Measuring and testing – Gas analysis – Impurity
Patent
1994-01-31
1995-09-05
Williams, Hezron E.
Measuring and testing
Gas analysis
Impurity
73 3107, G01D 1800, G01N 1304
Patent
active
054470536
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
The present invention relates to a measuring method for determining amounts of impurities contained in special gases (silane gas, disilane gas, and the like) for use in, for example, semiconductor manufacturing, in the case in which such a special gas is supplied through a pipe system, and furthermore relates to a device for use in such measurement.
BACKGROUND ART
Recently, the progress in the field of semiconductor manufacturing technology has been striking, and in particular, the demand for ultrafine structures and high levels of integration has become pressing; however, in conjunction with this, the necessity has arisen to maintain the environment of the manufacturing device in a state of ultrahigh purity (that is to say, purity on the level of parts per trillion). As a result, in the case in which sample gas of common gas (for example, argon gas, nitrogen gas, or the like) or special gas (for example, silane gas) having the necessary degree of ultrahigh purity for the manufacture of silicon substrates is supplied through a pipe system which serves as a gas flow path, it is necessary to determine the amount of impurities such as moisture and the like which are contained in the sample gas, on the level of parts per trillion.
Measuring methods for determining the impurity adsorption amount in common gases (argon gas, nitrogen gas, and the like), which were commonly employed, include the connection of a trace gas analyzer (atmospheric pressure ionization mass spectrometer) to the pipe end of a sample pipe through which this common gas is caused to flow, and measuring the amount of impurities flowing out of the pipe end of this sample pipe.
However, in the case in which such a special gas had corrosive or flammable characteristics, damage was done to the measurement system, or the handling of this gas presented difficulties, so that it was impossible to employ the measurement method which was used in the case of common gases. Accordingly, in the case of such special gasses, there was no method for confirming the relationship between impurity amounts and gas flow amounts, and the like, so that, in other words, only a rough estimate could be made, and this was insufficient for the purposes of the manufacture of semiconductors having the ultrafine structures discussed above.
The present invention solves the problems which were present in the conventional technology discussed above, and has as an object thereof to provide a device which is capable of conducting, easily, and on a level of parts per trillion, the measurement of impurity amounts and the like contained in special gasses which present difficulties in handling.
DISCLOSURE OF THE INVENTION
In order to attain the above object, the invention provides: to flow through a sample pipe, an interior surface of which has been subjected to passivation processing; ultrahigh purity level is attained; predetermined temperature; flow within the sample pipe;
a fifth step, wherein an amount of the special gas remaining within the sample pipe is removed;
a sixth step, wherein baking is conducted within the sample pipe until an ultrahigh level of purity is attained; and
a seventh step, wherein the amount of impurities desorbed from the inner surface of the sample pipe by means of the baking of the sixth process is measured.
The invention further provides: degree of purity; of a gas flow control meter; flow of the inert gas or the special gas; sample pipe, another end opening of which is connected to the first change-over valve, and which is capable of bidirectional flow change-over; valve; and pipe at a freely selected temperature.
In this case, a construction is preferable in which the inert gases or special gases are caused to pass through at least a gas connection part, which regulates discharged gases so that the purity level of each gas does not decline.
Furthermore it is preferable that the trace gas analyzer described above comprise an atmospheric pressure ionization mass spectrometer.
FUNCTION
First, by causing an inert gas having
REFERENCES:
patent: 5214952 (1993-06-01), Leggett et al.
Wiggins J. David
Williams Hezron E.
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