Automated inspection and metrology for 2.5D and 3D/TSV process assurance

The microelectronics industry continues to witness an ever-increasing movement towards heterogeneous integration leveraging the advantages of 2.5D and 3D/TSV in advanced semiconductor packaging and integration. New processes and physical structures are being developed to incorporate these advantages into fully functional manufacturable, reliable and cost effective devices. 3D wafer processing will rely heavily on advanced inspection and metrology capability in order to achieve the affordability and reliability necessary for commercial success. Automatic inspection is playing a key role in reducing the cycles of learning needed to develop these new processes and structures. Inspection strategies have been implemented which provide the required monitoring and process control. This paper will cover various inspection and metrology examples used in the monitoring of wafer finishing sector through the use of available Automated Optical Inspection (AOI) equipment. Focus is placed on those processes required to make the interconnect structures, as opposed those needed to create the internal TSVs themselves. Photolithography control, TSV reveal, redistribution, and metal feature dimensions, bump metrology, and defect detection, will be topics discussed in this paper. Lateral (in plane) dimensions were measured using a CCD camera, while Triangulation and Chromatic Confocal scanning where used for height measurement. Of course, in order to maximize yield and provide high reliability, defect detection at various steps in the overall process flow is critical. The AOI played a critical role in accelerating the end to end learning during wafer finishing fabrication.