JP2566137B2 - Thin film manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a thin film.

Prior art and its problems Technologies using thin films have become more and more important in recent years. There are various methods for forming this thin film. Among them, the vacuum thin film forming method is an important and indispensable factor in the knowledge industry centered on electronics, electronics industry, watch industry, optical industry such as camera, etc. It has become a technology. For that reason, research on the thin film, its manufacturing method itself, and its application is very active, and new films and methods are being developed one after another.

In particular, the inorganic thin film using the CVD method has been attracting attention because of its excellent film characteristics, and in particular, a film with little damage is obtained, and it is used for various purposes.

In this CVD method, a metal or semi-metal compound gas is fed as a source gas into the reaction chamber, and the inorganic gas is decomposed using energy such as heat or plasma in the reaction chamber and deposited to form a film. Is.

However, in the method of forming an inorganic thin film by the CVD method,
In principle, the presence of the source gas, which is the film component, is essential because the inorganic gas, which is the film component, must be present.
Therefore, if it is not a gas substance, it cannot be contained as a component in the plasma polymerized film, and depending on the film, CV
There is a restriction that it cannot be created by the D method.

In addition, even if gas is present, there are cases where it is extremely toxic and gas control is difficult.

For example, PH ₃ or B ₂ H ₆ gas is used in the conventional plasma CVD method to dope P or B into amorphous silicon. However, not only is the cost of the PH ₃ and B ₂ H ₆ gas high, but it is also extremely toxic, so exhaust gas treatment,
Since it is difficult to handle leaks, unreacted gas in the reaction chamber, etc., it is disadvantageous in terms of cost to deal with them.
Further, for example, when the substance to be doped is a metal, there are many difficulties such as not only the cost of the organic metal but also the danger of explosion and the difficulty of control due to sublimation.

On the other hand, in the film forming method by the sputtering method, a film can be formed by allowing a target to exist, but it is difficult to obtain a film with less damage as compared with the film forming method by the CVD method.

For example, when P or B is introduced, or when a target in which P or B is doped with Si is used and sputtering is performed in hydrogen plasma, hydrogenation is difficult and good photosensitivity cannot be obtained. There are drawbacks.

Also, if sputtering is performed in Ar plasma, the characteristics cannot be achieved due to damage of the film due to Ar. Furthermore, if the Si / P / B ratio is to be changed, it is practically impossible to prepare targets for all desired composition ratios.

Therefore, improvement of the conventional film forming technique is desired.

II Object of the Invention An object of the present invention is to provide a method for manufacturing a thin film, which enables efficient introduction of a dopant component, is easy and safe to manufacture, and is advantageous in terms of cost.

III Disclosure of the Invention Such an object is achieved by the present invention described below.

That is, the present invention allows an inorganic source gas of a metal or semimetal compound to flow between electrodes facing each other, and a plasma atmosphere is provided between the electrodes to form the inorganic source gas on a substrate provided on one of the electrodes. When chemical vapor deposition is performed, the working pressure is set to 0.05 to 5 Pa, and W / (FM) [where W
Is plasma input power (joule / sec), F is the flow rate of the inorganic source gas, M is the molecular weight of the source gas, and the unit of F · M is Kg / s.
ec] value is 10 ⁸ joule / Kg or more, a dopant component is contained in the other of the electrodes or a target provided on the other electrode, and the magnetic field of the substrate surface is applied in a direction orthogonal to the electric field between the electrodes. A method for producing a thin film, in which a magnetic field is applied to have an intensity of 10 to 10,000 G to form an inorganic thin film containing a dopant component of 10 ^{−4 to} 5 at% on the substrate.

IV Specific Configuration of the Invention Hereinafter, the specific configuration of the present invention will be described in detail.

The thin film of the present invention is a thin film formed by chemical vapor deposition by inflowing an inorganic gas under a plasma atmosphere, and is contained in an electrode material that constitutes an electrode used for generating plasma or a target arranged on the electrode. The dopant component to be contained is contained in the thin film.

The main component of the thin film of the present invention is approximately plasma CVD.
All that the law is applicable to are included.

For example, the following compositions are possible. In the following, commonly used source gas is added in parentheses.

