RF Match Network Pulsing for Plasma Uniformity Control
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Solution Overview
Problem
Existing RF plasma processing systems struggle with non-uniform plasma densities in reaction chambers, leading to uneven etch rates and yield issues in semiconductor manufacturing, which current monitoring techniques like probes and emission spectroscopy are unable to address quickly and accurately.
Innovation Solution
Implementing high-bandwidth sensors on various components of the reaction chamber to detect and analyze RF surface waves, allowing for rapid determination of plasma density uniformity by measuring amplitudes and phases of fundamental and harmonic frequencies, and using Fourier analysis to identify plasma faults within microseconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If probes with coatings and active electronics are used to monitor plasma density, then plasma density can be inferred, but the response time is slow (milliseconds or more) and the system is not sensitive enough to resolve non-uniformity issues quickly
Solution Approach 1:
The patent replaces mechanical/electronic probes with optical emission spectroscopy system. Instead of using physical probes that require coatings and active electronics (mechanical system), the invention uses optical detection methods (spectroscopy) to measure plasma density. This substitution enables faster response times and higher sensitivity because optical signals can be detected immediately without the limitations of probe coatings, electronics response, or physical exposure constraints.
Solution Approach 2:
The patent introduces optical emission spectroscopy as an intermediary measurement method. Rather than directly measuring plasma properties with probes, the system uses emitted light from the plasma as an intermediary signal that can be analyzed to infer plasma density. This intermediary approach allows non-intrusive, high-speed measurement without the limitations of direct probe contact.
2Measurement precision
If emission spectroscopy is used to determine plasma density profile, then plasma density can be measured, but the system requires multiple lines of sight and complicated analysis, making it costly and not fast enough
Solution Approach 1:
The patent makes the emission spectroscopy system multi-functional by using it for both spatially-resolved plasma density measurements and uniformity assessment. The same optical detection system analyzes emission spectra to determine both the magnitude and distribution of plasma density, eliminating the need for separate measurement systems and reducing overall complexity.
Solution Approach 2:
The patent segments the plasma measurement into discrete spectral lines that can be independently analyzed. By focusing on specific emission lines from particular plasma species, the system simplifies the analysis complexity while maintaining measurement precision. Each spectral line provides information about specific plasma conditions, allowing targeted analysis rather than attempting to interpret the entire spectrum at once.
3Reliability
If conventional monitoring techniques are used, then plasma density can be measured, but the systems are not fast enough to effectively resolve non-uniformity issues in real-time
Solution Approach 1:
The patent implements a feedback control system where emission spectroscopy measurements of plasma density uniformity are continuously monitored and fed back to adjust processing parameters in real-time. This closed-loop feedback enables the system to detect and correct non-uniformity issues during processing, maintaining reliable plasma density control while operating at high processing speeds that would be impossible with slower conventional monitoring techniques.
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
Enables prompt detection and correction of plasma non-uniformity, ensuring consistent etch rates and minimizing yield loss by rapidly adjusting processing conditions to maintain plasma density uniformity.
Implementation Method 1
sensors having a bandwidth greater than about 10 times the frequency of the highest frequency RF generator connected to that electrode... for detecting RF surface waves on an electrode
Implementation Method 2
Fourier analysis circuitry for analyzing the RF signals sensed by the sensors to determine amplitudes and phases of fundamental and harmonic frequencies
Data Source
AI summary
A method of controlling a radio frequency processing system, the method including determining an end time of a radio frequency pulse; stopping a load applied to the radio frequency processing system based on the end time of the radio frequency pulse; adjusting an additional load having a predetermined impedance applied to the radio frequency processing system in response to the determined end time; determining a start point of a second radio frequency pulse; and stopping the additional load before the second radio frequency pulse occurs.