Shared-Clock RF Power Supply Control for Lower IMD Reflection
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Solution Overview
Problem
Existing high-frequency power supply systems face challenges in reducing inter-modulation distortion (IMD) due to asynchronous frequency modulation control, leading to increased reflected wave power and inefficient power delivery to plasma reactors in semiconductor manufacturing.
Innovation Solution
A high-frequency power supply system with a matching device providing a common system clock to both high-frequency and low-frequency power supplies, allowing synchronous frequency modulation control, thereby minimizing IMD and ensuring accurate power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If frequency modulation control is performed using separate clocks in HF and LF power supplies, then each power supply can operate independently, but the control becomes asynchronous leading to increased IMD and reflected wave power
Solution Approach 1:
The patent merges the clock sources by providing a common system clock from the matching device to both the HF power supply (first power supply) and LF power supply (second power supply). This ensures synchronous operation of frequency modulation control while maintaining independent power supply functionality, thereby reducing IMD and reflected wave power.
2Adaptability or versatility
If impedance matching is achieved using motor-operated variable elements, then the matching device can adapt to plasma impedance changes, but the response speed is insufficient to follow rapid plasma impedance variations
Solution Approach 1:
The patent replaces motor-operated mechanical variable elements with electronically controlled variable elements that can be adjusted at high speeds through frequency modulation. This electronic control system responds rapidly to plasma impedance changes without the mechanical inertia limitations, achieving both adaptability and fast response.
3Reliability
If the HF power supply phase and power are adjusted based on LF trigger signals, then IMD can be reduced, but synchronization issues prevent correct offset adjustment and impedance computation
Solution Approach 1:
The patent implements a feedback mechanism where the matching device provides a system clock to both power supplies based on detected plasma impedance conditions. This synchronized feedback ensures that HF phase and power adjustments are made at precisely timed intervals coordinated with LF cycles, eliminating synchronization issues and enabling accurate impedance computation and IMD reduction.
Data Source
AI summary
To simplify a process of suppressing an increase in a reflected wave power caused by IMD, provided is a high-frequency power supply system for providing a high-frequency power to a load, including: a first power supply for supplying a first high-frequency power to the load; a second power supply for supplying a second high-frequency power to the load; and a matching device. The matching device provides a system clock to each of the first power supply and the second power supply. The second power supply outputs a second high-frequency voltage at a control period determined based on the system clock provided from the matching device. The first power supply outputs a first high-frequency voltage obtained by frequency modulation of a fundamental wave signal having a first fundamental frequency and through amplification, in each control period determined based on the system clock provided from the matching device.