Three-dimensional excimer laser micromachining using greyscale masks

Abstract

Greyscale masks have been successfully implemented in an excimer laser micromachining system to produce structures with a continuous profile. During this work, it was found possible to machine structures to depths of several tens of microns with no observable mask degradation. The greyscale mask transmissions were defined using a matrix of pixels whose dimension was smaller than the resolution limit of the optical system in the laser micromachining system. By reduction-projecting the greyscale mask pattern onto the workpiece, the local fluence at the workpiece could be predetermined and hence the local machining rates controlled. This enabled three-dimensional (3D) structures to be fabricated at the workpiece in a single machining operation. Under the experimental conditions used in this investigation, the rate at which material was ablated was found to depend linearly on the percentage transmission of the mask. Various test structures, including complex 3D-contoured fluidic channels, have been produced.

A study on curved surface laser ablation using beam profile approach

“…However, the technique was not explored in detail from fabrication point of view and the shape control of fabricated profiles was not investigated. Hayden (2003) also made greyscale masks using a computer algorithm. However, using these masks at different laser fluences resulted in significant distortion of the fabricated structures.…”

Sub-micron surface patterning by laser irradiation through microlens arrays

“…On the other hand, laser processing is one of the promising tools in non-contact material processing that gives the advantages of low cost and suitable for processing of any kind of materials [7,8]. Conventional laser processing technique by focusing the laser light using a lens only can achieve features in micron range [9].…”

Expanding grayscale capability of direct-write grayscale photomask by using modified Bi/In compositions

“…The surfaces of micromachined 3D features should have welldefined contours and curvatures for the fabrication of devices such as diffractive or refractive optical elements, microfluidic channel systems, etc. This grayscale photomask technology allows the creation of 3D structures via a low cost, short cycle time, single exposure process [1][2][3][4][5][6]. There are two types of grayscale photomasks: digital and analog.…”