JPH012244A - Electronic shower device for ion implantation equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic shower device for an ion implanter.

[Conventional technology]

In high-current ion implantation equipment used to implant ions such as As ions and p ions into wafers during semiconductor manufacturing, the oxide film on the wafer undergoes discharge due to charge-up due to ion charges. There is a risk of damage and perforation of the oxide film. For example, when forming an insulating layer with a voltage of several hundred A, the charge is increased at 12.5 mA at 3 degrees, and when the voltage reaches 100 V, a hole is formed in the formed film. For this reason, a method is generally used in which the ions from the ion source are neutralized using an electron shower.

Prior art electronic shower devices used for such purposes include those described in Japanese Patent Laid-Open No. 61-240551 and Japanese Patent Laid-Open No. 62-35444.

JP-A No. 61-240551 discloses that a hollow shield is formed in an annular shape around the central axis of the ion beam, and a part of the inside of this shield is cut out to form an annular shield that faces a substrate such as a silicon wafer. An electron shower source device is disclosed in which an opening is formed and a cut annular filament is provided in the shield outside the area connecting the substrate and the opening within the hollow shield.

Furthermore, Japanese Patent Application Laid-Open No. 62-35444 discloses a hollow electron gun consisting of an annular filament and an annular grid located coaxially with respect to the center #11m of the ion beam;
It has two magnetic field generators that are placed before and after the hollow electron gun and generate magnetic fields in opposite directions to each other,
An ion implanter configured to heat an annular filament in a hollow electron gun by applying electricity, extract thermionic electrons using an annular grid located in front of the annular filament, deflect and focus the electrons using a magnetic field generated by a magnetic field generator, and guide them to the wafer. A personal shower device is disclosed.

[Problem that the invention seeks to solve]

By the way, in an electronic shower device for an ion implanter, 25
Since the purpose is to irradiate the wafer with low-energy electrons of eV or lower to neutralize the charge-up caused by the ion beam, the filament cathode is
It is necessary to initially supply sufficient electrons so that the wafer does not become more negative than 125 V.

However, the conventional electrostatic method as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-240551 cannot completely neutralize the ion beam.

In other words, the filament of the electron gun used for neutralization is not directly opposed to the wafer in the implantation chamber to prevent contamination, but ion implantation with 4 lights and 1 light requires a strong magnetic field, so the cost is low. Energy particles are easily affected by this magnetic field, and in the static method, low-energy electrons cannot reach the wafer in the implantation chamber due to the free magnetic field of several Gauss.

Furthermore, in the electron shower device disclosed in Japanese Patent Application Laid-Open No. 62-35444, a mesh is used for the grid forming the extraction electrode, so that the electrons from the filament cathode are captured by the mesh, which increases the electron passage rate. It's bad. In addition, in the direction of the mesh, a space 1 of low-energy electrons is created due to the charge effect, which causes the electrons to return and enter the grid.Furthermore, since the voltage between the terminals of the filament cathode reaches 30V, the filament Electrons of appropriate energy are extracted from only a small portion of the cathode.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electronic shower device for an ion implanter that can sufficiently supply low-energy electrons to an ion beam by solving the problems of the prior art described above.
．． Our goal is to provide the following.

[Means for solving problems]

In order to achieve the above objective [j], a hollow electron gun is arranged coaxially with respect to the center axis of the ion beam, and a plurality of hollow electron guns are used to deflect and focus the electrons from the hollow electron gun overflowing into the ion beam. According to the present invention, in an electronic shower device for an ion implantation bag having several coils, the hollow electron gun includes a ring-shaped filament cathode, and a pair of ring-shaped tubes coaxially located in front of the ring-shaped filament cathode. It is composed of a Höhnelt m-pole, a pair of ring-shaped extraction electrodes, and a repeller with a U-shaped cross section surrounding these components.The ring-shaped filament cathode is electrically divided into two or more parts, and the repeller has a rear cylindrical part and The rear cylindrical portion has two annular disk portions extending radially inward from both ends thereof, and the rear circular disk portion and the annular disk portion F'i are electrically separated and have different potentials. applied.

The ring-shaped filament cathode can be divided into two or more haemogastric parts, for example, by providing the cathode with three or more terminals at predetermined intervals, and applying a voltage alternately between adjacent terminals of these terminals. It can be done like this.

[For production]

In the electronic shower device for an ion implantation device according to the present invention, electrons emitted from the ring-shaped filament cathode are collected at the center and drawn out by the Ehnelt cable located in front of the cathode, and the magnetic field produced by the coil is removed. The action guides low-energy electrons along the outer surface of the ion beam. In this case, the electrons emitted from the ring-shaped filament cathode can be extracted efficiently by appropriately selecting the spacing between the ring-shaped Wehnelt electrodes, and a potential valley is created in front of the extraction due to the space charge effect of low-energy electrons. Also, j of this potential valley,
The value of 1 can be raised by applying an appropriate potential to the two annular disc portions of the IJ Oler with a U-shaped cross section.

The ring-shaped filament cand is electrically divided into two or more parts, and the positive, negative, and
By applying voltage like plus and minus,
The heating current is the same, but the potential difference between the terminals is '72m'/4
r'/4------ or less, for example, the cathode is 6
When divided, even if the cathode has a total potential drop of 36V, the potential drop will be 2, 6V, and the electron energy will be within the range of ±3V.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

One example of the present invention shown in FIG. 1 is an ion implantation bag P (for use with a 7M clear shower system). It is positioned coaxially with respect to the @ line 3.

This hollow electron gun 1 includes a ring-shaped filament cathode 4, a pair of ring-shaped Wehnelt electrodes 5 and a pair of ring-shaped lead-out poles 6 arranged in the same manner on the front surface or inside of the ring-shaped filament cathode 4. , a glue roller 7 which has a U-shaped cross section and surrounds these rigging guides 4, 5, 6, and a shield member 8 on the outside of the rehabilitator 7.

