面向未来需求的细间距电化学沉积金凸点工艺

研究了电化学沉积金凸点的晶圆级直径和厚度分布及表面粗糙度随电镀电流密度和镀槽温度的变化.电化学沉积的金凸点在整个晶圆上的各个位置和方向上直径都增大了.当在40℃下电镀时,金凸点的直径分布与光刻胶的分布规律相似;而电镀温度为60℃时,金凸点的直径分布更倾向于对称分布.其次,当镀槽温度从40℃提高到60℃或者电镀电流密度从8 mA/cm2降低到3mA/cm2时,金凸点的厚度分布更加均匀.再次,60℃下电镀的金凸点表面粗糙度为130到160纳米并与电镀电流密度无关,但是在40℃下电镀时,表面粗糙度随着电镀电流密度的增加从82 nm急剧增加到1572 nm.

Fine pitch ECD gold bumping towards future demands

Wafer level diameter and thickness distribution and surface roughness of electrochemical depo-sition (ECD) Au bumps were studied with variations of electroplating current densities and bath tempera-tures. The diameter of ECD Au bumps was enlarged at all positions and directions of the wafer. When e-lectroplated at 40℃, the diameter distribution of Au bumps was similar to that of photoresist. While elec-troplated at 60℃, its distribution was more symmetric. Secondly, more uniform thickness distribution ofAu bumps was obtained when the bath temperature increased from 40℃ to 60℃ or the electroplating cur-rent density decreased from 8 mA/cm2 to 3 mA/cm2. Thirdly, the Au bumps electroplated at 60℃ exhib-ited the surface roughness of 130 - 160 nm independent of electroplating current densities. The Au bumpselectroplated at 40℃ exhibited the surface roughness being dramatically increased from 82 nm to 1572 nmwith electroplating current density increasing.