RTO and SiN: An Optimum Low-Cost Si Passivation
Peter Singer, Editor-in-Chief -- Semiconductor International, 7/1/2000
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The researchers report that the combination of RTO and SiN also reduced the gap in passivation quality between the different nitrides, allowing for a high degree of freedom in the SiN deposition conditions. Furthermore, this combination has been shown to enhance the stability of the surface passivation under thermal treatments such as screen-printed contact firing (used in solar cell production). Such passivation on the front and back of solar cells may lead to 17%-efficient screen-printed cells on thinner substrates (100 µm) with low bulk lifetimes (20 µsec), resulting in considerable cost reduction.
Textured surfaces revealed a similar trend as planar surfaces, but showed an expected greater amount of surface recombination. Therefore, effective RTO and SiN passivation is even more essential for textured surfaces, since surface recombination frequently can limit performance.
Analyze SiGe with AES and SRP
A quick, yet comprehensive, way to characterize silicon/silicon-germanium heterostructures is to use a combination of two readibly accessible techniques: scanning Auger electron spectroscopy (AES) and spreading resistance profile (SRP) measurements. In recent work at Arizona State University and Lawrence Semiconductor Research Labs (both in Tempe, Ariz.), researchers showed it's possible to determine the thickness, composition and doping concentrations in the various layers of heterostructures using only AES and SRP. They also were able to make measurements of depth profiles and virtual substrate in a straightforward manner.
The work, reported in Semiconductor Science and Technology (Vol. 15, No. 3), employed a Solid State Measurements SSM-150 SRP tool (and associated lapping equipment) and a PHI600 Auger multiprobe. SRP and AES measurements were calibrated by SEM and RBS data.
BST Used to Detect Hydrogen
Thin ferroelectric films of BST (barium-strontium-titanate) could be useful for detecting hydrogen gas, according to new work at the Nanyang Technological University in Singapore. There, according to a June paper in the Journal of the Materials Research Society, amorphous BST thin-film capacitive devices were made on a silicon substrate to detect hydrogen gas and study hydrogen-induced interfacial polarization potential. Experimental results showed that Schottky I-V behavior appears in these Pd/amorphous BST thin-film/metal capacitive devices. Enhanced interfacial dipole potentials as large as 4.5 V at 1000 ppm hydrogen gas in air also were observed, which is about seven times larger than the best value reported under similar testing conditions. It was shown that the hydrogen-induced interfacial polarization potential is closely correlated with the microstructure of ferroelectric thin films, and the enhancement of this interfacial polarization potential is mainly attributed to the high dielectric constant of amorphous ferroelectric thin films. A simple hydrogen interface-blocking model also is presented to explain this interesting phenomenon.
New Reference Source
Due to be published in September 2001, The Encyclopedia of Materials: Science and Technology is a newly commissioned reference work from Elsevier Science. More than 2000 articles will be compiled in an 11-volume printed set. Plus, there will be a Web version of the Encyclopedia with access provided on a site-license basis. The plan, say the developers, is to integrate multimedia features, such as 3-D, animatino, movie clips and color, wherever appropriate. The Web site also will be updated regularly with 100 new or revised articles each year. It is priced at around $5000. For more information, see www.elsevier.com/locate/emsat.
