Bias Voltage Frequency Controlled Angular Ion Distribution
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Solution Overview
Problem
Current plasma processing technologies face challenges in precisely controlling the angular distribution of ions, which affects the efficiency and selectivity of processes like etching and deposition, due to limitations in controlling ion energy and angle of incidence on workpieces.
Innovation Solution
The use of a bias voltage frequency, combined with a plasma sheath modifier aperture, allows for the control of ion energy distribution and angular ion distribution by shaping the plasma sheath and modifying the electric field lines, enabling precise control over ion incidence angles and energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a grid is placed between the plasma sheath and workpiece to direct ions, then angular ion distribution is controlled, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical grid system with an electromagnetic field-based solution. By applying a bias voltage to the workpiece holder, an electric field is generated that directly controls ion acceleration and angular distribution without requiring physical grids or mechanical structures in the plasma path.
Solution Approach 2:
The patent controls ion angular distribution by changing electrical parameters (bias voltage frequency and magnitude) rather than mechanical parameters (grid geometry and position). The bias voltage frequency is specifically adjusted to control the angular spread of ions, providing a more flexible and simpler control mechanism.
2Quantity of substance
If bias voltage is increased to attract more ions, then ion flux increases, but ion energy distribution becomes less controlled
Solution Approach 1:
The patent employs dynamic control of the bias voltage by using oscillating RF bias voltage at specific frequencies. This dynamic approach allows the system to control both the quantity and energy distribution of ions simultaneously, as the frequency and amplitude can be independently adjusted to optimize ion flux while maintaining precise energy distribution control.
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 enhances process control and selectivity, allowing for more accurate and efficient plasma processing, including anisotropic etching, isotropic etching, and directional film deposition, by tuning the plasma frequency and bias voltage applied to the sheath grid.
Implementation Method 1
The bias voltage generates an electrical field around the workpiece to attract ions through the sheath
Implementation Method 2
The field can accelerate positive ions and repel negative ions and electrons
Implementation Method 3
The plasma itself is generated using a high voltage power supply and an input gas. The plasma generates a collection of ions and electrons
Data Source
AI summary
The angular ion distribution in plasma processing is controlled using a bias voltage frequency. In one example, a plasma containing gas ions is generated in a plasma chamber. The plasma sheath is modified using an aperture disposed between the plasma sheath and the workpiece so that the plasma sheath takes a shape above the aperture. An oscillating radio frequency bias voltage is generated and applied to a workpiece holder. The workpiece holder applies the bias voltage to the workpiece to generate a workpiece bias voltage with respect to the plasma to attract ions across the plasma sheath toward the workpiece. The aperture and the frequency of the bias voltage control an angle at which the ions are attracted toward the workpiece.