(A) a single metal or metalloid Cu (CuCl _3), Al _{[AlCl 3, Al (CH 3)} 3, Al (C 2 H 5)
₃ ], Ti (TiCl ₄ ), Zr (ZrCl ₄ ), Ge (GeI ₂ ), Sn [Sn
_{Cl 4, Sn (CH 3)} 4, Sn (C 2 H 5) 4) ], Co (CoCl _3), C
r (CrI ₂ ), Fe (FeCl ₃ ), Si (SiCl ₄ , SiH ₂ Cl ₂ , SiH ₄ )
Etc. (b) Alloys Alloys of (a) above (c) Carbides SiC (SiCl ₄ + CH ₄ ), TiC (TiCl ₄ + C ₆ H ₅ CH ₃ , TiCl ₄ + C)
H ₄ ), ZrC (C ₆ H ₆ + ZrCl ₄ ), WC (WCl ₄ + C ₆ H ₅ CH ₃ ), etc. (d) Nitride Bn (BCl ₃ / N ₂ + H ₂ ), TiN (TiCl ₄ / H ₂ + N) ₂ ), ZrN, HfN
(HfCl ₄ / H ₂ + N ₂ ), VN (VCl ₄ / H ₂ + N ₂ ), TaN (TaCl ₅ / H ₂
+ N ₂ ), AlN, Si ₃ N ₄ (SiH ₄ + 4NH ₃ ), Th ₃ N ₄ (ThCl ₄ / N ₂
+ H ₂ ), etc. (e) Boride AlB (AlCl ₃ + BCl ₃ ), SiB ₂ (SiCl ₃ + BCl ₃ ), TiB ₂ (T
iCl ₄ + BBr ₃ ), ZrB ₂ (ZrCl ₄ + BBr ₃ ), HfB ₂ (HfCl ₄ + BB
r ₃ ), VB ₂ (VCl ₄ + BBr ₃ ), TaB (TaCl ₄ + BBr ₃ ), WB (W
Cl ₄ + BBr ₃ ), etc. (f) Silicide MoSi (MoCl ₅ + SiCl ₄ ), TiSi (TiCl ₄ + SiCl ₄ ), ZrSi
(ZrCl ₄ + SiCl ₄ ), VSi (VCl ₃ + SiCl ₄ ), etc. (g) Oxide Al ₂ O ₃ (AlCl ₃ / H ₂ + CO), SiO ₂ (SiCl ₄ / H ₂ + CO, SiH ₄
+ O ₂ ), Fe ₂ O ₃ (Fe (CO) ₅ ), ZrO ₂ (ZrCl ₄ / H ₂ + CO)
Etc. (h) Others GaAs _{[Ga (CH 3) 3 + AsH} 3 ], AlAs [Al (CH _{3) 3} + As
H ₃ ], etc.

In a plasma atmosphere using such a source gas
In performing the chemical vapor deposition by the CVD method, in the present invention,
The electrode material that constitutes the electrode used to generate the plasma is used, or the target is placed on the electrode.

That is, the target is placed on the electrode, or when the target is conductive, the target itself is used as the electrode.

In such a case, the target dopant is contained in the electrode or target used.

Avoid using gases that are traditionally highly toxic or expensive (eg PH ₃ , B ₂ H ₆ etc.) as dopants contained in the electrode material or target and are expensive and in some cases dangerous P, B, As, Al, Zn, Bi, S, Be, T from the standpoint of not using organic metal with properties
i, V, Ge, Ta, Pb, Cd, Ga, Be, Sn, Si and the like are used.

From the standpoint that it is difficult to dope a plasma polymerized film by the conventional CVD method, Mn, Sm, Er, Fe, Cr, Te, Co,
W, Ni, etc. are used.

Such dopants may themselves be electrode materials or targets. Alternatively, in general, the main constituent of the thin film to be formed with a dopant may be used as the electrode material or the target. The amount of the dopant in the electrode material or the target is arbitrary, but the amount of the dopant introduced into the thin film is on the order of the so-called doping level, that is, 10 at% or less, particularly 5 at% or less, and therefore the dopant amount is usually 10 ^-4 ~ It is about 5 at%.

The composition when the dopant is added to the electrode material or the target does not necessarily have to be the same as the main composition of the thin film to be formed, and may be appropriately determined according to the film composition. Then, the dopant is added to the main component of the thin film composition while controlling the plasma conditions.

When a source gas is introduced using a carrier gas as needed in a plasma atmosphere using such an electrode material or target and CVD is performed, the source gas and the dopant sputtered from the electrode material or target are deposited to form a thin film. Is formed.

That is, of the desired thin film components, components that cannot be obtained by CVD are obtained from the electrode material or the target.
And the film quality is equivalent to that of the plasma CVD film.

Next, the case of using a Si-based compound gas will be described in detail.

The source gas used is preferably a Si-based inorganic gas and is not particularly limited as long as it is such a gas, but a gas that is a gas at room temperature is preferable from the viewpoint of operability.

