WO1996036053A1

WO1996036053A1 - Ion beam emitter equipped with secondary particle detector, and secondary particle detection method

Info

Publication number: WO1996036053A1
Application number: PCT/JP1995/000907
Authority: WO
Inventors: Hifumi Tamura; Hiroyuki Sumiya; Katsumi Muto
Original assignee: Hitachi, Ltd.; Hitachi Instruments Engineering Co., Ltd.
Priority date: 1995-05-12
Filing date: 1995-05-12
Publication date: 1996-11-14

Abstract

It is an object of the present invention to provide an ion beam emitter for producing a thin, high-density ion beam that is used for micromachining and observation of a high-resolution secondary ion image (SIM image). The ion beam emitter comprises a selenoid (18), which surrounds a sample (8) and an objective lens (7) and produces a magnetic field in the same direction as the axis of the ion beam; and a secondary particle detection system (17) disposed over the objective lens (7) to detect the secondary electrons. Since the sample (8) can be placed in the proximity of the objective lens (7) in this structure, the objective lens (7) can be used for a short focus and thus a thin, high-density beam can be formed. As a result, high-precision micromachining can be made by utilizing the present invention, and high-sensitivity and high-resolution image observation can be realized.

Description

Specification

Ion beam with secondary particle detector

Irradiation equipment and secondary particle detection method

The present invention relates to an ion beam irradiation device with a secondary particle detector and a secondary particle detection method. Background art

In recent years, sample analysis, observation, and addition have been performed by irradiating the sample with ions. Such devices include, for example, a secondary ion mass spectrometer (SIMS Secondary Ion Mass Spectrometry), a scanning ion microscope (SIM Scanning Ion Microscope), and a FIB Focused Ion Beam. There is. In SIMS, the sample is irradiated with ions, and the secondary ions generated by the irradiation are analyzed by mass to identify the elements contained in the sample. In SIM, the shape of the sample is observed by detecting secondary electrons generated from the sample. Furthermore, in FIB, the sample is irradiated with ions again according to the observation result of the sample, and the sample is processed.

In these cases, a general configuration is to extract ions from an ion source as a beam, focus the ions with a lens, irradiate the sample, and detect secondary particles generated from the sample.

By the way, for example, FIB processing method (Tamotsu Noda, Hijiri Tamura) Bunseki 1: 2 (19989), secondary ion mass spectrometry, Surface Analysis Guidebook edited by The Surface Science Society of Japan 92 (1994) and Scanning ion microscope (MTBernius, GHMorrison) Conventionally, as described in Rev. Sci, Instrun, 58 (10) 1989, a secondary particle detector is provided between a lens and a sample. For this reason, the distance between the lens and the sample was set to be large for the detector. In the above conventional technique, the distance between the lens and the sample is large, so that ions from the ion source cannot be sufficiently focused on the sample. In other words, since the distance between the lens and the sample is large, the focal length of the lens has to be set long.Therefore, various aberrations of the lens are relatively large, which limits the narrowing of the ion beam. I was

For this reason, the conventional technology is remarkable especially in the semiconductor field, but cannot be used in an ultra-small area. Since the ion beam cannot be narrowed in this way, for example, it was difficult to evaluate the characterization of an extremely small region required for various material evaluations in SIMS. Also, with SIM, it was difficult to evaluate the processing accuracy in the processing step in the ultra-fine area. Furthermore, in FIB, there is a limit to miniaturization of processing.

An object of the present invention is to improve the narrowing of an incident ion beam and to perform analysis of a very small area, observation of a fine structure, and ultrafine processing. Disclosure of the invention

In order to solve the above-mentioned problems, the present invention provides a system in which ions from an ion source are focused on a lens group and irradiated on a sample, and secondary particles emitted from the sample are detected by a secondary particle detector. The secondary particle detector was configured such that the secondary particle detector was arranged above the objective lens.

More preferably, a magnetic field is formed near the sample, near the lens, or between the sample and the objective lens.

According to the above configuration, the distance between the objective lens and the sample is determined by the secondary particle detector. Therefore, the distance between the lens and the sample can be sufficiently reduced. Therefore, the focal length of the objective lens can be shortened, and accordingly, the spread of the beam due to various aberrations can be suppressed. As a result, the incident ion beam can be narrowed.

