The Role of Reactive Gas Pulsing Synchronized with Digitally Processed DC Sputtering

Abstract

The formation of functional metal oxide crystals is widely required in CMOS backend processes. Recently, digitally processed DC sputtering (DPDS) was developed as an alternative layer-by-layer process to pulsed-laser deposition (PLD) for device development. DPDS enables the alternating process of depositing ultra-thin layers of metals and oxidizing them by using pulses of reactive gases that are partially synchronized with the sputtering of specific metals. However, it was found that crystallites were formed inhomogeneously due to damage by oxygen radicals, and there was room for improvement in crystallinity. Therefore, pulsed non-radical oxidation (NRO) was introduced into DPDS to avoid radical damage. We therefore designed a DPDS sequence using dual-cathode sputtering and gas pulses synchronized with sputtering interruptions. The sufficient oxidation for the metal few layers using NRO was confirmed. We also demonstrated the space group control of monoclinic (Er_0.1Y_0.9)₂SiO₅ and the reduction of oxygen vacancies, due to DPDS-NRO.