JPH0535536B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electronic shower device that can be advantageously used to prevent charging of a substrate such as a silicon wafer when implanting ions into a substrate such as a silicon wafer in an ion implantation apparatus. It is something.

[Conventional technology] When manufacturing semiconductors, As ions and P are applied to wafers.
In a high-current ion implantation device used for implanting ions, the oxide film on the wafer may be damaged due to discharge due to charge-up by the ions, and there is a risk that perforations may occur in the oxide film. For example, when forming an insulating layer with a thickness of several hundred Å, the charge will rise at about 12.5 mA, and if the voltage reaches 100 V, holes will form in the formed film. Therefore, it is necessary to neutralize the ions from the ion source using an electronic shower.

For this purpose, the present inventor previously proposed
In Publication No. 240551, a hollow shield is provided in an annular shape around the central axis of the ion beam,
A part of the inside of this shield is cut out to form an annular opening facing a substrate such as a silicon wafer, and an annular opening is formed along the shield inside the hollow shield and outside the area connecting the substrate and the opening. An electronic shower source device equipped with a filament was proposed.

[Problems to be Solved by the Invention] By the way, such conventional electrostatic methods cannot completely neutralize the ion beam.
In other words, the filament of the electron gun used for neutralization is not directly opposed to the wafer in the implantation chamber to prevent contamination, but since ion implantation equipment requires a strong magnetic field, low-energy electrons are is easily affected by this magnetic field, and in electrostatic methods, low-energy electrons cannot reach the implant guide wafer due to stray magnetic fields of several Gauss.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic shower device for an ion implanter that can effectively introduce low-energy electrons into a workpiece in an implantation chamber using a magnetic field rather than the conventional electrostatic method.

[Means for Solving the Problems] In order to achieve the above object, an electronic shower for an ion implantation apparatus according to the present invention provides an electronic shower for an ion implanter that is arranged between an ion source and an implantation chamber so as to align with the central axis of the ion beam from the ion source. The hollow electron gun is located coaxially with respect to the hollow electron gun, and two magnetic field generators are arranged before and after the hollow electron gun and generate magnetic fields in opposite directions. One of the magnetic field generators disposed at the rear of the gun includes a plurality of spaced apart coils for guiding electrons from the hollow electron gun along the ion beam from the ion source; The cathode of the electron gun is positioned so as not to directly oppose the object to be processed in the implantation chamber, and low-energy electrons are introduced into the implantation chamber along with ions from the ion source.

[Function] In the electronic shower device for an ion implanter according to the present invention, two magnetic field generators placed before and after the hollow electron gun generate magnetic fields in opposite directions. Due to this action, a substantial portion of the electrons emitted from the hollow electron gun toward the central axis of the ion beam are sharply bent toward the implantation chamber along the central axis of the ion beam. The electrons thus bent toward the implantation chamber can be guided along the central axis of the ion beam by magnetic fields in the same direction generated from each coil of a magnetic field generator disposed behind the hollow electron gun. Thereby, low-energy electrons can be effectively introduced into the workpiece in the implantation chamber.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 schematically shows an electronic shower device for an ion implanter according to an embodiment of the present invention, in which 1 is a wall provided with an aperture 2 through which an ion beam from an ion source (not shown) is passed; It can consist of Reference numeral 3 designates a hollow electron gun, which includes an annular filament 3a made of tantalum, an annular grid 3b made of a mesh made of molybdenum inside the annular filament 3a, and a shield 3c made of carbon surrounding the annular filament 3a and the annular grid 3b. . To prevent contamination, the annular filament 3a of the hollow electron gun 3 is placed so that it cannot be directly seen from the wafer 6 mounted on the rotating holder 5 in the aluminum implanting chamber wall 4. The type electron gun 3 emits electrons in a direction substantially perpendicular to the central axis 7 of the ion beam.

