JPH03230466A - Ion implanter - Google Patents

Abstract

PURPOSE:To discharge excessive secondary electrons by covering the outermost periphery section of a disk with a secondary electron discharge plate. CONSTITUTION:A secondary electron discharge plate 10 covering the end section is provided insulatingly from a disk 1 via an insulator on the outermost periphery of the disk 1, and excessive secondary electrons generated when the disk 1 enters and goes out of an ion beam are discharged. An abnormal increase of the disk current due to excessive secondary electrons is prevented, and an ion implanter in which the disk current can invariably neutralize proper wafer charges by reflecting the wafer charged state is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an ion implantation device used in a process for manufacturing semiconductor devices.

[Prior Art] Ion implanters are used in many processes as means for introducing impurities into wafers. Among them, especially MOSFE
In processes that require a large amount of implantation, such as T source and drain implantation, there is a tendency to increase the beam current in order to improve throughput. For this reason, the electrification of the thick oxide film or resist on the surface of the wafer, which is the target, tends to increase more and more.

On the other hand, devices are becoming more susceptible to charging as wafers become larger in diameter and patterns become finer. and,
These synergistic effects cause problems such as non-uniform implantation amount and electrostatic damage to the gate oxide film.

Conventionally, in order to prevent electrostatic damage due to wafer charging, a method has been used in which electrons are supplied to the wafer at the same time as ion implantation to neutralize the charged charges.

The conventional technology will be explained below.

This ion implanter generates plasma containing desired ions in the ion source, extracts it using an electric field, accelerates it, and guides only the desired ions into the implantation chamber by passing it through an analysis magnet. It irradiates the area with an ion beam and supplies electrons.

FIG. 3 is a schematic configuration diagram of an implantation chamber of a conventional ion implantation apparatus. In the figure, 1 is a wafer, 2 is a disk on which the wafer 1 is mounted, 3 is a Faraday provided in front of the disk 2, 4 is a suppressor electrode, 5 is a disk current detector, 6
1 is a beam current detector, 7 is a disk current setting device, 8 is an electron emission amount controller, and 9 is a filament.

Next, the operation will be explained.

Suppressor electrode 3. The ion beam that has passed through the Faraday 4 is irradiated onto the disk 2 on which the wafer 1 is mounted.

Then, secondary electrons are generated from the disk 2 and arrive at the Faraday 3. At this time, a current corresponding to the sum of the amount of the ion beam and the amount of secondary electrons generated from the disk flows through the disk 2, and the value thereof is detected by the disk current detector 5.

Then, the current value flowing through the disk 2 and the current value flowing through the Faraday 3 are totaled and measured by the beam current detector 6, and the injection amount is calculated.

On the other hand, the electrons for neutralizing the electrification of the wafer are controlled according to the disk current, and when the disk current setter 7 is set to, for example, ±OmA, the current value detected by the disk current detector 5 is always For example, the current flowing through the filament 9 is controlled by the electron emission amount controller 8 so that the current is ±OmA. By controlling the disk current value to ±OmA in this manner, the charges accumulated on the wafer surface are neutralized, and the occurrence of electrostatic damage is suppressed.

[Problem to be solved by the invention]

Since the conventional ion implantation apparatus is configured as described above, it is necessary that the disk current always reflects the charge on the wafer surface. However, in reality, as shown in Figure 4, when the disk 2 rotates at a high speed of about 1100 orps and makes a translational movement as shown by the vertical arrow, all of the disks enter the ion beam. The wafer 1 is equally irradiated with the ion beam.

However, for the secondary electrons generated from the disk 2, the ion beam is located at the edge of the disk, for example, when the incident angle of the ions is 60°.
When the angle is irradiated to ~80°, the occurrence is 1.5 to several times as much as when the plane is irradiated. Therefore, in this case, the disk current apparently increases. To explain this situation using FIG. 5, when the disk current is zero, the disk 2 is not in the ion beam irradiation position 1, and the disk 2 moves translationally from there to the ion beam irradiation position. As the disk enters the
It increases again, and when the disk is completely ejected, it becomes zero again, and one scan ends. In the figure, when the disk current is constant, the entire disk 2 is irradiated with the ion beam.

As shown in the figure, in the disk translational motion of - times, there are two points where the disk current becomes high: when the disk enters the ion beam and when it exits the ion beam.

