JPS5917498B2 - Ion implantation device - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to improvements in ion implantation equipment.

[Background of the Invention] Currently, low-voltage arc discharge and microwave discharge methods are in practical use5 as ion sources for ion implantation devices, but in both cases, high-pressure discharge (positive high-voltage accelerating electrode and There is also the problem of discharge between negative voltage deceleration electrodes, and there is no solution to this problem with current technology.

[Object of the Invention] It is an object of the present invention to provide an ion implantation device that takes into consideration the above-mentioned problems.

[Summary of the Invention] In order to achieve the above object, in the present invention, a sample is placed on a rotatable disk, and the ion beam emitted from the ion source is transmitted by vertically moving the disk.
In an ion implantation device that implants uniformly onto a workpiece surface, when the ion beam is interrupted due to discharge of an accelerating voltage in the ion source during implantation, the interruption time ensures desired implantation uniformity. If it is less than the allowable time width, the implantation continues until i0; if the allowable time width is exceeded, the ion beam path is cut off and the feeding is stopped at the same time, and when the ion beam recovers, the implantation is uniform. It is constructed so that it can be re-inserted to ensure its integrity.

j5 [Embodiments and effects of the invention] Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 shows a rotary scanning type ion implantation apparatus according to an embodiment of the present invention. An ion beam 2 emitted from an ion source 1 is implanted onto the surface of a sample i0 placed on a rotating disk 3. Here, the disk 3 rotates at a constant speed from the electric motor 5 and the electric motor 6
Further, vertical driving is performed via the transmission jig T. however,
It is assumed that the rotational speed of the disk 3 is much faster than the vertical speed. In normal implantation, in order to obtain uniformity of implantation into the sample 4, the radial position R of the beam i52 on the disk 3 is measured by the measuring device 8, and the radial position R of the beam i52 on the disk 3 is measured via the A/R calculator (where A is a feed rate constant).
The vertical feed is inversely proportional to the radius. Next, the concept of operation when a discharge occurs during implantation will be explained with reference to FIGS. 2 and 3, and then the circuit of FIG. 1 will be explained.

FIG. 2 shows the vertical feeding operation during driving, and the horizontal axis is the radius R of the disc 3 relative to the beam 2 (however, the right side of the figure is the inner diameter side of the disc 3).

), the vertical axis represents the feed rate A/R. For driving, set the feed to R.
Characteristic diagram 24 shows changes in feed speed when the feed speed is set from 1 to R5. Further, in the same figure, it is assumed that the range from R2 to R4 is the A/R characteristic, and sample 4 exists between these. Now, during implantation, the discharge exceeded radius R3 (beam 2 was interrupted)
In this case, as soon as the shielding plate 17 (17 in FIG. 1) closes, the feed descends as indicated by the dotted line 25 and stops. If the discharge stops and the beam 2 recovers and you want to re-implant it, feed it backwards so that it sufficiently exceeds R3 as shown by the dotted line 26, and then repeat the dotted line 2.
As shown in 7, when the discharge occurs on the A/R feed rate characteristic 24 and the beam 2 is interrupted at the point R3, the shielding plate 17
Open the door and resume driving to ensure uniformity of driving. However, in actual implantation, the discharge is often instantaneous and it is inefficient to repeat the above operations.

Therefore, if the discharge time (the time during which the beam 2 is interrupted) is short and the desired uniformity can be ensured, it is better to continue the implantation as it is, and this will be explained with reference to FIG. FIG. 3 shows the change 28 in implantation current value, with the horizontal axis representing time t and the vertical axis representing implantation current 1. In FIG.

In the figure, the discharge below the allowable time width Twe that is below the implantation uniformity is the discharge at times 11 and T2 (TWl, tW2 and Twe).
) in this case, the input continues. T3 hour discharge (
TW3>Twe) is greater than the allowable time width, so the second
The re-driving operation explained in the figure is started, and the driving is restarted at time T4. However, the dotted line portion of the current change 28 in the figure indicates the return current value of the beam 2 while the shielding plate 17 is closed. In the circuit shown in FIG. 1, the current applied from the disc 3 is detected by the current amplifier 10, and the comparator 11 detects the applied current error (discharge or no discharge). When an error occurs when a discharge occurs, the output signal of the comparator 11 is detected by an error time width control circuit 12 consisting of a signal delay circuit 13 and an AND circuit 14.
In addition to this, when the allowable time width of the implantation uniformity explained above in FIG. 3 is exceeded, an output signal of the control circuit 12 is obtained. The output of the control circuit 12 is connected to flip-flop circuits 15 and 1.
6 is set, the shield plate 17 is closed to cut off the beam 2, and the switch 18 is switched from A to A to stop the vertical drive. Moreover, at the same time, the output signal of the control circuit 12 is
The gate of the AND circuit 19 is opened and the radius R position at the time of error occurrence is set in the storage register 20 from the measuring device 8. The circuit operation during discharging is performed as described above, and the implantation is temporarily interrupted. To resume driving after beam 2 recovers,
Reverse feed signal generation circuit 2 for vertical feed by pressing switch 21
2 is operated, and the disk 3 is fed through the electric motor 6 for a suitable time in the opposite direction to the feeding direction during driving (the feeding time indicated by the dotted line 26 in FIG. 2). When the reverse feed is completed, the signal generating circuit 22 resets the flip-flop circuit 16, switches the switch 18 from open to A, and switches the vertical feed to A/R feed. Subsequently, the output value of the register 20 and the output value of the measuring device 8 are compared by the matching circuit 23, and when a match is found (R in FIG. 2;
The flip-flop circuit 15 is set to the discharge position), the shielding plate 17 is opened, and the implantation of the beam 2 is resumed. The method of the present invention described above can be applied to a uniform implantation method against discharge errors in a general ion implantation device.

FIG. 4 is a diagram for explaining an application example of the present invention, and shows an example of an electric field scanning type ion implantation apparatus.

In the figure, a beam 2 emitted from an ion source 1 is swung horizontally by voltage changes applied to two deflection electrode plates 29 and is implanted into a sample 4 placed on a substrate 30, and the substrate 30 is moved to the ground. It is something to do. In the system shown in the figure as well, by providing the error time width control circuit and the vertical position reproduction control circuit described in FIG. 1, it is possible to compensate for the implantation efficiency and implantation uniformity with respect to discharge.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2 and 3 are characteristic diagrams for explaining the operation of the present invention, and FIG. 4 is a diagram showing an example of application of the present invention. .

Claims (1)

[Claims] 1. An ion implantation device in which a sample is placed on a rotatable disk, and the disk is fed so that the ion beam emitted from the ion source is uniformly implanted onto the sample surface,
When the ion beam is interrupted due to discharge of the accelerating voltage in the ion source during implantation, if the interruption time is less than the allowable time width that guarantees the desired implantation uniformity, the implantation is continued as is, and the ion beam is interrupted. If the interruption time exceeds the allowable time width, the ion beam path is interrupted and the feeding is stopped at the same time, and when the ion beam is recovered, implantation can be performed again to ensure implantation uniformity. An ion implantation device characterized by: