E-beam lithography at DTU Nanolab

dtu nanolab is the national center for nanofabrication and characterization in denmark and is located at the technical university of denmark dtu nanolab operates and maintains a large suite of advanced processing equipment within a 350 square meter open access pay-per-use cleanup facility the dtu nanolab cleaning facility is both used for academic research and small-scale production by our industry partners in this video we'll briefly illustrate the workflow of electron beam lithography and the capability of our dl9500fs system users of the dtu now lab cleanroom facility can be trained by our staff to run this kind of process themselves for their own research or production flows the process starts by spin coding an electron sensitive resist onto the substrate this is done on the fully automatic cassette 2-cassette coding system capable of running both 2 4 and 6 inch wafers user operation is very simple as one simply selects resist and final thickness from a list of predefined recipes in this example we use a csr 6200 resist and aim for resist thickness of 250 nanometers a precise amount of resist is dispensed onto the substrate and the substrate is spun at a specific rotational speed to achieve the desired thickness the rapidly changing colors indicate the resist layer thinning down to its final thickness the thickness is controlled by spin speed and resist viscosity and at the end of the process excess solvent is evaporated by baking the substrate on a hot plate and the wafer is ready for output and pickup by the user as a process control the thickness can be verified by ellipsometry the ellipsometer has a list of predefined recipes to choose from these will determine the wavelength interval and incident angles of the measurement and also what material model to fit the data to at the end of the measurement and data fitting the resist thickness is displayed for comparison to the target thickness in order to expose the substrate it must be placed in a dedicated cassette a suitable cassette in this case a six inch wafer cassette is unloaded from the autostagger the autostalker can hold up to 10 cassettes and is immensely useful for queuing up exposure jobs for instance for overnight exposures on substrates from different cassettes the chosen cassette is carefully removed from the loading bay and placed onto the preparation table cassettes are naturally available to suit various sample sizes from small chips to 8 inch wafers the wafer to be exposed is carefully placed and locked into position by the cover ring the sample is visually inspected and loaded to the auto stalker system by nanolab staff prior to exposure the job has to be set up and defined on the gl 9500 system in many cases this will involve some level of proximity or correction of the design pattern to account for the additional dose generated by backscattered electrons beamer will analyze the geometry and calculate a dose modulation that will ensure a uniform exposure dose for both densely packed and sparse areas of the design all relevant exposure and alignment parameters are written into the job definition and shot definition files ahead of exposure once everything is ready the substrate is moved into the exposure chamber and the calibration routine is performed this ensures that the shape and focus of the electron beam is optimized for best result once the calibration and beam optimization routine is completed the pattern writing will commence after exposure the cassette is unloaded and the substrate can be developed in one of our dedicated lithography rooms substrates can either be developed by hand in beakers or on an automated development tool the automated development tool is very simple to use the wafer is placed on a spinner stage and held by vacuum the user then selects the developing agent to use and development cycle time from a menu at the end of the development cycle the wafer is cleaned and dried for the user to pick up the substrate at this stage the pattern is visible and the substrate can be viewed under a microscope and as initial inspection most patterns defined by ebl will naturally have geometry that is not sufficiently visible in optical microscopes and hence one often have to use a scanning electron microscope to characterize the result of the process the substrate is placed on a suitable holder and gated through the load lock into the scanning electron microscope vacuum chamber where it can be imaged and analyzed the gel 9500 system at this you nanolab is equipped with a 100 kilo electron volt electron source and a 100 megahertz sub deflector scanner allowing a minimum drill time of 10 nanoseconds minimum beam size is about 4 nanometers and minimum shot pitch is 0.25 nanometers the system is capable of producing features down to about 10 nanometers if you wish to learn more about the tool our services or our cleanroom in general visit us at nanolab dtudk where you can also enjoy a virtual tour of our facility you

Channel: DTU Nanolab

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Id: 2bFUO201DS4

Length: 5min 53sec (353 seconds)

Published: Fri Sep 24 2021