JPH04184853A - Ion implanting device - Google Patents

Abstract

PURPOSE:To prevent electrostatic charge on a target effectively by supplying electrons to an ion irradiation area on the target through a slit in a mask board. CONSTITUTION:X-direction scan is made with ion beam using a scanning electrode 4, and the ion beam is projected onto a target 8 through a slit 22a in a mask board 22. Meantime, electrons emitted from a filament 14 are projected onto an electron emitting body 18, which emits secondary electrons 20, and these are passed through the slit 22a and cast onto the ion beam irradiation area on the target 8. Thereby negative electrostatic charge generated on the target 8 is neutralized.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention electrically scans an ion beam and
The present invention relates to a so-called hybrid scan type ion implantation apparatus that mechanically scans a target in a direction substantially perpendicular to the target, and more specifically, to an improvement in means for preventing charging of the target.

[Conventional technology]

A conventional example of this type of ion implantation apparatus is shown in FIG.

In this ion implanter, the ion source (not shown)
A scanning voltage (for example, a triangular wave voltage of several hundred Hz to 1000 Hz) is applied from a scanning power source 6 to a spot-shaped ion beam 2 that has been extracted from the ion beam and subjected to mass analysis, acceleration, etc. as necessary. Electrostatically scans in the X direction (for example, horizontal direction; the same applies hereinafter) using the scanning electrode 4 of
(The cross section of this ion beam 2 is shown with hatching in the figure. The same applies to other figures).

On the other hand, a target (for example, a wafer) 8 is held within the irradiation area of the ion beam 2 by a holder 10, and
A drive device 12 moves them in an direction perpendicular to the X direction.
The ion beam is mechanically scanned in a direction (for example, the vertical direction; the same applies hereinafter) at a frequency of, for example, several Hz, and by this and the above-mentioned scanning of the ion beam 2, ions are implanted uniformly over the entire surface of the target 8. .

In addition, in order to prevent the surface of the target 8 from being positively charged (charged up) and causing problems such as discharge, especially when the surface is an insulator, due to the irradiation with the ion beam 2, the surface of the target 8 is An electron irradiator 18 consisting of a filament 14 and an obliquely oriented plate is provided as an electron emission source on the upstream side of The secondary electrons 20 are emitted, and the secondary electrons 20 are mainly
is supplied to the target 8 and the ion beam 2 is applied to the surface of the target 8.
This is to neutralize the positive charge caused by

[Problem to be solved by the invention]

In the case of a hybrid scan type ion implantation apparatus, the cross section of the ion beam 2 irradiated onto the target 8 is band-shaped, and this band-shaped portion moves slowly over the target 8 as the target 8 is mechanically scanned.

However, with the conventional device as described above, the target 8
Since the secondary electrons 20 are supplied to a wide area (for example, almost the entire surface) on the target 8, the secondary electrons 20 are also supplied to the area of the target 8 that is not irradiated with the ion beam 2. In such a region, negative charging occurs due to the secondary electrons 20, which causes problems such as discharge.

In addition, in order to effectively prevent charging on the target 8, it is necessary to control the amount of secondary electrons 20 supplied to the target 8 to an amount that can just neutralize the positive charge caused by ions. With conventional devices, it is not known how to control the amount of secondary electrons 20 to exactly neutralize the charging caused by the ion beam 2. This is because even if you measure the balance of charges in the target 8, it will be the amount of electrons incident on a wide area of the target 8 and the amount of electrons incident on a wide area of the target 8.
It is the sum total of the amount of ions that are incident on only a portion, so even if such a balance is made to be approximately 0, for example, the area that is not hit by the ion beam 2 will have an excess of electrons,
This is because the region hit by the ion beam 2 will have an excess of ions.

Therefore, the main object of the present invention is to provide an ion implantation apparatus that improves the above-mentioned points and can effectively prevent charging of a target in a hybrid scan method.

[Means to solve the problem]

In order to achieve the above object, the ion implantation apparatus of the present invention includes a mask plate provided upstream of the target and having a slit through which the ion beam scanned in the X direction passes;
The present invention is characterized in that an electron emission source that emits electrons is provided upstream of the mask plate, and the electrons from the electron emission source are supplied to the target through the slits in the mask plate.

Further, an electron gun for emitting an electron beam and a scanning means for electrically scanning the electron beam in the X direction in synchronization with the scanning of the ion beam are provided upstream of the target, and the scanning means scans the electron beam. The target may be irradiated with an electron beam.

[Effect]

When electrons from the electron emission source are supplied to the target through the slits in the mask plate as described above, the electrons are supplied only to the region of the target that is irradiated with the ion beam. Therefore, charging of the target can be effectively prevented.

Furthermore, if the electron beam scanned by the scanning means is irradiated onto the target in synchronization with the ion beam as described above, the target will be irradiated with the ion beam and the electron beam at almost the same place at the same time. Become so. In this way, the target can be irradiated with ions and electrons that substantially correspond temporally and spatially, so that charging of the target can be more effectively prevented.

〔Example〕

FIG. 1 is a diagram partially showing an ion implantation apparatus according to an embodiment of the present invention. Components equivalent to those in the example of FIG. 4 are given the same reference numerals, and the differences from the conventional example will be mainly explained below.

In this embodiment, a mask plate 22 having an elongated slit 22a through which the ion beam 2 scanned in the X direction passes is provided upstream of the target 8 as described above.

In addition, the above-mentioned filament 14 constituting the electron emission source
and an electron irradiator 18 are provided upstream of this mask plate 22.

The secondary t-son 2 emitted from this electron irradiator 18
In this way, even if the secondary electrons 20 are emitted from the electron irradiator 18 to a wide area, the target 8 is supplied with the mask through the sleeves 22a of the mask plate 22. Slit 2 of plate 22
Since only the secondary electrons 20 that have passed through the ion beam 2a are supplied, the secondary electrons 20 are supplied only to the same band-shaped region of the target 8 that is irradiated with the ion beam 2.

Therefore, it is possible to prevent other regions on the target 8 from being negatively charged by electrons.

Moreover, since the target 8 is irradiated with substantially the same area as the ions and electrons, it becomes easy to control the amount of the secondary electrons 20 to neutralize the charge on the target 8. For example, if the charge balance at the target 8 is measured and it is
The amount of secondary electrons 20 emitted may be controlled so as to have a value close to 0.

Therefore, according to the above configuration, charging of the target 8 can be effectively prevented.

In addition, in the case of the hybrid scan method, it may be difficult to electrically float the target 8 (more specifically, the holder 10 that holds it) from the ground due to the structure of the drive device for the target 8. In that case, it is not possible to measure the current flowing through the target 8 and control the amount of secondary electrons 20 as described above. This can be dealt with by providing the following collector 24.

That is, as shown in FIG. 2, the area behind the slit 22a of the mask plate 22 where the ion beam 2 is irradiated, other than the target 8, is electrically insulated from the rest and passes through the slit 22a. A collector 24 that receives the coming ion beam 2 and secondary electrons 20 may be provided.

The ion beam 2 and the secondary electrons 20 are incident on the collector 24 under almost the same conditions as when they are incident on the target 8, and to put it simply, the beam current due to the ion beam 2 is
1 and secondary electrons 20 in the opposite direction. Collector current 1c (= In + It
) flows. Therefore, this collector current 1 is measured by the current measuring device 26, and this collector current 1. The amount of secondary electrons 20 is controlled (more specifically, the amount of secondary electrons 20 is controlled so that
The amount of emitted primary electrons 16 is controlled by controlling the current flowing through the source, thereby controlling the amount of secondary electrons 20? In this case, the secondary electrons 20 are supplied to the target 8 in an amount commensurate with the ion beam 2, and therefore the target 8 can be effectively prevented from being charged.

It is preferable that the collector 24 be brought close to the same state as the target 8. For example, when ion implantation is performed by tilting the ion beam 2 to the target 8 by an angle θ (also called a tilt angle) from the vertical direction, the collector 24 is also Preferably, it is tilted by an angle θ. Also, the distance from the mask plate 22 to the collector 24 is the same as the distance to the target 8,
It is preferable that the material of the collector 24 is also the same as that of the target 8.

In this way, the current measured by the collector 24 includes all of the charge balance of the ion beam 2, the secondary electron emission caused by its incidence, the secondary electron 20, and the secondary electron emission caused by its incidence. and their quantities simulate the situation on Target 8 fairly well. This is because, for example, the amount of secondary electrons emitted by an ion beam depends on the angle formed between the ion beam and the target (here, the target 8 or the collector 24).

