Wafer stress detection device

Abstract

The utility model provides a wafer stress detection device, which includes a support frame, a collimated light source, a polarizer, a sample carrier, a 1 / 4 wave plate, an analyzer, a camera assembly and an image processing assembly arranged on the support frame from bottom to top, wherein the camera assembly includes a camera and a telecentric lens, the telecentricity of the telecentric lens is less than 0.06°, and the distance between the collimated light source and the telecentric lens is 400-800mm. The utility model does not need to rotate the polarizer multiple times to obtain the polarizer rotation angle when the image grayscale value is the smallest. The polarizer 20 is driven to rotate at four angles by a rotating motor 30, and the stress value and stress 3D distribution of the entire shooting area of ​​the wafer to be tested can be measured, which significantly improves the accuracy and reliability of the detection and realizes a high-efficiency and high-precision one-time measurement of the internal stress of the wafer.

Description

Technical Field

[0001] The utility model relates to the technical field of stress detection, in particular to a wafer stress detection device. Background Art

[0002] Wafer internal stress refers to the pressure or tension inside the wafer. During the wafer manufacturing process, due to the effects and influences from various processes and other factors, when these factors disappear, some of the effects and influences remain in the wafer, thus generating internal stress. The existence and distribution of wafer internal stress will seriously affect the performance and stability of the wafer, so its internal stress distribution needs to be accurately detected. However, the existing technology of internal stress detection has a low degree of intelligence and the detection factors are not comprehensive enough, resulting in low detection accuracy.

[0003] For example, Chinese utility model patent 201810324254.7 discloses a multifunctional polarization stress meter, including a light source, a polarizer, a sample station, a wave plate module, an analyzer, and a camera assembly. The analyzer is driven by a motor to rotate so that the polarization axis of the analyzer and the polarizer are set at different angles, so that the image processing component can collect images with different brightness information. Finally, the image processing component calculates the internal stress of the wafer based on the brightness information of the multiple images obtained. Although this method has a certain improvement in efficiency compared to manual operation, it can only perform single-point measurement and cannot measure the stress of the entire sample at one time.

[0004] Therefore, it is necessary to design a wafer stress detection device to solve the above problems. Utility Model Content

[0005] The utility model aims to provide a wafer stress detection device which can measure the stress magnitude of a sample at one time with high efficiency and high precision.

[0006] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a wafer stress detection device, which includes a support frame, a collimated light source, a polarizer, a sample carrier, a 1 / 4 wave plate, an analyzer, a camera assembly and an image processing assembly arranged on the support frame from bottom to top, the camera assembly includes a camera and a telecentric lens, the telecentricity of the telecentric lens is less than 0.06°, and the distance between the collimated light source and the telecentric lens is 400-800mm.

[0007] As a further improved technical solution of the utility model, the illumination diameter of the collimated light source is 250-280 mm. The large diameter illumination range can cover the entire wafer sample, provide uniform illumination, and reduce the measurement error caused by edge effect and uneven illumination.

[0008] As a further improved technical solution of the utility model, the wavelength of the collimated light source is 500-600nm. This wavelength range is close to the yellow-green light region of the visible spectrum, has good penetration and reflectivity to silicon-based materials, is conducive to improving the sensitivity and resolution of detection, and reduces the absorption of light by the material, avoiding overheating problems.

[0009] As a further improved technical solution of the utility model, the object field of the telecentric lens is 300-400 mm, and the working distance is 500-600 mm.

[0010] As a further improved technical solution of the utility model, a rotating motor is also included, and the polarizer is arranged on the supporting frame through the rotating motor. Accurate rotation control can be achieved to adjust the polarization state of the light passing through, so that the device can flexibly respond to different measurement requirements, thereby improving the diversity and accuracy of the measurement.

[0011] As a further improved technical solution of the utility model, the rotation angle of the polarizer is 0°, 45°, 90°, and 135°. When the rotation angle of the polarizer is 0°, the polarization axes of the analyzer and the polarizer are perpendicular to each other. Such an arrangement can effectively reduce background noise, improve the extinction ratio of the system, and thus enhance the signal-to-noise ratio of the measurement signal.

