JPH0992198A - Ion implantation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly enable electrostatic destruction of a semiconductor wafer to be prevented and obtain an inexpensive ion implantation device. SOLUTION: An ion implantation device is provided with a support means 101 for supporting a semiconductor wafer 103 and an ion irradiation means (not illustrated) for irradiating an ion beam to a semiconductor wafer 103 supported on this support means 101. This device is additionally provided with an electrode 107 for charge radiation arranged in the neighborhood of the support means 101 so as to match part of range 104 of the ion beam which the ion irradiation means irradiates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus, and more particularly to an ion implantation apparatus equipped with electrostatic breakdown preventing means.

[0002]

2. Description of the Related Art Conventionally, an apparatus for implanting ions into a semiconductor wafer has been known and is called an ion implantation apparatus. Further, as such an ion implantation device, one provided with a means for preventing electrostatic breakdown of a semiconductor wafer is known.

Hereinafter, with respect to electrostatic breakdown of semiconductor wafers,
This will be described with reference to FIG. As shown in FIG. 4, the support plate 4
When ion implantation is performed by irradiating the surface of the semiconductor wafer 402 supported by 01 with the positive ion beam 403, the positive charge 404 is discharged to the ground through the resistance element 405 on the surface of the semiconductor wafer 402. But,
Due to the large resistance of the semiconductor wafer 402, some positive charges 404 remain on the surface of the semiconductor wafer 402, and the surface of the semiconductor wafer 402 is charged thereby. Then, the positive charge 404 related to this charging causes electrostatic breakdown of the semiconductor wafer. Further, when ions are implanted into the semiconductor wafer 402, secondary electrons 406 are emitted, which also increases the amount of positive charge on the surface of the wafer and promotes electrostatic breakdown.

On the other hand, when negative ions are implanted into the semiconductor wafer 402, negative charges are accumulated on the surface of the semiconductor wafer 402, but since the negative charges 405 are discharged as secondary electrons, the semiconductor wafer 402. The amount of electrostatic charge on the surface of is reduced, and electrostatic breakdown does not occur.

FIG. 5 is a sectional view conceptually showing a conventional example of an ion implantation apparatus provided with a means for preventing electrostatic breakdown.

In the figure, the support plate 501 is formed in a disk shape, and rotates about the shaft 502 at a constant speed. On the surface of the support plate 501, along the rotation direction,
A plurality of semiconductor wafers 503 are placed. This semiconductor wafer 503 is irradiated with a positive ion beam supplied from an ion source (not shown) along a range 504 through an accelerating means (not shown), a slit, or the like.

In such an ion implanter, the electrostatic breakdown preventing means is composed of a filament 505, a reflector 506, a target 508, an ammeter 509 and a negative feedback circuit 510. The filament 505 emits thermoelectrons 511 according to the amount of current. This thermoelectron 511
Are accelerated by the extraction electrode 507 and collide with the target 508. As a result, the target 508 emits the secondary electrons 512. Then, the secondary electrons 512 electrically neutralize the positive charges accumulated on the surface of the semiconductor wafer 503. At this time, the amount of positive charge remaining on the surface of the semiconductor wafer 503 can be known from the amount of fluctuation of the disk current 513 flowing through the ammeter 509. The negative feedback circuit 510 detects the fluctuation amount of the disk current 513 and controls the current flowing through the filament 505 based on the detection result.

According to the electrostatic breakdown preventing means having such a structure, the positive charges accumulated on the surface of the semiconductor wafer 503 can be reduced by the secondary electrons 512, and therefore, the occurrence of electrostatic breakdown can be prevented. Is effective in.

[0009]

However, in the electrostatic breakdown preventing means as shown in FIG. 5, as described above,
Since the negative feedback circuit 510 controls the thermoelectrons 511 and the secondary electrons 512 by following the change in the disk current 513, a transient excess or deficiency of the secondary electron amount easily occurs, and the semiconductor wafer In some cases, the amount of positive charges on the surface of 503 was temporarily increased to cause electrostatic breakdown. For example, in a standard ion implanter, the support plate 5
The rotation number of 03 is 1000 to 1200 rpm, but it takes 0.1 to 0.3 seconds from the change of the disk current 513 until the amount of generation of the secondary electrons 512 changes. Therefore, from the change of the disk current 513, A delay of about 6 rotations of the support plate 503 occurs before the change of the secondary electrons 512.

Further, the conventional electrostatic breakdown preventing means has a drawback that the structure is complicated and expensive.

The present invention has been made in view of the above drawbacks of the prior art, and an object of the present invention is to provide an inexpensive ion implanter capable of reliably preventing electrostatic breakdown of a substrate to be processed. And

[0012]

An ion implantation apparatus according to the present invention is a substrate supporting means for supporting a substrate to be processed, and an ion irradiation means for irradiating the substrate to be processed supported by the substrate supporting means with an ion beam. In the ion implantation apparatus including, further comprising a charge emitting electrode arranged in proximity to the substrate supporting means so as to come into contact with a part of the range of the ion beam irradiated by the ion irradiation means. Characterize.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view conceptually showing the structure of a main part of the ion implantation apparatus according to this embodiment.

In the figure, a disk-shaped support plate 101 is disposed inside the vacuum container 100. The support plate 101 rotates about the rotation shaft 102 at a constant speed. Further, a plurality of semiconductor wafers 103 are placed on the surface of the support plate 101 along the rotation direction. The semiconductor wafer 103 is irradiated with a positive ion beam supplied from an ion irradiation means (which is composed of an ion source, an acceleration means, a slit, etc.) (not shown) along a range 104. The rotating shaft 102 is connected to the wiring 105.
Therefore, it is grounded through the resistor 106.

