Cleaning and liquid contact with solids – Processes – Including use of vacuum – suction – or inert atmosphere
Reexamination Certificate
2000-05-22
2003-09-16
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including use of vacuum, suction, or inert atmosphere
C134S026000, C134S030000, C134S034000, C134S037000
Reexamination Certificate
active
06620258
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for washing instruments used in semiconductor industry with an inflammable and/or explosive washing liquid.
The invention also relates to an equipment for washing instruments used in semiconductor industry with an inflammable and/or explosive washing liquid.
In semiconductor industry, light-sensitive materials, or resists, are used in various manufacturing processes. In some processes, specific instruments, such as resist cups and the like, are used when such materials are handled, and therefore some material is left on the surface of the instruments. Before the instruments can be used again, the material residuals must be removed. At present, the instruments are cleaned by washing them with a suitable solvent in a commonly used fume cupboard, the solvent vapours generated in the cabinet being exhausted with an exhauster and the used liquiform solvent recovered. A problem with the current process is that ventilation for the removal of the solvent vapours is rather difficult and expensive to arrange, and solvent vapours released into the ambient atmosphere cause environmental problems. A further problem is high consumption of the solvent used as washing liquid per unit to be washed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and an equipment which allow an automated washing of these instruments which is both convenient and safe. The method of the invention is characterized in that the instruments to be washed are placed into a substantially gas-tightly closed washing space; that the air in the enclosed washing space is removed from the washing space by supplying an inert gas or gas mixture to the space, while allowing, at the same time, a gas mixture containing air in the washing space to be discharged from the washing space; that the instruments are washed by spraying them with the washing liquid, the washing liquid sprayed into the washing space being removed from the washing space; and that after the washing is completed, the gas mixture containing washing liquid vapour that is generated in the washing space is removed from the washing space by supplying an inert gas/gas mixture to the washing space and by discharging, at the same time, the gas mixture containing washing liquid vapour from the washing space.
Further, the equipment of the invention is characterized in that the equipment comprises a substantially gas-tightly closed washing space where the instruments to be washed are placed for the washing; means for spraying washing liquid onto the instruments; means for supplying an inert gas/gas mixture to the washing space; means for removing a gaseous mixture that is in the washing space from the washing space; and control means for controlling the equipment.
A basic idea of the invention is that the instruments to be washed are washed with an automated washing equipment, in a substantially gas-tightly closed washing space included in the equipment, the instruments to be washed being cleaned by flushing them with a suitable liquid. Another essential idea of the invention is that when the units to be washed are placed into the washing space, which is then closed, the air in the space is removed before the washing begins by supplying an inert gas or gas mixture, preferably nitrogen, to the space, thus eliminating the risk of fire or explosion. A yet further essential idea of the invention is that after the washing is completed, the solvent vapours in the washing space are removed by supplying again an inert gas or gas mixture to the space, thereby allowing solvent emissions to be recovered for further processing.
An advantage of the invention is that the risk of fire or explosion can be avoided because there is no oxygen in the washing space that would cause a fire or an explosion. Moreover, the quantity of solvent vapour emissions per wash is low because it depends on the quantity of vapours that can evaporate into the washing space in different circumstances. A further advantage is that when the solvent vapours are removed from the washing space to recovery by supplying inert gas to the washing space, the washing space can then be safely opened without any harmful vapours or gases being released into the atmosphere.
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Handbook of Semiconductor Wafer Cleaning Technology, Noyes Publications, p. XIV, 1993.
Lång Kari
Mäntylä Pertti
Kojair Tech Oy
Markoff Alexander
Young & Thompson
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