Illumination device, illumination adjustment method and wafer detection equipment

Abstract

The invention discloses an illumination device, an illumination adjusting method and wafer detection equipment. The device comprises an illumination light source, an illumination adjusting device and a wafer detection device, wherein the illumination light source comprises a light-emitting surface for exporting illumination light to the outside; the light-emitting surface adjusting part is used for adjusting the position of the light-emitting surface; the objective lens group comprises a plurality of objective lenses which are different in multiplying power and can be mutually switched, calibration data are pre-stored in the controller and comprise pupil plane size information, pupil plane position information and light-emitting surface position information of the objective lenses different in multiplying power, and the controller is used for adjusting the position of the light-emitting surface by the light-emitting surface adjusting part according to the multiplying power information of the objective lenses and the calibration data. According to the invention, rapid and automatic matching between the illumination system and pupil planes of objective lenses with different multiplying powers is realized, and uneven illumination and stray light caused by mismatching of the pupil planes are effectively eliminated.

Description

Technical Field

[0001] This application relates to the field of wafer inspection equipment technology, and in particular to an illumination device, an illumination adjustment method, and wafer inspection equipment. Background Technology

[0002] In semiconductor chip manufacturing, defect detection on the wafer surface is a crucial step in ensuring product yield. Optical imaging inspection methods are widely used due to their advantages of speed and non-contact operation. Among them, coaxial bright-field Köhler illumination is one of the mainstream illumination methods, providing uniform illumination and achieving conjugate imaging of the object plane and the pupil plane. However, stray light can be introduced into optical imaging inspection systems due to configuration issues of some optical components, posing a risk of degrading image quality.

[0003] However, in actual testing, to accommodate defects of different sizes, it is necessary to switch between objectives with different magnifications (such as 5X, 10X, 20X, 50X, etc.). Objectives with different magnifications have significant differences in numerical aperture (NA), exit pupil diameter, and pupil plane position (usually defined as the distance relative to the objective's mechanical positioning surface). In traditional Köhler illumination systems, the positions of the light source (emitting surface), field stop, and aperture stop (spatial filter) are usually fixed. When switching objectives, the fixed illumination cone cannot perfectly match the changed objective pupil plane, leading to several problems: 1) The illumination spot is larger than the objective entrance pupil, and excess light illuminates the internal structural components of the objective, generating stray light and reducing the image signal-to-noise ratio, such as... Figure 6 As shown in (a); 2) The illumination spot is smaller than the entrance pupil of the objective lens, resulting in insufficient illumination and a decrease in illuminance at the edge of the field of view, such as Figure 6 As shown in (b); 3) The incident surface of the illumination light entering the optical path loses its pairing relationship with the pupil surface of the objective lens, resulting in illumination defocus and a significant decrease in illumination uniformity, which can also cause problems such as image blurring.

[0004] To address the aforementioned issues, current industry solutions have significant limitations: First, mechanical displacement compensation is used, which involves manually adjusting the position of the light source or condenser lens group. This method is inefficient and heavily reliant on the operator's experience, making it difficult to achieve precise and rapid adjustments. Second, a beam splitting design is employed, which involves configuring independent relay lens groups for objectives of different magnifications to match the pupil plane. However, this greatly increases the complexity and cost of the system. Summary of the Invention

[0005] In view of this, this application provides an illumination device, an illumination adjustment method, and a wafer inspection equipment to solve the problem that existing illumination systems used in wafer inspection equipment are unable to quickly, accurately, and cost-effectively match the pupil surface with the illumination spot after switching between different magnification objectives.

[0006] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide an illumination device, which includes: an illumination source, including a light-emitting surface that directs illumination light to the outside; a light-emitting surface adjustment component connected to the illumination source for adjusting the position of the light-emitting surface; an objective lens group, including multiple objective lenses with different magnifications that can be switched between each other; and a controller, which has pre-stored calibration data, the calibration data including pupil size information, pupil position information, and light-emitting surface position information of objective lenses with different magnifications. The controller is used to acquire the magnification information of the currently working objective lens and control the light-emitting surface adjustment component to adjust the position of the light-emitting surface according to the magnification information and the calibration data.

[0007] As a further improvement of this application, the lighting device also includes a spatial filter and a filter adjustment component. The spatial filter is disposed on the light-emitting side of the lighting source, and the filter adjustment component is connected to the spatial filter for adjusting the aperture size of the spatial filter. The calibration data also includes the aperture size of the spatial filter corresponding to different magnification objectives. The controller is also used to control the filter adjustment component to adjust the aperture of the spatial filter according to the magnification information and calibration data.

