Position measuring device and adjusting system of reflective projection objective lens

Abstract

The invention relates to the technical field of optical engineering, and provides a reflective projection objective position measuring device and adjusting system.The measuring device comprises a measuring unit and a processing unit, the measuring unit comprises three grating interferometers, the three grating interferometers are arranged on the three side faces of a reflector respectively, and the processing unit is connected with the three grating interferometers. The grating interferometer is used for measuring the position information of the reflector and outputting a corresponding measurement signal; and the processing unit is used for receiving the measurement signals output by the three grating interferometers and determining the spatial pose information of the reflector based on the three measurement signals. According to the invention, through the grating interferometers arranged on the three side surfaces of the reflector, the position information of the reflector in multiple directions can be obtained, the processing unit is utilized to process multiple paths of measurement signals, the spatial pose information of the reflector can be solved, the accurate measurement of the position of the reflector is realized, the aberration correction capability and the imaging stability are effectively improved, and the measurement precision is improved. Therefore, the imaging quality of the reflective projection objective lens is improved.

Description

Technical Field

[0001] This invention relates to the field of optical engineering technology, and in particular to a position measuring device and adjustment system for a reflective projection lens. Background Technology

[0002] Chip manufacturing is a core component of the semiconductor industry, and its performance directly affects the quality and output of chip production. High-precision photolithography is crucial for transferring patterns on micro- and nano-scale integrated circuits. Reflective projection lenses, as core optical components in advanced photolithography technologies such as extreme ultraviolet (EUVL) and electron beam lithography (EBL), play a vital role in projecting the fine patterns on the photomask onto the silicon wafer with high fidelity. Since extreme ultraviolet light has a wavelength of only 13.4 nm, almost all optical materials exhibit strong absorption characteristics in this band, and there is a lack of usable transmissive optical materials. Therefore, a total internal reflection optical system must be used, utilizing multiple high-precision mirrors working together to complete the miniaturized projection of the pattern.

[0003] Reflective projection lenses, through the coordinated operation of multiple mirrors, can precisely project intricate patterns from a photomask onto a substrate. The imaging quality of a reflective projection lens is highly dependent on the surface accuracy and spatial positioning of each mirror. Even micron- or sub-nanometer-level positional shifts in the mirrors can introduce significant optical aberrations, such as spherical aberration, coma, and astigmatism, leading to blurred images, increased overlay errors, and severely impacting lithography resolution and process windows. To ensure system stability during long-term operation, reflective projection lenses are typically equipped with a position measurement system. This system captures these positional changes in real time and feeds precise measurement data back to the position control system, which then makes timely and precise adjustments to the mirrors. In this way, even during extended operation, the mirrors maintain a stable position, providing a solid guarantee for image quality. For example, some systems employ flexible adjustment mechanisms, using piezoelectric ceramics to drive the mirrors for fine-tuning. The position measurement system accurately measures the actual displacement of the mirrors and feeds this result back to the piezoelectric ceramic actuator, thereby achieving a closed-loop control mode for precise adjustment.

[0004] In existing technologies, position measurement systems typically employ capacitive sensing techniques to monitor real-time changes in the position of a reflector and feed the measurement data back to the control system. However, in practical applications, environmental disturbances such as instrument errors and environmental factors inevitably introduce phase errors into the measurement signal, thereby reducing the accuracy of the position feedback. Summary of the Invention

[0005] This invention provides a position measuring device and adjustment system for a reflective projection lens, which solves the problem of insufficient position measurement accuracy caused by instrument errors and environmental errors in the prior art. The device uses a grating interferometer to achieve accurate measurement of the reflective lens position, thereby improving the imaging quality of the reflective projection lens.

[0006] This invention provides a position measuring device for a reflective projection lens. The reflective projection lens includes a reflector, the reflector having a reflective surface and three side surfaces connected to the reflective surface. The device includes: The measurement unit includes three grating interferometers, which are respectively disposed on three sides of the reflector. The grating interferometers are used to measure the position information of the reflector and output corresponding measurement signals. The processing unit is used to receive measurement signals output by the three grating interferometers and determine the spatial pose information of the reflector based on the three measurement signals.

[0007] According to the present invention, a position measuring device for a reflective projection lens is provided, wherein each of the grating interferometers includes a grating ruler and a reading head, the grating ruler being disposed on the side of the reflector and the reading head being disposed opposite to the grating ruler.

[0008] According to the present invention, the position measuring device for a reflective projection lens is provided in which the measuring positions of the three grating rulers are located on a circle with the center normal of the reflective surface as the axis, and are evenly distributed along the circumference.

[0009] According to the position measuring device of a reflective projection lens provided by the present invention, each of the reading heads is connected to a preamplifier, and the preamplifier is connected to the processing unit.

[0010] According to the present invention, a position measuring device for a reflective projection lens is provided, wherein a light source is provided inside the preamplifier, and the light source is connected to the signal input end of the reading head through a first incident optical fiber and a second incident optical fiber in parallel.

[0011] According to the present invention, a position measuring device for a reflective projection lens is provided, wherein the preamplifier has a built-in photodetector, the photodetector is connected to the signal output end of the reading head through a first return optical fiber and a second return optical fiber in parallel, and the photodetector is used to convert the optical signal output by the reading head into an electrical signal and output it to the processing unit.

[0012] According to the present invention, a position measuring device for a reflective projection lens is provided, wherein the processing unit comprises: A signal subdivision module is connected to the three grating interferometers. The signal subdivision module is used to subdivide the measurement signal and output the position information corresponding to the three grating interferometers. A processing module, connected to the signal subdivision module, is used to determine the spatial pose information of the reflector based on the position information corresponding to the three grating interferometers.

[0013] The present invention also provides a position adjustment system for a reflective projection lens, comprising: The position measuring device for the reflective projection lens described in any of the above-mentioned items; The actuator is used to mount the reflector on the reflector base. A driver is connected to the processing unit and the actuator; The processing unit is used to generate a position adjustment command based on the deviation between spatial pose information and preset pose information; the driver is used to receive the position adjustment command and generate a drive signal based on the position adjustment command; the actuator is used to generate an action in response to the drive signal to adjust the pose of the reflector.

[0014] According to the present invention, a position adjustment system for a reflective projection lens includes an actuator comprising three drive motors disposed on the reflector base, the outputs of the drive motors being connected to the reflector, and the outputs of the three drive motors corresponding to the three corner regions of the reflector.

[0015] The position adjustment system for a reflective projection lens provided by the present invention further includes a clock synchronization unit, the output of which is connected to the processing unit, the preamplifier and the driver respectively.

[0016] The position measurement device for a reflective projection lens provided by this invention can simultaneously acquire position information of the reflective lens in multiple orientations by grating interferometers arranged on three sides of the reflective lens. The processing unit processes the multi-channel measurement signals to calculate the spatial pose information of the reflective lens, thereby achieving accurate measurement of the reflective lens position, effectively improving aberration correction capability and imaging stability, and thus improving the imaging quality, overlay accuracy and photolithography stability of the reflective projection lens. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the principle of the position measuring device for the reflective projection lens provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the reflective projection lens provided by the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the reflector and grating interferometer provided by the present invention.

[0021] Figure 4 This is a partial schematic diagram of the position measuring device for the reflective projection lens provided by the present invention.

[0022] Figure 5 This is a schematic diagram of the principle of the position adjustment system for the reflective projection lens provided by the present invention.

[0023] Figure label: 10. Mirror; 20. Mask; 30. Substrate; 40. Mirror base; 100. Measurement unit; 110. Grating interferometer; 111. Grating ruler; 112. Reading head; 1121. Return light coupler X; 1122. Return light coupler Y; 1123. Announcement collimator X; 1124. Announcement collimator Y; 120. Preamplifier; 121. Light source; 122. Photodetector; 123. Signal processor; 131. First input optical fiber; 132. Second input optical fiber; 133. First return optical fiber; 134. Second return optical fiber; 200. Processing unit; 210. Signal subdivision module; 220. Processing module; 300. Actuator; 400, driver; 500. Clock synchronization unit. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0027] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0029] The following is combined Figures 1-5 The present invention describes a position measuring device for a reflective projection lens.

[0030] An embodiment of the first aspect of the present invention provides a position measuring device for a reflective projection lens, wherein, as Figure 3 As shown, the reflective projection lens includes a reflector 10, which includes a reflective surface and three side surfaces connected to the reflective surface. By adjusting the spatial orientation of the reflector 10, the image aberration of the projected object can be effectively corrected, thereby optimizing the imaging quality of the reflective projection lens.

[0031] like Figure 1 and Figure 3 As shown, the position measuring device includes a measuring unit 100 and a processing unit 200. The measuring unit 100 includes three grating interferometers 110, which are respectively disposed on three sides of the reflector 10. The grating interferometers 110 are used to measure the position information of the reflector 10 and output corresponding measurement signals. The processing unit 200 is used to receive the measurement signals output by the three grating interferometers 110 and determine the spatial pose information of the reflector 10 based on the three measurement signals.

[0032] Understandably, three grating interferometers 110 are respectively mounted on three sides of the reflector 10 to measure position changes in each direction in real time and output corresponding measurement signals. The processing unit 200 is connected to the three grating interferometers 110, receives and processes the measurement signals from the three grating interferometers 110, and calculates the six-degree-of-freedom pose of the reflector 10 in space (including three translational and three rotational parameters) through spatial coordinate transformation relationship. This enables accurate measurement of the position and attitude of the reflector 10, provides precise feedback for aberration compensation and imaging optimization, and improves the imaging quality of the reflective projection lens and the overlay accuracy of the photolithography process.

[0033] The position measurement device for a reflective projection lens provided in this embodiment of the invention can simultaneously acquire position information of multiple orientations of the reflective lens 10 by using grating interferometers 110 arranged on three sides of the reflective lens 10. The processing unit 200 processes the multiple measurement signals to calculate the spatial pose information of the reflective lens 10, thereby achieving accurate measurement of the position of the reflective lens 10. This effectively improves aberration correction capability and imaging stability, thereby enhancing the imaging quality, overlay accuracy, and stability of the photolithography process of the reflective projection lens, and meeting the stringent requirements of advanced photolithography equipment for high-precision control of the optical system.

[0034] In one embodiment of the present invention, such as Figure 2 As shown, the reflective projection lens includes a six-sided reflector 10 located between the mask 20 and the substrate 30, forming a total internal reflection optical system to achieve high-fidelity projection of micro-nano patterns in extreme ultraviolet lithography.

[0035] Of the six mirrors, five are adjustable with six degrees of freedom; the remaining mirror 10 is rigidly fixed to the overall frame of the projection lens as a reference mirror to provide a stable optical reference. By independently controlling the spatial pose of the five adjustable mirrors 10, not only can key optical aberrations such as spherical aberration, coma, and astigmatism in the optical system be dynamically compensated, but also fine-tuning of the projected image ratio and field curvature correction can be achieved, thereby effectively improving imaging resolution, contrast, and overlay accuracy.

[0036] In this embodiment, the number of measurement units 100 matches the number of adjustable reflectors 10, and the two are set in a one-to-one correspondence. Each adjustable reflector 10 is equipped with an independent measurement unit 100. Each measurement unit 100 includes three grating interferometers 110, which are respectively installed on the three sides of the corresponding reflector 10 to measure the position change of the reflector 10 in multiple degrees of freedom directions, thereby realizing real-time monitoring of the spatial pose of each reflector 10.

[0037] In one embodiment of the present invention, such as Figure 3 As shown, the reflector 10 (i.e., the adjustable reflector) includes a reflecting surface and three side surfaces perpendicular to the reflecting surface. The three side surfaces are evenly distributed circumferentially around the central axis of the reflector 10, and the outer contours of the three side surfaces form an equilateral triangle structure, which has good structural symmetry and thermodynamic stability.

[0038] A grating interferometer 110 is set on each side. The measurement points of each interferometer are located on the same circle with the center normal of the reflecting surface as the axis. They are evenly distributed in the circumference, and the three measurement positions are at a 120° angle to each other on the circle. This forms a non-collinear and symmetrical three-dimensional measurement layout, which effectively enhances the sensitivity and decoupling capability of the multi-degree-of-freedom motion (including translation and tilt) of the reflecting mirror 10. It is beneficial to improve the accuracy and reliability of spatial pose calculation and provides a geometrically optimized measurement basis for realizing closed-loop control of the reflecting mirror 10.

[0039] Optional, such as Figure 3 As shown, each grating interferometer 110 includes a grating ruler 111 and a reading head 112. The grating ruler 111 is disposed on the side of the reflector 10, and the reading head 112 is disposed opposite to the grating ruler 111.

[0040] Understandably, each grating interferometer 110 consists of a grating ruler 111 and a reading head 112, forming a non-contact, high-precision displacement measurement device. The grating ruler 111 is fixed to the central region of the side of the reflector 10, with its length direction aligned with the length direction of that side. The reading head 112 is mounted on the fixed support structure of the reflective projection lens, facing the grating ruler 111 and maintaining a constant, minute measurement gap. During operation, the reading head 112 emits a coherent laser beam towards the grating ruler 111. Utilizing the diffraction and interference effects generated by the periodic microstructures on the grating surface, it detects the phase change caused by the movement of the reflector 10, thereby accurately calculating the real-time displacement at the nanometer or even sub-nanometer level.

[0041] It should be noted that placing the grating ruler 111 in the middle of the side can effectively reduce the lever effect and rotational coupling error caused by edge deformation or installation eccentricity, improve the stability of the measurement, and at the same time facilitate the realization of high-fidelity perception of the translation and tilt attitude of the reflector 10, providing accurate and reliable feedback signals for subsequent precision posture control.

[0042] Furthermore, the measurement positions of the three grating rulers 111 are located on a circle with the center normal of the reflecting surface as the axis, and are evenly distributed along the circumference.

[0043] Optionally, in each grating interferometer 110, the measuring surface of the grating ruler 111 is parallel to the XY plane, and its surface is engraved with a periodic grating structure located in the XY plane; the laser beam emitted by the reading head 112 is incident perpendicularly to the surface of the grating ruler along the Z-axis direction. By detecting the relative displacement of the grating in the XY plane along its engraving direction, high-precision measurement of the displacement in that direction is achieved.

[0044] It should be noted that the measurement direction of the grating interferometer 110 is perpendicular to the Z-axis, i.e., located in the XY plane. This arrangement makes it less sensitive to the linear thermal expansion displacement of the reflector 10 in the XY plane caused by temperature changes. Since thermal expansion usually manifests as in-plane deformation, and the measurement direction is orthogonal to the main thermal deformation direction, the resulting common-mode error and spurious displacement signal can be significantly suppressed. This effectively reduces the interference of ambient temperature fluctuations on the measurement results, improves the thermal stability of the system, and ensures high-precision and high-reliability position feedback even under complex working conditions, providing an accurate measurement basis for the control of the reflector 10.

[0045] In this embodiment, the grating ruler 111 is based on a two-dimensional planar grating structure and uses microcrystalline glass with a low coefficient of thermal expansion as the matrix material. This material has excellent thermal stability and can maintain minimal dimensional deformation under fluctuating temperature conditions, thus providing a reliable physical basis for high-precision measurement.

[0046] Specifically, two sets of orthogonal grating lines with a spacing of 2048 nm are fabricated on the grating surface using precision photolithography, forming a two-dimensional periodic structure. This structure supports synchronous displacement detection in the X and Y directions and can also serve as a high-resolution reference scale for multi-degree-of-freedom motion calculations. The two-dimensional grating is mounted on the side of the long side of the triangular reflector using photoresist. The photoresist layer has high bonding strength, low shrinkage, and good aging stability, ensuring a stress-free, high-precision rigid connection between the grating scale and the reflector 10. This effectively maintains their relative positional relationship under long-term operation and complex working conditions, effectively avoiding displacement drift caused by loose installation or thermal mismatch, and further improving the reliability of position measurement.

[0047] It should be noted that this embodiment uses three two-degree-of-freedom grating interferometers to achieve complete measurement of the six-degree-of-freedom pose (including three translational and three rotational degrees of freedom) of the mirror. Compared to the traditional system that requires six independent measuring elements to achieve six-degree-of-freedom sensing, this embodiment reduces the number of measuring elements by half, significantly reducing the hardware requirements for sensors and signal processing modules. Furthermore, while ensuring measurement accuracy, the system has higher integration, a more compact structure, and significantly reduced overall complexity, saving manufacturing costs and reducing installation, debugging difficulty, and subsequent maintenance workload.

[0048] In one embodiment of the present invention, such as Figure 4 As shown, each reading head 112 is connected to a preamplifier 120, which is connected to the processing unit 200.

[0049] It is understood that the measurement unit 100 includes three preamplifiers 120, each preamplifier 120 being connected to a reading head 112 in a one-to-one correspondence, that is, the interference light signal output by each reading head 112 is transmitted to the corresponding preamplifier 120.

[0050] Optionally, the preamplifier 120 has a built-in photodetector 122, which is used to convert the optical signal output by the reading head 112 into an electrical signal and output it to the processing unit 200.

[0051] Understandably, the preamplifier 120 integrates a photodetector 122, which converts the weak optical signal returned by the reading head 112 into an electrical signal. The photodetector 122 is connected to a signal processor 123, which performs low-noise amplification, bandpass filtering, and signal conditioning on the signal output from the photodetector 122 to improve the signal-to-noise ratio, eliminate high-frequency interference and DC drift, and ensure high fidelity of the measurement signal. The processed electrical signal is output in differential or analog voltage form and transmitted by the preamplifier 120 to the processing unit 200 for subsequent displacement calculation.

[0052] It should be noted that in a measurement unit 100, the three reading heads 112 correspond to independent preamplifiers 120. Each preamplifier 120's preamplification channel independently completes photoelectric signal conversion and amplification processing, thereby realizing the synchronous acquisition of displacement information of the three measurement points of the reflector 10.

[0053] In one embodiment of the present invention, such as Figure 4 As shown, a light source 121 is provided inside the preamplifier 120. The light source 121 is connected to the signal input terminal of the reading head 112 through a first optical fiber 131 and a second optical fiber 132 in parallel.

[0054] Understandably, the preamplifier 120 integrates a light source 121 (laser source), which serves as the optical reference for the grating interferometer 110. This light source 121 is connected to the signal input terminal of the reading head 112 via a first incident optical fiber 131 and a second incident optical fiber 132 arranged in parallel. The two incident optical fibers transmit laser beams with different polarization states or for different measurement paths (such as reference light and measurement light), respectively, thus achieving multi-degree-of-freedom interferometric measurement.

[0055] Optionally, the photodetector 122 built into the preamplifier 120 is connected to the signal output terminal of the reading head 112 via a first return optical fiber 133 and a second return optical fiber 134 in parallel.

[0056] Understandably, the photodetector 122 built into the preamplifier 120 is connected to the signal output end of the reading head 112 through the parallel first return optical fiber 133 and the second return optical fiber 134, and is used to receive the returned light signal after interference. The two return optical fibers transmit interference light from different optical paths respectively, ensuring that the change in the optical path difference between the reference light and the measurement light can be accurately captured.

[0057] In this embodiment, the first input optical fiber 131 and the second input optical fiber 132 are input optical fiber X and input optical fiber Y, respectively, and the first return optical fiber 133 and the second return optical fiber 134 are return optical fiber X and return optical fiber Y, respectively. The reading head 112 is provided with a return optical coupler X 1121, a return optical coupler Y 1122, an input optical collimator X 1123 and an input optical collimator Y 1124. The input optical collimator X is connected to the input optical fiber X, the input optical collimator Y is connected to the input optical fiber Y, the return optical coupler X is connected to the return optical fiber X, and the return optical coupler Y is connected to the return optical fiber Y.

[0058] It should be noted that by adopting an external light source 121 solution, the light source 121 is integrated inside the preamplifier 120, away from the displacement encoder (i.e., the reading head 112) installed near the reflector 10. All-fiber transmission between the light source 121 and the reading head 112, as well as the return of interference signals to the preamplifier 120, is achieved through the input and return optical fibers. This significantly reduces the heat released by the displacement encoder to the surrounding environment during operation. Especially in the vacuum environment relied upon by extreme ultraviolet lithography systems, where air convection cooling is limited, any local heat source can cause temperature gradients and micro-deformations of the structure, thereby affecting the relative position and wavefront quality of optical components. This embodiment effectively suppresses thermal drift and air disturbance (in non-vacuum regions) or structural deformation (in vacuum regions) caused by local temperature rise by moving the light source 121 out of the measurement area, thereby reducing interference with the overall thermal stability of the reflective projection lens. This low thermal interference characteristic helps maintain precise alignment and surface stability between components of the optical system, reduces thermal aberrations, and ultimately improves the system's imaging resolution, overlay accuracy, and long-term operational stability.

[0059] It should be noted that existing position measurement systems exhibit lag in response to sudden minute displacements or deformations of optical elements (reflector 10), making it difficult to identify abnormal states in a timely manner. This results in imaging errors that cannot be effectively warned of or avoided, affecting system reliability. Furthermore, in high-precision applications, existing position measurement systems are limited by insufficient feedback rates, failing to meet the demands of high-frequency, real-time control, leading to poor dynamic adjustment efficiency in closed-loop control. In addition, fluctuations in ambient temperature can cause thermal expansion or structural deformation of optical element materials, thereby altering their geometric dimensions and spatial position. Traditional measurement techniques (such as capacitive sensors) are sensitive to such thermally induced displacements and lack effective real-time compensation mechanisms, easily introducing significant measurement deviations. Simultaneously, external vibrations directly disturb the stability of optical elements, superimposing noise into the measurement signal and severely affecting the accuracy of position detection.

[0060] In contrast, the position measurement device proposed in this invention utilizes a grating interferometer 110 to achieve sub-nanometer-level real-time monitoring of the position of the reflector 10. It possesses high bandwidth and high resolution feedback capabilities, enabling rapid detection of minute abnormal displacements of optical components, achieving fault warning and proactive intervention, and significantly improving system reliability. The optimized measurement direction design effectively suppresses common-mode errors caused by thermal expansion in the XY plane. Combined with a low thermal expansion coefficient microcrystalline glass two-dimensional grating reference, it enhances the system's dimensional stability and measurement accuracy under temperature variations. Furthermore, the external light source 121, transmitted via optical fiber, significantly reduces the thermal load on the reading head 112 area, making it particularly suitable for vacuum environments and minimizing the impact of thermal disturbances on the objective lens system's imaging quality. Simultaneously, the system's multi-point arrangement provides a certain degree of vibration and noise suppression capability, and the high signal-to-noise ratio signal processing of the preamplifier 120 enhances anti-interference performance. In summary, this invention not only achieves higher precision and stability in position sensing but also significantly enhances real-time control capabilities in complex dynamic environments, providing a more reliable pose feedback solution for high-precision lithography systems.

[0061] In one embodiment of the present invention, such as Figure 4 and Figure 5 As shown, the processing unit 200 includes a signal subdivision module 210 and a processing module 220. The signal subdivision module 210 is connected to three grating interferometers 110. The signal subdivision module 210 is used to subdivide the measurement signal and output the position information corresponding to the three grating interferometers 110. The processing module 220 is connected to the signal subdivision module 210. The processing module 220 is used to determine the spatial pose information of the reflector 10 based on the position information corresponding to the three grating interferometers 110.

[0062] It is understood that the processing unit 200 includes a signal subdivision module 210 and a processing module 220. The signal subdivision module 210 is connected to the three grating interferometers 110 and is responsible for receiving the measurement signals output by each grating interferometer 110 and performing high-precision subdivision processing on them. The subdivision processing module 220 uses a subdivision card or embedded digital signal processing technology to perform interpolation calculations using the phase information of the orthogonal interference signals, thereby improving the resolution of the original grating signal from the nanometer level to the picometer level, thus achieving ultra-fine sensing of the minute displacement of the reflector 10 and outputting high-resolution position information corresponding to the three grating interferometers 110. The processing module 220 is connected to the signal subdivision module 210, receives the subdivided position information, and calculates the six-degree-of-freedom pose of the reflector 10 in space (including three translational degrees of freedom X, Y, and Z and rotational degrees of freedom around the X, Y, and Z axes), thereby realizing real-time measurement of the attitude of the reflector 10. For example, the three grating interferometers 110 are the first, second, and third grating interferometers, respectively. Their output measurement signals are processed by the signal subdivision module 210 to obtain their respective position information in the two-dimensional plane: the first grating interferometer corresponds to x1 and y1, the second to x2 and y2, and the third to x3 and y3. All six measurement data constitute a state vector [x1 y1 x2 y2 x3 y3], representing the real-time displacement of the three measurement points. The spatial pose of the reflector 10 is represented by six degrees of freedom parameters, namely three translational components [Δx Δy Δz] and three rotational components [Rx Ry Rz], collectively denoted as [xyz Rx Ry Rz]. The mapping relationship between this spatial pose and the multi-point measurement values ​​is established through a pre-calibrated spatial coordinate transformation matrix H.

[0063] Specifically, the positions of the three grating interferometers are denoted in the mirror coordinate system as follows: It should be noted that the mirror coordinate system uses the plane containing the reflecting surface of the mirror as the XY plane; the direction perpendicular to this plane is defined as the Z-axis, which is the normal direction along the center of the incident surface of the mirror; the X-axis and Y-axis are perpendicular to each other in the XY plane, forming a right-handed coordinate system.

[0064] In this embodiment, the positions of the three grating interferometers are not collinear, therefore the matrix is ​​invertible.

[0065] Each grating interferometer can only provide two in-plane displacement data, denoted as: This represents the displacement along the X-line of the grating. Displacement along the Y-axis of the grid line.

[0066] The three grating interferometers provide a total of 6 data streams, denoted as: Express the 6 data streams as a linear expression for "rigid body small displacement," and let the micro-displacement of the reflector be: For the i-th grating interferometer, the in-plane displacement of the grating is given by rigid motion, as follows: Writing out all three grating interferometers yields a 6×6 linear equation, denoted as: D = H ×P Where H is only related to { The three grating interferometers are not collinear, which means they are full rank.

[0067] It should be noted that matrix H is solved based on the installation geometry of the grating interferometer 110, the relative positional relationship between the measurement direction and the coordinate system of the reflector 10, and the rigid body kinematics model, to ensure that the coupling relationship between the displacement of the measurement point and the overall pose can be accurately reflected under any small displacement or attitude change.

[0068] It is understandable that, through spatial coordinate transformation, the local displacement information distributed on the three sides of the reflector 10 (position information measured by the three grating interferometers 110) can be integrated into the spatial pose information of the reflector 10 unit in space (a complete six-degree-of-freedom spatial pose), thereby achieving accurate measurement of the position of the reflector 10. Specifically, the spatial pose information of the reflector 10 is determined based on the following formula (1): [xyz Rx Ry Rz]=H×[x1 y1 x2 y2 x3 y3] (1) In this embodiment, the subdivision processing module 220 adopts a subdivision card, which also has a zero-point position determination function to ensure that the absolute zero-point position of the system is accurate.

[0069] Understandably, the signal subdivision processing module 220 uses a high-performance subdivision card to achieve high-precision demodulation and processing of the output signal of the grating interferometer 110. The subdivision card integrates a zero-point position determination function. This function identifies and locks the absolute reference point of each measurement channel when the system is powered on or initialized by recognizing the preset absolute zero mark (such as zero-point groove or magnetostrictive mark) on the grating ruler 111. This ensures that the position reference can be quickly and accurately reconstructed without repeated mechanical zeroing after each startup, effectively avoiding positioning deviations caused by zero-point drift or misjudgment, and ensuring the reliability of the system's long-term operation.

[0070] In this embodiment, the processing module 220 can be a CPU. The position information output by the subdivision card is transmitted to the CPU through the VME bus. The CPU determines whether the position of the reflector 10 meets the standard based on the difference between the preset position and the actual position (measured spatial pose information). If the reflector 10 does not reach the preset position, the CPU will control the actuator and other actuators to operate.

[0071] Understandably, the raw six-degree-of-freedom position data (i.e., [x1 y1 x2 y2 x3y3]) processed by the subdivision card is transmitted at high speed to the processing module 220 via the VME bus. This processing module 220 is composed of a CPU and has real-time data processing and closed-loop control capabilities. After receiving the position data, the CPU combines the pre-calibrated spatial coordinate transformation matrix H to calculate the spatial pose information of the reflector 10 in real time and compares it with the preset pose information (target position). If it is detected that the spatial pose information of the reflector 10 has not reached the target position or has drift exceeding the tolerance range, the CPU will calculate the position deviation in each degree of freedom, generate the corresponding deviation signal, and perform dynamic adjustment of the reflector 10 at the micrometer or even nanometer level to achieve the target position of the reflector 10.

[0072] It should be noted that, during system operation, this embodiment can continuously monitor the minute drift of the reflector 10 caused by environmental factors such as temperature changes, mechanical vibration, and airflow disturbances, and generate compensation signals in real time to drive the actuator to perform reverse correction, thereby effectively suppressing the problem of decreased imaging stability caused by external interference and significantly improving the dynamic stability of the reflector 10.

[0073] A second aspect of the present invention provides a position adjustment system for a reflective projection lens, such as... Figure 3 and Figure 5 As shown, the position adjustment system includes an actuator 300, a driver 400, and a position measuring device for the reflective projection lens provided in any of the above embodiments. The reflector 10 is mounted on the reflector base 40 via the actuator 300; the driver 400 is connected to the processing unit 200 and the actuator 300.

[0074] The processing unit 200 generates a position adjustment command based on the deviation between the spatial pose information and the preset pose information; the driver 400 receives the position adjustment command and generates a drive signal based on the position adjustment command; and the actuator 300 generates an action in response to the drive signal to adjust the pose of the reflector 10.

[0075] Understandably, the reflector 10 is mounted on the reflector base 40 via multiple actuators 300, achieving flexible support and multi-degree-of-freedom adjustable connection; the actuators 300 can respond to minute control signals to achieve precise displacement output at the nanometer or even sub-nanometer level.

[0076] The driver 400, acting as an intermediate execution unit, is connected to the processing unit 200 at one end and the actuator 300 at the other, and is responsible for receiving position adjustment commands from the processing unit 200. These commands are generated by the processing unit 200 based on the deviation between the actual spatial pose information of the reflector 10 calculated in real-time by the position measurement device and the preset target pose. After processing by the control algorithm, an error compensation signal is formed. The driver 400 converts this adjustment command into a drive signal (such as voltage, current, or pulse signal) suitable for the operation of the actuator 300 and outputs it precisely to each actuator 300. Under the action of the drive signal, the actuator 300 generates corresponding extension or tilting movements, thereby driving the reflector 10 to dynamically adjust in the X, Y, and Z translational directions and the rotational directions around the X, Y, and Z axes. This gradually eliminates pose deviations, causing the reflector 10 to approach and stabilize at the target position. This achieves real-time monitoring, precise control, and dynamic compensation of the reflector 10's pose, effectively suppressing the effects of environmental disturbances such as thermal drift and vibration, and significantly improving the imaging stability of the reflective projection lens and the overlay accuracy of the photolithography process.

[0077] In one embodiment of the present invention, the plurality of actuators 300 include three drive motors, which are disposed on the reflector base 40. The outputs of the drive motors are connected to the reflector 10, and the outputs of the three drive motors correspond to the three corner regions of the reflector 10.

[0078] Understandably, each reflector 10 is equipped with three drive motors and three grating interferometers 110, forming a high-precision reflector position adjustment unit. The three drive motors are distributed at the three corners of the reflector 10 unit, and are located on the same circumference with the center normal of the reflecting surface as the axis, and are evenly arranged circumferentially. The three drive motors are at a 120° angle to each other on this circumference.

[0079] Understandably, the driver 400 uses a motor driver, which is connected to the drive motor via a VMB serial cable. The motor driver receives control signals from the CPU in real time and converts them into precise drive voltage or current to drive the drive motor to produce corresponding micro-displacement movements, thereby adjusting the spatial pose of the reflector 10 through the drive motor.

[0080] In one embodiment of the present invention, a clock synchronization unit 500 is further included, the output of which is connected to the processing unit 200, the preamplifier 120 and the driver 400 respectively.

[0081] For example, the clock synchronization unit 500 outputs a highly stable, low-jitter clock signal, which is connected to and processed by the unit 200 (such as the CPU), the preamplifier 120, and the driver 400, respectively, to ensure that all hardware modules in the measurement and control link work together under a unified time reference.

[0082] Among them, the clock synchronization unit 500 is implemented by a clock card, which can provide clock pulses with nanosecond or even higher precision, effectively eliminating data sampling misalignment, control delay and phase lag caused by the asynchronous clocks of each module, significantly reducing system feedback delay and improving the response speed and stability of closed-loop control.

[0083] Understandably, the timing consistency of the entire system is ensured by the clock synchronization unit 500, and the measurement, calculation, driving and execution links achieve efficient coordination, ensuring high-precision closed-loop control of the position and state of the reflector 10, effectively dealing with dynamic disturbances such as temperature drift and mechanical vibration, and comprehensively improving the imaging quality of the reflective projection lens.

[0084] It should be noted that the CPU coordinates and controls the signal acquisition timing of the subdivision card, the working state of the preamplifier 120, and the operating rhythm of the motor driver.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A position measuring device for a reflective projection lens, characterized in that, The reflective projection lens includes a reflector, the reflector having a reflective surface and three side surfaces connected to the reflective surface; the device includes: The measurement unit includes three grating interferometers, which are respectively disposed on three sides of the reflector. The grating interferometers are used to measure the position information of the reflector and output corresponding measurement signals. The processing unit is used to receive measurement signals output by the three grating interferometers and determine the spatial pose information of the reflector based on the three measurement signals.

2. The position measuring device for a reflective projection lens according to claim 1, characterized in that, Each of the grating interferometers includes a grating ruler and a reading head, the grating ruler being disposed on the side of the reflector and the reading head being disposed opposite to the grating ruler.

3. The position measuring device for a reflective projection lens according to claim 2, characterized in that, The three measuring positions of the grating rulers are located on a circle with the center normal of the reflective surface as the axis, and are evenly distributed along the circumference.

4. The position measuring device for a reflective projection lens according to claim 2, characterized in that, Each of the reading heads is connected to a preamplifier, which is connected to the processing unit.

5. The position measuring device for a reflective projection lens according to claim 4, characterized in that, The preamplifier is equipped with a light source, which is connected to the signal input end of the reading head via a first and a second parallel optical fiber.

6. The position measuring device for a reflective projection lens according to claim 5, characterized in that, The preamplifier has a built-in photodetector, which is connected to the signal output end of the reading head via a first return optical fiber and a second return optical fiber in parallel. The photodetector is used to convert the optical signal output by the reading head into an electrical signal and output it to the processing unit.

7. The position measuring device for a reflective projection lens according to any one of claims 1 to 6, characterized in that, The processing unit includes: A signal subdivision module is connected to the three grating interferometers. The signal subdivision module is used to subdivide the measurement signal and output the position information corresponding to the three grating interferometers. A processing module, connected to the signal subdivision module, is used to determine the spatial pose information of the reflector based on the position information corresponding to the three grating interferometers.

8. A position adjustment system for a reflective projection lens, characterized in that, include: The position measuring device for a reflective projection lens as described in any one of claims 1 to 7; The actuator is used to mount the reflector on the reflector base. A driver is connected to the processing unit and the actuator; The processing unit is used to generate a position adjustment command based on the deviation between spatial pose information and preset pose information; the driver is used to receive the position adjustment command and generate a drive signal based on the position adjustment command. The actuator is used to generate an action in response to the drive signal to adjust the pose of the reflector.

9. The position adjustment system for a reflective projection lens according to claim 8, characterized in that, The actuator includes three drive motors, which are mounted on the reflector base. The outputs of the drive motors are connected to the reflector, and the outputs of the three drive motors correspond to the three corner regions of the reflector.

10. The position adjustment system for a reflective projection lens according to claim 8, characterized in that, It also includes a clock synchronization unit, the output of which is connected to the processing unit, the preamplifier and the driver respectively.

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