Mask-less lithography by individual control of ultra-violet light emitting diode array

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17560312
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Electron device/Electronic equipment
• Research Institution: Kumamoto University
• Principal Investigator: NAKAMURA Yusui Kumamoto University, Graduate School of Science and Technology, Professor, 大学院自然科学研究科, 教授 (00381004)
• Co-Investigator(Kenkyū-buntansha): KUBOTA Hiroshi Kumamoto University, Shock Wave and Condensed Matter Research Center, Professor, 衝撃・極限環境研究センター, 教授 (20170037) ; NAKADA Akira Kumamoto University, Graduate School of Science and Technology, Associate Professor, 大学院自然科学研究科, 助教授 (60302650) ; NAKA Yoshihiro Kumamoto University, Graduate School of Science and Technology, Research Associate, 大学院自然科学研究科, 助手 (30305007)
• Project Period (FY): 2005 – 2006
• Keywords: Crystal growth / Optical source technology / Electronic devices and systems / Semiconductor properties

Research Abstract

Final purpose of this research is to realize small mask-less exposure systems with low cost and high throughput. For the purpose, we have proposed a new method, in which two dimensionally aligned ultra-violet light emitting diode (LED) array should be controlled inc ividually. In this research during the fiscal years of 2005〜2006, our target is to try simple tests of lithography by controlling the ultra-violet LEDs individually.
As a first step, we have investigated how to form the ultra-violet LEDs. To form ultra-violet LEDs at low cost, we have planned making of poly-crystal hetero-junction structures, which includes ultra-violet light emitting layer (ZnO), electron injection layer (SnO_2), and hole injection layer (NiO). We would like to emphasize that formation of the hetero-junction with poly-crystal materials is a new and important approach for low-cost light-emitters on silicon or glass substrates, because epitaxial growth on lattice-matched substrates by moleculer beam epitaxy i s an expensive method even though high quality light emitters have been formed. Along this line, we used simple evaporation and sputtering to form those layers.
We have formed those layers at various conditions by evaporation and sputtering. As a result, ZnO layers showed cathode luminescence peak at 380nm at room temperature. For this measurement, we have changed our scanning electron microscope into cathode luminescence system by installing an optical fiber and monochromator. In case of SnO_2, we have formed high quality layers, which showed conductivity of 0.001Ωcm (n-type), transmittance of 90%, and bandgap of〜4eV. As a p-type wide bandgap material, we have formed of NiO layers, which showed conductivity of 0.3 Ωcm (p-type), transmittance of 40-50%, and bandgap of〜4eV. Recently, development of high-quality p-type wide bandgap material is intensively studied in the world because many applications are expected. Since our data of the NiO layers shows good values, we are planning to have presentation in a conference and submission to a journal.
As discuss above, we have studied wide bandgap materials for ultra-violet LEDs, which is aimed to develop small mask-less exposure systems with low cost and high throughput. In near future, we would like to complete ultra-violet LEDs by more improving quality of those materials.