Periodic Reporting for period 1 - CITCOM (A Complimentary Inspection Technique based on Computer Tomography and Plenoptic Camera for MEMS Components)

The term micro-electro-mechanical systems (MEMS) was traditionally used for micro-fabricated devices that converted electrical signals in movement (micro-actuators) or movement into electronic signals. The last category represents currently the bulk of the MEMS devices...


The term micro-electro-mechanical systems (MEMS) was traditionally used for micro-fabricated devices that converted electrical signals in movement (micro-actuators) or movement into electronic signals. The last category represents currently the bulk of the MEMS devices consisting of accelerometers, gyroscopes, inertial sensors, pressure sensors and microphones, which on a large scale find their way in automotive, gaming and mobile communication applications. However, presently the term MEMS is additionally being used for a much larger class of emerging devices and applications that are all being manufactured using micro-fabrication tools and equipment. These include miniaturized medical systems, micro-fluidic systems, Organ-on-Chip devices and implantable systems.
This new class of MEMS devices has been enabled by advancements in micro-fabrication materials and processing. Deep reactive ion-etching (DRIE), for instance, has seen tremendous progress whereby it has become feasible to etch straight through silicon wafers. New materials like cavity SOI are enabling the manufacture of new MEMS devices that up till now had not been possible. Sometimes underrated, also the assembly of these devices into packages and printed circuit boards (PCBs) has seen a tremendous development and is an essential part of the total manufacturing cycle. One thing all of those microsystems and MEMS devices have in common is that they are all (highly) three-dimensional in nature.
This poses a problem from a manufacturing point of view. Whereas the IC industry has developed many planar inspections tools, there is a more or less urgent need for inspection tools that can structurally inspect 3D micro structures. At the moment many of these new systems are only inspected electrically and not structurally, which may leave critical defects unnoticed. This is especially problematic for automotive and medical applications where reliability is of primary concern. Manual inspection is presently the only alternative, adding to the cost.
It is the aim of the CITCOM project to fill this gap in the manufacturing cycle by increasing the TRL-level of 3D imaging and X-Ray inspection equipment suitable for in-line MEMS and microsystems production environments. This shall improve the level of acceptance and ease the implementation of this kind of equipment at manufacturer?s sites such as Philips or Microsemi as a potential end-users within the project.

Work Performed

Based on the feedback from end-users within the consortium and those external to the project, obtained during current and on-going exploitation efforts, sound scenarios have been developed in order to ensure the above mentioned goal.
The introduction of relatively low TRL-level equipment into existing production environments is difficult because it might disturb the normal production flow. The CITCOM exploitation manager therefor devised the plan to implement the optical 3D inspection tool developed within the project onto a commercially available wafer prober. The latter one is established at manufacturing sites around the world at highest TRL-level. The actual optical CITCOM system will be implemented as a new feature or function of an existing system instead of a complete new development, and therewith lower the acceptance threshold for potential end-users.
Mostly due to size constraints the X-ray system cannot be implemented into a wafer prober and therefor will remain a separate machine. However, the software used for analyzing the generated X-ray images as well as the one controlling the entire data flow will be similar to the one used for the optical inspection system. The same software is already deployed and accepted at shop floor level. Hence it will increase the acceptance chance of potential customers to integrate the X-ray system next to running production lines.
After 18 months into the project hardware has been developed, improved and set up for both technologies in order to proceed with the software development. The latter one covers the control of the hardware, automated image acquisition and evaluation, data handling and interfacing to production floor environment. Part of the software development is running for many months already, e.g. for the automated defect recognition.
For increased sustainability, a more and more important topic in today?s world, CITCOM is further more investigating means and impact of potential recycling of components and systems filtered out during the inspection processes.
Below a more detailed list of activities, both concluded as well as ongoing once:
X-ray system
- Source optimized for field of application coordinated with efforts of detector evaluation and choice of the latter one. Source to be further optimized throughout the next months.
- Supporting system components, e.g. a vibration-damped table and mechanics, as well as the source and detector have been integrated and set-up.
- Handling system for large substrates (8? with potential for 12?) has been designed and awaits delivery of components for integration into the system.
- Development of control software for both, the handling system as well as the source/detector are ongoing.
Optical 3D system
- Two 3D cameras have been optimized and delivered, one for a 3x magnification lens, the other one for a 20x microscope optic.
- Acquisition software has been optimized resulting in 30% better depth estimation.
- A preliminary setup including positioning equipment, illumination, vibration-damped table and the two mentioned cameras have been set up.
- Development of control software for the handling system and the interface to the later wafer prober ongoing.
Automated defect recognition software
- Ongoing development of automated anomaly detection and metrology with first results based on sample images.
- Concept and software development for predictive maintenance on both systems ongoing.
- List of potential recycling companies within Europe established, work on analyzing the potential of recycling based on end-user sample applications ongoing.
- Participation to various workshops/conferences as part of dissemination and communication actions.
- Contact and visit of potential end-users outside of project consortium as part of exploitation activities.


X-ray systems of course exist already for analysis of single samples after component or equipment failure. However, as a system integrated next to a production line with software interfaces to the shop floor level it is a novelty, not to forget the automated defect recognition. With an optimized source/detector combination and the implemented large substrate handling system it will achieve larger throughput than current systems on the market.
3D optical inspection systems in itself are not new either. However, the technology employed in CITCOM, based on lightfield cameras, seamlessly integrated with the wafer prober and correlated 3D image and electrical and/or electromechanical data clearly goes beyond state of the art. Of course the 3D image data again will be evaluated automatically and at high speed (up to 80 frames per second or 50 cm2, depending on various parameters).
Based on end-user feedback we strongly believe that both systems will impact the actual production yield of complex MEMS and microsystems. Together with the activities on sustainability this will reduce waste and therefore having a positive impact on our environment.
A Complimentary Inspection Technique based on Computer Tomography and Plenoptic Camera for MEMS Components
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