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Mr. Stefan Lutter

 

 

Mr. Stefan Lutter

General Manager Bonder

SUSS MicroTec Lithography GmbH

 Education:

  • Master of Business and Engineering

 Experiences:

  • General Manager Bonder since 2013

  • Product Manager Temporary Bonding from 2010 – 2013

  • Product Manager Coater / Developer from 2008 – 2010

  • Working in various position for automotive MEMS and MEMS for  scientific instrumentation since 2000

 Abstract:

 

Novel Wafer Bonding Method with Improved Post-Bond Alignment for Automotive- and Consumer MEMS

Many of the traditional wafer level MEMS packaging processes are based on glass-frit-, anodic bonding or metal bond lines such as gold, which are not compatible with CMOS processing. Nowadays, there is a growing demand for silicon-to-silicon bonding methods that are CMOS compatible. This requirement is driven by the latest generation of automotive and consumer sensors which include accelerometers for airbag sensors, gyroscopes for anti-skid and anti-tilt systems or motion-, temperature- and gas sensing in many different consumer-, industrial- or IoT products.

AlGe based eutectic bonding not only overcomes most of the drawbacks associated with glass-frit and anodic bonding but also provides a practical solution for wafer level packaging for the aforementioned automotive- and consumer applications. Both, Al and Ge are CMOS and MEMS fab-friendly materials. In addition to offering a hermetically sealed bond line, AlGe also establishes an electrical contact between the two substrates, which is required or at least beneficial for many applications. 

Although the eutectic bonding process itself is well understood and already used in volume production there is still a need to improve the post-bond alignment accuracy and consistency as well as the throughput that traditional wafer bonding systems offer today. Better alignment control allows reducing the bond frame dimensions, which in turn allows increasing the number of devices per wafer, and therefore offers lower cost per device.

Post-bond alignment accuracy and consistency are both influenced by several factors such as the handling and transfer of the aligned wafer pair and thermal expansion that occurs when loading the wafers onto a pre-heated bonding chuck or ramping the temperature during the bonding process. In addition, wafer shift can occur during the removal of spacer flags that are used to keep wafers in separation during the pump down steps or squish of the actual bond line materials when bond force is applied at elevated temperatures.

A novel and innovative method has been developed which overcomes these challenges by locking in the alignment between the wafers prior to transferring them into the bond chamber. This method offers a significant improvement in both, the post-bond alignment accuracy as well as the consistency, and it can be applied to a variety of bond line materials that are used in eutectic and diffusion bonding. At the same time it enables higher throughput by faster wafer transfer and shorter bond cycle times.

 

 

 

 

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