Method for measuring clearance in proximity nanometer lithography

Abstract

The invention discloses a method for measuring clearance in proximity nanometer lithography and mainly aims at the controlling of the clearance of a masking silicon wafer in nanometer manufacturing technology, such as nano-imprint, wave zone plate array imaging and the like. The basic process of the method can be simply explained in the picture 1 that: incident plane waves pass through a silicon wafer gratings and a mask grating and diffract for multiple times, wherein the two periods of the gratings are approximate and the two gratings are overlapped with a certain gap; two beams of lateral diffracted light from the two gratings interfere with each other and are superposed, and form Moire interference fringes of which the period is amplified relative to the conventional gratings on the surfaces of the silicon wafer grating; and the fringes are imaged on a CCD image detector through an objective lens with certain multiplying power. The change of the gap between the two gratings causes the change of optical path difference of the two beams and then causes the change of the movement or phases of the interference fringes so that the aim of measuring the gap is fulfilled; the more approximate the period is, the higher the sensitivity of the measurement is; and, at the same time, because the periods of the two gratings are approximate, the included angle between the lateral diffracted light is very small, the frequency of the interference fringes is very low (namely, the period is long), and the requirement on the numerical aperture of the objective lens is low. With the development of microfabrication technology, the machining accuracy of the grafting is higher and the method has great significance for gap measurement in proximity nanometer lithography and the related field.

Description

technical field [0001] The invention relates to a gap measurement method used in proximity nanolithography, and belongs to the related fields of micro-nano processing and high-precision measurement. Background technique [0002] Optical lithography has always been the basis of large-scale integrated circuit industrial manufacturing technology. With the development of highly integrated circuits and related devices, IC feature sizes are getting smaller and smaller, and high-resolution lithography technology has been greatly developed. In addition, the rapid development of nanotechnology and the continuous reduction of the feature size of nanodevices have also promoted the development of nanolithography technology, such as nanoimprinting and zone plate array imaging lithography. Correspondingly, with the improvement of resolution and the adoption of large-size silicon wafers, the gap control and measurement of mask silicon wafers will become a severe challenge for proximity lit...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved in the present invention is: to overcome the weakness in principle of the existing gap measurement method, further improve the gap measurement accuracy, and at the same time overcome the influence of photoresist and other silicon wafer processes on gap measurement, and provide a proximity nanometer In-etch gap measurement method to accommodate increasing resolution of nanolithography

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