Abstract:High aspect ratio hole/slot microstructures are now widely used in the fields of micro-electro-mechanical systems (MEMS) and three-dimensional integrated circuits (3D-IC), and are fundamental process structures for micro and nano devices. With the development need for miniaturization and functionalization of devices, the depth-to-width ratio of hole/slot microstructures is constantly increasing. As an important parameter, depth has a direct impact on the device processing and device performance. The accurate measurement of the depth of micro-hole/slot structure is of great significance, but the measurement method faces great challenges and has become one of the difficult problems in the field of measurement. To address this issue, the measurement methods are divided into two major categories according to the non-optical and optical measurement methods, and the working principles of measurement methods such as scanning electron microscopy, scanning probe technique, white light microscopic interferometry, confocal microscopy and reflection spectroscopy are introduced. The research status of the depth measurements of micro hole/slot is introduced, and the advantages and disadvantages of each measurement method are summarized. Finally, the future development trend and research focus of high aspect ratio microstructure depth measurement are discussed to help the future research of high aspect ratio microstructure depth measurements.

Abstract:As the semiconductor industry develops and the device performance improves continuously, the feature size of semiconductor devices is becoming smaller and smaller, and the device structure is becoming more and more complex. Therefore, it urgently demands for the high performance of metrological instruments. This paper first introduces the measurement principle and the setup of through-focus scanning optical microscope (TSOM) method. This method can realize the nondestructive measurement of 3D geometric parameters, and has the advantages of high precision, fast speed, low cost, etc. It can meet the requirements of online applications. Then the paper introduces the research progress of TSOM method from two aspects: the construction of TSOM image and the extraction of structural parameters. Finally, it prospects the future research focus and development direction of TSOM method. This method is hopefully a new metrology method for China's semiconductor manufacturing industry, and provide important technical support for optimizing and upgrading China's semiconductor manufacturing process.

Abstract:Micro?nano detection technology aims to measure the characteristics of machined surface with micro/nano measurement accuracy, which plays an important role in controlling the machining process and establishing the relationship between surface characteristics and functions. Optical measurement method is an important part of micro?nano detection technology because of its high accuracy, fast speed and non?destructiveness. This paper introduces the common optical measurement methods of surface topography and film parameters, and compares and summarizes the characteristics and application occasions of each method in detail. The surface processed by micro?nano manufacturing technology has the development trend of miniaturization of structure and complexity of characteristics. Therefore, it is of great significance to build the multi-mode measurement system for micro?nano detection technology.

Abstract:Three-dimensional ultra-precision measurement technology plays a basic supporting role in improving high-end equipment manufacturing quality. With the progress of advanced manufacturing technology, improving measurement accuracy and expanding measurement range have become the key to the development of 3D ultra-precision measurement technology. In recent years, confocal 3D measurement technology has developed rapidly, and its application has gradually expanded from the biomedicine engineering to the manufacturing industry. This paper systematically introduces the research status and application progress of confocal measurement technology. The methods to improve the resolution of confocal 3D measurement and expand its measurement range are expounded from the perspective of technical principles. The relevant research results of interferometric confocal measurement, differential confocal measurement and spectral confocal measurement are compared and summarized. The application of confocal 3D measurement technology in surface profile measurement, microstructure feature size measurement and internal clearance measurement of key components are introduced in detail. On this basis, the future development direction of confocal 3D measurement technology is prospected with a view to providing technical reference for subsequent research.

Abstract:Multilayer micro nano films widely used in semiconductor, mechanical processing and other industries are usually formed by superposition of several single-layer films with nanometer thickness. Due to the limitations of process conditions in the manufacturing process, the film thickness may have uniformity errors, which will affect the performance of the films. Therefore, the accurate measurement of the film thickness is very important, and a nondestructive, high-precision and fast detection technology is urgently needed to measure and detect the thickness and uniformity of the film. This paper reviews the application status of multilayer films in different fields in recent years, analyzes the current technologies of multilayer thickness measurement, such as X-ray diffraction, and their shortcomings, and also reviews the research progress of ellipsometry. Finally, the application of machine learning in thickness measurement is introduced, and the prospect of the combination of machine learning and measurement in the future is discussed.

Abstract:Functional microstructure has the function of regulating light field or electronic conduction, and generally contains regular geometric shapes. Based on the ratio of depth to line width, it can be divided into high/low-aspect-ratio microstructures. At present, the detection of the geometric characteristic parameters of the microstructure is mainly conducted by SEM, which belongs to the destructive detection. The production line urgently needs non-destructive testing technology to monitor and improve its manufacturing process. This article systematically summarizes the progress made by the author's research team in the low-coherence microscopic-interference technology for nondestructive testing of three-dimensional (3D) morphology of microstructures in the past ten years. The white light microscopic interferometer is used to detect the 3D topography of ultra-smooth surfaces, steps, micro optical elements, micro mechanical elements and other low aspect ratio microstructures. A near-infrared micro interferometer is used to detect the 3D morphology of silicon based high aspect ratio microstructures. In this paper, the key technologies of the two band microscopic interference system and the tests of typical samples are described. The results show that white light micro interferometer and near-infrared micro interferometer are two kinds of high-precision nondestructive testing instruments. They can detect the 3D morphology of the microstructures with aspect ratio ≤4, and ≥20, respectively. The 3D topography data obtained by the microscopic-interference nondestructive testing technology will effectively promote the optimization of the manufacturing process of the microstructure and the further improvement of the performance of related devices.

