| CPC G03F 7/0035 (2013.01) [G03F 7/0005 (2013.01); G03F 7/30 (2013.01); G03F 7/70008 (2013.01); G03F 7/70291 (2013.01); G03F 7/70383 (2013.01); G03F 7/70416 (2013.01); G03F 7/705 (2013.01); G03F 7/70508 (2013.01); G03F 7/70558 (2013.01); G03F 9/7003 (2013.01)] | 19 Claims |
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1. A lithographic process for embossing three-dimensional microstructures, which have oversized structure heights, in a photostructurable carrier material using an exposure device, wherein, depending on exposure parameters of the exposure device in conjunction with exposure properties of the photostructurable carrier material, a maximum nominal penetration depth of an exposure and thus a resulting photostructuring of the carrier material are produced and an oversized structure height has a height which exceeds the value of the maximum nominal penetration depth, wherein the process comprises the following process steps:
—a— applying a photostructurable carrier material (1) to a substrate carrier (2), wherein the applied carrier material (1) has a layer height (H.1) and a flat surface (O.1) on an upper side opposite the substrate carrier (2), and wherein the exposure properties of the carrier material (1) can be changed by exposure to electromagnetic radiation;
—b— using information data as an input variable, wherein this information data contains information on the maximum nominal penetration depth of the selected photostructurable carrier material (1) and on a geometric shape of a three-dimensional microstructure to be embossed having an oversized structure height;
—c— performing a computer-aided modelling of a virtual three-dimensional structural model (10) of the microstructure to be embossed as a function of the information data according to step —b—, wherein the structural model (10) comprises topography data (T.10) of the microstructure to be moulded and a total height (H.10) of the structural model (10) to the microstructure to be moulded is determined on the basis of the topography data (T.10), which total height (H.10) is greater than the maximum nominal penetration depth of the electromagnetic radiation during exposure into the carrier material (1) and less than the applied layer height (H.1) of the carrier material (1);
—d— performing a computer-aided subdivision of the total height (H.10) of the three-dimensional structural model (10) into a number N (N≥2 to n) of sequentially stacked height layers, wherein each of the N (N≥2 to n) height layers corresponds to a single substructure (11, 12, 13) of the structural model (10), and wherein each one of the N (N≥2 to n) substructures (11, 12, 13) has a subheight (H.11, H.12, H.13), wherein the number N is an integer which is greater than or equal to the number 2, and wherein the number N (N≥2 to n) is selected such that each of the N (N≥2 to n) subheights (H.11, H.12, H.13) is less than or equal to a possible nominal penetration depth of the electromagnetic radiation deliverable by the exposure device when exposed into the carrier material (1), wherein the sum of the N (N≥2 to n) subheights (H.11, H.12, H.13) of the individual substructures (11, 12, 13) corresponds to the total height (H.10) of the structural model (10);
—e— calculating a virtual photomask (M.11, M.12, M.13) for each individual one of the N (N≥2 to n) substructures (11, 12, 13) of the structural model (10), wherein for each of the N (N≥2 to n) photomasks (M.11, M.12, M.13) respective topography data (T.11, T.12, T.13) of each individual substructure (11, 12, 13) is converted into corresponding values of an individual exposure dose, wherein an exposure dose calculated for a specific location (X, Y, Z) of a substructure (11, 12, 13) correlates with an individual height position (Z) of the same location (X, Y, Z) within the corresponding substructure (11, 12, 13);
—f— positioning a first virtual photomask (M.11), which corresponds to a first substructure (11) in the lowest height layer of the structural model (10), as well as alignment markings (20) on the surface (O.1) of the carrier material (1);
—g— performing an aligned exposure of the carrier material (1) using the alignment markings (20) arranged on the surface (O.1), wherein a structuring (S.11) of the first substructure (11) is written into the carrier material (1) starting from the surface (O.1) of the carrier material (1) by spatially resolved (X, Y, Z) exposure in accordance with the individual exposure dose defined in the first virtual photomask (M.11);
—h— performing a wet-chemical development (E) of the exposed portion of the carrier material (1) specified by the first virtual photomask (M.11), wherein surfaces of the structuring (S.11) of the first substructure (11) are smoothed as a function of a development rate of the carrier material (1) and of the calculated exposure dose until the surfaces of the structuring (S.11) are optically smooth (G) after exposure and development (E);
—i— obtaining a first intermediate product (21) of a partially structured carrier material, wherein the first intermediate product (21) contains the structuring (S.11) of the first substructure (11);
—j— positioning a further Nth (N≥2 to n) virtual photomask (M.12, M.13), wherein the Nth (N≥2 to n) virtual photomask (M.12, M.13) corresponds to the Nth (N≥2 to n) substructure (12, 13) in the next-higher Nth (N≥2 to n) height layer of the structural model (10) sequentially following the preceding (N−1) height layer, within the already structured structuring (S.11) of the preceding (N−1) substructure (11) of the preceding (N−1) intermediate product (21);
—k— performing an aligned further exposure of the preceding (N−1) intermediate product (21, 22, 23) on the basis of the alignment markings (20) arranged on the surface (O.1), wherein, starting from the already structured structuring (S.11) of the preceding (N−1) substructure (11), a structuring (S.12, S.13) of the Nth (N≥2 to n) substructure (12, 13) is written into the preceding (N−1) intermediate product (21) of a partially structured carrier material by spatially resolved (X, Y, Z) exposure in accordance with the individual exposure dose defined in the Nth (N≥2 to n) virtual photomask (M.12, M.13), wherein the structuring (S.12, S.13) of the Nth (N≥2 to n) substructure (12, 13) within the carrier material (1) is in each case deeper than the structuring (S.11) of the respective preceding (N−1) substructure (11);
—l— performing a wet-chemical development of the exposed portion of the carrier material (1) specified by the Nth (N≥2 to n) virtual photomask (M.12, M.13), wherein surfaces of the structuring (S.12, S.13) of the Nth (N≥2 to n) substructure (12, 13) are smoothed as a function of a development rate of the carrier material (1) and of the calculated exposure dose until the surfaces of the structuring (S.11) are optically smooth (G) after exposure and development (E);
—m— repeating a sequence of steps —j— (positioning of a further virtual photomask), —k— (further exposure) and —l— (further development) until all N (N≥2 to n) virtual photomasks (M.11, M.12, M.13) have been-structured layer by layer applied for exposure of the carrier material;
—n— obtaining a finished structured carrier material (30), wherein the finished structured carrier material (30) contains a structuring corresponding to the entire structural model (S.10) and its total height (H.10).
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