doi:10.1016/j.mejo.2005.09.010 
Copyright © 2005 Elsevier Ltd All rights reserved.
Lifetime control in silicon power P-i-N diode by ion irradiation: Suppression of undesired leakage
P. Hazdra
, 
and V. Komarnitskyy
Department of Microelectronics, Czech Technical University in Prague, Technická 2, CZ-16627 Prague 6, Czech Republic
Available online 3 November 2005.
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Abstract
The irradiation with high-energy (7.35 MeV) protons through a set of energy degraders was used to suppress leakage of the silicon power diodes subjected to local lifetime control. The aim was to modify the profile of recombination centers and to reduce production of vacancy complexes. The high-energy proton irradiation was compared with standard local lifetime killing by high-energy alphas. Recombination centers arising from irradiation were characterized after irradiation and subsequent annealing at 220 and 350 °C by deep level transient spectroscopy and I–V profiling. Static and dynamic parameters of irradiated diodes were also measured and compared. Results show that the applied irradiation with protons provides 3–10 times lower leakage compared to standard alphas for equivalent reduction of the reverse recovery current maximum. On the other hand, the excessive formation of hydrogen donors at high proton fluences and their diffusion during annealing at 350° decreases diode blocking capability.
Keywords: Lifetime control; Silicon; Irradiation; Protons; Alphas; Power diodes
Fig. 1. Doping profile of the P+PN−N+ diode with concentration profiles of recombination centers which were introduced by alphas and high-energy protons. Two locations of the damage peak, the anode (A) and the base side of the anode junction (B), were used for both projectiles.
Fig. 2. Majority carrier DLTS spectra of P+PN−N+ diode irradiated with 7 MeV alphas measured after irradiation (n.a.), and isochronal 40 min annealing at 220 and 350 °C, rate window 260 s−1.
Fig. 3. Majority carrier DLTS spectra of P+PN−N+ diode irradiated with 7.35 MeV protons measured after irradiation (n.a.), and isochronal 40 min annealing at 220 and 350 °C, rate window 260 s−1.
Fig. 4. Concentration profiles of the level 
measured by I–V profiling in the diode irradiated with standard alphas (8 MeV 1.4×109 cm−2) and high-energy protons (7.35 MeV 1.4×1010 cm−2). The position of the 
profile produced by protons is shifted for 326 μm towards the surface.
Fig. 5. The trade-off between the on-state voltage drop VF and the reverse-recovery current maximum IRMM measured on P+PN−N+ diodes irradiated with standard alphas (full) and high-energy protons (open) into region A (boxes) and B (circles).
Fig. 6. Reverse recovery waveforms of diodes irradiated with alphas (7 MeV He2+ 5×1011 cm) and high-energy protons (7.35 MeV H+2×1010 cm−2 through the foil) into region B (unannealed diodes, T=25 °C, IF=25 and 2 A, VDC=500 V).
Fig. 7. The impact of the fluence of alpha-particle (full) and proton (open) irradiation and subsequent annealing at 220 °C (circles) and 350 °C (triangles) on IRRM (upper) and the increase of the diode leakage ΔIR (lower)-damage placed into region A.
Fig. 8. The impact of the fluence of alpha-particle (full) and proton (open) irradiation and subsequent annealing at 220 °C (circles) and 350 °C (triangles) on IRRM (upper) and the increase of the diode leakage ΔIR (lower)-damage placed into region B.
Fig. 9. The impact of irradiation using high-energy protons on diode blocking characteristics measured at room temperature after irradiation (boxes) and subsequent annealing at 220 °C (circles) and 350 °C (triangles). Defects are placed into region B, fluences are 2×1012 (full) and 2×1011 (open) cm−2.
Fig. 10. The impact of irradiation using high-energy protons on diode blocking characteristics measured at room temperature after irradiation (boxes) and subsequent annealing at 220 °C (circles) and 350 °C (triangles). Defects are placed into region A, fluences are 2×1012 (full) and 2×1011 (open) cm−2.
Fig. 11. The impact of irradiation using alphas on diode blocking characteristics measured at room temperature after irradiation (boxes) and subsequent annealing at 220 °C (circles) and 350 °C (triangles). Defects are placed into region B, fluences are 1×1012 (full) and 1×1011 (open) cm−2.
Table 1.
Survey of electron traps identified in the N-base of irradiated and annealed diodes
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