CN119996830B

CN119996830B - Focus finding method, semiconductor detecting method, detecting apparatus and storage medium

Info

Publication number: CN119996830B
Application number: CN202510461202.4A
Authority: CN
Inventors: 宋博文; 陶陶; 黄有为; 陈鲁
Original assignee: Shenzhen Zhongke Feice Technology Co Ltd
Current assignee: Shenzhen Zhongke Feice Technology Co Ltd
Priority date: 2025-04-14
Filing date: 2025-04-14
Publication date: 2025-07-15
Anticipated expiration: 2045-04-14
Also published as: CN119996830A

Abstract

The application discloses a focus searching method, a semiconductor detection method, detection equipment and a storage medium, and belongs to the technical field of semiconductor detection. The method comprises the steps of controlling the objective table carrying the reference object and the object to be detected to move relative to the objective lens in the vertical direction, so that the reference object carried on the objective table and the objective lens are located at a plurality of different height distances in sequence in the vertical direction, and the objective table is provided with a first carrying area and a second carrying area. And when each height distance is reached, controlling to shoot the reference object on the object stage, and obtaining a reference image of the reference object when each height distance is reached. And determining a target height distance based on reference images of the reference object at a plurality of different height distances, wherein the target height distance is used for determining an initial height distance between the object stage or the object to be measured and the objective lens when the object to be measured is scanned. According to the application, the accuracy of the determined target height distance can be improved by introducing the reference object.

Description

Focus finding method, semiconductor detecting method, detecting apparatus and storage medium

Technical Field

The application relates to the technical field of semiconductor detection, in particular to a focus searching method, a semiconductor detection method, detection equipment and a storage medium.

Background

When detecting the semiconductor, the best object plane position is easily influenced by environmental factors to cause focal plane drift, and if the correction is not performed, the imaging quality may be reduced, and the accuracy and stability of defect detection may be affected. Therefore, in order to ensure that the image quality obtained in the film measurement process is kept in an optimal state, the optimal object distance of the current objective lens imaging needs to be accurately estimated before each film measurement. However, in the dark field detection system, the dark field detection system is often affected by the object space structure in the focusing process, that is, when the dark field detection system images an object with a periodic structure, a series of clear periodic images are formed in the focusing process, so that the judgment of the optimal object distance is interfered. In addition, the patterned wafer surface pattern typically has unpredictable structural undulations that, if focused on an unknown pattern of the patterned wafer as the object plane, can also cause focus to deviate from the optimal imaging object distance.

Disclosure of Invention

Aiming at the problems in the prior art, the application provides a focus searching method, a semiconductor detection method, detection equipment and a storage medium, and the accuracy of the determined target height distance can be improved by introducing a reference object, so that accurate focus searching is performed. The technical scheme is as follows:

in one aspect, a method for focus finding is provided, the method comprising:

Controlling the relative motion of an objective lens and an objective table carrying a reference object and an object to be detected in the vertical direction, so that the reference object carried on the objective table and the objective lens are sequentially located at a plurality of different height distances in the vertical direction, wherein the objective table is provided with a first carrying area and a second carrying area, the first carrying area is used for carrying the object to be detected, and the second carrying area is used for carrying the reference object;

When each height distance is measured, controlling the reference object on the object stage to shoot, and obtaining a reference image of the reference object when each height distance is measured;

and determining a target height distance based on reference images of the reference object at a plurality of different height distances, wherein the target height distance is used for determining an initial height distance between the objective table or the object to be measured and the objective lens when the object to be measured is scanned.

Optionally, after determining the target height distance based on the reference images of the reference object at a plurality of different height distances, the method further comprises:

And controlling the objective table to move to a corresponding height in the vertical direction according to the target height distance, and acquiring the height value of the upper surface of the reference object when the objective table is at the height as a target height value, wherein the target height value is used for indicating the height value of the upper surface of the region to be detected, which corresponds to the object to be detected when the object to be detected is at the initial scanning position.

Optionally, the determining the target height distance based on the reference image of the reference object at a plurality of different height distances comprises:

Determining a plurality of regions of interest in the reference image, determining a region energy set value corresponding to the regions of interest respectively, and determining an image energy set value corresponding to the reference image based on the region energy set values;

And determining the target height distance based on the image energy set values respectively corresponding to the plurality of reference images and the height distances respectively corresponding to the plurality of reference images.

Optionally, the determining, based on the plurality of the region energy concentration values, an image energy concentration value corresponding to the reference image includes:

and taking the average value of the plurality of regional energy set values as the image energy set value corresponding to the reference image.

Optionally, the determining the target height distance based on the image energy set values respectively corresponding to the plurality of reference images and the height distances respectively corresponding to the plurality of reference images includes:

obtaining a reference graph according to the values of the image energy sets and the height distances corresponding to the reference images respectively;

and determining the height distance corresponding to the maximum image energy concentration value in the reference graph as the target height distance.

Optionally, the determining the region energy concentration values corresponding to the plurality of the regions of interest respectively includes:

for each of a plurality of the regions of interest:

determining a central pixel in the attention area, wherein the central pixel is a pixel with the maximum gray value in the attention area;

A first sub-region, a second sub-region and a third sub-region in the concerned region are determined by taking the central pixel as the center, the first sub-region is positioned at the periphery of the central pixel, the second sub-region is positioned at the periphery of the first sub-region, and the third sub-region is other regions, positioned at the periphery of the second sub-region, in the concerned region;

based on the first sub-region, the second sub-region, and the third sub-region, respective region energy set values are determined.

