Encoder scale for an encoder system, encoder system, method for manufacturing an encoder system, and scanning probe microscope device

Abstract

The present invention relates to an encoder scale used in an encoder system for providing a position reference in a high-precision instrument such as a scanning probe microscope. The encoder scale comprises a carrier substrate, and the carrier substrate comprises an optical reference pattern for providing a position determination reference. The optical reference pattern comprises a pattern of structures that provide a characteristic local light reflectance to enable the position determination through optical sensing. The encoder scale further comprises a conductive layer of a conductive material to enable capacitive sensing in addition to the optical sensing. The present invention also relates to an encoder system for use with the above scale, a method for manufacturing the encoder scale, and a scanning probe microscope device.

Description

Technology Field

[0001] The present invention relates to an encoder scale used in an encoder system for providing a position reference in a high-precision instrument, an encoder system, a method for manufacturing an encoder system, and a scanning probe microscope device including an encoder scale. Background Technology

[0002] Encoder systems are typically applied to provide high-precision positioning references for high-precision instruments, such as microscopes. In particular, scanning probe microscopy systems typically feature encoder systems containing highly sensitive and accurate encoder scales used to determine the precise position of the microscope on the surface of a sample to be measured on a nanometer scale. In terms of the level of precision to be achieved with such encoder scales, it is crucial that the scales are well aligned with the desired orientation within the high-precision instrument, and that their alignment and offset with respect to at least the coordinates to be measured are accurately determined. Known encoder systems with 2D encoder scales typically enable monitoring of the encoder scale in three degrees of freedom, specifically in the X and Y directions (in a Cartesian coordinate system) and the Rz orientation (rotation around the z-axis). However, additional monitoring is required to achieve the highest level of precision required, for example, in scanning probe microscopy systems. For instance, sufficient signal strength of the encoder system signal is important to prevent degradation of the encoder system's performance.

[0003] The objective of the present invention is to provide an encoder scale that overcomes the disadvantages of existing scales and enables a higher level of control over the alignment state.

[0004] To this end, the present specification provides an encoder scale used in an encoder system for providing a position reference in a high-precision instrument, wherein the encoder scale comprises a carrier substrate, the carrier substrate comprises an optical reference pattern for providing a position determination reference, the optical reference pattern comprises a pattern of structures, the structures provide a characteristic local light reflectance to enable position determination through optical sensing, and the encoder scale further comprises a conductive layer of a conductive material to enable capacitive sensing in addition to optical sensing.

[0005] In the encoder scale of the present invention, an additional conductive layer is added to the optical components of the encoder system to enable the use of capacitive sensors by the encoder system. These capacitive sensors directly enable monitoring of the alignment of the encoder scale with respect to desired directions in additional degrees of freedom. In particular, by defining the x and y directions in the plane of the encoder scale, this enables monitoring of alignment in the z direction and in the Rx and Ry rotation directions. Consequently, misalignment of the plane of the encoder system (i.e., misalignment in the Rx and / or Ry directions) becomes measurable through the capacitive sensors, and any inaccuracy caused by such misalignment can be resolved (by correcting the alignment in the Rx and Ry rotation directions) or accounted for (since the misalignment is known). Additionally, the z position, i.e., the height of the encoder system on the encoder scale, becomes measurable. Thus, any deviation from the expected height is known to the system and can likewise be accounted for during measurement.

[0006] The carrier substrate can typically be provided by a glass substrate layer, but other suitable materials may, of course, be applied. For example, the carrier substrate may alternatively be provided by a ceramic layer, or by a resin or polymer having suitable properties. In many cases, a transparent carrier substrate may provide advantages, but this is not mandatory, and in some embodiments, the carrier substrate may be an opaque material that can optionally be covered by one or more additional layers. The teachings forming the basis of the present invention can be applied to various types of different carrier substrates.

