JP6142152B2 - Oil content measuring apparatus and oil content measuring method - Google Patents

Description

  The present invention relates to an oil content measuring apparatus and an oil content measuring method for measuring the amount of oil content contained in ammonia gas.

  If impurities are included in gases used in semiconductor manufacturing processes, etc., the quality of the semiconductor will be adversely affected. Therefore, high purity is required for these gases, and the impurities are measured and controlled so that they are below a certain concentration. It is necessary to There are various substances that are measured and controlled as impurities, one of which is oil. Here, the oil component generally refers to a hydrocarbon having a molecular weight of 200 to 400. Oil is often derived from compressor oil used when filling a container with gas under pressure, and is present as an impurity in many gases. As a method for measuring the oil content in the gas, for example, a gas containing oil is introduced into a tube filled with powder, and after the oil in the gas is absorbed into the powder, a solvent is introduced into the tube. There is disclosed a method for measuring an oil content in a gas, wherein the oil content absorbed in the powder is extracted and then the oil content dissolved in the solvent is analyzed (Patent Document 1).

On the other hand, ammonia gas is one of the gases used in the semiconductor manufacturing process, and is often used particularly as a nitrogen source in the manufacturing process of group III nitride semiconductors. A group III nitride semiconductor is used as a material for a blue or ultraviolet LED or a blue or ultraviolet laser diode, and is formed by silicon (Si), sapphire (Al ₂ O ₃ ) or nitridation by a method such as chemical vapor deposition (CVD). It is grown on a substrate such as gallium (GaN). In vapor phase growth of Group III nitride semiconductors, if carbon or the like derived from oil is mixed into the semiconductor film, the quality of the semiconductor deteriorates. Therefore, the oil in ammonia gas is measured and controlled so that it is below a certain concentration. It is necessary to
JP-A-5-126695

  In the conventional oil collecting method and oil collecting apparatus described in Patent Document 1, the oil contained in the gas is obtained by extracting the oil absorbed in the powder with a solvent and analyzing the oil dissolved in the solvent. However, when performing repeated measurements, it is necessary to replace the oil collection tube every time it is measured. There was also a problem that accurate and highly sensitive measurement was difficult due to the influence of external impurities such as oil. Accordingly, an object of the present invention is to provide an oil content measuring apparatus and an oil content measuring method which are easy to work and can perform accurate and highly sensitive measurement.

  As a result of diligent studies to solve these problems, the present inventors have determined that an oil content measuring device that measures the amount of oil contained in ammonia gas has an adsorbent that adsorbs the oil and an oil content that is desorbed from the adsorbent. By providing an analysis unit that is sealed from the outside, not only is the work easier when performing repeated measurements, but also contamination from outside is suppressed, so the amount of oil is accurate. The inventors have found that highly sensitive measurement is possible, and have reached the oil content measuring apparatus and the oil content measuring method of the present invention.

That is, the present invention is an oil content measuring apparatus for measuring the amount of oil contained in ammonia gas, comprising an adsorption cylinder filled with the oil adsorbent and an analysis unit for analyzing the oil desorbed from the adsorbent. This is an oil content measuring device.
Further, the present invention is an oil content measuring method for measuring the amount of oil contained in ammonia gas, the step of bringing ammonia gas into contact with an adsorbent and adsorbing the oil contained in the ammonia gas onto the adsorbent; An oil content measuring method comprising the steps of desorbing an oil component adsorbed by the adsorbent and analyzing the desorbed oil component.

