JP3505987B2 - Method and apparatus for forming silicon-based thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a silicon-based thin film used as a material for a TFT (thin film transistor) switch provided in each pixel of a liquid crystal display device, or used for an integrated circuit, a solar cell and the like. The present invention relates to a film forming apparatus capable of carrying out the method.

[0002]

2. Description of the Related Art The following method has been conventionally used as a method for forming a silicon-based thin film. That is, as a method of forming a silicon film, particularly a crystalline silicon film, CVD is used.
The method, especially the thermal CVD method is often used. In order to form a crystalline silicon film by the CVD method, it is usually necessary to keep the temperature of the film-formed article at 800 ° C. or higher. Also,
A PVD method such as a vacuum vapor deposition method or a sputter vapor deposition method is also used, but in this case also, in order to make the film crystalline, it is usually necessary to keep the temperature of the film-forming article at about 700 ° C. or higher. There is.

Further, in recent years, after forming an amorphous silicon film at a relatively low temperature by various CVD methods or PVD methods, as a post-treatment, heat treatment at about 800 ° C. or higher or at 600 ° C. for a long time of about 20 hours or longer. Heat treatment or laser annealing treatment is performed to form the film into a crystalline silicon film. Further, as a method of forming a silicon oxide film, a silicon nitride film or the like as a silicon compound film, a plasma CVD method or the like is often used.

[0004]

However, as described above, depending on the method of directly forming the crystalline silicon film by various CVD methods or PVD methods, for example, a relatively inexpensive low melting point glass as a glass substrate of a liquid crystal display device. Using
When a crystalline silicon film is formed to form a TFT on this substrate, the low melting point glass is 700
If it is kept at ℃ or 800 ℃, it will melt and distortion will occur. As described above, it is difficult to form a film on an article made of a material having relatively low heat resistance by the method of directly forming the crystalline silicon film by the CVD method or the PVD method.

Further, the method of obtaining a crystalline silicon film by performing the above-mentioned heat treatment or laser annealing treatment as a post-treatment has a large number of steps as compared with the method of directly forming a crystalline silicon film, and thus the productivity is poor. The laser annealing treatment has the drawbacks that the laser irradiation apparatus is expensive and it is difficult to obtain a film having a large area and good uniformity. Also, plasma C
When a silicon compound film is formed by the VD method, particles unnecessary for film formation are generated by a gas phase reaction and are easily mixed in the film, hydrogen is easily mixed in the film, and defects in the film are easily generated. The film obtained from the above has relatively poor electrical insulation, and further tends to have large internal stress and poor adhesion.

Therefore, the first object of the present invention is to provide a method for forming a silicon-based thin film, which can form a high-quality silicon-based thin film having desired characteristics with good productivity at a relatively low temperature.
And the subject. A second object of the present invention is to provide a method for forming a silicon-based thin film capable of forming a high-quality silicon film with good productivity at a relatively low temperature, typically a silicon film having good crystallinity. To do.

A third object of the present invention is to provide a method for forming a silicon-based thin film capable of forming a silicon compound film having good electrical insulation and film adhesion with good productivity at a relatively low temperature. To do. A fourth object of the present invention is to provide a film forming apparatus capable of forming a silicon-based thin film such as such a silicon film (typically a crystalline silicon film) and a silicon compound film.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted extensive research and obtained the following findings a to c. I. In converting the source gas containing a silicon-based gas into plasma and forming a silicon film under the plasma, for example,
The article is irradiated with an ion beam, and at this time, high-energy particles (fast ions, fast electrons, etc.) from the plasma are suppressed from entering the film-forming article, or the incident energy of the ion beam to the article is further reduced. Is controlled to a low level, the crystal growth can be promoted without damaging the film growth surface. B. Similarly, if a silicon compound film such as a silicon oxide film is formed, the amount of particles in plasma mixed into the film is reduced, the defects in the film and the hydrogen concentration in the film are reduced, and the film stress is relaxed. A film having excellent electric insulation and film adhesion can be obtained. C. At this time, by using a negative ion beam as the ion beam for irradiation, the ion irradiation can be performed even if the film formation surface of the film formation article or / and the film to be formed is made of an electrically insulating material. Positive charges on the surface of the article due to the negative ions are canceled by the negative ions, and the reduction of the ion irradiation effect due to the charge on the surface of the article or / and the film can be avoided.

Based on the above findings, the present invention provides the following method of forming a silicon-based thin film and the film forming apparatus of (a). A method of forming a raw material gas containing a silicon-based gas into plasma by supplying power, and forming a silicon-based thin film on a film-forming article under the plasma, the plasma being formed in the vicinity of the peripheral portion of the article, A method for forming a silicon-based thin film, comprising forming a film by irradiating the surface of the article with a negative ion beam. (a) The raw material gas supplied by the raw material gas supply means into the plasma generation chamber connected to the vacuum exhaust means is turned into plasma by the power supply by the gas plasmaization power supply means,
An apparatus for forming a film under the plasma on a film-formed article supported by a supporting means in the plasma generation chamber, the apparatus including means for irradiating the film-formed article with a negative ion beam. The film forming apparatus is characterized in that the power supply means can form the plasma in the vicinity of the peripheral portion of the film formation target article.

According to the method for forming a silicon-based thin film and the film forming apparatus of (a) of the present invention, by forming plasma in the vicinity of the peripheral edge of the film-forming article, fast ions (about 500 eV) from the plasma are formed. Since the high incidence of ions (higher energy) and high-speed electrons are suppressed from directly entering the film-formed article, when forming a silicon film, the growth of a good-quality silicon film that does not damage the film growth surface and has few defects. Is prompted. At the same time, by irradiating the surface of the article with an ion beam and appropriately selecting or adjusting the ion species and the ion acceleration energy, effects such as surface excitation, crystallinity improvement, and crystal orientation control can be obtained, and the movement of silicon atoms or Migration can be promoted, and a silicon film having good crystallinity can be formed on a film-formed article.

