JPH0754294B2 - Particle measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is capable of detecting in-process fine particles in a semiconductor room in a clean room or in a space under atmospheric pressure or atmospheric pressure such as in an atmospheric pressure CVD apparatus. Regarding the device.

<Prior Art> Conventionally, as a fine particle measuring device, a method is known in which a reaction tank is irradiated with laser light and the size of fine particles in a gas is determined based on scattered light. However, this method has the following drawbacks.

In principle, it is not possible to measure fine particles with a diameter of 0.1 μm or less due to the restriction of the wavelength of laser light. In addition, in the actual measurement, since the measuring device is measured outside the reaction tank, fine particles of 0.5 μm or less cannot be measured due to stains on the window. on the other hand,
High integration of semiconductor devices has progressed rapidly, and 1Mbit DRAM, 4M
In the bit DRAM process, the size of the fine particles to be controlled is
The level is 0.05 μm.

Since it is detected by an optical method, only the size of the fine particles is known, and no information about the composition of the fine particles is obtained.

<Problems to be Solved by the Invention> A technical problem to be solved by the present invention is to detect in-line fine particles having a diameter of about 0.05 μm existing in a space under atmospheric pressure or normal pressure, and at the same time, identify components. It is to realize a fine particle measuring device.

<Means for Solving the Problems> The structure of the present invention has a microwave source 3, a cavity 4 for introducing microwaves generated by the microwave source, and a detection window provided at one end through the vicinity of the center of the cavity. A reaction tube 5 having
One end is connected to the other end of the reaction tube and the other end is under normal pressure, and
Capillary tube 2 placed in a space containing fine particles
And exhausting means 6 for reducing the pressure in the reaction tube, and analysis means 7 provided adjacent to the detection window of the reaction tube, so that the exhausting means can atomize / ionize the inside of the reaction tube. Ions generated in the reaction tube by reducing the pressure, introducing a carrier gas into the reaction tube to generate plasma by the microwave and introducing a sample gas under normal pressure by the capillary tube, and by the fine particles contained in the sample gas The qualitative / quantitative analysis of the fine particles is performed by in-line analysis of the emission spectrum of the fine particles with the analyzer.

<Operation> In the case of microwave-induced plasma, the degree of vacuum in the reaction tube is
At a vacuum degree of around 10 Torr, thermal plasma of 4000 ° K or higher is generated. This excitation temperature is a temperature sufficient to dissociate (gasify / ionize) the fine particles contained in the sample gas. The space is at atmospheric pressure or atmospheric pressure, and the sample gas is introduced into the reaction tube through the capillary tube due to the pressure difference. The smaller the particle size of the fine particles in the sample gas is, the easier they are to dissociate, and the ionized fine particles emit light in a spectrum peculiar to the components. This is measured by using a spectroscope, or atomic ions are guided to a mass spectrometer and measured,
Quantitative measurement of fine particles and identification of components.

<Examples> The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, 1 indicates a clean room in a semiconductor process or a space under atmospheric pressure or atmospheric pressure such as an atmospheric pressure CVD apparatus. 2 is a capillary tube whose one end is inserted into the space 1 for collecting the sample gas SG, 3 is a microwave source, and 4 is a cavity into which the microwave from the microwave source 3 is introduced. Reference numeral 5 is a quartz reaction tube, which is installed so as to penetrate through the cavity 4 and is connected to the capillary tube 2 at one end thereof, and is provided with a carrier gas introduction part 5a for introducing a carrier gas CG such as argon or helium. Has been. A detection window 5b is provided at the other end of the reaction tube, and a gas discharge section 5c is provided. Reference numeral 6 denotes an evacuation means, which evacuates the inside of the reaction tube 5 through the gas exhaust part 5c. Reference numeral 7 is an analysis means provided toward the detection window 5b for qualitative / quantitative analysis of fine particles in the sample gas SG.
A mass spectrometer such as a spectroscopic analyzer or a quadrupole mass spectrometer is used as the analyzing means. 7a is a photomultiplier tube as a detector. A signal detector 8 includes a preamplifier 8a, an A / D converter 8b, an arithmetic processing circuit 8c using a microprocessor, and the like.

