Sarab Preet Singh

Phase stabilization by rapid thermal annealing in amorphous hydrogenated silicon nitride film

We have studied the effect of rapid thermal annealing (RTA) in the context of phase evolution and stabilization in hydrogenated amorphous silicon nitride (a-SiN(x):H) thin films having different stoichiometries, deposited by an Hg-sensitized photo-CVD (chemical vapor deposition) technique. RTA-treated films showed substantial densification and increase in refractive index. Our studies indicate that a mere increase in flow of silicon (Si)-containing gas would not result in silicon-rich a-SiN(x):H films. We found that out-diffusion of hydrogen, upon RTA treatment, plays a vital role in the overall structural evolution of the host matrix. It is speculated that less incorporation of hydrogen in as-deposited films with moderate Si content helps in the stabilization of the silicon nitride (Si(3)N(4)) phase and may also enable unreacted Si atoms to cluster after RTA. These studies are of great interest in silicon photonics where the post-treatment of silicon-rich devices is essential.

Growth kinetics and compositional analysis of silicon rich a-SiNx:H film: A soft x-ray reflectivity study

We report soft x-ray reflectivity measurements near the Si L2,3 absorption edge for Si-rich silicon nitride thin film obtained by Hg-sensitized photochemical vapor deposition. We demonstrate that the precise analysis of optical index profile derived over extended energy region gives compositional details of the film. This nondestructive approach is used in Si-rich silicon nitride film to reveal buried Si-rich interfacial layer. Further, the combined study of soft x-ray reflectivity and optical density obtained from the reflectivity fitting at various photon energies provide a qualitative estimation of the film composition and its growth.

Excitation dependent photoluminescence study of Si-rich a-SiNx:H thin films

We report photoluminescence (PL) investigations on Si-rich amorphous hydrogenated silicon nitride (a-SiNx:H) thin films of different compositions, using three different excitation lasers, viz., 325 nm, 410 nm, and 532 nm. The as-deposited films contain amorphous Si quantum dots (QDs) as evidenced in high resolution transmission electron microscopy images. The PL spectral shape is in general seen to change with the excitation used, thus emphasizing the presence of multiple luminescence centres in these films. It is found that all the spectra so obtained can be deconvoluted assuming Gaussian contributions from defects and quantum confinement effect. Further strength to this assignment is provided by low temperature (300 °C) hydrogen plasma annealing of these samples, wherein a preferential enhancement of the QD luminescence over defect luminescence is observed.

Impact of thermal annealing on interfacial layer and electrical properties of a-SiNx : H/Si

We report the impact of post-deposition thermal annealing (in nitrogen ambient) on the evolution of an interfacial layer between a hydrogenated amorphous silicon nitride (a-SiNx :H) thin film and a Si(100) substrate and its correlation with electrical properties. X-ray reflectivity measurements reveal that the SiNx films under different post annealing temperatures demonstrate variation in the density, thickness and roughness. Also it is found that the interface state density (Dit) is directly related to the interfacial layer density of the film rather than to the surface and interface roughness.

Optical and structural characterization of rapid thermal annealed non-stoichiometric silicon nitride film

A detailed optical and structural characterization is carried out of a silicon nitride film deposited by a Hg-sensitized photo-CVD technique and subsequently subjected to rapid thermal annealing (RTA). An attempt has been made to correlate ellipsometry data with x-ray reflectivity (XRR) and x-ray diffraction data. Both the optical constants and density of the film were found to increase after thermal treatment. RTA treatment resulted in substantial change in the refractive index with more compaction of the film. This is explained in terms of hydrogen terminated defects/voids created due to predominant out-diffusion of hydrogen with RTA treatment.

Recent Progress in the Understanding of Si-Nanostructures Formation in a-SiNx:H Thin Film for Si-Based Optoelectronic Devices

There has been a rapidly increasing interest in the synthesis and characterization of Si- nanostructures embedded in a dielectric matrix, as it can lead to energy-efficient and cost-effective Complementary Metal-Oxide-Semiconductor (CMOS)-compatible Si-based light sources for optoelectronic integration. In the present contribution, first an overview of the SiOx as a dielectric matrix and its limitations are discussed. We then review the literature on hydrogenated amorphous silicon nitride (a-SiNx:H) as a dielectric matrix for Si-nanostructures, which have been carried out using silane (SiH4) and ammonia (NH3) as the reactant gases. Our studies demonstrate that the least amount of hydrogen in the as-deposited (ASD) a-SiNx:H films not only allows in-situ formation of Si-nanostructures but also stabilizes silicon nitride (Si3N4) phase. The recent advances made in controlling the shape and size of Si-nanostructures embedded in a-SiNx:H matrix by swift heavy ion (SHI) irradiation are briefly discussed.

Si‐rich a‐SiNx:H Thin Film a Prospective Material for EUV Lithography: An Optical Response near Si L2,3‐edge

Using Indus‐I synchrotron radiation source, angle dependent soft x‐ray reflectivity measurements in the wavelength region (5–15 nm) near Si L2,3 edge have been performed on Si‐rich a‐SiNx:H (SRSN) thin film. The study shows that experimentally obtained δ values of SRSN film lie in between that of pure Si and Si3N4. Further, comparison of its optical constants with those of other silicon compounds such as SiC and SiO reveals the possibility of SRSN film as a potential material for the next generation 13.5 nm node extreme ultraviolet lithography technology.

Qualitative Estimation of Si‐rich a‐SiNx:H Thin Film Composition by Soft X‐ray Reflectivity Analysis

Soft x‐ray reflectivity measurements on Si‐rich a‐SiNx:H thin film near the Si L2,3 absorption edge are presented. We demonstrate that the combined study of soft x‐ray reflectivity and precise analysis of optical index profile derived over extended wavelength region lengths can provide a qualitative estimation of film composition.

Study of the optical response of Si-rich a-SiNx : H thin film near Si L2,3-edge using soft x-ray reflectivity

Angle-dependent soft x-ray reflectivity measurements in the photon energy range 82.67–248 eV near the Si L2,3 absorption edge have been performed on Si-rich a-SiNx : H (SRSN) thin film deposited by the Hg-sensitized photo-chemical vapour deposition technique. It is found that experimentally obtained δ (dispersion) values of the SRSN film lie in between that of pure silicon (Si) and silicon nitride (Si3N4). X-ray photoelectron spectroscopy measurements suggest that excess silicon is responsible for reducing optical constants values and hence by controlling the silicon amount one can tune the optical constants to desired values. We further compare the soft x-ray optical spectrum of the SRSN film with those of other silicon compounds such as silicon carbide (SiC) and silicon monoxide (SiO) near the Si L2,3 edge region to shows its possibility as a prospective material for the next generation 13.5 nm (91.85 eV) node extreme ultraviolet (EUV) lithography technology.

Optical and structural features of silicon-rich a-SiN x :H thin films

In this work we report a systematic study of fabrication parameters and post-heat treatment on the optical features has been done. Enhancement in optical constant on annealing is attributed phase separation into crystalline silicon (c-Si) and other phases due to out- diffusion of hydrogen. We further report the room-temperature photoluminescence from as-deposited hydrogenated amorphous silicon nitride (a-SiNx:H) films which could be due to formation of silicon nanocrystals and/or structural disorder.