JP2835383B2 - 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 ion source for continuously and stably extracting various ions with high current density and high efficiency by using high density plasma sputtering for a long time.

[Prior Art] Attempts have been made to extract gas ions such as argon and apply them to various sputtering, etching, surface modification and the like.

On the other hand, a technique capable of extracting not only gas but also metal ions with a large current is desired in various fields.

As the metal ion source, an evaporation type is usually the mainstream, and it is necessary to keep the evaporation source at a high temperature, and it has been difficult to extract ions of the high melting point material. On the other hand, although a sputter-type metal ion source has been devised, it has been generally impossible to extract ions continuously for a long time, and moreover, it was not possible to extract ions over a large area. Further, in the conventional ion source, gas and particles in the plasma were not sufficiently ionized.

In order to realize a large current ion source by using sputtering, it is necessary to maintain the plasma density at high density and high efficiency. To do so, secondary electrons (γ electrons) emitted from the target
It is important to confine the electron efficiently, but the conventional technology does not sufficiently confine the secondary electrons and cannot effectively transfer the energy of high-energy electrons to the plasma. It is hard to say that it is enough.

Also, extraction of ions from the high-density plasma was not sufficient.

[Problems to be Solved by the Invention] The conditions desired as an ion source can be summarized as follows: (1) large yield (large ion current); (2) few impurities; and (3) wide range of ion energy. (4) not only inert gas but also various ions such as metal ions can be taken out.

However, an ion source satisfying such a condition has not been realized so far.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel sputter-type ion source which can solve the above-mentioned drawbacks and can satisfy the above conditions.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a plasma generation chamber for introducing a gas to generate plasma,
First and second targets each made of a sputtering material provided at both ends of the plasma generation chamber and at least one of which is cylindrical, and an ion extraction mechanism provided at an end of the plasma generation chamber. A plasma control electrode provided inside the plasma generation chamber, and a magnetic field formed inside the plasma generation chamber, and the magnetic field is generated from one of the first and second targets to the other target. And a means for generating a magnetic flux that enters the ion source, wherein the ion extraction mechanism includes at least one porous grid that is convex toward the plasma generation chamber.

[Operation] According to the present invention, high-density plasma is generated in a low-pressure gas, sputtering is performed using the plasma, and ions generated therefrom can be continuously extracted with high current density and high efficiency.

That is, in the present invention, a target made of a sputtering material is installed at both ends in the plasma generation chamber,
The effect of confining the plasma by magnetic flux passing from one side of the target to the other, and the electric field mirror effect of reflecting secondary electrons (γ electrons) emitted from the target into the plasma by applying a negative potential to the target Metal ions can be efficiently extracted from the low-acceleration voltage and high-density plasma generated by using the ion-extraction mechanism including a convex porous grid.

EXAMPLES The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of an embodiment of a sputter type ion source according to the present invention using one convex porous grid.

At both ends in the plasma generation chamber 1, a flat target 2
And the cylindrical target 4, and the magnetic flux 11 by the electromagnet 10 is
An electromagnet 10 is arranged around the plasma generation chamber 1 so as to penetrate the surfaces of the targets 2 and 4.

The magnetic flux between the targets prevents the secondary electrons (γ electrons) generated from the target surface from dissipating in the direction perpendicular to the magnetic field, and further has the effect of confining the plasma. Generated.

2 (A), 2 (B) and 2 (C) show examples of magnetic field intensity distribution and potential distribution in the magnetic flux direction and the high-density plasma generation mechanism in the embodiment of the present invention shown in FIG.

In FIG. 1, the plasma generation chamber 1 is water-cooled in order to prevent a rise in temperature due to plasma generation. A gas introduction system (not shown) is directly connected to a gas introduction port 12 connected to the plasma generation chamber 1.

The flat target 2 is a water-coolable target holder 2A
The cylindrical target 4 is detachably fixed to a water-coolable target holder 4A. Holders 2A and 4A are insulators 2C and 4C, respectively.
Is fixed to the plasma generation chamber 1. 1D and 1E are shields, respectively.

A negative voltage is applied to the plasma generation chamber 1 from the power supplies 3 and 5 to the water-cooled targets 2 and 4 via holders 2A and 4A, respectively.

