All-polymer based fabrication process for an all-polymer flexible and parallel optical interconnect

Jilin Yang, Tao Ge, Chris Summitt, Sunglin Wang, Tom Milster, Yuzuru Takashima

College of Optical Sciences, University of Arizona1630 E. University Blvd., Tucson, AZ, USA 85721

Email: jyang@optics.arizona.edu

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OutlineIntroduction

Fabrication process - Process flow

- 45 degree mirror couplers - Waveguides photomask - Alignment process

Test results

Conclusions

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Introduction

Structure of Flexible Optical Interconnect:

Advantages:

High speed Flexible Metal less Maskless lithography

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Mirror coupler

The maskless lithography tool - Modulated Scanning Laser system at 365 nm - 2.1 address unit - Writing stage with X,Y and Z controlled motion - Print via BMP virtual masks over 1 in around 20 sec

Materials - Substrate: TOPAS 5013 (TOPAS advanced polymers, Inc, Florence KY) - Cladding: Epoclad (Micro resist technology, Berlin Germany), n=1.54 - Mirror and alignment marks: WPR 5100 (JSR Corporation, Sunnyvale CA) - Waveguides: AP2210B (Fujifilm, Valhalla, NY), n=1.60

Materials

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Process flow

Si wafer

Attached by polyimide tape

Coated with WPR 5100 and exposed by maskless lithography tool

45 degree mirror couplers and alignment marks left

Coated with cladding material

Coated with AP2210B and exposed using mask lithography

Waveguides structure left after developing

Coated with top cladding material

Remove Si wafer

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45 degree mirror couplers20

100

1.5

Alignment marks

Cross section of mirror strip under SEMAngle of slope=44.3

Gray scale bitmap pattern of mirror layer (Top View)

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Waveguides photomask

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Photomask for waveguides

Fused silica substrate

E-beam Cr coating

Spin coating AZ 3312

UV laser exposure

Development

Dissolve

Wash out

Gray scale bitmap pattern of mirror layer (Top View)

Alignment marks

Alignment mark

Waveguides material10

1.5

Waveguides material Index of refraction @ 530 nmAP2210B 1.6093

Alignment mark material Index of refraction @ 530 nmWPR 5100 1.6790

Optical path difference @ 530 nm:

- Due to the transparent materials and weak phase shift of the reflection light, it’s very difficult to be detected by conventional microscopy.

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Detection microscopyPhase contrast microscopy in reflection mode

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Phase contrast technique

/2

Test results

Alignment mark

Waveguides material10

1.5

Image obtained by objective with 5X magnification and 0.11 NA

Top view

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Alignment mark

Waveguides material10

1.5

Image obtained by objective with 5X magnification and 0.11 NA

Top view

Optimization

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Alignment process

Objective

Objective

Beamsplitter

Photomask Holder

Adjustable stage

Original:

Engineered:

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Alignment process

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Conclusions

• Proposed a fabrication process of all polymer flexible optical interconnect

• Phase-based alignment marks engineering combined with phase contrast detection technique increases 93% of the image contrast of the phase-based alignment marks

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Next step

• Print the well structured waveguides

• Following the process flow to complete the fabrication of optical interconnect and test the propagation performance

Acknowledgement

Sincere appreciation to JSR Micro, Inc. for providing WPR-5100 buffer coat material in the fabrication of the mirrors.

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Thank you

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