figure, the grating lines L11, L12, L21, L22 of the line grating have optical properties different from or complementary to the optical properties of the first and second extensive measuring regions M11, M12, respectively, i.e., the grating lines L11, L12, L21, L22 have, for example, a complementary phase shift Δ2 in the brightly displayed extensive first measuring region M11 with a phase shift Δ1, and a complementary phase shift Δ1 in the hatched extensive second measuring region M12 with a phase shift Δ2.

[0050] In an alternative variant of the filtering cross grating 131.1, for example from FIG. 5a, it may be provided that the superimposed regular line grating is formed in one dimension rather than two dimensions. This is for example the case in a first extension direction, for example in a longitudinal extension direction R L1 5a, only a line grating is provided, with grating lines L21 and L22 arranged along the first direction of extension. In this case, within each extensive measuring graduation area M11, M12, there are at least three areas separated from each other by grating lines L21, L22 only along the first direction of extension. In this variant, the second direction of extension, i.e., the transverse direction R, which is provided in FIG. 5a, is not provided. Q1 The first and second extension directions are oriented perpendicular to each other, and in this example, the longitudinal extension direction R L1 and the horizontal extension direction R Q1 Instead, along the second extension direction, i.e., the transverse extension direction R Q1 It is also possible in principle to arrange a one-dimensional line grid only along

[0051] In Fig. 5b, the filtering cross grating 131.1 from Fig. 5a is shown in a partial cross section, and the layer structure of this example will be explained below on the basis of Fig. 5b. In this figure, and also in the following figures, a first area period P 111.1 is shown with two adjacent first and second extensive measuring graduation areas M11, M12, respectively. B1A cross-sectional view of the cross grating 131.1 is shown. The cross grating 131.1 has a fully contiguous reflective layer 131.1a, which extends over the entire cross grating surface and is made of, for example, aluminum (Al) or chromium (Cr). A dielectric layer 131.1b, which is also fully contiguous, is arranged on top of it, and is, for example, silicon dioxide (SiO2). A structured layer 131.1c is arranged on top of the dielectric layer 131.1b, and this structured layer 131.1c contains a suitable reflective material in the hatched area. The reflective material can be, for example, a highly refractive dielectric material, a semiconductor material such as silicon (Si) or germanium (Ge), or a metal such as gold (Au), silver (Ag), or aluminum (Al).

[0052] A modified layer structure for the filtering cross grating 231.1, again configured as a binary grating, is shown in a partial cross section in FIG. 5c. Here, a substrate 231.1a, for example made of quartz glass or Zerodur, is directly surmounted by a structured layer 231.1b, which contains a suitable reflective material in the hatched areas. The reflective material may again be a highly refractive dielectric material, a semiconductor material such as silicon (Si), germanium (Ge), or a metal such as gold (Au), silver (Ag), or aluminum (Al).

[0053] Another variant for the filtering cross grating 331.1 is shown in partial cross section in FIG. 5d. A continuous metallic reflective layer 331.1b is arranged over the entire surface of a substrate 331.1a, for example, made of quartz glass or Zerodur. The reflective layer 331.1b can be made of aluminum (Al) or gold (Au). A dielectric layer 331.1c, also made of silicon dioxide (SiO2), is arranged on top of it, also over the entire surface. A structured layer 331.1d is arranged thereon, in which, in the hatched areas, a suitable reflective material, for example, gold (Au), silicon (Si), tantalum pentoxide (TaO5), or silicon nitride (Si3N4), is arranged.

[0054] A further modified layer structure for a suitable filtering cross grating 431.1 is shown in partial cross section in FIG. 5e. Unlike the example from FIG. 5d, instead of a reflective layer provided on the substrate 431.1a, a full-area dielectric mirror layer 431.1b is provided. This dielectric mirror layer 431.1b consists of a stack of several dielectric monolayers, which may be, for example, high-refractive-index materials, such as titanium dioxide (TiO 2 ), tantalum pentoxide (TaO 5 ), and low-refractive-index materials, such as silicon dioxide (SiO 2 ), arranged alternately. As in the previous example, a dielectric layer 431.1c and a structured layer 431.1d are arranged thereon. Silicon dioxide (SiO 2 ), for example, is considered as a material for the dielectric layer 431.1c, while titanium dioxide (TiO 2 ), silicon, or tantalum pentoxide (TaO 5 ) may be used for the structured layer.

[0055] A second variant 531.1 of a cross grating suitable for the first measuring graduation is shown in plan view in Fig. 6a and in partial cross section in Fig. 6b. Again, the basic grating design is first explained with reference to the plan view in Fig. 6a, and then the grating structure is explained with reference to the partial cross section in Fig. 6b. In this regard, essentially only the important differences with respect to the first cross grating variant from Fig. 5a will be explained below.

[0056] Essentially, this variant of the filtering cross grating 531.1, which can be used as a first graduation, also comprises first and second large-area graduation areas M11, M12 with two different optical properties arranged in a checkerboard pattern, which are overlaid with a two-dimensional line grating with grating lines L11, L12, L21, L22, as in the example of Fig. 5a. However, in this cross grating 531.1, an additional spacing area M13 is provided between the first and second large-area graduation areas M11, M12, which has a third optical property that differs in reflectivity and / or phase shift from the optical property of the first and second large-area graduation areas M11, M12. Thus, if the first and second extensive graduation regions M11, M12 have different phase shifts Δ1, Δ2, the spacing region M13 may have a phase shift Δ3 different from the phase shifts Δ1, Δ2, and may further be designed to be absorbent, i.e. have a reflectivity R=0. As can be seen from FIG. 6a, the spacing region M13 between the first and second extensive graduation regions M11, M12 has a phase shift Δ3 different from the phase shifts Δ1, Δ2, and may be designed to be absorbent, i.e. have a reflectivity R=0. L1 and the horizontal extension direction R Q1 along the same width P A1 , P A2 It has.

[0057] 6b, the filtering cross grating 531.1 from FIG. 6a is shown in a partial cross section, as in the previous example, with the layer structure being explained below on the basis of this partial cross section. A structured reflective layer 531.1b, for example made of chromium (Cr), aluminum (Al), or gold (Au), is arranged on a substrate 531.1a, for example made of Zerodur. A dielectric layer 531.1c is arranged on the substrate 531.1a, in the second large measuring graduation area M12, above the area covered by the reflective layer 531.1b. Suitable materials for this purpose include, for example, silicon dioxide (SiO2), tantalum pentoxide (TaO5), or titanium dioxide (TiO2).

[0058] 6a and 6b are therefore not designed as binary gratings but as so-called mixed amplitude / phase gratings. This grating requires slightly more production technology costs than the first cross grating variant, in terms of the number of lithography steps required. However, it offers the possibility of particularly efficient suppression of undesired higher diffraction orders.

[0059] A third variant 631.1 of a suitable filtering cross grating for the first measuring graduation is shown in plan view in Fig. 7a and in partial cross section in Fig. 7b. In the following, the basic grating design will first be explained based on the plan view in Fig. 7a and the grating structure will be explained based on Fig. 7b.

[0060] This variant 631.1 of the cross grating also comprises first and second extensive graduation fields M11, M12 arranged in a checkerboard pattern and having two different optical properties. These first and second extensive graduation fields M11, M12 are overlaid with a two-dimensional line grating having grating lines L11, L12, L21, L22, as in the example of Fig. 5a. Similar to the previous example, this cross grating also includes an additional spacing region M13 between the first and second extensive graduation fields M11, M12, which has a third optical property different from the optical property of the first and second extensive graduation fields M11, M12. However, unlike the cross grating variants of Figs. 6a and 6b, this spacing region M13 between the first and second extensive graduation fields M11, M12 is structured. As is evident from FIG. 7a, there, for example, the longitudinal and transverse extension directions R L1 , R Q1 A cross grating substructure is provided, which consists of square grating regions with different optical properties regularly arranged along the

