OES-Calibrated Gas Flow Control for Low-Rate Plasma Etching
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Solution Overview
Problem
In plasma dry etching processes for semiconductor manufacturing, controlling the intensity of the plasma beam at low flow rates of etching gas is challenging due to non-linear relationships, leading to inaccuracies in etching rates and potential bridging issues during via formation.
Innovation Solution
A method involving a plasma etcher with a flow rate controller recalibrated using optical emission spectroscopy (OES) to detect emitted light from plasma discharge, allowing for precise adjustment of etching gas flow rates and generation of low-intensity plasma beams for controlled etching, including the use of a series of low flow rates to establish a linear calibration curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional flow rate control is used in plasma dry etching, then the etching process can be performed, but the control of plasma beam intensity becomes inaccurate at low flow rates due to non-linear relationships
Solution Approach 1:
The patent implements a feedback mechanism where Optical Emission Spectroscopy (OES) continuously monitors the plasma emission intensity and provides real-time feedback to the control system. This closed-loop feedback allows the system to detect deviations from the desired plasma intensity and automatically adjust the gas flow rate to compensate for non-linear relationships, thereby maintaining accurate control at low flow rates where conventional open-loop control fails.
Solution Approach 2:
The patent replaces conventional mechanical flow rate sensing and control mechanisms with an optical-based OES monitoring system. Instead of relying on mechanical flow meters and controllers that exhibit non-linear behavior at low flows, the system uses optical emission spectroscopy to directly measure plasma intensity and infer flow rate, substituting mechanical control with optical detection and electronic control.
2Manufacturing precision
If low flow rates are used to generate low-intensity plasma beams, then precise etching at critical dimensions is enabled, but non-linear relationships cause inaccuracies in etching rates
Solution Approach 1:
The patent introduces OES monitoring as an intermediary measurement system that indirectly measures flow rate through plasma emission intensity. Instead of directly measuring gas flow rate with mechanical sensors that lack precision at low flows, the system uses plasma emission as an intermediate parameter that correlates with flow rate, enabling accurate inference of flow rate and etching conditions through optical measurement.
Solution Approach 2:
The patent changes the measurement parameter from direct gas flow rate (which has non-linear control characteristics at low flows) to plasma emission intensity (which provides linear and accurate feedback). By monitoring the optical emission spectrum and intensity of plasma species, the system transforms the measurement into a parameter that accurately reflects the actual plasma conditions and etching rate, enabling precise control at critical dimensions.
3Productivity
If conventional plasma beam intensity control is used, then the etching process can proceed, but bridging issues occur during via formation at critical dimensions
Solution Approach 1:
The patent implements dynamic control of plasma beam intensity by continuously adjusting the gas flow rate based on real-time OES feedback. Instead of using static or pre-programmed flow rates, the system dynamically adapts the plasma parameters during the etching process, maintaining optimal intensity levels that prevent bridging while ensuring complete etching of via structures. This dynamic adjustment allows the system to respond to varying plasma conditions and maintain precision throughout the etching cycle.
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 achieves precise control over etching processes, reducing the probability of bridging and ensuring accurate formation of vias with straight edges, even at critical dimensions like 3 nm, with an accuracy of less than 1% precision.
Implementation Method 1
monitoring emitted light generated by plasma discharge of the plasma beam. The method also includes calibrating the flow rate controller based on the emitted light from the plasma discharge
Implementation Method 2
monitoring emitted light generated by plasma discharge corresponding to the one or more plasma beams
Data Source
AI summary
In a method of controlling a plasma beam of a plasma etcher a flow rate controller of the plasma etcher is set to generate one or more flow rates of an etching gas corresponding to one or more plasma beams of the plasma etcher. The emitted light generated by plasma discharge corresponding to the one or more plasma beams of the plasma etcher is monitored. The flow rate controller is calibrated based on the one or more flow rates and a corresponding emitted light of the plasma discharge.