JP2003213411A - Film forming equipment using plasma - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A stable plasma state can be formed,
Provision of a film forming apparatus with excellent controllability of plasma state. SOLUTION: An electric shock is applied to a cathode target 2 to generate a plasma 10 for vapor deposition, and target ions in the plasma 10 for vapor deposition are guided to a sample substrate 4 to which a bias voltage is applied to form a thin film. In the apparatus, an ion beam 9 generated by the ion source 3 is irradiated on the cathode target 2 to generate a plasma 10 for vapor deposition. Ion beam 9
Irradiation generates and maintains the deposition plasma 10. Therefore, by controlling the ion beam 9, the state of the deposition plasma 10 can be stably controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus for applying electric shock to a target to generate plasma and guiding target ions in the plasma to a substrate to form a thin film.

[0002]

2. Description of the Related Art The plasma excitation method by cathodic arc discharge is characterized in that it can be excited in a low pressure region and has a high ionization rate in plasma. Therefore, this excitation method is used in a cathode arc ion film forming apparatus that guides material element ions to the surface of a sample substrate in high vacuum to form a film.

As an example of the cathode arc ion film forming apparatus, there is a film forming apparatus as disclosed in Japanese Patent Laid-Open No. 59-200760. In the cathode arc ion film forming apparatus, a target, which is a vapor deposition element material, is disposed on the cathode, and a high voltage is applied between the cathode and the anode to generate arc discharge. The target material is vaporized and ionized by the impact of the arc discharge, and cathode arc plasma is generated near the target surface. By guiding the target ions in the plasma to the surface of the sample substrate and depositing them, a thin film made of the target element is formed.

When the arc discharge is activated by the high electric field and the cathodic arc plasma is excited, the discharge is continued even at a lower electric field due to the effect of the excited plasma. That is, the function of the electric field between the electrodes changes from the dielectric breakdown for starting the arc discharge to the energy supply to the plasma.

Since the cathode arc ion film forming apparatus uses the electron flow emitted from the cathode as the discharge current, a high electric field for dielectric breakdown is required to start the arc discharge at room temperature and high vacuum. To do. Therefore, the shape of the discharge electrode is made to be a pointed shape to utilize the electric field concentration effect, or the distance between the anode and the cathode is changed to form a high electric field. In addition, a start-up electrode or a start-up high-voltage applying mechanism called a trigger device for starting arc discharge may be used.

[0006]

However, even if the arc discharge is maintained in a continuous state, the electric field state between the electrodes changes momentarily due to the consumption of the target due to the evaporation of the target material and the deposition of the deposit on the anode. However, the discharge state becomes unstable. When the discharge state becomes unstable and the arc current becomes small, the plasma is prevented from disappearing by restarting the trigger device. That is, during the film forming process, a start mode for starting arc discharge,
The continuous mode in which the arc discharge is sustained by the effect of plasma is repeated. At this time, since the magnitude of the electric field in each mode is extremely different and the discharge state changes abruptly, there is a problem that the state of plasma used as an ion source tends to be unstable.

An object of the present invention is to form a stable plasma state in a film forming apparatus which uses plasma generated by applying an electric shock to a target, and is excellent in controllability of the plasma state. To provide.

[0008]

An embodiment of the invention will be described with reference to FIG. (1) In the invention of claim 1, the cathode target 2 is bombarded by arc discharge to generate the cathode arc plasma 10, and the ions in the cathode arc plasma 10 are guided to the substrate 4 to which a bias voltage is applied to form a thin film. It is applied to the cathode arc ion film forming device for film formation, and the cathode target 2
The above-described object is achieved by providing ion irradiation means 3 and 8 for irradiating the cathode target 2 with the ion beam 9 for evaporating and ionizing the material of (1). By irradiation of the ion beam 9,
A cathode arc plasma 10 is generated. (2) The invention according to claim 2 is the cathode arc ion film forming apparatus according to claim 1, wherein the ion irradiation means is an EC
It uses an R-type ion source. (3) The invention of claim 3 is the cathode arc ion film forming apparatus according to claim 1 or 2, wherein a graphite target is used as the cathode target 2 and a DLC film is formed on the substrate 4.

