JPH06111751A - Ion implantation device - Google Patents

Abstract

PURPOSE:To uniformly return the secondary electrons generated from a specimen toward the surface of specimen upon stabilizing in terms of space and time. CONSTITUTION:As a secondary electron feedback means, a Faraday gauge 5 is installed in the neighborhood of the front surface of a specimen 3 held on a stage 2, wherein the Faraday gauge 5 is prepared by forming a conductive film 5c over the inner surface of a cylindrical body 5a with an insulative film 5b interposed. Thereby a constant potential is held over the whole area of the conductive film 5c when secondary electrons are accumulated on the film 5c within the gauge 5 at the time of ion beam implantation, and the potential is obtained which is stable even in terms of the space.

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 for irradiating a sample such as a semiconductor wafer with an ion beam to perform ion implantation, and particularly, to prevent charge-up on the sample surface during ion implantation. It is about structure.

[0002]

2. Description of the Related Art Conventionally, as an ion implanter of this type, there is an ion implanter disclosed in Japanese Patent Laid-Open No. 63-299043. FIG. 2 is a schematic cross-sectional view showing the structure in the vicinity of the front surface of the sample table of this conventional ion implantation apparatus. In the figure, 1 is an ion beam generated by an ion beam generator (not shown), 2 is a sample stage, 3 is a sample such as a semiconductor wafer held on this sample stage 2, 4
Are secondary electrons generated when the ion beam 1 is applied to the sample stage 2 or the sample 3, that is, when the ion beam is injected. Reference numeral 6 denotes a Faraday cup having a rectangular cylindrical shape so as to surround the sample 3. The Faraday cup 6 is composed of a cylindrical cup body 6a and an insulating film 6b formed on the inner surface thereof. Reference numeral 7 is an electrode for returning the secondary electrons 4 generated at the time of ion beam implantation into the Faraday cup 6, and this electrode 7 is given a predetermined negative potential from the DC power source 8 to the Faraday cup 6. Reference numeral 9 is an ammeter that measures the ion implantation amount flowing in the sample 3 as an ion current.

By the way, such an ion implanter is used in the process of manufacturing the MOS transistor shown in FIG. 3, for example, but when forming the field 13 or channel 14 of the transistor, B is used.
⁺ Ions and P ⁺ (As ⁺ ) ions are implanted, and As ⁺ ions are implanted to form the source 15 and the drain 16. In either case, since ions having a positive charge are implanted into the wafer 3 as a sample, when a resist 17 or a high resistance insulator such as the SiO ₂ oxide films 10 and 11 exists on the surface of the wafer 3. Is positively charged. When the charging potential becomes high, the resist 17 and the SiO ₂ oxide films 10 and 11 are destroyed or damaged, and the characteristics as a semiconductor device are deteriorated.

On the other hand, when the sample stage 2 or the wafer 3 is irradiated with the ion beam 1, secondary electrons 4 are generated. This 2
The secondary electrons 4 neutralize when they collide with the ions accumulated on the surface of the wafer 3, so that the charge on the surface of the wafer 3 is reduced. If the insulating film 6b is provided on the inner surface of the Faraday cup 6, the secondary electrons 4 initially charge on the insulating film 6b to form a negative potential, but when the negative potential becomes about 100V,
The secondary electrons 4 cannot be accumulated in the insulating film 6b, are repelled and are returned to the wafer 3, and as a result, the chances of colliding with the ions are increased and the charging is reduced. Negative potential 10 on electrode 7
Even if a voltage of about 0 V is applied, the secondary electrons 4 similarly repel and return to the direction of the wafer 3. In addition, in FIG.
0 is a field oxide film, 11 is a gate oxide film, and 12
Is the gate.

