Direct observation of electrically active interfacial layer defects which may cause threshold voltage instabilities in HfO2 based metal-oxide-silicon field-effect transistors

We show that a Si∕HfO2 interfacial layer defect with an electron spin resonance spectrum similar to that of some E′ center variants responds to oxide bias consistent with an amphoteric defect. The spectrum is weakly orientation dependent indicating that the defect does not reside in a completely amorphous matrix. The defect’s spin lattice relaxation time is much shorter than that of conventional E′ centers suggesting that the defect involves some coupling of a Hf atom to a nearby oxygen deficient silicon dangling bond defect. This defect very likely plays an important role in widely reported instabilities in HfO2 based transistors.