The above explanation is for the case where electrons for neutralizing the wafer are not supplied, but when actually supplying electrons, the supply amount is controlled by the electron emission amount controller 8 according to this disk current, so this In areas where the flow is high,
There was a problem in that more electrons than originally required by the wafer were supplied from the filament 9, and the wafer 1 was negatively charged, destroying the device.

This invention was made to solve the above-mentioned problems, and it prevents the abnormal increase in disk current due to the generation of excessive secondary electrons when the disk enters and exits the ion beam. The object of the present invention is to provide an ion implantation device in which the disk current always reflects the wafer charging state and can appropriately neutralize the wafer charge.

[Means for solving the problem] The ion implantation device according to the present invention includes a secondary electron emitting plate provided on the outermost periphery of the disk so as to cover the end of the secondary electron emitting plate, which is insulated from the disk. With the secondary electron emission plate,
It is designed to emit an excessive amount of secondary electrons that are generated when the ion beam enters the disk.

[Effect]

In this invention, a secondary electron emission plate insulated from the disk is provided on the outermost periphery of the disk so as to cover the edge thereof, and the secondary electron emission plate is used to direct the ion beam from the disk. Since the excessive amount of secondary electrons generated when the ion beam is ejected is emitted, it is possible to suppress changes in the disk current due to the excessive amount of secondary electrons when the ion beam enters the disk.

〔Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an ion implantation chamber of an ion implantation apparatus according to an embodiment of the present invention, in which the same reference numerals as in FIG. This is the attached secondary electron emission plate. The basic operation of the ion implantation device and the control method for supplying electrons for neutralizing the wafer are the same as in the conventional example, so their explanation will be omitted here.

Next, the effects will be explained.

In the ion implantation apparatus according to this embodiment, the secondary electron emission plate 10 is provided on the outermost periphery of the disk 2 and is insulated from the disk 2 by an insulating insulator 11. In this case, the secondary electron emission plate 10 is first irradiated with an ion beam, and then the disk 2
The ion beam will be irradiated onto the plane of the disk 2, but the secondary electron emission plate 10 is shaped to cover the edge of the disk 2, so that it emits an excessive amount of secondary electrons. Therefore, the ion beam is not directly irradiated to the edge of the disk, and therefore there is no abnormal emission of secondary electrons from disk 2 (as a result, the disk current shown in Figure 5 becomes higher than its original value). The phenomenon disappears, and the state shown in FIG. 2 is reached, and the disk current value correctly reflects the amount of electrification on the wafer.

By automatically controlling the amount of neutralizing electrons supplied from the filament 9 by the electron emission amount controller 8 according to this disk current, excessive neutralizing electrons as seen in the conventional example can be eliminated. Positive charging of the wafer can be suppressed without causing negative charging of the wafer due to supply.

In the above embodiment, the secondary electron emission plate 10 is attached to the disk 2 via the insulating insulator 11, but the secondary electron emission plate 10 does not necessarily need to be provided on the disk, and is attached to the edge of the disk. As long as the structure covers the disk and moves in accordance with the translational movement of the disk, it may be provided at another location, and the same effect as in the above embodiment can be obtained.

[Effects of the Invention] As described above, according to the ion implantation apparatus according to the present invention,
Since the secondary electron emission plate was installed to cover the edge of the disk, excessive electron emission that occurs when the ion beam enters and exits the disk is eliminated.
Abnormal increases in disk current due to the emission of secondary electrons are eliminated, and the amount of electron emission for charge neutralization can be optimally controlled according to the disk current, which eliminates negative charging when neutralizing the wafer's charge. This has the effect of greatly improving device yield and reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the implantation chamber of an ion implanter according to an embodiment of the present invention, FIG. 2 is a diagram showing changes in disk current in the present invention, and FIG. 3 is a diagram showing the implantation chamber of a conventional ion implanter. The configuration diagram, Figure 4, shows the 2
FIG. 5, which is a schematic diagram showing secondary electrons, is a diagram showing changes in disk current in a conventional example. In the figure, 2 is a disk, 5 is a disk current detector,
8 is an electron emission amount controller, IO is a secondary electron emission plate, and 11 is an insulating insulator. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In an ion implanter having an electron supply source that detects a disk current flowing through a target object, supplies an amount of electrons corresponding to the disk current to the target object, and reduces the charge on the target object, the ion implanter is insulated from the disk. 1. An ion implantation device comprising: a secondary electron emitting plate covering an end of the disk;