JPH0754293B2 - Particle measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is a fine particle measuring apparatus capable of in-process detection of fine particles in a reaction tank of an apparatus used as a film forming apparatus in a semiconductor process, such as a sputtering apparatus and a CVD apparatus Regarding

<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> The technical problem to be solved by the present invention is that the diameter is 0.05 μm.
It is to realize a fine particle measuring device capable of detecting fine particles of about m in-line and at the same time identifying components.

<Means for Solving the Problems> The structure of the present invention is configured to include a microwave generation unit, a waveguide for introducing the microwave generated by the microwave generation unit, and a microwave guided by the waveguide. A cylindrical cavity introduced from one end face, a magnet provided on the outer periphery of the cavity to form a magnetic field in a direction parallel to the traveling direction of the microwave, and a plasma provided on the outer periphery near the other end of the cavity to close the plasma. A magnet that generates a mirror magnetic field that can be contained, a capillary tube that connects the depressurized reaction tank 1 and the inside of the cavity to guide the sample gas in the reaction tank into the cavity, and the inside of the cavity that is connected near the other end of the cavity. Atomize /
A means for making the pressure lower than the pressure in the reaction tank to the extent that ionization is possible, and an analyzer for performing qualitative / quantitative analysis of the fine particles from the emission spectrum of the ions generated in the cavity by the fine particles contained in the sample gas. Prepare,
Atoms of fine particles contained in the sample gas are introduced by introducing the carrier gas in a state in which the microwave is accelerated in the cavity by cyclotron resonance and making the excitation temperature sufficient to dissociate the solid. It is characterized by performing ionization / ionization.

<Operation> When the frequency of the microwave and the strength of the magnetic field are selected to values satisfying the cyclotron resonance condition, the electrons are accelerated. In this state, when a carrier gas of argon gas or helium gas is flown into the cavity, plasma is generated. For example, plasma has a low electron density in the region of 10 ^-2 to 10 ^-4 Torr and becomes low temperature plasma, which has no ability to dissociate solids. The mirror magnetic field produces a high temperature plasma sufficient to confine the plasma and dissociate the solids. There is a pressure difference between the reaction tank and the cavity, and the sample gas is introduced into the plasma by this pressure difference, and the fine particles contained in the sample gas are dissociated and ionized. In this case, the smaller the particles, the easier the dissociation and ionization. Since the ionized fine particles have an emission spectrum specific to the components, if the fine particles are measured using a spectroscope, for example, the quantitative measurement of the fine particles and the identification of the components can be performed at the same time.

<Examples> The present invention will be described below with reference to the drawings. The figure is a block diagram of the apparatus of the present invention. The part (1) surrounded by the one-dot chain line is a CVD device as a reaction tank. Part (2) is the particle measuring device according to the present invention. In the portion (1), the CVD apparatus 1 includes a side wall 101, a quartz window 102, a lamp 103 as a heating means, a susceptor 104 horizontally installed in the reaction tank A and having a silicon wafer S mounted on the upper surface, and SiH ₄ Pipe 105 for guiding gas and NH ₃ gas onto the silicon wafer S, vacuum pump 106
Composed of and.

In the part (2), the fine particle measuring apparatus 2 has
A capillary tube 201 that guides the sample gas SG from the sample to the particle measuring apparatus, a microwave source 202, a microwave is introduced from a microwave source 202 through a waveguide 203, and a cylindrical cavity 204 used as a reaction tube, the microwave inside the cavity 204 are used. Magnet 20 that forms a magnetic field parallel to the traveling direction of
5. The sample gas SG from the capillary tube 201 and the carrier gas CG such as argon and helium are stored in the cavity 20.
4, the introduction pipe 206 leading to 4, the exhaust means 207 for exhausting gas from the cavity 204, and the vicinity of the open end of the cavity 204,
Magnet 208 for generating a mirror magnetic field for confining plasma, sample gas SG provided toward the open end 203a of the waveguide 203
It comprises an analysis means 209 for qualitatively and quantitatively analyzing the fine particles therein. In the case of this embodiment, the analyzing means 209 is a spectroscopic analyzing means using a diffraction grating 209a.