[0008] As a further improvement of this application, the light-emitting surface adjustment component includes an electric displacement stage, the light-emitting surface and the spatial filter are fixedly connected by a structural component and are mounted together on the electric displacement stage, the light-emitting surface adjustment component includes a driver that drives the electric displacement stage to move along the optical axis, and the filter adjustment component includes a driver that drives the spatial filter to change the light transmission aperture.

[0009] As a further improvement of this application, the lighting source includes an LED light source and an optical fiber optically coupled to the LED light source, with the light-emitting surface being the light-emitting end face of the optical fiber.

[0010] As a further improvement to this application, the spatial filter includes an electrically adjustable aperture.

[0011] As a further improvement of this application, the objective lens assembly also includes an objective lens converter and an encoder. The objective lens converter is electrically connected to the controller, and the encoder stores the magnification information of each objective lens. The encoder is used to send the magnification information of the objective lens to the controller after the objective lens converter converts the objective lens.

[0012] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide an illumination adjustment method for an illumination device, which is applied to one of the above-mentioned illumination devices; the method includes: using a controller to obtain the magnification information of the current working objective lens; using the controller to send an instruction to adjust the position of the luminous surface to the luminous surface adjustment component according to the magnification information and pre-stored calibration data, wherein the calibration data includes pupil size information, pupil position information and position information of the luminous surface of the illumination source for different magnification objectives; and enabling the luminous surface adjustment component to adjust the position of the luminous surface.

[0013] As a further improvement of this application, the calibration data also includes the aperture size of the space filter corresponding to different magnification objectives; the illumination adjustment method of the illumination device further includes: using the controller to send an instruction to adjust the aperture of the space filter to the filter adjustment component based on the magnification information and the pre-stored calibration data; and enabling the filter adjustment component to adjust the aperture of the space filter.

[0014] As a further improvement to this application, the calibration data is calculated based on the following relationship: The aperture size of the spatial filter and the pupil diameter of the objective lens satisfy the following: ; in, This indicates the transverse magnification confirmed by the illumination optical path of the wafer inspection equipment. This indicates the diameter of the objective lens's pupil plane. This indicates the aperture of the spatial filter.

[0015] As a further improvement of this application, the change in distance between the objective lens's pupil plane position and the pupil plane reference position, and the adjustment amount of the luminous surface position relative to the luminous surface reference position, satisfy the following: ; ; ; ; in, This indicates the axial magnification of the illumination optical path in a wafer inspection device. This indicates the change in distance between the objective lens's pupil plane position and a reference pupil plane position. This indicates the adjustment amount of the position of the luminous surface relative to the reference position of the luminous surface. Indicates the position of the pupil plane of the objective lens. Indicates the pupillary reference position. Indicates the position of the luminous surface. Indicates the reference position of the luminescent surface.

[0016] As a further improvement to this application, the transverse magnification is confirmed based on the focal length of the condenser lens group and the focal length of the illumination lens group in the illumination optical path of the wafer inspection equipment: ; in, Indicates the focal length of the illumination lens group. This indicates the focal length of the light-gathering lens group.

[0017] As a further improvement of this application, the controller obtains the magnification information of the current working objective lens, including: after the objective lens converter performs objective lens switching, it obtains the magnification information of the current working objective lens from the encoder and sends the magnification to the controller.

[0018] As a further improvement to this application, the step of pre-storing calibration data includes: for each magnification objective lens, acquiring an illumination spot image through the illumination optical path of the wafer inspection device; adjusting the spatial filter aperture size and light source position according to the sharpness and uniformity of the spot image; when the sharpness and uniformity reach the optimal level, recording the current spatial filter aperture size and light source position information, and corresponding it with the current objective lens magnification information.

[0019] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a wafer inspection device, including an illumination optical path, an imaging optical path, and a processor; the illumination optical path adopts one of the illumination devices described above; the illumination light emitted from the objective lens in the illumination device is used to form signal light on the wafer surface by reflection or scattering; the imaging optical path is used to receive the signal light to form an image; the processor is used to perform feature detection on the image to obtain defect information, or to perform feature measurement to obtain structural information.

[0020] The beneficial effects of this application are: 1. The illumination device of this application solves the illumination quality problem caused by changes in the objective lens pupil plane position by dynamically matching the position of the emitting surface through pre-stored parameters in the controller. This ensures that the emitting surface always maintains a conjugate relationship with the entrance pupil plane of objective lenses of different magnifications, thereby significantly improving the uniformity of illumination and avoiding uneven light intensity distribution in the field of view caused by position mismatch. At the same time, it accurately guides the illumination cone to the objective lens pupil plane, minimizing the positional stray light generated by light illuminating the internal mechanical structure, effectively improving the image signal-to-noise ratio.

