We report on a technology for multi-level microstructures manufacturing. Results are presented in the field
of multilevel diffractive optical elements (DOEs) fabrication. The DOEs presented as examples are Fresnel
lenses and Fourier computer generated holograms, calculated by means of a conventional Iterative Fourier
Transform Algorithm. The DOEs have a typical pixel dimension of 5x5 μm<sup>2</sup> and are up to 512 by 512 pixels in
The fabrication technique is based on polymer laser ablation through a chrome-on-quartz half-tone mask
with a demagnifying high NA lens. In our case, the mask is imaged onto the polymer with a 5x, 0.13 NA
reduction lens. The experimental results are presented and discussed.
Laser micromachining by ablation is an established technique for the production of 2.5D and 3D features in a wide
variety of materials. Mask projection techniques using excimer lasers have been used to fabricate microstructures on
large panels where diamond turning and reflow techniques have reached their limits. We have developed 3D structuring
tools based upon UV laser ablation of polymers to create large arrays of repeating micro-optical features.
Synchronization of laser pulses with workpiece movement allows layer-by-layer growth of deep structures with
outstanding repeatability. Here, we show recent developments in laser structuring with the combination of half-tone and
binary mask techniques. Significant improvements in surface quality are demonstrated for a limited range of structures.
The demand on performance for displays and opto-electronics is ever increasing and the industry is looking for ways to produce large area microoptical films to help that cause. While conventional techniques are reaching their limits for large area structuring, earlier reports show that it is possible to structure a few m<sup>2</sup> polymer film with microoptical features (>20 μm) by direct laser ablation. By employing the same optics and hardware studies were carried out to find the minimal feature size possible without compromising the area that can be processed. Looking at the sub-resolution ablation behaviour of Polycarbonate enables us to modify the so-called Synchronised Image Scanning (SIS) mask design to control shape and form of 3D-features only a few times bigger than the resolution limit of the laser ablation mask projection system. Results of optical 10μm and 5μm features are shown and discussed. The findings show that it is realistic to direct laser cut well defined optical 3D-features into polymer film with an unprecedented feature-area-ratio in excess of 1:10<sup>10</sup>.
Laser micromachining has great potential as a MEMS (micro-electro-mechanical systems) fabrication technique because of its materials flexibility and 3D capabilities. The machining of deep polymer structures with complex, well-defined surface profiles is particularly relevant to microfluidics and micro-optics, and in this paper we review recent work on the use of projection ablation methods to fabricate structures and devices aimed at these application areas. In particular we focus on two excimer laser micromachining techniques that are capable of both 3D structuring and large-area machining: synchronous image scanning (SIS) and workpiece dragging with half-tone masks. The methods used in mask design are reviewed, and experimental results are presented for test structures fabricated in polycarbonate. Both techniques are shown to be capable of producing accurately dimensioned structures that are significantly deeper than the focal depth of the projection optics and virtually free from fabrication artifacts such as the steps normally associated with multiple-mask processes.
Pulsed laser sources are widely used for the micro-processing of materials from the structuring and patterning of surfaces to the direct machining of devices. This paper discusses laser micro-processing techniques for the fabrication of microstructures with high accuracy and precision. Techniques discussed include laser mask projection techniques and direct beam micromachining using galvo-scanners and high precision motion stages, with a variety of different lasers. Examples of the application of these techniques to the manufacture of MEMS and MOEMS devices are discussed.
A novel laser micro-machining technique to produce high density micro-structures called Synchronized Image Scanning (SIS) was introduced a couple of years ago. Over this period of time, the technique was refined in a major effort to meet the needs of various industries.
There is an increasing demand for micro-structuring of large and super large area optical films, e.g. for Rear Projection TV, anti counterfeit packaging material and 3D displays. Especially in the display industry, where the screens are ever increasing in size, established micro-structuring methods like e-beam milling, diamond turning or the reflow technique struggle to keep up with the development.
This paper explains how it is possible to direct laser etch hundreds of millions of lenses into a 2 m x 1.5 m substrate. It looks at the advances made in SIS in recent years regarding seam reduction, overall accuracy and precision when structuring super large area optical films, and it presents the tools and subsystems needed to generate the features in those films. Furthermore, the potential of this exciting laser micro-machining technique for rapid prototyping for all sorts of optical and non-optical structures is mapped out.
A new laser mask projection technique, Synchronised Image Scanning (SIS), has been developed for the efficient fabrication of dense arrays of repeating microstructures on large area substrates. This paper details the technique and provides specific examples of the type of structures that can be produced. SIS is a laser micro-machining technique where the information for the ablation of a specific 3D feature is stored as a linear array on a chrome-on-quartz mask. The feature is then written by synchronised motion and laser firing, such that the firing frequency of the laser corresponds to the spatial pitch of the features. This requires highly accurate laser triggering with low-jitter signals, and accurate stages with high resolution encoders. An add-in for CAD software has been developed to generate the mask pattern efficiently and error-free, using the 3D designs. SIS allows for major improvements in the accuracy and speed with which 3D patterns can be created over large areas by laser ablation. Feature sizes down to a few microns can be produced with excellent surface quality. Large areas of microstructures have wide ranging applications in many areas. One example is the machining of large polymer master panels for electroforming to produce moulds for replication of display enhancement films.
Two new laser mask projection techniques Synchronized Image Scanning (SIS) and Bow Tie Scanning (BTS) have been developed for the efficient fabrication of dense arrays of repeating 3D microstructures on large area substrates. Details of these techniques are given and examples of key industrial applications are shown.
Novel methods using pulsed laser ablation have been developed for the manufacture of micro-devices with axial symmetry in ceramic materials. Such techniques allow the prototyping and production of micro-parts that are very difficult or even impossible to process by other mechanical and/or chemical methods. To demonstrate these techniques we have manufactured small conical counter-electrodes for use in a Scanning Atom Probe (SAP) instrument. This paper details all the innovative steps developed to produce the double cone shaped electrode and demonstrates the potential for mass production of other devices of similar shapes and dimensions. Many different laser processing strategies for fabricating the cones have been tried in order to achieve a result with satisfactory accuracy and quality. High quality devices have finally been produced in quantity using a combination of excimer laser mask projection and UV Yag laser cutting. The laser methods developed allow micro-parts of an overall size down to 0.1mm and tolerances of a few microns to be manufactured directly in ceramics, glasses, or crystalline materials.