[0061] Instead of the cross grating substructure according to Fig. 7a, other structuring variants may be provided in the spacing region M13. For example, it would be possible to form a so-called high-frequency grating with a very small grating period therein, which would have a reflectivity R = 0 in the spacing region M13. Likewise, a diffraction grating with only the weak 0th diffraction order could be arranged therein, which would also result in a reflectivity R = 0 in the spacing region M13.

[0062] Figure 7b shows the filtering cross grating 631.1 from Figure 7a in a partial cross section, similar to the previous example, and a possible layer structure of this variant will be explained below based on this partial cross section. On a substrate 631.1a, for example made of Zerodur or quartz glass, a full-area reflective layer 631.1b is arranged, which can consist of chromium (Cr), aluminum (Al), or gold (Au). On top of that, a full-area dielectric layer 631.1c is provided, which can consist of silicon dioxide (SiO2). On top of the dielectric layer 631.1c, a structured layer 631.1d is arranged, which can consist of titanium dioxide (TiO2), silicon, silicon nitride (Si3N4), chromium (Cr), or aluminum (Al).

[0063] With regard to alternative configurations of the optical position measuring mechanism according to the invention, there are of course further possibilities beyond the exemplary embodiment described. This means that the first measuring graduation can also be implemented not as a reflective grating, as in the illustrated example, but as a transmission grating in the form of an amplitude grating, in which case different grating regions have different transmission properties for the ray bundles passing through them.

[0064] Furthermore, not only the first measuring graduation can have the filter properties for the above-described disturbing higher diffraction orders: instead or in addition, the second measuring graduation can also be configured as a filter grating, in particular as a filtering cross grating.

[0065] In a further exemplary embodiment of the position measuring mechanism according to the invention, the second scale with the second measuring graduations can also be arranged tilted about its longitudinal extension. Finally, at least one of the measuring graduations used in the position measuring system according to the invention can also be configured as a so-called polarization grating, in which the resulting diffraction orders each have a defined polarization, i.e., the resulting + / -1 diffraction orders can be polarized orthogonally to one another, for example. Such polarization gratings are described, for example, in EP 3 739 300 A1. [Explanation of symbols]

[0066] 110 Tables 30, 40; 130.1, 130.2, 140.1, 140.2 scale G1, G2, G3; 31, 41; 1131.1, 1131.2, 1141.1, 1141.2, 1141.3, 1141.4 measuring scale 1141.1a, 1141.1b, 1141.2a, 1141.2b measurement scale area 131.1;231.1, 331.1;431.1;531.1;631.1 Cross grid 150.1~150.4 Scanning unit d1, d2 First and second intervals L11, L12; L21, L22 grid lines M11, M12 1st and 2nd large measuring scale ranges M13 spacing area P A1 , P A2 width P B1 First area periodicity P B2 Secondary domain periodicity R L1 Longitudinal direction R Q1 Lateral direction x,y measurement direction z direction

Claims

1. 1. An optical position measurement mechanism for capturing the relative position of at least two scales which are movable relative to each other along two measurement directions also in different planes and which are arranged crosswise relative to each other, - both scales each have at least one measuring graduation with grating areas with different optical properties regularly arranged along at least one measuring direction, the longitudinal extension of the scales being oriented parallel to the first or second measuring direction, respectively; - at said first scale, a division of the illumination ray bundle emitted by the light source into at least two partial ray bundles is carried out, said partial ray bundle then strikes said second scale and is reflected back towards said first scale, in an optical position measuring arrangement, wherein the back-reflected partial ray bundles impinge anew on the first scale and are recombined there, whereby at least one resulting signal ray bundle then propagates in the direction of a detection unit, via which one or more position-dependent scanning signals relating to a relative movement of the scale along the first or second measuring direction can be generated; 1. An optical position measuring system, comprising: at least one measuring graduation (G1, G2, G3; 31, 41; 1131.1, 1131.2, 1141.1, 1141.2) of at least one scale (30, 40; 130.1, 130.2, 140.1, 140.2) formed as a two-dimensional cross grating (131.1; 231.1, 331.1; 431.1; 531.1; 631.1), wherein the cross grating has a filtering effect such that disturbing relatively high diffraction orders are suppressed in the cross grating (131.1; 231.1; 331.1; 431.1; 531.1; 631.1).

