Material Issues in Real Device Application of Multi-function Hard Mask Process

We have studied the applicability of MFHM (Multi-Functional Hard Mask) process'. MFHM is very useful in terms of cost reduction and process simplicity compared to a-carbon process. In our study, MFHM/SOC (Spin on Carbon) showed a good etch selectivity at US (Photoresist/MFHM/SOC approximate to 1/1.4/7) and C/H (Photoresist/MFHM/SOC approximate to 1/1.4/10) if Si content is higher than 35wt%. Dry rework process is applicable for removal of all films and wet process is also possible for removal till 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-layer between photoresist and MFHM will be short-term solution. Defect 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.