In situ dry cleaning of Si wafer using OF₂/NH₃ remote plasma with low global warming potential

Abstract

Dry cleaning technology is an essential technique that can be applied to remove native oxide and various contaminants during the semiconductor manufacturing for nanoscale electronic devices. In this study, the in situ dry cleaning of silicon dioxide (SiO 2) with low global warming potential (GWP) gas mixtures has been investigated by sequential process steps composed of the reaction of SiO 2 surface by oxygen difluoride (OF 2) (GWP: <1)/ammonia (NH 3) remote plasma and the removal of the reacted compound layer by lamp heating. By using the optimized OF 2 /NH 3 (2:1) mixture for the surface reaction followed by the lamp heating at 200 °C to remove the reacted compound layer, a high-SiO 2 cleaning rate and etch selectivity over silicon nitride (>30:1) could be obtained due to the formation of the highest HF concentration on the SiO 2 surface at the OF 2 /NH 3 (2:1) gas ratio. The compound layer formed during the reaction was (NH 4) 2 SiF 6 observed for a previously investigated NF 3 (GWP: 17 200)/NH 3 plasma, but the dry SiO 2 cleaning rate and the etch selectivity over Si 3 N 4 obtained by the OF 2 /NH 3 plasma were higher than those by the optimized NF 3 /NH 3 plasma. The effects of OF 2 /NH 3 mixture dry cleaning on the electrical characteristics of metal-oxidesemiconductor (MOS) devices fabricated on the nano-scale trench patterned Si substrate with high aspect ratio were studied and compared with conventional wet and NF 3 /NH 3 mixture dry cleaning-based devices. Compared with other cleaning methods, OF 2 /NH 3 dry-cleaning shows the improved and reliable electrical characteristics such as sharper capacitance-voltage behavior, lower hysteresis, less interface trap charge and smaller contact resistivity. Therefore, it is believed that the in situ sequential dry SiO 2 cleaning with the OF 2 /NH 3 remote plasma can be applied as an essential cleaning method with extremely low GWP for fabricating next generation nano-scale devices.

Passivation of oxygen vacancy defects in conductive ZnO nanoparticles via low-temperature annealing in NF3

“…For example, after five months of storage in air, the resistivity of the as-prepared AZO nanoparticles increases by a factor of 12. This increase in resistivity is attributed to the surface adsorption of moisture or oxygen molecules, especially at the V O sites where the surface free energy is high [28]. These surface adsorbates not only trap the electrons and thus reduce the free carrier concentration of AZO nanoparticles (see supplementary figure S2 for details), but also increase the surface energy barrier that will hinder the electrons from transporting between adjacent nanoparticles.…”

Bridging the gap between surface physics and photonics

“…It can be expected that dry cleaning or etching methods, which are under an intense development [e.g. [289][290][291], become very useful to optimize also the contact interfaces in particular if these methods can be integrated with a metal-deposition instrument in situ manner without breaking a vacuum environment. It is worth noting that meaning of the dry cleaning methods is expected to increase in more general when threedimensional structuring of device components increases; when trenches become deeper and more narrow, because the wet chemical methods do not perform properly for such structures.…”

Interfacial properties of multicomponent plasma‐modified high‐performance fiber‐reinforced composites: A review

“…(A) SiO 2 cleaning under OF 2 /NH 3 mixture plasma. [16] (B) Presumed etching models for the N 2 -added hydrogen plasma. [17] (C) Functionalization of PDMS surface.…”