An Outline of a Complementary Inspection System for Micro-Electro- - - PowerPoint PPT Presentation
An Outline of a Complementary Inspection System for Micro-Electro- Mechanical System (MEMS) Devices Based on Radiography and Plenoptic Camera Speaker: Shu-Mei Tan a Alvin Chong a , Guojin Feng a , Jamil Kanfoud a , Tat-Hean Gan a,1 a Brunel
Speaker: Shu-Mei Tana Alvin Chonga, Guojin Fenga, Jamil Kanfouda, Tat-Hean Gana,1
aBrunel Innovation Centre (Brunel University London), Granta Park, Great Abington, Cambridge, CB21 6AL, United Kingdom 1 Corresponding Author. Prof. Tat-Hean Gan (email: Tat-Hean.Gan@brunel.ac.uk)
11.09.2018 - 13.09.2018
Introduction (MEMS and Project Overview) Samples Identified To Be Studied CITCOM System Overview Plenoptic Camera Subsystem Nano-focused X-ray Subsystem Inspection Procedure and Automated Defect Recognition (ADR) Conclusions and future work
Micro-Electro-Mechanical
The components are typically integrated on a single chip using
Typical MEMS devices usage for sensing: accelerometer,
Applications: Aerospace, automobile, medical, etc…
Example of MEMS – Analog Devices three-axis accelerometer ADXL330
Thermal infrared temperature sensor Inertial measuring unit (X-IMU) Network tunable filter Gas (Co) sensor Smart contact lens – detect glacoma
Smaller in size Lighter in weight Can have lower power consumption Can have higher sensitivity to input variations Can have high integration capability with electric circuits Cost-effective (mass production)
Scanning Intravascular Ultrasound (IVUS): Smart catheters used
Capacitive Micro-Machined Ultrasound Transducers (CMUTs)
CMUT is made by the deposition of three metal layers
Top metal electrode can move freely after the sacrificial centre
When
Schematic cross section of CMUT Optical micrograph image of CMUT IVUS scanning catheter and example
The Flex-to-Rigid (F2R) technology such as flex-foil approach is employed to allow electronics to fold around or
(i) F2R structures are fabricated (wafer scale) (ii) After fabrication the partly flexible structures are removed from the silicon wafer and assembled around the catheter tip. (iii) Final assembled CMUTs
Common defects such as scratches, foreign particles, lithography and etching problems.
Standard high temperature soldering or wire bonding
Example: organ-on-chip devices where the diagnostic
Silver filled epoxies are used as an alternative. Could cause quality issues. Excess glue shorting bond pads Insufficient glue Glue on top of cap (also misplaced)
Failure modes can developed during the microfabrication process and assembly of these MEMS
devices into packages and Printed Circuit Boards (PCBs).
Although there are planar inspection tools utilised for such MEMS devices quality assessment,
most of the inspection is based on electrical parameters. This potentially poses a problem from the manufacturing point of view where critical defect go un-noticed. especially for transport and medical applications, as the reliability is paramount.
Presence of subjective error dues to the use of manual or semi-autonomous inspection tool. Typically in a semi-autonomous inspection, operator have to manually orientate the MEMS
devices and define the test points which could be randomly selected. The likelihood of missing critical defects can be high in such testing approach and inevitably adds cost to the production.
The proposed system aims to tackle the reliability issues for MEMS devices (potential test cases
identified above) by offering an automated 3D structural inspection system applied to inspect high value component production at both in-line and near-line processes which is reliable, accurate and cost-effective.
Plenoptic camera (light field camera) to capture 2D image with
This is achieved by using micro-lens array (MLA) in front of the
MLA re-group sensors (e.g. CCD, CMOS) into small groups. Capture information on the direction, colour and luminosity of
Computationally reconstruct the light field (3D). Integration of the plenoptic camera, all optical and opto-
Aim towards in-line inspection (relatively fast). Integration of the plenoptic camera, all optical and opto-mechanical components, x-y
Automated Defect Recognition (ADR) based on classical image processing approach. Example of output – view in 3D point cloud of a component with foreign particle.
Aim towards near-line inspection. Preliminary results show a pixel based photon counting CMOS detector is promising due to image
Currently in-progress to select the optimum X-ray source and detector. Automated Defect Recognition (ADR) based on classical image processing approach.
As an illustration, single wafer may contain hundreds of MEMS/micro device. Step and scan (with an overlap between adjacent scan) will be required to image the complete
Image stitching is then performed to obtain a combined image. Subsequently, segmentation will be implemented for further post-process / analyze for feature
Step and scan Stitched image Segmentation
Overlapped scan One area scan
Silicon wafer Silicon wafer
Stitched image
Silicon wafer
One MEMS comonent
Total focused image and its Region of Interest (ROI) Estimated depth map and its ROI 3D point cloud view showing anomaly
Various noise reduction, features enhancement and
Inspected on CMUT sample. Some dark areas observed for certain CMUT highlighted in the red
These areas are enclosed so it’s unlikely to be foreign particles Suspected to be incomplete etching of the sacrificial aluminum layer. Such internal defect cannot be observed through optical inspection
Outline of the proposed CITCOM inspection system based on plenoptic camera
Preliminary tests conducted on CMUT have shown the applicability of both
Further work on optimising the hardware for better resolution, efficiency, image
Final trial planned to perform at End-Users’ facilities.
HORIZON 2020 research and innovation programme Grant Agreement no. 768883.