JP2849771B2 - Sputter type ion source - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming thin films of various materials on a sample substrate, or extracting ions for etching or modifying the surface of the thin film. Things,
In particular, the present invention relates to a novel sputter-type ion source for stably generating and extracting metal ions with high efficiency by using high-density plasma sputtering.

2. Description of the Related Art Conventionally, a so-called ion source for extracting ions generated in plasma using an extraction mechanism such as a grid has been widely used in various fields for etching and processing of various materials and thin films. Among them, a Kauffman-type ion source having a thermoelectron emission filament as shown in FIG. 4 is most commonly used. The Kaufman-type ion source has a filament 2 for emitting thermoelectrons in a plasma generation chamber 1 and discharges in a magnetic field generated by an electromagnet 3 for generating a plasma stabilizing magnetic field using the filament 2 as a cathode. The plasma 4 is generated, and ions in the plasma 4 are extracted as an ion beam 7 by using several extraction grids 6 while controlling the plasma 4 with a plasma control electrode 5 opposed to the plasma 4.

In an ion source represented by a conventional Kauffman ion source, thermoelectrons for plasma generation are extracted using a filament, and the filament material is sputtered and included in the extracted ions as impurities. Further, when a reactive gas such as oxygen is used as the plasma generating gas, the reactive gas reacts with the filament, and there is a drawback that continuous ion extraction cannot be performed for a long time.
In addition, this type of ion source has a drawback that its use is limited to extracting gas ions and cannot be used for extracting metal ions.

On the other hand, as an ion source capable of extracting metal ions over a large area, a sputter ion source has been proposed (for example, Spring Applied Physics Society of Japan, 1989, 30a-Z).
G-10, 524p). According to this type of ion source, most metal ions such as Al and Fe can be extracted over a large area.

[Problems to be Solved by the Invention] However, in the above-described sputter ion source, when an insulating film is formed, a thin film is formed on an insulating substrate, or processing such as etching or surface modification is performed. In some cases, ions cannot be effectively extracted due to charge-up of the substrate by the ion beam.

For this reason, a method may be used in which a filament for thermionic emission is arranged outside the ion source, for example, around the ion extraction port or the substrate, and the emitted electrons neutralize the charge of the ions to extract the ions. .

However, when such a method is applied to the above-mentioned sputter ion source, when impurities are mixed into the film from a heated filament or a reactive gas such as oxygen is introduced, the reactive gas and the filament There is a disadvantage that not only do they react with the material and release impurities, but also the life of the filament becomes extremely short.

An object of the present invention is to provide a sputter-type ion source for generating and extracting metal ions stably for a long time with high efficiency by using sputtering by high-density plasma.

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention provides a plasma generation chamber for generating a plasma by introducing a gas,
First and second targets provided at both ends inside the plasma generation chamber, and at least one of which is formed of a sputtering material, and a center of the cylindrical target among the first and second targets; An ion extraction mechanism provided on an axis, at least one first power supply for applying a negative potential to the plasma generation chamber to each of the first and second targets, and an interior of the plasma generation chamber. And a means for forming a magnetic field inside the plasma generation chamber and generating a magnetic flux exiting from one of the first and second targets and entering the other target. And a second power supply for applying a pulse voltage to the plasma control electrode.

[Operation] The present invention is capable of efficiently extracting metal ions generated by high-density plasma sputtering and forming a high-quality thin film on an insulator or an insulating film in a high vacuum. is there. In other words, the present invention combines a set of targets, at least one of which has a cylindrical shape, and adopts a target arrangement for confining high-speed secondary electrons required for high-density plasma generation in plasma. Can be generated, and the metal ions generated there can be efficiently extracted. In addition, since the ion extraction is pulsed and the ion charges are neutralized by the emitted electron beam at the same time, there is no charge on the substrate or film surface due to the ions, and the ions can be extracted stably on the insulator substrate. Alternatively, an insulating film can be formed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of a sputter type ion source of the present invention.

