Improving metal step coverage with reflow

New dry etching procedure is utilized and additional reflow process step is introduced into standard contact dry etching process. Physical cross-sectional FESEM pictures are compared and the metal step coverage of the sidewall and bottom of contact are measured. Experimental results indicate that increasing the metal thickness does not help to improve the metal step coverage for both sidewall and bottom of the contact. However, metal step coverage is improved with a new dry etching procedure and further improved with additional reflow process step after contact etch using furnace. This additional reflow step improves the metal step coverage by rounding off the sharp corners on the contact sidewalls without contact excessive CD loss and degrading device performance. This approach is extremely useful for deep contact formation.