Crack formation due to thermomechanical stresses generated by a dielectric polymer thicker than 20 µm and by that with high modulus during the bumpless chip-on-wafer (COW) process has been investigated. According to the stress simulation, thermal stresses increase with polymer thickness where the stress value ranges from 100 to 200 MPa for benzocyclobutene (BCB)-based resin. Thermal stresses in the hybrid structure using epoxy-based resin and BCB-based resin were calculated to be less than 100 MPa. Thus, the reduction of the thicknesses of the polymer as well as the Si chip was found to be effective in avoiding crack formation in the COW structure. Moreover, to investigate the crack driving force, the energy release rate (ERR) was calculated. The crack propagates toward the Si chip corner and the result is consistent with the experiment. On the COW structure, a thin Si chip and a low-modulus polymer expand the process window.
Significant reduction of the contact resistance of In0.TGaoaAs/Ni/W contacts (which were previously developed by sputtering in our laboratory) was achieved by depositing a W2N barrier layer between the Ni layer and W layer. The In07Gao.sAs/Ni/W2N/W contact prepared by the radio-frequency sputtering technique showed the lowest contact resistance of 0.2 ~mm after annealing at 550~ for 10 s. This contact also provided a smooth surface, good reproducibility, and excellent thermal stability at 400~ The polycrystalline W2N layer was found to suppress the In diffusion to the contact surface, leading to improvement of the surface morphology and an increase in the total area of the InxGa>~As between metal and the GaAs substrate. These improvements are believed to reduce the contact resistance.
The impact of chip-package interaction (CPI) on the mechanical reliability of Cu low-k interconnects was investigated using a 3D multi-level sub-modeling method. The analysis was focused on the die attach process for Pb-free solder where a high thermal load will occur during solder reflow before underfilling to maximize the packaging effect. We compared first the CPI for a CVD-OSG (k=3.0) with MSQ (k=2.7) and spin-on polymer (k=2.7) to investigate how better material properties can improve interconnect reliability. Then the study was extended to porous MSQ (k=2.3) to examine CPI for the 65nm node and beyond. Finally, requirements of the mechanical properties of low-k ILD for improving interconnect reliability are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.