[0021] 2. The illumination device of this application dynamically adjusts the aperture of the filter according to the pre-stored parameters so that the diameter of the illumination spot can be precisely matched with the pupil diameter of different objective lenses, thereby fundamentally suppressing stray light caused by aperture mismatch. This not only significantly improves the contrast and signal-to-noise ratio of the image, but also optimizes the light energy utilization rate, ensuring that the illumination system always works at the highest efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of one embodiment of the lighting device of the present invention; Figure 2 This is a schematic diagram of the electrical connection relationship of one embodiment of the lighting device of the present invention; Figure 3 This is a schematic diagram of the lighting optical path of one embodiment of the lighting device of the present invention; Figure 4This is a flowchart illustrating an embodiment of the illumination adjustment method for wafer inspection equipment according to the present invention; Figure 5 This is a schematic diagram showing the position and size of the objective lens pupil in an embodiment of the illumination adjustment method for wafer inspection equipment according to the present invention; Figure 6 This is a schematic diagram of the optical path showing the relative size relationship between the light spot and the objective lens pupil plane. In (a), the light spot is larger than the objective lens pupil plane, and in (b), the light spot is smaller than the objective lens pupil plane. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] The terms "first," "second," and "third" in this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative spatial positions and movements of components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] Figure 1 and Figure 2 This is a schematic diagram of the lighting device according to an embodiment of the present invention. Figure 1 and Figure 2 As shown, the lighting device includes: a light source 1, an objective lens group 3, a light-emitting surface adjustment component 5, and a controller 6.

[0027] The lighting source 1 includes a light-emitting surface 11 that directs the lighting light to the outside.

[0028] Specifically, this embodiment uses a high-brightness LED light source, whose emitted light is transmitted to the bright-field illumination optical path through an optical fiber. The light-emitting surface 11 is specifically the light-emitting end face of the optical fiber, which is located at the beginning of the illumination optical path, and its position can be precisely adjusted along the optical axis. The illumination source 1 preferably has high stability and long lifespan characteristics to ensure the consistency of illumination intensity during continuous detection.

[0029] Objective lens group 3 includes multiple interchangeable objectives with different magnifications (e.g., 1.5X, 2.5X, 5X, 10X, 20X), which are mounted on a rotatable or translational objective lens converter 31. Users can select objectives with different magnifications according to their testing needs; the objective lens converter 31 enables fast and accurate objective lens switching. The light-emitting surface adjustment component 5 is connected to the illumination source 1 and is used to adjust the position of the light-emitting surface 11.

[0030] Specifically, the light-emitting surface adjustment component 5 includes a high-precision electric displacement stage on which the optical fiber emitting end face (i.e., the light-emitting surface 11) is fixedly mounted via structural components. The displacement stage can move along the optical axis, thereby driving the light-emitting surface 11 to move together, achieving precise adjustment of the position of the light-emitting surface 11.

[0031] The controller 6 is pre-stored with calibration data, which includes pupil size information, pupil position information and luminous surface 11 position information of different magnification objectives. The controller 6 is used to obtain the magnification information of the current working objective and control the luminous surface adjustment component 5 to adjust the position of the luminous surface 11 according to the magnification information and calibration data.

[0032] Specifically, the controller 6 can be an embedded system or a programmable logic controller (PLC) 6, with a calibration data table pre-stored internally. This table contains pupil size information, pupil position information, and luminous surface 11 position information for each objective lens magnification. The controller 6 is electrically connected to the luminous surface adjustment component 5. When switching objectives, the controller 6 receives the current objective lens magnification information and automatically issues control commands based on the calibration data to drive the luminous surface adjustment component 5 to make corresponding adjustments.

[0033] Furthermore, such as Figure 1 and Figure 2As shown, the lighting device also includes a spatial filter 2 and a filter adjustment component 4. The spatial filter 2 is located on the light-emitting side of the lighting source 1. The objective lens group 3 includes multiple objective lenses with different magnifications that can be switched between each other. The filter adjustment component 4 is connected to the spatial filter 2 and is used to adjust the aperture size of the spatial filter 2. The calibration data also includes the aperture size of the spatial filter 2 corresponding to different magnification objective lenses. The controller 6 is also used to control the filter adjustment component 4 to adjust the aperture of the spatial filter 2 according to the magnification information and calibration data.

[0034] In addition, see Figure 1 The bright-field illumination optical path system of this wafer inspection equipment also includes: a condenser lens group 10, a field stop 20, a bright-field illumination lens group 30, a reflector 40, a beam splitter 50, a dichroic mirror 60, an autofocus module 70, an imaging lens group 80, and a bright-field camera 90. This bright-field illumination optical path system adopts the Köhler illumination method. The illumination light emitted by the illumination source 1 passes sequentially through the spatial filter 2, the condenser lens group 10, the field stop 20, the bright-field illumination lens group 30, the reflector 40, the beam splitter 50, and the dichroic mirror 60 before reaching the objective lens pupil. After passing through the objective lens, it is uniformly illuminated on the object surface. The emitting surface 11 of the illumination source 1 is conjugate to the objective lens pupil.