Abstract:High-precision grating displacement measurement system has the advantages of nanometer repetition accuracy, strong environmental adaptability, and easy expansion of dimensions. It can meet the measurement requirements of the precision manufacturing industry for the integration of meter-level measurement range, submicron-level accuracy and multi-dimensional measurement capability. It has important applications in high-end manufacturing, precision instruments and other fields. By studying the parameters of the measuring grating, the size and manufacturing accuracy of the measuring grating are improved. High-precision conical diffraction grating displacement measurement, high power subdividing steering interferometric grating displacement measurement, 品-shaped splicing large range grating displacement measurement and other technologies are proposed to achieve sub-micron measurement accuracy in hundreds of millimeter measurement range. From grating fabrication to measurement system development, theoretical analysis and technical verification are provided for improving measurement accuracy, resolution and range.

Abstract:Laser interferometer has the advantages of high measurement resolution and traceability of measurement results, and is increasingly widely used in nanometer measurement. The Michelson laser interferometers used in nano-measuring machine and linear expansion coefficient measuring device for low expansion materials, and the Fabry-Perot laser interferometer used in high-precision displacement measuring device are introduced in this paper. Combined with these typical applications , key problems in the interferometer optical system design, measurement environment control, the nonlinear error compensation of Michelson interferometer and the measurement range expansion of Fabry-Perot interferometer are analyzed and summarized. The principles and methods described in this paper are of great significance for the laser interferometer to achieve nanometer measurement accuracy, which can provide technical reference for the development of high-precision laser interferometer and wider applications of laser interferometers in nanometer measurements.

Abstract:In order to accurately and quickly extract the focus position of pixels in the image sequence of the focus stacking 3D microscopic vision measurement, a focus measure algorithm based on the maximum gradient is proposed. Two band-pass mask operators and four high-pass mask operators are designed, and the maximum value of the intensity change of each pixel with respect to adjacent pixels is extracted from the band-pass signal and the high-pass signal to indicate the degree of focus, so as to improve the ability of focus measure function to extract gradient information. The adaptive gradient threshold segmentation algorithm improves the sensitivity of focus measure and reduces the influence of large fluctuations and sub-peaks of the focus measure curve. The experimental results show that, compared with the classical spatial focus measure algorithm, the focusing measure algorithm based on maximum gradient has significantly improved its robustness, sensitivity, unbiasedness and unimodality, and has good practicability, which can effectively meet the requirements of focusing measure of micro-nanometer scale 3D microscopic measurement of complex contours.

Abstract:Fast structured illumination microscopy plays an important role in micro-nano detection due to the characteristics of high accuracy, high efficiency and strong adaptability. Traditional methods utilizes the linear region of the axial modulation response curve to achieve 3D topography recovery by building the relationship between the modulation and the actual height. However, the application of traditional methods is limited to its narrow dynamic measurement range since the linear region of axial modulation response curve is very short. In order to overcome the disadvantage, a double-differential fast structured illumination microscopy is proposed. By introducing two additional detection branches for building the double-differential axial modulation response curve to obtain a wider linear region, the proposed method can obtain a larger dynamic measurement range. Under the condition of a microscope objective with a numerical aperture of 0.9 and a magnification of 100, the dynamic measurement range is expanded from 380 nm to 760 nm in simulation and from 300 nm to 600 nm in actual experiment. The simulations and experimental results verify that the dynamic measurement range of double-differential fast structured illumination microscopy is twice as large as that of the traditional method under the same system parameters, which effectively broadens the application range of fast structured illumination microscopy.

Abstract:Thickness measurement of the thin films is crucial for chip manufacturing and integrated circuits. Ellipsometry has the advantage of high measurement precision. The ellipsometry parameters of the full spectrum can be obtained by utilizing the broad spectrum measurement method to realize the thickness measurement of the nano-scale films. In order to solve the problem of film thickness measurement on the transparent silicon substrate which is often seen in the semiconductor field and eliminate the superimposed signal of the silicon layer, this paper proposed a polarization separation spectral interference ellipsometry system. A Mach-Zehnder interferometer was built to achieve the thickness measurement of the film on the silicon substrate in the near-infrared band. Taking the silica film with a thickness of 100 nm as the specimen, the measurement precision of nanometer scale was achieved. The method proposed in this paper is applicable to the thickness measurement of the thin films on transparent or opaque substrates, which avoids the correction steps in the detection process or the change of the incident wavelength. It can be used in the high-precision detection of the finished products of film preparation processes and technologies such as chemical vapor deposition and molecular beam epitaxy.

Abstract:In order to meet the requirements of high-precision and non-contact measurement of small diameter deep hole parts, a set of high-precision optical measurement system suitable for large measurement range was developed. Based on the principle of dispersion confocal measurement, a micro displacement system is established, and a high-resolution optical measurement system is formed by combining the spectral analysis technology. Firstly, based on the dispersion confocal principle, the structure of dispersion objective lens is designed by using Zemax software. Secondly, the creeping structure is designed, and the motor is used to drive the reflector rotating to complete the radial geometric dimension measurements of different sections of the deep holes. Thirdly, the system error is analyzed by least square method and is compensated. Finally, an experimental platform was built to verify that the measurement range reached 5 mm and the measurement accuracy was better than 3.3 μm. It has the advantages of high measurement accuracy, large measurement range and compact structure, which is of great significance to solve the problem of the measurement of the inner diameter of small size deep hole parts.

Abstract:Because of the small measurement range and long measurement time, the traditional detection methods can not meet the requirements of on?line, in?machine and large?format detection. In this paper, a chip surface morphology measurement method combining white light scanning interferometry and atomic force microscopy is presented. Based on the analysis of the characteristics of white light scanning interferometry and atomic force microscopy, a measurement scheme with two complementary methods was constructed. Firstly, the white light scanning interferometry was used to scan and inspect the chip in a large range with a high speed, and then the atomic force microscopy was used to measure the key areas by fine scanning. The measurement system was designed and integrated. The testing results showed that the system can accurately detect the nano?scale surface morphology in a range of millimeter.

Abstract:To address the painful problems in the current research of visual tracking platform, such as the inability to have both large field of view and high resolution, and the difficulty of high-speed motion target tracking, we designed a novel visual tracking platform based on two-dimensional (2D) galvanometers. It can achieve real-time tracking of dynamic targets at 50 FPS and high-fidelity information acquisition after 100 × magnification, when we take into account the high frame rate and high resolution characteristics while ensuring the field of view. Firstly, the geometrical modeling of the optical system based on the 2D galvanometers is made, the coupling relationship between the optical path change and the dynamic angle of view is analyzed, and the coordinate transformation of the dual-camera cooperative system is completed. Secondly, for the real-time target tracking task, a target detection and tracking algorithm based on dynamic template matching and Kalman filter is adopted, which ensures the fast and accurate positioning of the target object. Finally, the performance of the system is evaluated from the four aspects of dynamic field of view, response speed, tracking target positioning accuracy and tracking target limit speed, and several typical scenarios are selected to analyze the application fields of the system. The results show that the special dual-camera cooperative working mode and extremely fast dynamic response characteristics of the system well compensate for the shortcomings that exist in a visual tracking platform, and have broad application in the fields of intelligent monitoring, intelligent transportation, and military defense. It is proved that our system has broad application prospects and high research value.

Abstract:Multi-degree-of-freedom (multi-DOF) cross-scale precision displacement driving platform has a wide range of applications in optical metrology and detection, semiconductor manufacturing, biomedical engineering, and many other fields. In view of the heavy structure of the serial multi-DOF piezoelectric driving platform, a compact two-dimensional parallel cross-scale piezoelectric precision displacement driving platform is developed, which is based on the piezoelectric flexure hinge mechanism and impact driving principle. The results of finite element simulation and experimental test show that the piezoelectric flexure hinge stator has a static displacement of 7.95 μm and a natural frequency of 11.80 kHz. The low frequency step displacement and high frequency smooth movement tests show that the principle prototype has a step displacement resolution of 100 nm and a smooth movement speed of 4.96 mm/s. The load force reaches above 100 mN. The principle prototype meets the basic technical requirements of multi-DOF cross-scale precision displacement drive, and shows good application value in micro and nano optical detection systems.

Abstract:The surface topography measurement technique and system based on structured light illumination is studied around the demand of high precision measurement of scattering surface and complex microstructure surface topography. A structured light illumination optical system with good structured light contrast and uniformity based on Kohler illumination combined with digital micromirror device (DMD) modulation is designed. A virtual slit SlitMask structured illumination confocal sectioning algorithm using Gaussian curve interpolation is proposed, and the surface topography reconstruction through iterative Gaussian fitting is achieved. A structured illumination surface topography measurement system is established and well verified by experimental tests. The accuracy and repeatability of the system are tested with a single groove specimen. The results show that the relative measurement error is 1.87%, and the standard deviation of the repeated measurement results is 0.0014 μm. Furthermore, tests on actual industrial samples such as glass multiple carved lines and turned surface prove that the system can not only be used for the measurement of reflective surfaces, but also has good measurement capability for scattered surfaces.

Abstract:Electron beam inspection equipment plays an important role in the yield monitoring of integrated circuits (IC) manufacture. Combining technologies of scanning electron microscopy, high-precision motion control, high-speed image processing and automatic defect classification, this equipment can inspect physical and electrical defects on IC wafers in IC manufacturing processes. In order to fill in the blank of localization, our team has independently developed the equipment. Key technical breakthroughs in high-resolution large field scanning imaging, 3D high-precision positioning with compensation, AI-assisted defect capture and classification have been made. The localized electron beam inspection equipment have already been developed and used in IC manufacture. This will accelerate the development of IC inspection technology in China.