JP4458855B2 - Method and apparatus for stage mirror mapping - Google Patents

Description

  The present invention relates generally to interferometry, and in particular to correct local surface characteristics such as photolithography stage mirrors in situ or off-stage interferometrically to increase distance measurement accuracy. The present invention relates to an interference spectroscopy apparatus and method capable of providing a signal.

  Interferometry is a well-established metrology that is widely used to measure and control many important dimensions in micromachining processes. This is particularly important in semiconductor manufacturing or the like, where accuracy requirements are 10 to 40% of important dimensions of 0.1 μm or less.

  Integrated circuits formed of semiconductor materials are made by sequentially depositing and patterning layers of different materials on a silicon wafer, which is usually a flat surface with Cartesian xy coordinates. It is in the exposure plane. This coordinate has a vertical z direction. The patterning process consists of a combination of photoresist exposure and development, followed by etching and doping of the underlying layer, followed by subsequent layer deposition. The result of this process is a complex and very inhomogeneous material structure on the micron scale on the wafer surface.

  Typically, each wafer contains multiple copies of the same pattern, referred to as “fields”, which are arranged on the wafer in a linear distribution, nominally known as a “grid”. . Often, but not always, each field corresponds to a single “chip”.

  The exposure process consists of projecting an image of the next layer pattern onto (and within) the photoresist spun onto the wafer. In order for the integrated circuit to function properly, each successively projected image must accurately match the pattern already on the wafer. The process of determining the position, orientation, and distortion of a pattern already on the wafer and then placing the pattern in an accurate relationship to the projected image is called “alignment”. The actual outcome, ie how accurately each successively patterned layer is matched to the previous layer, is called “overlay”.

  In general, the alignment process requires positioning by both translation and rotation, not only for wafer and / or projection images, but also for distortions of parts of the image in order to match the actual shape of the existing pattern. . Obviously, in order to obtain one pattern on another, the wafer and image must be accurately positioned. Often it is necessary to actually distort an image. Other effects, such as heat and vibration, may need to be corrected.

  The net result of all this is that the shape of the first level pattern printed on the wafer is not ideal, and all subsequent patterns are, to the extent possible, the first level printed pattern. It must be adjusted to fit the overall shape of the. Although the ability to compensate for these effects varies from exposure tool to exposure tool, distortion or shape variations that can be compensated generally include x and y magnification and skew. Combining these distortions with translation and rotation constitutes a complete set of transformations.

  The problem is to continuously match the projected image to a pattern already on the wafer, not simply positioning the wafer itself. As such, the exposure tool must be able to effectively detect or infer the relative position, orientation, and distortion of both the wafer pattern itself and the projected image.

  It is difficult to directly detect the circuit pattern itself. Therefore, alignment is performed by adding a reference mark or “alignment mark” to the circuit pattern. These alignment marks can be used to determine the position, orientation, and distortion of the reticle and / or the position, orientation, and distortion of the projected image. Since the alignment mark can also be printed on the wafer along the circuit pattern, the alignment mark can be used to determine the position, orientation, and distortion of the wafer pattern.

  Alignment marks typically consist of one or more transparent or opaque lines on the reticle that become “trench” or “mesa” when printed on the wafer. However, more complex structures such as gratings (which are simple periodic arrays of trenches and / or mesas) and checkboard patterns are also used. Usually, alignment marks are placed along the “kerf” edges of each field, or several “master marks” are distributed across the wafer. An alignment mark is necessary but not part of the chip circuit. Thus, from the chip manufacturer's point of view, alignment marks waste valuable wafer area or "real estate". As a result, alignment marks are being made as small as possible, often below a few hundred microns on one side.

  An alignment sensor is incorporated into the exposure tool to “see” the alignment mark. In general, there are separate sensors for the wafer, reticle, and / or projection image itself. Depending on the overall alignment strategy, these sensors may be entirely separate systems or may be effectively combined into a single sensor. For example, a sensor that can directly view the projected image is nominally “blind” with respect to the wafer mark, so a separate wafer sensor is required. However, a sensor that “sees” the wafer through the reticle alignment mark itself essentially aligns the reticle and the wafer simultaneously. Thus, no separate reticle sensor is required. In this case, the position of the alignment mark in the projected image is inferred from the position of the reticle alignment mark, and careful calibration of the reticle to the image position should have been performed prior to the alignment step. Please be careful.

  Further, as described above, sensors that optically detect wafer alignment marks are used in essentially all exposure tools. That is, the sensor projects light onto the wafer at one or more wavelengths and detects scattering / diffraction from the alignment mark as a function of position in the wafer plane. Many types of alignment sensors are widely used and their optical configuration covers all functions from simple microscopes to heterodyne grating interferometers. Also, depending on the sensor configuration, the operation for a given wafer type may be good or bad, so most exposure tools are equipped with multiple sensor configurations that provide a good overlay for the widest possible range of wafer types. It has become possible.

  The overall role of the alignment sensor is to determine the position of each predetermined subset of all alignment marks on the wafer in a coordinate system that is fixed relative to the exposure tool. These position data are then used to align using one of two common methods referred to as “global” and “field-by-field”.

  In global alignment, the location of the mark in a few fields is simply confirmed by an alignment sensor, and the data is combined to best fit to determine the optimal alignment of all fields on the wafer. Field-by-field alignment uses data collected from a single field and aligns only that field. Global alignment is usually faster (because not all fields are located on the wafer) and less sensitive to noise (to combine all data together to find the best overall fit) ). However, it does not rely on the overall optomechanical stability of the exposure tool because it uses best fit results in a feed forward or dead reckoning approach.

  Alignment is generally performed as a two-step process. That is, a fine alignment step (accuracy of tens of nanometers) is performed after an initial coarse alignment step (micrometer accuracy). Alignment requires the wafer to be positioned in all six degrees of freedom (three translations and three rotations). However, adjusting the wafer so that the wafer is in the projected image plane, i.e. leveling the wafer and focusing the projected image, has one translational freedom (optical axis, z-axis, or xy wafer). Movement along a parallel line perpendicular to the orientation of the image) and two rotational degrees of freedom (rotating the wafer surface to be parallel to the projected image surface), which is generally referred to as alignment Think of it as separate.

  When describing alignment, it usually means only in-plane translation (two degrees of freedom) and rotation about the projection optical axis (one degree of freedom). The reason for dividing in this way is because the required accuracy is different. The required accuracy for in-plane translation and rotation is generally on the order of tens of nanometers to nanometers, or about the minimum feature size or critical dimension (CD) to be printed on the wafer. It needs to be 20-30%. Current state-of-the-art CD values are on the order of 100 nm, and therefore the required alignment accuracy is well below 100 nm. On the other hand, the accuracy required for out-of-plane translation and rotation is related to the overall depth at which the focus of the exposure tool can be used and is generally closer to the CD value. Therefore, the accuracy required for out-of-plane wafer focusing and leveling is lower than for in-plane alignment. Similarly, focusing and leveling sensors are usually completely separate from “alignment sensors”, and focusing and leveling usually do not rely on patterns on the wafer. Only the wafer surface or its substitute needs to be detected. Nevertheless, this is still an important issue requiring precise knowledge of the vertical position (altitude) of the optical projection system above the wafer, among others.

  In performing the alignment, it is known to use a plane mirror interferometer, a passive zero shear interferometer, and an interferometer having an active beam steering member, ie an active zero shear interferometer. In active and passive zero shear interferometers, the accuracy of distance measurements can be increased by using beam conditioning to ensure that the beam carrying distance information is properly aligned to provide the best signal. Guaranteed. For a passive zero shear interferometer, a plane mirror measurement object is used as a member in the beam conditioner. For such interferometers, see for example: US Provisional Patent Application No. 60 / 314,345, entitled "Passive Zero-Shear Interferometer Using Angle-Sensitive Beam Splitter" (filed Aug. 23, 2001), currently US patent Application No. 10 / 207,314, title of the invention “passive zero shear interferometer” (filed on July 29, 2002), US Provisional Patent Application No. 60 / 314,568, Name “Zero-Shear Plane Mirror Interferometer” (filed on August 23, 2001), currently US patent application Ser. No. 10 / 227,167, title of invention “Multiple Path Interferometry” (August 2002) Filed on May 23), US Provisional Patent Application No. 60 / 314,569, title of the invention "Zero Shear Non-Planar Mirror Interferometer" (filed on August 23, 2001), currently US patent application 10/2 7, 166, title of invention “Optical Interferometry” (filed August 23, 2002), US Provisional Patent Application No. 60 / 352,425, title of invention “reduced” Differential beam shear multiple degree of freedom interferometer "(filed on Jan. 28, 2002), currently US patent application Ser. No. 10 / 352,616, entitled“ Multiple Path Interferometry ”(2003). Filed on Jan. 28).

  In an active zero shear interferometer, a dynamic member is used in the beam conditioner, and the angular direction of the dynamic member is controlled via feedback and / or feed forward devices, It is ensured that the beam carrying the distance information is properly aligned to obtain an optimal signal. Such interferometers are known, for example, in the following documents. Commonly owned international patent application PCT / US00 / 12097 (filed on May 5, 2000), entitled "Interference spectroscopy system with dynamic beam steering assembly for measuring angle and distance" And published on November 19, 2000 (WO 00/66969), commonly owned US Provisional Patent Application No. 60 / 314,570 (filed Aug. 23, 2001), title of invention "Direction of Input Beam Dynamic interferometer to control ", currently US patent application Ser. No. 10 / 226,591, filed Aug. 23, 2001 and published Jun. 23, 2003 (US-2003-0043384). ), US Provisional Patent Application No. 60 / 356,393 (filed on Feb. 12, 2002), title of invention “input measurement beam component and output reference beam”. An interferometer with a dynamic beam steering member that redirects the beam component ", currently US patent application Ser. No. 10 / 364,666 (filed on Feb. 11, 2003), entitled“ Dynamic Interferometer with a simple beam steering member ". All three applications are in the name of (Henry A. Hill).

  But even in the case of passive zero shear and active zero shear interferometers, when the stage mirror undergoes various movements, the shape of the various reflectors affects the achievable accuracy in distance and angle measurements. give. The reason that the shape of the various reflecting members affects the achievable accuracy is that the tilt change of the reflecting member in the optical path affects the length of the optical path and the beam direction. Normally, after the shape of such a reflective member, for example, a thin high aspect ratio mirror, is characterized off-stage, the reflective member is mounted on-stage. But this is often unacceptable. This is because the accuracy of off-stage characterization is not sufficient and / or the shape of the part is distorted by the mounting process itself compared to the shape being inspected, and changes in this shape introduce measurement errors Because there is a possibility that.

  Accordingly, it is an object of the present invention to measure the surface topography map of an on-stage reflector, such as a thin high aspect ratio mirror, in situ and off-stage with high spatial resolution to determine the optical path relative to the shape of the reflective surface. An interferometry apparatus and method capable of generating a correction signal that compensates for errors in both length and beam direction or checking the accuracy of the correction signal, the interferometry apparatus comprising an integrated optical assembly It is an object to provide an interference spectroscopic device and method that can be used.

  Another object of the present invention is to measure surface topography maps of on-stage reflectors, such as thin high aspect ratio mirrors, in-situ and off-stage with high spatial resolution to provide an optical path for the shape of the reflective surface. Interferometry apparatus and method capable of generating a correction signal that compensates for errors in both length and beam direction or checking the accuracy of the correction signal, scanning in one or two orthogonal axes What is required is to provide an interferometric spectrometer and method that may include an integrated optical assembly.

  Another object of the present invention is to place surface topography maps of on-stage reflectors, such as thin high aspect ratio mirrors, in-situ and off-stage with high spatial resolution and placed in orthogonal planes. An interference spectroscopy apparatus and method capable of generating a correction signal that compensates for errors in both the length of the optical path and the beam direction with respect to the shape of the reflecting surface or checking the accuracy of the correction signal, Is to provide an interferometry apparatus and method that may include an integrated optical assembly.

  Another object of the present invention is to place surface topography maps of on-stage reflectors, such as thin high aspect ratio mirrors, in-situ and off-stage with high spatial resolution and placed in orthogonal planes. An interferometry apparatus and method that can generate a correction signal that compensates for errors in both the length of the optical path and the beam direction with respect to the shape of the reflecting surface or that can check the accuracy of the correction signal. To provide an interferometry apparatus and method that only requires scanning in two orthogonal axes and the interferometry apparatus may include an integrated optical assembly.

  Yet another object of the invention is to use information generated from the operating characteristics of flat mirror interferometers, passive zero shear interferometers, and active zero shear interferometers to provide on-stage reflective members such as thin high The shape of the aspect ratio mirror can be measured in situ and off-stage to generate a high spatial resolution map of the reflective surface represented by the reference line, which can then be used to reflect the shape of the reflective surface. It is possible to generate a correction signal that compensates for errors in both the length of the optical path and the beam direction. The interferometer may include an integrated optical assembly.

  Yet another object of the invention is to use information generated from the operating characteristics of flat mirror interferometers, passive zero shear interferometers, and active zero shear interferometers to provide on-stage reflective members such as thin high The shape of the aspect ratio mirror can be measured in situ and off-stage to generate a high spatial resolution map of the reflective surface represented by the reference line, which can then be used to reflect the shape of the reflective surface. It is possible to generate a correction signal that compensates for errors in both the length of the optical path and the beam direction. Only scanning in one or two orthogonal axes is required, and the interferometer may include an integral optical assembly.

