Influence of annealing and Al2O3 properties on the hydrogen-induced passivation of the Si/SiO2 interface

Annealing at moderate temperatures is required to activate the silicon surface passivation by Al2O3 thin films while also the thermal stability at higher temperatures is important when Al2O3 is implemented in solar cells with screenprinted metallization. In this paper, the relationship between the microstructure of the Al2O3 film, hydrogen diffusion, and defect passivation is explored in detail for a wide range of annealing temperatures. The chemical passivation was studied using stacks of thermally-grown SiO2 and Al2O3 synthesized by atomic layer deposition. Thermal effusion measurements of hydrogen and implanted He and Ne atoms were used to elucidate the role of hydrogen during annealing. We show that the passivation properties were strongly dependent on the annealing temperature and time and were significantly influenced by the Al2O3 microstructure. The latter was tailored by variation of the deposition temperature (Tdep = 50 °C–400 °C) with hydrogen concentration [H] between 1 and 13 at.% and mass den...

[1]  S. George.  Atomic layer deposition: an overview. , 2010, Chemical reviews.

[2]  M. L. Reed,et al.  Chemistry of Si‐SiO2 interface trap annealing , 1988 .

[3]  Andre Stesmans,et al.  Si dangling-bond-type defects at the interface of (100)Si with ultrathin layers of SiOx,Al2O3, and ZrO2 , 2002 .

[4]  G. Dingemans,et al.  Er3+ and Si luminescence of atomic layer deposited Er-doped Al2O3 thin films on Si(100) , 2011 .

[5]  Makoto Konagai,et al.  High Quality Aluminum Oxide Passivation Layer for Crystalline Silicon Solar Cells Deposited by Parallel-Plate Plasma-Enhanced Chemical Vapor Deposition , 2009 .

[6]  H. Dekkers,et al.  Molecular hydrogen formation in hydrogenated silicon nitride , 2006 .

[7]  J. Stathis.  Dissociation kinetics of hydrogen‐passivated (100) Si/SiO2 interface defects , 1995 .

[8]  Wmm Erwin Kessels,et al.  Surface passivation of high‐efficiency silicon solar cells by atomic‐layer‐deposited Al2O3 , 2008 .

[9]  W. Beyer,et al.  Hydrogen stability in amorphous germanium films , 1991 .

[10]  A. Cuevas,et al.  Very low bulk and surface recombination in oxidized silicon wafers , 2002 .

[11]  M. Sanden,et al.  Effective passivation of Si surfaces by plasma deposited SiOx/a-SiNx:H stacks , 2011 .

[12]  R. M. Swanson,et al.  Photoinjected hot‐electron damage in silicon point‐contact solar cells , 1989 .

[13]  O. Anderson,et al.  Calculation of Activation Energy of Ionic Conductivity in Silica Glasses by Classical Methods , 1954 .

[14]  F. Duerinckx,et al.  Defect passivation of industrial multicrystalline solar cells based on PECVD silicon nitride , 2002 .

[15]  R. Preu,et al.  Very low surface recombination velocity on p-type c-Si by high-rate plasma-deposited aluminum oxide , 2009 .

[16]  Jan Benick,et al.  Thermal stability of the Al2O3 passivation on p‐type silicon surfaces for solar cell applications , 2009 .

[17]  Blair R. Tuttle,et al.  Energetics and diffusion of hydrogen in SiO 2 , 2000 .

[18]  G. Dingemans,et al.  Influence of the Oxidant on the Chemical and Field-Effect Passivation of Si by ALD Al2O3 , 2011 .

[19]  D. Fink,et al.  Hydrogen implantation and diffusion in silicon and silicon dioxide , 1995 .

[20]  H. Dekkers,et al.  Microstructure Characterization of Amorphous Silicon-Nitride Films by Effusion Measurements , 2006 .

[21]  Bernd Rech,et al.  Improved electrical transport in Al-doped zinc oxide by thermal treatment , 2010 .

[22]  C. R. Helms,et al.  The silicon-silicon dioxide system: Its microstructure and imperfections , 1994 .

[23]  Robert Mertens,et al.  Approach for Al2O3 rear surface passivation of industrial p‐type Si PERC above 19% , 2012 .

[24]  Armin G. Aberle,et al.  Surface passivation of crystalline silicon solar cells: a review , 2000 .

