JPH09330909A - Device and method for surface treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove residual components from the surface of a substrate to be treated by intermittently supplying a reactive gas to the gas introducing section of a nozzle with a pulse having a desired duty ratio and intermittently driving a cleaning means which removes a residual gas by blowing a cleaning gas along the surface of the substrate in accordance with the gas supplying timing of a gas supplying means. SOLUTION: A pulse valve 8 having a required duty ratio and number of pulses intermittently supplies a reactive gas to the gas introducing section 2P of a rubber nozzle and exhausts the gas. Since the valve 8 is used, the reactive gas can be introduced to the surface of a substrate S to be treated and the quality of a film can be improved remarkably by lowering the burden of a vacuum pump while a mach condition is instantaneously met and lowering the temperature of the high-density reactive gas to an arbitrary value. In addition, the gas plasma, etc., remaining on the surface of the substrate S can be removed, by forming a high-speed gas flow on the surface of the substrate S in a chamber by intermittently supplying an inert gas along the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to 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.

In this apparatus, as shown in FIG. 5, a high frequency induction coil is wound around a Laval nozzle (also referred to as a divergent nozzle) 1. This Laval nozzle is connected to the gas introduction part 2 and the gas introduction part 2 configured so that the cross-sectional area is gradually reduced, and has the smallest cross-sectional area A of the entire nozzle.
A throat portion (throat portion) 3 configured to have a diameter of 1 (diameter d1) and a throat portion 3 connected to the throat portion 3, and the cross-sectional area gradually increases at a predetermined spread angle, and the maximum cross-sectional area A2 (diameter d2) And the gas injection unit 4 configured to Then, when the reactive gas 6 is introduced from the gas introduction port 2a at the open end of the gas introduction unit 2, the gas introduction unit 2
Inside, the cross-sectional area gradually decreased with the progress of gas,
After being stabilized at the throat portion, the reactive gas that has been accelerated by adiabatic expansion in the gas injection pipe 4 and turned into plasma with a flow velocity higher than the sonic velocity is provided on the substrate S to be treated so as to face the nozzle outlet 4a. It is intended to be jetted against.

An induction coil 5 is wound around the outer periphery of the throat portion 3 so that a high frequency current can be passed through the induction coil 5. For this reason, when the induction coil 5 is energized, an induction electromagnetic field is formed in the throat portion 3, the gas that has been densified and passes through the throat portion 3 is heated and plasma-excited. Then, the plasma-excited high-density gas is expanded and accelerated by the expansion of the nozzle diameter of the gas ejection pipe 4 on the downstream side.
The supersonic plasma jet 7 is ejected from a.

Now, it is assumed that the high-density mixed gas 6 to be injected onto the substrate S to be processed is supplied from the gas inlet 2a 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 downstream gas ejection pipe 4 expands the nozzle due to the expansion of the nozzle, and the gas ejection port 4a ejects the supersonic plasma jet 7 toward the substrate to be processed.

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

By the way, according to the theory of gas dynamics, the ratio Pch / P0 between the stagnation pressure P0 of the introduced reactive gas 6 and the pressure Pch downstream of the injection port 4a is sufficiently small, and the throat part 3 is disconnected. When the ratio A2 / A1 of the area A1 and the cross-sectional area A2 of the injection port 4a exceeds 1, the gas is adiabatically expanded and the injection flow velocity becomes a supersonic velocity, that is, a flow velocity u higher than the sonic velocity a. Therefore, the stagnation pressure P0 of the reactive gas 6
It is necessary to keep the ratio Pch / P0 between the pressure Pch downstream of the injection port 4a and the condition value specified by the required Mach number. In other words, it is necessary to set the gas to be used above a certain specified flow rate and to select the exhaust capacity of the vacuum pump for evacuating the back of the chamber above a certain specified capacity. Further, as the flow rate is increased, the demand for the exhaust capacity of the vacuum pump becomes more serious. This applies not only to plasma surface treatment using a supersonic nozzle, but also to all surface treatments in which a high-speed gas stream is injected to perform surface treatment.