  Yet another object of the invention is to use information generated from the operating characteristics of flat mirror interferometers, passive zero shear interferometers, and active zero shear interferometers to provide on-stage reflective members such as thin high Measure the shape of the aspect ratio mirror in situ and off-stage to generate a high spatial resolution map of the reflective surface including the reference line on the surface of the reflective surface and the local rotation of the surface around the reference line This map can then be used to generate a correction signal that compensates for errors in both the optical path length and beam direction relative to the shape of the reflecting surface. The interferometer may include an integrated optical assembly.

  Yet another object of the invention is to use information generated from the operating characteristics of flat mirror interferometers, passive zero shear interferometers, and active zero shear interferometers to provide on-stage reflective members such as thin high Measure the shape of the aspect ratio mirror in situ and off-stage to generate a high spatial resolution map of the reflective surface including the reference line on the surface of the reflective surface and the local rotation of the surface around the reference line This map can then be used to generate a correction signal that compensates for errors in both the optical path length and beam direction relative to the shape of the reflecting surface. Only scanning in one or two orthogonal axes is required, and the interferometer may include an integral optical assembly.

  Yet another object of the present invention is to measure the shape of an on-stage reflective member, such as a thin high aspect ratio mirror, in situ and off-stage to determine the length of the optical path and the beam direction relative to the shape of the reflective surface. Interferometry apparatus and method capable of generating a high spatial resolution correction signal that compensates for errors in both, wherein the interferometry apparatus may include an integrated optical assembly It is to be.

  Yet another object of the present invention is to measure the shape of an on-stage reflective member, such as a thin high aspect ratio mirror, in situ and off-stage to determine the length of the optical path and the beam direction relative to the shape of the reflective surface. An interferometry apparatus and method capable of generating a high spatial resolution correction signal that compensates for errors in both, wherein only a scan in one or two orthogonal axes is required. Is to provide.

  Other objects of the present invention will become apparent in part and in part will become apparent from the following detailed description when read in conjunction with the drawings.

(Outline of the present invention)
Stage mirror around a reference line including one or more reference lines with high spatial resolution, including an optical assembly, with multiple degrees of freedom of the stage mirror and topography of the reflecting surface of the stage mirror Interferometer system that measures as required according to requirements, with corresponding local rotation of the reflective surface of the. With the interferometer system, the local tilt of the reference line in a plane having a surface normal perpendicular to the scanning direction and the local rotation of the reflecting surface around the reference line cause the beam reflected by the reflecting surface to Measured using measuring the angular change in direction with single optical path interferometry. The configuration of the interferometer system is such that multiple degrees of freedom are determined from a combination of measured surface linear and angular displacements. A reflective surface topography represented by a reference line and a local rotation of the reflective surface around the reference line includes two or more sets of reference lines on the reflective surface, along with associated local rotation measurements, It may be included. The baseline and associated local rotation may be measured in-situ within the lithography tool, or may be measured off-line before introduction or after removal from the lithography tool. The stage mirror also includes an optical assembly and is represented by the multiple degrees of freedom of the two and three stage mirrors and the local rotation of the reference mirror and the reflecting surface of the stage mirror about the reference line An interferometer system for measuring the topography of a reflective surface is described. All that is required to determine the topography of the stage mirror reflective surface represented by the reference line and the local rotation of the stage mirror reflective surface around the reference line is to scan in two orthogonal axes only. . The arrangement of the two and three stage mirrors is such that the reflective surfaces of the two and three stage mirrors are usually orthogonal or parallel to the other surfaces of the two and three stage mirrors. However, other angles such as 45 degrees may be used. The topography of the reflective surface may be measured with respect to a mirror used in end-use applications other than lithography tools.

  A method is also described in which the topography of one or more arrays of mirror surfaces, preferably arranged orthogonally, can be characterized in situ.

  In one aspect, an interferometry apparatus of the present invention includes a translation stage, an electromechanical device for selectively translating the translation stage in at least one of at least two orthogonal directions, and a predetermined with respect to the translation stage. At least one thin and elongated mirror having a reflective surface mounted in a manner and interferometer means for generating a plurality of measurement beams, the measurement beam projected onto the reflective surface and in at least one direction An interferometer means adapted and arranged to measure the displacement of the translation stage and at least the local tilt of at least one thin and elongated mirror, and an operation mode for selectively translating the translation stage; In this mode of operation, the at least one thin and elongated mirror and the interferometer means are moved relative to each other to provide a plurality of interferometer means. A surface normal perpendicular to the scanning direction, such that a selected one of the beams scans at least one thin and elongated mirror along at least one corresponding reference line extending along its longitudinal dimension. Generating at least one signal including information indicative of a local tilt of the reflecting surface along at least one corresponding reference line in at least one plane having a control means and extracting information contained in the at least one signal Signal and analysis means for determining the local shape of at least one thin and elongated mirror.

  In another aspect, the at least one signal further includes information indicating a position of the reflective surface in the at least one plane as a function of a scanning position along the at least one reference line.

  The structure, operation, and methodology of the present invention, together with other objects and advantages of the present invention, can be best understood by reading the detailed description in conjunction with the drawings. In the drawings, each part is assigned a number so that the part can be identified wherever the part appears in the various drawings.

(Detailed explanation)
Many embodiments of the invention are described herein. These embodiments are categorized into groups based on the type of information acquired about the reflective surface. In a first group of embodiments, a reference line on one reflecting surface or a reference line on each of two reflecting surfaces is determined with high spatial resolution. The two reflecting surfaces are substantially orthogonal to each other. In the second group of the embodiment, a pair of reference lines on one reflecting surface or a pair of reference lines on each of two reflecting surfaces is determined with high spatial resolution. The two reflecting surfaces are substantially orthogonal to each other. In a third group of embodiments, a pair of reference lines on the reflective surface and the associated local rotation of the reflective surface around the pair of reference lines, or a pair of reference lines and associated at each of the two reflective surfaces Local rotation is determined with high spatial resolution. The two reflecting surfaces are substantially orthogonal to each other. In a fourth group of embodiments, the combination of reference lines and associated local rotations in the three reflecting surfaces is determined with high spatial resolution. The three reflecting surfaces are substantially orthogonal to each other. In the group of the fourth embodiment, the measurement beam may be incident on the reflecting surface at an incident angle on the order of 45 degrees. Five different types of interferometers are used to measure linear and angular displacements of individual reflective surfaces in various embodiments and variations thereof.

  The accuracy of interferometric measurements of the displacement of an object including a reflective surface is generally unknown from the plane and from scanning and / or shearing the measurement beam across the reflective surface. It is influenced by deviation. Unexplained misalignment results from local displacement of the unexplained reflecting surface and local changes in the overall orientation of the reflecting surface. For this reason, some of the embodiments of the present invention are configured to measure the characteristics of the reference line within the reflective surface and the rotational characteristics of the reflective surface around the reference line.

The change measured in the relative phase of the components of the output beam of the interferometer is generally expressed as one or more terms of the form KLcos ² χ. Here, K is the wave number corresponding to the wavelength of the input beam to the interferometer, L is the physical length, for example, the distance from the interferometer to the measurement object, and χ is the component of the measurement beam. The angle formed with the measurement axis of the interferometer. If the stage orientation does not change substantially about an axis orthogonal to the measurement axis of the interferometer, the accuracy with which the associated chi changes need to be known is significantly relaxed and the relative phase Only the accuracy of the change is important. However, when there is a large systematic change in χ, for example 500 microradians due to pitch changes and stage yaw, the effect of deviating the reflecting surface from the plane can be significant. For example, consider an application where the stage position needs to be known to an accuracy of 0.1 nm (which may be required, for example, with EUV lithography tools). For a highly stable plane mirror interferometer (HSPMI) with values of L = 1 m and χ = 500 microradians, the accuracy that χ needs to be known is ≦ 50 nanoradians.

  Reference is now made to FIG. FIG. 1 shows a pair of orthogonally arranged interferometers that can characterize the shape of an elongated object mirror mounted on stage in situ with high spatial resolution along one or more reference lines. Or a schematic perspective view showing an interferometry system 15 using an interferometer subsystem. As shown in FIG. 1, the system 15 includes a stage 16. Stage 16 preferably forms part of a photolithography apparatus for making semiconductor products such as integrated circuits or chips. The stage 16 moves in a well-known reference coordinate system (schematically designated at 19), and is provided with a mount 21 for holding the photolithography wafer 23 and exposing it by the photolithography exposure unit 25. It has been. A thin high aspect ratio plane mirror 50 having a yz reflecting surface 51 elongated in the y direction is attached to the stage 16.

  Further, another thin high aspect ratio plane mirror 60 having an xz reflecting surface 61 elongated in the x direction is fixedly mounted on the stage 16. The mirrors 50 and 60 are mounted on the stage 16 so that their reflecting surfaces 51 and 61 are nominally orthogonal to each other. Stage 16 is otherwise mounted in a well-known manner to be nominally planar translation, but due to bearing and drive mechanism tolerances, x, y, and z Sometimes it goes through a small angle of rotation around the axis. In normal operation, the system 15 is configured to perform an operation that scans the set value x in the y direction.

  The interferometer (or interferometer subsystem) is fixedly mounted off-stage and is shown generally at 10. The purpose of the interferometer 10 is generally to measure the position of the stage 16 in the x direction and the angular rotation about the y and / or z axis as the stage 16 translates in the y direction, i.e., the reflective surface 51. And the angular rotation about the y and / or z axis as the stage 16 translates in the y direction. To do this, the interferometer 10 may be configured and arranged as one of many interferometry methods. For example, but not limited to, a plane mirror interferometer, a passive zero shear interferometer, or an active zero shear interferometer. For each type, the interferometric spectral beam travels along and along an optical path generally designated as 12 to and from mirror 50, as will be described in detail later as a separate embodiment.

  Another interferometer or interferometer subsystem 20, preferably the same type as that of interferometer 10, is fixedly mounted off-stage so that the position of stage 16 in the y direction and stage 16 translates in the y direction The angular rotation about the x and / or z axis is measured. To do this, the interferometer 20 sends and receives an interferometric spectral beam to and from the mirror surface 61 along an optical path generally designated as 22. Control, data processing, and housekeeping functions are preferably performed in a well-known manner by programming a multipurpose computer (e.g., specified at 17) to perform data processing and to transmit signals and data to the multipurpose computer and system 15. This is realized by exchanging between the two. Such exchange takes place via an interface schematically indicated by a two-way bold arrow.

  Reference is now made to FIG. Here, a first embodiment of the interferometers 10 and 20 is shown in the form of a plane mirror type, shown generally as 110, whose configuration consists of an elongated object mirror 50 mounted on-stage and The 60 shapes (represented by reference lines for each of the mirrors 50 and / or 60) can be characterized in situ. The configuration and arrangement of the interferometer 110 is adapted to measure changes in the average tilt and local tilt of the reflecting surface in the xy plane. The average slope is defined as the difference in distance in one direction, for example the x direction, relative to two distant positions on the reflective surface in the xy plane (separated by separating the two positions laterally). The

Interferometer 110 includes two high stability plane mirror interferometers (HSPMI) and an angular displacement interferometer. These are shown schematically in FIG. 2a as an integral optical assembly. Interferometer 110 will be described for operation as interferometer 10. It will be appreciated that interferometer 20 operates in a similar manner. The beam 134 includes two HSPMI measurement beams in contact with the reflective surface 51. The path of beam 134 corresponds to the path indicated by numeral 12 in FIG. The two HSPMIs measure changes in the displacements χ ₁ and χ ₁₀ of the reflecting surface 51 along the corresponding measurement axis. The displacements s ₁ and s _{10 in} FIG. 2a correspond to the displacements χ ₁ and χ ₁₀ respectively. The measured values of the displacements χ ₁ and χ ₁₀ are used to determine the displacement of the reflective surface 51 along the subsystem measurement axis, and the reflections associated with two points on the reflective surface 51 that are separated by a distance b _1. The average change in the orientation of the surface 51 is determined.

The change in local inclination of the reflecting surface 51 in the xy plane is determined by measuring the change in the direction of the beam once reflected by the reflecting surface 51. To do this, a portion of the reference / measurement beam of the χ ₁ measurement HSPMI is reflected as a beam 136 by the beam splitter BS2. A single optical path to the reflecting surface 51 is formed by the measurement beam component of the beam 136.

  The change in the propagation direction of the beam 136 is measured by the angular displacement interferometer 1010. FIG. 2 b schematically shows an angular displacement interferometer 1010. The explanation of the angular displacement interferometer 1010 is the same as that given for the angle interferometer in the following document. Commonly owned US Provisional Patent Application No. 60 / 351,496 (filed on Jan. 24, 2002), entitled "Interferometer for Measuring Changes in Optical Beam Direction" (Henri A. et al. Hill), currently included in US patent application Ser. No. 10 / 271,034 (filed Oct. 15, 2002). In addition, these content is taken in as a whole by reference in this specification. Other forms of angular displacement interferometers that may be incorporated into the first embodiment to measure changes in beam direction interferometrically without departing from the scope and spirit of the present invention are described in the following references: Are listed. Commonly owned U.S. Pat. Nos. 6,271,923 (granted on August 7, 2001) U.S. Patent Application Nos. 09 / 852,369 (filed May 10, 2001) and 2002 Published on Jan. 3, 2000 (Publication No. US-2002-01087), U.S. Patent Application No. 09 / 599,348 (filed on Jan. 20, 2000), U.S. Provisional Patent Application No. 60 / 201,457. (Filed on May 3, 2000), currently published US patent application Ser. No. 09 / 842,556 (filed on August 26, 2001) and published on March 21, 2002 (published) Number US-2002-0033951-A1). The contents of the commonly owned applications and patents cited are hereby incorporated by reference in their entirety.

