JPH0754959Y2 - Multi-stage accelerator tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a multistage accelerating tube used in an ion implantation apparatus or the like.

[Conventional technology]

Ion implanters were developed from charged particle accelerators that were originally used in the field of nuclear physics, and became industrially used as semiconductor manufacturing equipment in the 1970s. Was also advanced. Nowadays, it is indispensable for doping impurities into silicon and compound semiconductors, and research and practical applications are being carried out for modifying the surface and surface layers of various metals such as steel, ceramics, and polymers. Is.

Now, the ion implantation method is to ionize a substance to be implanted, select the ions, and then perform several KeV to several 100 KeV (recently M
There is also eV class), and the kinetic energy is used to drive into a solid substrate. The ion implanter is an ion source system that ionizes the elements to be implanted and extracts them as an ion beam, a mass analysis system that selects only ions of a prescribed mass, an acceleration system that imparts prescribed energy, and an end station that sets the wafer and performs the implantation process. It is composed of parts,
The path of the ion beam from the ion source system to the end station is all in high vacuum.

The structure of a conventional multistage accelerating tube in an accelerating system is shown in FIG.

FIG. 2 (a) is a schematic structural diagram of a conventional multistage accelerating tube, and FIG. 2 (b) is a diagram showing the potential distribution of FIG. 2 (a).

As shown in FIG. 2 (a), the conventional multistage accelerating tube has, for example, aluminum accelerating electrodes 1 to 9 and a suppressor electrode.
It consists of 10 and an insulating tube 11 that supports this at equal intervals. A voltage Va is applied to the accelerating electrode 1, and bleeder resistors 12 to 19 are connected to the accelerating electrodes 1 to 9, respectively, so as to give an equal potential sharing. A negative suppressor voltage Vs is applied to the suppressor electrode 10 to prevent secondary electrons generated by collision of ions with the ground-side electrode 9 from being accelerated in the accelerating tube, thereby suppressing generation of X-rays. ing. The arrow B indicates an ion beam.

[Problems to be solved by the device]

However, in the above-described conventional configuration, secondary electrons generated around the exit of the acceleration tube are prevented from being repelled by the suppressor electrode 10 to which the negative suppressor voltage Vs is applied and flowing backward in the acceleration tube. The secondary electrons generated in the accelerating tube flow backward in the accelerating tube and collide with the upstream electrode or the mask or pipe at the entrance of the accelerating tube, and X rays are generated by bremsstrahlung
Generate a line. Therefore, a large amount of lead for X-ray shielding is required around the device. In this case, the secondary electrons are generated by the collision between the ion beam and the electrode, the collision between the ion beam and the residual gas particles in the tube, and the like.

An object of the present invention is to provide a multistage accelerating tube capable of suppressing the generation of X-rays.

[Means for Solving the Problems]

The multistage accelerating tube of the present invention comprises a large number of accelerating electrodes to which a low voltage is applied in the order arranged from the upstream side to the downstream side of an ion beam, and at least one suppressor electrode arranged between the large number of accelerating electrodes. The suppressor electrode is connected to the accelerating electrode next to the accelerating electrode adjacent to the downstream side.

[Action]

According to the configuration of the present invention, the suppressor electrode is connected to the accelerating electrode at the next stage of the accelerating electrode adjacent to the downstream side, so that the same voltage as the connected accelerating voltage is supplied to the suppressor electrode. Therefore, a potential barrier is formed by supplying the suppressor electrode with a voltage lower than the voltage of the acceleration electrode adjacent to the suppressor electrode on the downstream side. This potential barrier traps the secondary electrons generated in the acceleration tube, and suppresses the backflow of the secondary electrons in the acceleration tube. As a result, it is possible to prevent X-rays from being generated by bremsstrahlung. Further, since the secondary electrons captured by the potential barrier cancel the space charge of the ion beam, the divergence of the ion beam in the tube can be suppressed. In addition, the suppressor electrode is supplied with the voltage applied to the accelerating electrode at the stage next to the accelerating electrode adjacent to the downstream side of the suppressor electrode, so that the Einzel lens effect is sufficiently obtained and the beam focusing effect is improved. it can.

〔Example〕

 An embodiment of this invention will be described with reference to FIG.

FIG. 1 (a) is a schematic structural diagram of a multistage accelerating tube according to an embodiment of the present invention, and FIG. 1 (b) is a diagram showing the potential distribution of FIG. 1 (a).

