Detection device and detection method for complex micro-nano structure

Abstract

The invention relates to a detection device and a detection method for a complex micro-nano structure. The device comprises a laser, a beam expanding and collimating system, a polaroid, a beam splitter prism and an image sensor, and can generate and shape light beams, the light beams are polarized to form measurement light, the measurement light is converged through a reflection or transmission light path, and finally a digital holographic interferogram is recorded by the image sensor. According to the method, reflection type measurement and transmission type measurement are combined, after a holographic interference pattern is obtained, object light wave complex amplitude distribution is obtained through the steps of image preprocessing, Fourier transform and the like, and then the three-dimensional shape of the micro-nano structure is analyzed. The problems that in the prior art, incident light is difficult to touch the bottom of a complex micro-nano structure, three-dimensional shape information is lost, the detection efficiency is low, the application range is limited, positioning is difficult and the like are effectively solved, an efficient and comprehensive micro-nano structure detection means is provided, the detection requirements of various functional materials are met, and the detection efficiency is improved. The method has remarkable technical advantages and wide application prospects.

Description

Technical Field

[0001] The present invention relates to the demand for precision optical detection technology in related fields such as chips, microfluidics, sensors, etc., and in particular to a detection device and a detection method for complex micro-nano structures. Background Art

[0002] The current measurement technology for complex micro-nano structures such as chips, sensors, and wafers lacks the ability to measure in three-dimensional axial direction with high precision. It faces the problem of low resolution or even inability to detect the surface of micro-structures with high aspect ratios. When the measuring beam is irradiated on the surface of the micro-nano structure, due to the specificity of the micro-nano structure, it triggers strong diffraction and scattering interference noise effects, greatly reducing the quality of the beam transmission energy in the optical system. Therefore, the three-dimensional information detection devices and detection technologies of complex micro-nano structures such as length, width, height, and aspect ratio have become the focus of the industry.

[0003] At present, the detection of micro-nano structures is mainly based on white light interferometers, laser confocal microscopes, atomic force microscopes and other detection devices, which have mature technology, superior performance and extremely high precision, but the measurement speed is slow, the detection cycle is as long as dozens of hours, the field of view is small, and it cannot meet the requirements of large-size device detection, and it is difficult to apply to online detection. The above shortcomings limit its application in chip microstructure measurement. At the same time, most of the existing microscopic imaging systems have complex structures, high purchase and maintenance costs, and require specialized senior technicians to manage the measurement, which greatly wastes human resources.

[0004] Existing digital holographic microscopes are generally either a single transmission structure or a single reflection structure. When testing some special samples, such as micro-optical devices with curvature, or micro-nano structures with both reflective and transmissive materials, the problem of inaccurate test results may occur due to the inability to simultaneously obtain sample test information of both transmission and reflection digital holographic microscopes. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a detection device for complex micro-nano structures. The device adopts a flat beam splitter and the like to construct a reflective microscope optical path or a transmissive microscope optical path system, so that the device overcomes the problem that the existing micro-nano structure measurement technology is only suitable for reflection or transmission measurement of a single-function sample to be measured, and realizes effective, in-situ, high-precision, non-contact, synchronous three-dimensional measurement of the microscopic morphology geometric parameters of the layered interface surface of transparent or non-transparent objects.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A detection device for complex micro-nano structures, comprising:

[0008] A laser for generating an initial light beam;

[0009] Beam expansion and collimation system, used to shape the beam generated by the laser to form parallel light for measurement;

[0010] The polarizer is used to polarize the parallel light. The polarized parallel light is converged to the beam splitter prism through the reflection microscope light path or the transmission microscope light path.

[0011] A beam splitter prism is used to combine the reference light wave and the object light wave and transmit them to the image sensor;

[0012] The image sensor is used to receive and record the digital holographic interference pattern formed by the superposition of the reference light wave and the object light wave; the image sensor is electrically connected to the computer.

