Calibrating Optical Path Degradation in Decoupled Plasma Nitridation
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Solution Overview
Problem
In the semiconductor industry, ensuring consistent plasma processing across different chambers is challenging due to variability in plasma state and optical emission spectra measurements, which can be affected by changes in window attenuation, leading to uncertainties in parameter settings and reduced process repeatability.
Innovation Solution
The use of a standardized light source to calibrate spectrometers ensures uniform comparison of optical emission spectra, and a method to determine and adjust for optical path changes by measuring and applying a correction factor to maintain peak operating efficiency and match chamber performance to a reference setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If optical emission spectra measurements are used to monitor plasma state, then plasma process information can be obtained, but measurement precision deteriorates due to window attenuation changes
Solution Approach 1:
A reference optical path with a reference window is introduced as an intermediary measurement channel. This reference path measures the attenuation characteristics separately, allowing the system to compensate for window degradation effects on the plasma measurement path, thereby maintaining measurement precision despite window attenuation changes.
Solution Approach 2:
The system measures and tracks changes in optical transmission parameters through the window over time. By monitoring the attenuation parameter changes and applying correction factors to the plasma emission spectra measurements, the system compensates for window degradation and maintains accurate plasma state information.
2Reliability
If chamber qualification procedures are performed frequently to ensure consistent plasma processing, then process repeatability is improved, but loss of time increases due to repeated calibration and maintenance
Solution Approach 1:
The system implements continuous monitoring of optical path transmission characteristics and plasma emission spectra. By providing real-time feedback on measurement quality and detecting drift or degradation trends, the system can alert operators before qualification thresholds are exceeded, allowing for timely maintenance while minimizing unnecessary chamber downtime.
Solution Approach 2:
The system performs preliminary measurements of optical path characteristics using a reference window to establish baseline attenuation values. By proactively identifying window degradation trends before they significantly impact plasma processing, the system enables planned maintenance during scheduled downtime rather than requiring unexpected chamber shutdowns.
3Manufacturing precision
If comprehensive plasma monitoring is implemented to ensure chamber matching, then manufacturing precision is improved, but device complexity increases due to additional monitoring equipment and procedures
Solution Approach 1:
The optical measurement system serves multiple functions: it monitors plasma emission spectra for process control, measures window attenuation characteristics for compensation, and provides baseline data for chamber qualification. By making the optical system multi-functional, the patent reduces the need for separate dedicated systems while maintaining comprehensive monitoring capability for improved manufacturing precision.
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 ensures consistent plasma processing across chambers by standardizing measurements and adjusting parameters based on corrected optical emission spectra, predicting and preventing deviations from acceptable dosing levels, thereby enhancing process repeatability and reducing chamber downtime.
Implementation Method 1
measuring with a spectrometer an optical intensity of radiation from a light source transmitted through an optical path containing a window
Implementation Method 2
the optical path causing attenuation to the radiation different from attenuation of the reference optical path
Data Source
AI summary
Methods for matching semiconductor processing chambers using a calibrated spectrometer are disclosed. In one embodiment, plasma attributes are measured for a process in a reference chamber and a process in an aged chamber. Using a calibrated light source, an optical path equivalent to an optical path in a reference chamber and an optical path in an aged chamber can be compared by determining a correction factor. The correction factor is applied to adjust a measured intensity of plasma radiation through the optical path in the aged chamber. Comparing a measured intensity of plasma radiation in the reference chamber and the adjusted measured intensity in the aged chamber provide an indication of changed chamber conditions. A magnitude of change between the two intensities can be used to adjust the process parameters to yield a processed substrate from the aged chamber which matches that of the reference chamber.