JPH05234564A - Ion implanting device - Google Patents

Abstract

PURPOSE:To provide an ion implanting device, which can reduce the contamination of a wafer due to particles generated by the collision of a part of ion beams to a structure on a beam line. CONSTITUTION:A first slow ion suppressor electrode 30 is provided between an analyzing slit 6 and an inlet part of an accelerating tube 8, on a second slow ion suppressor electrode 34 is provided in the immediately downstream side of a mask 16 of an inlet part of a Faraday case 22. The positive potential at about some hundreds times of the potential of the ion beam 2 passing through the slow ion suppressor electrodes 30, 34 is respectively given to the slow ion suppressor electrodes 30, 34 by slow ion suppressor power sources 32, 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus, and more specifically to a means for reducing contamination of a wafer by various particles and unnecessary ions generated in the apparatus.

[0002]

2. Description of the Related Art FIG. 3 is a side sectional view of an example of a conventional ion implantation apparatus. This ion implantation apparatus is an ion beam 2 extracted from an ion source (not shown) and subjected to mass analysis through an analysis electromagnet 4 and an analysis slit 6.
Are accelerated through the accelerating tube 8 and the Y scan electrodes 12 and X
After scanning in the Y direction (for example, the vertical direction) and the X direction (for example, the horizontal direction) by the scanning electrode 14, the platen 26
The wafer 24 held on the wafer is irradiated to perform ion implantation. The analysis slit 6 is placed at the beam focusing point generated by the action of the analysis electromagnet 4. An acceleration voltage is applied to the acceleration tube 8 from an acceleration power supply 10.

Further, secondary electrons emitted from the wafer 24 and the platen 26 due to the irradiation of the wafer 24 with the ion beam 2 are prevented from escaping to the ground, and the beam current flowing through the wafer 24 is accurately measured. For the purpose of performing the operation, the Faraday case 22 is provided from the periphery of the wafer 24 to the upstream side, and the suppressor electrode 18 having a negative potential by the suppressor power supply 20 is provided on the upstream side of the entrance of the Faraday case 22. There is. Two
8 is a beam current measuring device. A mask 16 is provided on the upstream side of the suppressor electrode 18 for the purpose of preventing the ion beam 2 from hitting the suppressor electrode 18.

Incidentally, on the beam line of the ion beam 2, some apertures, Q lenses and the like are provided in addition to those described above, but the illustration thereof is omitted here.

[0005]

In the ion implantation apparatus as described above, a part of the ion beam 2 is a structure on the beam line, for example, the analysis tube 4a of the analysis electromagnet 4, the analysis slit 6 and the acceleration. Collisions with the electrodes 8a of the tube 8, the scanning electrodes 12 and 14, and also with an aperture, a Q lens, and the like (not shown), particles (contaminant particles; for example, metal atoms or fine particles constituting the electrode or the structural material) jump out and There is a problem that the particles that have jumped out toward the inner wafer 24 side reach the wafer 24, which contaminates the wafer 24.

However, conventionally, there is no means for positively preventing such particles from reaching the wafer 24. As a conventional measure, there is a possibility that the ion beam 2 may collide. The material is made of a material that has a relatively small influence of contamination on the wafer (for example, carbon or silicon), or a geometric structure (for example, knife edge shape or saw tooth shape) in which sputtered particles are less likely to be ejected toward the wafer 24 side. It was stopped somehow.
However, with such means, the reduction of the contamination of the wafer 24 due to the particles was insufficient.

Therefore, the main object of the present invention is to provide an ion implantation apparatus capable of reducing the contamination of the wafer by the particles as described above.

[0008]

In order to achieve the above object, the first ion implantation apparatus of the present invention is provided between the analysis slit and the accelerating tube as described above, and more than the potential of the ion beam passing therethrough. A slow ion suppressor electrode to which a positive potential is applied is provided.

Further, in the second ion implantation apparatus of the present invention, a positive potential higher than the potential of the ion beam passing therethrough is applied to the Faraday case inlet just upstream or downstream of the mask as described above. A slow ion suppressor electrode is provided.

Further, the third ion implantation apparatus of the present invention is such that the first throwing device in which a positive potential is applied between the analysis slit and the accelerating tube as described above is higher than the potential of the ion beam passing therethrough. An ion suppressor electrode is provided, and a second slow ion suppressor electrode to which a positive potential is applied to the mask immediately upstream or immediately downstream of the ion beam passing therethrough is characterized. ..

[0011]

Function Many of the particles generated when a part of the ion beam collides with the structure on the beam line are positively charged (positively ionized). Some of these are charged when sputtered or emitted by the ion beam, and some are charged by colliding with ions in the ion beam after the sputtered or emitted fine particles.

