Shorted Coil Antenna Inductance Reduction Plasma Abatement
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Solution Overview
Problem
Conventional high density inductively coupled plasma (ICP) remote plasma sources for semiconductor processes face inefficiencies due to large coil antennas with high inductance, leading to suboptimal power operation and reduced destruction and removal efficiency (DRE) of perfluorinated compounds (PFCs), along with increased stray effects at higher frequencies.
Innovation Solution
A plasma source with a dielectric tube and a coil antenna having a plurality of turns, where at least one turn is shorted to reduce inductance, allowing higher power supply and increased processing volume, thereby improving DRE by creating multiple plasma zones within the dielectric tube for enhanced treatment efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a large coil antenna is used to surround the entire dielectric tube to provide sufficient residence time for PFC abatement, then the processing volume and residence time are improved, but the inductance increases causing nonoptimal power operation and foldback
Solution Approach 1:
The coil antenna is segmented into multiple sections with selective shorting of individual turns. This allows different sections to have different inductance characteristics, enabling the antenna to provide sufficient processing volume while avoiding excessive overall inductance that causes foldback. The segmentation principle is directly applied by dividing the coil into controllable sections rather than using a uniform large coil.
Solution Approach 2:
The coil antenna configuration is made dynamic through selective shorting of turns based on operating conditions. The system can adjust which turns are active and which are shorted, allowing optimization of the inductance-to-volume ratio for different processing requirements and power levels, preventing nonoptimal operation.
2Volume of moving object
If a large coil antenna with high inductance is used, then the processing volume increases, but the destruction and removal efficiency (DRE) of PFCs decreases to around 50%
Solution Approach 1:
Different sections of the coil antenna are given different characteristics through selective shorting. Certain sections have full turns for maximum inductance and plasma generation, while other sections have shorted turns to reduce inductance. This local differentiation allows optimization of plasma density and processing efficiency throughout the dielectric tube, achieving high DRE across the entire processing volume.
3Speed
If the frequency is increased to improve processing efficiency, then the abatement speed increases, but the large inductor carries high potential causing pronounced stray effects and capacitive coupling
Solution Approach 1:
The coil antenna inductance is dynamically adjusted through selective shorting of turns based on operating frequency. At higher frequencies where capacitive effects become problematic, certain turns are shorted to reduce inductance and minimize stray effects. This allows the system to operate at higher frequencies for improved abatement speed while controlling harmful capacitive coupling.
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
The solution achieves a DRE above 95% by reducing inductance and enabling higher power supply to the coil antenna, effectively improving the abatement of compounds in semiconductor processes while minimizing capacitive coupling and stray effects.
Implementation Method 1
High density inductively coupled plasma (ICP) may be used as the remote plasma source in abatement of PFCs
Implementation Method 2
a large inductor, such as the large coil antenna, can carry high potential, causing a more pronounced stray effect (capacitively coupling instead of inductively coupling)
Implementation Method 3
the RF signal electromagnetically couples into the chamber to excite and ionize the process gas, thereby forming a plasma in the chamber
Implementation Method 4
a plasma source may be coupled to a processing chamber to abate the compounds exiting the processing chamber
Data Source
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Figure 2B
AI summary
Embodiments disclosed herein include a plasma source, an abatement system and a vacuum processing system for abating compounds produced in semiconductor processes. In one embodiment, a plasma source includes a dielectric tube and a coil antenna surrounding the tube. The coil antenna includes a plurality of turns, and at least one turn is shorted. Selectively shorting one or more turns of the coil antenna helps reduce the inductance of the coil antenna, allowing higher power to be supplied to the coil antenna that covers more processing volume. Higher power supplied to the coil antenna and larger processing volume lead to an improved DRE.