JPS6354934A - Vapor phase exciter - Google Patents

Abstract

PURPOSE:To make the generation of plasma in the inside of a nozzle efficient by providing a construction or the like for microwave between a waveguide and the nozzle and also joining the waveguide and the nozzle and making the inside of the nozzle to a plasma generator. CONSTITUTION:The inside of a downstream chamber 4 is exhausted by a vacuum pump 11 and pressure difference is caused between an upstream chamber 3 and the downstream chamber 4. In case of feeding film nonforming gas to the inside of the upstream chamber 3 and also introducing microwave through a waveguide 2, microwave is introduced into a nozzle 1 and the plasma of film nonforming gas is generated in the nozzle. When plasma is introduced into the downstream chamber 4 by means of the above-mentioned pressure difference, film forming gas is fed through a feed ring 10 and thereby molecules of film forming gas are brought into contact with activated plasma, and a product is produced by vapor phase reaction. The product is stuck on a base material 5 and collected without sticking on the inner wall of the downstream chamber 4 because it is passed through the nozzle by the gas flow.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas phase excitation device using microwave discharge, and is applicable to, for example, a film forming device, an etching device, an ultrafine particle generator, Furthermore, it is expected to be applied to the formation of composite materials and fine ceramic materials.

In this specification, a contracting/expanding nozzle is one in which the opening area is gradually narrowed from the inlet side toward the middle part to form a throat, and the opening area is gradually expanded from this throat toward the outlet. Refers to a nozzle.

In addition, non-film-forming gas refers to a gas that does not produce film-forming ability by itself. Film-forming gas refers to a gas that produces film-forming ability when energy is applied, and a mixed gas of the gas and non-film-forming gas. say.

[Prior Art] Conventionally, as a gas phase excitation device using microwaves, one using electron cyclotron resonance (hereinafter referred to as ECR) is known. This device introduces microwaves guided by a waveguide into a plasma generation chamber, which is a cavity resonator, through a microwave introduction part made of a microwave-transparent material such as quartz. (Japanese Unexamined Patent Publication No. 57-177975), this gas phase excitation device can be used, for example, by plasma CVD (chemical vapor deposition).
When used in a device, the plasma is further guided to the deposition chamber,
In the film-forming chamber, the film-forming gas is brought into contact with the plasma and decomposed, and the products are collected on the substrate surface.

[Problems to be Solved by the Invention] However, a major problem in forming a film using microwave waves is fogging due to film adhesion on the microwave introduction window. This occurs not only in ECR devices. Furthermore, in the ECR plasma CvO apparatus, since the substrate on which the products are deposited is exposed to plasma, the surface of the substrate is likely to change in quality, and the collected products are also damaged by the plasma.

Further, when plasma exists on the substrate surface, a sheath region is formed between the substrate surface and the plasma, and ions are accelerated in this region, causing damage as in the case described above. Moreover, in such conventional equipment,
Etching other than vertically is extremely difficult.

[Means for Solving the Problems] Means for solving the above problems will be explained using FIG. 1, which corresponds to an embodiment of the present invention. The nozzle 1 is connected to the nozzle 1 through the quartz plate 8, which is characterized by making the inside of the nozzle 1 a plasma generation chamber.The quartz plate 8 blocks the atmosphere and vacuum, but other materials such as alumina and McCor etc. can also be used. An aperture 7 may be used between the waveguide 2 and the nozzle l for impedance matching. As shown in FIG. 3, the aperture 7 includes an inductive element (a), a capacitive element (b), a parallel resonant element (C), etc. Further, instead of the aperture, a slot antenna shown in FIG. 4 may be used to efficiently radiate microwaves from the waveguide.

A slot antenna is a waveguide whose end is closed and a horizontal slot (groove) is provided in it.The length of the slot is set at the station where the microwave wavelength is input, and the microwave radiation efficiency is maximized. This is what I did.

Regarding the mounting position of these apertures and Scott antennas, if there is a large impedance gap at the junction of waveguide 2 and nozzle 1, it is desirable to mount it at that point H, but there is not much impedance gap. In some cases, it is also possible to attach an aperture or slot antenna inside the waveguide or nozzle.

