Atomic Layer Deposition of Silicon Nitride from Bis(tert-butylamino)silane and N₂ Plasma

Abstract

Atomic layer deposition (ALD) of silicon nitride (SiNx) is deemed essential for a variety of applications in nanoelectronics, such as gate spacer layers in transistors. In this work an ALD process using bis(tert-butylamino)silane (BTBAS) and N2 plasma was developed and studied. The process exhibited a wide temperature window starting from room temperature up to 500 °C. The material properties and wet-etch rates were investigated as a function of plasma exposure time, plasma pressure, and substrate table temperature. Table temperatures of 300-500 °C yielded a high material quality and a composition close to Si3N4 was obtained at 500 °C (N/Si=1.4±0.1, mass density=2.9±0.1 g/cm3, refractive index=1.96±0.03). Low wet-etch rates of ∼1 nm/min were obtained for films deposited at table temperatures of 400 °C and higher, similar to that achieved in the literature using low-pressure chemical vapor deposition of SiNx at >700 °C. For novel applications requiring significantly lower temperatures, the temperature window from room temperature to 200 °C can be a solution, where relatively high material quality was obtained when operating at low plasma pressures or long plasma exposure times.

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

“…%. 23 In our case, closer inspection via XPS revealed a relative decrease in the C at. % from 13 at.…”

“…Film deposition HfN x thin films of $50 nm in thickness were deposited on 100 mm Si(100) substrates with 450 nm SiO 2 using an Oxford Instruments FlexAL ALD reactor, 23,24 equipped with an inductively coupled remote plasma (ICP) source with an alumina dielectric tube. The deposition chamber of the ALD reactor was pumped down by a turbomolecular pump to a base pressure of 1.6 Â 10 À6 Torr before every deposition and thereafter the substrate was transferred to the chamber from the load-lock.…”

Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

“…Specifically to address the needs of modern IC and memory processes we have purposely limited substrate temperatures to maximally 350 • C. We have found that across multiple chemistries, different commercial PEALD reactors, and a variety of process conditions, there is a strong correlation between the density of the SiN x films and their WER. In a recent evaluation of PEALD SiN x from BTBAS, 10 the WER and density of thin films was reported. The results presented there follow the correlation presented here well.…”

“…10,14,15 To improve thin film properties (crystallinity, morphology, density, trap density) rapid thermal annealing (RTA) is commonly used. However, the thermal budget of RTA should not exceed roughly 400 • C for most IC processes.…”

Plasma-Enhanced Atomic Layer Deposition of SiN–AlN Composites for Ultra Low Wet Etch Rates in Hydrofluoric Acid

“…[13][14][15] Previously, plasma annealing or extensions of in-cycle plasma during PEALD have shown similar improvements in thin film properties. 11,16 One of the benefits of ALD is the ability to deposit nanolaminates or composite films of several different materials by utilizing the cyclic nature of the deposition process. Historically this was introduced decades ago for HfO 2 -Ta 2 O 5 dielectric films in electroluminescent displays.…”