JPH02124447A - Light scattering type grain counter for reactive gas - Google Patents

Abstract

PURPOSE:To make it possible to perform substitution of gas quickly by providing an inactive gas introducing port to the side surface of a detecting cell where a gas stream is stagnated, and injecting clean inactive gas through the port. CONSTITUTION:A port 11 is provided at the side surface of a detecting cell part 2 of a light scattering type grain counter 1. Then, a valve 52 is closed, and valves 51, 53 and 54 are opened. Inactive gas is introduced into the apparatus. Then, part of the inactive gas is directly supplied into the port 11 by way of the valve 54 and a filter 4. The substitution of the gas in the detecting cell part 2 is completed in a short time. During this period, a sucking pump 3 is operated. Then, the valves 51 and 54 are closed, and the valve 52 is opened. Reactive gas is introduced, and counting is performed. In this way, the substitution of the gas is performed before the reactive gas is sucked. The inactive gas does not flow during the measurement of a flow rate. Therefore, errors can be suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light-scattering particle counter for reactive gases that ensures and facilitates gas replacement with inert gas before reactive gas suction. be.

[Conventional technology]

When measuring particle concentrations in semiconductor device manufacturing gases, reactive gases that can ignite just by contacting air (e.g. arsine, monosilane, diborane, etc.) are extracted after completely cutting off contact with air. Must. When measuring the particle concentration in a reaction gas using a light scattering particle counter, the commonly used method is to use nitrogen gas (N2).
Introduce an inert gas, such as ), the reactive gas to be measured is sampled. At this time, it goes without saying that the above gas replacement must be carried out to every corner inside the fluid system, and the above gas replacement is also necessary after the measurement is completed, so that the inside of the fluid system is not filled. Gas replacement with the above-mentioned inert gas is also performed when exhausting the reactive gas.

FIG. 3 shows a piping diagram for sampling a single reactive gas using an apparatus having a fluid system equivalent to a conventionally used general-purpose light scattering particle counter. Stainless steel, fluororesin, etc. are used as materials for the parts of the above device that come into contact with gas. In the figure, 1 is a light scattering particle counter, and 2 is a detection cell.

3 is a suction pump, 4 is a filter, 51, 52, and 53 are valves, and 6 is a flow meter.

G indicates the inflow of reactive gas, and N2 indicates the inflow of nitrogen gas. However, the valve 53 and the illustrated bypass circuit 8 are for equalizing the gas pressure between the gas inlet and the gas outlet of the light scattering particle counter 1, and are used to equalize the gas pressure between the gas inlet and the gas outlet of the light scattering particle counter 1. Not required when the pressure is normal pressure,
The operation of the conventional apparatus shown in FIG. 3 is as follows. That is, valves 51 and 53 are opened while valve 52 is closed, and N□ gas is introduced into the apparatus. On this occasion,
Suction＼ The pump 3 is operated, and then the valve 51 is closed and the valve 52 is opened to introduce the reactive gas G as the sample gas. Here, the time for introducing the N2 gas, that is, the gas replacement time, must be determined in advance by monitoring the oxygen concentration in the outlet gas.

Gas introduction part of the detection cell 2 (referred to as sample nozzle)
is a thin tube, and the gas flowing out from the tip becomes a thin jet stream, which is immediately sucked into the suction nozzle located below the detection cell 2, and the gas stream does not spread inside the detection cell 2 and becomes a jet stream. It passes through as.

Because light scattering particle counters emphasize particle detection performance,
The inside of the detection cell is formed into a complicated structure so as to generate the jet stream. As a result, a stagnation area is created in the gas flow, and most of the air in the detection cell is gradually replaced with inert gas by the turbulence of the jet flow and gas diffusion, and the gas is replaced. This will take an extremely long time.

The example shown in FIG. 4 is an improved device that overcomes the above drawbacks by allowing a larger amount of inert gas to flow in, and even if some air remains in the stagnant portion of the detection cell 2. 9 in Figure 0 is a total flow meter that prevents contact with reactive gas by an inert gas sheath.

Reference numeral 10 indicates a sheath flowmeter, and the other parts are the same as in the conventional example shown in FIG. The operation of this apparatus is as follows: First, N2 gas is introduced by opening each valve 51, 53, 54 while keeping valve 52 closed. The suction pump 3 is left in operation.

Next, the valve 54 is closed and the valve 52 is opened to introduce one reactive gas G. In the detection cell 2, the pipe portion covering the sample nozzle is called a sheath nozzle.1 The sheath nozzle usually has an inner diameter two to three times that of the sample nozzle, and can flow a large amount of inert gas. Since this inert gas flow in the sheath is allowed to flow even during measurement, the efficiency of gas replacement is superior to that of the above-mentioned conventional example.

