MgO Ceramic Electrostatic Chuck with Composite Electrodes
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Solution Overview
Problem
The existing electrostatic chucks with a ceramic base mainly containing MgO face issues of microcracking, warpage, and diffusion of electrode material into the dielectric layer, leading to functional failures and reduced throughput.
Innovation Solution
The use of specific conductive materials for the electrostatic and heater electrodes, such as those produced by firing metal powders like Ni, Co, and Fe, or their carbides, within a MgO ceramic base, along with a method involving the formation of laminates and hot pressing, to inhibit microcracking and electrode material diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrode materials are used in an MgO ceramic base, then the electrostatic chuck can be manufactured, but microcracking and warpage occur due to thermal expansion mismatch and material reactivity
Solution Approach 1:
The patent changes the material parameters of the electrode by using composite materials (metal powder + carbide powder) instead of pure metals. This modification adjusts the thermal expansion coefficient and chemical stability to match the MgO ceramic base, preventing microcracking and warpage while maintaining electrical conductivity.
Solution Approach 2:
The patent employs composite electrode materials consisting of metal powder (Ni, Co, or Fe) mixed with carbide powder (TiC, TaC, or NbC). This composite structure combines the high conductivity of metals with the thermal stability and chemical inertness of carbides, resolving the contradiction between electrical performance and structural stability in MgO ceramic bases.
2Ease of manufacture
If inappropriate electrode materials are used, then manufacturing is simpler, but electrode material diffuses into the dielectric layer causing functional failure
Solution Approach 1:
The carbide powder component in the composite electrode material provides chemical inertness and forms a stable barrier that prevents metal diffusion into the dielectric layer. This maintains electrode stability and prevents functional failure while still allowing straightforward fabrication processes.
Solution Approach 2:
The patent uses metal powders (Ni, Co, Fe) that are relatively inexpensive and can be easily applied through simple coating methods. The carbide component protects these metals from degrading or diffusing, effectively creating a durable electrode from materials that would otherwise be prone to degradation.
3Ease of manufacture
If non-matching thermal expansion coefficients are used between electrode and ceramic base, then manufacturing is easier, but warpage occurs during heating cycles
Solution Approach 1:
The composite electrode material's thermal expansion coefficient is adjusted through the ratio of metal to carbide components. The carbide portion (TiC, TaC, NbC) has a thermal expansion coefficient closer to MgO ceramic than pure metals do, reducing thermal stress and preventing warpage during heating and cooling cycles.
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 approach prevents microcracking, warpage, and electrode material diffusion, ensuring uniform temperature distribution and high throughput by selecting materials with matching thermal expansion coefficients and preventing reactivity with the MgO base.
Implementation Method 1
an electrostatic electrode configured to generate an electrostatic force on the wafer-supporting surface
Implementation Method 2
a heater electrode embedded therein, as needed, the heater electrode being configured to heat the wafer-supporting surface (also referred to as a 'resistance heating element')
Implementation Method 3
a conductive material produced by firing at least one metal selected from the group consisting of Ni, Co, and Fe
Data Source
AI summary
An electrostatic chuck includes an electrostatic electrode embedded in a ceramic base having a wafer-supporting surface capable of holding a wafer, the electrostatic electrode being parallel to the wafer-supporting surface. The ceramic base is composed of a dense ceramic having a MgO content of 99% by weight or more. The electrostatic electrode is a disc-like electrode composed of, for example, at least one metal selected from the group consisting of Ni, Co, and Fe. The electrostatic electrode includes a conductive tablet connected to the center thereof. The tablet is exposed at the bottom of a counter-bored hole formed so as to reach the tablet from a back surface of the ceramic base, and is connected to a feeding terminal, composed of Ni, inserted into the counter-bored hole.