In addition, in the above embodiment, the distribution of the secondary electrons 20 emitted from the electron irradiator 18 is biased, and the target 8 is not necessarily uniformly exposed to the secondary electrons 20 in the scanning direction of the ion beam 2 (that is, in the X direction). There may be cases where the secondary electrons 20 are not irradiated.

The embodiment shown in FIG. 3 can further improve this point.

That is, in the embodiment shown in FIG. 3, instead of the electron emission source consisting of the filament 14 and the electron irradiator 18 described above, an electron gun 28 that emits an electron beam 30 and an electron beam 30 are provided on the upstream side of the mask plate 22. A pair of scanning electrodes 32 are provided that scan in the X direction, and the electron beam 30 scanned by these electrodes is irradiated onto the target 8 through the slit 22a of the mask plate 22.

Moreover, the scanning of the electron beam 30 is synchronized with the scanning of the ion beam 2. That is, target 8
In this case, the ion beam 2 and the electron beam 30 are irradiated at approximately the same time and at approximately the same location. In order to do this, for example, as shown in FIG.
2 should be applied. Alternatively, a dedicated scanning power source may be provided for the scanning electrodes 32, and the output voltage from the scanning power source may be appropriately selected and synchronized with the output voltage from the scanning power source 6.

According to this embodiment, the target 8 can be irradiated with ions and electrons in a manner that substantially corresponds both temporally and spatially, so that charging of the target 8 can be more effectively prevented.

However, in this embodiment, since the electron beam 30 also scans in a strip like the ion beam 2, the mask plate 22 does not necessarily need to be provided.

Note that, unlike the above-mentioned sides, the holder 10 is attached to the tip of a swinging arm, and by rotating this arm back and forth, the target 8 held in the holder 10 draws an arc with the target 8 facing the ion beam 2. In this manner, scanning may be performed mechanically in the X direction substantially perpendicular to the X direction.

Moreover, an electromagnet may be used as the scanning means for the ion beam 2 and the electron beam 30.

In addition, in this specification, the X direction and the X direction only represent two orthogonal directions, and therefore, for example, the X direction may be viewed as a horizontal direction, a vertical direction, or even a direction tilted from these directions. You can also look at it as

〔Effect of the invention〕

As described above, the present invention provides the following effects.

In other words, if electrons from the electron emission source are supplied to the target through the slits in the mask plate, the target will be supplied with electrons almost only in the area that is irradiated with the ion beam, which will effectively reduce the charge on the target. can be prevented.

Furthermore, by synchronizing the electron beam scanned by the scanning means with the ion beam and irradiating the target, it is possible to irradiate the target with ions and electrons that almost correspond temporally and spatially. , charging of the target can be more effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram partially showing an ion implantation apparatus according to an embodiment of the present invention. FIG. 2 is a diagram partially showing the area around the collector electrode. FIG. 3 is a diagram partially showing an ion implantation apparatus according to another embodiment of the invention. Fourth
The figure is a diagram partially showing an example of a conventional ion implantation device. 2... Ion beam, 4... Scanning electrode, 8... Target, 10... Holder, 12... Drive device, 1
4... Filament, 18... Electron irradiation body, 20.
・・Secondary electron, 22・・・Mask plate, 22 a 1. −
Slit, 28...electron gun, 30...electron beam,
32...Scanning electrode.

Claims (2)

[Claims] (1) In an ion implanter configured to electrically scan the ion beam in the X direction and mechanically scan the target in the Y direction substantially orthogonal to the A mask plate having a slit through which the ion beam scanned by the ion beam passes is provided, an electron emission source for emitting electrons is provided on the upstream side of this mask plate, and the electrons from the electron emission source are passed through the slit of the mask plate. An ion implantation apparatus characterized in that the ion implantation apparatus is configured to supply ions to the target. (2) In an ion implantation apparatus configured to electrically scan the ion beam in the X direction and mechanically scan the target in the Y direction substantially perpendicular to the X direction, an electron beam is placed on the upstream side of the target. and a scanning means for electrically scanning the electron beam in the X direction in synchronization with the scanning of the ion beam, and irradiating the target with the electron beam scanned by the scanning means. An ion implantation device characterized by: