Magnetron-sputtered aluminum films for integrated circuit interconnections

Abstract

Aluminum films for integrated circuit (IC) contacts and interconnections are routinely deposited by thermal evaporation from resistance-heated, induction-heated and electron-beam-heated sources. Sputtering has not been used until recent advances produced magnetron sputter deposition equipment capable of depositing aluminum films compatible with IC requirements. This paper describes results of a study on magnetron-sputtered aluminum films for IC interconnections. A circular planar magnetron 20.3 cm in diameter was employed for film deposition on silicon substrates 7.6 cm in diameter moving on a circular path above the cathode. Metal coverage was better than 50% for oxides steps with 70° step angles and was equivalent to or better than that observed with other deposition techniques. Aluminum films typically 1 μm thick, having resistivities within 10% of the bulk value of 2.71 μΩ cm, were routinely deposited in this system. Film conductors 12 μm wide and 1.14 mm long, patterned on oxidized silicon substrates and coated with plasma-deposited SiO 2 were used for resistivity ratio RR(= ρ RT/ ρ 4.2K) measurements; the RRs lie in the range 35–50. The microstructure of magnetron-sputtered aluminum films is similar to that of conventionally deposited films. MOS capacitor structures fabricated on p-type silicon substrates with sputter-deposited aluminum films showed C-V characteristics comparable with those obtained by using aluminum films deposited from electron-beam-heated or induction-heated sources. Magnetron sputtering appears to produce films as suitable for IC contacts and interconnection applications as any other physical vapor deposition process and offers solutions to problems generated by the requirements of advanced device technology.