Optionally, the determining the respective region energy concentration value based on the first sub-region, the second sub-region, and the third sub-region includes:

determining an average noise based on pixels in the second sub-region and pixels in the third sub-region;

Determining a plurality of gray pixels in the first sub-region, wherein the plurality of gray pixels comprise a first pixel with the largest gray value in the first sub-region and at least one pixel with gray values sequentially smaller than the gray value of the first pixel;

determining a first energy value based on the plurality of gray scale pixels and the average noise;

determining a second energy value based on pixels in the second sub-region and the average noise;

The regional energy set value is determined based on the first energy value and the second energy value.

Optionally, the determining the first energy value based on the plurality of gray pixels and the average noise comprises:

subtracting the average noise from each gray pixel in the plurality of gray pixels to obtain a plurality of gray pixels from which the average noise is subtracted;

and adding the gray values of the gray pixels with the average noise subtracted, so as to obtain the first energy value.

Optionally, the determining a second energy value based on the pixels in the second sub-region and the average noise comprises:

Subtracting the average noise from each pixel in the second sub-area to obtain a plurality of pixels from which the average noise is subtracted;

And adding the gray values of the pixels with the average noise subtracted to obtain the second energy value.

Optionally, the determining the region energy concentration value based on the first energy value and the second energy value includes:

and determining the ratio of the first energy value to the second energy value as the regional energy set value.

Optionally, the reference is a standard part, the surface of the standard part is provided with a plurality of round pits with the same diameter and the same concave distance, and the round pits are arranged in a rectangular shape, or

The reference object is another object to be measured of a different type from the object to be measured located in the first bearing area.

Optionally, the bottom surfaces of the first and second carrying areas are at the same level.

In another aspect, a method of focus finding is provided, the method comprising:

Controlling the object stage carrying the reference object to move relatively to the objective lens in the vertical direction, so that the reference object carried on the object stage and the objective lens are sequentially positioned at a plurality of different height distances in the vertical direction;

controlling to shoot the reference object on the object stage when each height distance is reached, and obtaining a reference image of the reference object when each height distance is reached;

And determining a target height distance based on reference images of the reference object at a plurality of different height distances, wherein the target height distance is used for determining an initial height distance between the object stage or the object to be detected and the objective lens when the object to be detected is scanned when the object to be detected is carried on the object stage.

Optionally, the objective table is provided with a first bearing area, the first bearing area is used for bearing an object to be measured, and the reference object is the object to be measured.

In another aspect, a method for detecting a semiconductor is provided, the method comprising:

controlling the relative motion of an objective table carrying an object to be detected and an objective lens along a scanning direction to sequentially reach a plurality of scanning positions, wherein the object to be detected is a semiconductor sample, and controlling the relative motion of the objective table and the objective lens along a vertical direction according to a target height distance so that the upper surface of a region to be detected corresponding to the object to be detected in an initial scanning position is at a desired height, wherein the target height distance is determined based on the focus finding method;

In the scanning process, taking the upper surface of the region to be detected corresponding to the object to be detected at the initial scanning position at a desired height as focus following zero control to carry out full-follow focusing on the object to be detected, and after each scanning position carries out automatic focusing, controlling imaging on the object to be detected to obtain an image to be detected of the region to be detected corresponding to the current scanning position of the object to be detected;

and detecting the region to be detected based on the image to be detected.

In another aspect, there is provided a detection apparatus comprising:

the object stage is provided with a first bearing area, and the first bearing area is used for bearing an object to be detected;

the imaging light path component is used for carrying out optical imaging on the object to be detected and the reference object on the object stage through the objective lens, transmitting optical signals obtained by imaging to the detection sensor, and converting the optical signals into electric signals by the detection sensor so as to obtain a detection image of the object to be detected and/or a reference image of the reference object;

the driving assembly is used for driving the objective table and the objective lens to move relatively;

a processor configured to perform a method as described in any of the embodiments herein.

In another aspect, a computer readable storage medium is provided, in which a computer program is stored, which when executed by a processor, implements the steps of the above-described focus finding method or semiconductor detection method.

In another aspect, a computer program product is provided comprising instructions which, when run on a computer, cause the computer to perform the steps of the above-described focus finding method or semiconductor inspection method.

The technical scheme provided by the application has at least the following beneficial effects:

By introducing a reference object, wherein the reference object is positioned in a second bearing area of the objective table, and by controlling the objective table to move relative to the objective lens in the vertical direction and controlling the reference object on the objective table to shoot at each height distance, a plurality of reference images can be obtained, and then, the target height distance is determined according to the reference images of the reference object at a plurality of different height distances. The reference object is used for focusing, so that the situation that fixed graph characteristics are difficult to find as objects of focusing imaging due to different graph types corresponding to various areas of the object to be measured can be avoided, the accuracy of focusing can be improved, the imaging quality of the object to be measured can be improved in the subsequent process, the detection accuracy of the object to be measured can be improved, and the situation that errors are generated due to graph structure fluctuation and Talbot effect of the object to be measured when the object to be measured is directly focused can be avoided.

In addition, a reference graph is determined according to the values of the image energy sets and the height distances corresponding to the reference images, so that the target height distance can be directly determined from the reference graph in the subsequent process. Moreover, the average value of the plurality of regional energy concentration values is used as the image energy concentration value corresponding to the reference image, so that the accuracy of the determined target height distance can be improved.

Drawings

Fig. 1 is a schematic structural diagram of a detection device according to an embodiment of the present application;

FIG. 2 is a flow chart of a method for searching for focus according to an embodiment of the present application;

FIG. 3 is a schematic diagram of a stage according to an embodiment of the present application;

fig. 4 is a schematic structural diagram of a standard component according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a reference image according to an embodiment of the present application;

FIG. 6 is a schematic diagram of a region of interest according to an embodiment of the present application;

FIG. 7 is a schematic diagram of a reference graph provided in an embodiment of the present application;

FIG. 8 is a flow chart of another method for focus finding according to an embodiment of the present application;

fig. 9 is a flowchart of a method for detecting a semiconductor according to an embodiment of the present application.

