In an ellipsometer, a phase-modulated, polarized light beam is applied to a sample, electrical signals are obtained representing the orthogonal planes of polarization of the light after it has interacted with the sample and the constants of the sample are calculated from the two resulting electrical signals. The phase modulation is sufficiently small so that the calibration errors are negligible. For this purpose, the phase modulator phase modulates the light within a range of no more than ten degrees modulations peak to peak. The two electrical signals are expanded by Fourier analysis and the coefficients thereof utilized to calculate psi and delta.
The use of ellipsometry and polarimetry in analysis of partially polarized beams of electromagnetic radiation, such as result from simultaneous ellipsometric investigation of a plurality of identifiably separate laterally disposed regions on a patterned sample system, is disclosed. Practice of the present invention methodology enables evaluation of characterizing representative parameters of partially polarized beams of electromagnetic radiation, and laterally and vertically oriented physical dimensions and/or optical property(s) of at least two identifiably separate laterally disposed regions of a partially depolarizing sample system. The present invention identifies partially polarized electromagnetic beam characterizing partitioning representative parameter(s) which quantify electromagnetic beam intensity resulting from coherent and from incoherent addition of electric fields, respectively, as well as electromagnetic beam spacial and/or temporal coherence and degree of collimation characterizing representative parameters as mathematical model parameters which can be evaluated, in addition to investigated patterned sample system laterally and vertically oriented physical dimensions and/or optical property(s) characterizing representative parameters. The depolarizing effects of backside reflections associated with layers in sample system region(s) are also be included.
Systems and methods are disclosed for using ellipsometer configurations to measure the partial Mueller matrix and the complete Jones matrix of a system that may be isotropic or anisotropic. In one embodiment two or more signals, which do not necessarily satisfy any symmetry assumptions individually, are combined into a composite signal which satisfies a symmetry assumption. The individual signals are collected at two or more analyzer angles. Symmetry properties of the composite signals allow easy extraction of overlay information for any relative orientation of the incident light beam with respect to a 1D grating target, as well as for targets comprising general 2D gratings. Signals of a certain symmetry property also allow measurement of profile asymmetry in a very efficient manner. In another embodiment a measurement methodology is defined to measure only signals which satisfy a symmetry assumption. An optional embodiment comprises a single polarization element serving as polarizer and analyzer. Another optional embodiment uses an analyzing prism to simultaneously collect two polarization components of reflected light.
The invention provides methods and apparatus for encoding information pertaining to the polarimetric state of transversely propagated radiation--for example, electromagnetic waves--as a modulation of the radiation's frequency power spectrum. In a preferred embodiment, suitable for examining light, the radiation passes consecutively through two birefringent media, each having mutually perpendicular fast and slow axes both perpendicular to the propagation axis. The fast axis of the first medium is rotated with respect the fast axis of the second medium to form an acute angle therebetween. The output of the second birefringent medium comprises a complementary pair of interference fringe systems. The power spectrum of each interference system is modulated in a manner characteristic of the polarization state of the radiation. One of the systems is selected by a linear polarizer. The invention is suitable for use in conjunction with a conventional imaging spectrograph and detector.
Disclosed are laterally compact ellipsometer, polarimeter, reflectometer and the like material system investigating systems, and methods for their use. Input and output optical elements effect changes in orientation, (propagation direction), of a beam of electromagnetic radiation caused to pass therethrough by an essentially total internal reflection therein. In addition, a propagation direction diverted beam of electromagnetic radiation can be simultaneously, optionally, caused to have a phase retardation entered between orthogonal polarization components thereof by at least one of the input and output optical elements. The present invention enables relatively simple investigation of a sample system with a polarized beam of electromagnetic radiation which impinges thereupon at a less than Brewster Angle, small "spot" size effecting angle-of-incidence, with respect to a normal to a surface of an investigated material system.
Disclosed is an electromagnetic beam directing system and method which enables changing the direction of propagation of a beam of electromagnetic radiation without significantly changing the phase angle between orthogonal components therein. Two pairs of mirrors are oriented to form two orthogonally related planes such that phase shift entered to an electromagnetic beam by interaction with the first pair of mirrors is canceled by interaction with the second pair.
