Cryogenic Electrostatic Chuck Bonding to Prevent Delamination
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Solution Overview
Problem
Conventional electrostatic chucks used in microelectronic manufacturing experience delamination and failure due to thermal stresses in cryogenic applications, leading to increased costs and reduced processing yield, as standard adhesives cannot maintain bonds at sub-zero temperatures.
Innovation Solution
An electrostatic chuck assembly with a cooling plate made from an aluminum alloy and a bonding layer containing silicone material, which has a low coefficient of thermal expansion, is used to secure the electrostatic chuck, preventing delamination and maintaining a stable bond at cryogenic temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard adhesives are used to bond the cooling plate and electrostatic chuck, then the assembly can be manufactured easily, but the bond fails at cryogenic temperatures due to thermal stress
Solution Approach 1:
The patent changes the material parameters by selecting a bonding material (silicone-based adhesive or epoxy resin) specifically designed to maintain adhesive properties at cryogenic temperatures. This bonding material has a glass transition temperature below the operating temperature range, ensuring it remains flexible and maintains bond strength when cooled to −100° C. or lower, thus resolving the contradiction between ease of manufacture and reliability at cryogenic temperatures.
Solution Approach 2:
The patent addresses thermal expansion mismatch by carefully selecting materials with compatible coefficients of thermal expansion (CTE). The bonding material is chosen to have a CTE that bridges the gap between the aluminum cooling plate and the electrostatic chuck substrate, reducing thermal stress during temperature cycling. This prevents delamination while maintaining the bonding capability during assembly.
2Productivity
If the cooling plate is cooled to cryogenic temperatures to remove heat from the substrate, then processing yield improves, but delamination occurs due to thermal stress from CTE differences
Solution Approach 1:
The bonding material's glass transition temperature is changed to be below the cryogenic operating temperature, ensuring the material remains in a rubbery or flexible state rather than becoming brittle. This parameter change allows the bonding layer to accommodate thermal contraction at −100° C. or lower without failing, maintaining bond integrity while enabling high-yield cryogenic processing.
Solution Approach 2:
The patent employs a composite bonding structure that may include multiple layers or a hybrid material system combining silicone and epoxy components. This composite approach leverages the flexibility of silicone to accommodate thermal stress while maintaining the strong adhesion properties of epoxy, thus preventing delamination during cryogenic cooling while supporting high productivity operations.
3Productivity
If conventional electrostatic chucks are used in high temperature and high power fabrication, then processing capabilities are improved, but the bonding material delaminates due to thermal stress and high energy fields
Solution Approach 1:
The bonding material is selected with a glass transition temperature well above the maximum processing temperature to ensure it remains dimensionally stable and maintains bond strength under thermal stress. The material is also chosen for its resistance to high energy fields and plasma environments, preventing degradation and delamination during high-power fabrication processes.
Solution Approach 2:
The patent selects bonding materials and substrate materials with matched coefficients of thermal expansion to minimize differential thermal stress during high-temperature processing. This CTE matching prevents delamination caused by expansion/contraction cycles, enabling reliable operation during high-temperature and high-power fabrication while maintaining processing capability.
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 solution effectively handles cryogenic processing temperatures without cracking or delamination, ensuring reliable substrate support and reducing downtime and costs associated with electrostatic chuck failures.
Implementation Method 1
The cooling plate is exposed to a cryogenic fluid to remove heat from the substrate
Implementation Method 2
The delamination is brought on by thermal stresses in these bodies caused by the differences in thermal expansion coefficients of the various materials in the bodies
Data Source
AI summary
Embodiments of the present disclosure generally relate to an electrostatic chuck assembly suitable for use in cryogenic applications. In one or more embodiments, an electrostatic chuck assembly is provided and includes an electrostatic chuck having a substrate supporting surface opposite a bottom surface, a cooling plate having a top surface, where the cooling plate contains an aluminum alloy having a coefficient of thermal expansion (CTE) of less than 22 ppm/° C., and a bonding layer securing the bottom surface of the electrostatic chuck and the top surface of the cooling plate, where the bonding layer contains a silicone material.