JPS5842584B2 - Ion implantation device - Google Patents

Description

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

A fan-shaped magnetic field is used for mass separation in an ion implanter, especially in a high current beam (mA) ion implanter.

FIG. 1 is a diagram showing a conventional ion implantation device.

In the figure, an ion beam 2 emitted from an ion source 1 is deflected by a fan-shaped magnetic field (consisting of a magnetic field generating coil) 3 controlled by a magnetic field power supply 4, and only desired ion species pass through the gap between mass separation slits 5 and 60. and reaches the Faraday cup 9 on the driven side.

The correction slit 7.8 captures the ion current at the side edge of the beam, detects the drift of the deflection beam axis from the current difference between the two slits, and returns it to the magnetic field power source 4 to correct the magnetic field strength of the fan-shaped magnetic field 3.

In the figure, 10 is a differential amplifier, 11 is a magnetic field setting voltage source, and 12 is an output amplifier.

By the way, the spread shape (spread angle) of the ion beam 2 emitted from the ion source 1 depends on the beam extraction accelerating voltage in the ion source 1, the gas pressure (gas pressure of the implanted ion species data), the electric power required for plasma ion generation, and the extraction Depends on the electrode structure.

For this reason, the beam width at the correction slit 7.8 also changes, but at this time, the correction slit 7.8 always produces a small ion current that has almost no effect on the size of the ion beam reaching the Faraday cup 9. It is desirable to be in a position that allows you to capture the

However, in the conventional apparatus, it is not easy to detect the beam spread width, and as the beam width changes depending on the state of the ion source as described above, it is difficult to position and fix the correction slit.

In addition, in conventional devices, the correction slit is fixed, and its fixed position needs to be fixed at the beam width gap with the minimum width among the expected beam width changes. If it is fixed, a beam narrower than that will drift between the correction slits.

), a wider beam has the disadvantage that more ion current is consumed at the correction slit walls.

Furthermore, fixing the correction slit as described above has various drawbacks, such as the fact that the ion density distribution in the beam cross section changes under the influence of the fan-shaped magnetic field, so that a wider beam becomes smaller than the maximum beam current that can be obtained in the gap between the correction slits.

The present invention has been made in view of the above points, and provides an ion implantation apparatus that can extremely easily minimize the loss of the implantation beam and perform drift correction control of the fan-shaped magnetic field. .

Hereinafter, the present invention will be explained with reference to Examples.

FIG. 2 is a diagram showing an embodiment of the present invention.

In the figure, an ion beam 2 emitted from an ion source 1 is deflected by a fan-shaped magnetic field (consisting of a magnetic field generating coil) 3 controlled by a magnetic field power source 4, and only desired ion species pass through the gap between mass separation slits 5 and 6. It passes through and reaches the Faraday cup 9 on the side to be driven.

Correction slit? ', 8' captures the ion current at the side edge of the beam, detects the drift of the deflection beam axis from the current difference between both slits, and returns it to the magnetic field power source 4 to correct the magnetic field strength of the fan-shaped magnetic field 3.

In the initial state, switches 18, 19, 20°21.
22 has each contact as shown in the figure, and switch 1
8, 19, and 20 are assumed to be interlocked with the relay 15.

First, a desired ion species beam to be implanted into the Faraday cup 9 is adjusted and set by the voltage source 23, and is obtained by driving the magnetic field power source 4 via the amplifier 17.

Correction Surin)? ', 8' are connected to drive mechanisms (drive mechanisms combined with servo motors, etc.) 10 and 11, and can be driven perpendicular to the beam axis, and the beam combination ratio is determined by control circuits 24 and 25. controlled.

Now, taking the slit 7' as an example, the value of the voltage source 12 (VR
) determines the beam combination ratio of the slit 7', and the differential amplifier 13 adjusts the driving mechanism 1 so that the current value (IR) from the slit 7' and the value (VR) of the voltage source 12 are equal.
Multiply feedback by 0.

At this time, the voltage comparator 14 detects the zero output voltage of the differential amplifier 13 and causes the relay 15 to operate differentially.

Here, the relay 15 switches the switch 18 to the ground side to stop the drive mechanism 10 and fix the slit 7', and closes the switch 19 to maintain itself.

Furthermore, the relay 15 connects the contacts of the switch 20 to the differential amplifier 1.
Switch to the output side of 6.

On the other hand, in the case of the slit 8', the same operation is performed by the control circuit 25 having exactly the same circuit as the control circuit 24, and the slit 8' is fixed in conjunction with the relay (equivalent to the relay 15) in the control circuit 25, and the switch 21 is switched to the switch 20 side.

After that, the difference in the beam intake currents (IR, It,) between the slit 7' and the slit 8' is amplified by the differential amplifier 16, and the value added to the value of the voltage source 23 is added to the amplifier 17.
The magnetic field is applied to the magnetic field power source 4 via the magnetic field source 4, and beam drift correction is performed.

Furthermore, switch 22 is used to return the control system shown in the figure to its initial state.
It can be obtained by opening from ground once.

Thus, according to the invention, the correction slits 7', 8'
By combining these with the drive mechanisms io and i1 and controlling the beam combination ratio by the control circuits 24 and 25, it is possible to extremely easily minimize the loss of the implanted beam and perform drift correction control of the fan-shaped magnetic field 3.

[Brief explanation of the drawing]

Fig. 1 shows a conventional ion implantation device, and Fig. 2 shows a conventional ion implantation device.
FIG. 1 is a diagram showing an embodiment of the present invention. 1 ion source, 2... ion beam, 3... fan-shaped a field, 4... magnetic field power supply, 5, 6... mass separation slit,
7,7:8.8...Correction slit, 9...Faraday cup.

Claims (1)

[Claims] 1. An ion source that emits an ion beam, a mass separation means that forms a fan-shaped magnetic field to deflect the ion beam, separates desired ion species by mass, and sends them to a Faraday cup; the mass separation means and the Faraday cup; a correction slit means which captures the ion current at the side edge of the ion beam and is movable in a direction perpendicular to the beam axis of the ion beam, and the detected ion current is used to adjust the beam width of the ion beam. control circuit means capable of driving and controlling the correction slit means so as to minimize the amount of beam coupling accordingly; and correction for correcting the magnetic field strength of the fan-shaped magnetic field by detecting a drift of the deflection beam axis from the detected ion current. An ion implantation device comprising a control circuit means.