Silicon Nitride Films by Reactive Sputtering

Abstract

Silicon nitride films (from 500 to 7500A in thickness) have been deposited on silicon and silicon dioxide by reactive sputtering of a silicon cathode in a N2 glow discharge. Both d-c and rf sputtering have been investigated. Physical and chemical properties of silicon nitride films prepared by sputtering were examined in reference to the process variables. The rate of deposition was aDDroximately proportional to the square root of rf power density. Film density increased with power density, and decreased with gas pressure. Optimum gas pressure was in the range 3-10 x 10 -3 Torr. Higher pressures resulted in less dense and electronically leaky films. Dielectric constant and etch rate in HF solution appeared to correlate well with film density. Residual pressure higher than I-2 x 10 -6 Torr was found to have a most detrimental effect. Argon and nitrogen gas mixtures resulted in excess silicon incorporation in the deposited nitride films.Silicon dioxide has for the past several years been the most important material to serve the multiple function of insulation, passivation, and diffusion masking. Because of its chemical nature and its structural characteristics, there are a number of shortcomings inherent in silicon dioxide. The most serious of these is its low resistance to diffusion of certain impurities and to field migration of ions, which causes instability and deterioration of surface characteristics of electronic devices, and, in particular, field effect devices. From the properties of crystalline silicon nitride one may extrapolate to the generally superior properties of amorphous silicon nitride compared to silicon dioxide, except for higher electronic conductivity.Precisely because of its desirable high resistance to the diffusion of atomic, molecular, or ionic species, silicon nitride cannot be grown on a silicon substrate by thermal nitridation, either in nitrogen or in anhydrous ammonia, in contrast to the thermal oxidation of silicon in oxygen and in steam. Experiments with thermal nitridation (1) and plasma anodization (2) failed to produce coherent silicon nitride films on silicon substrates. In addition, thermal nitridation or oxidation has a limitation on the scope of its use to silicon only. A deposition method thus seems to be a more logical approach.Sterling and Swann (3) and Doo et al. (4) have succeeded in the deposition of continuous amorphous silicon nitride films by means of vapor phase reaction of silane and anhydrous ammonia. At the same time the authors and Pennebaker (5) also succeeded in obtaining continuous silicon nitride films, properly identified as silicon nitride (dielectric constant 6.0-7.0; IR absorption band at 11.5-12~) by means of d-c and rf reactive sputtering, respectively. Recently, others have described various processes for depositing silicon nitride (6).Sputtering deposition of insulating-passivating films over semiconductors is a process which involves more difficulties than the sputtering of metal films. Some of these are: (i) most insulating films are chemical compo...

Some Properties and Electrical Instabilities in RF Sputtered Niobium Oxide Films

“…4 are typical ones representing niobium oxide as sputtered in a pure oxygen atmosphere at power densities of 0.32, 0.80, and 1.25 W/cm 2, respectively, as well as the 800~ annealed specimens. Similar observations of the deterioration of the silicon surface properties in using high power densities were also reported by Hu and Gregor (13) and Salama ~14). These curves indicate that the total surface charge, as measured from the fiat-band voltage of the C-V characteristics, increases with sputtering power density.…”

“…The film thickness for the respective sample is tabulated in Table I. Low film density related to low power density has been reported (13,14). Similar observations of the deterioration of the silicon surface properties in using high power densities were also reported by Hu and Gregor (13) and Salama ~14).…”

Nitrogen as dopant in silicon and germanium

“…The absorption band at 950 c n -l strengthens, and the absorption band at 800 c n -I weakens and shifts to shorter wavelengths. It was suggested [81,82] that the absorption band at v2 = 950 cm-1 refers to crystalline silicon nitride, whereas the band at v1 = 800 ciii-1 to the amorphous one. A shift of the 800 cm-l band for the 1017 cni-2 implant after 1000 "C (20 min) annealing to the side of short wavelengths is found in [78].…”

Polarisation behaviour and corrosion initiation mechanisms of Mo coated with amorphous hydrogenated silicon alloy thin ceramic films

“…r o1 -r 1 and r o2 -r 2 ) of the anodic models (Table 2), and the data for d and i C,Mo (planar) . The value of d was estimated to be approximately 70 mm using equation (11) based on an overall average value of 10 23 A cm 22 for i C,Mo (planar) of bare Mo in the potential range -0 . 9 to -1 .…”