# Study on Single-Event Transient Hardness of Semi-Enclosed Gate NMOS
## 3 Analysis of Simulation Results
### Analysis of the Change of Current Peak Value Caused by Different LET Incidence  
To delve deeper into the analysis of the drain current simulation output results caused by heavy ions with different LET values incident on the semi-enclosed gate NMOS device, it is essential to examine the internal physical changes within the device post-incidence. The simulation primarily compares and analyzes the mechanisms of device changes following the incidence of particles with LET values of 20 MeV\(\cdot\)cm\({}^{2}\)/mg and 70 MeV\(\cdot\)cm\({}^{2}\)/mg. From Figure 11, it can be inferred that after heavy ions enter the semi-enclosed gate NMOS device, the radiation range of particles with a 20 MeV\(\cdot\)cm\({}^{2}\)/mg LET value is roughly similar to that of particles with a 70 MeV\(\cdot\)cm\({}^{2}\)/mg LET value. However, the average energy density of the 70 MeV\(\cdot\)cm\({}^{2}\)/mg LET particles within the device is nearly an order of magnitude higher than that of the 20 MeV\(\cdot\)cm\({}^{2}\)/mg LET particles. Consequently, the ionization density in the semi-enclosed gate NMOS device is also an order of magnitude higher for the 70 MeV\(\cdot\)cm\({}^{2}\)/mg LET particles. This results in the generation of more electron-hole pairs in the channel, enabling the drain to collect more electrons. This leads to the situation depicted in Figure 12, where Figure 12a represents the 20 MeV\(\cdot\)cm\({}^{2}\)/mg LET case and Figure 12b represents the 70 MeV\(\cdot\)cm\({}^{2}\)/mg LET case. From Figure 12, it is evident that, compared to the potential distribution caused by the 20 MeV\(\cdot\)cm\({}^{2}\)/mg LET particles, the high-potential region at the drain for the 70 MeV\(\cdot\)cm\({}^{2}\)/mg LET particles is smaller and shifted to the left. This configuration increases the distance between the high-potential drain and the low-potential source, resulting in a  
Figure 11: Heavy ion charge densities after incidence of different LET heavy particles. (**a**) Image at LET = 20 MeV\(\cdot\)cm\({}^{2}\)/mg; (**b**) image at LET = 70 MeV\(\cdot\)cm\({}^{2}\)/mg. Figure 10: Electric potential gradient distribution at 10\({}^{-9}\) s time. (**a**) Sectional view parallel to the conductive channel. (**b**) Sectional view perpendicular to the conductive channel. longer current path. This facilitates the flow of more electrons, allowing the drain to detect a higher current. Further supporting this analysis, Figure 13 provides a clearer conclusion. By comparing the current density maps in Figure 13a for the 20 MeV-cm\({}^{2}\)/mg LET case and Figure 13b for the 70 MeV-cm\({}^{2}\)/mg LET case, it is observed that, regardless of the LET value, the current density is highest in the channel, indicating that the channel is conducting. However, the average current density in the semi-enclosed gate NMOS device for the 70 MeV-cm\({}^{2}\)/mg LET case is an order of magnitude higher than that for the 20 MeV-cm\({}^{2}\)/mg LET case, generating more current. This explains why the simulation results show an increase in the peak drain current as the LET value increases. In summary, a higher LET value leads to an increased ionization density within the device, which subsequently causes an elevation in the average current density, thereby generating more pronounced transient current responses. This analysis provides a comprehensive understanding of how different LET values affect the single-event transient behavior of semi-enclosed-gate NMOS devices. It reveals that this influence mechanism is essentially consistent with that observed in conventional NMOS transistors. It can be concluded that, from the perspective of single-event transient mechanisms, there is no need to overly consider potential incompatibility caused by differences in single-event transient mechanisms when replacing traditional NMOS with enclosed-gate NMOS. This finding offers valuable insights for the design of radiation-hardened integrated circuits. Figure 12: Electrostatic potential of peak current moment.