JPH0488165A - Sputtering type ion source - Google Patents

Abstract

PURPOSE:To efficiently draw metal ions produced in high-density plasma formed in high vacuum by using a pair of targets, at least one of the targets is cylindrical, and disposing the targets so that the fast secondary electrons required for the formation of high-density plasma can be confined. CONSTITUTION:A plasma producing chamber 20 is connected to a sample chamber 33 through a grid 22 for drawing ions. Minus voltage is applied on a cylindrical target 24 and a planer target 23 from a power source 26 for the cylindrical target and from a power source 25 for the planer target, respectively, to the plasma producing chamber 20 in order to form high-density plasma and to cause efficient sputtering. Part of sputtered particles from the targets are ionized in the plasma. By drawing these ions, the plasma can be used as the ion source. The energy of the ions drawn from the plasma can be controlled mainly by varying the relative difference between voltages applied on the plasma producing chamber 20 and on the ion drawing grid 22, or by varying the acceleration voltage applied on a cylindrical anode, namely, a plasma controlling electrode 27.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention is applicable to the formation of thin films of various materials on sample substrates,
It also relates to equipment for extracting ions for etching the surface of thin films or for surface modification, and in particular, a new sputtering type that utilizes high-density plasma sputtering to generate and extract metal ions stably with high efficiency. It concerns an ion source.

[Prior Art 1] Conventionally, so-called ion sources that extract ions generated in plasma using an extraction mechanism such as a grid have been widely used in various fields for etching and processing various materials and thin films. Among these, a Kauffman type ion source equipped with a filament for thermionic release as shown in FIG. 4 is most commonly used. The Kaufmann type ion source has a filament 2 for thermionic emission inside a plasma generation chamber 1,
Using this filament 2 as a cathode, a discharge is caused in a magnetic field generated by an electromagnet 3 for generating a plasma stabilizing magnetic field, thereby generating plasma 4.
Plasma 4 is generated by plasma control electrodes 5 facing each other with
While controlling this, ions in the plasma 4 are extracted as an ion beam 7 using several extraction grids 6.

Since ion sources such as the conventional Kauffmann ion source use a filament to extract thermal electrons for plasma generation, the filament material is sputtered and included in the extracted ions as impurities. Furthermore, when a reactive gas such as oxygen is used as the plasma generating gas, there is a drawback that the reactive gas reacts with the filament, making it impossible to extract ions continuously for a long time. Moreover, this type of ion source has the disadvantage that its use is limited to extracting gas ions and cannot be used for extracting metal ions.

On the other hand, a sputter-type ion source has been proposed as an ion source that can extract metal ions over a large area (for example, 1989 Spring Japanese Society of Applied Physics, 30a-
ZG-10, 524p), with this type of ion source, it is possible to attract most metal ions such as Al and Fe over a large area.

[Problem to be Solved by the Invention 1] However, in the above-mentioned sputtering type 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. , due to the charge-up of the substrate due to the ion beam,
Ions could not be extracted effectively.

For this reason, a method is sometimes 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 electrons emitted there neutralize the charge of the ions to extract the ions. .

However, if such a method is applied to the above-mentioned sputter type ion source, impurities may enter the film from the heated filament, or if a reactive gas such as oxygen is introduced, the reactive gas and the filament may It not only reacts with the material and releases impurities (but also has the disadvantage that the life of the filament is extremely short).

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

[Means for Solving the Problems 1] In order to solve the above-mentioned technical problems, the present invention provides a plasma generation chamber in which gas is introduced to generate plasma, and a plasma generation chamber provided at both ends of the inside of the plasma generation chamber. , and at least one of which is made of a cylindrical sputtering material.
and a second target, an ion extraction mechanism provided on the central axis of a cylindrical target among the first and second targets, and an ion extraction mechanism provided in the first and second targets, respectively, for the plasma generation chamber. at least one first power source that applies a negative potential; a plasma control electrode provided inside the plasma generation chamber; and a plasma control electrode that forms a magnetic field inside the plasma generation chamber, and The present invention is characterized by comprising means for generating a magnetic flux that exits from one of the two targets and enters the other target, and a second power source that applies a pulse voltage to the plasma control electrode.

