JPH0574405A - Device and method for ion implanting - Google Patents

Abstract

PURPOSE:To suppress electrification of a wafer by controlling an electron shower in accordance with a position of the wafer with respect to an ion beam at the time of ion implantation. CONSTITUTION:This device is provided with a disk translation position detecting device 10 for detecting a translation position of a disk 1 during ion implantation, and an electron shower control device 11 for adjusting an electron shower quantity in synchronism with the detected position. The electron shower quantity is decreased when an ion beam 2 irradiates a periphery of a wafer 3, and is increased when the beam 2 irradiates the center thereof.

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 an ion implantation method, and more particularly to an apparatus and a method for suppressing electrostatic charge on a wafer during ion implantation.

[0002]

2. Description of the Related Art As shown in the partial front view of FIG. 4, a conventional ion implantation apparatus has a disk 1 having a plurality of wafers 3 mounted thereon.
While rotating at high speed, the disk 1 is translated according to the size of the wafer 3, and the ion beam 2 is irradiated to perform ion implantation. At this time, as a wafer charge suppressing device, an electron gun 4 and a metal target 6 are provided in the vicinity of the wafer 3 as shown in the vertical cross-sectional configuration diagram of FIG. Is generally used to suppress the electrostatic charge on the surface of the wafer 3.

Here, a method of controlling the amount of secondary electrons supplied will be described. Since the ion implantation is performed by irradiating the disk 1 on which a plurality of wafers 3 are mounted with an ion beam 2 of positive ions, a current (hereinafter referred to as a disk current) flowing from the disk 1 to the ground is detected by the disk ammeter 8. Here, the amount of electronic shower is adjusted so that the detected disc current value I _D becomes a set value (for example, zero). That is, the surface of the wafer 3 is charged with a positive charge by a certain time from the start of ion implantation. The disk current I _D flowing up to this point is integrated, and this is positively correlated with the amount of charge on the wafer. Assuming a certain value, the disk current I
_{When D} > 0, the amount of electron shower is increased to suppress positive charging, and when I _D <0, the amount of electron shower is decreased to suppress negative charging.

[0004]

The problems in the above-mentioned conventional ion shower device and electron shower control system of the ion implantation method will be described below. Conventionally, in ion implantation, as shown in FIG. 4, while rotating a plurality of disks 1 on which a plurality of wafers 3 are mounted at high speed, an ion beam 2 is applied to the wafers 3.
The scanning is performed according to the size of the disk. As this scanning method, a method of translating the disk 1 is generally used.

Here, in the conventional electronic shower control system using the disk current shown in FIG. 5, when the disk 1 is translated to a position where the ion beam 2 irradiates the vicinity of the center of the wafer 3, the disk current value I _D Becomes approximately equal to the beam current value I _B , and the ion beam 2
When the disk 1 is translated to a position where the laser beam irradiates the periphery of the wafer 3, the disk current value I _D is the beam current value I _D.
It is known from an experiment conducted by the inventor of the present application that the value increases about 5 times that of _B. This is the ion beam 2 during ion implantation.
This can be explained by the difference in the amount of secondary electrons emitted from the disk 1 irradiated on the disk. That is, when the area of the disk 1 irradiated with the ion beam 2 is relatively large, that is, when the periphery of the wafer 3 is irradiated with the ion beam 2,
When the amount of secondary electrons emitted from the disk 1 increases and the disk current value I _D exceeds the beam current value I _B , on the other hand, when the area of the disk 1 irradiated with the ion beam 2 is relatively small, that is, the wafer. When irradiating the vicinity of the center of No. 3, the amount of secondary electrons emitted from the disk 1 decreases, and the disk current value I _D decreases to about the beam current value I _B.

Therefore, when the ion beam 2 irradiates the vicinity of the center of the wafer 3, the disk current is small and the electron shower is small, while when the ion beam 2 irradiates the vicinity of the periphery of the wafer 3, the disk current is large. Even if the disk current I _D can be controlled to a set value (for example, zero) because a large amount of electronic shower is applied, it is not possible to efficiently control the positive charging in the central part of the wafer and the negative charging in the peripheral part. .. Therefore, there are problems that the uniformity of implantation is deteriorated and the insulating film on the wafer is broken.

[0007]

An ion implantation apparatus according to the present invention includes an electron shower including an electron gun and a target, a disk on which a wafer is irradiated with an ion beam, and a device for detecting a translational position of the disk. And an electronic shower controller that adjusts the amount of the electronic shower in synchronization with the detection position.

