Automatic focusing module and device for semiconductor detection and automatic focusing method

Abstract

The invention discloses an automatic focusing module and device for semiconductor detection and an automatic focusing method, and relates to the technical field of semiconductor detection. The automatic focusing module comprises a laser transmitter, an optical shaping element, a processor, an image sensor and a stepping motor, the processor is connected with the output end of the image sensor and the input end of the stepping motor, and the output end of the stepping motor is connected with a microscope; the processor can receive a current laser line image collected by the image sensor, the current laser line image is formed by thin-strip-shaped laser lines reflected by the surface of the wafer to be detected, and current defocusing data of the microscope are determined according to a difference comparison result of the current laser line image and the pre-calibrated laser line image. The pre-calibrated laser line image is an image when the microscope is in a focusing state, and controlling the stepping motor to move the microscope to the focusing plane according to the current defocusing data, thereby ensuring that the focal plane of the microscope is always accurately aligned with the surface of the wafer to be measured, and the imaging is clear.

Description

Technical Field

[0001] The present application relates to the field of semiconductor detection technology, and in particular to an autofocus module, device and autofocus method for semiconductor detection. Background Art

[0002] During the semiconductor defect detection process, the surface of the wafer will be warped due to its own stress, and the warping height can reach several hundred microns. The depth of field of the high-magnification microscope used to observe the wafer is extremely shallow, often only a few microns. In this case, the focal plane of the microscope will not be able to cover the warped area of ​​the wafer, which will lead to misjudgment or omission of defects, seriously affecting the accuracy and reliability of the detection results. Summary of the invention

[0003] In view of the above-mentioned defects or deficiencies in the related art, it is desired to provide an autofocus module, device and autofocus method for semiconductor detection, which can ensure that the focal plane of the microscope is always accurately aligned with the wafer surface during the defect detection process to achieve clear imaging.

[0004] In a first aspect, the present application provides an autofocus module for semiconductor detection, the autofocus module comprising a laser emitter, an optical shaping element, a processor, an image sensor and a stepper motor, the processor being respectively connected to an output end of the image sensor and an input end of the stepper motor, and the output end of the stepper motor being connected to a microscope;

[0005] The processor is configured to receive a current laser line image captured by the image sensor, wherein the current laser line image is formed by a thin strip laser line reflected from the surface of the wafer to be tested, and the thin strip laser line reflected from the surface of the wafer to be tested is shaped by the optical shaping element for shaping the point laser emitted by the laser emitter, and then irradiated on the surface of the wafer to be tested through the microscope and returned to the input end of the image sensor;

[0006] Determine current defocus data of the microscope based on a difference comparison result between the current laser line image and a pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image of the microscope when the microscope is in a focused state; and, based on the current defocus data, control the stepper motor to move the microscope to a focused plane.

[0007] Optionally, in some embodiments of the present application, the processor is specifically used to filter the current laser line image and extract the first center of mass point of the current laser line image in the horizontal direction; using the second center of mass point of the pre-calibrated laser line image in the horizontal direction as a reference, calculate the offset direction and offset distance of the first center of mass point relative to the second center of mass point, and use the offset direction and offset distance as the current defocus data.

[0008] Optionally, in some embodiments of the present application, the processor is further specifically configured to send a pulse width modulation wave corresponding to the offset direction and offset distance to the stepper motor.

[0009] Optionally, the processor in some embodiments of the present application is a field programmable gate array processor.

[0010] Optionally, in some embodiments of the present application, the optical shaping element includes a slit, a collimating lens and a beam splitter distributed in sequence along the direction of the output light of the laser emitter.

[0011] Optionally, in some embodiments of the present application, the image sensor is a complementary metal oxide semiconductor image sensor, and the maximum acquisition frequency of the complementary metal oxide semiconductor image sensor is 5000fps.

[0012] In a second aspect, the present application provides a semiconductor inspection device, comprising a microscope and the autofocus module described in any one of the first aspects.

[0013] Optionally, in some embodiments of the present application, the microscope includes a tube lens, an objective lens and a camera, the first end of the tube lens is connected to the objective lens, the second end of the tube lens is connected to the camera, the first end of the tube lens is relatively distributed to the second end of the tube lens, and the third end of the tube lens is connected to the autofocus module.

[0014] In a third aspect, the present application provides an auto-focusing method, the auto-focusing method is used for the semiconductor detection device described in any one of the second aspects, the auto-focusing method comprising:

[0015] Receive a current laser line image captured by the image sensor, wherein the current laser line image is formed by a thin strip laser line reflected from the surface of the wafer to be tested, wherein the thin strip laser line reflected from the surface of the wafer to be tested is shaped by the optical shaping element for shaping the point laser emitted by the laser emitter, and then irradiated on the surface of the wafer to be tested through the microscope and returned to the input end of the image sensor;

[0016] Determining current defocus data of the microscope according to a difference comparison result between the current laser line image and a pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image when the microscope is in a focused state;

[0017] According to the current defocus data, the stepper motor is controlled to move the microscope to a focus plane.

[0018] Optionally, in some embodiments of the present application, determining the current defocus data of the microscope according to the comparison result of the difference between the current laser line image and the pre-calibrated laser line image includes:

[0019] Filtering the current laser line image, and extracting a first centroid point of the current laser line image in the horizontal direction;

[0020] Taking the second centroid point of the pre-calibrated laser line image in the horizontal direction as a reference, calculate the offset direction and offset distance of the first centroid point relative to the second centroid point, and use the offset direction and offset distance as the current defocus data.

[0021] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0022] The embodiments of the present application provide an autofocus module, device and autofocus method for semiconductor detection. After the point laser emitted by the laser transmitter is shaped by an optical shaping element, it is irradiated on the surface of a wafer to be tested through a microscope. The thin strip laser lines reflected by the surface of the wafer to be tested are collected by an image sensor and a current laser line image is obtained. The current defocus data of the microscope is determined by comparing the difference between the current laser line image and the pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image when the microscope is in a focused state. Based on the current defocus data, the stepper motor can be controlled to move the microscope to the focusing plane, thereby ensuring that the focal plane of the microscope is always accurately aligned with the surface of the wafer to be tested during defect detection, and the imaging is clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of an auto-focus module structure provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of an incident light path on a surface of a wafer to be tested provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of a reflection light path on the surface of a wafer to be tested provided in an embodiment of the present application;

[0027] Figure 4 A schematic diagram of a defocus state provided in an embodiment of the present application;

[0028] Figure 5 A structural block diagram of a semiconductor testing device provided in an embodiment of the present application;

[0029] Figure 6 A schematic diagram of an auto-focusing method flow chart provided in an embodiment of the present application.

[0030] Reference numerals:

[0031] 1-autofocus module, 11-laser emitter, 12-optical shaping element, 13-processor, 14-image sensor, 15-stepping motor, 2-microscope, 21-tube lens, 22-objective lens, 23-camera, 3-semiconductor testing equipment. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Figures 1 to 6 The autofocus module, device and autofocus method for semiconductor detection provided by the embodiments of the present application are described in detail.

[0035] Please refer to Figure 1 , which is a schematic diagram of the structure of an autofocus module provided in an embodiment of the present application, the autofocus module 1 comprises a laser emitter 11, an optical shaping element 12, a processor 13, an image sensor 14 and a stepper motor 15, wherein the processor 13 is respectively connected to the output end of the image sensor 14 and the input end of the stepper motor 15, and the output end of the stepper motor 15 is connected to the microscope 2. In actual use, if Figure 2 and Figure 3 As shown, Figure 2 is a schematic diagram of the incident light path on the surface of the wafer to be tested. Figure 3Schematic diagram of the reflected light path of the surface of the wafer to be tested, so that the processor 13 can receive the current laser line image collected by the image sensor 14, and the current laser line image is formed by the thin strip laser line reflected by the surface of the wafer to be tested, and the thin strip laser line reflected by the surface of the wafer to be tested uses the optical shaping element 12 to shape the point laser emitted by the laser emitter 11 to obtain a 3mm×20um fine line spot, which is irradiated on the surface of the wafer to be tested through the microscope 2 and returned to the input end of the image sensor 14. For example, the optical shaping element 12 includes but is not limited to slits, collimating lenses and spectroscopes distributed in sequence along the direction of the emitted light of the laser emitter 11. For another example, the image sensor 14 is a complementary metal oxide semiconductor (CMOS) image sensor, and the maximum acquisition frequency of the complementary metal oxide semiconductor image sensor is 5000fps, which can achieve high-precision real-time focus tracking, and the wafer to be tested can be a non-patterned wafer or a patterned wafer, and can also be replaced by a panel. Furthermore, the processor 13 can determine the current defocus data of the microscope 2 based on the difference comparison result between the current laser line image and the pre-calibrated laser line image, where the pre-calibrated laser line image is the image when the microscope 2 is in a focused state, and based on the current defocus data, control the stepper motor 15 to move the microscope 2 to the focusing plane, thereby ensuring that the focal plane of the microscope 2 is always precisely aligned with the surface of the wafer to be tested during the defect detection process.

