Radio frequency diagnostics for plasma etch systems

Scott Bushman; Thomas F. Edgar; Isaac Trachtenberg; Norman Williams

doi:10.1117/12.186784

16 September 1994 Radio frequency diagnostics for plasma etch systems

Scott Bushman, Thomas F. Edgar, Isaac Trachtenberg, Norman Williams

Proceedings Volume 2336, Manufacturing Process Control for Microelectronic Devices and Circuits; (1994) https://doi.org/10.1117/12.186784
Event: Microelectronic Manufacturing, 1994, Austin, TX, United States

Abstract

Using control hardware and software connected to a personal computer, on-line measurements of the state of a plasma etcher can be used to integrate mathematical models, control algorithms, and equipment communications in a plasma etcher in order to develop a real-time monitoring and control system. Sensors available on the reactor include electrical probes for monitoring the rf voltage and rf current, laser interferometry for measurement of etch rate and end- point detection, and optical emission spectroscopy for relative species concentrations and reactor state measurements. Chamber pressure, rf power, and gas flow rates are manipulated variables in this system. We have developed steady-state models of the plasma etcher using these on-line diagnostics. The focus of this paper is the development of the rf power monitoring system located between the matching network and the plasma chamber. This sensor provides information about the voltage and current of the plasma chamber, the phase difference between them, and the dc bias voltage across the electrodes. Also measured are the capacitor positions of the automatic tuning network and the electrical characteristics before the matching network. For the parallel plate reactor and a CF₄/H₂/Ar plasma used in these experiments, we found that the impedance of the plasma was a nonlinear function of power and pressure. Using simple equivalent circuit models for the plasma discharge and for the transmission cable, we have computed the plasma impedance, actual delivered power, and sheath thickness over a range of operating conditions.

Citation Download Citation

Scott Bushman, Thomas F. Edgar, Isaac Trachtenberg, and Norman Williams "Radio frequency diagnostics for plasma etch systems", Proc. SPIE 2336, Manufacturing Process Control for Microelectronic Devices and Circuits, (16 September 1994); https://doi.org/10.1117/12.186784

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