JPH03219545A - Ion implanting device - Google Patents

Abstract

PURPOSE:To reduce the electric potential of a sample surface by forming a magnetic field on the sample surface radially from about the center of the sample to the outside of the outer circumference of the sample, thereby catching electrons including secondary electrons generated near the outer circumference in the magnetic field. CONSTITUTION:A sample 32 is held on a table 31, and stick magnets 33 are buried in the table 31 below the sample 32. The magnets 33 are radially arranged in such a manner that the S-poles 33b are laid on the outside of the outer circumference of the sample 32 and the N-poles 33a are laid close to about the center of the sample. In this constitution, when an ion beam is radiated on the sample and the table, about 1/2 secondary electrons generated from the table 31 is transported to the center part of the sample 32 by the magnetic field, attracted by the electrified potential by the implanted ions, and recombined with the ions or present on the surface to reduce the electrified potential. Thus, the failure of the device by damage of insulator is reduced in ion implanting process.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an ion implantation device, and in particular, to an ion implantation device that uses a magnetic field to capture secondary electrons generated when an ion beam is irradiated onto a sample stage or sample. The present invention relates to an ion implantation device equipped with means for generating ion.

[Conventional technology] The conventional ion implantation device is shown in FIG. 7 below.

This will be explained based on FIG. 8, FIG. 9A, and FIG. 9B.

FIG. 7 shows, for example, rNuclear Instru
ment and Method 1nPhys
ics Research B37/38 (198
9), pages 492 to 496j, showing a cross-sectional configuration near the sample stage of the Varian ion implantation device. Referring to the figure, a sample 2 is held on a sample stage 1 made of aluminum or the like. Opposed to sample 2,
A secondary electron capturing electrode 3 is arranged to capture secondary electrons generated when the sample stage 1 or the sample 2 is irradiated with the ion beam (arrow IB shown in FIG. 7).

Adjacent to this secondary electron trapping electrode 3, negative potential electrodes 4 and 5 for trapping surrounding space electrons are arranged. A beam stopper 6 is provided to allow the beam to pass in the direction or to block it. Not only the sample stage 1 but also the secondary electron capturing electrode 3. The negative potential electrodes 4 and 5 and the beam stopper 6 are also mainly formed of a conductor such as aluminum.

Next, the operation of the conventional ion implantation apparatus configured as described above will be explained. When the beam stopper 6 is in the "open" state, the ion beam is transported and irradiated onto the sample 2 mounted on the sample stage 1. The ion implantation device is
For example, it is used in the process of forming a MOS transistor shown in the schematic cross-sectional view of FIG. Referring to FIG. 8, for example, p-type field 11 and channel 12
When forming the source 13 and drain 14, boron ions B+ are implanted, and phosphorus ions (P) are implanted to form the source 13 and drain 14.
) and arsenic ions (As”) are implanted. In either case, positively charged ions are implanted into sample 2, so if there is a high-resistance insulator such as resist 15 or silicon oxide film on the wafer surface, it will become positively charged. do. Also, when ions are implanted, sample stage 1 or sample 2
Secondary electrons are generated due to ion implantation. According to such a conventional ion implantation device, the sample stage 1 and the sample 2
Many secondary electrons generated from the secondary electron trapping electrode 3 are captured by the secondary electron capturing electrode 3. In addition, many of the secondary electrons heading toward the sample 2 (to the right in Figure 7) recombine with ions at the periphery of the sample 2, and extremely few secondary electrons reach the center of the sample 2. . Therefore, the charged potential on the surface of the sample 2 becomes high, which causes electrostatic damage and causes device failure, particularly in the center of the sample 2.

In order to partially solve the problems of the conventional ion implantation equipment as described above, an ion implantation equipment that neutralizes positive ions with negative electrons, as shown in FIGS. 9A and 9B, has been proposed. This has already been proposed in JP-A-1-232653.

