Excimer laser photochemistry of lithographic systems

Laser photochemical methods are useful in the microchemical field and for microlithographic patterning of integrated circuits. For many reactions a difference in the going on and the result of the reaction is obtained at lamp or at laser initiation, respectively. For the photochemists engaged in lithography the most important properties are: intensity and collimated beam. Several excimer laser exposure systems have been developed in the last years, the importance of which is increasing. At high peak power densities of the excimer laser radiation, new phenomena in photochemical and/or lithographic behaviour are observed. The wavelength-dependent sensitivity of the positively working naphthoquinone diazide resists is caused by the change of the absorption spectrum within the pulse duration. The intensity-dependent gradation and resolution of the investigated negatively working azide resists are the result of the further excitation of the intermediately formed nitrenes.