Photoresist Coating Services: Spin Coat and Spray Coat for MEMS
Rogue Valley Microdevices provides photoresist coating services for MEMS photolithography, including both spin coat and spray coat processes on 100mm, 150mm, and 200mm wafers. As a U.S.-based, ITAR-registered MEMS foundry, we coat, expose, and develop in the same fab that builds complete MEMS devices.
Resist coating determines how faithfully every downstream pattern prints. Our engineers help you select the resist system and coating method that match your device materials, etch chemistries, and pattern requirements, so photolithography succeeds on the first pass instead of the third.
Whether your wafers are flat and film-covered or carry deep, previously etched MEMS features, we have a coating process that fits your device architecture and fabrication flow.
Photoresist Materials and Coating Capabilities
Successful lithography starts with matching the resist chemistry to your downstream etch selectivity and device geometry. We support a range of photoresist systems for flat and high-topography substrates:
| Resist Class | Coating Method | Typical Thickness | Engineering Purpose | Typical MEMS Use |
|---|---|---|---|---|
| Positive photoresist | Spin coat | 1.5µm to 3.5µm | Planar pattern transfer | Standard MEMS photolithography |
| Lift-off resist (LOR) | Spin coat | Scaled to metal thickness | Bilayer stack pattern definition | Clean noble-metal patterning without chemical etching |
| Thick photoresist | Spin or spray coat | Up to 10µm spin; 20µm to 25µm spray | Deep masking over vertical features | DRIE soft masks and deep etch masking |
| SU8 permanent resist | Spin coat | Per application | Chemically stable, permanent structural polymer | Microfluidic channels and bioMEMS devices |
| Polyimide | Spin coat | Per application | Permanent dielectric and stress buffer | Stress-buffer and passivation layers in device stacks |
These resist systems also serve as the soft masks for our co-located dry etch and wet etch lines, and the bilayer stacks behind our metal lift-off process, so every coating is tuned against the etch or lift-off step it will face.
Spray Coat Photoresist for High-Topography MEMS Structures
Many MEMS devices include deep cavities, tall structures, or non-planar surfaces that challenge traditional spin-coated photoresist. Spray coating solves this problem by distributing photoresist as a fine mist across the wafer surface, allowing the resist to coat sidewalls and recessed structures that spin coating cannot reach effectively.
We use spray coat photoresist to achieve conformal coverage on silicon wafers with deep features, trenches, or high-aspect-ratio microstructures. This enables reliable lithography on wafers that already contain etched MEMS features or thick deposited films.
Advantages of Spray-Coated Photoresist
- Uniform resist coverage over deep topography
- Improved coating on etched trenches and cavities
- Reliable lithography on high-aspect-ratio MEMS structures
- Reduced resist thinning near step edges
- Better pattern fidelity across complex microstructures
MEMS Applications for Spray Coat Lithography
Engineers typically turn to spray coating in later fabrication steps, when wafers already carry significant surface relief. Typical applications include:
- Patterning on deep reactive ion etched (DRIE) silicon structures
- Lithography over thick MEMS structural layers
- Patterning on wafers with etched cavities or trenches
- Microfluidic channel fabrication
- Optical MEMS device processing
- BioMEMS and lab-on-chip structures
Weighing the two methods for your device? Our guide comparing spin coat vs spray coat photoresist walks through when each approach wins.
Supported Wafer Sizes and Materials
We coat 100mm, 150mm, and 200mm wafers across a broad set of substrate materials:
- Silicon
- Silicon on insulator (SOI)
- Quartz
- Sapphire
- Glass
- GaN on silicon
- Silicon carbide
- Other specialty substrates
One Fab from Resist Coating to Finished Device
By combining spray coat and spin coat photoresist with precision mask alignment and wafer photolithography services, Rogue Valley Microdevices enables reliable patterning across complex MEMS device architectures. Because every step happens under one roof, you get one engineering team, full transparency into process decisions, and no hand-offs between vendors.
Explore our complete MEMS foundry capabilities to see how resist coating connects to deposition, etch, and lift-off in a single process flow.
Request Photoresist Coating Services
Send us your substrate, topography, and resist requirements. Our engineers will recommend the right coating method for your device and follow up with a clear, practical quote. Request a quote to get started.