JPS5945174B2 - Analysis magnet control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analysis magnet control device that facilitates the selection of ions in an ion implantation device and reliably extracts desired ions.

Generally, ion selection in an ion implantation apparatus involves changing the strength of the magnetic field of a mass spectrometer magnet to extract desired ions. Now, to explain the principle,
Charge q) An ion of mass m that is incident at right angles to the magnetic field with velocity vo traces a circular motion with a radius of = -0-.

Here, B is the strength of the magnetic field. Further, the velocity of the incident ion, vo, is expressed by Vo, where V is the accelerating voltage.

yotsuteni = dan Ku ~ / qB2 becomes.

Also, the magnetic field strength B is μN1 B=- It is expressed as

Here, μ is the magnetic permeability of the conductor, N is the number of turns of the coil wound around the magnet, ι is the length of the magnetic path, and I is the current flowing through the coil. It becomes yottete.

In the case of an ion implanter, the current 1 applied to the analysis magnet is changed to change the circular orbit of the ions and extract desired ions.

The control circuit for an analysis magnet, which is often used in conventional ion implanters, is shown in Figure 1 and explained. Ions are selected by changing the strength of the magnetic field by changing the current flowing through the coil of the analysis magnet 14. , the desired ions were selected.

In the figure, 1 is a variable resistor connected in series to a power supply 2, 3 is an operational amplifier that receives the output of the variable resistor 1, and one input terminal of the operational amplifier 3 is connected to the variable resistor 1.
The other input end is connected to the output end via a resistor 4, and is grounded via a resistor 5. 6 is a comparator, one input terminal of this comparator 6 is connected to the output terminal of the operational amplifier 3 via a resistor 7,
Voltmeter 9 and feedback resistor 1 via resistor 8
2, and the other input end is grounded.

The output terminal of the comparator 6 is connected to the base of a driving NPN transistor 10 whose collector is connected to the positive side of the power supply 2. 11,,11,...11
.

are NPN transistors connected in parallel, the commonly connected collectors of these transistors 11, to 11n are connected to the positive electrode side of the power supply 2, and the commonly connected emitters are connected to the voltmeter 9, and Connect to feedback resistor 12. The base of the transistor 111 is connected to the emitter of the transistor 10, and is also connected via a resistor 13 to the bases of the transistors 11, to 11n, respectively. Reference numeral 14 denotes an analysis magnet connected between the negative electrode side of the power supply 23 and ground. - This analysis magnet 14 has a function of selecting ions for the ion implantation device.

15 is a motor or a manual knob for moving the variable resistor 1.

In the control circuit of the ion implanter having such a configuration,
First, when the resistance value of the variable resistor 1 is changed by a motor or manually, the change is amplified by the operational amplifier 3 and its output is inputted to the comparator 6 manually.

On the other hand, since no voltage is initially generated across the feed pack resistor 12, the voltage fed back to the comparator 6 via the resistor 8 is zero. Therefore, an output appears on the output side of the comparator 6 that increases the current flowing through the analysis magnet 14, causing transistors 1 and 0 and transistors 111 to 11n to operate. Here, the current flowing through the analysis magnet 14 increases until the voltage from the operational amplifier 3 and the feedback voltage become equal, and when they become equal, the current stops increasing. Therefore, to select a desired ion, the current of the analysis magnet 14 can be changed by turning the motor or manual knob 15, and the desired ion can be selected. However, the problem here is that impurity gases or solids used in ion implantation devices are rarely composed only of the desired impurity, and generally form compounds with other substances.

Therefore, when these gases and solids are ionized, various ions are created. When you draw these spectra, you will find that some of them have peaks of other unnecessary ions right next to the peak of the desired ion, and if you are not careful enough, you may end up choosing the wrong ion. Also,
The power supply for the analysis magnet 14 is not very stable, and even when the ion beam is set at the highest point, it may shift. Further, in the comparator 6 in FIG. 1, the voltage generated when the variable resistor 1 is turned is compared with the voltage appearing across the feedback resistor 12. That is, the operation of this comparator 6 is similar to that of the operational amplifier 3.
The output voltage is generated at the feedback resistor 12.
A voltage of opposite polarity to the output voltage of the operational amplifier 3 is mixed by resistors 7 and 8 at the input of the comparator 6, and the difference voltage is amplified and generated at the output of the comparator 6. It has a so-called comparison/amplification effect. Then, based on the output of this comparator 6, transistor 10 and transistor 111
11n is operated to change the current of the analysis magnet 14. Therefore, if the voltage generated when the variable resistor 1 is turned is greater than the voltage generated across the feedback resistor 12, the analysis magnet 14
The current flowing through the feedback resistor 1 increases.
If the voltage developed across magnet 2 is higher, the current flowing through analysis magnet 14 will decrease. Then, when both voltages become equal, the current flowing through the analysis magnet 14VC becomes constant. Here, since this feedback resistor 12 conducts a large current, its resistance value will decrease due to the temperature rise due to the heat generated in the resistor even if it is cooled.
5 Things are changing.

