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PERFORMANCE AND DIAGNOSTIC MONITORING OF A REMOTELY CONTROLLED RF LOAD

IP.com Disclosure Number: IPCOM000239016D
Publication Date: 2014-Oct-01

Publishing Venue

The IP.com Prior Art Database

Abstract

The present disclosure generally relates to a radio frequency (RF) generator and, more particularly, to diagnostic monitoring of a RF generator.

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PERFORMANCE AND DIAGNOSTIC MONITORING OF A REMOTELY CONTROLLED RF LOAD

FIELD

[0001] The present disclosure generally relates to a radio frequency (RF) generator and, more particularly, to diagnostic monitoring of a RF generator.

BACKGROUND

[0002] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0003] Plasma etching is frequently used in semiconductor fabrication. In plasma etching, ions are accelerated by an electric field to etch exposed surfaces on a substrate. The electric field is generated based on RF power signals generated by a radio frequency (RF) generator of a RF power system. The RF power signals generated by the RF generator must be precisely controlled to effectively execute plasma etching.

[0004] A RF power system may include a RF generator, a matching network and a load (e.g., a plasma chamber). The RF generator generates RF power signals, which are received at the matching network. The matching network matches an input impedance of the matching network to a characteristic impedance of a transmission line between the RF

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generator and the matching network. This impedance matching aids in maximizing an amount of power forwarded to the matching network ("forward power") and minimizing an amount of power reflected back from the matching network to the RF generator ("reverse power"). Forward power may be maximized and reverse power may be minimized when the input impedance of the matching network matches the characteristic impedance of the transmission line.

[0005] Heuristic, feedback or feedforward approaches are typically used to control a RF generator to maximize power transferred to the matching network. Heuristic approaches include a set of rules that are used to direct a gradient based search method to provide a sensed response satisfying a predetermined criterion. A heuristic approach can include performing a search to tune frequency of a power amplifier circuit to minimize reverse power, increasing a step size of a search space, changing direction of the search, and initiating or ceasing a search. Heuristic approaches cannot be represented by a transfer function.

[0006] A feedback approach typically includes a feedback loop, which is used to minimize error between a power setpoint and an amount of power transferred from a RF generator and a matching network. The feedback loop may include sensors and a control module. The control module adjusts output power of an agile frequency RF power source (or power amplifier). The sensors may detect voltage, current, forward power and/or reverse power out of the power amplifier and generate sensor...