RF Pulse Matching for Plasma Stability in Semiconductor Etching
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Solution Overview
Problem
Existing semiconductor etching processes using continuous wave RF energy suffer from plasma-induced damage and instability, which limits etching selectivity and process adjustability, especially under 20 nm integrated circuit requirements.
Innovation Solution
A radio frequency (RF) pulse matching method and device that synchronize and control the pulse time sequences of upper and lower RF power supplies through matching devices, reducing impedance fluctuations and mutual interference, thereby stabilizing plasma and enhancing matching speed and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous wave RF energy is applied for plasma generation, then plasma can be maintained continuously, but plasma-induced damage increases and process stability deteriorates
Solution Approach 1:
The patent applies periodic pulsed RF action instead of continuous wave RF energy. The RF power is delivered in controlled pulses with specific duty cycles and frequencies, allowing plasma to be generated and maintained while periodically reducing energy input to minimize plasma-induced damage to the substrate. This periodic modulation resolves the contradiction by enabling continuous plasma presence while limiting harmful cumulative effects.
Solution Approach 2:
The system dynamically adjusts RF power delivery parameters including pulse width, duty cycle, and frequency based on real-time plasma conditions and process requirements. This dynamic control allows optimization of plasma density and reactivity while managing plasma-induced damage, improving process stability without sacrificing plasma quality.
2Productivity
If RF power is increased to improve etching rate, then productivity increases, but plasma instability and impedance fluctuations worsen
Solution Approach 1:
By delivering RF power in pulsed manner rather than continuously, the system can achieve higher peak powers during pulse periods to maintain high etching rates, while the off-periods allow plasma to stabilize and impedance to reset. This periodic delivery method decouples the relationship between average power and peak power, enabling high productivity without compromising plasma stability.
Solution Approach 2:
The system preemptively reduces RF power during off-periods of the pulse cycle to prevent excessive plasma density buildup and impedance fluctuations before they occur. This preliminary anti-action prevents plasma instability rather than correcting it after occurrence, maintaining stable plasma conditions throughout the etching process even at high productivity levels.
3Manufacturing precision
If pulse width is extended to improve etching uniformity, then manufacturing precision improves, but process adjustment window and selectivity are reduced
Solution Approach 1:
The system dynamically adjusts multiple pulse parameters including pulse width, duty cycle, frequency, and peak power independently to achieve optimal etching uniformity for different patterns and materials. This multi-parameter dynamic control provides a large process adjustment window, allowing fine-tuning of etching characteristics while maintaining manufacturing precision across varying process conditions.
Solution Approach 2:
The patent utilizes changes in multiple RF pulse parameters (pulse width, duty cycle, frequency, power level) to control plasma properties and etching characteristics. By independently adjusting these parameters, the system achieves precise control over etching uniformity while maintaining a wide process window for adapting to different materials, patterns, and desired outcomes, thus improving both manufacturing precision and adaptability.
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 RF pulse matching method and device improve the stability and speed of plasma matching, reducing plasma-induced damage and enhancing etching selectivity and process adjustability, particularly beneficial for advanced semiconductor processes.
Implementation Method 1
A radio frequency (RF) power supply provides RF energy to a chamber to ionize a special gas in a high vacuum state to generate a plasma including active particles
Implementation Method 2
presetting a matching threshold and initializing a pulse count value to a pulse reference value and loading pulse power to an upper electrode and a lower electrode... causing of the upper matching device to perform matching on the upper RF power supply or the lower matching device to perform matching on the lower RF power supply
Data Source
AI summary
A radio frequency (RF) pulse matching method includes presetting a matching threshold and initializing a pulse count value to a pulse reference value and loading pulse power to an upper electrode and a lower electrode. The upper electrode includes an upper RF power supply and a corresponding upper matching device. The lower electrode includes a lower RF power supply and a corresponding lower matching device. The method further includes collecting a pulse signal of the pulse power and calculating a matching parameter according to the pulse signal, determining a magnitude of the matching parameter relative to the matching threshold and resetting the pulse count value, causing the upper matching device to perform matching on the upper RF power supply or the lower matching device to perform matching on the lower RF power supply, and repeating processes until the upper RF power supply and the lower RF power supply are matched.