Radiant energy – Irradiation of objects or material – Ion or electron beam irradiation
Reexamination Certificate
2002-10-25
2004-06-15
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Ion or electron beam irradiation
C250S493100, C250S491100, C250S492100, C250S492210, C250S492220, C250S397000, C250S398000
Reexamination Certificate
active
06750462
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
An invention relates to an ion implanting method and apparatus for forming implanted regions with different dozes on a surface of a substrate.
2. Description of the Related Art
In recent years, there is a demand of forming implanted regions with different dose amounts on a surface of a single substrate. This is because forming such implanted regions is efficient to reduce a number of necessary substrates and steps in e.g. adjustment of an ion implanting apparatus and manufacturing semiconductor devices with different characteristics.
An example of a technique of ion-implantation to meet the above demand is described in JP-A-2000-15407.
As seen from
FIGS. 12A-C
, in a conventional ion implanting method by using a raster scan system of scanning an ion beam
4
in two vertical and horizontal directions (i.e. two-dimensionally), a scanning direction of the ion beam
4
is inverted around a center of a single substrate
2
, and then an ion implantation is performed for each of ¼ regions with different dose amounts on a surface of the substrate
2
. The dose amounts changes in accordance with a scanning speed of the ion beam
4
. Thus, four implanted regions with different dose amounts are formed on the surface of the substrate
2
.
In the above conventional ion implantation technique, the scanning direction of the ion beam
4
is inverted at the center of the substrate
2
. Before and after this inversion, the ion beam
4
passes processes of “deceleration”→“stopping”→“acceleration to an opposite direction” so that the scanning speed of the ion beam
4
decreases at the center of the substrate
2
. Owing to this, as seen from
FIG. 13
, an excessively implanted region
6
is generated linearly at the center of the substrate
2
.
Assuming that a diameter of the ion beam
4
in a spot shape is d
0
, a width W
1
of the excessively implanted region
6
become certainly larger than d
0
.
If the above problem is solved by some methods, a transient region
8
is generated in the above conventional ion implanting method as shown in FIG.
14
. The transient region is a region that dose amounts at boundaries between the implanted regions continuously changes (Herein after, referred to “a transient region”).
This is because the ion beam
4
has a limited size. Assuming that the diameter of the ion beam is d
0
, the width W
2
of the transient region
8
becomes d
0
.
Meanwhile, an available area which can be actually used to manufacture semiconductor devices in an entire surface of the substrate
2
is only an other area than the excessively implanted region and the transient region
8
. Therefore, in order to increase the available area, the diameter d
0
of the ion beam
4
must be decreased. However, when the diameter d
0
is decreased, a sectional area of the ion beam
4
is decreases. As a result, a beam current of the ion beam
4
is greatly decreased. It is not practical to take a long time to process the substrate
2
.
The above conventional ion implanting method adopts the raster scan system in which the ion beam
4
is scanned two-dimensionally (vertically and horizontally). However, a main trend of the present (probably so in the future) ion implanting method (apparatus) is a hybrid scan system as disclosed in e.g. JP-A-2001-143651 and JP-A-2001-185071, in which the entire surface of the substrate is subjected to ion implantation using both the electro-magnetic scanning of the ion beam and mechanical driving of the substrate. The above conventional technique cannot be applied as it is to this hybrid scan system.
Even if the concept of the above conventional ion implanting method could be applied to the hybrid scan system, both the scanning of the ion beam and a driving of the substrate must be carried out in a different manner from an ordinary hybrid scan system.
Both the devices for scanning the ion beam and for driving the substrate must be modified so that the scanning direction of the ion beam can be instantaneously changed while it is scanned and also the substrate can be driven or stopped with short steps and instantaneously in synchronism with the change of the direction of the ion beam. This makes the necessary control and mechanism complicate, and leads to high cost.
Therefore, the above modification cannot be easily realized.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an ion implanting method and apparatus for forming a plurality of implanted regions with different dose amounts on a surface of a substrate.
The ion implanting method and apparatus do not make any excessively implanted region. Further, it can decrease a width of a transient region of dose amounts without decreasing a beam current. Further more, it can be easily controlled. The transient region is a region that dose amounts at boundaries between the implanted regions continuously changes (Herein after, referred to “a transient region”).
In order to achieve the above objective, an ion implanting method of the present invention comprising:
implanting ions while one of a scanning speed of an ion beam and a driving speed of the substrate changes at a center of the substrate in order to separate for two implanted regions on the substrate with different dose amounts; and
rotating the substrate around its center by a predetermined angle after implanting ions while the ion beam is not applied to the substrate.
In the second aspect of the invention, the ion implanting method further comprising:
repeating by the implanting and rotation steps.
In the third of the invention, the method for implanting ions on a surface of a substrate according to claim 1, wherein implanting ions is performed by reciprocatively scanning an ion beam in an X direction by an electric field or a magnetic field and by reciprocatively and mechanically driving the substrate in a Y direction, which is substantially orthogonal to the X direction.
In the forth aspect of the invention, an apparatus for implanting ions on a surface of a substrate, the apparatus comprising:
a scanning device for reciprocatively scanning an ion beam in an X direction by an electric field or a magnetic field;
a driving device for reciprocatively and mechanically driving the substrate in a Y direction, which is substantially orthogonal to the X direction;
a rotating device for rotating the substrate around a center of the substrate;
a control device for controlling the rotating device and one of the scanning device and the driving device;
wherein the control device changes one of a scanning speed of the ion beam and a driving speed of the substrate so that ion implantation is performed to separate for two implanted regions on the substrate with different dose amounts, the control device controls the rotating device to rotate the substrate around its center by a predetermined angle after the ion implantation while the ion beam is not applied to the substrate, and the control device control to repeat the ion implantation and the rotation.
In accordance with these aspects of the inventions, since the ion implantation is implemented separately for the two implanted regions of the substrate with different dose amounts by the implanting step once performed, in combination with the rotating step, the plurality of implanted regions with different dose amounts can be formed within the surface of the substrate.
More specifically, assuming that the number of times of the implanting step is n
1
(n
1
is an integer of 2 or more), the number of times of the rotating step is n
1
−1. By executing these implanting step and rotating step, 2n
1
implanted regions with different dose amounts can be formed within the surface of the single substrate.
In addition, in these inventions, one of the scanning speed of the ion beam and the driving speed of the substrate is changed at the center of the substrate, but unlike the conventional technique, the scanning direction of the ion beam is not inverted within the surface of the substrate and the substrate is not driven and stopped with short s
Iwasawa Koji
Nagai Nobuo
Lee John R.
Nissin Electric Co. Ltd.
Vanore David A.
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