| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS-ThM |
| Session: | Plasma Sources |
| Presenter: | Chenhui Qu, University of Michigan |
| Authors: | C. Qu, University of Michigan S.J. Lanham, University of Michigan T. Ma, University of Houston T. List, University of Houston P. Arora, University of Houston V.M. Donnelly, University of Houston M.J. Kushner, University of Michigan |
| Correspondent: | Click to Email |
Pulsed inductively coupled plasmas (ICPs) are widely used for etching in semiconductor device fabrication. Pulse repetition frequencies (PRFs) of up to 10s kHz are commonly used for the high power density provided during the pulse-on period and the unique chemistry during the pulse-off period. The use of highly attaching halogen gases produces low electron densities during the pulse-off period, which can produce instabilities, E-H transitions and ignition delays when applying power. To mitigate these issues, a low-level power could be maintained during “pulse-off” to limit the minimum plasma density, therefore reducing ignition delays and enhancing plasma stability.
In this work, ICPs sustained by 1-5 kHz pulsed power using Ar/Cl2 mixtures at tens of mTorr were computationally and experimentally studied. The computations were performed with the 2-D Hybrid Plasma Equipment Model. The experiments include measurements of electron density (ne), temperature (Te) and electron energy distributions. The power is modulated during the pulse-off period and the transient behavior of the ICP was studied.
The computed Te reaches a quasi-steady state for both high and low power excitation. Some experimental results agree well with the predictions from the model while others show a reproducible delay in plasma ignition. The model predicts that within the skin-depth, Te spikes to a high value during the low-to-high power modulation and a low value during a high-to-low power modulation. Due to some averaging and energy loss that occurs during transit from the skin depth, both measurements and model results show little modulation in Te a few cm above the substrate. The influence of the power, pressure, PRF and duty cycle of the pulse profile on the bulk plasma properties will be discussed.
* Work supported by Samsung Electronics Co. Ltd., National Science Foundation and the DOE Office of Fusion Energy Sciences.