Structural Evolution of Chip to Chip Hybrid Bonding Interface after Temperature Cycling and High Temperature Storage Tests

Bonding technology is important in 2.5-dimensional and 3-dimensional interconnection, and now the bond pad pitch reaches about 10 μm. To get higher density interconnection, the hybrid bonding technique has already been developed and researched. Hybrid bonding is bumpless bonding technique, which can shrink the bond pitch below 10 μm, even to submicron. In the industry, the wafer-to-wafer hybrid bonding technology has been successfully developed, and further development is needed for chip-to-chip and chip-to-wafer hybrid bonding. On this basis, whether hybrid bonding chips can work stably for a long time in extreme temperature environments and temperature cycles, is still an important topic worth studying. So, this paper mainly focuses on evaluating reliability of bonding interface by observing the evolution in bonding interface microstructure after reliability testing, and also conducting shear force tests to characterize mechanical strength of bonding interface.This paper mainly conducts two kinds of reliability tests on samples which are bonded under different conditions such as temperature and bonding time. Chip-to-chip hybrid bonding samples will be tested, with pad size of 10 μm and pitch of 20 μm. In the reliability test, we carry out temperature cycle test and high temperature storage test based on JESD22-A104F.01 and JESD22-A103E.01. The temperature cycle test was conducted at -55 °C -125 °C for 50, 100, 200, and 300 times. In high temperature storage experiment, the samples will be placed at 150 °C for 50h, 100h, 200h, and 300h.After the test, bonding interface microstructure was observed by scanning electron microscope. In addition to this, mechanical properties of samples will be tested, such as shear force tests. From the experimental images, the evolution of microstructure and mechanical properties during reliability experiments can be evaluated. When high temperature storage time is 50h and temperature cycle is carried about 100 times, the shear force is relatively maximum and mechanical strength increases correspondingly, but it does not mean that chip performance increases, and electrical parameters such as resistivity may be negatively affected.In summary, microstructure of the bonding interface were observed to evaluate microstructure changes of chips during reliability tests. The mechanical properties of the bonding interface, such as shear strength, were evaluated to verify reliability of hybrid bonding structures. Overall, adjusting the bonding process parameters appropriately may result in better microstructure and reduced porosity.