UV-NIL with the FC150
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The SET FC150 primary function is to bond devices. But this flexible and open system includes all features required to perform Micro/Nano Replication by Hot Embossing Lithography, Soft Lithography or UV Nanoimprinting Lithography techniques. Hot Embossing Lithography has been successfully demonstrated as early as 1998 by VTT using a standard FC150 with Minor Software modification. |
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For the UV-NIL method which is based on a molding and curing of a photosensitive material, in-situ material dispense and subsequent UV curing are required. Depending on application, the photosensitive material can be dispensed before or after the alignment of the substrate with respect to the Template. The template which is engraved with 3D nano structures is pressed into the liquid resist to define the desired pattern. While the embossing head maintains a controlled pressure and secures the template to Substrate parallelism, UV curing is performed. The template is then lifted up and separated from the resist. |
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To perform that function on the SET FC150, the UV-NIL head and the accurate drop dispenser developed for the Nanoimprinting Stepper NPS300 have been adapted and implemented. The UV-NIL head includes an optical polished Template Support, Ultra Violet Light Generator and Neutal Gas Injection Nozzles. The exposure area is 40mm x 40mm with a mean power density of 120 mW/cm² and a uniformity of better than +8%/-13% on the entire area and better than +3% / -7% excluding the peripheral edge. |
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The UV source is arranged as a matrix made by 4 lines and 4 rows (16 modules), each module composed by 50 CMS UV LEDs (800 elementary LEDs in total). This configuration permits to achieve a good uniformity of the UV power density. The UV radiation is almost monochromatic (FWHM of 30 nm). Three different nominal wavelengths are available: 365 nm, 375 nm and 395 nm. As there is no other radiation in the visible range of the spectrum and no infrared, there is much less heat induced in the resin. Using LEDs presents several advantages. Lifetime of UV LEDs is much longer (typically several tens of thousands of hours) than the one of more classic UV sources such as Hg vapour lamps (typically several thousands of hours). There is no need for shutter (no vibration) since LEDs are ON only during the curing time. This is saving lifetime and reducing the heat generation. It is possible to pulse or strobe and / or adjust the emitted UV intensity. Handling LEDs is safe as there is no hazardous substance. Injecting Neutral Gas during imprinting contributes to reducing the Residual Layer Thickness and favors the filling of the template cavities A precise dispenser able to dispense tiny droplets of resist has been integrated. It enables the achievement of very thin residual layer. The size of the droplets varies with the viscosity and density of the resist,. F for example, droplets of 16 µg corresponds to a volume of 13 nl and a diameter of 300 µm; with another type of resist, droplets of 6 µg can be obtained corresponding to a volume of 5 nl and a diameter of 200 µm. The dispense pattern is programmable and can be optimized to match the template structures lay out. The advantages are reduction of the Imprinting time and increase of the residual layer thickness uniformity. |
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