JPH09310180A - Surface treatment, surface treating device, semiconductor device formed using the same and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treating method executing coating formation or etching giving a mass gradient to coating thickness with high controllability and to provide a device therefor. SOLUTION: The surface of the substrate to be treated is sprayed with gas plasma to execute surface treatment to the substrate to be treated. In this case, the treatment has a stage of generating the gas plasma by feeding a reactive gas into the electric field and exciting the plasma, a stage of adiabatically expanding the gas plasma and accelerating the same to a desired direction so as to regulate its flow velocity to the one higher than the velocity of sound and a stage of spraying the accelerated gas plasma toward the surface of the substrate to be treated slantly arranged so as to make a slant angle θto the accelerated direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method, a surface treatment apparatus, a semiconductor device formed by using the surface treatment apparatus, and a method for manufacturing the same, and more particularly, to film formation having a gradient in film thickness. A method and apparatus for enabling.

[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. 10, a high frequency induction coil is wound around a Laval nozzle (also referred to as a divergent nozzle) 1. This Laval nozzle 1 has a gas introduction portion 2 configured so that its cross-sectional area is gradually reduced.
And a throat portion (throat portion) 3 connected to the gas introduction portion 2 so as to have a minimum cross-sectional area A1 (diameter d1) in the entire nozzle, and a predetermined divergence angle connected to the throat portion 3 The cross-sectional area gradually expands with the maximum cross-sectional area A2
(Diameter d2) and the gas injection part 4 configured. Then, when the reactive gas 6 is introduced from the gas introduction port 2a at the opening end of the gas introduction unit 2, the cross-sectional area in the gas introduction unit 2 gradually becomes smaller as the gas advances, and is stabilized at the throat portion. After that, the reactive gas, which is accelerated by adiabatic expansion in the gas injection unit 4 and turned into plasma at a flow velocity higher than the sonic velocity, is injected to the substrate S to be processed provided so as to face the nozzle outlet 4a. It was done so.

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.

Since an electrodeless plasma device utilizing an induction electromagnetic field is used here, the plasma gas and the electrode are in direct contact as in the case of using a direct current (DC) plasma device, and as a result, It is possible to prevent the electrode material (tungsten or the like) from being mixed into the plasma gas due to the consumption of the electrode, and to prevent the mixing of impurities.

Now, it is assumed that the high-density reactive gas 6 to be injected onto the substrate S to be processed is supplied from the gas inlet 2a into the Laval nozzle 1. Then, as described above, in the throat portion 3, since the high frequency current is applied to the high frequency induction coil 5, an induction electromagnetic field is generated in the tube, and the energy of this field heats the high density gas to generate plasma. To be done.

The heated and plasmated high-density gas is expanded and accelerated due to the expansion of the nozzle by the gas jet pipe 4 on the downstream side, and becomes a supersonic plasma jet 7 from the gas jet port 4a to be treated substrate. Is jetted toward.

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

By the way, research on solar cells has been advanced in recent years, and a solar cell using a polycrystalline silicon thin film is a widely used device because it is easy to increase the area and is inexpensive. . As shown in FIG. 8, an example of a solar cell is a transparent electrode 1 formed on the surface of a glass substrate 10.
1 and a polycrystalline silicon p-layer 1 sequentially stacked on top of this
2p polycrystalline silicon i layer 12i, polycrystalline silicon n layer 1
A polycrystalline silicon thin film 12 having a three-layer structure composed of 2n,
Further, it is composed of a metal electrode 13 formed on this upper layer. By the way, there is a problem that such a polycrystalline silicon thin film has a low absorption efficiency for visible light.

Therefore, as shown in FIG. 2, a method is considered in which the polycrystalline silicon thin film 12 is made to have a film thickness gradient and the absorption light is increased by multiple reflection.

Generally, it is not easy to give a gradient to the thickness of the polycrystalline silicon thin film. Therefore, as shown in an example of the manufacturing process in FIGS. 9A to 9C, a transparent glass substrate is used. 10
A transparent electrode 11 made of an indium tin oxide layer is formed on the surface, a polycrystalline silicon layer 12 is formed, a film thickness gradient is formed by etching, and then a polycrystalline silicon p layer 12p is formed by ion implantation. Polycrystalline silicon i-layer 12i,
A polycrystalline silicon thin film 12 having a three-layer structure including a polycrystalline silicon n layer 12n is formed. And finally the metal electrode 1
Although it can be formed by forming No. 3, it is extremely difficult to form a film thickness gradient with good controllability by etching in the actual process. Further, even if a good gradient can be formed in the film thickness, the polycrystalline silicon i layer 12i and the polycrystalline silicon n layer 12n on the surface side have uniform film thicknesses at the time of ion implantation. Only the silicon p-layer 12p has a gradient,
There is a problem that a sufficient multiple reflection structure cannot be obtained.

