A chip overlay measurement device and method based on spatially encoded illumination

Abstract

The present invention discloses a chip overlay measurement device and method based on spatially encoded illumination, including a microscopic imaging unit for reflecting and imaging a chip to be detected to obtain an image, and obtaining an adjustment instruction to adjust the light until a high-precision measurement image is obtained; a computer control unit for obtaining the brightness and darkness information of the image analysis, calculating the error and then outputting or uploading the adjustment instruction; the microscopic imaging unit includes a laser driver, a converging lens, an adjustable aperture, a collimating objective lens, a focusing objective lens, a beam splitter prism I, a beam splitter prism II, a microscopic objective lens, a tube lens and an image sensor. The device of the present invention has a simple structure and is easy to integrate. By dynamically modulating the intensity and irradiation angle of the light through a spatial light modulator, the technical problems of poor image quality and low detection accuracy in the existing chip overlay measurement method caused by uneven illumination light and limited angle are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical detection, and particularly relates to a chip overlay measurement device and method based on spatial encoded illumination. Background Art

[0002] During the chip manufacturing process, real-time performance and defect detection are important steps to ensure the controllability of product quality. The optical overlay alignment at the critical layer directly affects the performance, yield, and reliability of the chip. With the improvement of chip integration, the reduction of line width, and the application of multiple lithography processes, the requirements for controlling overlay errors are becoming increasingly strict. Therefore, overlay error measurement has become one of the key process control steps.

[0003] Overlay error measurement is often carried out through an optical microscopy imaging system. This system will acquire the digital images of the target patterns of two layers of etch masks, and use digital image algorithms to calculate the center positions of each layer, thereby obtaining the value of the overlay error. Specifically, this method involves acquiring the images of the measurement marks of the current layer and the previous layer, and performing image analysis to determine the relative displacement of the two layers of measurement marks. In order to obtain the images of the measurement marks, a bright-field microscope is used, and the center of gravity of the measurement marks is determined by analyzing the gray level of the images, and then the displacement vector is obtained. Therefore, the image quality is crucial for the measurement result of the overlay error. Since the previous layer is covered by thin film layers of various materials, it is necessary to continuously adjust the focal length and the wavelength of the illumination light wave during the detection process to obtain high-contrast images. The inconsistent line width caused by light highlights and measurement occlusions is a common reason for measurement errors. Summary of the Invention

[0004] The purpose of the present invention is to provide a chip overlay measurement device and method based on spatial encoded illumination.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A chip overlay measurement device based on spatial encoded illumination, comprising:

[0006] A microscopic imaging unit, configured to reflect and image the chip to be detected to obtain an image, and acquire an adjustment instruction to perform light adjustment until a high-precision measurement image is obtained;

[0007] A computer control unit, configured to acquire the bright and dark information of the image, calculate the error, and then output or upload the adjustment instruction;

[0008] The microscopic imaging unit includes a laser driver, a converging lens, a variable aperture, a collimating objective lens, a focusing objective lens, a first beam splitting prism, a second beam splitting prism, a microscopic objective lens, a tube lens, and an image sensor. The converging lens, the variable aperture, and the collimating objective lens are coaxially arranged in sequence, and the variable aperture corresponds to the image-side focal plane of the converging lens and the object-side focal plane of the collimating objective lens respectively. The microscopic objective lens and the tube lens are coaxially arranged in sequence. The first beam splitting prism is located on the side of the collimating objective lens away from the variable aperture, and the second beam splitting prism is located between the microscopic objective lens and the tube lens. The first beam splitting prism and the second beam splitting prism are corresponding and parallel to each other. The focusing objective lens is arranged between the first beam splitting prism and the second beam splitting prism, and the image sensor is located on the side of the tube lens away from the second beam splitting prism. The laser driver is used to generate a white light source, and the white light source forms parallel light rays after passing through the converging lens, the variable aperture, the collimating objective lens, and the first beam splitting prism in sequence;

[0009] The microscopic imaging unit further includes a spatial light modulator. The spatial light modulator is located on the side of the first beam splitting prism away from the focusing objective lens. After obtaining an adjustment instruction through the spatial light modulator and adjusting the parallel light rays, the parallel light rays pass through the focusing objective lens, the second beam splitting prism, and the microscopic objective lens in sequence and finally converge on the chip to be detected and form an image on the image sensor.