[0005]

As described above, in the conventional ion implantation apparatus, the Faraday cup 6 arranged in the vicinity of the front surface of the sample stand or the sample is covered with the insulating film 6b, and the sample is formed on the insulating film 6b. The secondary electrons generated from the table and the sample are accumulated and negatively charged, so that the secondary electrons are returned to the sample side. However, since the state of the surface of the insulating film 6b in the Faraday cup 6 is not uniform, for example, the surface resistivity is not uniform, the charged electric charge amount is not uniform, and a part where the charging potential is high or a part where the charging potential is low occurs. There are places where it is difficult to repel electrons and return them to the sample side, which causes device damage due to wafer charging. The present invention has been made to solve the above-mentioned problems, and secondary electrons generated from the sample stage or sample can be uniformly and spatially and temporally pushed back toward the sample surface. The purpose is to obtain an ion implanter.

[0006]

An ion implanting apparatus according to the present invention comprises a conductive cylindrical main body formed to surround an ion beam in the vicinity of the front surface of a sample or a sample table, and an inner surface of the cylindrical main body. A secondary electron feedback means including the formed insulator and a conductive film formed on the inner surface of the insulator is provided. Further, an ion implantation apparatus according to another invention of the present invention comprises an insulating cylindrical main body formed to surround an ion beam near the front surface of a sample or a sample table, and an inner surface of the cylindrical main body. The secondary electron feedback means made of a conductive film is provided.

[0007]

In the present invention, secondary electrons generated when the sample or sample stage is irradiated with the ion beam are formed by interposing an insulator on the inner surface of the cylindrical main body constituting the secondary electron returning means. The conductive film or the conductive film itself formed on the inner surface of the insulating cylindrical body is momentarily charged up and the potential rises up to the energy of secondary electrons, after which it exits from the sample or sample stage. Secondary electrons are pushed back toward the sample. As a result, neutralization occurs on the sample surface, the charging potential is suppressed, and electrostatic breakdown is prevented.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the main structure showing an embodiment of the ion implantation apparatus according to the present invention. In this embodiment, the ion beam 1 is applied to the sample 3 held on the sample table 2 to perform ion implantation, which is similar to the conventional example shown in FIG. A conductive tubular body 5a, an insulating film 5b such as a silicon oxide film or a silicon nitride film coated on the inner surface of the tubular body 5a, and a surface of the insulating film 5b are formed in the vicinity of the front surface of the sample 3. Further, a Faraday gauge 5 made of a conductive film 5c of aluminum, copper or the like is provided to constitute a secondary electron returning means. Then, an electrode 7 is arranged adjacent to the Faraday gauge 5, and a predetermined negative potential from the potential of the Faraday gauge 5 is applied to the electrode 7 from a DC power source 8. The secondary electrons 4 generated when the laser beam 3 is irradiated are returned to the sample side. In the drawings, the same reference numerals indicate the same or corresponding parts.

In the structure of the above embodiment, when the sample stage 2 or the sample 3 is irradiated with the ion beam 1, the sample stage 2
And the secondary electrons 4 are generated from the sample 3. This secondary electron 4
When some of these occur, some of them reach the conductive film 5c formed on the inner surface of the Faraday gauge 5, and the conductive film 5c
c is negatively charged, and its charging potential rises to the energy of secondary electrons. However, after that, the secondary electrons 4 emitted from the sample stage 2 and the sample 3 are pushed back to the surface of the sample 3 by this charging potential. As a result, the charge-up of the sample during ion implantation, that is, the surface of the wafer 3 can be suppressed and electrostatic breakdown can be prevented.

By the way, in the structure of the conventional example shown in FIG. 2, when the inner surface of the Faraday cup 6 is covered with the insulating film 6b as described above, the secondary electrons 4 are accumulated on the insulating film 6b and charged. However, when the energy of the secondary electrons 4 is reached, the secondary electrons 4 will then repel, but it is difficult to keep the surface state of the insulating film 6b uniform, and insulators, metals, etc. will adhere. Then the surface condition changes. Therefore, it is difficult to make the accumulation of the secondary electrons 4 on the insulating film 6b constant spatially and temporally, the secondary electrons 4 cannot always be returned to the sample 3 side in the same state, and the device yield is high. Was uneven.

