Characterization of {111} planar defects induced in silicon by hydrogen plasma treatments

Hydrogenation of multicrystalline silicon for solar cell applications is considered to be an effective method of increasing the lifetime by passivating defects and impurities. Hydrogen plasma treated as-cut and chemically etched multicrystalline silicon samples have been studied by electron microscopy in order to investigate hydrogen defect formation at extended bulk defects. In chemically etched samples, the texture of the surface after hydrogen plasma treatment differs between different grains depending on grain orientation. In as-cut samples, hydrogen induced defects are formed on sawing defects that extend up to ∼5 μm below the Si surface. Intragranular defects are also observed in the ∼1 μm subsurface region. The density of defects is higher in as-cut samples than in chemically etched samples and the size of the defects increases with depth. Hydrogen induced structural defects on bulk dislocations and on dislocations in twin grain boundaries and stacking faults are found several microns below the sample surface. It is concluded that (i) the passivation efficiency of multicrystalline silicon substrates after H plasma treatment can be limited by the formation of hydrogen induced structural defects and that (ii) such defects can be used to getter unwanted impurities upon high temperature processing of the Si wafers.

“…Thus, one can expect that hydrogen may form precipitates and introduce structural defects. [11][12][13][14][17][18][19][20] …”

Section: Methodsmentioning

confidence: 99%

Section: Transmission Electron Microscopy Study Of Hydrogen Defect Fomentioning

confidence: 99%

Transmission electron microscopy study of hydrogen defect formation at extended defects in hydrogen plasma treated multicrystalline silicon

Nordmark

Holmestad

Walmsley

et al. 2009

“…[18][19][20][21] We have demonstrated that in certain experimental conditions, the surface roughness can be reduced down to 1-2 nm, while a plasma treatment at low power (50-100 W) results in inducing a high density of structural defects confined to a narrow band (30-50 nm) of Si adjacent to the treated surface. We have found and characterized three main types of induced defects, such as {111} planar defects, {001} planar defects, and nanocavities.…”

Section: Introductionmentioning

confidence: 90%

“…18 Once created, single vacancies diffuse inside the Si wafer even at room temperature. It has been shown 13,30 that hydrogen implantation followed by thermal annealing leads to the nucleation and growth of hydrogen related cavities.…”

Section: Laser Annealingmentioning

confidence: 99%

Laser treatment of plasma-hydrogenated silicon wafers for thin layer exfoliation

Ghica¹,

Nistor²,

Teodorescu³

et al. 2011

Influence of hydrogen plasma surface treatment of Si substrate on nickel silicide formation Effects of grain boundaries on performance and hot-carrier reliability of excimer-laser annealed polycrystalline silicon thin film transistors J. Appl. Phys. 95, 5788 (2004); 10.1063/1.1699504 Laser crystallization and structural characterization of hydrogenated amorphous silicon thin filmsWe have studied by transmission electron microscopy the microstructural effects induced by pulsed laser annealing in comparison with thermal treatments of RF plasma hydrogenated Si wafers aiming for further application in the smart-cut procedure. While thermal annealing mainly produces a slight decrease of the density of plasma-induced planar defects and an increase of the size and number of plasma-induced nanocavities in the Si matrix, pulsed laser annealing of RF plasma hydrogenated Si wafers with a 355 nm wavelength radiation results in both the healing of defects adjacent to the wafer surface and the formation of a well defined layer of nanometric cavities at a depth of 25-50 nm. In this way, a controlled fracture of single crystal layers of Si thinner than 50 nm is favored.

“…[35][36][37] One advantage of this method is that it also can texture ͕111͖ silicon and, therefore, has potential for texturing mc Si. 35 This is in contrast to pure hydrogen plasma treatments, [38][39][40][41][42][43][44][45][46][47][48] where texturing depends on grain orientation and hydrogen induced structural defects form in the bulk. [38][39][40][41][42][43][44][45][46][47][48] In the tungsten hot filament case, the high temperature, ϳ800°C ͑in contrast to ϳ250°C for H-plasma treatments [43][44][45][46][47] ͒, prevents hydrogen defect formation in the bulk.…”

Section: Introductionmentioning

confidence: 99%

Si substrates texturing and vapor-solid-solid Si nanowhiskers growth using pure hydrogen as source gas

Nordmark¹,

Nagayoshi

Matsumoto

et al. 2009

Self Cite

Scanning and transmission electron microscopies have been used to study silicon substrate texturing and whisker growth on Si substrates using pure hydrogen source gas in a tungsten hot filament reactor. Substrate texturing, in the nanometer to micrometer range of mono- and as-cut multicrystalline silicon, was observed after deposition of WSi2 particles that acted as a mask for subsequent hydrogen radical etching. Simultaneous Si whisker growth was observed for long residence time of the source gas and low H2 flow rate with high pressure. The whiskers formed via vapor-solid-solid growth, in which the deposited WSi2 particles acted as catalysts for a subsequent metal-induced layer exchange process well below the eutectic temperature. In this process, SiHx species, formed by substrate etching by the H radicals, diffuse through the metal particles. This leads to growth of crystalline Si whiskers via metal-induced solid-phase crystallization. Transmission electron microscopy, electron diffraction, and x-ray energy dispersive spectroscopy were used to study the WSi2 particles and the structure of the Si substrates in detail. It has been established that the whiskers are partly crystalline and partly amorphous, consisting of pure Si with WSi2 particles on their tips as well as sometimes being incorporated into their structure.