JPS6134843A - Ion milling machine - Google Patents

Abstract

PURPOSE:To achieve effective reduction of divergence of ion beams and improved machining precision by providing a beam shield at the central portion of a pick-up electrode. CONSTITUTION:Cathodes 15 are made of hair pin-like W filament and a plasma generator 16 serves as anodes which cooperate with the cathodes 15 to produce arc discharging therebetween. A pick-up electrode for picking up ions from plasma generated in the generator 16 in form of ion beams 30 is composed of a plasma electrode 21, accelerating electrode 21 and decelerating electrode 22 each having apertures in such a range that the beams 30 are directed only to a target and a substantially circular beam shield at the center thereof. This is effective to eliminate ion beams at the central portion which act most greatly on beam divergence, reducing mutual repulsion between ions and minimizing divergence of the beams. Therefore, machining precision can be remarkably improved.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an ion milling device that microfabricates the surface of a target by irradiating the target with an ion beam, and particularly relates to an ion milling device that finely processes the surface of the target by irradiating the target with an ion beam. The present invention relates to an ion milling device suitable for processing a target using an ion beam.

[Background of the invention]

Conventional ion milling equipment, which performs fine processing on the target surface by sputtering the target by irradiating the target with a wide ion beam with an energy of about 200 to 5000 V drawn from a plasma generation chamber, was
The configuration shown in the figure is used. The configuration of this ion milling device includes an ion source 1 that extracts a wide ion beam, a target 2 that is used for surface micromachining,
Target holder 3 that holds and cools the target
It also includes a vacuum container 4, a vacuum pump 5, and a neutralization filament 6 that supplies thermoelectrons for electrically neutralizing the ion beam.

The configuration of the ion milling device will be explained in more detail. Neutral gas 10 such as argon gas introduced from gas inlet 9
By applying a DC voltage between the anode 8 and the can-door, a positive pear is ionized and an extraction electrode 12.13 (fifth. (see figure) is extracted as an ion beam. The extracted ion beam is supplied with thermoelectrons for gaseous neutralization by the neutralizing filament 6, and is irradiated onto the target 2 fixed on the rotating target holder 3.

In a milling device that processes a large number of targets 2, the targets 2 are arranged in a circular pattern on a target holder 3 in order to utilize a uniform beam from an ion source. In the ion milling apparatus at this time, the ions in the peripheral part used for processing the target 2 are bent by the Coulomb repulsion of the ions running in the central part, which is not originally needed, and when they enter the target 2, the outer diameter Since the beam is greatly curved in the direction, it has the disadvantage of significantly reducing processing accuracy. Moreover, the above space charge effect has the characteristic that it becomes more pronounced as the beam diameter of the ion source becomes larger (ION
IC8 November 1978 issue, p.27゜28).

[Purpose of the invention]

An object of the present invention is to provide an ion milling device that eliminates the above-mentioned drawbacks of conventional ion milling devices, suppresses ion beam divergence by reducing the space charge effect, and has good processing accuracy. An object of the present invention is to provide an ion milling device in which even when a large number of targets are arranged on a target holder, the machining accuracy of all targets is good.

[Summary of the invention]

In order to process a large number of targets at once and increase production speed, it is necessary to increase the diameter of the ion source, but due to the space charge effect, the ion beam is , because it diverges significantly, conventionally, caliber 25
cnr was the practical limit, but as a result of intensive research, the present inventors found that although it is ionization that accurately determines the degree of contribution of the space charge effect, the central We focused on the part of the ion beam that has the greatest effect on beam divergence. Therefore, we further researched solutions to this problem and found that removing the ion beam in the center using a circular beam shield can most effectively reduce the divergence of the ion beam and improve processing accuracy. We obtained the following knowledge.

The present invention was developed based on this knowledge in order to achieve the above object, and is characterized by the fact that in the above-mentioned ion milling apparatus, the The point is to insert a roughly circular member into the ion beam extracted by the electrode.

In addition, a substantially circular beam seal is provided in the center of the extraction electrode that extracts the ion beam from the plasma generation chamber in the plasma generation container, and a part or all of the plasma generation chamber in the plasma generation container is hollow. It is located at a cylindrical point.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using an illustrated embodiment.

FIG. 1 and FIG. 2 show such an embodiment, and the target 2, target holder 3, vacuum container 4, vacuum pump 5, and neutralization filament 6 in FIG. Since it can be used with the same configuration as the device, it will be omitted from the explanation.

