Chamber Lid Heater Ring Assembly for Plasma Uniformity
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Solution Overview
Problem
Conventional plasma processing chambers face challenges in achieving uniform plasma distribution due to non-uniform heating of the chamber lid, which affects power transfer and leads to inconsistent processing results and particle contamination, particularly in the fabrication of submicron structures.
Innovation Solution
A lid heater assembly with a thermally conductive base and an insulated center core is used to maintain uniform temperature across the chamber lid, positioned to avoid interference with RF coils, and an RF shield is employed to enhance RF power coupling and plasma ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional heater with electrically heated element and grounded metal components is used, then the chamber lid can be heated, but plasma uniformity deteriorates and power transfer is reduced
Solution Approach 1:
The heater is segmented into three distinct components: an insulated center core, a thermally conductive base, and a heating element. This segmentation allows each component to perform its specific function independently - the insulated core maintains central temperature, the conductive base distributes heat uniformly, and the heating element provides controlled thermal energy, collectively improving plasma uniformity while maintaining heating effectiveness.
Solution Approach 2:
The thermally conductive base acts as an intermediary between the heating element and the chamber lid. It distributes thermal energy uniformly across the lid surface, preventing localized hot spots that would cause plasma non-uniformity. The base material properties are specifically selected to optimize heat distribution while maintaining electrical isolation.
2Strength
If grounded metal components are used in the heater, then structural support is provided, but RF power transfer to plasma is reduced
Solution Approach 1:
Grounded metal components are extracted from the heater assembly and replaced with electrically insulating materials. The heater structure now uses non-conductive materials for structural support, eliminating the harmful effect of grounded components on RF power transfer while maintaining necessary mechanical strength through alternative structural design.
Solution Approach 2:
The electrical conductivity parameter of the heater components is changed from conductive (grounded metal) to insulating (non-conductive materials). This parameter change eliminates the shielding effect that prevented RF power from reaching the plasma, allowing full power transfer while maintaining structural integrity through material selection and design.
3Loss of energy
If heating element is positioned close to chamber lid, then heating efficiency is improved, but temperature non-uniformity increases
Solution Approach 1:
The thermally conductive base serves as an intermediary heat distribution layer between the heating element and the chamber lid. It receives concentrated thermal energy from the heating element and redistributes it uniformly across the lid surface, maintaining heating efficiency while eliminating temperature non-uniformity through its high thermal conductivity properties.
Solution Approach 2:
The heating approach transitions from direct localized heating to distributed heating through the conductive base. The thermal energy is spread across the two-dimensional surface of the lid via the base's thermal conduction, converting a point-source heating problem into a distributed thermal field that achieves uniform temperature distribution.
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 solution improves plasma uniformity and RF power coupling, reducing heat loss and enabling more efficient processing of submicron structures by maintaining a consistent temperature profile and facilitating plasma ignition, even with challenging gases like SF6.
Implementation Method 1
a thermally conductive base (192) configured to contact the chamber lid (120)
Implementation Method 2
a heating element (198) disposed on the thermally conductive base (192)
Implementation Method 3
One or more coils 15, 16 are disposed over a chamber lid 18 of the chamber body 11. The coils 15, 16 ignite and maintain a plasma 17 in the processing volume 15 during processing.
Data Source
AI summary
Embodiments of the invention generally provide a lid heater for a plasma processing chamber. In one embodiment, a lid heater assembly is provided that includes a thermally conductive base. The thermally conductive base has a planar ring shape defining an inner opening. The lid heater assembly further includes a heating element disposed on the thermally conductive base, and an insulated center core disposed across the inner opening of the thermally conductive base.