In the oil content measuring apparatus and the oil content measuring method of the present invention, since it is not necessary to exchange the adsorbent even when performing repeated measurement, the work is facilitated, and contamination with external impurities is suppressed and accurate and highly sensitive. In addition to making it possible to measure the oil content, it is possible to continuously or intermittently measure the oil content contained in the ammonia flowing through the piping.
In addition, oil is usually a mixture of various hydrocarbons with different numbers of carbons. Therefore, in order to measure the amount of oil, the oil is separated and then quantified or analyzed by analyzing many analysis signals. Must. However, by using a flame ionization detector (FID) as an analysis means in the present invention, the oil component, which is a mixture of various hydrocarbons, is analyzed after being decomposed by FID, requiring the above-mentioned complicated work. Therefore, the amount of oil contained in ammonia gas can be quantified easily and accurately in terms of methane.
With the oil content measuring apparatus and the oil content measuring method of the present invention, it is possible to measure the oil content contained in ammonia in an amount of 0.1 vol ppm (methane conversion), for example.

  The present invention is applied to an oil content measuring apparatus and an oil content measuring method for measuring the amount of oil contained in ammonia gas. Hereinafter, although the oil content measuring apparatus and oil content measuring method of this invention are demonstrated in detail based on FIG. 1, FIG. 2, this invention is not limited by these. FIG. 1 is a block diagram showing an example of an oil content measuring apparatus of the present invention, and FIG. 2 is a block diagram showing an example of a vapor phase growth system using the oil content measuring apparatus of the present invention.

As shown in FIG. 1, the present invention is an oil content measuring apparatus for measuring the amount of oil contained in ammonia gas, an adsorption cylinder 6 filled with the oil adsorbent 7, and desorbed from the adsorbent 7. It is an oil content measuring apparatus provided with the analysis part 10 which analyzes oil content.
The present invention also includes a step of bringing ammonia gas into contact with an adsorbent and adsorbing oil contained in the ammonia gas to the adsorbent (adsorption step), and a step of desorbing oil adsorbed by the adsorbent (desorption step). And a step (analysis step) of analyzing the desorbed oil component.

  The adsorbent used in the present invention is not particularly limited as long as it is an adsorbent that does not suffer from adverse effects such as corrosion by ammonia and can adsorb oil, but is not limited to inorganic substances such as activated alumina, diatomaceous earth, molecular sieve, activated carbon and the like. Examples thereof include polymer adsorbents such as a system adsorbent and TENAX (registered trademark). As the adsorbent used in the present invention, TENAX (registered trademark) is particularly preferably used, but is not limited to TENAX (registered trademark). As shown in FIG. 1, the adsorbent used in the present invention is preferably used by being filled in an adsorption cylinder. The adsorption cylinder filled with the adsorbent preferably has a cylindrical shape, and is preferably made of a material having excellent heat resistance and corrosion resistance, such as stainless steel, but is limited to such a shape and material. There is nothing.

  In the adsorption step in the present invention, the temperature of the adsorbent is preferably 20 to 30 ° C. and particularly preferably room temperature, but is not limited to such a temperature. The flow rate of ammonia gas circulated through the adsorbent is preferably 25 to 500 ml / min, and the empty cylinder linear velocity (LV) of the ammonia gas circulated through the adsorption cylinder is 5 to 120 cm / sec. Although preferred, it is not limited to such flow rates and LVs. The circulation time per measurement is preferably 0.01 to 20 minutes, but is not limited to such a circulation time. When TENAX (registered trademark) is used as the adsorbent, the amount of TENAX (registered trademark) used is preferably 0.3 to 0.5 g, but is not limited to such an amount.

  In the present invention, when shifting from the adsorption stage to the desorption stage, ammonia removal by desorbing and removing at least a part of the ammonia adsorbed on the adsorbent, and the adsorbent without desorbing oil from the adsorbent by the ammonia removal It is preferable to perform oil content retention confirmation to confirm that the oil content is retained.