Specifically, SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , SiF ₄ , Si ₂ F ₆ , SiC
l ₄ , Si ₂ Cl ₆ , SiBr ₄ , Si ₂ Br ₆ , SiHF ₃ , SiHCl ₃ , SiHBr ₃ ,
SiHI ₃ and the like can be mentioned, and among them, SiH ₄ , Si ₂ H ₆ , SiF _{4 and the} like are preferable. These may be used alone or in combination.

The material of the electrode material or the target may be any material containing Si and a dopant, and specific examples thereof include amorphous silicon containing the dopant and polycrystalline silicon.

Avoid using gases that are traditionally highly toxic or expensive (eg PH ₃ , B ₂ H _6, etc.) as dopants contained in the electrode material or target, as well as expensive and in some cases P, B, As, Al, Zn, Bi, S, B from the standpoint of not using dangerous organic metals
e, Ti, V, Ge, Ta, Pb, Cd, Ga, Sn, etc. Mn, from the standpoint that it is difficult to dope plasma polymerized films by the conventional CVD method.
Sm, Er, Fe, Cr, Te, Co, W and Ni are particularly preferable examples.

The dopant content of the target is about 1 to 100 mol%.

A schematic diagram of one embodiment of an apparatus used for forming the thin film of the present invention is shown in FIG.

The raw material gas as described above flows into a predetermined gap between the electrodes 31 and 35. Then, an alternating high voltage of high frequency, for example, is applied between the electrodes.

The target 21 is attached to one electrode 31 of the electrodes 31 and 35.
However, adherends 25 such as substrates are placed on the other electrodes 35 so as to face each other. This way of placing is
The reverse is also possible. Also, as mentioned above, Target 21
Can also serve as an electrode.

In this case, the temperature of the adherend 25 is usually 0 to 1500 ° C.

The electrode 35 is connected to the frequency variable power source 4, and the other electrode 31 is grounded. The connection between the power supply and ground may be reversed. Further, a bias potential may be applied.

With such a structure, the dopant component contained in the target 21 can be introduced into the thin film formed on the adherend 25.

The portion 10 surrounded by the dotted line in FIG. 1 is usually installed in a vacuum chamber.

Such a thin film is formed under the following conditions. That is, W / (FM), which is a numerical value of how much plasma energy is given per introduced gas weight, where W is plasma input power (joule / sec) and F is an inorganic source gas (source gas). ) Flow rate, M is the molecular weight of the source gas F ・ M
The unit of Kg / sec] is 10 ⁸ joule / Kg or more, especially 1
It is preferably performed at a rate of 0 ⁹ joule / Kg or more. This value is 10
^If it is less than ⁸ joule / Kg, the dopant in the electrode material or the target cannot be efficiently taken into the film. The electrode area of the electrodes 31 and 35 shown in FIG. 1 is arbitrary, and the gap length between the electrodes 31 and 35 (the length indicated by g in the figure)
Can be set to a value that allows the most efficient depodization depending on the output of the plasma power supply and the electrode structure.

The flow rate of the raw material gas flowing between the electrodes depends on the plasma power supply output of the apparatus, and may be selected so that W / (FM) is equal to or more than the above value.

As the plasma generation source, any of a high frequency power source, a microwave power source, a direct current power source, an alternating current power source and the like can be used.

 The working pressure in the vacuum chamber shall be 0.05Pa-5Pa.

If this value is less than 0.05 Pa, plasma is not stably generated and the film cannot be efficiently created.If it exceeds 5 Pa, the mean free path becomes short and most of the dopant is trapped during film formation. Because it does not get lost. In the present invention, as shown in FIG. 1 (in FIG. 1, the magnetic field B is applied in the direction of the arrow), a so-called orthogonal electromagnetic field is applied in which a magnetic field is applied in a direction substantially perpendicular to the electric field. It is particularly preferred to have a shape.

By using the magnetic field in this way, the dopant can be effectively taken into the film.

Examples of such a system include a coaxial magnetron and a flat plate magnetron, but are not particularly limited.

In this case, the magnetic field strength on the surface of the adherend is about 10 to 10,000 G.

The film thickness, the content of the dopant component, the optical properties of the film (refraction) can be controlled by controlling the above W / (FM) during film formation, or by controlling the raw material gas flow rate, the raw material gas composition, and the operating pressure. It is possible to control the surface properties (contact angle, surface energy) of the film, the physical properties of the film (film hardness) and the like. As a carrier gas, Ar, N ₂ , He,
H ₂ , H ₂ / Ar mixed gas, etc. can be used.