[Problem to be solved by the invention]

In the conventional example described above, the flow rate of one reactive gas is determined as the difference between the readings Q and Q2 of the two flowmeters 9 and lO.

The reason why a flow meter is not connected to the inlet of the sample nozzle is that dust generation from the flow meter cannot be ignored. Generally, the ratio between the reactive gas flow rate Q, -Q and the sheath flow rate Q2 is 4
If the reading error of the flow rate Q2 of each flow meter is E, then the combination error E' is given by the following equation.

When =9, ε' = iX13.5, and for example, even if a flowmeter with an accuracy of ±3% is used, the error will be 19 to 41%, which has the disadvantage of poor measurement accuracy.

The present invention enables gas replacement within the detection cell to be completed efficiently in a short time, and there is no increase in error in reactive gas flow rate measurement.
The purpose is to obtain a light scattering particle counter for reactive gases.

[Means to solve the problem]

The above object is achieved by providing one or more inert gas inlets in the detection cell section.

[Effect]

A light scattering particle counter replaces the inside of the fluid system with an inert gas before starting to suck in the reactive gas that is the measurement target, but the structure of the detection cell prevents stagnation from occurring in the gas flow. This caused the gas replacement to take a long time. In the present invention, an inert gas introduction boat is provided on the side of the detection cell where stagnation occurs in the gas flow, and clean inert gas is directly injected from the port to efficiently complete gas replacement in a short time. Can be done. Also, the flow of reactive gas t g
During the +q constant, no inert gas is flowed during the measurement, so there is no increase in measurement error.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of the fluid system piping in a light scattering particle counter for reactive gas according to the present invention, and FIG. 2 is a diagram showing another embodiment of the fluid system piping. In FIG. 1, a boat 11 for directly injecting an inert gas such as nitrogen (N2) through a filter 4 is provided on the side of a detection cell 2 provided in a light scattering particle counter 1. However, the rest is the same as the conventional example shown in FIG. That is, a suction pump 3, a filter 4. It is provided with respective valves 51, 52, 53, 54, a flow meter 6, and a bypass 8 for adjusting the gas pressure between the gas inlet and the gas outlet. Note that materials such as stainless steel or fluororesin are used for the parts of this device that form the fluid system that come into contact with the gas.

When operating this device, valves 51, 53 and 54 are opened while valve 52 is closed, and inert gas is introduced into the device. However, the boat 1 installed on the side of the detection cell 2
Since the gas is directly supplied to the detection cell 1, gas replacement within the detection cell 2 can be efficiently completed in a short time. On this occasion,
Suction pump 3 is operated. Next, valves 51 and 54 are closed, valve 52 is opened, reactive gas is introduced, and counting is performed.1 Regarding the flow rate measurement of reactive gas, no inert gas is flowed during the measurement, so errors do not increase. .

In another embodiment of the present invention shown in FIG. 2, the inert gas port 11 in the detection cell is provided at one location in the above embodiment, whereas in this embodiment, the port 11 is provided at two locations. , differs from the above embodiment in that the gas replacement in the detection cell 2 is completed in a shorter time and that some of the components of the fluid system are incorporated into the light scattering particle counter 1. Of course, similar effects can be obtained.

〔Effect of the invention〕

As described above, the light scattering particle counter for reactive gases according to the present invention is a light scattering particle counter for reactive gases equipped with an inert gas filter, a flow meter, a control valve, etc.
r+ to start suctioning reactive gas? By providing one or more inert gas inlet ports in the detection cell section, gas replacement with clean inert gas can be performed quickly and the error in particle counting can be increased. This has the effect that there is nothing to do.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the fluid system piping in a light scattering particle counter for reactive gas according to the present invention, and FIG. 2 is a diagram showing another embodiment of the fluid system piping. FIG. 3 is a diagram showing an example of fluid system piping in a conventional light scattering particle counter for reactive gas, and FIG. 4 is a diagram showing another example of the above-mentioned conventional fluid system piping. 1...Light scattering particle counter for reactive gas 2...Detection cell 4...Filter 6.9.10...Flowmeter

Claims (1)

[Claims] 1. To perform gas replacement before starting suction of reactive gas in a light scattering particle counter for reactive gas equipped with an inert gas filter, a flow meter, a control valve, etc. A light scattering particle counter for reactive gas, characterized in that a detection cell section is provided with one or more inert gas inlets. 2. The inert gas filter, flow meter, control valve, etc. are incorporated into the main body of the light scattering particle counter, as set forth in claim 1. Light scattering particle counter.