Individually Controllable Element Tilt Measurement in Lithography
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Solution Overview
Problem
In lithographic apparatuses, the high intensity illumination beam can cause individually controllable elements, such as programmable mirror arrays, to heat up, leading to inaccuracies in the shape of the illumination beam due to unpredictable tilt changes in the elements, which affects the precision of the patterning process.
Innovation Solution
A measurement apparatus and method are introduced to determine the tilt angle of individually controllable elements in real-time using a separate radiation source and detector system, allowing for correction of tilt deviations and maintaining beam accuracy without interfering with the lithographic operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high intensity illumination beam is used to illuminate the patterning device, then the productivity and exposure speed are improved, but the individually controllable elements become heated causing tilt changes and beam shape deviations
Solution Approach 1:
The system uses a measurement beam to continuously monitor the tilt angle of individually controllable elements in real-time. The detector receives the measurement beam redirected by each element and determines its position, providing feedback on element orientation. This feedback loop allows the system to detect and correct tilt deviations caused by heating, maintaining beam shape accuracy despite high intensity illumination
Solution Approach 2:
A separate measurement beam acts as an intermediary to monitor element tilt without interfering with the main illumination beam. The measurement beam interacts with the individually controllable elements to provide tilt information, while the main illumination beam continues its patterning function. This intermediary approach allows simultaneous high-speed exposure and precise tilt monitoring
2Adaptability or versatility
If individually controllable elements are used to shape the illumination beam, then the adaptability and pattern flexibility are improved, but the heating effects cause unpredictable tilt changes reducing measurement precision
Solution Approach 1:
The system implements real-time feedback by measuring the actual tilt angle of each individually controllable element using a measurement beam and detector. This feedback allows the control system to compensate for thermal drift and maintain precise beam shaping, ensuring measurement precision is preserved despite heating effects from high intensity operation
Solution Approach 2:
The system replaces mechanical tilt sensors with an optical measurement approach. Instead of using mechanical devices to detect element orientation, the patent uses a measurement beam that reflects off or passes through the individually controllable elements, with the detector measuring positional changes. This non-contact optical method avoids adding mechanical complexity and interference to the heated elements
3Manufacturing precision
If a measurement system is added to monitor element tilt, then the beam accuracy is improved, but the device complexity increases
Solution Approach 1:
The measurement beam system serves multiple functions: it monitors element tilt angles, provides feedback for thermal drift compensation, and validates beam shaping accuracy. By using a single measurement infrastructure for multiple purposes, the system achieves high patterning accuracy without proportionally increasing complexity
Solution Approach 2:
The measurement beam acts as a non-intrusive intermediary that monitors element states without requiring direct physical contact or complex sensor integration with the individually controllable elements. This approach simplifies the overall system architecture while maintaining measurement capability
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 real-time measurement and correction of tilt angles in the controllable elements ensure precise control of the illumination beam, enhancing the accuracy and reliability of the patterning process by mitigating the effects of heating and other factors that cause tilt changes.
Implementation Method 1
an individually controllable element of an array of individually controllable elements capable of modulating a beam of radiation, is illuminated by the measurement beam and redirects the measurement beam
Implementation Method 2
a detector arranged to receive the redirected measurement beam and determine the position at which the redirected measurement beam is incident upon the detector
Data Source
AI summary
A measurement apparatus disclosed that has a radiation source configured to provide a measurement beam of radiation such that an individually controllable element of an array of individually controllable elements capable of modulating a beam of radiation, is illuminated by the measurement beam and redirects the measurement beam, and a detector arranged to receive the redirected measurement beam and determine the position at which the redirected measurement beam is incident upon the detector, the position at which the redirected measurement beam is incident upon the detector being indicative of a characteristic of the individually controllable element.