Note that as the waveguide 2, a rectangular waveguide, a circular waveguide, etc. can be used, and as the nozzle, as shown in FIG. C), a rectangular nozzle (d), a straight nozzle (e), etc. can be used. In FIG. 1, for convenience of explanation, the inflow side and the outflow side of the nozzle 1 are connected to each other in a closed system. There is. However, the inflow and outflow sides of the nozzle l in the present invention can be an open system even if it is a closed system, as long as a pressure difference is created between the two and the plasma can flow through while being exhausted on the downstream side. It's okay.

[Function] As shown in FIG. 1, when the non-film forming gas is supplied from the supply pipe 9 to the upstream chamber 3 and the downstream chamber 4 is evacuated by the vacuum pump 11, the upstream chamber 3 and the downstream chamber 4 are A pressure difference is created between the two. When microwaves are introduced into the nozzle 1 from the waveguide v2, plasma is generated within the nozzle 1 and flows into the downstream chamber 4 due to the pressure difference described above. When this plasma passes through the nozzle 1, when a film forming gas is supplied from the supply ring 10, the molecules of the film forming gas come into contact with this active plasma and are decomposed. By increasing the distance from the nozzle 1 to the substrate 5 for these excited active species, the concentration of short-lived active species can be reduced.

In addition, especially when using a contraction/expansion nozzle as a nozzle,
The contraction/expansion nozzle calculates the pressure ratio P/PO between the pressure Pa in the upstream chamber 3 and the pressure P in the downstream chamber 4, and the ratio A/A- between the opening surface gA- of the throat and the opening area A of the outlet. By adjusting it, the flow of the ejected gas can be made faster. If the pressure ratio P/P in the upstream chamber 3 and downstream chamber 4 is greater than the critical pressure ratio, the outlet flow velocity of the contraction/expansion nozzle becomes subsonic flow or less, and the gas is decelerated and ejected. Further, if the pressure ratio is equal to or lower than the critical pressure ratio, the outlet flow velocity of the contraction/expansion nozzle becomes a supersonic flow, and the gas can be ejected at a supersonic velocity.

Here, assuming that the velocity of the flow is U, the sound velocity at that point is a, the specific heat ratio of the gas is γ, and the flow is a compressible one-dimensional flow with adiabatic expansion, the Matsuha number M reached by the flow is It is determined by the following formula from the pressure Po of 3 and the pressure P of the downstream chamber 4,
In particular, when P/Pa is less than or equal to the critical pressure ratio, M is 1 or more.

Note that the sound velocity a can be determined by the following equation, where T is the local temperature and R is the gas constant.

a=rRT Further, the following relationship exists between the opening area A of the outlet, the opening area AI of the throat, and Matsuha fiM.

Therefore, by adjusting the pressure ratio P/Po according to M determined from equation (2) by the opening area ratio A/A'', the gas ejected from the contraction/expansion nozzle can be ejected as a properly expanded flow at supersonic speed. This proper expansion flow is a flow in which the gas pressure at the outlet is equal to the pressure P on the downstream side, and the beam speed U at this time is given by the following (3), assuming that the temperature on the upstream side is To. It can be determined by the formula.

When gas is ejected in a fixed direction as a properly expanded flow at supersonic speed as described above, the gas travels straight and becomes a beam while expanding the cross section of the jet immediately after ejection. This allows the gas containing active species to be ejected at supersonic speed through the space within the downstream chamber 4 with minimal diffusion, in a spatially independent state without interference with the wall surface of the downstream chamber 4. Become.

[Example] FIG. 1 shows an example in which a gas phase excitation device according to the present invention is used in a film forming apparatus.

As shown in FIG. 1, the film forming apparatus 100 has an upstream chamber 3 into which non-film forming gas and microwaves are introduced, and a downstream chamber 4 which serves as a film forming chamber, and a nozzle 1 which serves as a plasma generation chamber. It is attached to the tip of the upstream chamber 3.

A quartz plate 8 that allows transmission of microwaves is arranged on the rear wall of the upstream chamber 3, and the waveguide 2 is connected via this quartz plate 8. A diaphragm 7 shown in FIG. 2 is arranged on the upstream chamber 3 side of the quartz plate 8, and this microwave diaphragm 7 matches the impedance between the waveguide 2 and the plasma generation chamber.

A supply pipe 9 for introducing a non-film forming gas is provided near the opening of the nozzle 1 in the upstream chamber 3. Here, the non-film-forming gas is a gas that is turned into plasma by microwave discharge and does not have film-forming ability by itself. Specifically, for example, N2. N2. It is a gas such as Ar. On the other hand, a supply ring 10 for supplying film-forming gas is provided near the outlet of the nozzle l. The supply ring 10 is an annular pipe having a large number of small holes, and supplies a film forming gas to the plasma ejected from the nozzle l. Here, the film-forming gas is a gas that generates film-forming ability when activated, and is, for example, disilane gas.

