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

Interface electronic properties of silicon nitride (SiN x )/crystalline silicon (c-Si) are studied. The interface electronic properties are improved by changing NH 3 /SiH 4 flow ratios ( F NH3 / F SiH4 ) of a thin SiN x layer (≃6 nm in thickness) between c-Si and a thick SiN x layer (≃65 nm) deposited with F NH3 / F SiH4 =30, where both SiN x 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 SiN x /thin SiN x /c-Si diodes are 3 ×10 10 cm -2 eV -1 and 0.1 V, respectively. In the deposition of thin SiN x , the interface electronic properties are degraded by exposing Si x H y or N x H y species to a c-Si surface, where these species are produced by photodecomposition of NH 3 /SiH 4 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.