Tradeoff Between Low-Power Operation and Radiation Hardness of Fully Depleted SOI pMOSFET by Changing LDD Conditions

The interrelation between off-leakage as consideration of low-power operation and X-ray radiation hardness has been evaluated in view of optimizing the lightly doped drain (LDD) concentration of fully depleted silicon-on-insulator pMOSFET. The MOSFET with relatively low LDD concentration called ultralow-power P channel LDD (ULP-PLDD) shows a lower off-leakage of 0.1 pA/ $\mu \text{m}$ but limited X-ray radiation tolerance, such that the drain current is reduced by $\sim 80$ % after 112-kGy(Si) X-ray irradiation due to radiation-induced gate length modulation (RIGLEM), while the MOSFET with six times higher LDD concentration called radiation-hardened PLDD (RH-PLDD) shows much higher radiation tolerance that the drain current reduction is $\sim 20$ % for the same radiation dose because of RIGLEM improvement by the elimination of the offset structure employed in ULP-PLDD. The off-leakage of RH-PLDD is one order of magnitude higher than that of ULP-PLDD as $\mu \text{m}$ . It is shown that there is such a tradeoff between low-power operation and radiation hardness.