JPS59163743A - Ion source - Google Patents

Abstract

PURPOSE:To enhance magnetic flux density within an arc chamber and reduce the size of apparatus by providing, to both ends of arc chamber forming the magnetic field, a member for concentrating the line of magnetic force of a ferromagnetic body of such a shape that the area being in contact with the arc chamber is smaller than the area of opposite side. CONSTITUTION:Electrons emitted from a hot cathode 3 are ionized through collision with gas introduced from the gas introducing entrance 4. A ferromagnetic member 6 for concentrating the line of magnetic force is provided outside the upper and lower ends of an arc chamber 2 being held at a high voltage by a high voltage power supply 13. This concentration member 6 is formed in a trapezoid where the area being in contact with the arc chamber is narrow but the opposite area is wide. Owing to this ferromagnetic member 6, the magnetic flux passes through the internal side of arc chamber 2 and thereby a large magnetic flux density in the arc chamber can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source that generates implanted ions for an ion implantation device used for fT implantation of impurity ions into a semiconductor substrate during the manufacturing process of a semiconductor device.

The above-mentioned ion source is usually of the hot cathode type and requires a magnetic field to increase the flight distance of electrons emitted from the cathode and facilitate ionization. Among these ion sources, high-current ion sources, which have become popular recently, require a large magnetic field, but the ion source and the housing that houses the ion source have a large external shape. A large source magnet is used to form the magnetic field, but the leakage magnetic flux of the large source magnet affects the extraction electrode system, making it difficult to use.

An object of the present invention is to provide an ion source that solves the above problems.

The ion source of the present invention includes a hot cathode that emits thermionic electrons, an arc chamber having an ionized gas inlet and a generated ion outlet, and a source magnet that forms a magnetic field within the arc chamber. and, at both ends of the arc chamber, for the purpose of concentrating the lines of magnetic force formed by the source magnet in the arc chamber.
A magnetic flux concentrating member made of a ferromagnetic material is provided, the area of which is in contact with the arc chamber is smaller than the area of the opposite side.

Next, the present invention will be explained using examples.

FIG. 1 is a sectional view showing the construction of an embodiment of the present invention. In the figure, an arc chamber 2 is placed in the magnetic path of a source magnet 1. A linear hot cathode 3, which is insulated and spanned between approximately the center of the upper and lower walls of the arc chamber 2, is heated by electric power supplied from a cathode power source 11 and emits thermoelectrons. These electrons move toward the outer wall of the arc chamber 2 due to the voltage from the arc power source 12, and undergo cyclotron motion due to the magnetic field created by the source magnet 1, resulting in a longer electron flight path and more energy than the gas introduced from the gas inlet 4. Collisions and ionization.

The ions generated in this way are drawn out from the extraction port 5 in a desired direction by being attracted by the accelerating electric field of an extraction electrode (not shown). Magnetic force line concentration members 6 made of ferromagnetic material are provided outside both upper and lower ends of the arc chamber 2, which is maintained at a high voltage of about 80 KV. The concentrating member 6 has a trapezoidal cross-section, with a narrow area on the side in contact with the arc chamber and a wide area on the opposite side. The presence of the member 6 causes the magnetic flux that would otherwise pass through the arc chamber 2 to pass through the interior of the arc chamber 2, making it possible to obtain a greater magnetic flux density within the arc chamber than that obtained with conventional ion sources. In addition, if the present invention is applied to a conventional large source magnet and there is a margin in magnetic flux density, a smaller source magnet can be used instead of the conventional one, so the influence of the magnetic field on parts other than the arc chamber can be reduced. At the same time, it is useful for downsizing the device, and as a result, the cost of the device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention. 1... Source magnet, 2... Arc chamber, 3... Hot cathode, 4... Gas inlet, 5... Ion extraction Mouth, 6...
...Ferromagnetic member for concentrating magnetic lines of force, 11... Hot cathode power supply, 12... Arc power supply, 13...
・High voltage power supply. Agent Patent Attorney Shinotsu Uchihara 9〈ko202-

Claims (1)

[Claims] In a hot cathode ion source that requires a magnetic field from a source magnet, a ferromagnetic material whose area in contact with the arc chamber is smaller than that on the opposite side is placed at both ends of the arc chamber where the magnetic field is generated. An ion source characterized by being provided with a member for concentrating magnetic lines of force.