[0035] It should be noted that the spatial filter 2 is located on the light-emitting side of the illumination source 1, in front of the light-collecting lens group 10.

[0036] Specifically, the spatial filter 2 employs an electrically adjustable aperture structure, whose aperture diameter can be continuously or steppedly adjusted electronically. The function of the spatial filter 2 is to limit the diameter of the illumination beam, ensuring precise matching with the pupil diameter of the objective lens being used, thereby avoiding uneven illumination or stray light problems caused by an excessively large or small beam. The spatial filter 2 is mounted on an electrically operated stage. This stage can move along the optical axis, thereby moving the emitting surface 11 and the spatial filter 2 together.

[0037] The objective lens group 3 can switch between multiple objectives with different magnifications through the objective lens converter 31. Users can select different magnification objectives (e.g., 1.5X, 2.5X, 5X, 10X, 20X) according to their testing needs. The objective lens converter 31 can achieve fast and accurate objective lens switching.

[0038] The filter adjustment component 4 is connected to the spatial filter 2 and is used to adjust the aperture size of the spatial filter 2.

[0039] Specifically, the filter adjustment component 4 includes a precision stepper motor or servo motor for driving the variable aperture to change its light-transmitting aperture according to a control signal. This adjustment component features high resolution and high repeatability to ensure accurate aperture adjustment.

[0040] The controller 6 is electrically connected to the objective lens converter 31, the filter adjustment component 4, and the light-emitting surface adjustment component 5. When the objective lens converter 31 switches objectives, the controller 6 receives the magnification information of the current objective lens and automatically issues control commands based on the calibration data to drive the filter adjustment component 4 and the light-emitting surface adjustment component 5 to make corresponding adjustments.

[0041] It should be noted that, as Figure 3 As shown, the illumination source 1 uses a high-brightness LED to illuminate the brightfield illumination system through the fiber optic output end face. After being modulated by the spatial filter 2, the light-collecting lens group 10, and the field stop 20, it passes through the brightfield illumination lens group 30, the reflecting mirror 40, the beam splitter 50, and the dichroic mirror 60 before illuminating the pupil plane of one of the objective lenses in the objective lens group 3. Because the different objective lenses in the objective lens group 3 have different magnifications, the pupil plane position and exit pupil diameter of the objective lenses are different. In order to ensure sufficient illumination, the size of the illumination spot should match the exit pupil diameter of the objective lens, and the position of the light-emitting surface should be conjugate to the exit pupil position of the objective lens. Therefore, in this embodiment, the wafer inspection equipment uses the pre-stored parameters of the controller 6 to dynamically match the position of the emitting surface 11 and the aperture of the spatial filter 2, ensuring that the illumination spot can ideally match the size and position of the objective lens pupil at any magnification. This fundamentally eliminates stray light and uneven illumination caused by pupil mismatch, improves image quality and detection signal-to-noise ratio, and realizes automatic, fast, and precise adjustment of illumination parameters after objective lens switching. It overcomes the problems of low efficiency and poor consistency of manual adjustment, significantly improving equipment efficiency. Compared with the beam splitting scheme that designs an independent optical path for each objective lens, this invention achieves its function by adding movable parts and a control system to the existing Köhler optical path, resulting in a more compact system structure and significantly reduced cost.

[0042] Furthermore, in some embodiments, the light-emitting surface adjustment member 5 includes an electric displacement stage, the light-emitting surface 11 and the spatial filter 2 are fixedly connected by a structural member (not shown in the figure) and are mounted together on the electric displacement stage, the light-emitting surface adjustment member 5 includes a driver that drives the electric displacement stage to move along the optical axis, and the filter adjustment member 4 includes a driver that drives the spatial filter 2 to change the light transmission aperture.

[0043] In this embodiment, the light-emitting surface adjustment component 5 further includes a high-precision motorized displacement stage. The light-emitting surface 11 (i.e., the optical fiber output end face) and the spatial filter 2 are fixedly connected by a rigid structural component to form an integral assembly. This assembly is mounted on the motorized displacement stage and can move along the optical axis under the drive of the driver.

[0044] The filter adjustment component 4 includes another driver (such as a miniature stepper motor) for driving the blade structure inside the space filter 2 to change its light-transmitting aperture. Both drivers are connected to the controller 6, receiving control commands and executing corresponding actions.