[0012] As a further improved technical solution of the utility model, the fast axis of the 1 / 4 wave plate is 45° with the analyzer, which converts linear polarized light into circular polarized light or vice versa, thereby increasing the system's ability to detect different types of polarized light and facilitating the analysis of stress distribution inside the wafer.

[0013] As a further improved technical solution of the utility model, the camera assembly is also provided with a lifting motor, and the camera assembly moves up and down driven by the lifting motor. The sample carrier is provided with a horizontal motor to drive the sample carrier to move in the horizontal direction.

[0014] As a further improved technical solution of the utility model, the polarizer and the camera assembly are also provided with filters.

[0015] It can be seen from the above technical solutions that the wafer stress detection device of the utility model significantly improves the accuracy and reliability of detection through a carefully designed optical system and a finely adjusted mechanical structure, and realizes a high-efficiency and high-precision one-time measurement of the internal stress of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A wafer stress detection device according to an embodiment of the utility model.

[0017] Figure 2 This is a diagram of a wafer sample in one embodiment of the present invention.

[0018] Figure 3 for Figure 2 3D stress distribution of the wafer sample in . DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Please refer to Figure 1 As shown, the utility model provides a wafer stress detection device, which includes a support frame 90, a collimated light source 10, a polarizer 20, a sample carrier 40, a 1 / 4 wave plate 50, an analyzer 60, a filter 70, a camera component 80, an image processing component and a light shield 100 arranged on the outermost side.

[0021] The collimated light source 10 is used to provide parallel illumination, and its illumination diameter is 250-280 mm. The large diameter illumination range and parallel light can cover the entire wafer sample, provide uniform illumination, and reduce the measurement error caused by edge effect and uneven illumination. The wavelength of the collimated light source 10 is preferably 500-600 nm. This wavelength range is close to the yellow-green light region of the visible spectrum, and has good penetration and reflectivity to silicon-based materials, which is beneficial to improve the sensitivity and resolution of detection, while reducing the material's absorption of light and avoiding overheating problems. More preferably, the wavelength of the collimated light source is 525 nm.

[0022] The polarizer 20 is used to convert the light emitted by the light source 10 into linear polarized light. The polarizer 20 is arranged on the support frame 90 through the rotating motor 30 to generate linear polarized light of different angles. Preferably, the preset rotation angles of the polarizer 20 are 0°, 45°, 90°, and 135°.

[0023] The sample carrier 40 is located above the polarizer 20 and is used to carry the sample to be tested. A horizontal motor is provided between the sample carrier 40 and the support frame 90 to drive the sample carrier 40 to move in the horizontal direction, so as to facilitate accurate adjustment of the sample position.

[0024] The analyzer 50 is used to detect the polarization state of light. In this embodiment, when the rotation angle of the polarizer 20 is 0°, the polarization axes of the analyzer 50 and the polarizer 20 are perpendicular to each other. This arrangement can effectively reduce background noise, improve the extinction ratio of the system, and thus enhance the signal-to-noise ratio of the measurement signal. The fast axis of the 1 / 4 wave plate 60 is 45° to the analyzer, and the 1 / 4 wave plate 60 cooperates with the analyzer 50 to convert linear polarized light into elliptically polarized light.

[0025] The camera assembly 80 includes a camera 81 and a telecentric lens 82. The telecentricity of the telecentric lens is less than 0.06°, and the distance between the collimated light source and the telecentric lens is 400-800 mm. The object field of the telecentric lens 82 is 300-400 mm, and the working distance is 500-600 mm. A lifting motor is also provided between the camera assembly 80 and the support frame 90. The camera assembly 80 moves up and down along the support frame driven by the lifting motor to adjust the distance between the camera assembly and the sample.

