JPS58165238A - Ion beam apparatus - Google Patents

Abstract

PURPOSE:To stabilize and ion beam current, by detecting some of ions of prescribed kind and controlling an extracting electrode to keep the detected signal constant. CONSTITUTION:A eutectic alloy is put in an emitter 1, which is heated to liquefy the alloy. The liquefied alloy is ionized by an extractor 2. The ions are accelerated by a cathode 4 and then constricted to a predetermined diameter of flux by an incident reducing plate 10. The constricted ions proceed through the electric field between electrodes 11a, 11b and the perpendicular magnetic field between magnetic poles 12a, 12b. Among the incident ions, only ions with prescribed energy and mass pass through the opening of a reducing plate 13 and the other ions collide against it. The reducing plate 13 is so adjusted that although Pt ions and B ions are projected from the emitter 1, only the B ions pass through the opening of the reducing plate. Some of the B ions having passed through the opening are detected by a sensor 5, the detected current in which is proportional to an ion beam current moving to a material to be injected with the ions or exposed thereto. The detected current is changed into a voltage by a current-voltage converter 6. The voltage is compared with a set voltage E2 so that the differential voltage DELTAV is applied to a control circuit 8 to modify the extracting voltage between the emitter 1 and the extractor 2 to keep the magnitude of the ion beam current constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion beam device with stabilized ion beam current.

For example, EHD (Flec[ro l-1ydro
In an ion beam apparatus using a Dynamics type ion source, a single return circuit is provided to improve the stability of the ion probe current. 1st. The figure is a connection diagram showing the electrical configuration of this type of conventional device. In the figure, 1 is an emitter r from which an ion beam is emitted, and E1 is a power source for heating the emitter r. Here, a DC power source is used as El, but an AC power source may also be used. 2 is an extractor; 3 is an electrostatic condenser lens for converging the ion beam; a higher voltage is applied to the lens from a lens power source (not shown). 4 is a cathode, and the extractor 2 and the cathode 4 are provided with small holes through which the ion beam passes.

5 is a donut-shaped ion beam detector for detecting a part of the ion beam emitted from the emitter 1 and accelerated by the cathode 4; 6 is a current-voltage conversion circuit that converts the detected current in the detector 5 into voltage; It is. Reference numeral 7 denotes a setting circuit for setting the ion beam current, and the setting circuit 7 is composed of a differential amplifier U and a variable voltage source E2 that provides a setting voltage. 8 is a control circuit for controlling the ion extraction voltage between the emitter 1 and the extractor 2 using a deviation voltage from the setting circuit 7, and the control circuit 8 is a DC power supply.

It consists of a high frequency oscillator, high frequency transformer, rectifier, etc. [3 is an acceleration power source that generates an acceleration voltage for accelerating the ion beam applied between the emitter 1 and the cathode 4.

The operation of a conventional ion beam apparatus having such a configuration will be explained. For example, gallium ions are extracted and emitted from the emitter 1 heated by the heating power source E1 by the extractor 2, and the ions are accelerated by the cathode 4 to which a voltage is applied from the accelerating electric current @E3. A part of the accelerated ion beam is detected by the detector 5, and a current corresponding to the amount of the detected ion beam flows from the detector 5 to the conversion circuit 6, where it is converted into a voltage signal and sent to the setting circuit. 7 is input. Since the reference voltage [2 is applied to the differential amplifier U in the setting circuit, it is compared with the reference voltage E2 and outputted to the control circuit 8 as a deviation voltage ΔV. Upon receiving this, the control circuit 8 outputs the deviation voltage Δ
The ionome current is stabilized by changing the extraction voltage between the emitter 1, the extractor 1 and the extractor 2' by an amount corresponding to V. Note that the objective lens (Einzel lens) that focuses the ion probe onto the sample surface, the sample, and the system for observing the sample surface are omitted here.

By the way, in recent years, ion beam devices for performing maskless ion implantation, ion beam exposure, etc. have been attracting attention as devices that apply ion beams, but the ion species used in these devices include Si-B, As, Sb, etc. are used. However, these materials have a high melting point and therefore have low melting point eutectic alloys, such as AU-8i,
We decided to liquefy these alloys at relatively low temperatures using Pt-B, etc., and then ionize this liquid alloy! Therefore, desired ions are obtained. However, in the conventional control method, when stabilizing the ion probe, all components of the ionized eutectic alloy are kept constant;
1. Therefore, it was not possible to control the current value of a single ion species used for actual ion implantation or exposure to a constant value. This is because the composition ratio of the components of the eutectic alloy is not always the same, and the mixing ratio of the alloy changes even during emission due to differences in ionization rate and difference in evaporation amount.

