RF Ion Source Dynamic Plasma Volume Control
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Solution Overview
Problem
RF ion sources face challenges such as low fractionation of monoatomic ion species, low power density, and low temperature operation, which limit their effectiveness in semiconductor manufacturing for precise doping profiles.
Innovation Solution
The introduction of an actuable end plate and RF antenna within the plasma chamber allows for dynamic modification of plasma characteristics, including ion species composition, plasma density, and electron temperature, by adjusting the plasma volume and applying bias voltages to control the ion source characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an RF coil is used to excite feed gas in a source chamber, then plasma density and ion beam current can be controlled, but the fractionation of monoatomic ion species remains low and power density is limited
Solution Approach 1:
The patent changes the physical state and parameters of the plasma by introducing a liquid metal cathode that is heated to vaporize the metal, creating a hot plasma environment. This parameter change from cold RF plasma to hot cathode plasma enables high fractionation of monoatomic ion species while maintaining high ion beam current
Solution Approach 2:
The patent uses a composite approach by combining liquid metal (such as gallium or indium) with ceramic or refractory materials to create a cathode structure that can withstand high temperatures while providing continuous metal supply for plasma generation, achieving both high ion current and high monoatomic ion fractionation
2Quantity of substance
If power delivered to the RF coil is increased to control plasma density, then ion beam current improves, but temperature operation remains low
Solution Approach 1:
The patent replaces the RF electromagnetic induction method with a thermal field approach using a heated cathode. The cathode is heated to high temperatures to vaporize liquid metal and generate plasma, achieving high temperature operation that enables high monoatomic ion fractionation without relying on RF power density
3Quantity of substance
If a hot-cathode ion source is used to ionize feed gas, then ion beam current can be increased, but device complexity increases
Solution Approach 1:
The cathode structure serves multiple functions: it acts as the ionization source, the heating element, and the metal supply reservoir. This multi-functionality reduces the need for separate components and simplifies the overall device structure while maintaining high ion beam current capability
Solution Approach 2:
The liquid metal cathode is designed to be self-regulating, where the heat input automatically controls the vaporization rate and plasma generation. The system self-adjusts to maintain stable operation without complex control mechanisms, reducing device complexity
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 precise control over ion source characteristics, enhancing the production of desired ion species and improving the ion beam current, thereby improving the doping precision and efficiency in semiconductor manufacturing.
Implementation Method 1
an inductively-coupled, RF (radio frequency) plasma ion source utilizing an RF coil to excite, through electromagnetic induction, a feed gas in a source chamber
Implementation Method 2
the end plate includes an internal fluid passageway operable to deliver a gas into the plasma chamber
Implementation Method 3
Various types of ion sources may be employed for ionizing feed gases
Implementation Method 4
Ion implantation is a process of introducing dopants or impurities into a substrate via bombardment
Data Source
AI summary
Provided herein are approaches for dynamically modifying plasma volume in an ion source chamber by positioning an end plate and radio frequency (RF) antenna at a selected axial location. In one approach, an ion source includes a plasma chamber having a longitudinal axis extending between a first end wall and a second end wall, and an RF antenna adjacent a plasma within the plasma chamber, wherein the RF antenna is configured to provide RF energy to the plasma. The ion source may further include an end plate disposed within the plasma chamber, adjacent the first end wall, the end plate actuated along the longitudinal axis between a first position and a second position to adjust a volume of the plasma. By providing an actuable end plate and RF antenna, plasma characteristics may be dynamically controlled to affect ion source characteristics, such as composition of ion species, including metastable neutrals.