Electrostatic Chuck Warped Surface for Flatness
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Solution Overview
Problem
Conventional electrostatic chucks face issues with uneven temperature distribution and particle formation due to warping and thickness variations in the workpiece-chucking surface, leading to inadequate attracting force and thermal stress, which affects semiconductor wafer processing.
Innovation Solution
An electrostatic chuck with a built-in electric heating means featuring a base plate of carbon or carbon-based material, with strategically warped surfaces to ensure a flat workpiece-chucking surface when mounted, utilizing pyrolytic boron nitride and pyrolytic graphite layers, and machine-working to achieve uniform thickness and concave/convex shapes for optimal flatness and reduced particle generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the ceramic substrate is increased to suppress strain, then the rigidity is enhanced, but thermal stress accumulates inside the substrate and at interfaces, causing ruptures upon repeated temperature cycles
Solution Approach 1:
The invention changes the physical parameters of the ceramic substrate by controlling the grain size to 10 μm or less and adjusting the porosity to 30-50%, which fundamentally alters the mechanical and thermal properties to achieve both rigidity and thermal stress resistance
Solution Approach 2:
The invention uses a composite ceramic structure with controlled grain size and porosity, combining dense regions for rigidity with porous regions for stress relief, creating a material that simultaneously achieves high rigidity and thermal shock resistance
2Ease of manufacture
If a sintered body with sintering auxiliary agent is used as the ceramic substrate, then the manufacturing is easier, but strain occurs due to thermal stress from coefficient of thermal expansion differences, leading to deficient surface matching and disrupted temperature distribution
Solution Approach 1:
The invention changes the microstructural parameters of the ceramic by controlling grain size to 10 μm or less and porosity to 30-50%, which reduces thermal stress and improves surface flatness while maintaining manufacturability
Solution Approach 2:
The invention creates local quality variations within the ceramic substrate through controlled porosity distribution, where certain regions have different density and thermal properties to compensate for thermal expansion stresses and maintain surface flatness
3Strength
If a thicker ceramic substrate is used to suppress strain, then the rigidity is enhanced, but the heat capacity increases, requiring more time for temperature raising and lowering
Solution Approach 1:
The invention changes the thermal parameters by controlling grain size and porosity, creating a ceramic structure with optimized heat capacity that allows fast temperature cycling while maintaining rigidity
Solution Approach 2:
The invention uses a thin ceramic substrate with controlled porosity that provides sufficient rigidity while minimizing heat capacity, enabling rapid temperature changes required for high-productivity semiconductor processing
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 enhances in-plane temperature distribution and reduces particle formation, providing a stable and uniform attracting force, thus improving semiconductor manufacturing yields by ensuring a flat workpiece-chucking surface and minimizing thermal stress.
Implementation Method 1
an electroconductive layer (a2) to serve as a chucking electrode
Implementation Method 2
an electroconductive layer (b2) to serve as an electric heater element
Data Source
AI summary
The invention provides an electrostatic chuck in which a workpiece-chucking surface is made flat. An electrostatic chuck with a built-in electric heating means comprises a base plate formed of carbon or a carbon-based composite material and, successively formed on one surface of the base plate, an insulating layer (a1), an electroconductive layer (a2) to serve as a chucking electrode and an dielectric layer (a3) to form a workpiece-chucking surface and, successively formed on the other surface of the base plate, an insulating layer (b1) and an electroconductive layer (b2) to serve as an electric heater element, the electrostatic chuck improved in that the workpiece-chucking surface of the electrostatic chuck and an opposite surface thereof are warped to have a relationship selected from concavo-convex and convexo-concave, and in that the warping of the surfaces is in a manner such that the workpiece-chucking surface of the dielectric layer is rendered flat when the opposite surface of the electrostatic chuck is fastened to a machine.