CN220603845U

CN220603845U - Chip alignment measuring device based on space coding illumination

Info

Publication number: CN220603845U
Application number: CN202322252141.XU
Authority: CN
Inventors: 刘志平; 邱志群; 叶颖
Original assignee: Nano Science Instrument Equipment Shanghai Co ltd
Current assignee: Nanoscience Instrument Equipment (Hangzhou) Co.,Ltd.
Priority date: 2023-08-21
Filing date: 2023-08-21
Publication date: 2024-03-15
Anticipated expiration: 2033-08-21

Abstract

The utility model discloses a chip overlay measurement device based on space coding illumination, which comprises a microscopic imaging unit, the method comprises the steps of carrying out reflection imaging on a chip to be detected to obtain an image, and obtaining an adjusting instruction to carry out light adjustment until a high-precision measurement image is obtained; the computer control unit is used for acquiring the image analysis brightness information, calculating errors and outputting or uploading the adjustment instruction; the microscopic imaging unit comprises a laser driver, a converging lens, an adjustable diaphragm, 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 device has a simple structure, is easy to integrate, dynamically modulates the intensity and the irradiation angle of the light through the spatial light modulator, and solves the technical problems of poor quality and low detection precision of chip alignment detection images caused by uneven illumination light and limited angle in the existing chip alignment measurement method.

Description

Chip alignment measuring device based on space coding illumination

Technical Field

The utility model relates to the technical field of optical detection, in particular to a chip overlay measurement device based on space coding illumination.

Background

In the chip manufacturing process, real-time performance and defect detection are important steps for ensuring the quality controllability of products. The optical overlay alignment at the critical layer directly affects the performance, yield and reliability of the chip. With the improvement of chip integration, line width reduction and application of multiple photoetching processes, the control requirement on overlay errors is more and more strict. Overlay error measurement is therefore one of the critical process control steps.

Overlay error measurements are often made by optical microscopy imaging systems. The system can acquire the digital images of the two layers of the overlay target patterns, and calculate the center position of each layer by utilizing a digital image algorithm, so as to obtain the numerical value of the overlay error. In particular, the method involves acquiring images of current and previous layers of measurement indicia and performing image analysis to determine the relative displacement of the two layers of measurement indicia. In order to obtain an image of the measurement marker, a bright field microscope is used, and the center of gravity of the measurement marker is determined by analyzing the gray level of the image, thereby obtaining a displacement vector. Therefore, the image quality is critical to the overlay error measurement. Because the front layer is covered by a film layer made of various materials, the focal length and the wavelength of the irradiated light wave need to be continuously adjusted in the detection process so as to acquire a high-contrast image. Linewidth inconsistencies due to high light and measurement occlusion are common causes of measurement errors.

Disclosure of Invention

The utility model aims to provide a chip overlay measurement device based on space coding illumination.

In order to achieve the above purpose, the present utility model provides the following technical solutions: a chip overlay measurement device based on spatially coded illumination, comprising:

the microscopic imaging unit is used for reflecting and imaging the chip to be detected to obtain an image, and acquiring an adjusting instruction to adjust light until a high-precision measurement image is acquired;

the computer control unit is used for acquiring the image analysis brightness information, calculating errors and outputting or uploading the adjustment instruction;

the microscopic imaging unit comprises a laser driver, a converging lens, an adjustable diaphragm, a collimating objective, a focusing objective, a first beam splitting prism, a second beam splitting prism, a microscopic objective, a tube lens and an image sensor, wherein the converging lens, the adjustable diaphragm and the collimating objective are sequentially and coaxially arranged, the adjustable diaphragm corresponds to an image space focal plane of the converging lens and an object space focal plane of the collimating objective respectively, the microscopic objective and the tube lens are sequentially and coaxially arranged, the first beam splitting prism is positioned at one side of the collimating objective far away from the adjustable diaphragm, the second beam splitting prism is positioned between the microscopic objective and the tube lens, the first beam splitting prism and the second beam splitting prism are correspondingly and parallelly arranged, the focusing objective is positioned between the first beam splitting prism and the second beam splitting prism, and the image sensor is positioned at one side of the tube lens far away from the second beam splitting prism;

the microscopic imaging unit further comprises a spatial light modulator, the spatial light modulator is located on one side, far away from the focusing objective lens, of the first beam splitting prism, the spatial light modulator is used for acquiring an adjusting instruction and adjusting parallel light rays, and the parallel light rays are finally gathered on a chip to be detected through the focusing objective lens, the second beam splitting prism and the microscopic objective lens in sequence and imaged on the image sensor.

Further, the converging lens is composed of a plurality of coaxial lenses for converging light generated by the white light source at the adjustable aperture.

Further, the spectrum range of the white light source generated by the laser driver is 170nm-2100nm.

Further, the splitting ratio of the first splitting prism to the second splitting prism is 50:50, and the first and second beam-splitting prisms are depolarizing beam-splitting prisms.

Further, the spatial light modulator pixel size is 1920 x 1200.

Further, the microscope objective is a semi-apochromatic microscope objective.

