A method for high selective etch of Si₃N₄ and SiC with ion modification and chemical removal

Abstract

We demonstrated a high selective and anisotropic plasma etch of silicon nitride (Si3N4) and silicon carbide (SiC). The demonstrated process consists of a sequence of ion modification and chemical dry removal steps. The Si3N4 etch with hydrogen (H) ion modification showed a high selectivity to silicon dioxide (SiO2) and SiC films without hydro fluorocarbon film deposition which has been used in a conventional Si3N4 etch process. A self-limiting reaction was observed by changing the ion modification and removal step times. The SIMS analyzes indicated that the etch amount of Si3N4 depends on not only penetration depth of H ion but also H concentration in the ion modification step. In addition, we have developed selective etch of SiC with nitrogen (N) ion modification. These results suggest that the ion modification assisted etch enables us to obtain the high selective Si3N4 or SiC film by H or N ion modification, respectively.

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

“…However, the ion dose deviated on the sidewalls will be lower than the one received on horizontal surfaces and certainly not sufficient to induce a fully modified H rich layer. Kumakura et al 47 have shown that the etching rate of the H 2 implanted surface layer depends on the H ion dose. It increases…”

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

“…Posseme et al and Nakane et al have shown that H 2 plasma can be used to obtain selective etching of SiN versus SiO 2 , , while Kumakura et al showed that it is possible to selectively etch SiC versus SiO 2 and SiN using N 2 plasma. , Since the second half-cycle is the same in all literature reports, this suggests that the plasma modification step plays a detrimental role in controlling the etching selectivity between the different Si compounds. How the different plasma treatments affect the various Si compounds can therefore provide valuable insights into the possible ALE processes and enable control of the etching selectivity between materials.…”

“…The high etch selectivity was attributed to the inability of F-radicals to etch SiO 2 at room temperature. Recently, the plasma modification process was extended to SiC by Kumakura et al, 10 who showed that SiC can be selectively etched versus SiN and SiO 2 using N 2 plasma modification followed by F-radical etching. In the above examples, the exact reaction mechanism of the plasma modification of SiN and SiC is difficult to determine.…”

“…To meet these requirements using conventional dry-etching processes, trade-offs have to be made between etch selectivity and profile control. − Furthermore, preventing aspect-ratio-dependent etching (ARDE) and plasma-induced damage becomes increasingly challenging . To overcome these challenges, atomic layer etching (ALE) has recently gained considerable interest as an alternative etching technique. − …”

Importance of higher‐level excited species in argon remote plasma sources: Numerical modeling with consideration of detailed chemical reaction pathways

“…These studies have mainly been of an experimental nature in a pressure range from a few to tens of mTorr. [4][5][6][7][8][9][10][11][12][13] However, only a few experiments have been carried out in the Torr regime. [14][15][16][17] Although the pressure in several remote inductively coupled plasma (ICP) chambers is reported as typically being in the range of 0.01−1 Torr, the gas pressure in the RPS chamber is generally higher than expected because of the structure of RPS systems.…”