Further, when the surface treatment is performed by supplying the reactive gas, the reaction products may remain on the surface, which may cause problems such as deterioration of film quality and reduction of etching rate.

[0014]

As described above, in the conventional surface treatment using high-speed gas injection, a vacuum pump having an extremely high evacuation capacity is required, which increases the size of the apparatus and the cost. It was a cause of inviting. Further, during the surface treatment, there is a problem that the reaction product remains on the surface of the substrate to be treated, which causes deterioration of film quality and etching rate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a high-speed and highly reliable surface treatment without requiring a high vacuum evacuation capacity. Another object of the present invention is to provide a surface treatment apparatus which is compact, low-cost, and capable of highly reliable surface treatment.

[0016]

Therefore, the first feature of the present invention is that the surface treatment is performed by injecting a reactive gas onto the surface of the substrate to be treated provided in the processing chamber. In the apparatus, it has a vacuum evacuation means for evacuating the inside of the processing chamber to a desired pressure, a gas introduction part, and a gas injection part, and the reactive gas is injected from the gas injection part into the processing chamber. A nozzle that forms a gas flow path, a pulse gas supply unit that intermittently supplies the reactive gas as a pulse having a desired duty ratio to the gas introduction unit of the nozzle, and along the surface of the substrate to be processed. And a cleaning means for injecting a high-pressure cleaning gas to remove residual gas on the surface of the substrate to be processed, wherein the cleaning means is intermittent according to the pulse timing of the pulse gas supply means. It is to being driven to the.

A second feature of the present invention is a surface treatment apparatus which performs a surface treatment on a substrate to be treated by injecting a gas plasma onto the surface of the substrate to be treated, which is provided in the chamber. Vacuum evacuation means for evacuating to a pressure of 1, a gas introduction part configured so that the cross-sectional area gradually decreases, and connected to the gas introduction part, and configured to have a minimum cross-sectional area of the entire nozzle. Throat part,
Connected to the throat section, the cross-sectional area is gradually expanded with a predetermined spread angle, consisting of a gas injection section configured to take the maximum cross-sectional area, to adiabatically expand the gas passing through the nozzle, A supersonic nozzle forming a gas flow path to be accelerated so that the gas is injected from the gas injection unit into the processing chamber at a flow velocity higher than the speed of sound, and the gas introduction unit of the supersonic nozzle has a desired duty ratio. A pulse gas supply means for intermittently supplying the reactive gas as a pulse, a plasma generation means for plasma-exciting a gas passing through the nozzle in a part of the flow path of the supersonic nozzle, and a surface of the substrate to be processed. And a cleaning means for injecting a cleaning gas along the surface of the substrate to remove residual gas on the surface of the substrate to be processed. Depending on the timing, it is an induced to intermittently drive.

A third feature of the present invention is that a reactive gas is intermittently supplied from a gas exhaust port of a nozzle in which an injection port is installed in the process chamber, and a vacuum exhaust process of vacuum exhausting the process chamber to a desired pressure. And a gas supply step of forming an electric field in the flow path of the nozzle and plasma-exciting the gas to generate a gas plasma, and a flow velocity that is adiabatically expanding the gas plasma and is higher than the sonic velocity. In the surface treatment method of accelerating in a desired direction so that the surface of the substrate to be treated is surface-treated by introducing a high-speed gas plasma to the surface of the gas to be treated arranged in the vicinity of the injection port, The supply step is a step of intermittently supplying the reactive gas as a pulse having a desired duty ratio and a desired number of pulses, and in synchronization with the supply timing of the reactive gas. In that to include a washing step to remove residual gas plasma of the injected cleaning gas along the surface of the processed substrate the treated substrate surface.

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.

According to the present invention, since the reactive gas is supplied in a pulsed manner, the actual flow rate is reduced, and the stagnation pressure P0 of the reactive gas 6 and the injection port 4 are instantaneously set.
The ratio Pch / P0 to the pressure Pch downstream of a can be reduced, and a large Mach number can be obtained. Therefore, if the high-speed particles are efficiently introduced onto the substrate to be processed and subjected to the surface treatment, a high-speed gas flow can be formed extremely efficiently without requiring a large exhaust capacity for exhausting the chamber. This is because the gas flow rate is set instantaneously as a pulse above a certain prescribed flow rate, and the overall flow rate is small, and therefore the exhausting capacity of the vacuum pump for vacuuming the chamber back is not so required.