[0013] In some embodiments, the reflective microscope optical path includes: parallel light after polarization processing passes through a beam splitter prism to form a test light beam, the test light beam is projected onto a flat beam splitter, a portion of the test light beam is reflected to become a reference light wave, the reference light wave passes through the beam splitter prism, a reflector and an imaging lens in sequence and converges to the beam splitter prism; while another portion of the test light beam passes through the flat beam splitter and irradiates the first microscope objective lens, and passes through the first microscope objective lens to irradiate the surface of the sample to be tested placed on the multi-dimensional rotating table, and after being reflected by the sample to be tested, it serves as an object light wave of the reflective microscope optical path, passes through the first microscope objective lens, the flat beam splitter, the beam splitter prism, the reflector and the imaging lens in sequence and converges to the beam splitter prism.

[0014] In some embodiments, the transmission microscope optical path includes: parallel light after polarization treatment passes through a beam splitter prism to form a test beam, the test beam is projected onto a flat beam splitter, a portion of the test beam is reflected to become a reference light wave, the reference light wave is sequentially passed through the beam splitter prism, a reflector and an imaging lens and then converged to the beam splitter prism; while another portion of the test beam is transmitted through the flat beam splitter to illuminate the surface of the sample under test placed on the multi-dimensional rotating table, and passes through the sample under test as the object light wave of the transmission microscope optical path, sequentially passed through the second microscope objective lens, the reflector and the imaging lens and then converged to the beam splitter prism.

[0015] In some embodiments, the sample to be tested is a micro-nano structure material with reflective properties.

[0016] In some embodiments, the sample to be tested is a micro-nano structure material with transmissivity.

[0017] In some embodiments, the computer is also connected to control the multi-dimensional rotating stage and the plate beam splitter.

[0018] The present invention also provides a method for detecting a complex micro-nano structure, using the above detection device, comprising the following steps:

[0019] Using a reflective measurement system to form a reflective digital holographic interferogram;

[0020] Forming a transmission-type digital holographic interferogram using a transmission-type measurement system;

[0021] The obtained digital holographic interference pattern is subjected to image preprocessing, Fourier transform, spectrum extraction and inverse Fourier transform to obtain the complex amplitude distribution of the object light wave, and the three-dimensional morphology information of the micro-nano structure is analyzed based on it.

[0022] In some embodiments, the obtained digital holographic interference pattern is subjected to image preprocessing, Fourier transform, spectrum extraction and inverse Fourier transform to obtain the complex amplitude distribution of the object light wave, and the three-dimensional morphology information of the micro-nano structure is analyzed based on it, specifically:

[0023] The image correlation method is used to pre-process the digital hologram obtained by single frame acquisition to remove the stray and noise signals such as salt and pepper noise and Gaussian noise.

[0024] The pre-processed digital hologram is subjected to Fourier transform processing to obtain its corresponding spectrum map, and the spectrum map is subjected to iterative threshold segmentation using a spatial filtering method based on region recognition to extract +1 level spectrum information, which is then subjected to a center shift operation;

[0025] The frequency spectrum information after center shifting is processed by inverse Fourier transform algorithm, and the complex amplitude distribution of the entire measured object is obtained by image stitching and fusion algorithm;

[0026] The effective information of the object under test is judged by using the image information, and the phase reconstruction and phase difference compensation are performed by combining the method based on bilinear fitting and background segmentation and the phase unwrapping algorithm;

[0027] According to the corresponding relationship between phase information and geometric parameters, the continuous reconstructed phase information of the three-dimensional morphology of the micro-nano structure is accurately obtained, thereby determining the true three-dimensional morphology and geometric parameter dimensions of the measured sample.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Based on the original digital holographic measurement, the reflective and transmissive digital holographic measurement systems are integrated to eliminate the problem of precise alignment and the need for dedicated optical components to meet the detection needs of different functional materials.

[0030] 2. By rotating the multi-angle rotating table, the object to be measured can be precisely rotated and controlled at each angle, so that the incident light can reach the inside of the micro-nano structure well and be received by the detector through multi-directional inclined diffraction, reducing the scattering effect that causes the loss of surface shape in the high, deep, wide and large gradient areas of complex micro-nano structures, and obtaining a complete three-dimensional distributed hologram, rather than being limited to the morphological contour.

