<title>Study on high-accuracy displacement interferometer for lithography application</title>

Abstract

A measurement interferometer available for wafer stage metrology of lithography has been investigated by means of resolution-extending of optical subdivision based on commercial interferometers. Factors that determine the accuracy, linearity and repeatability of nanometer-scale measurements of displacements exceeding hundreds of millimeters and oftarget velocities exceeding hundreds ofmillimeters per second are also discussed.

Mechanical system and dynamic control in photolithography for nanoscale fabrication: A critical review

“…One is an external beam reflected by a stage mirror, and another one is an internally beam reflected by a mirror inside the interferometer 44,45 . As shown in Figure 16A, these two reflected beams will produce interference fringes composed of bright and dark bands 46 . The optical path change of the external beam can be calculated by counting the number of fringes.…”

“…Schematic of (A) a basic interferometer equipment and (B) a new designed equipment with double resolution‐extending of optical subdivision. Adapted with permission 46 . Copyright 2021, The Authors, published by SPIE…”

“…44,45 As shown in Figure 16A, these two reflected beams will produce interference fringes composed of bright and dark bands. 46 The optical path change of the external beam can be calculated by counting the number of fringes. To further enhance the resolution, a new design was proposed based on the traditional laser interferometer.…”

Identification and analysis of ghost reflection in the interferometers based on ZEMAX by optimization algorithms

“…Using different interference signal processing models, the interferometer can be categorized as either homodyne or heterodyne interferometer; according to the reflection of optical components that use mirrors or diffraction grating, it may also be divided into laser interferometer or grating interferometer. [1][2][3][4][5] The principle of the interferometer is that the Doppler effect produced by the displacement of the object to be measured is brought into the interference signal through the interfering beams, which go through a specific structure lens group. The phase shift of the interference signal can be obtained through a certain phase demodulation calculation, and the measurement results of the object displacement can be calculated based on the displacement calculation model.…”

“…Using different interference signal processing models, the interferometer can be categorized as either homodyne or heterodyne interferometer; according to the reflection of optical components that use mirrors or diffraction grating, it may also be divided into laser interferometer or grating interferometer 1 – 5 …”