JP2003109530A - Charged particle beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability in the X-ray analysis of a thinned sample by reducing beam tail and to facilitate positioning of the beam current measuring means (Faraday cup) used in the X-ray analysis. SOLUTION: A new diaphragm is provided at the bottom of the objective lens. And a tubular member constructed of a light element material as represented by carbon and beryllium is provided between the objective lens and a newly-provided diaphragm. And the newly-provided diaphragm and the Faraday cup are made in one-body structure and a means of controlling the position against the optical axis is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam apparatus, and more particularly to a charged particle beam apparatus suitable for highly accurate X-ray analysis of a thin sample.

[0002]

2. Description of the Related Art In a charged particle beam apparatus typified by a scanning electron microscope, desired information (for example, a sample image) is obtained from a sample by scanning a finely focused charged particle beam on the sample. Such a charged particle beam device is also used for the purpose of identifying the element of the sample by analyzing the X-ray excited by the electron beam with which the sample is irradiated. Normal X-ray analysis using a scanning electron microscope is to irradiate a bulk sample with an electron beam and detect the excited X-ray. However, since the irradiated electrons are scattered inside the bulk sample, X-ray generation occurs. The area expands and the spatial resolution of the analysis deteriorates. In order to avoid this, a method is known in which a thin sample is irradiated with an electron beam to prevent diffusion of the X-ray generation region. In this case, the irradiated electron beam passes through the sliced sample and is hardly scattered inside the sample,
Although the spatial resolution of the analysis region is improved, the amount of X-ray generation is significantly reduced as compared with the bulk sample.

As shown in FIG. 2, the intensity of the electron beam generally has a wide tail (beam tail 82) with a low intensity around the central peak (main beam 81).
have. One of the main causes of this beam tail is scattered electrons entering through the aperture of the diaphragm. This will be described with reference to FIG. A diaphragm device of a scanning electron microscope is usually arranged in a confined diaphragm space 200. Electron beam irradiated on the objective lens diaphragm 8 (diaphragm irradiation beam 400)
Part of the light passes through the opening to become the main beam 401, but most of the rest is irradiated to the outside of the opening. At this time, the electrons emitted to the outside of the opening are backscattered and fly in the enclosed space. In this way, the electrons (scattered electrons 102) that have repeatedly undergone multiple scattering in the enclosed space are transmitted through the aperture of the diaphragm again and irradiated onto the sample. The scattered electrons that have transmitted through the aperture of the diaphragm have a poor convergence and thus form a large beam tail around the main beam.

As shown in FIG. 4, in X-ray analysis of a thin sample, if a bulk region exists near the analysis point, this region is irradiated with the beam tail. The intensity of the beam tail is as low as several tenths to several hundredths of the intensity of the main beam, but the X-ray 10
3 Since the amount of X-rays generated is much larger than the amount of X-rays (X-rays 104 at the analysis point) in the thinned region, the X-ray intensity generated at the beam tail can be ignored with respect to the X-ray intensity generated from the analysis points. Disappear. As a result, characteristic X-rays generated from other than the analysis point are detected, and there is a problem that the reliability of elemental analysis is impaired. Conventionally, X of the thinned part that is not close to the bulk part
By performing line analysis, the effect of the beam tail was avoided.

On the other hand, it is necessary to control the probe current in order to maintain the quantitativeness in X-ray analysis. Usually, for this purpose, a current detection means (Faraday cup) is arranged under the objective lens diaphragm, and when measuring the current,
The Faraday cup was moved on the optical axis to measure the current.

[0006]

However, in the usual X-ray analysis, it is not possible to always judge whether the analysis point in the thinned region is sufficiently distant from the bulk portion, and therefore the obtained result contains information other than the analysis point. There was a problem in which the possibility of being mixed cannot be completely denied.

When moving the Faraday cup for measuring the probe current along the optical axis, in order to move the Faraday cup accurately along the optical axis, the unit closer to the electron source than the diaphragm is removed and the Faraday cup is removed. It was necessary to visually confirm the position of the Faraday cup, or to perform centering of the Faraday cup while monitoring the probe current. Further, even if the position of the Faraday cup is adjusted once, if the optical axis shifts by any chance, there is a problem that accurate current detection cannot be performed due to the position shift of the Faraday cup.

An object of the present invention is to reduce the beam tail to improve the reliability of X-ray analysis of a thin sample, and to position the Faraday cup with respect to the Faraday cup often used for X-ray analysis. Another object is to provide a charged particle beam device suitable for facilitating alignment.

