JPH06267492A - Electron showering device - Google Patents

Abstract

PURPOSE:To radiate a large quantity of low-energy primary electrons to a wafer with their heating value being suppressed, by providing a means for emitting electrons between a lead-out electrode and a decelerating electrode and a means for paralleling the emitted electrons. CONSTITUTION:An ion beam 13 is radiated to a wafer 11 set up in a rotary disc 10. An electron showering device 1 mounted on a Faraday's cup 9 is driven to radiate electron shower 14 to the wafer 11, thereby neutralizing a positive charge. Then, as an electrode for paralleling a locus, a focusing electrode 5 composed of a mesh-like or plural slits is provided to set the potential of the electrode 5 to be higher than those of a lead-out electrode 3, an electrode 4 for constituting an emission space and a decelerating electrode 6. Thereby, after the electrons pass through the electrode 5, they are abruptly decelerated between the electrode 5 and the electrode 6, so that the electrons may reach the electrode 6 at an angle close to nearly vertical thereto and the electrons passing through the electrode 6 may efficiently reach the wafer 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron shower apparatus added to an ion implantation apparatus used in a semiconductor ion implantation process or the like.

[0002]

2. Description of the Related Art FIG.
Of the conventional electron shower device disclosed in Japanese Patent Publication No.
It is sectional drawing which shows a schematic structure. In the figure, 1 is an electron shower device attached to a Faraday cup, 2 is a thermoelectron emission source (filament), 3 is a control grid, 5 is a screen grid, 6 is an electron emission port, and 11 is a rotating disk. A wafer, 12 is a disk bias power source, 13 is an ion beam, and 14 is an electron shower.

Next, the operation will be described. In FIG. 7, the wafer 11 is irradiated with the ion beam 13. At this time, the positive charges of the ions are accumulated on the insulator on the wafer to be in the positively charged state. Therefore, the electron shower device 1 attached to the Faraday cup for monitoring the ion beam current is driven to irradiate the wafer 11 with the electron shower 14 to neutralize the positive charge. More specifically, first, thermoelectrons are emitted from the filament 2, the thermoelectrons are formed into a beam shape by the control grid 3 / screen grid 5, and then emitted from the electron emission port 6 to the outside. The discharged electron shower 14 is given energy by the disk bias power source 12 toward the wafer 11 placed on the rotating disk, and
1 is irradiated. In this way, the positive charge of the wafer 11 is neutralized. At this time, conversely, in order to prevent the element from being destroyed by negative charging by electrons, a large amount of low-energy electrons of 20 eV or less corresponding to the breakdown voltage of the element such as a transistor which is a component of 4M-DRAM to ˜20 V is charged. A method of increasing the area of the electron emission port 6 is conceivable in order to emit the electrons into the inside.

[0004]

Since the conventional electron shower apparatus is constructed as described above, when the area of the electron emission port 6 is increased, the filament 2 in this embodiment is shown in FIG. 1 (b). Since they are arranged in a plane as described above, the amount of heat generated from the filament 2 becomes large, and there is a problem that the wafer 11 is adversely affected.

Further, the total length of the filament 2 becomes long,
Since the potential difference between both ends of the filament 2 becomes large, the energy of electrons generated at the end of the filament 2 where the potential difference with the wafer 11 is small becomes small. Therefore, there is a problem that the electron transport efficiency is reduced and the amount of electrons does not increase in spite of the increase in area.

The present invention has been made to solve the above problems, and an electron shower capable of emitting a large area, large current, low energy primary electron into a Faraday cup from a single linear filament. The purpose is to obtain the device.

[0007]

In the electron shower device according to the present invention, a deceleration electrode is installed after the extraction electrode, and means for diverging electrons between the extraction electrode and the deceleration electrode and the diverted electrons are provided. It is provided with means for parallelizing.

As a means for diverging the electrons, a divergence space formed by an electrode inserted between the extraction electrode and the focusing electrode and a means for collimating the diverged electrons are provided after the divergence space. In addition, at least one mesh or a focusing electrode having a plurality of openings is provided.

Further, the electrodes forming the diverging space and the extraction electrodes are formed at the same potential.

