**6. Impact of film doping level on the JL-DGFET transient response**

For JL-DGFET, we also investigated the impact of channel doping level on the drain current transient and bipolar amplification. Three channel doping levels have been considered in simulation: 1×1019, 2×1019 and 3×1019 cm-3. In JL-DGFET the channel thickness has to be sufficiently small in order to be able to fully deplete the channel of carriers and to turn the device off [29]. The higher the channel doping level, the smaller the film thickness needs to be. This condition is satisfied for all the doping levels and the film thickness considered here. All devices have been calibrated to fill the ITRS Low-Power requirements for the technology node corresponding to the year 2015 [5]. In order to facilitate the comparison, the gate work-function has been finely tuned to obtain the same off-state current (IOFF) for all devices.

When the channel doping increase, the floating body effects are enhanced and the drain current transient is longer, as shown in Fig. 15. Both the collected charge (Fig. 16) and bipolar ampli‐ fication (Fig. 17) increase with the channel doping. Impact ionization is also larger for higher doping levels, which additionally contribute to enhance the bipolar amplification. Very high values of the bipolar gain are found for a channel doping of 3×1019 cm-3, but these values are reduced when a larger ion track radius is considered in simulation. Finally, at very high LET the electric field collapses and the bipolar gain decreases below 2.5 for all devices.

0

0.1 1 10 100

Investigation of Sensitivity to Heavy-Ion Irradiation of Junctionless Double-Gate MOSFETs by 3-D Numerical Simulation

3×1019 cm-3

) and ion strike positions between the middle of the

) (for all ion strike

1×1019 cm-3 2×1019 cm-3 http://dx.doi.org/10.5772/57048

245

LET (MeV/(mg/cm2))

**Figure 17.** Bipolar amplification as function of LET in JL-DGFET for different film doping levels. VG=0 V and VD=0.75 V.

In conclusion, this chapter presented a detailed investigation of the radiation sensitivity of JL-DGFET by 3-D numerical simulation. In particular, the bipolar gain of JL-DGFET has been compared with that of more conventional inversion-mode devices such as FDSOI and IM-DGFET. We have firstly shown that for an ion strike in the middle of the channel, IM-DGFET shows a lower bipolar gain than JL-DGFET and FDSOI (for all LET values). We also studied the impact of various parameters of the ion track (characteristic time and track radius) on the drain current transient and bipolar gain of JL-DGFET. Our results show that modifying these parameters does not change the previous conclusion, the bipolar gain of IM-DGFET being always smaller than those of JL-DGFET and FDSOI. However, a thorough study of the bipolar gain as a function of the ion strike position along the channel showed that JL-DGFET has a lower bipolar gain than IM-DGFET and FDSOI for some particular conditions, precisely for

channel and the drain contact. These results are also confirmed by already published experi‐ mental and simulation data obtained on FD SOI MOSFETs with longer channels. JL-DGFET

is also better than FDSOI for low LET values below 0.5 MeV/(mg/cm2

20

40

Bipolar amplification

LET values superior to 20 MeV/(mg/cm2

Daniela Munteanu and Jean-Luc Autran

CNRS & Aix-Marseille University, Marseille, France

**7. Conclusion**

positions).

**Author details**

60

80

**Figure 15.** Drain current transient in JL-DGFET for different film doping levels. The incident ion LET is 1 MeV/(mg/cm2). VG=0 V and VD=0.75 V.

**Figure 16.** Collected charge in JL-DGFET for different film doping levels. The incident ion LET is 1 MeV/(mg/cm2). VG=0 V and VD=0.75 V.

Investigation of Sensitivity to Heavy-Ion Irradiation of Junctionless Double-Gate MOSFETs by 3-D Numerical Simulation http://dx.doi.org/10.5772/57048 245

**Figure 17.** Bipolar amplification as function of LET in JL-DGFET for different film doping levels. VG=0 V and VD=0.75 V.

### **7. Conclusion**

Collected charge (fC)

Time (s)

Time (s) 10-12 10-11 10-10 10-9 10-8 10-7

**Figure 16.** Collected charge in JL-DGFET for different film doping levels. The incident ion LET is 1 MeV/(mg/cm2). VG=0

10-12 10-11 10-9 10-8 10-10

**Figure 15.** Drain current transient in JL-DGFET for different film doping levels. The incident ion LET is 1 MeV/(mg/cm2).

3×1019 cm-3

1 1019 cm-3 2×1019 cm-3 3 1019 cm-3

1 1019 cm-3 2 1019 cm-3

Drain current (µA)

244 Computational and Numerical Simulations

VG=0 V and VD=0.75 V.

V and VD=0.75 V.

In conclusion, this chapter presented a detailed investigation of the radiation sensitivity of JL-DGFET by 3-D numerical simulation. In particular, the bipolar gain of JL-DGFET has been compared with that of more conventional inversion-mode devices such as FDSOI and IM-DGFET. We have firstly shown that for an ion strike in the middle of the channel, IM-DGFET shows a lower bipolar gain than JL-DGFET and FDSOI (for all LET values). We also studied the impact of various parameters of the ion track (characteristic time and track radius) on the drain current transient and bipolar gain of JL-DGFET. Our results show that modifying these parameters does not change the previous conclusion, the bipolar gain of IM-DGFET being always smaller than those of JL-DGFET and FDSOI. However, a thorough study of the bipolar gain as a function of the ion strike position along the channel showed that JL-DGFET has a lower bipolar gain than IM-DGFET and FDSOI for some particular conditions, precisely for LET values superior to 20 MeV/(mg/cm2 ) and ion strike positions between the middle of the channel and the drain contact. These results are also confirmed by already published experi‐ mental and simulation data obtained on FD SOI MOSFETs with longer channels. JL-DGFET is also better than FDSOI for low LET values below 0.5 MeV/(mg/cm2 ) (for all ion strike positions).

### **Author details**

Daniela Munteanu and Jean-Luc Autran

CNRS & Aix-Marseille University, Marseille, France
