Electron Wavefront Atomic Layer Etching With Precise Energy Control
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Solution Overview
Problem
Existing plasma processing methods struggle to precisely control the kinetic energy of free electrons to target the energy levels of atoms at the surface of a substrate, leading to potential damage and lack of selectivity in material processing.
Innovation Solution
The method involves generating a uniform gaseous plasma with controlled floating potential and applying a sequence of biasing potentials to create a wafer-scale electron wavefront that selectively targets and desorbs the atomic layer of the substrate, using a closed-loop control system to maintain precise energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma processing methods are used to accelerate electrons and ions towards the substrate surface, then material processing can be performed, but substrate damage occurs beyond the targeted physical alterations
Solution Approach 1:
The plasma processing is segmented into distinct phases: a modification phase where low-energy electrons (below damage threshold) perform targeted surface modification, followed by a removal phase where controlled desorption occurs. This segmentation allows precise control over which particles interact with the substrate at which stage, preventing damage while achieving the desired surface transformation.
Solution Approach 2:
The patent dynamically changes the energy parameters of electrons during processing. By controlling the plasma potential and applying time-varying bias signals, the electron energy is maintained below the damage threshold during the modification phase, then adjusted to enable controlled desorption in the removal phase. This parameter control ensures precise surface modification without substrate damage.
2Measurement precision
If externally applied bias signals are used to control electron energy, then processing can be performed, but the energy may not correlate to the electron energy thresholds of materials at the substrate surface due to unknown floating potential
Solution Approach 1:
The patent implements feedback control by measuring the actual floating potential of the substrate and using this measurement to adjust the applied bias signal. The controller modifies the bias signal in real-time based on the measured floating potential, ensuring that the electron energy precisely matches the material-specific thresholds. This feedback loop eliminates the uncertainty caused by unknown floating potential and enables selective processing of different materials.
3Ease of operation
If mechanical support is used to hold the substrate in the plasma, then processing can be performed, but the system complexity increases and control precision decreases
Solution Approach 1:
The patent replaces mechanical support systems with an electric field-based suspension system. The substrate is held in the plasma by balancing electrostatic forces through controlled biasing, eliminating the need for mechanical holders that interfere with plasma interaction and potential measurement. This substitution enables direct, precise control of the substrate's electrical potential without mechanical constraints.
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 allows for precise and selective etching of the atomic layer by controlling the kinetic energy of free electrons, minimizing substrate damage and enhancing processing accuracy.
Implementation Method 1
generating a volume of gaseous plasma including diluent species, reactive species, and electrons of a uniform steady state composition in a positive column of a DC plasma proximate a substrate
Implementation Method 2
igniting a plasma to remove the modified surface
Implementation Method 3
controlling the kinetic energy of free electrons such as to produce wafer scale waves of precisely controlled electrons
Implementation Method 4
applying to the substrate, via a periodic biasing signal referenced to the reference potential, a sequence of a positive biasing potential followed by a negative biasing potential and further followed by a zero biasing potential that is equal to the reference potential, thereby causing arrival of an electron wavefront with uniform energy and density across the surface of the substrate
Implementation Method 5
forming a corrosion layer on the substrate, the corrosion layer comprising corrosion layer species formed by adsorption of the reactive species to atoms of an atomic layer at the surface of the substrate
Implementation Method 6
based on the applying, drawing electrons from the volume of gaseous plasma to the surface of the substrate and imparting an energy level to drawn electrons for stimulating electron transitions in the corrosion layer species; and based on the stimulating, desorbing the corrosion layer species, thereby etching away the atomic layer
Data Source
Figure 1A
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Figure 1C
AI summary
Atomic layer etching (ALE) of a substrate using a wafer scale wave of precisely controlled electrons is presented. A volume of gaseous plasma including diluent and reactive species and electrons of a uniform steady state composition is generated in a positive column of a DC plasma proximate the substrate. A corrosion layer is formed on the substrate by adsorption of reactive species to atoms at the surface of the substrate. The substrate is positively biased to draw electrons from the volume to the surface of the substrate and impart an energy to the electrons so to stimulate electron transitions in the corrosion layer species, resulting in ejection of the corrosion layer species via electron stimulation desorption (ESD). The substrate is negatively biased to repel the electrons from the surface of the substrate back to the volume, followed by a zero bias to restore the steady state composition of the volume.