JPS6328874A - Reactor - Google Patents

Abstract

PURPOSE:To facilitate film-forming reaction, etc., by providing means of setting differential pressure between the upstream and downstream sides of a contracting-expanding nozzle attached to the inside of a reactor so as to prevent the flowing back of a film-forming gas, etc., and also to make an injection stream supersonic. CONSTITUTION:A film forming gas-feeding ring 4 is located on the downstream side of the contracting-expanding nozzle 1 attached to the 1-side of a reaction chamber 3, and an upstream chamber 8 is integral provided to the upstream side. A non-film- forming gas is supplied to the upstream chamber 8 and, while supplied with a film- forming gas from the film forming gas-feeding ring 4, the inside of the reaction chamber 3 is evacuated, so that pressure ratio between the upstream and downstream sides of the nozzle 1 is properly regulated. The above non-film-forming gas is spurted through the nozzle 1 into the reaction chamber 3 in a supersonic flow. When microwaves are sent from a microwave generator 13, microwave discharge takes place in the nozzle 1 and plasma is induced. Then, the active species, electrons, etc., produced by the above plasma are sent through the nozzle 1 in the form of a jet, which is brought into contact with the film-forming gas and activate it. The activated film-forming gas is allowed to adhere to the substrate 6, so that film formation can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reaction apparatus that performs, for example, film formation, etching, and generation of fine particles using plasma induced by microwaves.

[Prior Art] Conventionally, a reaction device that utilizes microwave plasma has been designed to induce plasma by supplying microwaves into a cavity resonator to generate electron cyclotron resonance, and to generate the induced plasma. It is known that a film is formed by sending the gas out of the cavity resonator and bringing it into contact with, for example, a film forming gas.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional reaction apparatus, when the film-forming gas is brought into contact with the plasma sent out outside the cavity resonator, a part of the film-forming gas is absorbed into the cavity resonator. There is a problem in that the microwaves flow back into the interior and form a film on the microwave introduction window. As the amount of film adhering to the microwave introduction window increases, it becomes difficult for microwaves to be introduced into the cavity resonator, and plasma is no longer induced, making it difficult to perform long-term continuous reaction processing with conventional reaction equipment. be.

Furthermore, although there are many active species in plasma, there is also the problem that these active species tend to lose their activity due to repeated collisions between molecules and atoms, making it difficult to carry out reactions that utilize the active species. That is, the current situation is that reactions using these active species must be performed in plasma, and plasma damage, which is a problem in plasma CVD, for example, cannot be avoided.

[Means for Solving the Problems] Means for solving the above problems will be explained with reference to FIG. 1, which corresponds to an embodiment of the present invention. The reactor is configured to be able to form a differential pressure between the upstream and downstream sides of the contraction/expansion nozzle 1.

In the present invention, the contracting/expanding nozzle 1 is defined as having an opening area gradually narrowed from an inlet 1a to become a throat part 1b, and then expanded again to become an outlet 1c, as shown in FIG. say something

[Function] Generally, when neutral molecules or atoms are ejected from a nozzle that has a differential pressure between the upstream and downstream sides, the pressure and temperature on the upstream side are po and to, and the pressure and temperature on the downstream side are P, T
and the specific heat ratio is γ, the following relationship holds true.

Further, when the Matsuhah number of the flow ejected from the nozzle is N, the following relationship holds true.

From the above equations (1) and (2), if the pressure ratio P/PO is made smaller, that is, if the pressure difference is made larger, the temperature T of the ejected flow will be lowered and the Matsuha number will be increased. That is, the translational force of molecules and atoms in the flow is increased, and the number of collisions between them is reduced.

When the diameter of the nozzle is D and the maximum Matsuha number reached is MT, the following relationship holds true.

MToe (PD)O' ・= ・= (3) According to the above equation (3), when D is large, MT also increases, but in reality, it is limited by the exhaust capacity on the downstream side. If the exhaust speed on the downstream side is S, the following relationship holds true.

So, 4 MTOC billion (4) According to the above equation (4), in order to increase MT, D must be decreased, and after all, there is a limit to increasing 111T.

By the way, in the case of the contraction/expansion nozzle l, if the cross-sectional area of the throat portion 1b is A and the cross-sectional area of the outlet 1c is A, the following relationship holds true, and the ejected flow can be accelerated to supersonic speed. .

By accelerating the ejected flow to supersonic speed using the contraction/expansion nozzle 1, the temperature of the flow can be significantly lowered and the translational force can be made extremely high, greatly reducing the number of collisions between molecules and atoms. can be done. Therefore, by inducing plasma within the contraction/expansion nozzle 1, the active species can be ejected while extending their lifespan, making it easier to carry out reactions using the active species. Also, the reduction/expansion nozzle 1
By bringing the film-forming gas or the like into contact with the plasma sent out from the nozzle 1, it is possible to prevent the film-forming gas or the like from flowing back due to the jet flow from the contraction/expansion nozzle 1. Furthermore, by making the jet flow supersonic, the flow can be made into a beam flow with good directionality, making it easier to perform reactions in specific areas.

[Example] FIG. 1 shows an example in which the present invention is used as a reaction apparatus for film formation, and numeral 1 in the figure is a contraction/expansion nozzle.

The contraction/expansion nozzle 1 is attached to one side of a reaction chamber 3 that can be evacuated by a pump 2. A film forming gas supply ring 4 is located downstream of the contraction/expansion nozzle l. The film-forming gas supply ring 4 is an annular tube having a large number of holes 5 formed on its inner circumferential surface, from which the film-forming gas is ejected. Further, on the other side of the reaction chamber 3 facing the contraction/expansion nozzle 1, a substrate holder 7 holding a substrate 6 is provided.