[0045] This integrated structural design not only simplifies the mechanical layout and reduces the difficulty of assembly and adjustment, but also ensures that the relative positions of the light-emitting surface 11 and the spatial filter 2 remain unchanged during the adjustment process, which is conducive to maintaining the stability of the optical conjugate relationship.

[0046] Furthermore, in some embodiments, the lighting source 1 includes an LED light source and an optical fiber optically coupled to the LED light source, with the light-emitting surface 11 being the light-emitting end face of the optical fiber.

[0047] Specifically, the illumination source 1 adopts a structure combining a high-brightness LED with fiber optic light guiding. The light emitted by the LED is coupled into one or more optical fibers, and after being conducted through the fibers, it is emitted from its light-emitting end face to form the illumination emitting surface 11. The advantage of using fiber optic light guiding in this embodiment is that it can isolate the LED light source (which may generate a lot of heat) from the main optical system, reducing the impact of the heat source on the imaging optical path; at the same time, the light-emitting end face of the fiber is small and easy to fix, which is beneficial for achieving precise adjustment of the position of the emitting surface 11. The light-emitting end face can preferably be optically polished to reduce light energy loss and scattering.

[0048] Furthermore, in some embodiments, the spatial filter 2 includes an electrically adjustable aperture.

[0049] Specifically, the spatial filter 2 is an electrically driven variable aperture, typically composed of multiple blades. These blades move synchronously under the drive of a actuator, forming a continuously variable central aperture. This electrically driven aperture possesses high precision and repeatability, and its aperture variation range should cover the required light-transmitting aperture for all objective lens magnifications. The controller 6 controls the movement of the actuator by sending pulse signals or analog voltage signals, thereby precisely setting the aperture size.

[0050] Furthermore, in some embodiments, the objective lens group 3 also includes an objective lens converter 31 and an encoder 32. The objective lens converter 31 is electrically connected to the controller 6, and the encoder 32 stores the magnification information of each objective lens. The encoder 32 is used to send the magnification information of the objective lens to the controller 6 after the objective lens converter 31 converts the objective lens.

[0051] Specifically, the objective lens group 3 is equipped with a multi-position objective lens converter 31, with each position housing an objective lens of a different magnification. The objective lens converter 31 incorporates an encoder 32 (such as an absolute encoder 32 or a rotary encoder 32), which identifies the magnification of the objective lens currently in its working position and converts this information into an electrical signal (such as a digital signal or a specific voltage value) for output. The objective lens converter 31 is electrically connected to the controller 6. When the user rotates the converter to switch objectives, the encoder 32 reads the position information in real time and sends the current objective lens's magnification code to the controller 6. The controller 6 then queries a pre-stored calibration data table and executes the corresponding adjustment commands.

[0052] Figure 4 This is a schematic flowchart of the lighting adjustment method of the lighting device according to an embodiment of the present invention. The lighting adjustment method of the lighting device is applied to a lighting device in one of the above embodiments. The lighting device includes: a lighting source, a spatial filter, an objective lens group, a filter adjustment component, a light-emitting surface adjustment component, and a controller.

[0053] like Figure 4 As shown, the lighting adjustment method of the lighting device includes steps S1 to S3.

[0054] Step S1: The controller acquires the magnification information of the current working objective lens.

[0055] Specifically, when the objective lens is switched, the controller obtains the magnification information of the switched objective lens.

[0056] Furthermore, step S1 specifically includes: after switching objectives, the objective converter obtains the magnification information of the currently working objective from the encoder and sends the magnification to the controller.

[0057] Specifically, the user manually or electrically rotates the objective lens converter to insert the objective lens of the desired magnification into the optical path. The rotational movement of the objective lens converter is detected in real time by its built-in encoder. The encoder generates a signal representing the current absolute position based on its own positioning principle (such as photoelectric, magnetoelectric, or mechanical contacts). This signal is sent to the control circuit of the objective lens converter, which decodes it into a specific objective lens magnification value (such as "10X"). The objective lens converter sends this magnification value to the main controller through a communication interface (such as RS-232, RS-485, Ethernet, or I / O signals). The controller receives and parses this information for subsequent querying of the calibration data table.

[0058] Step S2: The controller sends an instruction to the light-emitting surface adjustment component to adjust the position of the light-emitting surface based on the magnification information and the pre-stored calibration data. The calibration data includes pupil size information, pupil position information and light-emitting surface position information for different magnification objectives.

[0059] Specifically, after receiving the magnification information, the controller queries its internal calibration data table, which records the coordinates of the luminescent surface position corresponding to different magnification objectives. Then, based on the query result, the controller generates control commands and sends them to the luminescent surface adjustment mechanism, instructing it to drive the electric displacement stage to move the luminescent surface to the target position.

