JPH05117843A - Thin film forming method - Google Patents

Abstract

PURPOSE:To obtain a thin good crystalline film excellent in adhesive strength by allowing a part of a metallic vapor to reach a substrate as ion beam and by bombarding together with the metallic vapor and ion. CONSTITUTION:A metallic row material is heated at the metallic vapor generation part 1 in the vacuum chamber 11 to make vapor. The metallic vapor is heated by the heater 15. A thermoelectron is generated by the emission filament 3 to generate arc discharge between the emission filament 3 and the chamber 11. The metallic vapor is held by the radiation shield 10, 16 in the chamber 11. A metallic plasma is extracted as ion beam from the pore of plasma electrode 5, extraction electrode 6 and ground electrode 7. The substrate D is held by the substrate holder D at the position that ion beam and the metallic vapor is present. A part of the metallic vapor as vapor and a part as ion beam is allowed to reach the substrate D and the thin metallic film is formed by bombarding together with the metallic vapor and ion to the substrate D. As a result, the high purity thin film is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for simultaneously irradiating a substrate with ions of the same metal as vapor of metal to form a thin film of metal having excellent crystallinity and adhesion.

[0002]

2. Description of the Related Art A vapor deposition method is generally used to form a thin metal film on a substrate. In this method, a metal raw material is placed in, for example, a resistance heating heater, heated in a vacuum, evaporated, and applied to a substrate placed face down. The vapor that comes into contact with the substrate is cooled and solidifies on the substrate. In the case of a metal having a high melting point, a raw material metal is put in a crucible and irradiated with an electron beam to melt and evaporate it. The substrate is often heated. Alternatively, a sputtering method may be used.
In this method, a rare gas such as Ar is turned into plasma and is applied to a target of a metal plate to take out metal in the form of atoms, molecules, etc. to a substrate and deposit it there. Sputtering is often used to form thin films of compounds and oxides, but can also be used to form thin films of metals. Although a dense film can be formed, but the growth rate is slow, the evaporation method is used for those that can be evaporated.
Metal ion beams are used for various purposes. For example, in order to make the electric conductivity of a semiconductor p-type or n-type,
The metal is driven in as an ion beam as a punt.
Alternatively, a metal ion beam treatment may be performed for modifying a polymer material, modifying iron, and the like. The ion beam irradiates the object to be processed by extracting and accelerating the ions produced by the ion source by the action of the extraction electrode.

An apparatus has been proposed which simultaneously performs ion beam irradiation and vapor deposition. It is also called ion deposition, ion assist, dynamic mixing method, etc. The evaporator and the ion source are housed in the same vacuum chamber. An ion source, a vapor deposition device, that is, a crucible and a heater are provided obliquely below the substrate placed downward. A raw material for forming a thin film is contained in the crucible. This is heated by resistance heating or electron beam heating and evaporated. The evaporated raw material adheres to the substrate. An ion beam of a rare gas such as Ar is accelerated from the side to hit the substrate.
Since Ar ions have high kinetic energy, it is said that the surface of the substrate is activated and the adhesion between the vaporized substance and the substrate substance is improved. However, Ar ions having a high energy may enter the substrate and become impurities, so that the purity of the film is not good. It has also been pointed out that plasma is present in the vacuum chamber, which impedes the source material from vaporizing and reaching the substrate.

[0004]

The most common method of forming thin metal films is vacuum deposition. This has a high film forming speed and is highly practical. However, depending on the material, sufficient adhesion strength may not be obtained. The vapor-deposited material generally becomes polycrystalline but the crystallinity is not good in some cases. Crystallinity and adhesion can be improved by raising the temperature of the substrate, but depending on the substrate, it may melt or deteriorate if the temperature is too high. In such a case, a means other than raising the substrate temperature must be selected. It is an object of the present invention to provide an apparatus for forming a metal thin film which does not raise the substrate temperature so much and has excellent crystallinity and excellent adhesion.

[0005]

The apparatus of the present invention comprises an evaporation source for generating vapor of metal in a vacuum chamber, and a plasma which excites the vapor generated by the vapor source by discharge and heating to form plasma. A generation chamber and an ion extraction part for extracting metal plasma to form an ion beam,
A substrate holder for holding the substrate is included, and a part of the metal vapor reaches the substrate as vapor and is deposited there, and a part of the metal vapor becomes an ion beam to irradiate the substrate. Both of them are deposited on the substrate to form a thin film component, but since the energy and the electric charge when they collide with the substrate are different, it is possible to form different crystalline thin films by adjusting the ratio.

