Etch Parameter Adjustment for Overlay Error Reduction
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Solution Overview
Problem
The lithographic process faces challenges in reducing etch-induced overlay errors, which are introduced during the substrate etching process and affect the precise placement of features in integrated circuits, leading to tighter overlay specifications as device structures become smaller.
Innovation Solution
A method is introduced to change etch parameters by making measurements before and after etching, using a difference in metrics indicative of overlay errors or asymmetries to adjust the etch parameters, thereby optimizing the etching process to minimize overlay errors and improve edge placement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional trial and error method is used to set etch parameters, then the process is simple to operate, but the overlay precision and manufacturing precision deteriorate due to inability to accurately optimize etch parameters
Solution Approach 1:
The patent implements a feedback mechanism where metrology measurements of overlay error are taken before and after etching, and the difference is used to adjust etch parameters for subsequent substrates. This closed-loop feedback system enables continuous optimization of etch parameters to reduce overlay error while maintaining a manageable process through automated control.
Solution Approach 2:
The patent replaces the mechanical trial-and-error adjustment method with an automated measurement and control system. Metrology tools measure overlay error, and a control system automatically calculates and applies parameter adjustments, substituting manual iterative processes with automated optical measurement and computational control.
2Manufacturing precision
If etch parameters are optimized to reduce overlay error, then manufacturing precision improves, but the complexity of the process increases due to additional measurements and parameter adjustments
Solution Approach 1:
The system uses feedback from metrology measurements to automatically adjust etch parameters. Overlay error is measured before etching, and the measured values are fed back to modify etch parameters for subsequent substrates, creating a self-correcting process that improves precision without requiring complex manual intervention.
Solution Approach 2:
The patent systematically changes etch parameters based on measured overlay error. By varying parameters such as etch power, pressure, or gas flow rates in response to measurement data, the system optimizes edge placement accuracy while maintaining process control through structured parameter adjustment rather than uncontrolled complexity.
3Measurement precision
If multiple measurements are made to accurately determine overlay error, then measurement precision improves, but the production time increases
Solution Approach 1:
The patent performs overlay measurements before etching as a preliminary action, allowing the etch process to be optimized in advance. By measuring overlay error prior to etching and pre-calculating parameter adjustments, the system avoids needing to perform additional measurements after etching, thereby maintaining high throughput while ensuring measurement precision.
Solution Approach 2:
The system maintains continuous substrate processing by overlapping measurement and processing activities. While one substrate is being etched, measurements are being taken on the previous substrate, and parameter adjustments are being prepared. This continuous workflow minimizes idle time and maintains productivity while ensuring accurate measurements are obtained.
Data Source
AI summary
A method to change an etch parameter of a substrate etching process, the method including: making a first measurement of a first metric associated with a structure on a substrate before being etched; making a second measurement of a second metric associated with a structure on a substrate after being etched; and changing the etch parameter based on a difference between the first measurement and the second measurement.