Assembly and Inspection of LiquidAssembly and Inspection of Liquid Crystal on Silicon (LCoS) Devicesy ( )

Zichen Zhang1, Neil Collings1,*, L. Imbert 2, A.M. Jeziorska‐Chapman1, Mike Pivnenko1, 

W.A.Crossland11Electrical Engineering Division, Department of Engineering, University of 

Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 9BB, UK2Smart Equipment Technology S.A.S. 131, impasse Barteudet 74490 Saint 

Jeoire ‐ France

*Corresponding author: nc229@cam.ac.uk

Photonics & Sensors Group

Outline • LCoS Structure

• General Assembly Techniques

• Pre Inspection• Pre‐Inspection

• Inspection of Assembled  LCoS Test Cellsp

• Cell Gap Measurement

• Conclusion

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Architecture of Liquid Crystal on Silicon 

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Layer Structure of Liquid Crystal on Silicon Devices

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Standardization Assembly Procedures 

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Ultra Compact 40mm Fizeau Interferometer for Flat or Spherical Surfaces

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Pre‐Inspection of Substrates

The  Purpose of pre‐inspection of the substrates is  matching the curvatures of the silicon (the left figure) and the glass (the right figure).

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Assembled LCoS Test Cell 1

M i h lMeasurements in the centralarea is approximate 1nm/mmvariation in x‐direction and2.4 nm/mm variation in y‐direction.

10mm*15mm Assembled LCoS Test Cell 1

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Uniformity of LC layer Mappingy y pp g

1 435

1.440

1.4301.435

1.425

1.420

1.415

1.425

1.4301.410

1.4351.440 1.40

Photonics & Sensors Group

Assembled LCoS Test Cell 2

More measurements have beenimplemented indicating the locationf 48 i t f ll thi kof 48 points of cell gap thickness.

7mm*12mm Assembled LCoS Test Cell 2

Photonics & Sensors Group

8

6

nts

2

4

Cou

n

0

2

2.40 2.42 2.44 2.46 2.48 2.50 2.52

Thickness, μm

The Histogram of the 48 thickness measurements, where 26 of them are between 2.44um to 2.48 um; The Table summarize the cell thickness results. 

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Assembled LCoS Test Cell 3Only 2 dot measurements areimplemented. Because theconsistent interference color inconsistent interference color inthe central area illustrates abest result for the uniformityof the active area using theof the active area using themodern robotic machine.

7mm*12mm  Assembled  LCoS Test Cell 3 

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The Kadett Semi‐Automatic Device Bonder from SET for High Accuracy Assembly

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Conclusion• Optical pre‐inspection is employed for quality LCoSassembly techniquesassembly techniques

• Semi‐Automatic bonding device from S.E.T is used forexcellent accuracy assembly techniques

• Reproducibility of cell assembly results i e cell gapReproducibility of cell assembly results i.e. cell gapuniformity is ascertained .

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W i h t k l d th C b idWe wish to acknowledge the CambridgeIntegrated Knowledge Centre (CIKC) funded byg g ( ) yEPSRC, ALPS Electric (UK) and Smart EquipmentTechnology for their supportTechnology for their support.

Photonics & Sensors Group