Wafer Perimeter Mapping With Segmented Thief Electrodes for Uniform Plating
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Solution Overview
Problem
Significant plating non-uniformities often occur along the edge of semiconductor wafers due to irregularities in the electric field and mass-transfer non-uniformities, causing variations in film thickness.
Innovation Solution
A semiconductor plating system with a vessel assembly and weir thief electrode assembly that includes a controller to characterize the seal and openings on the wafer periphery by measuring electrical characteristics, adjusting current stolen by thief electrodes to achieve uniform film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a current thief is used to draw current away from the wafer edge, then plating thickness uniformity is improved, but the system complexity increases due to additional electrode configurations
Solution Approach 1:
The current thief electrode is divided into multiple segments positioned at different radial locations. Each segment can independently steal current at specific locations around the wafer periphery, allowing precise control of current distribution without requiring a complex single-electrode configuration.
Solution Approach 2:
Different segments of the current thief electrode are positioned to address local non-uniformities at specific locations around the wafer. This localized approach allows current stealing to be applied where needed most, improving plating uniformity without uniformly increasing system complexity across the entire electrode structure.
2Manufacturing precision
If multiple thief electrodes are used to address edge non-uniformities, then plating uniformity is improved, but the device complexity and control difficulty increase
Solution Approach 1:
The segmented current thief electrode structure serves multiple functions: it can steal current at different radial positions, address various patterns of edge non-uniformity, and adapt to different wafer loading configurations. This multi-functionality reduces the need for multiple separate electrode systems.
Solution Approach 2:
The system dynamically adjusts the current stealing amount at each thief electrode segment based on real-time measurements of plating non-uniformity. This dynamic control allows the system to adapt to varying conditions without requiring a fixed complex electrode configuration for every possible scenario.
3Manufacturing precision
If current stealing is increased at wafer edges, then plating thickness uniformity is improved, but mass transfer non-uniformities worsen
Solution Approach 1:
Instead of uniformly increasing current stealing across the entire wafer edge, the system applies partial current stealing only at specific locations where non-uniformity is measured. This targeted approach achieves the necessary thickness uniformity without excessively disrupting mass transfer throughout the entire electrolyte volume.
Solution Approach 2:
The system measures actual plating thickness or current distribution and uses this feedback to adjust current stealing amounts at different thief electrode segments. This closed-loop control ensures that current stealing is optimized to achieve uniformity without creating harmful mass transfer non-uniformities.
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 system provides real-time characterization and adjustment of current distribution to ensure uniform plating across the wafer, minimizing waste and optimizing the plating process.
Implementation Method 1
The wafer is then moved into the vessel of an electroplating processor where electric current is conducted through an electrolyte to the wafer, to apply a blanket layer or patterned layer of a metal or other conductive material onto the seed layer
Implementation Method 2
electric current is conducted through an electrolyte to the wafer
Implementation Method 3
The current thief operates by drawing current away from the edge of the wafer
Implementation Method 4
In such designs, current from the remote physical electrode is conducted through electrolyte to positions near the wafer
Data Source
AI summary
Conditions at the perimeter of the wafer may be characterized and used to adjust current stolen by the weir thief electrodes during a plating process to generate more uniform film thicknesses. An electrode may be positioned in a plating chamber near the periphery of the wafer as the wafer rotates. To characterize the electrical contacts on the seal, a wafer with a seed layer may be loaded into the plating chamber, and a constant current may be driven through the electrode into the conductive layer on the wafer. As an electrical characteristic of this current varies, such as a voltage required to drive a constant current, a mapping characterizing the seal quality or the openings in the mask layer may be generated.