JPH0594793A - High current ion source - Google Patents

Abstract

(57) [Summary] [Structure] The heating shield plate 8 is disposed between the filament 9 and the electrode 1. [Effect] The radiant heat of the filament is shielded by the heat shield plate and does not reach the electrode. Therefore, the thermal deformation of the electrode can be prevented, and the ion beam can be extracted two to three times as large as the conventional one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam milling apparatus equipped with an ion source for milling a resist on a substrate with an ion beam extracted from the ion source.

[0002]

2. Description of the Related Art In a conventional ion source that emits thermoelectrons by using a filament to generate plasma, a water-cooled copper tube is brazed to the electrode or the electrode is prevented from being thermally deformed by the radiant heat of the filament. The electrode was cooled by cooling the metal fitting to which it was attached with water.

In the method of brazing a water-cooled copper tube on the electrode itself, the distribution of the beam extraction holes becomes unbalanced, and in the method of cooling the outer circumference, temperature gradients occur at the central portion and the outer peripheral portion, and deformation is unavoidable. Increasing the filament input to increase the draw beam current density was limited.

Here, the Φ200 electrode is molybdenum (generally used as an electrode material, and has a coefficient of thermal expansion of 5.3).
× 10 ^-6 · k ^-1 ) and the periphery is fixed 10
When the temperature rises by 0 ° C., the central part is displaced by about 15 mm in the axial direction and becomes a spherical surface. Therefore, unlike a beam extracted from an ion source originally designed to have a uniform electrode interval, there is a drawback that the distribution is significantly deviated and the function as the ion source is lost.

[0005]

In the filament type ion source, the current density of the extracted ion beam is proportional to the filament power (that is, the amount of heat generation).

On the other hand, since the electrode is thermally deformed by the radiant heat of the filament, the electrode itself or the outer peripheral mounting portion is water-cooled, but only an ion beam having a current density below a certain value can be extracted.

An object of the present invention is to prevent the heat radiation of the filament from reaching the electrode surface, and therefore, even if the power of the filament is increased, the electrode is not thermally deformed and the ion beam having a current density several times that of the conventional one is used. Is to provide an ion source that can be extracted.

[0008]

A heat shield plate is provided in the middle so that the radiant heat of the filament does not reach the electrode surface.

The heat shield plate is geometrically shaped and dimensioned so that the filament does not allow the electrode to be seen.

The heat shield plate is electrically insulated from the plasma chamber and has the same potential as the filament.

Since the temperature of the heat shield plate may rise due to the radiant heat of the filament, and the radiant heat may be emitted by itself to heat the electrode, it may be water-cooled to make the heat shield effective.

[0012]

The plasma chamber is a container provided with an ion beam extraction electrode at its opening, and the filament is arranged substantially in the center thereof.

The filament has a high temperature (2700-2800).
Therefore, tungsten wire is usually used. Between the filament and the electrode, a heat shield plate having a size and shape that does not geometrically look into the electrode is attached, and the radiant heat emitted from the filament is absorbed by the inner surface of the plasma chamber.
It hits the heat shield and does not reach the electrode surface.

Therefore, the electrode is not heated by the radiant heat of the filament and thermal deformation does not occur.

It has been confirmed by experiments that the provision of the heat shield plate increases the arc current by 20 to 30% but does not affect the extraction of the ion beam.

[0016]

FIG. 1 shows a cross section of an example in which a heat shield plate 8 according to the present invention is attached to a filament type ion source.

In the ion source, the magnet 6, which forms a cusp magnetic field for confining the generated plasma 13, is evenly provided on the outer periphery of the electrode 1, the electrode support flange 2, the insulating cylinder 3, the insulating spacer 4, the plasma chamber 6 and the plasma chamber 6. The plasma chamber cover 7 is arranged and can be opened and closed for convenient replacement of the filament 9. Water on the plasma chamber cover 7,
Feedthroughs 10 and 11 for supplying electricity and gas are attached.

A vacuum exhaust pump (not shown) attached to the processing chamber 15 is used in the plasma chamber.

[0019]

[Equation 1]

The gas is exhausted to some extent, the gas is introduced into the plasma chamber, and the filament 9 is energized. By energization, the filament 9 becomes 2700 to 2800 ° k, which emits thermoelectrons and radiates radiant heat to the surroundings. The introduced gas is ionized by the thermoelectrons emitted from the filament, and plasma 13 is generated. The generated plasma is accelerated by the electric field applied to the electrode 1 and extracted as an ion beam to the processing chamber side.

On the other hand, as shown in the figure, the radiant heat of the filament 9 does not reach the electrode 1 by the heat shield plate 8 and therefore is not heated and does not undergo thermal deformation.

[0022]

According to the present invention, since the electrode is not heated and deformed by the radiant heat of the filament, the current density of the ion beam is reduced by two compared with the conventional filament type ion source without a heat shield plate. It can be tripled.

[Brief description of drawings]

FIG. 1 is a sectional view of a filament ion source provided with a heat shield plate.

FIG. 2 is a cross-sectional view of FIG. 1 viewed from the II-II direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode, 2 ... Electrode support flange, 3 ... Insulation cylinder, 4 ... Insulation spacer, 5 ... Plasma chamber, 6 ... Magnet, 7 ... Plasma chamber cover, 8 ... Heat shield plate, 9 ... Filament, 10,1
1 ... Feedthrough (electricity, water), 12 ... REIT line, 1
3 ... Plasma, 14 ... Ion beam, 15 ... Processing chamber.

Claims (2)

[Claims] 1. A filament type ion source which emits thermoelectrons from a filament to generate plasma,
A high current ion source characterized in that an electrode for extracting an ion beam and a heat shield plate having the same potential as the filament are provided between the filaments so that the radiant heat of the filament does not reach the electrode. 2. The high current ion source according to claim 1, wherein the heat shield plate is water-cooled.