In a further preferred configuration, by forming a magnetic field outside the objective lens, the secondary particles are subjected to a magnetic field confinement action, whereby the secondary particles are guided to the detector. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing the entire apparatus (ion beam apparatus).

FIG. 2 is a diagram showing details of secondary particle detection.

FIG. 3 is a diagram showing details of the detector.

FIG. 4 is a diagram showing a second embodiment.

FIG. 5 is a diagram showing a third embodiment.

FIG. 6 is a diagram showing a fourth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is an overall view of the ion beam device. In Fig. 1, Ga-LMIS (Liquid Metal Ion Source) and Duoplasmatron are mainly used as ion sources, and an ion beam is generated. The ion beam 10 generated from the ion source 1 is guided to the condenser lens 4 through the condenser lens aperture 3, reduced, and further passes through the objective lens aperture 6 to enter the objective lens 7. The objective lens 7 has a function of focusing the incident beam 10 on the sample 8. Deflection voltage provided between condenser lens 4 and objective lens 7 The pole 5 has the role of deflecting and scanning the primary ion beam 10 on the sample under arbitrary conditions. The scanning power supply 14 has a role for synchronously scanning the primary ion beam 10 and the electron beam of the CRT 10. Although omitted here, the first order beam 10 is subjected to CPU control, and is irradiated to an arbitrary position on the sample. For example, when the present ion beam apparatus is used as a SIM or SIMS, it is controlled so that the ion beam 10 is scanned over an arbitrary predetermined area on the sample. When used as a FIB, an ion beam 10 is irradiated to a predetermined position for repairing a circuit pattern.

A magnetic field generating coil 18 is provided outside the objective lens 7 and the sample 8 so as to surround them. As will be described in detail later, the secondary particles (secondary ions in the SIMS, secondary electrons or secondary negative ions in the SIMS) generated from the sample are pinched by the magnetic field of the magnetic field generating coil 18 ( Utilizing the confinement effect, it is efficiently guided above the objective lens 7 (from the sample 8 to the ion source 1). The secondary particles are guided by a deflecting magnetic field source 16 in a direction perpendicular to the ion beam, and are detected by a secondary particle detection system 17. Further, the signal of the secondary particle detection system 17 is amplified by the amplifier 15 and used as a video signal of the CRT 13 to form a secondary electron image. The secondary particle detection system 17, SIM, and FIB are secondary electron or secondary negative ion detectors, and the secondary ion detection system is SIMS.

Further, these will be described in detail. FIG. 2 shows the periphery of the objective lens shown in FIG. 1 in detail. In Fig. 2, the secondary particle detection system 17 is a (secondary electron detection system or secondary ion detection system) objective lens 7, sample 8 vacuum housing 12, primary ion beam, secondary electron 11 and In the present invention And a secondary electron deflection electrode 16 and a secondary particle detector 17. The magnetic field generating coil 18 is provided around the objective lens 7 and is provided inside the vacuum housing 12. As a result, a magnetic field distribution 19 in the same direction as the primary ion beam 11 is formed between the objective lens 7 and the sample 8. A secondary electron deflection magnetic pole 16 and a secondary particle detection system 17 are mounted on the upper part of the objective lens 7.

The irradiation of the primary ion beam 10 causes the secondary particles to be guided to the upper part of the objective lens while performing cycloidal motion (pinched by the magnetic field) by the action of a magnetic field. At this time, the radius r of the cycloid motion is determined by the following equation (1).

r ozf V (sine) / H… Equation (1)

V: Initial energy of secondary particle

Θ: Secondary electron incidence angle with respect to magnetic field direction

H: Magnetic field generated by the magnetic field generating coil

That is, from this equation (1), V is determined by the initial energy of the secondary electron and is about several volts. A relatively weak magnetic field: a few hundred gauss (H) confines the electron within a small radius and is constant. It turns out that it is possible to guide in the direction. When applied to an ion beam device, the sample and secondary particles in the ion beam path space up to the objective lens 7 in the same direction as the ion beam

(Secondary electrons or secondary ions). Thereby, the secondary electrons are guided to the upper part of the objective lens 7. Further, the secondary particles guided to the upper part of the objective lens 7 are guided in the vertical direction by the magnetic field of the deflecting magnetic field generation source 16, and are detected by the secondary particle detection system 17.

