JPH0628715Y2 - Electron energy distribution measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an apparatus configured to irradiate a target with electrons, for example, an ion implantation apparatus, an ion beam etching apparatus, or the like, in which a target including a wafer is irradiated with an ion beam. In addition, the present invention relates to an electron energy distribution measuring device used in a device or the like configured to emit electrons for antistatic purposes.

[Conventional technology]

FIG. 3 is a sectional view partially showing an example of a conventional ion implantation apparatus.

This apparatus is basically a target 8 in which an ion beam 2 is mounted in a vacuum and a wafer 12 is mounted on a holder 10.
In order to accurately measure the beam current of the ion beam 2 at that time, the target 8 is housed in the Faraday cage 6 and an electron is introduced into its entrance. A suppressor electrode 4 having a negative potential is arranged to prevent the gas from escaping to the upstream side. Further, inside the Faraday cage 6, there is provided a rotary Faraday flag 14 that receives the ion beam 2 and secondary electrons 20 described later when the target 8 is not irradiated with the ion beam 2.

Further, an electron generation source 16 is provided on the side of the Faraday cage 6 in order to prevent the surface of the wafer 12 from being positively charged due to the irradiation of the ion beam 2, particularly when the surface is an insulator. , The primary electron 18 extracted from this is applied to the facing surface in the Faraday cage 6, and the secondary electron 2 is emitted from there.
0 is emitted, and the secondary electrons 20 are irradiated on the target 8 to neutralize the positive charge on the wafer 12 by the ion beam 2.

In that case, the energy of the primary electron 18 is, for example, several hundred eV.
It is considered that the energy of the secondary electrons 20 has a distribution having a peak at about several eV.

[Purpose of device]

However, in the above-mentioned device, the high-energy primary electrons 18 (for example, about several hundred eV as described above) that are mixed with the secondary electrons 20 and are extracted from the electron generation source 16 are practically used. Is irradiated to the target 8 including.

In that case, among the devices provided on the surface of the wafer 12, a device having a low breakdown voltage causes a dielectric breakdown at about 10 V, but when a large number of high-energy electrons such as the primary electrons 18 are irradiated on the wafer 12, Since the higher the energy is, the higher the charging voltage by the electrons is, the greater the possibility of destroying the device on the wafer 12.

In order to prevent this, first, it is necessary to grasp the energy distribution of the electrons reaching the target 8, and the present invention aims to provide an electron energy distribution measuring device that makes it possible.

[Means for achieving the purpose]

The electron energy distribution measuring device of the present invention has a mesh-like or porous electrode that can be taken in and out at a position that blocks electrons toward the target as described above, a variable voltage DC power supply that applies a negative voltage to this electrode, and a flow to the target. An ammeter for measuring a current is provided.

[Action]

When the electrode is placed in a position that blocks electrons toward the target and a negative voltage is applied to it from the DC power supply, only electrons with energy equal to or higher than the energy corresponding to this voltage can pass through the electrode part and reach the target. An electric current corresponding to the amount flows through the ammeter. Therefore, the energy distribution of electrons reaching the target can be measured by changing the voltage and measuring the current.

〔Example〕

FIG. 1 is a sectional view partially showing an example of an ion implantation apparatus including an electron energy distribution measuring apparatus according to an embodiment. The same or corresponding parts as those of the apparatus of FIG. 3 are designated by the same reference numerals, and the difference from them will be mainly described below.

In this embodiment, a mesh or porous electrode 22 is provided in the Faraday cage 6 as described above, and the electrode 2
A variable voltage DC power source 26 for applying a negative voltage to the former is connected between the Faraday cage 2 and the Faraday cage 6, and an ammeter 28 for measuring the current flowing through the target 8 is further connected between the holder 10 and the ground to obtain an electron energy distribution. It constitutes a measuring device.

The reason why the electrode 22 is reticulated or porous is that electrons such as the secondary electrons 20 can pass through the electrode 22 and that the electric field is applied to the passage portion of the electron as uniformly as possible.

The electrode 22 also has a rotating shaft 24 to which it is attached.
When the wafer 12 is irradiated with the ion beam 2, the secondary electron 20 and the like toward the target 8 is placed at a position where the ion beam 2 and the like are not blocked by the rotation of the. I am able to move it.

At the time of measurement, the electrode 22 is placed at a position that blocks the secondary electrons 20 and the like directed to the target 8 as shown in the drawing, and a negative voltage V is applied thereto from the DC power supply 26. Of course, in that case, the ion beam 2 is stopped. Then, only electrons having an energy equal to or higher than the energy corresponding to the voltage V can pass through the electrode 22 and reach the target 8, and a current I corresponding to the amount flows into the ammeter 28.

When the voltage V is changed and the current I is measured, a graph as shown in FIG. 2 is obtained, for example. This graph shows the energy distribution of the electrons reaching the target 8, that is, the amount of energy and the amount of electrons. For example, among the electrons reaching the target 8, there are electrons having an energy equal to or higher than the energy corresponding to the voltage V ₁ in an amount corresponding to the current I ₁ .

Therefore, by measuring the current I by changing the voltage V as described above, it is possible to know, for example, how much high-energy electrons may adversely affect the devices on the wafer 12. it can. If such data is obtained, various measures can be taken, for example, reducing the energy of the primary electrons 18 extracted from the electron generation source 16 to an optimum level.

Although the ion implanter of the above example is of a type that electrostatically scans the ion beam 2, an ion implanter that mechanically scans the target, and also an apparatus other than the ion implanter can measure the electron energy distribution as described above. Of course, the device can be used.

[Effect of device]

As described above, according to this invention, the energy distribution of the electrons reaching the target can be easily measured.

[Brief description of drawings]

FIG. 1 is a sectional view partially showing an example of an ion implantation apparatus including an electron energy distribution measuring apparatus according to an embodiment. FIG. 2 is a graph showing an example of the measurement result by the electron energy distribution measuring device of FIG. FIG. 3 is a sectional view partially showing an example of a conventional ion implantation apparatus. 8 ... Target, 18 ... Primary electron, 20 ... Secondary electron, 22 ... Electrode, 26 ... DC power supply, 28 ... Ammeter.

Claims (1)

[Scope of utility model registration request] 1. A net-like or porous electrode which is used in an apparatus configured to irradiate a target with electrons and which can be put in and taken out from a position where electrons toward the target are blocked, and a voltage for applying a negative voltage to the electrode. An electronic energy distribution measuring device comprising a variable DC power source and an ammeter for measuring a current flowing through a target.