| With the continuous improvement of silicon-based MEMS technology and application,MEMS structure has developed from two-dimensional structure to three-dimensional structure.Because of its narrow and vertical air gap and large specific surface area,high aspect ratio micro groove structure is widely used in comb like microelectrode array,micro nano resonators,acceleration sensors,supercapacitors,gratings and other fields.In order to improve the quality of MEMS devices and ensure the yield of devices,it is necessary to measure and analyze the three-dimensional feature size of high aspect ratio of MEMS.In the three-dimensional feature size of high aspect ratio of MEMS,the depth,width and side wall angle have the greatest impact on the performance of MEMS devices.Therefore,accurate metrology for these parameters need to be solved in the process.The scattering measurement instrument designed in this paper is a kind of special optical instrument for measuring the linewidth and side wall angle of periodic high aspect ratio structure,it has the advantages of compact structure,wide spectral band and high measurement accuracy.In this platform,the linewidth and side wall angle are measured by polarized spectral scatterometry method.The thesis mainly includes the following three parts:(1)The principle of infrared spectrum scatterometry system for deep trench structure is described in detail,including the scattering modeling principle of periodic structure based on RCWA,the principle of the detection system based on reflective objective,the simulation of diffraction angle of MEMS deep trench structure,the simulation of spectrum sensitivity,etc.(2)The design and implementation of the instrument are introduced.The overall scheme of the scatterer is designed,the performance evaluation index is formulated,the measurement principle of the instrument is described.The selection of optical components,the design of optical circuit system and the ZEMAX simulation are completed.The principle prototype of the scatterer system is built and tested.(3)This paper describes the system calibration method of the instrument and carries out the experimental verification.The system calibration of the instrument mainly includes two aspects: nonlinear correction and wavelength accuracy correction,The experimental verification focuses on the reflectivity test and analysis of silicon-based Si O2 thin film samples and periodic deep trench samples.The experimental results show that compared with RC2 ellipsometer,the system calibration of the instrument is more accurate,When the film thickness is less than 5000 nm,the measurement error is less than1%,which meets the design requirements;In the verification of deep trench structure measurement,the consistency between the measured spectrum and the simulation spectrum also verifies the applicability of the proposed near infrared scattering measurement system. |
