Selective Oxide (SelOx) Deposition as Unique Gap-Fill Solution for Shallow Trench Isolation

Continuous shrinking of technology nodes in CMOS device fabrication raises the Aspect Ratio (AR) requirements for dielectric gap-fill applications. Especially for Shallow Trench Isolation (STI), processes are needed which have the capability to fill gaps with AR of 8:1 at 45 nm gap widths. This gap-fill capability but also a tunable SiO₂ film stress and no damage risks to underlaying materials are favoring Sub-Atmospheric-Chemical-Vapour-Deposition (SA- CVD) as preferred STI fill solution for Logic-/DRAM- technology nodes below 90 nm. Selective Oxide (SelOx) deposition as SA-CVD based STI fill technique was studied for a critical case, given by boundary device conditions (thermal budget < 950degC, taper angles >87deg and lateral isolation requirement due to under-laying Deep-Trench structures for the given DRAM type). All the presented results indicate that the SelOx deposition process has the potential as gap-fill solution for future technology nodes.