3D-IC thermo-compression collective bonding process using high temperature stage

As one of the methods to stack the 3D-IC fast, the collective bonding process using TCB (thermo-compression bonder) attracts attention [1-3]. In the collective bonding process, we can improve the throughput considerably by postbonding the multilayered pre-bonded chips at a time. However, when the number of the stacked chips increased, we found that the temperature difference between the upper layer and lower layer became large and the good solder connection was not obtained in all the layer in conventional TCB. Therefore, we reported that the collective bonding could be realized by using the heat insulation stage which can prevent an outflow of the heat from the bonding head [1]. By using the heat insulation stage, we could reduce the temperature difference to less than 10 o C for four layers, but it was necessary to reduce temperature difference more, depending on the kind of NCF. Besides, it was difficult to reduce difference of temperature when, for example, the number of the stacked chips increased more than eight layers. In this presentation, we report about new collective bonding process that is able to reduce the temperature difference by using high temperature backup stage. We could enable the high temperature process of the stage by using the wafer-handling mechanism which lifts a substrate from the stage every one bonding cycle.