AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS1-WeM

Paper PS1-WeM9
Macroscopic Diagnostics for In-Situ Measurement of Sidewall Charging During Plasma Etching

Wednesday, November 11, 2009, 10:40 am, Room A1

Session: Plasma Diagnostics, Sensors, and Control I
Presenter: E. Ritz, University of Illinois at Urbana-Champaign
Authors: E. Ritz, University of Illinois at Urbana-Champaign
J.A. Hoban, University of Illinois at Urbana-Champaign
M.J. Neumann, University of Illinois at Urbana-Champaign
D.N. Ruzic, University of Illinois at Urbana-Champaign
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In plasma etching processes, especially those with high aspect ratios, the leading type of manufacturing defects that occur are trenching, bowing and twisting. These defects cause failures in semiconductor devices such as processors and DRAM. In order to investigate the role of feature sidewall charging on these defects, a series of macroscopic diagnostics were implemented which are capable of measuring time-resolved charge buildup at several points along a feature profile. This in-situ diagnostic consists of alternating conducting and insulating layers made of copper and teflon, respectively, with an axial hole that acts as the feature via. The insulating layers create discrete measurement layers, provided by the copper electrodes, which can be independently monitored inside of a commercial etching tool in real time to determine how the incident current from the plasma varies along the feature depth. By measuring the current reaching the bottom of the feature, as compared to the mid-plane or the top, one can determine the influence of sidewall charging. To determine the effect of geometry on charging, several aspect ratios were used by maintaining the same device height but varying the diameter of the via. The entire diagnostic is 19.2mm tall with aspect ratios from 5:1 to 10:1. Plasma and charging experiments were conducted in a commercial silicon dioxide etch chamber with three available frequencies (2.0 MHz, 2.2 MHz, and 13.56 MHz) thus allowing study of frequency-dependent charging, as well. Typical powers ranged from 300W to 1000W resulting in sidewall current measurements on the order of milliamps. Typical plasma densities are 2*1012 ± 5*1011 cm-3 and electron temperatures are 3 ± 0.3 eV. Results from the diagnostics are shown for various plasma conditions and compositions.