Copper-related light-induced degradation in crystalline silicon
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School of Electrical Engineering |
Doctoral thesis (article-based)
| Defence date: 2015-04-24
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Author
Date
2015
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Mcode
Degree programme
Language
en
Pages
80 + app. 44
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 37/2015
Abstract
Unintentional copper and nickel impurities are common in silicon-based devices due to the abundance of contamination sources in industrial silicon crystallization and wafer processing lines. High solubility and diffusivity result readily in significant impurity concentrations, which cause charge-carrier recombination and reduce the device response. This work confirms that nickel diffuses as fast as copper in silicon, emphasizing the importance of contamination control in silicon-based devices. Copper contamination is known to form recombination-active defects in silicon during illumination, which is observed as copper-related light-induced degradation (Cu-LID). In order to identify the extent of degradation in silicon-based devices, this work focuses on determining the properties of Cu-LID in gallium-doped Czochralski (Cz) silicon, boron-doped Cz-Si, and boron-doped multicrystalline silicon. Cu-LID is determined to be predominantly a bulk recombination effect, and the formed defects are found to be stable at 200°C. Slower Cu-LID is observed in Ga-Si compared to B-Si, suggesting that Cu-LID formation is limited by the effective copper diffusivity. Cu-LID is shown to completely disappear after negative sample surface charging and illumination. The negative surface charge is achieved by corona charging or aluminum oxide deposition. Cu-LID removal is observed to have no impact on classical boron-oxygen-related light-induced degradation (BO-LID), which has previously been shown to recover at 200°C. Unlike BO-LID, the activation energy of Cu-LID is found to depend on the silicon doping concentration. Hence, Cu-LID and BO-LID are concluded to be two different degradation effects, which can occur simultaneously in silicon-based devices.Kiselbaserade elektroniska komponenter är ofta oavsiktligt förorenade av koppar och nickel från otaliga kontaminationskällor i industriella komponentframställningsprocesser. Metallernas höga diffusivitet samt löslighet leder fort till markanta orenhetskoncentrationer, vilka förorsakar rekombination av laddningsbärare och nedsatt komponentrespons. Denna avhandling bekräftar att nickel diffuserar lika fort som koppar i kristallint kisel, vilket betonar vikten av metallorenhetskontroll i kiselbaserade komponenter. Kopparorenheter förorsakar fotodegradadering (Cu-LID) i kisel via formationen av rekombinationsaktiva koppardefekter under illuminering. För att fastställa omfattningen av fotodegradadering i kiselbaserade komponenter, fokuserar denna avhandling på att identifiera egenskaper för Cu-LID i gallium-dopat Czochralski (Cz) kisel, boron-dopat Cz-Si och boron-dopat mångkristallint kisel. Cu-LID finnes orsaka främst bulkrekombination och de formade koppardefekterna är stabila i 200°C. Cu-LID sker långsammare i Ga-Si jämfört med B-Si, vilket antyder att fotodegraderingsprocessen begränsas av den effektiva koppardiffusiviteten. I avhandlingen förhindras kopparrelaterad fotodegradadering fullständigt genom att kombinera negativ kiselytladdning med illuminering. Den negativa ytladdningen skapas via deposition av koronaladdning eller aluminiumoxidtunnfilm. Avlägsning av Cu-LID inverkar inte på klassisk bor-syre-relaterad fotodegraderingen (BO-LID), som förekommer i kisel utan kopparföroreningar och försvinner i 200°C. I motsats till BO-LID beror aktiveringsenergin för Cu-LID på dopingkoncentrationen i kiselmaterialet. Följaktligen fastställs Cu-LID och BO-LID vara två skilda former av fotodegradering, vilka kan förkomma samtidigt i kiselbaserade elektroniska komponenter.Description
Supervising professor
Savin, Hele, Assistant Prof., Aalto University, Department of Micro and Nanosciences, FinlandKeywords
copper, degradation, lifetime, nickel, silicon, degradering, kisel, koppar, livstid, nickel
Other note
Parts
- [Publication 1]: J. Lindroos, M. Yli-Koski, A. Haarahiltunen, M. C. Schubert, and H. Savin, Light-induced degradation in copper-contaminated gallium-doped silicon, Physica Status Solidi - Rapid Research Letters 7, No. 4, p. 262-264 (2013). http://dx.doi.org/10.1002/pssr.201307011.
- [Publication 2]: J. Lindroos, M. Yli-Koski, A. Haarahiltunen, and H. Savin, Room-temperature method for minimizing light-induced degradation in crystalline silicon, Applied Physics Letters 101, 232108 (2012). http://dx.doi.org/10.1063/1.4769809.
- [Publication 3]: Y. Boulfrad, J. Lindroos, Mt. Wagner, F. Wolny, M. Yli-Koski, and H. Savin, Experimental evidence on removing copper and light-induced degradation from silicon by negative charge, Applied Physics Letters 105, 182108 (2014). http://dx.doi.org/10.1063/1.4901533.
- [Publication 4]: J. Lindroos and H. Savin, Formation kinetics of copper-related light-induced degradation in crystalline silicon, Journal of Applied Physics 116, 234901 (2014). http://dx.doi.org/10.1063/1.4904197.
- [Publication 5]: J. Lindroos, Y. Boulfrad, M. Yli-Koski, and H. Savin, Preventing light-induced degradation in multicrystalline silicon, Journal of Applied Physics 115, 154902 (2014). http://dx.doi.org/10.1063/1.4871404.
- [Publication 6]: J. Lindroos, D. P. Fenning, D. J. Backlund, E. Verlage, A. Gorgulla, S. K. Estreicher, H. Savin, and T. Buonassisi, Nickel: A very fast diffuser in silicon, Journal of Applied Physics 113, 204906 (2013). http://dx.doi.org/10.1063/1.4807799.