Multi-Zone Coil Antenna for Uniform Plasma Distribution
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Solution Overview
Problem
Inductively coupled plasma sources with multiple coils suffer from high inductance, leading to high voltage at the RF power terminal and inefficient operation, and create an M-shaped radial distribution of plasma ion density with pronounced minima at the wafer edge and center due to mutual coupling between coils.
Innovation Solution
A coil antenna design featuring inner and outer conductive lobes with specific geometries and overlapping patterns, along with variable capacitors and dual port RF power sources, to minimize inductance and compensate for nonuniform plasma ion density distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple coils are used in the antenna to control radial distribution of plasma ion density, then the ability to control plasma distribution is improved, but the inductance becomes very high causing very high voltage at the RF power terminal
Solution Approach 1:
The antenna is divided into multiple separate coils (typically three coils arranged in a triangular pattern) instead of a single continuous spiral. Each coil is electrically isolated and can be independently controlled, which reduces the total inductance while maintaining the ability to control radial plasma distribution through independent adjustment of each coil's RF power
Solution Approach 2:
Each coil segment is assigned a specific functional zone (central, intermediate, or edge region) and can be independently powered to create localized plasma density control. This allows different regions of the substrate to receive tailored plasma conditions without requiring the entire antenna to operate at high voltage
2Power
If a series capacitor is connected to reduce voltage at the RF power terminal, then the voltage is reduced, but the efficiency of the coil antenna is reduced
Solution Approach 1:
By segmenting the antenna into multiple independent coils, the total inductance is reduced to a level where voltage reduction can be achieved without requiring a series capacitor. The segmented structure inherently provides better impedance matching and lower reactive power requirements, eliminating the need for energy-lossy capacitor solutions
3Adaptability or versatility
If two or more coils are used in the antenna, then radial distribution control is improved, but an M-shaped radial distribution with pronounced minima at wafer edge and center is created due to mutual coupling
Solution Approach 1:
Each coil is assigned to control a specific radial zone (central coil for center region, intermediate coils for mid-radius regions, outer coils for edge regions). By independently adjusting the RF power to each coil, the system can compensate for mutual coupling effects and create a uniform plasma distribution across the entire substrate surface, eliminating the M-shaped density profile
Solution Approach 2:
The system dynamically adjusts the RF power level to each individual coil based on real-time plasma density requirements. This dynamic control allows the system to overcome the static mutual coupling problem by continuously optimizing the power distribution among coils to maintain uniform plasma density across the substrate
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
The design achieves a more uniform plasma ion density distribution and reduces inductance, enhancing the efficiency of the plasma reactor by optimizing the radial distribution of plasma ions.
Implementation Method 1
An inductively coupled plasma source includes one or more RF-driven inductive coils to deliver power to a plasma
Data Source
AI summary
A low inductance coil antenna for a plasma reactor has multiple radial zones of plural conductor lobes extending radially from respective RF supply and ground rings.