Study on the over-top-coating suppressing surface insoluble layer generation for chemical amplification resist

Most positive chemical amplification resists do not have enough stability to process delay. It has been claimed that airborne contaminants neutralize acids from photo-acid generators. It has been found by means of x-ray photoelectron spectroscopy that an onium salt used as a photo-acid generator is deficient at the surface of the prebaked resist film. The over-top coating using water-soluble polymers with organic acids has been investigated in order to not only separate the resist surface from airborne contaminants but also supply acids to the resist surface. We have succeeded in the suppression of the surface insoluble layer generation and of the pattern size change for more than 8 hours.