[0010] Further, the converging lens is composed of multiple coaxial lenses and is used to converge the light rays generated by the white light source at the variable aperture.

[0011] Further, the spectral range of the white light source generated by the laser driver is 170nm - 2100nm.

[0012] Further, the beam splitting ratios of the first beam splitting prism and the second beam splitting prism are 50:50, and both the first beam splitting prism and the second beam splitting prism are depolarization beam splitting prisms.

[0013] Further, the pixel size of the spatial light modulator is 1920×1200.

[0014] Further, the microscopic objective lens is a semi-apochromatic microscopic objective lens.

[0015] A method for overlay measurement of a chip overlay measurement device based on spatial encoding illumination includes the following steps:

[0016] Place the chip to be detected under the microscopic objective lens;

[0017] Reflect and image the chip to be detected through the microscopic imaging unit to obtain an image, obtain the light and dark information of the reflected light rays of the chip to be detected, and upload it;

[0018] The computer control unit analyzes the light and dark information, calculates the error, and outputs or sends an adjustment instruction according to the error;

[0019] The microscopic imaging unit obtains an adjustment instruction and adjusts the light until a high-precision measurement image is obtained.

[0020] Further, the specific method for the microscopic imaging unit to reflect and image the chip to be detected to obtain an image is as follows:

[0021] The white light source generated by the laser driver passes through a converging lens, a variable aperture, a collimating objective lens, and a first beam splitting prism in sequence to form parallel light rays. These parallel light rays pass through a focusing objective lens, a second beam splitting prism, and a microscopic objective lens in sequence and finally converge on the chip to be detected. After the light rays are reflected by the chip to be detected, they pass through the microscopic objective lens, the second beam splitting prism, and a tube lens in sequence and finally form an image on the image sensor.

[0022] Further, the specific method for the computer control unit to analyze the light and dark information, calculate the error, and output or upload the adjustment instruction according to the error is as follows:

[0023] The computer control unit analyzes the light and dark information, calculates the error, and makes a judgment according to the error. If the error is within the range, the measurement accuracy is satisfied and the measurement result is output; if the error is not within the range, the measurement accuracy is not satisfied, and the computer control unit sends an upload adjustment instruction.

[0024] Further, the specific method for the microscopic imaging unit to obtain an adjustment instruction and adjust the light until a high-precision measurement image is obtained is as follows:

[0025] The spatial light modulator obtains an adjustment instruction, controls the propagation direction, phase, and amplitude of the parallel light rays that are uniformly irradiated on the spatial light modulator after passing through the first beam splitting prism, and then the parallel light rays pass through the first beam splitting prism, the focusing objective lens, the second beam splitting prism, and the microscopic objective lens in sequence and finally converge on the chip to be detected. After the light rays are reflected by the chip to be detected, they pass through the microscopic objective lens, the second beam splitting prism, and a tube lens in sequence and finally form an image on the image sensor until a high-precision measurement image is obtained.

[0026] From the above technical solutions, it can be seen that the present invention has the following beneficial effects:

[0027] The device of the present invention has a simple structure and is easy to integrate. By dynamically modulating the intensity and irradiation angle of the light through the spatial light modulator, the technical problems of poor image quality and low detection accuracy of chip overlay detection caused by uneven illumination light and limited angle in the existing chip overlay measurement method are solved.

[0028] The chip overlay measurement method and device of the present invention can quickly achieve uniform illumination of the surface of the chip sample, thereby obtaining more accurate measurement results. It can be widely applied to the fields of optical imaging and detection, and provides a simple and feasible method and device for improving the accuracy of chip overlay measurement results. Description of the Drawings

[0029] Figure 1 Schematic structural diagram of the chip overlay measurement device of the present invention;

[0030] Figure 2 Effect diagram of light shielding on the surface of the chip to be measured of the present invention;

[0031] Figure 3 Flowchart of the chip overlay measurement method based on spatial encoding illumination of the present invention;

[0032] Figure 4 Effect diagram of the ordinary test result without using the method of the present invention;

[0033] Figure 5 Effect diagram of the test result of the present invention.

