Interface Electronic Properties between Silicon and Silicon Nitride Deposited by Direct Photochemical Vapor Deposition

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Abstract
Interface electronic properties of silicon nitride (SiNx)/crystalline silicon (c-Si) are studied. The interface electronic properties are improved by changing NH3/SiH4 flow ratios (F NH3/F SiH4) of a thin SiNx layer (≃6 nm in thickness) between c-Si and a thick SiNx layer (≃65 nm) deposited with F NH3/F SiH4=30, where both SiNx layers are formed by direct photochemical vapor deposition (photo-CVD). In the case of F NH3/F SiH4=120, the minimum interface-trap density and hysteresis obtained from the capacitance-voltage (C–V) characteristics of Al/thick SiNx/thin SiNx/c-Si diodes are 3 ×1010 cm-2 \cdotp eV-1 and 0.1 V, respectively. In the deposition of thin SiNx, the interface electronic properties are degraded by exposing SixHy or NxHy species to a c-Si surface, where these species are produced by photodecomposition of NH3/SiH4 gas mixtures. Injected carriers, which cause hysteresis of the C–V characteristics, are discussed in terms of the barrier height for tunneling and the number of interface traps.