Detailed Description

The application will be described in further detail below with reference to the drawings by means of specific embodiments. Wherein like elements in different embodiments are numbered alike in association. In the following embodiments, numerous specific details are set forth in order to provide a better understanding of the present application. However, one skilled in the art will readily recognize that some of the features may be omitted, or replaced by other elements, materials, or methods in different situations. In some instances, related operations of the present application have not been shown or described in the specification in order to avoid obscuring the core portions of the present application, and may be unnecessary to persons skilled in the art from a detailed description of the related operations, which may be presented in the description and general knowledge of one skilled in the art.

Furthermore, the described features, operations, or characteristics of the description may be combined in any suitable manner in various embodiments. Also, various steps or acts in the method descriptions may be interchanged or modified in a manner apparent to those of ordinary skill in the art. Thus, the various orders in the description and drawings are for clarity of description of only certain embodiments, and are not meant to be required orders unless otherwise indicated.

The numbering of the components itself, e.g. "first", "second", etc., is used herein merely to distinguish between the described objects and does not have any sequential or technical meaning. The term "coupled" as used herein includes both direct and indirect coupling (coupling), unless otherwise indicated.

Before explaining the focus searching method, the semiconductor detection method, the detection device and the storage medium in detail, the application scene and the implementation environment of the embodiment of the application are described.

In the detection system, environmental factors (such as temperature change, mechanical vibration, etc.) affect the position of the optimal object plane, and if no correction is performed, the imaging quality may be reduced, thereby affecting the accuracy and stability of detection. In the related art, the auto-focus scheme mainly relies on image contrast analysis to determine the optimal object distance. However, in a dark field imaging system, due to the significant influence of the object space structure, it is difficult to accurately determine the focal plane position, especially when a sample with a periodic structure is coherently imaged, a taber effect may occur, so that a series of clear periodic images may occur, and thus it is difficult to accurately determine the optimal object distance. In addition, the surface pattern of the object to be measured usually has unpredictable structural fluctuation, and focusing directly by using the pattern can cause focal plane deviation, so that imaging definition and defect detection accuracy are affected.

Based on the method, the embodiment of the application introduces the reference object, obtains the height distance of the optimal object distance by imaging the standard object, inputs the height distance as the initial focus following height into the automatic focus following system, realizes the dynamic adjustment in the whole-film scanning process, ensures that the imaging system can accurately and automatically follow, and always keeps the optimal focus plane. The method can effectively reduce the interference of environmental change and sample structure to the focusing process, thereby improving the accuracy and stability of automatic focusing and improving the reliability and consistency of detection results.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a detection apparatus according to an embodiment of the present application, where the detection apparatus includes a stage 1, an imaging optical path assembly 2, a driving assembly 3, and a processor 4, and the imaging optical path assembly 2 includes a detection sensor 21 and an objective lens 22.

The stage 1 has a first carrying region 11, and the first carrying region 11 is used for carrying an object to be measured.

In some embodiments, the stage 1 can move, and the stage 1 can move to drive the carried object to be measured.

In some embodiments, the stage 1 can move along the scanning direction, so as to drive the carried object to be tested to move along the scanning direction, so that the detection device can scan the surface of the whole object to be tested.

In some embodiments, the scan direction may be an X-axis direction, a Y-axis direction, or a planar direction (e.g., a horizontal or horizontal plane direction) defined by the X-axis and the Y-axis.

In some embodiments, the stage 1 can move along the optical axis direction of the objective lens 22, so as to drive the carried object to be tested to move along the optical axis direction of the objective lens 22. For example, the optical axis direction of the objective lens 22 may be a Z-axis direction (e.g., a vertical direction).

Thus, in some embodiments, the stage 1 can move along the Z-axis direction (e.g., the vertical direction), so as to drive the carried object to be tested along the Z-axis direction (e.g., the vertical direction).

In addition, in some embodiments, in order to perform focus searching by the reference object, that is, determine the target height distance by the reference object, please refer to fig. 1, the stage 1 further has a second carrying area 12, where the second carrying area 12 is used for carrying the reference object, so that when the stage 1 moves, the carried reference object can also be driven to move to perform the related steps.

It should be noted that, the object to be detected in the embodiment of the present application may be a semiconductor product such as a wafer, a chip, etc., and because there may be defects on the surface of the object, optical detection is required to be performed on the surface of the object, so as to control the quality of the product.

The imaging light path component 2 is used for carrying out optical imaging on the object to be detected and the reference object on the object stage 1 through the objective lens 22, and transmitting optical signals obtained by imaging to the detection sensor 21, wherein the detection sensor 21 is used for converting the optical signals into electric signals, so that a detection image of the object to be detected and/or a reference image of the reference object can be obtained.

In some embodiments, the detection sensor 21 may be a TDI (TIME DELAYED AND Integration) camera.

It should be noted that the imaging light path component 2 may further include other components besides the detection sensor 21 and the objective lens 22, for example, other optical devices such as a collimating lens, an optical filter, a beam splitter, and the like, which are disposed in the light path between the detection sensor 21 and the objective lens 22, and the imaging light path component 2 may further include a light source, wherein the illumination light emitted from the light source is projected onto the object to be detected carried by the stage 1 after passing through the objective lens 22, and the light reflected and scattered by the surface of the object to be detected is collected by the objective lens 22 and then is incident on the detection sensor 21. The light source may be any one of an LED (LIGHT EMITTING Diode), a xenon lamp, a mercury lamp, a halogen lamp, a laser plasma lamp, a laser-driven white light source lamp, so the illumination light may be white light, colored light, or laser.

