Optical System Controller for Lithography Dose Error Management
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Solution Overview
Problem
Photolithography systems face challenges in maintaining accurate energy delivery to the wafer due to variations in the pulsed light beam, leading to dose errors and instability, which conventional linear controllers often exacerbate.
Innovation Solution
A control system that determines energy errors and applies optimized control sequences to the optical source, minimizing dose errors while ensuring stability by using a combination of electronic processors and non-transitory storage media to manage energy metrics and control sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional linear controllers are used to control the optical source, then the control system is simple, but dose errors increase and stability deteriorates
Solution Approach 1:
The control sequence is divided into multiple individual control values, each corresponding to a specific pulse or group of pulses. This segmentation allows independent optimization of each control value to compensate for pulse-to-pulse energy variations, thereby improving dose accuracy without requiring a completely complex control architecture.
Solution Approach 2:
The controller pre-calculates and stores an optimal control sequence based on expected pulse energy variations before actual exposure. This preliminary action allows the system to proactively compensate for anticipated dose errors, improving manufacturing precision while keeping the real-time control system relatively simple.
2Reliability
If the control sequence is optimized for each pulse, then dose errors are reduced, but the control system becomes more complex
Solution Approach 1:
The system incorporates feedback from pulse-to-pulse energy measurements to dynamically adjust subsequent control values. This feedback mechanism improves system stability by continuously compensating for energy variations, while the automated feedback loop prevents excessive control sequence complexity through systematic adjustment rules.
Solution Approach 2:
The controller modifies control parameters (such as pulse energy, duration, or timing) based on measured deviations from target dose. By systematically changing these parameters in response to feedback, the system achieves high reliability without requiring overly complex control logic, as the parameter adjustments follow predetermined optimization criteria.
3Manufacturing precision
If real-time energy adjustment is implemented, then manufacturing precision improves, but processing time increases
Solution Approach 1:
The optimal control sequence is pre-calculated and stored before exposure begins. This preliminary computation eliminates the need for complex real-time calculations during exposure, thereby maintaining high energy delivery accuracy while minimizing processing time losses.
Solution Approach 2:
The system implements control adjustments at periodic intervals (e.g., every N pulses) rather than continuously for each pulse. This periodic approach maintains manufacturing precision by regularly correcting energy delivery accuracy, while reducing the computational overhead and processing time compared to continuous per-pulse adjustment.
Data Source
AI summary
A lithography system includes an optical source configured to emit a pulsed light beam; a lithography apparatus including an optical system, the optical system being positioned to receive the pulsed light beam from the optical source at a first side of the optical system and to emit the pulsed light beam at a second side of the optical system; and a control system coupled to the optical source and the optical lithography apparatus, the control system configured to: receive an indication of an amount of energy in the pulsed light beam at the second side of the optical system, determine an energy error, access an initial control sequence, the initial control sequence being associated with the optical source, determine a second control sequence based on the determined energy error and the initial control sequence, and apply the second control sequence to the optical source.