100mm Silicon Wafers for SU-8 Mold Fabrication
A graduate researcher requested silicon wafers to fabricate SU-8 molds for PDMS microfluidic device research. SU-8 photoresist patterned on silicon wafers is one of the most widely used fabrication methods for creating microfluidic channels, biomedical devices, MEMS structures, and lab-on-a-chip systems.
The researcher selected the following substrate:
Why Use Silicon Wafers for SU-8 Molds?
Silicon wafers provide an ultra-flat, dimensionally stable surface that allows SU-8 photoresist to form high-resolution microstructures with excellent feature definition. After photolithography, the patterned SU-8 layer serves as a reusable master mold for casting PDMS and other polymers used in microfluidics and biomedical research.
Researchers commonly use silicon wafers for:
- Microfluidic device fabrication
- PDMS casting and replication
- Semiconductor device development
- MEMS and sensor fabrication
- Biomedical and lab-on-a-chip research
- High-aspect-ratio lithography structures
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UniversityWafer, Inc. supplies 100mm silicon wafers, thermal oxide wafers, SOI wafers, and custom substrates for SU-8 processing, photolithography, microfluidics, and MEMS research.
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SU-8 Molds for PDMS Microfluidic Devices
SU-8 molds are commonly fabricated on silicon wafers and used as masters for casting PDMS microfluidic devices, biochips, lab-on-a-chip structures, and semiconductor research devices. SU-8 is an epoxy-based negative photoresist that can form thick, high-aspect-ratio patterns with nearly vertical sidewalls, making it useful for soft lithography and microfabrication.
Researchers often choose silicon substrates for SU-8 mold fabrication because silicon wafers provide a flat, clean, and dimensionally stable surface for photolithography. Proper wafer cleaning, dehydration baking, spin coating, UV exposure, post-exposure bake, and development are important steps for producing reliable SU-8 features.
Why Silicon Wafers Are Used for SU-8 Masters
A silicon substrate gives the SU-8 layer a smooth base for accurate pattern transfer. Silicon wafers with native oxide, thermal oxide, or silicon nitride surfaces are often selected depending on the adhesion, release, and device requirements. For PDMS casting, the SU-8 patterned silicon wafer acts as a reusable master mold.
After the SU-8 pattern is developed, premixed PDMS can be poured over the mold and cured. Once cured, the PDMS layer is peeled from the SU-8 master, creating channels, wells, or raised features used in microfluidic devices.
SU-8 Photoresist Benefits
SU-8 is popular in semiconductor and MEMS research because it supports thick-film processing, high-resolution lithography, and strong chemical resistance after crosslinking. It is especially useful when researchers need tall structures, narrow channels, or durable molds for repeated PDMS casting.
- Creates high-aspect-ratio microstructures
- Works well for PDMS soft lithography molds
- Can be patterned on silicon, glass, oxide, and nitride surfaces
- Provides strong mechanical stability after UV exposure and baking
- Useful for MEMS, biochips, sensors, and lab-on-a-chip research
SU-8 Mold Fabrication Process
The SU-8 mold process usually begins with a clean silicon wafer. The wafer is dehydrated to remove moisture, then SU-8 photoresist is spin coated to the target thickness. A soft bake removes solvent before UV exposure through a photomask. After exposure, a post-exposure bake helps crosslink the patterned regions, and the wafer is developed to remove unexposed SU-8.
Process temperature, bake time, exposure dose, and resist thickness must be controlled carefully. Thick SU-8 layers often need longer bake times and gradual heating or cooling to reduce cracking, stress, or delamination.
SU-8 Adhesion and Surface Preparation
Good adhesion depends on the substrate surface and cleaning method. Silicon wafers are often cleaned with solvent or other wafer-cleaning processes before coating. A dehydration bake around 120°C can help remove moisture and improve SU-8 adhesion to silicon.
HMDS is commonly used as an adhesion promoter for some photoresist processes, but SU-8 adhesion depends strongly on the surface material and process conditions. For SU-8 molds used with PDMS, researchers may also treat the mold surface with a release coating to make PDMS removal easier and protect the SU-8 master.
SU-8-Silicon Masters vs. Au-Epoxy Masters
SU-8-silicon masters are widely used for microfluidic and semiconductor research because they are easier to fabricate with standard photolithography and provide strong dimensional control. Au-epoxy masters may be useful for specialized applications where surface conductivity, optical behavior, or biosensing performance is important.
For most PDMS microfluidic molds, SU-8 patterned on silicon is the practical choice because it offers repeatable feature geometry, good surface quality, and compatibility with cleanroom lithography processes.
Applications for SU-8 Molds
SU-8 molds fabricated on silicon wafers are used in many research and production environments, including semiconductor device manufacturing, MEMS, microfluidics, biosensors, and biomedical diagnostics.
- Semiconductor device fabrication
- PDMS microfluidic device casting
- Biochips and lab-on-a-chip devices
- MEMS structures and sensors
- Carbon micromolds and high-aspect-ratio structures
- Biomedical diagnostic devices
Silicon Wafers for SU-8 Mold Research
UniversityWafer, Inc. supplies silicon wafers for SU-8 photoresist processing, PDMS casting, microfluidic mold fabrication, MEMS research, and semiconductor device development. Researchers can request wafers by diameter, thickness, orientation, resistivity, dopant type, polish, oxide thickness, or custom specifications.