JPS6262020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source device used in an ion implanter or the like.

An ion source device known as a high-temperature hollow cathode ion source heats an ionized substance at high temperature to vaporize it, collides the vaporized gas with thermoelectrons to ionize it, and draws it out to the outside. is well known. However, in the conventional apparatus, in order to heat the ionized substance, it was housed in a thermal oven and heated by a heater. According to such a configuration, ionized substances such as boron, phosphorus, arsenic, etc. can be vaporized by the above-mentioned thermal oven, but their melting points are lower than those of the above-mentioned ionized substances such as molybdenum. It has been extremely difficult to vaporize ionized substances with high boiling points and low vapor pressures using conventional thermal ovens. In other words, this type of thermal oven is made of a heat-resistant insulating material such as boron nitride, but its melting point is
In order to vaporize high melting point metals of 1800℃ or higher, such as metal ionized substances such as molybdenum,
Although it is necessary to heat the product to a temperature of 1800°C or higher, raising the temperature to this extent causes disadvantages such as the heating oven itself melting or releasing impurities, so in fact these It was not possible to vaporize the ionized substance.
Furthermore, even if vaporization occurs, it often adheres to the chamber wall by the time it reaches the point where it collides with the thermoelectrons, so unless the temperature of the chamber wall is raised above the temperature at which it vaporized, There are fewer opportunities for ionization, making it difficult to be ionized.

The object of the present invention is to easily generate ions that cannot be obtained using conventional ion source devices, that is, ions of high-melting point metals with a melting point of 1800° C. or higher.

In this invention, the ion source parts comprising the drawer cap, layer cap, anode electrode, and filament that constitute the ion generating section are formed using a metal ionizing substance made of a high-melting point metal with a melting point of 1800°C or higher used for generating desired ions. It is characterized by what it did.

The present invention will be explained below based on one embodiment shown in the drawings. In Figure 1, 1 is the ion extraction port 1A.
2 is a layer cap, 3 is a drawer cap having a
is an anode electrode, and 4 is a coiled filament. These are ion source parts forming the ion generating part A, and are used to generate a metal ionization substance made of a high-melting point metal with a melting point of 1800°C or higher, which is used to generate desired metal ions. It is formed using For example, when it is desired to obtain molybdenum ions, the ion source parts constituting the ion generating section A, the extraction cap 1, the layer cap 2, the anode electrode 3, and the filament 4 are made of molybdenum. 5 and 6 are rings made of a heat-resistant insulating material, 7 is an assembly rod, and 8 is a metal ionized substance such as molybdenum, which are provided as necessary. As shown in an enlarged view in FIG. 2, the ionized substance 8 is formed into a cylindrical shape, and a support portion 8A is also formed on the outer peripheral wall of the ionized substance 8. As shown in FIG. 1, the support portion 8A is attached to the filament 4 so as to be sandwiched therebetween by its spring action. 9 is a thermal oven, and 10 is a heater.

In the above configuration, when a current is passed through the filament 4, the filament 4 itself made of molybdenum generates heat and generates thermoelectrons. Usually, the exothermic temperature of the filament 4 can be 1,800 to 2,500°C or higher, so that even metal ionized substances with a high melting point, such as molybdenum, are easily vaporized and evaporated. When a voltage (usually DC 40 to 300 V) is applied between the anode electrode 3 made of molybdenum and the layer cap 2 made of molybdenum, and a discharge gas (e.g. argon, hydrogen, etc.) is supplied between the two, the anode electrode 3 and the layer cap 2 are connected to each other. A stable discharge occurs between the two and plasma is formed.
Molybdenum, which is an ionized substance, evaporates from the filament 4 as a result of being heated as described above, becomes a gas, and is drawn between the anode electrode 3 and the layer cap 2. Collision with thermionic electrons that eject from this causes ionization, resulting in ions. Since a direct current voltage for extraction (usually 5 to 30 KV) is applied between the extraction electrode (not shown) installed on the outside of the extraction cap 1 made of molybdenum and the housing, the voltage generated as described above is applied. Ions pass through the filament 4 and are extracted to the outside from the ion extraction port 1A. In this process, the ions may collide with the ionized substance 8 provided as necessary and the filament 4 that constitutes the ion generating section A, but since these are both heated to high temperatures, they adhere to them and compensate. It is rarely prompted.

According to the present invention, the ion source parts constituting the ion generating section A consisting of the drawer cap 1, the layer cap 2, the anode electrode 3, and the filament 4 are made of molybdenum, which is a high melting point metal with a melting point of 1800°C or higher and is used to generate the required ions. Since the ion source parts themselves are heated and vaporized, the generated ions collide with these ion source parts and the ionization efficiency is increased due to the sputtering effect, compared to conventional equipment. Ionization becomes much easier.

Note that using the ionized substance 8 as in the illustrated example,
When this is attached so as to be sandwiched by the spring action of the filament 4, the ionized substance 8
is now directly heated, and its vaporization is extremely easy and convenient.

Further, according to the present invention, since a part of the ion source parts themselves are vaporized, their shape deteriorates over time, but if they become unusable, they can be replaced with new parts. Normally, the filament 4 wears out quickly, but according to experiments conducted by the present inventor, it has been confirmed that a filament with a diameter of 1 mm can be used for several tens of hours.

As detailed above, in the device according to the present invention, the metal ionized substance is evaporated in the part that generates thermoelectrons and operates, so the ionization becomes easy and the melting point, which could not be obtained with conventional devices, is achieved. It has now become possible to easily generate ions using a metal ionizing substance made of a metal with a high melting point of 1800°C or higher.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a partially enlarged sectional view. 1...Drawer cap, 2...Layer cap, 3...Anode electrode, 4...Filament,
8...Ionized substance, A...Ion generation part.

Claims (1)

[Claims] 1. In an ion source device that vaporizes an ionized substance and ionizes it by colliding it with thermoelectrons generated by heat generation of a filament, a drawer cap, a layer cap,
The ion source components, consisting of the anode electrode and filament, are used to generate the desired ions.
An ion source device formed from a metal ionizable substance made of a metal with a high melting point of ℃ or higher.