JPS61101943A - Evaporating furnace for solid sample - Google Patents

Abstract

PURPOSE:To avoid error of thermal testing with a thermoelectric couple as well as preventing damage or shortening the life of a heater, by using a heater and a thermoelectric couple placed in the atmospheric pressure in order to increase and control the temperature of an evaporating furnace placed in a vacuum. CONSTITUTION:A solid sample collector 1, an ionization box 3, and a filament 4 are placed in a vacuum. On the other hand, a heater 2, a thermoelectric couple 8, and current terminals 9 to the heater 2 and the thermoelectric couple 8 are placed in the atmospheric pressure. Since the thermal conduction is through the air, it is possible to conduct heat without direct contact of the sample collector 1 and the heater 2, causing to prevent troubles such as damage from the different rate of expansion between them. And, since the thermal conduction by the heater 2 is performed under the atmospheric pressure, the temperature in the solid sample collector 1 can be tested accurately with the thermoelectric couple 8, resulting in a possibility of a highly accurate thermal control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an evaporation furnace for solid samples used in an ion source section of an ion implantation device.

[Background of the invention]

An ion implantation device that implants ions into a semiconductor surface heats a solid sample of arsenic or phosphorus in a vacuum to evaporate it, guide it into an ionization chamber, ionize it, and then accelerate the ions to create an ion beam for implantation. A method is taken to obtain

As a typical example of the conventional method, a solid sample evaporation furnace of a Freeman type ion source is shown in FIG. In this Freeman type evaporation furnace, a solid sample reservoir 1 is installed in the vacuum inside the ion source.
is heated by heater 2. As a result, the solid sample in the sample reservoir 1 evaporates, and the vapor is introduced into the ionization box 3. The steam introduced into the ion box 3 is filled with *I! of thermoelectrons generated from the filament 4. The ion beam is ionized and further extracted as an ion beam 6 by an extraction electrode 5.

However, in such a structure, in order to improve thermal contact between the evaporation furnace 7 and the heater 2, they are brought into close contact with each other. Therefore, there is a problem that the insulator of the heater 2 is damaged due to the difference in thermal expansion coefficient between the insulator of the heater 2, such as ceramic, and the material of the evaporation furnace, such as stainless steel. In addition, the inside of the evaporation furnace 7 is placed in a vacuum state, and if a chemical reaction occurs between the material of the heater 2 and the fixed sample in this vacuum state, the material of the heater 2 changes and its lifespan is shortened. there were. Furthermore, a thermocouple 8 is provided to detect the temperature of the sample reservoir 1, but this thermocouple 8 is also subjected to mechanical strain due to the difference in thermal expansion coefficient with the sample reservoir 1, resulting in an error in the detected temperature. There was a point.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an evaporation furnace for solid samples that can prevent damage to the heater and shorten its life, as well as eliminate temperature detection errors of the thermal lightning pair.

[Summary of the invention]

According to the present invention, the temperature increase and temperature control of an evaporation furnace placed in a vacuum are performed under atmospheric pressure.

(Embodiment of the Invention) Fig. 1 is a diagram showing an embodiment of an evaporation furnace according to the present invention, in which a solid sample reservoir 1, an ionization box 3, and a filament 4 are placed in a vacuum. The thermocouples 8 and their heaters 2. The current terminals 9 to the thermocouples 8 are placed under atmospheric pressure.

Note that the sample reservoir 1 and the heater 2 are arranged adjacent to the end of the evaporation furnace flange 10.
The ends of the ion source flange 11 are placed in a vacuum state in a chamber composed of the ion source flange 11, and the heater 2, thermocouple 8. It is configured so that only the area around the current terminal 9 is under atmospheric pressure. Also,
The flange 10 is designed to be cooled by a cooling water pipe 17.

FIG. 2 is a diagram showing the structure of a so-called microwave ion source which is constructed by combining the solid-state evaporation furnace of the present invention with a high-frequency electric field caused by microwaves and a plasma discharge caused by the resonance of a DC magnetic field.

In FIG. 2, the part indicated by the signal 12 is the evaporation furnace according to the present invention, and each component is indicated by the same symbol as in FIG. This evaporation furnace 12 has a transparent material 14 for introducing the micro-furnace 13 along the central axis of the ion source, so it is placed around the flange 11 for the ion source, and the solid sample evaporated from the sample reservoir 1 is The vapor is led to an ionization box 3 placed on the central axis of the ion source, where it is ionized.

The ionized sample is turned into plasma by the high-frequency electric field generated by the microwave 7 and the DC magnetic field generated by the excitation coil 15, and is accelerated by the accelerating voltage applied between the accelerating electrode 16 and the extraction electrode, and is converted into an ion beam 6. be drawn out.

Incidentally, FIG. 3 shows an enlarged view of the evaporation furnace 12 shown in FIG. 2.

As described above, according to the embodiment described above, the solid sample reservoir 1
Since the pressure between the heater 2 and the heater 2 is at atmospheric pressure, air is involved in heat conduction therebetween. Therefore, heat can be transferred even if the sample reservoir 1 and the heater 2 are not brought into close contact with each other.

This makes it possible to prevent accidents such as damage due to the difference in thermal expansion coefficients between the two. Further, since the heat conduction by the heater 2 is performed under atmospheric pressure, the temperature of the solid sample reservoir 1 can be detected with high accuracy by the thermocouple 8. As a result,
Temperature control can be performed with high precision.

Furthermore, since the heater 2 is under atmospheric pressure, cooling and replacement are easy, and there is no need to break the vacuum when replacing. Furthermore, since the temperature characteristics of the heater 2 and thermocouple 8 are measured under atmospheric pressure, there is no need to consider the effects of vacuum.6 [Effects of the Invention] As is clear from the above description, the present invention According to this method, it is possible to prevent damage to the heater and shorten its lifespan, and also to eliminate temperature detection errors caused by thermocouples, resulting in an ion beam that is controlled with high precision.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a microwave ion source using the present invention, FIG. 3 is an enlarged view of the evaporation furnace in FIG. 2, and FIG. 4 is a diagram showing an example of the present invention. 1 is a diagram showing a conventional configuration of an evaporation furnace of a Freeman type ion source. 1...Sample reservoir, 2...Heater, 3...Ionization box, 7゜SoIIIZJ

Claims (1)

[Claims] 1. For a solid sample for an ion source, consisting of a sample reservoir into which a solid sample is placed, a heater that heats the sample reservoir, a thermocouple that measures the temperature of the sample reservoir, and a flange with a cooling mechanism that supports them. An evaporation furnace for solid samples, characterized in that the heater and thermocouple are placed under atmospheric pressure.