Study of Copper Surface Preparation by Sequential Atomic Layer Wet Etching and Laser Annealing Treatments

Abstract

Atomic scale surface preparation, e.g. atomic layer etching, cleaning, local surface modifications and selective area deposition, becomes increasingly important for device scaling at sub-10 nm technology nodes in order to meet more stringent process variations and the highly selective process requirements. In the fully self-aligned via process, a topography is created by recess etching the underlying metal (copper) layer using chemical mixtures. In addition to a high compatibility with the materials exposed, one of the key requirements is to control the copper recessing such that the change in its roughness is kept at a minimum. The fundamental understanding and control of the polycrystalline surface reactions and interactions at the atomic scale are needed. In this paper, we will demonstrate the copper recess process for atomic layer wet etching (ALWE) with combination of laser thermal annealing (LTA) for surface smoothening.

Roughness and Uniformity Control during Wet Etching of Molybdenum

“…In this last section, wet etching of Mo in a stepwise manner will be discussed. A stepwise process using a sequence of an oxidation (step 1) followed by an oxide-dissolution (step 2) was evaluated in a similar manner as previous studies with Cu and Co [12,13]. The main requirements for wet-ALE etching are that step 1 is self limiting and step 2 selective.…”

Controlled and Uniform Wet Etching of Molybdenum Nanowires

“…Compared to the conventional wet etching processes, this is expected to provide a more controllable etching rate, because amorphous oxides can be formed isotropically. Such etching behavior has been previously explored for a range of metals, such as copper and cobalt [3,4]. Molybdenum (Mo) has been considered a promising candidate for interconnect applications by virtue of its high conductivity and thermal stability [5,6].…”