JPS62133659A - Electron microscope with neutral particle beam radiating device - Google Patents

Abstract

PURPOSE:To realize an optimum design and improve the resolution without resticting the form of a pole piece for an object lens, by forming a gaseous layer on the electron beam optical axis, and radiating the electron beams to the gaseous layer. CONSTITUTION:On the way that electron beams 3 pass through an intermediate chamber 8, the electron beams strike to the accumulated gas molecules g in the intermediate chamber 8, giving the speed V1 in the direction of the electron beam passing to the gas molecules g. When the initial speed of the gas molecules g is V0, the given speed V=V0+V1. Furthermore, since the electrons which passed through a differential exhaust throttle 7 and the gas molecules repeat striking again and again to accelerate the speed of the gas molecules g, almost all the gas molecules g are converted into neutral particle beams 3' and radiated over the sample 5. The neutral particles radiated over the sample strike to the sample with a kinetic energy mv<2>. Since such neutral particles are not charged, they flow straightly without deflection in the magnetic field of the object lens, and irradiate the analysis point, or the electron beam radiating point accurately. Therefore, the gas and impurities attached over the sample 5 are removed, and a clean sample can be observed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electron microscope in which a sample is irradiated with a neutral particle beam.

[Prior art] In an electron microscope, etc., an ion generator is attached to the side or diagonally above the objective lens, and the sample is irradiated with ions from the ion generator to clean gases, contaminants, etc. that have adhered to the sample surface. The sample is being cleaned.

[Problems to be Solved by the Invention] In the device configured in this way, the ion generator is attached to the side or diagonally above the objective lens, so there are restrictions on the shape of the objective lens pole piece. Therefore, when designing the pole piece for the objective lens, these must be taken into consideration, which limits the improvement in resolution. In addition, when cleaning a sample by irradiating ions onto the electron beam irradiation point of the sample, the ions are deflected, albeit slightly, in the magnetic field of the objective lens, causing the ions to reach the target analysis point, that is, the electron beam. Instead of irradiating the irradiation point, a point different from the analysis point is irradiated. Therefore, if the ions are deflected, if the analysis point of the sample is irradiated with ions and then analyzed using the ion beam irradiation point as the electron beam irradiation point, it is necessary to analyze the sample with gases or impurities that have not been cleaned. There was a problem with analyzing points.

The present invention has been made in view of the above points, and enables an optimal design without imposing restrictions on the shape of the pole piece for an objective lens, thereby improving resolution and reliably cleaning the analysis point of the sample. The purpose is to provide equipment.

[Means for Solving the Problems] The configuration of the present invention for solving the problems is such that between two chambers evacuated to a relatively high vacuum inside the mirror body, a vacuum space lower than that of the two chambers is provided. an intermediate chamber that is evacuated to irradiate the gas layer formed in the intermediate chamber with an electron beam, generate a neutral particle beam accelerated by the electron beam irradiation, and irradiate the sample placed below the intermediate chamber with the neutral particle beam. It is characterized by being configured to do so.

[Example 1] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention.

In FIG. 1, 1 is a mirror body, and 2 is a focusing lens for focusing an electron beam 3 from an electron beam generation source (not shown).

4 is an objective lens, and 5 is a sample placed inside the objective lens 4. Reference numerals 6 and 7 denote differential exhaust apertures, and an intermediate chamber 8 is formed by the differential exhaust apertures 6 and 7. The chambers on the electron beam source side and the objective lens side other than the intermediate chamber 8 are e.g. It is evacuated to a relatively high vacuum of 10-7 Torr.

Reference numeral 9 denotes an exhaust pump such as a turbo molecular pump connected to the intermediate chamber v8 via a valve 10, and the intermediate chamber 8 is evacuated to a high vacuum by the exhaust pump 9. 11 is a gas container filled with, for example, high-pressure nitrogen (N2) gas, and the nitrogen gas G in the gas container 11 is supplied to a pressure reducing valve 12. Introduced into the intermediate chamber 8 via the valve 13 and the nozzle 14, for example 10'To
The pressure is maintained at about rr.

In the apparatus configured as described above, the pressure P (Torr) in the intermediate chamber 8 is as follows:
(TOrr-Q/5ec), exhaust speed S of exhaust pump 9
(Q/5ea), nitrogen gas of P=Q/S stays and a gas layer is formed in the intermediate chamber.

In this state, when the electron beam 3 enters the intermediate chamber 8, in the process of passing through the intermediate chamber 8, the electron beam collides with the gas molecules Q retained in the intermediate chamber, causing the gas molecules q to have a velocity Vl in the electron beam passing direction.
give. Here, if the initial velocity of the gas molecule Q is VQ, it is given by V=VQ +Vl.

In addition, since the electrons and gas molecules Q that have passed through the differential exhaust aperture 7 repeatedly collide and accelerate the gas molecules Q, most of the gas molecules Q become neutral particles as shown in Figure 1. line 3'
Then, the sample 5 is irradiated.

Neutral particles that irradiate this sample collide with the sample with a kinetic energy of mV2. Since such neutral particles have no electric charge, they are not deflected in the magnetic field of the objective lens (they travel straight and accurately irradiate the electron beam irradiation point, which is the analysis point).

