Pumps – Condition responsive control of pump drive motor – Single motor control element responsive to means sensing...
Reexamination Certificate
2000-12-06
2002-07-23
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Single motor control element responsive to means sensing...
C438S689000, C438S758000, C414S217000, C417S053000
Reexamination Certificate
active
06422823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to devices and methods for controlling the atmosphere surrounding a sample such as a substrate wafer for fabricating semiconductors, for example, or any other item, during testing or manufacture.
2. Description of the Prior Art
In the semiconductor industry, for example, substrate handling systems are currently used to isolate the substrates from contaminating agents in white rooms. Several substrates are placed in a common collective box containing nitrogen or another neutral gas under pressure, as taught in the documents EP 0 582 018 A or U.S. Pat. No. 5,988,233 A. The atmosphere in the box is not controlled. The presence of the nitrogen or other neutral gas, which requires a transient step of degassing before vacuum treatment of the substrate, in an interface like that described in the same document EP 0 582 018 A, constitutes a problem. Another problem is the contamination resulting from gas flows during return to the treatment pressure, as a result of which a purge device like that described in the document U.S. Pat. No. 5,988,233 A may be provided.
In the documents U.S. Pat. No. 5,255,783 A and EP 0 854 498 A, several substrates can be transported in a common collective box, the atmosphere in which is at a reduced pressure established by an external source and which can contain a substitute neutral gas. The atmosphere of the box is not controlled. At the very most, the document EP 0 854 498 A teaches continuous agitation and filtering of the internal atmosphere, and the generation of an internal overpressure on opening the access door. All the above documents encourage collective transportation of the samples by grouping several of them in a common collective box.
Various micropump designs are known in the art, including thermal transpiration micropumps described in the document U.S. Pat. No. 5,871,336 A when applied to generating vacuum in a miniature gas analyzer employing a mass spectrograph or other miniature sensor ; thermal gas expansion micropumps described in the document U.S. Pat. No. 5,375,979 A; piezo-electric membrane micropumps described in the document U.S. Pat. No. 4,938,742 A for pumping liquids or gases in the fields of medication, biology, cooling and fuel supply ; micropumps which function by varying the volume of gases using Peltier-effect junctions described in the document U.S. Pat. No. 5,975,856 A when applied to acceleration, pressure or chemical composition sensors or to fluid control in the pharmaceutical or aerospace industry. None of the above documents describes or suggests an application to controlling the atmosphere in the treatment of samples such as semiconductor wafers.
An object of the invention is to design a device for placing the sample in a controlled atmosphere, and maintaining it therein, which is as close as possible to the conditions under which the sample is treated or used, and to eliminate or significantly reduce transient steps of atmosphere modification and adaptation that have previously been necessary between successive sample treatment or test operations.
The invention aims to bring the sample as close as possible to the conditions of use or treatment and to maintain it there.
SUMMARY OF THE INVENTION
To this end, the invention provides a method of testing samples or of transforming samples by etching and deposition, said method including a step of transporting the sample individually in a controlled vacuum in an individual enclosure. This significantly reduces the risk of contaminating the samples.
The size of the individual enclosure is preferably only slightly greater than that of the sample to be transported, so that the sample placed in the enclosure is surrounded by a small volume of atmosphere constituting a mini-environment.
The invention also provides a device for controlling the atmosphere which surrounds a sample, notably for using these methods, said device including:
a sealed individual enclosure conformed to contain said sample and to isolate it from the external atmosphere with a small volume interior atmosphere around said sample,
an array of micropumps fastened to said individual enclosure and adapted to generate and maintain a controlled vacuum in said individual enclosure, said array of micropumps being adapted to be connected to an electrical power supply,
transfer means for introducing said sample into said individual enclosure and extracting it therefrom.
The above device produces a mini-environment around the sample, significantly reducing the risk of contamination of the sample.
In a first embodiment, the combination of said individual enclosure and said array of micropumps constitutes a portable self-contained system including an internal electrical power supply for supplying power at least temporarily to said array of micropumps. It is therefore possible to move the sample between two successive workstations without necessitating any transient degassing operation such as has been necessary with pressurized nitrogen containers.
In another application, said combination of said individual enclosure and said array of micropumps is fixed and constitutes a transfer chamber in a semiconductor fabrication installation.
According to one advantageous facility, in particular for constituting a portable self-contained system, said array of micropumps comprises thermal transpiration micropumps. The heat sources for producing the thermal transpiration effect can be electrical resistances or Peltier-effect junctions. An advantage of these micropumps is that they have no moving parts, and therefore no parts that can be worn by friction. This can therefore achieve excellent reliability, and freedom from losses caused by friction.
Also, these micropumps do not release unwanted particles into the atmosphere.
Micromembrane micropumps, piezo-electric micropumps or gas thermal expansion micropumps in which the gases can be heated by electrical resistances or by Peltier-effect junctions can be used instead.
The interior atmosphere can be controlled by temperature and pressure microsensors and a gas analyzer controlling the micropumps via an onboard microcomputer.
Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, which is given with reference to the accompanying drawings.
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Tracy, Thermomolecular Pumping Effect, 1974, J. of Physics E. Scientific Instruments vol. 7, pp. 533-536.*
Orner et al, The Application of Thermal Transpiration to a Gaseous Pump, 1970, Trans. ASME J. of Basic Engineering, Jun. 1970, pp. 294-302.
Bernard Roland
Chevalier Eric
Alcatel
Liu Han L
Sughrue & Mion, PLLC
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