As described above, performing film formation or etching with a gradient in film thickness is effective not only for the solar cell but also for other devices or in the region where the wiring density is significantly different in each region. It is required when selecting the film thickness.

[0017]

As described above, the present invention is
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a surface treatment method and a surface treatment apparatus that perform controllable film formation or etching with a gradient in film thickness.

Another object of the present invention is to provide a highly efficient and highly reliable solar cell or semiconductor device.

[0019]

Therefore, a first feature of the present invention is that in a surface treatment method for treating the surface of a substrate to be treated by injecting a gas plasma onto the surface of the substrate to be treated, a reactive gas is added. By supplying into the electric field and exciting the plasma, a step of generating a gas plasma, a step of adiabatically expanding the gas plasma and accelerating in a desired direction so as to have a flow velocity higher than the sonic velocity, and with respect to the acceleration direction And injecting the accelerated gas plasma toward the surface of the substrate to be processed that is inclined so as to have an inclination angle θ.

A second feature of the present invention is that a cross-sectional area is gradually reduced in a surface treatment apparatus that performs a surface treatment on a substrate to be treated by injecting a gas plasma onto the surface of the substrate to be treated. A configured gas introduction part, a throat part connected to the gas introduction part and configured to have a minimum cross-sectional area of the entire nozzle, and a throat part connected to the throat part, and the cross-sectional area gradually increases with a predetermined spread angle. And a gas injection unit configured to have a maximum cross-sectional area, and the gas passing through the nozzle is adiabatically expanded and accelerated so as to be injected from the gas injection unit at a flow velocity higher than the sonic velocity. A supersonic nozzle forming a gas flow path, a plasma generating means for plasma-exciting a gas passing through the nozzle in a part of the flow path of the supersonic nozzle, and an inclination with respect to an acceleration direction of the gas plasma. The so as to have an angular θ lies in the and a substrate supporting means for supporting a substrate to be processed.

Further, a third feature of the present invention is that a first electrode formed on the surface of a substrate, a polycrystalline silicon thin film sequentially laminated on the first electrode, and a polycrystalline silicon thin film further laminated thereon are formed. A solar cell including a second electrode is characterized in that the polycrystalline silicon thin film has a pin or pn structure having a constant film thickness ratio throughout.

A fourth feature of the present invention is a method for forming a semiconductor device by sequentially laminating a first electrode, a silicon thin film having a pin or pn structure, and a second electrode on a surface of a substrate. In the step of forming the silicon thin film, the reactive gas is heated and supplied into the electric field to be turned into plasma to generate gas plasma, and the gas plasma is adiabatically expanded to have a flow velocity higher than the sonic velocity. Including a step of accelerating in a desired direction and a step of injecting the accelerated gas plasma toward the surface of the substrate that is inclined to have an inclination angle θ with respect to the acceleration direction, P with a constant film thickness ratio
It is characterized in that the silicon thin film is formed so as to form an in or pn structure.

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 plasma flow flows in the direction of the central axis of the nozzle even downstream of the nozzle outlet, but in actual operation, it also diffuses in the direction perpendicular to the traveling direction. Therefore, the plasma density decreases with increasing distance from the nozzle outlet. The present invention has been made paying attention to this point, and by inclining the substrate to be processed with respect to the nozzle outlet, the film formed becomes thinner as the distance d from the center of the nozzle increases. The rate of thinning, that is, the gradient of the film thickness can be arbitrarily changed by setting the inclination angle θ emitted from the nozzle outlet. On the other hand, when used for etching, by tilting the substrate to be processed with respect to the nozzle outlet, the etching rate becomes slower and the etching amount becomes smaller as the distance d from the center of the nozzle increases. The gradient of the etching amount can be arbitrarily changed by setting the inclination angle θ emitted from the nozzle outlet.