In the ion implantation method of the present invention, the amount of electron shower is reduced when the ion beam irradiates the periphery of the wafer and the amount of electron shower is increased when the center of the wafer is irradiated by using the above-mentioned apparatus. Is the method.

[0009]

The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional configuration diagram showing a charge control system of an ion implantation apparatus according to a first embodiment of the present invention. A translational position of a disk 1 during ion implantation is detected by a disk translational position detection device 10 and is determined according to the position. The system configuration is such that the electron shower control device 11 can control the electron gun 4 so as to obtain the amount of electron showers. As shown in FIG. 4, before the ion implantation is started, the disk 1 is previously rotated at a high speed of 500 to 1000 rpm at a position where the ion beam 2 is not irradiated, and the disk 1 is gradually translated to a position where the ion beam 2 is irradiated. Eventually, the ion beam 2 is irradiated onto the wafer 3 from the outer peripheral direction of the disk 1 toward the rotation center. Then, the wafer 3 starts to be irradiated with the ion beam 2.

The secondary electrons 7 thus obtained are maximized when the disk 1 translates to the position where the ion beam 2 irradiates the center of the wafer 3, and the disk 1 further translates in the direction of its own rotation center. The ion beam 2 is reduced as it moves away from the center of the wafer 3, and when the disk 1 translates to a position where the ion beam 2 does not irradiate the wafer 3, the emission of secondary electrons 7 is stopped. In this way, by generating the secondary electrons 7 according to the translational position of the disk 1, that is, the irradiation position of the ion beam 2 on the wafer 3, positive charging near the wafer center and negative charging near the wafer periphery are suppressed. Can be made In the experiment, under the condition that the arsenic ion implantation is performed with the acceleration energy of 70 keV and the beam current is about 10 mA, when the secondary electron is generated from about 5 mA and the ion beam irradiates the wafer center, the maximum value is about 30 mA. Good results have been obtained.

FIG. 2 is a sectional view showing the configuration of the second embodiment of the present invention. Similar to the first embodiment, the signal from the disk translational position detection device 10 is sent to the electronic shower control device 11 and the disk bias control device 12 that controls the variable voltage power supply 13 that applies a potential to the disk, and the signal is sent according to the translational position of the disk. A charge suppression system that changes the disk bias is used. That is, when the ion beam 2 irradiates the wafer 3, the disk bias is positively applied to attract the secondary electrons 7 generated by the electron shower to the disk 1, and the wafer 3 is suppressed from being positively charged. In the experiment, the disk bias was set in the range of +5 to -5 [V] to obtain a good image as in the first embodiment, and to generate 2
Since the secondary electron amount can be reduced as compared with the first embodiment,
The life of the electron gun and target can be extended.

[0012]

As described above, in the ion implantation apparatus and method of the present invention, the electron shower is not controlled by the disc current during the ion implantation, but the translation position of the disc, that is, the position of the wafer with respect to the ion beam is controlled. Since the electronic shower is controlled accordingly, the charging of the wafer surface can be effectively controlled. Therefore, FIG.
As shown in (a), the variation ratio of the implantation uniformity in the wafer surface is improved to about 1/2 when the conventional method and the apparatus are set to 1. Further, as shown in FIG. 3B, when the non-defective product ratio of the insulation film breakdown is taken and the conventional example is set to 1, the present invention improves to about 2.

[Brief description of drawings]

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

FIG. 2 is a vertical sectional view configuration diagram of a second embodiment of the present invention.

FIG. 3 is a diagram showing the effect of the present invention and is shown in FIGS.
Each is a comparison diagram with a conventional one.

FIG. 4 is a partial front view of a disk for explaining conventional ion implantation.

FIG. 5 is a vertical cross-sectional configuration diagram of a conventional ion implantation apparatus.

[Explanation of symbols]

 1 disk 2 ion beam 3 wafer 4 electron gun 5 primary electron 6 target 7 secondary electron 8 disk ammeter 9 beam receiver 10 disk translational position detection device 11 electronic shower controller 12 disk bias controller 13 variable voltage power supply

Claims (2)

[Claims] 1. An ion implantation apparatus having an electron shower including an electron gun and a target for suppressing electrification, and a disk on which a wafer to be irradiated with an ion beam is mounted, the disk detecting a translational position of the disk during ion implantation. An ion implantation apparatus comprising: a translational position detecting device; and an electron shower suppressing device that adjusts the electron shower amount in synchronization with the detected position. 2. An ion implanting device, wherein the amount of electron shower is reduced when an ion beam irradiates the periphery of a wafer and the amount of electron shower is increased when irradiating the center of the wafer. Method.