Automatic impedance matching method for plasma reaction chamber

Abstract

The invention relates to an automatic impedance matching method for a plasma reaction chamber. The method comprises the following steps that (a) an initial impedance value of an adjustable-impedance element is set; (b) whether reflection power measured on a coaxial cable is larger than a first threshold value or not is judged; if yes, the step (c) is performed, and if not, the step (b) is performed circularly; (c) whether the frequency of an RF power source is stable or not is judged; if yes, the step (d) is performed, and if not, the step (c) is performed circularly; (d) whether the reflection power measured on the coaxial cable is larger than a second threshold valve or not is judged; if yes, the step (e) is performed, and if not, the step (b) continues to be performed; (e) the impedance value of the adjustable-impedance element is adjusted through an adjusting step length, wherein the phase difference alpha between the adjusting step length and to-earth voltage and current and / or the value of V / Icosinealpha-50 are both positive or negative, and the second threshold value is larger than the first threshold value. The accurate impedance adjusting step length is provided for the adjustable-impedance element in the impedance matching circuit, and matching efficiency is improved.

Description

technical field [0001] The invention relates to the technical field of plasma processing, in particular to a method for automatically matching the impedance of a plasma reaction chamber. Background technique [0002] In a plasma processing apparatus, an RF power supply supplies power to a process chamber to generate a plasma. Plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules and free radicals. These active particles interact with the wafer or workpiece to be processed placed in the chamber and exposed to the plasma environment. Plasma reaction occurs on the surface to change the surface properties of the wafer or workpiece, thereby completing plasma etching or other processes. [0003] In the above-mentioned plasma processing apparatus, the RF power supply generally has an operating frequency of 13.56MHz, an output impedance of 50Ω, and is connected to the lower electrode of the plasma processing chamber through a coaxial c...

AI Technical Summary

Problems solved by technology

[0005] In the prior art, an adjustment step is usually manually selected randomly for adjustment, but the direction of adjustment and its specific size are not known, so this adjustment method often needs to go back and forth many times, which is inefficient and may Increased reflected power during conditioning, which adversely affects the plasma processing process

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