  Other forms of double-pass plane mirror configurations, such as commonly owned US Provisional Patent Application No. 60 / 356,394 (filed on Feb. 12, 2002), title of invention “Multiple Degrees of Freedom Interferometer of Separating Beam” (Henri A. Hill), currently US patent application Ser. No. 10 / 364,300 (filed on Feb. 11, 2003), and paper, “Differential Interferometer Device Principles for Distance and Angle Measurements”. , Advantages and Applications "(C. Zanoni), VDI Berichte Nr. 749, 93-106 (1989) can also be incorporated into the first embodiment without departing from the scope and spirit of the present invention. The contents of the cited US Provisional Patent Application No. 60 / 356,394 and the article by Tsanoy are hereby incorporated by reference in their entirety.

  Input beam 132 includes two orthogonally polarized components of different frequencies. The input beam 132, for example a laser source 130, can be any of a variety of frequency modulators and / or a laser. Generation of the two frequency components of the input beam 132 can occur at the source 130, for example, by laser-Zeeman splitting, acousto-optic modulation, or inside a laser using a birefringent member. The reference and measurement beam components of beam 132 are polarized orthogonally and parallel to the plane of FIG. 2a, respectively.

  System 15 normally operates to measure y translation, but when operating in a special mirror characterization mode, the shape of mirror surface 51 is aligned along a reference line in its xy plane. Measure on the spot. In the mirror characterization mode, the stage 16 translates in the y direction, and the measurement beam of the interferometer 10 scans the mirror surface 51 along the reference line. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction plane in the xy plane, contributions due to variations in the translation mechanism that moves the stage 16, periodic non-linearity, and the interferometer 10 And a signal containing information indicative of the steady and unsteady effects of the gas in the measurement path of the 20 beams. The orientation of the stage 16 is preferably such that, in a special mirror characterization mode, the measured beam components of the two HSPMI output beams and the output beam of the angular displacement interferometer 1010 are nominally zero shear. Selected.

  Simultaneously with the translation of the stage 16 in the y direction, the orientation of the mirror 61 is monitored by the interferometer 20 with respect to a fixed intercept point of the measurement beam of the interferometer 20 with the reflecting surface 61. This step makes it possible to measure the rotation of the stage 16 due to the mechanical contribution of its translation mechanism (bearing, drive mechanism, etc.). Using this information, two signals are generated. The first signal is from the interferometer 10 and the information contained in the change in the combination of the angular orientation of the stage 16 and the local tilt along the reference line and the angular orientation and reference line of the stage 16 And a change in the combination of the average slopes of the reflecting surfaces 51 along. The second signal is from the interferometer 20 and the information contained relates to the angular orientation of the stage 16 as a function of the displacement in the y direction.

  Information regarding the local inclination on the reflecting surface 61 is not used when determining the characteristics of the reference line in the reflecting surface 51. This is because the position of the stage 16 has not changed in the x direction during scanning in the y direction.

The first and second signals are combined to obtain information about the average and local tilts of the mirror surface 51 along its reference line, i.e., <dx / dy> and (dx / dy) _local , respectively, in the electronic processor. Extracted by 180 and computer 182. Next, <dx / dy> and (dx / dy) _local are processed by electronic processor 180 and computer 182 using integral transformations of <dx / dy> and (dx / dy) _local to obtain xy The χ displacement X ₁ (y) of the reference line in the plane is obtained as a function of y. By the integral conversion of <dx / dy>, information on the spatial frequency spectrum of X ₁ (y) is obtained in a state where the sensitivity to the spatial frequency of the reference line≈1 / b ₁ and its harmonics is low. In addition, (dx / dy) _local integral conversion provides information on the spatial frequency of X ₁ (y) that cannot be determined from the integral transformation <dx / dy>. The reference line represents the deviation of the surface of the reflecting surface 51 from the straight line in the xy plane, but does not represent the orientation of the straight line in the xy plane.

An algorithm as an example of processing by the electronic processor 180 and the computer 182 for obtaining the displacement X ₁ (y) will be described. Algorithm _is designed to provide _X 1 measured value _{X M,} 1 (y) of the _X 1 (y) having the minimum value for variations of the respective Fourier spatial frequency components of (y). Information about the Fourier transform of X ₁ (y), ie, F {X ₁ (y)}, is obtained from the Fourier transform of <dx / dy> and (dx / dy) _{local and} is as follows:

ここで、Ｋは２π×空間周波数である。反射面５１と接触しているビームのサイズが有限である効果によって、空間周波数のバンド幅が、Ｆ｛Ｘ_１（ｙ）｝について得られる情報の１／ｄに制限される。ここでｄはビームの直径である。ビームのサイズが有限である効果は、簡単に方程式（１）および（２）に取り入れることができるが、アルゴリズムの重要な特徴を、本発明の範囲および趣旨から逸脱することなく簡単な方法で示すために、ここでは省略している。Ｆ｛Ｘ_１（ｙ）｝はＫの関数である。方程式（１）から、フーリエ変換Ｆ｛＜ｄｘ／ｄｙ＞｝は、空間周波数≒１／ｂ_１およびその高調波に関して感度が低いことが明らかである。

Here, K is 2π × spatial frequency. The effect of the finite size of the beam in contact with the reflecting surface 51 limits the spatial frequency bandwidth to 1 / d of the information obtained for F {X ₁ (y)}. Where d is the beam diameter. The effect of finite beam size can be easily incorporated into equations (1) and (2), but presents important features of the algorithm in a simple manner without departing from the scope and spirit of the invention. Therefore, it is omitted here. F {X ₁ (y)} is a function of K. From equation (1), it is clear that the Fourier transform F {<dx / dy>} is less sensitive with respect to spatial frequency≈1 / b ₁ and its harmonics.

The variations of F {X ₁ (y)} obtained by equations (1) and (2) are σ ₁ ² and σ ₂ ² respectively, for example the individual F {given by equations (1) and (2) X ₁ (y)} power spectrum analysis. An algorithm for processing by electronic processor 180 and computer 182 to obtain {X _{M, 1} (y)} is formally expressed as:

次に、Ｆ｛Ｘ_Ｍ，１（ｙ）｝の逆フーリエ変換を、電子プロセッサ１８０およびコンピュータ１８２によって行なって、Ｘ_Ｍ，１（ｙ）を得る。

Next, an inverse Fourier transform of F {X _{M, 1} (y)} is performed by electronic processor 180 and computer 182 to obtain X _{M, 1} (y).

The spatial frequency bandwidth of X _{M, 1} (y) is approximately 1 / d due to the effect that the size of the beam in contact with the reflecting surface 51 is finite.

The effect of periodic errors is corrected in determining the measured quantities <dx / dy> and (dx / dy) _local . Periodic error correction involves modulating the position of the stage 16 in the x and y directions during a scan in the y direction and filtering the first and second signals to eliminate the effects of periodic errors. And done. By modulating the stage position, in the frequency space, the components due to the periodic errors of the first and second signals are converted into the first and second signals representing the shape of the reflecting surface 51 and the information about the rotation of the stage 16. Separate from the main component. Thereafter, the main signal components are separated in the electronic processor 180 and the computer 182 by spectral analysis such as finite Fourier transform. The amplitude of the modulation in the x and y directions is small compared to the diameter of the measurement beam, but large enough to properly separate the main signal component and the signal component due to the periodic error.

  Examples of periodic error correction techniques that may be incorporated into the first embodiment without departing from the scope and spirit of the present invention are described in the following documents. Commonly owned US Provisional Patent Application No. 60 / 337,478 (filed on Nov. 5, 2001), title of invention "periodic error correction and resolution improvement" (Henri A. Hill), currently No. 10 / 287,898 (filed Nov. 5, 2002). These contents are incorporated herein by reference in their entirety.

  Other examples of periodic error correction techniques that may be incorporated into the first embodiment without departing from the scope and spirit of the invention are described in the following references. Commonly owned US Provisional Patent Application No. 60 / 303,299 (filed on Jul. 6, 2001), entitled "Interference Spectroscopy System Using Angular Differences in Propagation Between Orthogonally Polarized Input Beam Components" And method "(Henri A. Hill and Peter de Groot), currently US patent application Ser. No. 10 / 174,149, published Jan. 9, 2003, publication number. US-2003-0007156-A1). These contents are incorporated herein by reference in their entirety.

  Other examples of periodic error correction techniques that may be incorporated into the first embodiment without departing from the scope and spirit of the invention are described in the following references. Commonly owned US Provisional Patent Application No. 60 / 314,490 (filed Aug. 23, 2001), entitled “Inclined Interferometer” (Henri A. Hill), currently US Patent Application No. 10 / 218,965 (published February 27, 2003, publication number US-2003-0038947). These contents are incorporated herein by reference in their entirety.

  A periodic error correction technique that may be incorporated in the first embodiment without departing from the scope and spirit of the present invention is described, for example, in the following document. Commonly owned US Pat. No. 6,137,574, entitled “System and Method for Characterizing and Correcting Periodic Errors in Distance Measurement and Dispersive Interferometry”, US Pat. No. 6,252,668b1 Description, Title of Invention “System and Method for Quantifying Nonlinearity in Interferometric Spectroscopy Systems”, US Pat. No. 6,246,481 (Granted on June 12, 2001), Title of Invention “Systems and Methods for Quantifying Nonlinearity in Interferometric Spectroscopy Systems”. All three are Henry A. The contents of the three patents and patent applications cited above, by Hill, are hereby incorporated by reference in their entirety.

  The effects of steady and unsteady changes in gas in the measurement paths 12 and 22 are corrected in the first embodiment for the required end use application. Techniques for correction of stationary and non-stationary effects are the same as those described in the following documents. Commonly owned U.S. Provisional Patent Application No. 60 / 335,963 (filed on Nov. 15, 2001), title of invention "Standing non-random variation of gas refraction in interferometer and stationary random Correction for the Effect of Variation ", currently US patent application Ser. No. 10 / 294,158 (November 14, 2002), US provisional patent application No. 60 / 352,061 (January 24, 2002). No. 10 / 350,522 (January 24, 2003), now entitled "Non-dispersive method and apparatus for correction of gas turbulence effects in interferometry". Filed on). Both Henry A. The contents of both patent applications cited by Hill and cited are hereby incorporated by reference.

Thus, a change in the direction of the measurement beam component of the beam 136 of the interferometer 10 in the xy plane and a change in the difference x ₁₀ -x ₁ are measured and the contribution caused by the change in stage rotation to these changes. Reveals the periodic error, the effect of the gas in the measurement path, and the shape of the mirror surface 51 along the reference line in the xy plane with high spatial resolution, which is Can be determined while mounted in the environment.

  An important feature of the present invention is to measure the orientation change of the surface using a single beam interferometer, which includes all spatial frequencies below the cutoff frequency given by 1 / d. Is included. Where d is the diameter of the measurement beam in a single beam interferometer. Measuring the orientation change of the surface using only two double-path interferometers, for example two HSPMIs, the spatial wavelength equal to the measurement axis spacing of the two double-path interferometers (eg corresponding to b1 in FIG. 2a) and its harmonics All the spectral components of the spatial frequency having are lost, so that the complete shape of the reflecting surface cannot be reproduced.

  Next, a corresponding reference line is generated for the reflecting surface 61. This is done by scanning in the x direction and repeating the procedure described for generating the reference line on the reflective surface 51.

  In the case of end-use applications where only information about a single reflective surface, eg, a reference line within reflective surface 51, is required, a single optical path angle interferometer within interferometer 20 can be used from the scope and spirit of the present invention. It will be apparent to those skilled in the art that it can be omitted without departing. It will also be apparent to those skilled in the art that only a single reference line needs to be measured, and the second interferometer 20 may include, for example, other forms of angle measuring interferometers, such as the cited Tsanoy The type illustrated and described in the paper, and US patent application Ser. No. 09 / 842,556 (filed on Apr. 26, 2001), entitled “Dynamic Interferometer for Angle Measurement”, March 2002. That is, the angle-measuring interferometer type illustrated and described in publication on the 21st of the month (publication number US-2002-0033951-A1) can be included.

  An important feature of the first embodiment is that the interferometers 10 and 20 are each integrated optical assemblies, which can contribute to increased interferometer stability with respect to measurement accuracy and compact design.

  An important advantage of the first embodiment is that the special mirror characterization mode of the first embodiment can be used as part of an in-process wafer procedure that does not compromise the throughput of the lithography tool. It may be incorporated into the processing. Specifically, the first and second signals can be obtained because the conditions for a special mirror characterization mode are satisfied during a series of in-process wafer procedures, after which x -When used to determine the shape of mirror surfaces 51 and 61 with high spatial resolution along the reference line in the y plane. The above conditions are such that the stage orientation 16 for a particular mirror characterization mode is such that the measured beam components of the two HSPMI output beams and the output beam of the angular displacement interferometer 1010 are nominally zero shear. It is a thing. The condition needs to be met only for a small subset of time used in processing the wafer to maintain effective in-process mirror characterization. As a further result, the change in shape represented by the reference surfaces of the reflective surfaces, eg 51 and 61, with respect to time may be monitored in-situ without compromising the throughput of the lithography tool.