In the section of the means for solving the above problems, the drawings of the embodiments of the present invention are used in order to make the present invention easy to understand, but the present invention is limited to the embodiments of the present invention. Not something.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment of a film forming apparatus according to the present invention. In the main chamber 1, a cathode target 2 which is a film forming material and constitutes a cathode, an ion source 3, and a sample substrate 4 which is a film forming target are provided. The ion source 3 corresponds to the anode of the conventional cathode arc ion film forming apparatus, and the film forming apparatus of the present embodiment can be regarded as a kind of cathode arc ion film forming apparatus. Cathode target 2
For example, DLC (Diamond Like Car
When depositing a carbon film such as bon), a graphite target is used. The inside of the main chamber 1 is evacuated to a high vacuum by a vacuum pump 5.

The ion source 3 has a plasma generating chamber 31 and a differential exhaust chamber 32. A gas such as argon is supplied from the gas supply source 6 to the plasma generation chamber 31, and the gas is excited by glow discharge and ionized to generate plasma. As a method for exciting plasma, a method using a hot filament, high frequency or ECR (Electro
n Cyclotron Resonance) and so on.

FIG. 2 is a schematic configuration diagram of the ion source 3 utilizing ECR. In the case of the ECR ion source 3, the plasma generation chamber 31 has a cavity resonator structure, and the plasma generation chamber 31 is connected to the plasma generation chamber 31 through the waveguide 33 and the quartz window 34 to 2.45 (GH).
The microwave of z) is introduced. An electromagnet coil 35 is arranged around the plasma generation chamber 31. The electromagnet coil 35 generates a magnetic field that satisfies the ECR condition in the plasma generation chamber 31, and forms a divergent magnetic field that draws the ion source plasma P from the opening 37 of the partition wall 36 to the differential exhaust chamber 32. In the case of the microwave of 2.45 (GHz), the ECR condition is satisfied at the magnetic field strength of 875 (G). When the ECR condition is satisfied, argon is excited and ionized, and an ion source plasma P containing argon ions is generated in the plasma generation chamber 31.

The differential exhaust chamber 32 is exhausted by the vacuum pump 7, and the neutral particles contained in the ion source plasma P flowing into the differential exhaust chamber 32 from the plasma generation chamber 31 are stored in the main chamber 1 by the vacuum pump 7. Exhausted to the outside.
Therefore, the inside of the differential exhaust chamber 32 is in a higher vacuum state than the inside of the plasma generation chamber 31 and functions as a buffer between the low vacuum plasma generation chamber 31 and the high vacuum main chamber 1. That is, the high vacuum of the main chamber 1 is maintained. Argon ions are extracted from the opening 38 of the differential evacuation chamber 32, and are irradiated onto the cathode target 2 as an ion beam 9.

Returning to FIG. 1, a positive voltage is applied to the ion source 3 by the power source 8 and is maintained at a high potential (for example, about 1 M (V)). On the other hand, the cathode target 2 has a ground potential. Therefore, the argon ions extracted from the opening 38 of the differential exhaust chamber 32 are not
The potential difference between the cathode target 2 and the cathode target 2 accelerates toward the cathode target 2. Since argon ions have MeV-order energy, when the ion beam 9 is applied to the cathode target 2 to release energy, the target material is vaporized and ionized. As a result, in the vicinity of the surface of the cathode target 2, the plasma 10 is centered on the portion irradiated with the ion beam.
(Hereinafter, referred to as deposition plasma 10) is generated.

