AVS 61st International Symposium & Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS-MoA

Paper PS-MoA10
Hydrofluorocarbon Gases for Selective, Low-Damage, Silicon Nitride Etching

Monday, November 10, 2014, 5:00 pm, Room 308

Session: Advanced FEOL/Gate Etching
Presenter: James Royer, American Air Liquide
Authors: J. Royer, American Air Liquide
R. Gupta, American Air Liquide
V. Pallem, American Air Liquide
Correspondent: Click to Email
Maintaining Moore’s law has introduced increasingly stringent process requirements for front-end device technologies. These requirements create considerable technical challenges for silicon nitride gate spacer etching. Etch processes must remove thin silicon nitride layers while maintaining stringent physical constraints and chemical integrity of the underlying substrate. Therefore, the etch gases must be tailored with appropriate functionality for selective silicon nitride etching. This study presents hydrofluorocarbon (HFC) etch gases which demonstrate selective etching of silicon nitride with respect to silicon oxide, and poly-silicon. Using a RIE plasma etch tool, the performance of each molecule is studied on blanket wafers and analyzed using spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Etch rates and selectivities for each HFC are evaluated over a range of O2 flow to determine the desirable process windows. Select HFCs have large process windows with infinite silicon nitride to poly-silicon selectivity due to fluorocarbon deposition on the poly-silicon. The fluorocarbon deposition layer on poly-silicon inhibits undesired silicon-carbide or silicon-oxide formation. XPS surface analysis and depth profiling shows a reduction in carbon and oxygen incorporation in poly-silicon compared to similar processes using the industry standard molecule, fluoromethane.