JPH04220938A - Neutralizing device of ion implantation device - Google Patents

Abstract

PURPOSE:To allow electrons to serve only for neutralizing positive charges on a semiconductor base board and prevent the base board from being charged negatively by furnishing a grid to control electrons bearing a low energy, and projecting electrons in such a way that the whole area of base board is dosed with them. CONSTITUTION:At the fore stage of a filament 2 emitting hot electrons. a grid 8 is furnished which is to control thermoelectron stream by impressing several volts on the filament 2. A lower acceleration voltage than conventional is impressed on this grid 8 and a semiconductor base board 7 as the anode side, and electrons 4 are cast directly on the base board 7. By the use of an electron gun as a three-electrode tube, the thermoelectrons emitted from the filament 2 are drawn out by the grid 8 on which a voltage of several volts is impressed, and positive charges on the base board are neutralized by dosing the surface of the base board 7 with the low energy electron stream which is at a low speed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation device for implanting ions into a semiconductor substrate, and more particularly to a neutralization device (hereinafter simply referred to as a neutralization device) in an ion implantation device for eliminating electrical charge on a semiconductor substrate.

0002

2. Description of the Related Art FIG. 2 is a schematic diagram showing an example of a conventional neutralization device. As shown in FIG. 2, this type of conventional neutralization device generates secondary electrons 5 through collision between a filament 2 that emits thermoelectrons, a Wehnelt electrode 1 that accelerates the thermoelectrons, and the accelerated electrons 4. It has a target 3. Next, the operation of this neutralization device will be explained. First, thermionic electrons are emitted from the filament 2, and the Wehnelt electrode 1
Due to the accelerating voltage applied between the target 3 and the electron 4
is pulled towards target 3. Next, as the thermoelectrons 4 collide with the target 3, the target 3
Secondary electrons 5 were emitted from the ion beam, and the secondary electrons 5 reached the semiconductor substrate 7 together with the ion beam, neutralizing the positive charges stored in the semiconductor substrate 7.

0003

[Problems to be Solved by the Invention] In this conventional neutralization device, the distance between the filament and the target is large, and the accelerating voltage applied between the filament and the target is several hundred to efficiently extract secondary electrons. Volts of voltage are required. However, the energy of the secondary electrons generated from the target ranges from low energy to high energy, and it is difficult to control this energy amount, and the secondary electrons often neutralize the positive charges on the semiconductor substrate. Not only this, but also the semiconductor substrate is negatively charged, which causes the problem that ion implantation becomes insufficient.

[0004]An object of the present invention is to provide a neutralization device that can control the electron flow without excessively irradiating electrons, in order to solve this problem.

[0005]

[Means for Solving the Problems] A neutralization device for an ion implantation apparatus according to the present invention controls a filament that emits thermionic electrons and a thermionic flow in the neutralization device for an ion implantation device that implants ions into a semiconductor substrate. The semiconductor substrate is characterized in that the semiconductor substrate is provided with a flat grid, and the semiconductor substrate is irradiated with electrons passing through the grid.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the neutralization device of the present invention. As shown in the figure, this neutralization device applies a voltage of several volts to the filament 2 in front of the filament 2 that emits thermionic electrons, and a grid 8 that controls the flow of thermionic electrons.
A grid 8 and a semiconductor substrate 7 on the anode side are provided.
The method is to apply a lower acceleration voltage than the conventional one to irradiate the semiconductor substrate 7 with electrons 4 directly. By using the electron gun, which is a triode, the thermoelectrons emitted from the filament 2 are extracted by the grid 2 to which a voltage of several volts is applied, and a low-speed, low-energy electron stream is generated on the surface of the semiconductor substrate 7. By applying , the positive charges on the semiconductor substrate are neutralized.

In another embodiment, in order to prevent contamination of the semiconductor substrate due to filament sputtering, a magnetic field is applied after the electrons are drawn out in a direction different from that of the semiconductor substrate using a grid. Electrons may be guided near the top of the semiconductor substrate and bombarded with electrons to neutralize the positive charge on the semiconductor substrate.

In both embodiments, a voltage within a few volts is applied between the filament 2 and the disk supporting the semiconductor substrate, and a voltage of several volts is applied to the grid 8 to generate electrons. By generating an electron cloud with an energy of several electron volts or less, it is possible to effectively eliminate static electricity without damaging the semiconductor substrate.

Furthermore, since the amount of thermoelectrons emitted by the filament 2 can be controlled by the grid 8, no more electrons are irradiated than necessary. Furthermore, since the grid 8 does not need to converge electrons, it may be an ordinary plate electrode provided with holes through which the electrons pass.

0010

Effects of the Invention As explained above, the present invention provides a grid for controlling low-energy electrons, and by irradiating the electrons so as to cover the entire area of the semiconductor substrate, the electrons neutralize the positive charges on the semiconductor substrate. This has the effect of providing a neutralizing device in an ion implantation device that is used only to neutralize the ions and does not negatively charge the semiconductor substrate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the neutralization device of the present invention.

FIG. 2 is a schematic diagram showing an example of a conventional neutralization device.

[Explanation of symbols]

1 Wehnelt electrode 2 Filament 3 Target ４　　　Electron 5 Secondary electrons 6 Ion 7 Semiconductor substrate 8 Grid

Claims (1)

[Claims] 1. A neutralization device for an ion implantation apparatus for implanting ions into a semiconductor substrate, which comprises a filament that emits thermionic electrons and a flat grid that controls the flow of thermionic electrons, and the neutralization device includes a filament that emits thermionic electrons, and a flat grid that controls the flow of thermionic electrons. A neutralization device in an ion implantation device characterized by irradiating a semiconductor substrate.