Control of Arsenic Doping during Low Temperature CVD Epitaxy of Silicon (100)

Abstract

In situ arsenic doping during chemical vapor deposition (CVD) epitaxy of silicon is investigated. At low temperatures (around 700ЊC), a high arsenic concentration accumulates on the silicon surface. With a hydrogen bake (at 950ЊC) the surface concentration is significantly reduced and autodoping is inhibited. After the bake, the capping layer is grown at 700ЊC. At this temperature, the arsenic segregation, back to the surface, is suppressed. With this procedure, a relatively low baking temperature of 950ЊC is sufficient to reduce the autodoping level below 2 ϫ 10 16 cm Ϫ3 . Solid-state diffusion of the underlying arsenic profile is relatively slow at this temperature. This allows the fabrication of very sharp arsenic doping profiles. It is also shown that the arsenic surface concentration is proportional to the concentration that is incorporated into the epi layer. Furthermore it is shown that, in contrast to (kinetically limited) silicon growth, the arsenic transport is limited by gas-phase diffusion at 700ЊC, making the doping level dependent on pressure, temperature, and hydrogen flow.

Reduction of UHF power transistor distortion with a nonuniform collector doping profile

“…To obtain a sharp arsenic spike in the profile, a newly developed technique was applied. Hereby the in situ arsenic doping is accurately controlled during the entire epi-growth process [4], [5]. The growth conditions (gas pressures, deposition time, and temperature) are kept well within the specification of the CVD equipment and no exceptional accuracy is required of any parameter.…”

Arsenic-spike epilayer technology applied to bipolar transistors

“…The major feature is that the well-known autodoping, related to arsenic, has been suppressed. The process is briefly described in Section II-B and a more detailed description is given in [2].…”

“…The top-layer is grown at 950 C and reduced pressure (60 torr). More details about this process are given in [2].…”

“…We have grown an n-type spike in the epilayer which counterdopes the out-diffused boron. The spike is fabricated with a novel epitaxial process in which arsenic autodoping is strongly suppressed [2]. With this process 50 nm wide arsenic spikes with a doping concentration varying from 10 to 2 10 cm are made and the thickness of the layer grown on top of the spike (top-layer) is controlled very accurately.…”

Reduction of UHF power transistor distortion with a non-uniform collector doping profile

“…They are based on the (commercially available) Philips BLW-898 bipolar UHF linear power transistor, intended for linear amplification of signals in the 470 to 860 MHz frequency band. Experimental collector doping profiles were fabricated by using a newly developed epitaxy process that enables fabrication of sharp (50 nm wide) arsenic doped spikes [4], [5]. …”