The deposition plasma 10 contains ions of the target material. For example, in the present embodiment where graphite is used as the target 2, carbon ions are included. A bias power source 11 is provided on the sample substrate 4.
Therefore, a negative bias voltage is applied, and the potential difference between the cathode target 2 and the sample substrate 4 due to this bias voltage causes the carbon ions in the deposition plasma 10 to be drawn into the sample substrate 4. In FIG. 1, reference numeral 12 indicates the ion flow of the material element.

Reference numeral 13 is a deflector which two-dimensionally scans the irradiation position of the ion beam 9 applied to the cathode target 2 on the target surface. By deflecting the ion beam 9 by the deflector 13, it is possible to irradiate the ion beam 9 on a wider area of the cathode target 2.
The consumption of the cathode target 2 can be made uniform.
Further, the plasma region of the deposition plasma 10 is expanded,
The wider area of the sample substrate 4 can be irradiated with the ion stream 12. Of course, the deflector 13 may be omitted.

In the ion beam sputtering apparatus, the target is also irradiated with the ion beam to form a film. However, the function of the ion beam and the film forming process are essentially different from those of the film forming apparatus of the present invention. In the case of sputtering, the number of atoms sputtered by the incidence of one ion is called the sputter rate, and the sputter rate changes depending on the energy Ei of the incident ion.

FIG. 3 is a diagram qualitatively showing the relationship between the sputter rate and the energy Ei. When the energy of ions increases up to the threshold energy Eit, spatter can be recognized. When the energy Ei is increased, the sputter rate also increases, but it gradually becomes saturated. If the energy Ei is further increased after the sputter rate is saturated, the sputter rate begins to decrease, and more ions enter the target material. Therefore, in the sputtering film forming apparatus, the film formation is performed with the energy that maximizes the sputtering rate. When a graphite target is used, sputtering is performed at about 1 (keV). Then, a thin film is formed by depositing the sputtered neutral particles (target particles) on the sample substrate.

On the other hand, in the present embodiment, the ion energy Ei is in the MeV order and is 1000 times as large as that in the case of sputtering film formation. Therefore, evaporation and ionization of the target material occur instead of the sputtering phenomenon.
As a result, arc discharge is generated by the ion current, and the deposition plasma 10 is generated. In the case of a cathodic arc ion film deposition system, unlike spatter that deposits neutral particles,
Material element ions of the deposition plasma 10 are drawn onto the sample substrate 4 to form a thin film. Therefore, the properties of the film can be adjusted by adjusting the bias voltage.

As described above, the film forming apparatus of the present embodiment that causes the ion source 3 to function as an anode has the following (a)
It has the advantages of (d). (A) In the conventional device, it is necessary to provide a mechanism for changing the distance between the anode and the cathode or a dedicated trigger device in order to form a high electric field for activating the arc discharge. On the other hand, in the film forming apparatus of the present embodiment, the deposition target plasma 10 can be easily generated by irradiating the cathode target 2 with the ion beam 9 from the ion source 3. Therefore, it is not necessary to provide a mechanical trigger mechanism as in the past. The ion source plasma P
Is generated by glow discharge in a gas atmosphere,
Discharge can be performed more easily than arc discharge due to dielectric breakdown in high vacuum.

(B) Since the differential evacuation chamber 32 is provided between the plasma generation chamber 31 and the main chamber 1, the film is formed by using plasma generated by discharge in a gas atmosphere, but in a high vacuum. It is possible to realize high-purity film formation in.

(C) By disposing the deflector 13 on the way of the ion beam 9 for irradiating the cathode target 2, it is possible to irradiate the ion beam 9 to a wide area on the surface of the cathode target. As a result, uneven distribution of the amount of consumption of the cathode target 2 can be reduced.

