Optical Emission Spectroscopy for Etching Monitoring
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Solution Overview
Problem
Current etching methods for semiconductor layers face challenges in accurately monitoring partial etching, especially at high pressures, due to the lack of correlation between emission signals and etch amounts, leading to variability and inefficiency in semiconductor processing.
Innovation Solution
The use of optical emission spectroscopy (OES) with signal integration and actinometry, involving existing inert gases, to non-invasively monitor the etching process, allowing for precise control of the plasma discharge based on integrated emission intensity compared to reference values, ensuring accurate partial etching of semiconductor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical emission spectroscopy is used to monitor etching, then real-time monitoring is achieved, but the emission signals do not correlate with etch amounts leading to measurement inaccuracy
Solution Approach 1:
The patent introduces an inert gas as an intermediary substance that emits optical signals during the etching process. This intermediary allows the monitoring system to indirectly measure etch progress through the emission intensity of the inert gas, which correlates with the amount of etching performed, thereby solving the lack of direct correlation between conventional emission signals and etch amounts
Solution Approach 2:
The patent changes the parameter being monitored from general plasma emission signals to the specific emission intensity of an inert gas added to the process. By monitoring the inert gas emission parameter, the system achieves accurate correlation with etch amounts, transforming an uncorrelated measurement into a precise monitoring method
2Manufacturing precision
If dry etching is used to penetrate constrained trenches, then better pattern transfer is achieved, but undesired etching of adjacent structures still occurs
Solution Approach 1:
The patent implements a feedback control system where the optical emission intensity of the inert gas is continuously monitored during etching. When the emission intensity reaches a predetermined threshold corresponding to the desired etch depth, the system automatically stops the etching process. This feedback mechanism enables precise control of etch depth, achieving good pattern transfer while preventing over-etching of adjacent structures
Solution Approach 2:
The patent introduces dynamic control of the etching process by continuously adjusting the process based on real-time emission monitoring. The etching process transitions from a static, predetermined duration to a dynamic process that adapts to actual etch progress, allowing precise termination at the target depth while protecting adjacent structures
3Manufacturing precision
If partial etching is performed to remove small thickness, then layer thickness is precisely controlled, but monitoring accuracy deteriorates at high pressures
Solution Approach 1:
The patent uses an inert gas as an intermediary that provides a strong, measurable emission signal even at high pressures where conventional etch byproducts may not emit detectable signals. The inert gas emission serves as a reliable mediator for monitoring partial etching progress, maintaining measurement accuracy across different pressure conditions
Solution Approach 2:
The patent changes the monitoring parameter from weak conventional emission signals to the strong emission intensity of the inert gas. This parameter change enables accurate detection of small thickness changes in partial etching, even at high pressures where signal detection is typically problematic
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 and efficient partial etching of semiconductor layers, reducing variability and improving semiconductor processing by correlating emission signals with etch amounts, even at pressures greater than 1 Torr, thus enhancing the quality and consistency of semiconductor devices.
Implementation Method 1
striking a plasma discharge
Implementation Method 2
ionize a gas mixture with the plasma subsystem
Implementation Method 3
measuring the intensity of emission from a reaction of plasma effluents with the layer
Data Source
AI summary
Embodiments may include a method of etching. The method may also include flowing a gas mixture through a plasma discharge to form plasma effluents. The method may further include flowing the plasma effluents through a plurality of apertures to a layer on a substrate. The layer may have a first thickness. In addition, the method may include etching the layer with the plasma effluents. The method may also include measuring the intensity of emission from a reaction of plasma effluents with the layer. The method may further include summing the intensity of the emission while the plasma effluents are being flowed to the layer to obtain an integrated intensity. The method may then include comparing the integrated intensity to a reference value corresponding to a target etch thickness. The method may include extinguishing the plasma discharge when the integrated intensity is equal to or greater than the reference value.