A Simulation Study on Large-Area Inductively Coupled Plasma for Uniformity Optimization
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ORIGINAL ARTICLE
A Simulation Study on Large‑Area Inductively Coupled Plasma for Uniformity Optimization Eui‑Jeong Son1 · Sung‑Hwan Cho1 · Ho‑Jun Lee1 Received: 17 May 2019 / Revised: 8 June 2020 / Accepted: 28 July 2020 © The Korean Institute of Electrical Engineers 2020
Abstract The characteristics of large-area inductively coupled plasma were investigated to optimize the uniformity using a selfconsistent simulation based on a drift–diffusion approximation with anisotropic transport coefficients. As the aspect ratio increases, a tendency toward uniform plasma conditions of electron density on 450 mm wafer is reflected by an increase in the input power ratio of the outer coil. In the case of an aspect ratio of 0.29 (radius: 350 mm, height: 200 mm), the power distribution has a ratio of about 1.4:8.6, and the non-uniformity of the 450 mm wafer region is less than 1%. A lower aspect ratio is advantageous in terms of plasma uniformity. The plasma uniformity can be negatively affected by the electron density distribution changing to M-shape in the case of a lower aspect ratio of 0.3. When designing the chamber, the ratio of the surface area to the volume must be considered due to the differences in the plasma characteristics according to the radii and heights. Keywords Inductively coupled plasma · 450 mm wafer · Aspect ratio · Uniformity optimization · Power distribution
1 Introduction Inductively coupled plasma has been applied in various ways in semiconductor processes. Recently, fine processing has been made possible for semiconductor devices, which have been miniaturized up to the nanometer level. However, it is necessary to improve productivity and reduce costs, which requires developing 450 mm wafer semiconductor processing equipment [1–3]. A large-area plasma device for semiconductor fabrication requires the ability to generate uniform high-density plasma and high power-transfer efficiency. Research has been done on a variety of ways to improve the uniformity of high-density plasma, such as dome-shaped windows, metal windows, serial-parallel antennas of various types, power distributions using dual frequencies, and external capacitors * Ho‑Jun Lee [email protected] Eui‑Jeong Son [email protected] Sung‑Hwan Cho [email protected] 1
[4–13]. However, there are not many studies on the uniformity optimization of large-area inductively coupled plasma for 450 mm wafer process. It takes much time and cost to do this experimentally because of the many variables. Thus, the plasma profile and parameters were predicted by fluid simulations. In this study, the power distribution of the antenna, electron density distribution, and uniformity of electrons were studied with different chamber size for the uniformity optimization of large-area inductively coupled plasma. The antenna has two turns, and the position was fixed. The total input power was fixed at 1000 W, and the power distribution ratio of the two antennas was studied for each condition. The electron density distribution at the center and the wafer chuc
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