University Ph.D. Dissertation Defense (October 19th) - Jungyup Kim
jykim87 at stanford.edu
Tue Oct 17 23:01:37 PDT 2006
Effective Surface Preparation Methods for Germanium Substrates
Department of Materials Science and Engineering, Stanford University
Advisor : Professor Yoshio Nishi
Co-Advisor : Professor Krishna Saraswat
Date : Thursday, October 19th, 2006
Time : 9:30AM (Refreshments served at 9:15AM)
Place : CISX Auditorium, Center for Integrated Systems
Germanium is gaining interest as a substrate for use in high mobility channel CMOSFETs applications. Effective surface cleaning is an important factor in realizing high mobility characteristics of the Ge substrate. Compared to the well established surface cleaning process for Si such as SC-1 and SC-2, little is known on the surface preparation techniques of Ge surfaces. Development of efficacious cleaning of Ge surfaces requires sound understanding of fundamental interactions between the cleaning solution and surface. Correlations between the aqueous solutions, contaminants and surface are also important. A robust cleaning process should have high contaminant removal with minimal consumption, roughness and good passivation characteristics.
Surface roughness is known to cause degradation in carrier mobility. This talk addresses the fundamental correlation between the etch rate and surface roughness. A novel method of improving the surface roughness with ozonated solution is also discussed. Metal removal efficiency is evaluated using a wafer scanning method and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Metal removal process developed by utilizing Pourbaix diagrams is evaluated. Methods of organic contaminant removal will be discussed. Effective passivation prevents re-oxidation and its detrimental effects. Ge passivation characteristics with hydrogen halide solutions are evaluated using X-ray Photoelectron Spectroscopy (XPS). Surface bonding structure is examined with highly surface sensitive synchrotron radiation XPS. Finally an effective surface clean process based on the results will be proposed.
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