Residence time effects on SiO2/Si selective etching employing high density fluorocarbon plasma

Abstract

Articles you may be interested inSurface kinetics modeling of silicon and silicon oxide plasma etching. I. Effect of neutral and ion fluxes on etching yield of silicon oxide in fluorocarbon plasmas Effect of nonsinusoidal bias waveforms on ion energy distributions and fluorocarbon plasma etch selectivityThe residence time effects on SiO 2 etching characteristics using inductively coupled plasma of C 4 F 8 alone were first studied in the range from 6 to 300 ms. It was then found that SiO 2 and Si etch rates were minimum at a residence time of 25 ms, at which the CF 1 ϩ ion density and the fluorocarbon polymer deposition rate measured at 130°C became maximum. From this good correspondence, the SiO 2 etching was considered to follow a reaction model where the CF 1 ϩ ions might contribute to the polymer deposition, thus suppressing the SiO 2 etching, and where the dominantly observed CF 3 ϩ ions could etch SiO 2 on the assumption of elevated SiO 2 surface temperature due to the ion bombardment. Next, in the condition of short residence times ͑Ͻ25 ms͒, Ar was added to C 4 F 8 in order to allow Ar ϩ ions to remove the fluorocarbon polymer film that is responsible for the reduction of the SiO 2 etch rate. For a residence time of 10 ms the SiO 2 etch rate continuously increased with the Ar concentration up to a maximum etch rate of 0.4 m/min for 90% Ar addition. Various plasma diagnostics demonstrated that the 90% Ar addition resulted in an increase of the CF x ϩ (xϭ1 -3), C ϩ , and Ar ϩ ion densities, in contrast to a decrease of the CF 3 radical density. Metastable Ar atoms as well as highly elevated electron temperature are considered to be responsible for the increasing ion species. Consequently SiO 2 /Si contact hole features with 0.18 m opening and 2 m depth were successfully fabricated employing the 90% Ar/C 4 F 8 mixture at a residence time of 10 ms. The He addition has also been investigated and showed similar changes in plasma characteristics to those observed for Ar addition, but the ''etch stop'' occurred. This probably resulted from the poor sputtering effect of He ϩ ions due to their light mass.

Improved etch characteristics of SiO2 by the enhanced inductively coupled plasma

“…The substitution of Ar is also known to help suppress excessive polymerization and improve etch rate by higher ion density. 10 It reveals a monotonic increase of ion density for the Ar percentage and shows a rapid increase near the 70% range. To avoid an abrupt increase of ion density, we chose a condition of 60% Ar to check the frequency dependence of ion density.…”

Gas flow characteristics of argon inductively coupled plasma and advections of plasma species under incompressible and compressible flows

“…As a result, the plasma species densities changed with the residence time, as observed in Ref. [19]. In addition, the density profile alters when changing the gap between the electrodes due to the competition of the above time scales, [20] or by considering a gas flow module into the fluid model or not, [21] in a capacitively coupled plasma source.…”

Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

“…10 above. The fact that several experimental works revealed that the CF þ ions are the most predominant ions in the C 4 F 8 ICP source 25,57,58 and that both our hybrid model with relatively simple surface kinetics, as well as the global model with more complete polymer surface kinetics, fail to predict this higher CF þ ion density, indicates that some mechanisms for the formation of CF þ ions are still missing from both models. It is not yet clear which mechanisms are missing, but some candidates might be the direct production of CF þ ions by ion bombardment on the surface polymer, or bulk dissociative charge exchange of ions with polymeric heavy fc neutrals.…”