Reflectance Spectrum Overlay for Etching CD Control
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Solution Overview
Problem
Current methods for controlling the critical dimension (CD) of fine line-and-space structures in semiconductor manufacturing are inaccurate and inefficient, particularly when dealing with complex structures like sparse and dense line-and-space patterns, due to limitations in measuring and controlling etching processes without directly measuring formed lines, leading to issues with throughput and precision.
Innovation Solution
A substrate processing control method that acquires and compares reflectance spectra from different fine structures using rigorous coupled wave analysis and scalar analysis to accurately measure and control pattern dimensions, allowing for precise etching control by overlapping reference spectra with actual measured spectra, enabling accurate control of CD values even in complex structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etching is ended without directly measuring formed lines, then throughput is maintained, but manufacturing precision of CD value deteriorates
Solution Approach 1:
The patent replaces direct physical measurement of formed lines with optical measurement of reflectance spectra during the etching process. By using light reflection characteristics to infer CD values, the system achieves precise measurement without stopping the etching process or requiring separate measurement equipment, thus maintaining throughput while improving CD value precision.
Solution Approach 2:
The patent introduces reflectance spectrum as an intermediary parameter to indirectly measure CD values. Instead of directly measuring the physical dimensions of formed lines, the system measures the optical properties (reflectance spectra) of the etched structure, which correlates with CD values, enabling precise control without direct measurement.
2Manufacturing precision
If feedback method or feedforward method is used to control etching, then manufacturing precision is improved, but device complexity increases due to dedicated measuring devices
Solution Approach 1:
The patent makes the etching apparatus itself multi-functional by integrating measurement capabilities directly into the etching system. The same apparatus that performs etching also measures reflectance spectra and controls CD values, eliminating the need for separate dedicated measuring devices and reducing overall system complexity.
Solution Approach 2:
The etching apparatus performs self-measurement and self-control by using its own optical system to measure reflectance spectra during the etching process. The system monitors its own processing state and adjusts parameters automatically, eliminating the need for external dedicated measuring and control devices.
3Reliability
If measurement is performed on substrates with both first and second fine structures, then comprehensive quality control is achieved, but measurement precision deteriorates due to spectral overlap
Solution Approach 1:
The patent segments the measurement process by analyzing reflectance spectra at different etching stages. By measuring the first fine structure during early etching and the second fine structure during later etching, the system separates the measurement of different structures, avoiding spectral overlap and maintaining measurement precision while achieving comprehensive quality control.
Solution Approach 2:
The patent employs dynamic measurement strategies where the measurement focus shifts between different fine structures based on etching progress. The system adaptively adjusts which structure is being measured and how the spectra are analyzed, enabling precise measurement of both structures despite their different dimensions and optical characteristics.
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 method allows for precise control of pattern dimensions in substrates with multiple fine structures, improving etching accuracy and throughput by accurately measuring and matching reflectance spectra, thus ensuring desired CD values are achieved during the etching process.
Implementation Method 1
a reflectance spectrum acquiring step of acquiring in advance a first reflectance spectrum of a reflection beam reflected from the first fine structure and a second reflectance spectrum of a reflection beam reflected from the second fine structure
Data Source
AI summary
In a substrate processing control method, a first process acquires a first-reflectance-spectrum of a beam reflected from the first-fine-structure and a second-reflectance-spectrum of a beam reflected from the second-fine-structure for each of varying-pattern-dimensions of the first-fine-structure when the pattern-dimension of the first-fine-structure is varied. A second process acquires reference-spectrum-data for each of the varying-pattern-dimensions of the first-fine-structure by overlapping the first-reflectance-spectrum with the second-reflectance-spectrum. A third process actually measures beams reflected from the first and the second-fine-structure, respectively, after irradiating light beam on to the substrate and acquiring reflectance-spectrums of the actual-measured beams as actual-measured spectrum data. A fourth process compares the actual-measured spectrum data with the respective reference-spectrum data and acquiring, as the measured pattern-dimension, one of the varying-pattern-dimensions corresponding to reference-spectrum data that is closely matches with the actual-measured spectrum data. A final process ends the processing of the substrate if the measured pattern-dimension reaches a value.