[0007] In some embodiments, the conductive layer is provided over an optical reference pattern comprising a pattern of structures. While this may be counterintuitive from the perspective of optical properties, the conductive layer becomes well measurable when positioned over the optical reference pattern. Additionally, in this orientation, the conductive layer may contribute to the optical signal, for example, by acting as an anti-reflective layer or by enhancing the optical signal intensity or contrast between regions of different optical properties within the optical reference pattern in other ways. For example, in some embodiments, the encoder scale is configured to enable position determination via optical sensing using optical radiation of a first wavelength, and the conductive layer has a thickness that depends on the first wavelength. It has been found that when the thickness of the conductive layer is properly matched to the (first) wavelength of the optical radiation, the conductive layer reduces optical loss and thereby enhances the signal intensity of the optical signal. Without being bound by theory, this is believed to be related to the conductive layer acting as an anti-reflective layer, that is, a quarter-wavelength layer that reduces directly reflected optical signals. Any portion of the optical signal reflected from the surface of the scale before reaching the structures forming the optical reference pattern reduces the signal-to-noise ratio (SNR) of the optical output signal. In other words, although the radiation in this portion is of exactly the same wavelength, it does not transmit any information because it was not reflected from the optical reference pattern. Therefore, reducing this fraction of radiation provides a better SNR.

[0008] In some of these embodiments, the thickness of the conductive layer is less than 2 micrometers; preferably less than 1 micrometer. Also, in some additional or other embodiments, the thickness of the conductive layer is a fraction of the first wavelength, said fraction being between 0.2 and 0.3, and preferably about 0.25 times the first wavelength. In this case, the function of the layer as a quarter wavelength layer will be enhanced. In some embodiments, the first wavelength is between 850 and 900 nanometers, and the thickness is between 170 nanometers and 250 nanometers or multiples thereof. This combination of a conductive layer of the proposed thickness and radiation has been found to provide a strong optical signal while simultaneously achieving the advantages described above—namely, enabling the use of capacitive sensors to monitor the alignment with respect to the z position and the Rx and Ry rotation axes.

[0009] In some embodiments, the pattern of the structures is obtained by surface deformation of the carrier substrate, and the conductive material is a metal. Here, the structure beneath the metal layer provides the local optical differences required to obtain the optical reference pattern, while the metal layer itself functions as a conductive layer that enables the use of the capacitive sensors described above. Without being bound by theory, the structure beneath the metal layer is believed to alter the surface roughness as a result of surface deformation previously performed to pattern the optical reference pattern. Light will be scattered differently due to the altered roughness (typically higher roughness). For example, increased roughness will result in more scattering than unidirectional (specular) reflection.

[0010] In addition, in further embodiments, the conductive material is an optically transparent conductive material, such as, for example, at least one semiconducting oxide of tin, indium, zinc, and cadmium, and metals such as silver, gold, and titanium nitride; for example, indium tin oxide (ITO). For example, indium tin oxide is a very suitable material. The use of an optically transparent conductive layer is preferred over an opaque layer from an optical perspective, and while achieving each of the above advantages enabling capacitive sensing, the conductive layer can also provide the preferred optical properties as described above. For example, the thickness of the transparent conductive layer can likewise provide further conductive properties to the encoder scale of the invention of the embodiments of this class, while improving optical signal intensity by matching to the wavelength of optical radiation.

[0011] In some embodiments, the carrier substrate may be covered with a metal layer, the pattern of structures is obtained by surface deformation of the metal layer, and the conductive layer is on the metal layer. For example, the metal layer may be covered with an ITO layer of appropriate thickness that is matched to the wavelength of optical radiation used to perform optical sensing.

[0012] According to a second embodiment, an encoder system for use with an encoder scale according to a first embodiment is provided, wherein the encoder system comprises one or more capacitive sensors in addition to an optical sensor, enabling the measurement of the proximity of the encoder scale to one or more capacitive sensors.

[0013] In addition, according to a third embodiment, a method for manufacturing an encoder scale used in an encoder system for providing a position reference in a high-precision instrument is provided, the method comprising: providing a carrier substrate; modifying the surface of the carrier substrate to obtain an optical reference pattern for providing a positioning reference, wherein the optical reference pattern is provided by a pattern of structures, and the structures provide a characteristic local light reflectance to enable positioning through optical sensing; and covering the optical reference pattern with a conductive layer of a conductive material to enable capacitive sensing in addition to optical sensing. In some embodiments, the conductive layer is provided to have a predetermined thickness such that the thickness of the conductive layer is matched to the wavelength of the optical radiation used to perform the optical sensing. For example, the thickness may be less than 2 micrometers or less than 1 micrometer. In other embodiments, the matching may be achieved such that the thickness of the conductive layer is a fraction of the wavelength of the optical radiation used in the encoder system for optical sensing of position.

