Electrostatic Chuck Protrusion Profile for Particle Reduction
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Solution Overview
Problem
Ceramic electrostatic chucks in semiconductor processing systems generate contaminant particles due to lapping processes and microcrystalline structure interactions, leading to substrate damage and contamination during wafer processing.
Innovation Solution
The use of protrusions with a non-arcuate plateau shaped top surface and radiused edges on the electrostatic chuck, which reduces normal and shear stress, minimizing particle generation and contamination by distributing forces uniformly across the contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If protrusions with arcuate or rounded tops are used to support the substrate, then the contact area is reduced, but shear stress concentrates on the protrusions causing particle generation and damage
Solution Approach 1:
The patent applies curvature in a controlled manner by providing radiused edges on the protrusions rather than sharp corners, while maintaining a plateau-shaped top surface. This distributes stress more evenly at the edges without creating the shear stress concentration that would result from sharp corners, thereby reducing particle generation while maintaining adequate contact area.
Solution Approach 2:
The patent differentiates between the top surface geometry and edge geometry of the protrusions. The top surface is plateau-shaped to maintain contact area, while the edges are radiused to reduce stress concentration. This local differentiation of geometric properties allows simultaneous optimization of both contact area and stress distribution.
2Ease of manufacture
If the ceramic material has a microcrystalline structure with grains aligned perpendicular to the surface, then manufacturing is facilitated, but shear stress causes microcrystallite damage and particle generation
Solution Approach 1:
The patent recognizes that the microcrystalline structure has directional properties and designs the protrusion geometry to account for this. By providing a plateau top surface with radiused edges, the stress is distributed in a manner that is less sensitive to the perpendicular grain alignment, reducing microcrystallite damage and particle generation while maintaining manufacturability.
Solution Approach 2:
The patent modifies the geometric parameters of the protrusions (plateau shape, edge radius) to change the stress distribution pattern. This parameter change makes the structure more tolerant of the microcrystalline grain orientation, reducing particle generation from shear stress while preserving the ease of manufacturing the perpendicular grain structure.
3Manufacturing precision
If lapping is used to produce a smooth ceramic surface, then surface finish is improved, but particles are generated and adhere to the surface
Solution Approach 1:
The patent extracts the problematic function of extensive lapping by designing protrusions with radiused edges that are less sensitive to minor surface irregularities. This reduces the need for aggressive lapping that generates particles, while still achieving adequate surface smoothness for proper substrate contact and stress distribution.
4Reliability
If protrusions are used to support the substrate away from electrodes, then electrostatic clamping is improved, but contact heat conduction becomes difficult to control
Solution Approach 1:
The patent optimizes the geometric parameters of the protrusions (height, diameter, plateau dimensions, edge radius) to achieve the desired balance. The plateau shape with radiused edges provides adequate contact area for controllable heat conduction while maintaining the substrate elevation needed for proper electrostatic clamping. The specific geometric parameters are selected to optimize both functions simultaneously.
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 minimizes particle transfer and damage to both the chuck and substrate, enhancing the cleanliness and reliability of semiconductor processing by reducing stress concentrations and maintaining a low surface roughness.
Implementation Method 1
the back side of a substrate, such as a semiconductor wafer, is held to the face of the electrostatic chuck by an electrostatic force
Implementation Method 2
Heat delivered to the substrate during processing can be transferred away from the substrate and to the electrostatic chuck by contact heat conduction with the protrusions
Data Source
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AI summary
An electrostatic chuck with a generally non-arcuate top surface shaped protrusions that has edge surfaces similar to a portion of a ellipse. The structure of the protrusions leads to the reduction of particulate material generated by interaction between the supported substrate and chuck. Reduced levels of scratching, abrasion, wear and particulate generation are achieved by improved smoothing and flattening of the protrusion surface.