JPH0793123B2 - Ion implanter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ion implantation apparatus.

(Prior Art) As is well known, in this kind of device, the ions extracted from the ion source are analyzed by a mass spectrometer using a magnetic field to analyze desired ions, and then the ions are injected into a target through a slit and an acceleration tube. I have to.

By the way, the mass number of ions analyzed by the above-described magnetic field mass spectrometer is proportional to the square of the magnetic flux density in the magnetic field, and is inversely proportional to the extraction voltage for extracting ions in the ion source apparatus. Since the magnetic flux density has a functional relationship with the coil current supplied to the analysis magnet coil, it can be said that the mass number is proportional to the square of the coil current and inversely proportional to the extraction voltage.

Therefore, conventionally, one of the extraction voltage, the magnetic flux density of the mass spectrometer or the coil current is detected, and the calculation unit performs the required calculation based on this, and the coil current is appropriately adjusted based on the calculation result. It is controlled so that ions having a desired mass number are analyzed by the mass spectrometer.

By the way, in this type of device, the ion source, the mass spectrometer, etc. are installed in the high voltage part determined by the acceleration voltage applied to the accelerating tube, so the information signals from these are transmitted to the calculation part in the low voltage part. However, it is common to convert this information signal into an optical signal and then transmit it to a low voltage portion using an optical transmission system.

However, since such an optical transmission system contains glass inside, an abnormality such as breakage may occur depending on the usage condition. When such an abnormality occurs, an erroneous information signal will be transmitted, and therefore, the erroneous calculation may be performed in the arithmetic unit, which may continue to implant ions having an erroneous mass value. .

(Problems to be Solved by the Invention) In the present invention, in an ion implantation apparatus equipped with a mass spectrometer by a magnetic field, even when an information signal is transmitted to an arithmetic unit using an optical transmission system, the abnormality of the optical transmission system is detected. The purpose is to allow detection and thus to accurately select the desired ionic species.

(Means for Solving Problems) The present invention is an arithmetic element of an arithmetic expression for determining a mass value by mass spectrometry, which is an information signal for at least one of a coil current and a magnetic flux density of a mass spectrometer,
And the information signal about the extraction voltage in the ion source is transmitted by the optical transmission system to the arithmetic unit at the low voltage portion, and the information signal transmitted from the optical transmission system of the abnormality detection target of the optical transmission system is targeted. It is characterized in that it is constantly compared with the reference signal and the abnormality of the optical transmission system as the abnormality detection target is monitored by the comparison.

(Embodiment) An embodiment of the present invention will be described with reference to the drawings. The first embodiment shown in FIG. 1 is a configuration intended for an abnormality of a signal transmission system regarding magnetic flux density. In FIG. 1, 1 is an ion source device, and 2 is an extraction voltage for extracting ions therefrom. Drawout power source, 3 is a slit part, 4 is a mass spectrometer,
The magnet portion 5 and the coil 6 are mainly configured. These are located in the high voltage area. Reference numeral 7 is an accelerating tube, and 8 is an accelerating power source for generating an accelerating voltage.

The optical signal in which the value of the voltage of the extraction power source 2 (extraction voltage) is converted is transmitted to the low voltage portion by the optical transmission system 9. The transmitted optical signal is converted by the telemeter 10 into an electric information signal corresponding to the extraction voltage, and given to the arithmetic unit 11.

The calculation unit 11 calculates a mass value according to a predetermined calculation formula based on an information signal from another telemeter 12 described later and the above-mentioned information signal from the telemeter 10. Ions selected based on the calculation result are displayed on the display unit 13.

When the desired ion species is not selected according to the above calculation result, a control command is given from the calculation unit 11 to the coil power supply (not shown) via another optical transmission system (not shown) to obtain the desired magnetic flux density. Control is performed so that the ion species of is selected.

The above configuration is not different from the normal one.
According to the present invention, in the embodiment shown in the figure, the case where the magnetic flux density is selected as one of the information signals is shown. Therefore, two Hall elements 14 and 15 are installed inside the magnet unit 5 at positions close to each other. . The electrical information signal corresponding to the magnetic flux density sensed by each Hall element is
It is amplified by 7 and converted into an optical signal. After that, they are transmitted by separate optical transmission systems 18 and 19.