When the resistance value changes, the voltage generated across it changes, and the current flowing through the analysis magnet 14 changes accordingly, resulting in a large deviation from the optimally adjusted value. If the set value deviates due to the above-mentioned causes, it is inconvenient that ion implantation must be stopped and readjustment must be made again.

In view of the above points, the present invention was devised to solve such problems and eliminate such drawbacks.The purpose of the present invention is to provide a simple circuit configuration that allows unnecessary ions to be disposed adjacent to each other. The desired ions can be reliably extracted, and the desired ions can be easily extracted by turning on the desired selection switch, and the set value can be changed due to fluctuations in power supply voltage or temperature rise. An object of the present invention is to provide a control device for an analysis magnet that can automatically correct the deviation of the ion beam and always align the ion beam to the highest point.

In order to achieve such an object, the present invention is designed to select desired ions from among various types of ions by adjusting beams corresponding to each type of ion and each type of desired ion beam to be the best. a plurality of variable resistors, a plurality of ion selection switches that correspond to the plurality of variable resistors and select each of the variable resistors with a changeover switch to take out desired ions; an operational amplifier that amplifies the output; a magnetic field strength measuring device that detects the strength of the magnetic field of the analysis magnet;
A device that converts the magnetic field strength detected by this magnetic field strength measuring device into an electrical signal, an electrical signal converted by this device, and a signal extracted by the ion selection switch and having a polarity opposite to the electrical signal. a first transistor whose base is connected to the output terminal of the comparator via a current limiting resistor;
and a second transistor that is operated by the output of the first transistor to change the current of the analysis magnet, and the output of the magnetic field strength measuring device that detects the strength of the magnetic field of the analysis magnet is measured by the output of the magnetic field. Feedback is applied to the comparator through a device that converts the intensity into an electrical signal.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing an embodiment of a control device for an analysis magnet for selecting ions in an ion implantation apparatus according to the present invention.

In FIG. 2, the same symbols as in FIG. It has the ability to select ions. Here, each of these variable resistors 11 to 1n is provided only for the necessary types of ions. Each ion is adjusted to a value that produces the maximum ion with each variable resistor, and the adjusted variable resistor is configured to be fixed. And this variable resistor 11,1,
. . 1n movers are connected to the input end of the operational amplifier 3 via ion selection switches 16, 16, . . . 16n, respectively. 17 is a magnetic field strength measuring device that detects changes in the magnetic field strength generated in the analysis magnet 14, and 18 is a device that converts the magnetic field strength detected by the magnetic field strength measuring device 17 into an electrical signal (hereinafter referred to as a Gauss meter). The output terminal of this Gaussmeter 18 is connected to a voltmeter 9 and also to the input terminal of a comparator 6 via a resistor 8.

Reference numeral 19 denotes a current limiting resistor connected between the output terminal of the comparator 6 and the base of the transistor 10.

Then, the magnetic field strength measuring device 1711C detects the strength of the magnetic field of the analysis magnet 14 that selects ions in the ion implanter, and the magnetic field strength detected by the magnetic field strength measuring device 17 is converted into an electric signal by the Gaussmeter 18. After that, in addition to the comparator 6, the desired ion is selected and compared with the extracted signal, and based on the output of the comparator 6, the analysis magnet 1 is
The ion implantation device is configured to control the strength of the magnetic field of 4, and the ion implantation device is configured to correspond to various ions in order to select desired ions from among various ions, and to control the strength of each desired ion beam in advance. The variable resistors 11 to 1n are adjusted so as to be the highest, and the variable resistors 11 to 1n are selected by a changeover switch (ion selection switch 161 to 16n), and an ion selection means is provided for extracting desired ions. There is.

