Control of arsenic doping during low temperature CVD epitaxy of silicon (100)

In situ arsenic doping during chemical vapor deposition (CVD) epitaxy of si licon is investigated. At low temperatures (around 700 degreesC), a high ar senic concentration accumulates on the silicon surface. With a hydrogen bak e (at 950 degreesC) the surface concentration is significantly reduced and autodoping is inhibited. After the bake, the capping layer is grown at 700 degreesC. At this temperature, the arsenic segregation, back to the surface , is suppressed. With this procedure, a relatively low baking temperature o f 950 degreesC is sufficient to reduce the autodoping level below 2 X 10(16 ) cm(-3). Solid-state diffusion of the underlying arsenic profile is relati vely slow at this temperature. This allows the fabrication of very sharp ar senic doping profiles. II is also shown that the arsenic surface concentrat ion is proportional to the concentration that is incorporated into the epi layer. Furthermore it is shown that, in contrast to (kinetically limited) s ilicon growth, the arsenic transport is limited by gas-phase diffusion at 7 00 degreesC, making the doping level dependent on pressure, temperature, an d hydrogen flow. (C) 2000 The Electrochemical Society. S0013-4651(00)03-052 -4. All rights reserved.