JPH0787086B2 - Low acceleration ion beam irradiation device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low-acceleration ion beam irradiation apparatus for irradiating a target made of a semiconductor material or another material with a low-acceleration ion beam.

[Conventional technology]

In general, there are many cases in which a DC high voltage of several tens of kV or more is applied between the ion source and the target to irradiate the target with a sufficiently accelerated ion beam, but there are also cases in which it is desired to irradiate the target with a low acceleration ion beam. . In this case, the voltage between the ion source and the target must be low, but it is known that the current of the ion beam that can be applied to the target from the ion source is proportional to the 3/2 power of the acceleration voltage. Therefore, a low acceleration ion beam irradiation device is generally used as shown in FIG.

The conventional device will be described with reference to FIG. 3. The ion generator 1 that generates positive ions and the ion accelerator 2 are connected to a DC power source E ₁ , and, for example, the voltage between the ion generator 1 and the target unit 13 is increased. A much higher acceleration voltage V _{1 of} about 30 kV is applied. Therefore, the positive ions from the ion source 1 are extracted and accelerated by the ion accelerator 2 at a voltage of about 30 kV, and are fixed to the ground potential in the upstream lens unit 3 in the transport (drift tube) T, for analysis. The light passes through the magnet unit 7, the downstream lens unit 8 and the like, and further passes through the conduit 14 and the like to irradiate the target unit 13 arranged inside the microscope or the like.

Here the target portion 13, the difference voltage between the voltage V ₁ of the DC power source E ₁ is connected to the DC power source E ₅ which gives a voltage reaches a predetermined low value. For example, the ion source 1 and the target unit 13
When the difference voltage between them, that is, the final acceleration voltage is about 1 kV, the voltage applied to the target unit 13 is about 29 kV. Further, the upstream lens unit 3, the analyzing magnet unit 7, and the downstream lens unit 8 are electrically insulated from the transport T made of a metal material, and the voltage value can be independently adjusted according to the acceleration voltage. DC power supply with variable voltage
It is connected to E ₂ , E ₃ and E ₄ .

Therefore, in this conventional example, the ions from the ion generation source 1 are low-accelerated at a voltage of about 1 kV and are irradiated onto the grounded target 13.

[Problems to be solved by the invention]

However, in general, a sample is irradiated with an ion beam at various accelerating voltages for observation. For example, when changing the setting from a certain set voltage to another voltage, the setting is made corresponding to that voltage. DC power source of variable voltage for each of the upstream lens unit 3, the analyzing magnet unit 7, and the downstream lens unit 8.
It was necessary to reset the voltages of E ₂ , E ₃ , and E ₄ , and this voltage adjustment took a very long time.

[Means for solving problems]

In order to eliminate such drawbacks, the present invention provides an ion beam acceleration unit, a transport including at least an upstream lens unit, an analysis magnet unit, and a downstream lens unit in the interior, and a variable voltage for the upstream lens unit. Of the ion generating source, a DC power source of variable voltage for the analyzing magnet unit, a DC power source of variable voltage for the downstream lens unit, and a biasing DC power source for biasing the transport. The voltage is a positive voltage V _{1 having} a smaller value than the acceleration voltage V ₂ of the ion beam acceleration unit.
In the low-acceleration ion beam irradiation apparatus for irradiating the target with the low-acceleration ion beam by setting the voltage of the transport to a negative voltage V ₆ having a larger value than the voltage V ₁ so that The DC power source for the upstream lens unit, the DC power source for the upstream lens unit, the DC power source for the analyzing magnet unit, and the DC power source for the downstream lens unit. It is characterized in that it is connected in series with the opposite polarity to and the other end is connected to the ground potential.

[Action]

As described above, even if the accelerating voltage is changed in this device, the voltage of the difference between the accelerating voltage and the bias voltage is always constant by adjusting the voltage of the bias DC power supply for biasing the transport. Therefore, once the voltage-adjustable high-voltage power supply for the upstream lens unit, the voltage-adjustable DC power supply for the analysis magnet unit, and the voltage-variable DC power supply for the downstream lens unit are set, the acceleration voltage can be changed. There is no need to make adjustments due to.

〔Example〕

In FIG. 1, the same symbols as those shown in FIG. 3 correspond to the members shown in FIG. In the present invention, the transport T is connected to a DC power source E ₆ for DC bias with a variable voltage, and the DC power source E ₆ is applied to the voltage of each of the upstream lens unit 3, the analyzing magnet unit 7, and the downstream lens unit 8. The variable DC power supplies E ₂ , E ₃ , E ₄ are connected in series between the ground and the DC power supplies so as to have opposite polarities. The transport T is covered with a cover C, and the cover is grounded. Therefore, in this embodiment, safety and electrostatic shield can be secured.

For example, the voltage V ₆ is about -49.5KV. Thus, although transport T is biased by the DC voltage V ₆ of about -49.5KV, target 13 is fixed to almost the ground potential.