In particular, since the analysis slit is where the ion beam is most narrowed down, there is a high probability that the particles collide with the ions in the ion beam and are ionized, and once this is accelerated by the accelerating tube. , It is difficult to prevent reaching the wafer.

According to the first ion implantation apparatus described above, positively charged particles generated on the upstream side of such an accelerating tube and not yet accelerated (this is called slow ion in this specification. In this specification, in addition to the usual narrowly defined ions, the charged ions of fine particles are also included in the term of the ion) in the present specification, and they are driven back by the electric field of the slow ion suppressor electrode to which a positive potential is applied, You can prevent it from entering the accelerator tube. As a result, the contamination of the wafer due to such particles can be reduced.

Further, according to the second ion implanter, positively charged particles (slow ions) generated between the exit of the acceleration tube and the mask at the entrance of the Faraday case are thrown to a positive potential. It can be driven back by the electric field of the ion suppressor electrode, preventing it from traveling towards the wafer. As a result, the contamination of the wafer due to such particles can be reduced.

Further, according to the third ion implanter, positive potentials are applied to both positively charged particles generated upstream of the acceleration tube and positively charged particles generated downstream of the acceleration tube. Driven by the electric fields of the first and second slow ion suppressor electrodes,
They can be prevented from reaching the wafer. Therefore, the contamination of the wafer due to the particles can be reduced more reliably.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side sectional view of an ion implanter according to an embodiment of the present invention. The same or corresponding portions as those of the conventional example of FIG. 3 are denoted by the same reference numerals, and the differences from the conventional example will be mainly described below.

In this embodiment, in order to obtain a greater effect, the analysis slit 6 and the accelerating tube 8 as described above are used.
The first slow ion suppressor electrode 3 between the inlet and the
0, and the second slow ion suppressor electrode 34 is provided immediately downstream of the mask 16 at the entrance of the Faraday case 22, that is, between the mask 16 and the suppressor electrode 18.
Is provided.

The slow ion suppressor electrode 30 has an opening matched to its shape so as not to hit the ion beam 2, and the whole shape may be a plate shape as shown in FIG. The shape may be a rectangular tube shape, as shown in FIG. 2, or may be a cylindrical shape, a parallel plate shape, or the like, but it is preferable that the shape matches the shape of the ion beam 2 passing therethrough as much as possible.

A first slow ion suppressor power source 32 is connected between the slow ion suppressor electrode 30 and the entrance of the accelerating tube 8 such that the former is on the positive side, whereby the slow ion suppressor electrode is provided. A positive electric potential of, for example, about several hundreds V is applied to the electric potential of the ion beam 2 passing therethrough (that is, an electric potential higher than the ground electric potential by the voltage of the acceleration power supply 10).

The slow ion suppressor electrode 34 is slightly smaller than the opening portion where the ion beam 2 does not hit, that is, the opening portion of the mask 16 in this example (more specifically, the ion beam 2
Is a plate-like member having a large opening.

A second slow ion suppressor power supply 36 is connected between the slow ion suppressor electrode 34 and the ground, with the former on the positive side, whereby the slow ion suppressor electrode 34 passes through the ion beam passing therethrough. A positive potential of, for example, about several hundred V is applied to the second potential (that is, the ground potential).

Many of the particles generated when a part of the ion beam 2 collides with the above-mentioned structure on the beam line are positively charged (positively ionized). Some of them are charged during the sputtering by the ion beam 2, and some of them are charged by colliding with the ions in the ion beam 2 after the sputtering.

In particular, since the ion beam 2 is narrowed down most by the analyzing electromagnet 4 in the analysis slit 6, the probability of particles colliding with the ions in the ion beam 2 and ionizing is high, and this is also the case. Once accelerated by the accelerator tube 8, it is difficult to prevent reaching (implanting) the wafer 24.

The first slow ion suppressor electrode 3
0 is a positively charged particle (slow ion) generated on the upstream side of the accelerating tube 8 and not yet accelerated.
Can be driven back by a positive electric field to prevent it from entering the accelerating tube 8. As a result, contamination of the wafer 24 due to such particles can be reduced. In particular, the particles that have reached the wafer 24 with low energy can be removed by washing, but the particles that have reached the wafer 24 with high energy cannot be removed even by washing because they have been injected into the wafer surface, and therefore the slow ions The suppressor electrode 30 has a great effect of preventing high-energy particles from reaching the wafer 24.