The ring-shaped filament cathode 4 of the hollow electron gun 1 is arranged so as not to be directly visible from the wafer (not shown) on which ions are implanted to prevent contamination. It is configured to emit electrons in a direction substantially perpendicular to the center line 3. That is, the rehearsal 7 consists of a rear cylindrical portion 7a and two annular disk portions 7b and 7c extending radially inward from both ends of the rear cylindrical portion 7a,
The rear cylindrical portion 7a and the annular disk portions 71:z7c are electrically decoupled, and each of these portions is supplied with a separate voltage (for example, the rear cylindrical portion 7a is supplied with a voltage of 125v1 and the annular disk portions 7b, 7c). OV) may be applied.

Further, the ring-shaped filament cathode 4 in the hollow electron gun 1 is electrically divided into two or more parts, and an example in which it is divided into six parts is shown in FIG. As shown in FIG. 2, the ring-shaped filament cathode 4 has six terminals 4a, 4b, 4c.
+4tL4e+4f is connected, terminals 4a, 4c, 4e
is connected to one terminal of the heating power source 9, and the terminals 4b, 4
d, 4f are connected to the other terminal of the power supply 9, so that the current IFit flows as shown by the arrow.

In the apparatus shown in Fig. 1, 10.11 and 12 are deflection and focusing coils, and the electrons extracted from the hollow tb: child 1 by the magnetic field generated by these coils 10, 11, and 12 are transferred to the ion bomb 2. It is bent along the central axis 3 and guided along the central axis 3 of the ion beam 2 .

In the illustrated embodiment, the ring-shaped filament cathode 4 of the hollow type 1°C is at a potential of -25V, the pair of Wehnelt electrodes 5 are at a potential of -25V to V, and the pair of lead-out ILF electrodes 6 are at a potential of -25V. +200V ~ +600V
At position 7a, the spacer 7 can have its rear cylindrical portion 7a set to -25V and its two annular disc portions 7b to OV.

The m3 diagram shows the magnetic field vector and the state of the electron beam determined based on the configuration η shown in Figure 1.
, 11.12 for 1300 AT each.

Cases of 1000 AT and 400 AT are illustrated. As can be seen from Figure 33, the magnetic field vector is initially directed toward the ion beam 2 in the vicinity of the hollow electron gun 1, and is then sharply bent by the ion beam 2. Electrons emitted from the ring-shaped filament cathode 4 of the hollow electron gun 1 by the action of the magnetic lines of force thus formed pass between a pair of ring-shaped Wehnelt electrodes 5, as shown by the arrow 13, and are emitted between a pair of ring-shaped Wehnelt electrodes 5. Extracting electrode 60
The ion beam 2 is guided through the ion beam 2.

〔Effect of the invention〕

As explained above, in the sub-shower device f4 for the ion implantation apparatus according to the present invention, the hollow electron gun has a ring-shaped filament cathode, a pair of ring-shaped Wehnelt electrodes, a pair of ring-shaped extraction electrodes, and these structures. Since the ring-shaped filament cathode is electrically divided into two or more parts, the difference between the high potential part and the low potential part is small, and the electrons from the ring-shaped filament cathode are It is possible to reduce the energy width of the electrons and efficiently extract low energy electrons.
In addition, by appropriately selecting the current flowing through the deflection and focusing coil and its direction, it is possible to guide low-energy electrons along the ion beam to the wafer, effectively preventing charge-up due to ion charges on the wafer. Can be done.

Furthermore, by applying an appropriate potential to the two annular disk parts of the spacer, it is possible to raise the potential value of the potential trough caused by the electron nine-way charge that is created in the electron extraction direction as a whole, and This makes it easier for electrons to pass through.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention, FIG. 2 is a diagram illustrating the electrical configuration of the main part of the device shown in FIG. 1, and FIG.
The figure is an explanatory diagram illustrating magnetic field vectors and electron trajectories by the apparatus of FIG. 1. In the figure, 1: hollow electron gun, 2: ion beam,
3: Center of ion beam - 0 (, 4: Ring-shaped filament cathode, 5: Pair of ring-shaped Wehnelt mk, 6: Pair of ring-shaped extraction electrodes, 7: Repeller, 7a: Rear cylindrical part, 7b = Annular disc part,
lO~12: Deflection and focusing coil. Figure 2 II' Point Ki -) -5→51-6→ → →
→ → → →−÷− Supplementary procedure amendment formula) % formula % 1. Indication of the case 1988 Patent Application No. 156709 2. Name of the invention Electronic shower device for ion implantation device 3. Person making the amendment Related Patent Applicant Address: 2500 Hagizono, Chigasaki City, Kanagawa Prefecture Name: Japan Vacuum Technology Co., Ltd. 4, Agent Drawing Figure 3

Claims (1)

[Claims] An electron shower device for an ion implanter, comprising a hollow electron gun arranged coaxially with respect to the central axis of an ion beam, and a plurality of coils that deflect and focus electrons from the hollow electron gun along the ion beam. The above-mentioned hollow electron gun includes a ring-shaped filament cathode, a pair of ring-shaped Wehnelt electrodes and a pair of ring-shaped extraction electrodes coaxially located in front of the ring-shaped filament cathode, and a cross-sectional core surrounding these components. The repeller electrically divides the ring-shaped filament cathode into two or more parts, and the repeller has a rear cylindrical part and two annular parts each extending radially inward from both ends of the rear cylindrical part. An electronic shower device for an ion implanter, characterized in that the rear cylindrical portion and the two annular disk portions are electrically separated and different potentials are applied to the rear cylindrical portion.