Measuring and testing – Gas analysis – Impurity
Patent
1994-01-31
1996-03-12
Williams, Hezron E.
Measuring and testing
Gas analysis
Impurity
73 1G, 73 2321, 7386481, 436 8, 436 18, G01N 3106, G01D 1800
Patent
active
054976529
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an evaluation method and device for determining quantities of absorbed impurities in common gases (argon gas, and the like) for use in, for example, semiconductor production, with respect to various types of materials.
BACKGROUND ART
In recent years, advances in semiconductor manufacturing technology have been striking, and there have been great demands for hyperfine structures; as a result of this, it has become necessary to maintain the environment of the manufacturing apparatus in a state of ultrahigh purity (that is to say, purity on the level of "ppt", or parts per trillion). As a result, in cases in which common gases of ultrahigh purity (for example, argon gas) are to be supplied through the medium of pipes which serve as gas flow conduits, it is necessary to determine, on the level of parts per trillion, the amount of impurities contained in the gas, such as moisture or the like, which adhere to the inner pipe surfaces, which comprise various materials.
Examples of conventionally known methods for the detection of adsorbed amounts include, for example, a method in which a microanalyzer (an atmospheric pressure ionization mass spectrometer) is connected to the pipe end of piping which is to be tested, a gas of ultrahigh purity is caused to flow into the piping from a gas purifier, and the amounts of impurities in the gas flowing out of the pipe end is measured.
However, in this conventional method, no account was taken of moisture which adhered to metal surfaces, and only the purity of the gas passing through the piping system which served as the gas conduit was measured, so that no precise determinations could be made with respect to the quality of the interior surfaces of the gas system.
The present invention was created in light of the abovedescribed problems in the conventional technology; it has as an object thereof to provide an evaluation method and an evaluation device for quantities of absorbed impurities which are capable of evaluating, on the order of parts per trillion, quantities of impurities contained in a gas which adsorb to a gas conduit comprising various materials.
DISCLOSURE OF THE INVENTION
In order to attain the above object, the present invention contemplates a method wherein in a first step an inert gas of ultrahigh purity is caused to flow into a sample-gas pipe; in a second step, the interior of this sample-gas pipe is baked to reach at least the level of background purity; in a third step, the interior of this sample gas pipe is placed in an atmosphere having a specified temperature; in a fourth step, the inflow of a sample gas having a specified concentration into the sample gas pipe is initiated; and in a fifth step when the quantities of impurities within the sample gas which adsorb to the inner surface of the sample gas pipe reach saturation, the inflow of the sample gas is changed to the inflow of an inert gas.
In this case, it is preferable for the evaluation of adsorbed impurities that the sample gas pipe be freely replaceable with pipes comprising various materials, or the inner surfaces of which have been subjected to various types of processing.
Furthermore, it is preferable that the inert gas and sample gas comprise argon gas.
In order to carry out the method of the present invention, it is preferable that the inventive apparatus be provided with: a first gas supply source, for supplying an inert gas of ultrahigh purity, a second gas supply source, for supplying a sample gas, the added impurity amounts of which are freely adjustable, through the medium of a gas flow control meter; change-over valves, which are capable of freely selected change-over in order to cause either an inert gas or a sample gas to flow into the sample gas pipe, and which are connected to one end opening of the sample gas pipe; a support mechanism, for supporting the sample gas pipe; a microanalyzer, which is connected to the other end opening of the sample gas pipe; and a heating mechanism, which is capable of maintaining the interio
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Wiggins J. David
Williams Hezron E.
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