Abstract
A multi-repeated photolithography method for manufacturing an incremental linear scale using projection lithography is presented. The method is based on the average homogenization effect that periodically superposes the light intensity of different locations of pitches in the mask to make a consistent energy distribution at a specific wavelength, from which the accuracy of a linear scale can be improved precisely using the average pitch with different step distances. The method’s theoretical error is within 0.01 µm for a periodic mask with a 2-µm sine-wave error. The intensity error models in the focal plane include the rectangular grating error on the mask, static positioning error, and lithography lens focal plane alignment error, which affect pitch uniformity less than in the common linear scale projection lithography splicing process. It was analyzed and confirmed that increasing the repeat exposure number of a single stripe could improve accuracy, as could adjusting the exposure spacing to achieve a set proportion of black and white stripes. According to the experimental results, the effectiveness of the multi-repeated photolithography method is confirmed to easily realize a pitch accuracy of 43 nm in any 10 locations of 1 m, and the whole length accuracy of the linear scale is less than 1 µm/m.
Highlights
Linear scale is an indispensable component of linear displacement sensors and is defined as the grating structure that is printed on a metal or glass substrate material by photolithography or mechanical scribing
Figure shows an image pitch linear scale, which is is fabricated bythe the multi-repeated projection lithography based on theofmask with measurement results of pitch are chosen from 10by consecutive adjacent projection pitches of accuracy that is scanned from accuracy, the linear which scale, which is fabricated the multi-repeated errors, and the minimum error is 41 nm
(a).errors by the(a) plane mask projection lithography lens; (b) An image of pitch projected from the mask with byscale, the projection lens; An image of pitch accuracy accuracy scanned from theerrors linear which is lithography fabricated by the(b) multi-repeated projection scanned from the linear scale, which is fabricated by the multi-repeated projection lithography based lithography based on the mask of (a)
Summary
Linear scale is an indispensable component of linear displacement sensors and is defined as the grating structure that is printed on a metal or glass substrate material by photolithography or mechanical scribing. In linear scale projection lithography, in addition to the above problems, the main factors that invariable, the quality of the grating lines will only be restricted by focusing accuracy and affectphotoresist the accuracy of lithography the of static and dynamic positioning accuracy, parallelism resolution, and theinclude inaccuracy the grating lines include alignment errors,the rotational of theand focal plane and photoresist plane on the scale, and the uniformity of light intensity distribution. The influences of verified that there is a proportional relationship between the grating strip repetitions and lithography internal pitch errors in the mask on the lithography accuracy are simulated and analyzed. The defocus errors caused by a skew focus plane or tilt photoresist plane on the scale are reduced and homogenized
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