The driving component 3 is used for driving the objective table 1 and the objective lens 22 to move relatively, and the driving component 3 can be used for driving the objective table 1 to move and the objective lens 22 to keep static, or the driving component 3 can be used for driving the objective lens 22 to move and the objective table 1 to move.

Illustratively, the driving component 3 drives the objective table 1 and the objective lens 22 to move relatively along the scanning direction, which may be that the driving component 3 drives the objective table 1 to move along the scanning direction while the objective lens 22 remains stationary, or that the driving component 3 drives the objective lens 22 to move along the scanning direction while the objective table 1 remains stationary, or that the driving component 3 drives the objective lens 22 to move while the objective lens 1 moves to realize the relative movement along the scanning direction.

As another example, the driving component 3 drives the objective table 1 and the objective lens 22 to move relatively along the optical axis direction of the objective lens 22, which may be that the driving component 3 drives the objective table 1 to move along the optical axis direction while the objective lens 22 remains stationary, the driving component 3 drives the objective lens 22 to move along the optical axis direction while the objective table 1 remains stationary, or the driving component 3 drives the objective lens 22 to move while the objective lens 1 moves to realize the relative movement along the optical axis direction.

Thus, the driving component 3 drives the objective table1 and the objective lens 22 to move relatively along the Z-axis direction (for example, the vertical direction), the driving component 3 may drive the objective table1 to move along the Z-axis direction (for example, the vertical direction) while the objective lens 22 remains stationary, the driving component 3 may drive the objective lens 22 to move along the Z-axis direction (for example, the vertical direction) while the objective table1 remains stationary, or the driving component 3 may drive the objective table1 to move and drive the objective lens 22 to move relatively along the Z-axis direction (for example, the vertical direction).

In some embodiments, the drive assembly 3 may be implemented based on piezoelectric, servo motor, DD motor, etc. drive components.

The processor 4 includes, but is not limited to, a central processing unit (Central Processing Unit, CPU), a micro control unit (Micro Controller Unit, MCU), a Field-Programmable gate array (Field-Programmable GATE ARRAY, FPGA), and Digital Signal Processing (DSP) or the like, for interpreting computer instructions and processing data in computer software.

In some embodiments, the processor 4 is capable of executing the various computer applications in the non-transitory computer readable storage medium to perform the corresponding steps and methods. For example, the Processor 4 may be implemented by software, hardware, firmware, or a combination thereof, and may use at least one of a Circuit, a single or multiple Application SPECIFIC INTEGRATED Circuit (ASIC), a Digital signal Processor (DIGITAL SIGNAL Processor, DSP), a Digital signal processing device (Digital SignalProcessingDevice, DSPD), a programmable logic device (Programmable Logic Device, PLD), a field programmable gate array (FieldProgrammable GATE ARRAY, FPGA), a Central Processor (Central ProcessingUnit, CPU), a controller, a microcontroller, a microprocessor, or any combination of steps therein, or may perform part of the steps of a focus finding method in various embodiments of the application, or may perform part of the steps of a method of detecting a semiconductor in various embodiments of the application, or may perform all of the steps of the method, or any combination of steps thereof, by the Processor 4.

Next, a detailed explanation will be given of the focus finding method provided by the embodiment of the present application.

Fig. 2 is a flowchart of a focus searching method according to an embodiment of the present application, where the method is applied to a processor in the above-mentioned detection device. Referring to fig. 2, the method includes the following steps:

Step 201, controlling a stage carrying a reference object and an object to be detected to move relative to an objective lens in a vertical direction, so that the reference object and the objective lens carried on the stage are sequentially located at a plurality of different height distances in the vertical direction, wherein the stage is provided with a first carrying area and a second carrying area, the first carrying area is used for carrying the object to be detected, and the second carrying area is used for carrying the reference object.

When the object to be detected is detected, because the pattern types corresponding to the areas of the object to be detected may be different, it is difficult to find the fixed pattern features as the object for focusing imaging, and therefore, a second bearing area for bearing the reference object except the first bearing area for bearing the object to be detected can be added on the objective table to perform the subsequent focusing searching process.

In some embodiments, the stage carrying the reference object and the object to be measured can be controlled to move, the objective lens is kept stationary, the stage is moved horizontally, so that the reference object carried on the stage is located right below the objective lens, and then the stage is controlled to move vertically, so that the reference object carried on the stage and the objective lens are located at a plurality of different height distances in sequence in the vertical direction.

In addition, in some embodiments, the objective may be controlled to move, the stage may be kept stationary, and the objective may be moved in a horizontal direction so that the objective is located directly above the reference object carried on the stage, and then, the objective may be controlled to move in a vertical direction so that the reference object carried on the stage and the objective are sequentially located at a plurality of different height distances in the vertical direction.

In some embodiments, the first carrying area and the second carrying area of the stage are shown in fig. 3, and as can be seen from fig. 3, the first carrying area is used for carrying the object to be measured, the second carrying area is used for carrying the reference object, and the second carrying area is connected with the second carrying area, so that the object to be imaged can be switched between the object to be measured and the reference object without greatly moving the stage or the objective lens.

In some embodiments, the reference may be a standard, where the surface of the standard has a plurality of circular pits with the same diameter and the same recess distance, and the plurality of circular pits are arranged in a rectangular shape, or the reference may be another object to be measured, which is different from the object to be measured in the first bearing area.

As an example, the reference may be a standard as shown in fig. 4, and as can be seen in fig. 4, the plurality of circular pits in the standard are all d in recess distance.

It should be noted that the reference object may be a standard component, or may also be another object to be measured in a different type from the object to be measured in the first bearing area, which is not limited in the embodiment of the present application.