The ion implantation device disclosed in the publication captures an ion beam 21 consisting of positive ions 21a such as B'', As'', and Psb+, with reference to FIGS. 9A and 9B. Wafer 23 with electrons 22
This method performs ion implantation by irradiating. A feature of this device is that the holder 25 of the wafer disk 24 is provided with a magnetic field generation source consisting of, for example, six rod-shaped magnets 26. These magnets 26 are for forming magnetic lines of force 27 on the surface 23a of the wafer 23. The magnetic field generation sources are embedded radially within the holder 25, for example, with their N poles abutting each other approximately at the center of the holder 25, and their S poles located on the outer periphery of the holder 25.

By providing the magnet 26 as described above, lines of magnetic force 27 are formed on the wafer surface 23a from the center of the wafer 23 toward the outer periphery. The positive ions 21a that have reached the wafer 23 enter the wafer 23, and at this time, positive charges 28 remain on the wafer surface 23a. On the other hand, the electrons 22a that have reached the wafer 23 together with the positive ions 21a
moves on the wafer surface 23a. However, since magnetic lines of force 27 are formed on the wafer surface 23a, the electrons 22a move in a direction across the magnetic lines of force 27 while performing clockwise or counterclockwise cycloidal motion depending on the motion vector upon reaching the wafer surface 23a. will be moved to. And during this movement, the electron 22a has a positive charge 28
The positive charge 28 is neutralized by collision with the positive charge 28.

As the electrons 22a move in a cycloidal motion on the wafer 23a, the probability of collision between the electrons 22a and the positive charge 28 increases, and the wafer surface 21a
The remaining positive charges 28 will be neutralized.

[Problems to be Solved by the Invention] In the ion implantation device disclosed in the above-mentioned Japanese Patent Application Laid-open No. 1-232653, the conventional ion implantation device shown in FIG.
Compared to a device without a bar magnet, the probability of collision between electrons and ions increases, resulting in a lower charging potential.

However, when electrons are not supplied from the electron generator and the sample 2 is an insulator or the insulator covers a considerable part of the surface of the sample, the secondary electron generation efficiency becomes less than 1. . Therefore, it is almost impossible to expect the effect of reducing the electrical charge by neutralizing ions by electrons.

Also, even if electrons are supplied, the magnet 26 will not hold the holder 2, as shown in FIGS. 9A and 9B.
5, there are many lines of magnetic force 27 formed by the magnet 26 on the surface of the wafer 23, which is the sample, from near the center to inside the outer periphery.
There is very little outside the outer periphery of the .

Due to the magnetic lines of force 27, the electrons that have reached the wafer surface 23a move in a cycloid around the magnetic lines of force 27, collide with positive ions, and neutralize the positive ions. However, the electrons that do not reach the surface 23a of the wafer 23
There is a problem in that the secondary electrons generated in the holder 25 near the outer periphery cannot be effectively used to neutralize positive ions because there are very few lines of magnetic force 27 to capture them.

In order to solve the above-mentioned conventional problems, this invention effectively captures secondary electrons generated from the sample and the sample stage around it using magnetic lines of force, transports them to the center of the sample, and implants them into the sample. The object of the present invention is to provide an ion implantation device that can lower the charged potential on the surface of a sample and prevent electrostatic damage by increasing the chance of recombination with positive ions.

[Means for Solving the Problems] In order to solve the above problems, the ion implantation apparatus of the present invention includes a sample stage on which a sample is placed, and an ion beam is irradiated onto the sample on the sample stage to implant ions. Equipped with means etc. The ion implantation apparatus of the present invention is characterized by having a magnetic field applying means that generates a magnetic field radially on the surface of the sample from near the center of the sample to outside the outer periphery of the sample.

[Function] According to the present invention, by having the above configuration, secondary electrons generated when an electron or ion beam is irradiated onto a sample stand or a sample can be converted into secondary electrons generated from a sample stand near the outer periphery of the sample. It captures electrons in a magnetic field and transports the captured electrons to the center of the sample. The thus captured secondary electrons are attracted to the charged potential of the ions implanted into the sample surface and recombine with the ions, thereby lowering the charged potential of the sample surface.

