Cleaning and liquid contact with solids – Processes – Hollow work – internal surface treatment
Reexamination Certificate
2000-09-21
2002-06-25
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Hollow work, internal surface treatment
C134S022150, C134S004000, C134S017000, C134S042000
Reexamination Certificate
active
06408860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a method for cleaning phosphorus from an MBE vacuum chamber and more specifically to a method for removing phosphorus from an MBE vacuum chamber safely and effectively by encasing it in frost on a panel in the chamber.
2. Discussion of the Background
In molecular beam epitaxy (MBE), materials are deposited on a substrate in a vacuum chamber. A number of different types of materials are used including phosphorus. One of the unfortunate properties of phosphorus, however, is that it is very flammable. While the phosphorus is being deposited on the substrate within the MBE vacuum chamber, much of the phosphorus is also deposited on the walls of the chamber and other fixtures or apparatus elements within the chamber. This presents a very real fire hazard when the chamber is opened for cleaning and maintenance.
First, there is the danger that since the phosphorus is flammable that it may be easily ignited. Further, in order to remove the phosphorus, it is necessary to scrape it out. The friction or sparks caused by scraping can ignite the phosphorus while the operator is performing the operation. If a solvent, such as methanol, is used, the operator is then exposed to even higher fire hazard. Thus, the traditional method (scraping and solvent wipe) is clearly incompatible with phosphorous and new techniques for removal are necessary.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a safe and efficient method of cleaning phosphorus from a vacuum chamber.
It is another object of this invention to provide a novel system for removing phosphorus and other dangerous chemicals from an MBE vacuum chamber without introducing unwanted materials.
It is a further object of,this invention to provide a safe and effective method for cleaning phosphorus from a vacuum chamber by encasing it in frost.
Briefly, these and other objects of the invention are achieved by intentionally introducing water vapor into an MBE system while a panel inside the chamber remains cold. Phosphorus which has been deposited on the cold panel will then be covered with a layer of frost so that it can be handled and cleaned safely in a water tank. Accordingly, the use of organic solvent is avoided.
REFERENCES:
patent: 4512812 (1985-04-01), Liebert et al.
patent: 5759287 (1998-06-01), Chen et al.
patent: 5843239 (1998-12-01), Shrotriya
patent: 5882424 (1999-03-01), Taylor et al.
patent: 5988187 (1999-11-01), Trussell et al.
patent: 6309460 (2001-10-01), Makishi
Block Thomas R.
Chin Patrick T.
Makishi Todd K.
Chaudhry Saeed
Gulakowski Randy
TRW Inc.
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