Weighted RF Plasma Generator for Wide Dynamic Range Pulsing
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Solution Overview
Problem
Existing RF bias generators face limitations in providing high power over a wide dynamic range and improved power density, particularly in the fabrication of high aspect ratio features in semiconductor devices, with conventional PWM and Chireix drive schemes being inefficient and limited to approximately 20 dB dynamic range and minimum pulse widths of 20 RF cycles.
Innovation Solution
A RF power generator system with a fixed power generation section and a weighted power generation section, utilizing series-connected power amplifiers and transformers, along with a harmonic filter, to achieve higher power output and improved dynamic range, capable of generating pulse waveforms with narrower pulse widths and lower duty cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional PWM and Chireix drive schemes are used, then the system is simple to operate, but the dynamic range is limited to approximately 20 dB and minimum pulse widths are limited to 20 RF cycles
Solution Approach 1:
The power amplifier is divided into multiple parallel channels, each capable of being independently controlled. This segmentation allows the system to achieve higher dynamic range by selectively activating different channels based on the required output power level, while maintaining operational simplicity through centralized control logic.
Solution Approach 2:
The system implements dynamic control of pulse width and duty cycle by adjusting the activation timing and duration of individual power amplifier channels. This enables the generation of narrow pulse widths below 20 RF cycles and variable duty cycles, adapting the system performance to specific process requirements.
2Power
If higher power output is achieved, then the power density increases, but the efficiency decreases with conventional drive schemes
Solution Approach 1:
The system activates only the necessary number of power amplifier channels required to achieve the desired output power level, rather than operating all channels at full capacity. This partial action approach maintains high efficiency by avoiding unnecessary energy consumption while still delivering the required power output for high aspect ratio etching.
Solution Approach 2:
The system changes operational parameters including pulse width, duty cycle, and channel activation patterns to optimize the balance between power output and efficiency. By dynamically adjusting these parameters, the system achieves high power density when needed while maintaining efficient operation during lower power demands.
3Manufacturing precision
If narrow pulse widths below 20 RF cycles are generated, then the etch rate and feature control improve, but the minimum pulse width limitation of conventional systems prevents this
Solution Approach 1:
The segmented power amplifier architecture with independently controllable channels enables precise control of pulse timing and duration. This segmentation allows the system to generate narrow pulses below 20 RF cycles by selectively activating channels for precise time intervals, achieving the required manufacturing precision for high aspect ratio feature control.
Solution Approach 2:
The system incorporates feedback control mechanisms that monitor the actual pulse width and power output, adjusting channel activation timing to achieve the target pulse duration. This feedback ensures that narrow pulse widths below 20 RF cycles are generated with high precision, enabling accurate etch rate control and feature dimensional accuracy.
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 system enables efficient generation of RF power with a dynamic range exceeding 20 dB and pulse widths below 20 RF cycles, meeting the power requirements for high aspect ratio etching in semiconductor fabrication, enhancing etch rate and feature control.
Implementation Method 1
a voltage across the transformer of each weighted power amplifier module is a fraction of the first voltage
Data Source
AI summary
A RF power generator having a fixed power generation section. The fixed power generation section includes a first plurality of power amplifiers each configured to receive a supply voltage and to output a respective first voltage. The RF power generator also includes a weighted power generation section including a plurality of weighted power amplifier modules. Each weighted power amplifier module includes a weighted power amplifier and an associated transformer. Each weighted power amplifier of the weighted power amplifier module receives a respective weighted supply voltage. The voltage across the transformer of each weighted power amplifier module is a fraction of the first voltage.