[0036] In some embodiments of the present application, the processor 13 can specifically filter the current laser line image, extract the first centroid point of the current laser line image in the horizontal direction, and then use the second centroid point of the pre-calibrated laser line image in the horizontal direction as a reference to calculate the offset direction and offset distance of the first centroid point relative to the second centroid point, and use the offset direction and offset distance as the current defocus data, for example Figure 4 As shown in the defocus state schematic diagram, during calibration, the stepper motor 15 can be manually adjusted to move a certain distance in the near defocus direction or the far defocus direction, so as to observe the offset change of the centroid point in the horizontal direction of the two laser line images, and establish a mapping relationship between the offset direction and the offset distance and the defocus data, and the defocus data can be the moving distance of the stepper motor 15. Further, the processor 13 can be a field programmable gate array (Field Programmable Gate Array, FPGA) processor, which can send a pulse width modulation (Pulse Width Modulation, PWM) wave corresponding to the offset direction and the offset distance to the stepper motor 15 to realize motor control.

[0037] As another aspect, the present application embodiment provides a semiconductor testing device. Figure 5, which is a structural block diagram of a semiconductor detection device provided in an embodiment of the present application, the semiconductor detection device 3 includes a microscope 2 and Figures 1 to 4 The autofocus module 1 of the corresponding embodiment.

[0038] In some embodiments of the present application, Figure 1 As shown in the example, the microscope 2 includes but is not limited to a tube lens 21, an objective lens 22 and a camera 23, wherein the camera 23 is used to image the wafer to be tested, wherein the first end of the tube lens 21 is connected to the objective lens 22, the second end of the tube lens 21 is connected to the camera 23, the first end of the tube lens 21 is relatively distributed with the second end of the tube lens 21, and the third end of the tube lens 21 is connected to the autofocus module 1, that is, the point laser emitted by the laser emitter 11 in the autofocus module 1 is shaped by the optical shaping element 12 and can be irradiated on the surface of the wafer to be tested through the tube lens 21 and the objective lens 22, and the stepper motor 15 and the laser emitter 11 can be located on the same side of the tube lens 21, or can be located on both sides of the tube lens 21 respectively.

[0039] The autofocus module and device for semiconductor detection provided in the embodiments of the present application use an optical shaping element to shape the point laser emitted by a laser transmitter, and then irradiate it on the surface of a wafer to be tested through a microscope. The thin strip laser lines reflected by the surface of the wafer to be tested are collected by an image sensor and a current laser line image is obtained. The current defocus data of the microscope is further determined by comparing the difference between the current laser line image and the pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image of the microscope when it is in a focused state. Based on the current defocus data, the stepper motor can be controlled to move the microscope to the focusing plane, thereby ensuring that the focal plane of the microscope is always accurately aligned with the surface of the wafer to be tested during defect detection, and the imaging is clear.

[0040] Based on the above embodiments, the present invention provides an automatic focusing method, which can be used for Figure 5 The semiconductor testing device 3 of the corresponding embodiment. Please refer to Figure 6 , which is a flow chart of an automatic focusing method provided in an embodiment of the present application, the automatic focusing method specifically comprises the following steps:

[0041] S101, receiving the current laser line image captured by the image sensor, the current laser line image is formed by the thin strip laser line reflected by the surface of the wafer to be tested, the thin strip laser line reflected by the surface of the wafer to be tested is shaped by the optical shaping element for the point laser emitted by the laser transmitter, and then irradiated on the surface of the wafer to be tested through a microscope and returned to the input end of the image sensor.

[0042] S102, determining current defocus data of the microscope according to a difference comparison result between the current laser line image and a pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image when the microscope is in a focused state.

[0043] Exemplarily, an embodiment of the present application can filter the current laser line image and extract the first center of mass point of the current laser line image in the horizontal direction, and then use the second center of mass point of the pre-calibrated laser line image in the horizontal direction as a reference to calculate the offset direction and offset distance of the first center of mass point relative to the second center of mass point, and use the offset direction and offset distance as the current defocus data.

[0044] S103, according to the current defocus data, controlling the stepper motor to move the microscope to the focus plane.

[0045] It should be noted that, for the description of the same steps and the same contents in this embodiment as those in other embodiments, reference can be made to the description in other embodiments and will not be repeated here.

[0046] The automatic focusing method for semiconductor detection provided in the embodiment of the present application uses an optical shaping element to shape the point laser emitted by a laser transmitter, and then irradiates it on the surface of a wafer to be tested through a microscope. The thin strip laser lines reflected by the surface of the wafer to be tested are collected by an image sensor and a current laser line image is obtained. The current defocus data of the microscope is further determined by comparing the difference between the current laser line image and the pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image of the microscope when it is in a focused state. Therefore, based on the current defocus data, the stepper motor can be controlled to move the microscope to the focusing plane, thereby ensuring that the focal plane of the microscope is always accurately aligned with the surface of the wafer to be tested during defect detection, and the imaging is clear.

