Ceramic Heater Shield Layout Against Plasma Electrode Coupling
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Solution Overview
Problem
In ceramic heaters used in plasma CVD processes, plasma that flows around to the back surface of the ceramic plate can couple with the heater electrode, leading to uncontrollable energization and potential abnormal conditions such as abnormal heat generation or expansion.
Innovation Solution
A ceramic heater design incorporating a planar shield portion on the back surface of the ceramic plate, connected to ground, to prevent plasma from coupling with the heater electrode, using conductive materials like ceramic coatings, metal meshes, or metal plates, and optionally side shields to further protect against plasma coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a planar shield portion is added to prevent plasma coupling with the heater electrode, then reliability is improved, but device complexity increases
Solution Approach 1:
A planar shield portion is introduced as an intermediary component between the plasma electrode and heater electrode. This shield portion, connected to ground potential, intercepts and redirects plasma flow before it can couple with the heater electrode, thereby preventing unwanted high-frequency current induction while maintaining clear separation between the plasma generation and heating functions
2Ease of manufacture
If the planar shield portion is connected to ground via a cylindrical conductor on the shaft surface, then ease of manufacture is improved, but device complexity increases
Solution Approach 1:
The ground connection path is relocated from the internal axial dimension to the external radial dimension of the cylindrical shaft. By providing connection surfaces on the outer surface of the shaft, the shield portion can be grounded without requiring members to pass through the shaft interior, simplifying assembly while adding external connection features
3Reliability
If the planar shield portion is embedded in the ceramic plate, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The planar shield portion and its recess in the ceramic plate are prepared in advance during manufacturing. The recess is formed with predetermined dimensions and positioning features that guide the shield portion into its correct location, ensuring reliable plasma shielding while accommodating normal manufacturing tolerances through the pre-designed fit
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
Prevents abnormal conditions like abnormal heat generation or expansion of the heater electrode by effectively shielding plasma from coupling, maintaining thermal uniformity and reducing noise interference.
Implementation Method 1
plasma that has flowed around to a surface (back surface) of the ceramic plate opposite to the wafer placement surface may be coupled to the heater electrode
Implementation Method 2
a planar shield portion arranged on the back surface of the ceramic plate or embedded in the ceramic plate so as to be closer to the back surface than the heater electrode, the planar shield portion being connected to ground
Implementation Method 3
a heater electrode... spaced apart from each other; a heater electrode connecting member arranged in the cylindrical shaft, the heater electrode connecting member being connected to the heater electrode
Data Source
AI summary
A ceramic heater includes a disk-shaped ceramic plate having a wafer placement surface on a front surface thereof, the ceramic plate having a plasma electrode and a heater electrode embedded therein in this order, from closest to the wafer placement surface to farthest, in such a manner that the plasma electrode and the heater electrode are spaced apart from each other; a cylindrical shaft that supports the ceramic plate from a back surface of the ceramic plate; a plasma electrode connecting member arranged in the cylindrical shaft and connected to the plasma electrode; a heater electrode connecting member arranged in the cylindrical shaft and connected to the heater electrode; and a planar shield portion arranged on the back surface of the ceramic plate or embedded in the ceramic plate so as to be closer to the back surface than the heater electrode, the planar shield portion being connected to ground.