Pulsed Electron Beam Annealing Ion Implanted Materials: Equipment and Results

A series of pulsed electron beam accelerators has been developed for the modification of material surfaces. Each facility produces an electron beam with an average particle energy of 10-100 keV, a fluence of 0.5 to 10 J/cm2 on the sample, and a pulse width of 20-200 nsec. The total energy stored (per pulse) varies between the different models from 15 to 1500J with a maximum repetition rate of 0.5 Hz. The uniform beam has a diameter of 1-10 cm. These accelerators are used for annealing ion implants. After processing, the surface exhibits perfect, dislocation-free crystal regrowth for single crystal materials. A variety of discrete electronic devices have been fabricated with characteristics comparable to those observed with optimum thermal (furnace) annealing procedures. The first production application of pulsed electron beam annealing will be for solar cell junction fabrication, where the high speed (1800 four-inch-diameter wafers per hour) and low power consumption give a strong cost advantage over competing furnace or pulsed laser equipment.