Ultra Shallow Junction Formation Using Diffusion from Silicides: I . Silicide Formation, Dopant Implantation and Depth Profiling

Abstract

Shallow junctions have been fabricated in a silicide-As-diffusion-source process using implantation of BF~ and As into thin silicides of cobalt, titanium, nickel, palladium, and platinum with emphasis on CoSi2. Ge-implantation was used in an attempt to amorphize the silicide prior to the boron introduction and thereby eliminate the possible channeling of boron in the polycrystalline silicide. Cross-section transmission electron microscopy (TEM) shows that Ge implantation created a heavily damaged layer of 10 nm in the silicide, which was restored to a polycrystalline state after annealing at 900~ for 10 s. For shallow boron depth profiling using secondary ion mass spectroscopy (SIMS), careful selection of the primary ion beam energy and angle was necessary to minimize ion beam mixing and shadowing due to surface roughness. The boron profile in a thick CoSi2, 300 nm, measured deeper than in a thin CoSi2, 50 nm, demonstrating the effect of SIMS shadowing. The effect of Ge-implantation on boron profiles was within the depth measurement error, indicating that no pronounced channeling had taken place in the silicide. Implant depths measured by SIMS agree well with those calculated by TRIM near the peak, but large deviations exist at the tail.

Ultra Shallow Junction Formation Using Diffusion from Silicides: II . Diffusion in Silicides and Evaporation

“…5b, 6b, and 7b, where B in NiSi, Pd2Si, and PtSi reached a concentration level of 1 x 102o am -3 at the interface after annealing at 800~ for lOs. Modeling.--In an attempt to model the dopant redistribution and evaporation, we assume, for a dopant/silicide system where dopant bulk diffusion is fast in the silicide (e.g., B in CoSi2 or As in TiSi2), that the total dopant, QT, in the silicide/silicon system can be expressed as QT = Qsur + Cs~d + Qsi --Qo + Qss + C~d + Qsi [1] where Q~ is the measured excess surface peak, comprised of Q0, a fixed amount on the silicide surface due to some dopant chemically bound to the silicide, and Qss, the dopant in solid solution due to surface segregation. The silicide thickness is d, C~t is the average dopant concentration in the silicide bulk after an annealing which allows a thorough diffusion in the silicide, and Qs~ the amount diffused into the Si substrate.…”

“…The sample preparation was described earlier (1,4). It is important to note, however, that the silicides used here were not capped.…”

Dynamic observation on the growth behaviors in manganese silicide/silicon nanowire heterostructures

“…Transition-metal silicide nanowires have been the subject of broad interest for their unique physical properties, good chemical stability, high quality interface with Si, excellent compatibility with Si device processing, and many superior functions available driven by their size effect. 2 Several synthetic approaches toward metal silicide NWs, including chemical vapor transport (CVT), 3,4 chemical vapor deposition (CVD), [5][6][7][8] hydrothermal process 9 and solid state reaction, [10][11][12] have been studied. Low resistivity metal silicides such as NiSi, 11,[13][14][15] NiSi 2 16 and PtSi 17,18 NWs have been fabricated for electric nano-device applications through solid state reaction, which is the chemical reaction caused by inter-diffusion of metal and Si atoms and subsequent phase transformation.…”