Etch Rate Control via Byproduct Concentration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current process control methods for semiconductor etching, such as endpoint control, rely on relative or indirect measurements that are limited in high-aspect ratio applications and lack accuracy, especially when aspect ratios exceed 30:1 and critical dimensions shrink below 21 nm.
Innovation Solution
The method involves measuring the concentration of SiF4 or other SiX4 byproducts using IR absorption with quantum cascade laser spectroscopy, combined with etch-profile modeling to determine etch rate, selectivity, and uniformity, allowing for absolute and in-situ process control beyond traditional methods' limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional endpoint control methods (relative or indirect measurements) are used, then the process control is simpler to implement, but the measurement precision deteriorates in high-aspect ratio applications and when critical dimensions shrink below 21 nm
Solution Approach 1:
The patent replaces traditional mechanical/optical measurement systems (reflectance, emission spectroscopy) with a chemical sensing system that directly measures etch byproduct concentrations. This substitution enables precise measurement in high-aspect ratio applications where traditional methods fail, as the chemical concentration measurements are not limited by geometric constraints like light penetration depth.
Solution Approach 2:
The patent introduces etch byproduct concentration as an intermediary parameter to indirectly measure etch rate and endpoint. Instead of directly measuring the physical state of the etched surface, the system measures the concentration of chemical byproducts (SiF4, SiBr4, SiCl4) generated during etching, which serves as a reliable proxy for process state and enables precise control.
2Manufacturing precision
If absolute and in-situ process control is implemented using byproduct concentration measurement, then the etch rate measurement accuracy improves, but the device complexity increases due to additional sensing and modeling requirements
Solution Approach 1:
The patent implements a feedback control system where etch byproduct concentrations are continuously measured and fed back to update the etch rate model in real-time. This feedback mechanism enables dynamic adjustment of process parameters to maintain precise etch rate control, with the model being continuously refined based on actual measurements rather than relying on pre-established correlations.
Solution Approach 2:
The patent changes the measurement parameter from physical/optical properties (reflectance, emission intensity) to chemical concentration parameters (byproduct gas composition). This parameter transformation enables accurate measurement of etch rate as a function of depth, since chemical concentrations directly reflect the amount of material removed regardless of feature geometry.
3Reliability
If traditional emission spectroscopy or reflectance methods are used for endpoint control, then the system is easier to operate, but the reliability deteriorates when aspect ratios exceed 30:1
Solution Approach 1:
The patent replaces optical/mechanical measurement systems with a chemical sensing system that measures etch byproduct concentrations. This substitution eliminates the fundamental limitation of traditional methods where light cannot penetrate deep into high-aspect ratio features, thereby maintaining reliable endpoint detection regardless of feature geometry while keeping the system relatively simple to operate.
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 enables precise endpoint detection, etch rate measurement as a function of depth, and uniformity assessment, enhancing run-to-run process matching and fault detection with high sensitivity, particularly in high-aspect ratio applications like DRAM and 3D-NAND etches.
Implementation Method 1
measuring the concentration of SiF4 or other SiX4 byproducts using IR absorption with quantum cascade laser spectroscopy
Data Source
AI summary
A method for dry processing a substrate in a processing chamber is provided. The substrate is placed in the processing chamber. The substrate is dry processed, wherein the dry processing creates at least one gas byproduct. A concentration of the at least one gas byproduct is measured. The concentration of the at least one gas byproduct is used to determine processing rate of the substrate.