Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2001-11-13
2003-11-25
Hassanzadel, Parviz (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230ER, C250S492300, C250S492200, C204S298010, C204S298050
Reexamination Certificate
active
06651582
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a method and device for irradiating an ion beam which conducts processing such as ion injection by irradiating the ion beam on a substrate. The present invention also relates to a method of manufacturing a semiconductor device by irradiating an ion beam onto a semiconductor substrate. More particularly, the present invention relates to a means for suppressing electric charging (charge-up) on a substrate surface in the case of ion beam irradiation.
FIG. 6
is a schematic side view showing an example of the conventional ion beam irradiation device. concerning a relation between a substrate
2
and an ion beam
14
, refer to the plan view of FIG.
2
.
This ion beam irradiation device conducts processing such as ion injection as follows. The spot-shaped ion beam
14
, which has been drawn out from an ion source (not shown) and subjected to mass separation and acceleration, is irradiated onto the substrate
2
(for example, a semiconductor substrate) held by a holder
16
while it is reciprocatedly scanned in the direction X (for example, in the horizontal direction) by an electric field or magnetic field.
The substrate
2
and the holder
16
are mechanically reciprocatedly scanned in the direction Y (for example, in the vertical direction), which is substantially perpendicular to the direction X, by a holder drive unit
18
. By the cooperation (hybrid scanning) of the above mechanical scanning with the scanning of the ion beam
14
, the overall surface of the substrate
2
is uniformly irradiated with the ion beam.
On the upstream side of the substrate
2
and the holder
16
, there is provided a plasma generating device
20
. The plasma generating device
20
generates plasma
30
and supplies it to a portion close to the substrate
2
so that electric charging on the surface of the substrate
2
caused by irradiation of the ion beam
14
can be suppressed.
The plasma generating device
20
generates the plasma
30
in such a manner that gas (for example, xenon gas) introduced into a plasma generating container
22
is subjected to ionization by arc discharge conducted between a filament
26
for emitting thermoelectrons and the plasma generating container
22
which is also used as an anode. In the periphery of the plasma generating container
22
, there is provided a magnetic coil
28
for generating, maintaining and transferring the plasma
30
.
Filament voltage VF (for example, about 5 V) for heating the filament is impressed upon the filament
26
by a DC filament power source
32
. Arc voltage V
A
(for example, about 10 V) is impressed upon between a positive electrode side end of the filament
26
and the plasma generating container
22
by a DC arc power source
34
.
Further, in this example, there is provided a cylindrical reflector electrode
38
in such a manner that the cylindrical reflector electrode
38
surrounds a region from the plasma generating device
20
to a portion close to the upstream side of the substrate
20
. A negative voltage, for example, a negative voltage of −5 V is impressed upon this reflector electrode
38
by a DC reflector power source
40
. Accordingly, the reflector electrode
38
pushes back electrons contained in the plasma
30
, which have been emitted from the plasma generating device
20
, to the center (that is, to a portion close to the route of the ion beam
14
).
An ammeter
36
is connected between a connecting section
33
, in which the filament power source
32
and the arc power source
34
are connected with each other, and the ground. It is possible for the ammeter
36
to measure plasma emitting current I
P
flowing between the plasma generating device
20
and the ground when the plasma
30
is emitted from the plasma generating device
20
.
When the ion beam
14
is irradiated onto the substrate
2
, a surface of the substrate
2
is positively charged by the positive electrical charge of the ion beam
14
. Especially when the surface of the substrate
2
is made of insulating material, the surface of the substrate
2
tends to be electrically charged. When the plasma
30
is supplied to a portion close to the substrate
2
in the case of ion beam irradiation, electrons contained in the plasma
30
are drawn onto the substrate surface which is positively charged, so that the positive electric charge is neutralized. When the positive electric charge is neutralized, drawing of electrons onto the substrate
2
is automatically stopped. In this way, it becomes possible to suppress the substrate surface from being positively charged when the substrate surface is irradiated with the ion beam.
When the plasma generating device
20
is provided as described above, it becomes possible to somewhat suppress the substrate surface from being electrically charged when it is irradiated with the ion beam. However, it is difficult to completely suppress the substrate surface from being electrically charged when it is irradiated with the ion beam.
The reason is described as follows. Electrons in the plasma
30
emitted from the plasma generating device
20
have an energy distribution, which is called Maxwell-Boltzmann's Distribution, for example, shown in FIG.
7
. In this distribution, there is a peak in a portion of 2 to 3 eV; however, it contains electrons having energy, the intensity of which is much higher than that (for example, 10 to 20 eV). Therefore, the electrons, the intensity of which is much higher than that, are supplied onto the substrate
2
, and the substrate
2
is negatively charged on the contrary. When the above electrons, the intensity of which is high, is supplied to the substrate
2
, the charging voltage of the substrate surface is increased to a voltage corresponding to energy of the electrons concerned.
For the reasons described above, it was impossible to sufficiently suppress the substrate surface from being electrically charged by the prior art. For example, it was a limit to suppress the charging voltage of the substrate surface to be in a range from 10 to 12 V.
However, recently, there has been a strong demand of decreasing the charging voltage of the substrate surface by more suppressing the electrical charging of the substrate surface.
For example, in the case where a semiconductor device is manufactured by ion injection conducted by irradiating an ion beam, there is a demand that the charging voltage is suppressed to be a value not higher than 6 V in the case of ion injection in order to prevent the occurrence of electric breakdown because the structure of a semiconductor device is has become fine recently.
This will be described in detail referring to an example in which a semiconductor device
12
shown in
FIG. 8
is manufactured. The semiconductor device is an example of FET (field effect transistor). More particularly, the semiconductor device is an example of MOSFET (MOS type field effect transistor). In the case where the semiconductor device
12
is manufactured, a semiconductor substrate (for example, the silicon substrate)
2
is used as the above substrate
2
, a gate oxide film
4
and an oxide film
6
for separation are formed in a predetermined region on the surface of the semiconductor substrate, and a gate electrode
8
is formed on a surface of the gate oxide film
4
.
When the semiconductor substrate
2
is irradiated with the ion beam
14
, dopant ions (for example, ions of boron, phosphorus or arsenic) are injected. Due to the foregoing, two impurity injection layers
10
are formed in the surface layers of the semiconductor substrate
2
on both sides of the gate electrode
8
and the gate oxide film
4
. For example, when ions of boron are injected as the dopant ions, these impurity injection layers
10
become the p-type, and when ions of phosphorus or arsenic are injected as the dopant ions, these impurity injection layers
10
become the n-type. For example, when the semiconductor substrate
2
is of the n-type, the pn-type joint is formed by injecting the p-type impurity layers
10
Ikejiri Tadashi
Sakai Shigeki
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hassanzadel Parviz
Nissin Electric Co. Ltd.
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