  The first embodiment includes thin, elongated, high aspect ratio mirrors 50 and 60 attached to stage 16, each of two mirrors 50 and 60 having a single planar reflective surface 51 and 61. Respectively. Other forms of object mirrors may be incorporated into the first embodiment without departing from the scope and spirit of the present invention. Another example is a thin and elongated high aspect ratio Porro prism, for example, as described in the following document. Commonly owned US Pat. No. 6,163,379 (granted on Dec. 19, 2000), entitled “Interferometer with inclined waveplate to reduce ghost reflection” (Peter de Grouse). This content is incorporated herein by reference in its entirety.

  A second embodiment of the interferometers 10 and 20 is a passive zero shear type, more specifically a zero differential shear type, schematically shown as 210 in FIG. The shape of the elongated object mirrors 50 and / or 60 mounted on-stage (represented by a reference line for each of the mirrors 50 and / or 60) can be characterized in situ with high spatial resolution. Yes. Interferometer 210 is configured and arranged to measure the change in average tilt of the reflective surface and the change in average local tilt in the xy plane. The average slope is defined as the difference in distance in one direction, for example the x direction, to two separate positions on the reflective surface in the xy plane (separated by separating the two positions laterally). The The average local slope is defined as the average of the local slopes measured at two remote locations in the xy plane.

  Interferometer 210 includes HSPMI for measuring linear displacement and a high stability plane mirror interferometer for measuring the average angular displacement of mirror 50 in an integrated optical assembly. Although interferometer 210 is described for operation as interferometer 10, it is understood that interferometer 20 operates in a similar manner. The input beam to the linear displacement interferometer is part of the output beam of the angular displacement interferometer and is expanded by a factor of two by the afocal lens system AF, and is linear regardless of the change in the orientation of the mirror 50. The direction of the measurement beam of the displacement interferometer is orthogonal to the reflecting surface 51. When the surface 51 changes its orientation by an angle α, the direction of the beam reflected by 51 changes by an angle 2α. When this reflected beam passes through the afocal system and the beam is spread twice, the change in direction of the transmitted beam is reduced from 2α to α. That is, the angle between the transmitted beam and the reflecting surface 51 is a constant that does not relate to the direction 51, and therefore can be designed to be 90 degrees. AF is for afocal. The output beam of the angular displacement interferometer has zero differential shear between the individual reference and measurement beam components. As a result, the differential beam shear between the linear displacement interferometer reference and the measured output beam components is zero. That is, the input beam to the linear displacement interferometer is conditioned to achieve a highly desirable zero differential beam shear condition, which reduces non-periodic non-linear errors.

Beams 234 include linear and angular displacement interferometer measurement beams that contact reflective surface 51. The path of beam 234 corresponds to the path indicated by numeral 12 in FIG. Changes in χ ₂ and θ ₂ of the reflective surface 51 are measured by linear and angular displacement interferometers, respectively. Linear displacement ₂ of Figure 2c corresponds to the displacement chi _2. The angle θ ₂ represents the average angular orientation of the reflecting surface 51 in xy and in the plane of FIG. 2c. The measured values of the displacements χ ₂ and θ ₂ are used to determine the displacement of the reflective surface 51 along the system measurement axis, and the reflective surfaces associated with two points on the reflective surface 51 that are separated by a distance b _2. The average change in 51 orientations is determined. Θ ₂ is also equal to the average slope associated with the two points in the xy plane.

  The average local tilt change of the reflecting surface 51 in the xy plane is determined by measuring the change in beam direction, and the beam reference and the measured beam component are once reflected by the reflecting surface 51. . To do this, a portion of the reference / measurement beam of the angular displacement interferometer is reflected as a beam 236 by the beam splitter BS1. A single optical path to the reflecting surface 51 is formed by each of the reference of the beam 236 and the measurement beam component. The reference and measurement beam components of beam 236 have zero differential shear. This is because, as described above, the differential beam shear of the output beam of the angular displacement interferometer is zero.

  The change in the average propagation direction of the components of the beam 236 is measured by an angular displacement interferometer 1010 shown schematically in FIG. Beam 236 is incident on interferometer 1010. The output beam contains information about the average propagation direction of the reference of the beam 236 and the measurement beam component in the plane of FIG. 2c, and thus the average of the local tilt of the reflective surface 51 at two positions separated by b2 in the x direction. Information is included. Information regarding the average tilt and average local tilt is obtained by the electronic processor 280 and computer 282 from the electrical interference signals generated by the average angular displacement interferometer and detectors in the interferometer 1010.

  System 15 typically operates to measure y translation, but when operating in a special mirror characterization mode, the shape of mirror surface 51 is aligned along a reference line in its xy plane. Measure on the spot. In the mirror characterization mode, the stage 16 translates in the y direction, and the measurement beam of the interferometer 10 scans the mirror surface 51 along the reference line. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction plane in the xy plane, contributions due to variations in the translation mechanism that moves the stage 16, periodic non-linearity, and the interferometer 10 And a signal containing information indicative of the steady and unsteady effects of the gas in the measurement path of the 20 beams.

  Simultaneously with the translation of the stage 16 in the y direction, the orientation of the mirror 61 is monitored by the interferometer 20 with respect to a fixed intercept point of the measurement beam of the interferometer 20 with the reflecting surface 61. This step makes it possible to measure the rotation of the stage 16 due to the mechanical contribution of its translation mechanism (bearing, drive mechanism, etc.). Using this information, two signals are generated. The first signal is from the interferometer 10 and the information contained therein is a change in the combination of the angular orientation of the stage 16 and the average local tilt of the xy plane of the reflective surface 51 and the stage 16. And the change in the combination of the average inclination in the xy plane of the reflecting surface 51 along the reference line. The second signal is from the interferometer 20 and the information contained relates to the angular orientation of the stage 16 as a function of the displacement in the y direction.

  Information regarding the average local inclination on the reflection surface 61 and the average inclination is not used when determining the characteristics of the reference line in the reflection surface 51. This is because the position of the stage 16 has not changed in the x direction during scanning in the y direction.

In electronic processor 280 and computer 282, the first and second signals are combined to produce an average tilt and an average local tilt of mirror 51 along its reference line in the xy plane, i.e., <dx / Extract information for each of dy> and (dx / dy) _local . Next, <dx / dy> and (dx / dy) _local are processed by electronic processor 280 and computer 282 using the integral transformation of <dx / dy> and (dx / dy) _local to obtain xy The χ displacement X ₂ (y) of the reference line in the plane is obtained as a function of y. By the integral conversion of <dx / dy>, information about the spatial frequency spectrum of X ₂ (y) is obtained in a state where the spatial frequency of the reference line≈1 / b ₂ and its sensitivity to harmonics is low. Also, the integral transformation (dx / dy) _local provides information about the spatial frequency of X ₂ (y) with a low sensitivity to the spatial frequency of the reference line≈1 / (2b ₂ ) and its odd harmonics. . The reference line represents the deviation of the surface of the reflecting surface 51 from the straight line in the xy plane, but does not represent the orientation of the straight line in the xy plane.

An algorithm as an example of processing by the electronic processor 280 and the computer 282 for obtaining the displacement X ₂ (y) will be described. Algorithm is designed to provide X 2 measurements X _{M, 2} of X _{2 (y)} having the minimum value for variations of the respective Fourier spatial frequency components of _{(y) ().} Information about the Fourier transform of X ₂ (y), ie F {X ₂ (y)}, is obtained from the Fourier transform of <dx / dy> and (dx / dy) _{local and} is as follows:

反射面５１と接触しているビームのサイズが有限である効果によって、空間周波数のバンド幅が、Ｆ｛Ｘ_２（ｙ）｝について得られる情報の１／ｄに制限される。ここでｄはビームの直径である。ビームのサイズが有限である効果は、簡単に方程式（４）および（５）に取り入れることができるが、アルゴリズムの重要な特徴を、本発明の範囲および趣旨から逸脱することなく簡単な方法で示すために、ここでは省略している。方程式（４）および（５）から、フーリエ変換Ｆ｛＜ｄｘ／ｄｙ＞｝は、空間周波数≒１／ｂ_１およびその高調波に関して感度が低いこと、およびフーリエ変換Ｆ｛＜（ｄｘ／ｄｙ）_{ｌｏｃａｌ}＞｝は、空間周波数≒１／（２ｂ_２）およびその奇数の高調波に関して感度が低いことが、明らかである。

The effect of the finite size of the beam in contact with the reflecting surface 51 limits the spatial frequency bandwidth to 1 / d of the information obtained for F {X ₂ (y)}. Where d is the beam diameter. The effect of finite beam size can be easily incorporated into equations (4) and (5), but presents important features of the algorithm in a simple manner without departing from the scope and spirit of the invention. Therefore, it is omitted here. From equations (4) and (5), the Fourier transform F {<dx / dy>} is less sensitive with respect to the spatial frequency≈1 / b ₁ and its harmonics, and the Fourier transform F {<(dx / dy) It is clear that _local >} is less sensitive with respect to spatial frequency≈1 / (2b ₂ ) and its odd harmonics.

The variations of F {X ₂ (y)} obtained by equations (4) and (5) are σ ₃ ² and σ ₄ ² respectively, for example the individual F {given by equations (4) and (5) X ₂ (y)} power spectrum analysis. An algorithm for processing by electronic processor 280 and computer 282 to obtain {X _{M, 2} (y)} is formally expressed as:

次に、Ｆ｛Ｘ_Ｍ，２（ｙ）｝の逆フーリエ変換を、電子プロセッサ１８０およびコンピュータ１８２によって行なって、Ｘ_Ｍ，２（ｙ）を得る。

Next, an inverse Fourier transform of F {X _{M, 2} (y)} is performed by electronic processor 180 and computer 182 to obtain X _{M, 2} (y).

The spatial frequency bandwidth of X _{M, 2} (y) is approximately 1 / d due to the effect that the size of the beam in contact with the reflecting surface 51 is finite.

Interferometer 210 zero differential beam shear characteristics [differential beam shear refers only to the beam shear of one beam relative to the other, where both beams are sheared by the same amount in the same direction. Is the result of measuring the average tilt and beam conditioning using a single optical path interferometer, but with zero differential beam shear characteristics, The amplitude of the periodic error in the electrical interference signal generated by each of the three interferometers is reduced. However, the remaining effects of periodic errors are corrected in determining the measured quantities <dx / dy> and (dx / dy) _local if necessary in the end use application of the second embodiment. The description of the technique used to correct the remaining effects of the periodic error is the same as the corresponding part of the description given in the first embodiment.

  The effects of steady and unsteady changes in gas in the measurement paths 12 and 22 are corrected in the second embodiment for the required end use application. The description of the technique used to correct the effects of steady and non-stationary changes in gas in the measurement paths 12 and 22 is the same as the corresponding part of the description given in the first embodiment.

  Next, a corresponding reference line is generated for the reflecting surface 61. This is done by scanning in the x direction and repeating the procedure described for generating the reference line on the reflective surface 51.

  The advantages of the second embodiment are the constraints on the angular orientation of the stage 16 (eg encountered in the first embodiment of the present invention) as a result of the zero differential shear feature of the output beam of the interferometer in the second embodiment. There is no such thing. In the first embodiment, the orientation of the stage 16 is preferably such that the beam shear of the measurement beam component of the output beam of the interferometer used to measure the local tilt change is not nominal. It was. This constraint exists in the first embodiment in order to obtain an optimal electrical interference signal with respect to amplitude from the angle interferometer used to measure the local tilt.

  Another advantage of the second embodiment is that, as a further result of the feature that the differential shear is zero and no restriction on the angular orientation of the stage 16, the mirror characterization mode of the second embodiment is The wafer processing may be incorporated as part of an in-process wafer procedure that does not compromise the throughput of the lithography tool. As a further result, changes in the shape of the reflective surfaces, eg 51 and 61, over time may be monitored in-situ without compromising the throughput of the lithography tool.

  Another advantage of the second embodiment is that the measured average slope and measured average local slope are at a spatial frequency that is two times higher than in the case of a change in linear displacement measured by HSPMI. It is to include information. This is a result of the difference in beam diameter for the angular displacement interferometer and HSPMI.

  An important feature of the second embodiment is that the interferometers 10 and 20 are each integrated optical assemblies, which can contribute to increased interferometer stability with respect to measurement accuracy and compact design.

  The remaining description of the second embodiment is the same as the corresponding portion of the description given in the first embodiment of the present invention.

  A variation of the second embodiment of interferometers 10 and 20 is a passive zero shear type, more specifically a zero differential shear type. This is shown schematically in FIG. 2d as 1210, the configuration of which is the shape of elongated object mirrors 50 and 60 mounted on stage (represented by a reference line for each of mirrors 50 and 60). Can be characterized on the spot with high spatial resolution. The difference of the second embodiment from the second embodiment is that information about local angular displacement is generated. In a variation of the second embodiment, changes in local angular displacement are measured, and in the second embodiment, changes in average local angular displacement are measured. As will be described later, the special mirror characterization mode used in the modification of the second embodiment is the same as the special mirror characterization mode of the first embodiment.

  The modified interferometers 10 and 20 of the second embodiment include many elements having the same element numbers as the elements of the second embodiment. Elements with the same element number perform similar functions. The change in local inclination of the reflecting surface 51 in the xy plane is determined by measuring the change in the direction of the beam once reflected by the reflecting surface 51. To do this, a portion of the reference / measurement beam of the angular displacement interferometer is transmitted as beam 1236 by beam splitter BS3. A single optical path to the reflecting surface 51 is formed by the measurement beam component of the beam 1236.

  The change in beam propagation direction 1236 is measured by an angular displacement interferometer 1010 as shown in FIG. 2d. FIG. 2 b schematically shows an angular displacement interferometer 1010.

  System 15 normally operates to measure y translation, but when operating in a special mirror characterization mode, it measures the shape of mirror surface 51 in-situ along its reference line. In the mirror characterization mode, the stage 16 translates in the y direction, and the measurement beam of the interferometer 10 scans the mirror surface 51 along the reference line. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction plane in the xy plane, contributions due to variations in the translation mechanism that moves the stage 16, periodic non-linearity, and the interferometer 10 And a signal containing information indicative of the steady and unsteady effects of the gas in the measurement path of the 20 beams.

  The orientation of stage 16 is preferably selected such that, in a special mirror characterization mode, the measured beam component of the input beam to angular displacement interferometer 1010 is nominally zero shear.

  As with the first embodiment of the present invention, a variation in local slope and a change in average slope are measured by a modification of the second embodiment. As a result, the remaining description of the modification of the second embodiment is the same as the corresponding part of the description given in the first embodiment.

  An important advantage of the second embodiment variant is that the special mirror characterization mode of the second embodiment variant is part of an in-process wafer procedure that does not impair the throughput of the lithography tool. As such, it may be incorporated into wafer processing. In particular, the first and second signals can be obtained when the conditions for a special mirror characterization mode are satisfied during a subset of the time used during wafer processing, after which , When used to determine the shape of the mirror surfaces 51 and 61 with high spatial resolution along the reference line in the xy plane. The conditions described above are such that the stage orientation 16 for a particular mirror characterization mode is such that the measured beam component of the input beam to the angular displacement interferometer 1010 is nominally zero shear. It is. The condition needs to be met only for a small subset of time used in processing the wafer to maintain effective in-process mirror characterization. As a further result, the change in shape represented by the reference surfaces of the reflective surfaces, eg 51 and 61, with respect to time may be monitored in-situ without compromising the throughput of the lithography tool.

  An important feature of the second embodiment variant is that the interferometers 10 and 20 are each integrated optical assemblies, which can contribute to increased stability of the interferometer with respect to measurement accuracy and compact design. is there.

  A third embodiment of interferometers 10 and 20 includes an active zero shear type interferometer. This is shown schematically in FIG. 2e as 310, the configuration of which is the shape of elongated object mirrors 50 and 60 mounted on stage (represented by a reference line for each of mirrors 50 and 60). Can be characterized on the spot with high spatial resolution. The configuration and arrangement of the interferometer 310 is adapted to measure changes in the average tilt and local tilt of the reflecting surface in the xy plane. The average slope is defined as the difference in distance in one direction, for example the x direction, relative to two distant positions on the reflective surface in the xy plane (separated by separating the two positions laterally). The

  Interferometer 310 includes two active zero shear plane mirror interferometers. Interferometer 310 will be described for operation as interferometer 10. The active zero shear interferometer used in the third embodiment is the same as the active zero shear interferometer described in the following document. No. 60 / 356,393 (filed on Feb. 12, 2002), commonly owned U.S. Provisional Patent Application No. 60/356, filed earlier, entitled “Dynamic Beam Redirecting Input Measurement Beam Component and Output Reference Beam Component”. Interferometer with steering member "(Henry A. Hill), currently US patent application Ser. No. 10 / 364,666 (filed on Feb. 11, 2003). This document is incorporated herein by reference in its entirety. As described in that application, the beam steering capability provided by the beam steering mirror is used to maintain the beam on a path perpendicular to the measurement object mirror by feedback or feed forward signals. Here, information regarding the orientation of the mirror 50 obtained by the interferometer 10 is used in the feed forward mode. Other forms of active zero shear interferometers may be incorporated into the third embodiment without departing from the scope and spirit of the present invention. For example, it is described in the following literature. PCT patent application (filed on May 5, 2000), title of invention “Interferometric Spectroscopy System with Dynamic Beam Steering Assembly for Measuring Angles and Distances”, published on November 19, 2000 ( Publication No. 00/66969), US Provisional Patent Application No. 60 / 201,457 (filed on May 3, 2000), title of the invention "Apparatus for measuring and / or controlling the differential path of a light beam" And method ", currently US patent application Ser. No. 09 / 842,556, published March 21, 2002 (publication number US-2002-0033951), US provisional patent application 60 / 314,570. (Filed on August 23, 2001), title of invention "Dynamic Interferometer Controlling Direction of Input Beam", currently US patent application Ser. No. 10 / 226,591. Specification, published on March 6, 2003 (Publication No. US-2003-0043384). The three applications are Henry A. Hill's name, which is incorporated herein by reference in its entirety.

The beam 334 includes two zero shear interferometer measurement beams that contact the reflective surface 51. The path of beam 334 corresponds to the path indicated by numeral 12 in FIG. Two zero shear interferometers measure the changes in displacements χ ₃ and χ ₃₀ along the corresponding measurement axis of the reflective surface 51, respectively. Displacement s3 and s30 in FIG. 2e corresponds to the displacement chi ₃ and chi _30. The measured values of the displacements χ ₃ and χ ₃₀ are used to determine the displacement of the reflective surface 51 along the subsystem measurement axis, and 2 on the reflective surface 51 separated by a distance b ₃ in the xy plane. The average change in orientation of the reflective surface 51 associated with one point is determined.

A change in local inclination of the reflecting surface 51 in the xy plane is determined by measuring a change in the beam direction once reflected by the reflecting surface 51. To do this, a portion of the output beam of an active zero shear interferometer that measures χ ₃ is reflected as beam 336 by beam splitter BS4. A single optical path to the reflecting surface 51 is formed by the measurement beam component of the beam 336.

  The change in the propagation direction of the beam 336 is measured by an angular displacement interferometer 1010 shown schematically in FIG. As a result of using an active zero shear interferometer, the differential beam shear between the reference and measurement beam components of beam 336 is zero, and the beam shear is reduced for each of the components of beam 336. The remaining description of the third embodiment for the angular displacement interferometer measurement is the same as the corresponding portion of the description made for the angular displacement interferometer measurement in the first and second embodiments. Reference may be made to FIG. FIG. 2f shows a schematic exploded perspective view of the central subassembly of FIG. 2e, including PBS, prism, and polo prism. FIG. 2g shows the path of travel as beam b1 propagates through one branch of the subassembly of FIG. 2f to one of two distinct locations on the mirror.

  System 15 normally operates to measure y translation, but when operating in a special mirror characterization mode, the shape of mirror surface 51 is aligned along a reference line in its xy plane. Measure on the spot. In the mirror characterization mode, the stage 16 translates in the y direction, and the measurement beam of the interferometer 10 scans the mirror surface 51 along the reference line. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction plane in the xy plane, contributions due to variations in the translation mechanism that moves the stage 16, periodic non-linearity, and the interferometer 10 And a signal containing information indicative of the steady and unsteady effects of the gas in the measurement path of the 20 beams.

  Simultaneously with the translation of the stage 16 in the y direction, the orientation of the mirror 61 is monitored by the interferometer 20 with respect to a fixed intercept point of the measurement beam of the interferometer 20 with the reflecting surface 61. This step makes it possible to measure the rotation of the stage 16 due to the mechanical contribution of its translation mechanism (bearing, drive mechanism, etc.). Using this information, two signals are generated. The first signal is from the interferometer 10 and the information contained therein is a change in the combination of the angular orientation of the stage 16 and the local tilt of the reflective surface 51 in the xy plane, and the stage 16. And a change in the combination of the average inclination in the xy plane of the reflecting surface 51. The second signal is from the interferometer 20 and the information contained relates to the angular orientation of the stage 16 as a function of the displacement in the y direction.

  Information regarding the local inclination and the average inclination on the reflecting surface 61 is not used when determining the characteristics of the reference line in the reflecting surface 51. This is because the position of the stage 16 has not changed in the x direction during scanning in the y direction.

The first and second signals are processed by electronic processor 380 and computer 382 to obtain an average and local tilt of mirror 51 along its reference line in the xy plane, i.e. <dx / dy>. And information for each of (dx / dy) _local . Next, <dx / dy> and (dx / dy) _local are processed by electronic processor 380 and computer 382 using the integral transformation of <dx / dy> and (dx / dy) _local to obtain xy In-plane χ displacement X ₃ (y) of the reference line is obtained as a function of y. The description of the processing in the third embodiment is the same as that described for the corresponding processing in the first embodiment. The reference line represents the deviation of the surface of the reflecting surface 51 from the straight line in the xy plane, but does not represent the orientation of the straight line in the xy plane.

The advantage of the third embodiment is that the effect of periodic errors is generally reduced as a result of using an active zero shear interferometer. However, the remaining effects of periodic errors are corrected in determining the measured quantities <dx / dy> and (dx / dy) _local in the third embodiment, if necessary for end-use applications. The description of the technique used to correct the remaining effects of the periodic error is the same as the corresponding part of the description given in the first embodiment.

  The effects of steady and non-stationary changes in gas in the measurement paths 12 and 22 are corrected in the third embodiment for the required end use application. The description of the technique used to correct the effects of steady and non-stationary changes in gas in the measurement paths 12 and 22 is the same as the corresponding part of the description given in the first embodiment.

  Next, a corresponding reference line is generated for the reflecting surface 61. This is done by scanning in the x direction and repeating the procedure described for generating the reference line on the reflective surface 51.

  The advantage of the third embodiment is that, as a result of the zero shear feature of the output beam of the interferometer in the third embodiment, constraints on the angular orientation of the stage 16 (eg encountered in the first embodiment of the present invention). There is no such thing. In the first embodiment, the orientation of the stage 16 is preferably such that the beam shear of the measurement beam component of the output beam of the interferometer used to measure the local tilt change is not nominal. It was. This constraint exists in the first embodiment and in a variant of the second embodiment that is optimal electrical interference with respect to amplitude from the angle interferometer used to measure the local tilt. This is to obtain a signal.

  Another advantage of the third embodiment is that, as a result of the zero shear feature and the absence of constraints on the angular orientation of the stage 16, the mirror characterization mode of the third embodiment can be used for wafer processing. In addition, it may be incorporated as part of an in-process wafer procedure that does not compromise the throughput of the lithography tool. As a further result, changes in the shape of the reflective surfaces, eg 51 and 61, over time may be monitored in-situ without compromising the throughput of the lithography tool.

  Two active zero shear and angular displacement interferometers 1010 in interferometers 10 and 20 include the integrated optical assembly in the third embodiment. This is an important feature of the third embodiment that using an integrated optical assembly contributes to increased stability of the interferometers 10 and 20 with respect to measurement accuracy and compact design.

  The remaining description of the third embodiment is the same as the corresponding portion of the description given in the first and second embodiments of the present invention.

  In the first three embodiments of the present invention, the reference lines are determined with high spatial resolution in the xy plane on the surfaces of the reflecting surfaces 51 and 61. In the next three embodiments of the present invention, in each of the reflective surfaces 51 and 61, a pair of reference lines with high spatial resolution in the xy plane makes the stage 16 orthogonal to the xy plane, that is, the z axis. Without being scanned or displaced along.

  The fourth embodiment of the interferometers 10 and 20 is a plane mirror type. This is shown schematically in FIG. 3a as 410, the configuration of which is represented by the shape of elongated object mirrors 50 and 60 mounted on stage (a pair of reference lines for each of mirrors 50 and 60). Can be characterized in situ with high spatial resolution in the two xy planes. The reference line pair is in the reflective surfaces 51 and 61.

The interferometer subsystem 410 shown schematically in FIGS. 3a and 3b includes two interferometer subsystems. Each of the two interferometer subsystems is the same as the interferometer subsystem 110 of the first embodiment. Two interferometer subsystems, the distance b ₅ only are separated in the z-direction, it is combined in layers in the optical assembly integrated. The same numbered elements in FIGS. 3a and 3b represent a single element of sufficient size to perform a similar function in FIGS. 3a and 3b, thus reducing the number of parts and the integrated optical assembly. This is one of the causes. Two interferometer subsystems measure changes in the displacements x ₄ and x ₄₀ and the displacements x ₁₀₄ and x ₁₄₀ of the reflecting surface 51 along the corresponding measurement axis. The displacements x ₄ and x ₄₀ and the displacements x ₁₀₄ and x ₁₄₀ correspond to the displacements s ₄ and s ₄₀ and the displacements s ₁₀₄ and s ₁₄₀ in FIGS. 3a and 3b, respectively.

