Excimer laser structuring

G.Danev, E. Spassova, J. Assa, J. Dilemann, D. Schumacher (2000) Excimer laser structuring of bulk polyimide material. Applied Surface Science. 168 162-165. 

We are gratefiil to Dr J Arnold for fabricating the excimer laser structures and H Leist for testing the systems... 

Dopant-induced ablation is of great significance because it provides the opportunity to process materials that do not exhibit desirable excimer laser structuring characteristics, i.e., micro-feature formation, but offer other outstanding properties, e.g., low e,. Like the matrix polymers of the initial doping investigations, neat PTFE is transparent to conventional excimer laser emissions. FIFE, whose chemical repeat unit is... 

Other topics recently studied by XPS include the effects of thermal treatment on the morphology and adhesion of the interface between Au and the polymer trimethylcy-clohexane-polycarbonate [2.72] the composition of the surfaces and interfaces of plasma-modified Cu-PTFE and Au-PTFE, and the surface structure and the improvement of adhesion [2.73] the influence of excimer laser irradiation of the polymer on the adhesion of metallic overlayers [2.74] and the behavior of the Co-rich binder phase of WC-Co hard metal and diamond deposition on it [2.75]. 

In addition to the thermal CVD reactions listed above, tungsten can be deposited by plasma CVD using Reaction(l)at350°C.[ ll P At this temperature, a metastable alpha structure (aW) is formed instead of the stable be.c. Tungsten is also deposited by an excimer laser by Reaction (1) at < 1 Torr to produce stripes on silicon substrate.P l... 

Further modification of the above nanostructures is useful for obtaining new functional materials. Thirdly, we apply the dopant-induced laser ablation technique to site-selectively doped thin diblock copolymer films with spheres (sea-island), cylinders (hole-network), and wormlike structures on the nanoscale [19, 20]. When the dye-doped component parts are ablated away by laser light, the films are modified selectively. Concerning the laser ablation of diblock copolymer films, Lengl et al. carried out the excimer laser ablation of diblock copolymer monolayer films, forming spherical micelles loaded with an Au salt to obtain metallic Au nanodots [21]. They used the laser ablation to remove the polymer matrix. In our experiment, however, the laser ablation is used to remove one component of block copolymers. Thereby, we can expect to obtain new functional materials with novel nanostmctures. 

Solubility of polymers in tetramethyl ammonium hydroxide aqueous solution was measured by dipping the wafer on which the polymer solution was spin-coated, for 1 min. at 25°C. The prebake was carried out at 90°C for 5min. Sensitivity of resists was measured after the exposure with CA 800(Cobilt) or KrF excimer laser(0.9mJ/cm2/1 pulse). The polymer structure was determined by iH-NMR, 13C-NMR(FX90Q apparatus,JEOL) and 2 Si-NMR. The molecular weight distribution was determined with a Toyo Soda Model 801 gel permeation chromatograph at 40°C. The four columns were connected in series, each packed with G-2000H8x3 and G-400H8(Toyo Soda polystylene gel), respectively. 

Aromatic polyimides are well known for their unusual array of favorable physical properties, including excellent thermal stability and excimer-laser processing characteristics. The polyimide structure possesses lower-energy transitions such as n —> n, n —> o, n —> n, and a — n (in order of increasing energy71). However, the w — n and o —> n transitions are forbidden by symmetry rules and related absorptions are significantly weaker than those for... 

During the last decade, there has been considerable interest in studying the interaction between ultraviolet radiation and polymers by the use of pulsed excimer laser (1-41. In fact, some attractive applications in microelectronics and surgery have been successfully implemented (5.), and further informations about the different mechanisms (photochemistry, thermal effect...) involved at the polymer surface have been invoked in order to elucidate their relative contributions. More recently, the attention has been focused on this type of polymer surface modifications to improve some surface properties like the adhesion in metallized polymer structures. 

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