Multi-Frequency RF Plasma Control for Ion Parameter Independence
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Solution Overview
Problem
Existing semiconductor device fabrication technologies face challenges in forming structures with deep openings and high aspect ratios between insulated conductor layers, as they struggle to independently control plasma ion density, ion energy distribution, and ion dissociation.
Innovation Solution
A method involving the use of at least three RF power sources of different frequencies to independently control ion energy distribution, ion density, and ion dissociation by adjusting the power levels and applying a magnetic field, allowing for simultaneous and separate adjustments without limiting one another.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional single or dual RF power sources are used, then device fabrication processes can be performed, but independent control of ion density, ion energy distribution, and ion dissociation is not achieved
Solution Approach 1:
The plasma processing system is segmented into multiple independent RF power sources operating at different frequencies (e.g., 13.56 MHz, 27.12 MHz, 40.68 MHz). Each frequency component independently controls specific plasma parameters: lower frequencies primarily control ion energy distribution, while higher frequencies control ion density and dissociation. This segmentation enables independent adjustment of each parameter without mutual interference.
Solution Approach 2:
The invention adds the frequency dimension to the traditional power control approach. Instead of controlling all plasma parameters through a single power level variable, the system utilizes multiple frequency dimensions, where each frequency component contributes differently to plasma physics processes. This dimensional expansion transforms a single-degree-of-freedom control system into a multi-degree-of-freedom system.
2Productivity
If ion density is increased to improve deposition rate, then productivity increases, but ion energy distribution and dissociation cannot be independently optimized
Solution Approach 1:
The system changes the frequency parameter of RF power sources to independently control different plasma characteristics. By adjusting the power levels at specific frequencies (e.g., increasing 27.12 MHz power for higher ion density while maintaining 13.56 MHz power for controlled ion energy), the system achieves both high deposition rates and precise structure formation without the traditional trade-off.
3Adaptability or versatility
If multiple RF power sources of different frequencies are used, then independent control of plasma parameters is achieved, but system complexity increases
Solution Approach 1:
Multiple RF power sources operating at different frequencies are integrated into a single plasma reactor system, with each frequency component serving multiple functions. For example, the 13.56 MHz source contributes to both ionization and heating, while the 27.12 MHz source provides enhanced ion density control. This multi-functionality reduces the need for additional specialized equipment.
Solution Approach 2:
The patent introduces magnetic field coils as intermediary components that work in conjunction with the multi-frequency RF power sources. The magnetic field acts as a mediator to enhance plasma confinement and control ion transport, providing an additional control mechanism that complements the RF frequency control and reduces the complexity of purely RF-based control systems.
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 approach enables precise control over ion energy distribution, ion density, and ion dissociation, enhancing the capability to form complex structures with deep openings and high aspect ratios in semiconductor devices.
Implementation Method 1
coupling RF power from at least three RF power source of three respective frequencies to plasma in the reactor
Implementation Method 2
coupling RF power from at least three RF power source of three respective frequencies to plasma in the reactor
Implementation Method 3
setting ion dissociation and ion density by selecting a ratio between the power levels of a remaining one of the three RF power sources and an applied magnetic field
Data Source
AI summary
A method of processing a workpiece in a plasma reactor includes coupling RF power from at least three RF power source of three respective frequencies to plasma in the reactor, setting ion energy distribution shape by selecting a ratio between the power levels of a first pair of the at least three RF power sources, and setting ion dissociation and ion density by selecting a ratio between the power levels of a remaining one of the three RF power sources and an applied magnetic field. The three respective frequencies can be an LF frequency, an HF frequency and a VHF frequency, wherein the first pair corresponds to the LF and HF frequencies and the second pair corresponds to the HF and VHF frequencies.