INTERFACIAL MICROSTRUCTURE AND REACTION AT THE SPIN-COATED FLUORINATED POLYIMIDE AL INTERFACE - SURFACE-ENHANCED X-RAY-DIFFRACTION AND TEM STUDIES/

Fluorinated polyimides (FPIs) are being investigated as interlevel die lectrics (ILDs) in future multilevel interconnect technologies because of their low intrinsic dielectric constant. This study investigates t he effect of thermal treatment in a pure nitrogen atmosphere on the in terfacial microstructure and chemistry at the interface between a FPI thin film and its contacted Al layer in FPI/Al/Ti/SiO2 multilayers by means of X-ray diffraction, transmission electron microscopy, and an e llipsometer. The FPI precursor, a solution of PMDA/6FDA/TFMOB/PPD was spin-coated onto the Al layer and then cured at 400 degrees C for one hour. It is found that the moisture and oxygen from the FPI layer rele ased during thermal treatment can lead to the oxidation of the interfa ce between the Al and the FPI. The TEM cross-sectional images and the electron diffraction patterns indicate that the oxidized interface is amorphous. The oxidation product is identified to be Al2O3 The oxidati on onset temperature is determined to be 415 degrees C, which is sligh tly higher than the curing temperature. The oxidation of the FPI/Al in terface results in an increase in the electrical resistance of the Al layer, and thus may lead to a reduction in its effective electrical th ickness.