SHAPE EVOLUTION OF ELECTRODEPOSITED COPPER BUMPS

The initial stage of bumps was electrodeposited at diffusion control o vervoltage. Their shapes were observed by scanning electron microscopy and are discussed with numerical fluid dynamics computation. The bump s were electrodeposited either by varying the Peclet numbers or by var ying dot diameters. For the Peclet number of 1.31 with 100 mu m dot di ameter, the bump shows a maximum height hump at the circumference of u pstream side and a lower hump exists at the downstream side. For 41.6, however, the hump at the upstream side slightly shifts to downstream and the hump becomes flat at the downstream side. The bump shows a max imum height at the upstream side for 200, 100, and 30 mu m in dot diam eter for the Peclet number of 1.31. A lower hump exists at the downstr eam side. The bump shapes become flat for 15, 10, and 5 mu m dot diame ters. These observed bump shapes are explained by the fluid dynamics c alculations of vortex evolution and penetration flow. The calculated f lux profiles coincide well with observed bump shapes.