In addition to the above-mentioned source gases, H ₂ , O ₂ , O ₃ , H ₂ O, N
_{2, NO, N 2 O,} NO X , such as NO _2, NH _3, CO, a reactive gas such as CO ₂ may be added as an additional gas 1 or more.

The molecular weight of such reactive gas or carrier gas is not considered as the molecular weight M of the raw material gas when calculating the above W / (FM) value.

An outline of the principle of chemical vapor deposition in a plasma atmosphere is that when a gas is kept at a low pressure and an electric field is applied, the small amount of free electrons present in the gas has a very large intermolecular distance compared to atmospheric pressure. , Receives electric field acceleration and acquires kinetic energy (electron temperature) of 5 to 10 eV.

When the accelerated electrons collide with atoms or molecules, they decompose atomic orbitals and molecular orbitals, and dissociate these into electrons, ions, neutral radicals, and other normally unstable chemical species.

The dissociated electrons are again accelerated by the electric field to dissociate another atom or molecule, and the chain action immediately turns the gas into a highly ionized state. And this is called plasma gas.

Since gas molecules have few opportunities to collide with electrons, they do not absorb much energy and are kept at a temperature close to room temperature.

Thus, the kinetic energy of electrons (electron temperature)
The system in which the thermal motion (gas temperature) of molecules is separated is called low-temperature plasma, and here, a situation has been created in which the chemical species can proceed the additive reaction while keeping the original form relatively. Is used to form a thin film on an adherend. Since low temperature plasma is used, there is no problem with the thermal effect on the adherend.

The thickness of the thin film thus formed is usually 10 to 50000Å
It is a degree.

An ellipsometer or the like may be used to measure the film thickness.

Further, in the case of Si type, the Si content of the thin film is 75 to 99.9 at%, and the content of the element of the dopant component is 10 ^{−4 to} 5 at%.

The analysis of the content of such elements may be performed according to SIMS (secondary ion mass spectrometry) or the like. When SIML is used, it may be calculated by counting Si and other elements on the surface of the thin film.

Alternatively, while performing ion etching with Ar, etc.,
Alternatively, the profiles of other elements may be measured and calculated.

Regarding the measurement of SIMS, Surface Science Basic Course Volume 3 (1984) Surface Analysis Basics and Applications (p70) “SIMS and LAM
MA ".

In addition, it can be measured by Auger, ESCA, ion microanalyzer (IMA), etc., but the most sensitive one is that it can measure a wide range of compositions.
SIMS.

By appropriately using the method for producing a thin film of the present invention, a film containing a dopant component or a film not containing a dopant component by arranging or removing the target or by using a target having a different kind of dopant component contained Alternatively, the film can be continuously laminated with a film containing another kind of dopant component.

The thin film of the present invention, which is a Si-based film, is effectively applied to a solar cell, a photosensitive drum, a photosensitive sensor, and the like.

V. Specific Actions and Effects of the Invention The present invention is to obtain a chemical vapor deposited thin film by injecting a source gas in a plasma atmosphere, and to form an electrode for generating plasma into an electrode material or a plasma atmosphere. The thin film is obtained by introducing the dopant component contained in the arranged target, and the dopant component which is difficult to be introduced by the CVD method can be efficiently and easily doped. Moreover, since it is not necessary to use a gas that is highly toxic or expensive, it is advantageous in terms of cost and safety.

Further, when the manufacturing method of the present invention is applied, control of the amount of dopant components, control of film thickness, etc. become extremely easy. By appropriately applying the manufacturing method of the present invention, it is possible to continuously form a film in which the kind of the dopant component is changed or the dopant component is removed.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail by showing specific examples of the invention.

Example As shown in FIG. 2, a solar cell 5 was produced by laminating each layer on a glass substrate.

First, a SnO ₂ film 52 having a thickness of 2000 Å was formed on a glass substrate (5 cm × 5 cm × 1 mm) 51 by sputtering. Using this as an adherend, P-doped α-amorphous silicon (molar ratio of Si: P = 1: 1: 1) was applied to a part of the surface of the SnO ₂ film 52 using a device having the same basic structure as in FIG. ) Target SiH ₄
Is used as a source gas (flow rate 5SCCM), and a H ₂ / Ar mixed gas (H ₂ amount 5 vol%: flow rate 2SCCM) is introduced as a carrier gas, respectively, and a P-doped Si amorphous film (hereinafter referred to as P-Si amorphous The so-called "membrane" 53 was formed to a thickness of 200Å. P content in the film is 1
was at%.

