W delta doping in Si(1 0 0) using ultraclean low-pressure CVD

W delta doping in Si epitaxial growth by WF ₆ and SiH ₄ reaction has been investigated using an ultraclean cold-wall low-pressure chemical vapor deposition (CVD) system. Atomic-layer order W deposition is performed on wet-cleaned Si(1 0 0) substrate at 100 °C using WF ₆ and SiH ₄ . Si epitaxial growth is achieved by SiH ₄ reaction at 480 °C on 4 × 10 ¹³ cm ^-2 W deposited Si(1 0 0), however, it is found that almost all the deposited W atoms segregate on the deposited Si film. It is also found that such segregation is suppressed by the atomic-order W diffusion into Si(100) substrate by the heat treatment at 520 °C before the Si deposition. In the case of the Si film deposited on the 1.3 × 10 ¹⁴ cm ^-2 W diffused Si, the reflection high-energy electron diffraction (RHEED) pattern indicates the crystallinity and the roughness degrade. In the case of the Si film deposited on the 5 × 10 ¹³ cm ^-2 W diffused Si, the RHEED pattern shows streaks with Kikuchi lines. As a result, the W delta doping in the Si epitaxial growth is achieved, in which the W concentration is as high as 6 × 10 ²⁰ cm ^-3 and the incorporated W atoms is confined within 2 nm-thick region.