AVS 59th Annual International Symposium and Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS1-WeA

Paper PS1-WeA2
Time Resolved Ion Flux Measurement in Pulsed ICP Plasmas

Wednesday, October 31, 2012, 2:20 pm, Room 24

Session: Plasma Diagnostics, Sensors and Control 2
Presenter: G. Cunge, LTM-CNRS, France
Authors: G. Cunge, LTM-CNRS, France
M. Darnon, LTM-CNRS, France
N.St. Braithwaite, The Open University, UK
E. Despiau-Pujo, LTM-CNRS, France
P. Bodart, LTM-CNRS, France
M. Brihoum, LTM-CNRS, France
M. Haass, LTM-CNRS, France
O. Joubert, LTM-CNRS, France
Correspondent: Click to Email
Pulsed ICP plasmas are a promising solution to several technological issues related to IC circuit fabrication. Recent results are indicating that pulsing the inductively coupled power and/or the RF biasing power allows to increase the etch selectivity and to reduce plasma induced damages in ultrathin layer. However, the reasons for these improvements remain unclear. In particular, the impact of plasma pulsing on the ion flux (and ion energy) in electronegative gases used for IC circuit fabrication has not been studied in details. In this work, we have used a capacitively-coupled planar ion flux probe to monitor the time variations of the ions flux in various plasmas (CF4, SF6, Cl2, HBr…etc) operated in an industrial etch reactor from AMAT. We will discuss in detail the experimental set-up that we have designed to carry out time resolved measurement and the issues associated with this measurement. Results will be presented from both electropositive (Ar, He) and electronegative (Cl2, BCl3, SiCl4, SF6) plasmas. We will first present the impact of the ICP source pulsing frequency and duty cycle on the ion flux. These results will be compared to those obtained from a global model. We will then discuss the impact of the RF biasing power on the ion flux in pulsed plasmas. Both the ICP source power and the RF bias power can be independently or synchronously pulsed. In the latter case different duty cycles and a phase delay can be used. During synchronized pulsing with a delay between the ICP and the rf bias pulses, some interesting instabilities (ion flux oscillations) are observed. They are related to the generation of ion acoustic waves by the rapid expansion (or collapse) of the sheath in front of the wafer when the RF bias pulse is applied to the chuck. These results will be eventually compared to IEDF measurements in pulsed plasmas and the consequences on pulsed plasma etch process design will be discussed.