Further, the deceleration electrode has a sectional shape which is concave toward the extraction electrode side.

[0011]

In the electron shower apparatus according to the present invention, the means for diverging the electrons and the means for collimating the diverged electrons are provided between the extraction electrode and the deceleration electrode. It is possible to release a large area in a short distance from the filamentous filament while suppressing the divergence angle.
It becomes possible to irradiate the wafer with secondary electrons.

Further, as a means for diverging the electrons, a divergence space constituted by an electrode inserted between the extraction electrode and the focusing electrode and a means for collimating the diverged electrons are provided after the divergence space. Further, by providing at least one mesh or a focusing electrode having a plurality of openings, it is possible to carry out with a relatively simple structure.

Further, in the above-mentioned electron shower device, by constructing the extraction electrode and the electrode for forming the divergence space at the same potential, the construction can be simplified while maintaining substantially the same effect.

Further, since the cross-sectional shape of the deceleration electrode is concave toward the extraction electrode side, the effect of suppressing electron divergence can be obtained.

[0015]

【Example】

Example 1. FIG. 1 (a) is a sectional view showing a first embodiment of the present invention. In the figure, 1 is an electron shower device attached to a Faraday cup 9, 2 is a thermoelectron emission source (filament), and 3 is an electron extraction device. Electrodes, 4 are electrodes for providing a divergence space, 5 are focusing electrodes, 6 is a deceleration electrode, 7 is a reverse current conductor for reducing the magnetic field generated by the filament heating current, 8 is a reflective electrode, and 11 is a rotating disk. A wafer placed on top of 10, a disk bias power source 12, a ion beam 13, an electron shower 14 and a divergence space 15.

Next, the operation will be described. In FIG. 1A, an ion beam 13 generated from an ion source and selected by a mass separator into only ions of a desired type is
The wafer 11 placed on the rotating disk 10 is irradiated. At this time, the positive charges of the ions are accumulated on the insulator on the wafer to be in the positively charged state. Therefore, the electron shower device 1 attached to the Faraday cup 9 for monitoring the ion beam current amount is driven to irradiate the wafer 11 with the electron shower 14 to neutralize the positive charge.

The driving of the electron shower device at that time will be described in detail. The thermoelectrons whose influence of the magnetic field generated by the filament heating current is reduced by the reverse current flowing through the reverse current conductor 7 are drawn from the filament 2 to the extraction electrode 3
Pulled out by. The electrons 14 are extracted while diverging due to the diverging lens effect of the extraction electrode 3, and then further spread in the diverging space 15 due to the space charge effect of the electron itself, so that the area can be expanded. However, since the potential of the deceleration electrode 6 is set lower than the potential of the extraction electrode 3 in order to avoid absorbing secondary electrons from the wafer 11 generated by the ion beam 13, it becomes a deceleration space and the space charge effect. Causes the electrons to diverge more than necessary. Therefore, the electrons at the end of the deceleration electrode 6 have a small incident angle with respect to the deceleration electrode 6 and cannot reach the deceleration electrode 6 and are reflected, so that they cannot be effectively used.
The state of the orbit at this time is shown in FIG. Needless to say, if the distance is short, the area cannot be increased. On the contrary, if the divergence angle is suppressed and the area is increased, the electron transport distance becomes long, and as a result, the electron shower device 1 becomes large.

Therefore, a focusing electrode 5 having a mesh shape or a plurality of slits is provided as an electrode for collimating the trajectories, and the potential of the focusing electrode is drawn out from the electrode 3, the electrode 4 for forming a diverging space, and the deceleration electrode potential 6. By setting it high, a focusing electric field is formed between the extraction electrode 3, the electrode 4 for forming the divergence space 15, and the focusing electrode 5. FIG. 3 shows the calculation result of the electric field when an example of the potential actually used is applied to each electrode. From the shape of the equipotential lines in FIG. 3 and the potential of the focusing electrode 5 being the highest value, it can be seen that a focusing electric field is formed. The electrode potential at this time is the same as the extraction electrode 3 with respect to the filament 2.
Is 100 V, and the electrode 4 for forming the divergence space 15 is 8
0V, the focusing electrode 5 was 200V, and the deceleration electrode was 15V. Due to this electric field, the electrons gradually change their orbits in a direction perpendicular to the focusing electrode 5 while diverging as a whole.