Next, the operation of the embodiment shown in FIG. 2 will be explained. First, when desired ions are to be taken out, one of the ion selection switches 161 to 16n corresponding to the desired ion type is turned on. When this changeover switch is turned on, the voltage of the variable resistor connected to this ion selection switch is input to the operational amplifier 3, the amplified output voltage is input to the comparator 6, and the voltage from the Gauss meter 18 is input to the operational amplifier 3. The current in the analysis magnet 14 is increased until the desired ion reaches the highest peak compared to . In other words, the operation of the comparator 6 is to mix the output voltage of the operational amplifier 3 with a voltage generated at the output of the Gaussmeter 18 and having a polarity opposite to that of the output voltage of the operational amplifier 3, using resistors 7 and 8. , the difference voltage is amplified and generated at the output of the comparator 6. So-called,
Acts as a comparison and amplification. Then, based on the output of this comparator 6, the transistor 10 and the transistors 111 to 1
1n to change the current of the analysis magnet 14. Here, an advantage of the present invention is that in the conventional circuit shown in FIG. 1, the voltage appearing across the feedback resistor 12 is used as the voltage fed back to the comparator 6. In Figure 2, the magnetic field strength measuring device 17 that detects the strength of the magnetic field of the analysis magnet 14, for example, a Hall element, measures the strength of the magnetic field and applies feedback to the comparator 6, so that the resistance value due to temperature rise is The current value of the analysis magnet 14 does not change due to a change in , and as described above, ions are analyzed using the equation expressed by .

Here, as described above, m is the mass of the ion, V is the accelerating voltage, q is the charge of the ion, and B is the strength of the magnetic field. In the ion implanter, M, V, and q are constant, and analysis is performed by changing the magnetic field strength B. Therefore, if the magnetic field strength B is accurate, the desired ions will be reliably produced. taken out.

In addition, in the embodiment shown in FIG. 2, since the feedback to the comparator 6 is performed by measuring the strength of the magnetic field, even if there are many types of ions, and unnecessary ions are adjacent to each other. In addition, even if the current flowing through the analysis magnet 14 changes due to voltage fluctuations in the power supply 2 and heat generated in the feedback resistor 12, which causes a resistance change, the current flowing through the analysis magnet 14 changes. The change in magnetic field strength corresponding to the current value is fed back to the comparator 6 and works to return the current value to the original value, so the ion beam is always maintained at its highest state. In addition, the desired ions can be easily selected by simply turning on the desired selection switch, eliminating the inconvenience of selecting the wrong ion, and eliminating this type of problem. As is clear from the above description, according to the present invention, desired ions can be reliably extracted even if unnecessary ions are adjacent to each other by a simple circuit configuration without using complicated means.
Further, since the desired ions can be easily selected by turning on the desired selection switch, the practical effect is extremely large.

It is also extremely effective in that it automatically corrects deviations in set values due to power supply voltage fluctuations, temperature rises, etc., and allows the ion beam to always be aligned at the highest point. As described above, the present invention has many advantages over conventional devices of this type, and is unique as a control device for an analysis magnet that selects ions in an ion implanter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a control circuit in a conventional ion implanter, and FIG. 2 is a block diagram showing an example of a control device for an analysis magnet for selecting ions in the ion implanter according to the present invention. 11-1n... Variable resistor, 3... Operational amplifier, 6... Comparator, 10, 11, ~11
n...Transistor, 14...Analysis magnet, 16,~16n...Ion selection switch, 17...Magnetic field strength measuring device, 18...
...Gaussmeter, 19...Resistance.

Claims (1)

[Claims] 1. Selecting ions in an ion implanter The strength of the magnetic field of an analysis magnet is detected, and the strength of the magnetic field of the analysis magnet is controlled based on the detected magnetic field strength.Ions are selected in an ion implanter. In order to select desired ions from among various ions, the analyzer magnet control device uses multiple variable resistors that correspond to each type of ion and are adjusted in advance to maximize each desired ion beam. , a plurality of ion selection switches that correspond to the plurality of variable resistors and select each of the variable resistors with a changeover switch to take out desired ions, and amplify the output selected by the plurality of ion selection switches. an operational amplifier, a magnetic field strength measuring device that detects the strength of the magnetic field of the analysis magnet, a device that converts the magnetic field strength detected by the magnetic field strength measuring device into an electrical signal, and an electrical signal converted by the device. and a signal taken out by the ion selection switch and having a polarity opposite to the electric signal, and a comparator for outputting a signal of the difference between the two, and a current limiting resistor connected to the output terminal of the comparator. a first transistor whose base is connected; and a second transistor that is operated by the output of the first transistor to change the current of the analysis magnet, and detects the strength of the magnetic field of the analysis magnet. A control device for an analytical magnet, characterized in that an output of a magnetic field strength measuring device is fed back to the comparator via a device that converts the magnetic field strength into an electric signal.