[0060] Furthermore, in some embodiments, the calibration data also includes the aperture size of the spatial filter corresponding to different magnification objectives. The illumination adjustment method of the illumination device further includes: using a controller to send a command to the filter adjustment component to adjust the aperture of the spatial filter based on the magnification information and pre-stored calibration data.

[0061] Specifically, the calibration data table records the ideal space filter aperture size corresponding to different magnification objectives. The controller generates control commands based on the query results and sends commands to the filter adjustment component, instructing it to adjust the aperture of the space filter to the target value.

[0062] Further steps, including pre-stored calibration data, include: 1. For each magnification objective lens, acquire the illumination spot image through the illumination optical path of the wafer inspection equipment.

[0063] Specifically, the objective lens to be calibrated (e.g., 10X) is moved into the working optical path, the illumination source is turned on, and the light emitted by it passes through the current spatial filter aperture and the position of the emitting surface, and then shines on the sample (or a blank silicon wafer) through the objective lens. The system's own imaging camera captures the image of the illumination spot at this time and transmits it to the image processing unit of the controller.

[0064] 2. Adjust the aperture size of the spatial filter and the position of the light source according to the clarity and uniformity of the light spot image.

[0065] Specifically, the image processing unit runs an algorithm to calculate the sharpness (e.g., based on a gradient function) and uniformity (e.g., calculating the standard deviation of the image's grayscale values) of the current image in real time. The controller issues instructions to fine-tune the aperture of the spatial filter and the position of the luminescent surface. After each adjustment, the image is reacquired and the sharpness and uniformity indices are calculated.

[0066] 3. When the sharpness and uniformity are optimal, record the current spatial filter aperture size and light source position information, and match them with the current objective lens magnification information.

[0067] Specifically, when the sharpness and uniformity indicators reach their optimal values ​​(or exceed the set threshold) at the same time, the controller records the spatial filter aperture value and the position coordinates of the emitting surface, binds this set of parameters with the magnification information of the current objective lens, and stores it in the calibration data table.

[0068] Furthermore, the calibration data is calculated based on the following relationship: The aperture size of the spatial filter and the pupil diameter of the objective lens satisfy the following: ; in, This indicates the transverse magnification confirmed by the illumination optical path of the wafer inspection equipment. This indicates the diameter of the objective lens's pupil plane. Indicates the aperture of the spatial filter; The change in distance between the objective lens's pupil plane position and the reference pupil plane position, and the adjustment of the luminous surface position relative to the reference luminous surface position, satisfy the following: ; ; ; ; in, This indicates the axial magnification of the illumination optical path in a wafer inspection device. This indicates the change in distance between the objective lens's pupil plane position and a reference pupil plane position. This indicates the adjustment amount of the position of the luminous surface relative to the reference position of the luminous surface. Indicates the position of the pupil plane of the objective lens. Indicates the pupillary reference position. Indicates the position of the luminous surface. Indicates the reference position of the luminescent surface.

[0069] Furthermore, the transverse magnification is confirmed based on the focal lengths of the condenser lens group and the illumination lens group in the illumination optical path of the wafer inspection equipment: ; in, Indicates the focal length of the illumination lens group. This indicates the focal length of the light-gathering lens group.

[0070] Specifically, please refer to the following: Figure 5 The pupil plane of an objective lens is generally located inside the objective lens. Its position is defined with reference to the positioning plane, and the distance Z between the two is defined as the pupil plane position parameter. The pupil plane size D is related to the objective lens's NA (nearest lens). Taking common objectives as examples, the pupil plane diameter and position at different objective magnifications are shown in Table 1 below: Table 1

[0071] The focal length of the illumination lens group needs to take into account factors such as the space constraints of the entire system, the field of view constraints of the illumination system, and the aperture constraints of the illumination system.

[0072] In one specific embodiment, the focal length of the illumination lens group can be selected within a range of 150~250mm. For example, when the focal length of the illumination lens group is selected as 200mm and the focal length of the light-gathering lens group is selected as 160mm, then: ; That is, the ratio of the objective lens pupil diameter to the spatial filter diameter is 1.25.

