Wafer Support Table Rod Coating for RF Impedance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wafer support tables used for plasma processes, the portion of the wafer above the RF electrode connected to a Ni- or Kovar-made rod can experience uneven heating, leading to a high temperature rise, which affects plasma treatment uniformity.
Innovation Solution
A thin film of a copper family element (such as Cu, Ag, or Au) is coated over the outer peripheral surface of the rod, from its base end to a predetermined position, to reduce impedance and prevent excessive heat dissipation, thereby minimizing temperature increases in the wafer above the rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a Ni- or Kovar-made rod is used to supply RF electric power to the RF electrode, then the rod can effectively transmit radio-frequency power, but the temperature of the rod becomes excessively high in the range below the Curie point due to large impedance, causing uneven heating and high temperature rise in the wafer portion above the rod
Solution Approach 1:
The patent applies local quality by coating only a specific region of the rod (from the base end to a predetermined position) with a copper family element thin film, rather than coating the entire rod. This localized coating approach reduces impedance and prevents excessive heat generation in the critical region where the rod connects to the RF electrode, while avoiding unnecessary coating in regions where it would not provide benefit or would increase cost. The coating region is strategically selected to address the temperature uniformity problem without wasting materials or adding unnecessary complexity.
2Temperature
If a thin film of copper family element is coated over the entire rod surface, then impedance is reduced and temperature rise is prevented, but manufacturing cost increases due to excessive use of expensive copper family elements
Solution Approach 1:
The patent implements local quality by restricting the copper family element coating to only the necessary region of the rod (from the base end to a predetermined position), rather than coating the entire surface. This selective coating approach maintains the temperature control benefit where it is needed most while significantly reducing the quantity of expensive copper family element materials required, thereby lowering manufacturing cost.
Solution Approach 2:
The patent applies partial action by coating only the essential portion of the rod with the copper family element thin film. The coating extends from the base end to a predetermined position that is sufficient to achieve the desired impedance reduction and temperature control, without extending unnecessarily to the entire rod length. This partial coating achieves the required functional effect while optimizing material usage and cost.
3Power
If the rod is entirely heated to high temperature, then RF power can be supplied effectively, but heat dissipation from the ceramic base through the rod is insufficient, leading to temperature rise in the wafer portion above the rod
Solution Approach 1:
The patent addresses the heat dissipation issue by applying local quality through selective coating of the rod. The copper family element thin film is coated on the region from the base end to a predetermined position, creating a localized low-impedance path that improves heat dissipation efficiency in the critical region without requiring the entire rod to be heated to high temperature. This localized modification enables effective RF power supply while improving thermal management.
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 effectively prevents high-temperature rises in the wafer above the RF electrode at a low cost by using a thin copper family element film, ensuring uniform plasma treatment while optimizing the use of expensive materials.
Implementation Method 1
because the copper family element (Cu, Ag or Au) has low impedance and a radio-frequency wave passes through the thin film of the copper family element due to the skin effect
Implementation Method 2
the temperature in a portion coated with the thin film of the copper family element (i.e., in a portion relatively far away from the ceramic base) is less apt to become high, and that portion does not impede dissipation of heat from the ceramic base
Data Source
AI summary
A wafer support table includes a ceramic base and a rod. The ceramic base has a wafer placement surface and includes an RF electrode and a heater electrode that are embedded therein in the mentioned order from the side closer to the wafer placement surface. A hole is formed in the ceramic base to extend from a rear surface toward the RF electrode. The rod is made of Ni or Kovar, is bonded to a tablet exposed at a bottom surface of the hole, and supplies radio-frequency electric power to the RF electrode therethrough. An Au thin film is coated over a region of an outer peripheral surface of the rod ranging from a base end of the rod to a predetermined position.