Low-Temperature Plasma-Assisted Atomic Layer Deposition of Silicon Nitride Moisture Permeation Barrier Layers

Abstract

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) approach, consisting of half-reactions of the substrate with the precursor SiH2(NH(t)Bu)2 and with N2-fed plasma. The deposited films have been characterized in terms of their refractive index and chemical composition by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). 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 the deposition temperature increases. The relative open porosity content of the layers has been studied by means of multisolvent ellipsometric porosimetry (EP), adopting three solvents with different kinetic diameters: water (∼0.3 nm), ethanol (∼0.4 nm), and toluene (∼0.6 nm). Irrespective of the deposition temperature, and hence the impurity content in the SiNx films, no uptake of any adsorptive has been observed, pointing to the absence of open pores larger than 0.3 nm in diameter. Instead, multilayer development has been observed, leading to type II isotherms that, according to the IUPAC classification, are characteristic of nonporous 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 that of state-of-the-art plasma-enhanced chemical vapor-deposited SiNx layers of a few hundred nanometers in thickness.

Ultrathin, transferred layers of thermally grown silicon dioxide as biofluid barriers for biointegrated flexible electronic systems

“…This option is, however, not suitable for capacitive, biosensing applications, and it has only limited value in other possible biointerface measurements, such as those based on thermal or optical interfaces. Barrier layers formed by other deposition techniques, such as plasma-assisted atomic layer deposition (ALD), O 3 -assisted ALD, and anodization show pinhole-like defects as well (39)(40)(41)(42). For example, although plasma-assisted ALD-deposited SiN x has a low intrinsic water vapor transmission rate, pinholes lead to extrinsic effects that limit the encapsulation performance of the entire barrier (40).…”

“…Barrier layers formed by other deposition techniques, such as plasma-assisted atomic layer deposition (ALD), O 3 -assisted ALD, and anodization show pinhole-like defects as well (39)(40)(41)(42). For example, although plasma-assisted ALD-deposited SiN x has a low intrinsic water vapor transmission rate, pinholes lead to extrinsic effects that limit the encapsulation performance of the entire barrier (40). The extent and nature of these types of extrinsic effects are expected to vary depending on the deposition methods, the deposition tools, and the detailed conditions for deposition and postprocessing, but they are unlikely to reach, on a consistent basis, the completely defect-free levels needed for the uses envisioned here.…”

Plasma-assisted atomic layer deposition of HfNx: Tailoring the film properties by the plasma gas composition

“…In order to demarcate the source of O in the HfN x films, a thin layer of dense SiN x ($10 nm) was deposited on top of the HfN x film ($30 nm) in situ, following the same recipe as reported by Andringa et al for the deposition of gas/moisture barrier layers. 36 A decrease in the O content to 10.2 at. % was observed for the HfN x films prepared with 10 s H 2 plasma exposure and SiN x capping layer implying that the O primarily incorporates during the deposition itself.…”

Review—Silicon Nitride and Silicon Nitride-Rich Thin Film Technologies: Trends in Deposition Techniques and Related Applications

“…• C. 91 Subsequent structural and chemical characterization of the SiN x layers indicated the absence of open pores larger than 0.3nm in diameter, with films as thin as 10 nm displaying good barrier properties. A second investigation examined low temperature PE-ALD (<300…”