In the plasma generation chamber 1, for example, a cylindrical anode electrode 8 is disposed as an electrode for plasma control via an insulator 8A. A positive voltage is applied to the anode electrode 8 from the power supply 9 to the plasma generation chamber 1. This anode 8
The plasma potential can be controlled by the potential applied to the electrodes 14, so that the extraction efficiency of the ions 14 can be improved.

At the center of the cylindrical target 4, a hemispherical convex porous grid 6 is arranged as an ion extraction mechanism. 6A and 6B
Is an insulator.

A voltage is applied to the grid 6 from a power supply 7. At that time, it is desirable to apply a negative potential from the plasma generation chamber 1.

It is preferable to apply a positive potential from the power supply 13 to the plasma generation chamber 1.

The energy of the extracted ions is controlled mainly by the potential of the anode 8 and the potential of the plasma generation chamber 1. Further, if the grid is kept lower than the potential of the plasma, the energy of the extracted ions can be controlled only by the voltage applied to the anode 8 even if the potential applied to the plasma generation chamber is the ground potential. From low ion energy to energy of several keV,
Ion energy can be controlled. FIG. 3 shows a change in ion energy with respect to the anode potential. At this time, the plasma generation chamber was set to the ground potential, and the grid potential was set to -50V. Ion energy increased linearly with anode potential.

In the present embodiment, the hemispherical porous grid 6 having a curvature radius of 55 mm is used as the convex grid, but the ion extraction amount is improved about five times as compared with the case where the flat porous grid is used. FIG. 4 shows the ion extraction characteristics. At this time, the Ar gas pressure was 5 × 10 ⁻⁴ Torr, and the sputtering power was 300
W, the grid voltage was −50 V, and the voltage applied to the anode was changed from 50 to 300 V while the plasma generation chamber was at ground potential. The energy of the ions on the horizontal axis in FIG. 4 is related to the voltage applied to the anode.

That is, in the target configuration of the ion source of the present invention, since the high-density plasma is confined between the two targets 2 and 4, the plasma density is relatively low at the center of the cylindrical target 4, and the plasma density is closer to the target. Because of the rise, when a flat grid is used, it is difficult to arrange the grid surface close to the high-density plasma. On the other hand, when a convex grid such as the hemispherical grid 6 is used, the ion extraction surface can be set along high-density plasma, so that the efficiency is much higher than when a flat grid is used. Ion extraction is possible.
By bringing the convex grid as close as possible to the high density part of the plasma, the extracted ion current can be increased. However, when the convex portion of the grid blocks the magnetic flux crossing the cylindrical target 4, the generation of plasma becomes unstable. Therefore, it is desirable that the side surface of the convex grid is along the magnetic flux 11 and that the position of the tip is set to a position that does not block the magnetic flux crossing the cylindrical target 4.

Here, the principle of high density plasma generation in the sputter type ion source of the present invention will be described in more detail with reference to FIG.

When high-speed ions collide with the target, high-speed secondary electrons (γ electrons) 15 are emitted from the target surface. The γ electrons emitted from this target are reflected by the electric field of both targets, and reciprocate between the targets while performing a cycloton motion around a magnetic flux running between the targets. γ
The electrons are confined between the targets until the energy becomes smaller than the magnetic binding energy of the magnetic flux, during which the collision with neutral particles promotes ionization. Further, the high-speed electron flow (electron beam) reciprocating between the targets further accelerates the ionization of neutral particles due to the interaction with the plasma. As described above, high-density plasma can be generated even at a low gas pressure.

In the apparatus of the present invention, discharge can be stably formed even at a lower gas pressure of the order of 10 ⁻⁵ Torr, and high-speed ion extraction is realized.

Next, the results of forming a film by extracting Al ions using the sputter ion source of the present invention will be described. After evacuating the vacuum of the sample chamber 16 to 5 × 10 ⁻⁷ Torr, Ar gas was discharged at a rate of 2.
The gas was introduced at a flow rate of 5 cc or 5 cc, and discharge was performed at a gas pressure of 5 × 10 ⁻⁴ Torr or 1 × 10 ⁻³ Torr in the plasma generation chamber. Here, the voltage applied to the flat target 2 is-
Fixed to 300V. Each of them shows a constant voltage discharge characteristic in which a discharge current increases like an avalanche from a certain voltage, indicating that high density plasma is growing. In the sputter ion source of the present invention, the voltage applied to the cylindrical target 4 and the flat target 2 can generate plasma with sufficiently high density even when they are different. Further, even when the voltages are the same, a sufficiently high rate of plasma generation can be realized. Electric power to be applied to the cylindrical Al target 4 is 300 to 900
Sputtered with W. The film was formed at room temperature without heating the sample while fixing the energy of the extracted ions to 300 eV. As a result, the Al film could be stably deposited continuously at a deposition rate of 1 to 20 nm / min for a long time.