Therefore, even if the flow rate is instantly increased, the total flow rate does not increase so much, so that a larger flow rate can be set.

This applies not only to plasma surface treatment using a supersonic nozzle, but also to surface treatment in general in which a high-speed gas stream is injected to perform surface treatment.

Further, according to the first, second and third aspects of the present invention, cleaning for high pressure along the surface of the substrate to be processed is performed in the vicinity of the surface of the substrate to be processed at the injection timing of the injection process. By injecting a gas to satisfactorily remove residual components such as residual gas plasma on the surface of the substrate to be treated, it becomes possible to perform a better surface treatment without mixing impurities. In the present invention, surface treatments such as film formation and etching are performed intermittently, so that it is possible to perform efficient and highly reliable surface treatments by removing residual components while the surface treatment is not performed. Becomes

The cleaning gas may be an inert gas such as argon or helium, but can be appropriately selected by adding a slightly reducing gas such as hydrogen.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in FIG. 1, the surface treatment apparatus according to the embodiment of the present invention uses a Laval nozzle to form a film on a substrate S to be processed. A pulse valve 8 which is intermittently supplied so as to form a pulse shape having a number of pulses is arranged so that high-pressure reactive gas is intermittently supplied and exhausted intermittently. .

In this device, the injection port 4 of the Laval nozzle is used.
a is disposed in a chamber 1 capable of being evacuated, and the chamber 1 is evacuated to a desired pressure Pch by a vacuum pump 9 composed of a mechanical booster pump 9a and a rotary pump 9b. The vacuum pump 9 and the pulse valve 8 are drive-controlled by the control means 10. The substrate to be processed is maintained at a desired temperature by the heater H provided on the substrate support. Furthermore, in this device, the nozzle is a supersonic nozzle under the conditions described below so that the reactive gas passing through the inside is adiabatically expanded and injected from the nozzle outlet 4a at a flow velocity u higher than the sonic velocity a. It is a Laval nozzle (also called Suehiro nozzle) that constitutes it.

The Laval nozzle is a medium-thin nozzle as shown in FIG. 2, and the reactive gas 6 (for example, a mixed gas of CH ₄ and H ₂ ) to be jetted onto the surface of the substrate S to be processed is introduced into the gas introducing portion 2P ( 50 mmΦ), and a gas introduction pipe 2 configured so that the cross-sectional area gradually decreases as the gas progresses,
Minimum cross-sectional area A1 (diameter d1: 16 mmΦ) for the entire nozzle
The throat part (throat part) 3 and the cross-sectional area gradually expand with a predetermined spread angle, and the maximum cross-sectional area A2 (diameter d
(2:40 mmΦ) and a gas injection pipe 4 from which a plasma flow 7 is injected from a gas injection port 4a. The substrate S to be processed is placed on the substrate support so as to face the plasma flow 7 ejected from the ejection port 4a of the Laval nozzle.

An induction coil 5 (coil diameter: 16 mm, number of coil turns: 5) is wound around the outer periphery of the throat portion 3 as a plasma generating means, and a high frequency current (500 W, 13.56 MHz) is applied to the induction coil 5. When an electric current is applied to the throat part 3, an induction electromagnetic field is formed in the throat part 3, and the gas passing through the throat part 3 is excited by plasma.

The high-density gas that has been turned into plasma is
The expansion of the nozzle due to the expansion of the nozzle by the gas ejection pipe 4 on the downstream side accelerates the expansion, and the supersonic plasma flow 7 from the gas injection port 4a.
And is jetted.

Here, if the divergence angle in the front and rear of the throat portion 3 is too large, separation of the boundary layer occurs on the wall surface, so it is necessary to set it to an appropriate size, for example, about 15 °.

