Cyclical Plasma Etching for Atomic Layer Precision
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Solution Overview
Problem
Conventional plasma etching techniques are inadequate for precisely removing very thin layers, such as atomic layers, without disrupting the underlying substrate material, as they often result in surface disruption due to ion bombardment and lack selectivity between different materials.
Innovation Solution
An apparatus and method for cyclical plasma etching that involves a process chamber with controlled dosing and bombardment steps, using a dosing controller for precise gas exposure and signal generators to manage plasma active species energy, allowing for sequential bias power adjustment to minimize substrate disruption and achieve precise etching of thin layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma etching is used to increase etch rate and productivity, then productivity is improved, but manufacturing precision deteriorates due to surface disruption of several atomic layers
Solution Approach 1:
The etching process is segmented into multiple cycles, each removing a fraction of the total required thickness. This allows the use of higher power plasma sources for efficiency while maintaining precision through iterative removal and inspection
Solution Approach 2:
The etching process uses periodic pulsing of the plasma source and substrate bias, alternating between etching phases and inspection phases. This periodic action enables precise control of removal depth while maintaining high overall etch rates through efficient duty cycling
2Manufacturing precision
If atomic layer etching with self-limiting behavior is used to achieve precise thin layer removal, then manufacturing precision is improved, but device complexity increases due to auxiliary electrodes and complex control schemes
Solution Approach 1:
The patent removes the auxiliary electrode from the system, using only the main plasma source and substrate bias control to achieve atomic layer etching. This simplifies the device architecture while maintaining precision through optimized pulsing sequences
Solution Approach 2:
The patent achieves precise etch control by dynamically changing plasma source power and substrate bias parameters during the etching cycle, rather than relying on fixed auxiliary electrodes. This parameter modulation enables self-limiting etch behavior with simpler hardware
3Manufacturing precision
If DC bias is precisely controlled to maintain self-limiting etching regime, then manufacturing precision is improved, but device complexity increases due to complex non-sinusoidal wafer bias schemes
Solution Approach 1:
The patent uses periodic pulsing of the substrate bias with simple sinusoidal or square waveforms, alternating between high bias for etching and low bias for termination. This periodic simplification achieves precise regime control without complex non-sinusoidal schemes
Solution Approach 2:
The patent dynamically adjusts substrate bias in real-time during the etching cycle using feedback from plasma diagnostics, enabling precise control of the etching regime through adaptive rather than pre-programmed complex waveforms
4Productivity
If ion bombardment energy is increased to improve etching efficiency, then productivity is improved, but manufacturing precision deteriorates due to substrate surface disruption
Solution Approach 1:
The high energy ion bombardment is segmented into multiple lower-energy pulses, each removing a small fraction of the material. This segmentation maintains surface integrity by preventing single-pulse disruption while achieving high overall etch rates through cumulative removal
Solution Approach 2:
The patent uses periodic modulation of ion bombardment energy, alternating between high-energy etching pulses and low-energy termination pulses. This periodic energy variation enables efficient material removal while preserving substrate surface integrity through controlled energy delivery
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
Enables the reproducible and precise removal of thin layers, ensuring that only the upper material is etched while the underlying material remains unperturbed, with controlled energy and gas dosing to prevent conventional plasma etching or sputtering, thereby maintaining selectivity and surface integrity.
Implementation Method 1
an electrostatically screened induction coupled plasma source
Implementation Method 2
positive ions of a plasma active species within the process chamber have a substrate bombardment energy in the range of 10eV to 100eV
Implementation Method 3
a dosing controller for controlling the flow of a process gas in the dosing step such that the substrate is exposed to a maximum dose of process gas
Data Source
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AI summary
There is provided an apparatus for cyclical plasma etching of a substrate, the apparatus comprising: a process chamber; a support within the process chamber for receiving the substrate to be etched; a controller for repeatedly applying a dosing step and a bombardment steps respectively; a dosing controller for controlling the flow of a process gas in the dosing step such that the substrate is exposed to a maximum dose of process gas in use of 1000 Langmuirs and said dose is controllable within an accuracy of 1 Langmuir; and a first signal generator coupled to the process chamber and a second signal generator coupled to the support within the process chamber, the first and second signal generators being configured such that in use positions ions of an plasma active species within the process chamber have a substrate bombardment energy in the range of 10eV to 100eV which is controllable within an accuracy of 5eV. There is also provided a method for cyclical plasma etching of a substrate using said apparatus.