FIG. 2 is a sectional view showing the main part of the apparatus according to the embodiment of the present invention.
In this figure, parts corresponding to the parts in FIG. 1 are designated by the same reference numerals. The cavity 4 is a disc type, and microwaves are introduced from the outer peripheral portion of the cavity 4, and the microwaves are concentrated in the center. For example, a Beanakker type cavity is used. The reaction tube 5 is installed so as to pass through the center of the cavity 4.

With such a configuration, the vacuum degree in the reaction tube 5 is reduced to about 10 Torr by the exhaust means 6, and the frequency is changed from the microwave source 3.
When the microwave of 2.45 GHz is guided into the cavity 4 and the carrier gas CG is flown, the thermal plasma PL of 4000 ° K or more is generated in the reaction tube 5.

On the other hand, the space 1 is kept at atmospheric pressure or normal pressure, and the sample gas SG is guided into the reaction tube 5 through the capillary tube 2 due to the pressure difference. The fine particles in the sample gas SG introduced into the plasma PL are dissociated and ionized. The smaller the diameter of the fine particles dissociated by plasma, the easier the dissociation is, and the fine particles having a diameter of 0.1 to 0.05 μm can be dissociated.

The ionized fine particles emit light with a spectrum peculiar to the components. If this emitted light is detected by the analyzing means 7 using, for example, a spectroscope, quantitative information of the fine particles can be obtained from the intensity of the spectrum, and the component is identified based on the wavelength of the spectrum.

<Effects of the Invention> The present invention has the following effects.

Fine particles having a diameter of 0.1 to 0.05 μm, which cannot be measured in principle by the conventional optical method, can be detected in-line.

In addition to obtaining quantitative information of fine particles, identification of components can be performed at the same time.

Since a capillary tube is used to perform sampling by the pressure difference between the reaction tube and the cavity, no special means for transferring the sample gas is required.

In plasma based on microwave induction, the smaller the particle size is, the easier it is to dissociate and ionize, and in principle it is suitable for the measurement of small particle size.

For example, if the space under normal pressure is inside the CVD device, when the impurities in it exceed a certain amount, immediately stop the work and clean the inside of the CVD device, or mark a lot as a defective product. By discarding, it is possible to prevent defects in products incorporating this.

[Brief description of drawings]

FIG. 1 is a block diagram of the apparatus of the embodiment of the present invention, and FIG. 2 is a sectional view showing the main part of the apparatus of the embodiment of the present invention. 1 ... Space under atmospheric pressure or normal pressure in semiconductor process, 2 ... Capillary tube, 3 ... Microwave source,
4 ... Cavity, 5 ... Reaction tube, 6 ... Exhaust means, 7
...... Analysis means, 8 …… Signal detector

Claims (1)

[Claims] 1. A microwave source 3, a cavity 4 for introducing microwaves generated by the microwave source, a reaction tube 5 penetrating near the center of the cavity and having a detection window at one end, and the reaction tube. One end of which is connected to the other end and the other end of which is under normal pressure and which is arranged in a space containing fine particles, and an exhaust means 6 for reducing the pressure in the reaction tube.
And an analysis means 7 provided adjacent to the detection window of the reaction tube, the pressure of the inside of the reaction tube is reduced to a level capable of atomization / ionization by the exhaust means, and a carrier gas is introduced into the reaction tube. Then, plasma is generated by the microwave and the sample gas under normal pressure is introduced by the capillary tube, and the emission spectrum of the ions generated in the reaction tube by the fine particles contained in the sample gas is analyzed inline by the analyzer. A fine particle measuring device characterized by performing qualitative / quantitative analysis of the fine particles.