Electron Bias Signal Control for Selective DC Plasma Processing
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Solution Overview
Problem
In DC plasma material processing, it is challenging to precisely control the kinetic energy of free electrons to target specific energy levels of atoms at the substrate surface due to uncertainties in the surface floating potential, leading to potential damage and lack of selectivity in processing.
Innovation Solution
A DC plasma system with a biasing signal generator that generates periodic biasing signals with active, neutralization, and initialization phases, referenced to a preset floating potential, allowing precise control of the kinetic energy of free electrons to match the energy levels of atoms at the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If externally applied bias signal is used to accelerate electrons towards substrate surface, then material processing can be performed, but the electron energy does not precisely match the energy levels of atoms at the substrate surface due to unknown surface floating potential
Solution Approach 1:
The system measures the surface floating potential of the substrate and uses this measurement as feedback to adjust the bias signal. The bias signal generator modifies the applied voltage based on the measured floating potential to ensure that the electron energy precisely matches the energy levels of atoms at the substrate surface, thereby resolving the contradiction between achieving precise energy control and dealing with unknown floating potential.
2Manufacturing precision
If high energy electrons are used to process substrate surface, then material transformation can be achieved, but substrate damage occurs beyond targeted physical alterations
Solution Approach 1:
The system dynamically adjusts the energy parameter of electrons by controlling the bias signal voltage. By precisely tuning the electron energy to match specific atomic energy levels at the substrate surface, the process achieves selective material transformation while avoiding excessive energy that would cause unwanted substrate damage.
3Speed
If bias signal is applied without referencing floating potential, then electron acceleration is achieved, but energy levels do not correlate with material-specific thresholds
Solution Approach 1:
The bias signal generator uses feedback from the measured surface floating potential to adjust the acceleration voltage. This ensures that while electrons are accelerated towards the substrate, their final energy levels precisely correlate with the material-specific energy thresholds, achieving both electron acceleration and energy level correlation.
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 precise and selective control of electron energy, reducing substrate damage and improving processing accuracy by ensuring that the kinetic energy of electrons exactly targets the energy levels of atoms, enhancing material processing outcomes.
Implementation Method 1
electrons and/or ions are accelerated towards the surface of the substrate... externally applied bias signal to the substrate may impart an energy to free electrons
Implementation Method 2
DC plasma reaction chamber configured to contain a DC plasma that is generated between an anode and a cathode
Data Source
AI summary
Systems and methods for material processing using wafer scale waves of precisely controlled electrons in a DC plasma is presented. A surface floating potential of a substrate placed atop a stage in a positive column of the DC plasma is adjusted and maintained to a reference potential. A periodic biasing signal referenced to the reference potential is capacitively coupled to the stage to control a surface potential at the substrate according to: an active phase for provision of kinetic energy to free electrons in the DC plasma for activation of targeted bonds at the surface of the substrate; a neutralization phase for repelling of the free electrons from the surface of the substrate; and an initialization phase for restoring an initial condition of the surface floating potential.