Further, by shortening the distance between the focusing electrode 5 and the deceleration electrode 6 within a range where there is no structural problem, the electrons are rapidly decelerated between the focusing electrode 5 and the deceleration electrode 6, so that the space charge is reduced. Deceleration electrode 6 with almost no divergence due to
Can be reached at an angle close to vertical, and the spread of the electron energy distribution is relatively small, so that it passes through the deceleration electrode 6 without being reflected. The orbit at this time is shown in Fig. 1.
It becomes like (b). The electrons that have passed through the deceleration electrode 6 finally reach the wafer with the energy set by the disk bias power supply 12. Also at this time, the spread of the electron energy distribution is relatively small, so that the wafer can be efficiently reached. As described above, since the area of the electron from the filament 2 can be increased in a short distance while suppressing the divergence angle, it is not necessary to arrange the filament in a plane shape, and the linear filament 2 can be used for an electron shower of a large area and a large current. 14 can be obtained. Therefore, it is possible to irradiate the wafer 11 with the electron shower 14 of low energy and large current while suppressing the amount of heat generation with a relatively simple configuration.

Example 2. Even if the electrode 4 for forming the divergence space 15 has the same potential as that of the extraction electrode 3, the same effect can be obtained, so that the structure can be simplified.

Example 3. The shape of the electrode 4 for forming the divergence space 15 may be any shape as long as the space does not hinder the divergence / focusing of electrons. For example, the divergence space 14 is tapered from the extraction electrode 3 toward the focusing electrode 5. It may be something that spreads out.

Example 4. The shape of the focusing electrode 5 may be any shape as long as it forms a focusing electric field between the extraction electrode 3, the electrode 4 for forming the divergence space 15, and the focusing electrode 5, and for example, is convex on the extraction electrode 3 side. It may have a cross section or a combination of a plurality of sheets.

Example 5. If the focusing electrode 5 alone exerts the focusing effect, an insulator may be used instead of the electrode 4 for forming the diverging space 15. For example, in FIG.
FIG. 7 is a cross-sectional view showing an embodiment in which an insulator for providing a divergent space is used, and 17 in the figure shows an insulator for providing a divergent space. The other components are the same as those in FIG.

Next, the operation will be described. By providing the divergence space 15 after the extraction electrode 3, the electrons are extracted while diverging due to the divergence lens effect of the extraction electrode 3 and then spread out in the divergence space 15 due to the space charge effect of oneself, so that the area is enlarged. What is done is almost the same as in the first embodiment. Here, the potential of the focusing electrode 5 is made higher than that of the extraction electrode 3 and the deceleration electrode 6, and the width of the focusing electrode 5 is shorter than that of the deceleration electrode 6, so that the electric field is bent at the end of the electrode. Therefore, a focusing effect occurs at the end of the focusing electrode 5 having a high electric potential. At this time, electron trajectories can be parallelized by appropriately selecting the width and potential of the focusing electrode 5. Further, by shortening the distance between the focusing electrode 5 and the deceleration electrode 6, the divergence due to the space charge effect is reduced and the divergence due to the deceleration can be minimized. Since the electrons from the filament 2 can be efficiently diverged / focused in this way, the low-energy primary electrons 14 can be emitted from a single linear filament 2 in a large area in a short distance while suppressing the divergence angle. Therefore, it becomes possible to irradiate the wafer 11 with a large amount of low-energy primary electrons 14 while suppressing the heat generation amount with a simple configuration.

Example 6. The focusing electrode 5 may have any shape other than the above as long as it provides a focusing effect. For example, as shown in FIG. 5, a plurality of electrodes may be used as the focusing electrode 5 to form a focusing electric field. is there. In these examples, a plurality of electrodes are arranged so as to form a concave accelerating electric field from the extraction electrode 3 toward the focusing electrode 5. Of course, all of these focusing electrode shapes are more effective when combined with the inventions of claims 2 and 3.