In this case, the film can be crystallized at a relatively low temperature. Further, since the silicon film having such crystallinity can be obtained in one step, the heat treatment after film formation can be omitted, and the productivity is good. Furthermore, by performing ion beam irradiation, the ion species is selected or the ion acceleration is performed at the time of the surface treatment of the interface between the film and the film-forming article, during the film formation, and during the surface treatment after the film formation. By adjusting the energy or by combining these, it is possible to perform film stress control, and thus film adhesion control, crystallinity control, crystal grain size control, crystal orientation control, and the like. In plasma CVD, the energy of reactive species due to plasma excitation covers a wide range of several eV to several 100 eV, and thus it is difficult to perform such control by simple plasma CVD.

When forming a silicon compound film,
By forming plasma in the vicinity of the peripheral portion of the film formation target object, direct incidence of fast ions (ions having energy higher than about 500 eV) or high speed electrons from the plasma on the film formation target object is suppressed. The growth of a silicon compound film with few defects is promoted without damaging the film growth surface. At the same time, the article surface is irradiated with an ion beam,
By properly selecting or adjusting the ion species and the ion acceleration energy, effects such as reduction of hydrogen concentration in the film, reduction of defects in the film, improvement of denseness of the film, and relaxation of film stress can be obtained, and good electrical conductivity can be obtained. A silicon compound film having insulation and film adhesion can be obtained.

Further, upon ion beam irradiation, an ion species is selected at the time of the interface treatment between the film and the article to be film-formed, during the film formation and at the time of the surface treatment after the film formation.
Alternatively, by controlling the ion acceleration energy, or by combining these, it is possible to perform film stress control and thus film adhesion control. When the article to be film-formed has a surface made of an electrically insulating material, or (and)
When an electrically insulating film such as a silicon compound film such as a silicon oxide film is formed, secondary electrons are emitted from the article or / and the surface of the film being formed by ion beam irradiation, and the article is then formed. Or (and) the film surface tends to be positively charged. In the conventional ordinary ion beam irradiation, positive ions mainly present in the plasma of the ion source gas are extracted to irradiate the film-forming article, and therefore, such an article surface or / and a film surface is positively charged and Along with this, the ion beam irradiation effect is likely to be reduced. On the other hand, according to the method of the present invention and the apparatus of (a), since the negative ions existing in the plasma of the ion source gas are extracted and irradiated to the film formation target, even if the surface thereof is an electrically insulating material. Even when a film-forming article consisting of, or (and) the film to be formed is an electrically insulating film such as a silicon compound film such as a silicon oxide film, the article or ( And) The negative ions cancel out the tendency of the film surface to be positively charged, and the reduction of the ion beam irradiation effect due to the charging of the surface is avoided. Also, device damage due to positive charging of the article or / and the membrane surface is avoided.

Further, in order to form the plasma in the vicinity of the peripheral edge of the article to be film-formed, as a specific example, in the apparatus of (a), the electrode included in the power supply means is:
Any one of a ring-shaped electrode, a cylindrical electrode, a coil-shaped electrode, a rigidano coil type electrode, a ring-shaped microwave introduction antenna, and the like facing the peripheral portion of the film-forming article may be adopted. The ion beam irradiation means may be capable of irradiating the film-forming target with an ion beam through the opening of the electrode.

Incidentally, in "a ring-shaped electrode, a cylindrical electrode, a coil-shaped electrode, a rigidano coil-type electrode, a microwave introducing antenna" which opposes the peripheral portion of the film-forming article, the electrode or the antenna is the film-forming article. In the state of facing the peripheral edge,
Not only when they literally face the peripheral edge of the film-forming article, but also at a position facing the peripheral edge so that plasma can be formed near the peripheral edge of the film-forming article, a position related to the peripheral edge, and the like. The case where it is arranged is also included. The same applies to this point hereinafter.

When using the ring-shaped electrode, the cylindrical electrode, or the coil-shaped electrode, a high-frequency power source is typically used as a power source included in the gas plasma power supply means. In the case of using the above-mentioned electrode of the rigid coil type, in order to obtain electron cyclotron resonance (ECR) plasma, a microwave power source is usually used as a power source and a magnetic field forming means is provided on the outer peripheral portion of the electrode of the rigid coil type. . In addition, a ring-shaped electrode, a cylindrical electrode,
When using the coiled electrode or the microwave introducing antenna, the magnetic field forming means may be provided on the outer peripheral portion of the antenna. By forming a magnetic field in this way, it becomes easy to form and maintain plasma even under a low pressure (under a high vacuum).

Based on the above findings, the present invention also provides the following silicon-based thin film forming method and (b) film forming apparatus. A method for forming a silicon-based thin film on an article to be film-formed under the plasma from a source gas containing a silicon-based gas by supplying electric power, wherein the degree of vacuum near the surface of the article is 1 × 10 ⁻³ Torr. A method for forming a silicon-based thin film, characterized in that the film is formed by irradiating the surface of the article with a negative ion beam while the film thickness is adjusted to 1 × 10 ⁻⁶ Torr. (B) The raw material gas supplied by the raw material gas supply means into the plasma generation chamber connected to the vacuum exhaust means is turned into plasma by the power supply by the gas plasmaization power supply means, and the inside of the plasma generation chamber is supported under the plasma. An apparatus for forming a film on a film-formed article supported by the means, the apparatus including means for irradiating the film-formed article with a negative ion beam, for forming a film on the film-formed article. The degree of vacuum in the vicinity of the surface of the article to be film-formed is 1 × 10 ⁻³ Torr to 1 × 1.
A film forming apparatus characterized in that it can be set to 0 ^-6 Torr.

According to the method for forming a silicon-based thin film and the film forming apparatus of (b) of the present invention, the degree of vacuum near the surface of the film-formed article is as high as 1 × 10 ⁻³ Torr to 1 × 10 ⁻⁶ Torr. By making a vacuum (low pressure), it is possible to irradiate the article surface with an ion beam, and by appropriately selecting or adjusting the ion species and ion acceleration energy,
When a silicon film is formed, effects such as surface excitation, improvement of crystallinity, control of crystal orientation are obtained, migration of silicon atoms is promoted, and a silicon film having good crystallinity is formed on an article to be film-formed. It Similarly, when a silicon compound film is formed, the surface of the article can be irradiated with an ion beam, and the ion species and the ion acceleration energy are appropriately selected or adjusted to reduce the hydrogen concentration in the film and the defects in the film. It is possible to obtain a silicon compound film having good electric insulation and film adhesion, since effects such as reduction of temperature, improvement of film density, and relaxation of film stress can be obtained.

Further, 1 × 10 ^-3 Torr to 1 × 10 ^-6 T
To turn the gas into plasma under a high vacuum called orr,
The vapor phase reaction is suppressed, the generation of unnecessary dust particles is reduced, the adhesion of impurities to the surface of the film-forming article or the film growth surface is suppressed, and a high-quality silicon film (typically a crystalline silicon film) or A silicon compound film having good electrical insulation can be obtained. In addition, since the gas is turned into plasma under high vacuum, the diffusion region of radicals contributing to film formation is widened, and thus a silicon-based thin film can be formed on a film-forming article having a large area. Furthermore, in the film forming step, the film does not adhere to the inner surface of the container where the film is formed, and the maintenance such as cleaning becomes easier.

Other functions and effects are similar to those of the above method and the device (a). Also in the method and the apparatus (a), it is considered that the degree of vacuum in the vicinity of the surface of the article to be film-formed is set to 1 × 10 ⁻³ Torr to 1 × 10 ⁻⁶ Torr. A silicon film (typically a crystalline silicon film) or a silicon compound film having good electric insulation can be obtained more efficiently.

The above method of the present invention and (a),
In the apparatus of (b), negative ion beam irradiation is performed as follows. In normal plasma, positive ions are mainly present as ions, and the existence probability of negative ions is low, but negative ions are generated by supplying high-frequency power with a high frequency of about 100 MHz or more to the ion source gas to generate plasma. It is possible to obtain a plasma having a high abundance ratio of. The upper limit of the frequency is not particularly limited, but considering the cost of the device and the like, up to about 3000 MHz is suitable. The frequency is more preferably about 100 MHz to 1000 MHz, and typically about 500 MHz. Then, the negative ions in the plasma are extracted by applying an appropriate extraction voltage, and the film-formed article is irradiated with the negative ions.

Since the electrons in the plasma can follow the power with the power of about 13.56 MHz which is usually used, the electron velocity (electron temperature) becomes relatively high as the power is supplied. On the other hand, when high-frequency power with a high frequency of 100 MHz or more is supplied and the raw material gas is made into plasma, the electrons cannot follow this high-frequency power, and as a result, the electron velocity (electron temperature) becomes low, and this low-speed electron is the source gas molecule Negative ions are generated by attaching to.

The above method and (a) and (b)
In this device, a magnetic field is formed as an energy filter in a region where the ion source gas is turned into plasma, and the electrons in the plasma are captured by the magnetic field, so that low-speed electrons can be generated more efficiently, and more negative ions are generated. it can. As an energy filter in this case, for example, an N pole is provided on one side and an S pole is provided on the opposite side (in the case of a permanent magnet), or such N pole and S pole can be formed (electromagnet). In the case of 1), the magnet members may be arranged in parallel at predetermined intervals.

Further, the above method and (a),
In the apparatus of (b), a silicon-based gas (monosilane (SiH ₄ ) gas, disilane (Si ₂ H ₆ ) gas, or other hydrogenated silicon gas is used as the source gas for the plasma.
Silicon fluoride gas such as silicon fluoride (SiF ₄ ) gas, silicon chloride gas such as silicon chloride (SiCl ₄ ) gas, tetraethyl-O-silicate (TEOS, S
i (C ₂ H ₅ O) ₄ ) gas or the like), or at least one gas of the silicon-based gas and a reactive gas (hydrogen (H ₂ ) gas, fluorine (F ₂ ) gas, Use of at least one gas selected from hydrogen fluoride (HF) gas, oxygen (O ₂ ) gas, dinitrogen oxide (N ₂ O) gas, nitrogen (N ₂ ) gas, ammonia (NH ₃ ) gas, etc.) You can

As the plasma source gas, oxygen-containing gas such as oxygen (O ₂ ) gas, dinitrogen oxide (N ₂ O) gas, nitrogen (N ₂ ) gas, ammonia (NH ₃ ) gas, TEOS gas, etc. When used as a gas, a silicon compound film such as silicon oxide or silicon nitride can be formed. When a gas containing no such oxygen-containing gas or nitrogen-containing gas is used, a silicon film can be formed.

The above method and (a),
In the apparatus of (b), as the ion species of the ion beam, an inert gas (helium (He) gas, neon (N
e) gas, argon (Ar) gas, krypton (Kr)
Gas, xenon (Xe) gas, etc.), the reactive gas exemplified as the source gas for the plasma, and the ions of at least one gas selected from the silicon-based gases exemplified as the source gas for the plasma can be used.

As the ion species of the ion beam, an oxygen-containing gas such as oxygen (O ₂ ) gas, dinitrogen oxide (N ₂ O) gas, nitrogen (N ₂ ) gas, ammonia (NH ₃ ) gas, TEOS gas, or the like, When a gas based on a nitrogen-containing gas is used, a silicon compound film such as silicon oxide or silicon nitride can be formed. These are electrically insulating films. When a gas containing no such oxygen-containing gas or nitrogen-containing gas is used, a silicon film can be formed. In addition,
In any case, a gas containing a silicon-based gas is used as the plasma source gas.

