Effect of sputtering process parameters on the uniformity of copper film deposited in micro-via

Abstract

Abstarct: With the increase of the density of interconnecting technology for chip packaging, it is required to form smaller vertical interconnect micro-via in insulating dielectric materials with advanced packaging technology. However, a continuous and uniform copper film cannot be formed on the sidewall of the micro-via after plasma etching due to the existence of the undercut at the top of the micro-via. This paper has developed an interconnecting process for depositing copper film in 5–10 μm polyimide micro-via based on DC magnetron sputtering technology and investigated the effect of sputtering process parameters on the uniformity of copper film deposited in micro-via. It is found that sputtering power, bias voltage and working pressure have a great influence on the uniformity of the deposited copper film at the sidewall of the micro-via, and these parameters will lead to the deposition gap. In contrast, the rotating speed and deposition time have little influence on the uniformity of copper film deposited on the micro-via, and there is no undeposited phenomenon on the side wall of the micro-via. When sputtering power is 50 W, bias voltage is −70 V, working pressure is 4 mtorr, rotating speed is 10 rpm, and deposition time 5000 s, the wall, bottom and top of the micro-via are covered by continuous copper film, and the copper film on the sidewall is continuous and homogeneous. The optimised process parameters can be sputtered in the micro-via with a diameter of 5–10 μm.

Keywords

• Copper film
• Magnetron sputtering
• Micro-via
• Uniformity
• Interconnecting technology