JPH08298093A - Scanning electron microscope and charged particle detecting method in scanning electron microscope - Google Patents

Abstract

PURPOSE: To discriminate energy of charged particles without arranging specific devices within a sample chamber to obtain a good image by installing a voltage applying means for varying potential in the vicinity of a sample by applying voltage to a functional member. CONSTITUTION: A voltage applying means 7 is set, voltage is applied to a functional member 5 arranged in the vicinity of a sample 2 with the voltage applying means 7 to produce an electric field in the vicinity of the sample 2. When the electric field is produced in the vicinity of the sample 2, charged particles having specific energy of the charged particles generated from the sample 2 are detected with a charged particle detector 4. Since intensity of the electric field can be adjusted with voltage applied to the functional member 5, by adjusting the voltage, charged particles having desired energy can be detected. Charged particles having desired energy can be detected without arranging a specific energy discriminating device in a sample chamber. Drop in emitting efficiency of charged particles caused by a space charge is reduced, and an image contrast can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning electron microscope and a method for detecting charged particles in a scanning electron microscope, and more particularly, to detecting charged particles emitted from a sample by irradiating the sample with an electron beam. The present invention relates to a scanning electron microscope provided with a container and a functional member having a specific function for observing a sample, and a charged particle detection method in the scanning electron microscope.

[0002]

2. Description of the Related Art Generally, a scanning electron microscope irradiates a sample while scanning it with an electron beam, detects charged particles from the sample with a charged particle detector, and outputs the output of the charged particle detector with the electron beam. An observation image is obtained by scanning and displaying in synchronization with scanning.

In such a scanning electron microscope, charged particles detected by a charged particle detector are passed through a charged particle discriminator so that only charged particles having a desired energy intensity among charged particles from a sample are passed. There is something to observe.

An example of such a scanning electron microscope is shown in FIG. The scanning electron microscope 30 shown in FIG.
The charged particle detector 31 is arranged below the objective lens 32, and the charged particle discriminating device 34 is arranged between the sample 33 and the charged particle detector 31. Here, 35 is a pollution control device in the sample chamber 39, and liquid nitrogen 37 is stored in the refrigerant container 36.
It is arranged inside to cool a cooling fin provided near the sample in the sample chamber 39.

As the charged particle discriminating device 34,
A Wien filter or an electrostatic filter is used. Here, the Wien filter is arranged such that the magnetic field and the electric field are perpendicular to each other, and the magnetic field and the electric field are perpendicular to the charged particles, and the forces exerted by the both on the particles are balanced to obtain a desired value. This is to sort out charged particles of energy.

[0006]

By the way, the conventional scanning electron microscope as described above has a structure in which the charged particle discriminating device is inserted between the sample, the objective lens and the charged particle detector. Besides being complicated, there is a problem that the working distance of the objective lens becomes long and the performance deteriorates.

Further, as described above, in such a scanning electron microscope, a functional member having various functions may be provided for observing a sample. In the above-mentioned example, as a functional member, a contamination prevention device is provided to prevent contamination of the sample and to maintain a high vacuum in the vicinity of the sample, and the cooling fins thereof are installed directly above the sample. In addition to pollution control devices, various types are used.

Therefore, mounting the above-mentioned energy discriminating device in the sample chamber of the scanning electron microscope in which various members are stored in this way complicates the entire device and increases the cost of the device. There's a problem. Further, in such a scanning electron microscope, when the sample is irradiated with an electron beam, the charged particles emitted onto the surface of the sample stay in the space, and a negative charge is generated. Space particles are formed by the particles that they have. In such a state, the secondary electrons emitted from the sample are in a saturated state on the surface of the sample, so that it is difficult for the charged particle detector to detect the secondary electrons, and there is a problem that an image with clear contrast cannot be obtained. .

Therefore, according to the present invention, it is possible to obtain a good image by discriminating the energy of the charged particles without disposing a special device in the sample chamber, and the secondary electrons are generated on the sample surface. An object of the present invention is to provide a scanning electron microscope capable of obtaining an image with good contrast even in a saturated state, and a charged particle detection method in the scanning electron microscope.

[0010]

In the present invention, the first means for solving the above problems is applied to a scanning electron microscope, and an electron beam 1 is irradiated onto a sample 2 as shown in FIG. In the scanning electron microscope 6, the charged particle detector 4 for detecting the charged particles 3 emitted from the sample 2 and the functional member 5 arranged in the vicinity of the sample 1 and having a specific function for observing the sample, The functional member 5 is connected to the functional member 5.
That is, the voltage applying means 7 for applying a voltage to change the potential in the vicinity of the sample 2 is provided.

