StructSure™
Photoresists & Specialty Chemicals
Photoresists & Specialty Chemicals
T-Gate Fabrication
Part of the Applications Notes Line
T-Gate Fabrication
T-shaped gates improve high electron mobility transistors (HEMTs) performance. T-gate structures are usually fabricated in high electron mobility heterostructures like InGaAs. Sub 50nm gate length result in reduced capacitance, high electron mobility, and ultra high RF characteristics. Tri-layer resist structures with a PMGI layer (aqueous developer) in between two PMMA layers (solvent developer) are being used for precise control of the T-gate shape to optimize device electrical properties.
LOR & PMGI: Benefits/Attributes
- Sacrificial layer to assist in fabrication of higher gate stem heights
- Excellent adhesion to III-V substrates
- Suitable for multi-layer processing
- Suitable for use as a protective separation layer between incompatible layers
- Allows gate head and gate foot to be written separately for improved resolution
- Can be used in a resist stack with low intermixing
PMMA: Benefits/Attributes
- Positive tone; E-beam imageable
- Wide range of film thicknesses
- Excellent adhesion to most substrates
 Definition of Gate Stem |
 Pattern Transfer to SiN |
 E-beam Litho. On Gate Stem |
 Final Trip Gate |
| Courtesy of Seoul Nat University | |
Process Flow
Courtesy of Raytheon