High energy ion irradiation effects on thin oxide p-channel MOSFETs

Abstract

P-channel MOSFETs of a commercial 0.25 /spl mu/m CMOS technology have been irradiated by high linear energy transfer (LET) iodine (I) and low LET silicon (Si) ions up to 300 Mrad(Si) and 500 Mrad(Si), respectively. Threshold voltage variations (/spl Delta/V/sub TH/) up to -0.46 V and -0.44 V have been measured at the highest I and Si doses. Both oxide positive trapped charge (/spl Delta/V/sub OX/) and interface states (/spl Delta/V/sub IT/) contribute to /spl Delta/V/sub TH/ with a ratio /spl Delta/V/sub IT///spl Delta/V/sub OX/=1 (<1) for high (low) LET ions. After 40 days at room temperature most of the positive charge is recombined by electron tunneling from the oxide interfaces, while only a small amount (6%-16%) of interface states is annealed. A huge 1/f noise increase (higher for I ions) is observed after irradiation. Finally radiation induced soft breakdown (radiation induced leakage current) conduction through the gate oxide is generated by high (low) LET ions for |V/sub g/|>1.6 V (>3.4 V).