Novel Laser Scan Lithography onto Deep Inside Surfaces of Fine Pipes Using a Reflection Rod

Abstract

A novel laser scan lithography for patterning in deep fine pipes using a reflection rod was developed. As a previous research, patterning results using an optical fiber rod or a light-emitting diode (LED) rod were reported. However, the minimum inner diameter was 6 mm, and the pattern width was approximately 200 µm. Here, more precise patterning onto the inside of much finer pipes using a novel reflection rod is demonstrated. A violet laser beam of 408 nm wavelength was shaped using a micropinhole and focused onto the inner surface of the pipe by way of a reflection rod of 500 µm diameter. The tip of the reflection rod was cut and polished in 45° mirror surface and the laser beam was bent in a right angle when reflected on the mirror surface. A beam spot observation system composed of a charge-coupled device (CCD) camera and a television monitor was also added to observe the laser beam spot during the exposure. Specimen pipes were coated with 1-µm-thick positive THMR iP-3300 (Tokyo Ohka Kogyo) resist and scanned using a linear stage and a rotation stage and exposed to the laser light. The inside lithography was demonstrated for fine pipes of 1 mm inner diameter. Helical patterns with space widths of 9–20 µm were successfully delineated even at the deep inside position 20 mm away from the pipe entrance. Dense helical patterns of 100 µm narrow pitch and 12 µm space width and character patterns of 15 µm space width were also successfully delineated.