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Study of Gate Electrode Materials on High K Dielectrics

Description: This problem in lieu of thesis report presents a study on gate electrode materials on high K dielectrics, including poly-SiGe and Ru. The stability of poly-SiGe in direct contact with Hf silicon-oxynitride (HfSiON) is studied by rapid thermal annealing (RTA), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). By performing a series of RTA treatments we found that as RTA thermal budgets reach 1050 C for 30s, the poly-SiGe layer begins to intermix with the HfSiON film, as observed by TEM. The maximum annealing condition for the Hf0.14Si0.23O0.46N0.17 film to remain stable in contact with poly-SiGe is 1050 C for 20s in high purity N2(99.9%) ambient. We also found that after 1000 C annealing for 60s in a nitrogen ambient, the poly-SiGe crystal phase structure was changed from a columnar structure to a large grain structure. For a metal gate, Ru was studied to determine N2annealing effects on sheet resistance of Ru sample electrodes and electrical characterization of Ru/HfSiOx/Si stack. Results show that a pure Ru metal gate is not a good choice for high k materials since it is hard to etch off, and different annealing conditions can cause large changes in the electrical behavior.
Date: August 2003
Creator: Yao, Chun

A Wet Etch Release Method for Silicon Microelectromechanical Systems (MEMS) Using Polystyrene Microspheres for Improved Yield

Description: One of the final steps in fabricating microelectromechanical devices often involves a liquid etch release process. Capillary forces during the liquid evaporation stage after the wet etch process can pull two surfaces together resulting in adhesion of suspended microstructures to the supporting substrate. This release related adhesion can greatly reduce yields. In this report, a wet etch release method that uses polystyrene microspheres in the final rinse liquid is investigated. The polystyrene microspheres act as physical barriers between the substrate and suspended microstructures during the final liquid evaporation phase. A plasma ashing process is utilized to completely remove the polystyrene microspheres from the microstructure surfaces. Using this process, release yields > 90% were achieved. It is found that the surface roughness of gold surfaces increases while that of the silicon is reduced due to a thin oxide that grows on the silicon surface during the plasma process.
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Date: May 2004
Creator: Mantiziba, Fadziso

Effect of Silyation on Organosilcate Glass Films

Description: Photoresist stripping with oxygen plasma ashing destroys the functional groups in organosilicate glass films and induce moisture uptake, causing low-k dielectric degradation. In this study, hexamethyldisilazane (HMDS), triethylchlorosilane and tripropylchlorosilane are used to repair the damage to organosilicate glass by the O2 plasma ashing process. The optimization of the surface functionalization of the organosilicate glass by the silanes and the thermal stability of the functionalized surfaces are investigated. These experimental results show that HMDS is a promising technique to repair the damage to OSG during the photoresist removal processing and that the heat treatment of the functionalized surfaces causes degradation of the silanes deteriorating the hydrophobicity of the films.
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Date: August 2004
Creator: Kadam, Poonam

Topics in micro electromechanical systems: MEMS engineering and alternative materials for MEMS fabrication.

Description: This paper deals with various topics in micro electromechanical systems (MEMS) technology beginning with microactuation, MEMS processing, and MEMS design engineering. The fabrication and testing of three separate MEMS devices are described. The first two devices are a linear stepping motor and a continuous rotary motor, respectively; and were designed for the purpose of investigating the frictional and wear properties of silicon components. The third device is a bi-stable microrelay, in which electrical current conducts through a secondary circuit, via a novel probe-interconnect mechanism. The second half focuses on engineering a carbon nanotube / SU-8 photoepoxy nanocomposite for fabricating MEMS devices. A processing method for this material as well as the initial results of characterization, are discussed.
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Date: August 2004
Creator: Chapla, Kevin