According to the present invention, the reactive gas to be jetted onto the surface of the substrate S to be processed is turned into plasma and becomes highly reactive (excited state, active state). Then, the plasma-excited gas is adiabatically expanded by the supersonic nozzle and accelerated so as to have a flow velocity higher than the sonic velocity, and this accelerated gas is jetted toward the surface of the substrate S to be processed.
In this way, the plasma-excited gas in a highly reactive state, that is, the plasma flow, reaches the substrate S to be processed, which is an injection target, at supersonic speed in a short time.

As a result, the plasma flow reacts with the surface of the substrate S to be processed while maintaining a high reactivity, and when the apparatus is used for film formation, it reacts with the substrate S to be processed. The adhesion with the product is improved, and the inconvenience of peeling off the reaction product can be avoided. Further, since the plasma flow reaches the surface of the substrate to be processed in a short time, the film forming speed is increased and the working efficiency is also improved. Further, the temperature of the gas that has been heated and turned into plasma is lowered to a temperature at which the substrate S to be processed can withstand due to adiabatic expansion, so that deterioration of the substrate S to be processed can be prevented.

Further, when the plasma generating means is constituted by a high frequency induction coil wound outside the nozzle, the reactive gas can be heated and turned into plasma without using an electrode which is in direct contact with the plasma gas. Therefore, impurities (electrode material) that accompany consumption of the electrode are not mixed in the generated plasma flow, and the film quality is improved during film formation. In addition, a clean etching surface can be obtained during etching.

Furthermore, according to the solar cell of the present invention,
Incident light can be taken in favorably, and high efficiency can be achieved by intra-film multiple reflection.

Further, according to the method of manufacturing a semiconductor device of the present invention, it is possible to obtain a pin structure in which the film thickness is controlled with high accuracy without causing surface contamination by merely inclining the substrate with respect to the plasma flow.

[0030]

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 is designed so that when the film is formed by using the Laval nozzle 1, the surface treatment apparatus has an inclination angle θ with respect to the acceleration direction of the plasma flow 7. It is characterized in that a glass substrate as the processing substrate S is arranged in an inclined manner, gas plasma is jetted, and a polycrystalline silicon film having an inclined film thickness structure is formed by a plasma CVD method. In this example, a multi-reflection solar cell as shown in FIG. 2 is formed, and the p-layer, the i-layer, and the n-layer of the polycrystalline silicon layer 12, which is the photoelectric conversion layer, have different thicknesses at the same ratio. Provide structure. The detailed structure of the polycrystalline silicon layer 12 of this solar cell is shown in FIG. In manufacturing, as shown in the manufacturing process diagrams in FIGS. 4A to 4C, first, the first electrode 1 is formed on the surface of the glass substrate 10.
1, an indium tin oxide layer is formed by a sputtering method or the like, and then the polycrystalline silicon p-layer 1 is sequentially formed on the first electrode 11 by using the surface treatment apparatus shown in FIG.
2p, a polycrystalline silicon i layer 12i, and a polycrystalline silicon n layer 12n are sequentially laminated. In this apparatus, by arranging the glass substrates in an inclined manner, it is possible to obtain a polycrystalline silicon thin film having a pin structure having a constant film thickness ratio throughout. Finally, the second electrode 13 made of chromium is formed again by the sputtering method or the like to complete the solar cell.

Next, the surface treatment apparatus will be described.
In this device, the reactive gas passing through the nozzle is adiabatically expanded and injected from the nozzle outlet 4a at a flow velocity u higher than the sonic velocity a under the conditions described later, which is a supersonic nozzle Laval nozzle ( Also called Suehiro nozzle)
1 is configured.

The Laval nozzle 1 is a medium-thin nozzle, and the reactive gas 6 (for example, a mixed gas of SiH ₄ and H ₂ ) to be sprayed on the surface of the glass substrate 10 as the substrate s to be processed.
Is introduced from the gas introduction port 2a (50 mmΦ), and the minimum cross-sectional area A1 (diameter d1:
16mmΦ) Throat (throat) 3 and the cross-sectional area gradually expands with a constant spread angle, and the maximum cross-sectional area A2
It is composed of a gas injection pipe 4 from which a plasma flow 7 is injected from a gas injection port 4a (diameter d2: 40 mmΦ). The glass substrate 10 as the substrate S to be processed is
It is arranged by a supporting means (not shown) so that the plasma flow 7 ejected from the ejection port 4a of the Laval nozzle 1 has an inclination angle θ.

