Development of high uniformity Al1-xScxN piezoelectric film stack dry etching process on 8-inch silicon wafers. (April 2023)

• Record Type: Journal Article
• Authors: Yan, Jiahui; Zhou, Yongxin; Zhang, Songsong
• Is Part Of: Vacuum. Volume 210(2023)
• Publication Date: 2023-04
• Subjects: ICP etching -- Pretreatment -- Al1-xScxN -- Uniformity -- Etching rate -- Selectivity; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2023.111907
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: This paper have investigated the basic properties of inductively coupled plasma reactive ion etching (ICP-RIE) of scandium doped aluminum nitride (Al1-x Scx N) thin films on 8-inch silicon wafers, and presented a pretreatment scheme which can effectively improve the etching uniformity and wafer yield in the mass fabrication of Al1-x Scx N-MEMS (micro-electromechanical systems) devices. Based on BCl3 /Ar pretreatment and Cl2 /Ar main etching scheme, an etching rate of 128 nm/min is obtained, with the low nonuniformity, and selectivity of 1.8 with respect to the loss of molybdenum (Mo) electrode is achieved, respectively. The relationship between etching parameters and etching uniformity is revealed in detail by the 5-step Al1-x Scx N etching model. Meanwhile, to optimize the etching compatibility in the fabrication of Al1-x Scx N-piezoelectric MEMS devices, a variety of etching masks (e.g. photoresist and silicon dioxide) are respectively used to obtain the consistent sidewall profile at different locations, with photoresist of 24° and silicon dioxide of 57°. Highlights: BCl3 -based pretreatment effectively reduces the etching nonuniformity on 8-inch silicon wafers and improves wafer yield. The ICP etching mechanism of Al1-x Scx N is discussed. The relationship between etching parameters and nonuniformity is revealed. Optimize recipe for high consistency on etching sidewalls.