New plasma approaches for atomic scale precision etching

Dr Nicolas Posseme

Univ. Grenoble Alpes


Plasma etching plays a key role in the fabrication of high performance devices but we are facing more complexity and atomistic scale dimension control. There is a need to develop processes meeting technology requirements: dimension control and film integrity with an atomic precision. Today the situation is plasma technologies improvement (Low Te, pulsing plasma) can partially meet the requirements of the most aggressive technological nodes. While atomic layer etching (ALE) seems an interesting alternative for the new emerging devices. This technique has been developed for more than 25 year and is today considered one of the most promising techniques for achieving the low process variability and film integrity. The ALE cycle starts with a modification step to form a reactive layer, followed by the modified/reactive layer removal selectively to the non-modified underneath layer. A variety of self-limiting mechanisms have widely been investigated in the literature. Thus, different modification mechanisms have been proposed like chemisorption, deposition, and conversion. While removal methods include thermal desorption, neutral beam, ion bombardment, chemical reaction or wet cleaning. In this context, we propose to present two original etching approaches which consist of quasi atomic layer etching of silicon nitride (Si3N4) based on film modification by H2 plasma and selective deposition/etching for 2D and 3D CMOS device realization, respectively.