Electroplating Contact Ring Seal with Notch Recess for Uniform Plating
Solution Overview
Problem
Electroplating processes on wafers with edge irregularities, such as notches, result in non-uniform metal film thickness due to current crowding, leading to reduced yield and increased complexity in manufacturing.
Innovation Solution
A contact ring seal with a recess or thin section at the notch area to increase the current flow path to a thief electrode, reducing current crowding and achieving more uniform plating by preferentially drawing current away from the notch region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal with an inward protrusion at the notch is used to maintain continuous sealing, then sealing reliability is improved, but current crowding at the notch increases causing non-uniform plating
Solution Approach 1:
The seal is designed with a thin section specifically at the notch region, creating local geometric variation. This thin section allows the seal to conform to the notch while maintaining overall sealing integrity, and simultaneously permits the thief electrode to access the notch region for current compensation without compromising the seal's continuous contact with the wafer edge.
Solution Approach 2:
The thief electrode acts as an intermediary element that compensates for the harmful effect of the notch geometry. By positioning the thief electrode to work through or near the thin section of the seal, it can draw excess current from the notch region, counteracting the current crowding effect while the seal maintains its sealing function.
2Reliability
If the seal covers a larger annular band at the wafer edge to ensure continuous sealing, then sealing reliability is improved, but the plated film thickness uniformity deteriorates due to current crowding
Solution Approach 1:
The seal geometry is modified locally at the notch region with a thin section, while maintaining full coverage elsewhere. This localized modification allows the seal to adapt to the notch geometry, enabling the thief electrode to access the notch area for current compensation without reducing the overall sealing coverage on the wafer edge.
Solution Approach 2:
The seal can be viewed as having different functional sections: a thick section for general sealing and structural support, and a thin section at the notch for geometric adaptation and thief electrode access. This segmentation allows each region to fulfill its specific function while working together to achieve both sealing reliability and plating uniformity.
3Ease of manufacture
If conventional contact ring seal geometry is used, then manufacturing simplicity is maintained, but current crowding at the notch causes thicker plating and reduced yield
Solution Approach 1:
Instead of redesigning the entire seal geometry, only a localized thin section is created at the notch region. This minimal modification maintains the overall simplicity of seal manufacturing while addressing the specific problem of current crowding at the notch, thereby improving wafer yield without significantly increasing manufacturing complexity.
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 ensures more uniform metal film thickness across the wafer, improving the yield and reducing the complexity of subsequent processing steps by minimizing the annular band at the edge of the wafer.
Implementation Method 1
Electrical current is passed through the electrolyte and the conductive layer. Metal ions in the electrolyte deposit or plate out onto the substrate
Implementation Method 2
Metal ions in the electrolyte deposit or plate out onto the substrate, creating a metal film on the substrate
Implementation Method 3
a seal seals the electrolyte away from the electrical contacts. The seal contacts the substrate surface radially inwardly of the electrical contacts, so that the contacts remain isolated from the electrolyte
Data Source
AI summary
An electro-processing apparatus has a contact ring including a seal which is able to compensate for electric field distortions created by a notch (or other irregularity) on the wafer or work piece. The shape of the contact ring at the notch is changed, to reduce current crowding at the notch. The change in shape changes the resistance of the current path between a thief electrode and the wafer edge to increase thief electrode current drawn from the region of the notch. As a result, the wafer is plated with a film having more uniform thickness.