[0014] In some embodiments, prior to the deformation step, the carrier substrate is covered with a metal layer, and during the deformation step, a patterning step is performed on the metal layer to provide a pattern of structures; and the step of covering the optical reference pattern with a conductive layer is performed by covering the optical reference pattern with a transparent conductive layer. For example, in some embodiments, the transparent conductive material comprises indium tin oxide (ITO), or at least one other semiconducting oxide of tin, indium, zinc, and cadmium, and metals such as silver, gold, and titanium nitride.

[0015] In other or additional embodiments, the carrier substrate undergoes a patterning step to provide a pattern of structures during the deformation step, and the step of covering the optical reference pattern with a conductive layer is performed by covering the patterned carrier substrate with a metal layer.

[0016] In addition, in a fourth aspect of the present invention, a scanning probe microscope device comprising an encoder system for providing a high-precision position reference is provided, wherein at least one of the following is provided: the encoder system is an encoder system according to a second aspect; the encoder system comprises an encoder scale according to a first aspect; or the encoder system comprises an encoder scale manufactured using a method according to a third aspect. Brief explanation of the drawing

[0017] The present invention will be further described by describing some specific embodiments of the invention with reference to the accompanying drawings. While the detailed description provides examples of possible embodiments of the invention, it should not be construed as describing the only embodiments within the scope of protection. The scope of protection of the invention is defined in the claims, and this description should be considered exemplary and not limiting to the invention. In the drawings: FIGS. 1a through 1g schematically illustrate an encoder system, an encoder scale, and an encoder system according to various embodiments of the present invention, comprising various exemplary optical reference patterns; FIGS. 2a to 2d schematically illustrate a method for manufacturing an encoder scale according to an embodiment of the present invention; FIGS. 3a to 3c schematically illustrate a method for manufacturing an encoder scale according to additional embodiments of the present invention; FIG. 4 schematically illustrates a cross-section of an encoder scale according to another embodiment of the present invention; FIG. 5 is a graph of the reflectance of an encoder scale according to one embodiment, which depends on the thickness of the conductive layer and the detection radiation of a specific wavelength; FIG. 6 schematically illustrates a scanning probe microscope system according to one embodiment of the present invention; and FIG. 7 schematically illustrates a method for manufacturing an encoder scale according to one embodiment of the present invention. Specific details for implementing the invention

[0018] FIG. 1a schematically illustrates an encoder system (2) according to one embodiment of the present invention. The encoder system (2) includes an encoder scale (6) that works in cooperation with the encoder system (15), each of which is illustrated in more detail separately in FIG. 1b and FIG. 1c, respectively. In FIG. 1a, the encoder scale (6) includes an optical reference pattern (7) schematically illustrated as a checkered surface of the scale (6). A person skilled in the art will understand that the checkered pattern (7) is merely exemplary and by no means limiting the invention. In practice, the optical reference pattern (7) may be provided in many different variations and designs, each suitable for a specific application or providing its own advantages. For example, a checkered pattern such as the illustrated optical reference pattern (7) may be used to represent orthogonal coordinates, but a completely different type of pattern may be similarly applicable to orthogonal coordinates or suitable for different types of coordinate systems. For example, in a cylindrical coordinate system, the use of a checkerboard pattern may not be very useful, and alternatively, the pattern may consist of, for example, multiple concentric circles and radially outward angle marking lines. Additionally, FIG. 1d schematically illustrates an alternative encoding in an optical reference pattern (7'), which is more commonly applied in atomic force microscopes. The pattern (7') is again shown in a perspective view and typically includes straight lines and right angles in a plan view (not shown). Again, this should not be considered to limit the invention. The pattern may likewise include oblique lines and planes, and / or acute or obtuse angles. In particular, it is also possible to apply a position encoder grid, where the actual position can be inferred from the local line pattern and / or the thickness ratio of the lines or the dimensions of the planes. Various alternative patterns (7'', 7''', 7'''') are illustrated in FIG. 1e, FIG. 1f, and FIG. 1g. The pattern of Fig. 1e includes position encoding.The patterns (7''' and 7'''') of FIGS. 1f and FIGS. 1g are different from the patterns (7 and 7') of FIGS. 1a and FIGS. 1d, but are also well usable in scanning probe microscope (SPM) systems. To those skilled in the art, many different types of optical patterns are available that can be suitably used with various different coordinate systems and can be used in combination with the present invention. In general, it should be noted that the invention described herein should not be interpreted as being limited to the explicitly described embodiments. Many of the described features are not essential to the inventive concept and are described herein primarily to be illustrative, that is, to enhance understanding of the invention. Various grid patterns are a good example; those skilled in the art will understand that the invention may be applied in combination with other patterns other than those described herein. To this end, the scope of protection should be understood to encompass the general concept of the invention.

