In Situ Mitigation of Subsurface and Peripheral Focused Ion Beam Damage via Simultaneous Pulsed Laser Heating

Abstract

Focused helium and neon ion (He(+)/Ne(+)) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+)/Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposure process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. These results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams.

Solid-state nanopore localization by controlled breakdown of selectively thinned membranes

“…The formation of voids in both crystalline and amorphous silicon through helium ion beam exposure has been previously reported. [52,55–59] Indeed, TEM imaging of samples exposed to He-ion doses of 10 17 ions/cm 2 or higher has revealed a dense band of helium-filled nano bubbles,[52,58,60] with the band’s width and depth beneath the bombarded surface dependent on the ion beam energy and dose. [52,61] It has been shown that peak helium implantation occurs at roughly the nuclear stopping range of the sample, while maximum bubble concentration may occur at a slightly shallower depth.…”

Review Article: Advanced nanoscale patterning and material synthesis with gas field helium and neon ion beams

“…However, bulk heating may be impractical for processing complex samples where diffusion of dopants, metallization, or barrier layers limit the sample temperature. Recently, a pulsed laser system mounted on a HIM chamber has been used to mitigate subsurface damage by supplying intermittent thermal energy pulses to the substrate 37 during He þ exposure. This method localizes the heat in the near surface region via strong optical coupling while targeting a specific region-of-interest in the lateral coordinate using a focused laser spot.…”

“…Similar to He þ , a strategy is necessary to mitigate Ne þ subsurface damage. The in situ pulsed laser-assisted exposure strategy has been shown to minimize subsurface damage induced from Ne þ milling; 37 however, more work is required because Ne þ generates more defects and implanted Ne is slower to diffuse than helium, and thus more photothermal energy is needed.…”

“…Recent work has shown that using synchronized laser irradiation during the graphene milling process can reduce the deleterious effects of backscattered He þ ions and recoil atoms in GNRs (Ref. 37) and promotes higher electrical conductivity. It is currently unclear whether the heat from the laser promotes defect healing or if it promotes the diffusion of defects out of the GNR and into the continuous film.…”

“…[157][158][159][160] As discussed earlier, subsurface defect generation is also concomitantly decreased at appropriate conditions. 37 The HIM also demonstrates exceptional potential as a probe for direct-writing defects into materials. This potential is primarily due to the mass of the He þ ion.…”