The cathode 15, which ionizes the neutral gas 19 by arc discharge, is made of a hairpin-shaped tungsten filament. The plasma generating container 1.6 also serves as an anode electrode for causing arc discharge between the plasma generating container 1.6 and the cathode 15. The plasma ordering container 16, which uses a partially double-cylindrical cylinder, is made of a non-magnetic material such as stainless steel so that the magnetic field lines of the permanent magnet 17 installed on the back of the container can be formed inside, and it is also made of a non-magnetic material such as stainless steel. This is a packet structure with alternating north and south poles that efficiently generates plasma. A DC voltage is applied between the cathode 15 and the plasma generation container 16, and a neutral gas 19 such as argon gas introduced from the gas inlet 18 is ionized by arc discharge to create plasma in the plasma generation container 16. Plasma generation container 1
6, a plasma electrode 21 with an aperture 28 in the range where only the target is irradiated with the ion beam 30, and a substantially circular beam shield 20 in the center;
It is composed of an acceleration electrode 22 and a deceleration electrode 23.

The effects of this embodiment are as follows.

(1) By making the plasma generation vessel 16 that forms the plasma generation chamber double cylindrical, it is possible to reduce the amount of neutral gas such as argon introduced into the plasma generation chamber. The capacity of the power supply can be reduced.

(2) By providing the beam shield 20 in the center of the extraction electrode or by making the plasma generation container 16 double cylindrical, it is possible to reduce the amount of neutral gas such as argon introduced into the plasma generation chamber. By limiting the range of the true aperture 28 that evacuates the vacuum chamber to only the periphery of the electrode that irradiates the target, the area of the target holder that is irradiated with the ion beam becomes smaller, thereby reducing the amount of waste material sputtered onto the target. can be reduced.

(4) Pulling out the ion beam 30 from the plasma created by ionizing a neutral gas such as argon gas - By adjusting the aperture range of the extraction electrode so that the ion beam is irradiated near the target, the target holder is Since the area irradiated with the ion beam becomes smaller, the capacity of the cooling device for the target holder can be reduced.

(5) Since the plasma is confined by the permanent magnet 17 with N poles and 8 poles arranged alternately, the magnetic field leaking into the target is small, the divergence of the ion beam due to the magnetic field is small, and the processing accuracy at the target is improved.

In addition, all of the plasma generation container 16 in FIG. 1 is made into a double cylinder, and the inner cylindrical part is
It is also possible to support extraction polarization, and in particular, the extraction electrode is easily cooled and deformation due to heat is small.

In addition, FIG. 3 shows another embodiment, in which, instead of the permanent magnet 17 in FIG. 1, a solenoid coil 25, 26 is used to flow current in the opposite direction so that the magnetic field on the axis of symmetry is small.
This has the effect of simplifying the structure compared to the embodiment shown in FIG.

Note that even if the plasma electrode 21 provided with the beam shield 2o of the present invention is used in place of the extraction electrode 12 of the conventional example shown in FIG. 4, the effect (2) of the embodiment shown in FIG.
There are effects up to 4). Such a substantially circular beam shield has the same effect even if it is provided in the plasma generation chamber or in the extracted ion beam.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention, the ion beam in the central portion, which has the greatest influence on beam divergence, can be removed, thereby reducing the mutual repulsion of ions,
Beam divergence can be made extremely small, and therefore machining accuracy can be significantly improved.In particular, even when a large number of targets are arranged over a wide area, each target can be machined with the same effect. It is very large.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of an ion milling device according to an embodiment of the present invention, FIG. 2 is a front view of an extraction electrode according to an embodiment of the present invention, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a partial cross-sectional view of an ion milling device according to an example, FIG. 4 is a configuration diagram of a conventional ion milling device, and FIG. 5 is a front view of a conventional extraction electrode. DESCRIPTION OF SYMBOLS 1... Ion source, 2... Target, 3... Target holder, 4... Vacuum container, 5... Vacuum pump, 6... Neutralization filament, 7, 15... Cathode, 8... Anode, 9.18... Gas inlet, 10.19... Neutral gas, 11... Container, 12.
13... Extraction electrode, 14, 25. 26... Solenoid coil, 16... Plasma generation container, 17...
- Permanent magnet, 20... Beam shield, 21... Plasma electrode, 22... Acceleration electrode, 23... Deceleration electrode, 24... Ground electrode flange.

Claims (1)

[Scope of Claims] 1. A plasma generation container constituting a plasma generation chamber, a filament that ionizes neutral gas introduced into the plasma generation chamber into plasma by arc discharge, and ions in the plasma generation chamber. An ion milling device that includes an ion source equipped with an extraction electrode that extracts the target as an ion beam, a vacuum container provided adjacent to the ion source, and a target holder that holds and cools a target within the vacuum container. An ion milling apparatus characterized in that the ion source is provided with a shielding body that shields a central portion of the ion beam. 2. The ion milling apparatus according to claim 1, wherein the shield is a substantially circular beam shield formed at the center of the extraction electrode. 3. Claim 1 or 2, wherein the plasma generation container is formed in a double cylindrical shape.
The ion milling device described in section. 4. The ion milling apparatus according to claim 4, wherein the shield is a central bottom portion of the plasma generation container formed in a double cylindrical shape.