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METHOD AND APPARATUS FOR REDUCING REFLECTED POWER IN HARMONICALLY RELATED RF GENERATORS

IP.com Disclosure Number: IPCOM000237022D
Publication Date: 2014-May-27

Publishing Venue

The IP.com Prior Art Database

Abstract

THE PRESENT INVENTION GENERALLY RELATES TO RADIO FREQUENCY (RF) GENERATORS AND, MORE PARTICULARLY, TO PHASE AND FREQUENCY CONTROL OF RF GENERATORS.

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METHOD AND APPARATUS FOR REDUCING REFLECTED POWER IN HARMONICALLY RELATED RF GENERATORS

FIELD

[0001] The present invention generally relates to radio frequency (RF) generators and, more particularly, to phase and frequency control of RF generators.

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 one or more radio frequency (RF) generators of a RF power system. The RF power signals generated by the RF generators must be precisely controlled to effectively execute plasma etching. Plasma can also be used for deposition of material, such as in plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), and plasma-enhanced atomic layer deposition (PE-ALD). In addition, the plasma can be excited by capacitive coupling (CCP) or inductive coupling (ICP). The plasma is a highly nonlinear load, meaning that the response to multiple frequency excitations is not a simple superposition of the individual frequency components. If multiple frequency drives are used, the RF power signals mix nonlinerarly

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and couple back to the RF power sources in complex ways, depending on pressures in, temperatures of, gas compositions in, and power levels provided to the plasma. This nonlinear mixing can cause difficulties for semiconductor manufacturing in the form of poor process repeatability and/or yield problems.

[0004] A RF power system may include one or more RF generators, a matching network, and a load, such as a plasma chamber. RF power signals generated by the RF generators may be used to drive a load to fabricate various components such as integrated circuits, solar panels, compact disks (CDs), digital versatile (or video) discs (DVDs), and the like. The load may include any of a number of elements or devices driven by a RF signal, including, by way of a non-limiting example, a plasma chamber. The load may include broadband mismatched loads (i.e. cables with mismatched resistor terminations), narrowband mismatched loads (i.e. a 2-element matching network) and resonator loads.

[0005] The RF power signals may be 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 generator and the matching network. This impedance matching aids in minimizing an amount of power applied to the...