JP2002148156A - Metallic impurity sampling container - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A metal impurity can be sampled safely and reliably without lowering the hydrolysis efficiency.
Provided is a metal impurity sampling container capable of improving analysis accuracy. SOLUTION: This is a sampling container 21 for sampling metal impurities in a semiconductor process gas,
A sample gas introduction pipe 24 and an exhaust pipe 25 are provided in a sealed container 23 containing a recovery liquid 22 for hydrolyzing a semiconductor process gas at a position not in contact with the recovery liquid 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sampling container for metal impurities, and more particularly, to a sampling container for hydrogen impurities such as hydrogen fluoride, hydrogen chloride, and hydrogen bromide, and hydrolyzing hydrogen iodide and ammonia. The present invention relates to a recovery liquid container for sampling trace metal impurities in a semiconductor process gas.

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated, higher quality silicon wafers are required. Although a CZ wafer is often used as a silicon wafer, it is considered that an epi-wafer is necessary for reducing crystal defects and improving electrical characteristics. However, the epi-wafer has a problem of heavy metal contamination generated in the epi-process, and has a great relationship with the corrosion of the gas system due to corrosive gas such as hydrogen chloride (HCl) used in the epi-process.

[0003] Therefore, regarding the gas used in the epi process, in addition to the quality of the gas filled in the container, a technique has been established that can evaluate metal impurities in the gas at a so-called POU (Point of Use) close to a semiconductor manufacturing apparatus. is important. If the analysis of metal impurities in the gas at the POU becomes possible, the gas supply system can be optimized, and the damage due to corrosion can be predicted and preventive measures can be taken at an early stage, and the yield and characteristics of the manufactured device can be improved. It can contribute to improvement.

[0004] Usually, analysis of metal impurities in hydrogen halide such as hydrogen chloride is performed by using a vessel 1 as shown in the schematic diagram of FIG.
1 is subjected to hydrolysis by bubbling a gas to be sampled introduced from a gas sampling line 13 into a recovery liquid 12 such as pure water, an aqueous solution of nitric acid, or an aqueous solution of hydrochloric acid. Mass spectrometer as an ion source (ICP-MS: Inductive Co
It uses a hydrolysis method of analyzing with a metal analyzer such as an upled Plasma-Mass Spectrometer. In this hydrolysis method, since impurities can be dissolved in the recovery liquid together with the gas, it is possible to collect the entire amount of the metal impurities regardless of whether the existing form is a volatile substance or a particulate substance, This is an extremely efficient sampling method.

[0005]

However, when this method is applied to hydrogen halide, the rate at which the gas is hydrolyzed is extremely high. However, there is a problem that the gas tends to flow backward to the upstream side of the gas sampling line 13, and the stability of the sampling cannot be secured.

[0006] This problem is particularly problematic when the gas pressure or flow rate is liable to change, such as POU in a semiconductor manufacturing process.
Specifically, it appears remarkably when the flow rate of the sample gas sharply decreases. To solve this problem, it is common practice to install a buffer tank between the collected liquid and the gas sampling line.

However, if the collected liquid moves to the buffer tank due to the backflow of the collected liquid, the amount of the collected liquid changes, so that an error occurs in the gas sampling amount and the metal impurities in the buffer tank are contaminated. There was such a problem of analytical accuracy.

In addition to the hydrolysis method, a column trap method,
Sampling methods such as the filter trap method and the residue method (residue method) can also be used. However, when the metallic impurities are present in the form of particulate matter, these methods can be used to change the flow rate of the sampling gas. It is also possible to perform a corresponding metal impurity analysis.
However, corrosive gases typified by hydrogen halides may react with metals to generate volatile metal compounds having a vapor pressure at room temperature. There is a problem that the recovery efficiency for volatile metal impurities is significantly reduced.

Therefore, the present invention prevents the recovery liquid from flowing back to the gas sampling line during hydrolysis even when a gas having a very high hydrolysis rate such as a hydrogen halide gas is used as the gas to be sampled. It is another object of the present invention to provide a metal impurity sampling container capable of safely and reliably sampling metal impurities without lowering the hydrolysis efficiency and improving the analysis accuracy.

[0010]

In order to achieve the above object, a metal impurity sampling container according to the present invention is a sampling container for sampling metal impurities in a semiconductor process gas having hydrolyzability. A sample gas introduction pipe and an exhaust pipe are provided at a position not in contact with the recovery liquid in a sealed container containing a recovery liquid for hydrolyzing the process gas, and in particular, the sample gas introduction pipe and the recovery liquid are provided. The distance (X) from the liquid level to the maximum level (L) of the recovered liquid level in the container is set to (3/4) L or less, preferably L / 10 to L / 2. And

[0011]

FIG. 1 is a schematic view showing one embodiment of a metal impurity sampling container according to the present invention. The sampling container 21 is provided with a sample gas introduction pipe (gas sampling line) 24 and an exhaust pipe 25 in a sealed container 23 containing a recovery liquid 22 for hydrolyzing a semiconductor process gas.
The sample gas introduction pipe 24 and the exhaust pipe 25 are respectively provided at positions where the tip openings thereof do not contact the recovery liquid 22.

