Application Research On Extraction Of Ultra-thin Film Spectral Ellipsometry Measurement Parameters Based On Sensitivity Analysis

With the rapid development of nanotechnology,the optoelectronic films are getting thinner and thinner due to the miniaturization of the size of optoelectronic devices and more complicated nanostructure.It is necessary to obtain the thickness and optical properties of ultra-thin films accurately,in order to the optimization of the novel optoelectronic device during the process of design and manufacturing control.Since the advantages of sub-nanometer high measurement accuracy,spectroscopic ellipsometry is widely used in measurement of ultra-thin optical constants and thickness.As a model-based metrology,the film parameters obtained by fitting the measured signatures with the calculated ones,the precision of the extracted film parameters mainly depend on the sensitivity of model parameters and the strong cross-correlations among them,when measurement configuration in ellipsometer fixed.The sensitivity of ellipsometry to film thickness and optical constants is often relatively lower during the many applications of the ellipsometry measurement of nanometer ultra-thin film.This fact presents a significant challenge for optical properties and thicknesses characteration of multilayered ultathin-film structures.This thesis builds on the problem of how to solve the high-precision extraction of ultra-thin film parameters,for which an evaluation method and model for high-precision of the extracted ultra-thin film parameters is proposed.The main contents and innovations include:Firstly,a methond and model for high-precision of the extracted ultra-thin film parameters is proposed based on the sensitivity analysis method to provide theoretical guidance for evaluating the high-precision extraction of ultra-thin film parameters by calculating the uncertainty and correlation coefficients of the parameters to be measured and unique analysis of results.Secondly,sensitivity simulation experiments for the typical ultra-thin film structure are carried out,the critical estimate of the thickness of the corresponding film with high precision extraction of the optical constant is analyzed,which shows that the sensitivity analysis method can be used to estimate the critical thickness of the films.Finally,an experimental study was carried out to measure the thickness accuracy of each layer of the typical multi-layer ultra-thin film structure in OLED,which lead to the evaluation of different measurement accuracy regions and optimization of the extraction strategy of the film thickness in the OLED multilayer structure.The results indicates the sensitivity analysis method can be used to the evaluation of the measurement accuracy of the multi-layer ultra-thin film thickness and optimization for the extraction strategy,which can improve the measurement accuracy of the key film due to the cross-correlation weakened between the parameters to be measured.