[0009]

In order to achieve the above object, a new diaphragm is provided under the objective lens diaphragm. In addition, a cylindrical member made of a light element material such as carbon or beryllium is arranged between the objective lens diaphragm and the newly provided diaphragm. This light element member prevents scattered electrons that have passed through the aperture of the objective lens aperture from colliding with the newly provided aperture and causing multiple scattering. In addition, the newly provided diaphragm and Faraday cup are integrated into a unit, and means for controlling the position with respect to the optical axis is provided. As a result, the axial alignment of the diaphragm also serves as the alignment of the Faraday cup. Since the axis alignment of the diaphragm can be determined by whether or not the beam has passed, it can be easily performed like the normal axis alignment in the objective lens diaphragm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a scanning electron microscope which is an example of the present invention. Between the cathode 1 and the first anode 2,
A voltage is applied by the high voltage control power source 20 controlled by the computer 40, and the primary electron beam 4 is extracted from the cathode 1 with a predetermined emission current. A high voltage control power source 20 controlled by a computer 40 is provided between the cathode 1 and the second anode 3.
Is applied with an acceleration voltage, the primary electron beam 4 emitted from the cathode 1 is accelerated, and advances to the lens system in the subsequent stage. The primary electron beam 4 is converged by the converging lens 5 controlled by the lens control power supply 21, and after the unnecessary area of the primary electron beam is removed by the objective lens diaphragm 8, the converging lens 6 controlled by the lens control power supply 22. , And the objective lens 7 controlled by the objective lens control power supply 23 to focus the light on the sample 10 as a minute spot. The objective lens 7 can take various forms such as an in-lens system, an out-lens system, and a snorkel system (semi-in-lens system). Further, a retarding method in which a negative voltage is applied to the sample to decelerate the primary electron beam is also possible. Further, each lens may be an electrostatic lens including a plurality of electrodes.

The primary electron beam 4 is supplied to the sample 10 by the scanning coil 9.
The top is scanned two-dimensionally. Sample 1 by irradiation of primary electron beam
A secondary signal 12 such as a secondary electron generated from 0 travels to the upper part of the objective lens 7, and is then separated from the primary electron by a quadrature electromagnetic field generating device 11 for separating a secondary signal to be a secondary signal detector. 13 is detected. The signal detected by the secondary signal detector 13 is amplified by the signal amplifier 14, then transferred to the image memory 25 and displayed on the image display device 26 as a sample image.

The deflection coils 51 of two stages are arranged at the same position as the scanning coil 9, and the position (observation visual field) of the primary electron beam 4 on the sample 10 can be two-dimensionally controlled.

The stage 15 can move the sample 10 in at least two directions (X direction, Y direction) in a plane perpendicular to the primary electron beam 4.

From the input device 42, it is possible to specify control conditions necessary for observation such as designation of accelerating voltage and stage control information, and information such as output and storage of the obtained image.

In the description of FIG. 1, the control processor unit is described as being integrated with the scanning electron microscope or equivalent thereto, but of course, the present invention is not limited to this, and the control processor provided separately from the scanning electron microscope body. You may process with.

In the charged particle beam apparatus having such a structure, the second portion is provided between the objective lens diaphragm 8 and the deflection coil 51.
The diaphragm 61 is arranged.

The configuration of the second diaphragm 61 is shown in FIGS.
This will be described with reference to FIG.

FIG. 5 is a schematic configuration diagram of the second diaphragm at the diaphragm position, which is an example of the present invention. Further, FIG. 6 is a top view of FIG. The second aperture plate 62 is provided with a second aperture hole 63 through which the primary electron beam 4 passes, and is attached to the aperture drive mechanism 66. The opening diameter of the second diaphragm hole 63 is required to be 5 times or less than the opening diameter of the objective lens diaphragm 8 because it is necessary to block the main beam 401 and the scattered electrons 102. An anti-scattering cylinder 64 made of a light element material such as carbon or beryllium is provided above the second throttle hole 63. The anti-scattering cylinder 64 is provided with the objective lens diaphragm 8 as much as possible.
It is desirable to place it close to. In addition, the second diaphragm plate 62
A Faraday cup 65 is provided at a distance L from the second aperture 63. The Faraday cup 65 is connected to the current measuring terminal 67. The diaphragm driving device 66 includes the second diaphragm plate 62.
Is provided with a mechanism for moving in the X and Y directions and a quantitative movement mechanism for the distance L, and the optical axis adjustment for adjusting the primary electron beam 4 so as to pass through the center of the second aperture hole 63, and the primary electron beam 4 It can be switched so that the Faraday cup 65 is irradiated. 7 is a schematic configuration diagram of the second diaphragm at the Faraday cup position, and FIG. 8 is a top view of FIG. 7. Since the primary electron beam 4 collides with the Faraday cup 65, from the current measuring terminal,
Beam current can be measured.

The positions of the second aperture 63 and the Faraday cup 65 may be interchanged. Further, the diaphragm driving device 6
No. 6 is configured such that the second throttle hole 63 and the Faraday cup 65 can be switched by a linear reciprocating motion, but the distance L
This is not limited if a mechanism capable of quantitative movement is prepared.