Displacement _{x 4} and _{x 40} are in one the x-y plane within Figure 3a. The displacements x ₁₀₄ and x ₁₄₀ are in the second xy plane of FIG. 3b. The first and second xy planes are separated by a distance b _{5 in the} z direction. Using the measured values of the displacement _{x 4} and _{x 40} and the displacement _{x 104} and _{x 140,} to determine the displacement of the reflective surface 51 along the subsystem measurement axes are separated by a distance _{b 5} in the z-direction. Using the difference between the displacement _{x 4} and _{x 40} and a measurement of the difference of the displacement _{x 104} and _{x 140,} to determine the slope of the average of the first and second respective the x-y plane within the reflecting surface 51 at the . The definition of average slope in the fourth embodiment is the same as the definition of average slope given in the first embodiment of the present invention. A change in the local inclination of the reflecting surface 51 in the first and second xy planes in the directions of the two beams once reflected at positions separated by the distance b ₅ by the reflecting surface 51 respectively. Determine by measuring the change.

  System 15 normally operates to measure y translation, but when operating in a special mirror characterization mode, it measures the shape of mirror surface 51 in-situ along its reference line. In a special mirror characterization mode, the stage 16 translates in the y direction and the measurement beam of the interferometer 10 scans the mirror surface 51 along a pair of reference lines spaced in the z direction. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction surface in the first and second xy planes, the contribution due to the variation in the translation mechanism that moves the stage 16 and the periodic nonlinearity A signal is generated that includes information indicating the characteristics and the steady and non-stationary effects of the gas in the measurement path of the beams of the interferometers 10 and 20. The orientation of stage 16 is preferably in a special mirror characterization mode, where the measured beam components of the four HSPMI output beams and the input beams to the two angular displacement interferometers 1010 are nominally zero shear. Selected to be.

  Simultaneously with the translation of the stage 16 in the y direction, the orientation of the mirror 61 is monitored by the interferometer 20 with respect to a fixed intercept point of the measurement beam of the interferometer 20 with the reflecting surface 61. This step makes it possible to measure the rotation of the stage 16 due to the mechanical contribution of its translation mechanism (bearing, drive mechanism, etc.). Using this information, two signals are generated. The first signal is from the interferometer 10 and changes in the combination of the angular orientation of the stage 16 and the local tilt of the reflecting surface 51 and the reflection along the angular orientation of the stage 16 and the two reference lines. It includes a set of four signals related to changes in the combined average slope of the surface 51. The second signal is from the interferometer 20 and the information contained relates to the angular orientation of the stage 16 as a function of the displacement in the y direction.

Information regarding the local inclination on the reflecting surface 61 is not used when determining the characteristics of the two reference lines in the reflecting surface 51. This is because the position of the stage 16 has not changed in the x direction during scanning in the y direction. The first and second signals are processed by electronic processor 480 and computer 482 to obtain the average tilt and local tilt of mirror 51 along the two reference lines. That is, <dx / dy> ₄ and ((dx / dy) _local ) ₄ (each along one of the baselines), and <dx / dy> ₅ and ((dx / dy) _local ) ₅ (respectively Along the second of the two reference lines). Next, <dx / dy> ₄ , ((dx / dy) _local ) ₄ , <dx / dy> ₅ , and ((dx / dy) _local ) ₅ are converted into <dx / dy> _local in electronic processor 480 and computer 482. / Dy> ₄ , ((dx / dy) _local ) ₄ , <dx / dy> ₅ , and ((dx / dy) _local ) ₅ using the integral transformation to process the first and second x− Obtain χ displacements X ₄ (y) and X ₄₀ (y) of two reference lines in the y plane as a function of y. The description of the processing in the fourth embodiment is the same as that described for the corresponding processing in the first embodiment.

If the effect of periodic error is necessary in the end use application of the fourth embodiment, <dx / dy> ₄ , ((dx / dy) _local ) ₄ , <dx / dy> ₅ , and (( dx / dy) _local ) is corrected in determining ₅ . The description of the technique used to correct the effect of the periodic error is the same as the corresponding part of the description given in the first embodiment.

  The effects of steady and unsteady changes in gas in the measurement paths 12 and 22 are corrected in the fourth embodiment for the required end use application. The description of the technique used to correct the effects of steady and non-stationary changes in gas in the measurement paths 12 and 22 is the same as the corresponding part of the description given in the first embodiment.

  The advantage of the fourth embodiment is that the shape of the two reference lines in the reflecting surface of the stage mirror can be determined without having to scan or displace the stage 16 in the z direction.

  An important feature of the fourth embodiment is that the interferometers 10 and 20 are each integrated optical assemblies, which can contribute to increased interferometer stability with respect to measurement accuracy and compact design.

  The remaining description of the fourth embodiment is the same as the corresponding part of the description given in the first embodiment of the present invention.

  The fifth embodiment of the interferometers 10 and 20 is a zero differential shear type. This is shown schematically as 510 in FIGS. 3c and 3d, which configuration is the shape of the elongated object mirrors 50 and 60 mounted on stage (a pair of reference lines for each of mirrors 50 and 60). Can be characterized in situ with high spatial resolution in the two xy planes. The reference line pair is in the surface of the reflecting surfaces 51 and 61.

The interferometer subsystem 510 shown schematically in FIGS. 3c and 3d includes two interferometer subsystems. Each of the two interferometer subsystems is the same as the interferometer subsystem 210 of the second embodiment. The two interferometer subsystems are separated in the z-direction by a distance b ₇ and are combined as a stack in an integrated optical assembly. The same numbered elements in FIGS. 3c and 3d represent a single element of sufficient size to perform a similar function in FIGS. 3c and 3d, thus reducing the number of parts and reducing the integral optical assembly. Contributes to the composition. Changes in the displacements χ ₅ and χ ₅₀ of the reflective surface 51 along the subsystem measurement axis of the reflective surface in two xy planes separated by a distance b _{7 in} FIGS. 3c and 3d by the interferometer subsystem, Changes in average slope <dx / dy> ₅ and <dx / dy> ₅₀ , and changes in average local slope <(dx / dy) _local > ₅ and <(dx / dy) _local > ₅₀ are measured. The The displacements χ ₅ and χ ₅₀ correspond to the displacements s ₅ and s ₅₀ in FIGS. 3c and 3d, respectively. The displacement χ ₅ , the average slope <dx / dy> ₅ , and the average local slope <(dx / dy) _local > ₅ are in one xy plane of FIG. 3c. The displacement χ ₅₀ , the average slope <dx / dy> ₅₀ , and the average local slope <(dx / dy) _local > ₅₀ are in the second xy plane of FIG. 3d. The first and second xy planes are separated by a distance b _{7 in the} z direction. The definitions of mean slope and mean local slope are the same as the corresponding definitions of mean slope and mean local slope given in the second embodiment of the invention.

Changes in the average local inclination of the reflecting surface 51 in the xy plane are reflected in the direction of the reference and measurement beams once reflected by the reflecting surface 51 at positions separated by a distance b _{6 in the} y direction. Determine by measuring the change.

  System 15 typically operates to measure y translation, but when operating in the mirror characterization mode, it measures the shape of mirror surface 51 in situ along its pair of reference lines. In the mirror characterization mode, the stage 16 translates in the y direction and the measurement beam of the interferometer 10 scans the mirror surface 51 along a pair of reference lines separated in the z direction. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction plane in the xy plane, contributions due to variations in the translation mechanism that moves the stage 16, periodic non-linearity, and the interferometer 10 And a signal containing information indicative of the steady and unsteady effects of the gas in the measurement path of the 20 beams.

  Simultaneously with the translation of the stage 16 in the y direction, the orientation of the mirror 61 is monitored by the interferometer 20 with respect to a fixed intercept point of the measurement beam of the interferometer 20 with the reflecting surface 61. This step makes it possible to measure the rotation of the stage 16 due to the mechanical contribution of its translation mechanism (bearing, drive mechanism, etc.). Using this information, two signals are generated. The first signal is from the interferometer 10, a change in the combination of the angular orientation of the stage 16 and the local tilt of the reflective surface 51, and the reflective surface 51 along the angular orientation of the stage 16 and a reference line pair. 4 sets of signals relating to changes in the combined average slopes of. The second signal is from the interferometer 20 and the information contained relates to the angular orientation of the stage 16 as a function of the displacement in the y direction.

Information regarding the local inclination on the reflecting surface 61 is not used when determining the characteristics of the two reference lines in the reflecting surface 51. This is because the position of the stage 16 does not change in the x direction during scanning in the y direction. The first and second signals are processed by electronic processor 580 and computer 582 to provide information about the average tilt and average local tilt of mirror 51 along one of the reference line pairs, i.e., <dx / dy, respectively. > ₆ and <(dx / dy) _local > ₆ and information about the average tilt and average local tilt of the mirror 51 along the second of the reference line pair, ie, <dx / dy> ₇ and < (Dx / dy) _local > ₇ . Next, <dx / dy> ₆ , <(dx / dy) _local > ₆ , <dx / dy> ₇ , and <(dx / dy) _local > ₇ are converted into <dx / dy> _local < ₇ within electronic processor 480 and computer 482. / Dy> ₆ , <(dx / dy) _local > ₆ , <dx / dy> ₇ , and <(dx / dy) _local > ₇ , and processing using the integral transformation, the first and second x− Obtain χ displacements X ₅ and X ₅₀ of the reference line pair in the y plane as a function of y. The description of the processing in the fifth embodiment is the same as that described for the corresponding processing in the second embodiment.

The property of the zero differential beam shear of the interferometer 510 reduces the amplitude of the periodic error in the electrical interference signal generated by each of the six interferometers of each of the interferometers 10 and 20. This is the result of measuring the average tilt using a single optical path interferometer and generating input beams for the linear displacement interferometer and the local tilt interferometer. However, the remaining effect of the periodic error is that the measurement amount <dx / dy> ₆ , <(dx / dy) _local > ₆ , <dx / dy> ₇ if necessary for the end use application of the fifth embodiment. , And <(dx / dy) _local > ₇ . The description of the technique used to correct the remaining effects of the periodic error is the same as the corresponding part of the description given in the first embodiment.

  The effects of steady and unsteady changes in gas in the measurement paths 12 and 22 are corrected in the fifth embodiment for the required end use application. The description of the technique used to correct the effects of steady and non-stationary changes in gas in the measurement paths 12 and 22 is the same as the corresponding part of the description given in the first embodiment.

  The advantages of the fifth embodiment with respect to beam diameter and high spatial frequency information, zero differential shear, and integrated optical assembly are the same as the corresponding advantages of the second embodiment of the present invention. The remaining description of the fifth embodiment is the same as the corresponding part of the description given in the second and fourth embodiments of the present invention.

  A variation of the fifth embodiment of interferometers 10 and 20 is a passive zero shear type, more specifically a zero differential shear type. This is shown schematically in FIGS. 3e and 3f as 1510, which configuration is the shape of the elongated object mirrors 50 and 60 mounted on stage (a pair of reference lines for each of mirrors 50 and 60). Can be characterized in situ with high spatial resolution in the two xy planes. The reference line pair is in the surface of the reflecting surfaces 51 and 61. The modification of the fifth embodiment is different from the fifth embodiment in that local angular displacement information is generated. In a variation of the fifth embodiment, changes in local angular displacement are measured, and in the fifth embodiment, changes in average local angular displacement are measured. The modification of the fifth embodiment with respect to the fifth embodiment is the same as the modification of the second embodiment with respect to the second embodiment.

The modified interferometers 10 and 20 of the fifth embodiment include many elements having the same element numbers as the modified elements of the second embodiment. Elements with the same element number perform similar functions. The interferometer subsystems are separated in the z-direction by a distance ₉ and are combined in a stack in an integrated optical assembly. The same numbered elements in FIGS. 3e and 3f represent a single element of sufficient size to perform a similar function in FIGS. 3e and 3f, thereby reducing the number of parts and the integrated optical assembly. This is one of the causes. Figure. The change in the local tilt of the reflecting surface 51 in the xy planes of 3e and 3f is determined by measuring the direction change of the beam once reflected by the reflecting surface 51.

  An important feature of the fifth embodiment variant is that each of the interferometers 10 and 20 is an integrated optical assembly that can contribute to increased interferometer stability with respect to measurement accuracy and compact design. is there.

  In the modification of the fifth embodiment, as in the modification of the second embodiment of the present invention and the fifth embodiment, a change in local slope and a change in average slope are measured. As a result, the remaining description of the modification of the fifth embodiment is the same as the corresponding part of the description made in the first embodiment, the modification of the second embodiment, and the fifth embodiment.

  The sixth embodiment of interferometers 10 and 20 is a zero shear type. This is shown schematically in FIG. 3g as 610, whose configuration is represented by the shape of the elongated object mirrors 50 and 60 mounted on stage (a pair of reference lines for each of the mirrors 50 and 60). Can be characterized in situ with high spatial resolution in the two xy planes. The pair of reference lines is in the reflective surfaces 51 and 61.

The interferometer subsystem 610 shown schematically in FIG. 3g includes two interferometer subsystems that share a common beam steering member. Each of the interferometer subsystems is the same as the interferometer subsystem 310 of the third embodiment, but has a central subassembly that is a mirror image of each other as shown in FIG. 3h. The interferometer subsystems are combined in an integrated optical assembly, separated by a distance b _{9 in the} z direction. The same numbered elements in FIGS. 3g and 3h represent a single element of sufficient size to perform a similar function in FIGS. 3g and 3h, thus reducing the number of parts and the integrated optical assembly. This is one of the causes. The interferometer subsystem changes the displacement of the reflective surface 51 along the system measurement axis and changes in the average and local tilts of the reflective surface in two xy planes separated by a distance ₉ Are measured. FIG. 3h is a schematic exploded perspective view of the central subassembly of FIG. 3g, including various PBSs, Polo prisms, and other prism members.

  The system 15 normally operates to measure y translation, but when operating in a special mirror characterization mode, the shape of the mirror surface 51 is set to a pair of references in its two xy planes. Measure in situ along the line. In the mirror characterization mode, the stage 16 translates in the y direction, and the measurement beam of the interferometer 10 scans the mirror surface 51 along the reference line. As a result, along with the angular orientation of the mirror surface 51 and the deviation of the surface from the x-direction plane in the two xy planes, the contribution due to the variation in the translation mechanism that moves the stage 16, periodic nonlinearities, and interference A signal is generated that contains information indicative of the steady and unsteady effects of the gas in the measurement path of the total 10 and 20 beams.

  Simultaneously with the translation of the stage 16 in the y direction, the orientation of the mirror 61 is monitored by the interferometer 20 with respect to a fixed intercept point of the measurement beam of the interferometer 20 with the reflecting surface 61. This step makes it possible to measure the rotation of the stage 16 due to the mechanical contribution of its translation mechanism (bearing, drive mechanism, etc.). Using this information, two signals are generated. The first signal is from the interferometer 10, a change in the combination of the angular orientation of the stage 16 and the local tilt of the reflective surface 51, and the reflective surface 51 along the angular orientation of the stage 16 and a reference line pair. 4 sets of signals relating to changes in the combined average slopes of. The second signal is from the interferometer 20 and the information contained relates to the angular orientation of the stage 16 as a function of the displacement in the y direction.

Information regarding the local inclination on the reflecting surface 61 is not used when determining the characteristics of the two reference lines in the reflecting surface 51. This is because the position of the stage 16 has not changed in the x direction during scanning in the y direction. The first and second signals are processed by electronic processor 680 and computer 682 to provide information about the average tilt and local tilt of mirror 51 along one of the pair of reference lines, i.e., <dx / dy> ₈ respectively. And <(dx / dy) _local > ₈ and information about the average tilt and local tilt of mirror 51 along the second of the reference line pair, ie <dx / dy> ₉ and <(dx / dy) _local > ₉ is obtained. Next, the average and local slopes are processed using integral transformations in electronic processor 680 and computer 682 to determine the χ displacement of the reference line pair in the first and second xy planes. as a function of y. The explanation of the processing in the sixth embodiment is the same as the explanation given for the corresponding processing in the first embodiment.

The property of the zero differential beam shear of the interferometer 610 reduces the amplitude of periodic errors in the electrical interference signal generated by each of the six interferometers of each of the interferometers 10 and 20. However, the remaining effect of the periodic error is that the measured quantity <dx / dy> ₈ , (dx / dy) ₈ , <(dx / dy) _local > if necessary in the end use application of the sixth embodiment. ₉ and <(dx / dy) _local > ₉ are corrected in determining. The description of the technique used to correct the remaining effects of the periodic error is the same as the corresponding part of the description given in the first embodiment.

  The effects of steady and unsteady changes in gas in the measurement paths 12 and 22 are corrected in the sixth embodiment for the required end use application. The description of the technique used to correct the effects of steady and non-stationary changes in gas in the measurement paths 12 and 22 is the same as the corresponding part of the description given in the first embodiment.

  An important feature of the sixth embodiment is that the interferometers 10 and 20 are each integrated optical assemblies, which can contribute to increased interferometer stability with respect to measurement accuracy and compact design.

  The advantages of the sixth embodiment with respect to zero shear are the same as the corresponding advantages in the third embodiment of the present invention. The remaining description of the sixth embodiment is the same as the corresponding portion of the description given in the third, fourth, and fifth embodiments of the present invention.

  In the next four embodiments of the present invention, the pair of reference lines in each of the reflecting surfaces 51 and 61 and the local angular rotation of the reflecting surface around the reference line are determined with high spatial resolution. The reference lines of the pair of reference lines are in the two xy planes.

  For each of the seventh, eighth, eighth variation, and ninth embodiment, the respective devices and methods of the fourth, fifth, fifth variation, and sixth embodiment, and additional angles A displacement interferometer. The eighth embodiment includes the fifth embodiment and an additional angular displacement interferometer. An additional angular displacement interferometer measures the local tilt change in the plane perpendicular to the xy plane along the individual reference line pairs. The procedure for determining individual reference line pairs is the same as the individual procedures of the fourth, fifth, and fifth modifications and the sixth embodiment of the present invention.

  The additional angular displacement interferometer in the seventh, eighth, eighth variation, and ninth embodiment is the same as the interferometer 1010 shown in FIG. The orientation of the additional interferometer is chosen to be sensitive to changes in the direction of individual beams in the plane orthogonal to the xy plane (ie, in the z-axis direction). For example, to change the fourth embodiment to the seventh embodiment, a portion of beams 436 and 1436 is separated by beam splitter BS10 and the portion is sent to additional angular displacement interferometer 1010A (FIG. 4). See). The angular displacement interferometer 1010A is the same as the interferometer 1010 of FIG. 3a except that it is rotated 90 degrees so as to be more sensitive to changes in the direction of the separated portion in the plane orthogonal to the xy plane. . The interferometer included in the additional angular displacement interferometer in the eighth embodiment measures the average direction of a pair of beams and the difference between the directions of the beam pairs.

  Reference is now made to FIG. FIG. 5 illustrates interferometry using three orthogonally arranged interferometer systems that can characterize the shape of an array of elongated object mirrors along a plurality of orthogonal reference lines with high spatial resolution in situ. 1 is a schematic perspective view showing a system 1015. FIG. As shown in FIG. 5, the system 1015 includes a stage 16. Stage 16 preferably forms part of a photolithography apparatus for making semiconductor products such as integrated circuits or chips. A thin high-aspect-ratio measuring object that includes plane mirrors 70 and 60 and is elongated in the x and y directions is attached to the stage. The mirror 60 has an xz reflecting surface 61 that is elongated in the x direction, and the mirror 70 has an yz reflecting surface 71 and an xy reflecting surface 72 that are elongated in the y direction. The stage translates along two orthogonal directions, x and y. Substantially does not scan in the z direction.

  An interferometer (or interferometer subsystem) that is fixedly mounted off-stage is indicated generally at 10. The purpose of the interferometer 10 is the same as that of the interferometer 10 of FIG. 1, and generally the position of the stage 16 in the x direction and the y and / or z axis as the stage 16 translates in the y direction. Measuring the angular rotation around, and therefore measuring the position of the reflective surface 71 in the x direction and the angular rotation about the y and / or z axis as the stage 16 translates in the y direction. . To do this, the interferometer 10 may be configured and arranged as one of many interferometry methods. For example, but not limited to, the interferometer system used for the first nine embodiments of the present invention and their modified interferometer 10. The interferometric spectral beam of the interferometer 12 moves along an optical path generally designated 12 with the mirror 70.

  Another interferometer or interferometer subsystem that is fixedly mounted off-stage is shown generally at 20. The purpose of the interferometer 20 is the same as that of the interferometer 20 of FIG. 1, and generally the position of the stage 16 in the y direction and the x and / or z axis as the stage 16 translates in the x direction. Measuring the angular rotation around, and thus measuring the position of the reflecting surface 61 in the y direction and the angular rotation about the x and / or z axis as the stage 16 translates in the x direction. . To do this, the interferometer 20 may be configured and arranged as one of many interferometry methods. For example, but not limited to, the interferometer system used for the first nine embodiments of the present invention and their variants of interferometer 20. To do this, the interferometer 20 sends and receives the interferometric spectral beam to and from the mirror surface 61 along an optical path generally designated 22.

  A third interferometer or interferometer subsystem that is fixedly mounted off-stage is shown generally at 30. The purpose of the interferometer 30 is generally to measure the position of the stage 16 in the z direction and the angular rotation about the x and / or y axis as the stage 16 translates in the x and y directions, and thus reflectivity. Measuring the position of the surface 61 in the y direction and the angular rotation about the x and / or y axis as the stage 16 translates in the x and y directions. To do this, the interferometer 30 sends and receives an interferometric spectroscopic beam to and from the mirror surface 71 along an optical path generally designated 32.

  To do this, the interferometer 30 may be configured and arranged as one of many interferometry methods. For example, but not limited to, interferometer systems used for the first nine embodiments of the present invention and their variants of interferometers 10 and 20.

  An example of a single optical path interferometer that may be used as the interferometer 30 by changing so as to measure a change in the propagation direction of the measurement beam is described in the following document. Commonly owned US patent application Ser. No. 09 / 853,114 (filed on May 10, 2001), title of the invention “That Miller Characterization” (Henri A. Hill), November 1, 2001 (Publication number US-2001-0035959-A1, which is hereby incorporated by reference in its entirety.

  A multi-path interferometer that can be used as the interferometer 30 by changing so as to measure a change in the propagation direction of the measurement beam is described in, for example, the following documents. Commonly owned US patent application Ser. No. 09 / 852,898 (filed May 10, 2001), entitled “Interferometry Spectrometer and Method for Accurately Measuring Altitude on Surface” (Henri A Hill), published November 29, 2001 (publication number US-2001-0046053-A1). This content is incorporated herein by reference in its entirety.

  Interferometer 30 typically includes an elongate reference mirror mounted off-stage, such as that described in the following document. Cited US patent application Ser. No. 09 / 853,114, published Nov. 1, 2001 (publication number US-2001-0035959), US patent application Ser. No. 09 / 852,898, Nov. 2001. Released on May 29 (publication number US-2001-0046053-A1). The mirror 71 may also include an elongated surface oriented at an angle such as 45 degrees with respect to the xy plane.

  The reference line with respect to the reflective surfaces 61 and 71 and the local surface rotation around the reference line are determined by procedures as described in the first nine embodiments of the present invention and variations thereof.

  A reference line in a reflective surface such as reflective surface 71, a corresponding reference mirror mounted off-stage, a reflective surface arranged at an angle such as 45 degrees and a local rotation of the reflective surface around the reference line Are determined by the interferometer 30 when the stage 16 is scanned in the x and y directions. The determination involves information about the stage orientation obtained from the interferometers 10 and 20 and the procedure described for determining the reference line relative to the reflective surfaces 61 and 71 and local surface rotation around the reference line. Use to do.

  Having described many embodiments of the apparatus of the present invention and variations thereof, reference is now made to the flow chart of FIG. Here, a general methodology for characterizing the topographic features of an object mirror in-situ is illustrated.

  The method begins at block 700, followed by the steps of block 702. Here, at least one elongated planar object mirror is mounted on a translation stage for movement in a plane. Alternatively, the start step 700 may be thought of as starting after performing step 702 in advance, and the start of the start step 700 is in a well-known manner, eg, an instruction from an operator via a computer work station. Note that this is done by

  The step of block 704 sends at least a pair of spatially separated beams from the first interferometer to the object mirror. Here, a plurality of interferometers may be used, and some additional interferometer may send a pair of spatial beams to mirrors in planes that are offset from each other in parallel or orthogonal planes. . This is the same as in block 720, which may optionally begin simultaneously with step 704 and subsequent steps.

  At block 706, the stage is moved along the elongated dimension of the mirror while the beam is projected onto the stage so that the beam scans the mirror surface along at least one reference line. Note that if step 720 is introduced, at least one other reference line exists in a plane orthogonal to the plane in which the other reference line exists.

  At block 708, both return beams from the mirror are monitored and the displacement of the mirror at a point on the mirror where the two beams are incident is measured while scanning the mirror along the reference line. Calculate the average slope of.

  At block 710, the mirror is scanned to monitor at least one component of the return beam that forms only a single optical path to the mirror with an angle measuring interferometer to measure its change in direction. This is done while generating a signal containing information about the local tilt of the mirror surface along the reference line.

  At block 712, the stage angle orientation is measured using another orthogonally arranged second interferometer that is in a position on the stage that does not translate as the stage moves in the direction of the long dimension of the mirror.

  At block 714, the displacement and average tilt information from the two beams, the local tilt information from the angle measurement interferometer, and the angular orientation of the stage are collected and integrated.

At block 716, the integrated information is processed to obtain a mirror topography along the one or more baselines used. Processing of the information is performed by a suitable electronic processor and computer, preferably using the <dx / dy> and (dx / dy) _local integral transformations described above. However, those skilled in the art will appreciate that other processing algorithms such as Fourier transforms, polynomials, or other forms of orthogonal representation may be useful.

  At block 718, the previous steps may be repeated as necessary for orthogonally mounted mirrors.

  At block 722, other interferometers may optionally be used to measure the rotation of the mirror surface about the reference line.

  It will be appreciated that one or more of the previously described or referenced interferometry devices may be used in carrying out the method described above.

  While specific embodiments and methods of the invention have been described, variations thereof will be apparent to those skilled in the art based on the teachings of the invention. For example, one or more of the various interferometer subsystems may be mounted on a translation stage and moved with the stage while the corresponding mirror may be mounted fixed relative to a reference coordinate system. it is obvious. The interferometer subsystem is also configured with various stacked arrays to provide multiple interferometric spectroscopy beams that are locally tilted along one or more reference lines that are offset in a direction perpendicular to the scanning direction. May be selectively operable to measure the local tilt information generated may be integrated or otherwise mathematically processed to determine the local mirror shape. Is clear. Also, the stage and elongated mirror of the present invention may be formed as a monolithic structure, and need not be a high aspect ratio mirror, can be thickened, and formed of a refractive member such as a prism optical member that performs a reflecting function. Obviously you can. Accordingly, all such modifications are intended to be included within the scope of the appended claims.

FIG. 1 is a schematic perspective view showing an interferometry system using a pair of orthogonally arranged interferometers or interferometer subsystems, mounted on-stage by the interferometers or interferometer subsystems. The shape of the elongated object mirror can be characterized in situ along one or more reference lines with high spatial resolution. FIG. 2a is a schematic plan view showing a first embodiment of the interferometer of FIG. FIG. 2b schematically shows an angular displacement interferometer used in the embodiment of FIG. 2a. FIG. 2c is a schematic plan view showing a second embodiment of the interferometer of FIG. 1, which is a passive zero shear type, more specifically a zero differential shear type. FIG. 2d is a schematic plan view showing a variation of the second embodiment of the interferometer of FIG. 1, which is a passive zero shear type, more specifically a zero differential shear type. FIG. 2e is a schematic plan view showing a third embodiment of the interferometer of FIG. 1, comprising an active zero shear type interferometer. FIG. 2f is a schematic exploded perspective view showing a portion of the embodiment of FIG. 2e. FIG. 2g is a schematic perspective view showing the path of a particular beam as it propagates through one branch of the component assembly shown in FIG. 2f. FIGS. 3a and 3b are schematic plan views showing a fourth embodiment of the interferometer of FIG. 1, which is a plane mirror type including two interferometer subsystems. Each of the two interferometer subsystems is the same as the interferometer subsystem of the first embodiment. The two interferometer subsystems are combined in an integrated optical assembly, separated by a distance b _{5 in the} z direction. FIGS. 3a and 3b are schematic plan views showing a fourth embodiment of the interferometer of FIG. 1, which is a plane mirror type including two interferometer subsystems. Each of the two interferometer subsystems is the same as the interferometer subsystem of the first embodiment. The two interferometer subsystems are combined in an integrated optical assembly, separated by a distance b _{5 in the} z direction. Figures 3c and 3d schematically show two interferometer subsystems comprising a fifth embodiment. Each of the two interferometer subsystems is the same as the interferometer subsystem of the second embodiment. Figures 3c and 3d schematically show two interferometer subsystems comprising a fifth embodiment. Each of the two interferometer subsystems is the same as the interferometer subsystem of the second embodiment. FIGS. 3e and 3f schematically show a variation of the fifth embodiment of the interferometer of FIG. 1, which is a passive zero shear type, more specifically a zero differential shear type. FIGS. 3e and 3f schematically show a variation of the fifth embodiment of the interferometer of FIG. 1, which is a passive zero shear type, more specifically a zero differential shear type. FIG. 3g is a schematic plan view showing a sixth embodiment of the interferometer of FIG. 1 of the zero shear type. FIG. 3h is a schematic exploded perspective view showing a sub-assembly of certain components of FIG. 3g. FIG. 4 is a schematic diagram illustrating an interferometer arranged for measuring local angular displacement in an orthogonal plane for use in a further embodiment of the present invention. FIG. 5 is a schematic perspective view showing an interferometry system using three orthogonally arranged interferometer systems that can characterize the shape of an array of elongated object mirrors in situ. FIG. 6 is a flow chart illustrating a general method for in-situ characterizing the topographic features of a mirror.

Claims (34)

A translation stage,
And electromechanical devices Ru is selectively translating the translation stage in at least one direction of at least two orthogonal directions,
And at least one mirror Ru mounted Tei in a predetermined manner with respect to the translation stage, and at least one mirror having a reflecting surface,
Interferometer means for generating a plurality of measurement beams for measuring the displacement of the translation stage in at least one direction and the local tilt of the respective region of the reflecting surface of the at least one mirror; wherein each of the plurality of measurement beams are constructed and arranged so as to be projected onto the respective regions of the reflecting surface, and the interferometer unit,
Control means having an operation mode, wherein the control means selectively translates the translation stage, the at least one mirror, and the interferometer means relative to each other in the operation mode, whereby the interference Each of several selected measurement beams of the plurality of measurement beams of the metering means scans a respective region of the reflective surface of the at least one mirror along at least one corresponding reference line. A local tilt of each scanned region of the reflective surface of the at least one mirror along the at least one corresponding reference line in at least one plane having a surface normal perpendicular to its scanning direction. Control means for generating at least one signal including information to indicate;
Wherein extracting the information contained in the at least one signal, comprising said signal and analysis means for determining the local shape of the at least one mirror, interferometry apparatus. Wherein at least one of the signals, further comprising information indicating the position of the reflecting surface in at least one plane as a function of scan position along the at least one reference line, interferometry system of claim 1. Wherein at least one of the signals, further comprising information indicating the slope of the average of the reflecting surface in at least one plane as a function of scan position along the at least one reference line, interferometry system of claim 1. Wherein at least one of the signals, further comprising information indicating the inclination of the position and the average of the reflecting surface in at least one plane as a function of scan position along the at least one reference line, interferometry according to claim 1 apparatus. The plurality of measurement beams include at least a pair of measurement beams, and each of the measurement beams of the at least a pair of measurement beams has a predetermined diameter and is spaced apart from each other by a predetermined distance along the scanning direction. disposed Te Tei Ru, interferometry system of claim 1. The interferometer means includes at least one angle measuring interferometer , and the at least one pair of measurement beams has an average inclination of the reflecting surface in the at least one plane at a scanning position along the at least one reference line. Configured and arranged to provide information that can be measured as a function , at least a portion of one of the measurement beams of the at least one pair of measurement beams is the mirror along the reference line in the plane after being reflected once by the mirror in order to measure the local slope of, received by the angle measuring interferometer, interferometry system of claim 5. Said interferometer means includes at least one angle measuring interferometer, said at least a pair of measurement beams, information about the position of the reflecting surface at the point corresponding to the projection of the measuring beam to the reflecting surface on are configured arranged to provide said one of at least a portion of the measurement beam of the at least a pair of measurement beams, to measure the local slope of the mirror along the reference line of the plane wherein after being reflected once by the mirror and received by the angle measuring interferometer for interference spectroscopy system of claim 5. The interferometer means includes one or more interferometers selected from the group consisting of a high stability plane mirror interferometer, a passive differential zero shear interferometer, an active zero shear interferometer, an angle interferometer , The interference spectroscopic apparatus according to claim 1. The signal and analysis means is configured to determine a local shape of the at least one mirror using a mathematical procedure selected from the group consisting of integral transformation, Fourier analysis, orthogonal function analysis, and polynomial expansion. by Tei Ru, interferometry system of claim 1. Wherein said at least one mirror, the translation stage and being mounted on the translation stage for movement with said interferometer means, the Ru Tei is mounted away from the translation stage, the interference of claim 1 Spectrometer. Said interferometer means, said translation stage and being mounted on the translation stage for movement with said at least one mirror, the away from the translation stage Ru mounted Tei, interference of claim 1 Spectrometer. The control means, the motion of the translation stage is Ru Tei is configured arranged to have another mode of operation is measured in at least one direction relative to the reference coordinate system, interferometry system of claim 1. The plurality of measurement beams include at least two pairs of measurement beams, each pair including two measurement beams, the two measurement beams having a predetermined diameter , and each other along the scanning direction. are separated by a predetermined distance, each pair are offset from each other in a direction perpendicular to the scanning direction, interferometry system of claim 1. The interferometry apparatus is configured to measure the plurality of measurements to measure a displacement of the translation stage in an orthogonal direction and at least a local tilt of a surface of at least one other mirror orthogonal to the surface of the at least one mirror. The interferometry apparatus according to claim 1 , configured and arranged to generate the plurality of measurement beams such that several preselected beams of the beams are arranged orthogonal to each other . Further comprising two or more orthogonally arranged mirrors, the corresponding interferometer means is mounted in a predetermined manner relative to the translation stage, each of the two or more orthogonally arranged mirrors being said interference The interferometric spectrometer according to claim 1 , wherein the control means is in the mode of operation for measuring a local shape of the mirror while moving relative to the corresponding one of the metering means. . Wherein said at least one mirror, said has a Tei, reflective side is arranged at 45 degrees with respect to the translation stage, interferometry system of claim 1. Wherein disposed on the translation stage, the at least one further including a photolithographic wafer mount moves together with said translation stage, interferometry system of claim 1. It mounted on the reference coordinate system, photolithographic exposure unit further including forming a mask pattern on the arranged wafer on the translation stage, interferometry system of claim 17. Mounting at least one mirror in a predetermined manner relative to a translation stage, the at least one mirror having a reflective surface;
A step of selectively translating the translation stage in at least one direction of the two orthogonal directions even without low,
Generating a plurality of interferometry beams, to measure the displacement of the translation stage in at least one direction and the local tilt of the respective region of the reflective surface of the at least one mirror; wherein each of the plurality of interferometry measurement beam Ru Tei is configured arranged to be projected onto the respective regions of the reflecting surface, comprising the steps,
Selectively translating the translation stage, the at least one mirror, and the plurality of interferometry beams with respect to each other in a first mode of operation, thereby selecting a selected one of the plurality of interferometry beams; some respective interferometry measurement beam so as to scan along at least one corresponding reference line of each region of the reflection surface of said at least one mirror, the surface normal that is perpendicular to the scanning direction Generating at least one signal including information indicative of a local tilt of a respective region of the reflective surface of the at least one mirror along the at least one corresponding reference line in at least one plane having;
Wherein by analyzing at least one signal, the extracting the information contained in the at least one signal, the and determining the local shape of the at least one mirror, interferometry. Wherein at least one of the signals, further comprising information indicating the position of the reflecting surface in at least one plane as a function of scan position along the at least one reference line, interferometry according to claim 19. Wherein at least one of the signals, further comprising information indicating the slope of the average of the reflecting surface in at least one plane as a function of scan position along the at least one reference line, interferometry according to claim 19. Wherein at least one of the signals, further comprising information indicating the inclination of the position and the average of the reflecting surface in at least one plane as a function of scan position along the at least one reference line, interferometry according to claim 19 Law . The plurality of interferometry beams include at least a pair of interferometry beams, and the interferometry beams of the at least a pair of interferometry beams have a predetermined diameter and are spaced from each other by a predetermined distance. Ru is arranged along the scanning direction apart Tei, interferometry according to claim 19. The at least one pair of interferometry beams is configured to provide information that can measure an average slope of the reflective surface in the at least one plane as a function of a scanning position along the at least one reference line. are arranged, said at least one of the at least a portion of the interference spectroscopic measurement beams of the pair of interferometry measurement beam, said to measure the local slope of the mirror along the reference line of the plane after being reflected once by the mirror and received by the angle measuring interferometer, interferometry according to claim 23. Before SL least one pair of interferometry measurement beam are constructed arranged such that said providing the information about the position of the reflecting surface at the point corresponding to the projection of the interferometry measurement beam to the reflecting surface, At least a portion of one of the at least one pair of interferometry beams is reflected once by the mirror to measure a local tilt of the mirror along the reference line in the plane. after the, received by the angle measuring interferometer, interferometry according to claim 23. The plurality of interferometry beams are one or more interferometers selected from the group consisting of a high stability plane mirror interferometer, a passive differential zero shear interferometer, an active zero shear interferometer, and an angle interferometer 20. Interferometry spectroscopy according to claim 19 provided by interferometer means comprising: The analysis step, the local shape of the at least one mirror, integral transformation, Fourier analysis, orthogonal function analysis is determined using a mathematical procedure selected from the group consisting of a polynomial expansion, to claim 19 The described interferometry. Further comprising other operating modes that are measured in at least one direction movement of the translation stage relative to the reference coordinate system, interferometry according to claim 19. Wherein the plurality of interferometry measurement beam includes interferometry measurement beam at least two pairs, wherein each pair of interferometry measurement beam at least two pairs comprises two interferometry measurement beam, said two interferometry measurement beam has a predetermined diameter, and wherein in the scanning direction are separated by a predetermined distance from each other, wherein each pair of interferometry measurement beam at least two pairs, mutually displaced in a direction perpendicular to the scanning direction and has, interferometry according to claim 19. The plurality of interferometry beams are used to measure a displacement of the translation stage in an orthogonal direction and at least a local tilt of a surface of at least one other mirror orthogonal to the surface of the at least one mirror. The interferometry method according to claim 19, wherein the interferometry method is configured and arranged such that several preselected interferometry beams are arranged orthogonal to each other . The method further includes mounting two or more orthogonally arranged mirrors on the translation stage , each of the two or more orthogonally arranged mirrors corresponding to one of the plurality of interferometric spectroscopy beams. while it is moving with respect to the beam, to measure the local shape of the mirrors in the first operation mode, interferometry according to claim 19. Wherein said at least one mirror, it said having mounted Tei, reflective side at 45 degrees with respect to the translation stage, interferometry according to claim 31. Further comprising the step of mounting on the translation stage to move at least one photolithographic wafer with the translation stage, interferometry according to claim 19. The wafer so as to form a mask pattern on the wafer while disposed on the translation stage, further comprising the step of at least once exposing the wafer, interferometry according to claim 33.

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