As shown in FIG. 1 (a), this multistage accelerating tube is different from the conventional multistage accelerating tube shown in FIG. 2 (a) in that four suppressors are formed in a ring shape between a pair of adjacent acceleration electrodes. Electrode 2
0,21,22,23 between accelerating electrodes 2 and 3, respectively, accelerating electrode 3
・ 4, between acceleration electrodes 4 and 5, and between acceleration electrodes 5 and 6. The suppressor electrode 20 provided between the accelerating electrodes 2 and 3 is supplied with a voltage by externally connecting to the accelerating electrode 4 having a lower potential than the adjacent accelerating electrode 3.
Similarly, the suppressor electrodes 21, 22 and 23 are also supplied with a lower potential voltage than the adjacent acceleration electrodes 4, 5 and 6, respectively.

Thus, the suppressor electrodes 20-23 are applied with a voltage lower than the applied voltage of the adjacent acceleration electrodes 3-6. Incidentally, in FIG. 1 (a), those corresponding to FIG. 2 (a) are designated by the same reference numerals.

In addition, as shown in FIG.
By applying a voltage lower than the voltage of the acceleration electrodes 3 to 6 adjacent to 23, the potential barrier V _b is formed. The two-dot chain line X shows the conventional case where the suppressor electrodes 20 to 23 are not provided.

Then, the potential barrier V _b captures the secondary electrons generated in the tube, and suppresses the secondary electrons from flowing backward in the acceleration tube. As a result, it is possible to prevent generation of X-rays due to bremsstrahlung, and it is possible to reduce or eliminate the shielding material for shielding X-rays, and to realize low cost and compactness of the device. Further, since the secondary electrons captured by the potential barrier _Vb cancel the space charge of the ion beam, the divergence of the ion beam in the tube can be suppressed. Further, since the suppressor electrodes 20 to 23 are supplied with the application electrodes of the accelerating electrodes 4 to 7 next to the accelerating electrodes 3 to 6 which are adjacent to the suppressor electrodes 20 to 23, the Einzel lens effect is sufficient. Therefore, the beam focusing effect can be improved.

Although four suppressor electrodes 20 to 23 are provided in addition to the conventional suppressor electrode 10 in this embodiment, one or more suppressor electrodes may be provided.

[Effect of device]

In the multi-stage accelerating tube of the present invention, the suppressor electrode is connected to the accelerating electrode next to the accelerating electrode adjacent to the downstream side, so that the same voltage as the connected accelerating voltage is supplied to the suppressor electrode. Therefore, a potential barrier is formed by supplying the suppressor electrode with a voltage lower than the voltage of the acceleration electrode adjacent to the suppressor electrode on the downstream side. This potential barrier traps the secondary electrons generated in the acceleration tube, and suppresses the backflow of the secondary electrons in the acceleration tube. As a result, it is possible to prevent generation of X-rays due to bremsstrahlung, and it is possible to reduce or eliminate the shielding material for shielding X-rays, and to realize low cost and compactness of the device. Further, since the secondary electrons captured by the potential barrier cancel the space charge of the ion beam, the divergence of the ion beam in the tube can be suppressed. Also,
Since the suppressor electrode is supplied with the voltage applied to the accelerating electrode at the stage next to the accelerating electrode adjacent to the downstream side of the suppressor electrode, the Einzel lens effect can be sufficiently obtained and the beam focusing effect can be improved.

[Brief description of drawings]

FIG. 1 (a) is a schematic structural diagram of a multistage accelerating tube according to an embodiment of the present invention, FIG. 1 (b) is a diagram showing the potential distribution of FIG. 1 (a), and FIG. 2 (a) is FIG. 2 (b) is a diagram showing the potential distribution in FIG. 2 (a), which is a schematic structural diagram of a conventional multistage accelerating tube. 1-9 ... Accelerator electrode, 10, 20-23 ... Suppressor electrode

Claims (1)

[Scope of utility model registration request] 1. A plurality of accelerating electrodes to which a low voltage is applied in the order arranged from the upstream side to the downstream side of an ion beam, and at least one suppressor electrode arranged between the plurality of accelerating electrodes, The suppressor electrode is a multi-stage accelerating tube connected to the accelerating electrode next to the accelerating electrode adjacent to the downstream side.