Therefore, according to one embodiment of the present invention, FIG.
As shown in FIG. 3, the inner surface of the main body of the Faraday gauge 5 is covered with the insulating film 5b, and the conductive film 5c is formed on the surface of the insulating film 5b. Therefore,
When the secondary electrons 4 are accumulated on the conductive film 5c by forming the conductive film 5c on the surface of the insulating film 5b forming the Faraday gauge 5, the conductive film 5c is insulated by the insulating film 5b. Therefore, a constant potential is maintained at any position of the conductive film 5c, and a spatially stable potential is exhibited. Therefore, the secondary electrons 4 can be fed back to the sample surface side stably and spatially and uniformly.
As a result, the effect of stabilizing the productivity of the device can be obtained by suppressing the charge-up on the surface of the sample and preventing electrostatic breakdown.

Although the Faraday gauge 5 is used as the secondary electron returning means for returning the secondary electrons 4 to the sample 3 side in the above embodiment, the present invention is not limited to this. A structure comprising an insulating tubular body formed to surround the beam 1 and a conductive film formed on the inner surface thereof or a conductive tubular body provided on the inner surface thereof is used as a secondary electron feedback device. Even if it is arranged in the vicinity of the front surface of the sample 3 as a means, the same effect as that of the above-mentioned embodiment can be obtained, and in the case of a conductive cylindrical body, the cleaning work of the portion becomes easy.

[0013]

As described above, according to the present invention, in the ion implantation apparatus, as secondary electron returning means for returning the secondary electrons generated from the sample stage or sample at the time of ion beam implantation to the sample side, By covering the inner surface of the cylindrical main body with an insulator and forming a conductive film on the surface of the insulator, or by forming a conductive film on the inner surface of the insulating cylindrical main body, a secondary electron is formed. Is accumulated in the conductive film, a constant potential is maintained at any place of the conductive film, and a spatially stable potential is exhibited. For this reason,
Secondary electrons can be returned to the sample surface side uniformly in a spatially and temporally stable manner. As a result, the charge potential on the surface of the sample can be suppressed, and highly accurate ion implantation that does not cause electrostatic breakdown can be performed.

[Brief description of drawings]

FIG. 1 is a main configuration diagram showing an embodiment of an ion implantation apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a conventional ion implantation apparatus.

FIG. 3 is a MOS device structure diagram created by using an ion implantation apparatus.

[Explanation of symbols]

 1 Ion beam 2 Sample stage 3 Sample (wafer) 4 Secondary electron 5 Faraday gauge 5a Cylindrical body 5b Insulating film 5c Conductive film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shintaro Matsuda 4-1-1 Mizuhara, Itami City, Hyogo Prefecture Mitsubishi Electric Co., Ltd. Kitaitami Works (72) Inventor Hirohisa Yamamoto 4-1-1 Mizuhara, Itami City, Hyogo Mitsubishi Electric Corporation Company Kita Itami Works (72) Inventor Katsuo Naito 47 Umezu Takaunecho, Ukyo-ku, Kyoto City, Kyoto Prefecture Nissin Electric Co., Ltd.

Claims (2)

[Claims] 1. An ion implantation apparatus for irradiating a sample with an ion beam to perform ion implantation, wherein a conductive tube is formed in the vicinity of the front surface of the sample or a sample table on which the sample is held so as to surround the ion beam. An ion implantation device comprising a cylindrical body, an insulator formed on the inner surface of the tubular body, and a conductive film formed on the inner surface of the insulator. 2. An ion implantation apparatus for irradiating a sample with an ion beam to perform ion implantation, wherein an insulating tube is formed near the front surface of the sample or a sample table on which the sample is held so as to surround the ion beam. An ion implantation device comprising a cylindrical main body and a conductive film formed on the inner surface of the cylindrical main body.