[0019] Considering the example illustrated in FIGS. 1a through 1c, the encoder system (15) may typically include optical sensors (11, 12-1, 12-2) to determine specific x and y coordinates with respect to a reference point, respectively. For example, sensors (11) and (12-1, 12-2) each enable the determination of two measurements of the current x and y coordinates of a specific point fixed to the positions of the sensors (11, 12-1, 12-2). In addition, by performing two measurements of the y coordinate, the sensors (12-1, 12-2) also enable the determination of deviations in alignment along the x and y directions. By determining the alignment error in the y direction, the alignment error in the x direction will also be known, since the x direction is perpendicular to the y direction. This alignment error is typically caused by misalignment or rotation around the z-axis and may be referred to as Rz orientation in terms of degrees of freedom. The coordinate system cross (20) shows the rotations Rx, Ry, Rz (rotation arrows around each axis) of the degrees of freedom and the respective vertical axes in the x, y, and z directions.

[0020] For clarity, an encoder scale (6) without an encoder system (15) is schematically illustrated in FIG. 1b. In FIG. 1c, an enlarged view of an encoder system (15) according to one embodiment of the present invention is illustrated. The encoder system (15) includes optical sensors (11) for the x direction as well as optical sensors (12-1, 12-2) for the y direction and the Rz direction. In addition, the encoder system (15) includes three capacitive sensors (14-1, 14-2, 14-3). The capacitive sensors (14-1 to 14-3) cooperate with the conductive layer (25) covering the encoder scale (6). Each of the capacitive sensors (14-1 to 14-3) enables the measurement of a local height on the surface of the encoder scale (6) (i.e., transversely to the surface). As illustrated in FIG. 1c, by measuring this height at three positions, it is possible to derive from it the misalignment in the z position as well as in the rotation directions Rx and Ry. Consequently, together with the optical sensors (11, 12-1, 12-2), the capacitive sensors (14-1, 14-2, 14-3) make it possible to determine the accurate position in three dimensions x, y, and z, as well as the rotation misalignment in each of the rotation directions Rz, Rx, and Ry. This is particularly useful in high-precision measuring instruments, such as microscopes, especially, for example, scanning probe microscope systems. However, the encoder scale of the present invention may also be applied to many other high-precision instruments that rely on the use of the encoder scale (6) to determine the current position.

[0021] FIGS. 2a through 2d schematically illustrate a method for manufacturing an encoder scale (6) according to an embodiment of the present invention. In such a method, in the first step illustrated in FIG. 2a, a carrier substrate (21) is provided. For example, the carrier substrate may be a glass plate, or it may be a different type of substrate such as a ceramic material, resin, polymer surface, etc., which can be used to create a very accurate optical structure suitable for optical sensing thereon.