When the inert gas ions are used for forming the silicon film, physical excitation control for crystallization becomes possible. In addition, hydrogen (H) of the reactive gas and the silicon-based gas is used in forming the silicon film.
Alternatively, (and) when a gas containing fluorine (F) is used as an ionic species, hydrogen atoms and fluorine atoms bond with silicon atoms in an amorphous phase in the film and vaporize them, thereby promoting crystallization of the film. Thus, dangling bonds in the silicon-silicon network and defects in the film are reduced, and a silicon film having higher quality crystallinity can be formed.

Since the ion source gas diffuses from the ion source into the film forming container, and conversely the source gas inside the film forming container diffuses into the ion source, the same gas is used as the film forming source gas and the ion source gas. When used, the gas may be introduced into the film forming container as the film forming raw material gas or may be introduced into the ion source as the ion starting material gas for both of them.

Further, it is preferable to irradiate the film-formed article with a low energy of about 10 eV to 500 eV. More preferably, it is about 30 eV to 100 eV. As a result, when forming a silicon film,
A silicon film having higher quality crystallinity can be formed without hindering the effects of surface excitation, crystallinity improvement, crystal orientation control, etc. by irradiating the film-forming article with an ion beam. When forming a silicon compound film,
It is possible to form a silicon compound film having good electrical insulation and film adhesion by obtaining effects such as reduction of hydrogen concentration in film, reduction of defects in film, improvement of film compactness, relaxation of film stress. it can.

Further, the above method and (a),
In the device of (b), by controlling the supply amount of the raw material gas and the magnitude and frequency of the electric power for converting the gas into plasma, the energy of the ions incident on the surface of the film-forming article from the plasma is made larger than 0 eV. It can be 500 eV or less, or low-energy radical species can be preferentially diffused from the plasma to the surface of the film-formed article. Thereby, the migration of silicon atoms can be promoted, and a silicon film having higher quality crystallinity can be formed on the film formation target article. Further, it is possible to form a silicon compound film having a good electrical insulating property with few defects without damaging the film growth surface.

The density of radical species can be controlled by adjusting the frequency of the gas plasma generation power. Further, the above method and (a) and (b)
In the apparatus, at least one gas of the inert gas, the reactive gas and the silicon-based gas is used as the ion species of the ion beam, and at least the silicon-based gas is used as a source gas of the plasma. One kind of gas, or at least one kind of gas of the silicon-based gas and at least one kind of gas of the reactive gas is used, and at this time, the number of silicon atoms and negative ions from plasma reaching the surface of the film-forming article. The ratio of the number of negative ions in the beam (Si / i transport ratio) to 0.
It is preferably about 1 to 100. This is Si /
This is because when the i transport ratio is smaller than 0.1, the amount of ions becomes excessive and film defects are likely to occur, and when it is larger than 100, the effect of promoting crystallization by ion irradiation becomes insufficient. Because.

The number of silicon atoms reaching the surface of the film-forming article can be controlled while monitoring the film thickness, and the number of negative ions reaching the surface of the film-forming article is the extraction voltage of ions from the ion source. It can be controlled by, for example, controlling the electric power for generating plasma in the ion source. In addition, the above method and (a),
In the apparatus (b), the temperature of the film-forming article is set to room temperature to 60.
It can be about 0 ° C. More preferably 300
It is in the range of ℃ to 600 ℃. According to the method and apparatus of the present invention, it is possible to obtain a silicon film (typically a crystalline silicon film) or a silicon compound film having good crystallinity at such a low temperature as compared with the conventional method. When the temperature is lower than room temperature, for example, in the case of a silicon film, an amorphous component is likely to increase in the formed silicon film, and the crystallinity may be lowered rather.

Further, the above method and (a),
In the apparatus of (b), when it is necessary to form a silicon film having higher crystallinity, after film formation, as a post-treatment,
The silicon film may be heat-treated at about 300 to 600 ° C. The heat treatment temperature is more preferably 400
It is in the range of ℃ to 600 ℃. The hydrogen concentration in the silicon-based thin film obtained by the above method can be set to 1 × 10 ²¹ cm ⁻³ or less, which is about one digit lower than that of the silicon-based thin film obtained by the ordinary CVD method. In the case of forming a crystalline silicon film, the hydrogen concentration in the film is set to a low value in this way, and the above-mentioned post-treatment makes it possible to form a silicon film having less voids and higher crystallinity. Further, the heating temperature can be lowered and the heating time can be shortened as compared with the conventional post-treatment performed for crystallization.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a diagram showing a schematic configuration of an example of a silicon-based thin film forming apparatus according to the present invention. This apparatus has a plasma generation chamber C, and the chamber C is connected to a vacuum exhaust unit 18 and a source gas supply unit 12. The raw material gas supply unit 12 includes a raw material gas source, a mass flow controller and the like, but these are not shown. Further, a film-forming article holding member 11 is installed in the chamber C, and the holding member 11 can be horizontally reciprocated by a driving unit (not shown) to carry the film-forming article 10 in and out. It is arranged on the heater 9 for heating. In addition, a cylindrical electrode 14 a is installed at a position facing the peripheral edge of the film-forming article 10 held by the holding member 11. A high frequency power supply 17a is connected to the electrode 14a via a matching unit 16. Also, the plasma generation chamber C
A magnet 100b for applying a magnetic field for maintaining stable plasma is provided at a position corresponding to the cylindrical electrode 14a on the outer periphery of the.

