Al tapered etching application to submicron multilevel interconnection process

Al tapered etching has been developed using 10
^-3
Torr magnetron RIE system in order to bury SiO
²
film 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∼-2
Torr Al RIE, is accomplished employing Cl
2
alone. 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 CHCl
3
of the deposition gas to Cl
2
of the etching gas. The 70° of the tapered side wall angle provides fully refilling of SiO
2
in 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 SiO
2
which gives an excellent step coverage enables us to refill SiO
2
in the space with an aspect ratio of 1.3 even at 80° tapered angle.