In some embodiments, the bottom surfaces of the first and second carrying areas are at the same level, thereby ensuring that the test object and the reference object are placed on the same level.

And 202, controlling to shoot the reference object on the object stage at each height distance to obtain a reference image of the reference object at each height distance.

That is, each time the object stage and the object lens are controlled to move relatively in the vertical direction, the reference object on the object stage is controlled to be shot at the height distance, and after the shooting at the height distance is completed, the height distance between the reference object and the object lens in the vertical direction can be changed, and then the reference object on the object stage is controlled to be shot. And repeating the steps to obtain the reference image of the reference object at each height distance, namely obtaining a plurality of reference images, wherein the height distances corresponding to each reference image in the plurality of reference images are different.

And 203, determining a target height distance based on the reference images of the reference object at a plurality of different height distances, wherein the target height distance is used for determining the initial height distance between the object stage or the object to be tested and the objective lens when the object to be tested is scanned.

After obtaining a reference image of the reference object at a plurality of different height distances, a target height distance may be determined based on the plurality of reference images.

In some embodiments, the bottom surfaces of the first and second carrying areas of the stage are at the same level, and the upper surface of the object to be measured and the upper surface of the reference object are also at the same level, so that the target height distance determined according to the reference image corresponding to the reference object can be used to determine the initial height distance between the stage and the objective lens when the object to be measured is scanned.

In addition, in some embodiments, the bottom surfaces of the first bearing area and the second bearing area of the stage may not be at the same horizontal plane, or the thickness of the object to be measured is different from the thickness of the reference object, so that the upper surface of the object to be measured and the upper surface of the reference object are not at the same horizontal plane, and therefore, the target height distance determined according to the reference image corresponding to the reference object can be used to determine the initial height distance between the upper surface of the object to be measured and the objective lens when the object to be measured is scanned. That is, the target height distance determined from the plurality of reference images is the height distance between the upper surface of the reference object and the objective lens, and therefore, the initial height distance between the upper surface of the object to be measured and the objective lens is equal to the target height distance.

In some embodiments, for each of the plurality of reference images, a plurality of regions of interest (i.e., ROIs, region of interest) in the reference image may be determined, then region energy set values corresponding to the plurality of regions of interest, respectively, are determined, and image energy set values corresponding to the reference image are determined based on the plurality of region energy set values, then the target height distance is determined based on the image energy set values corresponding to the plurality of reference images, respectively, and the height distances corresponding to the plurality of reference images, respectively.

That is, after the plurality of reference images are acquired, a plurality of corresponding regions of interest are determined for each reference image, and a corresponding region energy set value is determined for each of the plurality of regions of interest, so as to obtain a plurality of region energy set values corresponding to each reference image, and then the image energy set value corresponding to each reference image is determined according to the plurality of region energy set values.

As an example, please refer to fig. 5, fig. 5 is a schematic diagram of a reference image according to an embodiment of the present application. As can be seen from fig. 5, the reference image includes a plurality of regions, from which a total of 9 regions in the dashed box are selected as the regions of interest, and then the region energy set values corresponding to the 9 regions respectively need to be determined, so that the 9 region energy set values can be obtained, and thus the image energy set value corresponding to the reference image can be determined from the 9 region energy set values.

The above description is made with 9 regions of interest selected, or in application, any more or less regions in the reference image may be selected as regions of interest, depending on the case. The embodiment of the present application is not limited thereto.

In some embodiments, a region energy concentration value corresponding to each of the plurality of regions of interest may be determined as follows steps (1) - (3);

(1) A center pixel in the region of interest is determined, the center pixel being the pixel in the region of interest having the greatest gray value.

That is, the pixel having the largest gray value in the region of interest may be determined as the center pixel. For example, referring to fig. 6, fig. 6 is a schematic diagram of a region of interest according to an embodiment of the present application, and the center pixel is a gray area A0 in fig. 6.

(2) And taking the central pixel as a center, determining a first subarea, a second subarea and a third subarea in the attention area, wherein the first subarea is positioned at the periphery of the central pixel, the second subarea is positioned at the periphery of the first subarea, and the third subarea is other areas positioned at the periphery of the second subarea in the attention area.

As an example, please refer to fig. 6, the first sub-region is the white region A1 in fig. 6, the second sub-region is the hatched portion A2 in fig. 6, and the third sub-region is the black region A3 in fig. 6.

It should be noted that the area sizes of the first sub-area, the second sub-area, and the third sub-area in fig. 6 are only exemplary, and the area sizes of the first sub-area, the second sub-area, and the third sub-area may be changed according to circumstances in actual application. The embodiment of the present application is not limited thereto.

(3) Based on the first sub-region, the second sub-region, and the third sub-region, respective region energy set values are determined.

In some embodiments, the respective zone energy concentration values may be determined based on the first, second and third sub-zones as follows steps a-e;

a. an average noise is determined based on the pixels in the second sub-region and the pixels in the third sub-region.

Since the second sub-region and the second sub-region each include a plurality of pixels, it is necessary to calculate a noise value of each of the plurality of pixels. Illustratively, the noise value of each pixel is the difference between that pixel in the noisy image and that pixel in the region of interest, where noisy image refers to an image in which an unexpected random change in pixel value occurs due to various disturbances, such an image typically contains abnormal brightness or color fluctuations that do not originate from the original scene.

It should be noted that the above is described in terms of determining the noise of each pixel from the difference in the noisy image and the region of interest, or in application, the noise of each pixel may be determined in other ways.

After obtaining the noise corresponding to the plurality of pixels in the second sub-region and the third sub-region, the plurality of noises may be averaged, and the obtained average value may be determined as the average noise. Alternatively, the plurality of noises may be standard-shifted or median-shifted to determine the average noise. The embodiment of the present application is not limited thereto.

