Bifocal oblique incidence interference microscopic device for detecting extreme ultraviolet photolithographic mask defect

Abstract

The invention discloses a bifocal oblique incidence interference microscopic device for detecting an extreme ultraviolet photolithographic mask defect. The bifocal oblique incidence interference microscopic device comprises a 13.5nm extreme ultraviolet light source, a vacuum chamber, a vacuum sucking pump, an air flotation optical vibration isolation platform, an extreme ultraviolet charge coupled device (CCD), a five-dimensional mask adjusting and scanning workbench, a five-dimensional mask adjusting and scanning workbench controller and a bifocal wave zone plate oblique incidence interference microscopic optical component. The bifocal oblique incidence interference microscopic device can synchronously detect defects of vibration amplitude and bit phase extreme ultraviolet masks and has high vibration resistance and high precision; and the system cost is low.

Description

technical field [0001] The invention belongs to the field of extreme ultraviolet interference detection, in particular to a double-focal oblique-incidence interference microscopy device for defect detection of extreme ultraviolet lithography masks. Background technique [0002] Photolithography is to transfer the pattern on the mask plate to the photoresist coated on the surface of the silicon wafer by exposure method, and then transfer the pattern to the silicon wafer by developing, etching and other processes. Extreme ultraviolet lithography is a next-generation lithography technology that uses extreme ultraviolet light (EUV, 13.5nm) as the exposure wavelength and is oriented to the 22nm node, or even the 15nm node. Since any substance has absorption characteristics for EUV (13.5nm), a reflective reticle must be used in the exposure process, otherwise the reticle will absorb most of the EUV, resulting in insufficient exposure of the photoresist. Typical EUV reflective mas...

AI Technical Summary

Problems solved by technology

The main problem of this solution is that only the structural lines of the wider defects buried under the multilayer film can be detected, while the narrower lines are imaged, and the resulting image is larger than the width of the actual defect lines

In the article "Microscopy of extreme ultraviolet lithography masks with 13.2nm tabletop laser illumination" (OPTICS LETTERS,34(3):271-273,2009), F.Brizuela et al. proposed a transmission-type zone plate microscopic amplification scheme. The system uses a light source with a wavelength of 13.2nm, and adopts a hollowed-out zone plate concentrating illumination mask. The converging light is incident at an incident angle of 6°, and the light beam reflected from the mask passes through an off-axis zone plate (0.0625NA) to illuminate the image. Projected directly into the extreme ultraviolet CCD, the magnification is 660 times. The disadvantage of this system is that the energy utilization rate of the transmission zone plate is low, and it is still a traditional imaging method that is not sensitive to phase defects.

Tetsuo Harada et al proposed a mask for coherent scattering imaging in "Mask observation results using a coherent extreme ultraviolet scattering microscope at NewSUBARU" (Journal of Vacuum Science & Technology B, 27(6): 3203-3207, 2009) Defect detection system, which adopts the diffraction conduction theory of mirrorless imaging. By recording the pattern of scattered and diffracted beams, the far-field pattern can be used to reconstruct the amplitude and phase information of the electric field intensity and restore the surface morphology of the mask. This system eliminates all Reflectors reduce system cost, but this solution has complex algorithms and unreliable defect information

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