Device and method for detecting angle change of reflected light beam and film thickness measuring device

Abstract

The invention provides a device and method for detecting the angle change of a reflected light beam and a film thickness measuring device. The device comprises a detection light source, at least one optical isolator and a light beam adjusting module; the detection light source is used for generating an incident light beam in a polarization state; the at least one optical isolator is used for receiving the incident light beam to form a polarized incident light beam, the polarized incident light beam is transmitted to the light beam adjusting module, and the polarized incident light beam is parallel to a first incident light beam; the at least one optical isolator is also used for receiving a reflected light beam adjusted by the light beam adjusting module to form a polarization reflected light beam and emitting the polarization reflected light beam at a relatively separated angle with the transmission direction of the incident light beam; the light beam adjusting module is used for adjusting the field intensity distribution of the polarized incident light beam and enabling the polarized incident light beam to enter the surface of a to-be-measured body; and the light beam adjusting module is also used for receiving a collimated reflected light beam in the view field range of the light beam adjusting module and further adjusting the field intensity distribution of the reflected light beam to enable the reflected light beam to enter the optical isolator. According to the device and method for detecting the angle change of the reflected light beam and the film thickness measuring device of the invention, the incident light beam and the emergent light beam of detection light are separated by using a birefringent crystal and a Faraday rotation sheet; a pupil plane is arranged on an incident light path; and the pupil plane is segmented, so that the signal-to-noise ratio of the detector is improved. The device is simple in structure and easy for engineering realization.

Description

technical field [0001] The invention belongs to an acousto-optic measuring system and is mainly used for measuring metal films and dielectric films. Specifically, it relates to a device and method for detecting changes in reflected light. Background technique [0002] At present, the acousto-optic measurement in the prior art is mainly based on the following: the short-pulse laser is irradiated on the surface of the film sample, and the film 2 to be tested absorbs photons to generate thermoelastic deformation, forming a deformation zone on the surface; thermoelastic deformation generates sound waves that propagate on the solid surface and inside ; The longitudinal sound wave propagates to the interface (the junction of the substrate or the film and the film) to generate the first echo signal; the first echo signal reaches the upper surface, causing further changes in the deformation; the echo signal rebounds after hitting the upper surface , after the rebound hits the interf...

AI Technical Summary

Problems solved by technology

[0005] However, in the above-mentioned technical scheme, there are the following problems: the first problem is that the position adjustment accuracy of the first reflector 6c of the applied optical system is extremely demanding High, and its stability is also extremely high, the optical element undertakes the role of splitting the field intensity of the light spot, the requirements for the alignment and stability of the optical path are high, and the assembly of the optical path is relatively difficult; the second aspect is reflected in In terms of the complexity of the optical path, it is necessary to assemble the first reflector 6c and the second reflector 6d respectively, and in order to meet the requirement that the incident light within a certain angle can be effectively reflected and refracted, the parallel collimation and field strength interlacing between the two are also required. It needs to be precisely adjusted and designed. At the same time, two detectors are required at the end of the detection of the outgoing light. The increase in the use of optical components will also lead to an increase in cost; The light is further lost, and the change rate of the spot energy decomposition caused by the incident angle deviation caused by the deformation zone of the reflected detection light is more difficult to be detected, so the detection signal-to-noise ratio is low, about one part per million, and the incident light Waist divergence angle requirements are extremely high

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