JP3399230B2 - Ion irradiation equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ion irradiation in which a substrate is irradiated with an ion beam in a vacuum and subjected to a treatment such as ion implantation, as in an ion implantation apparatus. More specifically, the present invention relates to an improvement in means for suppressing charging (charge-up) of the substrate. 2. Description of the Related Art In this type of ion irradiation apparatus, particularly in a large current ion irradiation apparatus, charging of a substrate is one of the major problems, and a plasma shower is a means for solving the problem. FIG. 4 shows an example of a conventional ion irradiation apparatus using a plasma shower. This ion irradiation apparatus includes a holder 4 for holding a substrate (for example, a wafer) 6 and a Faraday cup 8 surrounding at least the upstream side (upstream of ion beam travel; the same applies hereinafter) of the holder 4.
And a suppressor electrode 32 provided at the entrance of the Faraday cup 8, a molding mask 38 provided further upstream of the suppressor electrode 32, and a catch provided downstream of the holder 4 in this example. The substrate 6 on the holder 4 is irradiated with the ion beam 2 through the forming mask 38, the suppressor electrode 32, the Faraday cup 8, and the reflector electrode 20, which will be described later, and ion-implanted into the substrate 6. Is performed. However, whether or not to provide the catch plate 16 and the forming mask 38 does not affect the essence of the present invention and is optional. The holder 4 may be a wafer disk for batch processing or a platen for single-wafer processing.
The illustrated one is an example of the former case, and is rotated in the direction of arrow A and translated in the direction of the front and back of the paper in the vacuum vessel. [0005] The Faraday cup 8 is also called a Faraday cage and is for preventing secondary electrons emitted from the ion beam 2 from hitting the substrate 6 or the holder 4 from escaping to the ground. This Faraday cup 8
The entrance 10 has, for example, a rectangular hole 12 through which the ion beam 2 passes. This Faraday cup 8
Is set to the same potential as the holder 6 and the catch plate 16 in this example, that is, electrically connected in parallel with the holder 6 and the catch plate 16, and
It is connected to the. The suppressor electrode 32 suppresses the leakage of electrons in the Faraday cup 8 to the upstream side, and a negative voltage of, for example, about -200 V is applied from the suppressor power supply 36 with respect to the Faraday cup 8. . This suppressor electrode 32 allows the ion beam 2 to pass through.
For example, it has a rectangular hole 34. The forming mask 38 has, for example, a rectangular hole 40.
Forming an ion beam 2 passing therethrough,
That is, the shape of the ion beam 2 is limited to a desired shape, and the ion beam 2 is electrically grounded. Further, in this example, when the surface of the substrate 6 is irradiated with the ion beam 2, especially when the surface is an insulator,
A plasma shower device 26 for generating a plasma 28 is provided outside the Faraday cup 8 in order to prevent a problem such as discharge due to positive charging. A cylindrical reflector electrode 20 is provided in the periphery of the Faraday cup 8 so as to be electrically insulated from the Faraday cup 8.
4 to -20 V, for example, based on the Faraday cup 8
About a negative voltage is applied. Holes 14 and 22 are provided on the side surfaces of the Faraday cup 8 and the reflector electrode 20 so as to face each other.
0 is inserted, and the plasma 28 generated in the plasma shower device 26 is introduced into the reflector electrode 20 through the introduction tube 30 by being pulled by the positive potential of the ion beam 2 or the like. Ions (positive ions; the same applies hereinafter) in the plasma 28 introduced into the reflector electrode 20 are attracted and captured by the reflector electrode 20 having a negative potential. On the other hand, the electrons in the plasma 28 are pushed back to the center of the Faraday cup 8 by the reflector electrode 20, and are drawn into the ion beam 2 passing through the Faraday cup 8 by the positive electric field. With substrate 6
To neutralize the positive charge accompanying the ion beam irradiation on the substrate surface. In this case, since the electrons in the plasma 28 have low energy (for example, about 20 eV or less), by supplying such low-energy electrons to the substrate 6 together with the ion beam 2, not only the substrate 6 is positively charged but also negatively charged. Can also be suppressed. However, in the above-mentioned ion irradiation apparatus, since a negative voltage is applied to the suppressor electrode 32 immediately upstream of the Faraday cup 8 with respect to the Faraday cup 8, the reflector is not used. Some of the ions in the plasma 28 introduced into the electrode 20 are drawn into the suppressor electrode 32 by the negative voltage and collide with the suppressor electrode 32,
Thereby, secondary electrons are emitted from the suppressor electrode 32, which may enter the Faraday cup 8 and the reflector electrode 20 through the hole 12 of the entrance portion 10 of the Faraday cup 8. Thus, the suppressor electrode 3
When viewed from the Faraday cup 8, the secondary electrons emitted from 2 have at least the potential of the suppressor electrode 32, that is, energy (for example, about 200 eV as described above) corresponding to the output voltage of the suppressor power supply 36, It has higher energy than the electrons in the plasma 28. When such high-energy secondary electrons enter the Faraday cup 8 and the reflector electrode 20,
It enters the substrate 6 together with the ion beam 2. In this case, since the substrate 6 can be negatively charged to a voltage corresponding to the energy of the incident electrons, when such high-energy electrons enter the Faraday cup 8 and the reflector electrode 20, the substrate 6 has a large negative charge. Will be caused. Accordingly, the present invention is to prevent ions in the plasma from the plasma shower device from colliding with the suppressor electrode on the upstream side, thereby preventing high-energy secondary electrons from entering the Faraday cup. It is a main object of the present invention to provide an ion irradiation device which can be used. [0015] According to an aspect of this inventions ion irradiation apparatus, the inlet portion of the reflector electrode is provided with a lid with a hole for the ion beam passes, and the inlet portion and the suppressor of the Faraday cup An ion suppressor electrode to which a positive voltage is applied with reference to the Faraday cup and which has a hole through which an ion beam passes is provided between the electrode and the electrode. According to the above configuration, the presence of the lid provided at the entrance of the reflector electrode makes it difficult to see the suppressor electrode from the exit of the plasma shower device. That is,
Since this lid physically interferes, ions in the plasma from the plasma shower device are less likely to be incident on the suppressor electrode. In addition , since the ion suppressor electrode to which a positive voltage is applied to the Faraday cup is present between the entrance of the Faraday cup and the suppressor electrode on the upstream side thereof, the ion suppressor electrode tends to go upstream from inside the Faraday cup. The ions are pushed back by the positive potential of the ion suppressor electrode. As a result, it is possible to prevent ions in the plasma from the plasma shower device from colliding with the suppressor electrode on the upstream side, and to prevent high-energy secondary electrons from entering the Faraday cup. As a result, negative charging of the substrate can be suppressed. FIG. 1 is a sectional view showing an example of an ion irradiation apparatus according to the present invention. Parts that are the same as or correspond to those in the conventional example of FIG. 4 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below. In this embodiment, the hole 4 through which the ion beam 2 passes is provided at the entrance of the above-mentioned reflector electrode 20.
4 is provided. The shape of this hole 44 is
It is preferable to make the shape correspond to the shape of the ion beam 2 passing therethrough, and to make the size as small as possible without impeding the passage of the ion beam 2. FIG.
An example of the shape of the lid 42 and the hole 44 is shown in FIG. Further, the ion beam 2 is placed between the entrance 10 of the Faraday cup 8 and the suppressor electrode 32.
Is provided with an ion suppressor electrode 46 having a hole 48 through which the gas passes. The shape of the hole 48 preferably corresponds to the shape of the ion beam 2 passing therethrough, and its size is preferably as small as possible without impeding the passage of the ion beam 2. FIG. 2 shows an example of the shape of the ion suppressor electrode 46 and the hole 48 thereof. The ion suppressor electrode 46 is connected to an ion suppressor power source 50 with, for example, 5
A positive voltage of about 0V to 100V is applied. According to the above configuration, the presence of the lid 42 provided at the entrance of the Faraday cup 8 makes it difficult for the suppressor electrode 32 to be seen from the exit of the plasma shower device 26 (more specifically, of the introduction tube 30). Become. That is,
