Improved sidewall doping of extensions by AsH<inf>3</inf> ion assisted deposition and doping (IADD) with small implant angle for scaled NMOS Si bulk FinFETs

Abstract

We demonstrate a novel photoresist-compatible FinFET doping technique that combines the advantages of deposition and implantation. Energy and deposition thickness optimization for the Ion Assisted Deposition and Doping (IADD) process provides excellent doping of nMOS extensions, thus reducing external resistance R EXT . On current I ON is improved by 6-8% for L G of 26-30 nm and by 15% for L G of 20 nm, with better SCE and DIBL. IntroductionSource/drain extensions for fins require good sidewall doping for low resistance. For isolated fins, this could be achieved by conventional beamline ion implant (I/I) with large tilt angles. However, large tilt is not possible in real technologies, where tight fin pitches result in implant shadowing by photoresist, e.g. nMOS shadowing by the photoresist required to block pMOS regions [1]. Limiting amorphization/damage is also a challenge, as narrow fins provide limited seed for high quality epitaxial regrowth [2]. Additionally, beam line I/I with small implant angles, e.g., 7-10°, has I ON /SCE tradeoff [3] even though bulk FinFET has superior SCE controllability than planar FET. The origin of the I ON limitation is that the fin bottom region cannot be doped unless the implant energy is high. Short channel control is limited by the leakage current through the center of the fin just below the plane of the STI oxide, where gate control is weak. To address these concerns IADD, which uses simultaneous dopant deposition and knock-in, has been developed.

Access resistance reduction in Ge nanowires and substrates based on non-destructive gas-source dopant in-diffusion

“…Si fin resistors have been demonstrated by a number of groups for this purpose. 13,14,15 To the best of our knowledge this is the first report of Ge fin resistors formed by top-down patterning.…”

Microwave plasma doping: Arsenic activation and transport in germanium and silicon

“…Plasma doping is a candidate technology for meeting these requirements. [8][9][10][11][12][13][14][15] Ueda et al reported high activated dose arsenic (As) conformal doping of 10 to 40 nm (aspect ratio > 2-4) silicon (Si) fin structures using a microwave RLSA™ plasma source using a radial line slot antenna and an AsH 3 gas process. 12) The source facilitates doping by supplying low energy ions and dopant radicals to the substrate ensuring minimum physical damage.…”

Light-Mediated Contact Printing of Phosphorus Species onto Silicon Using Carbene-Based Molecular Layers

“…When paired with a reactive interface, transfer printing can enable the delivery of monomolecular layers with regional p-/n-doping properties onto a semiconductor interface necessary for the development of ultrashallow doping strategies. Specifically, the immobilization of inorganic atoms, such as phosphorus and boron, to silicon is an essential component in the fabrication of ultrashallow doping interfaces for next-generation complementary metal–oxide–semiconductor (CMOS) transistors. , To maintain low series resistance in sub-10 nm CMOS transistors, surface junctions should exhibit abrupt depth profiles and high phosphorus/boron concentrations that help to negate short-channel effects. − Such properties cannot be achieved with current ion beam implantation techniques, which either produce broad, low-concentration dopant zones or inflict crystallographic damage upon the surface of a substrate over a micrometer range. − Alternatively, plasma doping studies have demonstrated the ability to generate more conformal doping profiles; however, surface quality concerns arising from the entrapment of dopant molecules at the oxide interface during implantation have also been reported . Scanning tunneling microscopy (STM) has been shown to produce atomically precise phosphorus-doped regions on silicon using a STM probe to cleave Si–H bonds and generate strong and chemically inert Si–P bonds in a site-by-site manner. , However, this deposition and patterning technique has very low throughput and requires ultrahigh vacuum conditions.…”

“… 29 − 31 Such properties cannot be achieved with current ion beam implantation techniques, which either produce broad, low-concentration dopant zones or inflict crystallographic damage upon the surface of a substrate over a micrometer range. 31 − 33 Alternatively, plasma doping studies have demonstrated the ability to generate more conformal doping profiles; 34 however, surface quality concerns arising from the entrapment of dopant molecules at the oxide interface during implantation have also been reported. 35 Scanning tunneling microscopy (STM) has been shown to produce atomically precise phosphorus-doped regions on silicon using a STM probe to cleave Si–H bonds and generate strong and chemically inert Si–P bonds in a site-by-site manner.…”