Immersible Plasma Coil Assembly for High Density Etching
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Solution Overview
Problem
Conventional transformer coupled plasma (TCP) processing chambers face issues such as high RF current requirements, window erosion, reduced plasma density, and increased plasma potential due to the remote placement of the source coil, which worsens with larger substrate sizes.
Innovation Solution
A coil assembly is positioned within the plasma processing chamber, hermetically sealed within an encapsulation structure, allowing direct exposure to the plasma and reducing RF current needs by minimizing the separation distance between the coil and substrate, thus eliminating the need for a quartz window and allowing scalable chamber design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source coil is positioned outside the chamber above the window, then the coil is protected from plasma exposure, but the plasma density at substrate level is reduced due to large diffusion distance
Solution Approach 1:
The system is segmented into two distinct regions: a plasma-exposed region containing the coil assembly, and a plasma-protected region containing the chamber components. The encapsulation structure creates a hermetic barrier that divides these regions, allowing the coil to be immersed in plasma while protecting sensitive components from direct plasma contact.
Solution Approach 2:
The encapsulation structure acts as an intermediary element between the plasma environment and the coil assembly. It provides a hermetic seal that allows the coil to be positioned within the plasma generation region while preventing plasma contamination of the coil terminals and support structures.
2Power
If large RF current is supplied to the source coil above the window, then sufficient RF electromagnetic field is generated within the chamber, but high-intensity electric fields cause erosion of the window
Solution Approach 1:
The harmful function of high-intensity electric fields is extracted and localized to a specific region (the encapsulation structure surrounding the coil). By confining the RF field generation within the encapsulated volume, the harmful effects are prevented from reaching the chamber window, while the useful function of plasma generation is maintained in the target region.
Solution Approach 2:
The encapsulation structure is designed to withstand and utilize the high-intensity RF electric fields that would otherwise harm the window. The hermetic seal allows the coil to operate at high power levels necessary for sufficient plasma generation, while the encapsulation materials are selected to resist plasma and RF field damage, converting the previously harmful high-power operation into a beneficial plasma source.
3Area of stationary object
If the chamber size is increased to accommodate larger substrates, then substrate processing capacity is improved, but the window size and thickness must increase requiring even higher RF currents
Solution Approach 1:
The coil assembly is transitioned from a position outside the chamber (above the window) to a position inside the chamber (immersed in the plasma generation region). This dimensional repositioning allows the RF field to be generated directly within the plasma volume, eliminating the need for high-power transmission through thick windows and enabling scalable chamber designs for larger substrates without proportionally increasing RF power requirements.
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 configuration achieves higher plasma density closer to the substrate with reduced contamination and improved defectivity control, enabling increased etch rates and precise critical dimension control, while reducing material sputtering and plasma potential.
Implementation Method 1
transmitting radiofrequency (RF) power to the coil device within the coil assembly. The RF power transforms the reactant gas into a plasma within the plasma generation region
Data Source
AI summary
A coil assembly includes an encapsulation structure having a coil placement region formed therein. One or more access ports are formed through the encapsulation structure to the coil placement region. The coil placement region is hermetically sealed by the encapsulation structure outside of the one or more access ports. A coil device is disposed within the coil placement region within the encapsulation structure. Terminals of the coil device are accessible through the one or more access ports formed through the encapsulation structure. The encapsulation structure is formed of a material suitable for exposure to a plasma. The coil assembly can be disposed inside of a plasma processing chamber and above a support structure, such that the coil assembly is in exposure to a plasma generated between the coil assembly and the support structure by radiofrequency power supplied to the coil device within the coil assembly.