Discharge physics and atomic layer etching in Ar/C4F6 inductively coupled plasmas with a radio frequency bias

Abstract

Atomic layer etching (ALE), a cyclic process of surface modification and removal of the modified layer, is an emerging damage-less etching technology for semiconductor fabrication with a feature size of less than 10 nm. Among the plasma sources, inductively coupled plasma (ICP) can be a candidate for ALE, but there is a lack of research linking discharge physics to the ALE process. In this study, we comprehensively investigated the discharge physics of ICPs with a radio frequency (RF) bias and Ar/C4F6 mixture to be considered for the ALE process. Detailed studies on the discharge physics were conducted in each step of ALE (i.e., modification step, removal step) as well as the whole cycle as follows: (1) In the general ALE cycle, plasma properties dependent on the chamber geometry and the discharge mode of the ICP were analyzed; (2) in the modification step, a plasma instability with molecular gas was observed. The timescale for molecular gas removal was also investigated; (3) in the removal step, changes in plasma characteristics with the RF bias power were studied. Based on measurements of these plasma physical parameters, the discharge condition for ALE was optimized. ALE was performed on various thin films, including a-Si, poly c-Si, SiO2, and Si3N4. For each thin film, thicknesses of 0.5–2.0 nm were etched per cycle, as in quasi-ALE. Finally, ALE was performed on a patterned wafer, and the etch thickness of 0.6 nm per cycle and fine etch profile were obtained.

Correlation with the Microstructure and Synergistic Physiochemical Etching Resistance of Nanocomposites under Fluorine-Containing Plasma Conditions

“…The ICP power and RF bias voltage were 1.5 kW and 600 V, respectively, where the stable and high-density plasma, called inductive (H) mode, is sustained without plasma instability caused by negative ions and/or dust particles. 25 The plasma density measured by a microwave cutoff probe was 9 × 10 10 cm −3 as the high plasma density, which also confirms the pure H mode regime of the ICP. 26 This test was conducted under power conditions slightly stronger than those previously used in research because it was necessary to study various etching mechanisms, including chemical, mixing, and physical etching of the ceramics.…”

“…The details of equipment and etching conditions are provided in Figure and Table . The ICP power and RF bias voltage were 1.5 kW and 600 V, respectively, where the stable and high-density plasma, called inductive (H) mode, is sustained without plasma instability caused by negative ions and/or dust particles . The plasma density measured by a microwave cutoff probe was 9 × 10 10 cm –3 as the high plasma density, which also confirms the pure H mode regime of the ICP .…”

“…Using the shadow mask frame made of nickel–cobalt alloy, the specimen was partially covered, except for the area to be plasma-etched, which had a width of 500 μm and 100 μm. Plasma etching tests were performed in a radio-frequency (RF) biased inductively coupled plasma (ICP) chamber using CF 4 (40 sccm), O 2 (10 sccm), and Ar (10 sccm) mixed gases . A CF 4 -rich atmosphere was maintained during the experiment.…”

“…Plasma etching tests were performed in a radio-frequency (RF) biased inductively coupled plasma (ICP) chamber using CF 4 (40 sccm), O 2 (10 sccm), and Ar (10 sccm) mixed gases. 25 A CF 4 -rich atmosphere was maintained during the experiment. The details of equipment and etching conditions are provided in Figure 1 and Table 2.…”

Brief Review of Atomic Layer Etching Based on Radiofrequency-Biased Ar/C4F6-Mixture-Based Inductively Coupled Plasma Characteristics

“…In recent years, the critical dimension of semiconductor device has been reduced by a few nanometers, and the aspect ratio of patterns has been increased [1][2][3][4]. Accordingly, the need for technologies with atomic-level control in semiconductor manufacturing processes has grown as well.…”