Showerhead Thermal Control via Resistive Element Measurement
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Solution Overview
Problem
Current thermal control systems for showerheads in substrate processing systems, which rely on thermocouples, are inaccurate due to interference from DC noise introduced by power inputs and plasma-induced biases, leading to unreliable temperature measurements and control.
Innovation Solution
A resistive thermal measurement system that uses a resistive element with a temperature-dependent resistance, encapsulated in an insulating material, to measure the showerhead's temperature by applying a DC voltage and measuring current, allowing for accurate temperature determination and control independent of DC noise, with optional additional resistive elements for over-temperature protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermocouples are used to measure showerhead temperature, then temperature measurement is enabled, but measurement precision deteriorates due to DC noise interference from power inputs and plasma-induced biases
Solution Approach 1:
The patent extracts the temperature sensing function from the thermocouple and implements it through a resistive element whose resistance changes with temperature. This resistive element is electrically isolated from the showerhead structure, removing it from the source of DC noise while maintaining thermal coupling through the thermal bond to the showerhead interior surface.
Solution Approach 2:
The patent introduces an intermediary thermal bond that couples the resistive element to the showerhead interior surface. This thermal bond acts as a mediator that transfers thermal information from the showerhead to the resistive element while maintaining electrical isolation, thus enabling accurate temperature measurement without direct electrical connection to the noisy showerhead structure.
2Reliability
If additional temperature measurement points are added for better control, then temperature control reliability improves, but device complexity increases
Solution Approach 1:
The patent segments the temperature measurement function by placing multiple discrete resistive elements at different locations on the showerhead interior surface. Each resistive element independently measures temperature at its specific location, enabling zonal temperature control and identification of hot spots without requiring a single complex measurement system.
Solution Approach 2:
The resistive element serves multiple functions: it acts as both the temperature sensor and is electrically isolated from the showerhead structure. This multi-functionality reduces the need for separate sensing and isolation components, thereby reducing overall system complexity while improving reliability through multiple measurement points.
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 resistive thermal measurement system provides accurate and reliable temperature control of the showerhead, unaffected by DC noise or plasma-induced biases, enabling precise heating management and preventing overheating, with the ability to measure temperature both during and outside heating cycles.
Implementation Method 1
a resistive element thermally bonded to the showerhead of the plasma chamber. The resistive element includes a single metal that changes resistance in response to a change in temperature of the single metal
Implementation Method 2
a resistive heater to heat the showerhead of the plasma chamber and a resistive element thermally bonded to the showerhead
Implementation Method 3
The resistive element is encapsulated in an insulating material to electrically insulate the resistive element from the showerhead, and the insulating material is a good conductor of heat
Data Source
AI summary
A showerhead for a plasma chamber comprises a resistive heater configured to receive power to heat the showerhead of the plasma chamber, and a resistive element thermally bonded to the showerhead of the plasma chamber. The resistive element changes resistance in response to a change in temperature of the showerhead. The resistive element is encapsulated in an insulating material to electrically insulate the resistive element from the showerhead. The insulating material is a good conductor of heat. The power to the resistive heater is received based on the resistance of the resistive element.