Sputter type ion source of the present invention is not only the extraction of Al ions and film formation using the same, but also Fe, MO, W, Ta, Cu, Co, Ni,
It can be used for extracting and forming almost all ions such as Cr, Ti, Nb, B, C, Si, Ge, Zr or alloys thereof, forming thin films, or modifying or etching the surface of materials. As a gas to be used, not only Ar but also an inert gas such as He, Ne, Kr, and Xe, and most reactive gases such as N ₂ , O ₂ , CH ₄ , H ₂ , and NH ₃ can be used. Thus, a compound film can be formed by ion extraction using reactive sputtering. Also. By performing sputtering using a compound target, ion beam generation of a compound film is also possible.

Further, as the target, a ring-shaped target can be used instead of the flat target. The cylindrical target need not be a cylinder, and may be a polygonal cylinder.

Further, in the above-described embodiment, as shown in FIG. 2, the maximum value of the magnetic field formed in the plasma generation chamber by the electromagnet 10 is set to a value of 500 G or more.
Even with this level, a sufficiently high density plasma can be generated.

In the present invention, the necessary magnetic field is obtained by an electromagnet,
It is apparent that the same effect can be obtained by using various permanent magnets or by combining them.

On the other hand, in this embodiment, a cylindrical anode is used as the anode electrode for plasma control. However, the same effect can be obtained by using a flat or rod-shaped anode, regardless of the shape.

As an embodiment of the present invention, as the ion extraction mechanism, 1
Although the case of only a single grid has been described, two convex grids may be combined.

In this embodiment, a hemispherical grid is used as the convex grid. However, since the gist of the present invention is to bring the grid surface closer to high-density plasma, the grid need not be spherical. For example, the shape may be a cone or a polygon. However, the position of the tip is as described above.

[Effects of the Invention] As described above, according to the present invention, by placing a grid in front of a high-density plasma generated by the interaction of a magnetic field and an electric field, a highly efficient metal can be formed in a low gas pressure. Ion extraction can be realized continuously and stably for a long time.

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 sectional view of an embodiment of a sputter type ion source according to the present invention, and FIG. 2 is a magnetic flux density distribution (A), a potential distribution (B) and a high magnetic flux distribution in a magnetic flux direction in the embodiment shown in FIG. FIG. 3 shows a density plasma generation structure (C). FIG. 3 shows a relationship between a voltage applied to a cylindrical anode electrode and
FIG. 4 is a diagram showing a change in extraction ion energy. FIG. 4 is a diagram showing an example of ion extraction characteristics. 1 ... plasma generation chamber, 2 ... flat target, 3,5,7,9,13 ... power supply, 4 ... cylindrical target, 6 ... hemispherical porous grid for ion extraction, 6A, 6B ... Insulator, 8: cylindrical anode, 10: electromagnet for generating magnetic field, 11: magnetic flux, 12: gas inlet, 14: ion beam, 15: secondary electron.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI H01L 21/3065 H01L 21/302 B (58) Investigated field (Int.Cl. ⁶ , DB name) C23C 14 / 34,4 / 00,14 / 46 H01L 21 / 203,21 / 302 H01J 37/30

Claims (1)

(57) [Claims] 1. A plasma generation chamber for generating a plasma by introducing a gas, and first and second cylinders each formed of a sputtering material provided at both ends of the plasma generation chamber and at least one of which is cylindrical. A target, an ion extraction mechanism provided at an end of the plasma generation chamber, a plasma control electrode provided inside the plasma generation chamber, and a magnetic field formed inside the plasma generation chamber; and Means for generating magnetic flux exiting from one of the first and second targets and entering the other target, wherein the ion extraction mechanism is convex toward the plasma generation chamber. A sputter-type ion source comprising at least one perforated grid.