The sample gas introduction pipe 24 is provided for collecting the gas introduced from the sample gas introduction pipe 24 into the sealed container 23.
In order to make the contact with the collection liquid 2 effectively, the opening of the tip of the sample gas introduction pipe 24 is directed toward the collection liquid 22 and the distance X between the tip of the sample gas introduction pipe 24 and the liquid level of the collection liquid 2
2, the maximum dimension L of the liquid surface, for example, the diameter if the sealed container 23 is cylindrical, or the length of the diagonal if the cross-sectional shape is a square such as a square, is (3/4) L or less, particularly (1/4) 10)
It is preferable to set in the range of L to (１ ／) L. If the distance X is too small, the collected liquid 22 may come into contact with the sample gas introduction pipe 24. If the distance X exceeds (3/4) L, the gas may not be sufficiently contacted with the collected liquid. .

On the other hand, the exhaust pipe 25 can be provided at any position where excess gas in the sealed container 23 can be exhausted, but the gas introduced into the sealed container 23 from the sample gas introducing pipe 24 is recovered. In order to more reliably prevent the gas from being exhausted without coming into contact with the liquid 22, it is preferable to provide the recovery liquid 22 and the sample gas introduction pipe 24 at positions as far as possible from each other.

In addition, hydrogen halide exhibits strong corrosiveness when it contains moisture. Therefore, when such impurities in the sample gas are collected, contamination from the sampling container 21 is prevented. , Polytetrafluoroethylene (PCTFE), polytetrafluoroethylene (PTF)
E), it is desirable to use a fluororesin such as ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer (PFA).

The size of the sampling container 21 is sufficient if the inner diameter is 10 mm or more in consideration of the gas contact time, and a container having an outer diameter of 35 mm is easily available as a container of this type. Therefore, this can be used. When the inner diameter is small, the area of the liquid surface of the recovered liquid becomes small, so that the contact efficiency with the gas is reduced. Note that a commercially available gas cleaning bottle can be used as the sampling container 21. When such a commercially available gas cleaning bottle is used, the pipe is placed so that the distance between the end face of the pipe and the liquid surface becomes a predetermined dimension. It may be cut and used.

The sample gas introduction pipe 24 and the exhaust pipe 25 may be pipes having a diameter of 1/16 or more in accordance with the gas flow rate. It is desirable to use a fluororesin such as ethylene chloride, polytetrafluoroethylene, or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

The flow rate of gas at the time of sampling, for example, the flow rate of hydrogen halide is 10 L / min or less, particularly 1 L / min.
min or less is preferable. If the gas flow velocity is too high, if the distance X is small, the liquid surface may undulate and the collected liquid 22 may come into contact with the sample gas introduction pipe 24, and the contact with the collected liquid may not be sufficiently performed. The sample gas may flow out of the exhaust pipe 25.

As described above, by providing the sample gas introducing pipe 24 in a non-contact state with the recovery liquid 22, when sampling metal impurities in the hydrogen halide whose hydrolysis rate is extremely high, the sample gas introducing pipe 24 is connected to the sample gas introducing pipe 24. Even if the flow rate of the introduced gas is greatly reduced, the recovery liquid 22 does not flow back to the sample gas introduction pipe 24, so that reliable sampling can be performed in a stable state. In addition, there is no need to install a buffer tank in the preceding stage, and the size of a set including the sampling container and the piping can be made much more compact than before.

The analysis of metal impurities after sampling can be performed by a device such as an ICP mass spectrometer, an ICP plasma emission spectrometer, or an atomic absorption spectrometer, as in the conventional case.

FIG. 2 is a system diagram showing an example of a sampling apparatus for sampling metal impurities in a sample gas using the sampling container of the present invention. The sampling device includes a pressure regulating valve 32 and a flow regulating valve 3 in a gas container 31 such as a cylinder filled with a semiconductor process gas.
3, a bypass path 40 having a three-way valve 34, valves 35 and 36, a flow meter (mass flow meter) 37, a check valve 38 and a valve 39, and a sampling vessel branched from the three-way valve 34 and via valves 41 and 42. A sample gas introduction pipe 24 connected to the sampling vessel 21 and valves 43, 44, 45,
An exhaust pipe 25 connected via a gas container 31;
And a purge gas introduction path 50 connected to the container valve 47 via a valve 48 and a filter 49.

In order to sample a sample gas with this sampling device, first, all the other valves are opened with the three-way valve 34 on the side of the sample gas introduction pipe 24 and the valve 48 of the purge gas introduction path 50 closed, and the gas container is opened. The pressure and the flow rate of the sample gas flowing out of 31 are set to predetermined values by the pressure control valve 32 and the flow control valve 33. With the flow rate stabilized, the sample gas introduction pipe 24 side of the three-way valve 34 is opened to start introduction of the sample gas into the sampling vessel 21, and the sampling operation is performed for a predetermined time.

