Technology for nanoperiodic doping of a metal oxide semiconductor field-effect transistor channel using a self-forming wave-ordered structure

Abstract

A self-forming nanostructure—a wave-ordered structure with a controllable period (20–180 nm)—results from the off-normal bombardment of amorphous silicon layers by low-energy (∼ 1–10 keV) nitrogen ions. The nanostructure has been modified by reactive-ion etching in plasma to form a periodic nanomask on the surface of the channel region of a metal–oxide–semiconductor field-effect transistor (MOSFET). Implantation of arsenic ions through the nanomask followed by the technological steps completing the fabrication of the MOSFET resulted in a periodically doped channel field-effect transistor (PDCFET), which can be considered as a chain of short-channel MOSFETs with a common gate. Having worse subthreshold characteristics, PDCFETs show greater drain current and transconductance than to MOSFETs without a periodically doped channel. This improvement in device performance is attributed to the fact that the channel length is cut by the length of high-conductivity doped areas in the channel and that the voltage is distributed between the areas, depressing the scaling rules for short-channel MOSFETs and allowing the channel to be less doped between the areas, thus keeping drift mobility high.

Stress-induced solid flow drives surface nanopatterning of silicon by ion-beam irradiation

“…Indeed, for ion energies ranging from 100 eV to 100 keV, IBS has shown a remarkable capability 2 to produce ordered nanoscale-sized patterns (mostly ripples and dots) over large areas (up to tens of cm 2 ) for a wide range of targets, including semiconductors, metals, and insulators. 3,4 However, despite its large potential for technological applications, 5 the promise of IBS as a fully controlled and understood method to tailor patterns with custom-designed properties has turned out hard to achieve. This is partly due to the huge time-scale separation among different processes that influence the system, which complicates the clear-cut identification of the main underlying physical mechanisms.…”

Designing self-organized nanopatterns on Si by ion irradiation and metal co-deposition

“…So-called wave-ordered nanostructures generated by lowenergy nitrogen ion irradiation of Si were investigated as periodic nanomasks to dope the channel region of field-effect transistors [15]. Low-energy ion beam irradiation of surfaces under simultaneous co-deposition of small amounts of metal atoms gives rise to pronounced self-organized surface nanopatterns.…”

Nanoscale model of surface erosion by ion bombardment

“…According to the equation (1) solution, obtained in ref. [2], sputtering smoothes the nanowaves that contradicts numerous observations of ripples (for instance [3]) and implementation of coherent wave structures [4].…”

“…It is a well-known fact that solids sputtering by O 2 , N 2 and noble gas ions results in ripple formation [3]. During the silicon bombardment by N + 2 ions under certain conditions, ordered wave structures with periods of 25-120 nm appear [4]. Regardless of the waves' origin, their growth is caused by the sputtering process only, whereas equation (1) predicts waves dyingout during the sputtering process.…”