Mid-Frequency Twin Magnetron Sputtering for Thin Film Batteries
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Solution Overview
Problem
Conventional sputtering processes for depositing thick cathode films in thin film batteries are economically inefficient due to slow deposition rates and often result in plasma arcing, which affects film quality, and require impedance matching that can be difficult to optimize.
Innovation Solution
A mid-frequency twin magnetron sputtering process is used to deposit lithium cobalt oxide films with higher deposition rates and reduced arcing, employing a dual-magnetron arrangement with a mid-frequency AC power source to stabilize the plasma and increase deposition throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sputtering processes are used to deposit cathode films, then film quality can be maintained, but deposition rates are slow making it economically difficult to manufacture thick cathode films
Solution Approach 1:
The patent changes the operating frequency parameter from conventional RF (13.56 MHz) to mid-frequency (100 kHz to 10 MHz range). This parameter change enables higher power coupling efficiency and higher deposition rates while maintaining plasma stability and film quality, resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent employs a dual magnetron configuration where the two magnetrons can be operated independently or in coordination. This dynamic setup allows optimization of deposition rate while maintaining plasma stability through coordinated control, achieving both high productivity and film quality
2Productivity
If sputter deposition rates are increased to improve productivity, then plasma arcing occurs which affects the quality of deposited films
Solution Approach 1:
By changing from RF to mid-frequency operation, the system achieves better power coupling and more stable plasma at higher deposition rates. The mid-frequency range optimizes the balance between power transfer efficiency and plasma stability, preventing arcing while maintaining high productivity
Solution Approach 2:
The patent implements impedance matching networks that provide feedback control to maintain optimal power coupling. This feedback mechanism adjusts operating parameters in real-time to prevent plasma arcing while maximizing deposition rate, ensuring both reliability and productivity
3Reliability
If impedance matching networks are added to improve plasma stability, then device complexity increases and it becomes difficult to identify correct impedance matching parameters
Solution Approach 1:
The mid-frequency operation inherently provides better impedance matching characteristics compared to RF. This parameter change reduces the complexity of impedance matching networks required, as the mid-frequency range naturally offers improved power coupling and reduced sensitivity to load variations
Solution Approach 2:
The dual magnetron system with mid-frequency operation exhibits self-regulating plasma stability characteristics. The system naturally tends toward stable operation at the optimized mid-frequency, reducing the need for complex external impedance matching control mechanisms
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 process achieves higher deposition rates and improves film quality by reducing arcing and impedance matching issues, allowing for the production of thicker cathode films with increased energy density and faster charging and discharging rates.
Implementation Method 1
A mid-frequency twin magnetron sputtering process is used to deposit lithium cobalt oxide films with higher deposition rates and reduced arcing
Implementation Method 2
employing a dual-magnetron arrangement with a mid-frequency AC power source to stabilize the plasma and increase deposition throughput
Data Source
AI summary
A thin film battery manufacturing method is provided for deposition of lithium metal oxide films onto a battery substrate. The films are deposited in a sputtering chamber having a plurality of sputtering targets and magnetrons. The sputtering gas is energized by applying a voltage bias between a pair of the sputtering targets at a frequency of between about 10 and about 100 kHz. The method can provide a deposition rate of lithium cobalt oxide of between about 0.2 and about 4 microns/hr with improved film quality.