Abstract
TSV (Through Silicon Via) is a core technology in 3D IC Package. The micro vias can be made by etching or laser drilling. Standard processes for TSV filling begin with seed layer deposition, followed by blind vias copper electroplating. If the aspect ratio of the TSV is higher than 5:1, the costly MOCVD process needs to be used to deposit the seed layer with good step coverage. A special designed electroplating machine and solution for high aspect ratio copper electroplating is needed. Some researchers even use PRP (periodic reverse plating) for void free copper electroplating instead of traditional DC power supply. This paper is based on Au to Au bonding process. Several Au to Au bonding conditions had been tested (Temperature, Pressure, Plasma source... ) and the result of the bonding strength is evaluated by pull test. Au bump bonding with the die thickness less than 25 μ m is demonstrated here and the Au-Au interface is perfectly bonded by SEM inspection and the shear strength is more than 30MPa. Au to Au bonding is also used in bottom-up Cu electroplating as bottom electrode. Wafer with 10μm diameter Au opening as etch mask is etched by ICP process and the etched wafer was bonded with an Au sputtered dummy wafer. The bonded pair is then thinned to expose the micro vias for copper electroplating. The SEM and X-Ray results show that the bottom-up Cu electroplating using Au to Au bonding as bottom electrode can fabricate the TSV of aspect ratio more than 6:1. Moreover, the void free bottom-up Cu electroplating uses traditional PCB copper electroplating machine instead of the expensive MOCVD seed layer deposition and PRP Cu filling. Thermal shock reliability test of the bottom-up Cu electroplated TSV are also studied in this paper. ©2008 IEEE.