[Function 1] The present invention is capable of efficiently extracting metal ions generated by sputtering using high-density plasma, and forming a high-quality thin film on an insulator or an insulating film in a high vacuum. be. That is, the present invention combines a set of targets, at least one of which is cylindrical, to create a target arrangement that confines high-speed secondary electrons necessary for high-density plasma generation in the plasma. can be generated, and the metal ions generated can be extracted efficiently. Moreover, since the ion extraction is done in a pulsed manner and the ion charge is simultaneously neutralized by the discharge electron beam, there is no charge-up of the surface of the substrate or film due to ions, and ions can be extracted stably even onto insulating substrates. Alternatively, it becomes possible to form an insulating film.

[Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

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

Gas for generating plasma is introduced into the plasma generation chamber 20 through an inlet 21. An ion extraction grid 22 is provided at one end of the plasma generation chamber 20.
is provided. In this embodiment, the grid 22 is composed of a single hemispherical porous grid. A voltage is applied to this 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 24 is provided near the grid 22. target 2
3 is removably fixed to a water-coolable metal support 23A. The support 23A is fixed to the lid 20B at the top of the plasma generation chamber 20, and the lid 20B is connected to the insulator 2.
3B to the upper wall 20A of the brass generation chamber 20. Similarly, the target 24 is removably fixed to a water-coolable metal support 24A. The support body 24A is fixed to the wall 20G of the plasma generation chamber 20 via an insulator 24B. Furthermore, the aforementioned grid 22 is fixed to the lower part of the support body 24A via an insulator 24G. The protruding ends 23D and 24D of the supports 23A and 24A also serve as electrodes, and are connected to a DC power source 25.
A negative potential with respect to the plasma generation chamber 20 can be applied to the targets 23 and 24 from and 26 .

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

An electromagnet 30 is provided around the outer periphery of the plasma generation chamber 20 for forming a magnetic field inside the plasma generation chamber.

Electromagnet 30 and targets 23 and 24 are positioned so that magnetic flux 31 generated by electromagnet 30 crosses both target surfaces, with the magnetic flux exiting the surface of one target and entering the surface of the other target. For example, a cylindrical target 24 with an inner diameter of 10 cm and a height of 5 cm is used, and a disc-shaped target 23 with a diameter of 8 cm is used, and the distance between the two targets is 8 cm.
m. It is desirable that the plasma generation chamber 20 be water-coolable. In order to protect the sides of targets 23 and 24 from plasma, it is preferable to provide a shield on the inner surface of the plasma generation chamber.

After evacuating the inside of the plasma generation chamber 20 to a high vacuum, gas is introduced from the gas inlet 21 and the voltage applied to the targets 23 and 24 is increased in the magnetic field by the electromagnet 30, causing discharge and generating plasma. .

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 has the effect of confining the plasma, resulting in high-density plasma in low gas pressure. is generated.

An example of a thin film deposition apparatus using the sputter type ion source of the present invention configured as described above will be explained with reference to FIG.

A sample chamber 33 is connected to the plasma generation chamber 20 with an ion extraction grid 22 in between. Although the sample chamber 33 and the plasma generation chamber 20 constitute one vacuum chamber, it is preferable to insulate them. Gas can be introduced into the sample chamber 33 through a gas inlet 34, and the chamber can be evacuated to a high vacuum by an exhaust system 35. Further, a substrate holder 36 for holding a substrate 37 is provided in the sample chamber 33, and a shutter 38 that can be opened and closed is provided between the substrate holder 36 and the ion extraction grid 22. Board holder 3
6 preferably has a built-in heater to heat the substrate 37, and also applies a DC or AC voltage to the substrate 37 to apply a bias voltage to the substrate during film formation.
It is desirable that the structure be such that sputter cleaning of the substrate is possible.

Next, with reference to FIG. 2, the plasma proliferation mechanism due to the movement of high-speed secondary electrons in the sputter type ion source according to the present invention will be explained.

The cylindrical target 24 and the plate-like target 23 are provided with a cylindrical target power source 26 and a plate-like target power source 25, respectively.
By applying a negative potential to the plasma generation chamber 2o, high-density plasma is generated and sputtering is efficiently caused. When the ions drawn into both targets 23 and 24 collide with the target surface, high-speed secondary electrons (γ electrons) 9 are released from the target surface. These high-speed secondary (γ) electrons 9 are accelerated by the electric fields 10 and 11 created by each target, and are restrained by the magnetic flux 31 running between the surfaces of these targets and move to the other target at high speed while performing a spiral motion. The high-speed secondary (γ) electrons 9 that reach the other target are also reflected by the electric field created by the target, resulting in high-speed secondary (γ) electrons 9
will be trapped between the two targets 23 and 24 while moving in a spiral manner.

This reciprocating motion of the high-speed secondary (γ) electrons 9 is confined until its energy is reduced by the binding energy of the magnetic flux, and during that time, ionization is accelerated by collisions with neutral particles and interaction with plasma. In the device of this example, 10-
'Discharge can be maintained stably even at lower gas pressures on the Torr level.

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

Factors that influence plasma generation include the gas pressure in the plasma generation chamber 20, the power input to the target, the magnetic field distribution, and the distance between targets.

The energy of the extracted ions is mainly transferred to the plasma generation chamber 20.
and the relative difference between the voltage applied to the ion extraction grid 22,
Or a cylindrical anode, i.e. plasma control electrode 2
It can be controlled by an accelerating voltage which is a potential applied to 7.

In the ion source according to the present invention, a positive voltage with respect to the plasma generation chamber 20 is applied to the cylindrical plasma control electrode 27 with an inner diameter of 10 cm and a height of 3 cm, for example, in the plasma generation chamber 20 from a plasma control electrode pulse power source 28. , the potential of the plasma can be controlled. The ion extraction grid 22 with an effective extraction diameter of 6 cm is floating.
potential. As a result, ions in the plasma can be extracted to the substrate 37 side as an ion beam 32.

At this time, the energy of the ions flying to the substrate 37 is
This corresponds to the difference between the potential of the plasma control electrode 27 and the voltage applied to the substrate 37.

Here, the ion extraction process when a pulse voltage is applied to this plasma control electrode, which is a feature of the present invention, will be explained based on FIG. 3.

FIG. 3(A) shows the ion extraction process with respect to the potential of the plasma control electrode in this example, and FIG. 3(B) shows the waveform of the applied pulse voltage and the extraction current waveform. When a rectangular pulse consisting of the plasma generation chamber potential (0■) and a positive voltage is applied to the plasma control electrode, ions are extracted from the plasma with a certain amount of energy when the voltage is positive. On the other hand, when the potential is at or below the plasma generation chamber potential (0■), electrons in the plasma are restrained by the magnetic field and diffuse toward the substrate 37 via the ion extraction grid 22. Therefore, before the surface of the substrate 37 is charged up due to the charge of ions extracted while the plasma control electrode potential is positive, stable ion extraction can be achieved by neutralizing the charge of the ions with the diffused electrons. can. The frequency of the pulse needs to be set faster than the charge diffusion frequency on the substrate 37, and in this case it is set to 5.
Ions can be extracted most efficiently in the range from KHz to 50 KHz. Further, the ratio of ion extraction time (duty) is not particularly limited, but a ratio of about 0.9 to 0.5 is efficient.

Next, the results of forming an Al*0* film by simultaneously drawing out 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 will be described.

After evacuating the vacuum level of the sample chamber 33 to 5xlO-'Torr, Ar gas was pumped at 5 cc/min and oxygen gas was pumped at 5 cc/min.
The cylindrical A1 target 24 was introduced at a flow rate of c and the gas pressure in the plasma generation chamber was set to 5xlO-'Torr.
The power input was set to 100 to 500 W and discharged.

The pulse voltage applied to the plasma control electrode 29 has a frequency of 30 KHz and an ion extraction duty of 7.
The film was deposited with a spherical porous grid as an ion extraction mechanism 22 at a floating potential as a square wave of 0% and 0 to 100V. At this time, film formation was performed on the sample stage at a temperature ranging from room temperature to 400°C. As a result, 0.5 to 3 nm
/win deposition speed, stable and efficient dense A1□0
．． The film could be deposited.

