Accurate layer thickness control and planarization for multilayer SU-8 structures

作者：Farrington Novak E S^*; Iezekiel Stavros

来源：Journal of Micro/ Nanolithography, Mems, and Moems, 2011, 10(1): 013019.

DOI：10.1117/1.3563599

• micromachining
• microsystems
• microelectromechanical systems
• millimeter-wave
• process control
• process optimization

A technique is developed to enable accurate layer thickness control and planarization in a multilayer SU-8 2000 micromachining process, while maintaining a high quality surface finish. Relying on carefully controlled mechanical lapping and polishing stages, layer thicknesses from 30-400 mu m have been routinely achieved to an accuracy of +/- 3 mu m with excellent planarity. High-aspect ratio structures (intended for use in a millimeter-wave engineering application) with up to five layers and of 770-mu m thickness have been fabricated using this method. The quality of the resulting surfaces has been investigated and characterized using scanning probe microscopy: a typical rms surface roughness of around 10 nm has been measured. The problem of air-bubble formation and migration encountered during the lapping stage has been documented along with a technique for their elimination. It is also shown that the common problem of the expansion of the lower layers in a multilayer structure due to solvent reabsorption can be effectively eliminated through careful process optimization.

• 出版日期2011-3