Radiant energy – With charged particle beam deflection or focussing – With target means
Reexamination Certificate
2000-11-09
2003-09-02
Lee, John R. (Department: 2881)
Radiant energy
With charged particle beam deflection or focussing
With target means
C250S310000, C250S311000, C250S3960ML
Reexamination Certificate
active
06614027
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of controlling an electrostatic lens, which is used in an apparatus which converges/diverges a charged particle beam such as an ion beam, electron beam, etc. by an electrostatic lens and sweep it in an electromagnetic field to be applied onto an object-to-be-irradiated (e.g. an ion implantation apparatus and an electron microscope), and such an ion implantation apparatus for performing the controlling method. More particularly, this invention relates to a means for preventing the beam current of the swept charged particle beam from becoming smaller than before control by the electrostatic lens by performing the control taking the size of the charged particle beam in a scanning direction in consideration.
2. Description of the Related Art
An ion beam is one of charged particle beams.
FIG. 4
shows an example of an ion implantation apparatus equipped with an electrostatic lens for converging or diverging the ion beam.
FIG. 5
shows an enlarged main part thereof.
The ion implantation apparatus as shown is basically the same as that disclosed in Japanese Patent Unexamined Publication No. Hei. 8-115701 (JP-A-8-115701), and is directed to a so-called hybrid parallel scanning system which sweeps an ion beam in reciprocation/parallel in an X-direction (e.g. horizontal direction) and drives an object-to-be-irradiated (e.g. wafer)
22
in reciprocation in a Y direction (e.g. vertical direction) substantially orthogonal to the X direction.
The ion implantation apparatus includes an ion source
2
for deriving the ion beam
4
, a mass analysis magnet
6
for selectively acquiring a specific ion species from the ion beam
4
derived from the ion source
2
, an accelerating tube
8
for accelerating or decelerating the ion beam
4
acquired from the mass analysis magnet
6
, a trimming Q lens
10
for removing the unnecessary part of the ion beam acquired from the accelerating tube
8
, an energy analysis magnet
12
for selectively acquiring an ion with specific energy from the ion beam
4
derived from the trimming Q lens
10
, a sweeping magnet
14
for sweeping the ion beam
4
derived from the energy analysis magnet
12
in the X direction by a magnetic field in this example, and a paralleling magnet
16
for bending the ion beam
4
derived from the sweeping magnet
14
again to parallel-sweep the ion beam
4
in cooperation with the sweeping magnet
14
, i.e. making a parallel ion beam
4
.
The ion beam
4
derived from the paralleling magnet
16
is applied to the object-to-be-irradiated
22
held in a holder
20
of a scanning mechanism
18
and ions are implanted into the object-to-be-irradiated
22
. In this case, the object-to-be-irradiated
22
is driven reciprocatively in the Y direction by the scanning mechanism
18
. Cooperation of the reciprocating driving of the object-to-be-irradiated
22
and sweeping of the ion beam
4
realizes uniform ion implantation into the entire surface of the object-to-be-irradiated
22
.
As shown in
FIG. 5
, upstream and downstream of the object-to-be-irradiated
22
, a front Faraday unit
36
and a back Faraday unit
44
are arranged for measurement of the ion beam
4
and shaping of the sweeping waveform thereof. The front Faraday unit
36
includes a front Faraday array
38
consisting of a plurality of Faraday cups
40
aligned in the X direction which is the scanning direction of the ion beam
4
. A back Faraday array
44
consists of a plurality of Faraday cups
46
aligned in the X direction. It should be noted that the front Faraday unit
36
is vertically moved to positions which correspond to the ion implantation into the object-to-be-irradiated
22
and the measurement by the front Faraday array
38
, respectively. At the time of measurement by the back Faraday array, the holder
20
is moved out of the way.
The front Faraday array
38
and back Faraday array
44
are basically the same as those disclosed in Japanese Patent Unexamined Publication No. Hei. 9-55179 (JP-A-9-55179). The beam currents measured by these elements are taken into a waveform shaping controller
50
via a current transducer
48
which is a current measuring means. The waveform shaping controller
50
, for example, performs the same control as disclosed in e.g. the above JP-A-9-55179. Namely, in short, the waveform shaping controller
50
creates a sweeping signal S(t) which causes the sweeping speed of the ion beam
4
on the object-to-be-irradiated
22
to approach a constant value. This signal is a function of time t. A sweeping power source
52
amplifies a sweeping signal S(t) into a sweeping current J(t), the sweeping current J(t) is supplied to the sweeping magnet
14
for its driving. In the present invention, it is to be understood that various changes and modifications may be made without restricting to the above control of JP-A-9-55179.
Meanwhile, it is necessary to implant the object-to-be-irradiated
22
with ions having desired energy and belonging to desired species by a desired quantity at substantially prescribed ion-implanting time.
The ion species are selected using the above mass analysis magnet
6
and energy analysis magnet
12
. The ion energy is determined using a power source (not shown) for the ion source
2
and/or an acceleration/deceleration power source (acceleration/deceleration power source
32
in
FIG. 6
) for the accelerating tube
8
. The quantity of ion implantation is controlled using the current value of the swept beam (current value of the swept ion beam
4
) measured by a dose Faraday
42
attached to the front Faraday unit
36
.
In order to carry out the ion implantation processing at a scheduled implanting time, the swept-beam current value of the ion beam which is to be applied to the object-to-be-irradiated
22
must be set at a prescribed value calculated from a necessary quantity of implantation and a scheduled implanting time.
A means for realizing this is a technique of controlling an electrostatic lens for converging/diverging a charged particle beam (ion beam
4
in the example) by an electric field or magnetic field. Generally, such an electrostatic lens is used to increase the swept beam current obtained at the position of the object-to-be-irradiated.
In this example, the electrostatic lens incorporated in the accelerating tube
8
is controlled. This technique will be mainly explained below. Incidentally, the technique of controlling the trimming Q lens
10
which is a four-pole type magnetic lens can be adopted.
The accelerating tube
8
shown in
FIG. 6
is basically the same as that disclosed in Japanese Patent Unexamined Publication No. Hei. 8-273895 (JP-A-8-273895). The accelerating tube
8
is directed to a two-gap three-pole type. The accelerating tube
8
has a structure in which a high voltage side electrode
26
and ground side electrode
28
are arranged within an insulator
24
and a focusing electrode
30
is arranged between both electrodes
26
and
28
. A voltage for acceleration or deceleration is applied between both electrodes
26
and
28
from an acceleration/deceleration power source
32
. A focusing voltage Vf is applied between the high voltage side electrode
26
and the focusing electrode
30
from the focusing power source
34
. Both power sources
32
and
34
can control the output voltage individually and independently. The electric field created among the three electrodes
26
,
30
and
28
serves as an electrostatic lens for converging or diverging the ion beam
4
. Therefore, an electrostatic lens is incorporated in the accelerating tube
8
.
Mainly referring to
FIG. 5
, an explanation will be given of a conventional method of increasing the swept beam current obtained at a position of the object-to-be-irradiated
22
in such a manner of controlling the electrostatic lens incorporated in the accelerating tube
8
.
All the plurality (e.g.
11
) of the Faraday caps
46
constituting the back Faraday
44
are connected in parallel to the current transducer
48
. In this state, the focus
Fernandez Kalimah
Finnegan Henderson Farabow Garrett & Dunner LLP
Lee John R.
Nissin Electric Co. Ltd.
LandOfFree
Method of controlling electrostatic lens and ion... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of controlling electrostatic lens and ion..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of controlling electrostatic lens and ion... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3066972