Example 7. FIG. 6 is a sectional view showing the construction of an electron shower device according to an embodiment of the present invention. In the figure, 6 is a deceleration electrode having a concave sectional shape toward the extraction electrode 3, and the other components are the same as those shown in FIG.

Next, the operation will be described. Claims 1-3
By using the deceleration electrode 6 having a concave cross-section toward the extraction electrode 3 in the above configuration, the electric field works in the deceleration space between the focusing electrode 5 and the deceleration electrode 6 in a direction to suppress the divergence of electrons, so that it is more efficient. It can emit low-energy electrons and, in turn, generates a large amount of low energy while suppressing the amount of heat generated.
It is possible to irradiate the wafer 11 with the next electron shower 14.

Example 8. The deceleration electrode may have any shape other than that shown in FIG. 6 as long as it has a concave shape such as a V-shape or a shape like a part of an arc.

Example 9. In all the embodiments of the present invention, the focusing electrode 5 and the deceleration electrode 6 are mesh-shaped or have a plurality of slits. However, these electrodes have poor mechanical strength. It is good to prevent deformation due to thermal expansion by supporting and freeing one end, or by giving both sides a thickness for reinforcement.

The present invention has the same effect with all electron sources other than filaments, such as plasma electron sources and field emission cathodes.

Furthermore, the present invention can be applied to other devices that use a large amount of electrons in the form of a shower, such as an electron generating portion of a flat panel display device.

[0032]

As described above, according to the present invention, the means for diverging the electrons and the means for collimating the diverged electrons are provided between the extraction electrode and the deceleration electrode. Can be emitted from a single linear filament in a large area in a short distance while suppressing the divergence angle, and it becomes possible to irradiate a large amount of low energy primary electrons onto the wafer while suppressing the heat generation amount. .

Further, as a means for diverging the electrons, a divergence space constituted by an electrode inserted between the extraction electrode and the focusing electrode and a means for collimating the diverged electrons are provided after the divergence space. Further, by providing at least one mesh or a focusing electrode having a plurality of openings, it is possible to carry out with a relatively simple structure.

In the electron shower device described above, the extraction electrode and the electrode for forming the divergence space are configured to have the same potential, so that the configuration can be simplified while maintaining substantially the same effect.

Further, by making the cross-sectional shape of the deceleration electrode concave toward the extraction electrode side, a further electron divergence suppressing effect can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing electron trajectories in a decelerating electric field.

FIG. 3 is a sectional view showing a focused electric field according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing the structure of a fifth embodiment of the present invention.

FIG. 5 is a structural cross-sectional view showing Embodiment 6 of the present invention.

FIG. 6 is a structural cross-sectional view showing Embodiment 7 of the present invention.

FIG. 7 is a sectional view showing a configuration of a conventional electron shower device.

[Description of Reference Signs] 1 electron shower device 2 source for thermoelectron emission 3 extraction electrode 4 electrode for providing divergence space 5 focusing electrode 6 deceleration electrode 7 reverse current supply means 8 reflection electrode 9 Faraday cup 10 rotating disk 11 wafer 12 Disk bias power supply 13 Ion beam 14 Electron shower 15 Divergence space 16 Equipotential line 17 Insulator for providing divergence space

Claims (4)

[Claims] 1. An electron shower device, which is mounted on an ion implantation apparatus and is used to neutralize the positive charging of a wafer by an ion beam, and which transports thermal electrons from a filament directly to the wafer. What has an extraction electrode for extracting and a deceleration electrode for making extracted electrons a desired energy, means for diverging electrons between the extraction electrode and the deceleration electrode, and means for collimating the diverged electrons An electron shower device characterized by being provided with. 2. In the electron shower apparatus, as means for diverging electrons, a divergence space formed by an electrode inserted between an extraction electrode and a deceleration electrode and a means for parallelizing the diverged electrons are provided. The electron shower device according to claim 1, further comprising a focusing electrode having at least one mesh or a plurality of openings provided after the space. 3. The electron shower device according to claim 2, wherein the electrode forming the diverging space and the extraction electrode have the same potential. 4. The electron shower device according to claim 1, wherein the deceleration electrode has a cross-sectional shape concave toward the extraction electrode side.