Relative stabilities of N-related defects in HfOxNy were extensively studied in terms of formation energies by using first-principles calculations. It was found that two O vacancies, coupled with 2 substitutional N atoms at O sites, was the predominant defect in a low O chemical potential (µO) with doubly positive [(NO)2(VO)2]+2 and neutral [(NO)2(VO)2]0 forms for the p-type and n-type Si substrates, respectively. On

the other hand, the negatively charged substitutional nitrogen [(NO)2]−2 predominated in a higher µO condition. A neutral defect, [(NO)2VO]0, was found to be stabilized in the mid-region of µO, which indicated that the O partial pressure was an important factor to control fixed charges that cause malfunction in HfOxNy-based devices. An electron counting concept was shown to be valid to predict the stable forms of the defects.

Chemical Controllability of Charge States of Nitrogen-Related Defects in HfOxNy - First-Principles Calculations. N.Umezawa, K.Shiraishi, Y.Akasaka, A.Oshiyama, S.Inumiya, S.Miyazaki, K.Ohmori, T.Chikyow, T.Ohno, K.Yamabe, Y.Nara, K.Yamada: Physical Review B, 2008, 77[16], 165130 (6pp)