An induction coil 5 (coil diameter: 16 mm, number of coil windings: 5) is wound around the outer periphery of the throat portion 3 as a plasma generating means. When a high frequency current is applied to the induction coil 5, the throat portion 3 is energized. An inductive electromagnetic field is formed in 3 and the gas passing through the throat portion 3 is heated and turned into plasma. Since an electrodeless plasma generating means utilizing an induction electromagnetic field is used here, D
Unlike the C plasma device, the plasma gas and the electrode are in direct contact with each other, and the electrode material (tungsten etc.) is not mixed into the plasma gas due to the consumption of the electrode, and the mixing of impurities is prevented. can do.

First, the glass substrate 10 on the surface of which the first electrode 11 is formed has an inclination angle θ: 20 with respect to the central axis of the nozzle.
The temperature of the substrate is 400 ℃
And Then, from the gas inlet 2a to the Laval nozzle 1
Inside, a mixed gas of SiH ₄ and H ₂ (SiH ₄ : 5 scc
m, H _2: 500sccm) the B ₂ H as an impurity gas
₆ (500 sccm in H ₂ dilution). In the throat section 3, when a high-frequency current (500 W, 13.56 MHz) flows through the high-frequency induction coil 5,
An induced electromagnetic field is generated in the tube, and the energy of this field heats the high-density gas into plasma.

The heated and plasmated high-density gas is expanded and accelerated due to the expansion of the nozzle by the gas jet pipe 4 on the downstream side, and is jetted as a supersonic plasma stream 7 from the gas jet port 4a. It By guiding this plasma flow 7 onto the glass substrate 10 installed with an inclination angle θ, a polycrystalline silicon p layer 12p is formed with a film thickness gradient structure. When the glass substrate is installed at an inclination angle θ, the film formed has a thickness of 1 μm at one end and about 5 μm at the other end. Here, the inclination angle θ is from 5 degrees
It is desirable to set it to about degree.

According to the theory of gas dynamics, in the case of diatomic gas, for example, the ratio P1 / P0 of the stagnation pressure P0 of the introduced reactive gas 6 and the pressure P1 downstream of the injection port 4a is about 0. 0.52 or less, the cross-sectional area A1 of the throat portion 3 and the injection port 4a
When the ratio of the cross-sectional area A2 (the divergent ratio) A2 / A1 exceeds 1, the gas is adiabatically expanded, and the injection velocity becomes a supersonic velocity, that is, the velocity u larger than the sonic velocity a.

The divergence angle α before and after 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 °.

The high-density reactive gas heated and plasmatized in the throat portion 3 is excited by the heat into a highly reactive state, that is, a state in which it easily reacts on the glass substrate 10. However, since this highly reactive gas has a very high temperature, and reaches as high as 10,000 degrees Celsius in some cases, when it is jetted onto the glass substrate 10, the glass substrate 10 can withstand this temperature. Sometimes there is not.

However, the Laval nozzle 1 is designed so that the reactive gas passing through the inside thereof is adiabatically expanded as described above, so that the Laval nozzle 1 is rapidly cooled in this adiabatic expansion process until it reaches the surface of the glass substrate 10. The temperature is appropriate so that the glass substrate is not deteriorated.
Since the temperature at this time is determined by the divergence ratio A2 / A1 (0.4 in this example), an arbitrary temperature can be obtained depending on the design conditions of the nozzle 1.

Furthermore, since the plasma flow 7 has a supersonic velocity, the time required to reach the glass substrate 10 is extremely short, and the state excited by heating and plasma generation before reaching the glass substrate 10 is the original. It never returns to the state. Thus, the temperature can be lowered to an appropriate temperature while maintaining the so-called excited state. Therefore, the adhesion between the indium tin oxide electrode 11 on the surface of the glass substrate 10 and the polycrystalline silicon p-layer 12p, which is a reaction product, is improved, and there is no inconvenience such as peeling of the reaction product. Therefore, the film quality can be improved. Further, since the injection is completed in a short time, the film forming speed is increased, and the working efficiency is also improved.

The phenomenon described above is explained as follows by the theory of one-dimensional fluid dynamics.

