Angular-Resolved Spectroscopic Lithography Characterization
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Solution Overview
Problem
Current lithographic inspection methods require significant time to measure both s and p polarized beams due to the need for quickly moving parts and alternating polarization, which increases throughput time.
Innovation Solution
An inspection apparatus with a light source providing orthogonal polarization directions, a lens to focus the beam, a non-polarizing beamsplitter to direct and receive the radiation, and a polarizing beamsplitter to separate the radiation into orthogonally polarized sub-beams, allowing simultaneous detection of the reflection spectrum by a detector system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alternating polarization measurement is used with shutters, then both s and p polarized beams can be measured, but the measurement time increases and throughput decreases
Solution Approach 1:
The patent combines the measurement of both s and p polarized beams into a single simultaneous measurement process. By using a polarizing beamsplitter to separate the reflected beam into two orthogonally polarized sub-beams and detecting both with a single detector array, the system eliminates the need for alternating measurements with shutters, thereby doubling the measurement throughput while maintaining polarization measurement accuracy
Solution Approach 2:
The patent replaces the mechanical shutter system with an optical beamsplitting system. Instead of using mechanically moving shutters to alternately block and pass s and p polarized beams, the invention uses a polarizing beamsplitter to optically separate both polarizations simultaneously and direct them to the detector array, eliminating mechanical movement and increasing measurement speed
2Measurement precision
If shutters are used to alternate between s and p polarizations, then polarization control is achieved, but the system requires many quickly moving parts increasing complexity
Solution Approach 1:
The patent replaces the mechanical shutter system with a stationary polarizing beamsplitter. The beamsplitter uses optical properties rather than mechanical movement to separate s and p polarized beams, eliminating quickly moving parts while maintaining precise polarization control through the optical axis orientation of the beamsplitter
Solution Approach 2:
The polarizing beamsplitter acts as an intermediary optical element that receives the reflected beam and separates it into s and p polarized sub-beams based on polarization orientation. This intermediary component enables polarization control without requiring mechanical shutters, reducing system complexity while maintaining measurement precision
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 configuration reduces the time required to measure both polarized beams, cutting the acquisition time in half and improving the efficiency of substrate property determination.
Implementation Method 1
a beamsplitter configured to separate the radiation beam once reflected from the surface of the substrate into two orthogonally polarized sub-beams
Implementation Method 2
a lens configured to focus the radiation beam onto a substrate
Implementation Method 3
detect simultaneously an angle-resolved spectrum of both radiation beams reflected from a surface of the substrate
Data Source
AI summary
Simultaneous measurement of two orthogonally polarized beams upon diffraction from a substrate is done to determine properties of the substrate. Linearly polarized light sources with their radiation polarized in orthogonal directions are passed via two non-polarizing beamsplitters, one rotated by 90° with respect to the other. The combined beam is then diffracted off a substrate before being passed back through a non-polarizing beamsplitter and through a phase shifter and a Wollaston prism before being measured by a CCD camera. In this way, the phase and intensities for various phase steps of the two polarized beams may thereby be measured and the polarization state of the beams may be determined. If the phase shifter is turned to zero (i.e. with no phase shifting), the grating of the substrate has its parameters measured with TE and TM polarized light simultaneously with the same detector system.