By the way, the neutral particle beam 3' accelerated by the electron beam 3
The wire diameter is determined by the wire diameter of the electron beam 3, and since the electron beam has a very high density, the wire diameter of the neutral particle beam.

The neutral particle beam shade can be arbitrarily varied. Therefore, if the analysis point on the sample surface is irradiated with a neutral particle beam to clean it, and then the point irradiated with the neutral particle beam is analyzed as the irradiation point with an electron beam, gases and impurities attached to the surface of the sample 5 can be removed. The clean sample that has been removed can be observed. In addition, with a device configured in this way, unlike conventional devices, there is no need to install an ion irradiation device near the objective lens pole piece, so the shape of the pole piece can be designed in the optimal shape. It is possible to improve resolution.

[Example 2] Figure 2 is a schematic configuration diagram showing another example of the present invention.
Components that are the same as those of the embodiment shown in the figures are given the same numbers and their explanations will be omitted. In the embodiment shown in FIG. 2, two electron beam deflection coils 15 and 16 are arranged above the intermediate chamber 8.

In a device configured in this way, (a) and (a) are shown in Fig. 2.
As shown in (b), the electron beam 3 can be deflected by the electron beam deflection coils 15 and 16 to irradiate the gas layer in the intermediate chamber 8. Therefore, the flight direction of the neutral particle beam can be changed by the deflected electron beam 3, and therefore the sample surface can be scanned by the neutral particle beam. If the sample information generated from the sample in conjunction with this scanning is detected by the detector 17 and displayed on the display device, a scanned image such as a secondary electron image by neutral particle beam irradiation can be displayed and surface analysis can be performed. I can do it.

It should be noted that the above embodiments are illustrative and can be modified. In the above embodiment, an electron beam deflection coil is arranged above the intermediate chamber 8 to deflect the electron beam and irradiate the gas layer in the intermediate chamber 8. (not shown) may be arranged to deflect only the electron beam. In this case, the few electrons that have passed through the intermediate chamber 8 are deflected by the electron beam deflection coil and do not irradiate the sample surface, so no sample information is generated due to electron beam irradiation, and therefore, no sample information is generated due to electron beam irradiation. Only sample information can be retrieved.

Furthermore, electron beam deflection coils may be provided above and below the intermediate chamber 8, respectively. In this case, the electron beam 3 is deflected by the electron beam deflection coil provided above to change the direction of flight of the neutral particle beam to scan the sample surface for area analysis, and the electron beam is placed below the intermediate chamber 8. If the very few electrons that have passed through the intermediate chamber 8 are deflected by the electron beam deflection coil so that they do not irradiate the sample surface, surface analysis can be performed with sample information removed by electron beam irradiation. .

Furthermore, in the above embodiments, the gas layer was formed by forming an intermediate chamber, but it is sufficient that the gas layer is formed on the optical axis.
An electron beam source for irradiating a gas layer may be provided separately from an electron beam source for irradiating a sample. [Effects of the Invention] As detailed above, according to the present invention, a gas layer is formed on the optical axis of an electron beam. However, since the gas layer is irradiated with an electron beam, the shape of the pole piece for the objective lens is not restricted, making it possible to optimize the design, improve resolution, and clean the sample surface of the sample. Provided is an apparatus for reliably analyzing the composition of.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of one embodiment of the present invention, and FIG. 2 is a schematic diagram of another embodiment. 1: Mirror body, 2: Focusing lens, 3: Electron beam, 4: Objective lens, 5: Sample, 6, 7: Differential exhaust aperture, 8: Intermediate chamber, 9
: Exhaust pump, 10, 13: Valve, 11: Gas container,
12: Pressure reducing valve, 14: Nozzle, 15.16: Electron beam deflection coil, 17: Detector.

Claims (2)

[Claims] (1) Two chambers evacuated to a relatively high vacuum within the mirror body are connected to an intermediate chamber evacuated to a lower vacuum than the two chambers in order to form a gas layer in the intermediate chamber. A gas supply means and an electron beam generation source provided above the intermediate chamber are provided, and the gas layer formed in the intermediate chamber is irradiated with an electron beam from the electron beam generation source, and by the electron beam irradiation. 1. An electron microscope equipped with a neutral particle beam irradiation device, characterized in that it is configured to generate an accelerated neutral particle beam and irradiate the neutral particle beam onto a sample placed below an intermediate chamber. (2) An intermediate chamber that is evacuated to a lower vacuum than the two chambers is connected between two chambers evacuated to a relatively high vacuum in the mirror body in order to form a gas layer in the intermediate chamber. a gas supply means; an electron beam generation source provided above the intermediate chamber;
means for deflecting the electron beam from the electron beam generation source,
A gas layer formed in the intermediate chamber is irradiated with an electron beam from the electron beam generation source, and a neutral particle beam accelerated by the electron beam irradiation is generated and the electron beam is deflected to generate the neutral particles. 1. An electron microscope equipped with a neutral particle beam irradiation device, characterized in that the direction of the beam is changed so that the neutral particle beam scans a sample placed below an intermediate chamber.