[0031] 3. Use machine vision imaging and intelligent perception recognition technology to replace manual operations, which not only reduces the manual burden, but also improves the measurement efficiency and the accuracy and consistency of the test results, meeting the needs of in-situ online scanning measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of a detection device for complex micro-nano structures of the present invention.

[0033] Figure 2 It is a schematic diagram of multi-dimensional rotation scanning splicing in the present invention.

[0034] Figure 3 It is a schematic diagram of the beam control principle of the flat beam splitter in the present invention.

[0035] Figure 4 It is a flow chart of the inversion algorithm of the geometric parameters of the three-dimensional morphology of the micro-nano structure of the present invention.

[0036] Wherein: 1-laser, 2-microscope, 3-collimating lens, 4-polarizer, 5-beam splitter, 6-flat beam splitter, 7-first microscope objective, 8-test sample, 9-multidimensional rotating table, 10-second microscope objective, 11-computer, 12-reflector, 13-imaging lens, 14-beam splitter, 15-imaging lens, 16 reflector, 17-image sensor. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with specific embodiments. These embodiments are used to illustrate the present invention but are not limited to the scope of the present invention. The implementation conditions adopted in the embodiments can be further adjusted according to the specific experimental environment, and the implementation conditions not indicated are usually the conditions in conventional experiments.

[0038] Based on the problem of specific micro-nanostructure measurement and characterization, the present invention proposes a detection device and a detection method for complex micro-nanostructures to achieve synchronous, in-situ, online, high-precision detection of three-dimensional morphology geometric parameters of complex micro-nanostructures with reflection and transmission functions. The detection device for complex micro-nanostructures includes a reflection microscope optical path and / or a transmission microscope optical path. The detection method for complex micro-nanostructures includes a reflection measurement system and / or a transmission measurement system, and the reflection measurement system and the transmission measurement system can be detection devices for complex micro-nanostructures that include a reflection microscope optical path and a transmission microscope optical path, respectively.

[0039] See also Figure 1The present invention discloses a detection device for complex micro-nano structures, comprising a measurement system body, the measurement system body comprising a laser light source 1 arranged in sequence, generally a laser with a longer length is selected so that the detection device is easy to assemble and adjust; a beam expansion and collimation system, which is composed of a microscope objective 2 and a collimating lens 3, and is used to generate parallel light, a polarizer 4, combined with a beam splitter prism 5, which rotates the polarization state of the polarizer so that the intensity and phase of the incident light are measured to obtain a hologram modulation; a semi-transparent and semi-reflective flat beam splitter 6, which serves to use the reflected light as a reference light wave and the transmitted light to illuminate the measurement object, thereby simplifying the optical path; followed by a first microscope objective 7 (used to measure a reflective measurement object), a sample to be measured 8, the sample to be measured is located on a multi-dimensional rotating table 9, a second microscope objective 10 (used to measure a transmissive measurement object) and a reflector 12, an imaging mirror 13, a beam splitter prism 14 and an image sensor 17 are arranged on the right side of the reflector 12. The main function of the imaging lens 13 is to perform Gaussian diffraction imaging on the measuring light beam, and the reference light and the test light are mainly combined by the beam splitter prism 14 so as to be superimposed into a digital hologram and imaged on the target surface of the image sensor 17. A reflector 16 is arranged behind the beam splitter prism 5, and an imaging lens 15 and a beam splitter prism 14 are arranged in sequence below the reflector 16, wherein the function of the imaging lens 15 is to image the reference light beam in proportion to the back of the beam splitter prism 14 and on the target surface of the image sensor 17. The image sensor 17, the multi-dimensional rotating stage 9 and the flat beam splitter 6 are respectively connected to the computer 11, which not only allows the incident light to effectively enter the complex micro-nano structure, but also obtains a spatial multi-directional digital hologram through the multi-dimensional rotating stage, and obtains the entire real three-dimensional morphological geometric parameters through the digital image stitching algorithm.

