Material lssues in Rea1 Device Application of Multi-function Hard Mask Process

Abstract

We have studied the applicability of MFHM (Multi-Functional Hard Mask) processl. MFHM is very usefill in terms of cost reduction and process simplicity compared to a-carbon process. ln our study, MFHM/SOC (Spin on Carbon) showed a good etch selectivity at L/S (Photoresist/MFHM/SOC ≈ 1.4/7) and C/H (Photoresist/MFHM/SOC &asymp l/1.4/10) if Si content is higher than 35wt%. Dry rework process is applicable for removal of a11 films and wet process is also possible for removal ti11 MFHM. However, footing of photoresist profile on MFHM is problematic. We have studied to know exact mechanism of footing and to find its solution. The introduction of inter-1ayer between photoresist and MFHM will be short-term solution. Defbet related to material is another issue in integration. Defect level is still high compared to a-carbon process but is not unbearable. Several approaches to solve footing and defect will be discussed in this paper.