A gas for generating plasma is introduced into the plasma generation chamber 20 from an inlet 21. At one end of the plasma generation chamber 20, a grid 22 for extracting ions is provided. In this embodiment, the grid 22 is composed of a single hemispherical multi-hole grid. A voltage is applied to the grid 22 from a power source (not shown). A flat target 23 is provided at the other end inside the plasma generation chamber 20, and a cylindrical target 23 is provided near the grid 22.
24 are provided. The target 23 is detachably fixed to a water-coolable metal support 23A. Support 23A
Is fixed to a lid 20B above the plasma generation chamber 20, and the lid 20B is fixed to a wall 20A above the plasma generation chamber 20 via an insulator 23B. Similarly, the target 24 is detachably fixed to a water-coolable metal support 24A. The support 24A is fixed to a wall 20C of the plasma generation chamber 20 via an insulator 24B. The grid 22 described above is fixed to a lower portion of the support 24A via an insulator 24C. The protruding ends 23D and 24D of the supports 23A and 24A also serve as electrodes, and can apply a negative potential to the plasma generation chamber 20 from the DC power supplies 25 and 26 to the targets 23 and 24.

A cylindrical anode electrode 27 as a plasma control electrode is provided inside the plasma generation chamber 20, and a pulse power supply 28 for applying a pulse voltage is connected to the anode electrode 27. Reference numeral 29 in FIG. 1 denotes an insulator.

An electromagnet 30 for forming a magnetic field inside the plasma generation chamber is provided on the outer periphery of the plasma generation chamber 20. The electromagnet 30 and the targets 23 and 24 are positioned so that a magnetic flux 31 generated by the electromagnet 30 traverses both target surfaces and the magnetic flux exits the surface of one target and enters the other target surface. For example, a cylindrical tubular target 24 having an inner diameter of 10 cm and a height of 5 cm can be set to 8 cm by using a disk-shaped target 23 having a diameter of 8 cm. It is desirable that the plasma generation chamber 20 be water-coolable.
In order to protect the side surfaces of the targets 23 and 24 from plasma, it is preferable to provide a shield on the inner surface of the plasma generation chamber.

After the inside of the plasma generation chamber 20 is evacuated to a high vacuum, a gas is introduced from the gas inlet 21 and the voltage applied to the targets 23 and 24 in the magnetic field generated by the electromagnet 30 is increased. . The ions in the plasma can be extracted as an ion beam 32. The magnetic flux between the targets prevents high-speed secondary electrons (γ-electrons) 9 generated from the target surface from dissipating in the direction perpendicular to the magnetic field, and further has the effect of confining the plasma. Is generated.

An example of a thin film deposition apparatus using the sputter type ion source of the present invention thus configured will be described with reference to FIG. A sample chamber 33 is connected to the plasma generation chamber 20 with an ion extraction grid 22 interposed therebetween. The sample chamber 33 and the plasma generation chamber 20 constitute one vacuum chamber, but it is preferable that the two are insulated. Gas can be introduced into the sample chamber 33 from the gas inlet 34, and can be evacuated to a high vacuum by the exhaust system 35. In the sample chamber 33, a substrate holder 36 for holding a substrate 37 is provided, and a shutter 38 that can be opened and closed between the substrate holder 36 and the ion extraction grid 22 is provided. The substrate holder 36 has a built-in heater
It is preferable to be able to heat the substrate 37, and it is also preferable to apply a DC or AC voltage to the substrate 37 to apply a bias voltage to the substrate during film formation and to perform sputter cleaning of the substrate. .

Next, referring to FIG. 2, a description will be given of a plasma multiplication mechanism by the movement of high-speed secondary electrons in the sputter type ion source according to the present invention.

By applying a negative potential to the plasma generation chamber 20 by the tubular target power supply 26 and the plate target power supply 25 to the tubular target 24 and the plate target 23, respectively, high-density plasma is generated, Sputters are generated efficiently. When the ions drawn into the targets 23 and 24 collide with the target surface, high-speed secondary electrons (γ electrons) 9 are emitted from the target surface. This high speed 2
The next (γ) electron 9 is the electric field generated by each target 10,1
It is accelerated by 1 and moves at high speed to the opponent's target while being spirally constrained by the magnetic flux 31 running between the target surfaces. The high-speed secondary (γ) electrons 9 that reach the target of the other party are also reflected by the electric field generated by the target, and as a result, the high-speed secondary (γ) electrons 9
It will be trapped in a spiral motion between 3,24. The reciprocating motion of the high-speed secondary (γ) electrons 9 is confined until the energy is reduced by the binding energy of the magnetic flux, and during that time, ionization is accelerated by collision with neutral particles or interaction with plasma. In the device of this embodiment, 10
Discharge can be sustained stably even at lower gas pressures of the order of ^-4 Torr.

