Pan Pacific Symposium Conference Proceedings

Equipment and Process Solutions for Low Cost High Volume Manufacturing Of 3D Integrated Devices

Authors: Markus Wimplinger, Jürgen Burggraf, Daniel Burgstaller, Thorsten Matthias, Harald Wiesbauer, Andreas Fehkührer, and Maria Schachinger
Company: EV Group
Date Published: 2/14/2012   Conference: Pan Pacific Symposium

Abstract: With end applications in the high performance server, mobile computing and smart phone space demanding ever higher performance of microelectronic devices while reducing power consumption and package size, the industry is preparing for the market introduction of 3D stacked devices based on TSV technology. The ability to reliably handle and process wafers with a thickness significantly less than 100µm plays a key role in enabling low cost, high volume manufacturing of TSVs with acceptable yield. Consensus has developed on the use of Temporary Bonding / Debonding Technology as the solution of choice for reliably handling thin wafers through backside processing steps. While the majority of the device manufacturing steps on the front side of the wafer will be completed with the wafer still at full thickness, it will be temporarily mounted onto a carrier before thinning and processing of the features on its backside. Once the wafer reaches the temporary bonding step, it already represents a significant value, as it has already gone through numerous processing steps. For this reason, inspection of wafers prior to non-reworkable process steps is of great interest. Within the context of Temporary Bonding this consideration calls for inline metrology that allows for detection of excursions of the temporary bonding process in terms of adhesive thickness, thickness uniformity as well as bonding voids prior to thinning of the product wafer.

This paper introduces a novel metrology solution capable of detecting all quality relevant parameters of temporarily bonded stacks in a single measurement cycle using an Infrared (IR) based measurement principle. Thanks to the IR based measurement principle, the metrology solution is compatible with both silicon and glass carriers. The system design has been developed with the inline metrology task in mind. This has lead to a unique system design concept that enables scanning of wafers at a throughput rate sufficient to enable 100% inspection of all bonded wafers inline in the Temporary Bonding system. Both, current generation temporary bonding system throughputs and future high volume production system throughputs as required by the industry for cost effective manufacturing of 3D stacked devices were taken into account as basic specifications for the newly developed metrology solution. Sophisticated software algorithms allow for making pass/ fail decisions for the bonded stacks and triggering further inspection, processing and / or re-work. Actual metrology results achieved with this novel system will be presented and discussed. In terms of adhesive total thickness variation (TTV) of bonded wafers, currently achieved performance values for post-bond TTV will be reviewed in light of roadmaps as required by high volume production customers.

Furthermore, the paper will review a suggested product flow considering inline metrology as well as additional offline inspection processes for making a final pass / fail decision.

Key Words: 

temporary bonding, debonding, inline metrology, adhesive TTV, thin wafer TTV, carrier wafer TTV, bonding voids

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