In the throat section 3, the high density reactive gas turned into plasma is highly reactive due to its heat,
That is, it is excited into a state in which it easily reacts on the substrate to be treated. However, this reactive gas has a very high temperature, and reaches as high as 10,000 degrees Celsius in some cases. Therefore, when the reactive gas is sprayed onto the substrate to be treated, the substrate itself can withstand this temperature. Sometimes there is not.

However, since the Laval nozzle is designed so that the reactive gas passing through the inside is adiabatically expanded as described above, the Laval nozzle is rapidly cooled in this adiabatic expansion process, and the substrate does not reach the surface of the substrate to be treated. The temperature is appropriate so that deterioration of the temperature does not occur. 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.

For example, when a mixed gas of 1 vol.% CH ₄ and H ₂ is used, it is assumed that the specific heat ratio γ = 1.38 although the exact value of the specific heat ratio of this gas is unknown. And
Here, the Suehiro ratio A2 / A1 was set to 6.25. This value is designed to realize the Mach number M = 5. At this time, the ratio of the chamber pressure P _ch to the stagnation pressure P ₀ , that is, the critical pressure ratio must satisfy the relationship of P _ch / P ₀ <0.39. In order to satisfy the relationship of P _ch / P ₀ <0.39 with the pulse valve completely opened, the exhaust capacity of the vacuum pump is 24000 L / mi when the flow rate of the reactive gas is 100 sccm.
n. Will be required. For this reason, a huge size vacuum pump was required.

On the other hand, the duty ratio of the pulse valve is 1/1
When set to 0, the flow rate of the reaction gas is 100 sccm only in the open state. The time average including the substantially closed state is 10 sccm. This flow rate is 2400 L / min. It means that

By using the pulse valve in this way, the load applied to the vacuum pump can be reduced while instantaneously satisfying the Mach condition, and the limitation caused by the vacuum pump or its occupied area can be eliminated.

Furthermore, according to the surface treatment method using the surface treatment apparatus of the present invention, the high-density and highly reactive gas can be lowered to an arbitrary temperature and introduced onto the substrate S to be treated. As a result, not only the work efficiency but also the film quality can be significantly improved.

In this embodiment, the coil 5 for exciting the plasma is arranged in the throat portion 3, but the invention is not limited to this, and the coil 5 can be arranged in any place of the nozzle. The duty ratio of the pulse valve is set to 1/10 here, but the duty ratio is 0.05 to 0.5.
It is desirable to set it to a degree, and it can be appropriately changed within this range.

Next, a second embodiment of the present invention will be described. As shown in FIG. 3, this surface treatment apparatus intermittently forms a high-speed plasma stream 7 by intermittently supplying a gas with a pulse valve 8, and after the high-speed plasma stream is injected, the next injection is performed. First, a high-speed gas flow is formed along the surface of the substrate S to be processed in the chamber,
A high-speed gas supply means 13 for removing gas plasma and the like remaining on the surface of the substrate to be processed is provided. This high-speed gas supply means is pulse-driven as shown in FIG. 4, for example, in synchronization with the drive timing of the pulse valve, and is configured to intermittently supply an inert gas such as helium or argon gas. In addition, first and second pressure sensors 11 and 12 configured to measure the pressure Pch in the chamber 1 and the pressure P0 of the stagnation portion 2s of the gas introduction pipe of the Laval nozzle are provided. Then, these first and second pressure sensors 11,
The outputs of 12 are respectively transmitted to the control means 10, and the control means 10 considers the pressure Pch in the chamber 1 and the pressure P0 of the stagnation portion 2s of the gas introduction pipe of the Laval nozzle, while taking into consideration the pulse valve 8, the high-speed gas supply means 13, And the drive of the vacuum pump 9 is adjusted.

The other parts are the same as those shown in FIG.
The configuration is the same as that of the embodiment described above, and the same components are designated by the same numbers.

Although the Laval nozzle has been described in the above embodiment, it goes without saying that a nozzle having a straight pipe 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.

For example, when the substrate temperature is set to 196 ° C. using a mixed gas of ₅ vol.% CF ₄ and O ₂ and the silicon substrate surface on which the resist pattern is formed is etched, a steep profile with an aspect ratio of 100 is obtained. It was possible to form a highly accurate trench having

The surface was reformed to good titanium nitride by exciting the surface of titanium by plasma excitation using ammonia gas as a reactive gas.