[Example] An example of the present invention will be described below based on the drawings. 1st
Figure A shows a front cross section of the vicinity of the sample stage of an ion implantation apparatus according to an embodiment of the present invention.

FIG. 1B shows a plan view of the ion implantation apparatus shown in FIG. 1A. Referring to FIGS. 1A and 1B, in the ion implantation apparatus of this embodiment, a sample 32 is held on a sample stage 31.

Further, a plurality of bar magnets 33 are embedded in the sample stage 31 below the sample 32. The bar magnets 33 are arranged radially such that the north pole 33a is located near the center of the sample 32 and the south pole 33b is located outside the outer periphery of the sample 32. A magnetic field exists radially between the N pole 33a and the S' pole 33b of the bar magnet 33.

In this magnetic field, as shown in FIGS. 2A and 2B, a portion of the magnetic lines of force 34 exist on the surface of the sample 32 and near the surface. When the sample stage 31 or the sample 32 is irradiated with the ion beam, secondary electrons are generated from the sample stage 31 and the sample 32. The secondary electrons have an energy of several tens of eV at most and are emitted upward from the sample stage 31 and the sample 32 at all angles. The generated secondary electrons are captured by magnetic lines of force 34 on and near the surfaces of the sample stage 31 and sample 32. As shown in FIG. 3, when an electron 36 enters a magnetic field 35 with a magnetic flux density B at an arbitrary angle (θ) and at a speed of ■, the electron receives a force of F-q-vxB. However, q is the amount of charge of electrons.

Unless the angle of incidence (θ) is 90°, the electrons 36 will be exposed to the magnetic field 3.
Performs a spiral movement that progresses while rotating around 5. If the magnetic field 35 does not exist, the electrons 36 will scatter in all directions, but in the presence of the magnetic field 35, the electrons 36 will scatter in all directions.
As mentioned above, it is captured by the magnetic field. Depending on the magnitude of the incident angle, there are two directions in which the helical motion advances: the same direction as the magnetic field direction as shown in FIG. 3, and the opposite direction. Secondary electrons are not emitted in a specific direction, but in all directions, so about half of the secondary electrons are emitted in the same direction as the magnetic field, and the remaining half are emitted in the same direction as the magnetic field. 0 The child will move in a spiral motion in the direction opposite to the magnetic field.

When the sample 32 is made of an insulator, or when the surface of the sample 32 is covered with a material such as resist, 2 The number of secondary electrons is one or less. Therefore, positive charging will occur.

On the other hand, if the sample 32 is made of metal such as aluminum, the number of secondary electrons generated per implanted ion will be two or more, as can be seen from the graph in Figure 4. . Therefore, many secondary electrons are generated from the sample stage 31 rather than the sample 32, and these secondary electrons are emitted upward from the sample stage 31 and the sample 32 at all angles with an energy of several tens of eV at most. .Therefore, the sample stage 31
If the secondary electrons generated can be efficiently transferred to the surface of the sample 32, they can be effectively used to neutralize the implanted ions. In the case of the magnetic field configuration shown in FIGS. 2A and 2B, approximately one-half of the secondary electrons generated from the sample stage 31 are transported toward the center of the sample 32. The transported secondary electrons are attracted to the charged potential caused by the ions implanted on the sample surface and recombine with the ions or exist on the surface, lowering the charged potential, thereby preventing damage to the insulator due to the charged potential. The occurrence of device defects in the ion implantation process due to this can be reduced.

In the above embodiment, the N pole 33a was arranged near the center of the sample 32, and the S pole 33b was arranged outside the outer periphery of the sample 32, but the N pole and the S pole were arranged in the opposite direction. You can.

Further, in the above embodiment, the bar magnet 33 is embedded in the sample stage 31 and placed behind all the samples 32, but the bar magnet 33 is not necessarily placed inside the sample stage 31. It is not necessary to embed and place everything. That is, for example, a part of the magnet may be located outside the sample stage 31 and behind the sample 32.

