J. Phys. Chem. B 1998, 102, 2193-2206
2193
Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures T. A. Jurgens-Kowal and J. W. Rogers, Jr.* Department of Chemical Engineering, UniVersity of Washington, Seattle, Washington 98195-1750 ReceiVed: March 28, 1997; In Final Form: January 7, 1998
Deposition of ultrathin silicon dioxide films on Mo(100) substrates by pyrolysis of tetraethoxysilane (TEOS) vapor has been investigated at temperatures between 300 and 860 K with X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and infrared reflection-absorption spectroscopy (IRRAS). Up to temperatures of ∼600 K, TEOS adsorbs on the Mo surface forming an ethoxysilyl intermediate, whereas at higher temperatures SiO2 is formed during the initial exposure, as evidenced by both XPS and IRRAS data. Deposition of silicon dioxide is reaction-limited in the temperature range studied with roughly a monolayer forming on the surface at 860 K. Heating the TEOSexposed Mo(100) surfaces to ∼1000 K yields ethylene as the predominant gas-phase decomposition product and improves both the stoichiometry and order of the films as indicated by an increase in the stretching frequency of the Si-O IRRAS peaks. A decrease in the amount of desorbed ethylene is observed as the deposition temperature increases from 300 to ∼600 K, and no significant desorption of any other decomposition products was detected at higher deposition temperatures. Carbon contamination is minimal in these SiO2 films.
I. Introduction For many years, silicon dioxide has been used extensively in large-scale integrated circuits, such as bipolar and metaloxide-semiconductor devices, because of its unique electrical and mechanical properties as an insulator. Tetraethoxysilane (TEOS) has gained popularity as a single-source precursor for SiO2 since it has many desirable properties and oxides of highquality can be produced by pyrolysis of TEOS at relatively low deposition temperatures.1-9 Low deposition temperatures are often required in high-performance integrated circuits where multilevel interconnect technology demands both deposition of a metal layer (often Al as a conduction path) and of a dielectric.10 Since the dielectric, or insulating layer, must be deposited on sharp metal lines without degradation of the metal or chemical reaction with the metal, the processing temperature is normally limited to
