JPH1050622A - Nozzle for surface treatment apparatus, surface treatment apparatus and surface treatment method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nozzle by which a large-area substrate can be uniformly surface-treated and with good reliability by a method, wherein a throat part whose cross section is minimum at the nozzle as a whole is connected to a gas introduction part whose cross section is reduced gradually toward a downstream part, a gas jet part whose cross section is gradually increased is installed in succession to the throat part and a reactive gas is jetted at a supersonic speed and in a long line shape. SOLUTION: A supersonic nozzle is constituted of a gas introduction part 1 whose lenght direction is long, as compared with its width direction and whose cross section becomes gradually small, a throat part 2 whose cross section is minimum at the nozzle as a whole, and a gas jet part 3 whose cross section increases gradually at a prescribed spread angle. A high-frequency power supply 6 which applies a high-frequency voltage across one pair of discharge electrodes 5a, 5b and to a passing reactive gas in order to excite a plasma is provided, so as to face both ends of the gas introduction part 1. The gas jet part 3 adiabatically expands the reactive gas which is passed inside the nozzle, and the gas is accelerated to a supersonic speed, to be jetted into a treatment chamber in a long line shape. As a result, a workpiece is conveyed rectilinearly in the length direction of the gas jet by conveyance rollers 8, and a large-area thin film can be formed at a high speed and uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nozzle for a surface treatment apparatus, a surface treatment apparatus and a surface treatment method using the same, and more particularly to a method for supplying a reactive gas.

[0002]

2. Description of the Related Art In a state in which a gas is converted into a plasma by an induction plasma method or a DC plasma jet method, and the gas is activated and the reactivity is enhanced, the plasma-converted gas is jetted at high speed toward the surface of a substrate to be processed. The technique of performing a surface treatment such as thin film formation or etching is already known, and is widely used for forming or etching a semiconductor thin film.

When a thin film is formed by using plasma, it is necessary to guide the gas, which has been converted into plasma and whose reactivity is enhanced, to reach the substrate to be processed at a supersonic speed in a short time. There is. This is for the following reasons. If the plasma gas cannot be guided to the substrate in a short time, the excited state (active state) cannot be maintained, and the adhesion between the substrate and the reaction product decreases, and This is because inconvenience such as peeling of an object may occur, or the film forming rate may be reduced, and the working efficiency may be reduced. In addition, in the case of etching, inconveniences such as a decrease in etching rate may occur.

[0004] Further, since the temperature of the gasified plasma is extremely high, when the gas reaches the substrate to be processed, the temperature of the gas must be lowered to a temperature that can withstand the substrate to be processed. If the temperature reaches a high temperature, not only the surface of the substrate to be processed is damaged, but also a film formation defect may occur.

[0005] It is also required to prevent impurities from being mixed into the plasma-formed reactive gas. This is because the contamination of the impurities causes deterioration of the film quality.

Accordingly, the present inventors have satisfied the above requirements,
A surface treatment apparatus having an improved structure has been proposed, which is intended to improve work efficiency, film quality and etching characteristics.

As shown in FIG. 8, a high frequency induction coil is wound around a Laval nozzle (also called a divergent nozzle). The Laval nozzle includes a gas introduction unit 101 configured so that a cross-sectional area gradually decreases,
A throat portion (throat portion) 102 connected to the gas introduction portion 101 and configured to have a minimum cross-sectional area A1 (diameter d1) over the entire nozzle; and a throat portion (throat portion) 102 connected to the throat portion 102 and cut at a predetermined spread angle. Gas injection pipe 1 configured so that its area gradually increases to have a maximum sectional area A2 (diameter d2).
03. And the gas introduction unit 101
When the reactive gas 106 is introduced from the gas introduction port 101a at the opening end of the gas introduction section 101, the cross-sectional area gradually decreases in the gas introduction section 101 with the progress of the gas, and is stabilized at the throat section. Accelerated by adiabatic expansion in tube 103,
The reactive gas that has been converted into plasma with a flow velocity greater than the sonic velocity is injected to the substrate to be processed 107 provided to face the nozzle outlet 103a.

