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Abstract :

High Throughput Debonding for 2.5D / 3D-IC Thin Wafer Handling


    Today’s thin wafer handling technologies for the fabrication of devices that have TSVs use temporary bonding to mount the device wafer to a support carrier for thinning and backside processing followed by room temperature debonding and cleaning. This process is one of the key enabling technologies for 2.5D and 3D-IC applications. At present almost every IDM, foundry and OSAT has temporary bonding and debonding equipment installed in their R&D- and pilot lines. Despite several announcements have been made we are still waiting to see the first 2.5D and 3D devices move into high volume. According to the industry it is the overall cost that 2.5D and 3D technologies add to the manufacturing process that is the major roadblock for moving into volume. While the actual bonding step has become a mature, well-mastered state-of the art process more focus is being put on the debonding step as it deals with high value, thinned device wafers so that debonding yield and throughput become major factors in the overall cost models for thin wafer handling. Debonding at room temperature is today’s method of choice for 2.5D and 3D devices as it ensures solder bump integrity by preventing metal diffusion or bump deformation. Novel materials for room temperature debonding offer simple process flows and improved thermal performance so that fewer compromises have to be made during high temperature backside processing. These new adhesives reach thermal stability of >300°C while the bonding temperatures are still in the 200°C range. This presentation describes some latest generation processes and materials for mechanical debonding at room temperature with controlled debond front propagation for minimal mechanical stress on the device wafer as used for making 3D stacked devices today. For some 2.5D applications where selective debonding or zero lift-off force carrier removal is required (e.g. fragile 3D MEMS devices) the use of laser assisted debonding offers a high throughput alternative to mechanical debonding and has therefore become very attractive to OSATs. A fully automated, high throughput excimer laser based debonding solution is presented which is compatible with the aforementioned high temperature stable adhesives. Debonding times of <60sec are achieved for a 300mm wafer followed by zero-force glass carrier lift-off. After carrier lift-off, wet chemical cleaning with dicing tape protection is used to remove adhesive residues from the thinned device wafers. This high throughput debonding solution enables lower cost of ownership which is crucial for moving into volume.