(D) As described above, in the conventional cathode arc ion film forming apparatus, when the discharge state becomes unstable and the arc current becomes small, the plasma is restarted by restarting the mechanical trigger device. Are prevented from disappearing. However, because it is a mechanical device, it is difficult to quickly respond to a sudden decrease in arc current,
The start-up mode and the continuous mode are repeated, and there is a problem that the plasma state greatly changes. On the other hand, in the present embodiment, since the state of the deposition plasma 10 is positively maintained by the energy supplied by the ion beam 9, the continuous mode can be stably continued. Even if the plasma state fluctuates significantly, the voltage of the power source 8 is adjusted to adjust the potential difference between the ion source 3 and the cathode target 2 to quickly return to the original state. Can be made.
That is, it is possible to realize a film forming apparatus having excellent controllability and stability of the deposition plasma 10.

[Modification] In the embodiment shown in FIG.
Although a positive voltage is applied to the ion source 3 to set the cathode target 2 to the ground potential, the ion source 3 may be in contact with the ground potential as shown in FIG. In this case, the cathode target 2 may be provided with the power source 20 and the potential of the cathode target 2 may be set to -V2 lower than the ground potential. However, when the potential of the substrate 4 is -V4, it is set as -V2> -V4. In the apparatus of FIG. 4, the energy of the ion beam 9 can be adjusted by changing the voltage of the power supply 20.

As another modification, FIG. 1 or FIG.
This apparatus may be separately provided with an anode electrode as used in a conventional cathode arc ion film forming apparatus. In this case, the vapor deposition plasma 10 is generated by irradiating the cathode target 2 with the ion beam 9 of the ion source 3.
After that, arc discharge is maintained between the anode electrode and the cathode target 2. After shifting to the continuous mode, the irradiation of the ion beam 9 is turned off. That is, the ion source 3
Is used instead of the conventional trigger device. If the arc current decreases during the sustain mode, the ion beam 9 is irradiated again to stabilize the arc discharge. As a result, as compared with the conventional cathode arc ion film forming apparatus using a mechanical trigger device, it is possible to more quickly respond to fluctuations in the deposition plasma 10.

In the above-described embodiments, the DLC film forming apparatus using graphite as the cathode target 2 has been described as an example, but the present invention is also applicable to a film forming apparatus using a target other than the graphite target. be able to.

In the correspondence between the embodiment described above and the elements in the claims, the ion irradiation means is an ion source 3 for generating the ion source plasma P to generate the ion beam 9, the ion source 3 and the cathode. The power source 8 supplies a potential difference to the target 2 to supply energy to the ion beam 9. Further, the deposition plasma 10 constitutes the plasma of claim 1.

[0028]

As described above, according to the present invention,
Plasma is generated and maintained by the irradiation of the ion beam by the ion irradiation means. Since the plasma state can be controlled by the amount of energy supplied by the ion beam, stable plasma can be generated by irradiating a stable ion beam. Since the control of the ion beam can be performed electrically, the controllability and stability of plasma are significantly improved as compared with the conventional cathode arc ion film forming apparatus using a mechanical trigger device.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a film forming apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of an ion source 3 using ECR.

FIG. 3 is a diagram qualitatively showing a relationship between a sputtering rate and energy Ei.

FIG. 4 is a diagram showing a modified example of the film forming apparatus.

[Explanation of symbols]

1 Main chamber 2 cathode target 3 ion source 4 Sample substrate 5,7 Vacuum pump 8, 11, 20 power supply 9 ion beam 10 Plasma for vapor deposition 13 Deflector 31 Plasma generation chamber 32 differential exhaust chamber P ion source plasma

Claims (3)

[Claims] 1. A film forming apparatus for forming a thin film by applying electric shock to a target to generate plasma, and guiding target ions in the plasma to a substrate to which a bias voltage is applied to form a thin film. A film forming apparatus comprising: an ion irradiation unit that irradiates the target with an ion beam that is vaporized and ionized, and the plasma is generated by the irradiation of the ion beam. 2. The film forming apparatus according to claim 1, wherein an ECR type ion source is used as the ion irradiation unit. 3. The film forming apparatus according to claim 1, wherein a graphite target is used as the target, and a DLC film is formed on the substrate.