Laser-driven boron diffusion into a Si epitaxial layer from a p⁺ boron-doped Si substrate

Experiments are described in which ∼0.2-s-wide argon laser pulses are incident on a 6-μm-thick n- Si epitaxial layer. Local melting and refreezing of both the layer and a small volume of the underlying p+ boron-doped Si substrate occur. In the molten phase, boron diffusion from the substrate is sufficient to make a low resistance path between the front surface and the substrate, with a nearly uniform dopant concentration of 5×10 18/cm3. The melted/recrystallized front surface diameter is ∼50 μm. Unique features and applications of this type of substrate contacting are discussed.