Physicochemical Characterization of Annealed PolySi/NIDOS/SiO₂ Structures

Abstract

Physicochemical characterizations of polysilicon thin multilayer films have been studied after annealing. In-situ heavily boron-doped polysilicon (poly=Si) and nitrogen-doped silicon (NIDOS) films were deposited by low-pressure chemical vapor deposition (LPCVD) onto an oxidized monocrystalline silicon substrate. Secondary ion mass spectrometry (SIMS) profiles showed a boron diffusion reduction in the NIDOS layer. In addition, Fourier transform infrared spectroscopy (FTIR) analysis clearly showed an evolution of the absorption picks related to the nitrogen atom in the complex form leading to boron atom activation in the films. Therefore, this multilayer structure can be largely used for metal-oxide-semiconductor (MOS) devices.

Study of Nitrogen Effect on the Boron Diffusion during Heat Treatment in Polycrystalline Silicon/Nitrogen-Doped Silicon Thin Films

“…This is certainly due to the dissociation of the Si-N and B-N-B bonds that enhances the formation of BN complexes and reduces the diffusion of B atoms. This result is in agreement with the works of Chao et al 33) We notice that the absorption intensity of the sp 3 BN complex is larger than the sp 2 BN one versus annealing conditions, 31) i.e., the concentration of the sp 3 BN complex in the film is larger than the h-BN.…”

“…These activation low values are due to the preference of N atoms for interstitial rather than substitutional sites. 31) The B diffusion coefficient values are 100 times smaller in the NIDOS layer than the one in the poly-Si layer. The NIDOS's B acceleration rates are greater than 1.…”

Complex boron redistribution kinetics in strongly doped polycrystalline‐silicon/nitrogen‐doped‐silicon thin bi‐layers

“…Two related processes limit the realization of this goal: (i) the enhanced redistribution of the B during the thermal dopant‐activation annealing, which causes B penetration through thin oxides from the p + poly‐Si gate into the underlying layers 3, and (ii) the formation of electrically inactive B clusters and B precipitates 4,5, which decreases the dopant activation rate. The use of low‐energy doping methods, co‐doping techniques, low thermal annealing temperatures, short annealing times, amorphous‐silicon layers, and thin Nitrogen‐Doped‐Silicon (NiDoS) layers have been practiced to avoid the doping depletion of p + polysilicon gate at the oxide interface 6–8. Currently, significant research efforts are focused on improving the B activation and reducing fast B diffusion behaviour; problem common to all the practiced methods and technics.…”

“…Currently, significant research efforts are focused on improving the B activation and reducing fast B diffusion behaviour; problem common to all the practiced methods and technics. In particular, recent studies have revealed that in‐situ NiDoS layers are efficient B redistribution barriers 7,8. However, several physical phenomena have so far not been modeled sufficiently.…”