The transmitted optical signal is received by the telemeters 12 and 20, where it is again converted into the electrical information signal.
Then, as described above, the output from the telemeter 12 is calculated as one calculation element of the calculation formula for calculating the mass value.
Given to 11. The outputs from both telemeters 12 and 20 are given to a comparator 21 where they are compared. When there is a difference between the two output values, it is determined that an abnormal state has occurred, and an output is output.

In the above configuration, if an abnormality occurs in any one of the Hall elements 14 and 15 or the optical transmission system 18 and 19, a difference occurs in the output from the telemeters 12 and 20. . An output is output from the comparator 21 based on this difference, which confirms that an abnormality has occurred in the measurement system. An abnormality is displayed based on the output from the comparator 21, and an interlock for stopping ion implantation is applied.

The second embodiment shown in FIG. 2 is intended for the abnormality of the signal transmission system with respect to the coil current flowing through the coil 6. In FIG. 2, 22 indicates a power source for supplying the coil current. Resistors 23 and 24 are inserted therein to detect the coil current from the respective resistors.

Even in this case, if there is an abnormality in the signal transmission system relating to one of the coil currents, a difference will occur in the outputs of both telemeters 12 and 20, so it can be confirmed that an abnormality has occurred in the measurement system.

The third embodiment shown in FIG. 3 is a configuration for the abnormality of the signal transmission system regarding the pull-out voltage of the pull-out power supply 2,
In this configuration, the information signal from the extraction power source 2 is transmitted to the telemeter 10 by the optical transmission system 9, but the extraction voltage is fixed unless the ion species is changed. Therefore, the output of the telemeter 10 is a constant voltage by the comparator 21. It should be compared with. Reference numeral 25 denotes a voltage terminal to which this constant voltage is applied.

Even in this case, if there is an abnormality in the signal transmission system of the extraction voltage, a difference will occur in the outputs of both telemeters 12 and 10,
It will be confirmed from now on that an abnormality has occurred in the measurement system.

(Effect of the Invention) As described in detail above, according to the present invention, the information signal necessary for the calculation for selecting the ion species is utilized by using the optical transmission system
When transmitting to the calculation unit for calculating the mass value in the low voltage part, when an abnormality occurs in the optical transmission system of the abnormality detection target, it becomes possible to immediately detect this.
Therefore, even when a required information signal is transmitted using the optical transmission system, it is possible to reliably select a desired ion species.

[Brief description of drawings]

1 to 3 are circuit diagrams each showing an embodiment of the present invention. 1 ... Ion source device, 2 ... Extraction power source, 4 ... Mass spectrometer, 5 ... Magnet part, 6 ... Coil, 9,18, 19 ...
… Signal transmission system, 10,12,20 …… Telemeter, 11 …… Computing unit, 21 …… Comparator, 22 …… Coil power supply, 23,24 ……
resistance,

Claims (1)

[Claims] 1. An ion source device, a mass spectrometer for analyzing desired ions by a magnetic field from ions extracted from the ion source device, and ions accelerated and injected into a target by the ions analyzed by the mass spectrometer. In an ion implanter having an accelerating tube, the ion source device and the mass spectrometer being installed in a high-voltage part determined by an accelerating voltage applied to the accelerating tube, a calculation unit for calculating a mass value is provided in a low-voltage part. Installed in, is an arithmetic element of the arithmetic expression for determining the mass value to be mass analyzed, the information signal about at least one of the coil current or magnetic flux density of the mass spectrometer,
And an information signal about an extraction voltage in the ion source device, each of which is provided with an optical transmission system for transmitting to the arithmetic unit, and an information signal transmitted by the optical transmission system of the abnormality detection target in the optical transmission system. An ion implantation apparatus is provided with a comparing means for constantly comparing the target reference signal with a target voltage, and monitoring the abnormality of the optical transmission system subject to the abnormality detection based on the comparison result by the comparing means.