According to the technical scheme, the utility model has the following beneficial effects:

the device has a simple structure, is easy to integrate, dynamically modulates the intensity and the irradiation angle of the light through the spatial light modulator, and solves the technical problems of poor quality and low detection precision of chip alignment detection images caused by uneven illumination light and limited angle in the existing chip alignment measurement method.

The chip alignment measuring device can quickly realize uniform illumination on the surface of a chip sample, so that a more accurate measuring result is obtained, the chip alignment measuring device can be widely applied to the fields of optical imaging and detection, and a simple and feasible device is provided for improving the precision of the chip alignment measuring result.

Drawings

FIG. 1 is a schematic diagram of a chip overlay measurement apparatus according to the present utility model;

FIG. 2 is a diagram showing the effect of shielding light on the surface of a chip to be tested according to the present utility model;

FIG. 3 is a graph showing the effect of a conventional test result without using the apparatus of the present utility model;

FIG. 4 is a graph showing the effect of the test results of the present utility model.

In the figure: a microscopic imaging unit 1; the device comprises a laser driver 1-1, a converging lens 1-2, an adjustable diaphragm 1-3, a collimating objective lens 1-4, a focusing objective lens 1-5, a first beam splitter prism 1-6, a second beam splitter prism 1-7, a microscope objective lens 1-8, a tube lens 1-9, an image sensor 1-10, a spatial light modulator 1-11, a computer control unit 2 and a chip to be tested 3.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Referring to fig. 1, the utility model provides a chip overlay measurement device based on space coding illumination, which comprises a microscopic imaging unit 1 and a computer control unit 2, wherein the microscopic imaging unit 1 comprises a laser driver 1-1, a converging lens 1-2, an adjustable diaphragm 1-3, a collimating objective lens 1-4, a focusing objective lens 1-5, a first beam splitter prism 1-6, a second beam splitter prism 1-7, a microscopic objective lens 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 diaphragm 1-3 and the collimating objective lens 1-4 are coaxially arranged in sequence from top to bottom, and the adjustable diaphragm 1-3 corresponds to the image space focal plane of the converging lens and the object space focal plane of the collimating objective lens respectively;

the converging lens 1-2 is composed of five coaxial lenses and is used for converging light rays generated by a white light source at the position of the adjustable diaphragm 1-3, the adjustable diaphragm 1-3 is positioned on the focal plane of the image side of the converging lens 1-2, the diameter of the adjustable diaphragm can be adjusted, the size of luminous flux in the measuring process is adjusted, stray light rays are restrained, and the uniformity of the light source is further improved; the object space focal plane of the collimating objective lens 1-4 is positioned on the adjustable diaphragm 1-3 and used for adjusting the parallel emergent light rays; the laser driver 1-1 is used for generating a white light source which is EQ-99CAL LDLS with a spectral range of 170nm-2100nm ^TM The laser drives a white light calibration light source for generating a broad spectrum light beam with high brightness and high stability, and the white light source sequentially passes through a converging lens 1-2, an adjustable diaphragm 1-3, a collimating objective lens 1-4 and a beam splitting prism 1-6 to form parallel light rays.

The microscope objective 1-8 and the tube lens 1-8 are coaxially arranged in sequence, wherein the microscope objective 1-8 is a semi-apochromatic microscope objective, the exit pupils of the microscope objectives with different multiplying powers are overlapped, the first beam splitter prism 1-6 is positioned at the lower end of the collimating objective 1-4, the second beam splitter prism 1-7 is positioned between the microscope objective and the tube lens, the first beam splitter prism 1-6 and the second beam splitter prism 1-7 are correspondingly and parallelly arranged, and the beam splitting ratio of the first beam splitter prism 1-6 and the second beam splitter prism 1-7 is 50:50, wherein 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 positioned at the upper end of the tube lens;

the microscopic imaging unit further comprises a spatial light modulator 1-11, the spatial light modulator 1-11 is positioned on the left side of the first beam splitting prism 1-6, after an adjusting instruction is acquired through the spatial light modulator 1-11 and parallel light rays are adjusted, the parallel light rays are finally gathered to a chip to be detected through the focusing objective lens, the second beam splitting prism and the microscope objective lens, after the light rays are reflected by the chip to be detected 3, the light rays are finally imaged on the image sensor through the microscope objective lens, the second beam splitting prism and the tube lens, the entrance pupil of the tube lens is overlapped with the pupil of the microscope, so that the uniformity of an image plane is better, and the measurement precision of chip alignment is improved. The size of the pixels of the spatial light modulator 1-11 is 1920 multiplied by 1200, the propagation direction, the phase and the amplitude of light can be precisely controlled, the light modulation such as the irradiation angle, the irradiation light intensity and the like can be realized, and the dynamic compensation is carried out on the system measurement error through the light modulation, so that the measurement precision of chip overlay is improved.

The object focal plane of the converging lens is positioned on the spatial light modulator, so that the conjugate relation between the spatial light modulator and the chip to be tested is realized; the focal plane of the converging lens is positioned on the pupil of the microscope objective lens to form kohler illumination, and finally, the modulation illumination of the chip to be tested is realized.