[0040] See also Figure 2 The schematic diagram of multi-dimensional rotation scanning splicing in the present invention is as follows: when the incident light irradiates the surface of the sample 8 to be tested, the computer controls the multi-dimensional rotating stage 9 to first move in the horizontal and vertical directions to ensure that the image sensor 17 can clearly obtain the image plane of the sample to be tested. This image plane is used as the reference plane, and then the spatial azimuth is rotated and controlled to ensure that the light beam can enter the micro-nano structure of the sample 8. Each time the control rotates to a position, a hologram needs to be collected. Finally, the collected multiple digital holograms are respectively processed by Figure 4 The process algorithm shown is used to process the three-dimensional morphological parameters obtained by inversion, and digital image fusion and splicing are performed to obtain all-round geometric parameter information.

[0041] See also Figure 3 The flat beam splitter designed in the present invention is located at the front end of the microscope objective lens. By utilizing its optical characteristics, a part of the incident light wave is reflected to generate a clean reference light wave, and a part is transmitted to generate a measuring light beam. By performing synchronous control through the computer 11, reference light and test light with different light intensity ratios and angles can be obtained, which is convenient for collecting digital holograms.

[0042] In some embodiments, the present invention further provides a complex micro-nano structure measurement method, comprising the following steps:

[0043] Step 1: Select a suitable laser 1 as the light source, shape the beam through the microscope objective 2 and the collimating lens 3 to form a standard parallel light, modulate the polarization state through the polarizer 4 to form a suitable measurement beam, and pass through the beam splitter prism 5 as a test beam.

[0044] Step 2: The test light beam passes through the flat beam splitter 6 with both transmission and reflection functions, and a part of the reflected light is used as the reference light wave of the holographic interference pattern. The reference light wave is reflected by the beam splitter prism 5, transmitted to the reflector 16 and reflected, and then successively passes through the imaging lens 15 to form an image that is reflected by the beam splitter prism 14 and transmitted to the image sensor 17 for reception as the reference light wave of the entire measurement system.

[0045] See also Figure 3 According to the actual situation, the flat beam splitter 6 of the present invention selects a suitable reflectivity and transmittance ratio (generally the ratio is 2:8) so that the intensity values ​​of the reference light and the test light meet the interference condition. At the same time, by controlling the multi-dimensional motion control rotating stage device, the angle between the reference light and the test light is adjusted to meet the detector space sampling theorem, ensuring the high quality of the subsequent hologram.

[0046] Step 3: When the sample 8 to be tested is a micro-nano structure material with reflective properties, when the sample 8 to be tested is placed on the upper end of the multi-dimensional rotating table 9, the test light beam passing through the flat beam splitter 6 is irradiated to the first microscope objective lens 7. At this time, the parallel light converges on the surface of the sample 8 to be tested placed on the multi-dimensional rotating table 9. By adjusting the multi-dimensional rotating table 9, the modulated light field carrying the three-dimensional morphological information of the micro-nano structure passes through the first microscope objective lens 7 and the flat beam splitter 6 again, is reflected by the beam splitter prism 5, and is transmitted to the image sensor 17 through the reflector 16, the imaging lens 15 and the beam splitter prism 14 as the object light wave of the reflective measurement system. By superimposing with the reference light wave in step 2 on the image sensor target surface 17, a reflective digital holographic interference pattern is formed. It should be noted that the image sensor 17, the multi-dimensional rotating table 9 for placing the measured object and the flat beam splitter 6 are synchronously controlled by the computer 11.

[0047] Step 4: For the sample 8 to be tested, which is a micro-nano structure material with transmission performance, the first microscope objective lens 7 can be removed first, and the test light beam is transmitted through the flat beam splitter 6 to irradiate the sample 8 to be tested on the upper end of the multi-dimensional rotating table 9, and the modulated light field carrying the three-dimensional morphological information of the micro-nano structure through the second microscope objective lens 10 is reflected by the reflector 12, and is transmitted to the image sensor 17 through the imaging lens 13 and the beam splitter prism 14, as the object light wave of the transmission measurement system, by superimposing with the reference light wave in step 2 on the image sensor target surface 17, a transmission digital holographic interference pattern is formed. It should also be noted that the image sensor 17, the multi-dimensional rotating table 9 for placing the measurement object, and the flat beam splitter 6 are synchronously controlled by the computer 11.

