Bipolar Electrostatic Chuck Assembly for Uniform Plasma Etching
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Solution Overview
Problem
Conventional electrostatic chucks face challenges in high-temperature operations due to thermo-mechanical stresses and uneven plasma distribution, leading to increased manufacturing costs and non-uniform etch rates across semiconductor substrates.
Innovation Solution
A bipolar electrostatic chuck assembly with a heat transfer plate and RF transmission tube, where RF power is transferred through a continuous interface to minimize plasma shift and reduce thermo-mechanical stresses, using a puck bonded to the heat transfer plate with chucking electrodes to maintain substrate clamping and plasma distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal electrodes are embedded within the ceramic chuck body, then electrostatic clamping field can be generated, but thermal expansion coefficient differences cause thermo-mechanical stresses that can fracture the ceramic at high temperatures
Solution Approach 1:
The chuck body is divided into separate components: a ceramic body portion and a metal collar portion with the electrode. The metal collar is positioned at the periphery and electrically connected to the ceramic body through a conductive path, allowing the electrode function to be segmented from the main ceramic structure. This segmentation prevents thermal stress concentration in the ceramic while maintaining electrostatic clamping capability.
Solution Approach 2:
A transition region or intermediate structure is provided between the metal electrode collar and the ceramic body. This intermediate structure accommodates the thermal expansion difference between metal and ceramic materials, acting as a buffer that reduces thermo-mechanical stresses. The intermediate structure may include a graded material composition or a flexible connection that allows differential thermal expansion without causing ceramic fracture.
2Strength
If the ceramic chuck body is made thicker to prevent fracture from thermal stresses, then structural integrity is improved, but manufacturing cost increases
Solution Approach 1:
The chuck assembly is segmented into a thin ceramic body portion and a separate metal collar portion. By moving the electrode function to the peripheral metal collar rather than embedding it throughout the ceramic body, the ceramic can be made thinner without compromising structural integrity. This reduces the amount of expensive ceramic material required while maintaining fracture resistance through the segmented design.
Solution Approach 2:
The electrode function is extracted from the ceramic body and relocated to a separate metal collar component positioned at the periphery. This extraction allows the ceramic body to be optimized for thermal and mechanical performance with reduced thickness, while the electrode functionality is provided by the metal collar. The separation eliminates the need for thick ceramic construction to accommodate embedded electrodes.
3Power
If RF power is applied to embedded electrodes to ignite plasma, then plasma generation is achieved, but the magnetic field shifts to one side causing uneven plasma distribution and non-uniform etch rates
Solution Approach 1:
The electrode configuration uses an asymmetric bipolar design with positive and negative electrodes positioned at opposite sides of the substrate. This asymmetric arrangement creates a balanced magnetic field that prevents the plasma from shifting to one side. The bipolar configuration ensures that the magnetic field lines are distributed symmetrically across the substrate, resulting in uniform plasma distribution and uniform etch rates across the entire substrate surface.
4Reliability
If conventional electrostatic chuck design is used, then substrate clamping is achieved, but additional processing steps are required to compensate for uneven plasma distribution
Solution Approach 1:
The bipolar electrode configuration with positive and negative electrodes positioned at opposite sides creates a balanced electromagnetic field that eliminates plasma shift. This asymmetric but balanced design achieves uniform plasma distribution across the substrate, eliminating the need for additional compensatory processing steps. The result is improved processing efficiency and productivity while maintaining reliable substrate clamping.
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 provides a cost-effective, high-temperature capable electrostatic chuck with improved plasma distribution and increased etch rate uniformity, reducing the need for additional processing steps and lowering manufacturing costs.
Implementation Method 1
RF power is applied to the embedded electrodes to ignite a plasma by generating a magnetic field that ignites processes gases to form a plasma
Implementation Method 2
Conventional electrostatic chucks typically include one or more electrodes embedded within a unitary chuck body which comprises a dielectric or semi-conductive ceramic material across which an electrostatic clamping field can be generated
Implementation Method 3
The RF transmission tube is configured to transfer RF power to the heat transfer plate
Data Source
AI summary
An electrostatic chuck assembly including a body including a body recess and a heat transfer plate disposed in the body recess, wherein the heat transfer plate includes an upper surface, a lower surface, a first opening, and a second opening. The electrostatic chuck assembly further includes an RF transmission tube configured to transfer RF power to the lower surface of the heat transfer plate. The electrostatic chuck assembly further includes a puck bonded to the upper surface of the heat transfer plate. The electrostatic chuck assembly further includes a first chucking electrode disposed in the first opening and a second chucking electrode is disposed in the second opening, wherein the first and second chucking electrodes are configured to transfer a chucking voltage to the puck.