That is, the relationship between the fluid temperature and the flow velocity in the adiabatic flow of perfect gas is expressed by the following equation.

T0 = T + (1/2) · {(γ−1) / (γ · R)} · (u) ² (1) Alternatively, T0 / T = 1 + {(γ−1) / 2} (M) ² (2) where T 0: total temperature of flow (approximately equal to temperature of throat section 3 which is a heating section) T: static temperature of flow (so-called temperature) γ: specific heat ratio of gas R: Gas constant u: Flow velocity M: Mach number.

The above equation (2) is obtained by rewriting the above equation (1) using the Mach number (u / a, a: speed of sound).
Further, the Mach number M is uniquely determined as a function of the Suehiro ratio A2 / A1.

From the above equation (1), it can be seen that in the adiabatic expansion process, the value of the total temperature T0 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.

From the equation (2), the temperature ratio T0 / T
Increases in proportion to the square of the Mach number M. For example, in the case of a diatomic gas (γ = 1.4), the Mach number M = 5
At this time, the temperature ratio T0 / T = 6. That is, it can be seen that the plasma temperature T can be lowered to a temperature suitable for the substrate S to be processed by adiabatically accelerating the reactive plasma heated to a high temperature to a high Mach number using the Laval nozzle 1. At this time, since the plasma particles are accelerated at a very high speed (for example, T = 1500
(K), γ = 1.4, R = 500 (J / kgK), M =
In the case of 5, u = 5123 (m / s)), the time to reach the substrate S to be treated (glass substrate 10) is very short, and the plasma is treated at a low temperature while maintaining the initial activation state. The substrate S can be reached.

Since the low-temperature / high-speed plasma stream 7 having high activity is supplied to the glass substrate 10 as the substrate to be treated as a particle bundle having a good directivity, the use efficiency of the raw material gas is extremely high. It also has Furthermore, as described above, the plasma does not cause contamination due to the electrode material.

Subsequently, the supply of B ₂ H ₆ as an impurity gas is stopped, a mixed gas of SiH ₄ and H ₂ is flown, and similarly, a polycrystalline silicon i layer 12i is formed with a film thickness gradient structure. The film formed here is 0.5 μm at one end,
The other end has a film thickness of about 2.5 μm.

Finally, PH ₃ as an impurity gas
(500 sccm diluted with H ₂ ) was caused to flow together with a mixed gas of SiH ₄ and H ₂ , and the polycrystalline silicon n layer 12n was similarly formed.
Are formed with a film thickness gradient structure. After that, the second electrode 13 made of chromium is formed by a sputtering method or the like to complete the solar cell. The solar cell thus formed was able to obtain a power generation efficiency of 4.2% due to the light confining effect due to the multiple reflection in the film. On the other hand, in the conventional solar cell formed with the inclination angle of 0, the power generation efficiency is 2.
8%.

As described above, according to this embodiment, a solar cell having a highly accurate film thickness gradient structure can be formed with good reproducibility. Further, the film thickness ratio can be made constant with good controllability only by switching the gas, an optimum film thickness gradient structure can be obtained, and the inclination angle of the joint surface can be well controlled. Becomes As compared with the case where a polycrystalline silicon film is formed as in the conventional method shown in FIG. 9 and then a graded film thickness structure is formed by etching, and the bonding surface is formed by performing ion implantation or the like, the position of the bonding surface and The controllability of the film thickness is also good and the reliability is high.

Although the glass substrate is used in the above embodiments, a stainless steel substrate may be used as the first electrode on the substrate side and the translucent electrode on the second electrode side.

Furthermore, according to 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, only the working efficiency can be improved. The quality of the film can be improved significantly.
In this embodiment, the coil 5 is provided on the throat portion 3, but the present invention is not limited to this, and the coil 5 can be provided at any location of the nozzle 1.

Next, a second embodiment of the present invention will be described.

