Nanomanufacturing of radial grating patterns by nanoimprint with a silicon mould for rotational angle measurement of micro gears

Micro gear is one of interesting micro machine elements for micro mechanisms in the next generation. In order to measure the rotational motions of meshing micro gears, a grating disk of a micro rotary encoder should be developed. For measurement of rotational accuracy of micro gears, it is necessary to utilise a pair of micro rotary encoders whose diameters are smaller than the reference diameter of micro gears to be measured to avoid the interference between the encoder and the rotational shaft. The focus of this article is to develop and manufacture radial grating patterns for such grating disks of micro rotary encoders. The designed grating disk has a diameter less than 1 mm and the number of gratings is up to 10,000, whose inner half pitch is corresponding to about 50 nm. It was manufactured with nanoimprint technique with a silicon master mould which is developed by EB writer and lithography technique. The radial grating patterns were successfully achieved homogeneously. The accuracy of the pitch and the line width are investigated and height of line and space is measured by AFM. It is found that it is possible to realise grating disks of a micro rotary encoder.