Hydrogen in low-pressure chemical-vapor-deposited silicon (oxy)nitride films

Abstract

Stability of hydrogen in silicon nitride films deposited by lowpressure and plasma enhanced chemical vapor deposition techniques J. Vac. Sci. Technol. B 7, 150 (1989); 10.1116/1.584707 Characterization of hydrogenation and dehydrogenation of postplasma treated lowpressure chemicalvapor deposited amorphous silicon films Silicon (oxy) nitride films ( SiO x Ny ) have been deposited onto silicon by low-pressure chemical vapor deposition using SiHzCl z , NzO and NH3 or ND 3 • Nuclear reaction analysis, elastic recoil detection, and Rutherford backscattering spectrometry have been used to determine the elemental composition of the films with emphasis on the hydrogen and deuterium content. In the as-deposited, NH 3 -grown films the bulk hydrogen concentration is about 3 at. % for an oxygen! nitrogen atomic ratio (OIN) smaller than 0.4, for OIN> 0.4 it is lower. In 900 and 1000·C vacuum annealed films the bulk hydrogen concentration as a function of OIN goes through a maximum at O/N ::::0.4. By comparing this observation with the D content in ND 3 -grown films as a function ofOIN, a model is deduced which explains this behavior. This model involves an oxygen induced increase of the electronegativity of the atoms to which hydrogen/deuterium is bound. Annealing at 1000 ·C in a Hz/N 2 gas mixture ofNH 3 -grown films results in bulk hydrogen concentrations ranging between those measured after the 1000 ·C vacuum anneal and the values for the as-deposited state. The chlorine concentration increases with increasing oxygen content in the oxynitride films from 0.04 at. % at OIN = 0 to 0.65 at. % at OIN = 00. Implications of the data and the proposed model for the electrical performance of the silicon (oxy ) nitrides are briefly discussed.

Characterization of LPCVD and PECVD silicon oxynitride films

“…For O/(0 + N) > 0.3 the ratio D/N in the films decreases with increasing oxygen content [8], whereas the concentration ratio N-H/N as measured with IR increases [14]. This apparent discrepancy between the ERD and the IR results may be found in the assumptions made to derive the relevant physicochemical information.…”

“…We conclude that the decomposition of NH, becomes more difficult in situations where more 0 is incorporated. Furthermore the N-H bonds become increasingly more stable against annealing for O/(0 + N) < 0.3 [8]. These two effects seem interrelated.…”

“…The presence of Si-H in the interfacial region has also been suggested on the basis of electrical measurements (see section 3.1). In fact, small hydrogen pile ups have been observed in H profiling measurements, but the significancy of the occurrence was doubted [8,34]. also because the H appeared not to remain with sufficient stability in the insulator films to allow for good statistics during profiling with high energy ion beams.…”

“…However in ERD the depth resolution for H is poor. To obtain the depth distribution of H, nuclear reaction analysis (NRA) is commonly used [8,9]. When the reaction *H("N, (uy)12C is used the depth resolution amounts to about 5 nm in the surface region.…”

Hydrogen distribution in oxynitride/oxide structures

“…As N,O is less reactive than NH, [8], the N,O/NH, ratio must be increased more than proportional to the desired O/N ratio. Thus the supply of hydrogen is strongly reduced when films with a high O/N ratio are grown.…”