The magnetic field confinement region of the secondary electrons can be arbitrarily changed by changing the magnetic field strength. In addition, when the detected particles are secondary electrons, the influence of the magnetic field on the primary ion beam focusing is particularly affected by the secondary electrons and secondary ions. The energy is as small as a few eV and the secondary electrons are negligible, especially because the mass is smaller than Yon.

Next, the details of the secondary particle detection system 17 will be described with reference to FIG. The secondary particle detection system 17 is a detector that combines a scintillator and a photomultiplier. The secondary particle detection system 17 is a scintillator 17c, a metal vapor-deposited thin film 17a attached to the scintillator surface, a supporting electrode 17b for applying the post-acceleration voltage and supporting the scintillator 17c. It consists of a post-acceleration power supply 17e, a scintillator 1c, a metal-deposited thin film 17a, and a photomultiplier tube 17d. During operation, a positive voltage of several 100 V to several kV is applied to the metal-deposited thin film 17 a adhered to the surface of the scintillator 17 c from the post-acceleration power supply 17 e through the support electrode 17 b through the support electrode 17 b. ing. Secondary electrons incident on the metal-deposited thin film 17 a are accelerated by the post-acceleration voltage at the subsequent stage, irradiate the scintillator 17 c, convert the electrons into light, and are detected by the photomultiplier tube 17 d. The output of the photomultiplier tube 17d is used for image formation as a video signal.

In this embodiment, since there is no obstacle between the sample 8 and the objective lens 7, the sample position can approach the objective lens 7 to a desired distance, and the focal length of the objective lens 7 can be shortened. Conventionally, the secondary particle detection system 17 was provided between the sample 8 and the objective lens 7 so that the focal length was at least about 30 mm.However, with this technique, the focal length can be reduced to 10 mm or less. A current density of about 30 A / cm ² was obtained, which was about three times higher, and the processing speed was improved about three times as compared with the Si sample. Also, the resolution of the scanned image was improved from 150 A to 30 A.

Next, a second embodiment will be described with reference to FIG. In this embodiment, parts different from the first embodiment will be described, and the other parts are the same as those in the first embodiment, and thus description thereof will be omitted. Hereinafter, the same applies to the third and fourth embodiments. is there.

FIG. 4 differs from the first embodiment only in that the magnetic field generating coil 31 for confining the secondary particles is taken out of the vacuum. The implementation results of this technique are exactly the same as in the first embodiment, and a description thereof will be omitted.In this case, since the confinement magnetic field generating coil 31 is taken out of the vacuum, it has a feature that the evacuation and the like are facilitated. _C. Further, a third embodiment will be described with reference to FIG. In FIG. 5, the use of the solenoid coil 41 bent in an arc shape as a means for guiding the secondary particles 11 guided to the upper part of the objective lens 7 to the secondary particle detection system 17 is shown in Examples 1 and 2. Different from 2. The primary ion beam passage of the solenoid coil 41 has a hole for passing the beam. In this technique, a magnetic field is formed along the axis of the solenoid coil 41,

11 is confined in a magnetic field and guided to the secondary electron detection system 17 along the central axis of the coil 41. Also in this embodiment, the magnetic field generating coil 18 provided on the outer periphery of the sample 8 and the objective lens 7 was used for both installation in a vacuum and installation outside the vacuum (not shown) to obtain similar results. Was.

Next, a fourth embodiment will be described with reference to FIG. In this embodiment,

In the first to third embodiments, the detection system is formed differently ₍ that is, FIG. 6 shows a secondary particle detection system 17 using the secondary electron multiplier 51. The configuration is shown in FIG. A commercially available secondary electron multiplier is used.The detection of secondary particles by this detector is almost the same as in Examples 1 to 3 and is omitted here.

