| 초록 |
Atomic control of semiconductor manufacturing is required to overcome fundamental limits for nanoscale patterning. Atomic layer etching (ALE) technology, which is the counterpart of atomic layer deposition (ALD) is a fast growing interest because of its ability to enable high uniformity, self-limiting thermal reaction, Ångström-level removal and extreme pattern fidelity. Current ALE chemistries are limited to etching of inorganic materials and use harsh halogen etchants, resulting in undesired effect on electronic properties of silicon. For a halogen-free process, a cyclic step-wise process was developed with alternating cycles of plasma species and etchants to remove conformal layers. However, this method is anisotropic in nature because the energized ions travel toward the surface in one direction only. To keep this step as self-limiting as possible, accurate control of the ion energies and process conditions are required. In this work, we introduce the isotropic etching (i.e., without the use of plasma species) process that relies on sequential gas-phase surface reactions and does not require harsh halogen etchants. For this purpose, organic molecules as etchants are utilized to eliminate various metal oxides (e.g., MgO, ZnO, Al2O3, HfO2, ZrO2) with atomic-scale precision and demonstrate the feasibility of etch selectivities depending on oxidation state of the elemental metal. The film morphology, etch rates, and chemical compositions are investigated by using various analytical methods including Scanning Electron Microscope (SEM), Auger electron spectroscopy (AES), X-Ray Fluorescence Spectrometry (XRF), spectroscopic ellipsometry (SE), and Atomic Force Microscopy (AFM). Also, we identify the layer-by-layer etching proceeds using a quartz crystal microbalance (QCM) and a quadrupole mass spectrometer (QMS). The ability to etch metal oxides films we demonstrate in this work may achieve isotropic ALE and holds potential for future applications involving high surface area and complex 3D structures for which Ångström-level control over material removal is inevitable. |
