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A 29Si-NMR INVESTIGATION OF AMORPHOUS HYDROGENATED SILICON NITRIDE

MARK A. PETRICH, RHETT E. LIVENGOOD, DENNIS W. HESS Department of Chemical Engineering, Berkeley, CA 94720-9989.

JEFFREY A.

REIMER AND

University of

California,

ABSTRACT We amorphous prepared studied magnetic shows a hydrogen

study of of a spectroscopic the results present was silicon nitride. The nitride hydrogenated was by plasma enhanced chemical vapor deposition and and solid-state nuclear with infrared absorption (IR) film This nitride resonance (NMR) spectroscopies. distribution of hydrogen: particularly interesting atoms are nearly exclusively bound to nitrogen.

INTRODUCTION as a silicon nitride is commonly used Plasma deposited and is being layer for integrated circuits passivation applications [11. considered for photovoltaic and dielectric of silane and The material is usually grown from a mixture the with consequent incorporation of hydrogen from ammonia, bonded hydrogen poses In passivation layers, this feed gases. layers, into other circuit a problem because it may diffuse step in As a first overall circuit performance. degrading of we address the problems understanding this phemomenon, and determining where the hydrogen is located in the material atoms. determining local bonding configurations of the silicon

EXPERIMENTAL Film Production film was prepared in a Our amorphous silicon nitride The electrode coupled, quartz plasma reactor. capacitively is 2.9 cm. spacing diameter is 5.7 cm and the electrode standard shown in Table 1, were fairly Reaction conditions, which is higher [1,2] with the exception of the power density, than usually reported. Substrate materials were crystalline The aluminum foil was dissolved in and aluminum foil. silicon NMR the film as a powder for the dilute HC1 to recover index, and refractive experiments. Table 2 gives thickness, compositional information about the film.

Mat. Res. Soc. Symp. Proc. Vo4.70. , 1986 Materials Research Society

338

Table 1 Reaction Conditions Silane Flow Rate -3 sccm Ammonia Flow Rate -30 sccm He Flow Rate -27 sccm RF frequency -13.56 MHz2 2 Power Density -2 Watts/cm Pressure -300 mtorr Substrate Temperature -300 0

Table 2 Film Properties Deposition Rate Refractive Index N/Si ratio inferred by comparing reported data Ell.

--

240 A/minute * 1.841 1.1

---

refractive

index

with

previously

Infrared Absorption Spectroscopy The IR absorption spectrum is shown in Figure 1. The N-H stretching mode at 3360 wavenumbers, Si-H stretching mode at 2160 wavenumbers, N-H bending mode at 1190 wavenumbers, and SiN modes at 850 wavenumbers have all been previously reported in films of this type. 11,2,3)

Wn-v.enurbers

Figure 1 Infrared Absorption Spectrum

339

Nuclear

Maqnetic

Resonance

We decided to study this film with NMR for two reasons: NMR is quantitative and NMR is selective. The NMR signal is directly proportional to the number of observed nuclei, which allows quantitative comparison of peak areas. The selectivity of NMR comes from our experimental ability to selecti