Functionalization of Silica Nanoparticles and Native Silicon Oxide with Tailored Boron-Molecular Precursors for Efficient and Predictive p-Doping of Silicon

Abstract

Designing new approaches to incorporate dopant impurities in semiconductor materials is essential in keeping pace with electronics miniaturization without device performance degradation. On the basis of a mild solution-phase synthetic approach to functionalize silica nanoparticles, we were able to graft tailor-made boronmolecular precursors and control the thermal release of boron in the silica framework. The molecular-level description of the surface structure lays the foundation for a structure−property relationship approach, which is readily and successfully implemented to dope non-deglazed silicon wafers. As the method does not require an additional oxide capping step and shows minimal risk of carbon contamination, as demonstrated by compositional and electrical characterizations of the wafers, it is perfectly adapted to advanced microelectronics manufacturing processes. ■ INTRODUCTIONDopants play a critical role in semiconductor devices and are therefore a major focus of research. 1−3 For instance, several doping strategies have emerged and led to significant improvements to drive impurities (dopant) inside pure substrates and to reduce the variability of targeted electronic devices, together with increased performances for nanoobjects. 4−11 However, improving dopant incorporation, avoiding randomness of concentration, and investigating diffusion phenomena still represent an outstanding challenge today, in particular with the development of smaller nanosized devices. 8 Indeed, increasing the performance in microelectronics has been directly related to the continuing shrinking of transistors 12 and thus to their optimized properties. The control of dopant concentration and distribution in semiconductors is essential, 8 and several methods such as single-ion implantation, 6 chemisorption of dopant from gaseous hydride molecules, 9,10 spin-on doping, 11 or single-atom doping 13 have been investigated. The monolayer doping (MLD) concept 14 appeared to be well-adapted to the medium doping range targeted for transistors or junctions in Fins as well as in nanowire structures. 15,16 However, transferring this process to the microelectronic industry is difficult because it requires a rather nonmanufacturing-friendly substrate (hydrofluoric acid deglazed silicon) and the use of a low-temperature, conformal SiO 2 evaporation capping to avoid dopant evaporation upon annealing. To circumvent this capping issue, the monolayer contact doping (MLCD) concept was recently proposed. 17,18 While providing good results in the formation of (ultra)shallow junctions, the use of two substrates (donor and acceptor) makes this ex situ technique not as straightforward as approaches related to MLD, relying on only one substrate.In this work, we show how to avoid these issues by the use of a simple bottom-up methodology based on the grafting of tailored boron-containing molecular precursors (anchoring/ self-protected) on the thin layer of native silica present on top of silicon wafers. This method takes advantage of (i) the presence of a...

Magnetic Memory from Site Isolated Dy(III) on Silica Materials

“…In that respect, we have demonstrated that the surface chemistry of a silica layer on passivated silicon wafers is analogous to that of high surface area silica nanoparticles and that identical surface species were found upon immobilization of molecules on both supports. 17,18 …”

Reaction of Bis(pinacolato)diboron with H-Si(100): The Pursuit of On-surface Hydrosilane Borylation Reactions

“…15,16 MLD has also been explored for other resists such as oxides, which helps minimize contamination from non-dopant species. [17][18][19][20][21] While solution phase processing allows for scalability, the high temperature anneal required for dopant incorporation limits the utility of wet chemistry methods as it limits dopant concentration to its solid solubility in Si and places restrictions on incorporating ultra-doping into traditional semiconductor fabrication processes. To obtain scalable routes to the transformational Si electronic behavior seen in APAM, we need solution phase chemistry processes that work without an anneal, namely processes involving direct Si-dopant chemistries.…”

Boron Monolayer Doping: Role of Oxide Capping Layer, Molecular Fragmentation, and Doping Uniformity at the Nanoscale

“…To date, most reports focus on studying the influence of surface chemistry used, molecular footprint, and details of capping layer used on the resulting doping levels. [ 18,27–32 ] The application of phenylboronic acid (PBA) monolayers in doping was previously studied, in part, for the formation of sharp p–i–n junctions in SiNWs, [ 17 ] for studying dopant diffusion and activation in SiNWs, [ 33 ] and for dopant patterning. [ 34 ] Herein, a systematic study to understand the impact of oxide cap deposition on the B‐doping by PBA monolayer is presented.…”