Study of stress in tensile nitrogen-plasma-treated multilayer silicon nitride films

Abstract

International audienceThe authors conducted a physico-chemical analysis of tensile sequential-nitrogen-plasma-treated silicon nitride films, which function as stressor liners in complementary metal oxide semiconductor (CMOS) technologies. These films are made of stacked nanometer-thick, plasma-enhanced, chemical vapor-deposited layers which were individually treated with N(2)-plasma, to increase stress. This study allowed us to monitor the evolution of the films' chemical composition and stress as a function of process parameters such as deposition and post-N(2)-plasma duration. Consistent with secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM) and other physico-chemical analysis results, it was shown that the elementary component of the films can be modeled with a bi-layer consisting of an untreated slice at the bottom that is covered by a more tensile post-treated film. In addition, we observed that longer plasma treatments increase residual stress, SiN bond concentration and layer density, while reducing hydrogen content. The stress increase induced by the plasma treatment was shown to correlate with the increase in SiN bonds following a percolation mechanism that is linked to hydrogen dissociation. Kinetics laws describing both SiN bond generation and stress increase are proposed and it is demonstrated that stress increase follows first-order kinetics. (C) 2011 American Vacuum Society

Dual mechanical behaviour of hydrogen in stressed silicon nitride thin films

“…The films were then formed by sequential deposition/plasma treatment steps. A more detailed description of the deposition process of these tensile films can be found in Morin et al 8 Compressive films were monolayer films deposited at low pressure (2 Torr) and increased plasma power (75 W) to improve atomic peening. The deposited thicknesses of both film families range from 130 to 680 nm.…”

“…Chemical bond types and densities were measured by combining spectroscopic ellipsometry (FX100 ellipsometer from KLA Tencor) and Fourier Transform InfraRed (FTIR) spectroscopy (BIO RAD QS 2200A from Accent). A specific analysis was applied to obtain an overall description of the film chemistry, 8 thus providing quantitative bond concentration results of 10 17 bonds cm À2 with an uncertainty of 60.5. Film density was measured, thanks to a high-precision weighting machine (Mentor SP3 from Metryx).…”

“…1,2 In particular, SiN has been widely used in microtechnology process flow for diverse applications: 3,4 as Etch Stop Layers (ESLs) for their hardness and chemical resistance, 3 as encapsulating layers for their ability to prevent copper diffusion in metal interconnections, 5 as passivation layers for their ability to prevent moisture absorption, 3 as capping passivating layers in microsystems, 6 as anti-reflective coatings for solar cells, 7 and as stress drivers to improve electron mobility of n-MOS transistors. 8 All these SiN thin films are usually amorphous (or nanocrystalline) and hydrogenated. Their chemical organisation has been extensively studied numerically.…”

Atomic Layer Deposition of Silicon Nitride Thin Films: A Review of Recent Progress, Challenges, and Outlooks

“…However, other important factors (e.g., precursors, plasma conditions, plasma treatment) which may modulate the stress were not studied. King and Triyoso et al reported that the intrinsic stress of PEALD SiN x films could be modulated to be either compressive or tensile by varying low-frequency power [ 4 , 5 ], which also holds true for PECVD SiN x films [ 122 , 123 ].…”

A two-step UV curing process for producing high tensile stressed silicon nitride layers

“…With introduction of the 90 nm node geometries the deposition of compressive stressed contact etch stop layers (CESL) for increasing hole mobility and tensile stressed CESL for enhancing electron mobility in dual-stressor liner technology have been introduced in logic device fabrication [1]. For creating highly tensile stressed silicon nitride (SiN) cap layers on NMOSFET, many techniques like in-situ nitrogen plasma treatments [2], multi-layer deposition [3], and subsequent ultraviolet (UV) [4,5] curing cycles have been developed. Conventional UV curing equipment uses broadband lamps at and above 220 nm wavelengths, preferably.…”