Some of the particles sputtered from the target are ionized in the plasma. By extracting these ions, they can function as an ion source.

Factors that affect the generation of plasma include the gas pressure in the plasma generation chamber 20, the power supplied to the target, the magnetic field distribution, the distance between targets, and the like.

The energy of the extracted ions is mainly
And the voltage applied to the ion extraction grid 22 or the acceleration voltage which is a potential applied to the cylindrical anode, that is, the plasma control electrode 27.

In the ion source according to the present invention, a positive voltage is applied from the plasma control electrode pulse power supply 28 to the plasma generation chamber 20 to the cylindrical plasma control electrode 27 having a height of, for example, 10 cm in the plasma generation chamber 20 and a height of 3 cm, The potential of the plasma can be controlled. Ion extraction grid 2 with an effective extraction diameter of 6 cm
2 is a floating potential. As a result, ions in the plasma can be extracted as an ion beam 32 to the substrate 37 side. At this time, the energy of the ions flying to the substrate 37 substantially corresponds to the difference between the potential of the plasma control electrode 27 and the voltage applied to the substrate 37.

Here, an ion extraction process when a pulse voltage is applied to the plasma control electrode, which is a feature of the present invention, will be described with reference to FIG.

FIG. 3A shows the process of extracting ions with respect to the potential of the plasma control electrode in this embodiment, and FIG.
Shows the waveform of the applied pulse voltage and the drawn current waveform. When a rectangular pulse composed of a plasma generation chamber potential (0 V) and a positive voltage is applied to the plasma control electrode, when the pulse is at a positive voltage, ions are extracted from the plasma with almost the same energy. On the other hand, when the potential is equal to or lower than the plasma generation chamber potential (0 V), electrons in the plasma diffuse to the substrate 37 side via the ion extraction grid 22 while being constrained by the magnetic field. Therefore, before the surface of the substrate 37 is charged up by the charge of the ions extracted while the plasma control electrode potential is positive, it is possible to stably realize the ion extraction by neutralizing the charge of the ions by the diffused electrons. it can. The frequency of the pulse must be set faster than the charge diffusion frequency on the substrate 37, in this case from 5KHz to 50KHz.
Ions can be extracted most efficiently in the KHz range. Further, the ratio (duty) of the ion extraction time is not particularly limited, but is preferably about 0.9 to 0.5.

Next, a description will be given of the result of forming an Al ₂ O ₃ film by simultaneously extracting Al ions and oxygen ions in an argon-oxygen mixed atmosphere using a thin film deposition apparatus using an ion source according to the present invention.

After evacuating the vacuum of the sample chamber 33 to 5 × 10 ⁻⁷ Torr, Ar
Gas was introduced at a flow rate of 5 cc / min and oxygen gas was introduced at a flow rate of 5 cc / min. The gas pressure in the plasma generation chamber was set at 5 × 10 ⁻⁴ Torr, and the electric power supplied to the cylindrical Al target 24 was discharged at 100 to 500 W. A pulse voltage applied to the plasma control electrode 29 has a frequency of 30 KHz, an ion extraction duty of 70%, a rectangular wave of 0 to 100 V, and an ion extraction mechanism.
The film was deposited with the spherical porous grid as 22 at floating potential. At this time, the sample stage formed a film in the range from room temperature to 400 ° C. As a result, a dense Al ₂ O ₃ film could be stably and efficiently deposited at a deposition rate of 0.5 to 3 nm / min.

Although the above-described embodiment was applied to the extraction of Al ions and the formation of a compound film thereof, the present invention is not limited to this, and it can be used for almost all film formation.
Most reactive gases such as nitrogen can be used.