[0034] In the figure: Microscopic imaging unit 1; Laser driver 1-1, Converging lens 1-2, Adjustable aperture 1-3, Collimating objective 1-4, Focusing objective 1-5, Beam splitter prism 1 1-6, Beam splitter prism 2 1-7, Microscopic objective 1-8, Tube lens 1-9, Image sensor 1-10, Spatial light modulator 1-11, Computer control unit 2, Chip to be measured 3. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Please refer to Figures 1-3 , the present invention provides a chip overlay measurement device based on spatial encoding illumination, including a microscopic imaging unit 1 and a computer control unit 2. The microscopic imaging unit 1 includes a laser driver 1-1, a converging lens 1-2, an adjustable aperture 1-3, a collimating objective 1-4, a focusing objective 1-5, a beam splitter prism 1 1-6, a beam splitter prism 2 1-7, a microscopic objective 1-8, a tube lens 1-9, and an image sensor 1-10. The laser driver 1-1, the converging lens 1-2, the adjustable aperture 1-3, and the collimating objective 1-4 are coaxially arranged in sequence from top to bottom, and the adjustable aperture 1-3 corresponds to the image-side focal plane of the converging lens and the object-side focal plane of the collimating objective respectively;

[0037] The converging lens 1-2 consists of five coaxial lenses and is used to converge the light rays generated by the white light source at the adjustable diaphragm 1-3. The adjustable diaphragm 1-3 is located on the image-side focal plane of the converging lens 1-2. The diameter of the adjustable diaphragm can be adjusted to regulate the light flux during measurement and suppress stray light, further improving the uniformity of the light source. The object-side focal plane of the collimating objective lens 1-4 is located on the adjustable diaphragm 1-3 and is used to adjust the light rays to emerge parallel. The laser driver 1-1 is used to generate a white light source, which is an EQ-99CAL LDLS with a spectral range of 170 nm - 2100 nm. TM The laser-driven white light calibration light source is used to generate a high-brightness and high-stability broadband spectral beam. This white light source sequentially passes through the converging lens 1-2, the adjustable diaphragm 1-3, the collimating objective lens 1-4, and the first beam splitter prism 1-6 to form parallel light rays.

[0038] The microscopic objective lens 1-8 and the tube lens 1-8 are coaxially arranged in sequence. Among them, the microscopic objective lens 1-8 is a semi-apochromatic microscopic objective lens, and the exit pupils of microscopic objective lenses with different magnifications coincide. The first beam splitter prism 1-6 is located at the lower end of the collimating objective lens 1-4. The second beam splitter prism 1-7 is located between the microscopic objective lens and the tube lens, and the first beam splitter prism 1-6 and the second beam splitter prism 1-7 are correspondingly and parallelly arranged. The splitting ratio of the first beam splitter prism 1-6 and the second beam splitter prism 1-7 is 50:50, and both the first beam splitter prism 1-6 and the second beam splitter prism 1-7 are depolarization beam splitter prisms. The focusing objective lens 1-5 is arranged between the first beam splitter prism 1-6 and the second beam splitter prism 1-7, and the image sensor 1-10 is located at the upper end of the tube lens.

[0039] The microscopic imaging unit further includes a spatial light modulator 1-11. The spatial light modulator 1-11 is located on the left side of the first beam splitter prism 1-6. After obtaining the adjustment instruction through the spatial light modulator 1-11 and adjusting the parallel light rays, the parallel light rays sequentially pass through the focusing objective lens, the second beam splitter prism, and the microscopic objective lens and finally converge on the chip to be detected. After the light rays are reflected by the chip to be detected 3, they sequentially pass through the microscopic objective lens, the second beam splitter prism, and the tube lens and finally form an image on the image sensor. The entrance pupil of the tube lens coincides with the pupil of the microscope, making the image plane uniformity better to improve the measurement accuracy of chip overlay. The pixel size of the spatial light modulator 1-11 is 1920×1200, which can precisely control the propagation direction, phase, and amplitude of light, realize light modulation such as irradiation angle and irradiation intensity, and dynamically compensate the system measurement error through light modulation to improve the measurement accuracy of chip overlay.

