An investigation into damage-free thin die pick and place for 3D stacking

As 3D integration matures and progresses a vital element of the success of stacking and packaging is the ability to pick very thin and potentially ultra thin die from dicing tape and place them accurately into a target position (whether in waffle packs, gelpaks or onto another wafer) without physical damage to the die. The ability to do this is dependent on the choice of tooling used to pick the die plus the choice of tape used to hold the wafer during dicing and subsequent handling steps. Consideration must be given to how the die may be physically released from the tape and the impact of the die size on the tooling used as part of the release mechanism. The interaction between three different ejection system concepts and settings in combination with four different dicing tapes based on two release mechanism; 1) UV and 2) thermal driven are studied. Focus is placed on key success criteria, namely the condition of the die post pick and place (cracks and chip outs) and the capability to pick all dies leaving no unpicked die on tape while taking the die size into account. It is found that the picking of even relatively large die dimensions, such as 20×20mm
²
from both tape types is possible with considerably high throughput with over 2000 units per hour, when the right process parameters are found. However, the die placement can cause issues because of weak die support. One solution is the usage of gelpak carriers, where the die is held flat and supported by a sticky layer. In general, the well known UV tape can successfully support thin die picking, where for some applications the thermal tape could be an attractive option.