Processability of thin-film, fine-line pattern on aluminum nitride substrates for HICs

The processability of a thin-film line pattern, 76-μm wide, on aluminum nitride (AlN) using sputter deposition and photolithography techniques is investigated. Results on the stability of AlN substrates in the processing environment, thin-film deposition, fine-line pattern generation and laser scribability of AlN are reported. It has been discovered that: (1) The surface of the AlN substrate decomposes to an amorphous aluminum hydroxide phase when the substrate soaked in deionized water at 100°C for 30 minutes or longer, (2) The surface of AlN oxidizes rapidly to α-Al₂O₃ when the substrate is heated in air above 1000°C. This oxidized layer readily cracks during rapid cooling, and (3) AlN is laser scribable, (4) 53% of the circuits on AlN had opens as compared to none on Al₂O₃. This is attributed to a surface roughness almost fourfold higher than that of Al₂O₃ substrates