Friday, September 25, 2015

Low temperature PEALD of SiN moisture permeation barrier layers from TU Eindhoven

This is really interesting! SiN is the fastest growing ALD film application in leading edge CMOS - for CVD it is I guess the opposite trend ;-) (originally posted by

Low temperature plasma-assisted atomic layer deposition of silicon nitride moisture permeation barrier layers

Anne-Marije Andringa, Alberto Perrotta, Koen de Peuter, Harm C.M. Knoops, Wilhelmus M.M Kessels, and Mariadriana Creatore
ACS Appl. Mater. Interfaces, Just Accepted Manuscript
DOI: 10.1021/acsami.5b06801
Publication Date (Web): September 22, 2015

Encapsulation of organic (opto-)electronic devices, such as organic light-emitting diodes (OLEDs), photovoltaic cells and field-effect transistors, is required to minimize device degradation induced by moisture and oxygen ingress. SiNx moisture permeation barriers have been fabricated using a very recently developed low temperature plasma-assisted atomic layer deposition (ALD), consisting of half-reactions of the substrate with the precursor SiH2(NHtBu)2 and with a N2-fed plasma. The deposited films have been characterized in terms of refractive index and chemical composition by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR), respectively. The SiNx thin film refractive index ranges from 1.80 to 1.90 for films deposited at 80 °C up to 200 °C, respectively, and the C, O and H impurity levels decrease when increasing the deposition temperature. The relative open porosity content of the layers has been studied by means of multi-solvent ellipsometric porosimetry (EP), adopting three solvents with different kinetic diameter: water (~ 0.3 nm), ethanol (~ 0.4 nm) and toluene (~ 0.6 nm). Irrespective of deposition temperature and hence impurity content in the SiNx films, no uptake of any adsorptive has been observed, pointing out the absence of open pores larger than 0.3 nm in diameter. Instead, multilayer development has been observed, leading to type II isotherms which, according to the IUPAC classification, are characteristic of non-porous layers. The calcium test has been performed in a climate chamber at 20 °C and 50% relative humidity to determine the intrinsic water vapor transmission rate (WVTR) of SiNx barriers deposited at 120 °C. Intrinsic WVTR values in the range of 10-6 g/m2/day indicate excellent barrier properties for ALD SiNx layers as thin as 10 nm, competing with the state-of-the-art plasma-enhanced chemical vapor deposited SiNx layers of a few hundreds nanometers- thick.