Electroplating Apparatus with Distributed Voltage Contacts
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Solution Overview
Problem
The electro-plating process for semiconductor wafers often results in non-uniform metal deposition rates due to voltage drops across the wafer, especially as the thickness of the seed layer decreases with down-scaling, leading to variations in deposition rates between edge and center portions.
Innovation Solution
The electro-plating apparatus applies a voltage to both the edge and center portions of the wafer, using a plurality of electrical contacts aligned along the edge and a retractable electrode for uniform voltage distribution, and incorporates a blade for fluid field control to ensure consistent plating solution concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage is applied only at the edge of the wafer, then the electro-plating process is simple, but the deposition rate becomes non-uniform across the wafer surface
Solution Approach 1:
The single voltage application point is segmented into multiple electrical contacts distributed across the wafer surface. This segmentation allows voltage to be applied at multiple locations simultaneously, creating a more uniform electric field distribution across the wafer, which directly addresses the non-uniform deposition problem while maintaining reasonable system complexity
Solution Approach 2:
Different regions of the wafer are provided with locally optimized voltage application through the distributed electrical contacts. This ensures that each local area receives appropriate voltage for uniform deposition, transforming the global uniformity problem into local quality control that can be achieved through strategic contact placement
2Length of moving object
If the seed layer thickness is reduced for down-scaling, then the device dimensions are improved, but the voltage drops increase causing greater deposition rate variations
Solution Approach 1:
The voltage application is segmented into multiple contacts to compensate for the increased voltage drops that occur with thinner seed layers. This segmentation reduces the current density through each contact and distributes the voltage application more evenly, mitigating the deposition non-uniformity that arises from reduced seed layer thickness
Solution Approach 2:
The voltage application transitions from a single-point (0D) or edge-based (1D) approach to a distributed 2D array of electrical contacts across the wafer surface. This dimensional change allows for better voltage distribution that compensates for the reduced seed layer thickness and its associated increased resistance
3Manufacturing precision
If multiple electrical contacts are used for voltage application, then the deposition uniformity is improved, but the device complexity increases
Solution Approach 1:
The electrical contact system is designed with multi-functionality, where the same distributed contact array serves both as voltage application points and as part of the wafer handling structure. This universality reduces the need for separate components, thereby limiting the increase in overall device complexity while maintaining the deposition uniformity benefits
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 approach achieves more uniform deposition rates across the wafer, improving the thickness profile of the plated metal layer and addressing the issue of non-uniformity caused by resistance variations in the seed layer.
Implementation Method 1
When a voltage is applied between the cathode and the anode, the atoms in the metal plate are ionized and migrate into the plating solution. The ions are eventually deposited on the wafer.
Implementation Method 2
When a voltage is applied between the cathode and the anode, the atoms in the metal plate are ionized and migrate into the plating solution.
Data Source
AI summary
A method of plating a metal layer on a work piece includes exposing a surface of the work piece to a plating solution, and supplying a first voltage at a negative end of a power supply source to an edge portion of the work piece. A second voltage is supplied to an inner portion of the work piece, wherein the inner portion is closer to a center of the work piece than the edge portion. A positive end of the power supply source is connected to a metal plate, wherein the metal plate and the work piece are spaced apart from each other by, and are in contact with, the plating solution.