On-the-fly Target Acquisition in Semiconductor Metrology
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Solution Overview
Problem
Current semiconductor metrology systems require a time-consuming 'Acquire' phase for target positioning and focusing, which limits throughput and measurement accuracy, especially as the number of targets and measurement requirements increase.
Innovation Solution
Implementing a metrology system that uses a split collection channel with a TDI sensor and analysis unit to derive positioning and focusing information during wafer movement, allowing for on-the-fly target acquisition and eliminating the need for a separate 'Acquire' phase by adjusting the stage motion and focus accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate Acquire phase is used for target positioning and focusing, then measurement accuracy is improved, but total measurement time increases
Solution Approach 1:
The system performs preliminary target acquisition and focusing actions during the Move phase by capturing images at multiple positions along the movement trajectory. This preliminary action allows the system to identify the optimal stopping position and focus settings before the stage comes to a complete stop, thereby eliminating the need for a separate Acquire phase and reducing total measurement time while maintaining measurement precision.
Solution Approach 2:
The system maintains continuous useful action by overlapping the Acquire phase with the Move phase. Image capture and target identification operations continue during stage movement rather than requiring the stage to be stationary, allowing simultaneous movement and acquisition activities that reduce overall cycle time while preserving positioning accuracy.
2Productivity
If fast acceleration and deceleration profiles are used for stage movement, then throughput is improved, but positioning accuracy deteriorates
Solution Approach 1:
The system determines the optimal stopping position and focus settings in advance during the movement phase by analyzing images captured at intermediate positions. This preliminary determination allows the stage to maintain fast acceleration and deceleration profiles while still achieving accurate positioning, as the final stop position is pre-calculated rather than requiring slow, precise stopping.
Solution Approach 2:
The system uses feedback from images captured during movement to dynamically adjust the stage stopping position and focus settings. By continuously monitoring target position and focus quality during the Move phase, the system can provide real-time feedback to optimize the final stopping position, maintaining high throughput with fast movement profiles while ensuring accurate positioning through active feedback control.
Data Source
AI summary
Metrology systems and methods are provided, which derive metrology target position on the wafer and possibly the target focus position during the movement of the wafer on the system's stage. The positioning data is derived before the target arrives its position (on-the-fly), sparing the time required in the prior art for the acquisition stage and increasing the throughput of the systems and methods. The collection channel may be split to provide for an additional moving-imaging channel comprising at least one TDI (time delay and integration) sensor with an associated analysis unit configured to derive wafer surface information, positioning and/or focusing information of the metrology targets with respect to the objective lens, during wafer positioning movements towards the metrology targets. Additional focusing-during-movement module and possibly feedbacking derived position and/or focus information to the stage may enhance the accuracy of the stopping of the stage.