Pulsed Electric Field Control of Plasma Ion Composition
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Solution Overview
Problem
Current plasma processing technologies face challenges in controlling the density, temperature, and composition of ions and radicals, as well as the energy of electrons in sub-atmospheric pressure plasmas, particularly in semiconductor applications, where precise control over ion and neutral species is necessary for effective doping and etching processes.
Innovation Solution
The method involves applying very fast electric-field pulses to modify the energy distribution of electrons in the plasma, which selectively affects electrons without significantly impacting ions, thereby optimizing the plasma composition by adjusting the ratio of ion species, ionization to dissociation, and excited state populations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma processing is used, then plasma is generated for doping and etching, but precise control over ion and neutral species composition is insufficient
Solution Approach 1:
The patent applies periodic pulsed electric fields to the plasma. The pulses are applied at specific frequencies and durations to selectively accelerate electrons during certain time intervals, enabling temporal control over electron energy distribution and consequently over ionization and dissociation rates, achieving precise control of plasma composition
Solution Approach 2:
The patent changes key plasma parameters by applying external electric field pulses. By adjusting pulse amplitude, width, and frequency, the electron energy distribution function is modified, which directly controls the ratios of ionization to dissociation and the densities of various ion and neutral species, providing versatile composition control
2Quantity of substance
If electron energy is increased to improve ionization ratio, then ionization to dissociation ratio increases, but electron energy distribution becomes harder to control
Solution Approach 1:
By applying periodic pulsed electric fields rather than continuous fields, the patent achieves transient electron acceleration. The pulse width and frequency can be tuned to control the fraction of electrons that gain high energy, while the majority remain at lower energies. This temporal modulation allows independent control of the high-energy electron population that drives ionization, decoupling it from the overall electron energy distribution
Solution Approach 2:
The patent dynamically adjusts the electric field parameters (amplitude, width, frequency) to control electron energy distribution. The pulsed nature creates a dynamic system where electron energy is continuously being redistributed through collisions during and between pulses, allowing real-time control of ionization rates without permanently altering the bulk electron energy state
3Productivity
If plasma density is increased for higher doping efficiency, then deposition on substrate increases, but process selectivity decreases
Solution Approach 1:
The patent changes the electron energy distribution through pulsed electric fields, which selectively enhances ionization processes. By increasing the fraction of high-energy electrons during the pulse, ion production is enhanced while the overall plasma density can be maintained at levels that avoid excessive neutral deposition, achieving decoupled control of ion flux and neutral flux to the substrate
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 control over plasma composition and density, leading to higher ionization ratios, reduced substrate deposition, and improved process directionality, enhancing the efficiency of plasma doping and deposition processes.
Implementation Method 1
The electrons subject to the applied fast rise E-field gain energy and travel through the plasma, ionizing, exciting, or dissociating the gas molecules in their path
Implementation Method 2
exciting the feed gas to generate a plasma
Data Source
AI summary
A method is disclosed for adjusting the composition of plasmas used in plasma doping, plasma deposition and plasma etching techniques. The disclosed method enables the plasma composition to be controlled by modifying the energy distribution of the electrons present in the plasma. Energetic electrons are produced in the plasma by accelerating electrons in the plasma using very fast voltage pulses. The pulses are long enough to influence the electrons, but too fast to affect the ions significantly. Collisions between the energetic electrons and the constituents of the plasma result in changes in the plasma composition. The plasma composition can then be optimized to meet the requirements of the specific process being used. This can entail changing the ratio of ion species in the plasma, changing the ratio of ionization to dissociation, or changing the excited state population of the plasma.