Electrostatic Chuck Segmented Electrodes for Focus Ring Control
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Solution Overview
Problem
Existing electrostatic chucks fail to sufficiently attract and cool focus rings during plasma processing, leading to increased wafer edge temperatures and reduced process yields due to inadequate control over Coulomb and Johnsen-Rahbek forces.
Innovation Solution
An electrostatic chuck design featuring a first ceramic member with a wafer holding surface and a second ceramic member with a focus ring holding surface, each with independent electrodes, allowing for separate voltage application to exert Coulomb and Johnsen-Rahbek forces, respectively, to effectively attract and cool the focus ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common electrode is shared between the wafer holding surface and the focus ring holding surface, then the device complexity is reduced, but it is not possible to set appropriate voltages for both the wafer and focus ring independently
Solution Approach 1:
The electrode structure is segmented into a first electrode for the wafer holding surface and a second electrode for the focus ring holding surface. This segmentation allows independent voltage application to each electrode, enabling separate control of electrostatic forces for wafer and focus ring attraction while maintaining structural integration.
2Ease of manufacture
If the same ceramic member is provided with both wafer attracting electrode and focus ring attracting electrode, then the manufacturing process is simplified, but it is difficult to attract the wafer with Coulomb force and the focus ring with Johnsen-Rahbek force simultaneously
Solution Approach 1:
Different regions of the ceramic member are assigned different functional properties: the first ceramic member region contains the first electrode for Coulomb force attraction of the wafer, while the second ceramic member region contains the second electrode for Johnsen-Rahbek force attraction of the focus ring. This local differentiation enables appropriate force mechanisms for each component while maintaining integration.
3Strength
If the focus ring is much greater in thickness than the wafer, then the focus ring structure is more robust, but it may not be sufficiently attracted to the electrostatic chuck and may be excessively heated
Solution Approach 1:
The voltage applied to the second electrode is optimized to generate sufficient Johnsen-Rahbek force for attracting the thick focus ring. By controlling the voltage parameter, the electrostatic attraction force is adjusted to match the increased thickness and mass of the focus ring, ensuring adequate attraction and cooling while maintaining structural integrity.
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 ensures robust attraction and cooling of focus rings, preventing warpage and improving plasma processing yields by allowing independent voltage control and using ceramic materials with specific resistivity ranges for reliable force exertion.
Implementation Method 1
the first ceramic member having a volume resistivity that allows Coulomb force to be exerted
Implementation Method 2
the second ceramic member having a volume resistivity that allows Johnsen-Rahbek force to be exerted
Data Source
AI summary
An electrostatic chuck includes a first ceramic member disk-shaped and having an annular step surface outside a circular wafer holding surface thereof, the annular step surface being at a lower level than the wafer holding surface, the first ceramic member having a volume resistivity that allows Coulomb force to be exerted; a first electrode embedded in the first ceramic member at a position facing the wafer holding surface; a second electrode disposed on the annular step surface of the first ceramic member, the second electrode being independent of the first electrode; and a second ceramic member having an annular shape and configured to cover the annular step surface having the second electrode thereon, the second ceramic member having a volume resistivity that allows Johnsen-Rahbek force to be exerted, wherein an upper surface of the second ceramic member is a focus ring holding surface on which a focus ring is placed.