Transparent and electrically conductive GaSb/Si direct wafer bonding at low temperatures by argon-beam surface activation

AbstractDirect wafer bonds of the material system n-GaSb/n-Si have been achieved by means of a low-temperature direct wafer bonding process, enabling an optical transparency of the bonds along with a high electrical conductivity of the boundary layer. In the used technique, the surfaces are activated by sputter-etching with an argon fast-atom-beam (FAB) and bonded in ultra-high vacuum. The bonds were annealed at temperatures between 300 and 400°C, followed by an optical, mechanical and electrical characterization of the interface. Additionally, the influence of the sputtering on the surface topography of the GaSb was explicitly investigated. Fully bonded wafer pairs with high bonding strengths were found, as no blade could be inserted into the bonds without destroying the samples. The interfacial resistivities of the bonded wafers were significantly reduced by optimizing the process parameters, by which Ohmic interfacial resistivities of less than 5mΩcm2 were reached reproducibly. These promising results make the monolithic integration of GaSb on Si attractive for various applications

Industrial PVD metallization for high efficiency crystalline silicon solar cells

In this paper we present first results concerning different thermal evaporation processes for thin aluminum layers, which are carried out on a pilot system with a throughput of up to 540 wafers/h (156x156 mm2). To qualify the processes the deposited aluminum layers were evaluated with respect to homogeneity and conductivity. Additionally the effect of the different processes on the passivation quality of a thermally grown 100 nm thick SiO 2 was analyzed by means of lifetime measurements, indicating a negligible effect of the conducted process variations on the passivation quality. Finally high-efficiency silicon solar cells were prepared to determine the overall potential and to compare it with an electron beam (e-gun) evaporation process, which is used as a standard process in our laboratory. An efficiency of up to 21% was achieved by the high deposition rate technique performing at least as well as our standard high efficiency process

All Copper NICE Modules

In this work the first All Copper NICE (New Industrial Solar Cell Encapsulation) modules with solder-freeribbon to finger interconnections are presented. Experiments were conducted to investigate if silver can be fully omitted from solar cells with copper plated fingers in combination with the NICE module technology. We could show that silver flash plating, front and rear silver busbars or pads can be omitted without compromising series resistance or module performance. All Copper NICE modules were manufactured with fillfactors up to 76.8 %