Pulsed Bidirectional RF Source Load Impedance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF power systems face challenges in accurately controlling ion energy distribution and directivity in plasma etching processes, particularly in three-dimensional etching and other precision applications, due to varying impedance loads and non-uniform power distribution across wafers, which affects the orthogonality and precision of ion incidence.
Innovation Solution
A RF power system comprising a master and auxiliary RF generator, where the auxiliary generator is controlled by a processor to adjust its phase and DC rail voltage based on electrical characteristics, ensuring phase alignment and optimal power delivery to achieve precise ion control, with a variable resistive load for dissipating reflected energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous wave RF signal is applied to the load, then the power delivery is stable, but the ability to control ion energy distribution and directivity is limited
Solution Approach 1:
The patent applies pulsed RF signals instead of continuous wave signals to the load. The RF generator delivers power in controlled pulses with specific duty cycles, frequencies, and phases. This periodic action enables precise control over ion energy distribution and directivity during plasma etching, while maintaining stable average power delivery through regulated pulse parameters.
2Ease of operation
If the RF signal amplitude is varied to change power, then the power control is simple, but the impedance matching deteriorates
Solution Approach 1:
The patent employs multiple parameters for RF signal control including amplitude, frequency, phase, and pulse duty cycle. By varying frequency and phase in addition to amplitude, the system maintains impedance matching across different power levels. The controller adjusts these parameters dynamically to optimize both power delivery and impedance matching conditions.
Solution Approach 2:
The system uses dynamic parameter adjustment where the RF generator continuously adapts frequency, phase, and amplitude based on real-time impedance conditions. This dynamic control allows the system to maintain optimal impedance matching while delivering variable power levels, rather than using static amplitude control.
3Device complexity
If a single RF generator is used, then the device complexity is low, but the precision of ion incidence control is insufficient
Solution Approach 1:
The patent divides the RF power delivery system into multiple independent RF generators, each connected to different electrodes (source electrode and bias electrode). This segmentation allows independent control of source power and bias power, enabling precise control over ion energy distribution and incidence angles. Each generator can be optimized for its specific function while working together to achieve overall process precision.
4Reliability
If the RF frequency is varied to improve impedance match, then the impedance matching improves, but the control of ion energy distribution becomes complex
Solution Approach 1:
The system incorporates feedback control where the controller monitors impedance conditions and automatically adjusts RF frequency, phase, and amplitude parameters to maintain optimal impedance matching. This closed-loop feedback mechanism simplifies the control process by automating the complex adjustments needed for frequency variation, reducing the burden on operators while maintaining precise impedance control.
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 enhances the precision and orthogonality of ion incidence, improving the accuracy of plasma etching processes by effectively managing impedance matching and power distribution, thereby meeting stringent tolerances in three-dimensional etching and other applications.
Implementation Method 1
a variable resistive load for dissipating reflected energy
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A radio frequency power system includes a master RF generator and an auxiliary RF generator, wherein each generator outputs a respective RF signal. The master RF generator also outputs a RF control signal to the auxiliary RF generator, and the RF signal output by the auxiliary RF generator varies in accordance with the RF control signal. The auxiliary RF generator receives sense signals indicative of an electrical characteristic of the respective RF signals output by the master RF generator and the auxiliary RF generator. The auxiliary RF generator determines a phase difference between the RF signals. The sensed electrical characteristics and the phase are used independently or cooperatively to control the phase and amplitude of the RF signal output by the auxiliary RF generator. The auxiliary generator includes an inductive clamp circuit that returns energy reflected energy back from a coupling network to a variable resistive load.