Derek Jenkins

Microfabrication of 3D terahertz circuitry

Advances in micro-fabrication techniques combined with accurate simulation tools has provided the means for the realisation of complex terahertz circuitry. Silicon micro-machining provides the way forward to fabricate accurate rugged structures. Multi-level deep reactive ion etching can be used to replace traditional machining methods achieving smaller feature size, improved surface finish and greater freedom in circuit layout. Photonic Bandgap waveguides enable three dimensional arrangements of active devices antennae and filters, and removes the requirement for metallisation of adjoining surfaces. This paper describes some of the state of the art terahertz circuit design and realisation using these techniques.

Profile control of SU-8 photoresist using different radiation sources

Patterning of thick layer SU-8 photoresist has been investigated with different radiation sources, including electron beam, X-ray, i-line stepper, UV mercury lamp with collimator, as well as two different types of UV contact maskaligner. Feature profiles with thickness up to 1 mm have been compared. Among all the radiation sources, x-ray exposure from a synchrotron radiation source is found to produce the best feature dimension control and has the highest feature aspect ratio. I-line stepper can also produce features with steep side wall but is limited to less than 200 micrometers resist thickness. The illumination parallelism is the key to control the resist profile, no matter what radiation sources are used. Other issues such as process condition become important when resist layer thickness is over 500 micrometers . Conditions for better profile control with thicker layer SU-8 photoresist are suggested.