Doping-type Dependence of Damage in Si Diodes Exposed to X-ray, Proton, and He + Irradiation MURI Meeting - June 2007 M. Caussanel 1, A. Canals 2, S. K. Dixit 3, M. J. Beck 4, A. D. Touboul 5, R. D. Schrimpf 6, D. M. Fleetwood 6, and S. T. Pantelides 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 Montpellier cedex 5, FRANCE 6 - Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN, 37235, USA Work supported by the AFOSR MURI Program Outline - Context - Samples & Experimental Set-up - Results and Discussion on - Lifetime measurements - I-V Characteristics - Summary

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

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

MURI Meeting - June Experimental Description Radiation Sample Type Characterization TypeDose/Fluence Measure ments Method X-rays Up to 500 krad (SiO 2 ) by steps n + /p junctions (N A = 4×10 16 cm -3 ) I-V Parameter Analyzer 1.8 MeV H + From 5.5×10 10 to cm -3 p + /n junctions (N D = 2.7×10 15 cm -3 ) Minority carrier lifetime Open-Circuit Voltage Decay method (OCVD) 1.4 MeV He +

MURI Meeting - June Sample Structure - Top View (Sandia TA 629TDC)

MURI Meeting - June Sample Structure - Cross-Section G1916A/W33 – includes 1100 C N 2 Post gate anneal before poly-Si

MURI Meeting - June Sample Structure - Ion range

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

MURI Meeting - June 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

MURI Meeting - June Reliability of the OCVD method: Measured lifetime checked with literature data Electron lifetime p-Si Source: IOFFE Institute

MURI Meeting - June 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 (2005)

MURI Meeting - June 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 SiO 2 /Si interface

MURI Meeting - June 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 (2006)

MURI Meeting - June 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

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