title: Four-quadrant gratings moiré fringe alignment measurement in proximity lithography.
abstract: This paper aims to deal with a four-quadrant gratings alignment method benefiting from phase demodulation for proximity lithography, which combines the advantages of interferometry with image processing. Both the mask alignment mark and the wafer alignment mark consist of four sets of gratings, which bring the convenience and simplification of realization for coarse alignment and fine alignment. Four sets of moiré fringes created by superposing the mask alignment mark and the wafer alignment mark are highly sensitive to the misalignment between them. And the misalignment can be easily determined through demodulating the phase of moiré fringe without any external reference. Especially, the period and phase distribution of moiré fringes are unaffected by the gap between the mask and the wafer, not excepting the wavelength of alignment illumination. Disturbance from the illumination can also be negligible, which enhances the technological adaptability. The experimental results bear out the feasibility and rationality of our designed approach.
authors.affiliation: Institution of Optics & Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
authors.forename: Jiangping
authors.initials: J
authors.lastname: Zhu
authors.forename: Song
authors.initials: S
authors.lastname: Hu
authors.forename: Junsheng
authors.initials: J
authors.lastname: Yu
authors.forename: Shaolin
authors.initials: S
authors.lastname: Zhou
authors.forename: Yan
authors.initials: Y
authors.lastname: Tang
authors.forename: Min
authors.initials: M
authors.lastname: Zhong
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhao
authors.forename: Minyong
authors.initials: M
authors.lastname: Chen
authors.forename: Lanlan
authors.initials: L
authors.lastname: Li
authors.forename: Yu
authors.initials: Y
authors.lastname: He
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D008029:Lighting / Q000379:methods*; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods*