Dual-Damascene Cu/Low-k Interconnect Fabrication Scheme Using Dissoluble Hard Mask Material

A Cu-low-k dual-damascene scheme is developed by employing a dissoluble hard mask material, AlO. High-selectivity etching, over 15, is achieved by using the AlO hard mask. After the etching, the remaining AlO dissolves in a postetch cleaning solution, making additional processing costs minimal. By using this scheme, the line-to-line capacitance reduces by 10% because no ashing is applied after low-k trench etching. Low-temperature deposition of AlO is found to be the key for the dissoluble property. When the deposition temperature is 100DGC or less, a wide range of conventional postetch cleaning solutions can be used to remove the remaining AlO hard mask.