Threshold voltage adjustment of pMOS-radiation field-effect transistor with thick thermal oxide

The pMOS-RADFET (radiation field-effect transistor) as a microdosimeter has been widely applied in spacecraft, medicine and personal dosimetry. Thick gate-oxide and zero threshold voltage (V_th) are two critical factors to achieve a high performance pMOS-RADFET. In this reported work, threshold voltage adjustment techniques for a thick gate oxide RADFET by B⁺ implantation are systematically simulated by Silvaco technology computer-aided design, including implanting energy, implanting dose and annealing conditions. Impurity distributions in gate oxide and silicon substrate are analysed. The results show that the thicker the gate oxide is, the higher the implanting energy and larger dose for tuning V_th to 0 V. Both the annealing temperature and the time have to be as low and as short as possible on the premise of sufficient ion activation.