2. The cross grating (131.1; 231.1; 331.1; 431.1; 531.1; 631.1) has first and second large measuring graduation areas (M1) with different optical properties arranged in a checkerboard pattern. １ , M1 ２ ), and the first and second large measuring graduation areas (M1 １ , M1 ２ ) in the longitudinal direction (R Ｌ１ ) along the first region periodicity (P Ｂ１ ) and in the longitudinal direction (R Ｌ１ ) and a transverse extension direction (R Ｑ１ ) along the second domain periodicity (P Ｂ２ ) are regularly arranged in a checkerboard pattern, and the first and second large measuring graduation areas (M1 １ , M1 ２ 2. The optical position measuring mechanism according to claim 1, wherein a one-dimensional or two-dimensional regular line grating is superimposed on the optical axis.

3. The line grating has a wide measuring graduation area (M1 １ , M1 ２ ) each having a line grating region, and the line grating region - the large measuring scale area (M1 １ , M1 ２ ) and extends over the entire length of the first extension direction (R Ｌ１ ;R Ｑ１ ) and are parallel to each other at a first distance (d １ ;d ２ ) are spaced apart by straight grid lines (L1 １ , L1 ２ ; L2 １ , L2 ２ ) and In the case of a two-dimensional line grating, the large measuring graduation area (M1 １ , M1 ２ ) and are spaced apart from each other at a second distance (d ２ ;d １ ) are spaced apart by straight grid lines (L2 １ , L2 ２ ; L1 １ , L1 ２ ) a second pair of the line grating regions extend in the first direction (R Ｌ１ ;R Ｑ１ ) along the large measuring graduation area (M1 １ , M1 ２ ) and maintains the same periodicity as In the case of a two-dimensional line grating, the line grating regions extend in the second direction (R Ｑ１ ;R Ｌ１ ) of the cross grating (131.1; 231.1; 331.1; 431.1; 531.1; 631.1) １ , M1 ２ 3. The optical position measurement mechanism according to claim 2, wherein the periodicity is the same as that of the optical axis.

4. The wide measuring scale area (M1 １ , M1 ２ ) in the first extending direction (R Ｌ１ ;R Ｑ１ ) and / or the second extending direction (R Ｑ１ ;R Ｌ１ ) along at least three of the grid lines (L1 １ , L1 ２ , L2 １ , L2 ２ 4. The optical position measuring mechanism of claim 3, wherein there are areas separated by a distance of 1000 .mu.m.

5. The different optical characteristics in the cross grating (131.1; 231.1; 331.1; 431.1; 531.1; 631.1) are: - different transmission properties and / or - different reflective properties and / or - Different phase shifts 3. The optical position measuring mechanism according to claim 2, wherein:

6. The cross grating (131.1; 231.1; 331.1; 431.1) is formed as a binary grating having two different optical properties, and the grating lines (L1 １ , L1 ２ , L2 １ , L2 ２ ) respectively correspond to the first and second large measuring graduation areas (M1 １ , M1 ２ 6. The optical position measurement mechanism according to claim 3, wherein the optical characteristic is different from the optical characteristic of the optical element.