[0040] The object-side focal plane of the converging lens is located on the spatial light modulator, realizing the conjugate relationship between the spatial light modulator and the chip to be detected; the image-side focal plane of the converging lens is located on the pupil of the microscopic objective lens to form Köhler illumination, ultimately realizing the modifiable illumination of the chip to be detected.

[0041] The image sensor uses the light reflected by the chip under test to obtain an image, collects the brightness information, and feeds it back to the computer processing unit. The computer further intelligently controls the spatial light modulator to modulate the light. After multiple feedback-control cycles, a high-precision measurement image is obtained.

[0042] A method for overlay measurement of a chip overlay measurement device based on spatial encoding illumination includes the following steps:

[0043] Place the chip to be detected under the microscope objective.

[0044] The white light source generated by the laser driver passes through a converging lens, an adjustable aperture, a collimating objective, and a beam splitter prism 1 in sequence to form parallel light. This parallel light passes through a focusing objective, a beam splitter prism 2, and a microscope objective in sequence and finally converges on the chip to be detected. After the light is reflected by the chip to be detected, it passes through the microscope objective, the beam splitter prism 2, and a tube lens in sequence and finally forms an image on the image sensor, obtaining the brightness information of the light reflected by the chip to be detected and uploading it.

[0045] The computer control unit analyzes the brightness information, calculates the error, and makes a judgment based on the error. If the error is within the range, the measurement accuracy is satisfied, and the measurement result is output; if the error is not within the range, the measurement accuracy is not satisfied, and the computer control unit sends an upload adjustment instruction.

[0046] The spatial light modulator obtains the adjustment instruction, controls the propagation direction, phase, and amplitude of the parallel light uniformly irradiated on the spatial light modulator after passing through the beam splitter prism 1. Then the parallel light passes through the beam splitter prism 1, the focusing objective, the beam splitter prism 2, and the microscope objective in sequence and finally converges on the chip to be detected, that is, controls the light intensity and irradiation angle on the surface of the chip under test. After the light is reflected by the chip to be detected, it passes through the microscope objective, the beam splitter prism 2, and a tube lens in sequence and finally forms an image on the image sensor until a high-precision measurement image is obtained.

[0047] Figure 2 It is an effect diagram of light occlusion on the surface of the chip under test. The specific situation is as follows: The light is obliquely incident on the surface of the chip under test. Due to the light being blocked, a shadow is generated on the left side.

[0048] Figure 4 It is the ordinary test result without using the method of the present invention. Figure 5 It is the target measurement result obtained according to the embodiment of the present invention. By comparing the results of the two figures, it shows that the method and device in the present invention can achieve more accurate measurement of the target area.

[0049] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A chip overlay measurement device based on spatial encoded illumination, characterized in that, Including: A microscopic imaging unit (1) for reflecting and imaging a chip to be detected to obtain an image, and obtaining an adjustment instruction to adjust the light until a high-precision measurement image is obtained; A computer control unit (2) for obtaining the bright and dark information of the image analysis, calculating the error and then outputting or uploading the adjustment instruction; The microscopic imaging unit includes a laser driver (1-1), a converging lens (1-2), an adjustable aperture (1-3), a collimating objective lens (1-4), a focusing objective lens (1-5), a first beam splitting prism (1-6), a second beam splitting prism (1-7), a microscopic objective lens (1-8), a tube lens (1-9) and an image sensor (1-10). The converging lens (1-2), the adjustable aperture (1-3) and the collimating objective lens (1-4) are coaxially arranged in sequence, and the adjustable aperture (1-3) corresponds to the image-side focal plane of the converging lens and the object-side focal plane of the collimating objective lens respectively. The microscopic objective lens (1-8) and the tube lens (1-9) are coaxially arranged in sequence. The first beam splitting prism (1-6) is located on the side of the collimating objective lens (1-4) away from the adjustable aperture. The second beam splitting prism (1-7) is located between the microscopic objective lens and the tube lens, and the first beam splitting prism (1-6) and the second beam splitting prism (1-7) are corresponding and parallel to each other. The focusing objective lens (1-5) is arranged between the first beam splitting prism (1-6) and the second beam splitting prism (1-7). The image sensor (1-10) is located on the side of the tube lens away from the second beam splitting prism. The laser driver (1-1) is used to generate a white light source, and the white light source passes through the converging lens (1-2), the adjustable aperture (1-3), the collimating objective lens (1-4) and the first beam splitting prism (1-6) in sequence to form parallel light; The microscopic imaging unit further includes a spatial light modulator (1-11). The spatial light modulator (1-11) is located on the side of the first beam splitting prism (1-6) away from the focusing objective lens. After obtaining the adjustment instruction through the spatial light modulator (1-11) and adjusting the parallel light, the parallel light passes through the focusing objective lens, the second beam splitting prism and the microscopic objective lens in sequence and finally converges on the chip to be detected and is imaged on the image sensor.

