AVS 47th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS2-ThA

Paper PS2-ThA1
Ion Energy Control for Enhanced Plasma Etch Selectivity

Thursday, October 5, 2000, 2:00 pm, Room 311

Session: Dielectrics I
Presenter: Y. Andrew, University of Wisconsin, Madison
Authors: Y. Andrew, University of Wisconsin, Madison
E. Ko, University of Wisconsin, Madison
J. Machima, University of Wisconsin, Madison
S.-B. Wang, University of Wisconsin, Madison
A.E. Wendt, University of Wisconsin, Madison
Correspondent: Click to Email
Ion energy distribution (IED) control@footnote1@ at the substrate during plasma etching has been examined for improvements in SiO@sub 2@/Si and SiO@sub 2@/photoresist etch selectivity. The IED is controlled using a tailored bias voltage waveform applied to the substrate in place of the conventional RF sinusoidal waveform. A periodic waveform consisting of a voltage ramp in combination with a short pulse produces a plasma sheath in front of the wafer with nearly time-invariant voltage, leading to a nearly monoenergetic ion flux at the substrate, as compared to the relatively broad IED typically produced by a sinusoidal waveform. A 13.56 MHz helicon etching tool, equipped with a substrate bias power supply capable of producing the tailored substrate bias waveform, has been used to etch blanket films of photoresist, Si and SiO@sub 2@ using sinusoidal and tailored bias voltage waveforms. Etch rates of the blanket films are measured in situ using laser interferometry. Results to be presented show improved selectivity with the tailored waveform and a broadened process window for selective etching of SiO@sub 2@ over silicon in fluorocarbon-based plasmas, and etch rate vs. ion energy data suggest physical mechanisms. Selective etching of SiO@sub 2@ over photoresist is also examined, as it is very desirable to reduce the demand for thick photoresist and the challenge it presents to lithography technology. Substantial improvements in SiO@sub 2@/photoresist selectivity are expected. @FootnoteText@@footnote 1@S. B. Wang and A.E. Wendt, "Control of ion-energy distribution at substrates during plasma processing" to be published, J. Appl. Phys., June 1999.