A Performance Testing Method of Bernoullie Picker for Ultra-Thin Die Handling Application

A performance testing method of the Bernoulli picker which can handle an ultra-thin die without contact are formulated, and a series of experiments are conducted to evaluate and optimize the performance of the picker. Die to wafer or die to die hybrid bonding and stacking is very promising scheme for the next 2.5D and 3D IC heterogeneous integration devices. To improve the quality and reliability of the devices with the hybrid bonding, it is crucial to prevent the voids and other defects in a die stacking. The Bernoulli picker that operates with the Bernoulli airflow principle is a core technology for the hybrid bonding. The competing effect of the jet force and the lifting force with respect to the die let the Bernoulli picker protect the plasma activation surface of the die due to the non-contact handling and avoid the misaligned die stacking due to the airflow driven self-alignment capability. However, as the thickness of the die becomes very thin less than 50 μm, the possibility of the die touching the surface of the Bernoulli picker increases since the warpage of the die increases due to the decrease of the die stiffness. In this paper, the authors build a method of evaluating whether the Bernoulli picker enables to handle the ultra-thin die without contact, and performs the evaluation under various process conditions to optimize the performance of the picker. To verify the performance of the Bernoulli picker, the following three items are tested: the warpage of the die, the levitation height of the die, and the restoration range of the die. The warpage and the levitation height of the die are the factors that verify the non-contact picking, and the restoration range of the die is the factor that evaluate the self-alignment capability of the die. Finally, it is confirmed that the ultra-thin die is successfully well aligned and bonded without voids using the optimized Bernoulli picker.