An interferometric optical lithography system utilizing a 442nm Helium Cadmium (HeCd) laser source has been developed. The HeCd laser was passed through a 2μm diffraction grating etched into a phase shift quartz mask to generate two mutually coherent light beams. The ±V’ diffraction orders were collected and interfered at angles ranging from o to 90° with respect to the substrate normal. Incident angles of 13, 26, 34, and 47° were implemented to produce corresponding pitches of 1.0, 0.5, 0.4 and 0.3μm, respectively. The smallest line width that was fabricated approached 0.10μm. In order to synthesize the behavior of conventional projection lithography one of the incident light beams was pulsed to adjust the intensity of that beam for variable transmissions producing a range of duty ratios. Images were acquired from scanning electron micrographs (SEM’s) for each of the cases analyzed.
Cropanese, Frank C.
"Interferometric Lithography Optical System Utilizing a 442nm HeCd Laser,"
Journal of the Microelectronic Engineering Conference: Vol. 12
, Article 3.
Available at: http://scholarworks.rit.edu/ritamec/vol12/iss1/3