Here, the induction coil 5 is wound around the outer periphery of the throat portion 102, and the induction coil 105
A high-frequency current can be supplied to the power supply. For this reason, when the induction coil 105 is energized, the throat 1
An induced electromagnetic field is formed in the gas flow 02, and the gas passing through the throat section 102 is heated and plasma-excited. Then, the plasma-excited high-density plasma gas expands and accelerates due to the expansion of the nozzle diameter of the gas ejection pipe 103 on the downstream side, and is ejected as a supersonic plasma jet 104 from the gas ejection port 103a.

Now, it is assumed that a high-density mixed gas 106 to be injected into the substrate 107 to be processed is supplied from the gas inlet 101a into the Laval nozzle. Then, a throat electromagnetic field is generated as described above, and a high-density gas is plasma-excited by the energy of this field.

The high-density gas that has been turned into plasma is
The gas is expanded and accelerated by the gas jet tube 103 on the downstream side due to the expansion of the nozzle, and is formed as a supersonic plasma jet 104 from the gas jet 103a toward the substrate to be processed.

By using such a surface treatment apparatus, it is possible to improve the working efficiency, the film quality and the etching characteristics in a relatively small area.

Meanwhile, the area of solar cells and image sensors has been increasing, and there is a demand to form a uniform high-quality thin film on a substrate having a large area such as 1 mx 1 m. . However, the conventional nozzle as described above has a problem that it is difficult to efficiently form and etch a thin film on a large-area substrate.

[0013]

As described above, the conventional surface treatment using high-speed gas injection is performed on a minute area, and a thin film is formed and etched efficiently on a large-area substrate. Was difficult.

The present invention has been made in view of the above circumstances, and has as its object to realize a uniform and highly reliable surface treatment for a large-area substrate.

[0015]

Accordingly, a first feature of the present invention is that a nozzle for a surface treatment apparatus for performing a surface treatment on a substrate to be processed by injecting a reactive gas onto the surface of the substrate to be processed has a width. The length direction is long enough to the direction,
A cross section in the width direction along the flow path constitutes all the same sheet-shaped flow path, and as it goes downstream, the gas introduction section is configured such that the cross-sectional area is gradually reduced, and is connected to the gas introduction section, A throat portion configured to have a minimum cross-sectional area over the entire nozzle, and a gas injection portion connected to the throat portion and configured so that the cross-sectional area is gradually expanded with a predetermined divergence angle, The gas passing through the nozzle is adiabatically expanded and accelerated from the gas injection unit into the processing chamber so as to have a flow velocity larger than the speed of sound, so that the reactive gas injection surface is formed into a long linear shape. To be swayed.

According to a second aspect of the present invention, there is provided a surface treatment apparatus for performing a surface treatment of a substrate to be processed by injecting gas plasma onto a surface of the substrate to be processed provided in the processing chamber. Vacuum evacuation means for evacuation to a desired pressure, the length direction is sufficiently long with respect to the width direction,
A cross section in the width direction along the flow path constitutes all the same sheet-shaped flow path, and as it goes downstream, the gas introduction section is configured such that the cross-sectional area is gradually reduced, and is connected to the gas introduction section, A throat portion configured to have a minimum cross-sectional area over the entire nozzle, and a gas injection portion connected to the throat portion and configured to gradually expand the cross-sectional area with a predetermined divergence angle, The gas passing through the nozzle is adiabatically expanded and accelerated from the gas injection unit into the processing chamber so as to have a flow velocity larger than the speed of sound, so that the reactive gas injection surface is formed into a long linear shape. A supersonic nozzle that forms a gas flow path to be disturbed, plasma generation means for plasma-exciting a gas passing through the nozzle at a part of the flow path of the supersonic nozzle, and the gas introduction of the supersonic nozzle Further comprising: gas supply means for supplying the reactive gas; and conveyance means for relatively conveying the substrate to be processed in a direction perpendicular to a longitudinal direction of a gas injection unit of the supersonic nozzle. Surface treatment.

Preferably, the plasma generating means passes through the supersonic nozzle via a pair of discharge electrodes disposed at both ends of a gas introduction portion or a throat portion of the supersonic nozzle so as to face each other. That is, the high-frequency power is applied to the reactive gas.

Preferably, the plasma generating means includes a pair of discharge electrodes disposed on an outer wall along a longitudinal direction of a gas introduction portion or a throat portion of the supersonic nozzle so as to face each other. Thus, high-frequency power is applied to the reactive gas passing through the supersonic nozzle.