[0022] Starting with a glass carrier substrate (21), a contrast layer (22) may be applied to the upper surface of the carrier substrate (21). The contrast layer may include, for example, a metal or other material suitable for providing sufficient contrast to the encoder scale (6) to create an optical reference pattern (7) thereon. For example, in the embodiments illustrated in FIGS. 2a through 2d, a metal layer (22) that is subsequently modified may have been applied to create an optical reference pattern (7). In FIG. 2c, the surface of the encoder scale (6) is modified to create a plurality of optical structures (23) thereon that together form an optical reference pattern (7). For example, the layer (22) may be modified by patterning channels (24) in a plurality of directions to create the structures (23), for example, as individual islands on the surface of the glass substrate (21). Patterning can be performed by any suitable method, such as laser patterning, etching, etc. This creates an optical reference pattern (7) that can be detected using optical detection by optical sensors (11, 12-1, 12-2). In FIG. 2c, the layer (22) is interrupted by channels (24). Alternatively, the channels may be deeper than shown in FIG. 2c and may extend at least partially into the layer (21). Next, in the step of FIG. 2d, according to the present invention, a conductive layer (25) is applied to the encoder scale (6) over the optical reference pattern (7). As can be understood, the metal forming the metal layer (22) in FIG. 2b may be electrically conductive, but after patterning in FIG. 2c, the layer (22) may no longer be conductive due to the channels (24) formed within the layer (22) that interrupt the conductivity. The conductive layer (25) of Fig. 2d again adds conductivity to the surface of the encoder scale (6).Consequently, the capacitive sensors (14-1 to 14-3) of FIG. 1c can be used to locally determine the height of the encoder system (15) on the surface of the encoder scale (6). The layer (25) can be created, for example, by an optically transparent conductive layer. For example, an indium tin oxide (ITO) layer adds conductivity to the surface of the encoder scale (6) available for use with the capacitive sensors (14) while providing excellent results in preserving the optical properties of the optical pattern (7).

[0023] As further explained below in relation to FIG. 5, additional advantages can be obtained by tuning the thickness of the layer (25) to a preferred wavelength of optical radiation used for optical detection by sensors (11, 12-1, 12-2). This will be further explained below.

[0024] An alternative method for manufacturing an encoder scale (6) is illustrated in FIGS. 3a through 3c. In FIG. 3a, a suitable carrier substrate (21) is provided, which may again be a glass plate, for example. In FIG. 3b, the surface of the carrier substrate (21) is modified to provide an optical reference pattern (7). Multiple channels (26) (or different patterns) in two vertical directions may be formed by patterning (e.g., laser patterning, or etching, or other suitable patterning method). This provides optical structures (23) on the surface that together form the optical reference pattern (7). Next, in the step of FIG. 3c, the surface of the carrier substrate (21) will be covered with an electrically conductive metal layer (27). This will enable the capacitive sensors (14) to obtain information regarding the z position and rotational alignment in the Rx and Ry rotation directions. As can be understood, by requiring fewer steps to manufacture the encoder scale (6), the method illustrated in FIGS. 3a through 3c provides a convenient alternative to the more complex method of FIGS. 2a through 2d. However, in the latter, i.e., the method of FIGS. 2a through 2d, a better measurability of each of the degrees of freedom is typically obtained, because the encoder scale (6) produced using the method of FIGS. 2a through 2d provides not only good optical properties of the optical reference pattern (7) but also optimal electrical properties of the surface of the encoder scale (6). In the embodiment produced using the method of FIGS. 3a through 3c, the optical properties of the encoder scale (6) obtained in FIG. 3c are somewhat reduced by the optical properties of the metal layer (27), but are sufficiently good to obtain acceptable results for the encoder system (15) in various applications.

[0025] An additional alternative embodiment as a cross-sectional view is shown in FIG. 4. Here, a glass carrier substrate (21) is patterned using laser patterning to provide an optical reference pattern (7). This optical reference pattern is immediately covered by a transparent conductive layer (27') which can be formed of ITO. Optionally, to further improve the contrast of the optical reference pattern (7), the surfaces of the islands (23) or channels (28) may be modified. Among the described alternatives, the alternative obtained using the manufacturing method of FIG. 2a through 2d clearly provides the most optimal electrical and optical properties.

