Flash Tube Radiation Annealing of BF2-Implanted Silicon

Abstract

Laser and electron beam annealing of ion-implanted semiconductor are currently of great interest as alternatives to thermal annealing. It is known that unconventional annealings are essentially extensions of thermally induced recovery and regrowth processes which are dependent on power density, annealing time and energy balance. The annealing mechanism does not seem to depend on the coherence of the source. Any source capable of applying short and intense heat pulses should suffice for rapid annealing. For large areas processing and economic considerations, a high power density, short pulse flash tube radiation annealing may be more advantageous than other unconventional annealing methods. With appropriate control, light pulses from flash tube heat up the surface layer of ion-implanted silicon very rapidly and may anneal out the damage or recrystallize the amorphous layer.Two inches in diameter and about 10 mil in thickness wafers of 3-5 Ω-cm, phosphorus doped, (001) and (111) oriented silicon were implanted at room temperature with 100 keV BF+2 ions to doses of 1 x 1014 to 1 x lO16/cm2. A demountable flash tube was used to anneal the samples with 100 μsec FWHM pulses and energy density (ED) ranging from 19.6 to 41.1 J/cm2. The fill pressure of air was kept beloe 30 torr. Optical and scanning electron microscopy (OM and SEM) were used to study the changes of silicon surface after annealing. Transmission electron microscopy (TEM) was performed to investigate the microstructural changes. Four point probe method was applied to measure the sheet resistivity.