Offset angle measuring devices, methods, and semiconductor equipment and process products

Abstract

This application discloses an offset angle measuring device, method, and semiconductor equipment and program product, relating to the field of semiconductor manufacturing. Addressing the problem that current offset angle correction of semiconductor equipment requires disrupting the vacuum environment of the semiconductor equipment, this application provides an offset angle measuring device, comprising: a signal acquisition module for acquiring the interference signal from a laser interferometer; a feature extraction module for determining the signal intensity and background noise of the interference signal; a signal processing module for determining the fringe contrast based on the signal intensity and background noise; wherein the fringe contrast is the ratio of signal intensity to background noise; and an offset calculation module for determining the offset angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage based on the fringe contrast. This device can achieve offset angle correction without disrupting the vacuum environment of the semiconductor equipment, ensuring the accuracy of semiconductor equipment measurements.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing, and in particular to an offset angle measuring device, method, and semiconductor equipment and process products. Background Technology

[0002] In the semiconductor manufacturing field, high-precision semiconductor equipment, such as semiconductor measurement equipment, typically uses high-precision displacement stages, such as six-degree-of-freedom stages (6-DoF stages), to achieve wafer leveling and focusing. These stages can be used in conjunction with laser interferometers to complete wafer measurements. The displacement stage and laser interferometer are located within a vacuum cavity system.

[0003] In the actual assembly of semiconductor equipment, structural stress deformation caused by vacuum cavity assembly process or mechanical deformation caused by temperature gradient can cause a hidden initial angular offset between the optical axis of the laser interferometer and the mirror surface of the reflector. This angular offset will cause the effective operable angle range of the displacement stage to be distorted from a symmetrical range to an asymmetrical range, affecting the accuracy of the displacement stage.

[0004] To correct the aforementioned angular offset, an autocollimator system (including an autocollimator and optical components such as a beam splitter and a cornerstone prism) can be used. The beam splitter separates the measurement beam from the laser interferometer, and the cornerstone prism deflects the light path to guide it onto the target surface separated by the autocollimator. The offset angle is then calculated by measuring the center offset distance of the light spot on the target surface.

[0005] However, the above solution requires the introduction of additional devices, and all operations must be completed in the open state of the vacuum cavity system. In other words, the above solution will destroy the vacuum environment of the vacuum cavity system and cannot provide a means of monitoring the offset angle when the semiconductor device is working normally. The application scenarios are limited. For example, when the laser interferometer optical path is offset due to vacuum stress release or thermal deformation during the operation of the semiconductor device, the above solution cannot be used to monitor the offset angle and make corrections, which affects the performance of the displacement stage and ultimately affects the measurement accuracy of the device. Summary of the Invention

[0006] This application discloses an offset angle measuring device, method, semiconductor equipment, and program product, which can correct the offset angle and improve measurement accuracy when the semiconductor equipment is working normally.

[0007] In a first aspect, this application provides an offset angle measuring device, comprising: a signal acquisition module for acquiring interference signals from a laser interferometer; a feature extraction module for determining the signal intensity and background noise of the interference signal; a signal processing module for determining a fringe contrast based on the signal intensity and the background noise; wherein the fringe contrast is the ratio of the signal intensity to the background noise; and an offset calculation module for determining the offset angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage based on the fringe contrast.

[0008] This device acquires interference signals through a signal acquisition module and multiplexes these signals using a feature extraction module, a signal processing module, and an offset calculation module. This expands the functionality of the interference signals to calculate the spatial angular offset of the laser interferometer, specifically the offset angle between the laser interferometer's optical axis and the stage mirror. Specifically, the fringe contrast is determined by extracting the signal intensity and background noise components from the interference signal. Since fringe contrast directly reflects interference efficiency, and an increase in the offset angle significantly reduces interference efficiency, the fringe contrast can be used to calculate the offset angle and complete the measurement. Therefore, this device eliminates the need for additional optical components such as beam splitters and corner prisms. Furthermore, it does not disrupt the vacuum environment of the semiconductor equipment. By multiplexing the interference signals output by an existing laser interferometer to measure the offset angle, this device can effectively observe the semiconductor equipment even when its vacuum cavity is closed. Therefore, even if the optical path of the laser interferometer shifts due to vacuum stress release or thermal deformation during the application of semiconductor equipment, this device can still monitor the aforementioned angular shift and take compensation measures to avoid measurement errors. It has strong applicability to various scenarios, improves the performance of the displacement stage, and thus improves the overall measurement accuracy of the equipment.

[0009] In one possible implementation, the signal acquisition module is a photoelectric conversion module; the photoelectric conversion module is used to receive the interference beam (optical signal) of the laser interferometer and perform photoelectric conversion on the interference beam to obtain the interference signal (electrical signal).

[0010] In this embodiment, a photoelectric conversion module is used as the signal acquisition module for the interference signal. This converts the interference beam, which is an optical signal, into an electrical signal form, i.e., the interference signal, which is easier to process and calculate subsequently. This facilitates the implementation of the feature extraction module, signal processing module, and offset calculation module.

[0011] In one possible implementation, the photoelectric conversion module includes: an optical fiber interface, a coupling lens, and a photosensitive device; the optical fiber interface is disposed at the vacuum cavity of the semiconductor device for transmitting optical signals from inside the vacuum cavity to outside the vacuum cavity; the coupling lens is disposed corresponding to the optical fiber interface and the photosensitive device for coupling the optical signal output from the optical fiber interface to the target surface of the photosensitive device; the photosensitive device is used to convert the optical signal received by the target surface into an electrical signal.

[0012] This embodiment presents a simple and reliable structure for a photoelectric conversion module. The fiber optic interface allows the optical signal (i.e., the interference beam) from the vacuum cavity to the outside without compromising the vacuum seal of the semiconductor device. The coupling lens couples the interference beam from the fiber optic interface to the target surface of the photosensitive device, enabling the photosensitive device to convert the received optical signal into an electrical signal, thus completing the photoelectric conversion module's function.

[0013] In one possible implementation, the fiber optic interface is a fiber optic connector flange.

[0014] In this embodiment, a fiber optic connector flange is used as the aforementioned fiber optic interface. The fiber optic connector flange has the advantage of good sealing performance, which can effectively ensure that the vacuum environment of the laser interferometer is not damaged.

[0015] In one possible implementation, the feature extraction module includes a bandpass filter and a low-pass filter; wherein the bandpass filter is used to extract the signal intensity of the interference signal; and the low-pass filter is used to extract the background noise of the interference signal.

[0016] In this embodiment, different frequency components of the interference signal are extracted separately using bandpass and lowpass filters to extract the signal intensity and background noise components, providing reliable data support for subsequent determination of fringe contrast. Furthermore, this embodiment is simple, reliable, and easy to implement in practical engineering.

[0017] In one possible implementation, it further includes: a waveform display module; the waveform display module is connected to the offset calculation module and is used to display the signal strength, background noise and fringe contrast of the interference signal, as well as the offset angle determined by the offset calculation module.

[0018] In this embodiment, the signal characteristics of the interference signal extracted from the vacuum cavity are visualized by the waveform display module, including signal strength, background noise, stripe contrast, and offset angle.

[0019] In one possible implementation, the offset calculation module includes: a distance calculation module for determining the spot center offset distance based on the fringe contrast, the distance between the laser interferometer and the displacement stage mirror, and the laser interferometer spot radius; and an angle calculation module for determining the offset angle based on the spot center offset distance.

[0020] In this embodiment, the offset distance of the laser spot center is determined by the distance calculation module based on the fringe contrast, the distance between the laser interferometer and the displacement stage mirror, and the laser interferometer spot radius. Then, the final offset angle is determined by the angle calculation module based on the offset distance of the spot center obtained by the distance calculation module. Therefore, this embodiment provides a simple and reliable offset calculation scheme, ensuring high efficiency and ease of implementation in obtaining the offset angle.

[0021] In one possible implementation, it further includes: a stepping control module for controlling the displacement stage to perform stepping deflection along a first direction or a second direction; wherein the first direction and the second direction are opposite directions; a signal monitoring module for monitoring the change in the fringe contrast of the interference signal; and an offset orientation module for determining the opposite direction of the stepping deflection direction as the offset direction if the trend of the change in the fringe contrast is non-monotonic.

[0022] In this embodiment, the stepping control module is used to achieve controllable and quantitative changes in the displacement stage's deflection angle. Furthermore, the signal monitoring module detects the signal strength of the interference signal during this deflection angle change. Since the fringe contrast of the interference signal is negatively correlated with the deflection angle, monitoring the trend of fringe contrast change can be considered as monitoring the trend of deflection angle change. Further, it is known that regardless of the rotation direction of the stepping deflection, as long as the stepping deflection direction is the opposite of the deflection direction, the rotation will definitely cause the deflection angle to pass through the 0° point. At this time, even if the stepping deflection direction remains unchanged, the deflection angle will exhibit a characteristic of first decreasing (before passing the 0° point) and then increasing (after passing the 0° point), i.e., a change in monotonicity. Therefore, the opposite direction of the stepping deflection direction can be determined as the deflection direction. Furthermore, combined with the previously determined deflection angle, all characteristics of the deflection angle can be determined, which is beneficial for subsequent deflection angle correction.

[0023] In one possible implementation, the system further includes: an attitude compensation module for generating a spatial attitude compensation vector based on the offset direction and the offset angle; and an offset correction module for correcting the angular offset of the displacement stage using the spatial attitude compensation vector.

[0024] In this embodiment, a spatial attitude compensation vector corresponding to the deflection angle is generated by the attitude compensation module. Since both the offset direction and the offset angle are determined, the displacement stage deflects by the same offset angle in the opposite direction of the offset direction to correct the deflection angle, thus obtaining the spatial attitude compensation vector. Furthermore, the deflection angle correction process is completed by the offset correction module based on the spatial attitude compensation vector determined by the attitude compensation module, achieving automated correction of the laser interferometer displacement stage, improving correction efficiency while ensuring accuracy.

[0025] In one possible implementation, it further includes: an initialization module for controlling the deflection of the displacement stage to cause the measurement beam of the laser interferometer to deviate from the effective area of ​​the displacement stage mirror; an aliasing calibration module for controlling the rotation of the half-wave plate of the laser interferometer until the fringe contrast reaches the minimum value during this rotation process; and a reset module for controlling the reset of the displacement stage and enabling the signal acquisition module.

[0026] In this embodiment, the principle of determining the offset direction is used to additionally implement the polarization aliasing calibration function of the laser interferometer. Specifically, the initialization module controls the deflection of the displacement stage, causing the measurement beam of the laser interferometer to leave the effective area of ​​the displacement stage mirror. Then, the aliasing calibration module controls the rotation of the half-wave plate in the laser interferometer. During this rotation, the fringe contrast of the interference signal is continuously monitored. Since the root cause of polarization aliasing lies in the systematic error caused by frequency cross-leakage due to optical element defects, polarization degradation, or assembly errors, it manifests as a periodic nonlinear displacement deviation. The introduction of periodic nonlinear errors causes fluctuations in the fringe contrast of the interference signal. Therefore, when the fringe contrast is at its minimum, it indicates that this error has been suppressed to a minimum, i.e., polarization aliasing suppression is achieved. Based on this embodiment, after implementing polarization aliasing calibration and suppression, the adverse effects of polarization aliasing on laser interferometer measurements can be avoided, thereby further improving measurement accuracy.

[0027] Secondly, this application provides a semiconductor device, including a laser interferometer, a displacement stage, and the offset angle measuring device provided in any of the above embodiments. Because it includes the aforementioned offset angle measuring device, it can achieve the effects provided by that device. That is, this semiconductor device can indirectly measure the offset angle by multiplexing existing interference signals without introducing additional optical components such as beam splitters or corner prisms, without disrupting the vacuum environment of the semiconductor device, and can still perform effective observation even when the vacuum cavity of the laser interferometer is closed. Therefore, even if the semiconductor device experiences angular displacement of the laser interferometer's optical path due to vacuum stress release or thermal deformation during application, the generation of the offset angle can still be monitored and compensation measures can be taken to avoid measurement errors and ensure the high measurement accuracy of this semiconductor device.

[0028] Thirdly, this application provides a method for measuring an offset angle, comprising: acquiring an interference signal from a laser interferometer; determining the signal intensity and background noise of the interference signal; determining a fringe contrast based on the signal intensity and the background noise; wherein the fringe contrast is the ratio of the signal intensity to the background noise; and determining the offset angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage based on the fringe contrast. This method can achieve the function of the offset angle measuring device described in the first aspect above, and can bring the same technical effect. Please refer to the description in the first aspect above for details.

[0029] In one possible implementation, determining the offset angle between the optical axis of the laser interferometer and the reflector of the displacement stage based on the fringe contrast includes: determining the center offset distance of the light spot based on the fringe contrast, the distance between the laser interferometer and the reflector of the displacement stage, and the light spot radius of the laser interferometer; and determining the offset angle based on the center offset distance of the light spot.

[0030] In this embodiment, the offset distance of the laser spot center is determined by the fringe contrast, the distance between the laser interferometer and the displacement stage mirror, and the laser interferometer spot radius. This replaces manual measurement to determine the offset distance of the spot center. Furthermore, after obtaining the offset distance of the spot center, the final offset angle can be determined based on it. Therefore, this embodiment provides a simple and reliable offset calculation scheme. It eliminates the need for manual measurement of the offset distance of the laser spot center in the laser interferometer, thus eliminating the need for additional measuring tools within the vacuum chamber. The offset angle determination achieved in this way does not disrupt the vacuum environment of the semiconductor device, ensuring high efficiency and ease of implementation in obtaining the offset angle.

[0031] In one possible implementation, the method further includes: controlling the displacement stage of the laser interferometer to perform step deflection along a first direction or a second direction; wherein the first direction and the second direction are opposite directions; monitoring the change in the fringe contrast of the interference signal; and if the trend of the change in the fringe contrast is non-monotonic, determining the opposite direction of the step deflection direction as the offset direction.

[0032] In this embodiment, the deflection angle is controlled and quantitatively varied by stepping the displacement stage along a defined direction. Since there is a negative correlation between the fringe contrast of the interference signal and the offset angle, monitoring the trend of fringe contrast variation can be considered as monitoring the trend of offset angle variation. Furthermore, it is known that regardless of the rotation direction of the stepping deflection, as long as the stepping deflection direction is opposite to the offset direction, the rotation will always cause the offset angle to pass through the 0° point. At this point, even if the stepping deflection direction remains unchanged, the offset angle will exhibit a characteristic of first decreasing (before passing the 0° point) and then increasing (after passing the 0° point), i.e., a change in monotonicity. Therefore, the opposite direction of the stepping deflection direction can be determined as the offset direction. Combining this with the previously determined offset angle completes the determination of all characteristics of the offset angle, which is beneficial for subsequent offset angle correction.

[0033] In one possible implementation, the method further includes: generating a spatial attitude compensation vector based on the offset direction and the offset angle; and correcting the angular offset of the displacement stage using the spatial attitude compensation vector. This implementation can achieve automated calibration of the displacement stage, improving calibration efficiency while ensuring calibration accuracy.

[0034] In one possible implementation, the method further includes: controlling the deflection of the displacement stage to cause the measurement beam of the laser interferometer to leave the effective area of ​​the displacement stage mirror; controlling the rotation of the half-wave plate of the laser interferometer until the fringe contrast reaches the minimum value during this rotation process; controlling the displacement stage to reset and return to the step of acquiring the interference signal of the laser interferometer.

[0035] In this embodiment, the principle of determining the offset direction is used to additionally implement the polarization aliasing calibration function of the laser interferometer. Specifically, the initialization module controls the deflection of the displacement stage, causing the measurement beam of the laser interferometer to leave the effective area of ​​the displacement stage mirror. Then, the aliasing calibration module controls the rotation of the half-wave plate in the laser interferometer. During this rotation, the fringe contrast of the interference signal is continuously monitored. Since the root cause of polarization aliasing lies in the systematic error caused by frequency cross-leakage due to optical element defects, polarization degradation, or assembly errors, it manifests as a periodic nonlinear displacement deviation. The introduction of periodic nonlinear errors causes fluctuations in the fringe contrast of the interference signal. Therefore, when the fringe contrast is at its minimum, it indicates that this error has been suppressed to a minimum, i.e., polarization aliasing suppression is achieved. Based on this embodiment, after implementing polarization aliasing calibration and suppression, the adverse effects of polarization aliasing on laser interferometer measurements can be avoided, thereby further improving measurement accuracy.

[0036] Fourthly, this application provides an offset angle measuring device, including a processor, which is used to execute the offset angle measuring method provided in any embodiment of the third aspect. This device can achieve the technical effects brought about by the offset angle measuring method provided in any embodiment of the third aspect, as detailed in the description of the third aspect above.

[0037] Fifthly, this application provides a computer program product comprising a computer program for executing the offset angle measurement method provided in any of the embodiments described in the third aspect. This computer program product can achieve the technical effects brought about by the offset angle measurement method provided in any of the embodiments of the third aspect, as detailed in the description of the third aspect above.

[0038] In a sixth aspect, this application provides a computer-readable storage medium comprising a computer program for performing the offset angle measurement method provided in any of the embodiments described in the third aspect. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A structural diagram of a semiconductor quantity detection device provided in an embodiment of this application; Figure 2 A structural diagram of an offset angle measuring device provided in an embodiment of this application; Figure 3 A structural diagram of a vacuum cavity internal offset angle measuring device provided in an embodiment of this application; Figure 4 A structural diagram of a vacuum chamber external part offset angle measuring device provided in an embodiment of this application; Figure 5 This is a partial structural diagram related to determining the offset direction in an offset angle measuring device provided in an embodiment of this application; Figure 6 A schematic diagram of a three-dimensional spatial coordinate system provided for an embodiment of this application; Figure 7 A schematic diagram of an angular component of rotation about the Y-axis provided in an embodiment of this application; Figure 8 This application provides a partial structural diagram of an offset angle measuring device related to attitude compensation. Figure 9 This is a partial structural diagram related to aliasing calibration in an offset angle measuring device provided in an embodiment of this application; Figure 10 A flowchart illustrating an offset angle measurement method provided in this application embodiment; Figure 11 A flowchart of another offset angle measurement method provided in an embodiment of this application.

[0041] Explanation of reference numerals in the attached figures: 100 - Equipment; 101-Vacuum cavity; 102-Vacuum pump; 103-Laser interferometer; 1031-Mirror; 1032-Half-wave plate; 104-Displacement stage; 105-Displacement calculation module; 200-Offset Angle Measuring Device; 201 - Signal Acquisition Module; 2011 - Fiber optic interface; 2012 - Coupling lens; 2013 - Photosensitive device; 2014 - Discrete high-voltage circuit; 2015 - Boost chopper circuit; 2016 - Transimpedance amplifier; 202 - Feature Extraction Module; 2021 - Bandpass filter; 2022 - Low-pass filter; 2023 - Low-speed analog-to-digital converter; 203-Signal processing module; 204-Offset calculation module; 205-Waveform display module; 206-Power supply module; 207-Stepping control module; 208-Signal monitoring module; 209-Offset orientation module; 210-Attitude compensation module; 211-Offset correction module; 212-Initialization module; 213-Aliasing calibration module; 214-Reset module. Detailed Implementation

[0042] In the semiconductor manufacturing field, some semiconductor equipment has high precision requirements, and some components inside the equipment need to work in a vacuum environment, such as semiconductor measurement equipment or some semiconductor manufacturing equipment.

[0043] like Figure 1As shown, device 100 is a semiconductor quantity measurement device. The vacuum chamber system of device 100 includes a vacuum chamber 101 and a vacuum pump 102. The vacuum chamber system provides the necessary vacuum environment for the components within the vacuum chamber. The vacuum pump 102 is used to evacuate the vacuum chamber 102 to achieve the required vacuum level. A laser interferometer 103 and a displacement stage 104 are located within the vacuum chamber 101. The laser interferometer 103 provides ultra-high precision displacement measurement for the wafer. The displacement measurement value can be used as a closed-loop feedback signal to control the movement of the displacement stage 104, eliminating motion errors in real time and achieving nanometer / sub-nanometer level absolute positioning accuracy, repeatability, and motion control performance. Specifically, the displacement measurement value can be calculated from the interference signal output by the laser interferometer 103 using a displacement calculation module 105. It should be noted that the reflector 1031, a key component of the laser interferometer, is fixed to the displacement stage. As the terminal reflective element of the measurement optical path, the reflector 1031 is actually part of the laser interferometer 103, but is mounted on the displacement stage 104. When the displacement stage 104 moves, the reflector 1031 moves accordingly, causing a change in the optical path of the measurement beam, thereby altering the phase difference with the reference beam and generating a detectable interference signal. The displacement stage 104 can be used to achieve motion control functions such as high dynamic response, multi-dimensional error compensation, and complex trajectory tracking. Specifically, taking the displacement stage 104 as a six-degree-of-freedom (6-DoF) precision displacement stage as an example, it can perform rotational motion adjustment along three axes and six directions (each axis includes clockwise and counterclockwise rotational directions) in the three-dimensional spatial coordinate system XYZ. This is used to achieve wafer leveling and focusing, and works in conjunction with the laser interferometer 103 to achieve ultra-precision positioning and measurement of the wafer. The six degrees of freedom refer to free movement along three axes of the three-dimensional spatial coordinate system XYZ (right-handed coordinate system), rotating clockwise or counterclockwise, for a total of six directions. To facilitate the degree-of-freedom adjustment of the displacement stage 104, laser interferometers 103 can be installed in the X-axis and Y-axis directions respectively. The displacement stage 104 primarily changes the relative angle between the mirror surface of the reflector 1031 (or simply the "reflector surface") and the optical axis of the laser interferometer 103 (or simply the "interferometer optical axis") through rotational motion Rx / Ry around the X / Y axes (Rx, also known as pitch, refers to the object's rotation around the X-axis; Ry, also known as yaw, refers to the object's rotation around the Y-axis). When this relative angle change exceeds a critical value, the two coherent light spots of the laser interferometer 103 will spatially separate, causing amplitude attenuation of the interference signal components. Therefore, the aforementioned critical value, or the maximum value of the aforementioned relative angle change (maximum allowable rotation angle), can be used as the core acceptance criterion for the laser interferometer 103.

[0044] However, in the actual assembly of semiconductor equipment, structural stress deformation caused by vacuum cavity bonding or mechanical deformation caused by temperature gradients can create a hidden initial deflection angle between the optical axis of the laser interferometer and the reflecting mirror. This deflection angle (or angular offset) can cause asymmetric compression of the effective working range of the displacement stage, or distortion of the actual operable angle range of the displacement stage. For example, it can be distorted from the theoretically symmetrical range [-α, +α] to the asymmetric range [-α1, +α2] (α1≠α2), requiring correction of this angle range. In related technologies, an autocollimator system independent of the semiconductor equipment is needed to correct the aforementioned deflection angle. The autocollimator system includes an autocollimator and optical components such as a beam splitter and a corner prism. The specific correction process involves splitting the measurement beam of the laser interferometer using a beam splitter, then reversing the optical path using a corner prism to guide it to the target surface separated by the autocollimator. The offset angle is then calculated by measuring the center offset distance of the light spot on the target surface to determine the deflection angle.

[0045] However, the above solution requires the introduction of additional optical components such as beam splitters and corner prisms within the vacuum cavity, and all operations must be performed in an open cavity state. Once the vacuum cavity is closed, the autocollimator system loses its observability of the internal state of the vacuum cavity and cannot observe angular shifts. In this case, if angular shifts occur in the laser interferometer's optical path due to vacuum stress release or thermal deformation, it will directly cause measurement errors, but there is a lack of effective real-time monitoring methods outside the cavity, ultimately leading to irreversible degradation of displacement measurement accuracy. In other words, the above solution disrupts the vacuum environment of the semiconductor device's vacuum cavity, making it impossible to provide angular shift monitoring methods when the semiconductor device (mainly laser interferometers and displacement stages that must operate within the semiconductor device's vacuum cavity) is functioning normally, thus limiting its application scenarios. For example, limited application scenarios include: if the semiconductor device experiences angular shifts in the interferometer's optical path due to vacuum stress release or thermal deformation during operation, these cannot be monitored and corrected using the above solution, affecting the accuracy of wafer displacement measurement.

[0046] Therefore, in order to solve the problem that current offset angle correction schemes will damage the vacuum environment, this application provides an offset angle measuring device and a measuring method.

[0047] This application provides an offset angle measuring device 200, which can be used as a module independent of a vacuum cavity. It is used to observe the offset angle between the optical axis of a laser interferometer 103 and the mirror surface of a reflector 1031 within a vacuum cavity without disrupting the vacuum environment. The offset angle measuring device 200 only needs to receive the interference signal output from the laser interferometer 103 as input to achieve offset angle observation, without needing to be installed within the vacuum cavity. This embodiment does not limit the specific location of the offset angle measuring device 200; it can be integrated into a semiconductor device or used as a detachable optional module separate from the semiconductor device, depending on the actual application requirements. The specific structure of this device is as follows... Figure 2 As shown, it includes: The signal acquisition module 201 is used to acquire the interference signal of the laser interferometer.

[0048] The feature extraction module 202 is used to determine the signal strength and background noise of the interference signal.

[0049] The signal processing module 203 is used to determine the fringe contrast based on the signal strength and background noise. The fringe contrast is the ratio of the interference signal strength to the background noise.

[0050] The offset calculation module 204 is used to determine the offset angle between the optical axis of the laser interferometer and the reflective surface of the displacement stage based on the fringe contrast.

[0051] Before describing the specific embodiments of the components of the offset angle measuring device 200 provided in this application, the principle by which this device can determine the offset angle will be explained: First, it should be noted that the offset angle to be calculated by this device refers to the angle of deviation between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031. When the angular offset between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031 exceeds a certain specific value, the two coherent light spots of the laser interferometer 103 will spatially separate (the aforementioned specific value can be called the critical value, which can be determined by observing the offset angle value when the two coherent light spots of the laser interferometer 103 spatially separate), thereby causing the amplitude of the interference signal component to attenuate. Among them, the two components of the interference signal are the alternating current (AC) component representing the signal intensity and the direct current (DC) component representing the background noise. In optical measurement, the AC component specifically refers to the alternating component in the interference signal that changes with the phase, that is, the signal intensity (also called fringe amplitude) mentioned in the feature extraction module 202 above, which is the carrier of the effective signal. In optical measurements, the DC component specifically refers to the constant background light intensity that does not change with interference; it belongs to the noise floor, i.e., the background noise mentioned in the feature extraction module 202 above. The ratio of the AC component to the DC component (AC / DC value, i.e., fringe contrast) directly reflects the interference efficiency. An angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031 significantly reduces the interference efficiency. Therefore, this application concludes that the fringe contrast (AC / DC value) of the interference signal is negatively correlated with the angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031.

[0052] This application can reflect the magnitude of the aforementioned deflection angle (i.e., the offset angle) through the fringe contrast of the interference signal, without needing to open the vacuum cavity to introduce additional optical components such as beam splitters and corner prisms to deflect the measurement beam of the laser interferometer 103 to the separation target surface of the autocollimator system, nor is it necessary to measure the center offset distance of the light spot projected onto the separation target surface. The offset angle can be observed simply by acquiring the interference signal output by the laser interferometer 103 during normal operation. Furthermore, the interference signal itself is the signal output by the laser interferometer 103 during normal operation and can be used as feedback input for the displacement calculation module in the semiconductor device to control the movement of the displacement stage 104. The displacement calculation module in the semiconductor device does not need to be located within the vacuum cavity, as previously explained, the laser interferometer 103 requires a vacuum environment during operation. In other words, the current laser interferometer 103 supports outputting interference signals outside the vacuum cavity without disrupting the vacuum environment. This device only requires the input of an interference signal to function, so it does not need to be placed inside a vacuum chamber. It can support the observation of the offset angle without disrupting the vacuum environment inside the vacuum chamber, and then the offset angle can be adjusted. It has strong applicability to various scenarios, improves the performance of the displacement stage, and thus improves the overall measurement accuracy of the equipment.

[0053] The functions of each component module of the offset angle measuring device 200 provided in this application are described below: The signal acquisition module 201 is designed to acquire the interference signal output by the laser interferometer 103, facilitating subsequent processing by other modules. It should be noted that the interference signal directly output by the laser interferometer 103 is typically in optical signal form. However, in actual signal analysis and processing implemented using hardware devices or software methods, electrical signals are often processed. In one embodiment, the signal acquisition module 201 is used to convert the optical signal into an electrical signal. It is understood that the optical signal can also be converted into other signal forms that are convenient for subsequent processing and calculation, adapting to the processing modes of other modules; no limitation is imposed.

[0054] When the signal acquisition module 201 is used to convert the interference signal from the optical signal form directly output by the laser interferometer 103 into an electrical signal form that is convenient for subsequent processing, then the front-end and rear-end stages of the signal acquisition module 201 involve two different forms of interference signals: optical signals and electrical signals. For ease of distinction in the following descriptions of embodiments, such as... Figure 2 As shown, the interference signal in optical form, directly output by the laser interferometer 103, is referred to as the "interference beam," while the electrical signal obtained by the signal acquisition module 201 from the interference beam is referred to as the "interference signal." That is, in subsequent embodiments, the interference signal refers to the electrical signal, and the optical signal directly output by the laser interferometer 103 is referred to as the interference beam.

[0055] Based on the above, this application provides an optional implementation: the signal acquisition module 201 is a photoelectric conversion module. The photoelectric conversion module receives the interference beam from the laser interferometer 103 and performs photoelectric conversion on the interference beam to obtain an interference signal. In this embodiment, the interference beam in optical signal form is converted into an interference signal in electrical signal form, which is easier to process, to facilitate subsequent determination and correction of the deflection angle based on the interference signal. This reduces the implementation difficulty of the device and improves the efficiency of deflection angle determination and correction.

[0056] After the signal acquisition module 201 acquires the interference signal, the feature extraction module 202, signal processing module 203, and offset calculation module 204 perform subsequent processing on the interference signal to determine the magnitude of the deflection angle. Specifically, the function of the feature extraction module 202 is to extract features from the interference signal to determine the signal intensity (AC component) and background noise (DC component) of the interference signal. The signal processing module 203 determines the fringe contrast (AC / DC value) based on the signal intensity and background noise determined by the feature extraction module 202. This fringe contrast directly reflects the interference efficiency of the laser interferometer 103. As can be seen from the above conclusion, it can also reflect the magnitude of the deflection angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031. Therefore, the offset calculation module 204 is used to determine the offset angle (i.e., the magnitude of the deflection angle) based on the fringe contrast. Therefore, the function of the feature extraction module 202 is to extract signal features. Based on the conversion of the optical signal output by the laser interferometer 103 into an electrical signal by the signal processing module 203, the feature extraction module 202 extracts the AC and DC components of the electrical signal. This can be achieved through corresponding electrical signal processing circuits or modules, and this embodiment does not impose any restrictions on this. As for the signal processing module 203 and the offset calculation module 204, they can be implemented by devices with certain data processing capabilities, such as microcontrollers, field-programmable gate arrays (FPGAs), etc., and this embodiment also does not impose any restrictions.

[0057] On the other hand, as explained in the above embodiments, the core of this device lies in calculating the offset angle by reusing the interference beam output by the existing laser interferometer 103, thereby avoiding the problem of disrupting the vacuum environment inside the vacuum cavity of the semiconductor device and realizing the correction of the deflection angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031. Under this principle, the above modules only need to perform optical signal acquisition, signal feature extraction, and simple data processing, making implementation easy. To further illustrate the offset angle measuring device 200 provided in this application, optional implementation methods are provided below for each module in this device.

[0058] In an embodiment where the signal processing module 203 is a photoelectric conversion module, for example, such as Figure 3 and Figure 4 As shown: The photoelectric conversion module (i.e., signal acquisition module 201) includes an optical fiber interface 2011, a coupling lens 2012, and a photosensitive device 2013. For example... Figure 3 As shown, the fiber optic interface 2011 is disposed at the vacuum cavity 101 of the semiconductor device, used to transmit optical signals from inside the vacuum cavity 101 to outside the vacuum cavity 101; the coupling lens 2012 is disposed correspondingly to the fiber optic interface 2011 and the photosensitive device 2013, as shown. Figure 4 As shown, the optical signal output from the optical fiber interface 2011 is coupled to the target surface of the photosensitive device 2013; the photosensitive device 2013 is used to convert the optical signal received by the target surface into an electrical signal.

[0059] The fiber optic interface 2011 is used to guide the interference beam out of the vacuum cavity without disrupting the vacuum environment, for subsequent determination of the offset angle. The coupling lens 2012 is used to couple the interference beam to the target surface of the photosensitive device 2013, forming an alignment-free optical path. This ensures that even if the optical path between the photosensitive device 2013 and the fiber optic interface 2011 is not strictly aligned, the interference beam can still be accurately received by the photosensitive device 2013 and converted into an interference signal in the form of an electrical signal, guaranteeing the reliability of the entire conversion process and facilitating subsequent offset angle calculation.

[0060] Furthermore, this embodiment also provides a further implementation scheme for the aforementioned fiber optic interface 2011: the fiber optic interface 2011 is a fiber optic connector flange. A flange is a disc-shaped metal connector with good sealing properties. It can ensure the seal between the fiber optic connector and the vacuum chamber 101, thereby extracting the interference beam without compromising the vacuum seal of the vacuum chamber.

[0061] Furthermore, for the aforementioned photosensitive device 2013, an optional implementation is as follows: Figure 4 As shown, this can be achieved using an avalanche photodiode (APD). The APD can convert optical signals to μA-level current signals (efficiency > 85%), thus eliminating dependence on an optical platform. Further examples include... Figure 4 As shown, the APD can be used in conjunction with the discrete high-voltage circuit 2014, which provides a bias voltage to the APD to achieve the required photoelectric conversion. Furthermore, the discrete high-voltage circuit 2014 provides the bias voltage only if there is a power input; in practical applications, it can be used as follows... Figure 4As shown, the boost chopper circuit 2015 (commonly known as the BOOST circuit) boosts the power signal provided by the voltage module (e.g., to 215V) to meet the power supply requirements of the isolated high-voltage circuit. Optionally, the power module 206 can use a lithium polymer battery pack (7.4V / 5000mAh), which outputs ±12V voltage through a voltage regulator circuit, thereby achieving intelligent charge and discharge management and supporting continuous operation for ≥10 hours.

[0062] Furthermore, the APD can convert optical signals to current signals. If it is further necessary to convert the current signal to a voltage signal, a corresponding current-to-voltage conversion module can be added. For example... Figure 4 As shown, the current signal output by the APD can be converted into a voltage signal by a transimpedance amplifier 2016 (TIA). In one example, the TIA is used to convert the μA-level current signal output by the APD into a mV-level voltage signal.

[0063] In one embodiment, corresponding to the signal processing module 203 converting the optical signal (interference beam) output by the laser interferometer 103 into an electrical signal (interference signal), the feature extraction module 202 extracts the AC and DC components of the electrical signal. Therefore, the feature extraction module 202 can be implemented by a corresponding electrical signal processing circuit or module. In a possible application scenario, this embodiment provides an optional solution for the feature extraction module 202, such as... Figure 4 As shown, the feature extraction module 202 includes a band-pass filter 2021 (BPF) and a low-pass filter 2022 (LPF). The band-pass filter 2021 is used to extract the AC component (signal strength) of the interference signal, while the low-pass filter 2022 is used to extract the DC component (background noise) of the interference signal. In this embodiment, by utilizing the characteristic that the AC component (signal strength) and DC component (background noise) of the interference signal belong to signal components of different frequencies, two filters with different passbands are used to extract signal components within a specific frequency band, i.e., extracting the required signal strength and background noise. The entire structure is simple and reliable, with high extraction efficiency and accuracy.

[0064] In addition, it should be noted that, as Figure 4 As shown, the above optional solutions do not constitute a limitation on the feature extraction module 202. The feature extraction module 202 may also include more or fewer devices than those shown in the above embodiments. For example, as... Figure 4As shown, the feature extraction module 202 can also add a low-speed analog-to-digital converter 2023 to the output of the low-pass filter 2022 to convert the analog signal output by the low-pass filter 2022 into a digital signal for convenient subsequent processing.

[0065] As explained above, for signal processing module 203, the fringe contrast is the ratio between the AC component and the DC component of the interference signal. Therefore, given that the AC and DC components are determined, signal processing module 203 can perform a division operation. Currently, various mature data processing devices exist that can perform division functions, and any of them can be used as signal processing module 203 in this device. The appropriate device can be selected arbitrarily according to actual needs; this embodiment does not impose any restrictions on this.

[0066] For example, such as Figure 4 As shown, the signal processing module 203 can be implemented using a programmable gain amplifier (PGA). The PGA is used to determine the ratio between the AC component (signal strength) and the DC component (background noise) output by the feature extraction module 202, thereby obtaining the stripe contrast (AC / DC value). Furthermore, the PGA can also be used to perform other signal processing, such as improving the signal-to-noise ratio. Additionally, in an optional implementation, such as... Figure 4 As shown, the signal processing module 203 can also be equipped with a high-speed analog-to-digital converter (250M_ADC; where 250M represents the speed and ADC represents an analog-to-digital converter) at the output of the PGA to convert the analog signal output by the PGA into a high-speed digital signal for subsequent equipment to receive.

[0067] Regarding the offset calculation module 204, as described above, there is a negative correlation between the fringe contrast of the interference signal and the offset angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031. Therefore, the offset calculation module 204 can be implemented using a built-in mathematical model or a hardware circuit capable of calculating a similar negative correlation; this embodiment does not impose any limitations on this. Based on the fringe contrast as input, the corresponding offset angle is output to determine the offset angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031, which assists in subsequent correction of the offset angle.

[0068] In one optional implementation, the offset calculation module 204 includes a distance calculation submodule for determining the center offset distance of the light spot based on the fringe contrast, the distance between the laser interferometer 103 and the reflector 1031, and the light spot radius of the laser interferometer 103; and an angle calculation submodule for determining the offset angle based on the center offset distance of the light spot.

[0069] The calculation process in the distance calculation submodule described above can be represented by the following formula: AC / DC = cos( )- (1); In the formula, AC / DC represents the ratio of the AC component to the DC component, which is also the fringe contrast. a It represents the offset distance between the centers of the two light spots caused by the backlight offset due to the deflection angle; r Characterizes the spot radius of laser interferometer 103.

[0070] Furthermore, assume that the distance between the laser interferometer 103 and the elongated reflector 1031 of the displacement stage 104 is... b If the offset angle is X, then the following expression applies to calculating the offset angle X in the angle calculation submodule: X = arccos( (2); In the above two formulas, r and b All values ​​are known quantities and can be obtained through prior measurement or by specifying the design parameters of the laser interferometer 103. The AC / DC value can be determined through the feature extraction and signal processing described above. Based on equation (1), the parameter offset distance can be determined by the distance calculation submodule through AC / DC. a Then calculate the offset distance. a Substituting into equation (2), the final offset angle X is obtained by the angle calculation submodule, thus realizing the calculation of the offset angle.

[0071] Specifically, both the distance calculation submodule and the angle calculation submodule in the offset calculation module 204 can be implemented using devices with data processing capabilities, such as FPGAs. The distance calculation submodule and the angle calculation submodule can be implemented using different FPGAs. Alternatively, as... Figure 4 As shown, it is implemented by an FPGA, that is, the FPGA integrates calculation sub-modules that implement the above formulas (1) and (2) respectively.

[0072] In summary, the offset angle measuring device 200 provided in this application utilizes the ratio of the interference signal intensity (AC component) to the background noise (DC component), i.e., the fringe contrast, to reflect the interference efficiency. It selects the interference beam output by the laser interferometer 103 to measure the offset angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031. This allows for offset angle correction without disrupting the vacuum environment of the laser interferometer 103, enabling effective observation of the semiconductor device even when the vacuum cavity 101 is closed. Therefore, even if the semiconductor device experiences angular offset in the optical path of the laser interferometer 103 due to vacuum stress release or thermal deformation during application, this device can still detect and compensate for the offset, preventing measurement errors and ensuring high measurement accuracy for the semiconductor device.

[0073] On the other hand, in addition to the modules given in the above embodiments, the offset angle measuring device 200 provided in this application may also include more modules to achieve more diverse functions. For example, the device further includes a waveform display module 205. The waveform display module 205 is connected to the offset calculation module 204 and is used to display the signal strength of the interference signal, background noise, and fringe contrast, as well as the offset angle determined by the offset calculation module 204.

[0074] For example, the waveform display module 205 can be a hardware device such as an oscilloscope that can be used to display the characteristics of a signal waveform. Optionally, the oscilloscope can be integrated into the same device as the FPGA in the above embodiments. Or, in another optional embodiment, the oscilloscope is implemented independently of the FPGA described above. Figure 4 As shown, the FPGA and oscilloscope transmit waveform data via a communication connection (such as PCIe, Peripheral Component Interconnect Express, a high-speed serial computer expansion bus standard). This enables the oscilloscope to display the signal characteristics of the interference signal, including the offset angle obtained by the offset calculation module 204, thereby providing data support for subsequent offset angle correction.

[0075] On the other hand, the above embodiments mainly focus on determining the deflection angle (offset angle) between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031. However, the offset direction is also an important attribute of the aforementioned deflection angle. In this regard, this application provides an optional solution for determining the offset direction. For example, the above-mentioned device further includes: a stepping control module 207, used to control the displacement stage 104 to perform stepping deflection along a first direction or a second direction; wherein the first direction and the second direction are opposite directions; a signal monitoring module 208, used to monitor the change in the fringe contrast of the interference signal (the interference signal can be provided by the signal acquisition module 201); and an offset orientation module 209, used to determine the opposite direction of the stepping deflection direction as the offset direction if the trend of the change in fringe contrast is non-monotonic.

[0076] Because the fringe contrast (AC / DC value) of the interference signal is negatively correlated with the offset angle, and there is a specific position with a zero offset angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031, at this time, regardless of the direction of movement of the stage 104, the offset angle will increase (the magnitude of the offset angle is an absolute value, regardless of positive or negative direction), correspondingly reducing the fringe contrast. In semiconductor devices, the stage 104 mainly moves by rotational motion Rx / Ry around its X / Y axes. Rotation around an axis results in an angle on a plane perpendicular to that axis, which is one angular component of the offset angle. Therefore, the offset angle between the stage 104 and the optical axis of the laser interferometer 103 can include two angular components: an angular component radx (rotation around the X-axis) and an angular component rady (rotation around the Y-axis). For ease of understanding, let's first illustrate with an example of one angular component: like Figure 6 As shown, assuming the angular component rady, representing rotation about the Y-axis, is an angle of rotation in the XOZ plane. Figure 7 As shown, assuming the X-axis is the initial direction of rady (i.e., rady = 0°), then regardless of whether the rotation is clockwise or counterclockwise, when rotating away from the X-axis, the angular component rady tends to increase, corresponding to a decrease in the fringe contrast value; when rotating closer to the X-axis, the angular component rady tends to decrease, corresponding to an increase in the fringe contrast value; and if this rotation direction remains unchanged, a monotonic change will occur when the rotation angle crosses the X-axis direction. For example... Figure 7As shown in the figure, assuming a clockwise rotation around the Y axis and assuming that the angular component rady = n°, 0° < n < 90° at the initial moment, the angular component decreases before rotating to the X-axis direction. However, when rady = 0°, the magnitude (absolute value) of the angular component will increase instead when rotating clockwise. That is, when rotating in the same direction, if it is found that the monotonicity of the angular component changes suddenly at a certain moment, it means that the current rotation direction is from the initial angular component (n°) to the initial direction (i.e., the 0° direction), that is, the opposite direction of the offset direction. Based on the above principle, the offset direction on the current angular component can be determined. Based on the same principle, the offset direction of the angular component radx rotating around the X axis can be determined. Furthermore, after determining the offset directions of the two angular components rotating around the X axis and the Y axis, the offset direction of the offset angle can be obtained comprehensively.

[0077] In addition, it should be noted that the step control module 207 in this embodiment can control the displacement stage 104 to perform step deflection around the X axis and the Y axis in clockwise or counterclockwise (i.e., the first direction or the second direction) in any order. This embodiment does not limit this and the order of the deflection directions can be selected according to actual needs.

[0078] As can be seen from the above, this embodiment provides a scheme for determining the offset direction. Specifically, by controlling the deflection angle of the displacement stage 104 in a controllable and quantitative manner (i.e., performing step motion control on the displacement stage 104), the change of the fringe contrast of the interference signal during the change of the deflection angle is monitored. When the change trend of the fringe contrast shows non-monotonicity, it means that the 0° point is just passed, that is, it indicates that the current step deflection direction is the opposite direction of the offset direction. Based on this, the offset direction of the deflection angle can be determined in this embodiment. Based on the offset direction determined in this embodiment and combined with the offset angle determined in the above embodiment, the unique and accurate deflection angle can be determined, which is beneficial to the subsequent efficient and accurate correction of the deflection angle, thus better ensuring the measurement accuracy of the semiconductor device.

[0079] After the offset angle and the offset direction of the deflection angle are determined, the deflection angle can be corrected. This embodiment provides an adaptable optional solution for this, such as Figure 8 As shown in the figure, the above device further includes: an attitude compensation module 210, configured to generate a spatial attitude compensation vector according to the offset direction and the offset angle; an offset correction module 211, which corrects the angular offset of the displacement stage 104 through the spatial attitude compensation vector.

[0080] In this embodiment, firstly, based on the aforementioned determined offset angle and offset direction, a compensation angle can be determined from the opposite direction of the offset direction with the same offset angle, which is also the determination of the aforementioned spatial attitude compensation vector. Then, the spatial attitude compensation vector is used to correct the deflection angle. Specifically, when the displacement stage 104 deflects the compensation angle based on the spatial attitude compensation vector, a deflection with the same offset angle but opposite offset direction can be achieved, thereby completely eliminating the deflection angle, thus completing the correction of the angular offset of the displacement stage 104. The entire scheme is easy to implement, requires no manual intervention, and its correction efficiency and accuracy are significantly better than manual correction, which is beneficial for further improving the measurement accuracy of semiconductor equipment.

[0081] In another alternative implementation, such as Figure 9 As shown, the above-mentioned device further includes: an initialization module 212, used to control the deflection of the displacement stage 104 so that the measurement beam of the laser interferometer 103 is removed from the effective area of ​​the reflector 1031; an aliasing calibration module 213, used to control the rotation of the half-wave plate 1032 in the laser interferometer 103 until the signal intensity of the interference signal reaches the minimum value in this rotation process; and a reset module 214, used to control the reset of the displacement stage 104 and enable the signal acquisition module 201.

[0082] In this embodiment, the polarization aliasing calibration function of the laser interferometer 103 can be realized. Specifically, the measurement beam of the laser interferometer 103 is deflected away from the effective area of ​​the reflector 1031 by controlling the deflection of the displacement stage 104. Then, the half-wave plate 1032 in the laser interferometer 103 is rotated, and the fringe contrast (i.e., AC / DC value) of the interference signal is constantly monitored during this rotation. Since polarization aliasing is a systematic error caused by frequency cross-leakage due to optical element defects, polarization degradation, or assembly errors in the laser interferometer 103, it manifests as a periodic nonlinear displacement deviation. The periodic nonlinear displacement deviation causes fluctuations in the fringe contrast of the interference signal. Among them, the deflection angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031 is an important reason for the occurrence of polarization aliasing. Therefore, when the fringe contrast is at its minimum, it indicates that this error has been suppressed to a minimum, that is, the suppression of polarization aliasing is completed. After realizing the calibration and suppression of polarization aliasing based on this embodiment, the adverse effects of polarization aliasing on the measurement of the laser interferometer 103 can be avoided, thereby further improving the measurement accuracy.

[0083] Based on the above embodiments, this embodiment also provides a semiconductor device, including the offset angle measuring device 200 provided in any of the above embodiments, as well as a laser interferometer 103 and a displacement stage 104. Since the embodiments of the semiconductor device section correspond to the embodiments of the above-mentioned device section, please refer to the description of the embodiments of the device section for the embodiments of the semiconductor device section, which will not be repeated here.

[0084] The semiconductor device provided in this embodiment can measure the angle of deviation between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031 while maintaining an intact vacuum environment through the offset angle measuring device 200, thereby completing the correction. Based on this advantage, the semiconductor device provided in this embodiment can accurately monitor the relative angle between the optical axis of the laser interferometer 103 and the mirror surface of the reflector 1031 even during operation. Even if angular deviations occur in the interferometer's optical path due to vacuum stress release or thermal deformation during normal operation of the semiconductor device, the angle of deviation can still be accurately measured and corrected, avoiding measurement errors caused by the angle of deviation and ensuring the measurement accuracy of the semiconductor device.

[0085] Based on the above embodiments, this embodiment also provides an offset angle measurement method, which can be implemented by the offset angle measuring device provided in the above embodiments, or by a semiconductor device integrating the above offset angle measuring device. The method flow is as follows: Figure 10 As shown, it includes: S1: Acquire the interference signal from the laser interferometer.

[0086] S2: Determine the signal strength and background noise of the interference signal.

[0087] S3: Determine the stripe contrast based on signal strength and background noise.

[0088] The stripe contrast is the ratio of signal strength (AC component) to background noise (DC component) (AC / DC value).

[0089] S4: Determine the offset angle between the optical axis of the laser interferometer and the reflective surface of the displacement stage based on the fringe contrast.

[0090] Since steps S1 to S4 of this method correspond one-to-one with the signal acquisition module, feature extraction module, signal processing module, and offset calculation module in the above-described device embodiments, specific embodiments of steps S1 to S4 can be found in the description of the above-described device embodiments, and will not be repeated here.

[0091] The offset angle measurement method provided in this embodiment expands the functionality of the interference signal by multiplexing it to calculate the spatial angular offset of the laser interferometer, i.e., the offset angle between the interferometer's optical axis and the stage mirror. Specifically, the fringe contrast (i.e., the AC / DC ratio) is determined by extracting the interference signal intensity (AC component) and background noise (DC component) from the interference signal. Since the AC / DC ratio directly reflects the interference efficiency, and an increase in the offset angle significantly reduces the interference efficiency, the offset angle can be indirectly calculated using the AC / DC ratio to complete the measurement. Therefore, this method does not require the introduction of additional optical components such as beam splitters or corner prisms. Furthermore, it does not disrupt the vacuum environment of the semiconductor device, indirectly measuring the offset angle by multiplexing existing interference signals. This allows for effective observation of the semiconductor device even when its vacuum cavity is closed. Therefore, even if the semiconductor device experiences angular offset in the laser interferometer's optical path due to vacuum stress release or thermal deformation during application, this method can still detect and compensate for the offset, avoiding measurement errors and ensuring high measurement accuracy.

[0092] Regarding the determination of the offset angle achieved in step S4 above, this embodiment also provides an optional solution. Step S4 specifically includes: S41: Determine the center offset distance of the laser spot based on the fringe contrast, the distance between the laser interferometer and the mirror of the displacement stage, and the laser interferometer spot radius.

[0093] S42: Determine the offset angle based on the offset distance of the light spot center.

[0094] Similarly, steps S41 and S42 provided in this embodiment correspond to the distance calculation module and angle calculation module in the above-described device embodiments, respectively. Therefore, specific embodiments of steps S41 and S42 in this embodiment can be found in the description of the distance calculation module and angle calculation module in the above-described device embodiments, and will not be repeated here.

[0095] This embodiment determines the offset distance of the laser spot center by using fringe contrast, the distance between the laser interferometer and the displacement stage mirror, and the laser interferometer spot radius. This replaces manual measurement to determine the offset distance of the spot center. Furthermore, after obtaining the offset distance of the spot center, the final offset angle can be determined based on it. Therefore, this embodiment provides a simple and reliable offset calculation scheme. It eliminates the need for manual measurement of the offset distance of the laser spot center in the laser interferometer, thus eliminating the need to install corresponding measuring tools within the laser interferometer, and therefore eliminating the need to disrupt the vacuum environment of the semiconductor device. The offset angle determination achieved in this way does not require opening a cavity in the vacuum chamber, ensuring high efficiency and ease of implementation in obtaining the offset angle.

[0096] On the other hand, besides the offset angle, the offset direction is also a crucial attribute of the deflection angle. This embodiment provides an alternative method for determining the offset direction. In one implementation, such as... Figure 11 As shown, the above method also includes: S51: Controls the displacement stage of the laser interferometer to perform step deflection along the first or second direction.

[0097] The first direction and the second direction are opposite directions.

[0098] S52: Monitor the change in fringe contrast of the interference signal.

[0099] S53: If the trend of stripe contrast change is non-monotonic, determine the opposite direction of the step deflection direction as the offset direction.

[0100] Similarly, steps S51 to S53 provided in this embodiment correspond to the stepping control module, signal monitoring module, and offset orientation module in the aforementioned device embodiments, respectively. Therefore, specific embodiments of steps S51 to S53 in this embodiment can be found in the descriptions of the stepping control module, signal monitoring module, and offset orientation module in the aforementioned device embodiments, and will not be repeated here. This embodiment can determine the offset direction of the deflection angle. Based on the offset direction determined in this embodiment, combined with the offset angle determined in the aforementioned embodiments, an accurate deflection angle can be determined. This facilitates efficient and accurate subsequent correction of the deflection angle, thereby further improving the measurement accuracy of the semiconductor device.

[0101] Once the offset angle and offset direction are determined, the offset angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage can be uniquely determined. That is, the data basis for offset angle correction is met, and offset angle correction can be performed. Based on this, this embodiment provides an optional offset angle correction method, which further includes: S61: Generate a spatial attitude compensation vector based on the offset direction and offset angle.

[0102] S62: Corrects the angular offset of the displacement stage using the spatial attitude compensation vector.

[0103] Similarly to the above embodiments, steps S61 and S62 provided in this embodiment correspond to the attitude compensation module and offset correction module in the above-mentioned device partial embodiments, respectively. Therefore, specific embodiments of steps S61 and S62 in this embodiment can be found in the description of the attitude compensation module and offset correction module in the above-mentioned device partial embodiments, and will not be repeated here. This embodiment can realize the automatic correction of the deflection angle between the optical axis of the laser interferometer and the reflecting mirror surface of the displacement stage, improving the correction efficiency while ensuring the accuracy of the correction, thus ensuring the measurement accuracy of the semiconductor equipment.

[0104] As described in the above technical section, there are many causes of polarization aliasing, such as defects in optical components, polarization degradation, or frequency cross-leakage due to assembly errors. The deflection angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage is one of the important causes of polarization aliasing, but not the only one. The method provided in the above embodiments can accurately and efficiently solve the polarization aliasing problem caused by the deflection angle. Based on this, this embodiment further provides a polarization aliasing calibration method for other problems, to further solve polarization aliasing problems caused by reasons other than the deflection angle. Specifically, such as... Figure 11 As shown, the above method also includes: S71: Controls the deflection of the displacement stage to make the measurement beam of the laser interferometer deviate from the effective area of ​​the displacement stage mirror.

[0105] S72: Controls the rotation of the half-wave plate in the laser interferometer until the fringe contrast reaches its minimum value during this rotation process.

[0106] S73: Control the displacement stage to reset and return to the step of acquiring the interference signal of the laser interferometer.

[0107] Similarly to the above embodiments, steps S71 to S73 provided in this embodiment correspond to the initialization module, aliasing calibration module, and reset module in the above-mentioned device embodiments, respectively. Therefore, for specific embodiments of steps S51 to S53 in this embodiment, please refer to the description of the stepping control module, signal monitoring module, and offset orientation module in the above-mentioned device embodiments, which will not be repeated here.

[0108] In this embodiment, the principle of determining the offset direction described above is used to additionally implement the polarization aliasing calibration function of the laser interferometer. Specifically, by controlling the deflection of the displacement stage, the measurement beam of the laser interferometer is separated from the effective area of ​​the displacement stage mirror, providing a prerequisite for polarization aliasing calibration. Then, the half-wave plate in the laser interferometer is rotated. During this rotation, the fringe contrast of the interference signal is continuously monitored. When the interference signal intensity is at its minimum, it indicates that the error has been suppressed to a minimum, that is, polarization aliasing suppression is completed. Based on this embodiment, after implementing polarization aliasing calibration and suppression, the adverse effects of polarization aliasing on laser interferometer measurements can be avoided, thereby further improving measurement accuracy.

[0109] This embodiment also provides an offset angle measuring device, including a module or unit for implementing the above-described offset angle measuring method. In one implementation, the offset angle measuring device includes a processor, which is used to execute the steps of the offset angle measuring method provided in any of the above embodiments, such as steps S1~S4 (S41, S42), S51~S53, S61 and S62, and S71~S73.

[0110] This application also provides a computer program product. The computer program product includes a computer program for performing the steps of the offset angle measurement method provided in any of the above embodiments, such as steps S1~S4 (S41, S42), S51~S53, S61 and S62, and S71~S73.

[0111] This application also provides a readable computer storage medium. This readable computer storage medium stores a computer program for performing the steps of the offset angle measurement method provided in any of the above embodiments.

[0112] Each of the above modules or units can be implemented by software, hardware, or a combination of software and hardware. For example, when determining the offset angle, the signal acquisition module, feature extraction module, signal processing module, and offset calculation module in the above embodiments can all be implemented based on software.

[0113] In this application, "implemented through software" means that the processor reads and executes program instructions stored in memory to implement the functions corresponding to the aforementioned modules or units. Here, the processor refers to a processing circuit capable of executing program instructions, including but not limited to at least one of the following: a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a microcontroller unit (MCU), or an artificial intelligence processor, etc., and other processing circuits capable of running program instructions. In other embodiments, the processor may also include circuits with other processing functions (such as hardware circuits for hardware acceleration, bus and interface circuits, etc.). The processor can be presented as an integrated chip, for example, as an integrated chip whose processing function only includes executing software instructions, or it can also be presented as a SoC (system on a chip), that is, on a single chip, in addition to the processing circuit capable of running program instructions (usually referred to as the "core"), it also includes other hardware circuits for implementing specific functions (of course, these hardware circuits can also be implemented separately based on ASIC or FPGA). Correspondingly, the processing functions, in addition to executing software instructions, may also include various hardware acceleration functions (such as AI calculation, encoding / decoding, compression / decompression, etc.).

[0114] In this application, "implemented in hardware" means that the functions of the above-mentioned modules or units are implemented through hardware processing circuits that do not have program instruction processing capabilities. These hardware processing circuits can be composed of discrete hardware components or integrated circuits. To reduce power consumption and size, integrated circuits are typically used. Hardware processing circuits can include ASICs (application-specific integrated circuits) or PLDs (programmable logic devices); PLDs can include FPGAs (field-programmable gate arrays), CPLDs (complex programmable logic devices), and so on. These hardware processing circuits can be a single packaged semiconductor chip (e.g., packaged as an ASIC); or they can be integrated with other circuits (e.g., CPUs, DSPs) and packaged into a single semiconductor chip. For example, multiple hardware circuits and a CPU can be formed on a silicon substrate and packaged into a single chip; this type of chip is also called a SoC. Alternatively, circuits for implementing FPGA functions and a CPU can be formed on a silicon substrate and encapsulated into a single chip; this type of chip is also called a SoPC (system on a programmable chip).

[0115] It should be noted that when this application is implemented through software, hardware, or a combination of both, different software or hardware can be used, and it is not limited to using only one type of software or hardware. For example, one module or unit can be implemented using a CPU, while another module or unit can be implemented using a DSP. Similarly, when implemented using hardware, one module or unit can be implemented using an ASIC, while another module or unit can be implemented using an FPGA. Of course, it is not limited to using the same software (e.g., all through a CPU) or the same hardware (e.g., all through an ASIC) to implement some or all modules or units. Furthermore, those skilled in the art will understand that software is generally more flexible but less performant than hardware, while hardware is the opposite. Therefore, those skilled in the art can choose software, hardware, or a combination of both based on actual needs.

[0116] It should be understood that the terms "first," "second," etc., used in this application are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order.

[0117] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "joining" should be interpreted broadly, for example, they can be fixed connections, detachable connections, mating connections or integral connections; those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0118] It should be understood that "multiple" as used in this application means at least two, that is, two or more.

[0119] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0120] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

Claims

1. An offset angle measuring device, characterized in that, include: The signal acquisition module is used to acquire the interference signal from the laser interferometer. The feature extraction module is used to determine the signal strength and background noise of the interference signal; A signal processing module is configured to determine the stripe contrast based on the signal intensity and the background noise; wherein the stripe contrast is the ratio of the signal intensity to the background noise. The offset calculation module is used to determine the offset angle between the optical axis of the laser interferometer and the reflective surface of the displacement stage based on the fringe contrast.

2. The offset angle measuring device according to claim 1, characterized in that, The signal acquisition module is a photoelectric conversion module; The photoelectric conversion module is used to receive the interference beam from the laser interferometer and perform photoelectric conversion on the interference beam to obtain the interference signal.

3. The offset angle measuring device according to claim 2, characterized in that, The photoelectric conversion module includes: an optical fiber interface, a coupling lens, and a photosensitive device; The optical fiber interface is located in the vacuum cavity of the semiconductor device and is used to transmit optical signals from inside the vacuum cavity to outside the vacuum cavity. The coupling lens is configured correspondingly to the optical fiber interface and the photosensitive device, and is used to couple the optical signal output from the optical fiber interface to the target surface of the photosensitive device. The photosensitive device is used to convert the optical signal received by the target surface into an electrical signal.

4. The offset angle measuring device according to claim 3, characterized in that, The fiber optic interface is a fiber optic connector flange.

5. The offset angle measuring device according to any one of claims 1 to 4, characterized in that, The feature extraction module includes: a bandpass filter and a lowpass filter; The bandpass filter is used to extract the signal intensity of the interference signal; the lowpass filter is used to extract the background noise of the interference signal.

6. The offset angle measuring device according to any one of claims 1 to 5, characterized in that, Also includes: Waveform display module; The waveform display module is connected to the offset calculation module and is used to display the signal strength, background noise, and fringe contrast of the interference signal, as well as the offset angle determined by the offset calculation module.

7. The offset angle measuring device according to any one of claims 1 to 6, characterized in that, The offset calculation module includes: The distance calculation module is used to determine the center offset distance of the laser spot based on the fringe contrast, the distance between the laser interferometer and the displacement stage mirror, and the laser interferometer spot radius. An angle calculation module is used to determine the offset angle based on the offset distance of the light spot center.

8. The offset angle measuring device according to any one of claims 1 to 7, characterized in that, Also includes: A stepping control module is used to control the displacement stage to perform stepping deflection along a first direction or a second direction; wherein the first direction and the second direction are opposite directions; A signal monitoring module is used to monitor the change in the fringe contrast of the interference signal; The offset orientation module is used to determine the opposite direction of the step deflection direction as the offset direction if the trend of the change in the stripe contrast is non-monotonic.

9. The offset angle measuring device according to claim 8, characterized in that, Also includes: An attitude compensation module is used to generate a spatial attitude compensation vector based on the offset direction and the offset angle. The offset correction module corrects the angular offset of the displacement stage using the spatial attitude compensation vector.

10. The offset angle measuring device according to any one of claims 1 to 9, characterized in that, Also includes: An initialization module is used to control the deflection of the displacement stage so that the measurement beam of the laser interferometer is removed from the effective area of ​​the displacement stage mirror. The aliasing calibration module is used to control the rotation of the half-wave plate of the laser interferometer until the interference signal intensity reaches the minimum value during this rotation process; A reset module is used to control the reset of the displacement stage and enable the signal acquisition module.

11. A semiconductor device, characterized in that, It includes a laser interferometer, a displacement stage, and an offset angle measuring device as described in any one of claims 1 to 10.

12. A method for measuring offset angle, characterized in that, include: Acquire the interference signal from the laser interferometer; Determine the signal strength and background noise of the interference signal; The stripe contrast is determined based on the signal strength and the background noise; wherein the stripe contrast is the ratio of the signal strength to the background noise. The offset angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage is determined based on the fringe contrast.

13. The offset angle measurement method according to claim 12, characterized in that, Determining the offset angle between the optical axis of the laser interferometer and the reflecting mirror of the displacement stage based on the fringe contrast includes: Based on the fringe contrast, the distance between the laser interferometer and the displacement stage mirror, and the laser interferometer spot radius, the spot center offset distance is determined; The offset angle is determined based on the offset distance of the light spot center.

14. The offset angle measurement method according to claim 12 or 13, characterized in that, Also includes: The displacement stage is controlled to perform step deflection along a first direction or a second direction; wherein the first direction and the second direction are opposite directions; Monitor the change in the fringe contrast of the interference signal; If the trend of the stripe contrast change is non-monotonic, the opposite direction of the step deflection direction is determined as the offset direction.

15. The offset angle measurement method according to claim 14, characterized in that, Also includes: A spatial attitude compensation vector is generated based on the offset direction and the offset angle; The angular offset of the displacement stage is corrected by the spatial attitude compensation vector.

16. The method for measuring offset angle according to any one of claims 12 to 15, characterized in that, Also includes: The displacement stage is deflected so that the measurement beam of the laser interferometer is removed from the effective area of ​​the displacement stage mirror; Control the rotation of the half-wave plate of the laser interferometer until the fringe contrast reaches the minimum value during this rotation process; The displacement stage is reset and the process returns to the step of acquiring the interference signal from the laser interferometer.

17. An offset angle measuring device, characterized in that, Includes a processor, which is configured to implement the offset angle measurement method as described in any one of claims 12 to 16 when executing.

18. A computer program product, characterized in that, It includes a computer program for performing the offset angle measurement method as described in any one of claims 12 to 16.

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