As described above, the following results were mainly found in the examples of the present invention. In the FIB processing device and the secondary ion mass spectrometer (SIMS device), the effect that the objective lens 7 can be used at a short focus is as follows.

The refinement of the primary ion beam has been improved, and the processing miniaturization limit and SIM image (Scanning Ion microscopy Image) image resolution have been reduced by one-third and one-third, respectively. And reduced to about 1/5. Furthermore, since the signal is acquired from the same direction as the primary ion beam incident direction, the observation of the sample surface without shadows is possible, and the processing accuracy and the image quality of SIM have been significantly improved. In addition, the use of a short focus has become possible, the current density of the primary ion beam on the sample has been improved, and the processing speed in micromachining has been improved by about three times. In addition, the brightness of the SIM image was improved about three times. In addition, the limit of SIMS microanalysis has been improved from 1 O nm to 2 nm.

To explain this embodiment in more detail, in a general ion beam apparatus, a secondary electron as a signal is guided to the upper part of the objective lens, and the sample and the objective lens space can be made a free space. Close to the lens. As a result, the objective lens can be used with a short focal length, the beam divergence due to various aberrations is minimized, and the formation of a high-density microbeam is facilitated. In addition, secondary electrons as signals are extracted from the primary ion beam irradiation direction, which has the characteristic that correct signals can be obtained.

From these characteristics, the following effects can be practically obtained. First, the following effects can be achieved when the purpose is microfabrication such as the fabrication of various microelements such as I C.

1) Improvement of fineness and processing accuracy by narrowing the beam

2) Processing speed is improved by increasing beam density

Next, the following effects can be obtained when applied to analyzers such as SIMS.

I) Secondary electrons are captured as signals from the primary ion beam incident direction, enabling real images without shadows (improved image quality)

Π) Ultra fine bundle of beams is possible and image resolution is significantly improved in) Signal density increases due to improved beam density, enabling bright image formation Industrial applicability

As described above, according to the present invention, an incident beam can be narrowed, and it is possible to cope with a miniaturized region, which is useful for an apparatus and a method using an ion beam.

Claims

The scope of the claims

1. An ion source that generates ions, a unit that extracts the ions as a beam, a lens group that focuses the ion beam and irradiates the sample, and a detector that detects secondary particles emitted from the sample 2 An ion beam irradiation apparatus with a secondary particle detector, wherein the detector is provided on the ion source side of an objective lens of the lens group.

2. The method according to claim 1, wherein magnetic field forming means for forming a magnetic field near the sample, near the objective lens, or between the sample and the objective lens is provided. Ion beam irradiation device with secondary particle detector.

3. The ion beam irradiation apparatus with a secondary particle detector according to claim 2, wherein said objective lens and said magnetic field forming means are both placed under substantially vacuum.

4. The secondary particles according to claim 2, further comprising a vacuum chamber for keeping the objective lens substantially under a vacuum, and further comprising providing the magnetic field generating means outside the vacuum chamber. Ion beam irradiation device with detector.

5. The ion beam irradiation device with a secondary particle detector according to claim 1, wherein the detector includes a type that converts secondary particles into light and detects the light.

6. The ion beam irradiation device with a secondary particle detector according to claim 1, wherein the detector includes a type that detects electrons.

7. The ion beam irradiation apparatus with a secondary particle detector according to claim 1, further comprising a magnetic field generating means for guiding the secondary particles passing through the objective lens to the detector.

8. The secondary particles that have passed through the objective lens are forwarded using a solenoid coil. The ion beam irradiation device with a secondary particle detector according to claim 1, wherein the ion beam irradiation device is configured to be guided to the detector.

9. The lens system according to claim 1, wherein the lens group includes at least an objective lens and a condenser lens, and the detector is disposed between the objective lens and the condenser lens. An ion beam irradiation device with a secondary particle detector.

10. Generate ions, take them out as an ion beam, focus this ion beam and irradiate it to the sample. Secondary particles generated by the irradiation on the side where the ions are generated from the point of the convergence A secondary particle detection method characterized by detecting a particle.

11. The secondary particle detection method according to claim 10, wherein a magnetic field is generated in the vicinity of the focal point.