An ion source 2 having a circular cross section is provided at a position facing the holding member 11 with the cylindrical electrode 14a interposed therebetween. An ion source gas supply unit 1 is connected to the ion source 2, and a high frequency power source 4 is connected to the ion source 2 via a matching unit 3 for gas plasma conversion. In addition, a magnet 100a is also provided around the ion source 2 to enter a magnetic field for maintaining stable plasma. The gas supply unit 1
Also, a gas source and the like are included, but these are not shown. Further, the ion source 2 has three electrodes for extracting ions (acceleration electrode, deceleration electrode,
It has an extraction electrode system 21 composed of a ground electrode). An acceleration power supply 5 and a deceleration power supply 6 are connected between the extraction electrode system 21 and the ion source 2. Further, in the ion source 2, a plurality of bar-shaped magnets B arranged in parallel in the horizontal direction at predetermined intervals are provided, and these constitute an energy filter. A plan view of an energy filter including a plurality of rod-shaped magnets B is shown in FIG. The excitation method of the ion source 2 is a high frequency type here, but other types such as a filament type and a microwave type can be adopted. Further, the extraction electrode system is not limited to the three-electrode structure, and may be one to four electrodes.

In carrying out the method of the present invention using this apparatus, the article 10 to be film-formed is held by the holding member 11 and carried into the plasma generation chamber C and set at a predetermined film-forming position on the heater 9. At the same time, the inside of the chamber C is set to a predetermined degree of vacuum by operating the vacuum exhaust unit 18. Next, the raw material gas supply unit 1
2 introduces a raw material gas containing a silicon-based gas into the plasma generation chamber C from 2 and supplies high frequency power from the high frequency power supply 17a to the cylindrical electrode 14a through the matching device 16 to plasmaize the introduced gas, Plasma is formed at a position indicated by middle 13, that is, inside the cylindrical electrode 14a and in the vicinity of the peripheral edge of the film-forming article 10. As the source gas, at least one gas of silicon-based gas or at least one gas of silicon-based gas and at least one gas of reactive gas is used.

At the same time, an ion source gas is introduced from the ion source gas supply unit 1 into the ion source 2, and a 100 MHz to 3000 MHz from the power source 4 is supplied to the ion source gas via the matching unit 3.
More preferably, high-frequency power having a high frequency of 100 MHz to 1000 MHz is supplied to generate plasma at a position in the ion source indicated by 8a in the figure. Since the ion source gas is made into plasma by supplying high-frequency power of high frequency of 100 MHz or more, the electrons in the generated plasma cannot follow this power, resulting in electron temperature (velocity).
Will be lower. Further, due to the action of the magnetic field (energy filter) formed by the rod-shaped magnets B arranged in parallel in the ion source, the electrons in the plasma rotate in the magnetic field and become trapped. Then, the low-velocity electrons thus generated adhere to the source gas molecules to generate negative ions, and plasma having a high negative ion abundance ratio is formed at a position 8b in the figure.

Then, by applying an appropriate voltage to the extraction electrode system 21 by the power supplies 5 and 6, negative ions are extracted from the plasma 8b at an acceleration energy of 10 eV to 500 eV, more preferably 30 eV to 100 eV, and the cylindrical electrode 14a is charged. The film-forming article 10 is irradiated with the negative ion beam through the opening. At least one gas selected from an inert gas, a reactive gas and a silicon-based gas is used as the negative ion source gas.

As a result, silicon is deposited on the film-forming article 10.
A system thin film is formed. In addition, here, during film formation,
The degree of vacuum near the surface of the article 10 is 1 × 10^-3Torr ~ 1x
10 ^-6Plasma generation chamber to be within Torr range
Adjust the vacuum degree of. Further, the temperature of the film-forming article 10 is high.
Room temperature to 600 ° C. The method described above
And according to the device, the plasma 13 is mainly around the periphery of the article 10.
Since it is formed at the position facing the part,
Since the degree of vacuum near the surface of the product 10 is high (gas pressure is low),
To fast ion and fast electron article 10 in plasma 13
The amount of incident light is small, and direct incidence is suppressed.
It does not damage the surface and has good crystallinity with few defects.
It has a good electrical insulation with few silicon films or few defects.
The growth of the silicon compound film is accelerated.

Further, the article 10 is irradiated with an ion beam,
Since the irradiation energy is controlled to a low level of 500 eV or less, when a silicon film is formed, the effects of surface excitation, crystallinity improvement, crystal orientation control, etc. due to ion beam irradiation are not hindered and the migration of silicon atoms is prevented. Is promoted to form a silicon film having good crystallinity on the article 10. Further, when a silicon compound film is formed, effects such as reduction of hydrogen concentration in the film, reduction of defects in the film, improvement of film density, and relaxation of film stress can be obtained.
A silicon compound film having good electrical insulation and film adhesion can be obtained.

Further, since a normal ion source extracts and irradiates positive ions mainly existing in plasma, the surface of the article to be deposited and / or the film to be formed is made of an electrically insulating material. In the case of, the irradiation ions emit electrons from the surface of the article or / and the film to positively charge the surface, and it is easy to reduce the effect of subsequent ion beam irradiation. In this case, since the film-forming article is irradiated with the negative ion beam, even in such a case,
The positive charge on the surface of the film-formed article or / and the film is canceled by the negative ions, and the reduction of the ion irradiation effect is avoided.

When forming a silicon film, it is not necessary to raise the temperature of the article 10 above 600 ° C. to crystallize the film during film formation. From this, for example, a glass having a relatively low melting point and an inexpensive glass is used as a glass substrate for a liquid crystal display device, and a crystalline silicon film for a TFT or the like can be formed thereon. Further, since the crystalline silicon film is obtained in one step, the heat treatment after the film formation can be omitted, and the productivity is good. Even when heat treatment is applied because it is necessary to improve the crystallinity, the temperature is 300 ° C to 600 ° C, which is lower than the conventional temperature, and the heating time is conventional (20 hours or more).
Can be shorter.