FIG. 5 shows that at least the outlet of the nozzle 1 has a desired pressure P1 so that the outlet pressure P1 of the nozzle 1 can be adjusted to an arbitrary pressure and the pressure ratio P1 / P0 can be set to an arbitrary value. 2 shows an embodiment arranged in the chamber 18 controlled by the above. In addition, the same components as those in FIG. As shown in FIG. 5, the throat portion 3 and the gas injection pipe 4 are provided in the vacuum chamber 18, and the support 14 that supports the substrate S to be processed in an inclined state is provided in the chamber 18. Has been done. The air in the vacuum chamber 18 is the exhaust pump 2
Exhausted by 3. The amount of gas supplied to the gas introduction pipe 2 is adjusted by the first adjusting valve 21 for adjusting the amount of gas supply arranged in the gas supply pipe 16, and the outlet pressure P1 of the jet plasma flow 7 is adjusted by P1. Second regulating valve 22 for
Will be adjusted by The pressure P0 in the gas introduction pipe 2 is P0
The outlet pressure P1 of the gas injection pipe 4 is detected by the measuring gauge 19 and the outlet pressure P1 of the gas injection pipe 4 is detected by the P1 measuring gauge 20, and the detection results are used as feedback signals to adjust the first and second adjusting valves 21 and 22. Then, the pressure ratio P1 / P0 is set to a predetermined value. In addition, 1
Reference numeral 7 is a high frequency power source for supplying a current to the high frequency induction coil 5.

In this example, an optical position detecting device as shown in FIG. 6 and a method for manufacturing the same will be described. Here, a mixed gas of SiH ₄ and H ₂ is used as the reactive gas 6 to be supplied, and the amorphous silicon i layer 32 is formed so as to have a film thickness gradient structure. Here, as the substrate S, the one in which the first electrode 31 made of a metal thin film was formed on the surface of the alumina ceramic substrate 30 was used as the ejection target. Then, the divergence ratio A2 / A1 is set to about 6, the second adjusting valve 22 and the first adjusting valve are set so that the inside of the chamber 18 is about 10 mTorr and the pressure ratio P1 / P0 is about 1.4 / 1000. Valve 21 was adjusted. Under this condition, the Mach number M of the supersonic plasma jet 7 is about 5.

The high frequency induction coil 5 was supplied with a current of 13.56 MHz at 1 kW while being cooled.

As a result, the high-density and highly reactive mixed gas was jetted at supersonic speed and supplied onto the substrate S. As a result, an amorphous silicon thin film having high adhesion to the substrate S was formed on the substrate S. Here, as a result of spraying (film formation) for 20 minutes, the film thickness was 1 μm at one end and 5 μm at the other end. When this amorphous silicon thin film was evaluated by SEM observation and X-ray diffraction, it was found to be a dense amorphous film.

Then, a transparent conductive oxide film (TCO) of tin oxide or the like is formed on the upper layer as the transparent second electrode 33 to complete the optical position detector.

Furthermore, as shown in FIG. 7, a first electrode 31, an amorphous silicon layer 32 having a graded film thickness structure, and a transparent second electrode 33 are formed on a substrate 30, and a terminal 3 is formed.
It is also applicable to a position sensor or the like for detecting the moving position of No. 4.

In each of the above-mentioned embodiments, an example of forming a silicon thin film has been described.
A graphite thin film can be formed by using a mixed gas of H ₄ and H ₂ , and c-BN can be formed by using an NH ₄ gas and a B ₂ H ₆ gas as the reactive gas 6.

By changing the reactive gas 6,
Various surface treatments such as etching, oxidation and nitriding can be performed with this apparatus.

In the embodiment, the gas is heated and turned into plasma by the high frequency induction coil 5, but other electrodeless plasma devices such as ECR plasma and helicon plasma may be used.

Further, in the embodiment, all the gas 6 to be injected onto the substrate S to be processed is supplied from the inlet 2a which is the inlet of the nozzle 1 in the first embodiment, and in the second embodiment.
The gas is supplied from the inlet 2a via the supply pipe 16, but the gas 6 is supplied at a position upstream of the gas flow path from the position where the coil 6 is heated and turned into plasma. If so, it can be provided at any position.

When a semiconductor film is grown and impurities are added, a doping material serving as a donor or an acceptor is mixed with a gas such as SiH ₄ , and the mixed gas 6 is heated and turned into plasma. The coil 5 may be supplied from a position upstream of the position of the coil 5. However, only the doping material may be supplied from a position downstream of the position where the coil 5, that is, the plasma generating means is arranged. Since the amount of the doping material is very small, it does not hinder the adiabatic expansion of other gases such as SiH ₄ .

