Chemical Vapor Deposition of Metallic Films at Low Temperatures: Precursor Synthesis and Hydrogen-Assisted Reaction Chemistry

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

This project aims for greater understanding of thin film growth/deposition, achievement of new routes to chemical vapor deposition of metal diboride thin films, and atomic layer deposition (ALD) of copper, tantalum, and other metallic films, all at low substrate temperatures. The scientific goal is to understand the chemistry of film formation using in situ optical, mass, and electron spectroscopies. The approach involves four parallel efforts: 1) New precursor molecules will be synthesized that are designed for the growth of Cu, Ta, and other metals using hydrogen plasma enhanced atomic layer deposition, and for the growth of ZrB2, MgB2, and other diboride alloys using hydrogen plasma enhanced CVD. 2) Film growth strategies using the new precursors will be developed: deposition of Cu and Ta by hydrogen plasma enhanced ALD, CrB2 by thermal CVD (chemical vapor deposition), and MgB2 by hydrogen plasma enhanced CVD. CrB2 and MgB2 growth will be investigated using precursors Cr(B3H8) 2 and Mg(B3H8) 2 recently discovered by the PIs. Heteroepitaxial growth of single crystal films of ZrB2 and CrB2 on Si(111) and MgB2 films on ZrB2 or CrB2 will be explored, as well as the synthesis of ZrB2 or CrB2 nanotubes using multi-walled C nanotubes as a template. 3) Film formation pathways will be analyzed using in situ spectroscopies to determine the mechanisms that govern ALD and CVD processes. Surface reactions will be analyzed using downstream mass spectroscopy, reflection IR absorption, quartz crystal microbalance, temperature programmed desorption, and Auger electron spectroscopy. Where applicable, isotopic labeling (D for H) will be utilized. Both static (post-growth) and dynamic (during growth) surfaces will be studied, including the use of time-modulated fluxes. Conformal coverage experiments on trench substrates will be used to extract the surface reaction probability of precursors, as a function of temperature and the concurrent flux of atomic hydrogen. Nucleation, composition, and surface roughness will be studied using real time spectroscopic ellipsometry. 4) Film structure and properties will be evaluated, including crystal structure, electrical conductivity, and performance as impurity diffusion barriers. Deposition, annealing, and analysis of structures consisting of Cu/Ta/Si or Cu/CrB2/Si will be carried out to determine Cu in-diffusion into Si. %%% The project addresses fundamental materials science and chemistry research issues associated with electronic/photonic materials having technological relevance, and emphasizes the integration of research and education. The project will support four graduate students, and 1-2 undergraduates per year conducting summer projects or senior theses. The UIUC SURGE (Support of Under-represented Groups in Engineering) and WISE (Women in Science and Engineering) programs will be utilized to assist with broadening participation by under-represented groups. Research results will be broadly disseminated by presentations at international conferences and by publication in scientific journals. Industrial microelectronics organizations, e.g., IBM, Intel, Novellus, or Applied Materials, will be visited to present and discuss project results to enhance university/industry interactions. The project is co-supported by the MPS/DMR and MPS/CHE Divisions. ***