The second means of the present invention relates to a method for detecting charged particles in a scanning electron microscope, which irradiates a sample 1 with an electron beam 1 to detect charged particles 3 emitted from the sample 2. Placed near the particle detector 4 and the sample 2,
In a scanning electron microscope equipped with a functional member 5 having a specific function for observing a sample, a voltage is applied to the functional member 5 to change the potential of the sample 2 and the vicinity of the sample, and a charged particle detector is used. It is to detect the charged particles 3.

Further, in each of the above-mentioned means, the functional member 5 can be used as a cooling member of the contamination preventing device for the sample chamber.

Further, in each of the above means, the functional member 5 may be a reflecting mirror for detecting cathodoluminescence.

[0014]

According to the present invention, when a voltage is applied to the functional member arranged in the vicinity of the sample by the voltage applying means,
An electric field is generated near the sample. Then, when an electric field is generated in the vicinity of the sample, the charged particles having a specific energy among the charged particles generated from the sample will be detected by the charged particle detection device. The strength of this electric field can be adjusted by the voltage applied to the functional member, and by adjusting this voltage, charged particles having a desired energy can be detected. Therefore, it is possible to detect charged particles of desired energy without providing a special energy discriminating device in the sample chamber.

Further, when a positive voltage is applied to the functional member, space charges are swept away, the emission efficiency of charged particles such as secondary electrons can be improved, and an image with good contrast can be obtained. The image charge can be improved by promoting positive charge-up on the sample surface.

[0016]

EXAMPLES Examples of a scanning electron microscope and a method for detecting charged particles in the scanning electron microscope according to the present invention will be described below.

FIG. 2 shows the configuration of the scanning electron microscope according to the present invention. In this embodiment, as shown in FIG. 2, in the scanning electron microscope, the sample 2 is arranged below the objective lens 8 in the sample chamber 10 of the lens barrel 9. A charged particle detector 4 for detecting charged particles from the sample is provided above the objective lens 8.

Further, in this embodiment, a cooling fin 14 of a pollution control device 11 is arranged between the sample 2 and the objective lens 8 to prevent contamination in the sample chamber 10 and increase the degree of vacuum. ing. In this embodiment, the pollution control device 11 is
It corresponds to the functional member in each means described above.

As in the case of the conventional example, the pollution preventing device 11 is constructed by arranging liquid nitrogen 13 in the refrigerant container 12 and cooling the cooling fins 14, and in the present embodiment. A power supply device 15 as a voltage applying means is connected to the cooling fin 14 so that an arbitrary plus / minus voltage can be applied.

Therefore, according to the scanning electron microscope of the present embodiment, it is possible to form a desired electric field in the vicinity of the sample without providing a special energy discriminating device in the sample chamber. Charged particles can be detected.

For example, when a part of the sample has a potential of -V volt, the secondary electron emission energy distribution is 0 volt as shown in FIG. 3 (shown by the curve A in FIG. 3). ), The distribution is shifted to the higher side (shown by the curve B in FIG. 3).

Here, when a negative potential is applied to the cooling fins 14, only charged particles having an energy equal to or higher than the energy indicated by C in FIG. 3 are shown (hatched in FIG. 3), as in the case where the energy discriminating device is provided. Is detected by the charged particle detector, and a clearer contrast can be obtained as compared with the case where all charged particles are detected.

Further, according to this embodiment, the cooling fins 14 are
When a sample is heated and observed by applying a negative voltage to, the thermo-electrons generated from the sample are suppressed so that they cannot be detected by the charged particle detector, thereby improving the image contrast. Can be improved.

On the other hand, when the cooling fins 14 are positively applied, it is possible to reduce the decrease in the charged particle emission efficiency due to the space charge due to the retention of the charged particles emitted on the sample surface 2.

Further, the image contrast can be improved by promoting positive charge-up on the sample surface,
The pattern of the insulator on the conductor can be easily observed.

That is, generally, the magnitude of the acceleration voltage of the incident electron beam and the emission efficiency of the charged particles to be emitted are compared as shown in FIG. That is, the emission efficiency of charged particles emitted when an electron beam with a low acceleration voltage is irradiated is
It may exceed 100%. Note that here, only the efficiency of the discharged charged particles is a problem, and the energy conservation law is satisfied.