Although the above embodiment was applied to extracting Al ions and forming a film of its compound, it is not limited to this, and can be used for almost any film formation, and the gas species to be introduced may also be
Most reactive gases can be used, such as nitrogen.

Further, in the above embodiment, an electromagnet was used as the magnetic circuit for the plate-shaped target, but it is also possible to use a permanent magnet. Although a hemispherical porous grid was used as the ion extraction mechanism 22, a flat porous grid or two
A grid consisting of one sheet or three sheets may also be used. Furthermore, the shape of the cylindrical target does not have to be cylindrical, and even if it is polygonal, the essential effects of the present invention will not change.

Furthermore, in the above-described embodiments, the power source for the target is separate, but the effect remains the same even if the power source is integrated and electrically connected to each other. Further, the power source may be a direct current negative power source, an alternating current power source, or a high frequency power source. However, when both are high-frequency power sources, it is desirable to align both phases as much as possible; of course, only one may be a DC power source.

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

[Effect of the invention 1 As explained above, according to the present invention, metal ions can be generated and extracted with high efficiency using sputtering in a high vacuum, and various high-quality thin films can be formed. ,
The ion source according to the present invention is capable of forming films on insulating substrates or forming insulating films. It can also be applied to texture or etching.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the sputter-type ion source of the present invention applied to a thin film deposition apparatus, and FIG. 2 is a plasma plasma in the embodiment of the sputter-type ion source of the present invention shown in FIG. A conceptual diagram for explaining the magnetic field strength distribution in the direction of the central magnetic flux and the high-density plasma generation mechanism. Figures 3 (A) and (B) show the pulse voltage waveform applied to the plasma control electrode, changes in the extraction ion current, and ion FIG. 4, which is a diagram for explaining the extraction process, is a schematic diagram of a typical gas ion source (Kaufman type) using a conventional filament. 1... Plasma generation chamber, 2... Filament, 3... Electromagnet for plasma stabilizing magnetic field generation, 4... Plasma, 5... Plasma control electrode, 6... Ion extraction grid) mechanism , 7... Ion beam, 9... High-speed secondary electrons, lO... Electric field above cylindrical target, 11... Electric field above plate-shaped target, 20... Plasma generation chamber, 2L... Plasma Gas inlet for generation chamber, 22... Ion extraction grid) mechanism, 23... Plate target, 24... Cylindrical target, 25... Power supply for plate target, 26... Cylindrical Target power supply, 27... Plasma control electrode, 28... Pulse power supply for plasma control electrode, 29...
Insulator, 30... Electromagnet for generating plasma stabilizing magnetic field, 31...
- Magnetic flux, 32... Ion beam, 33... Sample chamber, 34... Gas inlet for sample chamber, 35... Exhaust system, 36... Substrate holder, 37... Substrate, 38. ··Shutter. (vinegar

Claims (1)

[Scope of Claims] 1) A plasma generation chamber in which a gas is introduced to generate plasma; and first and second chambers made of a sputtering material, each of which is provided at both ends of the interior of the plasma generation chamber, and at least one of which is cylindrical. a second target; an ion extraction mechanism provided on the central axis of a cylindrical target among the first and second targets; and a second target connected to the plasma generation chamber, respectively. at least one first power source that applies a negative potential; a plasma control electrode provided inside the plasma generation chamber; a plasma control electrode that forms a magnetic field inside the plasma generation chamber; A sputter-type ion source comprising: means for generating magnetic flux that exits from one of the targets and enters the other target; and a second power source that applies a pulse voltage to the plasma control electrode. . 2) The sputter type ion source according to claim 1, wherein the cylindrical target is provided at an end on the ion extraction mechanism side of both ends of the plasma generation chamber. 3) The sputter type ion source according to claim 1, wherein the plasma control electrode is provided between the first target and the second target. 4) The sputter type ion source according to claim 1, wherein the ion extraction mechanism is composed of at least one flat plate. 5) The sputter type ion source according to claim 1, wherein the ion extraction mechanism is comprised of a convex porous grid.