The second slow ion suppressor electrode 3
4 can repel positively charged particles (slow ions) generated between the exit of the accelerating tube 8 and the mask 16 by the positive electric field and prevent them from proceeding toward the wafer 24. As a result, contamination of the wafer 24 due to such particles can be reduced.

Of course, the slow ion suppressor electrodes 30 and 34 as described above can block not only metal ions but also other organic ion particles, positively charged powder particles, etc. Is also effective in reducing the adherence to the wafer 24.

Note that the second slow ion suppressor electrode 34 may be provided immediately upstream of the mask 16 contrary to the above example, and even in this case, the same effect as the above example can be obtained. In this case, the opening of the slow ion suppressor electrode 34 can be made slightly smaller than the opening of the mask 16 (more specifically, by the amount of spread by the scanning of the ion beam 2). Further, in this case, since the slow ion suppressor electrode 34 having a positive potential with respect to the ion beam 2 is exposed, the electrons in the ion beam 2 are attracted to the slow ion suppressor electrode 34 and the ion beam 2
It is preferable to provide a ground potential plate (shielding mask) having an opening slightly smaller than the opening immediately upstream of the slow ion suppressor electrode 34 in order to prevent the diffusion of the ions.

Further, in the above, the ion implantation apparatus for fixing the wafer 24 and scanning the ion beam 2 in the X and Y directions has been described as an example, but the present invention is not limited to this. 2 is fixed and a so-called batch type ion implanter for rotating and translating a wafer disk having a plurality of wafers 24 mounted thereon, or the ion beam 2 is electrically scanned in one direction so that the wafer 24 is substantially The present invention can also be applied to a so-called hybrid scan type ion implanter that mechanically scans in a direction orthogonal to each other.

[0029]

As described above, according to the first ion implantation apparatus of the present invention, the suppressor electrode to which the positive potential is applied to the positively charged particles generated on the upstream side of the accelerating tube and not yet accelerated. Can be driven back by the electric field in and blocked from entering the accelerator tube. As a result, the contamination of the wafer due to such particles can be reduced.

Further, according to the second ion implanter of the present invention, the positively charged particles generated between the exit of the acceleration tube and the mask at the entrance of the Faraday case are slow ion suppressors to which a positive potential is applied. It can be driven back by the electric field of the electrode, preventing it from moving towards the wafer. As a result, the contamination of the wafer due to such particles can be reduced.

Further, according to the third ion implantation apparatus of the present invention, both positively charged particles generated upstream of the acceleration tube and positively charged particles generated downstream of the acceleration tube have positive potentials. The applied electric fields of the first and second slow ion suppressor electrodes, respectively, can be driven back to prevent them from reaching the wafer. Therefore, the contamination of the wafer due to the particles can be reduced more reliably.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ion implantation device according to an embodiment of the present invention as seen from the side.

FIG. 2 is a perspective view showing an example of an analysis slit and a slow ion suppressor electrode in FIG.

FIG. 3 is a cross-sectional view of an example of a conventional ion implantation device as seen from the side.

[Explanation of symbols]

 2 Ion beam 6 Analysis slit 8 Accelerating tube 16 Mask 22 Faraday case 24 Wafer 30 First slow ion suppressor electrode 32 First slow ion suppressor power supply 34 Second slow ion suppressor electrode 36 Second slow ion suppressor power supply

Claims (3)

[Claims] 1. An ion implanter having a structure for irradiating a wafer with an ion beam through an analysis slit and an accelerating tube provided on the downstream side thereof, wherein the potential of the ion beam passing therethrough is provided between the analysis slit and the accelerating tube. An ion implanter characterized by being provided with a slow ion suppressor electrode to which a positive potential is applied. 2. An ion implanter having a structure in which an ion beam is irradiated to a wafer through a Faraday case provided from the periphery of the wafer to an upstream side thereof and a mask provided at an entrance thereof, in an ion implantation apparatus immediately upstream or immediately above the mask. An ion implanter characterized in that a slow ion suppressor electrode to which a positive potential is applied to the downstream side of the potential of the ion beam passing therethrough is provided. 3. The wafer is irradiated with an ion beam through an analysis slit and an accelerating tube provided on the downstream side thereof, and through a Faraday case provided from the periphery of the wafer to the upstream side thereof and a mask provided at the entrance thereof. In the ion implantation apparatus having the structure described above, a first slow ion suppressor electrode, which is applied with a positive potential higher than the potential of the ion beam passing therethrough, is provided between the analysis slit and the acceleration tube, An ion implanter characterized in that a second slow ion suppressor electrode to which a positive potential is applied to the upstream side or immediately downstream side of the ion beam passing therethrough is provided.