Silicon Nitride Etch via Oxidation Reaction in Fluorocarbon/Oxygen Plasma:A First-Principle Study

• 作者: Du Zhang Mingmei Wang Yu-Hao Tsai
• 来源期刊: 微电子制造学报
• 学科: 工学
• 关键词: 3D-NAND oxide NITRIDE OXYNITRIDE plasma ETCH FIRST-PRINCIPLE
• 年，卷（期）: 2018,（1）
• 页码范围: 2-10
• 页数: 9页
• 分类号: TN

摘要

Conducting all-in-one etch process for 3D-NAND fabrication requires close etch rate(E/R)for SiO2 and Si3N4;however,to attain comparable and high etch rate for both materials is challenging.In this work,we performed first-principle studies on the etching mechanism of Si3N4 in fluorocarbon/oxygen plasma.The feasibility of using fluorocarbon/oxygen plasma to etch Si3N4 while attaining close E/R to SiO2 through the complementary nitride to oxynitiride(SiOxNy)transformation has been identified.Such transformation involves two stages:N atom elimination and Si-O bond formation.By modeling the essential chemical reactions on the Si3N4 surface,we shed light upon the underlying mechanisms behind both stages.We simulated the N-elimination reactions involving the formation and desorption of NO and FNO molecules as well as the substitution with F atoms.We found that N atoms can be eliminated by forming NO molecules,especially with the assistance of F-substitution in Si-N bond breaking.The predicted O-additive energies indicates that forming SiOxNy structure after N-elimination is possible.Following that,the dependency of chemistries favoring either high E/R or active SiOxNy formation on the fluorocarbon/oxygen ratio was discussed.We hope that the work will build a foundation for future studies on pursuing all-in-one ON etch process via the surface modifications.