라디칼 선택적 흡착과 이온에너지 제어를 통한 원자층 식각으로의 적용성 연구

Abstract

As the technology industry developed highly due to the Fourth Industrial Revolution, the demand and importance of high-performance semiconductor devices such as FinFET (Gate All Around), and 3D NAND Flash Memory increased. However, Since the existing dry etching is impossible to precisely etch, there is a limit to the manufacture of high-performance semiconductor devices. To solve this problem, Atomic layer etching (ALE), a new method of replacing the existing dry etching, has emerged. But the process time is long and when plasma is discharged in the adsorption step, other particles such as ions and electrons are generated in addition to radicals, and are accelerated by the electric field to unintentionally etch the surface. In this study, To solve the problems of surface damage and long process time, the ALE process technology which removes ions and electrons and selectively adsorbs radicals during the adsorption step was studied. In addition, precise etching was performed by controlling the amount of ion energy and ion flux in the desorption step through the bias driving frequency and pulse. This was applied to the atomic layer etching process. Using the Ion saturation current probe, It was confirmed that Ions and electrons could be grounded through mesh-gird and radicals could be selectively adsorbed by confirming that the Ion current generated during the adsorption step is zero. In addition, It was confirmed that Ion energy and Ion flux can be adjusted with bias frequency and pulse by analyzing the Ion energy distribution function with the Retarding Field Energy Analyzer. Thereafter, Atomic layer etching process was performed with an SOI wafer using radical selective adsorption and Ion energy control. As a result, EPC(Etch per cycle)s of 1.1Å/cycle were measured for both 12.56MHz, 41.68MHz, and 60MHz bias frequency at 7V. In the case of an atomic layer etching process while applying a bias in the form of a pulse, 1.1Å/cycle was confirmed when the pulse duty was 100% and 60%. At pulse duty 30%, the EPC was reduced at 12.56MHz, 41.68MHz. because the Ion flux required for etching was insufficient. But at 60MHz, ion flux was sufficient even at pulse duty 30%, the EPC of 1.1Å/cycle was confirmed. In this study, More precise etching was possible through radical selective adsorption using mesh-grid and Ion energy controll using bias driving frequency and pulse.