Sector Shunt Circuits for Plasma Density Uniformity Control
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Solution Overview
Problem
Current RF plasma processing systems face challenges in controlling plasma density uniformity within reaction chambers, leading to non-uniform etch rates and yield issues in semiconductor manufacturing, as existing monitoring techniques are not sensitive or fast enough to detect deviations in plasma density in real-time.
Innovation Solution
The implementation of high-bandwidth sensors mounted on various components of the RF plasma processing system, including electrodes and pedestals, to detect and analyze RF surface waves, allowing for rapid determination of plasma density uniformity and immediate corrective actions to prevent non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If emission spectroscopy is used to determine plasma density profile, then plasma density uniformity can be measured, but the system requires multiple lines of sight and complicated analysis, making it not sensitive or fast enough
Solution Approach 1:
The patent extracts the essential measurement function from complex emission spectroscopy systems by using simple photodetectors positioned to detect light emitted from specific regions of the plasma. Instead of requiring multiple lines of sight and complicated analysis, the system uses strategically placed detectors that directly measure plasma density through light intensity, eliminating the complexity while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical and analytical complexity of emission spectroscopy with an optical detection system using photodetectors. The system substitutes complicated spectral analysis with direct optical intensity measurement, achieving faster response times and simpler implementation while maintaining sensitivity to plasma density variations
2Measurement 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)
Solution Approach 1:
The patent replaces probes with coatings and active electronics with a passive optical detection system using photodetectors. This substitution eliminates the slow response inherent in coated probes that require thermal or chemical equilibration, achieving near-instantaneous response by directly detecting light emission from the plasma without physical contact or complex electronics
Solution Approach 2:
The patent introduces light as an intermediary between the plasma and the detection system. Instead of directly measuring plasma properties with slow-responding probes, the system uses light emission as a mediator that carries plasma density information to photodetectors, enabling fast, non-contact measurement with millisecond or microsecond response times
3Speed
If high-bandwidth sensors are mounted on electrodes and pedestals to detect RF surface waves, then rapid detection of plasma density deviations is enabled, but the device complexity increases
Solution Approach 1:
The patent makes the electrodes and pedestals serve dual functions: their primary function for plasma generation and support, and a secondary function as mounting structures for high-bandwidth sensors. The sensors detect RF surface waves that naturally propagate on these components, eliminating the need for separate sensor mounting structures and reducing overall system complexity while enabling rapid plasma density monitoring
4Reliability
If non-uniform plasma density is not detected quickly, then irreversible wafer processing errors occur, but fast detection systems are costly to implement
Solution Approach 1:
The patent uses inexpensive photodetectors and simple optical components instead of costly fast-response plasma diagnostic equipment. The system achieves rapid detection capability through clever use of naturally occurring RF surface waves and light emission, avoiding the need for expensive specialized sensors while maintaining the ability to detect plasma density deviations before they cause wafer defects
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 solution enables prompt detection of plasma density deviations, ensuring uniformity and preventing irreversible wafer processing errors, thereby improving the yield and quality of semiconductor fabrication.
Implementation Method 1
Each sensor has a bandwidth greater than about 10 times the frequency of the highest frequency RF generator connected to that electrode and is disposed on a surface of the electrode
Data Source
AI summary
A radio frequency plasma processing system including a reaction chamber, an electrode having an electrode symmetry axis, the electrode disposed in the reaction chamber, and a plurality of plates, each having an electrically conducting layer, disposed in the reaction chamber azimuthally with respect to the electrode symmetry axis around a perimeter of the electrode at a gap from the electrode surface, each of the plurality of plates connected to an electrical ground through a variable reactance circuit.