Wavelength turning phase-shift point-diffraction interference measuring device and method thereof

Abstract

A wavelength turning phase-shift point-diffraction interference measuring device and a method thereof belong to the field of surface profile measuring devices and methods for optical elements based on phase-shift point-diffraction interferometers. The device comprises a tunable laser light source module, a point-diffraction interference module and a control system; the tunable laser light source module comprises a tunable laser, a first spectroscope, a second spectroscope, a wavemeter and a dynamometer; the point-diffraction interference module comprises a beam adjusting mirror assembly, a needle hole plate, an interferometer imaging mirror assembly and a CCD (Charge Coupled Device) camera; the control system comprises a tunable laser control module, a CCD camera collection control module and a main-control computer. The device can realize phase shift and accomplish phase-shift point-diffraction interference measurement by using a wavelength-tunable laser, does not adopt a piezoceramic phase shifter PZT (Piezoe-lectric Transducer) or utilize a piezoceramic moving pyramid reflecting mirror or other mechanical moving components for phase shift, overcomes the technical problems that a mechanical phase shift device is high in manufacturing difficulty and high in cost, and stress deformation errors is caused by dead weight of a mechanical phase-shift device.

Description

technical field [0001] The invention belongs to the field of optical element surface shape detection devices and methods based on phase-shift point diffraction interferometers, and in particular relates to a wavelength-tuned phase-shift point diffraction interferometry device and a method thereof. Background technique [0002] In order to achieve the required resolution and critical size of the projection lithography objective lens, the wave aberration of the optical system needs to reach the diffraction limit. The extreme ultraviolet lithography works in the extreme ultraviolet band with a wavelength of 13-14nm, which requires the wave aberration of the optical system It should be less than 1nmRMS, and the surface deviation of a single reflector should be 0.25nmRMS. To achieve such high-precision optical processing, high-precision optical detection technology must first be realized. Conventional interferometric detection technologies such as Fizeau interferometer and Tiema...

AI Technical Summary

Problems solved by technology

[0006] In order to solve the existing method of phase shift along the optical axis of the inspected mirror when the existing point diffraction interferometer using piezoelectric ceramic phase shifter (PZT) to realize phase shift interferometry measures the spherical or aspheric inspected mirror It will cause the phase shift between the edge of the inspected mirror and its center to be different in the normal direction, and when the surface size of the inspected optical element is large, it is difficult to manufacture the heavy-duty phase shifter, and it will be affected by the self-weight stress during the phase shift. causing errors in the measurement results

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