Semitransparent Ion Screen for High-Ion Energy Low-Bias Current Plasma Control
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Solution Overview
Problem
Current high-density-plasma CVD processes face challenges in maintaining independence between ion current and ion energy control due to low RF source power and high bias power configurations, leading to non-uniformities in semiconductor substrates, which are difficult and time-consuming to resolve.
Innovation Solution
The implementation of a semitransparent ion screen above the substrate in an inductively coupled plasma (ICP) system, allowing 5% to 20% ion and electron flow, enables increased minimum source power while keeping plasma density independent of RF bias power, allowing for high-ion energy with low bias power and straightforward ion energy control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low RF source power and high bias power are used to provide deep treatment, then ion energy is increased, but independence between ion current/density control and ion energy control is lost
Solution Approach 1:
An ion screen is introduced as an intermediary component between the plasma source and substrate. The screen allows selective transmission of ions (5-20% transmission) while blocking most electrons, enabling independent control of ion energy through bias power applied to the screen without affecting plasma density sustained by source power.
Solution Approach 2:
The plasma processing system is segmented into distinct functional zones: the plasma generation region controlled by source power, the ion acceleration region controlled by bias power on the ion screen, and the substrate processing region. This segmentation allows independent optimization and control of ion current/density and ion energy.
2Use of energy by moving object
If low RF source power and high bias power are used to provide deep treatment, then ion energy is increased, but non-uniformities in processed substrates occur
Solution Approach 1:
The ion screen acts as a mediator that uniformizes ion distribution before acceleration. By allowing only 5-20% of ions to pass through while blocking electrons, the screen creates a more uniform ion flux distribution that, when accelerated by bias power, reduces non-uniformities on the substrate surface.
Solution Approach 2:
The ion screen introduces local quality differences in the plasma-substrate interaction zone. Different regions of the screen can have different transmission characteristics, and the screen itself creates localized electric field distributions that promote uniform ion acceleration and deposition across the substrate.
3Adaptability or versatility
If plasma configuration changes are made to accommodate differing requirements, then system adaptability is improved, but implementation complexity increases
Solution Approach 1:
The ion screen enables dynamic adjustment of plasma configuration through electrical biasing. By applying different bias powers to the ion screen, the system can dynamically adapt ion energy and flux without physical reconfiguration, simplifying implementation compared to fixed configuration changes.
Solution Approach 2:
The system achieves adaptability through parameter changes in the ion screen bias power rather than physical configuration changes. This allows continuous adjustment of ion energy (50-500 eV) and flux independently, providing versatility without the complexity of mechanical or structural modifications.
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 configuration allows for high-ion energy deposition with reduced non-uniformities, maintaining independence of plasma density from bias power, thereby improving substrate uniformity and simplifying plasma control.
Implementation Method 1
an inductively coupled plasma (ICP) source disposed in or on the processing chamber
Implementation Method 2
The ion screen is configured to allow 5% to 20% of ions and electrons to flow through the ion screen
Implementation Method 3
applying RF bias voltage to the bias electrode... the RF bias power is almost completely spent on accelerating ions
Implementation Method 4
high-ion energy with low bias power... linearly controlling ion energy based on the RF bias power
Implementation Method 5
an inductively coupled plasma (ICP) source disposed in or on the processing chamber... using the source power to control ion current
Implementation Method 6
Placing the ion screen close to the substrate, prevents the bias electric field applied between the ion screen and the substrate from sustaining the plasma in the area between the ion screen and the substrate
Data Source
AI summary
Exemplary semiconductor processing systems may include a processing chamber, an inductively coupled plasma (ICP) source disposed in or on the processing chamber, and a support configured to position a substrate. The support can be disposed at least partially within the processing chamber and can include a bias electrode. An ion screen may be disposed within the chamber to be above a substrate on the support. The ion screen is semitransparent to ions and electrons so that the density of plasma sustained above the ion screen is unaffected by RF bias power applied to the bias electrode. Plasma energy control is therefore accomplished while maintaining independence of plasma density from RF bias power so that high ion energy and low bias current may be afforded.