| 摘要 |
A composite hard mask is disclosed that helps formation of an integrated circuit (IC), for example, a magnetic random access memory (MRAM) cell with ultra-small lateral dimension, especially 65 nm or finer ones. The hard mask element contains a heavy metal Ta layer and carbon layer atop the Ta. The IC or MRAM device pattern is first transferred from photoresist to carbon layer by ashing using gas(es) comprising oxygen, and then to heavy metal Ta layer using gas(es) comprising Fluorine. Alternatively, A dielectric layer selected from SiO2, SiN, SiON or SiC can be added atop the C layer to form a tri-layer hard mask element. By adding a thin dielectric layer above the carbon layer, the etching selectivity between photoresist and carbon layer can be further improved. Such a hard mask element is particularly needed for ultra-fine lithography including 193 nm lithography in which photoresist is thin and not sufficient to prevent a Ta layer from being etched away before a good hard mask is completely formed. |
