Change in ion beam induced current from Si metal-oxide-semiconductor capacitors after -ray irradiation

Si金属-酸化膜-半導体キャパシタからのイオンビーム誘起電流の線照射による変化

大島 武; 小野田 忍; 平尾 敏雄; 高橋 芳浩*; Vizkelethy, G.*; Doyle, B. L.*

Oshima, Takeshi; Onoda, Shinobu; Hirao, Toshio; Takahashi, Yoshihiro*; Vizkelethy, G.*; Doyle, B. L.*

トータルドーズ効果がシングルイベント効果に及ぼす影響を明らかにする目的で、n型及びp型シリコン(Si)基板上に金属-酸化膜-半導体(MOS)キャパシタを作製し、線照射前後のイオンビーム誘起過渡電流(TIBIC)測定を行った。室温にて6.3kGy(SiO)の線照射を行ったMOSキャパシタの容量-電圧特性からフラットバンドシフトを求めたところ、n型は12.3V、p型は15.2Vという値が得られた。酸素15MeVマイクロビーム入射によるTIBIC測定を行ったところ、線照射によりn型ではTIBICシグナルのピークが低下、p型では増加した。TIBICシグナルピークの印加電圧依存性を調べたところ、n型では13V、p型では15Vシフトさせると照射前後で印加電圧依存性が一致することが見いだされた。この値は、フラットバンドシフトと良い一致を示しており、このことより、線照射により酸化膜中に発生した固定電荷に起因するゲート電圧のシフトがTIBICシグナルに影響したといえる。

Metal-Oxide-Semiconductor (MOS) capacitors were made on both n- and p-type Si substrates (n-MOS, and p-MOS). These MOS capacitors were irradiated with -rays at a dose of 6.3 kGy (SiO) at room temperature. The capacitance-voltage characteristics for MOS capacitors were measured before and after irradiation. The flat band shift for n-MOS and p-MOS capacitors due to -ray irradiation was -12.3 V and -15.2 V, respectively. As for the generation of interface traps, the values for n-MOS and p-MOS capacitors were estimated to be 0.510 and 1.710/cm, respectively. Transient Ion Beam Induced Current (TIBIC) obtained from these MOS capacitors were compared before and after -ray irradiation. For n-MOS capacitors, the peak height of TIBIC signals decreased after -ray irradiation. On the other hand, the peak height of TIBIC signals for p-MOS capacitors increased after -ray irradiation. The applied bias dependence of the peak height of TIBIC signals for MOS capacitors irradiated with -rays can be matched to that for ones before -rays irradiation by shifting the voltage by -13 V for n-MOS capacitors and by -15 V for p-MOS capacitors. These voltage values are in good agreement with the flat band voltage shifts due to -ray irradiation. Since flat band shift occurs due to the generation of positive charge trapped in gate oxide, the change in TIBIC signals observed for MOS capacitors due to -ray irradiation can be interpreted in terms of positive charge generated in oxide.