  By performing such ammonia removal, it is possible to prevent adverse effects on the analysis means in the analysis stage, such as corrosion by high-concentration ammonia. In particular, when FID is used as an analysis means, if high-concentration ammonia is introduced into the FID, the baseline of the FID becomes unstable due to hydrogen generated by the decomposition of the ammonia. Baseline instability can be prevented. This ammonia removal is preferably performed by circulating a carrier gas through the adsorbent and discharging the carrier gas accompanied by the desorbed ammonia to the outside. The temperature of the adsorbent at the time of ammonia removal is set as appropriate so that ammonia can be desorbed without desorbing oil from the adsorbent. When TENAX (registered trademark) is used as the adsorbent, the temperature is 20 to 30 ° C. It is preferable that it is normal temperature. The flow rate of the carrier gas circulated through the adsorbent is preferably 30 to 60 ml / min, and the LV of the carrier gas circulated through the adsorption cylinder is preferably 7 to 15 cm / sec. It is not limited to such a flow rate and LV.

  In addition, after the above-described ammonia removal, it is possible to measure the oil content more accurately and with high sensitivity by confirming that the oil content is retained on the adsorbent without desorbing from the adsorbent by the ammonia removal. The oil content retention check is preferably performed by confirming that the analysis means for measuring the oil content does not detect the oil content accompanying the carrier gas when the carrier gas is passed through the adsorbent. It is preferable that the temperature of the adsorbent at the time of confirming oil retention is the same temperature as the above-mentioned ammonia removal. In addition, the flow rate of the carrier gas flowing through the adsorbent is preferably the same flow rate and LV as the above-described ammonia removal, but is not limited to such a flow rate and LV.

  In the present invention, the means for desorbing the oil adsorbed by the adsorbent is preferably a heating means such as a heater. For example, in the oil content measuring apparatus of FIG. 1, the adsorbent 7 is heated through the adsorption cylinder 6 by the heater 8 provided outside the adsorption cylinder 6, and the oil adsorbed on the adsorbent 7 is desorbed. In addition, when desorbing oil, it is preferable to circulate the carrier gas through the adsorbent. By introducing the carrier gas accompanied by the desorbed oil into the analyzer, the desorption and analysis steps can be performed continuously. Become. The carrier gas may be appropriately selected from inert gases such as nitrogen, helium, and argon, but argon is particularly preferable.

  In the desorption stage in the present invention, the temperature of the adsorbent is appropriately set in consideration of the heat resistance of the adsorbent and the desorption temperature of the oil. When TENAX (registered trademark) is used as the adsorbent, the temperature is 250 to 350 ° C. It is preferable that Further, the flow rate of the carrier gas circulated through the adsorbent is preferably 30 to 60 ml / min, and the empty cylinder linear velocity (LV) of the carrier gas circulated through the adsorption cylinder is 7 to 15 cm / sec. However, it is not limited to such a flow rate and LV.

  In the present invention, the means for analyzing the oil desorbed from the adsorbent is preferably an analysis means having sensitivity to the oil and having substantially no sensitivity to ammonia, for example, FID. preferable. At the time of desorption of the oil from the adsorbent, a small amount of ammonia is also desorbed in addition to the oil. By using such an analysis means, only the oil can be quantified by the analysis unit. In addition, the amount of oil adsorbed by the adsorbent is quantified in terms of methane by introducing carrier gas accompanied by desorbed oil into the analyzer and continuing desorption until no oil is detected in the analyzer. Can do. In the present invention, the amount of oil contained in ammonia gas can be calculated from the amount of oil measured in the analysis stage and the amount of ammonia gas flowing to the adsorbent, and the oil content thus calculated is calculated. Is the concentration value in terms of methane. The calculation formula at that time is, for example, (concentration of oil in ammonia [volppm]) = {(amount of oil detected in analysis unit [ml]) / (amount of ammonia flowing into the adsorption cylinder [ml])} × 1,000,000 [volppm].

