The ellipsometry is known as very high precision metrology for thin film thickness measurement. Using conventional types of ellipsometer, they can measure only single point of film thickness with spectroscopic ellipsometric parameters or multiple points of film thickness with single wavelength ellipsometric parameters. As semiconductor industry grows rapidly it is needed more efficient and accurate metrology and it recognized that ellipsometry is the only solution in nondestructive and in-situ measurement. Ellipsometry combining with spectral imaging concept can meet these demands and novel spectral imaging ellipsometry with mono axial power spectrograph is proposed in this thesis for simultaneous measurements of spatial and spectral ellipsometric parameters.
The mono axial power spectrograph is composed of entrance slit, holographic transmission grating, cylindrical doublet, and two dimensional CCD (Charge Coupled Detector) camera. The manufactured spectrograph shows that it is less than 1 nm wavelength accuracy, 100 ㎛ spatial resolution, and 15 nm spectral resolution. Using this manufactured spectrograph, spectral imaging ellipsometer is realized. The manufactured ellipsometer is rotating polarizer and analyzer type, and the incident angle is fixed to 70 degrees for visible range measurements. Generally transmission gratings, the dispersive component in spectrograph show dichroic response dependent on the polarization state of incident light. So the optical model for rotating optical components ellipsometer considering this dirchoric property has been proposed, and its azimuth calibration methods have been proposed also.
It is used DFTM(Discrete Fourier Transform Method) with more than 512 angular positions of analyzer to measure Fourier coefficients in conventional ellipsometry, but it degrades measurement time dramatically in rotating polarizer and analyzer type ellipsometer. So novel FFM(Four Frame Method) has been proposed in this thesis. FFM can save measurement time, but natively intensity measurements at only four analyzer positions can cause erroneous results in Fourier coefficients compared with that of DFTM. In the FFM, many repetitions of measurements for light intensity at each analyzer positions can solve these shortcomings. That is, conceptually to reduce random noise in ellipsometric measurements, conventional DFTM uses spatial averaging technique, but novel FFM uses temporal averaging technique. Using FFM the measurement time can save more than ten times as fast compared with conventional DFTM.
For evaluating the performance of manufactured spectral imaging ellipsometer, it has been shown results of thickness measurement for uniformly deposited silicon dioxide film on silicon substrate and one dimensionally patterned silicon dioxide film on silicon substrate. The results show that the accuracy of the spectral ellipsometer is 3 nm thickness accuracy and 100 ㎛ spatial resolution.