Further, here, 1 × 10 ⁻³ Torr to 1 ×
Since the raw material gas is turned into plasma under a high vacuum of 10 ⁻⁶ Torr, the gas phase reaction is suppressed, the generation of unnecessary particles is suppressed, and the adhesion of impurities to the film-forming article 10 is suppressed, so that a high quality crystal is obtained. A silicon film having a property or a silicon compound film having a good electric insulating property can be obtained. Further, as described above, since the raw material gas is turned into plasma under high vacuum, the diffusion region of radicals contributing to film formation is widened, and a silicon-based thin film can be formed even on a large-area film-formed article 10. . Further, the amount of film deposited on the inner surface of the plasma generation chamber C is small, and therefore the frequency of cleaning the chamber C is low.

Further, in the apparatus of FIG. 1, the cylindrical electrode 14a is used to form the plasma at the position facing the peripheral edge of the film-forming article, but instead of this, a ring-shaped electrode,
A coiled electrode can also be used. In addition to the cylindrical electrode 14a, a rigid coil type electrode or a ring-shaped microwave introducing antenna is used, and the high frequency power source 17 is used.
A microwave power source can be connected to this instead of a.

When the plasma is not formed on the peripheral portion of the film-forming article, the gas pressure in the plasma generation chamber C is set to 1 × 1.
Even if only 0 ^-3 Torr to 1 × 10 ^-6 Torr is used, irradiation with a negative ion beam can be performed, and crystallization of a silicon-based thin film or reduction of defects in a silicon compound film and improvement of film adhesion can be promoted. . In this case, in the conventional parallel plate type plasma CVD apparatus, an apparatus as shown in FIG. 2 provided with an ion source at a position facing the film-forming article can be used.

This apparatus has a film forming chamber C ', in which a high frequency electrode 14 and a ground electrode 11' facing the high frequency electrode 14 are installed. The electrode 11 'is a holder for supporting the film forming article 10. And also has a heater 9'for heating the article therein. The film forming chamber C'can be evacuated to a desired degree of vacuum by the vacuum evacuation unit 18 ', and the film forming raw material gas can be supplied from the gas supply unit 12'.

A high frequency power source 4'is connected to the high frequency electrode 14 via a matching unit 3 '. In addition, in the film forming chamber C ′,
An ion source 2'for irradiating the film-forming article 10 on the holder 11 'with an ion beam is additionally provided. This ion source 2'has substantially the same structure and operation as the ion source 2 in the apparatus shown in FIG.

In forming a silicon-based thin film by the method of the present invention using this apparatus, the film-forming target 10 is carried into the film-forming chamber C'and set in the holder 11 '. Also,
The film forming chamber C'is evacuated by the operation of the vacuum evacuation unit 18 ', while the source gas is introduced into the film forming chamber from the gas supply unit 12'. By controlling the introduction of the raw material gas or by controlling the introduction of the raw material gas and the exhaust of the exhaust unit 18 ′, the degree of vacuum in the vicinity of the surface of the film ^- forming article 10 is set to 1 × 10 ⁻³ Torr to 1
While maintaining the temperature in the range of × 10 ^-6 Torr and maintaining the temperature of the film-forming article 10 at room temperature to 600 ° C, the electrode 1
High-frequency power is supplied between 4 and 11 'to turn the film-forming raw material gas into plasma. Further, from the ion source 2 ′ to the film-forming article 10
The negative ion beam toward the ion irradiation energy of 10 eV
Irradiation is performed at 500 eV, more preferably 30 eV to 100 eV, and thus a silicon-based thin film is formed on the surface of the article 10 under the plasma 13.

