The Effect of Pulse-Reverse Plating Time on Blind Micro Via Filling

Horizontal pulse-reverse plating system was employed for blind micro via (BMV) filling process. The reverse plating time, frequency, and current shape was controlled or modified to observe the influence factors on BMV filling and thickness uniformity. Pulse-reverse plating system can reduce the surface thicknesses and had good ability to filling high aspect hole. During reverse time plating, the etching rate of surface copper was larger than that of via copper and it helped the filling of BMV. It mechanism was due to the effects of geometry and surface absorption of leveller. The dimple thickness showed an inverse ratio with reverse time. Reverse time dominated the reverse reaction of CudegharrCu²⁺+2e^-, and had influence on surface uniformity. Ferric ionic also plays an important role in the plating system. It reacts as a reductant which controls the reduction rate of Cu²⁺ and prevents the formation of void in the BMV. The reverse time was control in the range of 2-8 ms. It can be found that longer reverse time (8 ms) accelerated the via filling, however it also result in a poor quality of copper. Optical microscope, thickness measurement (SMES-4P), electrical polishing, optical profilometer, and scanning electronic microscope (SEM) were employed to characterize the physical morphology of the plating process.