Preferably, the plasma generating means includes a pair of discharge electrodes disposed on the inner wall along the longitudinal direction of the gas introduction portion or the throat portion of the supersonic nozzle so as to face each other. The configuration is such that high-frequency power is applied to the reactive gas passing through the supersonic nozzle.

More preferably, said plasma generating means is provided in a gas introduction portion or a throat portion of said supersonic nozzle, along a longitudinal direction, so as to oppose each other at right angles to a gas flow. The configuration is such that high-frequency power is applied to a reactive gas passing through the supersonic nozzle via a mesh-shaped discharge electrode.

In a third method of the present invention, a vacuum evacuation step of evacuating the processing chamber to a desired pressure and an injection port provided in the processing chamber, wherein the length direction is sufficiently long with respect to the width direction,
A cross section in the width direction along the flow path constitutes all the same sheet-shaped flow path, and as it goes downstream, the gas introduction section is configured such that the cross-sectional area is gradually reduced, and is connected to the gas introduction section, A throat portion configured to have a minimum cross-sectional area over the entire nozzle, and a gas injection portion connected to the throat portion and configured to gradually expand the cross-sectional area with a predetermined divergence angle, The gas passing through the nozzle is adiabatically expanded and accelerated from the gas injection unit into the processing chamber so as to have a flow velocity larger than the speed of sound, so that the reactive gas injection surface is formed into a long linear shape. A gas supply step of supplying a reactive gas from a gas supply port of a supersonic nozzle that forms a gas flow path to be hampered, and forming an electric field in the flow path of the nozzle and exciting the gas by plasma , Generating a plasma and adiabatically expanding the gas plasma to accelerate the gas plasma in a desired direction so as to have a flow velocity larger than the sonic velocity, and moving the substrate to be processed in the vicinity of the injection port in the longitudinal direction of the supersonic nozzle. A second object of the present invention is to conduct a two-dimensional surface treatment on the surface of the substrate to be processed by introducing high-speed gas plasma to the surface of the gas to be processed while transporting the substrate perpendicularly to the direction.

In the apparatus and method of the present invention,
Strictly speaking, "adiabatic" state cannot be created, but the term "adiabatic" is used to mean a state where heat flow is extremely low.

The supersonic nozzle is configured so that the cross-sectional area is gradually enlarged at the gas injection section, and the maximum cross-sectional area is formed within the gas injection section at the outlet.
It is not necessary to take the maximum cross-sectional area over the entire nozzle.

According to the present invention, a long nozzle is formed.
A two-dimensionally uniform curtain-like supersonic airflow can be formed. By scanning this, it is possible to perform a two-dimensionally uniform surface treatment with good workability. The present invention can be applied not only to plasma surface treatment using a supersonic nozzle, but also to general surface treatment in which high-speed gas flow is applied to perform surface treatment.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the surface treatment apparatus according to the embodiment of the present invention is formed so that the length direction is sufficiently long with respect to the width direction and the cross-sectional area is gradually reduced. 1 and a throat portion 2 connected to the gas introduction portion 1 and configured to have a minimum cross-sectional area over the entire nozzle, and a throat portion 2 connected to the throat portion 2 and having a predetermined divergence angle to gradually increase the cross-sectional area. And a pair of discharge electrodes 5a, 5 disposed at both ends of the gas inlet 1 so as to face each other.
b, and a high-frequency power source 6 for applying a high-frequency voltage to the reactive gas passing through the gas inlet through these to excite the reactive gas.
The gas passing through the nozzle is adiabatically expanded, accelerated from the gas injection unit 3 into the processing chamber so as to have a flow velocity larger than the sonic velocity, and the reactive gas injection surface has a slight width. The substrate 7 to be processed is transported perpendicularly to the longitudinal direction of the gas injection portion of the supersonic nozzle by the transport roller 8 to form a two-dimensional thin film. Is performed.

