Multipolar Electrostatic Chuck Layout for Wafer Flatness in Plasma Processing
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Solution Overview
Problem
Existing electrostatic chucks (ESCs) face challenges in maintaining wafer flatness during plasma processing due to high process-induced stress from mismatched thermal expansion and 3D structures, leading to wafer bow and warpage, which affects sidewall profiles and temperature control.
Innovation Solution
An electrostatic chuck with a monolithic insulating substrate embedded with a multipolar configuration of electrodes and an RF electrode, synchronized to apply DC bias signals for clamping and RF signals for plasma generation, ensuring uniform electrostatic gripping and efficient plasma processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional electrostatic chuck is used to hold the wafer, then the wafer can be clamped for plasma processing, but high process-induced stress from mismatched thermal expansion and 3D structures causes wafer bow and warpage, leading to inadequate flatness
Solution Approach 1:
The electrostatic chuck divides the clamping function into multiple independent electrode zones (central, intermediate, edge zones) that can be controlled separately. This segmentation allows differential voltage application to compensate for stress-induced warpage in different wafer regions, maintaining flatness despite high process-induced stress from thermal expansion mismatch and 3D structures.
Solution Approach 2:
The electrostatic chuck dynamically adjusts the voltage applied to each electrode zone during the plasma processing sequence. By switching between clamping voltages (to maintain flatness) and release voltages (to accommodate stress changes), the system adapts to varying stress conditions throughout the processing cycle, preventing both bow and warpage.
2Manufacturing precision
If DC bias signals are continuously applied to maintain wafer clamping, then wafer flatness is maintained, but plasma generation and processing cannot be performed
Solution Approach 1:
The electrostatic chuck implements periodic switching between clamping mode (DC bias applied) and plasma processing mode (DC bias removed, RF power applied). This periodic action allows the wafer to be firmly clamped for flatness during positioning, then released for plasma processing, and re-clamped to maintain flatness during subsequent processing steps, achieving both flatness and productivity.
Solution Approach 2:
The electrostatic chuck applies DC bias signals in advance to clamp the wafer flat before plasma processing begins. This preliminary clamping action ensures the wafer starts in a flat state, and by strategically timing the release and re-application of DC bias during the processing sequence, the system maintains flatness without continuously preventing plasma generation.
3Manufacturing precision
If multiple electrode zones are controlled independently to compensate for warpage, then wafer flatness is improved, but device complexity increases
Solution Approach 1:
The electrostatic chuck assigns different voltage levels to different spatial zones (central, intermediate, edge) based on the local stress distribution pattern. This local quality approach targets compensation specifically where needed (edge zones with higher stress) rather than uniformly across the entire wafer, improving flatness while limiting the complexity increase to manageable voltage switching patterns.
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 enhanced wafer flatness and uniform plasma processing, improving sidewall profiles and backside temperature control, suitable for advanced plasma processing of semiconductor wafers.
Implementation Method 1
a plurality of electrodes embedded in the insulating substrate, in a multipolar configuration to receive multiple DC bias signals
Implementation Method 2
a radio frequency (RF) electrode embedded in the insulating substrate... configured to generate an RF signal
Data Source
AI summary
An electrostatic chuck (ESC) for holding a workpiece in a plasma processing chamber, where the ESC includes a monolithic insulating substrate with a top surface; a plurality of electrodes embedded in the insulating substrate, the plurality of electrodes being in a multipolar configuration to receive multiple DC bias signals from a first power supply circuit; and a radio frequency (RF) electrode embedded in the insulating substrate, the plurality of electrodes being located between the top surface and the RF electrode, the RF electrode including a contact node configured to be coupled to a second power supply circuit configured to generate an RF signal.