Surface Passivation of (100)-Oriented GaAs with Ultrathin Fluoropolymer Films Deposited by Radio Frequency Magnetron Sputtering of Poly(tetrafluoroethylene)

Abstract

Ultrathin fluoropolymer films of about 4 nm in thickness were deposited on the HCl-etched ͑100͒-oriented GaAs single-crystal substrates via radio frequency plasma sputtering of a poly͑tetrafluoroethylene͒ ͑PTFE͒ target. X-ray photoelectron spectroscopy ͑XPS͒ results indicated that the sputter-deposited PTFE ͑s-PTFE͒ ultrathin film, having a dielectric constant comparable to that of the PTFE film ( ϳ 2.1), could effectively passivate the HCl-etched GaAs͑100͒ substrate under various environments. The growth of the oxide layer was effectively hindered by the s-PTFE barrier when the HCl-etched GaAs͑100͒ surface was exposured to air for several hundred hours. The surface oxidation rate was also reduced significantly in the presence of the s-PTFE barrier when the HCl-etched GaAs͑100͒ was exposed to water and the H 2 O 2 solution. XPS and time-of-flight secondary mass spectrometry results indicated that the deposited s-PTFE film was oxygen-free and consisted of -(CF 2 ) n -units with different end groups. The 180°peel adhesion test results suggested that the s-PTFE film adhered strongly to the GaAs͑100͒ surface.

Protective applications of vacuum-deposited perfluoropolymer films

“…The surface oxidation rate was reduced significantly in the presence of the PTFE barrier when the HCI-etched GaAs (100) was exposed to water and the H 2 O 2 solution. The 180° peel adhesion test showed that the PTFE film adhered strongly to the GaAs (100) surface [19]. The like results were obtained later but on (100) Si substrate by RF sputtering [20], by LA and pulsed electron beam deposition [21].…”