Although not shown, at least the injection port 3a of the nozzle is disposed in a chamber capable of evacuating,
This chamber is evacuated to a desired pressure _Pch by a vacuum pump including a mechanical booster pump and a rotary pump. The substrate to be processed is maintained at a desired temperature by a heater (not shown). Further, in this device, the nozzle is operated at a supersonic speed under the conditions described later so that the reactive gas passing therethrough is adiabatically expanded and injected from the injection port 3a of the nozzle at a flow velocity u greater than the sonic velocity a. Configure the nozzle.

This nozzle is a thin nozzle having a medium cross section.
The reactive gas 6 (for example, a mixed gas of CH ₄ and H ₂ ) to be injected onto the surface of the substrate 7 to be treated is introduced into the gas introduction section 1 (cross section width w:
50 mmΦ), and a gas inlet 1 configured so that the cross-sectional area gradually decreases as the gas progresses, and a throat (throat) 2 that forms the smallest cross-sectional area A1 (width d1: 16 mmΦ) across the nozzle. , The cross-sectional area gradually increases with a predetermined spread angle, and the maximum cross-sectional area A2 (width d2: 40 m
(mΦ) from the gas injection port 3a. Then, the substrate 7 is continuously moved by the transport roller 8 so as to face the linear plasma flow 4 ejected from the ejection port 3a of the nozzle.

A pair of discharge electrodes 5a and 5b are disposed on the outer walls at both ends of the throat portion 2 as plasma generating means, and a high-frequency current (500 W, 1 W) is applied to the discharge electrodes 5a and 5b.
When a current of 3.56 MHz is applied, an induced electromagnetic field is formed in the throat section 3, and the gas passing through the throat section 2 is plasma-excited.

The high-density gas that has been turned into plasma is
The gas is expanded and accelerated due to the expansion of the nozzle by the gas ejecting portion 3 on the downstream side, and is ejected from the gas ejecting port 3a as a supersonic curtain-shaped plasma flow 4.

Here, if the cross-sectional divergence angle before and after the throat portion 2 is too large, separation of the boundary layer occurs on the wall surface, so that it is necessary to set it to an appropriate size, for example, about 15 °. In the throat section 2, the plasma-converted high-density reactive gas is excited by the heat into a highly reactive state, that is, a state in which the gas easily reacts on the substrate to be processed. From the experimental results, for a two-dimensional long nozzle, the same effects as those of the conventional Laval nozzle can be obtained for the three-dimensional cross section. Further, when the calculation is performed by expanding the three-dimensional cross section, the calculation result in the cross-sectional view is obtained. It can be seen that they almost match.

Incidentally, the temperature of the reactive gas is very high, and in some cases, reaches as high as 10,000 degrees. Therefore, when the reactive gas is sprayed onto the substrate to be processed, the substrate to be processed itself has the temperature. May not be able to endure.

However, since the reactive gas passing through the inside is designed to be adiabatically expanded, the reactive gas is rapidly cooled during the adiabatic expansion process, and is not sufficiently deteriorated before reaching the surface of the substrate to be processed. Get the right temperature. Since the temperature at this time is determined by the divergent ratio A2 / A1, an arbitrary temperature can be obtained depending on the design conditions of the nozzle.

According to the theory of one-dimensional hydrodynamics, the relationship between the fluid temperature and the flow velocity in the adiabatic flow of a complete gas is expressed by the following equation.

T ₀ = T + (1/2) · {(γ−1) / (γ · R)} · (u) ² (1) Alternatively, T ₀ / T = 1 + ｛(γ−1) / 2｝ · (M) ² (2) where, T ₀ : the total temperature of the flow (substantially equal to the temperature of the throat portion 3, which is a heating unit) T: the static temperature of the flow (so-called temperature) γ: the specific heat of the gas Ratio R: gas constant u: flow velocity M: Mach number.

The above equation (2) is obtained by rewriting the above equation (1) using Mach numbers (u / a, a: sound velocity).
The Mach number M is uniquely determined as a function of divergent ratio A ₂ / A _1.

From the above equation (1), it can be seen that in the adiabatic expansion process, the value of the total temperature T ₀ is kept constant, so that the static temperature T decreases as the flow velocity u increases. That is,
The higher the flow rate, the more rapid the temperature drop.

Further, according to the surface treatment method using the surface treatment apparatus of the present invention, a high-density and highly reactive gas can be reduced to an arbitrary temperature and guided onto the substrate 7 to be treated. As a result, a uniform film can be formed over a large area, and not only the working efficiency but also the film quality can be greatly improved.