In this case, the temperature of the adherend is 300 ° C and the gas pressure is 0.5Pa.
While maintaining at 1000W, 13.56MHz high-frequency power source, a so-called orthogonal electromagnetic field with a static magnetic field of 600G (membrane surface) was applied, and the W / (FM) value was 8.4 × 10 ⁹ . did. The film formation time was 3 minutes.

The electrodes 31 and 35 were Si electrodes, and the length g of the gap between the electrodes 31 and 35 was 3 cm.

Next, using the same device, except for the above target,
An Si amorphous film 54 was formed on the P-Si amorphous film 53 to a thickness of 5000Å.

In this case, the flow rate of SiH ₄ is 50 SCCM, carrier gas (H ₂ / A
r) The flow rate of the mixed gas is 500 SCCM, and the temperature of the adherend is 200
~ 350 ℃, 500W, 13.56 while maintaining the gas pressure at 50Pa
A high frequency power source of MHz was used. In this case, since no dopant was added, the amount of SiH ₄ gas was increased, the reaction pressure was increased, and the W / (FM) value was set low. The film formation time was 25 minutes.

Further, using the same apparatus on the Si amorphous film 54, the target is B-doped α-amorphous silicon (molar ratio Si: B = 20: 1), and the B-doped Si amorphous film ( Hereinafter, a B-Si amorphous film) 55 was formed to a thickness of 100 Å. The B content in the film was 0.05 at%.

The conditions in this case were the same as those for forming the P-Si amorphous film 53, and only the gas pressure was changed to 1 Pa. The film formation time was 2 minutes.

Furthermore, an ITO film with a thickness of 500 Å is formed on the B-Si amorphous film 55.
56 was provided by sputtering.

The SnO ₂ film 52 and the ITO film 56 of the laminated body manufactured in this way
Al electrodes 57 and 58 were installed on the respective surfaces to form a solar cell 5.

When the conversion efficiency of the solar cell 5 thus manufactured was measured, it was 8.1%, which was practical.

Further, by using the manufacturing method of the present invention, P and B
Si amorphous film containing Si as a dopant component can be easily manufactured, and P-Si amorphous film, Si amorphous film, B-
It was also confirmed that the Si amorphous film can be continuously formed.

 From the above, the effect of the present invention is clear.

In the above solar cell, P-Si amorphous film and B-
An attempt was made to form a Si amorphous film without applying a static magnetic field, and as a result, P or B was hardly incorporated into the film and the solar cell did not operate. Further, when the P-Si amorphous film and the B-Si amorphous film were manufactured, the W / (FM) value was
When an attempt was made under the condition of 10 ⁷ joule / kg (SiH ₄ 30SCCM, W = 7W), no film could be formed with or without applying a magnetic field.

[Brief description of drawings]

FIG. 1 is a schematic view showing one mode of a thin film manufacturing apparatus used for manufacturing the thin film of the present invention. FIG. 2 is a cross-sectional view of a solar cell manufactured by applying the thin film of the present invention. Explanation of symbols 1 ... Thin film manufacturing equipment, 21 ... Target, 25 ... Adherend, 31, 35 ... Electrodes, 4 ... AC and variable frequency power supply, → B ... Magnetic field direction (arrow), g ...... electrode gap length, 5 ...... solar cell, 51 …… glass substrate, 52 …… SnO ₂ film, 53 …… P-Si amorphous film, 54 …… Si amorphous film, 55 …… B-Si amorphous film, 56 ... ITO film, 57,58 ... Al electrode

Claims (2)

(57) [Claims] 1. An inorganic source gas of a metal or semi-metal compound is introduced between electrodes facing each other, a plasma atmosphere is provided between the electrodes, and the inorganic source gas is placed on a substrate provided on one of the electrodes. When performing chemical vapor deposition, the working pressure is 0.05 to 5 Pa, W / (FM) [where W is the plasma input power (joule / sec), F is the flow rate of the inorganic source gas, and M is the source gas. The unit of F / M in molecular weight is Kg / se
c] value is 10 ⁸ juele / Kg or more, a dopant component is contained in the other of the electrodes or a target provided on the other electrode, and the magnetic field of the substrate surface is perpendicular to the electric field between the electrodes. A method for producing a thin film, wherein a magnetic field is applied to have an intensity of 10 to 10,000 G to form an inorganic thin film containing a dopant component of 10 ^{−4 to} 5 at% on the substrate. 2. The method for producing a thin film according to claim 1, wherein the inorganic source gas is Si-based.