  The oil content measurement using the oil content measuring apparatus of FIG. 1 is performed as follows, for example. First, in the adsorption stage, in order to prevent adverse effects such as corrosion due to high-concentration ammonia, the valves (5, 9) are operated, the ammonia gas is passed through the adsorbent 7, the adsorption stage is performed, and then the analysis unit Exhaust from the gas outlet 11 to the outside without passing through 10. During this time, the valve 4 may be operated to exhaust the carrier gas from the gas outlet 11 to the outside without passing through the adsorbent 7 and the analysis unit 10. Thereafter, by operating the valves (4, 5, 9), the ammonia gas is exhausted from the gas outlet 11 without passing through the adsorbent 7 and the analysis unit 10, and the carrier gas is passed through the adsorbent 7 for analysis. After removing ammonia by exhausting from the gas outlet 11 to the outside without passing through the part 10, the valves (5, 9) are operated to guide the carrier gas that has passed through the adsorbent 7 to the analysis part. Confirm that 10 does not detect oil. Next, in the desorption stage and the analysis stage, the valves (4, 5, 9) are operated to exhaust the ammonia gas from the gas outlet 11 to the outside without passing through the adsorbent 7 and the analysis unit 10, and the carrier. The gas is desorbed and analyzed through the adsorbent 7 and the analysis unit 10 and then exhausted from the gas outlet 11 to the outside. In addition to the adsorption stage, the adsorbent 7 is maintained at a predetermined adsorption temperature such as normal temperature without operating the heater 8 in the above-described ammonia removal and oil retention check, and in the desorption stage and the analysis stage, the heater 8 is maintained. May be heated to a predetermined desorption temperature. The pressure at any stage is not particularly limited, but it is usually carried out under normal pressure.

  By repeating such an operation, the amount of oil contained in the ammonia gas flowing through the piping can be measured continuously or intermittently. Further, the amount of oil contained in the ammonia gas supplied to the vapor phase growth apparatus can be obtained by incorporating the oil content measurement apparatus of the present invention into the vapor phase growth system as shown in FIG. 2 and repeating the above-described operation. Can be measured continuously.

  The present invention is suitable for use in a semiconductor manufacturing process by vapor phase growth such as CVD using ammonia, and measures and controls the oil concentration in ammonia as an impurity as in the manufacturing process of a group III nitride semiconductor. It is particularly suitable for a semiconductor manufacturing process that requires a large amount. In addition, the present invention is useful for measuring oil contained in ammonia gas that is inexpensive but not subjected to purification treatment to the extent that it can be used in a semiconductor manufacturing process, such as industrial ammonia. For example, as shown in FIG. 2, the oil content measuring apparatus of the present invention is provided between a vapor phase growth apparatus in which a vapor phase growth reaction for forming a semiconductor is performed and an ammonia supply source provided upstream thereof, or a vapor phase growth apparatus. It is provided between oil removing means (not shown) provided upstream thereof, and continuously or intermittently measures the amount of oil contained in the ammonia gas flowing through the pipe between the ammonia supply source and the vapor phase growth apparatus. be able to.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these.

[Example 1]
(Production of oil content measuring device and vapor phase growth system)
An oil content measuring apparatus as shown in FIG. 1 was manufactured as follows. First, a stainless steel adsorption cylinder 6 having an inner diameter of 3 mm and a length of 200 mm is filled with 0.4 g of TENAX (registered trademark) (filling length 150 mm) as an adsorbent 7, and a heater 8 is attached to the adsorption cylinder 6. did. An analysis unit 10 made of FID was connected to these, and the oil content measuring apparatus of FIG.
Next, the oil content of FIG. 1 manufactured as described above is applied to a group III nitride semiconductor vapor phase growth system including a vapor phase growth device 18 to which an ammonia gas supply source 12, an exhaust gas treatment device 19 and the like are connected. A measurement apparatus was incorporated to complete the vapor phase growth system as shown in FIG. As a supply source of ammonia gas, a cylinder filled with industrial ammonia was used.