[25]  D. Biro,et al.  Silicon Surface Passivation by Thin Thermal Oxide/PECVD Layer Stack Systems , 2011, IEEE Journal of Photovoltaics.

[26]  C. Ballif,et al.  Very fast light-induced degradation of a-Si:H/c-Si(100) interfaces , 2011 .

[27]  R. Brendel,et al.  Effective surface passivation of crystalline silicon using ultrathin Al2O3 films and Al2O3/SiNx stacks , 2009 .

[28]  Jan Benick,et al.  High efficiency n-type Si solar cells on Al2O3-passivated boron emitters , 2008 .

[29]  Andre Stesmans,et al.  Degradation of the thermal oxide of the Si/SiO2/Al system due to vacuum ultraviolet irradiation , 1995 .

[30]  G. Dingemans,et al.  Excellent Si surface passivation by low temperature SiO2 using an ultrathin Al2O3 capping film , 2011 .

[31]  S. Glunz,et al.  Excellent silicon surface passivation with 5 Å thin ALD Al2O3 layers: Influence of different thermal post‐deposition treatments , 2011 .

[32]  J. Werner,et al.  Efficient defect passivation by hot-wire hydrogenation , 1997 .

[33]  Harold Dekkers,et al.  Very low surface recombination velocities on p-type silicon wafers passivated with a dielectric with fixed negative charge , 2006 .

[34]  H. Wagner,et al.  Determination of the hydrogen diffusion coefficient in hydrogenated amorphous silicon from hydrogen effusion experiments , 1982 .

[35]  G. Dingemans,et al.  Influence of the Deposition Temperature on the c-Si Surface Passivation by Al2O3 Films Synthesized by ALD and PECVD , 2010 .

[36]  Helmut Stiebig,et al.  Transparent conducting oxide films for thin film silicon photovoltaics , 2007 .

[37]  Wmm Erwin Kessels,et al.  Silicon surface passivation by ultrathin Al2O3 films synthesized by thermal and plasma atomic layer deposition , 2010 .

[38]  G. Dingemans,et al.  Hydrogen induced passivation of Si interfaces by Al2O3 films and SiO2/Al2O3 stacks , 2010 .

[39]  Bruce E. Deal,et al.  ESR centers, interface states, and oxide fixed charge in thermally oxidized silicon wafers , 1979 .

[40]  E. Bassous,et al.  Charge in SiO2 ‐ Al2 O 3 Double Layers on Silicon , 1973 .

[41]  W. Beyer,et al.  The diffusion of hydrogen and inert gas in sputtered a-SiC:H alloys: Microstructure study , 2006 .

[42]  D. Macdonald,et al.  Thermal activation energy for the passivation of the n-type crystalline silicon surface by hydrogenated amorphous silicon , 2009 .

[43]  Wmm Erwin Kessels,et al.  On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3 , 2008 .

[44]  H. Dekkers,et al.  Hydrogen diffusion in silicon from plasma-enhanced chemical vapor deposited silicon nitride film at high temperature , 2008 .

[45]  Wmm Erwin Kessels,et al.  Ultralow surface recombination of c-Si substrates passivated by plasma-assisted atomic layer deposited Al2O3 , 2006 .

[46]  B. Hoex,et al.  Stability of Al2O3 and Al2O3/a-SiNx:H stacks for surface passivation of crystalline silicon , 2009 .

[47]  V. Verlaan,et al.  Composition and bonding structure of plasma-assisted ALD Al2O3 films , 2010 .

[48]  S. Pantelides,et al.  Migration, incorporation, and passivation reactions of molecular hydrogen at the Si ‐ Si O 2 interface , 2004 .

[49]  M. Verheijen,et al.  Controlling the fixed charge and passivation properties of Si(100)/Al2O3 interfaces using ultrathin SiO2 interlayers synthesized by atomic layer deposition , 2011 .

[50]  W. Beyer.  Diffusion and evolution of hydrogen in hydrogenated amorphous and microcrystalline silicon , 2003 .

[51]  Andre Stesmans,et al.  Interaction of Pb defects at the (111)Si/SiO2 interface with molecular hydrogen: Simultaneous action of passivation and dissociation , 2000 .

[52]  W. Beyer.  Characterization of microstructure in amorphous and microcrystalline Si and related alloys by effusion of implanted helium , 2004 .