AES AND HRTEM STUDY OF AN A-SINX-H/W/WSIX/A-SINX-H MULTILAYER STRUCTURE REALIZED BY PEVCD

A multilayer insulator-metal-insulator capacitive structure was realized by plasma-enhanced chemical vapour deposition for a discharge frequency of 35 kHz. The chosen materials were amorphous hydrogenated silicon nitride as the insulator and tungsten as the metal. An interlayer of tungsten silicide used as an adhesion layer is deposited between W and a-SiN(x):H. An AES depth profiling study coupled with high-resolution transmission electron microscopy observation showed the presence of interphases: the interfacial zone between a-SiN(x):H and W is constituted by a WN(x) interphase approximately 10 nm deep. Small crystallites are observed in tungsten-based materials. The presence of a mixed phase containing tungsten, silicon, nitrogen and a small amount of oxygen is obvious and noticed on the AES spectra at the WSi(x)/a-SiN(x):H interface: its thickness appears to be approximately 7 nm.