Effects of process parameters on microloading in subhalf-micron aluminum etching

Microloading effect is one of the challenging phenomena in sub-halfmicron aluminum etching, which represents the decreasing etch rate with shrinking pattern size and open area. Process parameters should be optimized to control etch rate difference in different feature sizes. In this experiment, it is found that pressure and BCl3/Cl2 gas flow ratio are two major factors to affect on etch rate microloading. Under the standard BCl3/Cl2 chemistry, optimizing process parameters is not enough to reduce microloading sufficiently. Therefore, additional gas is introduced to suppress microloading effect less than 10%. N2 or CHF3 gas addition is not effective to improve microloading effect through polymerization mechanism. It is observed that CF4 gas addition is the most successful to minimize microloading effect by enhancing ion assisted chemical reaction in small feature size.