Structural properties of N-rich a-Si - N:H films with a low electron-trapping rate

Abstract

Hydrogenated amorphous silicon nitride films with a high nitrogen content were prepared by RF plasma-enhanced chemical vapour deposition from a mixture of and at . The influence of the main operating variables on the quality of the material was examined. Characteristics and properties of the films were investigated using optical absorption, infrared spectroscopy, x-ray photo-electron spectroscopy and capacitance - voltage measurements. From infrared transmission and reflection measurements, it was found most of the IR peaks obtained by direct transmission in the range , which have often been mentioned in the literature, are caused not by absorption but rather by a strong reflection due to the Reststrahlen effect. IR studies carried out with polarized light revealed an anisotropic beam - sample interaction probably due to short-range phonon vibration modes: a parallel `LO mode' (), a parallel and perpendicular `TO mode' (). For sufficiently high values of the N/Si ratio, a decreasing percentage of or an increasing RF power leads to a decrease in the trapped charge density which should be related simultaneously to an increase in the N/Si ratio and a decrease in the Si - H bond density in the deposited films. It is suggested that, under our experimental conditions, the charged particle bombardment due to the RF discharge does not play an important role in the charge trapping and that the trapping rate seems to be controlled only by the nature of the traps.

Plasma treatment studies of MIS devices

“…A similar decrease in (D ) with the increase in the flow ratio of NH 3 /SiH 4 for the films prepared without NH 3 plasma pretreatment has also been reported by others [29,30]. The values of (D ) are observed to depend strongly on film composition and decreases with increase in the N/Si ratio.…”

“…The refractive index n decreases from 1.83 to 1.72 for the samples prepared without NH 3 plasma pretreatment while n decreases from 1.80 to 1.67 for the NH 3 plasma pretreated samples as the flow ratio of NH 3 /SiH 4 increases from 1.33 to 12.66 corresponding to silicon-rich to nitrogen-rich films. A similar decrease of refractive index n with increase in the flow ratio of NH 3 /SiH 4 for the silicon nitride films prepared without NH 3 plasma pretreatment has also been reported by others [29,30,32]. The small decrease in the refractive index for the NH 3 plasma pretreated samples may be ascribed to the slight increase in the N/Si ratio because of the nitridation.…”

Impact of SiN Composition Variation on SANOS Memory Performance and Reliability Under nand (FN/FN) Operation

“…In an earlier work [19], it has been shown that the characteristics of nonstoichiometric SiN traps demonstrate a strong 0018-9383/$26.00 © 2009 IEEE decrease in the trapped charge density when films become rich in N-H bonds. It has also been shown [20], [21] that the Sirich (Si + ) SiN has higher electron trap density at relatively shallow energy levels, allowing them to get readily discharged of the electrons during E operations [22].…”

Opto-Structural Properties of Silicon Nitride Thin Films Deposited by ECR-PECVD

“…It increases quite rapidly to a limit value of 3.8 eV as the refractive index n decreases to value close that of Si 3 N 4 (see Figure 2, Table 1). This is mainly due to the optical properties controlled by Si-N and N-H bonds [19]. Tauc slope B could provide details on the spreading tails of valence and conduction bands.…”