[0073] Table 2 below shows the correspondence between the diameters of several common objectives and spatial filters: Table 2

[0074] Specifically, as shown in Table 2 above, five magnifications were selected for the objectives: 1.5X, 2.5X, 5X, 10X, and 20X. Their exit pupil diameters were 16mm, 24mm, 20mm, 18mm, and 11mm, respectively. Based on the ratio of the objective exit pupil diameter to the filter diameter being 1.25, the spatial filter diameters can be calculated to be 12.8mm, 19.2mm, 16mm, 14.4mm, and 8.8mm, respectively. In practical use, the focal lengths of the illumination and condenser lens groups can be adjusted as needed, and different objective lens diameters can be selected. This can be achieved by simply calculating according to the formula above and then changing the diameter of the spatial filter. The spatial filter is conjugate to the exit pupil of the objective lens. Without a spatial filter, to ensure illumination at all magnifications, the diameter of the light spot illuminating the objective lens's exit pupil should be at least 24mm (taking the maximum case of 2.5X), and the diameter of the spatial filter should be 19.2mm. When switching to 20X, the diameter of the illumination spot is larger than the objective lens's exit pupil diameter (24mm > 11mm), resulting in stray light. By using a spatial filter and adjusting its diameter to 8.8mm, the light spot illuminating the objective lens's exit pupil becomes 11mm, which perfectly matches the exit pupil diameter of the 20X objective lens, reducing stray light.

[0075] In this embodiment, the pupil plane position is defined as the distance relative to the objective lens reference plane. Simultaneously, the distance between the emitting surface and the reference surface can be defined as... When the objective lens is switched from 20X magnification to 10X magnification, the change in pupil position is: At this point, the position of the luminous surface needs to be adjusted by an amount of... It satisfies the definition of axial magnification: .

[0076] Using the position of the 20X objective lens as a reference, we have: Table 3

[0077] The sign of the numerical value indicates the direction of adjustment relative to the reference plane. Therefore, in order to achieve magnification matching between the spatial filter, the emitting surface, and the objective lens, it is necessary to change the aperture diameter of the spatial filter and the position of the emitting surface; when switching the objective lens magnification, it is also necessary to switch the aperture and position of the spatial filter simultaneously.

[0078] Step S3: Adjust the position of the light-emitting surface using the light-emitting surface adjustment component.

[0079] Specifically, after receiving the instruction, the light-emitting surface adjustment component drives the corresponding motor to perform the adjustment action.

[0080] Furthermore, in some embodiments, when the calibration data also includes the aperture size of the space filter corresponding to different magnification objectives, the illumination adjustment method of the illumination device further includes: adjusting the aperture of the space filter using a filter adjustment component.

[0081] Specifically, after receiving the command, the filter adjustment component drives the corresponding motor to perform the adjustment action.

[0082] The illumination adjustment method for wafer inspection equipment in this embodiment enables the illumination device to quickly and automatically complete the matching adjustment of the illumination optical path after objective lens switching through the above steps, ensuring uniform and efficient illumination at any magnification, thus laying the foundation for high-precision defect detection.

[0083] The present invention also provides a wafer inspection device, which includes an illumination optical path, an imaging optical path, and a processor.

[0084] The lighting path uses the lighting device mentioned in the above embodiments, see details. Figure 1-3 Of course, the illumination light emitted from the objective lens in the illumination device is used to form signal light on the wafer surface through reflection or scattering.

[0085] The imaging optical path is used to receive signal light to form an image; for example... Figure 1 In this setup, the illumination path and imaging path are coaxially aligned, sharing a single objective lens and some optical components. Of course, the imaging path and illumination path can also be non-coaxial. For example, the illumination path can be tilted and the beam cannot be perpendicular to the wafer surface, while the imaging path can be symmetrically aligned along the wafer surface normal to create a bright-field imaging mode, or asymmetrically aligned to create a dark-field imaging mode.

[0086] The processor is used to perform feature detection on images acquired by the imaging optical path to obtain defect information, or to perform feature measurement to obtain structural information. It can be understood that the processor processes images using conventional image processing methods, such as using existing defect detection algorithms to perform feature detection, obtaining defect information such as stains, foreign objects, scratches, and defects through image feature recognition and analysis; or using existing structural measurement algorithms to perform feature measurement, measuring structural features of the image through methods such as triangulation and interferometry to obtain information such as the height, width, and length of the structural features.

[0087] The above are merely embodiments of this application and do not limit the scope of this patent application. Any equivalent structural or procedural changes made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A lighting device, characterized in that, It includes: Lighting source, including the light-emitting surface that directs the illumination light to the outside; Objective lens group, which includes multiple objectives with different magnifications that can be switched between each other; A light-emitting surface adjustment component, connected to the lighting source, is used to adjust the position of the light-emitting surface; The controller has pre-stored calibration data, which includes pupil size information, pupil position information, and position information of the luminescent surface for different magnification objectives. The controller is used to acquire the magnification information of the current working objective and control the luminescent surface adjustment component to adjust the position of the luminescent surface according to the magnification information and the calibration data.

