In a joint research project with Sharp and TDK, the Laboratory for Advanced Optical Technology, part of the National Institute of Advanced Industrial Science and Technology, has developed a novel lithography technology that uses visible light to create a micropattern 100 nm in size (around one-sixth the wavelength of visible light). When existing optical lithography techniques are used to create this type of micropattern, expensive photolithography devices are required as the short wavelength light source. In this research, a red semiconductor laser (635 nm wavelength) was used as the light source, resulting in a low-cost technology to produce micropatterns. Further development of this research may allow application to master production technologies for advanced high-capacity optical disks.

The new technology uses the heat generated by laser light irradiation to create a pattern on a resist membrane. This technique is known as heat lithography and previously there were problems with limits to the miniaturization possible with this reaction. The key to the new technology lies in a novel substrate structure that miniaturizes the region of thermogenesis.

The research used an optical disk substrate overlaid with a membrane, which efficiently absorbs laser light and generates heat, and coated on the outer surface with a photoresist that reacts to light. The test sample was exposed by rotating the sample and irradiating with a red laser from the inner side of the substrate. By controlling the laser power and rotation speed, the researchers were able to restrict the heat spread to an area much smaller than the laser spot (ca. 1 µm). The technique was used to create a line pattern with a line width of 110 nm and a dot pattern with dots 80 nm in diameter. One of the key factors in being able to miniaturize the pattern is thought to be the use of the heat generated by the substrate, and not heat directly from the resist membrane.