Development of a vacuum-compatible hydrodynamic spindle using an ionic liquid as a lubricant

• Simple and compact hydrodynamic spindle using ionic liquid as lubricant was proposed.
• The proposed spindle using ionic liquid can be used in vacuum.
• The outgassed products from the spindle were very low in vacuum during rotation.
• The spindle has high rotational accuracy and can be used to EB mastering equipment.

The importance of beam machining and extreme ultraviolet lithography technologies in the area of precise and fine machining used for high-density optical discs, integrated circuits and patterned media of hard disc drives (HDDs) is rapidly increasing.In this paper, a very simple vacuum-compatible rotary spindle is proposed that uses an ionic liquid as a lubricant with a very low vapor pressure. The usefulness of the proposed spindle lubricated by an ionic liquid was experimentally confirmed by measuring the partial pressures of outgassed products during rotation of the spindle in the vacuum chamber, measuring the accuracy of movement of the rotary table and machining circular grooves by an electron beam in a scanning electron microscope (SEM). It was found that the proposed spindle could be used in vacuum, and the partial pressures of outgassed products were almost the same as those of a clean, empty vacuum chamber. In addition, it was confirmed that by using the proposed spindle, circular grooves with diameters of 200 and 400 μm, 450 nm width and 40 nm depth could be machined on a photoresist surface coated on a silicon wafer in vacuum of an SEM.

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