[0026] FIG. 5 illustrates the effect of matching the thickness of the ITO layer (25) to the wavelength used for optical sensing. The graph in FIG. 5 illustrates the reflectance of the encoder scale (6) for two angles of incidence (AoI): a graph (51) perpendicular to the surface (0 degrees) and a graph (52) under an angle of 45 degrees to the surface. The wavelength of the applied optical radiation is indicated as 900 nanometers. For this wavelength, it appears that an optimal value is obtained at about 230 nanometers, which is roughly 1 / 4 wavelength. As can be understood, at this thickness, the ITO layer can act as a 1 / 4 wavelength layer that cancels out surface reflections from the surface of the encoder scale (6). Thus, the usable portion of the output signal, that is, the portion reflected from the optical reference pattern (7) under the conductive layer (25), becomes more prominent in the output signal without glare from the surface of the encoder scale (6). Accordingly, adding a transparent conductive ITO layer (25) having a carefully selected thickness that matches the required wavelength makes it possible to reduce optical noise signals caused by glare from the surface of the encoder system, for example, and thus improve the signal-to-noise ratio (SNR) of the decoder signal. Consequently, the conductive layer (25) not only enables the determination of accurate position and alignment states in 6 degrees of freedom, but also improves the optical output signal of the encoder system and increases the accuracy of the positioning obtained thereby. As further followed from FIG. 5, the effect on reflectivity also occurs at multiples of thicknesses above 230 nanometers. Thus, selecting different thicknesses, for example, about 470 nanometers (or about 700 nanometers), can likewise improve the SNR of the output signal while further improving conductivity. As can be understood, however, thicker layers may simultaneously reduce optical properties by reducing the intensity of reflected radiation (which must be transmitted through the thicker layer).Therefore, by carefully selecting the thickness while considering the above, an optimal value between optical and electrical properties can be found.

[0027] In FIG. 6, a scanning probe microscope system (1) according to one embodiment of the present invention is schematically illustrated. The system (1) includes an encoder system (15) according to one embodiment of the present invention, and the encoder system (15) cooperates with an encoder scale (6) according to the present invention. In FIG. 6, the scanning probe microscope system (1) includes a base (5) and a substrate carrier (3). The drawing shows only a portion of the substrate carrier (3) and the base (5) of the SPM system (1), and dotted lines indicate where the drawing is cut off for illustrative purposes only. The base (5) includes an encoder scale (6) that provides a coordinate reference grid plate. The encoder scale (6) is part of a grid encoder system consisting of the scale (6) and at least one encoder system (15). While the application of a single encoder system (15) may be sufficient to provide accurate position information to the scan head (30) in many embodiments, alternatively, in a system such as the system (1) according to some embodiments of the present invention, a plurality of encoder systems (15) may cooperate with the encoder scale (6). For example, each element moving within the workspace (2) between the sample carrier (3) and the encoder scale (6) may include an encoder system (15) that cooperates with the encoder scale (6) to determine its position based on a coordinate reference grid plate of the scale (6). Such an element may be provided, for example, by the scan head (30) shown in FIG. 6. Each additional encoder system (if any) that cooperates with the encoder system (15) and the scale (6) cooperates with the reference grid to obtain coordinate data of its current position on the scale (6).

[0028] The scan head (30) may include various different elements, but at least includes an encoder system (31) and a miniature atomic force microscope unit (32). The miniature AFM unit (32) includes a probe (35) comprising a cantilever (36) and a probe tip (37). The probe tip (37) is used to scan across the surface of a substrate, for example, using an acoustic signal applied to the substrate, the probe (35), or both, to determine the geometric shape of the surface topography of the substrate or the precise locations of structures embedded beneath the surface of the substrate. In the example illustrated in FIG. 1c, a conventional topography measurement is schematically illustrated. Thus, the miniature AFM (32) includes a probe (35), a laser (41) (e.g., a semiconductor laser), and an optical sensor (38). The laser (41) and the optical sensor (38) together form an optical beam deflection unit (OBD unit), which enables the accurate determination of the deflection of the probe tip (37) by surface structures detected by the AFM. The laser (41) and the optical sensor (38) are controlled by a controller (40) that obtains sensor signals from the optical sensor (38) and also obtains position data, for example, from an encoder system (31). This is transmitted to the system electronics (1). In the embodiment illustrated in FIG. 1c, the scan head (30) includes an onboard processor (40) used as a controller for the scan head. A person skilled in the art will understand that a distributed controller may be located somewhere within the SPM system to perform the same and / or additional tasks as described herein.

[0029] In FIG. 6, the encoder system (15) is mounted on the scan head (30), and the scan head (30) is mounted on the arm (10) of the positioning unit. Electrical connections (19-1 and 19-2) for data transmission from the scan head (30) and the encoder system (15) to the central controller (not shown) of the system (1) are provided through the electrical connection interface (18) at the end of the arm (10) to which the scan head (30) is connected. FIG. 6 illustrates a separate connection (19-2) from the encoder system (15) to the central controller, but a person skilled in the art will understand that data transmission can alternatively be integrated through the controller (40) and transmitted through a single connection (19).

