The Effects of Displacement Damage on Ionization Effect in SiO₂ Layer of Bipolar Transistor

The interaction mechanism between displacement damage and ionization damage in SiO2 layer has been researched on gate-controlled lateral p-n-p transistor (GLPNP). The sequential irradiation experiments of 400-keV O ions with high dose rate $\gamma $ -rays were carried out, and the degradation and defect evolution results of the device were analyzed by the reciprocal change of current gain change, gate sweep (GS) curve, and deep level transient spectrum (DLTS) results. The results show that there is a negative direct synergistic effect between 400-keV O ions and Co- $60~\gamma $ -rays in GLPNP. At the same time, combined with the GS curve and DLTS results, it can be concluded that the displacement defects of 400-keV O ions in SiO2 layer of GLPNP transistors will capture the holes generated by Co- $60~\gamma $ -rays, thus forming a large number of positive oxide charges ( $N_{\mathrm {ot}}$ ). These $N_{\mathrm {ot}}$ are like “space charge wall,” hindering the movement of protons and holes to the Si/SiO2 interface, and thus inhibiting the generation of interface trap ( $N_{\mathrm {it}}$ ). Due to the decrease of $N_{\mathrm {it}}$ and the increase of positive $N_{\mathrm {ot}}$ , the damage of transistor is weakened. The experimental results show the effects of displacement damage on the ionization effect in SiO2 layer and, more important, provide direct evidence for the space charge model.