Normal Incidence Broadband Spectroscopic Polarimeter Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical measurement techniques face challenges in accurately focusing broadband probing beams on non-flat semiconductor wafers due to chromatic aberration and difficulty in adjusting optical systems, particularly with curved mirrors, which also affect beam polarization control.
Innovation Solution
A normal incidence broadband spectroscopic polarimeter is developed, utilizing a light source, beam splitting element, focusing unit, polarizer, first curved reflector element, and first flat reflector element to achieve easy focus adjustment without chromatic aberration, while maintaining polarization properties and using flat mirrors to control the optical path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lens is used to focus the broadband probing beam, then the beam can be focused onto the sample, but chromatic aberration occurs causing different wavelengths to focus at different locations
Solution Approach 1:
The patent replaces the lens-based focusing system with a curved mirror-based system. The curved mirror focuses the broadband probing beam without introducing chromatic aberration, as mirrors reflect all wavelengths at the same angle according to the law of reflection, unlike lenses that refract different wavelengths at different angles. This substitution resolves the contradiction by maintaining focus accuracy while eliminating the reliability issue of chromatic aberration.
2Reliability
If curved mirrors are used to focus the beam, then chromatic aberration is eliminated, but the optical path alignment becomes more difficult and requires simultaneous adjustment of the entire optical system
Solution Approach 1:
The patent introduces a flat mirror as a separate, adjustable component in the optical path between the curved mirror and the sample. This segmentation allows the flat mirror to be independently adjusted to control the optical path direction and focusing position, decoupling the alignment requirements from the entire optical system. The flat mirror can be positioned and oriented separately to achieve the desired beam direction without requiring simultaneous adjustment of all other components.
3Reliability
If a single curved mirror is used for focusing, then chromatic aberration is avoided, but the polarization state of the broadband beam changes due to different reflectivity and phase change for S and P polarized light
Solution Approach 1:
The patent introduces a polarizer as an intermediary component in the optical path. The polarizer controls and standardizes the polarization state of the broadband probing beam before it reaches the curved mirror and sample. By placing the polarizer at a specific position in the optical path, the system can maintain consistent polarization characteristics throughout the measurement process, compensating for the polarization changes that occur during reflection from the curved mirror.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for high-accuracy measurement of anisotropic and inhomogeneous samples by maintaining beam quality and polarization, enabling precise measurement of three-dimensional profiles and material optical constants within periodic structures.
Implementation Method 1
a beam splitting element set in an optical path between the light source and the focusing unit, and the beam splitting element is used to pass through a part of the beam from the light source before incident on the focusing unit, and receive the beam reflected from a sample
Implementation Method 2
a focusing unit, wherein: the beam splitting element set in an optical path between the light source and the focusing unit, and the beam splitting element is used to pass through a part of the beam from the light source before incident on the focusing unit
Implementation Method 3
by using at least one flat reflector element to change the propagation direction of the focused beam, the probing beam can focus on the surface of the sample at normal incidence
Data Source
AI summary
A kind of normal incidence broadband spectroscopic polarimeter which is easy to adjust the focus, has no chromatic aberration, maintains the polarization and has simple structure. The normal incidence broadband spectroscopic polarimeter can make the probe beam normal incidence and focus on the sample surface by using at least one flat reflector element to change propagation direction of the focused beam. Moreover, the normal incidence broadband spectroscopic polarimeter contains at least one polarizer as to measure the anisotropy or non-uniform samples, such as three-dimensional profile and material optical constants of thin films consisting of the periodic structure. An optical measurement system including the normal incidence broadband spectroscopic polarimeter is also provided.