Dual-Mesh Electrostatic Chuck for High-Power RF Plasma Etching
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Solution Overview
Problem
Current electrostatic chucks (ESCs) fail to withstand high voltage and high bias power conditions in plasma etching processes, leading to issues like dielectric breakdown, plasma ignition, and increased wafer de-chucking difficulties due to charge buildup and temperature fluctuations.
Innovation Solution
The design incorporates a dual mesh electrode structure within the electrostatic chuck, with a lower mesh connected to the upper mesh via pegs, forming a Faraday cage that shields against charge buildup and reduces capacitance, thereby preventing helium ignition and enhancing RF power conduction while maintaining thermal uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high bias power (20 KW) is applied to achieve high aspect ratio plasma etching, then etching performance is improved, but the electrostatic chuck experiences dielectric breakdown and bond failures
Solution Approach 1:
The electrostatic chuck is divided into multiple segments: a top plate with gas holes, a dielectric layer, and a bottom plate with RF electrodes. This segmentation allows each layer to perform its specific function - the top plate enables plasma access, the dielectric provides insulation, and the bottom plate delivers RF power, collectively enabling high power operation without dielectric breakdown
Solution Approach 2:
A dielectric layer is introduced as an intermediary between the top plate and bottom plate. This dielectric layer acts as a mediator that withstands the high voltage differential while allowing RF power to couple through to the plasma, preventing direct electrical breakdown across the entire chuck structure
2Productivity
If high RF plasma power is applied to increase etch rate, then productivity is improved, but the ESC surface temperature changes at a higher rate causing thermal instability
Solution Approach 1:
The bottom plate is equipped with multiple RF electrodes distributed across its surface, creating localized heating zones. This allows RF power to be applied locally at specific regions rather than uniformly across the entire chuck, enabling better thermal management and reduced temperature fluctuations during high power operation
Solution Approach 2:
The bottom plate serves multiple functions: it provides structural support, acts as an RF power delivery system through embedded electrodes, and functions as a thermal management component. This multi-functionality allows the same component to handle both power delivery and thermal stability requirements
3Adaptability or versatility
If gas holes are designed into the ESC to enable plasma access, then process capability is improved, but plasma ignition occurs in the holes at high power causing reliability issues
Solution Approach 1:
The top plate and bottom plate are both biased to the same plasma potential through the dielectric layer, creating an equipotential structure. This eliminates large voltage differentials across the gas holes, preventing plasma ignition within the holes while still allowing plasma to access the wafer through the hole array
4Device complexity
If a single mesh electrode is used in the electrostatic chuck, then device complexity is low, but capacitance is high leading to reduced RF power conduction efficiency
Solution Approach 1:
The single mesh electrode is segmented into multiple RF electrodes distributed across the bottom plate. This segmentation reduces the overall capacitance of the system by distributing the electrical load across multiple smaller electrode elements, thereby improving RF power conduction efficiency and reducing reactive power
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 solution increases the etch rate by up to 10% and reduces arcing and bond failures, allowing the ESC to handle higher plasma powers and frequencies effectively.
Implementation Method 1
a lower mesh connected to the upper mesh via pegs, forming a Faraday cage that shields against charge buildup and reduces capacitance
Implementation Method 2
an electrostatic chuck... with a lower mesh connected to the upper mesh via pegs, forming a Faraday cage that shields against charge buildup
Data Source
AI summary
An electrostatic chuck is described that has radio frequency coupling suitable for use in high power plasma environments. In some examples, the chuck includes a base plate, a top plate, a first electrode in the top plate proximate the top surface of the top plate to electrostatically grip a workpiece, and a second electrode in the top plate spaced apart from the first electrode, the first and second electrodes being coupled to a power supply to electrostatically charge the first electrode.