With such a configuration, in the CVD apparatus 1, the susceptor 104 on which the silicon wafer S is placed is heated by the lamp 103, and NH ₃ gas and SiH ₄ gas are introduced from the pipe 105 to guide the silicon wafer S.
A silicon nitride film is formed on top. Reaction tank A and cavity
There is a pressure difference with 204 (in reaction tank A: 10 ^{-1 to 1} Tor
r, inside cavity 204: 10 ^-2 to 10 ^-4 Torr), sample gas
SG is guided into the cavity 204 by this pressure difference.

Microwave from the microwave source 202 is introduced into the cavity 204 through the waveguide 203, and the microwave frequency is changed to 2.45GH.
z, when the strength of the magnetic field by the magnet 205 is 875 Gauss,
The cyclotron resonance condition is satisfied, the electrons are accelerated by the cyclotron motion, and the dissociation efficiency of neutral particles increases.
In this state, when a carrier gas CG of argon gas or helium gas is flown through the introduction pipe 206, plasma PL is formed. The plasma PL has an electron density of about 10 ¹⁰ electrons / cm ^{3 in} the region of 10 ^-2 to 10 ^-4 Torr, and has a low temperature plasma with an excitation temperature of 1000 ° K or less, which has no ability to dissociate solids. Magnet 20
When confining the plasma by a mirror magnetic field due 8 electrons again and high electron density is accelerated in this region is obtained, 10 ¹²
When the electron density is about 10 ¹³ electrons / cm ^{3, the} excitation temperature is sufficient to dissociate the solid. The fine particles in the sample gas SG introduced into the plasma PL are dissociated by the plasma and ionized. Such plasma by electron cyclotron resonance can dissociate and ionize a solid having a diameter of 0.1 to 0.05 μm even under reduced pressure.

The ionized fine particles have an emission spectrum unique to each component. This luminescence is detected by the analysis means 209. Quantitative information of fine particles is obtained from the spectrum intensity, and the component is identified based on the wavelength of the spectrum. The analyzing means 209 is not limited to a spectroscope, and similar information can be obtained by measuring dissociated atomic ions using a mass spectrometer. Also magnet 205,20
If a permanent magnet is used for 8, the device can be downsized.

<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 tank and the cavity, no special means for transferring the sample gas is required.

In plasma based on electron cyclotron resonance, the smaller the particle size, the easier the particle is to dissociate and ionize, which is in principle suitable for measuring the small particle size.

For example, when the amount of impurities in the reaction tank exceeds a certain amount, immediately stop the work and clean it, or discard a certain lot as a defective product to prevent defects in the product incorporating it. Can be done.

[Brief description of drawings]

The figure is a block diagram of the apparatus of the present invention. 1 ... CVD device, 102 ... Quartz window, 103 ... Heating means, 1
04 …… Susceptor, 106 …… Vacuum pump, 2 …… Particle measuring device, 201 …… Capillary tube, 202 …… Microwave source, 203 …… Waveguide, 204 …… Cavity, 205 …… Magnet, 206 …… Introduction tube, 207 ... Exhaust means, 208 ... Mirror, magnet for generating magnetic field, 209 ... Analytical means, 209a ... Diffraction grating, SG ... Sample gas, CG ... Carrier gas, PL ...
plasma

Claims (1)

[Claims] 1. A microwave generating means 202 and a waveguide 203 for introducing the microwave generated by the microwave generating means.
A cylindrical cavity 204 for introducing the microwave guided by the waveguide from one end face, and a magnet 205 provided on the outer periphery of the cavity for forming a magnetic field in a direction parallel to the traveling direction of the microwave. , A magnet 208 provided on the outer periphery near the other end of the cavity for generating a mirror magnetic field for confining plasma, and connecting the depressurized reaction tank 1 and the inside of the cavity with the sample gas in the reaction tank 1 into the cavity. The capillary tube 201 for guiding, means for connecting the vicinity of the other end of the cavity to lower the pressure in the reaction vessel 1 to the extent that atomization / ionization in the cavity is possible, and the fine particles contained in the sample gas The cavity is provided with an analyzer 209 for performing qualitative / quantitative analysis of the fine particles from the emission spectrum of the ions generated in the cavity. In order to atomize / ionize the fine particles contained in the sample gas, the carrier gas is introduced in a state accelerated by cyclotron resonance at a temperature of, and the sample gas is introduced in-line after the excitation temperature is high enough to dissociate the solid. Characteristic particle measuring device.