We employed a grating profile measurement method, which is based on the combination of multiwavelength scatterometry and artificial neural network, to determine the critical dimensions of submicrometer-period photoresist gratings with wavy sidewall profiles. Six laser beams in three wavelengths and two orthogonal polarizations were adopted for the scatterometry measurement, and the incident angle of each beam was chosen following principles that we propose for achieving high sensitivity. We measured diffraction efficiencies of a large number of photoresist gratings made on glass substrates and high-reflectivity multilayer substrates coated with a chromium thin-film layer, and determined the grating groove parameters using a neural network model. The experimental results are statistically compared with results extracted from scanning electron micrographs. Good agreements between the indirect, neural network predicted results and the direct, scanning electron microscopy results are obtained.

We present a new method for in situ monitoring of a grating profile during the development process to control the critical dimensions of surface-relief rectangular photoresist gratings on transparent substrates. A He-Ne laser of visible wavelength is employed as the monitoring light source. We determine the height of the grating ridges from the first minimum value of the diffraction intensity curve of the zeroth transmission order and then obtain the duty cycle of the grating from the diffraction intensity of the -1st transmission order. The effectiveness of our method has been demonstrated through the fabrication of rectangular photoresist gratings of 1200, 2200, and 3000 lines/mm on glass substrates. The experimental results are statistically compared with results extracted from scanning electron micrographs. Good agreement between the online, real-time measured results and the scanning electron microscopy results is obtained.

This paper presents a method for on-line measuring photoresist grating profiles during the development process by detecting the diffraction efficiencies of surface-relief photoresist gratings on transparent substrates. A He-Ne laser of 594.1 nm wavelength is employed as the monitoring light source. Firstly, the groove depth of a grating is determined from the minimum value of the monitoring curve of the 0 th -order transmission intensity. Then, with the groove depth known, the duty cycle of the grating is measured from the -1 st -order transmission intensity. The feasibility of our method has been demonstrated through fabrication of many rectangular photoresist gratings of 1200, 2200, and 3000 lines/mm on glass substrates. Good agreement between the on-line, real-time measured results and the scanning electron microscopy results is obtained.