Dual-Mode Ion Source for Shallow Junction Formation
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Solution Overview
Problem
Conventional ion sources in semiconductor production facilities face inefficiencies at low implant energies, leading to reduced ion current delivery and increased implant times, and are unable to efficiently generate ions for shallow junction depths, with existing sources either breaking up molecules or lacking sufficient plasma for high productivity.
Innovation Solution
An ion source with dual operating modes: a cold mode for gentle ionization of molecules and clusters, and a hot mode for plasma formation and ionization, utilizing separate electron sources and dopant materials to maintain high productivity across a wide range of energies, including low energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional hot cathode ion sources are used to generate mono-atoms, then high output of ion species is achieved, but molecules and clusters are broken up reducing productivity improvement
Solution Approach 1:
The patent applies dynamics by making the electron beam energy variable and adjustable. The system transitions from static high-energy electron bombardment that breaks molecules to dynamic low-energy electron beams (20-1200 eV) that gently ionize molecules and clusters without fragmentation, enabling high productivity at low implant energies while maintaining molecular integrity
Solution Approach 2:
The patent changes the critical parameter of electron beam energy from conventional high values to a specific range of 20-1200 eV. This parameter change enables gentle ionization that preserves molecular and cluster structures while maintaining high ion production rates, resolving the contradiction between ion output and molecular preservation
2Productivity
If ion implanters are designed for high implant energies, then efficient operation is achieved, but performance at low implant energies deteriorates with much lower ion current delivery
Solution Approach 1:
The patent makes the ion source universal by enabling it to operate effectively across the entire energy spectrum from low to high implant energies. The electron beam ionization system can generate sufficient ion currents at low energies (preserving molecules) while also maintaining high productivity at conventional high energies, eliminating the need for separate optimized sources
3Power
If directly heated cathodes with small diameter wire filaments are used, then electron emission is achieved, but lifetime is reduced due to degradation in corrosive plasma environment
Solution Approach 1:
The patent extracts the filament from the corrosive plasma environment by using an indirectly heated cathode configuration. The filament is positioned outside the arc chamber and heats the cathode through radiative or conductive coupling, allowing the cathode to emit electrons into the plasma while the filament itself remains protected from chemical degradation, significantly extending system lifetime
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 dual-mode ion source enhances ion current delivery and productivity at low energies, allowing for efficient shallow junction formation and extended operation without maintenance, while maintaining high output of conventional ion species.
Implementation Method 1
An indirectly heated cathode includes a relatively massive cathode which is heated by electron bombardment from a filament and emits electrons thermionically
Implementation Method 2
a first electron source configured to ionize the first dopant material in the first operating mode
Data Source
AI summary
Ion sources and methods for generating molecular ions in a cold operating mode and for generating atomic ions in a hot operating mode are provided. In some embodiments, first and second electron sources are located at opposite ends of an arc chamber. The first electron source is energized in the cold operating mode, and the second electron source is energized in the hot operating mode. In other embodiments, electrons are directed through a hole in a cathode in the cold operating mode and are directed at the cathode in the hot operating mode. In further embodiments, an ion beam generator includes a molecular ion source, an atomic ion source and a switching element to select the output of one of the ion sources.