According to this device and method, the device of FIG.
Good crystallinity at relatively low temperature, similar to film formation
It is possible to obtain a silicon film having Good electricity
Obtain a silicon compound film with air insulation and film adhesion
be able to. Next, using the apparatus shown in FIGS.
A concrete example in which a silicon-based thin film is formed by a bright method
And the silicon-based thin film obtained as a result will be described.
In addition, using a conventional parallel plate type plasma CVD device
A comparative example in which a silicon-based thin film is formed will also be described.
In addition, in each of the following Examples and Comparative Examples, the film-forming article was changed.
100 times each. Example 1 (silicon film formation, by the apparatus of FIG. 1)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 100MHz   Raw material gas SiH_Four  50%                                 H₂      50%   Film forming pressure 1 × 10^-FourTorr   Ion beam ion species H^-, SiHx^-               Irradiation energy 100 eV               High frequency for excitation 500MHz   Deposition temperature 300 ℃   Film thickness 1000Å Example 2 (silicon dioxide (SiO 2₂) Membrane formation, by the apparatus of FIG. 1)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 100MHz   Raw material gas SiH_Four  20%                                 N₂O 80%   Film forming pressure 1 × 10^-FourTorr   Ion beam ion species H^-, Ox^-, SiHx^-               Irradiation energy 100 eV               High frequency for excitation 500MHz   Deposition temperature 300 ℃   Deposition film thickness 1500Å Example 3 (silicon nitride (SiN_x) Membrane formation, by the apparatus of FIG. 1)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 100MHz   Raw material gas SiH_Four  20%                                 NH₃    80%   Film forming pressure 1 × 10^-FourTorr   Ion beam ion species H^-, NH_x ^-, SiHx^-               Irradiation energy 100 eV               High frequency for excitation 500MHz   Deposition temperature 300 ℃   Deposition film thickness 1500Å Example 4 (silicon film formation, by the apparatus of FIG. 2)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 100MHz   Raw material gas SiH_Four  50%                                 H₂      50%   Film forming pressure 1 × 10^-FourTorr   Ion beam ion species H^-, SiHx^-               Irradiation energy 100 eV               High frequency for excitation 500MHz   Deposition temperature 300 ℃   Film thickness 1000Å Example 5 (silicon dioxide film formation, by the apparatus of FIG. 2)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 100MHz   Raw material gas SiH_Four  20%                                 N₂O 80%   Film forming pressure 1 × 10^-FourTorr   Ion beam ion species H^-, Ox^-, SiHx^-               Irradiation energy 100 eV               High frequency for excitation 500MHz   Deposition temperature 300 ℃   Deposition film thickness 1500Å Comparative Example 1 (silicon film formation, parallel plate type plasma CVD apparatus)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 13.56MHz   Raw material gas SiH_Four  50%                                 H₂      50%   Film forming pressure 2 × 10^-1Torr   Deposition temperature 300 ℃   Film thickness 1000Å Comparative Example 2 (silicon dioxide film formation, parallel plate type plasma CVD apparatus)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 13.56MHz   Raw material gas SiH_Four  20%                                 N₂O 80%   Film forming pressure 2 × 10^-1Torr   Deposition temperature 300 ℃   Deposition film thickness 1500Å Comparative Example 3 (silicon nitride film formation, parallel plate type plasma CVD apparatus)   Article to be film-formed Alkali-free glass substrate and                                 Each of silicon wafer <100>   High frequency for plasma excitation 13.56MHz   Raw material gas SiH_Four  20%                                 NH₃    80%   Film forming pressure 2 × 10^-1Torr   Deposition temperature 300 ℃   Deposition film thickness 1500Å Next, each obtained in Examples 1 and 4 and Comparative Example 1
Fourier-exchange infrared spectroscopy (FT) of silicon film
-IR), X-ray diffraction analysis (XRD) and laser Raman analysis
The hydrogen concentration was measured and the crystallinity was evaluated by optical analysis. Well
In addition, heat treatment was performed as a post-treatment to examine the change in crystal structure.
It was In addition, device characteristics can be measured by measuring electron mobility.
evaluated. ・ FT-IR Membrane samples obtained in Examples 1 and 4 and Comparative Example 1
About the wave number 2000cm^-1Si-H (Stretching-
band) Quantitative determination of hydrogen concentration in the film from the integrated intensity of absorption peak
As a result of analysis, in each of the film samples according to Examples 1 and 4,
5 x 10²⁰cm ^-3In contrast to the following, according to Comparative Example 1
Membrane sample is 2 × 10^{twenty two}cm^-3Met. Book like this
The membrane samples obtained according to Inventive Examples 1 and 4 are compared.
The hydrogen concentration was significantly lower than that according to Example 1. ・ XRD Each of the film samples according to Example 1 and Example 4 has 111 faces.
(2θ = 28.2 °) and 220 planes (2θ = 47.2)
) Peak was detected and the crystal of silicon (cubic) was detected.
The sex was confirmed. On the other hand, the film sample according to Comparative Example 1
It was confirmed to have a morphus structure. ・ Laser Raman spectroscopy Each film sample according to Example 1 and Example 4 had a crystallization
Peak due to recon (Raman shift = 515-520c
m^-1) Is detected, a crystal grain of 100Å to 2000Å is recognized.
Was given. On the other hand, the membrane sample according to Comparative Example 1 is
Peak due to the structure (Raman shift = 480 cm)^-1)But
was detected. ·Heat treatment Membrane samples obtained in Examples 1 and 4 and Comparative Example 1
As a post-treatment, heat treatment in vacuum at 500 ° C for 8 hours
When applied, the film sample according to Comparative Example 1 was
Although it was not crystallized as it was,
So, from 100Å to 2000Å to 500Å to 3000Å
The crystal grain size was increased. ・ Electron mobility The film sample according to Comparative Example 1 is 0.1 cm²/ V ・ s power
Although the child mobility was shown, the membrane support according to Examples 1 and 4 was used.
Samples with a crystal grain size of 100Å are 0.5 cm²/ V
・ S, with a crystal grain size of 2000Å, 50 cm²/ V · s
The electron mobility of is shown.

Regarding the silicon dioxide films obtained in Examples 2 and 5 and Comparative Example 2, and the silicon nitride films obtained in Example 3 and Comparative Example 3,
Hydrogen concentration was measured by Fourier exchange infrared spectroscopy (FT-IR). Moreover, the electrical characteristics were evaluated by measuring the leak current and the dielectric strength voltage. FT-IR For each silicon dioxide film sample obtained in Examples 2 and 5 and Comparative Example 2 and each silicon nitride film sample obtained in Example 3 and Comparative Example 3, wave number 200
When the hydrogen concentration in the film was quantitatively analyzed from the Si—H (Stretching-band) absorption peak integrated intensity at 0 cm ⁻¹ , it was 1 × 10 ²¹ cm ⁻³ or less in the film samples according to Examples 2 and 4. And the film sample according to Comparative Example 2 has 2 × 10 ²² c
It was m ^-3 . Thus, the membrane samples obtained according to Examples 2 and 4 of the present invention had a significantly lower hydrogen concentration than that according to Comparative Example 2. -Electrical characteristics Regarding the silicon dioxide film samples obtained in Examples 2 and 5 and Comparative Example 2, the leak current and the dielectric withstanding voltage were measured. The leak current of the film samples according to Examples 2 and 5 was 1x10. ^-11 A / cm ² or less, insulation withstand voltage is 1
The film according to Comparative Example 2 has a leak current of 1 × 10 ⁻¹⁰ A / cm ² and a withstand voltage of 8 MV / cm.
It was MV / cm.

For each of the silicon nitride film samples obtained in Example 3 and Comparative Example 3, the leak current,
When the withstand voltage was measured, the film sample according to Example 3 had a leak current of 5 × 10 ⁻¹¹ A / cm ² or less, and the withstand voltage was 8 MV / cm, whereas the film according to Comparative Example 3 had a leak current. The electric current was 5 × 10 ⁻¹⁰ A / cm ² , and the withstand voltage was 5 MV / cm.