B. A plurality of gray scale pixels in the first sub-region are determined, wherein the plurality of gray scale pixels comprise a first pixel with the largest gray scale value in the first sub-region and at least one pixel with the gray scale value smaller than the gray scale value of the first pixel in sequence.

That is, a plurality of pixels having the largest gray value in the first sub-region, that is, a first pixel having the largest gray value in the first sub-region and at least one pixel having a gray value sequentially smaller than the gray value of the first pixel, need to be determined. As an example, assuming that there are pixels P1, P2, P3, P4, P5, and P6 in the first sub-region, and that the pixel P1 is the pixel having the largest gray value in the first sub-region, the gray values of the pixels P2, P3, P4, P5, and P6 are sequentially reduced, if 4 gray pixels are required to be selected, the pixels P1, P2, P3, and P4 may be determined as gray pixels.

C. A first energy value is determined based on the plurality of gray scale pixels and the average noise.

In some embodiments, the average noise may be subtracted from each of the plurality of gray pixels to obtain a plurality of gray pixels from which the average noise is subtracted, and then the gray values of the plurality of gray pixels from which the average noise is subtracted are added to obtain the first energy value.

After the plurality of gray pixels and the average noise are determined, the average noise needs to be subtracted from each gray pixel in the plurality of gray pixels, so that noise interference is reduced, and the accuracy of the determined regional energy concentration value is improved. And then determining the gray value of each gray pixel for a plurality of gray pixels subtracted with the average noise to obtain the gray value corresponding to the gray pixels subtracted with the average noise, and then adding the gray values to determine the first energy value.

D. a second energy value is determined based on pixels in the second sub-region and the average noise.

In some embodiments, the average noise may be subtracted from each pixel in the second sub-region to obtain a plurality of pixels from which the average noise is subtracted, and then the gray values of the plurality of pixels from which the average noise is subtracted are added to obtain the second energy value.

After determining the average noise, the average noise may be subtracted from each pixel in the second sub-area to reduce noise interference and improve accuracy of the subsequently determined energy concentration value of the area. And then, for all pixels in the second subarea after the average noise is subtracted, determining the gray value of each pixel to obtain the gray value of each pixel in the second subarea, and then, adding the gray values to determine a second energy value.

E. A region energy set value is determined based on the first energy value and the second energy value.

In some embodiments, after the first energy value and the second energy value are obtained, a ratio of the first energy value and the second energy value may be determined as a regional energy set value.

The above description is described with respect to determining the ratio of the first energy value and the second energy value as the area energy set value, or in application, the area energy set value may be determined by other manners. The embodiment of the present application is not limited thereto.

And (c) for each region of interest, determining a region energy concentration value corresponding to each region of interest according to the steps a-e, and taking an average value of the region energy concentration values as an image energy concentration value corresponding to a corresponding reference image after obtaining a plurality of region energy concentration values.

Continuing with the description above, since the image energy set value of each of the plurality of reference images is an average value of the region energy set values corresponding to the plurality of regions of interest in the reference image, in the subsequent process, the target height distance is determined according to the image energy set values respectively corresponding to the plurality of reference images, so that the accuracy of the determined target height distance can be improved, more accurate focus finding can be performed, and further, the imaging quality when the object to be detected is detected in the subsequent process is provided.

In some embodiments, in order to quickly determine the target height distance and still obtain the target height distance in a subsequent process, a reference graph may be obtained according to the height distances corresponding to the multiple image energy sets and the multiple reference images, and the height distance corresponding to the maximum image energy set value in the reference graph is determined as the target height distance.

Based on the above description, the image energy set value corresponding to each reference image can be determined, and thus, a plurality of image energy set values can be obtained. Moreover, since the plurality of reference images are obtained by photographing the reference object on the object stage under different height distance control, each of the plurality of reference images has a corresponding height distance and an image energy concentration value. Accordingly, the reference graph may be determined according to the image energy concentration value and the height distance to which the plurality of reference images respectively correspond.

After the reference graph is obtained, the imaging quality is highest corresponding to the point with the highest image energy concentration value in the reference graph, and therefore, the height distance corresponding to the point with the highest image energy concentration value can be determined as the target height distance.

As an example, please refer to fig. 7, fig. 7 is a schematic diagram of a reference graph provided in an embodiment of the present application, wherein a horizontal axis of the reference graph is a height distance, and a vertical axis is an image energy set value, and as can be seen from fig. 7, when the height distance is X, the corresponding image energy set value is highest, and the image energy set value is Y, which indicates that the corresponding imaging quality is highest when the height distance is X, so the height distance X can be determined as the target height distance.

In some embodiments, after determining the target height distance based on the reference images of the reference object at a plurality of different height distances, the stage may be further controlled to move to a corresponding height in the vertical direction according to the target height distance, and a height value of the upper surface of the reference object when the stage is at the height is obtained as a target height value, where the target height value is used to indicate a height value of the upper surface of the region to be measured corresponding to the object to be measured when the object to be measured is at the initial scanning position.

That is, there may be a case where the upper surface of the object to be measured is not at the same level as the upper surface of the reference object because the bottom surfaces of the first and second carrying areas of the stage are not at the same level, or because the thickness of the object to be measured is different from the thickness of the reference object, and therefore, after determining the target height, it is also necessary to acquire the height value of the upper surface of the reference object at that height of the stage as the target height value.

Therefore, in the subsequent process, the target height value can be determined as the height value of the upper surface of the to-be-detected area corresponding to the to-be-detected object in the initial scanning position, so that the imaging quality of the to-be-detected object in the to-be-detected area during detection is improved, and the detection precision of the to-be-detected object is further improved.

