CVD Showerhead Temperature Control via Convection and Feedback
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Solution Overview
Problem
CVD showerheads experience temperature variations during continuous batch processing, leading to wafer-to-wafer non-uniformity and particle formation due to thermal cycling, which affects film deposition quality and throughput.
Innovation Solution
A temperature-controlled CVD showerhead system with enhanced heat dissipation using a convective cooling fluid passageway, a thermally coupled back plate with an embedded heater, and a temperature sensor for precise temperature control, along with radiative cooling and RF filtering to maintain stable temperatures across multiple stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If showerhead temperature is controlled using conventional methods, then temperature stability is partially maintained, but wafer-to-wafer uniformity deteriorates due to thermal cycling and emissivity changes
Solution Approach 1:
The patent implements a feedback control system using a thermocouple to measure showerhead temperature and a controller to adjust heater power accordingly. This closed-loop feedback mechanism continuously monitors temperature and makes real-time adjustments to maintain stable temperature despite thermal cycling from wafer processing, directly resolving the contradiction between manufacturing precision and temperature stability.
Solution Approach 2:
The patent changes the temperature control parameter from open-loop estimation to closed-loop measured temperature using thermocouple feedback. This parameter change enables precise maintenance of showerhead temperature at the exact set point, improving both wafer-to-wafer uniformity and temperature stability simultaneously.
2Stability of the object's composition
If showerhead reaches equilibrium temperature through continuous processing, then temperature stability improves, but processing time increases and throughput decreases
Solution Approach 1:
The patent applies preliminary heating action through the heater element to bring the showerhead to the desired temperature set point before wafer processing begins. This preliminary action eliminates the need to wait for natural equilibrium during processing, maintaining temperature stability while avoiding processing delays that would reduce throughput.
Solution Approach 2:
The patent maintains continuous temperature control through the feedback system and heater, ensuring the showerhead remains at the optimal temperature throughout processing without interruption. This continuous useful action eliminates idle time waiting for equilibrium, thereby maintaining both temperature stability and high throughput.
3Use of energy by moving object
If RF power is applied to showerhead for heating, then heating efficiency improves, but parasitic discharge in gas feed lines occurs
Solution Approach 1:
The patent extracts the heating function from the RF plasma process and implements it through a separate heater element. This separation removes the harmful parasitic discharge effect from the gas feed lines while maintaining effective heating capability, as the heater provides controlled thermal energy without generating RF-induced parasitic discharges.
Solution Approach 2:
The patent introduces a heater as an intermediary device between the power source and the showerhead heating process. This intermediary provides the necessary thermal energy for temperature control without the harmful side effects of direct RF application, eliminating parasitic discharge while maintaining heating efficiency.
4Adaptability or versatility
If showerhead components have different thermal expansion coefficients, then material selection flexibility improves, but particle formation increases due to thermal cycling
Solution Approach 1:
The feedback control system maintains stable showerhead temperature, minimizing thermal cycling amplitude. This reduces the magnitude of thermal expansion and contraction regardless of material differences, thereby reducing particle formation from coating delamination while preserving the ability to use materials with different thermal expansion coefficients.
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 ensures accurate and stable temperature control, reducing wafer-to-wafer non-uniformity, minimizing particle formation, and increasing throughput by maintaining consistent film properties and reducing thermal cycling effects.
Implementation Method 1
The temperature sensor may be a thermocouple attached to the face plate
Implementation Method 2
additional convective cooling using a fluid in a fluid passageway
Implementation Method 3
The heater may be an electrical resistance heater and may be embedded in the back plate
Implementation Method 4
increased radiation from a back plate
Implementation Method 5
the showerhead temperature may provide an additional parameter for process optimization
Data Source
AI summary
A temperature controlled showerhead for chemical vapor deposition (CVD) chambers enhances heat dissipation to enable accurate temperature control with an electric heater. Heat dissipates by conduction through a showerhead stem and fluid passageway and radiation from a back plate. A temperature control system includes one or more temperature controlled showerheads in a CVD chamber with fluid passageways serially connected to a heat exchanger.