Lithography Inspection Apparatus Using Variable Retarder for Polarization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current scatterometry methods, such as those using spectroscopic and angularly resolved scatterometers, do not accurately measure the phase difference and amplitude of diffracted radiation across the entire azimuthal range, leading to incomplete information and potential errors due to the need for multiple devices that absorb radiation and require calibration.
Innovation Solution
An inspection apparatus and method that focuses a radiation beam on a substrate at various incident and azimuth angles, polarizes the beam into two directions, uses a variable retarder to impose a wavelength-dependent phase shift, and detects the angle-resolved spectrum of both polarization directions simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple devices are used to measure polarization parameters, then measurement coverage is improved, but device complexity and calibration requirements increase
Solution Approach 1:
The patent combines multiple measurement functions into a single scatterometer device by integrating a polarizing beamsplitter that simultaneously measures s-polarized and p-polarized radiation intensities. This eliminates the need for multiple separate devices and reduces calibration complexity while maintaining comprehensive polarization measurement capability across all azimuthal angles.
Solution Approach 2:
The scatterometer is designed to perform multiple measurement functions simultaneously - measuring both s and p polarized intensities, operating at all azimuthal angles, and providing complete polarization state information through a single integrated optical path with a polarizing beamsplitter and detector array.
2Measurement precision
If multiple devices in series are used, then measurement capability is improved, but radiation absorption increases
Solution Approach 1:
The patent uses a single optical path with a polarizing beamsplitter that divides the reflected radiation into s and p polarized components simultaneously, rather than passing the beam through multiple devices in series. This minimizes radiation absorption and maintains signal strength while achieving complete polarization measurement.
3Productivity
If intensity-only measurement is used, then measurement speed is improved, but measurement precision deteriorates
Solution Approach 1:
The patent performs preliminary polarization decomposition by using a polarizing beamsplitter to separate s and p polarized components before detection. This allows simultaneous measurement of both intensity and polarization state information in a single step, maintaining measurement speed while enabling precise phase difference and amplitude determination through the measured intensity ratios.
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
Enables precise measurement of phase difference and amplitude of diffracted radiation throughout the entire azimuthal range, reducing errors and enhancing data accuracy without the need for multiple devices, thus providing more comprehensive and reliable metrology data.
Implementation Method 1
an optical element configured to focus a radiation beam onto a substrate at a range of incident and azimuth angles such that the radiation beam reflects from the substrate
Implementation Method 2
a polarizing device configured to polarize the radiation beam into two different polarization directions
Implementation Method 3
a variable retarder configured to retard the two polarization directions by a certain amount so as to impose a variable phase shift on the reflected radiation beam, the variable phase shift being dependent on the wavelength of the radiation beam
Implementation Method 4
a detector system configured to detect simultaneously an angle-resolved spectrum of the two polarization directions of the radiation beam
Data Source
AI summary
The measurement of two separately polarized beams (Ix, Iy) upon diffraction from a substrate (W) in order to determine properties of the substrate is disclosed. Circularly or elliptically polarized radiation is passed via a variable phase retarder in order to change the phase of one of two orthogonally polarized radiation beams with respect to the other of the two beams. The phase change is dependent on the wavelength of the polarized beam. The relative phases of the two radiation beams and other features of the beams as measured in a detector gives rise to properties of the substrate surface.