The present invention was made in view of the above points, and includes an ion source that generates two or more different types of ions, and a system in which the generated and accelerated ions are incident, and specific ions are selected based on the mass of the ions. The object is achieved by comprising an ion selection means for detecting a part of the specific ions, an ion detection means for detecting a part of the specific ions, and a control means for controlling the ion source so as to keep the detection signal from the ion detection means constant. This is an ion beam device that can control the ion beam current of the desired ion species to a constant value.

Hereinafter, the present invention will be described in detail with reference to the drawings.

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

In the figure, the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted. B in the figure is an ion beam, 10
is an entrance aperture plate that focuses the ion beam B to a fixed beam diameter. 11a and 11b are a pair of electrodes facing each other, and 12
A is a pair of magnetic poles facing 12b (not shown). The electric field due to the 118.11b and the magnetic poles 12a, 12b
The central axes of the magnetic fields almost coincide with each other. Also 11a, 11
Although not shown in this drawing, a control voltage and a control current are supplied between the terminals b and between 12a and 12b, respectively. Note that 13 is an exit diaphragm plate, and the above input diaphragm plate 10. A pair of (7) electrodes 11a, 1 lb-1t (1) magnetic poles 12a, 12b and an exit aperture plate 13 constitute a charged particle filter as an ion selection means, and a donut-shaped detection device is provided below the ion selection means. A container 5 is arranged.

In the above configuration, a eutectic alloy such as Pt-8 is placed in the emitter 1, and the alloy is liquefied by heating the emitter 1. The liquid alloy is ionized and extracted by the extractor 2, and further accelerated by the cathode 4. The accelerated ion beam B is focused to a constant beam diameter by the entrance aperture plate 1o, and is focused by the electrode 11a.
, 11b and the magnetic poles 12a, 12b.
The object travels through a magnetic field that is orthogonal to the electric field created by the electric field. Of the ions that enter this field, only ions with predetermined energy and mass pass through the aperture of the aperture plate 13 provided below the field. Other ions cannot pass through the aperture plate 13 and collide with the aperture plate 13. In this embodiment, the strengths of the electric and magnetic fields are adjusted so that out of the Pt ions and 8 ions emitted from the emitter 1, only the B ions pass through the aperture of the aperture plate 13. Aperture plate 1
A part of the B ions that have passed through the detector 3 are detected by the detector 5. The detection current detected by the detector 5 is proportional to the ion beam current directed toward the implanted material or the exposed material (not shown) placed below the detector 5, and the current is converted into a current-to-voltage converter. The voltage is converted into voltage by the device 6. The voltage converted here is input to the setting circuit 7, compared with the set voltage E2, and outputted to the control circuit 8 as a deviation voltage ΔV. This causes the control circuit 8 to control the deviation voltage Δ
1 for the amount corresponding to ■. Gate Mitter 1 and 1 Extractor 2
By changing the extraction voltage between the two, the ion beam current of B ions incident on the detector 5, that is, the value of the ion beam current irradiated onto the material, is controlled so as to always be constant.

It should be noted that the present invention is not limited to the above embodiment apparatus, and in the embodiment, a so-called Wien filter using orthogonal electric and magnetic fields was used as an ion selection means.
Other ion selection means may be used, such as a filter that spatially separates an electric field and a magnetic field, or a means for selecting specific ions using only a magnetic field. Furthermore, although a donut-shaped detector is used as the ion detection means, for example, a knife-etch type detector may also be used. Furthermore, in the above embodiment, the ions are detected after passing through the exit diaphragm plate of the charged particle filter, but if there is room for locating the detector, the detector may be placed in front of the diaphragm plate, or the ions may be detected in front of the diaphragm plate itself. It is also possible to provide positional resolution to detect ions near the beam axis of the specific ions to be sorted. Furthermore, since the isotope ions of the ions to be sorted out are generated in proportion to the amount of the ions to be sorted out, the same effect can be obtained even if some of the isotope ions are detected.

As described above, the present invention uses an ion source that generates different types of ions, and in an apparatus that selects and uses specific ions, some of the specific ions selected by the ion selection means are used. By detecting the ion beam and controlling the extraction electrode so as to keep this detection signal constant, the current of the ion beam actually used for processing or implantation can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing the electrical configuration of a conventional device, and FIG. 2 is a configuration diagram showing an embodiment of the ion beam device according to the present invention. 1: Emitter, 2: Extractor, 3: Electrostatic lens, 4: Cathode, 5: Detector, 6: I-■ conversion circuit, 7
: Setting circuit, 8: Control circuit, 10: Incidence aperture plate, 11a
, 11b: electrode, 12a: magnetic pole, 13: exit aperture plate,
B: Beam. Patent applicant JEOL Ltd. Representative Tadao Kase Figure 1

Claims (1)

[Claims] an ion source that generates one or more types of ions, an ion selection means for selecting specific ions by the ion exchange upon which the generated and accelerated ions are incident;
An ion beam apparatus comprising an ion detection means for detecting a part of the specific ions, and a control means for controlling the ion source so that a detection number 4M from the ion detection means is constant.