In addition, in some embodiments, when the depth of field of the imaging system is greater than the range in which the optimal object distance may drift, or when the optimal object distance is insensitive to environmental parameters such as temperature, the focus may not be found, i.e. the focal plane is calibrated, but the object to be detected is directly moved to the nominal object plane for subsequent detection, so that the focus finding process and the reference object introduction are not required, and the process can be simplified.

According to the embodiment of the application, the reference object is introduced and is positioned in the second bearing area of the objective table, the objective table and the objective lens are controlled to move relatively in the vertical direction, the reference object on the objective table is controlled to be shot when each height distance is formed, a plurality of reference images can be obtained, and then the target height distance is determined according to the reference images of the reference object when the reference object is positioned at a plurality of different height distances. The reference object is used for focusing, so that the situation that fixed graph characteristics are difficult to find as objects of focusing imaging due to different graph types corresponding to various areas of the object to be measured can be avoided, the accuracy of focusing can be improved, the imaging quality of the object to be measured can be improved in the subsequent process, the detection accuracy of the object to be measured can be improved, and the situation that errors are generated due to graph structure fluctuation and Talbot effect of the object to be measured when the object to be measured is directly focused can be avoided. In addition, a reference graph is determined according to the values of the image energy sets and the height distances corresponding to the reference images, so that the target height distance can be directly determined from the reference graph in the subsequent process. Moreover, the average value of the plurality of regional energy concentration values is used as the image energy concentration value corresponding to the reference image, so that the accuracy of the determined target height distance can be improved.

Fig. 8 is a flowchart of another focus searching method according to an embodiment of the present application, where the method is applied to the processor in the detection device. Referring to fig. 8, the method includes the steps of:

Step 801, controlling the object stage carrying the reference object to move relative to the objective lens in the vertical direction, so that the reference object carried on the object stage and the objective lens are sequentially positioned at a plurality of different height distances in the vertical direction.

In some embodiments, the stage has a first carrying region for carrying an object to be measured, and the reference object is the object to be measured. That is, the focusing can be directly performed according to the object to be measured, and only the first carrying area is needed to carry the object to be measured, i.e. the object to be measured can be used as the reference object.

Step 802, controlling to shoot the reference object on the object stage at each height distance to obtain a reference image of the reference object at each height distance.

Step 802 is the same as step 202 described above, please refer to the relevant content of step 202, and the description thereof is omitted here.

Step 803, determining a target height distance based on reference images of the reference object at a plurality of different height distances, wherein the target height distance is used for determining an initial height distance between the object stage or the object to be tested and the objective lens when the object to be tested is scanned when the object to be tested is carried on the object stage.

In some embodiments, for each of the plurality of reference images, a plurality of regions of interest in the reference image is determined, then, a region energy set value corresponding to each of the plurality of regions of interest is determined, and based on the plurality of region energy set values, an image energy set value corresponding to the reference image is determined, then, a target height distance is determined based on the image energy set value corresponding to each of the plurality of reference images, and a height distance corresponding to each of the plurality of reference images.

The detailed process of determining the target height distance is described in detail in the above step 203, and will not be described herein, please refer to the above.

According to the embodiment of the application, the object to be detected is used as the reference object, no additional reference object is required to be introduced, the focus searching can be directly carried out based on the object to be detected, the focus searching process can be carried out on different objects to be detected more pertinently, and the accurate target height distance can be determined for different objects to be detected.

Fig. 9 is a flowchart of a method for detecting a semiconductor according to an embodiment of the present application, where the method is applied to a processor in the above-mentioned detecting device. Referring to fig. 9, the method includes the steps of:

and 901, controlling the relative motion of a stage carrying an object to be detected and an objective lens along a scanning direction to sequentially reach a plurality of scanning positions, wherein the object to be detected is a semiconductor sample, and controlling the relative motion of the stage and the objective lens along a vertical direction according to a target height distance so that the upper surface of a region to be detected corresponding to the object to be detected when the object to be detected is at a desired height in an initial scanning position, wherein the target height distance is determined based on any embodiment of the focus finding method.

That is, the target height distance may be determined by the focus searching method in any of the above embodiments, and thus, control may be performed according to the determined target height distance, so that the upper surface of the area to be measured corresponding to the initial scanning position of the object to be measured is at a desired height, that is, at the target height value.

In the scanning process, the upper surface of the region to be detected corresponding to the object to be detected at the initial scanning position is used as focus following zero point control to perform full-follow focusing on the object to be detected, and after each scanning position is subjected to automatic focusing, the object to be detected is controlled to be imaged to obtain an image to be detected of the region to be detected corresponding to the current scanning position of the object to be detected.

In some embodiments, the object to be detected corresponds to different areas to be detected at different scanning positions, and scanning and imaging of the surface of the object to be detected can be completed by imaging the different areas to be detected of the object to be detected at a plurality of different scanning positions.

And 903, detecting the region to be detected based on the image to be detected.

For example, the region to be detected may be subjected to defect detection based on the image to be detected.

It will be appreciated that step 903 may be based on existing or future detection algorithms to detect the corresponding region to be detected based on the image to be detected.

According to the embodiment of the application, the target height distance is determined by the reference image, and the expected height of the upper surface of the region to be detected corresponding to the object to be detected in the initial scanning position is determined according to the target height distance, so that the expected height is used as the focus following zero point control to carry out full-follow focus following on the object to be detected, the dynamic adjustment in the scanning process can be realized, the accurate automatic following can be determined, and the optimal focus plane is always maintained.

Reference is made to various exemplary embodiments herein. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope herein. For example, the various operational steps and components used to perform the operational steps may be implemented in different ways (e.g., one or more steps may be deleted, modified, or combined into other steps) depending on the particular application or taking into account any number of cost functions associated with the operation of the system.