[0030] The encoder system (15) of the system (1) of FIG. 6 is similar to the encoder system (15) illustrated in FIG. 1c. As can be seen, the encoder system (15) includes optical sensors (11, 12-1, 12-2) and further includes capacitive sensors (14-1 to 14-3).

[0031] FIG. 7 further schematically illustrates a method for manufacturing an encoder scale (6) according to one embodiment of the present invention. The method (60) begins by providing a carrier substrate in step (62). On the carrier substrate, a contrast layer may be applied in step (64). For example, this may be the contrast layer (22) also illustrated in FIG. 2d. This contrast layer may be patterned by performing step (66) using, for example, laser patterning or other suitable techniques. The patterning creates a pattern of structures (e.g., (23)) having trenches or openings (e.g., (26)) that act as an optical reference pattern (7) when illuminated, for example, by optical sensing radiation. Then, in step (68), a conductive layer may be applied to the surface of the encoder scale (6). As can be understood, in certain embodiments of the present invention, step (64) may be omitted as shown in FIGS. 3a to 3c.

[0032] The terms used to describe specific embodiments are not intended to limit the invention. The singular forms “a,” “an,” and “the” used herein are intended to include plural forms unless the context clearly indicates otherwise. The term “and / or” includes any and all combinations of one or more of the associated listed items. It will be understood that the terms “comprising” and / or “comprising” specify the presence of the specified features but do not exclude the presence or addition of one or more other features. Furthermore, it will be understood that when a specific step of a method is referred to as following another step, unless otherwise specified, it may directly follow said other step or one or more intermediate steps may be performed before performing the specific step. Likewise, when a connection between structures or components is described, it will be understood that, unless otherwise specified, this connection may be established directly or through intermediate structures or components.

[0033] The present invention is described more fully below with reference to the accompanying drawings, in which embodiments of the invention are illustrated. In the drawings, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic and / or cross-sectional drawings of possible idealized embodiments and intermediate structures of the invention. In the description and drawings, the same numbers refer to the same elements throughout. Relative terms and their derivatives should be interpreted as referring to the orientations depicted in the drawings being described or discussed. These relative terms are for convenience of description and do not require the system to be configured or operated in a specific orientation unless otherwise specified.

[0034] The present invention has been described in terms of some specific embodiments. It will be understood that the embodiments illustrated in the drawings and described herein are for illustrative purposes only and are not intended to limit the invention in any way. The operation and configuration of the invention are to be apparent from the foregoing description and the accompanying drawings. It will be apparent to those skilled in the art that the invention is not limited to any of the embodiments described herein and that modifications that are to be considered to be within the scope of the appended claims are possible. Furthermore, kinematic reversals are also essentially disclosed and are considered to be within the scope of the invention. Additionally, any of the components and elements of the various disclosed embodiments may be combined or incorporated into other embodiments as necessary, required, or preferred, without departing from the scope of the invention as defined in the claims.

[0035] In the claims, any reference numerals should not be interpreted as limiting the claims. When used in this specification or the appended claims, the terms “comprising” and “comprising” should not be interpreted in an exclusive or limiting sense, but rather in a comprehensive sense. Accordingly, the expression “comprising” as used in this specification does not exclude the presence of other elements or steps in addition to those listed in any claim. When used in this specification or the appended claims, expressions such as “comprising” should be interpreted in a comprehensive sense of “comprising at least” rather than as a limiting enumeration. Furthermore, the singular should not be interpreted as being limited to “only one,” but instead is used to mean “at least one” and does not exclude the plural. Features not specifically or explicitly described or claimed may be additionally included in the structure of the invention within the scope thereof. Any of the claimed or disclosed devices or parts thereof may be combined together or separated into additional parts without departing from the claimed invention, unless otherwise specifically stated. Expressions such as “means for” should be read as “components configured for” or “members configured for” and should be interpreted to include equivalents to the disclosed structures. The use of expressions such as “important,” “desirable,” “particularly desirable,” etc., is not intended to limit the invention. Additions, deletions, and modifications within the authority of a person skilled in the art may be made without generally departing from the spirit and scope of the invention as defined by the claims. The invention may be practiced differently from as specifically described herein and is limited only by the appended claims.

