Two-step cycling process alternating implantation and remote plasma etching for topographically selective etching: Application to Si3N4 spacer etching

Abstract

This article proposes an original method to achieve topographically selective etching. It relies on cycling a two-step process comprising a plasma implantation step and a removal etching step using remote plasma source process. Both steps can be achieved in the same reactor prototype chamber, which has the capability to produce both capacitively coupled plasma and remote plasma (RP) discharges. It is shown that in RP processes, an incubation time exists before the etching starts. The introduction of a plasma implantation step prior to the RP step allows us to selectively functionalize the horizontal surfaces of the material with respect to the vertical surfaces, thanks to the ion directionality. The modifications induced by the implantation allow us to modify the incubation time between an implanted and a nonimplanted material offering a process window with infinite etch selectivity between horizontal and vertical surfaces. This approach has been demonstrated on Si 3 N 4 blanket films with the perspective to be applied to the Si 3 N 4 spacer etching process in which etch selectivity is a key issue. For this particular application, a cycling process comprising an H 2 plasma implantation and a He/NH 3 /NF 3 remote plasma process has been developed. The H 2 implantation modifies the Si 3 N 4 surface state by incorporating oxygen contaminants coming from the reactor wall and creating dangling bonds. This surface functionalization considerably reduces the incubation time. New insights into the etching mechanisms of Si 3 N 4 films exposed to NH 3 /NF 3 remote plasma are proposed and explain why the presence of Si-O bonds is mandatory for the initiation of the etching.

Reaction Mechanism and Selectivity Control of Si Compound ALE Based on Plasma Modification and F-Radical Exposure

“…ALE, like its deposition counterpart atomic layer deposition (ALD), relies on the self-limiting half-reactions to achieve atomic-level thickness control. , The first ALE half-reaction typically consists of a surface modification step, by either the reaction with a gaseous precursor or a plasma treatment. The modified layer is removed in the subsequent half-reaction, during which volatile reaction products are formed by, for example, a plasma exposure, ,, thermal treatment, − or precursor exposure . Ideally, both half-reactions are self-limiting resulting in the controlled removal of material independent of particle fluxes.…”

“…Over the years, several different materials systems have been investigated for plasma ALE. ,− Etch processes for the etch of Si compound materials have gained significant interest due to their widespread use in semiconductor manufacturing, for example, their use as etch stop layer or mandrel in spacer defined multiple patterning approaches . In these applications, a high etch selectivity between different Si compound materials, such as SiN, SiO, and SiC, is essential. ,− The etching of SiO 2 has been reported by Wang et al using a combination of fluorocarbon (FC) deposition, and argon- or oxygen-ion bombardment .…”

“…8,11 The first ALE half-reaction typically consists of a surface modification step, by either the reaction with a gaseous precursor or a plasma treatment. The modified layer is removed in the subsequent half-reaction, during which volatile reaction products are formed by, for example, a plasma exposure, 9,11,12 thermal treatment, 13−15 or precursor exposure. 16 Ideally, both half-reactions are self-limiting resulting in the controlled removal of material independent of particle fluxes.…”

Gate spacers etching of Si3N4 using cyclic approach for 3D CMOS devices

“…24,25 Another approach is to modify Si 3 N 4 using light ions followed by selective removal of the modified layer. [26][27][28] Both techniques show high selectivity and limited c-Si recess for 2D applications. They could be used for 3D architectures but would need significant optimization.…”

Surface Modification of Dielectric Substrates by Broad Beams of High-Energy Atoms of Inert Gases

“…Ion implantation is a method for injecting high-energy atoms into the surface of a solid to modify its near-surface layer [1][2][3][4][5]. There can be modifications to chemical, physical, mechanical properties and microstructure of the layer.…”