Ion beam charge neutralizer and method therefor

Details Ion beam charge neutralizer and method therefor Ion beam charge neutralizer and method therefor

2003-03-27

2004-11-09

Wells, Nikita (Department: 2881)

Radiant energy

Irradiation of objects or material

Irradiation of semiconductor devices

C250S492200, C250S492300, C250S42300F, C250S251000, C315S111810

Reexamination Certificate

active

06815697

ABSTRACT:

This application claims priority to prior application JP 2002-88122, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to an ion beam charge neutralizer and an ion beam charge neutralizing method in an ion implanter having a mechanism for linearly and reciprocally scanning an ion beam by an electric field or a magnetic field. This invention also relates to an ion beam charge neutralizer and an ion beam charge neutralizing method in an ion implanter having a mechanism for forming a sheet-like or a ribbon-like ion beam through an ion extracting member or a beam line.
In production processes of semiconductor integrated circuits, ion implanters are widely used because impurities can be accurately and precisely introduced into a microscopic area on a surface of a wafer. Since the ion implanter implants charged ions, i.e., ions having electric charges, into the wafer to be processed, there arises a problem of charge accumulation (charge-up) onto the wafer.
Generally, the ions to be implanted have positive electric charges. Therefore, in order to suppress the charge-up, negative electric charges (electrons) are supplied. For example, use is made of a method of actively supplying electrons produced by collision of ions against a wall of a beam line and another method of supplying secondary electrons produced near the wafer by the use of an electron gun. Among others, a plasma shower (or a plasma flood gun) is widely used as a method capable of supplying electrons having relatively low energy.
In a batch-type ion implanter, the wafer is placed on a rotary disk adapted to perform linear reciprocal movement so as to enable ion implantation throughout an entire surface of the wafer. In this event, a beam trajectory or orbit is fixed with respect to the beam line. The plasma shower is disposed in the vicinity of the beam. By the potential of the beam, the electrons are supplied from the plasma shower.
Referring to
FIG. 1
, description will be made of an existing plasma shower used in the batch-type ion implanter.
A plasma generating gas
16
is introduced into an arc chamber
15
. A filament
17
is heated by a power supply
18
and an arc voltage
19
is applied between the filament
17
and the arc chamber
15
. As a consequence, a plasma is generated in the arc chamber
15
. Setting is appropriately made so that an ion beam
28
is located in the vicinity of the arc chamber
15
. Then, electrons are extracted by a potential built up by the ion beam
28
so that the charge-up by the beam is suppressed. By arranging a shower tube
37
and applying a negative potential
38
to the shower tube
37
, it is possible to promote the supply of electrons from the arc chamber
15
to the beam.
On the other hand, in an ion implanter having a mechanism for scanning the beam by making the beam itself perform linear reciprocal movement, the relative position of the beam and the plasma shower is continuously varied. This makes it difficult to stably supply the electrons. In view of the above, various methods are proposed in order to stably supply the electrons from the plasma shower to the scanned beam.
For example, in order to promote the supply of electrons to the ion beam scanned in a wide area from an ion beam charge neutralizer, proposal is made of various methods of applying a magnetic field to a beam scanning area.
In a first conventional technique (JP 7-176290 A), an extracting hole of a plasma arc chamber is arranged in parallel to a beam scanning direction. The magnetic field is applied by coils in parallel to the beam scanning direction.
In a second conventional technique (JP 8-190887 A), the plasma arc chamber is arranged at the center of the beam scanning area to be perpendicular to the beam scanning direction. A magnetic field spreading outward from the center is applied by coils.
In a third conventional technique (JP 9-147785 A), the plasma arc chamber is arranged at the center of the beam scanning area to be perpendicular to the beam scanning direction. A magnetic field spreading outward from the center throughout a whole of the beam scanning area is applied by coils.
In a fourth conventional technique (JP 10-27569 A), the plasma arc chamber is arranged at the center of the beam scanning area to be perpendicular to the beam scanning direction. An a.c. magnetic field synchronized with the beam reciprocation is applied by coils in parallel to the beam scanning direction.
In a fifth conventional technique (JP 10-172502 A), the third conventional technique is improved by providing an electric field for electron reflection. Furthermore, a magnetic field is applied in parallel to the beam scanning direction.
In each of the above-mentioned plasma showers, the supply of the electrons may be unintentionally prevented because the applied magnetic field itself excessively constrains or binds the electrons in some cases. In order to avoid such prevention of the supply of the electrons, the magnetic field must accurately and precisely be generated. However, it is not always easy to generate a magnetic field exactly as desired.
In order to synchronize beam reciprocation and the magnetic field, a complicated mechanism is required to form a circuit. In addition, it is difficult to confirm whether or not the trajectory of the electrons is controlled in the manner exactly as desired. Furthermore, in case where the coil is used, the mechanism itself is increased in scale.
As a sixth conventional technique (S. Sakai et al., International Conference on Ion Implantation Technology Proceedings, September 2000, pp. 592595), a radio frequency antenna is used to generate a plasma covering a wide area. In this event, a large-scale and complicated mechanism is required to produce, propagate, and control a radio frequency wave.
As a method of supplying the electrons extracted from the plasma arc chamber to the beam after the electrons are introduced into a secondary chamber, proposal is made of the following techniques.
In a seventh conventional technique (JP 2756704 B), a mesh-type electrode is arranged in the secondary chamber for the purpose of exclusively supplying low-energy electrons to the ion beam.
In an eighth conventional technique (JP 6-203788 A), low-energy secondary electrons produced as a result of collision of the extracted electrons against a wall of the secondary chamber are supplied to the ion beam by applying a magnetic field.
However, the seventh and the eighth conventional techniques are addressed to the batch-type ion implanter and do not intend the supply of electrons over a wide area.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a charge neutralizer, a charge neutralizing method, and an ion implanter comprising the charge neutralizer, which neutralizer is capable of stably supplying electrons to a scanned ion beam over a wide area by confining the electrons by the use of cusp magnetic fields generated by arranging a plurality of sets of permanent magnets.
It is another object of this invention to provide a charge neutralizer, a charge neutralizing method, and an ion implanter comprising the charge neutralizer, which neutralizer is capable of stably supplying electrons to a whole of a sheet-like or a ribbon-like ion beam over a wide area by confining the electrons by the use of cusp magnetic fields generated by arranging a plurality of sets of permanent magnets.
According to this invention, there is provided an ion beam charge neutralizer, in which electrons extracted from an arc chamber and pooled in an electron accumulating member are uniformly supplied throughout an entire area of a scanning area of the parallelized ion beam, which is extracted from an ion source as a normal ion beam, and the extracted normal ion beam is reciprocally scanned over a specific range in accordance with continuous-variable control drive of an electric field or a magnetic field, and the scanned ion beam is parallelized with an electric field or a magnetic field, and the parallelized ion beam is traveling towards a

Affiliated with

Also associated with

Rating

Ion beam charge neutralizer and method therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Ion beam charge neutralizer and method therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ion beam charge neutralizer and method therefor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3311035