Inductive Coupling Antenna Impedance Control for Plasma Uniformity
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Solution Overview
Problem
Current plasma processing devices face challenges in generating high-density plasma over large areas with uniform distribution, while maintaining low RF potential at the antenna feeding portion to prevent dielectric window abrasion and foreign matter generation, especially as substrate sizes increase and high-frequency power is applied.
Innovation Solution
A plasma processing device with a vacuum container, a lower electrode, and an inductive coupling antenna where one end is connected to a high-frequency power source via a matching circuit and the other end is open, featuring an impedance adjustment circuit that can adjust the reactance component from capacitive to inductive load, and using a spiral-shaped coil antenna with multiple turns to enhance plasma density and uniformity, along with a variable capacitor for flexible plasma distribution control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-frequency power is increased to generate high-density plasma over large area substrates, then plasma density and processing productivity are improved, but RF potential at the antenna feeding portion increases causing dielectric window abrasion and foreign matter generation
Solution Approach 1:
The patent changes the electrical parameter configuration of the antenna system by introducing an impedance adjustment circuit that can switch between capacitive and inductive coupling modes. This allows optimization of the RF potential distribution at the feeding portion while maintaining high plasma density, thereby preventing dielectric window abrasion even at high power levels
Solution Approach 2:
The impedance adjustment circuit acts as an intermediary between the RF power source and the antenna. It controls the reactance component to adjust the RF potential at the feeding portion, serving as a mediator that decouples the relationship between high power input and high potential at the dielectric window interface
2Area of stationary object
If antenna length is increased to cover large area substrates, then processing area is improved, but inductance increases requiring higher RF potential which exacerbates ion attack on dielectric window
Solution Approach 1:
The patent changes the electrical parameter configuration by using an impedance adjustment circuit that can provide inductive reactance compensation. This allows long antennas to be used for large area processing while the circuit compensates for the increased inductance, keeping the RF potential at the feeding portion low and reducing ion attack on the dielectric window
3Device complexity
If capacitively coupled plasma processing is used, then device simplicity is maintained, but plasma density is low resulting in long processing time and reduced productivity
Solution Approach 1:
The patent introduces a dynamically adjustable impedance circuit that can change its reactance component between capacitive and inductive modes. This dynamic adjustment enables the system to achieve high-density plasma characteristics similar to inductive coupling while maintaining the basic simplicity of the capacitive coupled device structure
Solution Approach 2:
By changing the electrical parameter configuration through the impedance adjustment circuit, the system transitions from low-density capacitive coupling to high-density plasma generation. The circuit modifies the effective impedance seen by the RF power source, enabling high plasma density without fundamentally changing the device architecture
4Productivity
If inductive coupling antenna is used to generate high-density plasma, then plasma density and productivity are improved, but RF potential at feeding portion increases causing foreign matter generation
Solution Approach 1:
The impedance adjustment circuit serves as an intermediary that controls the RF potential at the antenna feeding portion. It mediates between the high power input required for high productivity and the need to keep potential low to prevent dielectric window damage and foreign matter generation
Solution Approach 2:
The patent changes the electrical parameters by adjusting the reactance component of the impedance circuit. This allows optimization of the power transfer efficiency to maintain high plasma density for productivity while simultaneously controlling the RF potential to minimize ion attack and foreign matter generation
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 solution enables the generation of high-density, uniform plasma over large areas with reduced RF potential at the antenna feeding portion, minimizing dielectric window abrasion and foreign matter generation, and allowing for adjustable plasma distribution and density according to various processing conditions.
Implementation Method 1
an antenna which is arranged to face the lower electrode to form inductive coupling
Implementation Method 2
a reactance component of a combined impedance by the impedance adjustment circuit is adjustable from a capacitive load to an inductive load
Data Source
AI summary
The present invention provides a plasma processing device including a vacuum container that has controllable internal pressure, gas supply means, an electrode that is provided in the vacuum container and has an upper surface on which a substrate is placed, and an antenna that is arranged to face the electrode to form inductive coupling, in which the antenna that is configured to form the inductive coupling includes one end connected to a high-frequency power source via a matching circuit, and the other end that is an open end, a length of the antenna is less than ½λ of a wavelength (λ) of an RF frequency, an impedance adjustment circuit connected in parallel to the antenna is connected to an RF feeding side of the antenna, and a reactance component of a combined impedance by the impedance adjustment circuit is adjustable from a capacitive load to an inductive load with respect to the RF frequency supplied to the antenna.