Cold Stripper for High Energy Ion Implanter
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Solution Overview
Problem
High-energy ion implantation using tandem accelerators faces energy contamination during the stripping process, which reduces the yield and predictability of ion implantation depths, especially in complex and miniaturized semiconductor devices.
Innovation Solution
A cold stripper is introduced in the ion implanter system, featuring a stripper tube with a hollow cavity, gas introduction, and active cooling to control temperature and pressure, reducing the need for gas and minimizing energy contamination by maintaining optimal conditions within the stripper tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a stripper is used to strip electrons from ions in a tandem accelerator, then the ions can be accelerated to high energy, but energy contamination occurs during the stripping process
Solution Approach 1:
The patent changes the temperature parameter of the stripper from conventional (room temperature or hot) to cold (cryogenic temperatures using liquid nitrogen or liquid helium cooling). This parameter change reduces the gas pressure in the stripper, thereby reducing energy contamination while maintaining effective electron stripping. The cold temperature causes gas molecules to condense on the stripper tube walls, creating a lower pressure environment that minimizes unwanted ion-molecule collisions.
Solution Approach 2:
The patent creates an inert environment by using cryogenic temperatures to condense gas molecules onto the stripper tube walls, effectively removing them from the beam path. This inert environment reduces the number of gas molecules available to cause energy contamination through unwanted collisions with the ion beam, while still allowing necessary stripping gas to be present at controlled levels.
2Reliability
If gas is introduced into the stripper tube to strip electrons, then electron stripping efficiency improves, but energy contamination increases
Solution Approach 1:
The patent changes the temperature parameter to cryogenic levels, which fundamentally alters the behavior of the stripping gas. At these low temperatures, the gas pressure is reduced significantly, but the stripping efficiency is maintained because the cold walls condense gas molecules that would otherwise cause contamination, while still allowing sufficient gas density for effective electron stripping in the beam path.
Solution Approach 2:
The cold stripper tube walls act as an intermediary that selectively removes excess gas molecules through condensation while allowing the necessary stripping gas to remain in the beam path. This intermediary mechanism separates the function of electron stripping from the harmful effect of energy contamination by controlling gas molecule distribution.
3Device complexity
If conventional strippers are used in tandem accelerators, then the system structure is simple, but energy contamination reduces manufacturing precision
Solution Approach 1:
The patent introduces cryogenic cooling as a new operational parameter for the stripper, transforming it from a simple room-temperature component to a temperature-controlled device. This parameter change significantly reduces energy contamination, thereby improving ion implantation depth precision and manufacturing yield, while the added cooling infrastructure represents a manageable increase in system 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
The cold stripper effectively reduces energy contamination, enhancing the precision and yield of high-energy ion implantation by maintaining controlled temperature and pressure, ensuring ions are implanted at desired depths with reduced unpredictability.
Implementation Method 1
one or more cooling passages in the stripper tube, and a coolant pump coupled to the one or more cooling passages to circulate a coolant through the one or more cooling passages
Implementation Method 2
The electrons on the negative ions are then stripped by passage through a charge exchange region (referred to as a 'stripper')
Data Source
AI summary
A cold stripper for a high-energy ion implanter system is provided. The cold stripper including a stripper tube having a hollow cavity, a first aperture in the stripper tube to admit an ion beam of positively charged ions into the hollow cavity and a second aperture in the stripper tube to discharge the ion beam from the hollow cavity, a gas pump coupled to the hollow cavity to introduce a gas into the hollow cavity, one or more cooling passages in the stripper tube, and a coolant pump coupled to the one or more cooling passages to circulate a coolant through the one or more cooling passages.