Relationship between x-ray-produced holes and interface states in metal-oxide-semiconductor capacitors

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Abstract
Metal‐silicon dioxide‐silicon capacitors were irradiated with soft x rays to 40 krads (SiO2) with different biases (−3 to +12 V) at 83 K. The number of interface states generated after samples were warmed was found to bear a linear relation with the flatband voltage shift measured before warm up. A one‐to‐one relationship was observed between the number of interface states generated in the central 0.7‐eV portion of the Si band gap during a one year storage at room temperature and the number of holes that moved to the Si–SiO2 interface during warm up. Annihilation of the x‐ray‐generated holes by photoinjection of electrons before warm up prevented the generation of interface states. Both experiments support a cause‐and‐effect relationship between holes in the oxide and interface states generated in the metal‐oxide semiconductor structure.