Static Magnetic Field Control for Uniform Wafer Plasma Etching
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Solution Overview
Problem
Plasma etching processes in semiconductor fabrication often suffer from spatial non-uniformities due to variations in ion density and energy, leading to inconsistent results across the semiconductor wafer, which are influenced by the transmission paths of radiofrequency signals and the presence of magnetic fields.
Innovation Solution
The implementation of a static magnetic field, generated by DC currents applied to magnetic coils positioned above, below, and surrounding the plasma processing region, helps to minimize localized charged species accumulation and improve plasma and etch uniformity by controlling electron diffusion and ion distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If radiofrequency signals are transmitted through the plasma processing volume to generate plasma, then plasma is generated for material removal and modification, but spatial non-uniformities in plasma characteristics occur due to variations in radiofrequency signal power transmission
Solution Approach 1:
A static magnetic field is introduced as an intermediary to control charged species transport in the plasma. The magnetic field, generated by DC-powered magnetic coils positioned around the plasma processing volume, acts as a mediator that influences ion and electron motion without directly participating in the plasma generation process, thereby reducing spatial non-uniformities caused by radiofrequency signal variations
Solution Approach 2:
The patent applies a static magnetic field with controlled strength (typically 1-100 Gauss) to modify the physical parameters of plasma transport. By changing the magnetic field parameter, the mobility and distribution of charged species are altered, compensating for the non-uniform energy deposition from radiofrequency signals and achieving more uniform plasma characteristics across the wafer surface
2Manufacturing precision
If magnetic fields are present in the plasma processing volume, then charged species transport is influenced, but localized charged species accumulation occurs leading to non-uniform plasma characteristics
Solution Approach 1:
The patent applies a relatively weak static magnetic field (1-100 Gauss) that is sufficient to influence charged species transport through the Lorentz force but not strong enough to cause complete magnetization or excessive accumulation. This partial action approach allows control over ion and electron mobility while avoiding the formation of localized charged species pockets that would create non-uniform plasma characteristics
3Manufacturing precision
If multiple magnetic coils are used to generate static magnetic field, then plasma uniformity is improved, but device complexity increases
Solution Approach 1:
The magnetic field generation system is segmented into multiple independent DC-powered coils positioned at different locations around the plasma processing volume. This segmentation allows each coil to be controlled separately to create a composite magnetic field pattern that optimizes plasma uniformity across the wafer surface while managing the complexity through modular coil units
Solution Approach 2:
The magnetic coils serve multiple functions: they generate the static magnetic field for charged species control, provide a means to adjust field strength and distribution patterns, and can be configured to address different types of non-uniformities. This multi-functionality justifies the added complexity by providing versatile control over plasma characteristics
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 reduces radial non-uniformity of etch rates and improves the verticality of etched features, resulting in more consistent and uniform plasma processing across the wafer surface.
Implementation Method 1
a first DC power supply configured to apply a first DC current to the first magnetic coil during the plasma processing, the applied first DC current producing a magnetic field in the plasma processing region that reduces non-uniformity of the plasma
Data Source
AI summary
A system for performing a plasma process on a wafer is provided, including: a chamber configured to receive a wafer for plasma processing and having an interior defining a plasma processing region in which a plasma is provided for the plasma processing of the wafer; a first magnetic coil disposed above the chamber and centered about an axis perpendicular to a surface plane of the wafer and through an approximate center of the wafer; a first DC power supply configured to apply a first DC current to the first magnetic coil during the plasma processing, the applied first DC current producing a magnetic field in the plasma processing region that reduces non-uniformity of the plasma.