Paper PS-ThM1
New Plasma Source Generating High Radical Flux With Low Ion and Photon Flux

Thursday, November 2, 2017, 8:00 am, Room 22

Substrate cleaning of organics utilizes a range of technologies that includes wet processing, barrel ashers, and microwave driven downstream plasmas. In this work, we introduce a unique inductively coupled downstream source configuration to generate high density radical concentrations (>1.1E+17 cm^-3) but without high ion and photon fluxes typically found in conventional inductively coupled plasmas. Although the plasma discharge tubes are isolated from the treatment chamber, they deliver a large concentration of free radicals. The low ion and photon exposure significantly reduces the opportunity for damage to sensitive layers. This inductive plasma arrangement prevents local heating and charging on the wafer, and behaves similarly as a microwave downstream plasma. However, a higher oxygen radical flux promotes more efficient organic layer cleaning and/or removal of photoresists even when low thermal budgets are a constraint.

This work will first describe the High Density Radical Flux (HDRF) source and characterize its behavior in generating high radicals flow and low ions in local downstream, on the wafer surface. Second, several applications using the HDRF technology will be discussed. These applications will include cleaning of 30:1 aspect ratio (AR) silicon vias, removal of sacrificial layers in MEMS structures, low temperature photoresist removal, and surface smoothing of Bosch generated sidewalls using micro-isotropic etching. With a low local electrical potential, due to the limited ions present in the process chamber, the HDRF is particular efficient with 3D structures on the wafer (e.g. MEMS and other high AR features) where preventing ion shielding effects is important.