Introducing novel film type adhesives into thin wafer handling technology for 3D TSV packaging applications

In this paper, the authors focus on the evaluation of novel film type thermo-plastic adhesives in thin wafer handling technology for temporary bonding purposes. The main advantages of the film type adhesives over spin coat adhesives are better uniformity of film, TTV control and high thermal stability of the film. Film type-A material has been developed and evaluated for thermal slide-off thin wafer handling applications. For temporary bonding evaluation, extensive DOE matrix has been generated and executed to identify the optimum bonding conditions. Initially adhesive films are vacuum laminated on silicon carriers and eventually bonded using thermal bonding process. Total six different bonding conditions have been considered and bonding loads have been chosen from 3kN to 9.5kN and temperatures are in the range of 150 to 210°C. Preliminary evaluation results are supposed to be feasible, but ideal thin wafer handling demands 0% voids in bonded pairs at any stage. To meet this requirement, the authors were extensively focused on the improvement of film materials and optimization of lamination and bonding parameters. 3D IC process simulation tests are also required to ensure that the adhesives layers are reliable enough for further process. For this purpose, temporary bonded pairs have been thoroughly tested through various 3D IC processes like back grinding, dielectric curing, vacuum stability and chemical stability tests. Finally de-bonding evaluation of the films is carried out at temperature ranges of 200 to 250°C. Based on the results achieved, the authors were able to identify the characteristics of the currently developed film type temporary bonding and de-bonding adhesive and direction for the further optimization.