Segmented RF Antenna for Plasma Density Control
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Solution Overview
Problem
Conventional inductively coupled plasma processing apparatuses face challenges in achieving uniform plasma density distribution, particularly in the diametrical direction, especially when dealing with large-diameter plasmas or low-pressure processes, due to issues with voltage drop and wavelength effects, which complicates the control of plasma density profiles.
Innovation Solution
The apparatus employs an RF antenna segmented into inner, intermediate, and outer coils with gaps in a radial direction, connected in parallel, and equipped with variable capacitors to adjust electrostatic capacitances, allowing for precise control of plasma density distribution by varying the currents in each coil, thereby achieving uniformity and flexibility in plasma profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional single RF antenna is used, then the apparatus structure is simple, but the plasma density uniformity on the substrate is insufficient
Solution Approach 1:
The RF antenna is divided into multiple independent coil units (first coil unit, second coil unit, third coil unit) with different diameters. Each coil unit can be controlled independently through separate impedance matching circuits, allowing precise control of plasma density distribution across different radial regions to achieve uniform plasma density on the substrate.
2Manufacturing precision
If multiple coil units with different diameters are used, then plasma density uniformity is improved, but the control complexity increases due to voltage drop and wavelength effects
Solution Approach 1:
Impedance matching circuits are introduced as intermediary components between the power supply and each coil unit. These circuits independently control the impedance of each coil unit, simplifying the control of plasma density distribution by decoupling the interactions between coils of different diameters and eliminating voltage drop and wavelength effects.
3Adaptability or versatility
If the RF antenna is divided into multiple coil units, then plasma profile control flexibility is enhanced, but the apparatus complexity and cost increase
Solution Approach 1:
The antenna system is segmented into multiple coil units, each capable of independent impedance control. This segmentation enables flexible adjustment of plasma profiles by independently tuning each coil unit's impedance to optimize plasma density distribution for different processing requirements.
Solution Approach 2:
The impedance of each coil unit is made dynamically adjustable through impedance matching circuits. This dynamic control allows the system to adapt to different plasma processing conditions and achieve optimal plasma density uniformity across various operating parameters and substrate types.
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 configuration effectively and easily controls plasma density distribution within the donut-shaped plasma, ensuring proper profiles even at low pressures or for large-diameter plasmas, enhancing the uniformity and reproducibility of plasma processes.
Implementation Method 1
A high frequency AC magnetic field having magnetic force lines is generated around the RF antenna by a high frequency current flowing in the RF antenna. The magnetic force lines of the high frequency AC magnetic field are transmitted to the processing space within the chamber via the dielectric window. As the RF magnetic field of the high frequency AC magnetic field changes with time, an inductive electric field is generated in an azimuth direction within the processing space. Then, electrons accelerated by this inductive electric field in the azimuth direction collide with molecules or atoms of the processing gas so as to be ionized.
Data Source
AI summary
A plasma processing method for performing a plasma process on a processing target substrate is provided. The plasma processing method includes: segmenting a RF antenna into an inner coil, an intermediate coil, and an outer coil with gaps therebetween in a radial direction, respectively, the inner coil, the intermediate coil and the outer coil being electrically connected to one another in parallel between a first node and a second node; providing a variable intermediate capacitor and a variable outer capacitor between the first node and the second node, the variable intermediate capacitor being electrically connected in series to the intermediate coil, the variable outer capacitor being electrically connected in series to the outer coil, no reactance device being connected to the inner coil; and controlling plasma density distribution on the processing target substrate by selecting or variably adjusting electrostatic capacitances of the intermediate capacitor and the outer capacitor.