Ceramic Heater Gap Design for Leak Current Suppression
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Solution Overview
Problem
Ceramic susceptor materials face challenges in transmitting infrared radiation and transferring heat efficiently, leading to excessive temperature increases and leak currents between RF electrodes and heaters, which hinder effective heating of substrates.
Innovation Solution
A ceramic member design featuring a first base body with an embedded electrode and a second base body with an embedded heating resistor, joined with a controlled gap, where the gap's dimensions and thermal conductivity optimize heat transfer and minimize leak currents, with optional filling with a medium of higher thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic material with high thermal conductivity (such as aluminum nitride) is used for the susceptor, then heat transfer from the heater is improved, but the insulating property is reduced causing leak current between the RF electrode and heater
Solution Approach 1:
The susceptor is divided into two separate ceramic base bodies (first base body with RF electrode, second base body with heater) that are joined together. This segmentation allows each base body to be made of high thermal conductivity ceramic while maintaining electrical insulation through the joining structure and gap, thus resolving the contradiction between heat transfer efficiency and insulating property.
Solution Approach 2:
A joining structure with a controlled gap (0.1mm to 5mm) is introduced between the two ceramic base bodies. This gap acts as an intermediary that maintains electrical insulation while allowing thermal coupling through radiation and conduction, enabling both high heat transfer efficiency and adequate insulating property simultaneously.
2Productivity
If the heater is positioned close to the substrate for efficient heating, then heating efficiency is improved, but excessive temperature increase causes wire breaking
Solution Approach 1:
The gap between the heater and first base body (0.1mm to 5mm) serves as a thermal intermediary that enables efficient heat transfer to the substrate while preventing excessive temperature concentration that could damage heater wires. This controlled spacing optimizes both heating efficiency and temperature control.
Solution Approach 2:
The invention optimizes the gap dimension parameter (0.1mm to 5mm) to achieve the best balance between heating efficiency and temperature control. By carefully controlling this geometric parameter, the system achieves high productivity without compromising component reliability.
3Reliability
If the gap between the first base body and second base body is large, then leak current is suppressed, but heat transfer from heater to substrate is inhibited
Solution Approach 1:
The invention optimizes the gap dimension parameter within a specific range (0.1mm to 5mm) to achieve the best compromise between leak current suppression and heat transfer efficiency. This parameter optimization ensures that the gap is large enough to suppress leak current but small enough to maintain effective thermal coupling for heating the substrate.
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 suppresses excessive heat inhibition and leak currents, allowing for precise temperature control and efficient heating of substrates, while maintaining the structural integrity of the ceramic components.
Implementation Method 1
a heating resistor embedded in a second base body 20 made of a ceramic sintered body
Implementation Method 2
the heat generated from the heater is not readily transferred through the parent material
Implementation Method 3
heating of the substrate placed on the upper surface of the placement susceptor member by the heater is achieved with radiant heat transfer by infrared radiation
Data Source
AI summary
A ceramic heater includes an RF plate having a placement surface on which a wafer is to be placed, and made of a ceramic sintered body in which an RF electrode is embedded; and a heater plate made of a ceramic sintered body in which a heater is embedded, the RF plate and the heater plate being joined with a space interposed therebetween on a side opposite to the placement surface. The relationship among a minimum height H (mm) of the space in a direction perpendicular to the placement surface, a proportion A of a total area of portions where the RF plate and the heater plate are joined, with respect to an area of a plane along the placement surface that is defined by an outer edge of the placement surface, and a distance D (mm) between the RF electrode and the heater, satisfies H/A≤1000 and H/A+(D−H)/(1−A)≥14.