Browsing by Subject "Ellipsometry"
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Item Ellipsometric techniques for determining oxide layer thickness on aluminum.(Texas Tech University, 1975-05) Lydon, Malcolm WebbEllipsometry is an optical tool used for measuring the thickness of extremely thin films. Ordinarily, useful results can be obtained only for very smooth layers of uniform thickness. This study describes an attempt to employ ellipsometric techniques to rough, non-uniform layers such as the natural oxide layers on ALCLAD, an aircraft aluminum. The method uses the formulas pertinent to ellipsometry on ideal layers, but interprets the layer thickness and the substrate conductivity in a phenomenological fashion. Traditional ellipsometric procedures are followed and the data obtained from a sample are plotted on a coordinate system derived from the parameters for ideal oxide layers on ideal aluminum, with substrate conductivity serving as a phenomenological parameter. Once the data have been plotted, values can be determined for the effective layer thickness and effective substrate conductivity. From features of internal consistency, it appears that the obtained parameters characterize the ALCLAD samples in a useful way.Item Endpoint detection of silicon wafer etching(Texas Tech University, 1985-12) Sinor, Timothy WayneThis thesis describes the results of an investigation into the use of plane polarized light for performing in situ endpoint monitoring of oxide thickness during the etching of silicon wafers. The continuous monitoring of the oxide thickness can be accomplished by analysis of the reflection characteristics of the plane polarized light. This information then allows the etching to be terminated when the oxide thickness approaches zero, thus, providing a means to control the etching process. To accomplish on line monitoring of the oxide thickness, plane polarized light from an argon ion laser passing through a rotating half-wave plate which alternately switches the polarization from transverse electric (TE) to transverse magnetic (TM). The modulated laser light is specularly reflected from the oxide-coated silicon wafer and is sensed by a silicon photo-detector. A.C. detection techniques are employed to measure the normalized reflectance intensity which is related to the thickness of the oxide coating. Oxide thicknesses on the order of 1000 A can be measured with the device to an accuracy of about 0.4%. Oxide thicknesses less than 50 A cannot be measured with accuracy.