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Have questions or need more information? Learn more about our microfabrication services. Contact our team of experts today and get personalized assistance with your microlens array or on-chip lens projects.
On-chip microlens engineering & foundry services
At CSEM, our expertise covers the entire development cycle, from microlens design & specifications, tooling and prototyping to small and medium volume production. Whether you require a complete development, design inputs, or just microlens masters/tools, we are here for you.
Enhance your imager and emitter performance with custom on-chip microlenses
While many semiconductor foundries can provide standard photoresist-based microlens arrays (MLAs) for small pixel imagers (e.g. for smartphone cameras), more advanced and custom micro-optics solutions are not easily accessible. However, well adapted MLAs enable boosting of the collection efficiency of advanced imagers such as Single Photon Avalanche Diodes (SPADs) and silicon photomultipliers (SiPMs), thereby also boosting their photosensitivity dramatically. On light emitters, well designed and aligned MLAs provide a much better emission by collimating light beams from VCSELs, micro-LEDs and from/to Photonics Integrated Circuits (PICs). Whether you have full wafers, only a few chips, or are at the design phase, we can help you enhance your device performance with customized micro-optics.
Our micro-optics project workflow: from design to production
A standard project comprises three phases, each of them subject to customer approval and potential further iterations for optimization.
1. Microlens design study
Based on the required parameters for each individual case, we perform modeling, simulations (ray tracing) and tolerancing to identify the microlens geometry which maximizes performances. This includes an analysis of the active wafer to be microlensed and the optical and environmental specifications.
This Zemax 3D model used in the microlens design process showcases a 3 by 3 microlens array with its residual layer on top of a 3 by 3 single photon avalanche diodes (SPAD) array. This comprises, from top to bottom: a grid modeling the front-side interconnects, a passivation layer, an intermediate layer and a crystalline silicon layer embedding circular photodiode active areas. DOI
2. Microlens tooling
- Microlens master fabrication at wafer level and extensive quality control. Wafer scale thermal reflow-based process yielding extremely low surface roughness.
- Mold/stamp fabrication and test replications on dummy substrates (chips or wafers) to validate the process.
- Definition with the customer of the quality control procedure to be used in production and detailed acceptance criteria.
3. Prototyping / small- to medium-volume production
Sketch illustrating the MLA UV-replication process: The MLA mold produced in the second MLA tooling phase is aligned in a mask aligner to the customer’s chip/wafer. The selected microlens material is dispensed in liquid state. Then the microlens material is imprinted and UV cured. Finally, the registered MLA is demolded.
Why choose our on-chip microlens solutions?
- Monolithic on-chip microlens integration on wafers up to 200 mm, on bare dies down to 2×2 mm² or even on packaged dies
- Microlens diameter ranging from a few µm to a few mm
- Microlens aspect ratio, diameter/height, from 2.6 (contact angle, CA = 75°) to >25 (very flat).
- Access to various microlens materials depends on the applications (automotive, space, radiation tolerant, cryogenic etc.)
- <2 µm lens/device alignment accuracy
- ISO9001 certified 150 and 200 mm wafer cleanroom
- Independent and innovative on-chip microlens foundry located in the heart of Europe
- Confidentiality
- Fast and professional, with a proven track record
Geometrical parameters of microlens arrays
Showcasing applications and expertise in microlens technology
All about microlens arrays: Frequently asked questions
What is the compatible wafer size?
Can you work with diced bare dies?
Can you work with packaged dies?
If the wafer/reticle embeds other chips that do not need MLA, can you restrict/define areas with and without microlens material?
Is it possible to request prototypes only?
Is it possible to perform only certain processes or services?
Can you ramp up production?
What about aspheric or free-form microlenses?
How do you guarantee the quality of production?
Can I use your equipment myself?
Are you ISO-9001 certified?
Are you ISO-13485 certified?
Can you participate in EU or Swiss research tenders?
Selected references on microfabrication of on-chip microlens arrays
F. Zanella, et al., Advanced microlens origination by thermal reflow, Proc. SPIE PC12898, PC1289805, Presented at SPIE OPTO (2024). DOI
C. Bruschini, et al., Challenges and prospects for multi-chip microlens imprints on front-side illuminated SPAD imagers, Optics Express, 31 (13), 21935-21953 (2023). DOI
T. Offermans, et al., PHABULOuS: manufacturing of large surfaces with free-form micro-optics, In Digital Optical Technologies 2023 (Vol. 12624, pp. 96-101). SPIE. DOI
F. Zanella, et al., Optimization of microlens arrays for photon detectors. In Quantum Optics and Photon Counting 2023 (p. PC1257005). SPIE. DOI
F. Zanella, et al., UV-replicated microlenses for quantum devices. In : Quantum Sensing and Nano Electronics and Photonics XIX. SPIE, 2023. p. 55-58. DOI
F. Zanella, et al., Manufacturing acceleration of free-form micro-optical arrays (FMOAs) with CAD algorithms. In Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XVI (Vol. 12433, pp. 91-96). SPIE 2023. DOI
C. Bruschini, et al., High-efficiency fill factor recovery using refractive microlens arrays imprinted on 0.5-256 kpixel front-side illuminated SPAD imagers, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XVI. Vol. 12433. SPIE, 2023. DOI
F. Zanella, et al., Increasing the quantum efficiencies of advanced photonics imagers with microlens arrays. Precision Photonic Systems, 22 (2022) DOI
F. Zanella, et al., Microlens testing on back-illuminated image sensors for space applications, Applied Optics, 59, 3636-3644 (2020). DOI
J. Mata Pavia, et al., Measurement and modeling of microlenses fabricated on single-photon avalanche diode arrays for fill factor recovery, Optics Express, 22, 4202-4213 (2014). DOI
M. T. Gale, et al., Replication technology for optical microsystems, Optics and Lasers in Engineering 43 (2005) 373–386, DOI
C. Gimkiewicz, et al., Wafer-scale replication and testing of micro-optical components for VCSELs, Proceedings of SPIE Vol. 5453 (SPIE, Bellingham, WA, 2004) · 0277-786X/04/$15, DOI