Cyclic etching of silicon oxide using NF3/H2 remote plasma and NH3 gas flow

• Published in: Plasma processes and polymers Vol. 18; no. 11
• Main Authors: Gill, You Jung, Kim, Doo San, Gil, Hong Seong, Kim, Ki Hyun, Jang, Yun Jong, Kim, Ye Eun, Yeom, Geun Young
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.11.2021
• Subjects: Adsorption; Ammonia; cyclic etching; Etching; Fluorosilicates; Gas flow; Hydrogen fluoride; NF3; Plasma etching; remote plasma; Selectivity; Silicon dioxide; Silicon oxides; SiO2
• ISSN: 1612-8850; 1612-8869
• DOI: 10.1002/ppap.202100063

Selective isotropic cyclic dry etching of silicon oxide (SiO2) was investigated using a three‐step cyclic process composed of hydrogen fluoride (HF) adsorption by NF3/H2 remote plasma and reaction with NH3 gas flow to form ammonium fluorosilicate ((NH4)2SiF6), and desorption by heating. The variation of the ratio of NF3:H2 (2:1 to 1:3) and adsorption time (10–180 s) showed the highest etch selectivity of SiO2 over Si3N4 at 1:2 ratio of NF3:H2 and with the adsorption time of 20 s. The etch selectivity higher than 40 was observed with 20 s of adsorption time with a 1:2 ratio of NF3:H2 remote plasma and the total etch depth was linearly increased with the increase of cycles with the SiO2 EPC of ~7.5 nm/cycle. Selective isotropic cyclic dry etching of SiO2 was investigated using a three‐step cyclic process composed of HF adsorption by NF3/H2 remote plasma and reaction with NH3 gas flow to form (NH4)2SiF6, and desorption by heating. The etch selectivity higher than 40 was observed and the total etch depth was linearly increased with the increase of cycles with the SiO2 EPC of ~7.5 nm/cycle.