AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS-MoM

Paper PS-MoM11
Studies on Highly Selective Si3N4 Spacer Etching over Si/SiO2 using CH3F/O2 Plasmas

Monday, October 28, 2013, 11:40 am, Room 104 C

Session: Innovative Chemistries for Advanced Etch Processes
Presenter: B. Parkinson, TEL Technology Center, America, LLC
Authors: B. Parkinson, TEL Technology Center, America, LLC
A. Raley, TEL Technology Center, America, LLC
A. Ranjan, TEL Technology Center, America, LLC
K. Kumar, TEL Technology Center, America, LLC
P. Biolsi, TEL Technology Center, America, LLC
Correspondent: Click to Email
Recent advancements in device scaling have led to the widespread introduction of 3-D gate structures (i.e. FINFET, tri-gate). Introduction of 3D structures has increased the challenges of spacer etching. Planner gate structures typically require shorter over -etches (10-30%) and thus requirement of selectivity of spacer film over underlying films (Si and SiO2) is not as stringent as for 3-D structures. In the case of 3D gate structures, the spacer film will also surround the Si-fins. Surface of Si-fins must be pristine (residue-free and without surface modification) in order for epitaxial silicon growth. Complete removal of SiN around Si-fins typically requires over-etches ranging from 150 to 300%. This dramatic increase in OE time requires an increase in spacer film selectivity to Silicon (fins) and Silicon Oxide (gate-mask and isolation Oxide). CH3F/O2 based etching chemistries are typically used to achieve high Nitride-to-Oxide and Nitride-to-Silicon selectivity. This paper explores a CH3F/O2 chemistry created in a RLSATM plasma reactor. The impact of block photoresist masking on oxidation etching mechanisms is presented. An analysis of plasma characteristics using Optical Emission Spectroscopy (OES) is also provided. Experimental results indicate a correlation between ion energy (derived from peak-to-peak voltage, Vpp), passivation over SiN/Si/SiO2 (derived from gas-phase radical concentration) and selectivity. Microwave power and pressure provides control of relative concentrations of etchants/passivants (via control of electron energy distribution) and ion energies can be tuned by bias power. High Nitride-to-Oxide selectivity and minimal Si-and SiO2-loss can be effectively achieved by balancing passivation layer on SiN/Si/SiO2 and tuning Microwave Power and pressure to provide optimal Vpp.