Pseudo-Staircase Waveform Control for Plasma Ion Energy
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Solution Overview
Problem
Conventional RF plasma-assisted etching processes fail to adequately control sheath properties and ion energies, leading to undesirable plasma processing results such as excessive sputtering of mask layers and sidewall defects in high-aspect ratio features.
Innovation Solution
A pseudo-staircase voltage waveform is generated using a network of capacitors and switches to control ion energy distribution, enabling digital control of ion energies and maintaining a constant negative voltage on the electrode through current compensation without an external current source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional RF plasma-assisted etching processes are used, then the etching process can be performed, but the sheath properties and ion energies cannot be adequately controlled, leading to excessive sputtering and sidewall defects
Solution Approach 1:
The voltage waveform is segmented into multiple discrete voltage levels (e.g., -200V, -400V, -600V, -800V) that can be independently selected and applied to the electrode. This segmentation allows precise control of ion energy by choosing specific voltage steps, enabling fine-tuned control of ion bombardment energy to achieve desired etching results while minimizing mask sputtering and sidewall defects
Solution Approach 2:
The system dynamically switches between different voltage levels during the etching process using pulsed voltage application. The voltage waveform can be adjusted in real-time to maintain constant negative voltage on the electrode through current compensation, allowing adaptive control of ion energy distribution throughout the processing cycle
2Manufacturing precision
If conventional RF plasma-assisted etching processes are used, then the etching process can be performed, but excessive sputtering of the mask layer occurs
Solution Approach 1:
The system changes the voltage parameter applied to the electrode from conventional continuous RF sinusoidal waveforms to pulsed DC voltage waveforms with specific discrete levels. By selecting appropriate voltage steps and pulse durations, the ion energy distribution is optimized to reduce mask sputtering while maintaining effective etching, directly addressing the harmful sputtering effect
3Manufacturing precision
If conventional RF plasma-assisted etching processes are used, then the etching process can be performed, but sidewall defects are generated in high-aspect ratio features
Solution Approach 1:
The voltage waveform parameters are changed to provide pulsed DC voltage with controlled rise and fall times, allowing ions to accelerate in a more controlled manner. This results in narrower ion energy distribution and reduced lateral ion scattering, thereby minimizing sidewall defects in high-aspect ratio features while maintaining etching throughput
4Manufacturing precision
If a network of capacitors and switches is used to generate pseudo-staircase voltage waveform, then digital control of ion energies is enabled, but hardware area consumption increases
Solution Approach 1:
The voltage control is segmented into discrete steps using a capacitor array where each capacitor corresponds to a specific voltage level. This segmented approach enables digital control of ion energy with minimal hardware - simply by switching between pre-charged capacitors, achieving fine control without requiring complex continuous regulation circuitry
Solution Approach 2:
Capacitors are pre-charged to specific voltage levels before the etching process. During processing, the desired voltage is instantly applied by switching the pre-charged capacitor into the circuit, eliminating the need for complex real-time voltage regulation hardware and reducing overall system area while maintaining precise control
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 finer control of ion energy distribution, enabling etching of different materials with greater selectivity and deposition of films with improved properties, while reducing hardware area consumption and improving plasma uniformity.
Implementation Method 1
a capacitor array, wherein the second switch is coupled between the output node and the capacitor array, wherein the capacitor array comprises: a first capacitor coupled to the second switch
Implementation Method 2
a plasma is formed in a processing chamber and ions from the plasma are accelerated towards a surface of a substrate
Implementation Method 3
ions are accelerated from the plasma towards the substrate across a plasma sheath
Data Source
AI summary
Embodiments provided herein generally include apparatus, plasma processing systems and methods for generation of a waveform for plasma processing of a substrate in a processing chamber. Embodiments of the disclosure include an apparatus and method for generating a pseudo-staircase waveform that includes coupling, during a first phase of generating a waveform, a first voltage supply to an output node; coupling, during a second phase of generating the waveform, a first capacitor between the output node and an electrical ground node; and coupling during a third phase of generating the waveform, the first capacitor and a second capacitor in a series path between the output node and the electrical ground node.