Al tapered etching application to submicron multilevel interconnection process

Al tapered etching has been developed using 10^-3Torr magnetron RIE system in order to bury SiO²film in the submicron space between Al lines. In this RIE system, a directional etching without a thick side wall protection film which is observed in a usual 10^-1∼-2Torr Al RIE, is accomplished employing Cl2alone. Thus, this etching reaction is mainly performed by the Cl ion bombardment under the lower chlorine concentration due to the lower pressure. Consequently, the side wall angle can be controlled precisely by mixing CHCl3of the deposition gas to Cl2of the etching gas. The 70° of the tapered side wall angle provides fully refilling of SiO2in the space pattern with an aspect ratio of 1.3 by bias sputtering. This coincides well with simulation results. In addition, the ArF excimer laser CVD of SiO2which gives an excellent step coverage enables us to refill SiO2in the space with an aspect ratio of 1.3 even at 80° tapered angle.