INCUBATION ABLATION PATTERNING OF POLYMER SURFACES WITH SUB-MU-M EDGE DEFINITION FOR OPTICAL STORAGE DEVICES

By exposure to low fluence UV laser radiation, the optical absorption coefficient of subsurface polymer material can be increased ("incubation") with spatial control, using a suitable contact mask, proper imaging of the mask, or laser direct writing. Spatially selective ablation of polymethylmethacrylate (PMMA) is then achieved with large area XeCl excimer laser pulses at 308 nm. In this way. the transfer of spatial information to the material can be decoupled from the high laser fluence removal ("ablation") step. The advantages are: The mask is exposed to only low fluence laser radiation - damage is avoided. Since the mask can be removed before the ablation step, mask contamination by the ablated plume cannot occur. Using this incubation/ablation method, PMMA surfaces can be patterned (248 nm/308 nm) with submicrometer spatial control and edge contrasts better than 0.2-mu-m. This has impact on optical storage technology and laser surface processing techniques in general. The smallest single structure obtained was somewhat smaller than 0.5-mu-m in diameter up to now, given by the mask.