Multi-Zone Electrostatic Chuck for Wafer Flatness Control
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Solution Overview
Problem
Larger wafers in semiconductor manufacturing, such as 300 mm and 450 mm, experience severe warpage issues that lead to manufacturing defects due to non-uniform chucking and particle contamination during processing, which existing electrostatic chucks fail to adequately address.
Innovation Solution
An electrostatic chuck with multiple concentric zones and independently controlled power supply units, combined with a control unit that measures wafer flatness and adjusts voltage application patterns to reduce warpage and prevent particle contamination, allowing for precise and uniform wafer holding and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional electrostatic chuck is used to hold large wafers, then the wafer can be chucked, but wafer warpage becomes severe and chucking uniformity deteriorates
Solution Approach 1:
The electrostatic chuck surface is divided into multiple concentric zones (center zone, intermediate zone, outer zone) that can be independently controlled. Each zone has its own power supply unit, allowing differential voltage application to address non-uniform wafer warpage by applying higher voltage to edge zones and lower voltage to center zones, thereby improving chucking uniformity across the entire wafer surface.
2Manufacturing precision
If voltage is applied to the electrostatic chuck to flatten the wafer, then wafer flatness improves, but particle contamination increases due to non-uniform chucking
Solution Approach 1:
Different zones of the electrostatic chuck are assigned different voltage levels based on the local warpage characteristics of the wafer. The center zone, intermediate zone, and outer zone each receive customized voltage application, creating locally optimized chucking conditions that prevent excessive force concentration and reduce particle generation while maintaining overall wafer flatness.
Solution Approach 2:
The electrostatic chuck system dynamically adjusts voltage levels across different zones based on real-time wafer flatness measurements. The control unit receives flatness data and automatically modifies the voltage distribution pattern, transitioning from static uniform voltage application to dynamic adaptive voltage control, thereby optimizing both flatness and particle reduction.
3Productivity
If the electrostatic chuck releases the wafer quickly, then productivity improves, but particle contamination occurs due to abrupt de-chucking
Solution Approach 1:
The voltage reduction during wafer release is implemented in multiple sequential steps rather than a single abrupt change. The control unit sequentially reduces voltage across different zones over time, creating a periodic or staged release action that gradually reduces electrostatic force. This prevents sudden wafer detachment and particle generation while maintaining acceptable processing throughput.
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 reduces wafer warpage and minimizes particle contamination by applying and removing voltages in a controlled manner, ensuring uniform wafer flatness and reducing the risk of defects during semiconductor processing.
Implementation Method 1
an electrostatic chuck (also referred to as ESC or e-chuck) is often employed to solve the problem of wafer warpage
Data Source
AI summary
An apparatus and a method for holding a wafer are provided in this disclosure. The wafer holding apparatus includes: an electrostatic chuck, the electrostatic chuck having a plurality of concentric zones; a plurality of power supply units, each adapted for applying a voltage to one of the zones of the electrostatic chuck independently; and a control unit, adapted for controlling each of the power supply units independently to start or stop applying the voltage to a corresponding zone of the electrostatic chuck. Surface flatness is improved when the wafer is chucked on the wafer holding apparatus according to the disclosure, and the risk of particle contamination can be reduced when the wafer is flattened and gets back into warpage from flatness.