In this embodiment, the film formation has been described, but the present invention is also applicable to etching and the like. In the above embodiment, the substrate is transported, but the substrate may be transported at a desired speed on the nozzle side.

In this embodiment, the discharge electrodes for exciting the plasma are arranged at both ends of the gas introduction part.
Without being limited to this, it can be changed as appropriate.

Next, a second embodiment of the present invention will be described. As shown in FIG. 2, the surface treatment apparatus is characterized in that the discharge electrodes 15a and 15b are formed in a mesh shape and are arranged so as to be orthogonal to the gas flow in the nozzle. The other parts are formed in exactly the same manner as in the first embodiment. In this case, since the gas flow directly contacts the discharge electrode, it is necessary to use an electrode material that does not easily react with the reactive gas.

As a third embodiment of the present invention, as shown in FIG. 3, the discharge electrodes 25a and 25b are arranged along the inner wall of the gas inlet 1 of the nozzle. . The other parts are formed in exactly the same manner as in the first embodiment. Also in this case, since the gas flow directly contacts the discharge electrode, it is necessary to use an electrode material that does not easily react with the reactive gas.

As shown in FIG. 4 as a fourth embodiment of the present invention, discharge electrodes 35a and 35b are arranged along the outer wall of the gas introduction section 1 of the nozzle, and the inside of the nozzle is heated by induction heating. The passing gas may be excited by plasma.

As a fifth embodiment of the present invention, as shown in FIG. 5, discharge electrodes 45a and 45b are arranged along the inner wall of the throat portion 2 of the nozzle, and a high-frequency power source 6 applies a high-frequency voltage. Alternatively, the gas passing through the nozzle may be plasma-excited. Further, as a sixth embodiment of the present invention, as shown in FIG. 6, a reactive gas supplied here from a gas supply pipe 11 penetrating through a gas introduction part 1 of a nozzle is used as a plasma exciting means as a waveguide 55. May be excited by the microwave 12 that has passed through.
Other parts are formed in the same manner as in the above embodiment. As shown in FIG. 7, the gas supply pipe 11 is configured to be blown in a direction perpendicular to the pipe from holes provided at equal intervals in a part of the pipe.

Although the Laval nozzle has been described in the above embodiment, it goes without saying that a nozzle having another structure may be used.

In addition, in the above-described embodiment, the film forming method has been described. However, it is needless to say that the present invention is not limited to the film forming method but can be applied to the etching.

[0046]

As described above, according to the present invention, a uniform thin film can be formed or etched efficiently over a large area at high speed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a surface treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a surface treatment apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a surface treatment apparatus according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a surface treatment apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a surface treatment apparatus according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a surface treatment apparatus according to a sixth embodiment of the present invention.

FIG. 7 is a view showing a gas supply pipe of the surface treatment apparatus.

FIG. 8 is a diagram showing a conventional surface treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas introduction pipe 2 Throat part (throat part) 3 Gas injection pipe 4 Plasma flow 5a, 5b Discharge electrode 6 High frequency power supply 7 Substrate to be processed 11 Gas supply pipe 12 Microwave 15a, 15b Discharge electrode 25a, 25b Discharge electrode 35a, 35b Discharge electrode 45a, 45b Discharge electrode 55 Waveguide 101 Gas introduction tube 102 Throat (throat) 103 Gas injection tube 104 Plasma flow 105a, 105b Discharge electrode 106 High frequency power supply 107 Substrate to be processed

Claims (7)