2. The chip overlay measurement device based on spatial coding illumination according to claim 1, wherein: The converging lens (1-2) is composed of a plurality of coaxial lenses and is used to converge the light generated by the white light source at the adjustable aperture (1-3).

3. The chip overlay measurement device based on spatially encoded illumination according to claim 1, wherein: The spectral range of the white light source generated by the laser driver (1-1) is 170nm - 2100nm.

4. The chip overlay measurement device based on spatially encoded illumination according to claim 1, wherein: The splitting ratios of the first beam splitting prism (1-6) and the second beam splitting prism (1-7) are 50:50, and both the first beam splitting prism (1-6) and the second beam splitting prism (1-7) are depolarization-free beam splitting prisms.

5. The chip overlay measurement device based on spatial coding illumination according to claim 1, wherein: The pixel size of the spatial light modulator (1-11) is 1920×1200.

6. The chip overlay measurement device based on spatially encoded illumination according to claim 1, characterized in that: The microscopic objective lens (1-8) is a semi-apochromatic microscopic objective lens.

7. The overlay measurement method of an overlay measurement device for a chip based on spatially encoded illumination according to claim 1, characterized in that Including the following steps: Place the chip to be detected under the microscopic objective lens; Reflect and image the chip to be detected through the microscopic imaging unit to obtain an image, obtain the bright and dark information of the reflected light of the chip to be detected and upload it; The computer control unit analyzes the bright and dark information, calculates the error, and outputs or sends an adjustment instruction according to the error; The microscopic imaging unit obtains an adjustment instruction and performs light adjustment until a high-precision measurement image is obtained.

8. A method for overlay measurement of a chip overlay measurement device based on spatially encoded illumination according to claim 7, characterized in that: The specific method for reflecting and imaging the chip to be detected by the microscopic imaging unit to obtain an image is as follows: The white light source generated by the laser driver sequentially passes through a converging lens, a variable aperture, a collimating objective lens, and a beam splitter prism 1 to form parallel light rays. These parallel light rays sequentially pass through a focusing objective lens, a beam splitter prism 2, and a microscopic objective lens and finally converge on the chip to be detected. After the light rays are reflected by the chip to be detected, they sequentially pass through the microscopic objective lens, the beam splitter prism 2, and a tube lens, and finally form an image on the image sensor.

9. The overlay measurement method of an overlay measurement device for a chip based on spatially encoded illumination according to claim 7, wherein: The specific method for the computer control unit to analyze the light and dark information, calculate the error, and output or upload an adjustment instruction according to the error is as follows: The computer control unit analyzes the light and dark information, calculates the error, and makes a judgment based on the error. If the error is within the range, the measurement accuracy is satisfied, and the measurement result is output; if the error is not within the range, the measurement accuracy is not satisfied, and the computer control unit sends an upload adjustment instruction.

10. The overlay measurement method of an overlay measurement device for a chip based on spatially encoded illumination according to claim 7, characterized in that: The specific method for the microscopic imaging unit to obtain an adjustment instruction and perform light adjustment until a high-precision measurement image is obtained is as follows: The spatial light modulator obtains an adjustment instruction, controls the propagation direction, phase, and amplitude of the parallel light rays that are uniformly irradiated on the spatial light modulator after passing through the beam splitter prism 1. Then the parallel light rays sequentially pass through the beam splitter prism 1, the focusing objective lens, the beam splitter prism 2, and the microscopic objective lens and finally converge on the chip to be detected. After the light rays are reflected by the chip to be detected, they sequentially pass through the microscopic objective lens, the beam splitter prism 2, and a tube lens, and finally form an image on the image sensor until a high-precision measurement image is obtained.

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