Delta-doping of boron atoms by photoexcited chemical vapor deposition

Abstract

Boron delta-doped structures in Si crystals were fabricated by means of photoexcited chemical vapor deposition (CVD). Core electronic excitation with high-energy photons ranging from vacuum ultraviolet to soft x rays decomposes B2H6 molecules into fragments. Combined with in situ monitoring by spectroscopic ellipsometry, limited number of boron hydrides can be delivered onto a Si(100) surface by using the incubation period before the formation of a solid boron film. The boron-covered surface is subsequently embedded in a Si cap layer by Si2H6 photo-excited CVD. The crystallinity of the Si cap layer depended on its thickness and the substrate temperature. The evaluation of the boron depth profile by secondary ion mass spectroscopy revealed that boron atoms were confined within the delta-doped layer at a concentration of 2.5 × 1020 cm−3 with a full width at half maximum of less than 9 nm, while the epitaxial growth of a 130-nm-thick Si cap layer was sustained at 420 °C.

Soft X-ray Reflection Spectroscopy for Nano-Scaled Layered Structure Materials

“…This approach enables to reconstruct a highly precise chemically- and spatially- resolved nano-scaled interfacial map up to tens of nanometre thickness within a few atomic percent in a non-destructive manner. The developed approach is demonstrated on a silicon-boron thin film structure because of its emerging technological interest, where boron is used as a p-type dopant in Si-based microelectronics 40 . However, the approach is applicable to other complex layered structures as well.…”