Time-multiplexed etching, the Bosch process, is a technique consisting of alternating etch and deposition cycles to produce high aspect-ratio etched features. The Bosch process uses SF 6 and C 4 F 8 as etch and polymer deposition gases, respectively. In these experiments, polymer thickness is controlled by both C 4 F 8 gas flow rates and by deposition cycle time. The authors show that polymer thickness can be used to control wall angle and curvature at the base of feature walls. Wall angle is found to be independent of trench width under thin-polymer deposition conditions. Experimental results are compared to results obtained by other researchers using the more conventional simultaneous etch/deposition technique.
Satellites in the range of 10–50 kg require small propulsion devices to perform station-keeping tasks in orbit. Low-temperature co-fired ceramic structures provide a unique platform to produce a reliable, low-cost micropropulsion system. The design uses microchannels embedded in the ceramic substrate to create a nozzle and embedded catalyst chamber. A hydrogen peroxide monopropellant is injected into a silver-coated catalyst chamber structure. The monopropellant decomposes into hot gas, which is expelled through the nozzle producing thrust. A thermal energy balance and a kinetic model is presented along with performance testing
We have coimplanted carbon and a series of elements (B, N, Al, P, Ar, Ga, As, and Kr) in GaAs to study the effect of both implant damage and stoichiometry on activation. Electrical activity of C was found to increase due to the additional damage caused by coimplantation of a heavy element regardless of the chemical nature of the coimplant. Maintaining stoichiometry by coimplanting a group III element further increased activation in substrates heavily damaged during implantation. Activation of 65±3%, corresponding to a sheet free-carrier concentration of 3.5×1014 cm−2, was achieved by coimplanting Ga and annealing at 950 °C for 10 s.
Raman spectra of carbon-doped GaAs and InP show two peaks which are characteristic of C clusters with sp2 bonding. The peaks are seen in C-implanted GaAs and InP following either rapid thermal annealing or furnace annealing. The peaks are also seen in heavily doped epilayers following furnace annealing. Various mechanisms for C precipitation are discussed. Experimental evidence suggests that the loss of the group V component at the surface during annealing may play a role in the precipitation of C.
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