JPH0982230A - Ion source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly build up an ion source when metal vapor is used by performing heat conduction to a solid fuel placed in a part where heat is hardly transmitted within a sample chamber from a heat conducting rod having good heat conductivity in addition to heat transmission by contact surface. SOLUTION: A round rod-shaped heat conducting rod 6 is extendingly installed along the axial direction of a cylindrical sample chamber 21 from the bottom of the sample chamber 21 in a part where heat of a solid sample 22 filled in the sample chamber 21 of an oven 2 is hardly transmitted, that is a central part. When the oven 2 is used, electric current is applied through a heater 22. The solid sample 22 within the sample chamber 21 can be heated from the both sides of outside and inside through the side surface of the sample chamber 21 and a heat conducting rod 6. The solid sample 22 in the sample chamber 21 of the oven 2 is quickly vaporized, vapor 24 generated is introduced into a plasma generating part 1 through a vapor introducing nozzle 27 and a vapor introducing inlet 15 of a vapor introducing part 16. Quick building up of an ion source is made possible by heating the solid sample from the inside and the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source having an oven for heating a solid sample so that vapor from the oven can be used as an ion species, and more specifically, an oven sample. The present invention relates to a means for improving the rate of temperature rise of a sample filled in the central part of a chamber and enabling high-speed startup of an ion source when using metal vapor or the like.

[0002]

2. Description of the Related Art In recent years, material control using fast ions such as surface modification by ion irradiation and impurity injection into semiconductors has become popular. These ions are obtained by ionizing a gas or solid sample. In particular, in an ion source of a type that generates plasma and draws out ions, a gas is ionized by electrons, so a solid sample such as a metal that is solid at room temperature is in a vaporized state, that is, metal vapor is introduced into the plasma product. There is a necessity to do it.

An oven having a hollow sample chamber and a heater as a heat source for heating and vaporizing a solid sample is usually used to generate such metal vapor.

A conventional example of this type of ion source is shown in FIG.
This ion source is called a Freeman type ion source, and includes a plasma generation unit 1 that generates plasma (not shown) using the introduced ion species and a solid sample 22 filled in a sample chamber 21, for example. An oven 2 is provided which is heated by a heater 23 such as a sheath heater to generate steam 24. The plasma generation unit 1 is supported by an ion source flange 3, and the oven 2 is an oven flange 25 attached to the ion source flange 3.
Is supported by. 26 is a current introducing terminal for the heater 23.

The plasma generating part 1 has a plasma generating container 12 having a slit 11 on the front surface thereof, and a rod-shaped filament 13 as a cathode is disposed inside the plasma generating container 12 along the slit 11. There is. Also,
A gas inlet 14 is provided on the side wall of the plasma generating container 12,
Steam inlets 16 each having a steam inlet 15 are provided at the bottom.

A gas 4, which is a gas ion species, such as arsenic, is supplied to the gas inlet 14 from a gas source (not shown) via an opening / closing valve 41.

The oven 2 heats a granular or pellet-shaped solid sample 22 contained in the sample chamber 21, for example, phosphorus or metal, by a heater 23 provided outside the sample chamber 21, and vapor 24 as a solid ion species. And a vapor introducing nozzle 27 is provided in the front part of the sample chamber 21. The tip portion of the vapor introducing nozzle 27 is inserted into the vapor introducing portion 16 of the plasma generating portion 1. Therefore, the vapor 24 passes through the vapor introducing nozzle 27 and the vapor introducing portion 16 and the plasma generating container 12 Will be introduced in. A thermocouple or other temperature measuring device 28 is installed at the bottom of the sample chamber 21, and the current supplied to the heater 22 is controlled by a signal from the thermocouple 28 to keep the temperature of the sample chamber 21 constant. 29 is the vapor introducing nozzle 27
It is a nozzle retainer that can press.

