Copper Distributions in Sputtered Al‐Si‐Cu Electrode

Abstract

Copper distributions in the thickness direction of magnetron sputtered Al‐Si[1.5 weight percent (w/o)]‐Cu(3.0 w/o) films (3300Å thick) have been measured by a 1.5 MeV He+ Rutherford backscattering spectrometry (RBS) technique. Here, optimized film thickness of 3300Å for analyzing precise copper distribution measurement was determined by RBS spectrum simulation. These films have good electromigration resistance as interconnection layers. The copper distribution is not uniform in the thickness direction in the as‐deposited films. That is, peak copper concentration reaches 12 w/o at the near interface with the silicon dioxide. The formation of a higher copper concentration layer leads to insufficient clearing of fine pattern aluminum line engraving by reactive ion etching. The copper distribution changes rapidly and this peak disappears when performing sintering. More uniform copper distribution can be attained with the short duration sintering by rapid thermal annealing at 450°C as compared with furnace sintering. Therefore, acceptable fine pattern aluminum line etching is expected in this film.