Papers by Keyword: SPV

Abstract: An extremely low level of metal contamination is required for specific devices like memories and CMOS Image sensors. Most of past work in the literature has focused on blanket wafer decontamination, since metrology is mostly adapted to flat surfaces. Metal removal efficiency has been compared between blanket wafers versus high aspect ratio deep trenches wafers. Two different metrology technics enable a quantitative and spatial metal removal determination on patterned wafers. Efficient cleaning in high aspect ratio structures requires much longer cleaning recipes than on flat surfaces.

Abstract: In this work we report the results of a set of experiments carried out to assess the ability of recombination lifetime measurements for the detection of palladium contamination in silicon. Palladium is found to be a very effective recombination center, so recombination lifetime measurements are a very sensitive method to detect palladium in silicon. The surface segregation of palladium was monitored by the reduction of its recombination activity in the silicon volume. The palladium segregation at the wafer surface was checked by selective etching, and by Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX) analysis.After validating recombination lifetime measurements for palladium detection, we use these measurements to define suitable approaches to the prevention of palladium contamination of silicon devices. The efficiency of a diffusion barrier layer (silicon nitride) and of decontamination by wet cleaning are tested.

Abstract: The deposition of thin and ultra-thin layers requires extremely clean, smooth and defect-free Silicon (Si) substrate surfaces as starting point. The preparation-induced surface micro-roughness and surface coverage of the substrates often affect the initial layer growth, the morphology or the adhesion of deposited layers. Si device fabrication includes multiple wet cleaning and etching steps involving different oxidizing and etching solutions, which modify the surface electronic properties according to fixed charges and defect states present on the surface. Depending on the details of the device structure, surface conditioning methods have to be carefully optimized to achieve the desired electronic interface properties.

Abstract: Aluminum oxide (AlO_x) is currently under intensive investigation for use in surface passivation schemes in solar cells. AlO_x films contain negative charges and therefore generate an accumulation layer on p-type silicon surfaces, which is very favorable for the rear side of p-type silicon solar cells as well as the p⁺-emitter at the front side of n-type silicon solar cells. However, it has been reported that quality of an interfacial silicon sub-oxide layer (SiO_x), which is usually observed during deposition of AlO_x on Silicon, strongly impacts the silicon/AlO_x interface passivation properties [1]. The present work demonstrates that a convenient way to control the interface is to form thin wet chemical oxides of high quality prior to the deposition of AlO_x/a-SiN_x:H stacks by the plasma enhanced chemical vapor deposition (PECVD).

Abstract: For further enhancement of solar energy conversion efficiency the passivation of silicon (Si) substrate surfaces and interfaces of Si-based solar cell devices is a decisive precondition to reduce recombination losses of photogenerated charge carriers. These losses are mainly controlled by surface charges, the density and the character of rechargeable interface states (D_it) [], which are induced by defects localised in a small interlayer extending over only few Å. Therefore, the application of fast non-destructive methods for characterization of the electronic interface properties directly during the technological process has received an increasing interest in recent years.

Abstract: The dominance of crystalline silicon (Si) in photovoltaics can be ascribed partly to the extensive knowledge about this material, which has been accumulated in microelectronics technology. Methods to passivate Si interfaces, which were developed for microelectronic device technologies, have been extended to solar cell manufacturing in the past. These methods, however, have been optimised for polished substrates, and do not work so effective with textured surfaces, which commonly used in the fabrication of high efficiency Si solar cells to enhance anti-reflection properties.

Abstract: The Macroporous Nanocrystalline TiO₂ Thin Film Was Prepared by Dipping-Coating Method. Polystyrene (PS) Microspheres Template Was Used as Pore-Forming Assistant and TiO₂ Sol Was Used as Precursor. the Photoelectric Characteristics of the Samples Were Studied Using Surface Photovoltage (SPV) and Photoacoustic (PA) Techniques. the Presence of a Small Amount of Residual Template Damages the Integrity of the Porous TiO₂ Film with Inverse Opal Structure, and TiO₂ May Be Restricted in Certain Application Fields as Photonic Crystals. a Small Amount of Residual Template Changes the Surface Photovoltaic Properties of the Porous TiO₂ Film, Resulting Mainly in the Broadened Scope and the Increased Intensity of SPV Response.