Pulsed Electrode Voltage Boost for Stable Plasma Etching
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Solution Overview
Problem
The challenge in semiconductor manufacturing is maintaining plasma stability during high aspect ratio feature formation, as traditional pulsing techniques consume a significant amount of plasma electrons, causing perturbations that affect the reliability of plasma-assisted etching processes.
Innovation Solution
A plasma processing system that uses a capacitive element and voltage source coupled in parallel to an electrode, with specific switch configurations to reduce bulk electron consumption, allowing for a voltage boost without destabilizing the plasma, thereby improving plasma sustainability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional pulsing techniques are used to establish DC bias, then the voltage bias can be achieved, but bulk electron consumption causes severe plasma instability and extinction
Solution Approach 1:
The patent introduces a capacitor as an intermediary energy storage element between the plasma source and the substrate. The capacitor accumulates charge during the plasma generation phase and discharges it during the bias application phase, thereby mediating the energy transfer and avoiding direct electron consumption from the plasma bulk. This resolves the contradiction by enabling voltage bias application without destabilizing the plasma.
Solution Approach 2:
The system performs preliminary charge accumulation in the capacitor during phase one (plasma generation) before the actual bias application is needed. By pre-storing the necessary electrical energy in the capacitor, the system avoids the need to draw electrons from the plasma bulk at the moment of bias application, thus maintaining plasma stability while achieving the required voltage bias.
2Power
If bulk electrons are consumed to establish DC bias, then the voltage requirement is met, but plasma sustainability and stability are severely perturbed
Solution Approach 1:
The capacitor serves as an intermediary that decouples the DC bias application from direct plasma electron consumption. It stores electrical energy independently and releases it when needed, allowing the plasma to maintain its electron population and sustainability while still achieving the required bias voltage across the substrate.
Solution Approach 2:
The patent changes the temporal and electrical parameters by using pulsed voltage application instead of continuous DC bias. The voltage is applied in controlled pulses with specific duration and amplitude, allowing the plasma to recover between pulses and maintain sustainability. The capacitor enables this parameter transformation by storing energy during one phase and releasing it during another.
3Manufacturing precision
If high ion energies are used for etching, then etching performance improves, but electron consumption increases and plasma stability deteriorates
Solution Approach 1:
The capacitor acts as an intermediary that enables high voltage bias application for high energy ion acceleration without directly consuming plasma electrons. This allows the system to achieve high ion energies needed for superior etching performance while the plasma bulk remains stable and sustainable, resolving the contradiction between etching quality and plasma reliability.
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 reduces the load on plasma electrons, enhancing the stability and sustainability of the plasma, which leads to more consistent and reliable plasma-assisted etching results, improving within-wafer and wafer-to-wafer process performance and device yield.
Implementation Method 1
a capacitive element selectively coupled to the bias electrode. The capacitive element may be configured to reduce a number of bulk electrons drawn from the plasma to establish a direct current (DC) bias at the bias electrode
Data Source
AI summary
Embodiments provided herein generally include apparatus, plasma processing systems and methods for boosting a voltage of an electrode in a processing chamber. An example plasma processing system includes a processing chamber, a plurality of switches, an electrode disposed in the processing chamber, a voltage source, and a capacitive element. The voltage source is selectively coupled to the electrode via one of the plurality of switches. The capacitive element is selectively coupled to the electrode via one of the plurality of switches. The capacitive element and the voltage source are coupled to the electrode in parallel. The plurality of switches are configured to couple the capacitive element and the voltage source to the electrode during a first phase, couple the capacitive element and the electrode to a ground node during a second phase, and couple the capacitive element to the electrode during a third phase.