Hydrogenated amorphous silicon films deposited by electron cyclotron resonance chemical vapor deposition at room temperature with different radio frequency chuck powers

Abstract

In this work, we present the morphological and electrical characterization of hydrogenated amorphous siliconfilms, which were deposited at room temperature on a n+-type silicon substrate using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique. To study the hydrogen incorporation into the films, radio-frequency (RF) chuck powers of 1 W, 3 W and 5 W in the silicon substrates were applied during the ECR-CVD depositions. The deposited films were p+ doped using boron ion implantation (B+ I/I) and annealed at 1273 K, using a Rapid Thermal Annealing (RTA) process for dopant activation. The hydrogen concentration, the crystalline level, the surface roughness were obtained by, respectively, Fourier-transform infrared spectroscopy of the as-deposited films; Raman spectroscopy and atomic force microscopy of the films, after the B+ I/I and RTA. The Fourier-transform infrared and Raman spectra were deconvoluted as gaussian curves to extract the molecular bond concentration between silicon and hydrogen and their vibrational modes, respectively. These analyses indicated that: the H concentration is reduced with the increase of RF chuck powers, and, the films changed from totally amorphous to partially crystalline, respectively, when are compared the structures, before and after the B+ I/I and RTA. Diodes with three p+ a-Si/n++c-Si structures were fabricated with aluminun electrodes and current-voltage curves were extracted, indicating that the devices, with films deposited with 5 W, presented the best results, with ideality factor of 1.1.