Further, the magnet is not limited to a bar magnet, and similar effects can be achieved even if other permanent magnets or electromagnets such as those described in the following embodiments are used.

2 FIG. 5 shows another embodiment of the present invention. This example is
A case is shown in which an electromagnet 37 is used as a magnetic field applying means for generating lines of magnetic force 34 on the surface of the sample stage 31. This electromagnet 37 has a bar-shaped yoke 37a located below the sample 32 and above the sample stage, similar to the bar magnet 33 in the above embodiment.
It is embedded in 1. An electromagnetic coil 37b is wound around this rod-shaped yoke 37a, and by passing a current through this coil 37b, radial lines of magnetic force 3
4 can be generated.

FIG. 6 shows yet another embodiment of the invention. In this embodiment, an electromagnet 38 is used as a magnetic field applying means, and a part of the electromagnet 38 is disposed outside the sample stage 31. In this embodiment, the magnetic pole portion of the U-shaped yoke 38a of the electromagnet 38 is embedded inside the sample stage 31 and located below the sample 32. An electromagnetic coil 38b is wound around a portion of the yoke 38a located outside the sample stage 31, and by passing a current through this electromagnetic coil 38b, three radial lines of magnetic force 34 are generated on the surface of the sample stage 31. I can do it.

The embodiment shown in FIG. 5 and FIG.
The same effects as the embodiment shown in the figures can be achieved.

[Effects of the Invention] As described above, according to the present invention, by forming a radial magnetic field on the surface of the sample from near the center of the sample to the outside of the outer periphery, the ion beam is directed toward the sample stage or the sample. The secondary electrons generated when irradiated with
Secondary electrons, including those generated from the sample stage near the outer periphery of the sample, can be efficiently captured in the magnetic field, and the captured secondary electrons can be efficiently transported to the center of the sample. therefore,
The generated secondary electrons can be effectively used to lower the charging potential, and this has the unique effect of providing an ion implantation apparatus that does not cause device failure due to electrostatic discharge damage.

[Brief explanation of drawings]

FIG. 1A is a front sectional view showing a sample stage of an ion implantation apparatus according to an embodiment of the present invention, and FIG. 1B is a partially sectional plan view thereof. FIG. 2A is a partially enlarged front sectional view of the sample stage of the same example.
FIG. 2B is a partially enlarged plan view of the sample stage. FIG. 3 is an explanatory diagram showing the behavior of electrons with respect to lines of magnetic force. FIG. 4 is a graph showing the secondary electron generation rates of various materials. FIG. 5 is a partially enlarged front sectional view of a sample stage in another embodiment of the present invention. FIG. 6 is a partially enlarged front sectional view of a sample stage in still another embodiment of the present invention. FIG. 7 is a sectional view of a main part of a conventional ion implantation device. Figure 8 shows a MOS formed using an ion implantation device.
) is a schematic cross-sectional view showing a transistor. Figure 9A is a side sectional view showing the vicinity of the sample stage of a conventional ion implanter that partially solves the problems of the conventional ion implanter shown in Figure 7, and Figure 9B is a side sectional view of Figure 9A viewed from the left. This is a diagram. 5 In the figure, 31 is a sample stage, 32 is a sample, 33 (↓ bar magnet, 33a is the N pole of the bar magnet 33, 33b is the S pole of the bar magnet 33, 34 is a line of magnetic force, 35 is a magnetic field, 36 is an electron, 37 ．．
38 is an electromagnet. In addition, in the figures, the same reference numerals indicate the same or equivalent elements. 6 Fig. 2A 34: Stone Capability Elbow Fig. 2B/□727/2:ゝ\\J31 JP-A-3 219545 (6) Fig. 6 Fig. 7 Fig. 38: Denkoseki

Claims (1)

[Scope of Claims] An ion implantation device comprising a sample stage on which a sample is placed, and means for irradiating the sample placed on the sample stage with an ion beam to implant ions, the method comprising: An ion implantation apparatus comprising a magnetic field applying means for generating a magnetic field radially on the surface of the sample from near the center of the sample to outside the outer periphery of the sample.