Photoresist technique

The microstructure was realized by a dry-film photoresist technique and based on established techniques from printed circuit board technology [142], Dry resists are available as thin films, e.g. of thickness 50 or 100 pm. The resist films are encased in other polymer materials which are later removed. The resist films can be deposited on various base materials such as silicon or polymers giving mechanical stability. Lamination is carried out with a roller laminator. Then, exposure is made and spray development without any solvents follows. The process steps can be repeated at multi-laminated structures. Closed structures can be made in this way. 

This special volume Polymers and Light deals with very recent developments of photon interactions with polymers, in areas outside the scope of the familiar photoresist technique and optical lithography. Recent developments in microlithography still apply the same processing steps (irradiation of the photoresist through a mask followed by a subsequent wet chemical development step), but with new photoresist materials, and new irradiation sources, i.e. excimer lasers that emit in the UV, e.g. at 157, 193, and 248 nm. Excimer lasers are now the main photon sources for microlithography in many research laboratories and in industry. 

Mandrels for perforated products and gauzes must be made so that the surface has the necessary arrangement of conducting and non-conducting zones. This is usually achieved by photoresist techniques. The prospective mandrel is covered with a thin layer of a liquid which may be hardened by a photochemical reaction and then exposed to the appropriate pattern of light of the required wavelength. 

The photochemistry of aromatic azides reeeives eontinuous attention because of their useful applications in heterocyclic syntheses, photoresist techniques and photoaflfinity labeling [1,2,3,4,5]. The key reaction in all cases is the photoinduced N-N2 bond dissociation with formation of highly reactive intermediate, nitrene. The main quantitative parameter of this reaction is the photodissociation quantum yield (cp), which determines the azide photoactivity. 

Screen printing makes use of a screen, a steel or itylon cloth, on which a motive is printed by the photoresist technique. Some ink is deposited. The ink is transferred on the substrate through the sieve mesh, at least on the parts not printed on the cloth, by passing a squeegee, which induces a high shear stress (see Figure 11.37). 

A Pt catalyst was applied by dry and wet techniques. By means of sputtering using a mask process protecting parts of the microstructure, the micro channel bottom was coated selectively. In addition, an y-alumina layer was applied by the sol-gel technique. Initially, the whole micro structure was covered by such a layer. Then, photoresist was applied and patterned so that only the channel part remained covered. After removal of the exposed photoresist and unprotected y-alumina, only the channel bottom was coated with y-alumina. 

This technique is used to transfer a computer-generated pattern onto a substrate. Here, a film of photoresist is spin-coated onto the substrate and exposed to UV light through a photolithographic mask the light exposure transfers the desired pattern to the photoresist. Depending on whether the resist material is positive or negative , the photoresist... 

Spectroscopic ellipsometry is a non-destructive, interface sensitive, in situ technique for interface characterization. Time resolved ellipsometric spectroscopy was used to determine the mechanism of electrochemical deposition of photoresists on copper electrodes under potentiostatic, anodic conditions. Nucleation of photoresist deposition occurs randomly. During the early stages of nucleation the semi-spherical particles are separated by about 100 A. The deposits tend to grow like "pillars" up to 50 A. Further growth of the "pillars" lead to coalescence of the photopolymer deposits. 

Conformance of dry film to the copper surface is a concern, particularly with stiff films. One way to improve conformance is to coat a low viscosity photopolymer liquid direcdy on the substrate. Several coating techniques are available to deposit photoresists directly onto metal substrates. These techniques involve dissolving/dispersing the ingredients in a solvent, coating the solution on the substrate and removing the solvent. Some of the material is lost during the... 

Positive imaging techniques, 19 201 Positive ion spectroscopy, 24 107 Positive photochromism, 6 588 Positive photoresists, 20 280-281 Positive photosensitive polyimides,... 

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