A charge emission electrode 107 is arranged near the support plate 101 so as to contact a part of the range 104 of the ion beam. This charge emission electrode 107 is
The wiring 108 is connected to the rotating shaft 102.
As a result, the charge discharging electrode 107 and the support plate 101 have the same potential.

FIG. 2 is a perspective view conceptually showing an example of a specific shape of the charge discharging electrode 107.

As shown in the figure, the charge emission electrode 10
No. 7 is formed so that the area of the surface 107a perpendicular to the range 104 of the ion beam is smaller than the area of the cross section 104a of the range 104. Thereby, the semiconductor wafer 103
It is possible to prevent the charge emitting electrode 107 from becoming a coating when ion implantation is performed.

The surface 107b of the charge emission electrode 107 parallel to the traveling direction of the ion beam is made as long as possible in order to reduce the resistance to the ion beam.

Here, it is desirable that the charge discharging electrode 107 is formed of a material that is unlikely to cause metal contamination of the semiconductor wafer 103. This is because when metal contamination occurs on the semiconductor wafer 103, crystal defects occur near the surface of the wafer, which causes deterioration of the quality of semiconductor elements. In an ordinary ion implantation apparatus, the slits of the ion irradiation means are formed of carbon, and the support plate 101 and the like are formed of aluminum. Therefore, the charge emission electrode 107 is formed of carbon or aluminum. It is possible to suppress the generation of metal contamination. Further, when a silicon wafer is used as the semiconductor wafer, it is possible to prevent the metal contamination from occurring by forming the charge emitting electrode 107 with silicon.

FIG. 3 is a perspective view conceptually showing another example of the specific shape of the charge discharging electrode 107.

In the charge emission electrode 107 shown in FIG.
The area of the surface 107a perpendicular to the range 104 of the ion beam is made smaller than the area of the cross section 104a of the range 104 so that the charge emitting electrode 107 does not become a coating at the time of ion implantation. Plane 1 parallel to the direction
07b is formed in a mesh shape to reduce the resistance to the ion beam.

In the ion implantation apparatus as shown in FIGS. 1 to 3, the semiconductor wafer 10 has a positive ion beam emitted from an ion irradiation means (not shown) along the range 104.
3 is irradiated, the positive charges 109 supplied to the semiconductor wafer 103 flow out to the ground via the wiring 105 and the resistance element 106, but some positive charges 109 remain on the surface of the semiconductor wafer 103.

However, in this embodiment, the charge emitting electrode 107 is provided near the support plate 101.
Since 07 is provided and the charge emitting electrode 107 is in contact with a part of the range 104 of the ion beam, the positive charge 109 on the surface of the semiconductor wafer 109 can be moved. Therefore, according to the present embodiment, electrostatic breakdown of the semiconductor wafer 109 due to this positive charge 109 can be prevented.

The positive charge 109 on the surface of the semiconductor wafer 109 can be moved by the charge discharging electrode 107 because the positive charge 109 on the surface of the semiconductor wafer 109 is
This is because the ion beam is used as a medium and flows into the charge emission electrode 107.

In this embodiment, the wiring 108 is used to set the charge emitting electrode 107 and the support plate 101 to the same potential (see FIG. 1), but the potential difference between the charge emitting electrode 107 and the support plate 101 is set. Is not particularly limited, and may be a potential difference that causes the positive charges 109 to move. For example, by providing a power source (not shown) between the charge emission electrode 107 and the support plate 101 and making the potential of the charge emission electrode 107 lower than the potential of the support plate 101, the positive charge 109 can be moved. It is also possible to promote.

As described above, according to this embodiment, electrostatic breakdown can be prevented only by providing the charge discharging electrode 107, so that the electrostatic breakdown can be prevented by a very inexpensive means. You can

Further, since the negative feedback circuit used in the conventional electrostatic breakdown preventing means is not required, there is no problem that the charge amount on the wafer surface increases due to the delay in removing the positive charges 109. Therefore, electrostatic breakdown of the semiconductor wafer can be reliably prevented.

[0029]

As described in detail above, according to the present invention, it is possible to provide an inexpensive ion implanting device which can surely prevent electrostatic damage to a substrate to be processed.

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing a configuration of a main part of an ion implantation apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view conceptually showing an example of a specific shape of a charge discharging electrode.

FIG. 3 is a perspective view conceptually showing another example of the specific shape of the charge discharging electrode.

FIG. 4 is a conceptual diagram for explaining the principle of electrostatic breakdown of a semiconductor wafer.

FIG. 5 is a sectional view conceptually showing one configuration example of a conventional ion implantation device.

[Explanation of symbols]

 100 Vacuum Container 101 Support Plate 102 Rotating Shaft 103 Semiconductor Wafer 104 Ion Beam Range 105 Wiring 106 Resistance 107 Charge Emitting Electrodes 107a and 107b Surface of Charge Emitting Electrode

Claims (3)

[Claims] 1. An ion implantation apparatus comprising a substrate supporting means for supporting a substrate to be processed, and an ion irradiating means for irradiating the substrate to be processed supported by the substrate supporting means with an ion beam. An ion implantation apparatus further comprising a charge emission electrode disposed in proximity to the substrate supporting means so as to come into contact with a part of the range of the ion beam irradiated by. 2. The ion implantation apparatus according to claim 1, wherein the charge discharging electrode is set to have the same potential as the substrate supporting means or a potential lower than that of the substrate supporting means. 3. The ion implantation apparatus according to claim 1, wherein the charge discharging electrode is formed of aluminum, carbon or silicon.