After a lapse of a predetermined time, the three-way valve 34 is closed on the side of the sample gas introduction pipe 24, the container valve 47 is closed, and the valve 4 is closed.
8 is opened to purge the system by introducing a purge gas, for example, nitrogen gas, and further, the sample gas introduction pipe 24 side of the three-way valve 34 is opened to purge the system on the sampling container 21 side. After completion of the purging, the concentration of metal impurities in the sample gas can be measured by analyzing the metal component contained in the recovered liquid in the sampling container 21 with a suitable analyzer.

At this time, in the conventional sampling container,
When the three-way valve is closed and the introduction of the sample gas into the sampling container is stopped, the sample gas in the sample gas introduction pipe dissolves in the recovery liquid, and the recovery liquid flows backward in the sample gas introduction pipe. For example, a purge gas introduction valve is provided between the three-way valve 34 and the sampling container 21,
The three-way valve 34 must be switched to stop the introduction of the sample gas, and at the same time, the purge gas introduction valve must be opened to introduce the purge gas into the sample gas introduction pipe to prevent the recovery liquid from flowing back.

On the other hand, in the case of the sampling container of the present invention, even if the three-way valve 34 is closed, the collected liquid remains in the sample gas introduction pipe 24.
Since there is no backflow into the inside, the transition from the end of the sampling operation to the purging operation can be performed easily and quickly.

[0025]

EXAMPLE 1 Metal impurities in hydrogen chloride were analyzed using a sampling apparatus having the structure shown in FIG. Sampling container is P
A product made of FA having an internal volume of 125 cc, a diameter of 45 mm, and a liquid surface area of about 1590 mm ² was used, and pure water was used as a recovery liquid. Further, a PFA pipe having an outer diameter of 6 mm was used for the sample gas introduction pipe and the exhaust pipe, and the distance between the tip of the sample gas introduction pipe and the liquid level was 15 mm.

Under these conditions, the gas flow rate dependence of the hydrolysis efficiency was measured by changing the flow rate of the sample gas. The gas supply amount to the sampling container was obtained by multiplying the mass flow rate per unit time adjusted by the mass flow controller by the sampling time. The amount of hydrogen chloride gas recovered in the recovery liquid was determined by measuring the weight of the sampling container containing the recovery liquid before and after recovering the gas, and the difference was defined as the recovery gas amount. The measurement results are shown below. The amount of rise in the liquid level was about 3 mm.

Gas flow rate [sccm] Gas supply rate [g] Gas recovery rate [g] Recovery efficiency [%] 300 10.5 10.3 98 500 9.0 8.5 94

Example 2 The distance dependence of the hydrolysis efficiency was measured in the same manner as in Example 1 except that the gas flow rate was set to 500 sccm and the distance between the tip of the sample gas introduction tube and the liquid surface was changed. The results are shown below.

Distance [mm] Gas supply amount [g] Gas recovery amount [g] Recovery efficiency [%] 15 9.0 8.5 94 25 9.0 7.7 86

Example 3 Two types of ammonia gas (A, B) were used as sample gases, and metal impurities in each ammonia gas were measured. The distance between the tip of the sample gas introduction tube and the liquid surface was 15 mm, and the gas flow rate was 500 sccm. The sampling amount of ammonia gas was 10 g. Other sampling conditions were the same as in Example 1.

After concentrating the collected solution subjected to the sampling operation 20 times, the amount of the metal is determined by the atomic absorption method.
The metal impurity concentration [wtppb] in each ammonia gas was calculated from the total flow rate. The results are shown below.

Sample FeNiCrAlSiA 4.2 <0.6 <0.1 <0.6 <6 B <0.3 <0.6 <0.1 <0.6 10

[0033]

As described above, the metal impurity sampling container of the present invention can suppress the backflow of the recovery liquid with respect to the variation in the flow rate of the sample gas, so that the sampling of the semiconductor process gas is stable and the precision is high. Metal analysis becomes possible. This makes it possible to analyze the metal impurities in the gas even during the operation of the semiconductor manufacturing process, thereby making it possible to clarify the maintenance time of the gas equipment and to contribute to the improvement of the yield and the characteristics of the manufactured device.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a metal impurity sampling container of the present invention.

FIG. 2 is a system diagram showing an example of a sampling device for sampling metal impurities in a sample gas using the sampling container of the present invention.

FIG. 3 is a schematic view showing an example of a conventional sampling container.

[Explanation of symbols]

Reference numeral 21: sampling container, 22: recovered liquid, 23: sealed container, 24: sample gas introduction pipe, 25: exhaust pipe

Claims (2)

[Claims] A sampling container for sampling metal impurities in a semiconductor process gas having a hydrolyzability, wherein the sampling container is in a sealed container for storing a recovery solution for hydrolyzing the semiconductor process gas and is not in contact with the recovery solution. A sampling container for metal impurities, wherein a sample gas introduction pipe and an exhaust pipe are provided. 2. The distance (X) between the sample gas inlet tube and the liquid level of the recovered liquid is the maximum dimension (L) of the recovered liquid level in the container.
2. The metal impurity sampling container according to claim 1, wherein the amount is not more than (3/4) L.