Abstract
Boron doping patterns characterized by very sharp lateral edge definition and 300–1000-nm linewidths have been written in silicon by localized heating with a diffraction-limited cw laser beam. The tightly focused beam generates free dopant atoms, and simultaneously promotes solid- state diffusion into the substrate. The nonlinear dependence of diffusion rates on temperature results in linewidths substantially narrower than both the temperature and the laser beam profiles on the surface. An enhancement is observed in diffusion rates under the strong thermal gradients created.