Dielectric Window Cooling With Air Amplifiers Under High Back Pressure
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Solution Overview
Problem
Current cooling systems for dielectric windows in plasma processing devices, such as liquid and fan cooling systems, are inefficient and prone to failure under high back pressure, leading to inadequate heat removal and potential thermal cracking.
Innovation Solution
The implementation of an air amplifier system in conjunction with a plenum that provides a pressurized air flow of at least 30 cfm at a back pressure of 1 in-H2O or higher, effectively directing cooling air to the dielectric window to manage elevated temperatures and heat distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid cooling systems are used to cool dielectric windows, then cooling efficiency is improved, but system complexity and cost increase, and thermal gradients causing cracking may occur
Solution Approach 1:
The patent applies pneumatic cooling by introducing a gas (typically nitrogen or air) through nozzles positioned near the dielectric window. This gas flow absorbs heat from the window surface through convection and carries it away, providing effective cooling without the complexity of liquid cooling systems. The pneumatic system avoids issues with liquid containment, nucleation, and thermal gradient-induced cracking while maintaining efficient heat removal.
2Device complexity
If fan cooling systems are used to cool dielectric windows, then system simplicity is improved, but cooling effectiveness deteriorates under high back pressure conditions
Solution Approach 1:
The cooling system is segmented into multiple independent nozzle units distributed across the dielectric window surface. Each nozzle provides localized cooling to specific high-heat regions, allowing the system to maintain simplicity while achieving effective heat removal. The segmented approach enables targeted cooling without requiring a complex centralized system, and each nozzle operates independently to overcome back pressure effects.
Solution Approach 2:
The patent implements local quality by positioning nozzles to provide concentrated cooling precisely where heat loads are highest on the dielectric window. Rather than uniform cooling across the entire surface, the system directs cooling gas to specific regions experiencing elevated temperatures, maximizing cooling effectiveness while minimizing system complexity and gas consumption.
3Device complexity
If passive cooling is used for dielectric windows, then system simplicity is improved, but cooling effectiveness is insufficient under high electromagnetic energy exposure
Solution Approach 1:
The cooling system operates on a self-service principle where the plasma process itself provides part of the cooling mechanism. The plasma gas, already present in the chamber for the semiconductor fabrication process, serves dual purposes: maintaining the plasma reaction and providing convective cooling to the dielectric window. This eliminates the need for separate active cooling systems while maintaining effective temperature control under high electromagnetic energy exposure.
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 enables efficient cooling of dielectric windows under high electromagnetic energy exposure, preventing thermal gradients and cracking, and maintaining airflow even under pressures that stall traditional fan cooling systems.
Implementation Method 1
The Coanda effect is utilized to attach the air jet to the outer surface of the dielectric window
Implementation Method 2
A low pressure region can be created using, for example, a venturi or other suitable device
Implementation Method 3
the dielectric properties of the window (tangent-δ) may result in the direct absorption of RF or microwave power
Implementation Method 4
the energy can be transmitted through a dielectric window that is formed through the vacuum chamber... transform at least a portion of the plasma processing gas into plasma
Data Source
AI summary
In one embodiment, a plasma processing device may include a dielectric window, a vacuum chamber, an energy source, and at least one air amplifier. The dielectric window may include a plasma exposed surface and an air exposed surface. The vacuum chamber and the plasma exposed surface of the dielectric window can cooperate to enclose a plasma processing gas. The energy source can transmit electromagnetic energy through the dielectric window and form an elevated temperature region in the dielectric window. The at least one air amplifier can be in fluid communication with the dielectric window. The at least one air amplifier can operate at a back pressure of at least about 1 in-H2O and can provide at least about 30 cfm of air.