[0048] Figure 2 The present invention obtains spatial multi-angle digital holographic technology by controlling the multi-dimensional rotating table 9, and obtains the three-dimensional morphology geometric parameter information of the micro-nano structure in all directions. Regardless of whether it is a reflective or transmissive measurement system, the multi-dimensional rotating table 9 is controlled by a computer. First, the multi-dimensional rotating table 9 is moved horizontally and vertically to ensure that the image sensor 17 can clearly obtain the image plane of the sample under test, and this image plane is used as the reference plane. On this basis, the spatial azimuth is then rotated and controlled to ensure that the incident light fully enters the micro-nano structure of the sample under test 8. Each time the control rotates to a suitable position, the image sensor 17 needs to collect a hologram, such as Figure 4 As shown, the image sensor 17 obtains digital holograms at different spatial positions shown by w1, w2, w3 and w4, and then uses Figure 4 The process algorithm shown in the figure is used to process the three-dimensional geometric parameter information obtained by inversion, and digital image fusion and splicing are performed to obtain the true three-dimensional geometric parameters of the measured sample in the complete space w. This method makes high-frequency information sufficient and further improves the measurement and detection accuracy.

[0049] Step 5: Regardless of whether it is a transmission measurement or a reflection measurement system, the image correlation method is first used to preprocess the hologram obtained by a single frame acquisition, such as removing stray and noise signals such as salt and pepper noise and Gaussian noise. Secondly, the preprocessed hologram is Fourier transformed to obtain its corresponding spectrum map, and the spectrum map is iteratively threshold segmented using a spatial filtering method based on region recognition to extract +1 level spectrum information and perform a center shift operation on it. Then, it is processed by an inverse Fourier transform algorithm to obtain the complex amplitude distribution of the phenomenon carrying micro-nano structure information. Combined with step 4, the image splicing and fusion algorithm is used to obtain the complex amplitude distribution of the entire object under test. Due to the specificity of the micro-nano structure, there is dislocation information with unreliable values ​​distributed in the peripheral area of ​​the image, and very few peak information is distributed in the central area. The image information is used to judge the effective information of the object under test, and finally the phase is reconstructed and compensated. See step 6 for details.

[0050] Step 6: For the complex amplitude in step 5, first use the method based on bilinear fitting and background segmentation and phase unwrapping algorithm to perform phase reconstruction and phase difference compensation. First, the least squares method is used to fit the entire phase distribution Φ1(x,y) to compensate for the coarse phase distortion. Then, use the following formula

[0051]

[0052] By compensating for the phase distortion, the compensated phase distribution Φ1(x,y) first-order phase gradient Φ(x,y) is obtained, and the sample-free background area is obtained by threshold segmentation and morphological processing using image processing algorithms. Finally, the phase distribution Φ1(x,y) background area is subjected to a second least squares fitting to eliminate the residual phase distortion. Through the correspondence between phase information and geometric parameters, the continuous reconstructed phase information of the three-dimensional morphology of the micro-nano structure is accurately obtained, thereby determining the true three-dimensional morphology and geometric parameter size of the sample under test. The relationship between the three-dimensional morphology parameters and the reconstructed phase is:

[0053]

[0054] In the formula, Φ is the reconstructed phase distribution, λ is the laser band, and Δn is the refractive index of the micro-nanostructure material. For redundant reflective micro-nanostructures, the denominator is π, and for transmissive micro-nanostructures, the denominator is 2π.

[0055] The above embodiments are only illustrative of the principles and effects of the present invention. A person skilled in the art may make several modifications and improvements without departing from the inventive concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A detection device for complex micro-nano structures, characterized in that: include: A laser (1) for generating an initial light beam; Beam expansion and collimation system, used to shape the beam generated by the laser to form parallel light for measurement; The polarizing plate (4) is used to perform polarization processing on the parallel light; the parallel light after polarization processing is converged to the beam splitting prism (14) through the reflection microscope light path or the transmission microscope light path; A beam splitter prism (14) for combining a reference light wave and an object light wave, and transmitting the combined light waves to an image sensor (17); An image sensor (17) is used to receive and record a digital holographic interference pattern formed by the superposition of a reference light wave and an object light wave; the image sensor (17) is electrically connected to a computer (11).

