Insulative Cover Ring Layout for Uniform Wafer Edge Etching
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Solution Overview
Problem
Plasma etching processes in semiconductor fabrication face issues such as non-uniform etching due to tilting angles and via-to-metal overlap near the wafer edge, exacerbated by high RF power and prolonged etching, leading to quality and yield concerns.
Innovation Solution
The introduction of an insulative cover ring with inner and outer annular portions over the conductive focus ring modifies the electric field, adjusting plasma sheath thickness and ion incident angle to achieve uniform plasma distribution and reduce tilting angles and via-to-metal overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high RF power is used in plasma etching, then etching speed is improved, but non-uniform etching and tilting angles occur near the wafer edge
Solution Approach 1:
The patent applies local quality by creating non-uniform plasma distribution through the focus ring structure. The focus ring has different properties at different locations (inner, middle, outer portions) to locally adjust plasma characteristics. This allows the etching process to maintain uniformity across the wafer surface even at high RF power by compensating for edge effects through localized plasma modification.
Solution Approach 2:
The patent changes plasma parameters by introducing the focus ring structure that modifies the electric field distribution. This alters the plasma sheath thickness and ion incident angle locally across the wafer surface, enabling uniform etching at high RF power by dynamically adjusting plasma parameters rather than maintaining constant conditions.
2Duration of action of moving object
If prolonged etching is performed, then complete material removal is achieved, but via-to-metal overlap increases near the wafer edge
Solution Approach 1:
The focus ring structure implements local quality by differentiating plasma characteristics in different radial zones. The inner, middle, and outer portions of the focus ring create localized plasma modifications that prevent excessive etching at the wafer edge during prolonged processes, thereby maintaining via alignment precision even as etching continues for extended durations.
Solution Approach 2:
The patent applies preliminary anti-action by using the focus ring to pre-compensate for edge effects before they cause via-to-metal overlap. The modified electric field and plasma distribution proactively counteract the tendency toward non-uniform etching that would otherwise develop during prolonged processing, preventing alignment issues before they occur.
3Manufacturing precision
If focus ring is used to control plasma, then plasma distribution is improved, but electric field modification complexity increases
Solution Approach 1:
The focus ring serves as an intermediary component between the plasma source and the wafer surface. It mediates the electric field distribution by providing a structured interface that naturally modifies plasma characteristics without requiring complex control systems. The focus ring translates simple electric field applications into sophisticated plasma distribution patterns through its geometric structure.
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 addresses non-uniform etching and via-to-metal overlap issues, enhancing the quality and yield of semiconductor fabrication by ensuring consistent plasma distribution across the wafer surface.
Implementation Method 1
a focus ring surrounded by the chuck and configured to focus an electric field to control an etch direction of the plasma etching process
Implementation Method 2
a cover ring lying over the focus ring and configured to modify the electric field
Implementation Method 3
igniting a plasma within the chamber
Data Source
AI summary
A semiconductor manufacturing apparatus for performing a process is disclosed. An apparatus includes a chamber configured to receive a wafer for an etching process; a conductive focus ring disposed within the chamber and configured to focus an electric field to control an etch direction of the etching process; and an insulative cover ring disposed within the chamber, wherein the insulative cover ring is configured to modify the electric field, wherein the insulative cover ring has an inner annular insulative portion and outer annular insulative portion, and wherein a gap is defined between the inner annular insulative portion and the outer annular insulative portion.