(Oil content measurement experiment)
Using the oil content measuring apparatus (FIG. 1) and the vapor phase growth system (FIG. 2) thus manufactured, an oil content measurement experiment was performed under normal pressure. First, the valve 4 was operated to exhaust 30 ml / min of carrier gas (argon) from the gas outlet 11 without passing through the adsorbent 7 and the analysis unit 10. Then, by operating the valve 14, unpurified industrial ammonia gas 50 ml / min (LV: 12 cm / sec) that has not passed through the ammonia purifier 13 is sampled for 1 min using the flow controller 16, and the valve ( 5 and 9), after passing the ammonia gas inlet 2 through the adsorbent 7 at normal temperature, the gas is discharged outside from the gas outlet 11 without passing through the analyzer 10, and the exhausted ammonia gas is discharged to the exhaust gas treatment device 19 Purified by.

  Thereafter, by operating the valves (4, 5, 9), the ammonia gas is exhausted from the gas outlet 11 without passing through the adsorbent 7 and the analyzer 10, and the carrier gas is 30 ml / min (LV: 7 cm / min). sec) was passed through the adsorbent 7 and exhausted to the outside from the gas outlet 11 without passing through the analyzer 10, and then the valves (5, 9) were operated to pass through the adsorbent 7. A carrier gas of 30 ml / min (LV: 7 cm / sec) was introduced to the analysis unit 10, and it was confirmed that the analysis unit 10 did not detect oil.

  Next, the adsorbent 7 was heated to 300 ° C. using the heater 8. Thereafter, by operating the valves (4, 5, 9), the ammonia gas is exhausted from the gas outlet 11 without passing through the adsorbent 7 and the analysis unit 10, and the carrier gas is 30 ml / min (LV: 7 cm / sec). ) Was exhausted from the gas outlet 11 to the outside through the adsorbent 7 and the analysis unit 10 maintained at 300 ° C. The exhausted ammonia gas was purified by the exhaust gas treatment device 19. The analysis is continued until the FID of the analysis unit 10 no longer detects oil, and the amount of oil determined by the FID of the analysis unit 10 and the flow rate of ammonia gas determined based on the sampling time based on the sampling flow rate of ammonia gas. When the amount of oil in ammonia gas was calculated, it was 0.27 volppm in terms of methane.

  The present invention is suitable for use in a semiconductor manufacturing process by vapor phase growth such as CVD using ammonia, and measures and controls the oil concentration in ammonia as an impurity as in the manufacturing process of a group III nitride semiconductor. It is particularly suitable for a semiconductor manufacturing process that requires a large amount.

It is a block diagram which shows an example of the oil content measuring apparatus of this invention. It is a block diagram which shows an example of the vapor phase growth system using the oil content measuring apparatus of this invention.

DESCRIPTION OF SYMBOLS 1 Oil content measuring device 2 Ammonia gas inlet 3 Carrier gas inlet 4, 5, 9, 14 Valve 6 Adsorption cylinder 7 Adsorbent 8 Heater 10 Analysis part 11 Gas outlet 12 Supply source of ammonia gas 13 Ammonia purification device 15 Supply source of carrier gas 16, 17 Flow rate controller 18 Vapor phase growth apparatus 19 Exhaust gas treatment apparatus 20 Discharge line

Claims (4)

An oil content measuring method for measuring the amount of oil contained in ammonia gas, the step of bringing ammonia gas into contact with an adsorbent to adsorb the oil contained in the ammonia gas onto the adsorbent, and a carrier gas as the adsorbent. oil measurement method by circulation, the adsorbent is characterized by comprising the steps of desorbing heated by the heating means of oil adsorbed, the step of analyzing the oil that the desorbed. The oil content measuring method according to claim 1 , wherein the amount of oil content contained in the ammonia gas flowing through the pipe is continuously or intermittently measured. 2. The oil content measuring method according to claim 1 , wherein the concentration of the oil content contained in the ammonia gas is calculated from the amount of the oil content measured in the stage of analyzing the desorbed oil content and the flow rate of the ammonia gas to the adsorbent. Oil measuring method according to claim 1 for measuring the amount of oil contained in industrial ammonia gas.

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