Pacco, AntoineAntoinePaccoNakano, TeppeiTeppeiNakanoLoyo Prado, JanaJanaLoyo PradoLai, Ju-GengJu-GengLaiKawarazaki, HikaruHikaruKawarazakiAltamirano Sanchez, EfrainEfrainAltamirano Sanchez2025-07-312025-01-162025-07-3120240167-9317WOS:001392636300001https://imec-publications.be/handle/20.500.12860/45085In this work, an etching process for the controlled and partial recess of tungsten metal was developed. The process comprises two steps which can be repeated: a thermal oxidation of the tungsten followed by the oxide dissolution in an acidic or basic solution. During the first step the W metal is heated in the presence of O3 gas in the temperature range of 210–290 °C forming a WO3 oxide. During the second step this thermally grown oxide is then selectively dissolved towards the underlying W metal. Both NH4OH and H3PO4 were down selected as the best wet chemical dissolution agents in terms of dissolution rate and selectivity. By utilizing this combined thermal/wet-chemical cyclic etch process, the total W recess can be tuned on the nanoscale based on oxidation temperature and total number of cycles. This process was then applied for the deep recess (∼180 nm) of narrow (∼20 nm) tungsten trenches for the fabrication of the bottom contacts in complementary field-effect transistors (CFET).Journal article10.1016/j.mee.2024.112304WOS:001392636300001OXIDATION