Doping-type Dependence of Damage in Si Diodes Exposed to X-ray, Proton, and He + Irradiation

1. MURI Meeting - June 2007 Doping-type Dependence of Damage in Si Diodes Exposed to X-ray, Proton, and He+ Irradiation M. Caussanel1, A. Canals2, S. K. Dixit3, M. J. Beck4, A. D. Touboul5, R. D. Schrimpf6, D. M. Fleetwood6, and S. T. Pantelides4 1 - LP2A, Université de Perpignan Via Domitia, Perpignan, 66860, FRANCE 2 - TRAD, Labege, 31674, FRANCE 3 - Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN 37235, USA 4 - Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA 5 - LAIN-UMR CNRS 5011, Université Montpellier II, F-34095 Montpellier cedex 5, FRANCE 6 - Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN, 37235, USA • Outline • - Context • Samples & Experimental Set-up • Results and Discussion on • - Lifetime measurements • - I-V Characteristics • - Summary Work supported by the AFOSR MURI Program

2. Context: For more than 40 years n-Si ≠ p-Si under radiation (1/2) • 1962 & 1988: disparities after electron irradiation from • very lowenergy (a few 100 keV [1]) to highenergy [2] 1. H. Flicker et al., Phys. Rev., 128, p. 2557 (1962) 2. C. J. Dale et al., IEEE Trans. Nucl. Sci., 35, p. 1208 (1988)

3. Context: For more than 40 years n-Si ≠ p-Si under radiation (2/2) • - 1993 [3]: for NIEL<1 keV cm2/g • in n-Si: • Damage Coefficient ∝ NIEL • in p-Si: Damage Coefficient ∝ NIEL2 1974 3. G. P. Summers et al., IEEE Trans. Nucl. Sci., 40, p. 1372 (1993) 1990 1965 4. J. R. Srour et al., IEEE Trans. Nucl. Sci., 50, p. 653 (2003) - n-Si/p-Si difference ∝ fraction of damage due to low-energy PKA [4]

4. Experimental Description

5. Sample Structure - Top View(Sandia TA 629TDC)

6. Sample Structure - Cross-Section G1916A/W33 – includes 1100 C N2 Post gate anneal before poly-Si

7. Sample Structure - Ion range

8. Minority Carrier Lifetime Measurement Set-up Vg removed Method based on the Open-Circuit Voltage Decay method (OCVD) Lifetime value is extracted from the linear part of the curve:

9. Reliability of the OCVD method:Measured lifetime checked with literature data Hole lifetime in n-Si (may be reduced by High-T post-ox anneal) Source: IOFFE Institute

10. Reliability of the OCVD method:Measured lifetime checked with literature data Electron lifetime p-Si Source: IOFFE Institute

11. I-V Characteristics under X-ray Radiation Evidence that carrier trapping occurs at certain surfaces within the sample. ➙ This sensitivity of the surface regions of these diodes to defect buildup is consistent with recent results obtained on VDMOSFETs [6] 6. J. A. Felix et al., IEEE Trans. Nucl. Sci., 52, p. 2378 (2005)

12. X-ray Irradiation Impact on the Voltage Drop across the Junction during Lifetime Measurement • The voltage drop across the sample is reduced after the X-ray irradiation : • the higher the dose, the higher the reduction. • - n+/p reduction > p+/n reduction. ➙ Also evidence of trapped charge at a SiO2/Si interface

13. Ion Irradiation Impact on the Voltage Drop across the Junction during Lifetime Measurement • Like X-rays, ion irradiation lowers the closed-circuit voltage drop across the sample. • ➙ trapped charge within bulk • p+/n reduction > n+/p reduction • ➙ this trend is opposite to X-ray radiation Consistent with recent theoretical work [5], which demonstrated that Frenkel pairs are generally more stable in p-Si than in n-Si. (Frenkel pairs act as electron trap in n-Si) 5. M. J. Beck et al., IEEE Trans. Nucl. Sci., 53, p. 3621 (2006)

14. Ion Irradiation Impact on Bulk Lifetime Electron lifetime in p gets reduced more by both H+ & He+ irradiations than hole lifetime in n by a 2-3× factor This is despite the n doping being ~ 13x lower than the p doping

15. Summary X-ray, H+ and He+ irradiation of n+/p and p+/n diodes (I-V & lifetime measurements) • - Surface trapping: n+/p more sensitive than p+/n • - Bulk trapping: n+/p less sensitive than p+/n • - Agreement with recent experiments and theory