2. The complex micro-nanostructure detection device according to claim 1, characterized in that: The reflective microscope optical path comprises: parallel light after polarization treatment passes through a beam splitter prism (5) to form a test light beam, the test light beam is projected onto a flat beam splitter (6), a portion of the test light beam is reflected to become a reference light wave, the reference light wave passes through the beam splitter prism (5), a reflector (16) and an imaging lens (15) in sequence and then converges to the beam splitter prism (14); another portion of the test light beam passes through the flat beam splitter (6) to irradiate a first microscope objective lens (7), and passes through the first microscope objective lens (7) to irradiate a surface of a test sample (8) placed on a multi-dimensional rotating platform (9), and after being reflected by the test sample (8), serves as an object light wave of the reflective microscope optical path, passes through the first microscope objective lens (7), the flat beam splitter (6), the beam splitter prism (5), the reflector (16) and the imaging lens (15) in sequence and then converges to the beam splitter prism (14).

3. The complex micro-nanostructure detection device according to claim 1, characterized in that: The transmission microscope optical path comprises: parallel light after polarization treatment passes through a beam splitter prism (5) to form a test light beam, the test light beam is projected onto a flat beam splitter (6), a portion of the test light beam is reflected to become a reference light wave, the reference light wave passes through the beam splitter prism (5), a reflector (16) and an imaging lens (15) in sequence and then converges to the beam splitter prism (14); and another portion of the test light beam passes through the flat beam splitter (6) to irradiate the surface of a test sample (8) placed on a multi-dimensional rotating table (9), and passes through the test sample (8) as an object light wave of the transmission microscope optical path, passes through a second microscope objective lens (10), a reflector (12) and an imaging lens (13) in sequence and then converges to the beam splitter prism (14).

4. The complex micro-nanostructure detection device according to claim 2, characterized in that: The sample (8) to be tested is a micro-nano structure material with reflective properties.

5. The complex micro-nanostructure detection device according to claim 3, characterized in that: The sample (8) to be tested is a micro-nano structure material with transmissivity.

6. The complex micro-nanostructure detection device according to claim 1, characterized in that: The computer (11) is also connected to control the multi-dimensional rotating stage (9) and the flat beam splitter (6).

7. A method for detecting complex micro-nano structures, using the detection device as claimed in claim 1, characterized in that: The following steps are involved: Using a reflective measurement system to form a reflective digital holographic interferogram; Forming a transmission-type digital holographic interferogram using a transmission-type measurement system; The obtained digital holographic interference pattern is subjected to image preprocessing, Fourier transform, spectrum extraction and inverse Fourier transform to obtain the complex amplitude distribution of the object light wave, and the three-dimensional morphology information of the micro-nano structure is analyzed based on it.

8. The method for detecting complex micro-nano structures according to claim 7, characterized in that: The obtained digital holographic interference pattern is subjected to image preprocessing, Fourier transform, spectrum extraction and inverse Fourier transform to obtain the complex amplitude distribution of the object light wave, and the three-dimensional morphology information of the micro-nano structure is analyzed based on it, specifically: The image correlation method is used to pre-process the digital hologram obtained by single frame acquisition to remove the stray and noise signals such as salt and pepper noise and Gaussian noise. The pre-processed digital hologram is subjected to Fourier transform processing to obtain its corresponding spectrum map, and the spectrum map is subjected to iterative threshold segmentation using a spatial filtering method based on region recognition to extract +1 level spectrum information, which is then subjected to a center shift operation; The frequency spectrum information after center shifting is processed by inverse Fourier transform algorithm, and the complex amplitude distribution of the entire measured object is obtained by image stitching and fusion algorithm; The effective information of the object under test is judged by using the image information, and the phase reconstruction and phase difference compensation are performed by combining the method based on bilinear fitting and background segmentation and the phase unwrapping algorithm; According to the corresponding relationship between phase information and geometric parameters, the continuous reconstructed phase information of the three-dimensional morphology of the micro-nano structure is accurately obtained, thereby determining the true three-dimensional morphology and geometric parameter dimensions of the measured sample.

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