Claims

Claim 1 An encoder scale used in an encoder system for providing a position reference in a high-precision device, wherein the encoder scale comprises a carrier substrate, the carrier substrate comprises an optical reference pattern for providing a position determination reference, the optical reference pattern comprises a pattern of structures, the structures provide a characteristic local light reflectance for enabling the position determination through optical sensing, and the encoder scale further comprises a conductive layer of a conductive material for enabling capacitive sensing in addition to the optical sensing. Claim 2 In claim 1, the encoder scale, wherein the conductive layer is provided on the optical reference pattern comprising a pattern of structures. Claim 3 In paragraph 2, the encoder scale is configured to enable position determination through optical sensing using optical radiation of a first wavelength, and the conductive layer has a thickness dependent on the first wavelength. Claim 4 An encoder scale according to claim 3, wherein the thickness of the conductive layer is less than 2 micrometers; preferably less than 1 micrometer; or the thickness of the conductive layer is a fraction of the first wavelength, said fraction is between 0.2 and 0.3, preferably about 0.25 times the first wavelength; or the first wavelength is between 850 and 900 nanometers, and the thickness is between 170 nanometers and 250 nanometers or a multiple thereof. Claim 5 An encoder scale according to any one of claims 1 to 4, wherein the pattern of the structures is obtained by surface deformation of the carrier substrate, and the conductive material is a metal. Claim 6 In any one of claims 1 to 4, the conductive material is an optically transparent conductive material, and is, for example, a semiconducting oxide of at least one of tin, indium, zinc, and cadmium, and metals such as silver, gold, and titanium nitride; an encoder scale, for example, indium tin oxide (ITO). Claim 7 In claim 6, the carrier substrate is covered with a metal layer, the pattern of the structures is obtained by surface deformation of the metal layer, and the conductive layer is on the metal layer, an encoder scale. Claim 8 An encoder scale according to any one of claims 1 to 7, wherein the carrier substrate is a glass plate. Claim 9 An encoder system for use with an encoder scale according to any one of claims 1 to 8, wherein the encoder system comprises one or more capacitive sensors in addition to an optical sensor, enabling the measurement of the proximity of the encoder scale to the one or more capacitive sensors. Claim 10 A method for manufacturing an encoder scale used in an encoder system for providing a position reference in a high-precision device, comprising: providing a carrier substrate; modifying the surface of the carrier substrate to obtain an optical reference pattern for providing a position reference, wherein the optical reference pattern is provided by a pattern of structures, and the structures provide a characteristic local light reflectance to enable the position determination through optical sensing; and covering the optical reference pattern with a conductive layer of a conductive material to enable capacitive sensing in addition to the optical sensing. Claim 11 A method according to claim 10, wherein the conductive layer is provided to have a predetermined thickness such that the thickness of the conductive layer is matched to the wavelength of the optical radiation used to perform the optical sensing. Claim 12 A method according to claim 10 or 11, wherein prior to the deformation step, the carrier substrate is covered with a metal layer, and during the deformation step, a patterning step is performed on the metal layer to provide a pattern of the structures; and the step of covering the optical reference pattern with the conductive layer is performed by covering the optical reference pattern with a transparent conductive layer. Claim 13 In claim 12, the transparent conductive material comprises indium tin oxide (ITO), or at least one additional semiconducting oxide of tin, indium, zinc, and cadmium, and metals such as silver, gold, and titanium nitride. Claim 14 A method according to claim 10 or 11, wherein the carrier substrate undergoes a patterning step to provide a pattern of the structures during the deformation step, and the step of covering the optical reference pattern with the conductive layer is performed by covering the patterned carrier substrate with a metal layer. Claim 15 A scanning probe microscope device comprising an encoder system for providing a high-precision position reference, wherein the encoder system is an encoder system according to claim 9; the encoder system comprises an encoder scale according to any one of claims 1 to 8; or the encoder system comprises an encoder scale manufactured using a method according to any one of claims 10 to 13.

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