Synthesis and characterization of chiral polyacrylates and their applications as positive tone photoresists

To estimate the effects of diastereomeric copolymers as photoresists, diastereomeric copolymers containing chiral and racemic bornyl methacrylates (BMAs) were synthesized. Both alicyclic BMAs were synthesized from (-)-borneol and (±)-borneol, and then copolymerized with t-butyl methacrylate (t-BMA), tetrahydro-pyranyl methacrylate (THPMA), and α-methacryloxy- γ-butyrolactone (MABL). The glass transition temperature of the copolymers was found to increase with an increase in the content of alicyclic bornyl groups in the copolymers. To investigate the effect of both the alicyclic butyrolactone and the bornyl groups on photosensitivity, thermal property, and etching resistance, the synthesized alicyclic copolymers were used to prepare photoresists with photoacid generators. The sensitivity and the contrast of the photoresists were calculated. This investigation demonstrated that the existence of alicyclic butyrolactone and bornyl groups increases the etching resistance of photoresists. It was also found that high stereo hindered bornyl structures disturb and restrict the mobility of the polymer chain, leading to an increase in the thermal stability of the polymers. A real pattern recording of photoresists with PR3 composition was performed; an optimal sensitivity of 20 mJ/cm² and resolution of 1 μm of positive tone photoresists with 1 μm thickness was achieved.