On the other hand, when about the low-speed ion acceleration voltage between the ion source 1 and the target portion 13 500V, the voltage V ₁ of the DC power source E ₁ is about
It becomes 500V. From the relationship between the voltage V ₆ of the DC power source E ₆ of the DC power source E ₁ of voltages V ₁ and the voltage-varying DC bias, the acceleration portion 2
The acceleration voltage V ₂ between the input side and the output side of is about 50 kV,
After all, the extraction voltage or acceleration voltage is about 50 kV. When it is desired to change the low ion acceleration voltage about 700V is the voltage V ₁ of the DC power source E ₁ to about 700V, if the voltage of the DC power source E ₆ and -49.3KV, after all, the acceleration portion 2 input The accelerating voltage V ₂ between the output side and the output side is about 50kV, which is the same as before changing the accelerating voltage.
7. There is no need to change the voltage values of the DC power supplies E ₂ , E ₃ , E ₄ of the downstream lens unit 8. Here, the upstream lens unit 3, the analyzing magnet unit 7, and the downstream lens unit 8 are electrically insulated from the inner wall of the transport T.

According to this embodiment, even when the target of the target unit 13 is such that a voltage such as ceramics or a living thing cannot be applied, a sufficiently high voltage is applied between the ion generation source 1 and the target unit 13, Since a large amount of ions can be extracted and accelerated from the ion generation source 1, a large amount of low-acceleration ion beam can be applied to the target at low potential, but the DC power supply can be changed by changing the acceleration voltage.
A good ion beam condition can be obtained simply by adjusting E ₆ .
Adjustment work becomes easy.

In this embodiment, if the transport T is completely electrically insulated at the joint with the accelerating portion 2, the transport T may be grounded as usual.

FIG. 2 shows a specific example of the low acceleration ion beam irradiation apparatus according to the present invention. In FIG. 2, the same symbols as those shown in FIG. 1 correspond to the members shown in FIG. . Although the power supplies and the like are omitted, the voltage application is the same as in FIG.

In the transport T, an auxiliary deflection system unit 4, a bellows 5, an upstream gate valve 6 and the like are sequentially provided between the upstream lens unit 3 and the analyzing magnet 7. Further, on the output side of the upstream lens portion 8, a downstream gate valve 9, an intermediate connection portion 10 for performing electrical insulation, etc. are arranged. Then, the ion beam generated from the ion source 1 and passing through these is subjected to a predetermined deflection by the electron microscope internal prism portion 11 provided inside the electron microscope portion 12, and the target 1
Irradiate 3 '.

Here, the exhaust pipes 14 and 14 ′, one end of which is connected to the transport T and the other end of which is connected to an external diffusion pump, are provided with electrical insulating portions 14 A and 14 ′ A in the middle thereof, and the transport T and the diffusion pump are provided. Electrically insulate the side. Further, the transport T is electrically insulated from the electron microscope portion 12 by the electric insulating portion 15. Furthermore, the operating rods of the upstream gate valve 6 and the downstream gate valve 9 are also electrically insulated from the transport T.

〔The invention's effect〕

As described above, according to the present invention, even when the target cannot be applied with a voltage like ceramics or living things, a sufficiently high voltage is applied between the ion generation source and the target part to generate ions. Since a large amount of ions can be extracted from the source and accelerated, a large amount of low-acceleration ion beam can be applied to the target at low potential, but the DC power supply E ₆ for DC bias can be changed by changing the acceleration voltage. A good ion beam condition can be obtained simply by adjusting, and the adjustment work is greatly facilitated.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of low-acceleration ion beam irradiation according to the present invention, and FIG. 2 is a diagram for explaining an embodiment of a low-acceleration ion beam irradiation device according to the present invention.
The figure is a diagram for explaining a conventional example. 1 ... Ion source, 2 ... Accelerator 3 ... Upstream lens, 4 ... Auxiliary deflection system 5 ... Bellows, 6 ... Upstream gate valve 7 ... Analysis magnet, 8 ... Downstream lens 9 …… Downstream gate valve, 10 …… Intermediate connection part 11 …… Electron microscope internal prism part, 12 …… Electron microscope part. 13 …… Target part E ₂ …… DC power supply E ₃ for upstream lens part ₃ …… DC power source E for analysis magnet unit 7 ₄ DC power source for the DC power source E ₆ ...... DC bias for ...... downstream lens portion 8

Claims (3)

[Claims] 1. A transport comprising at least an ion beam accelerating section, an upstream lens section, an analyzing magnet section and a downstream lens section inside the ion generating source, a variable voltage DC power source for the upstream lens section, and the analyzing section. A variable voltage DC power supply for the magnet unit, a variable voltage DC power supply for the downstream lens unit, and a biasing DC power supply for biasing the transport are provided, and the voltage of the ion generation source is set to the ion beam acceleration unit. By setting the voltage of the transport to a negative voltage V ₆ having a larger value than the voltage V ₁ so that the positive voltage V ₁ having a smaller value than the acceleration voltage V ₂ of In a low-acceleration ion beam irradiation apparatus for irradiating an accelerated ion beam, the bias power source is a variable voltage DC power source and the upstream lens unit power source is used. A variable pressure direct current power source, a variable voltage direct current power source for the analysis magnet section, and a variable voltage direct current power source for the downstream lens section, which are connected in series in reverse polarity and the other end is connected to ground potential. Characteristic low acceleration ion beam irradiation device. 2. The low acceleration ion beam irradiation apparatus according to claim 1, wherein the transport is covered with an installed cover. 3. The low-acceleration ion beam irradiation apparatus according to claim 1, further comprising an electric insulation portion for electrically insulating the transport from an electron microscope.