Technology
Micro-transfer printing (MTP) enables the integration of diverse materials and devices, such as III-V and LiNbO3 components, onto a single platform. With high alignment accuracy and efficient use of source material, MTP facilitates cutting-edge photonic integrated circuits (PICs), all while maintaining compatibility with existing manufacturing workflows.
Process flow
Micro-Transfer Printing involves three key stages:
- the preparation of the target wafer
- the release of source wafer components
- the transfer process
One main benefit of micro-transfer printing is that source- and target wafer processing is separated. Only at the printing stage, which happens at the Back-End-of-Line (BEOL), the source and target materials are combined.
Source wafer processing
Components such as III-V SOAs, LNO modulators or other functional elements are fabricated on the source wafer with a sacrificial release layer. This release layer is selectively etched to free the devices, while tether structures keep them anchored to the wafer surface. This step ensures the devices are ready for pickup by the transfer stamp.
Target Wafer processing
The target wafer usually undergoes normal front-end of line processing to form photonic circuits and back-end-of-line (BEOL) processing to deposit and pattern metal interconnects and dielectric layers. Thereafter, local openings in the stack are often created that will enable efficient coupling to the transfer printed components. After transfer printing, the amount of post-processing on the wafer is usually limited to creating an electric redistribution layer and a passivation step.
Transfer process and coupling methods
A PDMS stamp with micro-engineered posts is aligned to the released components on the source wafer using high-precision pattern recognition systems. The stamp picks up the components by breaking the tethers and transfers them to the target wafer. Upon alignment with the designated placement sites, the components are printed onto the target wafer. This process can be repeated in a massively parallel manner to achieve high throughput and efficient material utilization while maintaining an alignment accuracy of < 0.5 um.
Several coupling methods, such as evanescent coupling and direct coupling methods, can be used, fitted to the need of different platforms and components.
Publications
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Micro-transfer-printed short-wave infrared InP-on-silicon tunable laser
Xin Guo et al., Optics Letters, doi.org/10.1364/OL.549540, (2025)
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Centimetre-scale micro-transfer printing toenable heterogeneous integration of thin filmlithium niobate with silicon photonics
Margot Niels et al, Opt. Mater. Express 15, doi.org/10.1364/OME.551748, (2025)
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A High-speed heterogenous lithium tantalate silicon photonics platform
M. Niels et al, arxiv, doi.org/10.48550/arXiv.2503.10557
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Heterogeneous integration of a High-Speed Lithium Niobate Modulator on Silicon Nitride using Micro-Transfer Printing
T. Vanackere, et al.. APL Photonics https://doi.org/10.1063/5.0150878 (2023)
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Present and future of micro-transfer printing for heterogeneous photonic integrated circuits
Gunther Roelkens et al. APL Photonics . https://doi.org/10.1063/5.0181099 (2024)
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Integrated Resonant Electro‐Optic Comb Enabled by Platform‐Agnostic Laser Integration
I. Luntadila Lufungula et al. , Lasers & Photonics Reviews, doi:10.1002/lpor.202400205 (2024)
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III-V-on-Si3N4 widely tunable narrow-linewidth laser based on micro-transfer printing
B. Pan, et al., Photonics Research, 11(12), doi:10.1364PRJ.530925 (2024)
