Lithography Overlay Error Correction via Layered Reference Features
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Solution Overview
Problem
Lithographic processes face challenges in accurately determining the position of features on substrates due to placement errors caused by temperature changes and projection system distortions, leading to overlay errors and reduced yield.
Innovation Solution
A method and system that measure the position of a feature on a substrate, calculate the placement error based on the relative position of reference features on different layers, and use this information to determine an updated position for precise alignment and positioning, accounting for placement errors and projection system-induced shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If automated process control systems are used to correct overlay errors, then manufacturing precision is improved, but device complexity increases due to additional measurement and correction systems
Solution Approach 1:
The patent implements feedback control by measuring the actual positions of alignment marks on the substrate, comparing them to intended positions, calculating placement errors, and using these errors to determine corrected positions for subsequent layers. This closed-loop feedback system continuously refines positioning accuracy without requiring complex external intervention systems.
Solution Approach 2:
The patent introduces alignment marks as intermediary reference features on the substrate that mediate between the projection system and the actual pattern features. These marks serve as intermediaries for measurement and correction, simplifying the control system by providing direct reference points rather than requiring complex indirect measurement methods.
2Manufacturing precision
If alignment measurements are performed on multiple layers, then manufacturing precision is improved, but measurement time increases
Solution Approach 1:
The patent performs preliminary alignment measurements on the first layer to determine placement errors before exposing subsequent layers. By calculating corrected positions based on first-layer measurements and applying these corrections in advance to the exposure parameters for later layers, the system achieves multi-layer precision without requiring time-consuming measurements on each individual layer.
Solution Approach 2:
The patent performs measurements on a subset of alignment marks and layers that are sufficient to characterize the placement errors, rather than measuring every possible feature. By selecting representative alignment marks and using mathematical models to extrapolate corrections across the entire substrate, the system achieves comprehensive correction with minimal measurement time.
Data Source
AI summary
A method, system and program for determining a position of a feature referenced to a substrate. The method includes measuring a position of the feature, receiving an intended placement of the feature and determining an estimate of a placement error based on knowledge of a relative position of a first reference feature referenced to a first layer on a substrate with respect to a second reference feature referenced to a second layer on a substrate. The updated position may be used to position the layer of the substrate having the feature, or another layer of the substrate, or another layer of another substrate.