Synchronized Metrology for Overlay Shift Reduction
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Solution Overview
Problem
Traditional integrated metrology systems in semiconductor fabrication face challenges in maintaining alignment accuracy and reducing overlay (OVL) shift between different wafers with varying numbers of exposure fields, leading to unsynchronized measurement processes that can cause delays, temperature variations, and reduced APC effectiveness.
Innovation Solution
A synchronized integrated metrology system that adjusts IM scanner settings based on the number of exposed fields, using a control unit with a synchronization unit to select appropriate OVL measurement zone patterns, ensuring proportional OVL measurements are performed within a sufficient time frame, thereby synchronizing the flow of wafers and minimizing temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional integrated metrology systems perform OVL measurements on wafers with varying numbers of exposure fields, then measurement coverage is maintained, but OVL shift increases and alignment accuracy deteriorates
Solution Approach 1:
The system dynamically adjusts the number of OVL measurements and measurement zone patterns based on the number of exposure fields in each wafer. The control unit receives wafer information, determines the appropriate measurement configuration, and adjusts IM scanner settings in real-time to maintain synchronized measurements across wafers with different exposure field counts, thereby reducing OVL shift while maintaining measurement coverage.
2Productivity
If the IM scanner performs fixed number of OVL measurements, then measurement consistency is maintained, but manufacturing throughput decreases due to unsynchronized operations
Solution Approach 1:
The system dynamically adjusts the number of OVL measurements and measurement zone patterns based on the number of exposure fields in each wafer. The control unit receives wafer information, determines the appropriate measurement configuration, and adjusts IM scanner settings in real-time to maintain synchronized measurements across wafers with different exposure field counts, thereby reducing OVL shift while maintaining measurement coverage.
3Ease of operation
If unsynchronized metrology operations are performed, then measurement simplicity is maintained, but temperature variations increase and measurement quality deteriorates
Solution Approach 1:
The control unit receives real-time information about the number of exposure fields from the exposure scanner and uses this feedback to determine the appropriate OVL measurement configuration. This closed-loop control ensures that the IM scanner performs measurements synchronized with the exposure process, maintaining stable temperature conditions and measurement quality while adjusting operation complexity based on actual wafer characteristics.
Data Source
AI summary
The present disclosure relates to a method of semiconductor processing. The method includes, receiving a first wafer having a photoresist coating on a face of the first wafer. An exposure unit is used to perform a first number of radiation exposures on the photoresist coating, thereby forming an exposed photoresist coating. The exposed photoresist coating is developed, thereby forming a developed photoresist coating. An OVL measurement zone pattern is selected from a number of different, pre-determined OVL measurement zone patterns based on at least one of: the first number of radiation exposures performed on the first wafer or a previous number of radiation exposures performed on a previously processed wafer, which was processed before the first wafer. A number of OVL measurements are performed on the developed photoresist coating within the selected OVL measurement zone pattern.