Wafer Placement Table With Non-Uniform Cooling Substrate Thickness
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Solution Overview
Problem
Wafer placement tables with metal joining layers face stress damage due to significant temperature differences in the vertical direction, as the metal joining layer has limited stress relaxation properties and a higher Young’s modulus compared to resin layers, which can lead to damage in the cooling substrate.
Innovation Solution
A wafer placement table design featuring a ceramic substrate with a metal-ceramic composite cooling substrate and a metal joining layer, where the thickness of the lower part of the cooling substrate is greater than or equal to 13 mm or 43% of the overall thickness, reducing the likelihood of stress damage in the upper part by minimizing temperature differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a metal joining layer is used to join the ceramic substrate to the cooling substrate, then thermal conductivity is improved, but stress relaxation capability deteriorates
Solution Approach 1:
The patent changes the physical parameters of the metal joining layer by controlling its thickness to be 1 mm or less. This parameter change allows the layer to maintain high thermal conductivity while reducing its rigidity and improving stress relaxation capability, thereby resolving the contradiction between thermal conductivity and stress relaxation.
2Strength
If the upper part of the cooling substrate is made thicker, then structural strength is improved, but temperature difference in vertical direction increases
Solution Approach 1:
The patent applies local quality by making the cooling substrate thickness non-uniform: the upper part has a smaller thickness (5-15 mm) to reduce thermal resistance and temperature difference, while the lower part has a larger thickness (10-30 mm) to provide structural strength and support. This localized differentiation resolves the contradiction between strength and temperature uniformity.
3Reliability
If a resin layer is used to join the ceramic substrate to the cooling substrate, then stress relaxation is improved, but thermal conductivity deteriorates
Solution Approach 1:
The patent uses a metal joining layer as an intermediary between the ceramic substrate and cooling substrate. By making this intermediary layer extremely thin (1 mm or less), it provides sufficient stress relaxation while maintaining high thermal conductivity, thus avoiding the thermal conductivity problem of resin layers while keeping stress relaxation benefits.
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
The design effectively prevents stress-induced damage to the upper part of the cooling substrate by maintaining a smaller thickness above the cooling medium passage, enhancing thermal uniformity and reducing the risk of warpage and cracks, while maintaining high thermal conductivity for efficient heat removal.
Implementation Method 1
The metal joining layer has a higher thermal conductivity than a resin layer, and thus can provide a heat removing capability required when a wafer is treated with high-power plasma
Implementation Method 2
a cooling substrate made of a metal-ceramic composite and having a cooling medium passage formed therein
Data Source
AI summary
A wafer placement table includes a ceramic substrate having a wafer placement surface on an upper surface thereof and containing an electrode therein, a cooling substrate made of a metal-ceramic composite and having a cooling medium passage therein, and a metal joining layer configured to join a lower surface of the ceramic substrate to an upper surface of the cooling substrate. A thickness of a lower part of the cooling substrate below the cooling medium passage is greater than or equal to 13 mm, or greater than or equal to 43% of an overall thickness of the cooling substrate.