Further, in the above-described embodiment, the electromagnet is used as the magnetic circuit for the plate-shaped target, but a permanent magnet can be used. Although a hemispherical perforated grid is used as the ion extraction mechanism 22, a flat perforated grid or a grid composed of two or three plates may be used. Further, the cylindrical target shape does not need to be cylindrical, and the essential effect of the present invention does not change even if it is polygonal.

Further, in the above-described embodiment, the power supply for the target is provided separately, but the effect is the same even if the power supply is integrated and electrically connected to each other. The power supply may be a DC negative power supply, an AC power supply, or a high-frequency power supply.
However, if both are high-frequency power supplies, it is desirable to align both phases as much as possible. Of course, only one may be a DC power supply.

Furthermore, in the above-described embodiment, it is possible to additionally arrange an electromagnet, a yoke, or a permanent magnet to control the magnetic field distribution.

[Effects of the Invention] As described above, according to the present invention, metal ions are generated and extracted with high efficiency by using sputtering in a high vacuum.
Various high-quality thin films can be formed, and a film can be formed on an insulating substrate or an insulating film can be formed. INDUSTRIAL APPLICABILITY The ion source according to the present invention can be applied to forming a high-quality film with little damage at high speed and high stability at a low substrate temperature, material surface modification, or etching.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the sputter ion source of the present invention applied to a thin film deposition apparatus, and FIG. 2 is a plasma in one embodiment of the sputter ion source of the present invention shown in FIG. FIG. 3A and FIG. 3B are conceptual diagrams for explaining a magnetic field intensity distribution in the center magnetic flux direction and a high-density plasma generation mechanism. FIG. 4 is a diagram for explaining a drawing process, and FIG. 4 is a schematic configuration diagram of a typical gas ion source (Kaufman type) using a conventional filament. DESCRIPTION OF SYMBOLS 1 ... Plasma generation chamber, 2 ... Filament, 3 ... Electromagnet for generating a plasma stabilizing magnetic field, 4 ... Plasma, 5 ... Plasma control electrode, 6 ... Ion extraction (grid) mechanism, 7 ... Ion beam 9 High-speed secondary electrons 10 Electric field on a cylindrical target 11 Electric field on a plate target 20 Plasma generating chamber 21 Gas inlet for plasma generating chamber 22 Ion extraction (Grid) mechanism, 23 ... plate target, 24 ... tube target, 25 ... plate target power supply, 26 ... tube target power supply, 27 ... plasma control electrode, 28 ... plasma control electrode Pulse power supply for 29, ... insulator, 30 ... electromagnet for generating a magnetic field for stabilizing plasma, 31 ... magnetic flux, 32 ... ion beam, 33 ... sample chamber, 34 ... gas inlet for sample chamber, 35 ... … Exhaust system, 36 …… Substrate holder, 37 ... board, 38 ... shutter.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI H01L 21/31 H01L 21/302 D (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 14/00-14/58 C23F 4 / 00 H01L 21 / 302,21 / 31,21 / 285

Claims (5)

(57) [Claims] 1. A plasma generation chamber for generating a plasma by introducing a gas, a first and a second plasma generation chamber provided at both ends inside the plasma generation chamber, at least one of which is formed of a cylindrical sputtering material. A target; an ion extraction mechanism provided on a central axis of a cylindrical target among the first and second targets; and a negative potential with respect to the plasma generation chamber in the first and second targets, respectively. At least one first power supply for applying a voltage; a plasma control electrode provided inside the plasma generation chamber; and a magnetic field formed inside the plasma generation chamber; Means for generating magnetic flux exiting one of the targets and entering the other target; a second power supply for applying a pulse voltage to the plasma control electrode; Sputter ion source, characterized in that it includes. 2. The sputter ion source according to claim 1, wherein said cylindrical target is provided at an end of said plasma generation chamber on the side of said ion extraction mechanism. 3. The sputter ion source according to claim 1, wherein said plasma control electrode is provided between said first target and said second target. 4. The sputter ion source according to claim 1, wherein said ion extraction mechanism comprises at least one flat plate. 5. The sputter ion source according to claim 1, wherein said ion extraction mechanism comprises a convex porous grid.