Wavelength Calibration Assembly with Protective Top Layer
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Solution Overview
Problem
Existing metrology tools face challenges in accurately measuring small features on substrates due to contamination in vacuum chambers, which affects the stability and efficiency of diffractive elements, leading to reduced performance and accuracy.
Innovation Solution
An assembly for calibrating radiation wavelength is proposed, comprising a diffracting element with a bottom layer having a lateral periodic structure and a top layer with a flat surface. This configuration minimizes the impact of contaminants by depositing them on a flat surface, reducing their effect on diffraction properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffracting element is used for wavelength calibration in a vacuum chamber, then measurement precision is improved, but contamination on the diffracting element reduces reliability over time
Solution Approach 1:
A protective top layer is introduced as an intermediary between the contaminating environment and the diffracting periodic structure. This top layer acts as a barrier that prevents contaminants from directly contacting and degrading the diffractive elements, while still allowing the calibration function to operate effectively.
Solution Approach 2:
The diffracting element is segmented into distinct functional layers: a bottom layer containing the lateral periodic structure responsible for diffraction, and a top layer providing protection. This segmentation allows each layer to perform its specific function independently, with the top layer protecting the sensitive diffractive structures below.
2Device complexity
If contaminants are present in the vacuum chamber, then device complexity is reduced, but measurement precision deteriorates due to affected diffraction properties
Solution Approach 1:
The protective top layer converts the harmful effect of contamination into a beneficial protective barrier. Instead of contaminants directly degrading the diffractive element, they are blocked by the top layer, effectively turning a potential harm into a protective feature that maintains 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
The proposed assembly enhances the stability and accuracy of metrology tools by reducing the impact of contaminants on diffractive elements, thereby improving the calibration of radiation wavelengths and maintaining performance over time.
Implementation Method 1
a bottom layer having a lateral periodic structure for diffracting radiation at an upper surface of the bottom layer
Implementation Method 2
a top layer having a lower surface that is adjacent to the periodic structure and an upper surface that is flat... to reflectively diffract the radiation
Data Source
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AI summary
An assembly for calibrating a radiation wavelength. The assembly can be provided in a metrology apparatus. The assembly comprises an input configured to receive radiation. The assembly further comprises a diffracting element for diffracting radiation. The diffracting element comprises a bottom layer having a lateral periodic structure for diffracting radiation at an upper surface of the bottom layer, and a top layer having a lower surface that is adjacent to the periodic structure and wherein the top layer has a top surface that is flat. The diffracting element is arranged to receive the radiation on the upper surface of the top layer, and to reflectively diffract the radiation such that the radiation exits the diffracting element via the upper surface of the top layer. The assembly further comprises a detector configured to detect the diffracted radiation.