The slit 1 of the plasma generating container 12
An extraction electrode system composed of a plurality of electrodes is usually provided in front of 1, but the illustration thereof is omitted here.

Next, an operation example will be described. First,
When the solid sample 22 is used as the ion species, the sample chamber 2
Electric power is supplied from a power source (not shown) to the heater 23 provided outside 1 to heat the heater 23 to vaporize the solid sample 22 filled in the sample chamber 21.

Further, power is supplied to the filament 13 through a current introducing terminal 17 connected to a power source (not shown),
While heating the filament 13, an arc voltage is applied between the filament 13 and the plasma generation container 12 from a power source (not shown), and the vapor 24 from the oven 2 is introduced into the plasma generation container 12 as an ion species. When an arc discharge is generated between the filament 13 and the plasma generation container 12, plasma is generated in the plasma generation container 12.

The ion beam 5 can be extracted from this plasma through the slit 11 by the action of the electric field applied to the extraction electrode system (not shown).

Next, when the ion species is switched to the gas 42, the heater 23 of the oven 2 is de-energized, and the on-off valve 41 is opened instead, and the plasma generation chamber 12 is opened from the gas source through the gas inlet 14. When the gas 4 is introduced into the plasma generation container 12 and the filament 13 is heated and an arc discharge is generated between the filament 13 and the plasma generation container 12 as in the case of using the solid sample 22 described above, Plasma is generated in the.

Such an ion source has an advantage that it is possible to switch between a solid ion species and a gas ion species in a short time.

[0014]

However, in the ion source having the above-mentioned structure, the solid sample 22 is heated by the heater 23 provided outside the sample chamber 21 in order to vaporize the solid sample 22 which is a desired substance. At this time, the solid sample 22 inside the sample chamber 21 is heated with a certain temperature distribution. That is, the solid sample 22 in the portion close to the inner wall of the sample chamber 21 close to the heater 23, which is a heat source, has a high temperature rising rate, but the solid sample 22 is far from the heater 23, for example, when the shape of the sample chamber 23 is cylindrical. If so, the solid sample 22 in the central portion has a slow temperature rising rate.

It is considered that this is because the solid sample 22 is usually in the form of small particles or pellets, the contact area between the solid samples 22 is small, and the heat transfer is extremely poor.

As described above, when the temperature rising rate of the solid sample 22 filled in the sample chamber 21 becomes nonuniform, the vapor flow rate to the plasma generating section 1 is insufficient when a predetermined ion beam amount is extracted from the ion source. However, there are inconveniences such as a long startup time of the ion source.

This tendency has been desired in recent years to be used particularly for a long time. For this reason, when the sample chamber is enlarged,
Particularly noticeable, and its improvement is strongly desired.

Therefore, according to the present invention, the heat is rapidly transferred to the solid sample in the portion where the heat is difficult to transfer in the sample chamber,
The main purpose of the present invention is to provide an ion source that can be heated and vaporized quickly, can secure a predetermined evaporation flow rate in a short time, and can be quickly started up.

[0019]

In order to achieve the above object, in the ion source of the present invention, a heat conduction rod is erected in a sample chamber of an oven for vaporizing a solid sample so as to be in contact with the solid sample. It is characterized by

According to the above structure, the heat transfer to the solid sample in the portion where the heat is difficult to transfer in the sample chamber is not limited to the conventional heat transfer between the samples having a small contact area from the outside, and the heat transfer to the sample chamber Since heat is also transferred from the heat transfer rod with good thermal conductivity via the solid sample, the solid sample can be rapidly heated from both the outside and the inside, so that the required vapor flow rate can be reached in a short time, and It enables high-speed start-up of the ion source when using steam such as steam.

[0021]

1 is a sectional view of an essential part showing an oven portion of an ion source according to an embodiment of the present invention. In addition, the same reference numerals as those in the conventional example of FIG. 2 indicate the same or corresponding parts. In the following, differences from the conventional example will be mainly described.

