Variations of trap states and dangling bonds in CVD Si3N4 layer on Si substrate by NH3/SiH4 ratio

This study is concerned with deep trap densities and energy levels in CVD Si₃N₄ layers deposited on Si substrates at 700°C with various gas flow ratio NH₃/SiH₄. As the ratio NH₃/SiH₄ increases from 10 to 1000, the trap density decreases from 8 × 10^l9 t0 2 x l0¹⁹cm⁻³, and energetical distribution of trap states becomes lower and/or electron emission probability from trap states less. The results are discussed in terms of chemical and optical properties of Si₃N₄ film revealed by infrared absorption, Auger electron spectroscopy, and ellipsometry. It is shown that (i) Si dangling bonds create deep trap states and (ii) 0 and H atoms act as terminators to decrease trap density. A part of this paper was presented at the 23rd Annual Electronic Materials Conference, University of California, Santa Barbara, 1981. On leave from Yasu Plant, IBM Japan Ltd., Yasu-cho Shiga 520-23, Japan.