[0006]

The device of the present invention is very similar to a metal ion source, but it is not the one that generates only ion beams unlike the ion source. Instead, the vapor of the metal reaches the substrate directly. In order to do this, the area of the opening of the evaporation source is increased so that the vapor does not turn into plasma and a part of the vapor flies to the substrate side. Steam is generated by heating the metal contained in the crucible with a heater. A radiation shield is provided on the inner wall of the vacuum chamber to keep the steam at a high temperature. For example, arc discharge is used to convert the metal vapor into plasma. Alternatively, plasma may be generated by applying a high frequency between the parallel electrode plates to cause a discharge. Steam can also be turned into plasma by microwaves. Alternatively, an ECR plasma device may be used. The ion beam is accelerated and hits the substrate, but vapor cannot spread to the vacuum chamber by diffusion and cannot reach the substrate without some vapor pressure. However, when the vapor pressure of the metal becomes high, plasma may be difficult to be generated, so the vapor pressure needs to be appropriately adjusted. Since the present invention uses both ion beam irradiation and vapor deposition in a combined manner, it is similar to the aforementioned ion vapor deposition method. However, the above-mentioned ion deposition uses a rare gas as plasma and ion beams, which are not components of the thin film. Therefore, if they enter the thin film, they become impurities, which is not desirable. The present invention is different from the conventional ion vapor deposition method in that the ion is not the same but the same metal as vapor is the same.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. The overall configuration is metal vapor and ion generator A, shutter
B, a film formation rate monitor C, a substrate and a substrate holder-D, a mass spectrometer E and the like. The shutter B is a plate for passing or blocking the flow of ion beams and vapor. The plate may be attached to the shaft and moved in the axial direction so as to be opened and closed, or may be rotated around the rotary shaft. The film formation speed monitor C is made of, for example, a crystal oscillator or the like, and can determine the film thickness from a change in oscillation frequency. The substrate holder is an object that supports the substrate and includes a heater. It may also be rotatably supported. Illustration of the heater and the rotating mechanism is omitted here. The mass analyzer E is for obtaining the energy and mass of the ion beam. If the energy is known, the mass can be calculated. This exemplifies the one using a sector magnet. Ions that have passed through the slit enter the magnet and are bent by the magnetic field. Only ions that describe an arcuate orbit of a certain radius of curvature enter a detector such as a Faraday cup. This allows the number of ions of a particular mass to be measured. This is for investigating the intensity and mass distribution of ions before or after the substrate and the substrate holder are installed at fixed positions. The structure below the shutter B is well known. Although the whole of these is inside the vacuum chamber, the illustration of the whole vacuum chamber is omitted for simplicity.

The structure of the metal vapor and the ion generating section A will be described. This is the most important part of the present invention.
The metal vapor generation unit 1 is provided so as to project laterally from the vacuum chamber 11. Inside the vacuum chamber 11, a heater filament 2, an emission filament 3 and the like are provided. These are filaments such as W and Ta stretched between electrodes. Both of them generate heat when they have their own power source and are energized. Since the emission filament 2 has a cathode potential and the vacuum chamber 11 has an anodic potential, thermoelectrons are emitted from the emission filament 2 and an arc discharge is generated between the emission filament 2 and the vacuum chamber 11. Hi
The filament 2 is for heating only. The anode potential is set so that electrons are not emitted from here. This has a long life because there is no spatter due to positive ion collisions.

The inner wall of the vacuum chamber 11 has a side surface radiation shield.
A field 4 is provided. This is a thin plate of Ta formed into a tubular shape and stacked in one or more layers. The heat inside the vacuum chamber 11 is prevented from escaping to the outside. Vacuum chamber 1
On the outlet side of 1, there are a plasma electrode 5, a lead electrode 6 and a ground electrode 7. These are metal electrode plates having holes for extracting one or many ion beams. A high positive voltage is applied to the plasma electrode 5. Since it is in contact with plasma, the plasma electrode is sometimes called a positive electrode or an acceleration electrode. A negative voltage is applied to the extraction electrode 6 to prevent secondary electrons from returning. Since it forms a direct electric field for extracting positive ions, it is also called an extraction electrode, but it is sometimes called a negative electrode. The above-mentioned shutter, substrate and the like are provided in front of the ground electrode 7, and the gas introduction port 8 is provided in a part of the wall surface of the vacuum chamber 11. From here, a gas such as Ar for plasma excitation can be introduced. A magnet 9 is provided along the outer wall of the vacuum chamber 11. This is to generate an internal cusp magnetic field to confine the plasma.

An upper lid radiation shield 10 is provided at right angles to the axial direction of the chamber. This protects the upper lid 13 from high heat and traps the heat inside the vacuum chamber 11.
The metal vapor generator 1 has a crucible 14 containing a metal raw material. A heater 15 is provided near the crucible 14. This is a method in which the metal raw material inside the crucible is heated and melted into steam. A radiation shield 16 is also provided here. The raw material evaporates and part of it becomes plasma by arc discharge. This is extracted as an ion beam by the action of the extraction electrode system. Since the opening of the metal vapor generator 1 is large, the vapor actively reaches the inside of the vacuum chamber 11, but most of the vapor remains as vapor, passes through the holes of the electrode system, diffuses, and reaches the substrate. This is similar to normal vapor deposition, which is cooled on a substrate to become a solid. The same material is used as the ion beam to reach the substrate and to be vapor deposited. The present invention is characterized here. However, the driving force reaching the both substrates is different. In the case of an ion beam, it collides with the substrate due to the strong force of the electric field. On the other hand, since the vapor simply diffuses due to the difference in vapor pressure, it takes a long time from vaporization to reaching the substrate. Also, since vapor is not a charged particle, it cannot be confined by a magnetic field. If it comes into contact with a wall surface with low temperature, it may be cooled and adhere to it. Therefore, a radiation shield is provided to prevent steam from directly hitting the wall surface. Even if steam hits the radiant shield, it simply bounces off because of its high temperature. The radiation shield thus has a double meaning.

Kinetic energy is also quite different. AEON Bee
Although the mum has an energy of a few keV, the energy of vaporized atoms is a few tens of eV or less. When it is difficult to adhere to the substrate only with the evaporating raw material, the ion beam collides with the substrate with strong energy, so that the adhesion between the substrate and the vaporized atoms is improved. The ratio between the amount of metal vapor and the amount of ions can be controlled by the conductance of the ion extraction unit, the ionization rate, the electron temperature, and the like. The ionization rate is
It depends on the discharge conditions such as arc voltage, arc current and vapor density. That is, the ratio of vapor to ions can be controlled by setting the discharge parameters. As a structural measure of the device, the ratio of ions can be increased by increasing the distance between the extraction electrode and the substrate. Moreover, the ratio of steam can be increased by increasing the opening area of the steam generation source. The energy of ions can be changed by changing the acceleration voltage applied to the plasma electrode. In general, the ionic current is a space charge limited current, and is therefore proportional to the 3/2 power of the potential difference between the plasma electrode and the extraction electrode and inversely proportional to the square of the distance (gap length). When it is desired to change only the energy while keeping the current amount constant, adjustments such as changing the voltage and the gap length are made.

The deposition rate can be observed in-situ by the film formation rate monitor C. When the substrate is a conductor, the amount of ions flows to the substrate, so that the amount of ions can be known by the current. Also, shutter B
If it also has a function as a calorie meter, the intensity of the ion beam can be measured at the beginning and end of the measurement with the shutter B closed. This is a value including other ions. Accurately, the desired ion may be selected by the mass spectrometer and then the intensity of the ion beam may be measured.
In this figure, the substrate is perpendicular to the beam, but the substrate may be inclined with respect to the beam. Then, the crystallinity of the film can be changed. Further, when a rare gas such as Ar gas is introduced from the gas introduction port to generate plasma, metal vapor, metal ions, and gas ions are mixed, and the degree of freedom in film formation increases. In this case, the ratio of the metal ion and the rare gas ion can be measured by the mass spectrometer at the subsequent stage.

[0013]

According to the present invention, when a metal thin film is formed on a substrate, the metal vapor and the ion beam are supplied to the substrate at the same time. Therefore, a thin film having excellent crystallinity and excellent adhesion to the substrate. Can be obtained. This is the energy of metal ions
This is because the substrate is activated and vapor easily adheres. There is already a method of applying a rare gas at the same time as steam, but this is likely to contain impurities such as high energy rare gas ions entering the inside of the thin film, but this is not the case in the present invention. A high-purity thin film can be formed. Generally, when the temperature of the substrate is raised, the adhesion is improved. However, in this case, the present invention is particularly effective when the substrate may be adversely affected or the substrate may be melted. This is because it is possible to form a film with good adhesion while keeping the substrate at a relatively low temperature.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a thin film forming apparatus of the present invention.

[Explanation of symbols]

 A metal vapor and ion generation part B shutter-C film formation rate monitor D substrate and substrate holder E mass analyzer 1 metal vapor generation part 2 heater filament 3 emission filament 4 side radiation shield 5 plasma electrode 6 extraction electrode 7 Ground electrode 8 Gas inlet 9 Magnet 10 Top lid radiation shield 11 Chamber 12 Insulation spacer 13 Top lid 14 Crucible 15 Heater 16 Radiation shield 17 Insulator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Fujiwara, 47 Umezu Takaune-cho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd. (72) Inventor Koji Matsunaga 47 Umezu Takaunecho, Ukyo-ku, Kyoto City Nissin Electric Co., Ltd.

Claims (1)

[Claims] 1. A vacuum chamber capable of evacuating the interior, a metal vapor generator provided in a part of the vacuum chamber for heating a metal raw material to generate vapor, and a metal vapor provided in the vacuum chamber Heater for heating,
Emission filament which is heated at a depot potential to generate thermoelectrons to generate an arc discharge between the anode chamber and a chamber which is an anode, and which is provided along the inner wall of the vacuum chamber to hold metal vapor in the vacuum chamber. And a plasma electrode having an ion through hole for extracting metal plasma as an ion beam, an extraction electrode, a ground electrode, and a substrate for holding the substrate at a position where the ion beam and metal vapor exist. It consists of a holder, part of the metal vapor remains as vapor, and part of it becomes an ion beam to reach the substrate so that the metal vapor and the ions hit the substrate at the same time. A thin film forming apparatus, which forms a thin film of