From the above results, in Examples 1 and 4 of the present invention, the silicon film having good crystallinity, which was not obtained in Comparative Example 1 using the parallel plate type plasma CVD apparatus, was obtained at a low temperature of 300 ° C. It can be seen that it was obtained. In the second and fifth embodiments of the present invention, parallel plate plasma CVD is used.
A silicon oxide film having a good electric insulating property, which was not obtained in Comparative Example 2 using the apparatus, was not obtained in Comparative Example 3 using the parallel plate type plasma CVD apparatus in Example 3 of the present invention, which was excellent. It can be seen that the silicon nitride films having the electric insulating property were obtained.

[0054]

According to the present invention, it is possible to provide a method for forming a silicon-based thin film which can form a high-quality silicon-based thin film having desired characteristics with high productivity at a relatively low temperature. Further, according to the present invention, it is possible to provide a method for forming a silicon-based thin film capable of forming a high-quality silicon film with good productivity at a relatively low temperature, typically a high-quality silicon film having crystallinity.

Further, according to the present invention, it is possible to provide a method for forming a silicon-based thin film capable of forming a silicon compound film having good electric insulation and film adhesion. Further, according to the present invention, it is possible to provide a film forming apparatus capable of forming a silicon-based thin film such as the silicon film and the silicon compound film.

[Brief description of drawings]

1A is a diagram showing a schematic configuration of an example of a film forming apparatus according to the present invention, and FIG. 1B is a plan view of an energy filter in FIG. 1A.

FIG. 2 is a diagram showing a schematic configuration of another example of the film forming apparatus according to the present invention.

[Explanation of symbols]

1 Ion source gas supply section 2,2 'ion source 21 Extraction electrode system 3, 3 ', 16 Matching device 4, 4'17a High frequency power supply 5 acceleration power supply 6 Deceleration power supply 8a Plasma in ion source 8b Plasma with a high proportion of negative ions in the ion source 9,9 'Heater for heating film-forming target 10 Article to be film-formed 11 Film forming article holding member 11 'Ground electrode and holder 12, 12 'Raw material gas supply unit 13 Film forming source gas plasma 14 high frequency electrodes 14a Cylindrical electrode 18, 18 'Vacuum exhaust unit 100a, 100b magnet C, C'Plasma generation chamber B magnet

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23C 14/00-16/56 C30B 29/06 H01L 21/203-21/205

Claims (16)

(57) [Claims] 1. A method of forming a silicon-based thin film on a film-forming article under the plasma by converting a source gas containing a silicon-based gas into a plasma by supplying electric power, the plasma being in the vicinity of a peripheral portion of the article. And forming a film by irradiating the surface of the article with a negative ion beam. 2. A method of forming a silicon-based thin film on a film-formed article under the plasma by converting a source gas containing a silicon-based gas into a plasma by supplying electric power, wherein the degree of vacuum near the surface of the article is 1 × 10 ^-3 Torr ~ 1 × 10 ^-6 Tor
The method for forming a silicon-based thin film is characterized in that the surface of the article is irradiated with a negative ion beam to form a film. 3. The degree of vacuum near the surface of the film-forming target is 1 ×
The method for forming a silicon-based thin film according to claim 1, wherein the pressure is 10 ⁻³ Torr to 1 × 10 ⁻⁶ Torr. 4. As the ion species of the negative ion beam,
The ions of at least one gas selected from an inert gas, a reactive gas, and a silicon-based gas are used.
A method for forming a silicon-based thin film as described above. 5. The negative ion beam is supplied with an ion energy of 1
The method for forming a silicon-based thin film according to claim 4, wherein the irradiation is performed at 0 eV to 500 eV. 6. The raw material gas used is at least one gas of silicon-based gas, or at least one gas of silicon-based gas and at least one gas of reactive gas. A method for forming a silicon-based thin film as described above. 7. The gas according to claim 4, wherein at least one gas of silicon-based gas or at least one gas of silicon-based gas and at least one gas of reactive gas is used as the raw material gas. Method for forming silicon-based thin film. 8. The method for forming a silicon-based thin film according to claim 6 or 7, wherein the energy of ions incident on the surface of the film formation article from the plasma is 500 eV or less. 9. The low-energy radical species are preferentially diffused from the plasma to the surface of the film-formed article.
Alternatively, the method of forming a silicon-based thin film according to item 7. 10. The ratio (Si / i transport ratio) between the number of silicon atoms from the plasma that reaches the surface of the film-forming article and the number of negative ions of the negative ion beam is 0.1 to 100. Method of forming a silicon-based thin film of. 11. The temperature of the film-forming target is from room temperature to 600.
The method for forming a silicon-based thin film according to claim 1, wherein the temperature is set to ° C. 12. The method for forming a silicon-based thin film according to claim 1, wherein after the film formation, a heat treatment at 300 ° C. to 600 ° C. is applied to the silicon-based thin film as a post-treatment. 13. The method for forming a silicon-based thin film according to claim 1, wherein the silicon-based thin film is a silicon film. 14. The method for forming a silicon-based thin film according to claim 1, wherein the silicon-based thin film is a silicon compound film. 15. A raw material gas supplied by a raw material gas supply means into a plasma generation chamber connected to a vacuum exhaust means is turned into plasma by power supply by a gas plasmaization power supply means, and the plasma generation chamber under the plasma. An apparatus for forming a film on a film-forming article supported by the supporting means of the above, which comprises means for irradiating the film-forming article with a negative ion beam, and the power supply means supplies the plasma to the plasma. A film forming apparatus, which can be formed in the vicinity of a peripheral portion of a film formation target article. 16. The film forming apparatus according to claim 15, wherein the negative ion beam irradiation means is capable of irradiating ions with an ion energy of 10 eV to 500 eV.