Magnetic field generating coils 8 and 9 are attached to the front and rear outer walls of the shield 3c of the hollow electron gun 3, respectively, and these coils 8 and 9 are configured to generate magnetic fields in opposite directions. . Two other magnetic field generating coils 10 and 11 are shown between the magnetic field generating coil 9 and the driving chamber wall 4.
These magnetic field generating coils 10 and 11 are placed farther from the center line 7 of the ion bee than the magnetic field generating coils 8 and 9 are. These two magnetic field generating coils 9, 10, 11 are the magnetic field generating coil 9.
The electron beam is bent along the central axis 7 of the ion beam by the magnetic field generated by the magnetic field generating coil 9.
It acts to guide you along. Note that 12 is a casing wall made of aluminum, 13 is a mounting member made of SUS, and 14 is a shield member.

The magnetic field generating coil 8 provided on the outer wall in front of the shield 3c of the hollow electron gun 3 constitutes one of two magnetic field generating devices, and the magnetic field generating coils 9, 10, and 11 constitute the other magnetic field generating device. It consists of

The implanting chamber wall 4, the rotary holder 5, the wafer 6 inserted on the rotary holder 5, and the shield member 14
is actually arranged at a predetermined angle with respect to the central axis 7 of the ion beam, as shown by the imaginary line in FIG.

FIG. 2 shows an example of the magnetic field vector calculated based on the device shown in FIG. The state of the magnetic field vector is shown when the magnetic field generating coil 9 behind the shield 3c of the electron gun 3 is set to -500 AT, and the magnetic field generating coils 10 and 11 are each set to -300 AT. As can be seen from this figure, magnetic field generating coils 8 and 9 are provided before and after the hollow electron gun 3.
Near the hollow electron gun 3, the magnetic field vector initially points toward the central axis 7 of the ion beam, then sharply curves along the central axis 7 of the ion beam. The vector is the central axis 7 of the ion beam
It extends almost parallel to the The electrons emitted from the hollow electron gun 3 while rotating around the lines of magnetic force formed in this way are aligned with the central axis 7 of the ion beam.
can be guided along.

The range of the magnetic field can be selected to be 10 to 30 Gauss in one example, but may be 100 Gauss depending on the case.

When the 200KeV, 12.5mA As ⁺ beam is 95% neutralized, the potential at the ion center is 8V,
Electrons of 8ev or more do not contribute to neutralizing the ion's space charge in the absence of a magnetic field, but according to the present invention, since the electrons are restrained by the magnetic field, it is possible to reliably neutralize the ion beam. can.

In the illustrated embodiment, a total of four magnetic field generating coils are used, but of course more or fewer coils can be used, and the arrangement of each coil can be changed as necessary.
The electron gun may also be divided into a plurality of pieces and each may be arranged on the same circumference.

[Effects of the Invention] As explained above, in the electronic shower device for an ion implanter according to the present invention, mutually opposite magnetic fields generated by the two magnetic field generators placed before and after the hollow electron gun are used. The electrons from the hollow electron gun are guided along the central axis of the ion beam by the action of the magnetic field generated in the same direction from each coil of the magnetic field generator placed behind the hollow electron gun. As a result, even in the presence of a stray magnetic field of several Gauss, low-energy electrons can be effectively introduced into the workpiece in the implantation chamber, thereby reliably neutralizing the ion beam and discharging the workpiece. It is possible to prevent discharge due to charge-up on the workpiece, and to increase the uniformity of the ion implantation amount on the workpiece.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing magnetic field vectors based on calculations using the apparatus shown in FIG. In the figure, 3...Hollow type electron gun, 6...Wafer,
7... Central axis of the ion beam, 8, 9, 10,
11... Magnetic field generation coil.

Claims (1)

[Claims] 1. A hollow electron gun located coaxially with the central axis of the ion beam from the ion source between the ion source and the implantation chamber, and a hollow electron gun arranged in front and behind the hollow electron gun and facing oppositely to each other. and two magnetic field generators configured to generate magnetic fields, one of the magnetic field generators disposed at the rear of the hollow electron gun generates magnetic fields from the hollow electron gun along the ion beam from the ion source. Equipped with multiple coils spaced apart to guide the electrons,
The cathode of the hollow electron gun is positioned so as not to directly oppose the object to be processed in the implantation chamber, and low-energy electrons are introduced into the implantation chamber along with ions from the ion source. Electronic shower device for ion implantation equipment.