Ceramic Heater Thermocouple Path for Accurate Wafer Temperature
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Solution Overview
Problem
In ceramic heaters, the separation between the wafer placement surface and the outer circumferential thermocouple results in inaccurate temperature measurements of the wafer, as the measured temperature differs from the actual temperature.
Innovation Solution
A ceramic heater design that includes a thermocouple path between the resistance heater and the wafer placement surface, with a thermocouple insertion hole allowing the thermocouple to be inserted closer to the wafer, ensuring accurate temperature measurement by positioning the temperature measurement portion between the resistance heater and the wafer placement surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the thermocouple is placed on the outer circumferential side of the ceramic substrate, then the thermocouple can be easily accessed and installed, but the temperature measurement becomes inaccurate because the wafer placement surface and thermocouple are separated
Solution Approach 1:
The patent introduces a third dimension by creating a vertical thermocouple path through the thickness of the ceramic substrate, allowing the thermocouple to be inserted from the lower surface and positioned at the wafer placement surface level, thus achieving both accessibility and measurement accuracy
Solution Approach 2:
The patent introduces a thermocouple path as an intermediary structure that connects the externally accessible thermocouple insertion hole with the wafer placement surface, enabling accurate temperature measurement while maintaining ease of thermocouple installation and replacement
2Ease of operation
If the thermocouple path is made wide to facilitate thermocouple insertion, then ease of operation improves, but misalignment between upper and lower plates becomes more problematic
Solution Approach 1:
The patent applies different quality requirements to different parts of the thermocouple path: the upper plate groove is made wide for easy thermocouple insertion, while the lower plate opening is made narrower to reduce sensitivity to misalignment, creating local optimization in each region
Solution Approach 2:
The patent designs the thermocouple path with a width transition that anticipates and compensates for potential misalignment between upper and lower plates during assembly, allowing for tolerance accommodation before the actual alignment issue occurs
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 design enables correct temperature measurement of the wafer by positioning the thermocouple close to the wafer, improving measurement accuracy compared to traditional designs.
Implementation Method 1
a resistance heater (22, 24) embedded in the lower plate (P2)
Implementation Method 2
the outer circumferential thermocouple (50) is inserted into the thermocouple path (27) so as to reach a position between the wafer placement surface (20a) and the resistance heaters (22, 24)
Data Source
AI summary
A ceramic heater includes a ceramic substrate, a resistance heater, a cylindrical shaft, a thermocouple path, and a thermocouple insertion hole. The disc-shaped ceramic substrate has a wafer placement surface at an upper surface. The resistance heater is embedded in the ceramic substrate. The cylindrical shaft supports the ceramic substrate from a lower surface of the ceramic substrate. The thermocouple path is provided between the resistance heater and the wafer placement surface and extends from a start position on a center side to an end position on an outer circumferential side inside the ceramic substrate. The thermocouple insertion hole is open at an inner shaft region of the lower surface of the ceramic substrate surrounded by the cylindrical shaft and communicates with the thermocouple path.