Abstract:
The method utilizes the physical phenomenon known as dispersion of the optical rotation. After passage of linearly polarized electromagnetic radiation through the optically active environment (rotator), with the rotating power characterized by a parameter p, and then through the analyzing polarizer, the function R(p) can be measured. For the given active medium and the relative orientation of polarization planes of the input light beam and the analyzing polarizer, R(p) has an unambiguous relation with the spectrum I(null) of the analyzed radiation (null stands for wavelength) and allows its unambiguous determination by special mathematical methods. In devices based on the above mentioned principle a linearly polarized collimated beam of analyzed radiation propagates through the optical rotator then passes through the analyzer and strikes a single-channel or multi-channel detector which measures R(p) as a function of the parameter p. Finally the desired spectrum is calculated from the known functional relation between the measured rotogram R(p) and I(null).
Abstract:
A Spectroscopic Rotating Compensator Material System Investigation System including a Dual Waveplate Pseudo-Achromatic Compensator System, and a Photo-Array for simultaneously detecting a Multiplicity of Wavelengths, is disclosed. The Spectroscopic Rotating Compensator Material System Investigation System is calibrated by a Mathematical Regression based technique involving, where desirable, Parameterization of Calibration Parameters. Calibration is possible utilizing various dimensional Data Set(s) obtained with the Spectroscopic Rotating Compensator Material System Investigation System in a “Material System present” or in a Straight-through” configuration, said data sets being variously normalized to D.C., A.C. or combination D.C. and A.C. components thereof.
Abstract:
This invention provides an inexpensive, noninvasive optical method of quantitatively determining the volume fraction of anisotropic material in a mixture of anisotropic and isotropic material, and more particularly for determining the volume fraction of noncubic crystalline material in a mixed-phase specimen having noncubic crystalline material intermixed with cubic crystalline material. Polarized light is impinged on the specimen and the reflectance or transmission difference between two orthogonal polarization directions is measured. In cubic regions the reflectance or transmission is the same along both polarization directions so the contributions to the difference cancel, leaving a signal only from the noncubic regions. The optical difference can be measured as a function of wavelength and critical points in the band structure, including the band gap, can be profiled. From the band structure the film composition can be determined. This measurement is particularly suited to measuring III-V nitride semiconductor specimens having regions with zincblende symmetry mixed with regions of wurtzite symmetry.
Abstract:
An apparatus for determining the optical retardation of a material. The apparatus includes a light source emitting light along a light path, and a lens disposed in the light path intermediate the light source and a sample of the material. A waveguide directs the light from the light source to the sample and directs light reflected from the sample to a wavelength analyzer, whereby the wavelength analyzer detects the wavelengths of the reflected light. The apparatus of the present invention includes a sole polarizing element disposed in the light path intermediate the light source and the wavelength analyzer.
Abstract:
An optical quadrature interferometer is presented. The optical quadrature interferometer uses a different state of polarization in each of two arms of the interferometer. A light beam is split into two beams by a beamsplitter, each beam directed to a respective arm of the interferometer. In one arm, the measurement arm, the light beam is directed through a linear polarizer and a quarter wave plate to produce circularly polarized light, and then to a target being measured. In the other arm, the to reference arm, the light beam is not subject to any change in polarization. After the light beams have traversed their respective arms, the light beams are combined by a recombining beamsplitter. As such, upon the beams of each arm being recombined, a polarizing element is used to separate the combined light beam into two separate fields which are in quadrature with each other. An image processing algorithm can then obtain the in-phase and quadrature components of the signal in order to construct an image of the target based on the magnitude and phase of the recombined light beam.
Abstract:
A non destructive method of spectroscopic ellipsometry adapted to measure the width of features in periodic structures, particularly those features which are less than one micron wide. The method is also adapted to make comparisons between a known reference structure and a sample structure, and to control the fabrication of periodic structures in a plasma etching reactor. Peaks in functions DELTA and PSI versus wavelength are monitored and correlated against reference curves, permitting etching conditions to be modified. This technique avoids the need for use of scanning electron microscopy to measure the linewidth, which is a destructive method. It also posses an advantage over scatterometry which requires several detectors arrayed at different angles from an incident beam to measure the different diffracted orders.
Abstract:
An ellipsometer system which includes a pivotal dispersive optics positioned to receive polychromatic light from an analyzer thereof, without further focusing after reflection from a substrate system, is presented. In addition, a stationary compensator, positioned between an analyzer and the dispersive optics, which serves to reduce detector element polarization dependent sensitivity to light entering thereto after it interacts with the dispersive optics, is disclosed. The use of a light fiber to carry light from a source thereof, to a polarization state generator, is also disclosed. The method of the present invention can include application of mathematical correction factors to, for instance, substrate system characterizing PSI and DELTA values, or Fourier ALPHA and BETA coefficients.