Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2000-04-28
2003-04-29
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S492300, C250S492100, C315S111810, C315S111610, C313S359100
Reexamination Certificate
active
06555831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ion implanting apparatus of carrying out ion implanting by irradiating to a substrate ion beam brought out from an ion source having a plurality of filaments, and in particular an improvement of means for controlling beam current of the ion beam brought out from the ion source to be at a predetermined value and an excellent uniformity as well.
2. Description of the Related Art
A conventional example of this kind of ion-implanting apparatus is shown in FIG.
8
. This ion implanting apparatus is also called as an ion doping apparatus (or an ion implanting apparatus of non-mass separating type) which directly irradiates to a substrate
14
an ion beam
12
of large area brought out from the ion source
2
as it is, not passing through a mass separator, so as to carry out the ion implanting to the substrate
14
. When implanting the ion, if required, the substrate
14
may be mechanically scanned within an area of implanting the ion beam, for example, in directions from an inside to an outside of this
FIG. 8
drawn paper. The substrate
14
is such as a glass substrate or semi-conductor substrate.
The ion source
2
is also called as a bucket type ion source (or a multi-polar magnetic field type ion source) which has a plurality of filaments
6
(for example, three) within a plasma production container
4
, so that an arc discharge is generated between each filament
6
and the plasma production container
4
to ionize gas of the ion source and generate the plasma
8
, and the ion beam
12
is brought out from the plasma
8
by an extension electrode system
10
. A magnet for forming multi-polar magnetic field is not illustrated.
To the respective filaments
6
, in this example, filament sources
16
are connected, and filament current IF heating the filament
6
can be independently passed from each filament source
16
to each filament
6
.
For controlling the beam current of the ion beam
12
brought out from the ion source
2
to be at a predetermined value, this ion implanting apparatus receives a further ion beam
12
and measures the beam current in a plurality of positions within a plane crossing with the ion beam
12
. The ion implanting apparatus is provided with a plurality of beam current measuring instruments
18
, the number of which is more (for example 24) than the number of the filaments
6
and provided with a control apparatus
20
which demands an average value of the beam current IB measured by the respective beam current measuring instruments
18
and controls increase and decrease by the same amount of the filament currents IF passing to the respective filaments
6
such that the average value approaches to a fixed value.
Each of the beam current measuring instruments
18
is composed of such as Faraday cup, and is disposed, for example, in a straight line within an irradiating area of the ion beam
12
. While the ion beam
12
is measured by the beam current measuring instrument
18
, the substrate
14
is moved to a place not to interrupt the ion beam
12
.
In the ion implanting apparatus, the ratio of the filament current IF passing to the respective filaments
6
is set in advance such that the uniformity of the ion beam
12
is made good, and the ion implanting apparatus is operated.
However, since changing manners of the respective filaments
6
with time passing are ordinarily different one another, if serving the above mentioned control apparatus
20
which increases and decreases by the same amount the filament current IF flowing to the respective filaments
6
, there arises a problem that the uniformity of the ion beam
12
is worsened with the time passing of the filaments
6
.
JP-A-3-134937 discloses a technology of providing the beam current measuring instruments of the same number as that of the filaments, and controlling the filament current flowing to the respective filaments such that the beam current to be measured by the respective beam current measuring instruments meets the set values.
Although, in this published technology, it seems to be possible to uniform the ion beams by making the respective set values equal one another, actually the control of the filament current flowing to one filament gives influences to plasma density in the vicinity of other filaments, and gives in its turn influence to beam current to be measured by other beam measuring instruments, that is, the controls of the filament current affect one another. If a beam current of one measuring point is controlled to be at a predetermined value, another beam current at another measuring point gets off from the predetermined value, and if trying to control this off beam current to be at the predetermined value, that beam current controlled to have been at the one measuring point gets off from the predetermined value. This is a serious problem that the control causes hunting and does not converge.
There is further proposed an (PJ-A-11-123973), in which the filament current is controlled to pass to the filaments in accordance with a plurality of beam current measuring instruments and the beam current measured thereby, and a control apparatus is equipped which performs a current value control routine and a uniformity control routine at least once respectively. The ion implanting apparatus prevents deterioration of the uniformity of the ion beam due to change of the filaments by time passing so as to control the beam current of the ion beam to be at the predetermined value and the excellent uniformity as well. One example thereof will be explained with reference to
FIGS. 15
to
20
.
The ion implanting apparatus illustrated in
FIG. 5
is also called as the ion doping apparatus (or the ion implanting apparatus of non-mass separating type) which directly irradiates to the substrate
14
the ion beam
12
of large width brought out from the ion source
2
as it is, not passing through the mass separator, so as to carry out the ion implanting to the substrate.
The substrate
14
is supported on a substrate holder
13
which is somewhat larger than the substrate
14
, and both are scanned reciprocally in a direction of arrow D within the irradiating area of an ion beam
12
brought out from the ion source
2
by means of a holder scanning mechanism
15
.
The substrate holder
13
and the substrate
14
are, for example, rectangular (square or rectangle) as shown in FIG.
16
. The plane shape of the ion beam
12
is, for example, rectangular as shown in FIG.
16
.
The ion source
2
is also called as the bucket type ion source (or the multi-polar magnetic field type ion source) which has a plurality of filaments
6
(for example, three) within the plasma production container
4
, so that an arc discharge is generated between each filament
6
and the plasma production container
4
to ionize gas of the ion source and generate the plasma
8
, and the ion beam
12
is brought out from the plasma
8
by the extension electrode system
10
. The magnet for forming multi-polar magnetic field is not illustrated.
To the respective filaments
6
, in this example, the filament sources
16
are connected, and the filament current IF heating the filament
6
can be independently passed from each filament source to each filament
6
.
For controlling the beam current of the ion beam
12
brought out from the ion source
2
to be at the predetermined value, this ion implanting apparatus further receives the ion beam
12
and measures the beam current in a plurality of positions at a downstream of the scanning area of the substrate holder
13
. The ion implanting apparatus is provided with a plurality of beam current measuring instruments
18
, the number of which is more (for example 24) than the number of the filaments
6
and provided with the control apparatus
20
which controls the filament current IF to be passed to the respective filaments
6
from the respective filament sources
16
in accordance with the beam current IB measured by the respective beam current measuring instruments
18
.
Each of
Ando Yasunori
Konishi Masashi
Maeno Shuichi
Finnegan Henderson Farabow Garrett & Dunner LLP
Nissin Electric Co. Ltd.
Vanore David A
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