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The present study reports the impact of process conditions and post annealing treatment on the stress and physico-chemical properties in different types of plasma enhanced atomic layer deposited (PEALD) SiNx films. More specifically, the SiNx films deposited at 500 °C were annealed subsequently at 1000 °C in N2 ambient for different times ranging between 30 and 6750 s and were subjected to thickness, mass, refractive index, chemical bonds and structure, H content, N/Si stoichiometry, morphology, roughness, and uniformity monitoring. Depending on the deposition process conditions, we confirm the possibility to form, at 500 °C with PEALD, some very compressive SiN films with reduced hydrogen content by controlling the plasma conditions along the deposition process. More interestingly, these compressive films with low hydrogen concentration exhibit high thermo-mechanical stability compared to hydrogenated PEALD and plasma enhanced chemical vapor deposition silicon nitride from this study or reported in the literature, films which typically tend to become tensile with a similar annealing sequence. These results confirm the importance of the plasma power to engineer the as-deposited silicon nitride stress but also highlight the role of hydrogen in the thermal instability of these layers, a low H concentration being needed for a better mechanical stability. [ABSTRACT FROM AUTHOR]

Abstract: A comparison of mechanical properties of amorphous silicon nitride thin films deposited with various techniques used for microelectronic applications was conducted. Nitride films with thicknesses less than 80nm were deposited on (001) oriented silicon wafers by using various methods: low pressure chemical vapor deposition (LPCVD), rapid thermal CVD (RTCVD), atomic layer deposition (ALD) and plasma enhanced CVD (PECVD). The wafer curvature method was used to show that the as-deposited LPCVD, RTCVD and ALD films exhibited tensile residual stresses that decreased with silicon richness. In contrast, the stress of the PECVD as-deposited layers ranged from tensile to ultra-compressive, depending on the exposure to high plasma power and ion bombardment during growth. After high temperature annealing, the LPCVD, RTCVD and ALD nitride stresses were almost unchanged, indicating that these films/substrate systems have significant thermal mechanical stability. In contrast, it was observed that, regardless of the initial stress, the annealed PECVD films developed tensile stress after high temperature treatment, with the same dependence of stress on refractive index as was found with the other deposition techniques. The Young''s moduli, measured by performing nano-indentation on 200nm thick nitride layers, were found for most samples to be correlated with film density. [Copyright &y& Elsevier]

Abstract: To go further in the comprehension of hydrogen desorption mechanisms from PECVD (Plasma Enhanced Chemical Vapour Deposited) silicon nitride, a method to determine the chemical composition of amorphous silicon nitride films using fast and non destructive characterization techniques has been developed. In particular, Silyph name="sbnd" />H, Sincentrations are calculated from Fourier transform infra red spectroscopy, ellipsometry and mass measurement. Next, different PECVD silicon nitride films were annealed at 600°C during 2min. Results show that hydrogen desorption from PECVD silicon nitride depends on film mass density and main chemical reactions leading to hydrogen desorption are identified thanks to the determination of Sincentrations. [Copyright &y& Elsevier]

The 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 N2-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-N2-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. [ABSTRACT FROM AUTHOR]

Abstract: Local stressors techniques are extensively used in CMOS technologies starting with the 90nm node to compensate the mobility loss induced by extensive scale down. The purpose is to generate some strain within the silicon channel to enhance carrier mobility. To achieve nMOS performance at the 45nm node, gate stressors are required in addition to standard nitride liners. With this option, the stress generated within the gate is directly transmitted into the channel and more than 10% gain in saturation current is achievable on nMOS. Stress is generated within the polysilicon gate through annealing under a capping liner. After liner removal, a part of this stress is memorized within the gate material. Final gate stress depends on both polysilicon pre-treatments and liner properties. This paper deals with material studies performed on capping liners in parallel to tests on electrical devices. Important parameters to generate stress under capping are presented. This allows providing a simple model and guidelines for further optimization. [Copyright &y& Elsevier]

Abstract: In the framework of the development of strained channel materials, the mechanical stress induced in silicon by a silicon nitride stressor layer is studied. The investigated samples are sub-micrometric periodic arrays of polysilicon lines deposited on thermally oxidised single crystal (001) Si substrate and capped with silicon nitride. We compare the stress induced in the silicon substrate by three layouts: without Si3N4, with a tensile Si3N4 or with a compressive Si3N4 layer on top of the poly lines. The periodic strain field in silicon is investigated by high resolution X-ray diffraction which is very sensitive to local strain (<10−4) and is non-destructive. The lines array induces a periodic strain field in silicon, which gives rise to distinct satellites in reciprocal space. The intensity of these satellites is related to the strain field in one cell. X-ray reciprocal space maps are measured on a 4 circles goniometer with a laboratory source. First experimental mappings around the symmetrical 004 Si Bragg peak are presented here. Elastic calculations are performed with a Finite Element Modelling code in order to extract the displacement field that is useful for structure factor calculations within kinematical approximation. The calculations are necessary for explaining the experimental reciprocal space maps intensity envelope and comparing the strain induced by the three investigated layouts. [Copyright &y& Elsevier]