Vazgen Melikyan, Aristakes Hovsepyan, Tigran Harutyunyan

1. SCHEMATIC PROTECTION METHOD FROM INFLUENCE OF TOTAL IONIZATION DOSE EFFECTS ON THRESHOLD VOLTAGE OF MOS TRANSISTORS Vazgen Melikyan, Aristakes Hovsepyan, Tigran Harutyunyan Presenter: Honorable Scientist of Armenia, Sci.D., Professor V. Melikyan EWDTS’09, Moskow Synopsys Armenia Educational Department

2. Content Synopsys Armenia Educational Department Introduction Influence of TID effects on threshold voltage of MOSFETs Suggested protection method Simulation Results Conclusion

3. Introduction • Influence of TID effects on MOS transistors • Subthreshold and leakage currents Carrier mobility and transconductance of transistors • Threshold voltage shifts • TID – Total Ionization Dose Synopsys Armenia Educational Department

4. Introduction Subthreshold and leakage currents Source: [4] Synopsys Armenia Educational Department

5. Introduction Carrier Mobility μ0 – pre-irradiation mobility Δ Nit - number of interface traps per unit area introduced by ionizing radiation α - technology dependant parameter (α = 7 ± 1.3 ×10−13 ) Source: [3] Synopsys Armenia Educational Department

6. Radiation Induced Threshold Voltage Shits - change in threshold voltage due to holes trapped at the interface - change caused by the charging of interface traps D - radiation dose in rads tox - gate oxide thickness in nanometers, - yield of holes as a function of field (E) and irradiating particle energy ( ) - a technology dependent factor. Source: [1-2] Synopsys Armenia Educational Department

7. Radiation Induced Threshold Voltage Shits p-MOS n-MOS Synopsys Armenia Educational Department

8. Pre- and Post Irradiation Curves of n-MOS Dashed line is closed n-MOS curve under 12MRad irradiation Synopsys Armenia Educational Department

9. Gate VGS=VTHN Drain Source GND Electrons p-substrate n+ n+ VSB GND Suggested Protection Method Body effect of n-MOS transistor When VBS , VTH Source: [5] Synopsys Armenia Educational Department

10. VD MN1 VB VG GND MNB1 MPB1 0V -3.3V GND -3.3V Suggested Protection Method MN1 is the transistor, which should be protected. Bulk potential of MN1 is controlled by transistors MPB1 and MNB1. Synopsys Armenia Educational Department

11. Closed n-MOS Current Depending on TID before protection after protection Synopsys Armenia Educational Department

12. Closed n-MOS Current Depending on VDS under 12MRad before protection after protection Synopsys Armenia Educational Department

13. Conclusion • Advantages • Protection from threshold voltage shifts caused by high radiation levels (>20MRad) • Circuit simplicity • Disadvantages • Substrate of transistor is not connected directly to ground (body effect) • Increase of circuit area (about 3 times) • Circuit requires additional negative supply (-3.3V) Synopsys Armenia Educational Department

14. References [1] D. Pan, H. W. Li, B. W. Milamowski, “A Radiation-Hard Phase-Locked Loop”, Industrial Electronics, ISIE '03, IEEE International Symposium, Vol. 2, June 9-11, 2003, pp.901-906. [2] J. R. Srour, J. M. McGarrity, “Radiation Effects on Microelectronics in Space”, Proceedings of the IEEE, Vol. 76, No. 11, November, 1988, pp.1443-1469. [3] A. P. Gnana Prakash, S. C. Ke, K. Siddappa, “High-energy radiation effects on subthreshold characteristics, transconductance and mobility of n-channel MOSFETs”, Semiconductor Science and Technology, Volume 18, No. 12, 2003, pp. 1037-1042. [4] A. Stabile, V. Liberali, C. Calligaro, “Design of a rad-hard library of digital cells for space applications”, 15th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2008. Aug. 31-Sept. 3, 2008, pp. 149-152. [5] R. Jacob Baker, “CMOS Circuit Design, Layout and Simulation”, Second Edition, 2005, pp.135-140. Synopsys Armenia Educational Department

15. Thank You Synopsys Armenia Educational Department