Photolithography
Introduction
Photolithography is a process used to transfer a pattern from a mask to a substrate. This is achieved by spinning on a photosensitive resist layer and exposing it to UV light via a patterned mask which causes the resist to cross link or breakdown depending on the resist tone. The photoresist is then developed in a solution to remove the unwanted material. The substrate can then move onto the next process e.g. metal deposition, etching etc.
Multiple layers can be built up on a single device by using the alignment capabilities of the EVG620 and appropriate alignment markers in the mask design.
The minimum feature size that can be defined with photolithography depends on a number of factors:
- Wavelength of exposure
- Photoresist used
- Photoresist thickness
- Subsequent processing considerations
The minimum feature sized acheived at MCN using photolithography is 800nm with a subsequent metal lift-off process. For smaller dimensions the user should consider using Electron Beam Lithography.
MCN supplies a number of photoresists some of which are:
- AZ4562 positive tone, general purpose
- AZ9260 positive tone, high aspect ratio
- AZ1512HS positive tone, high resolution
- AZ5214E image reversal resist
- AZMIR701 positive tone, high resolution
- AZnLOF2070 negative tone, for lift of process
In addition to the mask aligner MCN hosts the following lithography equipment:
Applications
Photolithography is central to most micro and nanofabrication applications including microfluidics, cantilever fabrication etc.
Equipment
- EVG620 mask aligner and exposure system
- Suss Delta80 RC photoresist spinner with hotplate
- Laurell photoresist spinners
- UV Flood light source from ABM
- Ovens for resist baking
- Fume hoods for cleaning and developing
Contacts
For information and training on these tools and related processes, please contact:
Douglas Mair - douglas.mair@monash.edu
Patterned AZ2070nLOF resist on silicon substrate
