Résine photosensible | EPFL Graph Search

La résine photosensible (appelée aussi photorésine et parfois photorésist) est un matériau photosensible utilisé dans de nombreux procédés industriels, comme la photolithographie ou la photogravure, afin de former un revêtement protecteur ajouté à la surface d'un substrat. Classes de résines photosensibles Les résines photosensibles peuvent être classées en deux groupes, les résines « positives » et les résines « négatives » :

une résine « positive » est un type de résine photosensible pour laquelle la partie exposée à la lumière devient soluble au révélateur et où la partie de résine photosensible non exposée reste insoluble ;
une résine « négative » est un type de résine photosensible pour laquelle la partie exposée à la lumière devient insoluble au révélateur et où la partie de résine photosensible non exposée reste soluble.

Absorption aux UV et à des longueurs d'onde plus courtes Les résines photosensibles sont habituellement utilisées à des longueurs

Nouvelles technologies de microstructuration de type UV-LIGA et fabrication de composants micromécaniques

This study presents two techniques of structuration of type UV-LIGA (Lithographie, Galvanisierung und Abformung) based on the use of two thick photoresists which are a dry film resist called Riston® from DuPont and the new SU-8 negative-working resist from IBM. The relating processes to the structuration of these photoresists and some applications are presented too. The minimal resolution of the Riston® films has been found to be 30 µm for lines and trenches, and 40 µm for isolated holes in a 50 µm-thick film. A technique for the structuration of multilevel superimposed cavities has been set up. The verticality of the sidewalls (85.5°deg. to 87.5°deg) has been measured on film thicknesses between 25 and 100 µm. The SU-8 process has been studied and is presented. Some optical and mechanical properties have been analysed. We have determined a coefficient of light attenuation of 5.18 [db/mm] at 365 nm, a coefficient of thermal expansion of 52 [ppm/°C] and a biaxial modulus of 5.18 GPa. The verticality of the walls depends on the exposure energy and has been found to be higher than 89°deg. Layers from 750 nm to 2 mm can be exposed in one time, which seems to be the state-of-the art for a UV-photoresist to our knowledge. A specific process for the electroforming in multi-level superimposed cavities has been developed. With an adequate dosage of a leveling agent (coumarin) in the electrolytic Watt bath of nickel, a change in the growth rate of the high and the low level of the mold has been demonstrated. This rate is harmonised to obtain a flat deposition on the top surface of the formed structure. The UV-LIGA techniques developed in this thesis have found applications in the field of the-micromechanics. A flexible gearwheel, whose teeth are bound to the center via three integrated spring, and a multilevel gear system are the main realizations obtained by electroforming. These two structures have been used in a mechanism with a special watch mechanism and in a microreducer based on an electrostatic rotary micromotor. We have experimented with success the plastic injection of a gear system having 1.4 mm in height and 3 mm in diameter. Its mold has been electroformed on a master in SU-8. Theses microparts have demonstrated their functionality and have been mounted in commercialy-available-low-cost watches. All the process step of the LIGA technique have been established. The main advantages of this fabrication method are a better control of the tolerances and an improvement of the rugosity (against the wire electrodischarge machining technology). This technique is also cheaper and easier to start than X-LIGA.

EPFL1998

Mechanical characterization of a new high-aspect-ratio near UV-photoresist

Philippe Renaud

Characterization of the mechanical and thermal properties of the high aspect- ratio, negative, UV resist, SU-S has been carried out. This resist allows for a broad range of thicknesses to be obtained with a single spin process. Standard exposure with a UV aligner has produced outstanding aspect ratios, 15 for lines and trenches. This type of performance lends itself well to MEIMS applications, packaging, micromolds, spacers, etc. Because of the simplicity of use of the resist in addition to the large range of possible applications, the process dependent mechanical and thermal properties must be understood in order to completely exploit the potential of the resist.

1998

Microfabrication d'objets composites fonctionnels en 3D et à haut facteur de forme, par procédés UV-LIGA et microstéréolithographie

Sébastien Jiguet

The present thesis deals with new composite photoresists for the UV-LIGA and microstereolithography microfabrication processes. The aim is to build functional 3D objects, with high aspect ratio. Two projects have been investigated in parallel for each microfabrication process. Their similitude is the use of dry or colloidal particles to prepare photosensitive formulations. The first project is focused on the well-known negative tone photoresist SU-8. This epoxy resin is used for the UV-LIGA processes, because of its high aspect ratio. As a thick photoresist, the main applications of the SU-8 are for moulding or for making inert structures (supports). However, the SU-8 structures show some cracks and unstickings of the substrate, due to the internal stress of the epoxy resin, which is the main disadvantage of the SU-8 photoresist. In order to avoid or to decrease the cracks, silica particles have been dispersed into the photosensitive matrice. The new composite photoresist is photosensitive to UV irradiations, and allows the fabrication of composite structures, which show a better adhesion on quartz, and silicon substrates, and a better sonication resistance. The SU-8 photoresist is also used for packaging applications as a non functional material, because of its electrical isolation properties. The idea to enhance its electrical conductivity comes from its high aspect ratio and the aim to microfabricate, directly, electrical structures without a moulding step. Silver particles have been used to make a photosensitive composite material, which can be applied to the UV-LIGA process. The obtained structures are electrically conductive, even at a low percolation threshold (6%vol.), and their thicknesses range up to 20 µm. It has been shown that electrodes and screens for absorbing electromagnetic waves are possible. The second project is focused on the microfabrication of 3D complex objects by microstereolithography. These objects are usually in polymer and to widen their applications to the biomedical world, alumina particles have been added to the photoresist, a photosensitive acrylate resin. Ceramic composite objects with complex form have been built by the integral microstereolithography, and their resolution is similar to the one of polymer objects. In order to obtain ceramic objects, photosensitive composite formulations need to be highly loaded in alumina powder. That induces rheological problems, such a higher viscosity, which have been overcome by modyfying the microstereolithography process. After a thermal treatment, the ceramic composite objects, highly loaded are transformed into ceramic objects without any deformations, and cracks.

EPFL2004

Nouvelles technologies de microstructuration de type UV-LIGA et fabrication de composants micromécaniques

EPFL1998

Microfabrication d'objets composites fonctionnels en 3D et à haut facteur de forme, par procédés UV-LIGA et microstéréolithographie

Sébastien Jiguet

EPFL2004