2. The lighting device according to claim 1, characterized in that, It also includes a spatial filter and a filter adjustment component. The spatial filter is disposed on the light-emitting side of the lighting source, and the filter adjustment component is connected to the spatial filter and is used to adjust the aperture size of the spatial filter. The calibration data also includes the aperture size of the space filter corresponding to different magnification objectives. The controller is also used to control the filter adjustment component to adjust the aperture of the space filter according to the magnification information and the calibration data.

3. The lighting device according to claim 2, characterized in that, The light-emitting surface adjustment component includes an electric displacement stage. The light-emitting surface and the spatial filter are fixedly connected by a structural component and are mounted together on the electric displacement stage. The light-emitting surface adjustment component includes a driver that drives the electric displacement stage to move along the optical axis. The filter adjustment component includes a driver that drives the spatial filter to change the light transmission aperture.

4. The lighting device according to claim 1, characterized in that, The lighting source includes an LED light source and an optical fiber optically coupled to the LED light source, wherein the light-emitting surface is the light-emitting end face of the optical fiber.

5. The lighting device according to claim 2, characterized in that, The spatial filter includes an electrically adjustable aperture.

6. The lighting device according to claim 2, characterized in that, The objective lens assembly also includes an objective lens converter and an encoder. The objective lens converter is electrically connected to the controller, and the encoder stores the magnification information of each objective lens. The encoder is used to send the magnification information of the objective lens to the controller after the objective lens converter converts the objective lens.

7. A method for adjusting the lighting of a lighting device, characterized in that, It is applied to the lighting device as described in any one of claims 1-6; The lighting adjustment method includes: The magnification information of the current working objective lens is obtained using the controller; The controller sends an instruction to the light-emitting surface adjustment component to adjust the position of the light-emitting surface based on the magnification information and pre-stored calibration data. The calibration data includes pupil size information, pupil position information, and position information of the light-emitting surface of the illumination source for different magnification objectives. Enable the light-emitting surface adjustment member to adjust the position of the light-emitting surface.

8. The lighting adjustment method according to claim 7, characterized in that, The calibration data also includes the aperture size of the space filter corresponding to different magnification objectives; The lighting adjustment method further includes: The controller sends a command to the filter adjustment component to adjust the aperture of the spatial filter based on the magnification information and pre-stored calibration data. Enable the filter adjustment to adjust the aperture of the spatial filter.

9. The lighting adjustment method according to claim 8, characterized in that, The calibration data is calculated based on the following relationship: The aperture size of the spatial filter and the pupil diameter of the objective lens satisfy the following: ； in, This indicates the transverse magnification confirmed by the illumination optical path of the wafer inspection equipment. This indicates the diameter of the objective lens's pupil plane. This indicates the aperture of the spatial filter.

10. The lighting adjustment method according to claim 9, characterized in that, The change in distance between the objective lens's pupil plane position and the reference pupil plane position, and the adjustment of the luminous surface's position relative to the reference luminous surface position, satisfy the following: ； ； ； ； in, This indicates the axial magnification of the illumination optical path in a wafer inspection device. This indicates the change in distance between the objective lens's pupil plane position and a reference pupil plane position. This indicates the adjustment amount of the position of the luminous surface relative to the reference position of the luminous surface. Indicates the position of the pupil plane of the objective lens. Indicates the reference position of the pupil. Indicates the position of the luminous surface. Indicates the reference position of the luminescent surface.

11. The lighting adjustment method according to claim 9, characterized in that, The transverse magnification is determined based on the focal length of the condenser lens group and the focal length of the illumination lens group in the illumination optical path of the wafer inspection equipment: ； in, Indicates the focal length of the illumination lens group. This indicates the focal length of the light-gathering lens group.

12. The lighting adjustment method according to claim 7, characterized in that, The controller acquires the magnification information of the current working objective lens, including: After switching objectives, the objective converter obtains the magnification information of the currently working objective from the encoder and sends the magnification to the controller.

13. The lighting adjustment method according to claim 8, characterized in that, The steps for pre-stored calibration data include: For each magnification objective lens, an illumination spot image is acquired through the illumination optical path of the wafer inspection equipment; Adjust the aperture size of the spatial filter and the position of the light source according to the sharpness and uniformity of the light spot image; When sharpness and uniformity are at their best, record the current spatial filter aperture size and light source position information, and correlate them with the current objective lens magnification information.

14. A wafer inspection device, characterized in that, Includes illumination optical path, imaging optical path, and processor; The illumination optical path adopts the illumination device according to any one of claims 1-6; the illumination light emitted from the objective lens in the illumination device is used to form signal light on the wafer surface by reflection or scattering; The imaging optical path is used to receive the signal light to form an image; The processor is used to perform feature detection on the image to obtain defect information, or to perform feature measurement to obtain structural information.

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