The application of focused ion beam (FIB) technology in microfabrication has become increasingly popular. Its use in microfabrication has advantages over contemporary photolithography or other micromachining technologies, such as the ability to process without masks and being accommodating for a variety of materials and geometries. With the surface modification of the LED/air interface, like microlens array, the light emitting at large angle can be extracted because the incident angle at the interface will be less than the critical angle without total internal reflection. A microlens feature has been fabricated on GaN LED top surface (p-GaN layer) and back side (sapphire substrate) by scanning a focused Ga ion beam. The lens shape can be modulated by using computer-controlled beam direct writing and dwell time during milling process. We have used this technique even to create a sophisticated lens surface of Fresnel microlens array which can't be created with the conventional etching methods. In addition, the resistivity of p-GaN layer is highly sensitive to the
process-induced damages during surface texturing, it is difficult to apply dry etching to p-GaN layer. Our method of using gas-assisted focused ion beam
etching (GAFIBE) can enhance the etching rate by the assistance of chemical reaction with minimized ion dose density to provide nearly damage-free etching by varying the beam current, pixel dwell time and refresh time. Our study emphasis on direct milling and maskless techniques which can distinguish the FIB technology from the contemporary photolithography process and provide a vital alternative to it.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0129108-110429 |
| Date | 29 January 2008 |
| Creators | Kuo, Kwei-Kuan |
| Contributors | Ikai Lo, Ming-Kwei Lee, Wen-Tai Lin, Liann-Be Chang, Wen-Kuan Yeh, Tsu-Hsin Chang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0129108-110429 |
| Rights | not_available, Copyright information available at source archive |
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