[0048]

As described above, according to the present invention, a high-speed gas flow is formed very efficiently without requiring a large exhaust capacity for exhausting the chamber, and impurities are not mixed by residual gas. It is possible to perform highly efficient and highly reliable surface treatment.

[Brief description of drawings]

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

FIG. 2 is an explanatory view showing a nozzle used in the surface treatment apparatus of the first embodiment of the present invention.

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

FIG. 4 is a diagram showing a drive timing of the device.

FIG. 5 is a diagram showing a conventional surface treatment apparatus.

[Explanation of symbols]

 1 chamber 2 gas introduction pipe 3 throat part (throat) 4 gas injection pipe 5 induction coil 6 gas 7 plasma flow 8 pulse valve 9 vacuum pump 9a mechanical booster pump 9b rotary pump 10 control means 11 first sensor 12 second Sensor 13 High-speed gas supply means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H01L 21/28 301 H01L 21/28 301R 21/31 21/31 B 21/3205 21/88 M

Claims (3)

[Claims] 1. A surface treatment apparatus for treating the surface of a substrate to be treated by injecting a reactive gas onto the surface of the substrate to be treated provided in the chamber, wherein the inside of the chamber is evacuated to a desired pressure. A nozzle having a vacuum evacuation means, a gas introduction part, and a gas injection part, and forming a gas flow path from the gas injection part so as to inject a reactive gas into the processing chamber; and the gas of the nozzle. A pulse gas supply unit that intermittently supplies the reactive gas as a pulse having a desired duty ratio to the introduction portion, and a cleaning gas is injected along the surface of the substrate to be processed to obtain the substrate to be processed. A cleaning means for removing residual gas on the surface, wherein the cleaning means is driven intermittently in accordance with the pulse timing of the pulse gas supply means. 2. A surface treatment apparatus for performing a surface treatment on a substrate to be treated by injecting a gas plasma onto the surface of the substrate to be treated provided in the treatment chamber, wherein a vacuum for exhausting the inside of the treatment chamber to a desired pressure. Exhaust means, a gas introduction part whose cross-sectional area is gradually reduced, a throat part connected to the gas introduction part and having a minimum cross-sectional area of the entire nozzle, and the throat part And a gas injection unit configured to have a maximum cross-sectional area, the cross-sectional area of which is gradually enlarged with a predetermined spread angle, and the gas passing through the nozzle is adiabatically expanded to form a gas injection unit. From the above, a supersonic nozzle forming a gas flow path that accelerates so as to inject into the processing chamber at a flow velocity higher than the sonic speed, and a desired duty in the gas introduction part of the supersonic nozzle. A pulse gas supply means for intermittently supplying the reactive gas as a pulse having a ratio; a plasma generation means for plasma-exciting a gas passing through the nozzle in a part of the flow path of the supersonic nozzle; And a cleaning means for injecting a high-pressure cleaning gas along the surface of the substrate to remove residual gas on the surface of the substrate to be processed, the cleaning means comprising the pulse timing of the pulse gas supply means. Surface treatment device characterized by being driven intermittently according to 3. A vacuum evacuation process of evacuating the processing chamber to a desired pressure, and a gas supply process of intermittently supplying a reactive gas from a gas supply port of a nozzle having an injection port installed in the processing chamber. And a step of forming an electric field in the flow path of the nozzle and plasma-exciting the gas to generate a gas plasma, and a desired direction so that the gas plasma is adiabatically expanded to have a flow velocity higher than the sonic velocity. In the surface treatment method in which the surface of the substrate to be treated is surface-treated by introducing a high-speed gas plasma to the surface of the gas to be treated arranged in the vicinity of the injection port, the gas supply step is performed at a desired duty. In the step of intermittently supplying the reactive gas as a pulse having a ratio, in the vicinity of the surface of the substrate to be treated, in synchronization with the supply timing of the reactive gas, Surface treatment method, characterized in that along the surface of the treated substrate to inject cleaning gas described above to include the cleaning step of removing the residual gas plasma treated substrate surface.