[0026] When measuring the internal stress of the wafer, the operator first performs a baseline measurement before placing the sample. Through the test software operation, the motor controls the polarizer to rotate 0°, 45°, 90°, and 135°, and shoots the background image of the corresponding rotation angle. Then the sample to be tested is placed on the sample carrier 40. During the entire measurement process, the light shield 100 needs to be pulled down to avoid the influence of ambient light on the test results. The light emitted by the light source 10 becomes elliptically polarized light after passing through the polarizer 20, the sample to be tested, and the 1 / 4 wave plate 50. Due to the stress inside the wafer, the polarized light is decomposed into two beams of polarized light with an optical path difference and polarization directions perpendicular to each other after passing through the wafer. After passing through the analyzer 60, the transmitted light intensity image in the direction of the transmission axis is obtained. The camera component above the analyzer 60 transmits the captured image to the image processing component, and the image processing component calculates the internal stress of the wafer based on the captured image brightness information. When the polarizer is rotated at an angle of 0°, the polarization axes of the analyzer 60 and the polarizer 20 are perpendicular to each other, and the camera assembly 80 captures the image at this time, and then transmits the captured image to the image processing assembly, which collects the brightness information of the captured image. After the collection is completed, a corresponding instruction is issued to start the motor 30, and the motor 30 drives the polarizer 20 to rotate according to the preset 45°. When the polarizer 20 rotates to the predetermined position, the motor 30 stops working, and the polarizer 20 stops rotating. The camera assembly 80 captures the image at this time and transmits the captured image to the image processing assembly, which collects the received image brightness information. After the collection is completed, the polarizer driving motor is controlled to start, and this is repeated. The motor drives the analyzer to rotate by 0°, 45°, 90°, and 135° in sequence. After the image processing assembly completes the collection of the image brightness information at the four angles, the internal stress of the wafer to be tested is calculated according to the embedded data processing software.

[0027] like Figure 2 As shown, the sample under test is the R5 calibration piece. After being tested by the wafer internal stress detection device of this embodiment, the result is as follows Figure 3As shown, the maximum optical path difference measured by the calibration piece is 120.1nm, and the theoretical optical path difference is 120.7nm, so the measurement accuracy is better than 1nm. The utility model does not need to rotate the polarizer multiple times to obtain the polarizer rotation angle when the image gray value is the smallest. The utility model only drives the polarizer 20 to rotate at four angles by the rotating motor 30, and can measure the stress value and stress 3D distribution of the entire shooting area of ​​the wafer to be measured, thereby expanding the measurement range and solving the technical problems of low measurement efficiency and large measurement error in single-point measurement in the prior art.

[0028] Terms such as "upper" and "lower" used herein to indicate spatial relative positions are used for the purpose of convenience to describe the relationship of one feature relative to another feature as shown in the drawings. It is understood that, depending on the placement of the product, the terms of spatial relative positions may be intended to include different orientations other than those shown in the drawings, and should not be construed as limitations on the claims.

[0029] In addition, the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. The understanding of this specification should be based on the technical personnel in the relevant technical field. Although this specification has described the present invention in detail with reference to the above embodiments, ordinary technical personnel in the field should understand that the technical personnel in the relevant technical field can still modify or make equivalent substitutions to the present invention, and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A wafer stress detection device, characterized in that: The invention comprises a support frame, a collimated light source, a polarizer, a sample carrier, a quarter wave plate, an analyzer, a camera assembly and an image processing assembly which are arranged on the support frame in order from bottom to top. The camera assembly comprises a camera and a telecentric lens. The telecentricity of the telecentric lens is less than 0.06°. The distance between the collimated light source and the telecentric lens is 400-800mm.

2. The wafer stress detection device according to claim 1, characterized in that: The illumination diameter of the collimated light source is 250-280 mm.

3. The wafer stress detection device according to claim 1, wherein: The wavelength of the collimated light source is 500-600nm.

4. The wafer stress detection device according to claim 1, wherein: The object field of the telecentric lens is 300-400 mm, and the working distance is 500-600 mm.

5. The wafer stress detection device according to claim 1, wherein: It also includes a rotating motor, and the polarizer is arranged on the supporting frame through the rotating motor.

6. The wafer stress detection device according to claim 1, wherein: The rotation angle of the polarizer is 0°, 45°, 90°, and 135°. When the rotation angle of the polarizer is 0°, the polarization axes of the analyzer and the polarizer are perpendicular to each other.

7. The wafer stress detection device according to claim 1, characterized in that: The fast axis of the 1 / 4 wave plate is at 45° with respect to the polarizer.

8. The wafer stress detection device according to claim 1, wherein: The camera assembly is also provided with a lifting motor, and the camera assembly moves up and down driven by the lifting motor. The sample carrier is provided with a horizontal motor to drive the sample carrier to move in the horizontal direction.

9. The wafer stress detection device according to claim 1, characterized in that: The polarizer and the camera assembly are also provided with filters.

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