Immersion Lithography Route Optimization for Residual Liquid Defects
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Solution Overview
Problem
Current methods to reduce defects in device manufacturing using immersion lithography, such as slowdowns to prevent residual immersion liquid, often decrease throughput and may not be necessary as they overpredict defects, leading to unnecessary reductions in production speed.
Innovation Solution
A method that predicts locations at risk for residual liquid, tests these predictions by exposing substrates, and selectively applies route modifications based on actual defect data to minimize throughput reduction while reducing defects, using a computer program to determine and apply the necessary route modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If route modifications (slowdowns) are applied to prevent residual immersion liquid, then manufacturing precision is improved, but productivity deteriorates
Solution Approach 1:
The patent applies route modifications locally only at specific fields identified as high-risk for residual liquid, rather than applying slowdowns globally across the entire substrate. The system calculates a liquid loss risk for each field and selectively modifies the exposure route only where necessary, thereby reducing defects at critical locations while maintaining normal processing speed elsewhere to preserve throughput.
Solution Approach 2:
The patent dynamically adjusts exposure parameters (such as exposure speed or pause duration) based on the calculated liquid loss risk for each field. By changing these parameters selectively according to risk assessment rather than applying uniform modifications, the system achieves defect reduction at high-risk locations without unnecessarily reducing overall productivity.
2Manufacturing precision
If route modifications are applied based on predicted liquid loss, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary calculation of liquid loss risk for each field before actual exposure based on the substrate route and field arrangement. This advance assessment allows the system to identify high-risk fields in advance and apply modifications only where necessary, avoiding unnecessary time loss from blanket slowdowns while ensuring defects are prevented at critical locations.
Solution Approach 2:
The patent applies route modifications partially only to high-risk fields rather than to all fields. By identifying and treating only the subset of fields with significant liquid loss risk, the system achieves sufficient defect reduction without the excessive time loss that would result from applying modifications universally across the entire substrate.
3Manufacturing precision
If immersion liquid is used to improve resolution, then manufacturing precision is improved, but object-generated harmful factors increase
Solution Approach 1:
The patent converts the potential harm of residual immersion liquid by using the substrate route information and field arrangement to predict and identify where liquid loss is most likely to occur. This predictive capability transforms the harmful residual liquid issue into a controllable parameter, allowing the system to maintain the benefits of immersion lithography (improved resolution) while preventing defects at identified high-risk locations through selective route modifications.
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
This approach allows for a targeted reduction in defects by identifying only necessary route modifications, thereby maintaining throughput while effectively minimizing manufacturing defects caused by residual immersion liquid.
Implementation Method 1
a liquid layer of a liquid having a relatively high refractive index is interposed in a space between a projection system of the apparatus and the substrate... The effect of the immersion liquid is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the liquid than gas
Data Source
AI summary
A device manufacturing method using a lithographic apparatus having a localized immersion system for confining an immersion liquid to a space between a projection system and a substrate to be exposed by the projection system, the method including: predicting a set of first locations on the substrate having a risk of residual liquid from the immersion system when exposed using an initial route for a substrate to expose a plurality of fields thereon; determining a set of modifications to the initial route to reduce the risk of residual loss; test exposing at least one test substrate using the initial route; obtaining a set of second locations of defects in the exposed test substrate; selecting a subset of the set of modifications by comparing the first locations and the second locations; and exposing a plurality of production substrates using the initial route modified by the selected subset of modifications.