Deposition of a-Si:H thin films using tailored voltage waveform plasmas: impact on microstructure and stability

WANG, JUNKANG; LONGEAUD, CHRISTOPHE; VENTOSINOS, FEDERICO; DAINEKA, DMITRI; YAAKOUBI, MUSTAPHA EL; JOHNSON, ERIK V.

physica status solidi (c)

WILEY-VCH Verlag GmbH & Co. KGaA

Lugar: Weinheim; Año: 2016

Exciting processing plasmas using non-sinusoidal, ?Tailored?voltage waveforms (TVWs), have recently beenshown to be effective to separately control the maximumion bombardment energy (IBE) and the ion flux on eachelectrode in the capacitively coupled plasma (RF-CCP)processes. In this work, we use it to deposit hydrogenatedamorphous silicon (a-Si:H) thin films from hydrogendilutedsilane by low temperature plasma-enhancedchemical vapor deposition. The impact of using TVWson the material?s structural and electronic properties isexamined. Excessively low IBE can lead to a high Si-H2bonded hydrogen content within the deposited films,which results in a deterioration of the material stabilityupon light-soaking, detectable at a microstructure level.A low content of hydrogen bonded in a Si-H2 configurationand a low sub-gap density of states was observed inthe film deposited using a ?sawtooth-down? type ofwaveform. Such excitation also produced the a-Si:Hfilms with the best transport properties (majority and minoritycarrier μτ-products and the ambipolar diffusionlength) and stability under light-soaking.