Plasma Bias Pulse Width Control for RF Power Reflection Reduction
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Solution Overview
Problem
Current plasma processing methods face challenges in efficiently controlling the substrate potential and plasma impedance during plasma processing, leading to suboptimal etching results and reflection of source radio-frequency power.
Innovation Solution
A plasma processing method that involves generating plasma in a chamber and applying a voltage pulse from a bias power supply to a substrate support, with the duration length of the voltage pulse changed to alter the substrate potential, and adjusting the source frequency to reduce power reflection, thereby optimizing the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a voltage pulse is applied to the substrate support to draw ions into the substrate, then the etching efficiency is improved, but the substrate potential control becomes difficult leading to power reflection
Solution Approach 1:
The patent applies periodic voltage pulses to the substrate support instead of continuous DC voltage. The pulse width is specifically controlled to be 1/10 to 1/5 of the RF cycle period, creating a periodic action that allows the plasma impedance to track the RF power supply impedance, thereby reducing power reflection while maintaining ion draw efficiency
Solution Approach 2:
The patent changes the parameter of voltage application from continuous DC to pulsed voltage with specific timing characteristics. By controlling the pulse width relative to the RF cycle period and adjusting the pulse frequency, the system optimizes both etching efficiency and power transfer, resolving the contradiction between productivity and energy loss
2Ease of operation
If the radio-frequency voltage is alternately switched between ON and OFF, then the plasma generation is controlled, but the substrate potential fluctuates causing etching uniformity issues
Solution Approach 1:
The patent applies the voltage pulse to the substrate support in advance during the RF ON period, before the RF power is switched OFF. This preliminary action establishes a stable substrate potential that prevents fluctuations during the RF switching transition, thereby maintaining etching uniformity while preserving plasma generation control
Solution Approach 2:
By synchronizing the voltage pulse application with the RF cycling at specific phase relationships (pulse width of 1/10 to 1/5 of RF period), the system creates a periodic control scheme that stabilizes substrate potential during RF switching, resolving the contradiction between operational ease and manufacturing precision
3Productivity
If a DC negative pulse voltage is applied to the substrate holding electrode, then ions are drawn into the substrate, but the substrate potential cannot be precisely controlled leading to power reflection
Solution Approach 1:
The patent replaces DC negative pulse with periodic pulsed voltage where the pulse width is precisely controlled to be 1/10 to 1/5 of the RF cycle period. This periodic action with specific timing provides precise control over substrate potential by leveraging the natural impedance matching between plasma and RF supply at these time scales, thereby improving measurement precision while maintaining ion draw efficiency
Solution Approach 2:
The system uses the inherent feedback mechanism of RF plasma impedance to automatically adjust and stabilize substrate potential. By operating at pulse widths that match the plasma response time (1/10 to 1/5 of RF period), the system achieves self-regulating potential control without requiring external feedback loops, resolving the precision control issue
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 enhances the control over substrate potential and plasma impedance, improving the efficiency of the etching process and reducing power reflection, resulting in better etching outcomes.
Implementation Method 1
applying a voltage pulse from a bias power supply to a bias electrode of the substrate support in order to draw ions from the plasma into the substrate
Implementation Method 2
generating plasma in a chamber of a plasma processing apparatus
Data Source
AI summary
A plasma processing method includes (a) generating plasma in a chamber of a plasma processing apparatus including a substrate support provided in the chamber and supporting a substrate placed thereon, (b) applying a voltage pulse from a bias power supply to a bias electrode of the substrate support in order to draw ions from the plasma into the substrate, and (c) repeating (b). In (c), a duration length of the voltage pulse is changed to change a potential of the substrate.