Abstract
The change in electrode impedance of semiconductor equipment due to repetitive processes is a major issue that creates process drift. In the current plasma etch chamber with a dual-frequency power system, the high-powered radio frequency (RF) source contributes to the enhancement of the plasma density, and the low-frequency bias power at the bottom electrode is adopted to enhance the injected ion energy in the plasma. The impedance control of the top electrode in dual-frequency capacity coupled plasma limits the impedance matching capability of the RF matching system because it only considers the high-frequency RF source. To control the precise impedance in dual-frequency semiconductor equipment, independent impedance control is required for each frequency. In this study, the impedance corresponding to a specific frequency was independently controlled using L (inductor) and C (capacitor). A 60 MHz stop filter and VVC were used to control 2 MHz impedance at a specific point, and a 2 MHz stop filter and VVC were used to control 60 MHz impedance. In the case of 2 MHz impedance control, the 2 MHz impedance changed from 10.9−j893 to 0.3−j62 and the 60 MHz impedance did not change. When controlling the 60 MHz impedance, the 60 MHz impedance changed from 0.33 + j26.53 to 0.2 + j190 and the 2 MHz impedance did not change. The designed LC circuits cover the impedance of 60 and 2 MHz separately and are verified by the change in the capacitance of the vacuum variable capacitors implemented in the RF impedance matching system.
Highlights
Biasthe power is usedrapidly in various ways from butIn high dual-frequency capacity coupled plasma (DF-capacitively coupled plasma (CCP)) equipment in the etch process, 2 MHz frequencies are not used well because the ion energy rapidly decreases when it exceeds of bias power is the most common because high selectivity can be produced through
In the CCP equipment, 2, 27, and 60 MHz were supplied to the bottom electrode, and an impedance control circuit was inserted to block a specific frequency in the top electrode
This study proposed an radio frequency (RF) filter circuit design for dual-frequency RF impedance control to improve the wafer uniformity in the plasma etch process by independently controlling the chamber impedance between the source electrode or antenna and the bottom electrode via reactive plasma
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The semiconductor process becomes complicated, and the process time is extended because of the 3D device geometry with a high aspect ratio To alleviate this problem, several studies are being conducted to increase the frequency and improve the plasma uniformity. High frequencies can increase radical production rates because of the elastic collision of electrons, which process processes through chemical reactions with ions. Due to this characteristic, studies using very high frequencies (VHFs) are being conducted [7,8]. In dual-frequency semiconductor equipment, VVC is used to withstand high power, and frequency tuning and electronic matchers are being developed to increase matching speed.
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