PLASMONIC NANOLITHOGRAPHY MACHINE (PLM)
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Abstract
The Plasmonic Nanolithography Machine (PLM) is a prototype that adopts near field maskless plasmonic nanolithography to achieve 45 nm line widths at 45 nm half pitch. A plasmonic lens floating on a hydrodynamic air bearing rides on a disc with about a 35-mm radius writable substrate surface. A UV laser is used to excite surface plasmons in the lens, which, in turn, expose resist on the disk. The disc spins at nominally 1000 RPM and the lens traverses it in the radial direction. The machine linearly moves the lens across the disk. The traverse length is 42.4 mm, the alignment time is less than one minute, and the average traverse speed is 5 µm/s. The PLM's traverses the lens with a resolution of less than 5 nm and an angular error of less than 1 μrad.The PLM is composed of a base and carriage. Two Halbach linear array motors move the carriage in the radial direction. The advantage of using the Halbach linear array is that it provides smooth contactless linear motion that is directly proportional to the current applied without generating much heat.Vacuum preloaded air bearings are used to carry the carriage at a 5-micron flying height on diamond-turned surfaces located on the base. The air bearings have high angular stiffness, which makes them a good choice to reduce pitch and yaw errors. Eddy current dampers are used on the PLM to provide the necessary damping during the carriage motion. The main advantage of these dampers is that they provide a smooth linear damping that is directly proportional to the carriage speed. At 5 μm/s carriage speed, the dampers provide about 4.28 mN damping force.The PLM has many piezoelectric actuators that align and adjust the distance between the plasmonic lens and a pre-focusing lens that focuses the UV laser on the plasmonic lens. Also, capacitance gauges are used on the tailor-made pre-focusing flexure to determine the pre-focusing position.The PLM has built-in interferometers. Their functions are to monitor the vibration of the plasmonic lens during the writing process so its position may be controlled. The carriage motion is constrained by two Hall-effect limit switches that provide a contactless means to stop the writing process when necessary. Also, there are pressure limit switches to monitor the pressure of the air bearings' air supply, and when triggered they stop the process and give an alarm to the user.