The upstream side of the contraction/expansion nozzle 1 is an upstream chamber 8 formed integrally with the contraction/expansion nozzle 1, into which a non-film forming gas is supplied. Here, the film-forming gas is a gas that produces a film-forming ability when activated, and is, for example, disilane gas or 5iHa gas. Further, the non-film-forming gas is a gas that does not produce a film-forming ability by itself, and is, for example, a gas such as H2, 82, Ar, or the like.

A microwave generator 13 is connected to the downstream side of the contraction/expansion nozzle 1, that is, to the upstream chamber 8 side, via a waveguide 12 with an isolator 9, a power monitor 10, and a three-stub tuner 11 interposed therebetween.

Further, an inner sleeve 15 extends from the waveguide coaxial converter 14 along the center of the contraction/expansion nozzle 1 . The contraction/expansion nozzle 1 and the inner shaft 5 are of a coaxial type made of a good electrical conductor.

While supplying a non-film-forming gas to the upstream chamber 8 and a film-forming gas from the film-forming gas supply ring 4, the reaction chamber 3 is evacuated by the pump 2 to maintain the pressure on the upstream and downstream sides of the enlarged nozzle 1. When the ratio is adjusted appropriately, the non-film forming gas is ejected from the contraction/expansion nozzle 1 into the reaction chamber 3 as a supersonic flow. At the same time, when microwaves are sent from the microwave generator 13, microwave discharge is generated within the contraction/expansion nozzle 1, thereby inducing plasma. Activated species, electrons, etc. generated by this plasma are also sent out as a jet from the contraction/expansion nozzle 1, and while in an active state, come into contact with the film forming gas sent out from the film forming gas supply ring 4 and activate it. The activated film forming gas flows to the substrate 6 and forms a film thereon.

2 to 6 show other embodiments in which plasma is generated by microwaves within the contraction/expansion nozzle 1. In FIG.

The one in Fig. 2 is divided into parts that are easy to manufacture, with the center and lower parts of the top surface of the contraction/expansion nozzle 1 being a conductor part 16 of good electrical conductivity, and the other part being an insulating part 17 of an electrical insulator. It is a nozzle type. Microwaves can also be supplied to the conductor portion 16 using a coaxial cable 19, as shown in FIG.

In the one in Fig. 3, the upper and lower parts of the contraction/expansion nozzle 1 are the conductor parts
The middle part is an insulating part 17, and the center part is
An inner shaft 15 that is a good electrical conductor is provided. This has the advantage of easily generating microwave discharge even when the distance between the upper and lower conductor parts 16 is large.

In the one shown in FIG. 4, a strip-shaped conductor part 16 is provided at the upper part of the contraction/expansion nozzle 1 at right angles to the flow direction, the entire lower part is made into the conductor part 16, and the other part is made into an insulating part 17. This has the advantage that the position of the upper conductor portion 16 in the flow direction can be appropriately determined and the position where microwave discharge is generated can be adjusted in the flow direction.

The one in Fig. 85 is an electromagnet 1 that is slidable in the flow direction around the coaxial type contraction/expansion nozzle 1 explained in Fig. 1.
9. In this way, plasma can be induced within the contraction/expansion nozzle 1 by cyclotron resonance, and the distribution of the plasma density can also be controlled. The diverging magnetic field also allows the transport of ionic species.

The one in FIG. 6 is a combination of a contraction/expansion nozzle 1 similar to that shown in FIG. 2 and a permanent magnet 20. In this case as well, plasma can be induced by cyclotron resonance as in the case of FIG. 5, and the plasma density can also be controlled. Further, since the plasma can be confined within the contraction/expansion nozzle 1 by the mirror magnetic field, only neutral radicals can be selectively ejected.

To briefly touch on cyclotron resonance, if the microwave frequency is 2.45 GHz, the magnetic field strength is 875 G.
When the auss occurs, resonance occurs, microwave energy is efficiently absorbed, and a dense plasma with high decomposition efficiency is generated. In addition, electrons tend to move along magnetic lines of force and have diamagnetic properties, so in the case of a diverging magnetic field as shown in Figure 5, they fly out along the lines of magnetic force.
In the case of a mirror magnetic field as shown in Figure 6, the lines of magnetic force are closed, so the electrons are confined within them.

[Effects of the Invention] As explained above, according to the present invention, it becomes possible to transport active species generated in plasma, solve the problem of contamination of the microwave introduction part, and furthermore, it is possible to separate the plasma and the substrate. It is also possible to avoid plasma damage caused by. In addition, since the active species are converted into a beam and transported in a fixed direction, it is possible to not only minimize the yield loss due to interference with the reaction chamber walls or flow diffusion, but also to separate spatially independent targets. The reaction can be carried out without any interference in the area,
It is possible to obtain highly pure products due to the ideal reaction field.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention as a film-forming reaction device, and FIGS. 2 to 6 show other examples in which plasma generated by microwaves is generated in a contraction/expansion nozzle. It is a figure showing an example. 1: Reduction/expansion nozzle, 1a Two inlets, 1b: Throat,
1c: Outlet, 2: Pump, 3: Reaction chamber, 4: Film forming gas supply ring, 5: Hole, 6: Substrate, 7: Substrate holder, 8:
Upstream chamber, 9-near isolator-110: power monitor,
11: Nissley stub tuner, 12: waveguide, 13:
microwave generator, 14: waveguide coaxial converter, 15: inner shaft, 16: conductor part,
17: Insulation section, 18 twin coaxial cable, lS: Electromagnet, 2
0: Permanent magnet. Figure 1. Figure 2 Figure 3 Figure 4 Figure 5 Section 6

Claims (1)

[Claims] 1) A reaction device characterized in that it is configured to be able to form a differential pressure between the upstream side and the downstream side of a nozzle that can induce plasma inside by microwaves.