DUV Laser Alignment Metrology With Closed-Loop Optical Correction
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Solution Overview
Problem
The alignment of a master oscillator in a lithographic apparatus is time-consuming and prone to variations over time, requiring manual maintenance and potentially blocking the output light beam.
Innovation Solution
A light source apparatus comprising a gas discharge stage, a sensing apparatus, an optical arrangement, an adjustment apparatus, and a control apparatus, which images light from distinct object planes onto the sensing apparatus, allows for dynamic control of alignment errors, and reduces alignment times and variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual alignment of the master oscillator is performed, then alignment can be achieved, but alignment time is excessive and variations occur over time
Solution Approach 1:
The patent replaces manual mechanical alignment operations with an automated optical sensing system. The sensing apparatus detects alignment status and the control apparatus automatically adjusts optical components, eliminating the need for time-consuming manual alignment while maintaining or improving precision.
Solution Approach 2:
The system enables self-alignment through the sensing apparatus that continuously monitors and the control apparatus that automatically corrects alignment deviations. The master oscillator system serves itself by detecting and correcting its own alignment status without external manual intervention.
2Reliability
If manual alignment maintenance is performed, then alignment can be maintained, but the output light beam may be blocked and productivity is reduced
Solution Approach 1:
The sensing apparatus provides continuous feedback on the alignment status of the master oscillator to the control apparatus. This closed-loop feedback system maintains alignment reliability by detecting deviations and triggering automatic corrections without blocking the light beam or requiring operational interruptions.
Solution Approach 2:
The automated sensing and control system operates continuously without interrupting the light beam output. The useful action of maintaining alignment continues uninterrupted, eliminating the need to stop the system for manual maintenance and thereby preserving productivity.
3Measurement precision
If the sensing apparatus monitors alignment, then alignment errors can be detected, but system complexity increases
Solution Approach 1:
The sensing apparatus serves multiple functions: it detects alignment status, provides feedback to the control apparatus, and enables automatic correction. By consolidating these functions into a single integrated system, the patent reduces overall complexity compared to having separate manual alignment tools and procedures.
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 solution significantly reduces alignment times and variations of the master oscillator, enabling more efficient and stable operation of the lithographic apparatus by dynamically controlling quantifiable alignment errors.
Implementation Method 1
an optical arrangement configured to image light from a plurality of distinct object planes within the gas discharge stage onto the sensing apparatus
Implementation Method 2
a gas discharge stage comprising an optical amplifier comprising a chamber configured to hold a gas discharge medium, the gas discharge medium outputting a light beam
Data Source
AI summary
A light source apparatus includes a gas discharge stage, a sensing apparatus, an optical arrangement, an adjustment apparatus, and a control apparatus. The gas discharge stage includes an optical amplifier including a chamber configured to hold a gas discharge medium outputting a light beam, and a set of optical elements configured to form an optical resonator around the optical amplifier. The optical arrangement is configured to image light from a plurality of distinct object planes within the gas discharge stage onto the sensing apparatus. The adjustment apparatus is in physical communication with one or more optical components within the gas discharge stage and is configured to modify at least one geometric aspect of the optical components. The control apparatus is communication with the sensing apparatus and the adjustment apparatus and is configured to provide a signal to the adjustment apparatus based on an output from the sensing apparatus.