Investigation of metallic glass as thermal absorption layer for laser thermal lithography

• Main Author: Wong, Hsien Han.
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Materials
• Online Access: http://hdl.handle.net/10356/38816
• Institution: Nanyang Technological University

A study on the feasibility of using the metallic glass AlNiGd as an absorption layer for laser thermal lithography was done. From characterisation experiments done, it was found that metallic glasses have the phase change properties required to be used as a recording layer in rewritable optical discs. Using this phase change property to control the heat profile of the absorption layer irradiated by laser, patterns can be formed on a dielectric layer that was deposited above it by means of selective etching. This ability to create patterns allows laser thermal lithography to be used in DVD-ROM mastering process. Glass substrates were sputter deposited with 3 layers of materials. ZnS-SiO2 served as the first layer to provide bonding for the AlNiGd layer above it. This was followed by another layer of ZnS-SiO2 to function as the active layer on which dots were created. A blue laser of wavelength 405 nm was used to write dots on the sputtered substrates. The laser heated up the absorption layer which re-radiated the heat to the dielectric layer above. This induced a chemical reaction which made the dielectric layer more resistant to etching. The written substrates were then etched in HF and subsequently analysed using AFM. Experimental variables include laser power, thermal absorption layer thickness and dielectric layer thickness. Results show that it is possible to record dots as small as 125 nm in diameter. This shows that laser thermal lithography can produce smaller patterns compared to optical lithography, and is comparatively cheaper and faster than electron beam lithography. As such, it can be used as an alternative method to produce DVD-ROM master discs.