Plasma enhanced atomic layer deposition of silicon nitride using magnetized very high frequency plasma

Abstract

To obtain high-quality SiNx films applicable to an extensive range of processes, such as gate spacers in fin field effect transistors (FinFETs), the self-aligned quadruple patterning (SAQP) process, etc., a study of plasma with 
higher plasma density and lower plasma damage is crucial in addition to study on novel precursors for SiNx
plasma-enhanced atomic layer deposition (PEALD) processes. In this study, a novel magnetized PEALD process 
was developed for depositing high-quality SiNx films using di(isopropylamino)silane (DIPAS) and magnetized 
N2 plasma at a low substrate temperature of 200°C. The properties of the deposited SiNx films were analyzed and compared with those obtained by the PEALD process using a non-magnetized N2 plasma source under the same 
conditions. The PEALD SiNx film, produced using an external magnetic field (ranging from 0 to 100 G) during 
the plasma exposure step, exhibited a higher growth rate (~1 Å/cycle) due to the increased plasma density. 
Additionally, it showed lower surface roughness, higher film density, and enhanced wet etch resistance compared 
to films deposited using the PEALD process with non-magnetized plasmas. This improvement can be attributed 
to the higher ion flux and lower ion energy of the magnetized plasma. The electrical characteristics, such as 
interface trap density and breakdown voltage, were also enhanced when the magnetized plasma was used for the 
PEALD process. Furthermore, when SiNx films were deposited on high-aspect-ratio (30:1) trench patterns using 
the magnetized PEALD process, an improved step coverage of over 98% was achieved, in contrast to the 
conformality of SiNx deposited using non-magnetized plasma. This enhancement is possibly a result of deeper 
radical penetration enabled by the magnetized plasma.