Ceramic Heater Layout to Eliminate Thermocouple Hole Cool Spots
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ceramic heaters have a cool spot above the thermocouple insert hole due to the resistance heating elements not overlapping the hole, leading to temperature uniformity issues on the wafer placement surface.
Innovation Solution
The ceramic heater design includes resistance heating elements embedded in the ceramic plate, with at least one element positioned above the bottom of the thermocouple insert hole and overlapping it in plan view, ensuring even heating across the wafer placement surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance heating elements are positioned away from the thermocouple insert hole, then the thermocouple can accurately measure temperature, but cool spots form on the wafer placement surface reducing temperature uniformity
Solution Approach 1:
The heating elements are positioned to provide localized heating directly above the thermocouple insert hole, creating different heating zones. This ensures the area above the hole receives sufficient heat while other areas maintain their heating characteristics, eliminating cool spots and improving overall temperature uniformity without compromising measurement accuracy
2Temperature
If resistance heating elements are positioned to overlap the thermocouple insert hole, then temperature uniformity improves, but the thermocouple measurement may be affected by direct heating
Solution Approach 1:
The heating elements are positioned in the horizontal plane to overlap the thermocouple insert hole, while the thermocouple extends vertically into the hole to measure temperature at the bottom. This spatial separation in different dimensions allows the heating elements to warm the area above the hole without directly heating the thermocouple junction, maintaining both temperature uniformity and measurement accuracy
3Reliability
If the thermocouple insert hole is deep, then temperature measurement reliability increases, but manufacturing complexity increases
Solution Approach 1:
The thermocouple insert hole depth is optimized to a specific range (0.055-0.4 times the ceramic plate thickness) to achieve the desired balance. This parameter optimization ensures sufficient depth for reliable temperature measurement while maintaining manufacturability through controlled depth specifications that can be achieved with standard manufacturing processes
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 enhances temperature uniformity on the wafer placement surface by reducing the likelihood of cool spots, thereby improving heating efficiency and consistency.
Implementation Method 1
two or more resistance heating elements embedded in the ceramic plate and provided for corresponding two or more divided zones of the wafer placement surface
Implementation Method 2
a thermocouple insert hole provided in a shaft inner region... to receive a thermocouple that measures the temperature of the middle area of the ceramic plate
Data Source
AI summary
A ceramic heater includes: a ceramic plate having a wafer placement surface on its upper surface; two or more resistance heating elements embedded in the ceramic plate and provided for corresponding two or more divided zones of the wafer placement surface; a tubular shaft supporting the ceramic plate from a lower surface of the ceramic plate; a thermocouple insert hole provided in a shaft inner region that is a portion of the lower surface of the ceramic plate defined by the tubular shaft; and four or more resistance heating element terminal holes provided in the shaft inner region and corresponding to both ends of the two or more resistance heating elements. At least one of the two or more resistance heating elements is located above a bottom of the thermocouple insert hole and has a portion overlapping the thermocouple insert hole in plan view.