Deposition of fluorinated polyimide consisting of 6FDA and TFDB into microscale trenches using supercritical carbon dioxide

Abstract

Fluorinated polyimide (PI) consisting of 2,2-bis(3,4-anhydrodicarboxyphenyl)-hexafluoropropane (6FDA) and 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFDB) were deposited on silicon wafers with patterned microscale trenches. The deposition was carried out in supercritical carbon dioxide (scCO2) with 5mol% N,N-dimethylformamide (DMF). The effects of the monomer concentration and deposition temperature on the deposition of fluorinated PI inside the microscale trenches were studied to clarify the appropriate conditions for the deposition of fluorinated PI using scCO2. The monomer concentration and deposition temperature studied were in the ranges of 0.28×10−2–1.1×10−2mol/dm3 and 150–250°C, respectively. The amount of deposited fluorinated PI inside the trenches increased with increasing monomer concentrations and deposition temperature. Moreover, the time course of the phase behavior in the reactor was also investigated during the deposition, and the time-dependent changes in the shapes and amount of deposited fluorinated PI inside the microscale trenches were also investigated. Finally, the relationship between the trench size and the deposition behavior was studied, and the trenches of width-depth sizes of 1.5–23.5, 3–26, and 5–30μm could be completely filled with fluorinated PI simultaneously.