Characterization of Ion Implanted Silicon Annealed with a Graphite Radiation Source
A Varian IA-200 isothermal annealer has been used to anneal ion implantation damage and electrically activate dopants in As and B implanted silicon with minimal redistribution of the impurity. The anneal occurs in vacuum using infrared radiation from a resistively heated sheet of graphite. Good quality anneals of /sup 11/B implanted samples have been obtained with minimal boron diffusion. Arsenic implanted wafers have also be annealed with excellent results except for a substantial loss of As which occurs unless the wafer has an SiO/sub 2/ cap. The anneal quality of (100) wafers was independent of dose, however, the anneal quality of the (111) wafers improved with increasing As dose.
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.
Electrical Behavior of Group III and V Implanted Dopants in Silicon
The anneal behavior of layers implanted with dopants from column III (B, Al, Ga, and Tl) and column V (As, Sb, and Bi) in silicon substrates has been investigated. The ranges of implant conditions were energy 20–50 keV, dose 1013–1015/cm2, and substrate temperature 23°–500°C. Hall‐effect and sheet resistivity measurements were used to determine the effective number of carriers/cm2 (Ns)eff and the effective mobility μeff. Analysis of nonuniform distributions of carrier densities and mobilities on these measurements shows that the values of (Ns)eff and μeff can be misleading unless the effect of the depth distributions is allowed for. These distributions have been determined in some cases by the use of layer removal techniques combined with Hall‐effect and sheet resistivity measurements. We find in well‐annealed implanted samples that the dependence of the mobility on carrier density follows that determined for bulk silicon. In many cases deviation from this relation can be accounted for on the basis of com...