The goal of photolithography is the fabrication or transfer of planar or three dimensional microstructures onto a substrate (bulk micromachining) or onto films on a substrate (surface micromachining).
- Mask design and coordination of mask fabrication with pre-selected vendors
- Patterning of resist materials in thicknesses from 100 nm to 200 µm
- Aspect ratios (height/width) up to 10 (depending on resist thickness)
- Highest possible resolution 300 nm (depending on resist thickness)
- Fabrication of multilayer structures
- Design qualification of processes and tools
- Implementation and commissioning of processes at customers' own sites
- Masking for dry and wet etching (e.g. DRIE, BHF)
- Patterning of thin films (e.g.Lift-off)
- Patterning in preparation for electroplating (e.g. UV-LIGA)
- Direct fabrication of micro structured components (e.g. SU-8)
Photolithography was originally developed for the fabrication of integrated microelectronic circuits out of silicon. It has, over time, become the foundation for most microfabrication processes. So far, no other process approach offers the same precision with as low process times and high productivity as photolithography.
The starting point is a photoresist, with physical properties that change upon exposure to radiation. The resist material is coated onto the substrate through a method appropriate for the process (spin coating, spray coating, lamination). The solubility of the resist is modified by radiating the layer selectively (e.g. UV exposure through a mask). A suitable developer solution can then dissolve the exposed areas (for positive resists, e.g. AZ1512) or unexposed areas (for negative resists, e.g. SU-8) as desired.
With the equipment available at MNT, structures with resolutions of a few micrometers can be fabricated on film thicknesses ranging from a few hundreds of nanometers to hundreds of micrometers.