Why photonics manufacturing demands more from a cleanroom
In photonics manufacturing, the cleanroom does not just protect the product. It directly determines whether the process works at all.
Photonic chips guide light through microscopic channels called waveguides, with dimensions measured in hundreds of nanometres. A single particle landing on one of these channels during fabrication creates a permanent defect that scatters light, disrupts signal transmission, and cannot be corrected after the fact. A vibration during lithography shifts the pattern. A temperature drift during deposition changes the film thickness. None of these can be undone.
These are not edge cases. They are the everyday reality of photonics manufacturing, and they happen when the cleanroom environment is not designed specifically around the process.
Most cleanrooms are not. They are designed around generic ISO classifications and standard HVAC assumptions. For photonics, that is not enough.
What the cleanroom must control
Particle cleanliness
Critical fabrication steps including waveguide formation, lithography, etching, and optical coupling require ISO Class 1 to ISO Class 5. Packaging and testing can operate at ISO Class 6 or ISO Class 7. But classification alone does not tell the full story.
Beyond airborne particles, surface cleanliness at molecular level matters just as much. Trace organic contamination on optical surfaces reduces coating adhesion, introduces absorption losses, and affects the uniformity of deposited films. Chemical management strategy and material selection are part of the contamination control plan, not separate from it.
Vibration
Lithography tools and optical alignment stations have zero tolerance for floor vibration. Vibration from HVAC equipment, pumps, or building structure causes alignment errors in waveguide patterning and shifts bonded components out of position at sub-micron scale.
Vibration strategy must be defined at building and cleanroom design level. Addressing it at equipment level alone is too late and too limited.
Temperature stability
The optical properties of silicon, silicon nitride, and indium phosphide all change with temperature. During deposition and etching, temperature instability causes film thickness and etch depth variations that shift waveguide performance away from design targets. During optical assembly, thermal drift in fixtures and components introduces signal losses that cannot be reversed after bonding.
Temperature control to within ±0.5°C is typically required across the fabrication environment, with tighter control in lithography and deposition zones.
Humidity
Too high, and photoresist absorbs moisture, reducing pattern accuracy during lithography. Too low, and electrostatic discharge risk increases, damaging sensitive detector and modulator structures. Humidity must be maintained between 40 and 55 percent relative humidity, with tighter control in photoresist coating and exposure zones.
Specialised lighting
Photoresist is sensitive to ultraviolet and short-wavelength visible light. Any zone where photoresist is handled must use yellow or amber filtered lighting. This must be specified for the correct zones from the outset. It cannot be retrofitted without disruption.
What makes photonics cleanrooms harder to get right than semiconductor cleanrooms
Photonics and semiconductor manufacturing share many processes. But a photonics facility needs infrastructure that does not exist in a conventional semiconductor cleanroom:
- Optical alignment and testing stations require vibration-isolated surfaces and stable thermal environments within the cleanroom itself, not in a separate test area
- Multi-platform processing means a single facility often handles silicon photonics, silicon nitride, and indium phosphide wafers, each with different chemical requirements and contamination sensitivities
- End-face preparation and fibre coupling requires a dedicated clean zone free from particulates that would contaminate the optical interface
- Active device integration, meaning bonding III-V laser chips to silicon photonic wafers, requires controlled adhesive processes and optical alignment under cleanroom conditions
A photonics cleanroom cannot be a semiconductor cleanroom with optical test equipment added. The layout, zoning, chemical management, vibration isolation plan, and lighting strategy must be designed around the specific processes from the beginning
Where standard cleanroom design fails photonics manufacturers
- The most common failure is over-reliance on ISO classification as the primary design driver. An ISO Class 5 room that does not account for floor vibration, airborne molecular contamination, or zone-specific humidity control will still fail to support the process reliably.
- The second most common failure is designing the cleanroom without understanding which process steps are the most sensitive and where in the facility they happen. A generic layout that treats all zones equally creates unnecessary cost in low-sensitivity areas and insufficient control in high-sensitivity ones.
- The third failure is designing for today’s process without accounting for how it will change. Photonics is a fast-moving industry. The platform running today may not be the only one running in three years. A cleanroom that cannot be upgraded or reconfigured without major disruption becomes a constraint on the business.
ABN Cleanroom Technology
ABN Cleanroom Technology designs, maintains and builds cleanrooms for photonics manufacturers and research facilities across Europe. Through Configure-to-Order Plus, every parameter is defined around the actual process before any building block is selected.
Pre-engineered and validated building blocks from the ADAPTUS platform are then configured around those inputs. ABN’s decentralised VIX system manages airflow and classification at zone level, calibrated to actual process load, so sensitive lithography and alignment zones get what they need without overcapacity elsewhere.
The result is a cleanroom built for the process, upgradable as the process evolves, and predictable in performance from day one.