Low Temperature Photosensitive Polyimide Based Insulating Layer Formation for Microelectromechanical Systems Applications

• DOI: 10.1007/s11664-015-4076-y
• Publication Date: 2015-10-18T19:50:45Z
• Authors: J. Fan; T. Zhu; W. J. Wu; S. H. Tang; J. Q. Liu; L. C. Tu
• Keywords: 0103 physical sciences; 7. Clean energy; 01 natural sciences

Photosensitive polyimide (PSPI) based insulating layer fabrication for microelectromechanical systems (MEMS) application has been systematically investigated in this work. The PSPI was spin coated on a silicon substrate as an insulating layer between two metal lines. In consideration of thermal properties, a low temperature hard bake process was carefully optimized. Finally, the polyimide insulating layer was hardened by exposure to air at 80°C for 120 min + 150°C for 60 min + 180°C for 60 min + 250°C for 60 min + 350°C for 60 min in a dry furnace. Using this optimized hardening process, the outgassing effect in post-fabrication heat treatment can be completely eliminated, which presented an excellent thermal resistance in MEMS fabrications. The reliability test was accomplished through an immersion in organic solvent and acid/base solution in order to verify the corrosion resistance of the PSPI frame for insulating application. The excellent resistance which is on the order of 108 Ω between two metal lines, shows an outstanding insulating property.