The image sensor obtains an image by utilizing light reflected by the chip to be detected, acquires light and shade information, feeds back the light and shade information to the computer processing unit, and the computer further intelligently regulates and controls the spatial light modulator to modulate the light, and obtains a high-precision measurement image after multiple feedback-regulation.

Working principle: placing a chip to be detected below the microscope objective; a white light source generated by a laser driver sequentially passes through a converging lens, an adjustable diaphragm, a collimating lens and a beam splitting prism I to form parallel light, the parallel light sequentially passes through a focusing lens, a beam splitting prism II and a micro-lens to be finally gathered to a chip to be detected, the light sequentially passes through the micro-lens, the beam splitting prism II and a tube lens after being reflected by the chip to be detected, and finally is imaged on an image sensor to obtain light and shade information of the reflected light of the chip to be detected and is uploaded; the computer control system calculates errors after analyzing the light and shade information, judges according to the errors, and if the errors are within the range, the measurement accuracy is met and a measurement result is output; if the error is not in the range, the measurement accuracy is not met, and the computer control system sends an uploading adjustment instruction; the space light modulator acquires an adjusting instruction, controls the propagation direction, the phase and the amplitude of parallel light rays which are uniformly irradiated on the space light modulator after passing through the first beam splitting prism, and then the parallel light rays are finally gathered to a chip to be detected through the first beam splitting prism, the focusing objective lens, the second beam splitting prism and the micro objective lens in sequence, namely, the light ray intensity and the irradiation angle of the light rays irradiated to the surface of the chip to be detected are controlled, and after being reflected by the chip to be detected, the light rays sequentially pass through the micro objective lens, the second beam splitting prism and the tube lens, and finally are imaged on the image sensor until a high-precision measurement image is acquired.

Fig. 2 is a diagram of the effect of shielding light on the surface of a chip to be tested, specifically: the light is obliquely incident on the surface of the chip to be tested, and shadow is generated on the left side due to the fact that the light is shielded.

Fig. 3 is a general test result without using the method of the present utility model, and fig. 4 is a target measurement result obtained according to an embodiment of the present utility model. By comparing the results of the two figures, the method and the device can realize more accurate measurement on the target area.

Although embodiments of the present utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the utility model, the scope of which is defined in the appended claims and their equivalents.

Claims

1. Chip overlay measuring device based on space coding illumination, characterized by comprising:

the microscopic imaging unit (1) is used for carrying out reflection imaging on the chip to be detected to obtain an image, and acquiring an adjusting instruction to carry out light adjustment until a high-precision measurement image is acquired;

the computer control unit (2) is used for acquiring the image analysis brightness information, calculating errors and outputting or uploading the adjustment instruction;

the microscopic imaging unit comprises 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 first beam splitter prism (1-6), a second beam splitter prism (1-7), a microscopic objective (1-8), a tube lens (1-9) and an image sensor (1-10), wherein the converging lens (1-2), the adjustable aperture (1-3) and the collimating objective (1-4) are coaxially arranged in sequence, the adjustable aperture (1-3) respectively corresponds to an image side focal plane of the converging lens and an object side focal plane of the collimating objective, the microscopic objective (1-8) and the tube lens (1-9) are coaxially arranged in sequence, the first beam splitter prism (1-6) is positioned at one side of the collimating objective (1-4) away from the adjustable aperture, the second beam splitter prism (1-7) is positioned between the microscope and the tube lens, the first beam splitter prism (1-6), the second beam splitter prism (1-7) is correspondingly arranged and parallelly, the first beam splitter prism (1-7) is arranged at one side of the beam splitter prism (1-5) away from the collimating lens (1-7), the laser driver (1-1) is used for generating a white light source, and the white light source sequentially 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) to form parallel rays;

the microscopic imaging unit also comprises a spatial light modulator (1-11), wherein the spatial light modulator (1-11) is positioned on one side of the first beam splitting prism (1-6) far away from the focusing objective lens, and after an adjusting instruction is acquired through the spatial light modulator (1-11) and parallel light rays are adjusted, the parallel light rays pass through the focusing objective lens, the second beam splitting prism and the microscopic objective lens in sequence and finally are gathered on a chip to be detected and imaged on the image sensor.

2. The chip overlay measurement apparatus based on space-coded illumination of claim 1, wherein: the converging lens (1-2) is composed of a plurality of coaxial lenses for converging light generated by a white light source at the adjustable aperture (1-3).

3. The chip overlay measurement apparatus based on space-coded illumination of 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 apparatus based on space-coded illumination of claim 1, wherein: the splitting ratio of the first splitting prism (1-6) to the second splitting prism (1-7) is 50:50, and the first beam splitter prism (1-6) and the second beam splitter prism (1-7) are depolarization beam splitter prisms.

5. The chip overlay measurement apparatus based on space-coded illumination of claim 1, wherein: the spatial light modulator (1-11) has a pixel size of 1920 x 1200.

6. The chip overlay measurement apparatus based on space-coded illumination of claim 1, wherein: the microscope objective (1-8) is a semi-apochromatic microscope objective.