[0047] As another aspect, the present invention provides a computer-readable storage medium for storing program code for executing Figure 6 Any implementation manner of the auto-focus method in the corresponding embodiment.

[0048] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and modules described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0049] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms. The modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment.

[0050] In addition, each functional module in each embodiment of the present application may be integrated into a processing unit, or each module may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of a software functional unit. If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a computer-readable storage medium.

[0051] Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the autofocus method of each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0052] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An autofocus module for semiconductor detection, characterized in that: The autofocus module (1) comprises a laser emitter (11), an optical shaping element (12), a processor (13), an image sensor (14) and a stepping motor (15), wherein the processor (13) is respectively connected to an output end of the image sensor (14) and an input end of the stepping motor (15), and the output end of the stepping motor (15) is connected to a microscope (2); The processor (13) is configured to receive a current laser line image captured by the image sensor (14), wherein the current laser line image is formed by a thin strip of laser line reflected from the surface of the wafer to be tested, wherein the thin strip of laser line reflected from the surface of the wafer to be tested is shaped by the optical shaping element (12) on the point laser emitted by the laser emitter (11), and then irradiated onto the surface of the wafer to be tested through the microscope (2) and returned to the input end of the image sensor (14); Determine current defocus data of the microscope (2) based on a difference comparison result between the current laser line image and a pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image of the microscope (2) when it is in a focused state; and, based on the current defocus data, control the stepper motor (15) to move the microscope (2) to a focused plane.

2. The autofocus module according to claim 1, characterized in that: The processor (13) is specifically used to filter the current laser line image and extract a first centroid point of the current laser line image in the horizontal direction; using a second centroid point of the pre-calibrated laser line image in the horizontal direction as a reference, calculate an offset direction and an offset distance of the first centroid point relative to the second centroid point, and use the offset direction and the offset distance as the current defocus data.

3. The autofocus module according to claim 2, characterized in that: The processor (13) is further specifically configured to send a pulse width modulation wave corresponding to the offset direction and the offset distance to the stepping motor (15).

4. The autofocus module according to any one of claims 1 to 3, characterized in that: The processor (13) is a field programmable gate array processor.

5. The autofocus module according to claim 4, characterized in that: The optical shaping element (12) comprises a slit, a collimating lens and a beam splitter which are sequentially distributed along the direction of the light emitted by the laser emitter (11).

6. The autofocus module according to claim 4, characterized in that: The image sensor (14) is a complementary metal oxide semiconductor image sensor, and the maximum acquisition frequency of the complementary metal oxide semiconductor image sensor is 5000 fps.

7. A semiconductor testing device, characterized in that: The semiconductor detection device (3) comprises a microscope (2) and the autofocus module (1) according to any one of claims 1 to 6.

8. The semiconductor testing device according to claim 7, characterized in that: The microscope (2) comprises a tube lens (21), an objective lens (22) and a camera (23); the first end of the tube lens (21) is connected to the objective lens (22); the second end of the tube lens (21) is connected to the camera (23); the first end of the tube lens (21) and the second end of the tube lens (21) are arranged opposite to each other; and the third end of the tube lens (21) is connected to the autofocus module (1).

9. An automatic focusing method, characterized in that: The auto-focusing method is used for the semiconductor detection device according to any one of claims 7 to 8, and the auto-focusing method comprises: Receive a current laser line image captured by the image sensor, wherein the current laser line image is formed by a thin strip laser line reflected from the surface of the wafer to be tested, wherein the thin strip laser line reflected from the surface of the wafer to be tested is shaped by the optical shaping element for shaping the point laser emitted by the laser emitter, and then irradiated on the surface of the wafer to be tested through the microscope and returned to the input end of the image sensor; Determining current defocus data of the microscope according to a difference comparison result between the current laser line image and a pre-calibrated laser line image, wherein the pre-calibrated laser line image is an image when the microscope is in a focused state; According to the current defocus data, the stepper motor is controlled to move the microscope to a focus plane.

10. The automatic focusing method according to claim 9, characterized in that: The step of determining the current defocus data of the microscope according to a difference comparison result between the current laser line image and a pre-calibrated laser line image comprises: Filtering the current laser line image, and extracting a first centroid point of the current laser line image in the horizontal direction; Taking the second centroid point of the pre-calibrated laser line image in the horizontal direction as a reference, calculate the offset direction and offset distance of the first centroid point relative to the second centroid point, and use the offset direction and offset distance as the current defocus data.

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