Anisotropic High Resistance Ionic Current Source for Electroplating
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving uniform electroplating thickness and current distribution across semiconductor wafers due to the terminal effect, which becomes more pronounced with the use of thin and resistive seed layers, leading to variations in potential between the center and edge of the wafer.
Innovation Solution
The implementation of anisotropic high resistance ionic current sources (AHRICS) with specially shaped plates that redistribute ionic current, such as convex or concave plates with varying distances from the substrate, to ensure uniform plating across the wafer surface, regardless of seed layer resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thin and resistive seed layers are used, then manufacturing precision and device scaling are improved, but terminal effect increases causing non-uniform plating
Solution Approach 1:
The patent applies local quality by creating non-uniform current distribution through strategically placed auxiliary cathodes and anodes at different locations around the wafer. These electrodes provide localized current compensation to specific regions (center vs. edge) to counteract the terminal effect caused by thin seed layers, enabling uniform plating despite the resistive seed layer properties.
Solution Approach 2:
The patent changes electrical parameters (current density, voltage distribution) by introducing auxiliary electrodes that modify the overall current field. By controlling the current through these auxiliary electrodes, the system compensates for the high resistance of thin seed layers and achieves uniform plating thickness across the wafer surface.
2Device complexity
If conventional plating is used with resistive seeds, then process simplicity is maintained, but power consumption increases and plating uniformity deteriorates
Solution Approach 1:
The patent introduces auxiliary cathodes and anodes positioned at specific locations (center and edge regions) to create localized current paths. This configuration reduces the overall voltage requirement by providing alternative current routes through the electrolyte, thereby reducing power consumption while maintaining plating uniformity without significantly increasing system complexity.
3Productivity
If higher current is applied to compensate for seed resistance, then plating rate increases, but terminal effect worsens causing edge thickening
Solution Approach 1:
The patent segments the current delivery system into multiple independent electrode pairs (main anode-cathode plus auxiliary anodes-cathodes). Each segment can be controlled independently to deliver current to specific regions of the wafer. This segmentation allows the system to maintain high overall plating rates while distributing current uniformly across different radial positions, preventing edge thickening.
Solution Approach 2:
The patent changes the spatial distribution of current density by introducing auxiliary electrodes with controlled current magnitudes. By adjusting the current parameters of auxiliary electrodes relative to the main electrodes, the system achieves both high productivity and uniform plating thickness control, counteracting the terminal effect that would otherwise cause edge thickening.
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
AHRICS effectively reduces the terminal effect, achieving uniform plating across a wide range of seed layer resistances without the need for dynamic adjustments, reducing power demands and improving radial plating uniformity, and can be integrated with existing electroplating systems.
Implementation Method 1
specially shaped high resistance plates that provide anisotropic ionic conductance and current re-distribution effects to modulate the current density profile on the working cathode substrate
Implementation Method 2
The wafer acts as a cathode, at which the metal ions from the electrolyte are being reduced to form the metal layer
Implementation Method 3
Without compensation, this leads to significantly thicker plating at the edge of the wafer than at the center region of the wafer. The center to edge variation in potential is usually termed as the 'terminal effect'
Data Source
AI summary
An electroplating apparatus that promotes uniform electroplating on the substrates having thin seed layers includes a convex anisotropic high resistance ionic current source (AHRICS), such as an electrolyte-permeable resistive domed plate. The AHRICS is positioned in close proximity of the substrate, so that a distance from the central portion of the AHRICS to the substrate is smaller than the distance from the edge portion of the AHRICS to the substrate. The apparatus further includes a plating chamber configured to hold the electrolyte and an anode. The apparatus further includes a substrate holder configured to hold the substrate. In some embodiments, the apparatus further includes a secondary (thief) cathode configured to divert ionic current from the near-edge region of the substrate.