A base body 5 is provided in the downstream chamber 4 at a position opposite to the outlet of the nozzle l. This base 5 is a base holder 6
It is attached to and configured to be able to slide back and forth. Further, the substrate holder 6 is capable of heating or cooling the substrate 5 under optimal temperature conditions during film formation.

Furthermore, during film formation, the downstream chamber 4 is evacuated by a vacuum pump 11, so that surplus gas, reaction gas, etc. are directly exhausted.

The film forming apparatus having the above configuration operates, for example, as follows. First, when the downstream chamber 4 is evacuated by the vacuum pump 11, a pressure difference is generated between the upstream chamber 3 and the downstream chamber 4. On the other hand, when a non-film-forming gas is supplied into the upstream chamber 3 and microwaves are sent from the waveguide 2, the microwave is introduced into the nozzle 1 through the microwave window, and the plasma of the non-film-forming gas flows into the nozzle. Occurs in When this plasma flows into the downstream chamber 4 due to the above-mentioned pressure difference, when the film forming gas is supplied from the supply ring 10, the molecules of the film forming gas 2 come into contact with the active plasma, a gas phase reaction occurs, and the products are arise.

Since this product passes through the nozzle due to the gas flow, the product does not adhere to the inner wall of the downstream chamber 4, but is deposited and collected on the substrate 5.

In FIG. 1, the distance between the base 5 and the nozzle 1 is several tens++
If the substrate 5 is separated by about several hundred millimeters, the substrate 5 will not be exposed to the plasma, and only the excited radical particles will reach the substrate, allowing film formation and etching to be performed with less damage caused by the plasma.

In the above example, if hydrogen gas is used as the non-film-forming gas and silane gas is used as the film-forming gas, and the substrate temperature is 200°C, the deposit will be a porous silicon film, and if it is 400°C, it will be an amorphous silicon film. . Moreover, at room temperature, a film of tens to hundreds of fine particles can be obtained.

Also, contrary to the above, if you want to actively transport the plasma to the substrate, the pressure in the reaction chamber should be set to 10"4 Torr or less,
It is also possible to carry out transport by the effect of a magnetic field.

FIG. 2 shows an embodiment of a device used in such a case. In the apparatus shown in FIG. 2, a slot antenna 13 is formed in the microwave introducing section, and an electromagnet 12 is arranged around the rectangular nozzle 101. The other configurations are the same as those of the above embodiment. In Figure 2,
Plasma generated within the rectangular nozzle 101 is guided to the base 5 by a divergent magnetic field created by the electromagnet 12.

[Effects of the Invention] As explained above, according to the present invention, plasma can be efficiently generated within the nozzle, and active species generated by the plasma or the plasma itself can be transported to the substrate with beam properties. can.

In addition, the selection of these active species can be controlled by the pressure in the downstream chamber, the distance between the nozzle and the substrate, or the magnetic field. For example, by increasing the distance between the nozzle and the substrate, the concentration of short-lived active species can be reduced. In addition to this, plasma damage to the substrate can be prevented. Therefore, film formation and etching can be performed with less damage caused by plasma.

Furthermore, since the nozzle provides a pressure difference before and after the nozzle, there is less back-diffusion and it is possible to prevent fogging due to film adhesion on the microwave introduction window.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing one embodiment of the present invention, FIG. 3 is a diagram showing an example of the shape of the aperture, FIG. 4 is a perspective view of the slot antenna, and FIG. 5 is an example of the shape of the nozzle. FIG. 1: Nozzle (plasma generation chamber), 2: Waveguide, 3: Upstream chamber, 4: Downstream chamber (*film chamber), 5: Substrate, 7: Aperture, 8: Quartz plate, 12: Electromagnet, 13 Nislot antenna.

Claims (1)

[Scope of Claims] 1) A gas phase excitation device characterized in that a waveguide and a nozzle are joined, and the inside of the nozzle is used as a plasma generation chamber. 2) The gas phase excitation device according to claim 1, characterized in that a microwave aperture is provided between the waveguide and the nozzle. 3) The gas phase excitation device according to claim 1, characterized in that a slot antenna is provided between the waveguide and the nozzle.