Characterization of nitrogen-rich silicon nitride films grown by the electron cyclotron resonance plasma technique

Abstract

Short title: "Characterization of silicon nitride films grown by electron cyclotron resonance".Classification numbers (PACS): 61.43. Er, 68.55.Ln, 77.84.Bw, 78.30.Ly, 81.15.Gh, 82.80.Yc ABSTRACTAmorphous hydrogenated silicon nitride films have been deposited by the electron cyclotron resonance plasma technique, using N 2 and SiH 4 as precursor gases. The gas flow ratio, deposition temperature and microwave power have been varied in order to study their effect on the properties of the films, which were characterized by Rutherford back-scattering spectrometry, elastic recoil detection analysis (ERDA), Fourier transform infrared spectroscopy, and ellipsometry. All samples show N/Si ratios near or above the stoichiometric value (N/Si=1.33). The hydrogen content determined from ERDA measurements is significantly higher than the amount detected by infrared spectroscopy, evidencing the presence of non bonded H.As the N 2 /SiH 4 gas flow ratio is increased (by decreasing the SiH 4 partial pressure), the Si content decreases and the N-H concentration increases, while the N content remains constant, resulting in an increase of the N/Si ratio. The decrease of the Si content causes a decrease of the refractive index and the density of the film, while the growth ratio also decreases due to the limiting factor of the SiH 4 partial pressure. The infrared Si-N stretching band shifts to higher wavenumbers as the N-H concentration increases.The increase of deposition temperature promotes the release of H, resulting in a higher incorporation of N and Si into the film and a decrease of the N/Si ratio. The effect of increasing the microwave power is analogous to increasing the N 2 /SiH 4 ratio, due to the increase in the proportion of nitrogen activated species. 1 I INTRODUCTIONSilicon nitride (SiN x :H) is an extensively used dielectric in both silicon and III-V semiconductor device technologies. The most usual applications include passivation layers [1,2], optoelectronic devices [3,4], thin film transistors (TFTs) [5,6], and metal-insulatorsemiconductor (MIS) devices [7,8]. Plasma deposited silicon nitride has also emerged as a passivating material for crystalline silicon solar cells, which simultaneously provides good antireflection properties [9,10].Electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) is a well established technique for the deposition of SiN x :H films. As other plasma techniques, it allows low deposition temperatures, satisfying the requirements of ultra large scale integration technology (ULSI) [11,12]. Additionally, substrates are placed outside the plasma region, reducing the damage produced by ion bombardment [13]. Finally, the ECR technique is a very efficient method for the activation of the precursor gases [14,15], obtaining high density plasmas and making possible the use of N 2 instead of NH 3 , thereby reducing the H content of the films.There is extensive research devoted to the analysis of the properties of amorphous hydrogenated silicon nitride films deposited by ECR [...

Annealing-free Si3N4 frequency combs for monolithic integration with Si photonics

“…22, a decrease in the NH 3 gas flow inevitably translates into an increase in the deposition rate. Regarding nitride-rich silicon nitride films, the deposition rate is of the order of 17 nm/min, 23 which is much higher than our deposition rate too.…”

Structural and mechanical properties of amorphous silicon carbonitride films prepared by vapor-transport chemical vapor deposition

“…2(b). The shift of the bands from 779 cm − 1 ([N]= 0 at.%) to 850 cm − 1 ([N]= 27 at.% ) strongly suggests that N atoms are substituted for C atoms in the Si-C local environments since the Si-N stretching vibration in a-SiN films is known to occur in the range of 840-910 cm − 1 [26]. Furthermore, the band intensity decreased by~50% as a result of increasing the N content in the films from 0 to 27 at.%.…”

Stress induced crystallization of hydrogenated amorphous silicon

“…However, nitrogen rich-SiN x also has a lower refractive index relative to stoichiometric silicon nitride films. The volume expansion of a superstoichiometric SiN x film induces a compressive stress in the SiN x film, and the density is reduced [20,21]. Therefore, it was speculated that as the refractive index was reduced from the ideal Si 3 N 4 value (~2.05), the TCE value of the SiN x would increase.…”