Stable material modication with polymers incorporation for broad application in microfabrication

The aim of this thesis is to improve SU-8 fracture resistance in order to eliminate micro crack formation during fabrication of microelectromechanical system (MEMS). An amphiphilic block copolymer incorporation, as an efficient method of material toughening without changing its original properties, is successfully applied.

The novelty of the study consists in design and synthesis of the most optimal copolymer composition, which can self-assemble in SU-8 resin. In the first part of the thesis, solubility prediction with the Hansen Solubility Parameters method is described in details and poly(ethyl ethylene)-b-poly(2-vinylpyridine) (PEE-b-P2VP) is found to be a suitable modifier for SU-8.

Synthesis of this copolymer is performed by living anionic polymerization followed with a selective hydrogenation reaction in order to stabilise the structure. All synthesised copolymers are characterized with various analytical techniques. The second part of the thesis describes modified SU-8 blends.

Thermal stability, structural organization, components interaction, hardness and brittleness of the composites are described. Finally, lithographic properties of modified SU-8 blends have been tested. Commercial SU-8 and the modified blends demonstrate identically patternability and high aspect ratio structures can be obtained regardless of PEE-b-P2VP content.

In conclusion, a recommendation of SU-8 modification with as little as 5 wt.% of PEE30-b-P2VP69 is made in order to avoid micro crack formation and its growth during MEMS production. Fabricated from this blend films are easily patterned and have Young's modulus similar to original SU-8.