As described above, according to the present invention, a highly reactive gas containing few impurities is generated, and the temperature of this gas is lowered to a temperature suitable for processing by the time it reaches the substrate to be processed. Moreover, since the highly reactive gas can reach the substrate to be treated at a supersonic velocity within a short time, the treatment can be completed in a short time while maintaining sufficient reactivity. As a result, the quality of the film is significantly improved and the work efficiency is dramatically improved.

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, although the film forming method has been described in the above embodiment, it is needless to say that the present invention is not limited to film forming and can be applied to etching. In etching, it is possible to achieve highly efficient etching without damaging the underlying material.

[0069]

As described above, according to the present invention, it is possible to form a film having a graded film thickness structure with extremely good controllability and good film quality, and in the case of etching or the like, the underlying layer is damaged. It is possible to perform the gradient etching with no control and with good controllability.

[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 a schematic view showing a solar cell formed by the surface treatment apparatus of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of the same.

FIG. 4 is a manufacturing process diagram of the solar cell.

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

FIG. 6 is a diagram showing an optical position detection device formed by a surface treatment device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing another apparatus formed by the surface treatment apparatus of the present invention.

FIG. 8 is a diagram showing a conventional solar cell.

FIG. 9 is a manufacturing process diagram of a conventional solar cell.

FIG. 10 is a diagram showing a conventional surface treatment apparatus.

[Explanation of Codes] 1 Laval nozzle 2 Gas introduction pipe 3 Throat part (throat) 4 Gas injection pipe 5 High frequency induction coil 6 Reactive gas 7 Plasma flow 10 Glass substrate 11 First electrode 12 Polycrystalline silicon layer 12p Polycrystalline silicon p layer 12i polycrystalline silicon i layer 12n polycrystalline silicon n layer 13 second electrode 14 support 16 gas supply pipe 17 high frequency power supply 18 vacuum chamber 19 P0 measuring gauge 20 P1 measuring gauge 21 first adjusting valve 22 second Regulator valve 23 Exhaust pump 30 Glass substrate 31 First electrode 32 Amorphous silicon layer 33 Second electrode

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // H01L 21/205 H01L 31/04 X

Claims (4)

[Claims] 1. A surface treatment method for performing a surface treatment of a substrate to be treated by injecting a gas plasma onto the surface of the substrate to be treated, by supplying a reactive gas into an electric field to excite the plasma to form a gas plasma. And a step of accelerating the gas plasma in a desired direction so that the gas plasma is adiabatically expanded to have a flow velocity higher than the sonic velocity, and an inclination angle θ is formed with respect to the acceleration direction of the gas plasma. And a step of injecting the accelerated gas plasma toward the surface of the substrate to be processed arranged. 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; A throat part connected to the gas introduction part and configured to have a minimum cross-sectional area of the entire nozzle, and a throat part connected to the throat part, and the cross-sectional area gradually expands at a predetermined spread angle to take the maximum cross-sectional area. And a gas injection unit configured as described above, and a supersonic velocity that constitutes a gas flow path that accelerates the gas passing through the nozzle to be adiabatically expanded and injected from the gas injection unit at a flow velocity higher than the sonic velocity. A nozzle, plasma generation means for plasma-exciting a gas passing through the nozzle in a part of the flow path of the supersonic nozzle, and an inclination angle θ with respect to the acceleration direction of the gas plasma Surface treatment apparatus is characterized in that comprising a substrate supporting means for supporting the substrate to be processed 3. A sun including a first electrode formed on a surface of a substrate, a polycrystalline silicon thin film sequentially laminated on the first electrode, and a second electrode laminated further on the polycrystalline silicon thin film. In the battery, the semiconductor device, wherein the polycrystalline silicon thin film has a pin or pn structure having a constant film thickness ratio throughout. 4. A method of forming a semiconductor device by sequentially laminating a first electrode, a silicon thin film having a pin or pn structure, and a second electrode on a substrate surface, wherein the step of forming the silicon thin film comprises: A step of generating a gas plasma by supplying a reactive gas into the electric field to excite the plasma; a step of adiabatically expanding the gas plasma and accelerating the gas plasma in a desired direction so as to have a flow velocity higher than a sonic velocity; A step of injecting the accelerated gas plasma toward the surface of the substrate that is inclined so as to have an inclination angle θ with respect to the acceleration direction of the gas plasma. A method of manufacturing a semiconductor device, wherein the silicon thin film is formed so as to have a pin or pn structure.