In such a case, as shown in FIG. 4, for example, the integrated circuit 20 is used as a sample and the integrated circuit 2 is used.
In the case where 0 forms the insulator pattern composed of the oxide layer 22 by disposing the electrode 23 on the substrate 21,
Charged particles such as secondary electrons and backscattered electrons emitted from the electrode 23 which is a conductor are particles of negative charge, so positive charges remain in the oxide layer 22 which is an insulator, and the oxide layer 22 on the sample is The positive charge may be charged up.

When a positive voltage is applied to the cooling fin 14 in such a state, the efficiency of releasing particles having a negative charge from the electrode 23 is increased, and the positive charge amount of the oxide layer 22 is increased to increase the positive charge. The charge increases. Then, on the image, the plus area becomes a dark portion and the minus area becomes a bright portion, so that the contrast becomes clearer and the pattern of the oxide layer 22 and the electrode 23 becomes easy to observe.

FIG. 6 shows a second embodiment of the scanning electron microscope according to the present invention. In the present embodiment, the scanning electron microscope is capable of analyzing cathodoluminescence (CL), which is a phenomenon in which a sample emits light when irradiated with an electron beam. In this scanning electron microscope, the reflecting mirror 16 is provided immediately above the sample, and the light generated from the fine region irradiated with the electron beam is incident on the spectroscope 18. In the present embodiment, the pollution prevention device 11 corresponds to the functional member in each of the above-mentioned means, and a power supply device 18 as a voltage applying means is connected to the reflecting mirror 16 so that the reflecting mirror 16 is provided with plus / minus. An arbitrary voltage can be applied.

Therefore, according to the present embodiment, similarly to the first embodiment, it is possible to detect charged particles having a desired energy without providing a special energy discriminating device in the sample chamber, and the space charge can be detected. It is possible to reduce the decrease in the discharge efficiency of the charged particles due to, and to promote the positive charge-up on the sample surface to improve the image contrast.

In the above embodiments, the pollution preventing device and the reflecting mirror are described as the functional members for applying the voltage, but other functional members arranged near the sample, for example, backscattered electron detection. It may be a container.

[0032]

As described above, according to the present invention, the potential near the sample is changed by applying the voltage to the functional member arranged near the sample of the scanning electron microscope.
It is possible to detect charged particles of desired energy at low cost without providing a special energy discriminating device in the sample chamber, and it is possible to reduce the decrease in the emission efficiency of charged particles due to space charge. The effect that the positive charge-up on the sample surface can be promoted and the image contrast can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of a scanning electron microscope according to the present invention.

FIG. 2 is a cross-sectional view of essential parts showing the configuration of the first embodiment of the scanning electron microscope according to the present invention.

FIG. 3 is a diagram showing a state of detection of charged particles when a cooling fin is applied to the negative in the scanning electron microscope shown in FIG.

FIG. 4 is a diagram showing a state in which charged particles are released from a sample when a cooling fin is positively applied in the scanning electron microscope shown in FIG.

FIG. 5 is a diagram showing the acceleration voltage of an electron beam and the efficiency of charged particles emitted from a sample with respect to incident electrons.

FIG. 6 is a cross-sectional view of essential parts showing the configuration of a second embodiment of the scanning electron microscope according to the present invention.

FIG. 7 is a cross-sectional view of essential parts showing the configuration of a conventional scanning electron microscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron beam 2 Sample 3 Charged particle 4 Charged particle detector 5 Functional member 6 Scanning electron microscope 7 Voltage application means

Claims (4)

[Claims] 1. A sample (2) is irradiated with an electron beam (1),
A charged particle detector (4) for detecting charged particles (3) emitted from the sample (2) and a functional member (5) arranged near the sample (1) and having a specific function for observing the sample. In the scanning electron microscope (6), a voltage applying means (7) connected to the functional member (5) and applying a voltage to the functional member (5) to change the potential in the vicinity of the sample (2) is provided. Scanning electron microscope. 2. A sample (1) is irradiated with an electron beam (1),
A charged particle detector (4) for detecting charged particles (3) emitted from the sample (2) and a functional member (5) arranged near the sample (2) and having a specific function for observing the sample. In a scanning electron microscope provided, a scanning type in which a voltage is applied to the functional member (5) in order to change the potential of the sample (2) and the vicinity of the sample, and the charged particle detector detects the charged particles (3). A method for detecting charged particles in an electron microscope. 3. The method for detecting charged particles in a scanning electron microscope according to claim 1 or a scanning electron microscope according to claim 2, wherein the functional member (5) is a cooling member of a contamination preventing device for a sample chamber. 4. The method for detecting charged particles in a scanning electron microscope according to claim 1 or a scanning electron microscope according to claim 2, wherein the functional member (5) is a reflecting mirror for detecting cathodoluminescence.