Since the lid 42 physically hinders, ions in the plasma 28 introduced into the reflector electrode 20 from the plasma shower device 26 do not easily reach the suppressor electrode 32. Further, the ion suppressor electrode 46 to which the above-mentioned positive voltage is applied to the Faraday cup 8
Is present between the inlet 10 of the Faraday cup 8 and the suppressor electrode 32 on the upstream side of the Faraday cup 8, ions that are going to the upstream side from inside the Faraday cup 8 are pushed back by the positive potential of the ion suppressor electrode 46. Will be. As a result, the plasma shower device 26
It is possible to prevent ions in the plasma 28 from colliding with the suppressor electrode 32 on the upstream side. That is, all the ions are collected by the reflector electrode 20 having a negative potential. As a result, it is possible to prevent high-energy secondary electrons from entering the Faraday cup 8, and to suppress negative charging of the substrate 6. It should be noted that electrons in the plasma 28 introduced into the reflector electrode 20 are attracted to and collide with the positive potential ion suppressor electrode 46, whereby secondary electrons are emitted from the ion suppressor electrode 46. Although it is conceivable, since the ion suppressor electrode 46 is at a positive potential with respect to the Faraday cup 8, the secondary electrons emitted from the ion suppressor electrode 46 are returned to the ion suppressor electrode 46 by the positive potential. Never enter the Faraday cup 8. Therefore,
The secondary electrons do not cause the substrate 6 to be negatively charged. Further, on the upstream side of the ion suppressor electrode 46, there is a suppressor electrode 32 having a negative potential with respect to the Faraday cup 8, and the secondary ions emitted from the ion suppressor electrode 46 as described above. Since the electrons are pushed back by the negative potential, there is no possibility that the secondary electrons escape to the upstream side. Therefore, there is no problem that the leakage of the secondary electrons from the Faraday system causes an error in the measurement of the beam current of the ion beam 2 by the beam current measuring device 18. The above plasma shower device 26
For example, a plasma shower device that generates plasma in two stages as described in Japanese Patent Application Laid-Open No. 7-78587 may be used. In this case, the plasma is more efficiently introduced into the reflector electrode 20. can do. Further, on the further upstream side of the molding mask 38, a further suppressor electrode to which a negative voltage is applied with respect to the ground potential is provided.
There is a case where a ground potential analyzing slit for performing mass separation is provided, but is not shown here. Further, a suppressor electrode to which a negative voltage is applied may be provided so as to surround a gap between the Faraday cup 8 and the catch plate 16, but this is also not illustrated here. As described above, according to the present invention, the lid provided at the entrance of the reflector electrode makes it difficult for the ions in the plasma from the plasma shower device to reach the suppressor electrode, and has a positive potential. Ion suppressor electrode
Try to go upstream from inside the Faraday cup
Since the ions that can push back possible, the ions in the plasma from the plasma shower device is prevented from colliding with the suppressor electrode on the upstream side, to prevent the secondary high-energy electrons from entering the Faraday cup Can be. As a result, not only positive charging of the substrate but also negative charging can be effectively suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an example of an ion irradiation device according to the present invention. FIG. 2 is a front view of the ion suppressor electrode in FIG. FIG. 3 is a front view of a lid of a reflector electrode entrance in FIG. 1; FIG. 4 is a sectional view showing an example of a conventional ion irradiation apparatus. [Description of Signs] 2 Ion beam 4 Holder 6 Substrate 8 Faraday cup 20 Reflector electrode 24 Reflector power supply 26 Plasma shower device 28 Plasma 32 Suppressor electrode 36 Suppressor power supply 42 Lid 46 Ion suppressor electrode 50 Ion suppressor power supply

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-78587 (JP, A) JP-A-6-203785 (JP, A) JP-A-2-144841 (JP, A) JP-A-9-97 147789 (JP, A) JP-A-8-138618 (JP, A) JP-A-6-36732 (JP, A) JP-A-5-234564 (JP, A) JP-A-4-359854 (JP, A) JP-A-5-275047 (JP, A) JP-A 63-99752 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37/317 C23C 14/48 H01J 37/20 H01L 21/265

Claims (1)

(57) [Claim 1] A holder for holding a substrate, and a cylindrical Faraday cup surrounding at least the upstream side of the holder and preventing escape of secondary electrons to the ground. A cylindrical reflector electrode provided at a peripheral portion in the Faraday cup and to which a negative voltage is applied with reference to the Faraday cup; and a cylindrical reflector electrode provided so as to face the Faraday cup and a side surface of the reflector electrode. A plasma shower device that is provided outside the Faraday cup and generates plasma and introduces the plasma into the reflector electrode through the hole of the Faraday cup and the reflector electrode; and a plasma shower device that is provided at an entrance of the Faraday cup. Negative voltage is applied with respect to the Faraday cup, and the ion beam passes A suppressor electrode having a hole, wherein the ion beam is applied to the substrate on the holder through the hole of the suppressor electrode, the inside of the Faraday cup, and the inside of the reflector electrode. There is provided a lid with a hole for passing, and
Between the inlet of the Faraday cup and the suppressor electrode
Positive voltage is applied with respect to the Faraday cup
Having an aperture through which the ion beam passes
An ion irradiation device provided with a suppressor electrode .