A method is proposed for forming hillock-free aluminum-based alloy bus lines for active-matrix liquid-crystal displays (LCDs). Aluminum (Al)-based alloy films are deposited using an Al target containing boron (B) or nickel (Ni) in a sputtering ambient containing nitrogen. The Al-Ni films deposited using an Al target containing Ni showed excellent hillock resistance: virtually no hillock formation after thermal treatment at around 400 and no significant increase in resistivity. These films also showed good patternability with a simple wet etching: a smooth line edge and a gently tapered profile. These films are thus suitable for the bus lines of active matrices.