Dual Level RF Pulsing Frequency Tuning
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Solution Overview
Problem
Conventional methods for frequency tuning in semiconductor processing chambers using dual level pulsed RF power are inadequate due to the slow speed of variable capacitor movements and insufficient tuning at every state change during high-frequency dual level pulsing processes, leading to inefficient energy coupling and potential damage from charge accumulation.
Innovation Solution
Implement a method that alternates between two different non-zero power levels and frequencies in a process chamber, adjusting frequencies to achieve desired impedance and minimize reflected power, with stored last known tuned values used for initial frequency settings during power level transitions, allowing for fast and reliable frequency tuning between plasma on states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable capacitors are used for frequency tuning in dual level pulsing, then frequency can be adjusted between high and low states, but the tuning speed is too slow to keep up with high frequency pulsing
Solution Approach 1:
The patent replaces the mechanical variable capacitor system with an electronic frequency synthesis system. Instead of mechanically adjusting capacitors to change frequency, the system uses a phase-locked loop (PLL) with a voltage-controlled oscillator (VCO) and digital frequency control. This substitution of mechanical adjustment with electronic control enables tuning speeds that can keep up with high-frequency dual-level pulsing operations.
Solution Approach 2:
The patent changes the fundamental parameter control method from mechanical capacitor position to electronic frequency synthesis parameters. The PLL system controls the VCO frequency through digital division ratios and reference frequencies, allowing rapid parameter changes without mechanical movement. This enables the system to switch between high and low frequency states at speeds compatible with dual-level pulsing requirements.
2Reliability
If dual level pulsing is implemented to prevent charge accumulation damage, then device reliability improves, but the complexity of frequency tuning increases
Solution Approach 1:
The patent implements a universal frequency control system that handles both high and low power states through a single PLL-based frequency synthesis architecture. The same VCO and PLL circuitry serve dual purposes: generating frequencies for both pulsing levels and providing automatic frequency control. This multi-functionality reduces overall system complexity compared to having separate tuning mechanisms for each power state.
Solution Approach 2:
The patent incorporates feedback control through the phase-locked loop system. The PLL continuously monitors and adjusts the VCO frequency to maintain accurate frequency synthesis for both high and low power states. This feedback mechanism automatically compensates for frequency drift and ensures precise frequency control without requiring complex manual tuning procedures for each pulsing state.
3Loss of energy
If frequency tuning is performed at every state change in dual level pulsing, then energy coupling efficiency improves, but the response time becomes insufficient due to slow capacitor movement
Solution Approach 1:
The patent replaces mechanical capacitor adjustment with electronic frequency synthesis that can change frequencies instantaneously. The PLL-based system can switch between frequency states in microseconds or less, compared to the slow mechanical movement of variable capacitors. This enables frequency tuning to keep pace with every state change in dual-level pulsing, minimizing reflected power without time loss.
Solution Approach 2:
The patent implements preliminary frequency preparation by maintaining the frequency synthesis system in a ready state with pre-configured division ratios and reference frequencies for both high and low power states. When a state transition is commanded, the system can quickly switch to the appropriate frequency without requiring time-consuming mechanical adjustment. This preliminary preparation eliminates tuning response delays.
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 efficient frequency tuning in dual level pulsed power processes, reducing reflected power and maximizing energy coupling, thus preventing damage from charge accumulation and ensuring reliable semiconductor processing.
Implementation Method 1
the first frequency is adjusted to a second frequency to achieve a desired impedance at the first pulsed power between the RF power source and a load
Implementation Method 2
the power from a radio frequency (RF) power source may be coupled through a dynamically tuned matching network to an antenna or electrode within the reactor
Implementation Method 3
The pulsed power is coupled from the antenna or electrode to process gases within the reactor to form a plasma
Data Source
AI summary
Methods and apparatus for frequency tuning in process chambers using dual level pulsed power are provided herein. In some embodiments, a method for frequency tuning may include providing a first pulsed power at a first frequency while the first frequency is adjusted to a second frequency, wherein the first frequency is a last known tuned frequency at the first pulsed power, storing the second frequency as the last known tuned frequency at the first pulsed power, providing a second pulsed power at a third frequency while the third frequency is adjusted to a fourth frequency, wherein the first pulsed power and the second pulsed power are different and non-zero, and wherein the third frequency is a last known tuned frequency at the second pulsed power, and storing the fourth frequency as the last known tuned frequency at the second pulsed power.