In the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. Additionally, as will be appreciated by one of skill in the art, the principles herein may be reflected in a computer program product on a computer readable storage medium preloaded with computer readable program code. Any tangible, non-transitory computer readable storage medium may be used, including magnetic storage devices (hard disks, floppy disks, etc.), optical storage devices (CD-to-ROM, DVD, blue Ray disks, etc.), flash memory, and/or the like. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create means for implementing the functions specified. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including means which implement the function specified. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified.

While the principles herein have been shown in various embodiments, many modifications of structure, arrangement, proportions, elements, materials, and components, which are particularly adapted to specific environments and operative requirements, may be used without departing from the principles and scope of the present disclosure. The above modifications and other changes or modifications are intended to be included within the scope of this document.

The foregoing detailed description has been described with reference to various embodiments. However, those skilled in the art will recognize that various modifications and changes may be made without departing from the scope of the present disclosure. Accordingly, the present disclosure is to be considered as illustrative and not restrictive in character, and all such modifications are intended to be included within the scope thereof. Also, advantages, other advantages, and solutions to problems have been described above with regard to various embodiments. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, system, article, or apparatus. Furthermore, the term "couple" and any other variants thereof are used herein to refer to physical connections, electrical connections, magnetic connections, optical connections, communication connections, functional connections, and/or any other connection.

Those skilled in the art will recognize that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. Accordingly, the scope of the invention should be determined only by the following claims.

Claims

1. A method of focus finding, the method comprising:

For each of a plurality of reference images, determining a plurality of regions of interest in the reference image, determining a region energy set value corresponding to each of the plurality of regions of interest, determining an image energy set value corresponding to the reference image based on the plurality of region energy set values, obtaining a reference graph according to the image energy set values and the height distances corresponding to each of the plurality of reference images, and determining the height distance corresponding to the largest image energy set value in the reference graph as a target height distance, wherein the target height distance is used for determining an initial height distance between the object stage or the object to be tested and the objective lens when the object to be tested is scanned.

2. The focus finding method according to claim 1, wherein after the height distance corresponding to the maximum image energy concentration value in the reference graph is determined as a target height distance, the method further comprises:

3. The focus finding method according to claim 1, wherein the determining an image energy concentration value corresponding to the reference image based on a plurality of the region energy concentration values includes:

4. The focus finding method according to claim 1, wherein the determining the region energy concentration values corresponding to the plurality of the regions of interest, respectively, includes:

for each of a plurality of the regions of interest:

5. The focus finding method of claim 4, wherein said determining respective zone energy concentration values based on said first, second, and third sub-zones comprises:

6. The focus finding method of claim 5, wherein said determining a first energy value based on said plurality of gray scale pixels and said average noise comprises:

7. The focus finding method according to claim 5 or 6, wherein said determining a second energy value based on pixels in said second sub-area and said average noise comprises:

8. The focus finding method according to claim 7, wherein said determining the area energy concentration value based on the first energy value and the second energy value comprises:

9. The method of claim 1, wherein the reference object is a standard part, the surface of the standard part has a plurality of circular pits with the same diameter and the same recess distance, and the plurality of circular pits are arranged in a rectangular shape, or

10. The focus finding method of claim 1, wherein bottom surfaces of the first bearing region and the second bearing region are at the same level.

11. A method of focus finding, the method comprising:

Determining a plurality of regions of interest in a plurality of reference images, determining a region energy set value corresponding to the regions of interest respectively, determining an image energy set value corresponding to the reference image based on the region energy set values, determining a target height distance based on the image energy set value corresponding to the reference images respectively and a height distance corresponding to the reference images respectively, wherein the target height distance is used for determining an initial height distance between the object stage or the object to be tested and the object lens when the object to be tested is scanned when the object stage is loaded with the object to be tested;

wherein the determining the region energy concentration values corresponding to the plurality of the regions of interest respectively includes:

for each of a plurality of the regions of interest:

The method includes determining an average noise based on pixels in the second sub-region and pixels in the third sub-region, determining a plurality of gray scale pixels in the first sub-region, including a first pixel having a largest gray scale value in the first sub-region and at least one pixel having a gray scale value sequentially smaller than that of the first pixel, determining a first energy value based on the plurality of gray scale pixels and the average noise, determining a second energy value based on the pixels in the second sub-region and the average noise, and determining a median value of the region energy set based on the first energy value and the second energy value.

12. The method of claim 11, wherein the stage has a first carrying region for carrying an object to be measured, and the reference object is the object to be measured.

13. A method of inspecting a semiconductor, the method comprising:

Controlling the relative motion of a stage carrying an object to be detected and an objective lens along a scanning direction to sequentially reach a plurality of scanning positions, wherein the object to be detected is a semiconductor sample, and controlling the relative motion of the stage and the objective lens along a vertical direction according to a target height distance so that the upper surface of a region to be detected corresponding to the object to be detected when the object to be detected is at an initial scanning position is at a desired height, and the target height distance is determined based on the focus finding method according to any one of claims 1 to 12;

and detecting the region to be detected based on the image to be detected.

14. A detection apparatus, characterized by comprising:

the object stage is provided with a first bearing area, wherein the first bearing area is used for bearing an object to be detected, and a second bearing area, and the second bearing area is used for bearing a reference object;

the imaging light path component is used for carrying out optical imaging on the object to be detected and the reference object on the object stage through the objective lens, transmitting optical signals obtained by imaging to the detection sensor, and converting the optical signals into electric signals by the detection sensor so as to obtain a detection image of the object to be detected and a reference image of the reference object;

a processor for performing the method of any one of claims 1 to 13.

15. A computer readable storage medium, characterized in that the medium has stored thereon a computer program executable by a processor to implement the method of any one of claims 1 to 13.