Design And Development Of Ultraviolet Spectroscopic Ellipsometer With Rotating Polarizer

Ellipsometer can obtain the geometric shape and optical information of the sample by detecting the change of polarization state before and after the reaction between the polarized light and the sample.It has the advantages of fast and accurate,non-contact and no damage,low cost and easy integration,and is widely used in the measurement and calibration of nano-film thickness and material optical constants.With the wide application of high-k materials,wide bandgap semiconductors,and ultra-thin films in the fields of optoelectronics and microelectronics,there is an urgent need to develop ultraviolet and deep ultraviolet spectroscopic ellipsometers to meet the measurement and characterization needs of these materials.The performance of the spectroscopic ellipsometer depends on the use spectral range of the polarization modulation device.Commonly used polarization modulation devices include rotating compensator,photoelastic modulator,liquid crystal retarder and rotating polarizer,etc.Due to the serious dispersion and low transmittance of the compensator in the ultraviolet band,the expansion of the rotary compensator ellipsometer to the ultraviolet and deep ultraviolet bands is more difficult and costly.Photoelastic modulators have high requirements for the measurement environment and complex calibration,and ultraviolet light will destroy the optical properties of liquid crystal molecules.These problems limit the expansion of photoelastic and liquid crystal modulated ellipsometers to ultraviolet and deep ultraviolet bands.In contrast,the rotating polarizer has the advantages of wide spectrum achromatic dispersion,low cost,simple operation and easy to extend to deep ultraviolet.This thesis designs and develops a rotating polarizer ultraviolet spectroscopic ellipsometer,which will be used in high-k materials and wide band gap.It has a wide range of application prospects in the measurement of nano film materials such as semiconductors and ultra-thin films.This thesis focuses on the design and development of the rotating polarizer ultraviolet spectroscopic ellipsometer,and elaborates the research background,system working principle,system design and construction,system performance evaluation and application testing,etc,the specific content includes:The working principle of the rotating polarizer ultraviolet spectroscopic ellipsometer(RPSE)is described in detail,the system measurement model and data processing method are deduced,and the data processing method of nano-film ellipsometric measurement based on the transmission matrix method is introduced,and the spectral ellipsometry data processing and system calibration method based on fourier coefficient fitting and LM algorithm are proposed.A rotating polarizer(deep)ultraviolet spectroscopic ellipsometer suitable for the 190-400 nm band is designed and developed.Combined with the system measurement principle,gave a detailed system design and development process,including system optical path design,mechanical structure and control system design,key component selection,system assembly integration and debugging.Based on the proposed system calibration and test methods,the built-up rotating polarizer ultraviolet spectroscopic ellipsometer has been fully calibrated and tested,including system calibration and measurement testing,system performance testing and evaluation,etc.and finally application tests were carried out on typical samples such as silicon dioxide,silicon,and silicon nitride,which further verified the accuracy and repeatability of the developed system for measuring the thickness of nano-films.