FIG. 9 is a schematic diagram of multiple scattering that occurs in the throttle chamber. The scattered electrons 102 generated in the diaphragm chamber 200 are
It is almost blocked by the second diaphragm 61. Further, the scattered electrons 102 that collide with the second diaphragm 61 and are diffusely reflected are blocked by the scattering prevention cylinder 64, and multiple scattering is suppressed.

As described above, the analysis point of the sample 10 is irradiated with the main beam 401 having a reduced beam tail, and X-rays generated from other than the analysis point can be reduced, which has been a problem in the past. The reliability of X-ray analysis can be improved.

Further, since the second diaphragm 61 adjusts the optical axis through the second diaphragm hole 63, it can be switched to the Faraday cup simply by moving the distance L quantitatively, and the central position adjustment for the Faraday cup is not necessary.

[0024]

According to the present invention, since the beam tail of the charged particle beam with which the sample is irradiated can be reduced, there is an effect that the reliability of the X-ray analysis of the thin sample is particularly improved. Also, X
This has the effect of facilitating alignment of the beam current measuring means (Faraday cup) required for line analysis.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a scanning electron microscope which is an example of the present invention.

FIG. 2 is a schematic diagram of a beam intensity distribution with which a sample is irradiated.

FIG. 3 is a schematic diagram of multiple scattering that occurs in a throttle chamber.

FIG. 4 is an explanatory view of the influence of scattered electrons in X-ray analysis of a thin sample.

FIG. 5 is a schematic configuration diagram of a second diaphragm at a diaphragm position that is an example of the present invention.

6 is a top view of FIG.

FIG. 7 is a schematic configuration diagram of a second diaphragm at the Faraday cup position.

8 is a top view of FIG. 7.

FIG. 9 is a schematic diagram of multiple scattering that occurs in a throttle chamber.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... 1st anode, 3 ... 2nd anode, 4 ... Primary electron beam, 5 ... 1st converging lens, 6 ... 2nd converging lens, 7 ... Objective lens, 8 ... Objective lens diaphragm, 9 ... Scanning Coil, 10
... sample, 11 ... orthogonal electromagnetic field (EXB) generator for secondary signal separation, 12 ... secondary signal, 13 ... secondary signal detector, 14
... signal amplifier, 15 ... stage, 20 ... high-voltage control power supply,
21 ... 1st converging lens control power supply, 22 ... 2nd converging lens control power supply, 23 ... Objective lens control power supply, 24 ... Scan coil control power supply, 25 ... Image memory, 26 ... Image display device, 2
7 ... Image processing device, 31 ... Electrical visual field control power supply, 40 ...
Computer, 41 ... Storage device, 42 ... Input device, 51
... Electric field moving coil, 61 ... Second diaphragm, 62 ... Second
Diaphragm plate, 63 ... Second diaphragm hole, 64 ... Scatter prevention cylinder, 65 ...
Faraday cup, 66 ... Aperture drive device, 67 ... Current measurement terminal, 81 ... Main beam, 82 ... Beam tail, 10
1, 102 ... Scattered electrons, 103 ... X-rays from bulk, 1
04 ... X-ray of analysis point, 105 ... Thin section of sample, 106 ...
Bulk part of sample, 107 ... Transmission electrons, 200 ... Space of diaphragm chamber, 400 ... Irradiation beam of diaphragm, 401 ... Main beam.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01J 37/252 H01J 37/252 AF terms (reference) 2G001 AA03 BA05 BA07 CA03 EA04 GA01 GA06 GA11 GA13 HA13 JA02 JA04 MA05 SA01 SA04 5C033 BB01 NN07 PP01

Claims (3)

[Claims] 1. A charged particle source, a charged particle optical system that converges a charged particle beam emitted from the charged particle source and scans the sample, and an objective that limits a convergence angle of the charged particle beam with which the sample is irradiated. A charged particle beam device comprising a lens diaphragm and detection means for detecting secondary signal particles generated from a sample by scanning the charged particle beam, and acquiring a sample image by a signal of the secondary signal particle detection means, A charged particle beam device, wherein a second diaphragm having an opening diameter of 5 times or less of the opening diameter of the objective lens diaphragm is arranged between the objective lens diaphragm and the deflecting means of the charged particle beam. 2. The first diaphragm according to claim 1, comprising a portion having an opening through which a charged particle beam can pass, and a current measuring means for measuring a current of the charged particle beam. A charged particle beam device comprising moving means for moving the position of the current measuring means onto the optical axis of the charged particle beam. 3. The charged particle beam device according to claim 1 or 2, wherein a tubular member made of a light element is arranged between the opening of the second diaphragm and the objective lens diaphragm. A charged particle beam device characterized by: