Light source module, optical focusing system, semiconductor device, and focusing control method

Abstract

This application relates to the field of semiconductor detection technology, and more particularly to a light source module, an optical focusing system, a semiconductor device, and a focusing control method. The light source module comprises multiple monochromatic light sources mounted on a substrate, each emitting light with a different wavelength, and each monochromatic light source includes at least one sub-light source. The light source module can be controlled to emit multiple illumination beams using a preset illumination mode, providing multiple independent or combined illumination channels for the subsequent focusing process. This allows the optical focusing system based on the light source module to utilize the chromatic aberration of different wavelengths of light to form a series of focal points at different positions along the axial direction, significantly expanding the effective axial focusing range of the measurement. Furthermore, the system organically integrates the light source module with a first mask, an objective lens module, a first beam splitter, a first detection subsystem, a second detection subsystem, and a processor, forming a complete, efficient, and high-precision autofocus closed-loop system.

Description

Technical Field

[0001] This application relates to the field of semiconductor detection technology, and in particular to a light source module, an optical focusing system, a semiconductor device, and a focusing control method. Background Technology

[0002] In modern optical inspection, machine vision, industrial automation, and precision measurement, autofocus technology is a key component for achieving high-precision imaging and stable detection. Traditional autofocus methods mainly include contrast detection, phase detection, and eccentric masking. Among these, eccentric masking is widely used in detection scenarios with low contrast, weak texture, or highly reflective surfaces due to its advantages such as being unaffected by the surface texture of the object being measured, fast response speed, and strong environmental adaptability.

[0003] Currently, the eccentric mask method projects specific light spots or stripes and combines this with an image sensor to analyze the position or deformation of the light spots to achieve focus feedback and dynamic focusing. However, due to the limitations of the modulation depth and dispersion characteristics of existing light sources in the eccentric mask method, the system is prone to sensitivity degradation or signal saturation when detecting large-scale displacements, making it difficult to simultaneously meet the needs of coarse adjustment at long distances and fine adjustment at close distances. Summary of the Invention

[0004] In view of this, this application proposes a light source module, an optical focusing system, a semiconductor device, and a focusing control method to solve the technical problem that optical focusing systems cannot simultaneously handle coarse adjustment at long distances and fine adjustment at close distances.

[0005] According to one aspect of this application, a light source module is provided for use in an optical focusing system, comprising:

[0006] substrate;

[0007] Multiple monochromatic light sources are disposed on the substrate, and each monochromatic light source emits light with a different wavelength;

[0008] Each of the monochromatic light sources includes at least one sub-light source, and in each of the monochromatic light sources, at least one of the sub-light sources is located within a preset space, wherein the preset space is a half-space defined by a preset plane in which the optical axis of the optical focusing system is located.

[0009] By setting multiple monochromatic light sources of different wavelengths in the light source module, the module can emit multiple illumination beams with different wavelengths. Since beams of different wavelengths will focus at different depths along the optical axis due to axial chromatic aberration when passing through the optical focusing system, the focal positions of each illumination beam are different. Simultaneously, by placing at least one sub-light source from each monochromatic light source within a half-space defined by a preset plane containing the optical axis of the optical focusing system, when the focal position changes (i.e., defocusing), a predictable directional shift and offset will occur in the center of the light spot or the image on the image plane of the optical focusing system. Therefore, by capturing the direction and amount of this shift, the optical focusing system can clearly determine the specific direction and amount of lens movement required, thereby achieving precise refocusing. Based on this mechanism, utilizing the characteristic that beams of different wavelengths naturally distribute at different axial depths due to axial chromatic aberration, the system constructs multiple simultaneously existing and spatially discrete independent illumination channels for focal plane measurement. Each of these channels corresponds to a specific axial focusing depth, thus significantly expanding the effective axial focusing range of the measurement and improving the optical focusing efficiency of the optical focusing system.

[0010] In one possible implementation, each monochromatic light source comprises a sub-light source, and all sub-light sources are located within the preset space. Since all sub-light sources are located on the same side of the optical axis (within the preset half-space), when defocusing occurs, the light spot or image on the image plane will exhibit a highly consistent and interference-free directional shift. Compared to schemes where sub-light sources are distributed on both sides of the optical axis, this ensures that the system captures only a single, clear shift direction, significantly reducing the risk of misjudgment and improving the robustness of focus direction determination. Simultaneously, since each monochromatic light source contains only a single sub-light source, there is no need to coordinate the switching timing of multiple sub-light sources at the same wavelength, simplifying the driving circuitry and control logic.

[0011] In one possible implementation, each monochromatic light source includes multiple sub-light sources, and the number of sub-light sources located in the preset space within each monochromatic light source is ≥1. By setting multiple monochromatic light sources with different wavelengths in the light source module, the chromatic aberration of different wavelengths of light in the optical system can be used to form a series of focal points at different positions along the axial direction (Z-axis). These focal points cover a larger axial range than a single wavelength, thereby extending the theoretical focal plane operating range of the optical focusing system.

[0012] In one possible implementation, the monochromatic light source comprises an even number of sub-light sources, each of which is symmetrically distributed about the optical axis. This symmetrical arrangement of sub-light sources of the same wavelength on both sides of the optical axis not only generates illumination for generating defocus signals on one side of a predetermined space, but also generates illumination for differential compensation or extending the linear range on the other side.

[0013] In one possible implementation, the sub-light sources located within the preset space are arranged along a straight line or an arc. This arrangement corresponds to different positions on the objective lens pupil plane. Thus, since the sub-light sources can be arranged along a straight line or an arc, the light emitted by them, after passing through the illumination system, will illuminate the objective lens pupil plane at different angles and positions. This distribution on the pupil plane affects the characteristics of the defocus signal (e.g., slope). By adjusting the arrangement, the sensitivity, linear range, and measurement accuracy of the optical focusing system can be flexibly designed and optimized to adapt to different types of samples and detection requirements.

[0014] In one possible implementation, the emitting surfaces of the multiple monochromatic light sources are arranged coplanarly. By ensuring that the emitting surfaces are coplanar, the object distance of the light emitted by all sub-light sources is consistent when it enters the subsequent optical system. This simplifies the optical design, allowing the same collimating lens to collimate all beams, avoiding additional aberrations and optical path offsets introduced by different object distances, and ensuring the optical consistency of the entire light source module.

[0015] In one possible implementation, the sub-light sources belonging to the same monochromatic light source have identical shapes. By setting the sub-light sources of the same wavelength to have identical shapes, the first illumination patterns they form on the sample under test are also identical and symmetrical. This ensures that the defocus signal obtained through differential calculation has good symmetry and consistency, simplifies subsequent signal processing algorithms, and improves measurement accuracy.

[0016] In one possible implementation, the shape of each sub-light source includes any of the following: strip-shaped, circular, or elliptical. This allows for customization of the illumination pattern according to specific application requirements. The sub-light sources can be designed in different shapes. For example, when detecting structures with small linewidths, strip-shaped sub-light sources can be used to match their orientation and improve contrast; during regular focusing, circular sub-light sources can be used to obtain a symmetrical response signal. This flexibility allows the optical focusing system to better adapt to samples with different characteristics.

[0017] In one possible implementation, the focal plane movement range of the optical focusing system differs for different monochromatic light sources. Due to chromatic aberration, light of different wavelengths converges at different focal points after passing through the objective lens module. Therefore, when switching to a monochromatic light source of a different wavelength, the focal plane (i.e., the optimal focal plane position) of the optical focusing system shifts as a whole. The magnitude of this shift is the focal plane movement range. Thus, by utilizing the chromatic aberration of different wavelength monochromatic light sources, the illumination wavelength can be switched simply by switching the monochromatic light source, allowing for a rapid and mechanically non-mechanical change of the focal plane of the optical focusing system. This provides a new and faster dimension for focal plane adjustment compared to methods relying solely on moving the focusing lens. Because the focal plane movement range differs for different monochromatic light sources, the focal positions of each wavelength can be pre-designed so that they are aligned end-to-end or partially overlapped axially, thereby significantly expanding the overall focal plane working range of the optical focusing system without reducing sensitivity.

[0018] In one possible implementation, the wavelengths of the light emitted by each of the monochromatic light sources are all in the visible band. Because visible light is highly compatible with the response characteristics of the imaging system, it can provide image information with high signal-to-noise ratio and high contrast. At the same time, visible light source technology is mature, stable, and easy to modulate, and will not cause unexpected photochemical damage to the sample under test. It takes into account focusing accuracy, system compatibility, and detection safety, and is suitable for optical focusing systems using the eccentric mask method.

[0019] In one possible implementation, each of the monochromatic light sources includes any one of the following: a laser diode and a light-emitting diode. This allows for flexible selection of the light source type based on specific application requirements. For example, a laser diode can be selected for scenarios requiring extremely high brightness and excellent monochromaticity; while a light-emitting diode can be selected for scenarios prioritizing low cost, high reliability, and ease of multi-chip integration.

[0020] In one possible implementation, the substrate integrates circuitry for driving the monochromatic light source, and the substrate includes any of the following: a printed circuit board, a ceramic substrate. This allows for the selection of a suitable substrate for different application scenarios.

[0021] According to another aspect of this application, an optical focusing system is provided, applied in a semiconductor device, for focusing a sample under test within the semiconductor device, comprising:

[0022] The aforementioned light source module is used to emit multiple light beams according to a preset lighting pattern.

[0023] A first mask is disposed behind the light source module and is used to spatially modulate the multiple illumination beams to form multiple first illumination patterns that correspond one-to-one with the multiple illumination beams.

[0024] An objective lens module, disposed behind the first mask, is used to focus the plurality of first illumination patterns onto the surface of the sample to be tested, and to collect multiple reflected beams generated by the surface of the sample to be tested, wherein the multiple reflected beams correspond one-to-one with the plurality of first illumination patterns;

[0025] The first beam splitter is disposed behind the objective lens module and is used to split the multiple reflected beams into the first detection optical path and the second detection optical path.

[0026] A first detection subsystem is disposed in the first detection optical path. The first detection subsystem includes at least one first detection unit, and each first detection unit includes:

[0027] A second mask and a first detection module are sequentially arranged along the first detection optical path. The second mask is used to perform spatial filtering on the multiple reflected beams transmitted through the first detection optical path. The first detection module is used to collect the multiple reflected beams transmitted from the second mask to the first detection optical path to obtain multiple first electrical signals, wherein the multiple first electrical signals correspond one-to-one with the multiple reflected beams.

[0028] A second detection subsystem is disposed in the second detection optical path. The second detection subsystem includes at least one second detection unit, and each second detection unit includes:

[0029] A second detection module is disposed in the second detection optical path. The second detection module is used to collect the multiple reflected beams transmitted in the second detection optical path to obtain multiple second electrical signals, wherein the multiple second electrical signals correspond one-to-one with the multiple reflected beams; and,

[0030] The processor is configured to determine the defocusing amount of the sample under test based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode.

[0031] Thus, by employing the aforementioned optical focusing system and light source module, the chromatic aberration of different wavelengths of light within the optical system can be utilized to form a series of focal points at different positions along the axial direction (Z-axis). These focal points cover a larger axial range than a single wavelength, thereby extending the theoretical focal plane operating range of the optical focusing system. Furthermore, by organically integrating the light source module with the first mask, objective lens module, first beam splitter, first detector subsystem, second detector subsystem, and processor, a complete, efficient, and high-precision autofocus closed-loop system is formed. Because the light source module can provide multi-wavelength, flexibly configurable illumination, the entire optical focusing system can achieve rapid and accurate focusing on different samples within a wider operating range, significantly improving the applicability and performance of semiconductor devices.

[0032] In one possible implementation, the preset lighting mode includes at least one of the following: a full-source sequential lighting mode, a single-source lighting mode, and a multi-source collaborative lighting mode;

[0033] The full-light source sequential lighting mode is wherein each of the sub-light sources in the light source module is turned on and illuminated in sequence according to a preset timing sequence.

[0034] The single-source illumination mode controls the sub-sources of the target monochromatic light source corresponding to the current focal plane position among the multiple monochromatic light sources to turn on and emit light sequentially;

[0035] The multi-source coordinated lighting mode controls the monochromatic light source corresponding to the current focal plane position among the multiple monochromatic light sources to work together to emit light. The coordinated activation means that multiple sub-light sources are activated simultaneously in two separate activations. The sub-light sources activated simultaneously in each activation belong to different monochromatic light sources and are located on the same side of the preset plane. The sub-light sources activated in the two separate activations are located on different sides of the preset plane.

[0036] The focal plane movement range varies depending on the preset lighting mode.

[0037] In this way, by providing multiple preset illumination modes, the processor in the optical focusing system can flexibly select the appropriate mode for different application scenarios. For example, during the initial large-scale search of the focal plane, a full-source sequential illumination mode can be used to quickly acquire signals of multiple wavelengths and determine the approximate height range of the sample under test. When the focal plane is close to the target, the system can switch to a single-source illumination mode, using a symmetrical monochromatic light source of a single wavelength for high-precision tracking. When both a large range and high-speed response are required, a multi-source collaborative illumination mode can be used to acquire differential signals of multiple wavelengths in a single acquisition, expanding the equivalent measurement range and increasing the sampling frequency. Because different modes correspond to different focal plane movement ranges, seamless transitions from coarse to fine adjustment can be achieved through mode switching, balancing working range and accuracy.

[0038] In one possible implementation, the preset lighting mode includes at least one of a full-source sequential lighting mode and a single-source lighting mode. The light source module includes N monochromatic light sources, the first detection subsystem includes one first detection unit, and the second detection subsystem includes one second detection unit, where N ≥ 1. Because a time-division multiplexing approach is used, the signals from different light sources are separated in time and can therefore be received sequentially by the same set of detection units. This greatly simplifies the system structure and reduces hardware costs. By using time-division multiplexing, time is traded for space, and a single set of detection units is used to acquire multi-channel signals, making it suitable for cost-sensitive applications where sampling speed requirements are not particularly high.

[0039] In one possible implementation, the preset illumination mode includes a multi-source collaborative illumination mode. The light source module includes N monochromatic light sources, the first detection subsystem includes N first detection units, and the second detection subsystem includes N second detection units, where N ≥ 1. Thus, because it has the same number of parallel detection units as the monochromatic light sources (N parallel first detection units and N parallel second detection units), it is possible to simultaneously illuminate and detect sub-light sources of different wavelengths. This completely solves the speed limitation problem of time-division multiplexing mode. In the multi-source collaborative illumination mode, signals corresponding to all wavelengths can be obtained with a single illumination and acquisition, greatly improving the data sampling rate. This allows the optical focusing system to keep up with high-speed moving samples (such as rapidly scanning wafer platforms), achieving real-time and precise focusing control, and significantly improving the throughput of the detection equipment.

[0040] In one possible implementation, the first distance between the central axis of the first mask and the optical axis of the optical focusing system differs from the second distance between the central axis of the second mask and the optical axis. This difference in distances results in different offsets of the first and second masks relative to the optical axis in a direction perpendicular to the optical axis. By setting different offsets, the static offset point, i.e., the zero-point position, of the optical focusing system can be finely adjusted. This design provides additional degrees of freedom for system calibration, compensating for inherent aberrations or assembly errors in the optical system, ensuring that the zero point of the defocus measurement signal (NSC curve) precisely coincides with the actual physical focal plane, and improving focusing accuracy.

[0041] In one possible implementation, the first detector in the first detection module and / or the second detector in the second detection module are multi-quadrant detectors. By setting the first detector as a multi-quadrant detector, positional changes of the first sub-beam can be monitored, providing additional alignment information. By setting the second detector as a multi-quadrant detector, positional changes of the second sub-beam can be monitored, providing additional alignment information.

[0042] In one possible implementation, the first mask forms a conjugate surface with the surface of the sample under test, and the surface of the sample under test forms a conjugate surface with the second mask. Since the first mask is imaged onto the surface of the sample under test by the objective lens mode, and simultaneously, the surface of the sample under test is imaged onto the plane of the second mask, the first mask and the surface of the sample under test are conjugate. Therefore, the pattern on the first mask is clearly and accurately projected onto the surface of the sample under test, ensuring the quality of the illumination pattern. The surface of the sample under test is conjugate with the second mask, so when the sample is out of focus, the image reflected back from its surface becomes blurred or shifted on the plane of the second mask. This is the core principle of spatial filtering for out-of-focus detection. This double conjugate relationship constitutes a perfect optical information transmission chain, ensuring precise control of the entire physical process from illumination modulation to signal demodulation, and is the physical basis for the system to achieve high-precision focusing.

[0043] In one possible implementation, the system further includes:

[0044] A collimating lens is disposed at the front end of the first mask and is used to collimate the multiple illumination beams;

[0045] The second beam splitter is disposed between the first mask and the objective lens module, and is used to transmit the multiple illumination beams to the objective lens module; and to reflect the multiple reflected beams to the first beam splitter; or, to reflect the multiple illumination beams to the objective lens module; and to transmit the multiple reflected beams to the first beam splitter.

[0046] In this way, the collimating lens is used to convert the divergent light emitted by the light source module into parallel light, so as to uniformly illuminate the first mask. The collimating lens ensures that the illumination beam illuminates the first mask at the same angle and with uniform intensity, improving illumination efficiency and quality. The second beam splitter enables the coaxial design of the illumination optical path (i.e., the optical path containing the illumination beam) and the detection optical path (i.e., the optical path containing the reflected beam), making the system structure more compact and avoiding the additional aberrations and assembly difficulties caused by optical path separation.

[0047] In one possible implementation, the first detection module includes a first converging mirror and a first detector arranged sequentially along the first detection optical path; the first converging mirror is used to converge the multiple reflected beams transmitted from the second mask to the first detection optical path; the first detector is used to collect the converged multiple reflected beams to obtain multiple first electrical signals.

[0048] The second detection module includes a second converging mirror and a second detector, which are arranged sequentially along the second detection optical path. The second converging mirror is used to converge the reflected beam transmitted from the first beam splitter to the second detection optical path. The second detector is used to collect the converged multiple reflected beams to obtain multiple second electrical signals.

[0049] Thus, the first converging mirror is used to focus the spatially filtered reflected light beam onto the photosensitive surface of the first detector, thereby improving light energy utilization. By setting the first converging mirror, it is possible to ensure that weak light signals are effectively collected, improving the system's detection sensitivity and signal-to-noise ratio. The second converging mirror is used to focus the reflected light beam onto the photosensitive surface of the second detector, thereby improving light energy utilization. By setting the second converging mirror, it is possible to ensure that weak light signals are effectively collected, improving the system's detection sensitivity and signal-to-noise ratio.

[0050] According to another aspect of this application, a semiconductor device is provided, comprising:

[0051] The aforementioned optical focusing system.

[0052] Thus, because this semiconductor device incorporates the aforementioned optical focusing system, it possesses all the advantages of such systems: rapid and accurate autofocus over a wider sample height range, significantly improving the device's detection accuracy, stability, and yield. This is crucial for high-precision applications such as wafer defect detection and critical dimension measurement.

[0053] According to another aspect of this application, a focus control method is provided, the method being applied to the aforementioned semiconductor device, the method comprising:

[0054] The light source module is controlled to emit multiple illumination beams according to a preset illumination mode;

[0055] The first mask is used to spatially modulate the multiple illumination beams to form a plurality of first illumination patterns that correspond one-to-one with the multiple illumination beams;

[0056] The objective lens module focuses the plurality of first illumination patterns onto the surface of the sample to be tested and collects multiple reflected beams generated by the surface of the sample to be tested, wherein each of the multiple reflected beams corresponds one-to-one with the plurality of first illumination patterns.

[0057] The first beam splitter splits the multiple reflected beams into the first and second detection optical paths;

[0058] In the first detection optical path, after spatial filtering of the beam using the second mask, multiple first electrical signals are acquired by the first detection module, and the multiple first electrical signals correspond one-to-one with the multiple reflected beams.

[0059] In the second detection optical path, multiple second electrical signals are directly acquired by the second detection module, and the multiple second electrical signals correspond one-to-one with the multiple reflected beams.

[0060] The defocusing amount of the sample to be tested is determined based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode.

[0061] Based on the defocusing amount, the sample to be tested is controlled to move to the focusing position.

[0062] The above method fully executes the entire process from illumination modulation, reflected light collection, spectroscopic detection to signal processing, thus enabling real-time and accurate acquisition of the defocus information of the sample under test. By utilizing the combination of the first electrical signal (defocus sensitive) and the second electrical signal (reference), the influence of light source fluctuations and sample reflectivity changes can be effectively eliminated, improving the robustness and accuracy of defocus calculation. Finally, sample movement is controlled in a closed loop based on the defocus amount, achieving automatic focusing.

[0063] In one possible implementation, the preset lighting mode includes a full-source sequential lighting mode, and controlling the light source module to emit multiple lighting beams according to the preset lighting mode includes:

[0064] The system controls each of the sub-light sources in the light source module to be lit independently in a preset time sequence; wherein, during the lighting period of each sub-light source, the first detection subsystem simultaneously collects a first electrical signal corresponding to each sub-light source and the second detection subsystem simultaneously collects a second electrical signal corresponding to each sub-light source.

[0065] In this way, by using time-division lighting and synchronous acquisition, even with a small number of hardware channels used for detection (such as only one first detection unit and one second detection unit), the signals of different sub-light sources (first electrical signal and second electrical signal) can be separated. This mode has a simple hardware structure and low cost, and is suitable for occasions where the sampling speed requirement is not high, or for initial large-scale search of the focal plane.

[0066] In one possible implementation, the preset lighting mode includes a multi-source collaborative lighting mode, wherein controlling the light source module to emit multiple lighting beams according to the preset lighting mode includes:

[0067] The system controls multiple sub-light sources in the light source module to work together to emit light, wherein:

[0068] The first group of coordinated activation includes controlling the simultaneous lighting of each sub-light source located on the same side of the preset plane. During the simultaneous lighting of each sub-light source on the same side of the preset plane, the first detection subsystem simultaneously collects a first electrical signal corresponding to each sub-light source and the second detection subsystem simultaneously collects a second electrical signal corresponding to each sub-light source.

[0069] The second group of coordinated activation includes controlling the simultaneous illumination of each sub-light source located on the other side of the preset plane. During the simultaneous illumination of each sub-light source on the other side of the preset plane, the first detection subsystem simultaneously acquires a first electrical signal corresponding to each sub-light source, and the second detection subsystem simultaneously acquires a second electrical signal corresponding to each sub-light source.

[0070] In this way, the multi-source collaborative illumination mode can simultaneously acquire signals from multiple sub-sources by illuminating them once. Therefore, compared to the all-source sequential illumination mode, more information can be obtained in the same amount of time, improving sampling efficiency. Especially in systems with parallel detection channels, it is possible to rapidly acquire signals from both sides of the optical axis, providing synchronous data pairs for subsequent differential calculations, which is beneficial for improving the tracking performance of high-speed moving samples.

[0071] In one possible implementation, determining the defocus amount of the sample to be tested based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode includes:

[0072] Acquire the first and second electrical signals corresponding to when each of the sub-light sources is lit;

[0073] For each sub-light source, its corresponding first electrical signal and second electrical signal are processed to obtain the corresponding single defocus amount signal;

[0074] Based on each individual defocus signal, the defocus amount of the sample under test is determined by calculation using a preset band combination.

[0075] In this way, by determining a single defocus signal for each sub-light source based on the first and second electrical signals, the influence of light intensity fluctuations is eliminated, ensuring that each individual defocus signal accurately reflects the defocus information under that illumination channel. Then, through preset band combination calculations, information from multiple channels can be fused to obtain a more accurate and robust overall defocus value. This hierarchical processing method improves the algorithm's flexibility and adaptability.

[0076] In one possible implementation, determining the defocus amount of the sample under test based on each of the individual defocus signals through a preset band combination includes:

[0077] Based on the wavelength and spatial arrangement of the multiple sub-light sources, the individual defocus signals of each sub-light source belonging to the same wavelength are differentially combined to obtain the defocus signal corresponding to each wavelength.

[0078] The defocus amount of the sample under test is determined based on the defocus amount signals corresponding to each wavelength.

[0079] In this way, by differentially analyzing symmetrical sub-light sources of the same wavelength, common-mode noise (such as ambient light disturbances and sample surface inhomogeneities) can be effectively suppressed, improving the signal-to-noise ratio. Simultaneously, different wavelengths have different focus offsets, and the linear operating ranges of their differential signals ("wavelength-corresponding defocus signal") may differ and overlap. Therefore, a suitable band signal can be selected based on the current defocus range, or the two can be fused to extend the overall linear measurement range.

[0080] In one possible implementation, determining the defocus amount of the sample under test based on the defocus amount signals corresponding to each wavelength includes:

[0081] The defocus signals corresponding to each wavelength are subjected to translation calibration processing to obtain the processed signals, so that the processed signals are always positive or always negative within a defocus measurement range.

[0082] The maximum value among the absolute values ​​of the processed signal is determined as the normalized defocus amount signal used to characterize the focus state.

[0083] Based on the calibration relationship between the normalized defocus signal and the defocus amount, the defocus amount of the sample to be tested is determined.

[0084] In this way, by shifting the defocus signals corresponding to each wavelength, the signals of different wavelengths always cover the positive and negative regions throughout the entire measurement range. Therefore, by taking the maximum absolute value, a normalized defocus signal that is monotonic, unambiguous, and highly sensitive over a large range can be obtained. This is equivalent to stitching together the linear working ranges of multiple wavelengths, achieving the goal of expanding the total measurement range without reducing sensitivity. Furthermore, based on the calibration relationship and table lookup, the defocus value can be accurately obtained to drive the stage for closed-loop focusing.

[0085] Other features and aspects of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0086] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this application together with the specification and serve to explain the principles of this application.

[0087] Figure 1 A block diagram of a semiconductor device according to an embodiment of this application is shown;

[0088] Figure 2 This diagram shows a structural schematic of an optical focusing system according to an embodiment of the present application;

[0089] Figure 3 This diagram shows a structural schematic of a light source module according to an embodiment of the present application;

[0090] Figure 4 A schematic diagram of the structure of a light source module according to another embodiment of this application is shown;

[0091] Figure 5 A schematic diagram of the structure of a light source module according to another embodiment of this application is shown;

[0092] Figure 6 A schematic diagram showing the focal planes corresponding to monochromatic light sources of different wavelengths in a light source module according to an embodiment of this application is provided.

[0093] Figure 7 This diagram illustrates a timing diagram for controlling a sub-light source according to an embodiment of this application.

[0094] Figure 8 A timing diagram for sub-light source control according to another embodiment of this application is shown;

[0095] Figure 9 This diagram shows a structural schematic of an optical focusing system according to an embodiment of the present application;

[0096] Figure 10 A schematic diagram of an optical focusing system according to another embodiment of this application is shown;

[0097] Figure 11 A flowchart of a focus control method according to an embodiment of this application is shown;

[0098] Figure 12 This illustrates a defocus signal curve corresponding to Example 1 of an embodiment of this application;

[0099] Figure 13 This illustrates another defocus signal curve corresponding to Example 1 of an embodiment of this application;

[0100] Figure 14 This illustrates another defocus signal curve corresponding to Example 1 of an embodiment of this application;

[0101] Figure 15 This illustrates another defocus signal curve corresponding to Example 1 of an embodiment of this application;

[0102] Figure 16This diagram illustrates the relationship between the position of the focusing lens and the position of the focusing surface according to an embodiment of this application.

[0103] Explanation of reference numerals in the attached figures:

[0104] 10-Semiconductor equipment;

[0105] 100-Optical focusing system;

[0106] 101 - Light Source Module;

[0107] 111-Substrate; 121-Monochromatic light source; 1211-Sub-light source; M-Preset plane; m1-First half-space; m2-Second half-space;

[0108] 102 - First mask;

[0109] 103 - Objective lens module;

[0110] 301-Focusing lens; 302-Focusing motor; 303-Reflecting mirror; 304-Objective lens;

[0111] 104 - First beam splitter;

[0112] 105 - First Detection Subsystem;

[0113] 501 - First Detection Unit;

[0114] 511 - Second Mask;

[0115] 521 - First Detection Module;

[0116] 5211 - First converging mirror; 5212 - First detector;

[0117] 106 - Second Detection Subsystem;

[0118] 601 - Second Detection Unit;

[0119] 611 - Second Detection Module;

[0120] 6111 - Second converging mirror; 6112 - Second detector;

[0121] 107-processor;

[0122] 108-Collimating Lens;

[0123] 109 - Second beam splitter;

[0124] 200-Imaging System;

[0125] 300-Sports Table;

[0126] 400-Control System;

[0127] 20 - Sample to be tested. Detailed Implementation

[0128] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0129] As used herein, the terms “comprising,” “including,” “having,” or variations thereof are open-ended and include one or more of the stated features, integrals, elements, steps, components, or functions, but do not exclude the presence or addition of one or more other features, integrals, elements, steps, components, functions, or groups thereof.

[0130] When an element is referred to as “connected,” “coupled,” “responding,” or a variation thereof relative to another element, it may be directly connected, coupled, or responding to another element, or there may be an intermediate element present.

[0131] Although the terms first, second, third, etc., may be used herein to describe various elements / operations, these elements / operations should not be limited by these terms. These terms are only used to distinguish one element / operation from another. Therefore, without departing from the teachings of the inventive concept, a first element / operation in some embodiments may be referred to as a second element / operation in other embodiments.

[0132] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0133] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0134] In the field of semiconductor inspection, autofocus technology can be applied to scenarios requiring high-precision defocus detection using multi-beam illumination, spatial modulation, and dual-channel differential detection. In wafer defect inspection equipment, it rapidly and automatically focuses on patterned samples (such as wafers and chips), ensuring clear defect identification. In thin film thickness measurement systems, it combines reflected light information to precisely control the focal plane, reducing misjudgments caused by film layer interference. In silicon wafer bonding alignment, it compensates for minute defocusing at bonding interfaces in 3D integrated packaging. In mask / template inspection, it performs non-destructive focusing imaging of photomasks or nanoimprint templates, avoiding contact damage.

[0135] Taking semiconductor manufacturing as an example, eccentric masking plays a crucial role in the inspection of semiconductor structures, including wafer defect detection and advanced packaging inspection. In eccentric masking, the optical focusing system is the core equipment ensuring the accuracy of microscopic inspection. It ensures a clear image is always obtained during high-speed scanning or when the sample surface changes by adjusting the focal length of the optical system in real time. However, in related technologies, the optical focusing system in eccentric masking relies solely on the focal plane adjustment method of moving the focusing mirror with a focusing motor. When faced with assembly calibration, environmental fluctuations, and sample differences, it reveals significant shortcomings due to limitations in the modulation depth and dispersion characteristics of the light source. For example, different wafer samples may require specific working distances (distance between the objective lens and the sample surface). For instance, thin wafers require shorter working distances, while samples with protective adhesive require longer working distances. The method of using a focusing motor to move the focusing lens to change the focusing surface is adopted. However, due to the limitations of the modulation depth and dispersion characteristics of existing light sources, the system is prone to sensitivity reduction or signal saturation when detecting large-range displacements. It is difficult to meet the needs of coarse adjustment at long distances and fine adjustment at close distances. This means that the system can only detect different wafers with thickness differences within the limited focusing range of the focusing lens, which greatly limits the use of the system.

[0136] To address the aforementioned technical problems, embodiments of this application provide a semiconductor device 10, such as... Figure 1 As shown, the semiconductor device 10 includes an optical focusing system 100, an imaging system 200, a motion stage 300, and a control system 400. The motion stage 300 is used to carry and move the sample 20 under test (e.g., a wafer). The optical focusing system 100 is used for illumination and dynamically adjusts the focal length or Z-axis position based on real-time detected changes in image sharpness or distance, ensuring that the sample 20 maintains optimal focal plane even with surface undulations or multi-layered structures. The imaging system 200 is used to acquire high-resolution optical images of the surface of the sample 20 to obtain information on surface morphology and defects. The motion stage 300 is used to carry and control the multi-dimensional movement of the sample 20 in the X, Y, and Z directions, achieving a comprehensive scan of the sample 20. The control system 400 controls the optical focusing system 100 and the movement of the motion stage 300. The semiconductor device 10, based on the optical focusing system 100, can precisely adjust and control its focal plane position to ensure clear imaging and high-precision detection of the surface of the sample 20.

[0137] The semiconductor device 10 provided in this application embodiment, because it includes the optical focusing system 100 described below, possesses all the advantages of the optical focusing system 100, namely, it can achieve fast and accurate autofocus over a wider sample height range, thereby significantly improving the device's detection accuracy, stability, and yield. This is crucial for high-precision applications such as wafer defect detection and critical dimension measurement.

[0138] Next, the optical focusing system and its components provided in the embodiments of this application will be described in detail with reference to the accompanying drawings.

[0139] In one possible implementation, such as Figure 2 As shown, this application embodiment also provides an optical focusing system 100, which includes a light source module 101, a first mask 102, an objective lens module 103, a first beam splitter 104, a first detection subsystem 105, a second detection subsystem 106, and a processor 107.

[0140] The light source module 101 is used to emit multiple light beams according to a preset lighting mode.

[0141] The light source module 101 is the system's illumination source, used to generate active illumination light. This illumination light includes at least one type, with different wavelengths for different types of illumination light and the same wavelength for each beam of the same type of illumination light. An illumination beam refers to the light emitted by the light source module 101 used to illuminate the sample 20 under test. Each illumination beam includes at least one illumination light emitted by the light source module 101. The light source module 101 can independently control the emission of each illumination light, facilitating flexible settings for the at least one illumination light included in the illumination beam. A preset illumination mode refers to a predetermined control strategy for the lighting sequence and combination of each monochromatic light source in the light source module 101. By emitting multiple illumination beams using a preset illumination mode, the light source module 101 can provide multiple independent or combined illumination channels for subsequent focal plane measurements, laying the foundation for expanding the measurement range and improving measurement accuracy. Because the light sources can be flexibly controlled in terms of timing and combination, illumination can be performed according to the corresponding preset illumination mode based on different detection needs and scenarios, thus adapting to different samples under test and application scenarios.

[0142] A first mask 102 is disposed behind the light source module 101 and is used to spatially modulate the multiple illumination beams to form multiple first illumination patterns that correspond one-to-one with the multiple illumination beams.

[0143] The first mask 102 is an optical element with a specific pattern, such as a substrate or grating with a specific shape (e.g., stripes) etched onto a chromium layer. It is located at the rear end of the light source module 101, i.e., in the subsequent optical path of the light source module 101, with its center on the optical axis of the optical focusing system 100. When one of the multiple illumination beams passes through the first mask 102, its spatial intensity distribution is modulated by the mask's pattern, forming a first illumination pattern with a specific shape. That is, each illumination beam forms a corresponding first illumination pattern after passing through the first mask 102, achieving a one-to-one correspondence between the illumination beam and the first illumination pattern. The specific pattern of the first illumination pattern is the same as the pattern of the first mask 102. Because the multiple illumination beams emitted by the light source module 101 independently illuminate the first mask 102 and form multiple corresponding light spots on it, multiple corresponding first illumination patterns are generated after spatial modulation. These initial illumination patterns, acting as structured light, are projected onto the sample 20 under test by the subsequent system. Changes in their focus state directly affect the distribution of the reflected beam, thus enabling detection and perception.

[0144] The objective lens module 103 is disposed behind the first mask 102 and is used to focus the plurality of first illumination patterns onto the surface of the sample 20 to be tested, and to collect multiple reflected beams generated by the surface of the sample 20 to be tested, wherein the multiple reflected beams correspond one-to-one with the plurality of first illumination patterns.

[0145] The objective lens module 103 is the core imaging component of the optical focusing system 100. It typically consists of a set of high-precision, high numerical aperture lenses. Its function is to accurately image the first illumination pattern from the first mask 102 onto the surface of the sample 20 under test. Simultaneously, it is responsible for collecting light reflected or scattered from the sample surface, forming reflected beams. Since the first illumination pattern is imaged onto the surface of the sample 20, the surface of the sample 20 will then form reflected beams in response to that first illumination pattern, ensuring that each reflected beam corresponds to a specific first illumination pattern; that is, multiple reflected beams correspond one-to-one with multiple first illumination patterns. Because the objective lens module 103 simultaneously performs imaging and light collection functions, it can project the first illumination pattern onto the sample 20 under test and efficiently collect the reflected beams carrying the surface height information (i.e., defocus information) of the sample 20, transmitting this information to the subsequent detection systems (first detection subsystem and second detection subsystem). The number of reflected beams corresponds one-to-one with the number of first illumination patterns, ensuring that the information from each illumination channel is independent and distinguishable.

[0146] A first beam splitter 104 is disposed after the objective lens module 103 and is used to split the multiple reflected beams into a first detection optical path and a second detection optical path. For clarity, in this application, the beam split into the first detection optical path from each reflected beam is referred to as the first sub-beam, and the beam split into the second detection optical path is referred to as the second sub-beam.

[0147] The first beam-splitting element 104 is a beam-splitting device, such as a beam-splitting prism or a semi-transparent mirror. Positioned behind the objective lens module 103, and referencing the propagation direction of the reflected beam, the first beam-splitting element 104 splits the incident reflected beam into two beams at a certain ratio (e.g., 50:50), which then propagate along two different optical paths. Because of the first beam-splitting element 104, the same reflected beam can be divided into two paths: one for forming a focal plane detection signal (F-path, i.e., the first electrical signal), and the other for forming a light intensity normalization reference signal (N-path, i.e., the second electrical signal). This enables differential detection of focusing information, eliminates the influence of factors such as light source fluctuations, and improves measurement accuracy and stability.

[0148] A first detection subsystem 105 is disposed in the first detection optical path. The first detection subsystem 105 includes at least one first detection unit 501. Each first detection unit 501 includes a second mask 511 and a first detection module 521 sequentially disposed along the first detection optical path. The second mask 511 is used to spatially filter the multiple reflected beams (i.e., multiple first sub-beams) transmitted through the first detection optical path. The first detection module 521 is used to collect the multiple reflected beams (i.e., multiple first sub-beams) transmitted from the second mask 511 to the first detection optical path, obtaining multiple first electrical signals. The multiple first electrical signals correspond one-to-one with the multiple reflected beams (i.e., multiple first sub-beams). This is because the first sub-beams in each reflected beam arrive at the first detection module 521 at different times and are collected to form corresponding first electrical signals, thus ensuring a one-to-one correspondence between the multiple first electrical signals and the multiple reflected beams.

[0149] The first detection optical path is one of the optical paths split by the first beam splitter 104. The first mask 102 and the second mask 511 can be gratings. The first mask 102 and the second mask 511 have the same structure but are staggered in position. The projections of the second mask 511 and the first mask 102 on the imaging plane (or focal plane) are offset by a preset distance. When the illumination light passes through this dual-mask structure, they form their respective projected images on the imaging plane (i.e., the plane where the image sensor is located or the focal plane conjugate thereto). Since the two masks are laterally offset from their original positions, their projections on the imaging plane will also exhibit a certain relative displacement. When the sample 20 under test is at the optimal focal plane, the image is clear, the projection edges of the two masks are clearly distinguishable, and their relative offset remains constant. However, when defocusing occurs, due to blur diffusion, the change in the relative position of the two projections will cause changes in image contrast or correlation. By analyzing the offset, overlap, or cross-correlation peak of the two projected images, the direction and degree of defocusing can be detected, thereby achieving high-precision autofocus. The first detection module 521 is a photoelectric conversion device used to convert received optical signals into electrical signals. When the sample 20 under test is at different defocus positions, the position or distribution of the first sub-beam in the reflected beam on the second mask 511 changes, resulting in a change in the light energy passing through the second mask 511. The first detection module 521 collects this change in light intensity and converts it into a first electrical signal. Because the second mask 511 acts as a spatial filter, converting the defocus state into a change in light intensity, the first electrical signal carries precise defocus information.

[0150] A second detection subsystem 106 is disposed in the second detection optical path. The second detection subsystem 106 includes at least one second detection unit 601, and each second detection unit 601 includes a second detection module 611 disposed in the second detection optical path. The second detection module 611 is used to collect the multiple reflected beams (i.e., second sub-beams) transmitted in the second detection optical path to obtain multiple second electrical signals. The multiple second electrical signals correspond one-to-one with the multiple reflected beams (i.e., second sub-beams). This is because the second sub-beams in each reflected beam arrive at the second detection module 611 at different times and are collected to form corresponding second electrical signals, thus ensuring a one-to-one correspondence between the multiple second electrical signals and the multiple reflected beams.

[0151] The second detection optical path is a different optical path split from the first detection optical path by the first beam splitter 104. The second detection module 611 is also used for photoelectric conversion. The second detection subsystem 106 directly collects the light intensity of the reflected beam without modulation by the second mask 511. Therefore, its output second electrical signal mainly reflects the change in illumination light intensity and does not contain defocus information. Because these second electrical signals correspond one-to-one with multiple reflected beams, they can be used as reference signals to normalize the detected first electrical signal, thereby eliminating interference caused by light source fluctuations or changes in sample surface reflectivity, making the final defocus calculation result more accurate and robust.

[0152] The processor 107 is configured to determine the defocus amount of the sample 20 to be tested based on the plurality of first electrical signals, the plurality of second electrical signals and the preset illumination mode.

[0153] The processor 107 can be hardware with data processing capabilities, such as an industrial control computer, a digital signal processor (DSP), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). The processor 107 receives electrical signals from the first detection subsystem 105 and the second detection subsystem 106, and is communicatively connected to the first detection module 521 and the second detection module 611 (e.g., through a direct connection) to receive the plurality of first electrical signals and the plurality of second electrical signals. The processor 107 can also be communicatively connected to the light source module 101 (e.g., through a direct connection) to control the light source module 101 to emit an illumination beam. Because the processor 107 simultaneously obtains the first electrical signal (F-channel signal) carrying defocus information and the second electrical signal (N-channel signal) used for normalization, the current defocus direction and magnitude can be accurately calculated through calculation (e.g., for each illumination beam, calculating the normalized S-curve signal of F / N, i.e., the NSC (Normalized Signal Contrast) signal). By combining preset lighting modes, it can identify which light source(s) are currently in use, thereby selecting an appropriate calculation model or calibration curve, and ultimately accurately determining the defocus amount.

[0154] The optical focusing system 100 provided in this application embodiment, by employing the light source module 101 described below, can utilize the chromatic aberration of different wavelengths of light in the optical system to form a series of focal points at different positions along the axial direction (Z-axis). These focal points cover a larger axial range than a single wavelength, thereby extending the theoretical focal plane working range of the optical focusing system 100. Furthermore, by organically combining the light source module 101 with the first mask 102, objective lens module 103, first beam splitter 104, first detection subsystem 105, second detection subsystem 106, and processor 107, a complete, efficient, and high-precision autofocus closed-loop system is formed. Because the light source module 101 can provide multi-wavelength, flexibly configurable illumination, the entire optical focusing system 100 can achieve rapid and accurate focusing on different samples within a larger working range, significantly improving the applicability and performance of the semiconductor device 10.

[0155] Next, the light source module 101 in the optical focusing system 100 will be described in detail.

[0156] like Figures 3-5 As shown, this application embodiment also provides a light source module 101, which includes: a substrate 111 and a plurality of monochromatic light sources 121. The plurality of monochromatic light sources 121 are disposed on the substrate 111. The wavelengths of the light emitted by each monochromatic light source 121 are different. Each monochromatic light source 121 includes at least one sub-light source 1211. In each monochromatic light source 121, at least one sub-light source 1211 is located within a preset space, wherein the preset space is a half-space defined by a preset plane M in which the optical axis of the optical focusing system 100 is located (e.g., ...). Figure 3 The first half-space m1 or the second half-space m2 shown. That is, the preset space is the half-space pointed to by the normal vector of the preset plane M where the optical axis of the optical focusing system 100 is located.

[0157] The substrate 111 serves as a base for supporting and fixing the monochromatic light source 121. In some embodiments, the substrate 111 can be a printed circuit board (PCB), a ceramic substrate, or a metal substrate, etc., and this application is not limited thereto. In some embodiments, the substrate 111 may integrate circuitry for driving the monochromatic light source 121, providing independent power and control signals to each sub-light source 1211. This makes the light source module 101 a highly integrated module, facilitating installation and replacement. Moreover, since the driving circuitry is integrated on the substrate 111, an external controller (such as a processor 107) can directly and precisely control the lighting and shutting down of each sub-light source 1211 through a simple interface (such as a ribbon cable), without the need for an additional complex driving board. This highly integrated design greatly simplifies the electrical connections of the system, reduces electromagnetic interference, and improves the reliability and stability of the entire system.

[0158] In this context, a monochromatic light source 121 refers to a light source with a specific center wavelength. Multiple monochromatic light sources 121 may have different wavelengths; for example, the light emitted by a monochromatic light source 121 could be red, green, blue, etc. By utilizing light of different wavelengths, the optical focusing system 100 can achieve different focal positions at different wavelengths, thereby expanding the range of focal plane movement. For example, such as... Figure 6 As shown, the light source module 101 includes two monochromatic light sources 121 with corresponding wavelengths of λα and λβ, forming two focal planes at different positions along the axial direction (Z-axis). A sub-light source 1211 refers to the smallest light-emitting unit constituting a monochromatic light source 121. Each monochromatic light source 121 can be composed of one or more sub-light sources. For example, a monochromatic light source 121 emitting red light can be composed of one red LED chip (sub-light source) or multiple red LED chips. The preset space is defined by the preset plane M containing the optical axis of the optical focusing system 100. The optical axis of the optical focusing system 100 refers to the reference axis that determines the beam propagation path in the optical focusing system 100. It is the design and assembly reference for all core optical components (such as the objective lens module 103 and the first beam splitter 104), and the straight line containing the center of curvature of the surfaces of each optical component constituting the optical focusing system 100. This preset plane M is a plane containing the optical axis, which can divide the entire space into two half-spaces. The preset space refers to one of these two half-spaces. For example, if the vertical plane passing through the optical axis is taken as the boundary, the preset space can be the left half space or the right half space of the preset plane M.

[0159] By setting multiple monochromatic light sources 121 of different wavelengths in the light source module 101, the light source module 101 can emit multiple illumination beams of different wavelengths. Since the beams of different wavelengths will focus at different depth positions in the optical axis direction due to axial chromatic aberration when passing through the optical focusing system 100, the focal positions of each illumination beam are different from each other. At the same time, at least one sub-light source in each monochromatic light source 121 is set in the half-space defined by the preset plane M where the optical axis of the optical focusing system 100 is located, so that when the focal position changes (i.e., defocusing), it will directly cause the center of the light spot or the image on the image plane of the optical focusing system 100 to undergo a predictable directional shift and shift amount. Therefore, by capturing the direction and amount of this offset, the optical focusing system 100 can clearly determine the specific direction and amount of lens movement required, thereby achieving precise refocusing. Based on this mechanism, utilizing the characteristic that light beams of different wavelengths are naturally distributed at different axial depths due to axial chromatic aberration, the system constructs multiple independent illumination channels that coexist simultaneously and are spatially discrete for focal plane measurement. Each of these channels corresponds to a specific axial focusing depth, thereby expanding the effective axial focusing range of the measurement and improving the optical focusing efficiency of the optical focusing system. In addition, by flexibly controlling the timing and combination of each wavelength monochromatic light source 121, the optical focusing system 100 can dynamically switch illumination modes according to detection requirements (for example, prioritizing the use of long-wavelength beams for large-stroke coarse adjustment, and then switching to short-wavelength beams for high-precision fine adjustment). Therefore, it can effectively meet the needs of long-distance coarse adjustment and close-distance fine adjustment under the same hardware architecture, thereby improving the focusing efficiency of the optical focusing system. Furthermore, integrating multiple wavelength monochromatic light sources 121 onto the same substrate not only simplifies the system structure and improves integration and reliability, but also supports rapid wavelength switching without mechanical movement.

[0160] In one possible implementation, when each monochromatic light source 121 includes a sub-light source 1211, all sub-light sources 1211 are located within the preset space. Thus, since all sub-light sources 1211 are located on the same side of the optical axis (within the preset half-space), when defocusing occurs, the light spot or image on the image plane will exhibit a highly consistent and interference-free directional shift. Compared to a scheme where sub-light sources are distributed on both sides of the optical axis, this ensures that the system captures only a single, clear shift direction, significantly reducing the risk of misjudgment and improving the robustness of focus direction determination. Simultaneously, since each monochromatic light source 121 contains only a single sub-light source 1211, there is no need to coordinate the switching timing of multiple sub-light sources 1211 at the same wavelength, simplifying the driving circuit and control logic.

[0161] In one possible implementation, each monochromatic light source 121 includes multiple sub-light sources 1211, and the number of sub-light sources 1211 located in the preset space in each monochromatic light source 121 is ≥1. Each monochromatic light source 121 can contain multiple sub-light sources 1211 and can be distributed on both sides of the optical axis (i.e., ensuring that at least one sub-light source 1211 is in the preset space), providing great flexibility for the design of the light source module 101.

[0162] In some embodiments, if the monochromatic light source 121 includes an even number of sub-light sources 1211, each sub-light source 1211 can be symmetrically distributed about the optical axis. This arrangement of sub-light sources 1211 of the same wavelength symmetrically on both sides of the optical axis not only generates illumination for generating a defocus signal on one side of a preset space, but also generates illumination for differential compensation or extending the linear range on the other side. Because the number and position of the sub-light sources 1211 can be flexibly configured, the slope, linear range, and symmetry of the defocus signal (NSC curve) can be finely controlled, thereby optimizing the performance of the optical focusing system 100. The symmetrical distribution can be as follows: Figure 3 The axisymmetric distribution shown can also be as follows: Figure 5 The distribution is centrally symmetrical. When there are multiple monochromatic light sources 121 containing an even number of sub-light sources 1211 in the light source module 101, the symmetrical distribution of the even number of sub-light sources 1211 of different monochromatic light sources 1211 can be the same or different, and this application does not impose any restrictions on this. For example, if each monochromatic light source 121 includes two sub-light sources 1211, the two sub-light sources 1211 of each monochromatic light source 121 can be symmetrically distributed about the optical axis. In this way, by symmetrically distributing the sub-light sources 1211 of the same wavelength about the optical axis, the defocus signal can be obtained through differential calculation (e.g., subtracting the signal of the right sub-light source from the signal of the left sub-light source). This differential method can effectively suppress common-mode noise caused by light source intensity fluctuations, sample reflectivity inhomogeneity, etc., significantly improving the signal-to-noise ratio and measurement accuracy. Furthermore, the symmetrical distribution ensures that the generated differential signal has good linearity and symmetry near the zero point, making the detection of the defocus amount more accurate and reliable.

[0163] In one possible implementation, the sub-light sources 1211 located within the preset space are arranged along a straight line or an arc. Arrangement along a straight line or an arc means that the emission center points of the sub-light sources 1211 within the preset space can approximately fall on a straight line or an arc concentric with the optical axis. Furthermore, when the monochromatic light source 121 includes an even number of sub-light sources 1211, the multiple sub-light sources 1211 within the monochromatic light source 121 can be symmetrically distributed about the optical axis (including axial symmetry and centrosymmetry). This arrangement corresponds to different positions on the pupil plane of the objective lens. Thus, since the sub-light sources 1211 can be arranged along a straight line or an arc, the light they emit, after passing through the illumination system, will illuminate the pupil plane of the objective lens at different angles and positions. This distribution on the pupil plane affects the characteristics of the defocus signal (e.g., slope). By adjusting the arrangement, the sensitivity, linear range, and measurement accuracy of the optical focusing system 100 can be flexibly designed and optimized to adapt to different types of samples and detection requirements.

[0164] In one possible implementation, the emitting surfaces of the plurality of monochromatic light sources 121 are arranged coplanarly. Coplanarity of emitting surfaces means that the emitting surfaces of each sub-light source 1211 within all monochromatic light sources 121 are located on the same plane. In integrated packaging, this means that the emitting surfaces of all sub-light sources 1211 are adjusted to the same height after grinding or packaging. By ensuring coplanarity of emitting surfaces, the object distance of the light emitted by all sub-light sources 1211 is consistent when entering the subsequent optical system. This simplifies optical design, allowing the use of a single collimating lens 108 to collimate all beams, avoiding additional aberrations and optical path offsets introduced by different object distances, and ensuring the optical consistency of the entire light source module 101.

[0165] In one possible implementation, the sub-light sources 1211 belonging to the same monochromatic light source 121 have the same shape. Here, "same shape" means that for multiple sub-light sources 1211 of the same wavelength, such as two sub-light sources LED1 and LED4 of λα, the geometry (e.g., rectangular, circular, elliptical) and size of their emitting regions are identical. Thus, by setting the sub-light sources 1211 of the same wavelength to have the same shape, the first illumination pattern they form on the sample 20 under test is also identical and symmetrical. This ensures that the defocus signal obtained through differential calculation has good symmetry and consistency, simplifies subsequent signal processing algorithms, and improves measurement accuracy.

[0166] In one possible implementation, the shape of each of the sub-light sources 1211 can include any of the following: strip-shaped, circular, or elliptical. The shapes of the light emitted by sub-light sources 1211 of different shapes also differ; for example, a strip-shaped sub-light source 1211 can produce linear illumination light; a circular sub-light source 1211 produces a circular light spot; and an elliptical sub-light source 1211 produces an elliptical light spot. Thus, the illumination pattern can be customized according to specific application requirements, and the sub-light sources 1211 can be designed in different shapes. For example, when detecting structures with small linewidths, a strip-shaped sub-light source 1211 can be used to match its direction and improve contrast; during conventional focusing, a circular sub-light source 1211 can be used to obtain a symmetrical response signal. This flexibility allows the optical focusing system 100 to better adapt to test samples 20 with different characteristics.

[0167] In one possible implementation, the focal plane movement range of the optical focusing system 100 corresponds to different monochromatic light sources 121. The focal plane movement range refers to the axial distance at which the optical focusing system 100 can effectively operate. Due to chromatic aberration, light of different wavelengths converges at different focal points after passing through the objective lens module 103; for example, the focal point of blue light may be closer to the objective lens than that of red light. Therefore, when switching to a monochromatic light source 121 of a different wavelength, the focal plane (i.e., the optimal focal plane position) of the optical focusing system 100 shifts as a whole. The magnitude of this shift is the focal plane movement range. Thus, by utilizing the chromatic aberration of the monochromatic light sources 121, the illumination wavelength can be switched simply by switching the monochromatic light source 121, allowing for a rapid and mechanically non-mechanically compliant change of the focal plane of the optical focusing system 100. This provides a new and faster dimension for focal plane adjustment compared to methods relying solely on moving the focusing lens. Because different monochromatic light sources correspond to different focal plane movement ranges, the focal positions of each wavelength can be pre-designed so that they are connected end to end or partially overlapped in the axial direction, thereby greatly expanding the total focal plane working range of the optical focusing system 100 without reducing sensitivity.

[0168] In one possible implementation, the wavelengths of the light emitted by each of the monochromatic light sources 121 can all be in the visible band. This is because visible light is highly compatible with the response characteristics of the imaging system 200, providing high signal-to-noise ratio and high contrast image information; at the same time, visible light source technology is mature, stable, and easy to modulate, and will not cause unexpected photochemical damage to the sample 20 under test, thus balancing focusing accuracy, system compatibility, and detection safety, making it suitable for optical focusing systems 100 using the eccentric mask method.

[0169] In one possible implementation, each monochromatic light source 121 may include a laser diode (LD), a light-emitting diode (LED), etc., and this application does not limit this. Sub-light sources 1211 within the same monochromatic light source 121 all use the same light-emitting element, such as LEDs. Laser diodes (LDs) are characterized by high brightness, good directionality, and excellent monochromaticity; light-emitting diodes (LEDs) have advantages such as long lifespan, low cost, relatively wide spectral width, and ease of integration. Thus, the type of light source can be flexibly selected according to specific application requirements. For example, for scenarios requiring extremely high brightness and excellent monochromaticity, LDs can be selected; for scenarios pursuing low cost, high reliability, and ease of multi-chip integration, LEDs can be selected.

[0170] Next, we will continue to explain the implementation of the optical focusing system 100.

[0171] In one possible implementation, based on the aforementioned light source module 101, the preset illumination mode used in the optical focusing system 100 may include at least one of the following: a full-source sequential illumination mode, a single-source illumination mode, and a multi-source collaborative illumination mode. Since the emission wavelengths of different monochromatic light sources 121 are different, the focal plane movement range corresponding to the different preset illumination modes is different.

[0172] The full-source sequential illumination mode controls the sequential activation of each sub-light source 1211 in the light source module 101 according to a preset timing sequence. Specifically, the full-source sequential illumination mode allows each sub-light source 1211 to be activated sequentially and emit light independently according to the preset timing sequence. The preset timing sequence may include a first activation timing sequence for each monochromatic light source 121 and a second activation timing sequence for each sub-light source 1211 within the same monochromatic light source 121. In the full-source sequential illumination mode, the activation order of each monochromatic light source 121 is determined based on the first activation timing sequence, and the activation order of each sub-light source 1211 within each monochromatic light source 121 is determined based on the second activation timing sequence. Thus, based on the preset timing sequence, the acquired first and second electrical signals can be correlated with each sub-light source 1211 in the full-source sequential illumination mode, facilitating subsequent calculations.

[0173] For example, in Example 1, suppose... Figure 3 The four sub-light sources 1211 in the light source module 101 are LED1, LED2, LED3, and LED4 from left to right (LED2 and LED3 belong to the same monochromatic light source with a wavelength of λβ, and LED1 and LED4 belong to the same monochromatic light source with a wavelength of λα). The full-light source sequential lighting mode follows... Figure 7 If LED1, LED4, LED2, and LED3 are turned on sequentially as shown in the timing diagram, then the following can be detected: Figure 7The first electrical signal (F1, F4, F2, F3) and the second electrical signal (N1, N4, N2, N3) are shown.

[0174] The single-source illumination mode involves controlling the sub-sources 1211 of the target monochromatic light source corresponding to the current focal plane position among the plurality of monochromatic light sources 121 to sequentially emit light. In this mode, the processor 107 selects a corresponding monochromatic light source 121 based on the approximate position of the current system focal plane (for example, if currently operating near the focal plane range of λα, then selecting the λα monochromatic light source), and then illuminates only the sub-sources under that monochromatic light source 121, and sequentially acquires the first electrical signal and the second electrical signal.

[0175] The multi-source coordinated illumination mode controls the monochromatic light sources 121 corresponding to the current focal plane position to collaboratively turn on and emit light. Collaborative activation refers to activating multiple sub-light sources 1211 (at least two) simultaneously in two separate activations. The sub-light sources 1211 activated simultaneously in each activation belong to different monochromatic light sources and are located on the same side of the preset plane M. The sub-light sources 1211 activated in the two separate activations are located on different sides of the preset plane M. In other words, collaborative activation refers to grouped collaborative light emission. The first group of collaborative activations includes controlling the simultaneous illumination of all sub-light sources 1211 located on the same side of the preset plane M, and the second group of collaborative activations includes controlling the simultaneous illumination of all sub-light sources 1211 located on the other side of the preset plane M.

[0176] For example, in Example 2, the light source module 101 has a total of six sub-light sources 1211, namely LED1, LED2, LED3, LED4, LED5, and LED6. LED1 and LED6 belong to a single monochromatic light source A, LED2 and LED5 belong to a single monochromatic light source B, and LED3 and LED4 belong to a single monochromatic light source C. LED1, LED2, and LED3 are located to the left of a preset plane M, while LED4, LED5, and LED6 are located to the right of the preset plane M. If the monochromatic light sources corresponding to the current focal plane position are single monochromatic light sources A and B, then in the multi-light source collaborative lighting mode, according to... Figure 8 The timing sequence shown first turns on LED1 and LED2, then turns on LED5 and LED6, which allows detection of... Figure 8 The first electrical signal (F1, F2, F5, F6) and the second electrical signal (N1, N2, N5, N6) are shown.

[0177] In this way, by providing multiple preset illumination modes, the processor 107 in the optical focusing system 100 can flexibly select according to different application scenarios. For example, during the initial large-scale search of the focal plane, the full-source sequential illumination mode can be used to quickly obtain signals of multiple wavelengths and determine the approximate height range of the sample 20 under test. When the focal plane is close to the target, it can be switched to the single-source illumination mode, using a symmetrical monochromatic light source 121 of a single wavelength for high-precision tracking. When both a large range and high-speed response are required, a multi-source collaborative illumination mode can be adopted, acquiring differential signals of multiple wavelengths in a single acquisition, which expands the equivalent measurement range and increases the sampling frequency. Because the focal plane movement range corresponding to different modes is different, seamless transition from coarse to fine adjustment can be achieved through mode switching, balancing the working range and accuracy.

[0178] In one possible implementation, if the preset lighting mode includes at least one of a full-source sequential lighting mode and a single-source lighting mode, then the light source module 101 includes N monochromatic light sources 121, the first detection subsystem 105 includes one first detection unit 501, and the second detection subsystem 106 includes one second detection unit 601, where N≥1 and N is a positive integer. Specifically, when the preset lighting mode only includes a full-source sequential lighting mode and / or a single-source lighting mode, regardless of how many monochromatic light sources 121 are included in the light source module 101 (N≥1), its backend only requires one set of common detection units (i.e., a first detection unit 501 consisting of a second mask 511 and a first detection module 521, and a second detection unit 601 consisting of a second detection module 611). Because a time-division lighting method is used, the signals from different light sources are separated in time and can therefore be received sequentially by the same set of detection units. This greatly simplifies the system structure and reduces hardware costs. By using time-division multiplexing, time is traded for space, and a single detection unit is used to acquire multi-channel signals. This method is suitable for application scenarios that are cost-sensitive and do not have particularly high requirements for sampling speed.

[0179] In one possible implementation, if the preset illumination mode includes a multi-source collaborative illumination mode, then the light source module 101 includes N monochromatic light sources 121, the first detection subsystem 105 includes N first detection units 501, and the second detection subsystem 106 includes N second detection units 601, where N ≥ 1. Thus, because it has the same number of parallel detection units as the monochromatic light sources 121 (N parallel first detection units 501 and N parallel second detection units 601), it is possible to simultaneously illuminate and detect the sub-light sources 1211 of different wavelengths in the monochromatic light sources 121. This completely solves the speed limitation problem in the time-division multiplexing mode. In the multi-source collaborative illumination mode, signals corresponding to all wavelengths can be obtained with a single illumination and acquisition, greatly improving the data sampling rate. This allows the optical focusing system 100 to keep up with high-speed moving samples (such as rapidly scanning wafer platforms), achieving real-time and precise focusing control, and significantly improving the throughput of the detection equipment.

[0180] In one possible implementation, the first distance between the central axis of the first mask 102 and the optical axis of the optical focusing system 100 is different from the second distance between the central axis of the second mask 511 and the optical axis. The central axis of the mask refers to the center line of the pattern on the mask. The difference between the first and second distances results in different offsets of the first mask 102 and the second mask 511 relative to the optical axis in a direction perpendicular to the optical axis. By setting different offsets, the static offset point, i.e., the zero-point position, of the optical focusing system 100 can be finely adjusted. This design provides additional degrees of freedom for system calibration, can compensate for inherent aberrations or assembly errors in the optical system, ensures that the zero point of the defocus measurement signal (NSC curve) precisely coincides with the actual physical focal plane, and improves focusing accuracy.

[0181] In one possible implementation, the first mask 102 forms a conjugate surface with the surface of the sample 20 under test, and the surface of the sample 20 under test forms a conjugate surface with the second mask 511. In optical imaging, a conjugate surface refers to a one-to-one correspondence between the object plane and the image plane. Since the first mask 102 is imaged onto the surface of the sample 20 under test by the objective lens module 103, and simultaneously, the surface of the sample 20 under test is imaged onto the plane containing the second mask 511, the first mask 102 and the surface of the sample 20 under test are conjugate. Therefore, the pattern on the first mask 102 is clearly and accurately projected onto the surface of the sample 20 under test, ensuring the quality of the illumination pattern. Because the surface of the sample 20 under test is conjugate with the second mask 511, when the sample 20 under test is out of focus, the image reflected back from its surface will become blurred or shifted on the plane of the second mask 511. This is the core principle of spatial filtering for defocus detection. This dual conjugate relationship constitutes a perfect optical information transmission chain, ensuring that the entire physical process from illumination modulation to signal demodulation is precisely controllable, and is the physical basis for the system to achieve high-precision focusing.

[0182] In one possible implementation, such as Figure 9 , Figure 10 As shown, the optical focusing system 100 may further include a collimating lens 108 and a second beam splitter 109. The collimating lens 108 is disposed at the front end of the first mask 102 and is used to collimate the multiple illumination beams. The second beam splitter 109 is disposed between the first mask 102 and the objective lens module 103. The second beam splitter 109 is used to transmit the multiple illumination beams to the objective lens module 103; and to reflect the multiple reflected beams to the first beam splitter 104; or, the second beam splitter 109 is used to reflect the multiple illumination beams to the objective lens module 103; and to transmit the multiple reflected beams to the first beam splitter 104.

[0183] The collimating lens 108 can be a single lens or a lens group composed of multiple lenses, used to convert the diverging light emitted by the light source module 101 into parallel light to uniformly illuminate the first mask 102. The collimating lens 108 ensures that the illumination beam illuminates the first mask 102 at the same angle and with uniform intensity, improving illumination efficiency and quality. The second beam splitter 109 enables the illumination optical path (i.e., the optical path containing the illumination beam) and the detection optical path (i.e., the optical path containing the reflected beam) to be coaxial, making the system structure more compact and avoiding additional aberrations and assembly difficulties caused by optical path separation.

[0184] In one possible implementation, such as Figure 9 , Figure 10As shown, the first detection module 521 may include a first converging mirror 5211 and a first detector 5212 arranged sequentially along the first detection optical path. The first converging mirror 5211 is used to converge the multiple reflected beams transmitted from the second mask 511 to the first detection optical path; the first detector 5212 is used to collect the converged multiple reflected beams to obtain multiple first electrical signals. The first converging mirror 5211 is used to converge the spatially filtered reflected beams onto the photosensitive surface of the first detector 5212 to improve light energy utilization. By setting the first converging mirror 5211, weak light signals can be effectively collected, improving the detection sensitivity and signal-to-noise ratio of the system. In some embodiments, the first detector 5212 can be a multi-quadrant detector (also called a four-quadrant detector), which can monitor the positional changes of the first sub-beam and provide additional alignment information. In the case that the first detector 5212 is a multi-image detector, the second mask 511 may not be set in the first detection unit 501. This is because the multi-image detector can directly calculate the defocus amount by comparing the energy distribution of the first sub-beam in each quadrant, which can replace the spatial filtering of the second mask 511.

[0185] In one possible implementation, such as Figure 9 , Figure 10 As shown, the second detection module 611 may include a second converging mirror 6111 and a second detector 6112. The second converging mirror 6111 is used to converge the reflected beam in the second detection optical path onto the second detector 6112. The second converging mirror 6111 and the second detector 6112 are arranged sequentially along the second detection optical path. The second converging mirror 6111 is used to converge the reflected beam transmitted from the first beam splitter 104 to the second detection optical path; the second detector 6112 is used to collect the converged multiple reflected beams to obtain multiple second electrical signals. The second converging mirror 6111 is used to converge the reflected beam onto the photosensitive surface of the second detector 6112 to improve light energy utilization. By setting the second converging mirror 6111, it is possible to ensure that weak light signals are effectively collected, thereby improving the detection sensitivity and signal-to-noise ratio of the system. In some embodiments, the second detector 6112 can be a multi-image detector (such as a four-quadrant detector), which can monitor the positional changes of the second sub-beam and provide additional alignment information.

[0186] In one possible implementation, such as Figure 9As shown, the objective lens module 103 may include a focusing lens 301, a focusing motor 302, a reflecting mirror 303, and an objective lens 304. The focusing lens 301 is disposed at the rear end of the second beam splitter 109, and the focusing motor 302 is used to adjust the focal length of the focusing lens 301. The reflecting mirror 303 is located at the rear end of the focusing lens 301 and is used to reflect the illumination beam (i.e., the first illumination pattern) to the objective lens 304, or to reflect the reflected beam from the objective lens 304 to the focusing lens 301. The objective lens 304 is located between the reflecting mirror 303 and the sample 20 to be tested, and is used to converge the illumination beam (i.e., the first illumination pattern) onto the surface of the sample 20 to be tested, and to converge multiple reflected beams generated from the surface of the sample 20 to the reflecting mirror 303.

[0187] The focusing mirror 301 is a movable lens or lens group located at the rear end of the second beam splitter 109 (i.e., after the second beam splitter 109 along the optical path propagation direction) for fine adjustment of the optical path of the illumination beam. The focusing motor 302 is connected to the focusing mirror 301 and, in response to control commands from the processor 107, drives the focusing mirror 301 to move along the optical axis, thereby adjusting the focal length of the focusing mirror 301 and changing the focal plane position of the entire objective lens module 103. The reflecting mirror 303 is a highly reflective optical element located at the rear end of the focusing mirror 301. Its function is to deflect the illumination beam (i.e., the beam carrying the pattern of the first mask 102) passing through the focusing mirror 301 by 90 degrees or a specific angle, allowing it to enter the objective lens 304. Simultaneously, it also reflects the reflected beam from the objective lens 304, carrying sample information, back to the focusing mirror 301, achieving optical path refraction and making the system structure more compact. Objective lens 304 is a high-magnification, high-numerical-aperture microscope objective located between the reflecting mirror 303 and the sample 20 under test. Its core function is to highly focus the illumination beam reflected by the reflecting mirror 303 (i.e., the first illumination pattern, which is the same as the pattern of the first mask 102; for example, if the first mask 102 is a grating, then the first illumination pattern is the grating pattern) onto the surface of the sample 20 under test, forming a clear illumination spot; at the same time, it is also responsible for collecting the reflected beam generated on the surface of the sample 20 under test, focusing it, and transmitting it back to the reflecting mirror 303.

[0188] In this way, the objective lens module 103, by setting up a focusing mirror 301, a focusing motor 302, a reflecting mirror 303, and an objective lens 304, achieves precise control of the optical path and multi-level adjustment of the focal plane. Specifically, the illumination beam emitted by the light source module 101 and modulated by the first mask 102 passes sequentially through the collimating mirror 108 and the second beam splitter 109 before entering the objective lens module 103. Inside the objective lens module 103, the illumination beam first passes through the focusing mirror 301, and after the reflecting mirror 303 deflects the optical path, it is focused onto the surface of the sample 20 under test by the objective lens 304. The reflected beam then returns along the original path, passing again through the objective lens 304, the reflecting mirror 303, and the focusing mirror 301, before being guided by the second beam splitter 109 to the first beam splitter 104.

[0189] Among them, the focusing motor 302 can drive the focusing lens 301 to move, enabling the system to achieve a large range of mechanical adjustment of the focal plane to cope with the test samples 20 with different thicknesses or different working distance requirements, such as thin wafers or samples with protective adhesive, thus solving the problem of limited adjustment range of pure optical lenses.

[0190] Moreover, this mechanical adjustment method, combined with the multi-wavelength light source module 101, constitutes a multi-stage, wide-range focusing system. For example, the focusing motor 302 can be used to drive the focusing lens 301 to achieve coarse adjustment of the focal plane, moving the system's focal plane to the desired approximate range; then, monochromatic light sources 121 of different wavelengths are used for fine defocus detection and compensation. Because mechanical adjustment and optical wavelength adjustment complement each other, on the one hand, the total focusing stroke is extended through mechanical movement, and on the other hand, high-precision detection at each mechanical position is ensured through multi-wavelength light sources, ultimately achieving both wide-range and high-precision autofocus.

[0191] Next, we will continue to explain the implementation of the focusing control method applied to the optical focusing system 100.

[0192] like Figure 11 As shown, the focusing control method provided in this application embodiment may include steps S701-S708. This method can be applied to the semiconductor device 10.

[0193] In step S701, the light source module 101 is controlled to emit multiple illumination beams according to a preset illumination mode.

[0194] The processor 107, acting as the control core, can first send control commands to the light source module 101 according to a preset lighting mode. The driving circuit integrated on the substrate 111 of the light source module 101 can precisely control the lighting timing and current of each sub-light source 1211 based on the control commands, enabling it to emit multiple illumination beams according to the preset lighting mode. The preset lighting modes include a full-light source sequential lighting mode, a single-light source lighting mode, and a multi-light source collaborative lighting mode. The processor 107 can then select a mode from the preset lighting modes that covers the focal plane adjustment range of the focusing lens 301 at its current location to control the light source module 101.

[0195] In step S702, the first mask 102 is used to spatially modulate the multiple illumination beams to form a plurality of first illumination patterns that correspond one-to-one with the multiple illumination beams.

[0196] In step S703, the objective lens module 103 focuses the plurality of first illumination patterns onto the surface of the sample to be tested 20 and collects the multiple reflected beams generated by the surface of the sample to be tested 20, wherein the multiple reflected beams correspond one-to-one with the plurality of first illumination patterns.

[0197] In step S704, the multiple reflected beams are split into the first detection optical path and the second detection optical path by the first beam splitting element 104.

[0198] In step S705, in the first detection optical path, after the beam is spatially filtered by the second mask 511, multiple first electrical signals are acquired by the first detection module 521, and the multiple first electrical signals correspond one-to-one with the multiple reflected beams.

[0199] In step S706, in the second detection optical path, multiple second electrical signals are directly acquired by the second detection module 611, and the multiple second electrical signals correspond one-to-one with the multiple reflected beams.

[0200] In step S707, the defocusing amount of the sample 20 to be tested is determined based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode.

[0201] In step S708, the sample 20 to be tested is moved to the focusing position based on the defocus amount. Alternatively, the sample 20 to be tested can be moved to the focusing position based on the defocus amount.

[0202] In this process, after the light source module 101 emits an illumination beam, the beam passes sequentially through the first mask 102, the collimating lens 108 (if present), the second beam splitter 109, and the objective lens module 103, ultimately forming multiple first illumination patterns on the surface of the sample 20. The reflected beam returns along the original path, passing through the second beam splitter 109 and the first beam splitter 104, and is then split into the first detection optical path (F path) and the second detection optical path (N path). In the first detection optical path, the reflected beam is first spatially filtered by the second mask 511, and then collected and converted into a first electrical signal by the first detection module 521 (including the first converging lens 5211 and the first detector 5212). In the second detection optical path, the reflected beam is directly collected and converted into a second electrical signal by the second detection module 611 (including the second converging lens 6111 and the second detector 6112). The processor 107 synchronously reads these electrical signals (including the first and second electrical signals) and, in conjunction with the currently used preset illumination mode, calculates the defocus amount using a built-in algorithm. Finally, the processor 107 controls the stage (not shown in the figure) carrying the sample 20 to be tested to move along the Z-axis according to the defocus amount until the focus position is reached.

[0203] The above method fully executes the entire process from illumination modulation, reflected light collection, spectroscopic detection to signal processing, thus enabling real-time and accurate acquisition of the defocus information of the sample 20. By utilizing the combination of the first electrical signal (defocus sensitive) and the second electrical signal (reference), the influence of light source fluctuations and sample reflectivity changes can be effectively eliminated, improving the robustness and accuracy of defocus calculation. Finally, sample movement is controlled in a closed loop based on the defocus amount, achieving automatic focusing.

[0204] The implementation of step S701 varies depending on the preset lighting mode, and will be explained below:

[0205] When the preset lighting mode is a full-source sequential lighting mode, step S701 may include: controlling each of the sub-light sources 1211 in the light source module 101 to independently light up in a preset timing sequence (e.g., Figure 7 As shown in the diagram, during the illumination period of each of the sub-light sources 1211, the first detection subsystem 105 simultaneously acquires a first electrical signal corresponding to each of the sub-light sources 1211, and the second detection subsystem 106 acquires a second electrical signal corresponding to each of the sub-light sources 1211. Thus, by employing a time-division lighting and synchronous acquisition method, even with a small number of hardware channels used for detection (such as only one first detection unit 501 and one second detection unit 601), the signals (first electrical signal and second electrical signal) of different sub-light sources can be separated. This mode has a simple hardware structure and low cost, making it suitable for applications where sampling speed requirements are not high, or for initial large-scale focal plane searches.

[0206] When the preset lighting mode is a multi-source collaborative lighting mode, step S701 may include: controlling multiple sub-sources 1211 in the light source module 101 to turn on and emit light in a coordinated manner, which may be divided into a first group of coordinated activation and a second group of coordinated activation.

[0207] The first group of coordinated activation includes: controlling each sub-light source 1211 located on the same side of the preset plane M to light up simultaneously, wherein, during the simultaneous lighting of each sub-light source 1211 on the same side of the preset plane M, the first detection subsystem 105 collects a first electrical signal corresponding to each sub-light source 1211 and the second detection subsystem 106 collects a second electrical signal corresponding to each sub-light source 1211.

[0208] The second group of coordinated activation includes: controlling each sub-light source 1211 located on the other side of the preset plane M to light up simultaneously, wherein, during the simultaneous lighting of each sub-light source 1211 on the other side of the preset plane M, the first detection subsystem 105 collects a first electrical signal corresponding to each sub-light source 1211 and the second detection subsystem 106 collects a second electrical signal corresponding to each sub-light source 1211.

[0209] In this way, the multi-source collaborative illumination mode can simultaneously acquire signals from multiple sub-sources by illuminating them once. Therefore, compared to the all-source sequential illumination mode, more information can be obtained in the same amount of time, improving sampling efficiency. Especially in systems with parallel detection channels, it is possible to rapidly acquire signals from both sides of the optical axis, providing synchronous data pairs for subsequent differential calculations, which is beneficial for improving the tracking performance of high-speed moving samples.

[0210] When the preset illumination mode is a single-source illumination mode, step S701 may include: controlling each sub-source 1211 of the target monochromatic light source corresponding to the current focal plane position among the plurality of monochromatic light sources 121 to be sequentially turned on. During the illumination of each sub-source 1211, a first electrical signal corresponding to the sub-source 1211 is simultaneously acquired by the first detection subsystem 105 and a second electrical signal corresponding to the sub-source 1211 is acquired by the second detection subsystem 106. In this way, when the focal plane is close to the target, it can be switched to the single-source illumination mode to use a symmetrical monochromatic light source 121 with a single wavelength for high-precision tracking.

[0211] In one possible implementation, step S707 may include: acquiring a first electrical signal and a second electrical signal corresponding to the illumination of each of the sub-light sources 1211; processing the first electrical signal and the second electrical signal for each sub-light source 1211 to obtain a corresponding single defocus signal; and determining the defocus amount of the sample 20 under test by calculating based on each single defocus signal using a preset band combination. The preset band combination corresponds to the preset illumination mode. Thus, because a single defocus signal is determined for each sub-light source based on the first and second electrical signals, the influence of light intensity fluctuations is eliminated, ensuring that each single defocus signal accurately reflects the defocus information under that illumination channel. Then, by calculating using the preset band combination, information from multiple channels can be fused to obtain a more accurate and robust comprehensive defocus amount. This hierarchical processing method improves the flexibility and adaptability of the algorithm.

[0212] The preset band combinations are based on the currently enabled lighting mode (including sequential lighting with all light sources, multi-light source coordinated lighting, or single-light source lighting) and the wavelength characteristics of the activated sub-light sources, and are a predefined layered signal fusion strategy. Specifically, the wavelengths and spatial arrangements of the sub-light sources participating in the calculation are selected according to the lighting mode. When the sub-light sources are symmetrically distributed, differential operations are performed by grouping by wavelength; when multiple sub-light sources of the same wavelength are asymmetrically distributed, mean or median fusion is used to improve signal robustness.

[0213] In some embodiments, a single defocus signal can be calculated using the following formula:

[0214] NSCij_1=signal ij_1=Fij_1 / Nij_1;

[0215] NSCij_2=signal ij_2=Fij_2 / Nij_2;

[0216] Wherein, NSCij_1 represents a single defocus signal corresponding to the sub-light source 1211 located on one side of the preset plane M in the j-th pair of sub-light sources 1211 of the i-th monochromatic light source 121, and Fij_1 and Nij_1 represent the first and second electrical signals corresponding to the sub-light source 1211 located on one side of the preset plane M in the j-th pair of sub-light sources 1211 of the i-th monochromatic light source 121, respectively. NSCij_2 represents a single defocus signal corresponding to the sub-light source 1211 located on the other side of the preset plane M in the j-th pair of sub-light sources 1211 of the i-th monochromatic light source 121, and Fij_2 and Nij_2 represent the first and second electrical signals corresponding to the sub-light source 1211 located on the other side of the preset plane M in the j-th pair of sub-light sources 1211 of the i-th monochromatic light source 121, respectively.

[0217] The preset band combination is determined by the currently used preset illumination mode and the wavelength of the light emitted by the actually activated sub-light source 1211. In some embodiments, the defocus amount of the sample 20 under test is determined based on the individual defocus signals using the preset band combination. This can include: differentially combining the individual defocus signals of each sub-light source 1211 belonging to the same wavelength according to the wavelength and spatial arrangement of the multiple sub-light sources 1211 to obtain the defocus signal corresponding to each wavelength; and determining the defocus amount of the sample 20 under test based on the defocus signals corresponding to each wavelength. In this way, by differentially combining symmetrical sub-light sources of the same wavelength, common-mode noise (such as ambient light disturbances and sample surface inhomogeneities) can be effectively suppressed, improving the signal-to-noise ratio. Simultaneously, different wavelengths have different focus offsets, and the linear operating ranges of their differential signals ("wavelength-corresponding defocus signals") may differ and overlap. Therefore, a suitable band signal can be selected based on the current defocus range, or the two can be merged to expand the overall linear measurement range.

[0218] Wherein, the wavelength corresponding to each monochromatic light source 121 is λi. Further, through differential combination, the defocus signal NSCλi corresponding to wavelength λi is calculated. Wherein:

[0219] If there is only one pair of sub-light sources 1211 in the i-th monochromatic light source 121 (j=1, that is, there are 2 sub-light sources 1211 in the i-th monochromatic light source 121), then NSCλi=NSCλi1=NSCi1_1-NSCi1_2.

[0220] If the number of pairs j of sub-light sources 1211 in the i-th monochromatic light source 121 is a positive integer Q greater than or equal to 2 (that is, if there are 2 or more pairs of sub-light sources 1211 in the i-th monochromatic light source 121, or if there are 4 or more even numbers of sub-light sources 1211 in the i-th monochromatic light source 121), then NSCλi can be calculated by calculating the mean, median, etc. For example, if calculated by the mean, then NSCλi = (NSCλi1 + NSCλi2…NSCλiQ) / Q.

[0221] In some embodiments, after determining the defocus signal corresponding to each wavelength (i.e., the defocus signal NSCλi corresponding to wavelength λi), the defocus amount of the sample 20 under test is determined based on the defocus signal corresponding to each wavelength. This can include: performing translation calibration processing on the defocus signal corresponding to each wavelength to obtain a processed signal, such that the processed signal is always positive or always negative within a defocus measurement range; determining the maximum absolute value of the processed signal as the final normalized defocus signal used to characterize the focus state; and determining the defocus amount of the sample 20 under test based on the calibration relationship between the normalized defocus signal and the defocus amount. In this way, by performing translation processing on the defocus signal corresponding to each wavelength, the signals of different wavelengths always cover the positive and negative regions throughout the entire measurement range. Therefore, by taking the maximum absolute value, a normalized defocus signal that is monotonic, unambiguous, and highly sensitive over a large range can be obtained. This is equivalent to stitching together the linear working ranges of multiple wavelengths, achieving the goal of expanding the total measurement range without reducing sensitivity. Furthermore, by looking up the table based on the calibration relationship, the value of the defocus amount can be accurately obtained, which is used to drive the stage to perform closed-loop focusing.

[0222] Translation calibration involves linearly shifting the defocus signal of each wavelength channel by applying a wavelength-specific offset. The purpose of translation calibration is to convert defocus signals of different wavelengths into a unipolar form (positive or negative values ​​throughout) to achieve seamless splicing of multi-wavelength signal ranges.

[0223] The defocus signal NSCλi corresponding to wavelength λi undergoes translation calibration to obtain the processed signal NSCλi', which can be calculated using the following formula:

[0224] NSCλi'=NSCλi+Ci

[0225] Here, NSCλi' is the processed signal obtained after shifting and calibrating the defocus signal NSCλi corresponding to wavelength λi. Ci is the shift amount corresponding to wavelength λi, so that NSCλi' is a positive or negative value.

[0226] Next, the signal with the largest absolute value among the multiple obtained NSCλi' is selected as the normalized defocus signal NSC, that is:

[0227] NSC=max(abs(NSCλ1'), abs(NSCλ2'),..., abs(NSCλN'))

[0228] Where abs(NSCλ1'), abs(NSCλ2'), ..., abs(NSCλN') represent the absolute values ​​of the processed signals (NSCλ1', NSCλ2', ..., NSCλN') corresponding to wavelengths λ1, λ2, ..., λN, respectively.

[0229] The calibration relationship between the normalized defocus signal and the defocus amount can be predetermined, and the determination process is as follows:

[0230] After completing the structural construction of the optical focusing system 100, a standard sample with a high reflectivity plane (such as a flat silicon wafer) is used as the calibration object. The control system 400 controls the motion stage 300 carrying the sample 20 to move precisely along the optical axis (Z-axis) in small steps, from the negative defocus position to the positive defocus position, covering the entire designed measurement range. At the same time, at each Z-axis position, the processor 107 controls the light source module 101 to emit light according to the preset illumination mode, and collects the corresponding first and second electrical signals through the first detection subsystem 105 and the second detection subsystem 106. Then, for each Z-axis position, the processor 107 calculates the final calibration normalized defocus amount signal NSC0 according to the above formula. Finally, the calculated NSC0 value is mapped one-to-one with the corresponding Z-axis position (defocus amount) to form a mapping table or fitting function as the "calibration relationship between the normalized defocus amount signal and the defocus amount". This calibration relationship can be stored in the memory of processor 107 in the form of a look-up table (LUT), or it can be obtained by polynomial fitting to obtain a continuous function expression: .in, Indicates the amount of defocus. This is the fitted function obtained from the calibration.

[0231] It is understood that the above-mentioned method for determining the calibration relationship between the normalized defocus signal and the defocus amount is an illustrative method. Those skilled in the art can set the method for determining the calibration relationship between the normalized defocus signal and the defocus amount according to actual needs, and this application does not limit it.

[0232] The following examples illustrate the implementation of the focus control method in the embodiments of this application.

[0233] For example, suppose the light source module 101 includes three monochromatic light sources as shown in Table 1 below. Each monochromatic light source includes 2, 4, and 2 sub-light sources, respectively. Sub-light sources L11_1 and L11_2 are symmetrically arranged based on a preset plane M, as are sub-light sources L21_1 and L21_2, L22_1 and L22_2, and L31_1 and L31_2. Then, based on Tables 1 and 2, the individual defocus signal and the corresponding wavelength defocus signal of each sub-light source can be obtained.

[0234] Table 1. Comparison Table of Individual Defocus Signals

[0235]

[0236] Table 2 Calculation Table of Defocus Signal

[0237]

[0238] Then, when the preset lighting mode is the full-source sequential lighting mode, the defocus signal NSCλi corresponding to each wavelength is obtained as shown in Table 2: the defocus signal NSCλ1 for the λ1 band, the defocus signal NSCλ2 for the λ2 band = ((NSC21_1-NSC21_2)+(NSC22_1-NSC22_2)) / 2, and the defocus signal NSCλ3 for the λ3 band. Then, the normalized defocus signal NSC = max(abs(NSCλi')…) = max(abs(NSCλ1'), abs(NSCλ2'), abs(NSCλ3')) = max(|NSCλ1+C1|,|NSCλ2+C2|,|NSCλ3+C3|).

[0239] When the preset lighting mode is a multi-source collaborative lighting mode and the activated monochromatic light sources are the first and third monochromatic light sources, the defocus signals corresponding to wavelengths λ1 and λ3 are obtained as shown in Table 2: the defocus signal for the λ1 band is NSCλ1, and the defocus signal for the λ3 band is NSCλ3. Then, the normalized defocus signal NSC = max(abs(NSCλ1'), abs(NSCλ3')) = max(|NSCλ1+C1|, |NSCλ3+C3|).

[0240] When the preset lighting mode is a single-source lighting mode and the target monochromatic light source that is turned on is the first monochromatic light source, the defocus signal NSCλ1 corresponding to wavelength λ1 is first obtained as shown in Table 2. Then, since the defocus signal corresponding to λ1 is NSCλ1, the normalized defocus signal is directly determined based on NSCλ1, that is, NSC=|NSCλ1+C1|.

[0241] So, still based on Figure 3 Taking Example 1 as an example, for Figure 3 In Example 1, the light source module 101 has LED1 and LED4 as the first pair of sub-light sources 1211 in the first monochromatic light source. LED1 and LED4 are located on opposite sides of a preset plane M (i.e., the j values ​​of LED1 and LED4 are 1 and 2 respectively), and the wavelength of the emitted light is λ1 = λα. LED2 and LED3 are the first pair of sub-light sources 1211 in the second monochromatic light source. LED2 and LED3 are located on opposite sides of the preset plane M (i.e., the j values ​​of LED2 and LED3 are 1 and 2 respectively), and the wavelength of the emitted light is λ2 = λβ. When the preset lighting mode is a full-light source sequential lighting mode, LED1, LED4, LED2, and LED3 are lit sequentially, and the following can be detected: Figure 7 The first electrical signal (F1, F4, F2, F3) and the second electrical signal (N1, N4, N2, N3) are shown. When the preset lighting mode is a full-source sequential lighting mode, the defocus amounts corresponding to LED1 and LED4 form the defocus signal NSCλα of the λα band: NSCλ1 = NSCλ11 = NSC11_1 - NSC11_2 = F1 / N1 - F4 / N4. Similarly, the defocus amounts corresponding to LED2 and LED3 form the defocus signal NSCλβ of the λβ band: NSCλβ = NSCλ2 = NSCλ21 = F2 / N2 - F3 / N3. Therefore, the normalized defocus signal NSC = max(|NSCλα + C1|, |NSCλβ + C2|).

[0242] Further reference Figures 12-14 The defocus signal curves corresponding to each sub-light source 1211 can be obtained when the preset illumination mode is the full-light source sequential illumination mode. Figure 15 As shown in the normalized defocus signal NSC curve, it can be seen that the use of multiple monochromatic light sources 121 by the light source module 101 makes the linear range of NSC the sum of the linear ranges of the multiple monochromatic light sources 121, thereby effectively expanding the working range of the focusing system and increasing the tracking focus range.

[0243] Next, still with Figure 3 Taking Example 1 as an example, the relationship between the focal plane adjustment range and the position of the focusing lens 301 under different preset illumination modes is explained.

[0244] Then targeting Figure 3 As shown in Example 1, the preset lighting modes of the light source module 101 include the following three:

[0245] Single light source illumination mode 1: The target monochromatic light sources that are turned on are LED1 and LED4, that is, the LED with wavelength λα is turned on.

[0246] Single light source illumination mode 2: The target monochromatic light sources that are turned on are LED2 and LED3, that is, the LED with wavelength λβ is turned on.

[0247] Full-source sequential lighting mode: LED1-LED4 are turned on in sequence according to a preset timing, that is, LEDs with wavelengths of λα and λβ are turned on.

[0248] like Figure 16 As shown in Table 3, the focal plane positions under different preset illumination modes at different focusing lens positions are: if the focusing lens position is A and single-source illumination mode 1 is used, the focal plane is ZAα; if the focusing lens position is B and single-source illumination mode 2 is used, the focal plane is ZBβ; the focal plane adjustment range of the optical focusing system using the full-source sequential illumination mode is ZBβ-ZAα. This range is larger than ZBα-ZAα and ZBβ-ZAβ under single-source illumination mode 1 and single-source illumination mode 2. As shown in Table 3, the focal plane adjustment range corresponding to different preset illumination modes varies under different focusing lens positions. When controlling the light source module 101 to emit light, the processor 107 can naturally select a more suitable preset illumination mode based on the current position of the focusing lens.

[0249] Table 3. Correspondence between the current position of the focusing lens and the focal plane adjustment range

[0250]

[0251] It should be noted that although the above embodiments have been used as examples to illustrate the light source module, optical focusing system, semiconductor device, and focusing control method, those skilled in the art will understand that this application is not limited thereto. In fact, users can flexibly set each part and step according to their personal preferences and / or actual application scenarios, as long as it conforms to the technical solution of this application.

[0252] Regarding the focusing control method implemented by the control system 400 and processor 107 in this application, those skilled in the art should understand that these control functions can be implemented in software, purely in hardware logic circuits, or in a combination of software and hardware. The mechanical structure for which protection is sought in this application does not depend on the choice of the above implementation method, but the specific implementation carrier of the control method can take different forms.

[0253] In one feasible implementation, the control system 400 can be implemented in software, that is, the processor 107 reads and executes the program instructions stored in the memory to complete the functions corresponding to each control step. The processor 107 can be any processing circuit with program instruction execution capability, including but not limited to: central processing unit (CPU), microprocessor (MCU), digital signal processor (DSP), programmable logic controller (PLC), embedded microcontroller, or a chip dedicated to motion control (such as a motion control coprocessor). The processor can exist in the form of a single chip (such as a microcontroller) or can be implemented in the form of a system-on-a-chip (SoC). In this case, in addition to the processor core, the chip can also integrate some hardware acceleration circuits or dedicated peripheral interfaces (such as PWM output, quadrature encoder interface, CAN controller, etc.) for directly driving motors, cylinders or other mechanical actuators.

[0254] In another feasible implementation, the control system 400 can be implemented purely in hardware, that is, the control logic is completed by hardware processing circuits that do not have program instruction execution capabilities. These hardware processing circuits can be built from discrete components (such as logic gates, flip-flops, and comparators), but to reduce size and improve reliability, they are typically implemented using integrated circuits, such as application-specific integrated circuits (ASICs) and programmable logic devices (PLDs), including field-programmable gate arrays (FPGAs) and complex programmable logic devices (CPLDs). These hardware circuits can receive sensor signals from the mechanical system (such as limit switches, encoders, and force sensors), process them through combinational or sequential logic, and directly output drive signals (such as PWM waves and relay contact signals) to solenoid valves, servo drivers, or stepper motor drivers, thereby controlling the movement of the mechanical actuators.

[0255] This application does not limit all control functions to using the same implementation method. For example, the timing control part can be implemented using a PLC, while the high-speed response part can be implemented using pure hardware logic; or, one control module (such as position closed loop) can be implemented by an FPGA, and another control module (such as human-machine interaction) can be implemented by an MCU. Those skilled in the art can flexibly choose software, hardware, or a combination of both based on factors such as the real-time requirements, cost, and power consumption of the mechanical system. However, regardless of the implementation method used, as long as it implements the control method described in the claims of this application and can drive the corresponding mechanical structure to complete the predetermined action, it falls within the protection scope of this application.

[0256] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A light source module, used in an optical focusing system, characterized in that, include: substrate; Multiple monochromatic light sources are disposed on the substrate, and each monochromatic light source emits light with a different wavelength; Each of the monochromatic light sources includes at least one sub-light source. In each monochromatic light source, at least one of the sub-light sources is located within a preset space, such that when the focal position of the light changes, it will shift on the image plane of the optical focusing system. The optical focusing system achieves focusing by capturing the direction and amount of the shift. The preset space is a half-space defined by a preset plane where the optical axis of the optical focusing system is located.

2. The light source module according to claim 1, characterized in that, Each of the monochromatic light sources includes a sub-light source, and all the sub-light sources are located within the preset space.

3. The light source module according to claim 1, characterized in that, Each monochromatic light source includes multiple sub-light sources, and the number of sub-light sources located in the preset space in each monochromatic light source is ≥1.

4. The light source module according to claim 3, characterized in that, The monochromatic light source includes an even number of sub-light sources, and each of the sub-light sources is symmetrically distributed about the optical axis.

5. An optical focusing system, applied in a semiconductor device, for focusing a sample to be tested within the semiconductor device, characterized in that, include: The light source module as described in any one of claims 1 to 4 is used to emit multiple illumination beams according to a preset illumination mode; A first mask is disposed behind the light source module and is used to spatially modulate the multiple illumination beams to form multiple first illumination patterns that correspond one-to-one with the multiple illumination beams. An objective lens module, disposed behind the first mask, is used to focus the plurality of first illumination patterns onto the surface of the sample to be tested, and to collect multiple reflected beams generated by the surface of the sample to be tested, wherein the multiple reflected beams correspond one-to-one with the plurality of first illumination patterns; The first beam splitter is disposed behind the objective lens module and is used to split the multiple reflected beams into the first detection optical path and the second detection optical path. A first detection subsystem is disposed in the first detection optical path. The first detection subsystem includes at least one first detection unit, and each first detection unit includes: A second mask and a first detection module are sequentially arranged along the first detection optical path. The second mask is used to perform spatial filtering on the multiple reflected beams transmitted through the first detection optical path. The first detection module is used to collect the multiple reflected beams transmitted from the second mask to the first detection optical path to obtain multiple first electrical signals, wherein the multiple first electrical signals correspond one-to-one with the multiple reflected beams. A second detection subsystem is disposed in the second detection optical path. The second detection subsystem includes at least one second detection unit, and each second detection unit includes: A second detection module is disposed in the second detection optical path. The second detection module is used to collect the multiple reflected beams transmitted in the second detection optical path to obtain multiple second electrical signals, wherein the multiple second electrical signals correspond one-to-one with the multiple reflected beams; and, The processor is configured to determine the defocusing amount of the sample under test based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode.

6. The optical focusing system according to claim 5, characterized in that, The preset lighting modes include at least one of the following: full-light source sequential lighting mode, single-light source lighting mode, and multi-light source collaborative lighting mode; The full-light source sequential lighting mode is a mode in which each sub-light source in the light source module is turned on and illuminated in sequence according to a preset timing sequence. The single-source illumination mode controls the sub-sources of the target monochromatic light source corresponding to the current focal plane position among multiple monochromatic light sources to turn on and emit light sequentially; The multi-source coordinated lighting mode controls the monochromatic light source corresponding to the current focal plane position among the multiple monochromatic light sources to coordinately turn on and emit light. The coordinated turning on means turning on in two separate times, with multiple sub-light sources turning on simultaneously each time. The sub-light sources that turn on simultaneously each time belong to different monochromatic light sources and are located on the same side of the preset plane, while the sub-light sources that turn on in the two separate times are located on different sides of the preset plane. The focal plane movement range varies depending on the preset lighting mode.

7. The optical focusing system according to claim 6, characterized in that, The preset lighting mode includes at least one of the full-light source sequential lighting mode and the single-light source lighting mode; the light source module includes N monochromatic light sources; the first detection subsystem includes one first detection unit; and the second detection subsystem includes one second detection unit, wherein N≥1; or, The preset lighting mode includes the multi-light source collaborative lighting mode, the light source module includes N monochromatic light sources, the first detection subsystem includes N first detection units, and the second detection subsystem includes N second detection units, where N≥1.

8. The optical focusing system according to any one of claims 5 to 7, characterized in that, The first distance between the central axis of the first mask and the optical axis of the optical focusing system is different from the second distance between the central axis of the second mask and the optical axis.

9. A semiconductor device, characterized in that, include: The optical focusing system as described in any one of claims 5 to 8.

10. A focusing control method, characterized in that, The method is applied to the semiconductor device as described in claim 9, and the method includes: The light source module is controlled to emit multiple illumination beams according to a preset illumination mode; The first mask is used to spatially modulate the multiple illumination beams to form a plurality of first illumination patterns that correspond one-to-one with the multiple illumination beams; The objective lens module focuses the plurality of first illumination patterns onto the surface of the sample to be tested and collects multiple reflected beams generated by the surface of the sample to be tested, wherein each of the multiple reflected beams corresponds one-to-one with the plurality of first illumination patterns. The first beam splitter splits the multiple reflected beams into the first and second detection optical paths; In the first detection optical path, after spatial filtering of the beam using the second mask, multiple first electrical signals are acquired by the first detection module, and the multiple first electrical signals correspond one-to-one with the multiple reflected beams. In the second detection optical path, multiple second electrical signals are directly acquired by the second detection module, and the multiple second electrical signals correspond one-to-one with the multiple reflected beams. The defocusing amount of the sample to be tested is determined based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode. Based on the defocusing amount, the sample to be tested is controlled to move to the focusing position.

11. The method according to claim 10, characterized in that, The preset lighting mode includes a full-source sequential lighting mode, and controlling the light source module to emit multiple lighting beams according to the preset lighting mode includes: The system controls each of the sub-light sources in the light source module to be lit independently in a preset time sequence; wherein, during the lighting period of each sub-light source, the first detection subsystem simultaneously collects a first electrical signal corresponding to each sub-light source and the second detection subsystem simultaneously collects a second electrical signal corresponding to each sub-light source.

12. The method according to claim 10, characterized in that, The preset lighting mode includes a multi-source collaborative lighting mode, and controlling the light source module to emit multiple lighting beams according to the preset lighting mode includes: The system controls multiple sub-light sources in the light source module to work together to emit light, wherein: The first group of coordinated activation includes controlling the simultaneous lighting of each sub-light source located on the same side of the preset plane. During the simultaneous lighting of each sub-light source on the same side of the preset plane, the first detection subsystem simultaneously collects a first electrical signal corresponding to each sub-light source and the second detection subsystem simultaneously collects a second electrical signal corresponding to each sub-light source. The second group of coordinated activation includes controlling the simultaneous illumination of each sub-light source located on the other side of the preset plane. During the simultaneous illumination of each sub-light source on the other side of the preset plane, the first detection subsystem simultaneously acquires a first electrical signal corresponding to each sub-light source, and the second detection subsystem simultaneously acquires a second electrical signal corresponding to each sub-light source.

13. The method according to any one of claims 10 to 12, characterized in that, Determining the defocus amount of the sample to be tested based on the plurality of first electrical signals, the plurality of second electrical signals, and the preset illumination mode includes: Acquire the first and second electrical signals corresponding to when each of the sub-light sources is lit; For each sub-light source, its corresponding first electrical signal and second electrical signal are processed to obtain the corresponding single defocus signal; Based on each individual defocus signal, the defocus amount of the sample under test is determined by calculation using a preset combination of bands.

14. The method according to claim 13, characterized in that, The step of determining the defocus amount of the sample under test based on each of the individual defocus signals through a preset band combination calculation includes: Based on the wavelength and spatial arrangement of the multiple sub-light sources, the individual defocus signals of each sub-light source belonging to the same wavelength are differentially combined to obtain the defocus signal corresponding to each wavelength. The defocus amount of the sample under test is determined based on the defocus amount signals corresponding to each wavelength.

15. The method according to claim 14, characterized in that, Determining the defocus amount of the sample under test based on the defocus amount signals corresponding to each wavelength includes: The defocus signals corresponding to each wavelength are subjected to translation calibration processing to obtain the processed signals, so that the processed signals are always positive or always negative within a defocus measurement range. The maximum value among the absolute values ​​of the processed signal is determined as the normalized defocus amount signal used to characterize the focus state. Based on the calibration relationship between the normalized defocus signal and the defocus amount, the defocus amount of the sample to be tested is determined.

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