Effect of Laser Parameters on the Exposure and Selective Etch Rate in Photostructurable Glass

摘要

Photostructurable glass-ceramic materials have received significant attention due to their utility in aerospace engineering and microtechnology. For example, the ability to fabricate structures in glass is important in the design and integration of microscale electronic, optical and fluidic devices. Direct-write pulsed ultraviolet (UV) laser processing techniques have been utilized recently to create patterned three-dimensional (3D) microstructures in a lithium-aluminosilicate glass (Foturan~(TM), Schott Corp.). The direct-write microfabrication process involves the formation of an initial latent image in the glass via UV laser radiation. Thermal-induced ceramization is utilized to develop the latent image into a permanent image. Material removal and microstructure fabrication are then accomplished by preferential isotropic etching of the developed regions. Precise control of the laser processing parameters is essential to ensure efficient and consistent microstructure fabrication. Unfortunately, detailed information does not exist regarding the influence of the laser characteristics on the exposure and photochemical etch rate in photostructurable glass. The present study investigated the effects of laser power (fluence) on the selective chemical etch rate in Foturan glass. The results will facilitate precise timed-etch procedures for volumetric processing of 3D microstructures in photostructurable glass. Variation of the laser exposure during direct-write patterning affects the etch conditions and permits the concurrent formation of microscale features with markedly different aspect ratios. This direct-write variable exposure processing technique also facilitates the formation of variegated aspect ratio structures on a common substrate following a single batch etch without the need for a complex masking sequence.