Applications Of Scatterometry In Grating Profile Measurement And Fabrication Of Echelette Gratings

Scatterometry, which is based on the measurement of far-field diffraction responses of periodic structures, is a sort of methods for accurate grating topography extraction. The non-contact, nondestructive and rapid-response features of scatterometry make it preferred in all kinds of online and offline applications. By use of scatterometry, we designed four kinds of online and offline grating profile measurement methods for different types of photoresist gratings and echelette gratings in this dissertation work. With some of the above measurement methods, we fabricated some echelette gratings whose local area diffraction efficiency and stray light level meet the commercial grating standards.For photoresist gratings with wavy sidewall profiles on a chrome film, we employed a profile measurement method, which is based on the combination of multi-wavelength scatterometry and artificial neural network, to determine their critical dimensions. From the experimental results of 1480 lines/mm gratings, we verified the precisions of this method for grating ridge height and duty cycle are about 18nm and 1.3%, respectively.For rectangular photoresist gratings on transparent substrates, we presented an in situ monitoring method during the development process. By use of the extreme values of monitoring curves of both the 0th and the -1st transmission orders, we determined the two profile parameters at the same time. From the experimental results, we verified the validity of this in situ monitoring method. For 1200 lines/mm gratings, the measurement precisions of this method for height of grating ridges and duty cycle of gratings are about 22nm and 1.7%, respectively. Meanwhile, in this dissertation we designed another offline measurement method to ensure the grating profile parameters got from the in situ monitoring method was correct, and tested the accuracy of this method.For ion-beam etching process of echelette gratings by use of rectangular-profile photoresist masks and grazing ion-beam incidence, we designed an online endpoint detection method. By experimental verifications, the success rate of this method is above 60%.The ion-beam etching process model of echelette grating fabrication is improved by accurate control of photoresist grating profiles and etching time. From a large number of experiments, we determined the technical details of echelette grating fabrication, such as the way of grating substrate cleaning, the processing steps of photoresist spinning, and optimized parameters of postbake and hardbake.