RF Extraction Plate for Charge Neutralized Ion Beam
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Solution Overview
Problem
Conventional ion beam processing apparatuses face challenges in achieving charge neutralization on semiconductor substrates with oxide layers, leading to non-uniform etch patterns and damage due to accumulated positive charge, especially when using pulsed DC voltage systems.
Innovation Solution
The use of an RF generator to establish a positive dc self-bias voltage at the extraction plate, combined with a ground plate, allows for continuous extraction of positive ions and intermittent extraction of electrons, preventing charge buildup on the substrate through an asymmetric electrode configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pulsed DC voltage is applied to neutralize substrate charge, then charge neutralization is achieved, but non-uniform etch patterns and substrate damage still occur due to incomplete neutralization
Solution Approach 1:
The system applies RF voltage periodically to the extraction plate, creating alternating phases of ion extraction and electron emission. This periodic action allows the substrate charge to be continuously neutralized during electron emission phases while maintaining ion beam processing during ion extraction phases, achieving complete charge neutralization that prevents etch pattern non-uniformity
Solution Approach 2:
The system changes the voltage parameter from DC to RF, enabling the extraction plate to switch between positive bias (for ion extraction) and negative bias (for electron emission). This parameter change allows dynamic control of charge neutralization effectiveness, ensuring complete neutralization that prevents substrate damage and maintains etch uniformity
2Reliability
If RF voltage is applied to the extraction plate, then continuous ion extraction and charge neutralization are achieved, but system complexity increases
Solution Approach 1:
The RF-powered extraction plate performs multiple functions: it extracts positive ions during positive half-cycles and emits electrons for charge neutralization during negative half-cycles. This multi-functionality eliminates the need for separate ion source and electron neutralization systems, reducing overall system complexity while achieving complete charge neutralization
Solution Approach 2:
The extraction plate serves itself by using the same component to both extract ions and neutralize charge through RF-driven electron emission. This self-service approach eliminates the need for additional neutralization electrodes or separate control systems, simplifying the overall system structure while maintaining complete charge neutralization
3Productivity
If substrate is located proximate the plasma chamber for compact system, then processing efficiency is improved, but charge buildup on substrate increases
Solution Approach 1:
The RF-powered extraction plate acts as an intermediary between the plasma chamber and substrate, providing both ion extraction and electron-mediated charge neutralization. This intermediary function allows the substrate to be positioned close to the plasma chamber for high processing efficiency while maintaining charge neutrality through continuous electron emission during RF negative half-cycles
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 enables efficient charge neutralization, reducing substrate damage and achieving uniform etching patterns by maintaining the ion beam's energy and current properties while eliminating the need for expensive pulsed DC power supplies and insulation transformers.
Implementation Method 1
an RF generator electrically coupled to the extraction plate, the RF generator establishing a positive dc self-bias voltage at the extraction plate with respect to ground potential when the plasma is present in the plasma chamber
Implementation Method 2
Ions are extracted through an aperture of special geometry located in an extraction plate that is placed proximate a plasma
Implementation Method 3
allows for continuous extraction of positive ions and intermittent extraction of electrons, preventing charge buildup on the substrate through an asymmetric electrode configuration
Data Source
AI summary
A processing apparatus may include a plasma chamber to house a plasma and having a main body portion comprising an electrical insulator; an extraction plate disposed along an extraction side of the plasma chamber, the extraction plate being electrically conductive and having an extraction aperture; a substrate stage disposed outside of the plasma chamber and adjacent the extraction aperture, the substrate stage being at ground potential; and an RF generator electrically coupled to the extraction plate, the RF generator establishing a positive dc self-bias voltage at the extraction plate with respect to ground potential when the plasma is present in the plasma chamber.