7. The cross grating (531.1; 631.1) is positioned between the first and second large measuring graduation areas (M1 １ , M1 ２ ) between the interval region (M1 ３ ), and the spacing region (M1 ３ ) are located within the first and second large measuring graduation areas (M1 １ , M1 ２ 6. The optical position measurement mechanism according to claim 2, wherein the optical position measurement mechanism has a third optical characteristic different from the optical characteristic of the first optical characteristic.

8. The first and second large measuring graduation areas (M1 １ , M1 ２ ) between the spacing regions (M1 ３ ) in the longitudinal extension direction (R Ｌ１ ) and the horizontal extension direction (R Ｑ１ ) along the same width (P Ａ１ , P Ａ２ 8. The optical position measuring mechanism according to claim 7, further comprising:

9. The spacing region (M1 ３ 8. The optical position measuring mechanism according to claim 7, wherein the optical position measuring element is structured.

10. The measuring graduations (41; 1141.1, 1141.2) of the second scale (40; 140.1, 140.2) are formed as reflective linear gratings (141.1), and the linear gratings (141.1) are oriented in a longitudinal direction (R Ｌ２ 2. The optical position measuring system according to claim 1, further comprising measuring graduation areas (1141.1a, 1141.1b, 1141.2a, 1141.2b) regularly arranged along the axis of the measuring graduation area and having different phase-shifting effects on the bundle of light rays reflected thereby.

11. 11. The optical position measuring mechanism according to claim 10, characterized in that the linear grating (141.1) of the second scale (40; 140.1, 140.2) has a filtering effect such that certain diffraction orders n>1 are suppressed.

12. 2. The optical position measuring system according to claim 1, further characterized in that at least one of the measuring graduations (G1, G2, G3; 31, 41; 1131.1, 1131.2, 1141.1, 1141.2) is shaped in such a way that the resulting diffraction orders each retain a defined polarization.

13. At least one of the scales (30, 40; 130.1, 130.2, 140.1, 140.2) has a longitudinal extension (R Ｌ１ , R Ｌ２ 2. The optical position measuring mechanism according to claim 1, wherein the optical position measuring mechanism is disposed at an angle about a center of gravity.

14. 10. A configuration comprising a table and a plurality of optical position measurement mechanisms according to claim 1, - said table (110) is arranged to be movable along two orthogonal measurement directions (x, y) in a horizontal movement plane; - two first scales (130.1, 130.2) are arranged on opposite sides of said table (110), at least one second scale (140.1, 140.2) is arranged in a plane spaced apart from the horizontal plane of movement along a direction (z) that intersects both first scales (130.1, 130.2) at an angle of 90° in the stationary state, said direction (z) being oriented orthogonal to said plane of movement; a plurality of scanning units (150.1 to 150.4) are stationarily arranged adjacent to the opposite sides of the table (110) with the first scales (130.1, 130.2), each of the scanning units (150.1 to 150.4) including a light source and a detection unit; A configuration characterized by:

15. - both first scales (130.1, 130.2) each have a reflective measuring graduation (1131.1, 1131.2) in the form of a two-dimensional cross grating (131.1; 231.1; 331.1; 431.1; 531.1; 631.1), the longitudinal extension of which (R Ｌ１ ) and is disposed at an angle relative to the horizontal movement plane, - said second scale (140.1, 140.2) is aligned in the longitudinal direction (R Ｌ２ ) in two parallel tracks extending parallel to the longitudinal direction (R), the measuring graduations (1141.1, 1141.2, 1141.3, 1141.4) are each formed as a reflective linear grating, and the linear gratings are aligned in the respective longitudinal direction (R Ｌ２ 15. The arrangement according to claim 14, characterized in that the reflective measuring graduation (1141.1, 1141.2, 1141.3, 1141.4) has regularly arranged graduation areas (1141.1a, 1141.1b, 1141.2a, 1141.2b) along a horizontal axis, the grating plane of the reflective measuring graduation (1141.1, 1141.2, 1141.3, 1141.4) being oriented parallel to the horizontal movement plane.

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