JPS63281338A - Primary ion radiating device - Google Patents

Abstract

PURPOSE:To improve the operability to set the magnetic field strength by providing two-stage apertures at the rear stage of the magnetic field, detecting the ion current after the primary ion separation, and feeding it back to an exciting circuit. CONSTITUTION:Only ions 6 with the specific mass number pass an aperture 4, and apertures 5A, 5B electrically insulated with an insulator 14 detect ions with a large opening angle respectively. When the magnetic field strength is slightly stronger than the optimum value, the orbit radius of an ion beam 2B becomes slightly small, and the detection current of the detector 5B is larger than that of the detector 5A. A subtractor 8 subtracts the detection current 7B from the detection current 7A, and the subtracted value 8A becomes negative. An adder 10 adds 8A to the preset value 9A, but when 9A is positive, 8A is negative, and the added result 10A becomes smaller. When an exciting circuit 11 is operated with this added result 10A, the magnetic field strength becomes slightly weak. As a result, the detection currents 7A, 7B of the detectors 5A, 5B become equal, and the primary ions 6 pass the center of the aperture.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This device relates to a primary ion irradiation system such as a secondary ion mass spectrometer, and in particular has a magnetic field type primary ion separation device and is easy to set up and operate for primary ion irradiation. Regarding the irradiation system.

[Conventional technology]

Figure 3 shows a conventional primary ion irradiation system.

The two ion sources IA and IB produce primary ions 2, A, and 2, respectively.
Generate B. The polarity of the magnetic field 3 is set by an excitation circuit 10 based on a signal from an operating section 9 . Depending on this polarity, either primary ion 2A or 2B is selected.

The figure depicts the case where 2B is selected. Ions 2B generated from ions IB contain impurity ions 12 and some neutral particles 13 in addition to desired ions 6. The magnetic field strength is set by operating the excitation circuit 11 using the operating section 9 so that when these ions or neutral particles enter the magnetic field 3, the ions 6 pass through the aperture 15. At this time, the impurity ions 12 having a lighter mass than the ions 6 pass through a smaller orbital radius and are blocked by the aperture 15. Also, neutral particles 1
3 travels straight without being deflected by the magnetic field and is intercepted by the aperture 152). High-mass impurity ions also pass through the same trajectory as the neutral particles 13 and are blocked by the rear aperture 15.

The primary ions 6 that have passed through the aperture 15 in this manner become highly pure primary ions. Furthermore, by changing the polarity of the magnetic field 3, the primary ions IA from the ion source IA can be selected. When these primary ions are used in a secondary ion mass spectrometer or local ion implantation, there is no interference from neutral particles or impurity ions, and highly accurate analysis and implantation can be achieved.

However, when selecting a desired ion 6 from the primary ions 2B, the current intensity of the primary ions 6 flowing into the sample 18 is set by operating the operating section 9. When an impurity ion with a mass number close to that of the primary ion 6 exists in the primary ion 2B,
Settings may be incorrect. For this reason, the setting operation of the operation unit 9 is important.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, no consideration was given to the operability of setting the magnetic field strength, and there were cases where the mass number was set to an incorrect mass number or the mass number was set slightly off. If the mass number is incorrect, the analysis or implantation using the primary ion beam becomes useless, and if the mass number is set slightly off, there is a problem of poor stability.

An object of the present invention is to detect the ion current after primary ion separation and feed it back to the excitation circuit, thereby setting accurate magnetic field strength and greatly improving operability.

[Means for solving problems]

The above purpose is to provide two stages of apertures after the magnetic field, the first stage aperture performs low resolution separation of primary ions, and the second stage aperture performs high resolution separation. The second stage aperture is achieved by dividing the aperture into two parts in the magnetic field separation direction, detecting the ion current in each part, and feeding it back to the excitation circuit to equalize the detection current of each of the two part apertures.

[Effect]

The magnetic field deflects the primary ion beam. The low-resolution aperture blocks the separated ion beam and allows only the ion beam of a predetermined mass number to pass through. The second aperture regulates the opening angle from the ion source to achieve high resolution separation. This aperture is electrically insulated and divided into two parts, each of which detects an ion current with a large opening angle. When the magnetic field strength is not set to the optimum value, each detection current becomes unbalanced. The optimum value can be set by operating the excitation circuit depending on the difference in current value and the polarity of the difference. This prevents incorrect settings.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The ion sources IA and IB are attached to the primary ion irradiation axis at a predetermined angle and generate ions 2A and 2B. By setting the polarity and strength of the magnetic field 3, the primary ion beam 2B
Among them, the specific mass ion 6 can be selected. The light mass ions 12 contained in the primary ion beam 2B are intercepted by the rear aperture 4 through a small orbital radius. Further, the neutral particles 13 contained in the secondary ion beam 2B are not deflected in the magnetic field and travel straight, and are blocked by the aperture 4.

Ions with a higher mass than the ion beam 6 also pass through a larger orbital radius and are intercepted by the aperture 4 5). In the end, only ions 6 with a specific mass number enter the aperture 4.
pass through. After the aperture 4, there is an aperture with a smaller aperture diameter. This aperture is composed of apertures 5A and 5B electrically insulated by an insulator 14, as shown in FIG. Apertures 5A and 5B collect ions with a large opening angle after passing through aperture 4.
Detect each. Now, when the magnetic field strength is slightly stronger than the optimal value,
The orbital radius of the ion beam 2B becomes slightly smaller and the detector 5
Detector B has a larger detection current than detector 5A.

A subtracter 8 subtracts rain detection currents 7A and 7B.

It is assumed that when 7B is subtracted from 7A, the subtracted value 8A becomes negative polarity. Adder 10 adds set value numbers 9A to 8A from setter 9. However, when 9A has positive polarity, 8A has negative polarity, so the addition result 10A becomes small. When the excitation circuit 11 is operated with this addition result of 10A, the magnetic field strength becomes slightly weaker. In the end, the detection currents 7A and 7 of the pole extractors 5A and 5B
B will be equal. In other words, the primary ions 6 pass through the center of the aperture.

〔Effect of the invention〕

According to the present invention, the magnetic field is roughly set until ions of a specific mass number pass through the low-resolution aperture 4, and then the magnetic field is automatically set so that it passes through the center of the high-resolution aperture 5. (1) Magnetic field setting operations can be performed accurately without mistakes.

(2) Operation becomes easier with rough settings.

(3) Stability is improved because fluctuations in magnetic field strength can also be corrected.

There are effects such as

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a detector of the present invention, and FIG. 3 is a diagram showing a conventional embodiment. IA, IB...Primary ion source, 2A, 2B...Primary ion beam, 3...Magnetic field, 4...Low resolution aperture, 5...High resolution aperture, 8...Subtractor,
10... Adder, 11... Excitation circuit.

Claims (1)

[Claims] 1. Consists of primary ion generation means, primary ion separation means having a magnetic field, means for controlling the strength of the magnetic field, means for allowing only specific primary ion species to pass through and blocking other ion species, and focusing means. In the primary ion irradiation device, a blocking means having a hole diameter larger than an effective primary ion beam diameter depending on the aperture angle of the primary ions is provided after the primary ion separation means, and further electrically insulated in the primary ion separation direction at the subsequent stage. It is characterized by comprising: a primary ion detecting means divided into two; a subtracting means for determining the difference in detection current of each detecting means; a means for adding the subtraction result and an operation signal; and a means for controlling the magnetic field by the added signal. Primary ion irradiation equipment.