Thermally isolated cryopanel for MBE reevaporation
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Solution Overview
Problem
In molecular beam epitaxy processes, high vapor pressure deposition materials face significant challenges due to reevaporation of gases from cryopanels, which are susceptible to temperature variations and radiant heat, leading to unstable vacuum conditions.
Innovation Solution
The implementation of thermally isolated and radiatively shielded cryopanels, separate from liquid cooling panels and heat sources, to minimize reevaporation and maintain optimal pressure stability in the deposition region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional cryopanel is used to pump the deposition region, then volatile high vapor pressure species are condensed and removed from the chamber, but radiant heat from effusion sources causes temperature variations on the cryopanel surface leading to reevaporation of pumped gases
Solution Approach 1:
The system divides the cryopanel into distinct temperature zones using multiple independent cryogenic cooling channels. Each channel can be controlled separately to maintain different temperatures in different regions of the cryopanel, allowing the surface facing effusion sources to remain cold enough to prevent reevaporation while other regions perform pumping functions.
Solution Approach 2:
The patent changes the temperature parameter across different regions of the cryopanel by providing independent cryogenic cooling control to each zone. This allows optimization of local temperatures to prevent reevaporation in heat-exposed areas while maintaining effective pumping temperatures in other areas.
2Productivity
If the cryopanel is positioned close to effusion sources for effective pumping, then gas pumping efficiency is improved, but thermal radiation from the sources heats the cryopanel surface causing reevaporation
Solution Approach 1:
The patent introduces thermal barriers or shields as intermediary elements between the effusion sources and the cryopanel surface. These intermediaries block or reduce radiant heat transfer to the cryopanel while allowing the cryopanel to remain in position for effective pumping of volatile species.
Solution Approach 2:
The system addresses the thermal problem by adding a spatial dimension to the solution through multi-zone cooling channels arranged in specific three-dimensional configurations. This allows heat management in the direction of radiant exposure while maintaining pumping effectiveness in the deposition direction.
3Temperature
If liquid cooling panels are used to cool effusion sources, then source temperature control is improved, but these panels become additional heat sources that can thermally affect the cryopanel
Solution Approach 1:
The patent extracts or isolates the cryopanel thermally from the liquid cooling panels used for effusion source cooling. This is achieved through thermal barriers, vacuum insulation, or physical separation that prevents heat transfer from the liquid cooling panels to the cryopanel, allowing independent temperature control of each component.
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 solution effectively reduces reevaporation of high vapor pressure gases, providing stable vacuum conditions and optimal pressure stability during the deposition process, enhancing the quality and uniformity of thin films deposited in molecular beam epitaxy.
Implementation Method 1
The cryoshroud functions to pump the growth chamber, particularly the growth region, by condensing residual species
Implementation Method 2
A cryopanel in accordance with the present invention is preferably substantially isolated from any source of heat of the deposition system in which it is used that could cause reevaporation
Implementation Method 3
radiant heat can impinge upon different surface portions of the cryopanel or adjacent chamber structure at different times during a typical deposition process
Data Source
AI summary
The present invention relates to vacuum depositions systems and related deposition methods. Vacuum deposition systems that use one or more cyropanels for localized pumping of a deposition region where a substrate is positioned are provided. The present invention is particularly applicable to pumping and minimizing reevaporation of high vapor pressure deposition materials during molecular beam epitaxy.