JPH0458445A - Electron beam source - Google Patents

Abstract

PURPOSE:To prevent sputtering due to ions of acceleration electrode for evading metal contamination in an acceleration region and an ion generation region by covering a surface of an acceleration cathode opposing to an acceleration anode with an insulator. CONSTITUTION:A surface of an acceleration cathode 2 facing to an acceleration cathode 4 is covered with an insulator 3. For the insulator 3, ceramics can be used in addition to a glass plate. Ions accelerated inside an acceleration region reach the whole surface of the acceleration cathode 2 so as to extinguish space charge due to electrons near the hole of an acceleration cathode 2 while in the other area, ions come to strike the insulator surface, however, ions have no such energy as to sputter an insulator. Accordingly, contamination of a plasma region due to sputtering and metal contamination of a semiconductor wafer can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electron beam source that can be used for surface treatment of semiconductor wafers by recrystallization, etching of semiconductor wafers, and film formation.

(Prior Art) FIG. 2 shows this conventional electron beam source. In FIG. 2, 5 is a plasma region, 2 is an accelerating cathode, 6 is an electron beam accelerating region, 4 is an accelerating anode, and 7 is an ion generating region. The operation of this conventional electron beam source when used for etching a semiconductor wafer will be explained. Argon gas is supplied from the inlet 11a and exhausted from the exhaust ports 12a and 12b to create an argon atmosphere of approximately 10-' Torr in the plasma region 5, and approximately 10-' Torr in the electron beam acceleration region 6. Create a moderate argon atmosphere. or,
Chlorine gas is supplied from the inlet 11b and discharged from the exhaust port 12c to create a chlorine atmosphere of approximately N'l0-3) in the ion generation region 7.

An electric field created in the plasma region 5 by the discharge power source 8 accelerates electrons from the cathode in an argon atmosphere to generate plasma. The acceleration power source 9 establishes a potential gradient in the electron beam acceleration region 6 toward the acceleration electrode 4 and accelerates electrons diffusing from the plasma region through the holes in the acceleration cathode 2 . The potential of the acceleration power source is set to about 100 V so as to give the electrons energy that maximizes the ionization cross section of the chlorine atoms by the accelerated electrons. These accelerated electrons are transferred to the accelerated anode 4
It enters the ion generation region 7 through the hole and generates chlorine plasma. A semiconductor wafer (
(not shown).

The feature of this conventional device is that it can supply a large current with low energy, that is, even though the accelerating voltage in the electron beam accelerating region is low, the current passing through the accelerating anode is IOA
It is possible to generate a relatively large current. When ions from the plasma in the ion generation region 7 pass through the holes in the acceleration anode 4 and leak into the electron beam acceleration region 6, these ions are accelerated in the opposite direction to the electrons and reach the vicinity of the holes in the acceleration cathode. This is because the space charge caused by electrons near this hole is neutralized, and the suppression of the leakage of electrons from the plasma region 5 by the space charge is eliminated.

(Problems to be Solved by the Invention) When ions are accelerated toward the acceleration cathode 2 within the acceleration region 6, the ions hit the entire acceleration cathode 2, causing sputtering. As a result, there was a problem that not only the wall surface of the acceleration region 6 was contaminated, but also the ions entered the ion generation region 7 through the holes of the acceleration anode 4 and contaminated the semiconductor wafer.

(Means for Solving the Problem) An object of the present invention is to provide a low-energy, high-current electron beam source that prevents sputtering of accelerating electrodes by ions and avoids metal contamination in the accelerating region and ion generation region. .

This object is achieved according to the invention by covering the surface of the accelerating cathode facing the accelerating anode with an insulating material.

(Function) The ions accelerated in the acceleration region reach the entire surface of the acceleration cathode 2, and near the holes of the acceleration cathode 2, the space charge caused by electrons disappears, and in other areas, the ions hit the surface of the insulator. However, ions do not have enough energy to sputter an insulator.

(Embodiment) An embodiment of the low-energy, high-current electron beam source of the present invention is shown in FIG. The same parts in FIG. 1 as in FIG. 2 are designated by the same reference numerals, and their explanation will be omitted.

As shown in FIG. 1, the surface of the accelerating cathode 2 facing the accelerating cathode 4 is covered with an insulator 3. Although the insulator 3 is a glass plate in this embodiment, it may also be made of ceramics or the like. A magnetic field may be applied in the axial direction to restrain the plasma in the plasma region 5, the electron beam in the electron beam acceleration region, and the plasma in the ion generation region 7 in the radial direction. When using the electron beam source of the present invention for recrystallization treatment of the surface layer of a semiconductor wafer, the plasma region 5 and the acceleration region 6 each have a beam of 10
-')-L and 10-')-L to create an argon gas atmosphere. An argon gas atmosphere of about 1.0-3) is created in the ion generation region 7. A semiconductor wafer (not shown) is placed on the collector electrode 13 and heated to a high temperature by irradiating it with an electron beam to melt the surface layer of the wafer and promote recrystallization.

When using the electron beam source of the present invention for etching semiconductor wafers, the same argon atmosphere as in the recrystallization process is created in the plasma region and acceleration region. A chlorine atmosphere of approximately 1O-3) is created in the ion generation region 7. Electrons are injected into this chlorine atmosphere to generate plasma, and the ions of the plasma are irradiated onto the semiconductor wafer on the collector 13 for etching. Since there is no contamination due to sputtering, it is possible to etch a semiconductor wafer with a thick wafer density of about 64 mega DRAM.

(Effects) As is clear from the above, according to the present invention, contamination of the plasma region and metal contamination of the semiconductor wafer due to sputtering can be avoided. Furthermore, wear and tear of the accelerating cathode due to sputtering can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the invention. FIG. 2 is a longitudinal sectional view of a conventional electron beam source. In the figure: 2 is an accelerating cathode, 3 is an insulator, 4 is an accelerating anode, 5 is a plasma region, 6 is an electron beam acceleration region, 7 is an ion generation region, and 13 is an electron beam collector. Figure 1

Claims (1)

[Claims] An electron beam source in which a plasma region, an accelerating cathode, an electron beam accelerating region, an accelerating anode, and an ion generation region are provided in this order, characterized in that a surface of the accelerating cathode facing the accelerating anode is covered with an insulator. Beam source.