[Claims] 1. A nozzle for a surface treatment apparatus for performing a surface treatment on a substrate to be treated by injecting a reactive gas onto a surface of the substrate to be treated, wherein a length direction is sufficiently long in a width direction, and a flow path is provided. A cross section in the width direction along the same constitutes the same sheet-shaped flow path, and a gas introduction section configured so that the cross-sectional area gradually decreases toward the downstream, and connected to the gas introduction section, the entire nozzle A throat portion configured to have a minimum cross-sectional area at the throat portion, and a gas injection portion connected to the throat portion and configured to gradually expand the cross-sectional area with a predetermined divergence angle, the nozzle The gas passing therethrough is adiabatically expanded, accelerated from the gas injection unit into the processing chamber so as to have a flow velocity larger than the speed of sound, and injected so that the injection surface of the reactive gas forms a long linear shape. Be Nozzle surface treatment apparatus according to claim and. 2. A surface treatment apparatus for performing a surface treatment of a substrate to be processed by injecting gas plasma onto a surface of the substrate to be processed provided in the processing chamber, wherein a vacuum is evacuated to a desired pressure in the processing chamber. The evacuation means, the length direction is sufficiently long with respect to the width direction, and the width direction cross section along the flow path constitutes the same sheet-shaped flow path, and the cross-sectional area gradually decreases toward the downstream. And a throat portion connected to the gas introduction portion and configured to have a minimum cross-sectional area over the entire nozzle, and a throat portion connected to the throat portion, the cross-sectional area having a predetermined spread angle. A gas injection unit configured to be gradually expanded, and adiabatically expands the gas passing through the nozzle so that the gas injection unit has a flow velocity larger than the sonic velocity in the processing chamber. A supersonic nozzle which forms a gas flow path so that the injection surface of the reactive gas can be ejected so as to form a long linear shape, and passes through the nozzle at a part of the flow path of the supersonic nozzle Plasma generating means for plasma-exciting the gas to be generated; gas supply means for supplying the reactive gas to the gas introduction part of the supersonic nozzle; and perpendicular to the longitudinal direction of the gas injection part of the supersonic nozzle. A surface treatment apparatus comprising: a conveyance unit for relatively conveying the substrate to be processed, thereby enabling two-dimensional surface treatment. 3. The supersonic nozzle passes through the supersonic nozzle via a pair of discharge electrodes disposed at both ends of a gas introduction portion or a throat portion of the supersonic nozzle so as to face each other. 3. The surface treatment apparatus according to claim 2, wherein the apparatus is configured to apply high frequency power to the reactive gas. 4. The plasma generating means includes a pair of discharge electrodes disposed on an outer wall along a longitudinal direction of a gas introduction portion or a throat portion of the supersonic nozzle so as to face each other. 3. The surface treatment apparatus according to claim 2, wherein high-frequency power is applied to the reactive gas passing through the sonic nozzle. 5. The plasma generating means includes a pair of discharge electrodes disposed on the inner wall along a longitudinal direction of a gas introduction portion or a throat portion of the supersonic nozzle so as to face each other. 3. The surface treatment apparatus according to claim 2, wherein high-frequency power is applied to the reactive gas passing through the sonic nozzle. 6. The plasma generating means includes a pair of mesh-like members arranged in a gas introduction portion or a throat portion of the supersonic nozzle so as to be opposed to each other in a longitudinal direction at right angles to a gas flow. The surface treatment apparatus according to claim 2, wherein high frequency power is applied to the reactive gas passing through the supersonic nozzle via the discharge electrode. 7. A vacuum evacuation step of evacuating the processing chamber to a desired pressure, wherein an injection port is provided in the processing chamber, the length direction is sufficiently long with respect to the width direction, and the width direction along the flow path is provided. A cross section constitutes the same sheet-shaped flow path, and a gas introduction section configured so that the cross-sectional area gradually decreases as going downstream, and is connected to the gas introduction section, and has a minimum cross-sectional area of the entire nozzle. A throat portion configured to have the following configuration, and a gas injection portion connected to the throat portion and configured to gradually expand the cross-sectional area with a predetermined divergence angle, and a gas passing through the nozzle. Adiabatic expansion, accelerated from the gas injection unit into the processing chamber so as to have a flow velocity larger than the speed of sound, and the gas flow path so that the reactive gas injection surface is injected so as to form a long linear shape. Super sound forming A gas supply step of supplying a reactive gas from a gas supply port of a nozzle; a step of forming an electric field in a flow path of the nozzle and exciting the gas by plasma to generate a gas plasma; Adiabatic expansion of the substrate to accelerate in a desired direction so as to have a flow velocity larger than the sonic velocity, and transporting the substrate to be processed in the vicinity of the injection port in a direction perpendicular to the longitudinal direction of the supersonic nozzle. A surface treatment method, wherein a surface treatment of the substrate to be treated is performed by introducing high-speed gas plasma to the surface.