Dissertation/Thesis Abstract

Reduction of shallow boron and phosphorus diffusion by co -implantation
by Vanderpool, Aaron, Ph.D., Arizona State University, 2006, 177; 3311792
Abstract (Summary)

Control of Boron and Phosphorus Transient Enhanced Diffusion (TED) is the key to the development of high performance n and p type Ultra Shallow Junctions (USJ). Carbon, Fluorine, and Germanium co-implants can be used to reduce or modify the Boron or Phosphorus Interstitialcy Clusters (BIC or PIC) that drive TED. Substitutional Carbon (Cs) or Fluorine-Vacancy (F-V) clusters do this by consuming the interstitials that drive TED by Carbon Kick-out or F-V annihilation. Germanium does this by inhibiting Interstitialcy formation through local lattice strain. It has been found that certain combinations of these techniques can combine to maximize TED reduction and several of the mechanisms have been characterized. Low energy 5keV Germanium and Carbon have yielded a Boron USJ with a junction depth (xj) of 16.8 nm and a sheet resistance (Rs) of 602 Ω/□, while 8keV Fluorine and Carbon have formed a Phosphorus USJ with xj = 29.5 nm and Rs ≈ 150 Ω/□. In addition record levels of Boron TED control have been found using Carbon and 12keV Phosphorus co-implants (xj = 13.3 nm). Record levels of Phosphorus TED control have been found using Carbon and 4keV Boron co-implants (xj = 22.2 nm). In these cases the counter-dopant below the USJ is probably forming PIC or BIC consuming interstitials more efficiently than non-electrical dopants dramatically limiting TED. For Phosphorus USJ there is a strong TED dependence on Boron co-implant energy. Uphill diffusion has been observed if the Phosphorus implant energy is below 3 keV, or without amorphization, and increases as Boron co-implant energy decreases. This work has also found the first experimental evidence of F-V clustering acting to limit TED in USJ by toggling the order of Halo implantation which generates a vacancy distribution. This causes a change in Boron diffusion that is well explained by the lack or presence of the F-V clusters. In addition, Phosphorus TED shows a slight decrease as Fluorine co-implant energy decreases and seems to optimally place the F-V clusters at 8keV.

Indexing (document details)
School: Arizona State University
School Location: United States -- Arizona
Source: DAI-B 69/04, Dissertation Abstracts International
Subjects: Materials science
Keywords: Boron, Co-implantation, Diffusion, Phosphorus
Publication Number: 3311792
ISBN: 9780549596035