Commissariat A l'Energie Atomique ((CEA) Paris, FR) and Centre National De La Recherche ((CNRS) Paris, FR) detail an industrial scale nano-imprint lithography technique which has diverse advantages over known methods according to U.S. Patent 7,682,515.
Inventors Corinne Perret, Cecile Gourgon and Stephan Landis say the method enables the same resolutions to be obtained as electronic lithography much faster and at lower cost. In practice, the objective is to product nanostructures (structures on a submicron scale, typically from a few tens to a few hundreds of nanometers) over large areas. It may have particular applications in the production of high-density magnetic storage components, optical components based on photonic crystals, and biotechnologies.
Inventors Corinne Perret, Cecile Gourgon and Stephan Landis say the method enables the same resolutions to be obtained as electronic lithography much faster and at lower cost. In practice, the objective is to product nanostructures (structures on a submicron scale, typically from a few tens to a few hundreds of nanometers) over large areas. It may have particular applications in the production of high-density magnetic storage components, optical components based on photonic crystals, and biotechnologies.
The inventive method includes a preparation step during which the substrate is covered with a layer, a pressing step in which a mould including a pattern of recesses and protrusions is pressed into part of the thickness of the aforementioned layer, at least one etching step in which the layer is etched until parts of the surface of the substrate have been stripped, and a substrate etching step whereby the substrate is etched using an etching pattern which is defined from the mould pattern. The preparation step includes a sub-step consisting of the formation of a lower sub-layer of curable material, a step involving the curing of said layer and a sub-step including the formation of an outer sub-layer which is adjacent to the cured sub-layer. Moreover, during the pressing step, the above-mentioned protrusions in the mould penetrate the outer sub-layer until contact is reached with the cured sub-layer.
Nano-imprinting consists in pressing a mold into a polymer covering a substrate of silicon or another appropriate material. The mold is typically produced in silicon by standard lithography/etching techniques and is pressed into a layer of polymer heated to above its glass transition temperature so that it is deformable. After cooling and removal of the mold, the patterns of the mold are imprinted in negative form in the polymer.
To prevent potentially destructive contact between the mold and the substrate that supports the polymer, a thin residual layer of polymer is intentionally left at the bottom of the protruding patterns of the mold. The pressures applied to the mold are such that, if the mold and the substrate were to come into direct contact, the two wafers would be weakened and could break. To guarantee the presence of this residual layer, the initial polymer thickness is chosen so that, at the end of pressing, the polymer fills the recesses of the patterns of the mold.
To prevent potentially destructive contact between the mold and the substrate that supports the polymer, a thin residual layer of polymer is intentionally left at the bottom of the protruding patterns of the mold. The pressures applied to the mold are such that, if the mold and the substrate were to come into direct contact, the two wafers would be weakened and could break. To guarantee the presence of this residual layer, the initial polymer thickness is chosen so that, at the end of pressing, the polymer fills the recesses of the patterns of the mold.
The CEA and CNRS consists of a lithography method involving substrate pressing that can be implemented on an industrial scale with a moderate number of operations, which yields good accuracy of the lithographed and then pressed patterns, with moderate pressing pressures, times and temperatures.
The invention represents a simplification compared to known solutions, including lift-off techniques, since it provides accurate control over the depth of penetration of the mold all over the layer, which contributes to obtaining high accuracy of reproduction when etching the pattern of the mold.
Lithography has been compared in importance to the wheel and the printing press in its importance to modern society. It is the process by which computer chips and many electronic components are fabricated.
The invention represents a simplification compared to known solutions, including lift-off techniques, since it provides accurate control over the depth of penetration of the mold all over the layer, which contributes to obtaining high accuracy of reproduction when etching the pattern of the mold.
Lithography has been compared in importance to the wheel and the printing press in its importance to modern society. It is the process by which computer chips and many electronic components are fabricated.
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