Tomoyuki Yuba

Effect of Photo-active Compound Structure on Photosensitivity of Positive Photosensitive Polyimide

The photo-active compound (PAC) in positive tone photosensitive polyimide (posi PSPI) was investigated in order to obtain good photo lithographic performance (small development loss and good photosensitivity). When the PAC structure was changed posi PSPI showed different levels of photosensitivity and development loss. The development loss and photosensitivity showed a good correlation. The lower development loss posi PSPI showed lower photosensitivity. From the molecular orbital calculation, the PAC in the lower development loss posi PSPI had a lower dipole moment than that in the larger development loss posi PSPI. In addition, dissolution rate measurement (DRM) results suggest that posi PSPI may have two layers from the point of dissolution. The dissolution rate of the surface layer in posi PSPI was shown to be lower than that of a bottom layer. This suggests that PAC using the lower development loss posi PSPI may exist mainly on its surface. These results are quite important for the design of good posi PSPI.

Improvement of chemical resistance of positive-tone photosensitive polyimide coatings in the electroless plating process

We found that positive-tone photosensitive polyimide (posi-PSPI) shows not to be compatible for electroless Ni/Au plating process which are used for Au micro bumping. In order to meet compatibility for the process, we improved chemical resistance of positive-tone photosensitive polyimide especially for electroless plating process. Changing of polyimide polymer structure is most effective to obtain chemical resistant for the electroless plating process. The obtained PSPI are useful for saving bumping process and reliable in forming pattern.