In this embodiment, the solid sample 22 filled in the cylindrical sample chamber 21 of the oven 2 described above has a round bar shape from the bottom of the sample chamber 21 to a portion where heat is not particularly transmitted to the solid sample 22, that is, the central portion. The heat conducting rod 6 is extended along the axial direction of the sample chamber 21. In this way, the heat conduction rod 6 is erected integrally with the bottom of the sample chamber 21. Therefore, the heat conduction rod 6 is made of the same material as the sample chamber 21.

The material of the heat conducting rod 6 is not particularly limited, but the point is that it does not cause a chemical reaction with the solid sample 22 used at high temperature, and it is preferable that it has excellent heat conductivity. For example, stainless steel or silver can be used.

In the above-mentioned embodiment, the heat conducting rod 6 is made of the same material as the sample chamber 21 so as to stand upright, but instead of this, it is made of the same or different material as the sample chamber 21. A screw hole may be formed at the bottom of the sample chamber 21, and the heat conduction rod 6 having a thread at one end may be screwed into the screw hole. Alternatively, the sample chamber 2 may be welded.
Needless to say, the heat conducting rod 6 may be provided upright on the bottom portion of 1.

The position at which the heat conducting rod 6 is erected is preferably the center of the sample chamber 21, but the position is not limited to this. The heat of the solid sample 22 filled in the sample chamber 21 is transferred. The hard sample may be in contact with the solid sample 22. Therefore, if there is a space in the space, a plurality of pieces may be installed upright, which is convenient because the solid sample 22 can be further efficiently heated.

The shape of the heat conducting rod 6 is not particularly limited, and may be determined in consideration of the shape and size of the solid sample 22, heat transfer, etc., and may be rod-shaped, triangular prism-shaped or polygonal. It may be formed into a columnar shape, a plate shape, or a shape in which a brim portion that spreads radially is formed.

To explain an operation example, when the oven 2 is used, the heater 22 is energized. As a result, the sample chamber 2 passes through the wall surface of the sample chamber 21 and the heat conduction rod 6.
The solid sample 22 in 1 can be heated from both outside and inside. Therefore, the sample chamber 21 of the oven 2
The solid sample 22 of is rapidly vaporized, and the generated vapor 2
4 is introduced into the plasma generation unit 1 through the vapor introduction nozzle 27 and the vapor introduction port 15 of the vapor introduction unit 16.
Of course, at this time, the on-off valve 41 of the gas line is closed.

In the above-mentioned embodiment, the case where the sample chamber 21 has a cylindrical shape has been described, but the present invention is not limited to this, and it is needless to say that it may be a polygonal shape or a polygonal shape.

In each of the above-mentioned embodiments, the sheath heater is used as the heater 23.
Of course, the present invention is not limited to this, and can be applied to, for example, an oven using a nichrome wire or another metal wire as the heater 23.

[0030]

As described above, according to the present invention, the heat transfer to the solid sample in the portion where the heat is difficult to transfer in the sample chamber is not limited to the conventional heat transfer between the samples having a small contact area, Since heat is also transferred from the heat-conducting rod having a high thermal conductivity through the sample chamber, the solid sample can be heated from both the outside and the inside, so that the required vapor flow rate is reached in a short time. As a result, it is possible to quickly start up the ion source when using vapor such as metal vapor.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an oven portion of an ion source according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a conventional ion source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation part 2 Oven 21 Sample chamber 22 Solid sample 23 Heater 24 Vapor 6 Heat conduction rod

Claims (1)

[Claims] 1. A plasma generation part for generating plasma using the introduced ion species and a plasma generation part having a vapor introduction port, and a solid sample filled in the sample chamber is heated by a heater to generate vapor. In an ion source including an oven and introducing steam from the oven as an ion species into the plasma generation unit, a heat conduction rod is erected in the sample chamber so as to be in contact with the solid sample. An ion source characterized by that.