JP2008267981A - Sample observation method using electron beam apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To observe irregularities of the surfaces of a sample without having to directly irradiate an electron beam to the surfaces of the sample. <P>SOLUTION: In a sample observation method using an electron beam apparatus for observing the state of the surfaces of samples by irradiating an electron beam to the sample and detecting secondary electrons emitted from the sample, a dielectric material is mounted onto the sample, and the sample and the dielectric material are brought into contact to generate contact charging. By observing the contrast of surface potential induced in the surfaces of the dielectric material caused by contact charging on the basis of images using secondary electrons, irregularities of the surfaces of the sample are observed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electron beam apparatus that observes a sample surface using an electron beam, for example, a sample observation method using a scanning electron microscope, a liquid crystal substrate inspection apparatus, an EB tester, and a semiconductor substrate inspection apparatus.

The electron beam device converges the electron beam from the electron gun and irradiates the sample surface as an electron beam, detects secondary electrons generated from the sample, and scans the irradiation position of the electron beam on the sample surface. Is used to observe the sample.

  When observing the surface of a dielectric sample using a scanning electron microscope, which is one of the electron beam devices, it is necessary to make the surface to be observed conductive by evaporating a conductive thin film such as gold. There is. This is because the electrons incident on the sample are accumulated on the surface of the dielectric sample, and the balance between the irradiated electron beam and the secondary electrons generated from the sample is lost. Is to prevent.

As an example of the prior art, Patent Document 1 describes preventing a charge-up phenomenon by depositing a thin film such as carbon or gold when observing an insulating sample surface.
JP-A-9-43289

  When observing the surface of a dielectric sample using a scanning electron microscope, it is necessary to make the surface to be observed conductive by evaporating a conductive thin film such as gold to prevent charge-up. . In order to deposit a conductive thin film such as gold on the sample surface, vapor deposition using a vacuum apparatus is generally used, but it is a very time-consuming operation. Some samples are not suitable for heating during vapor deposition.

Furthermore, when the sample surface is observed using a liquid crystal substrate inspection apparatus or the like, the sample may be damaged by the electron beam irradiation, or the sample may be soiled.

In order to solve the above-described problems, the present invention provides a sample observation method using an electron beam apparatus that observes the state of a sample surface by irradiating the sample with an electron beam and detecting secondary electrons emitted from the sample. In this case, a dielectric material is placed on the sample and contact charging is caused by bringing the sample and the dielectric material into contact with each other, and the contrast of the surface potential induced on the surface of the dielectric material due to the contact charging is secondary. It is characterized by observing the unevenness of the sample surface by observing with an image using electrons.

According to the observation method of the present invention, the sample is not directly irradiated with the electron beam. Therefore, when this is used in a scanning electron microscope, a substrate inspection apparatus, or the like, the effects described later can be obtained.

When observing a dielectric sample surface with a scanning electron microscope, it is possible to observe irregularities on the sample surface without taking charge-up prevention means by vapor deposition of a conductive thin film such as gold, which has been conventionally required. . Further, even a sample that is weak against heat and cannot withstand the heating during vapor deposition can be observed.

When observing the surface of a sample in a liquid crystal substrate inspection apparatus or the like, the sample is not damaged by the electron beam irradiation and the sample is not contaminated.

  An embodiment of the present invention will be described by taking a scanning electron microscope as an example with reference to the drawings. FIG. 1 is a schematic configuration diagram when the observation method of the present invention is carried out using a scanning electron microscope.

  The scanning electron microscope 1 includes an electron gun 2 and an anode 3 that irradiate a primary beam 12, a condenser lens 4 that focuses the primary beam 12, and an objective that focuses the primary beam 12 on a dielectric material 16 placed on a sample 15. Lens 6, deflection coil 5 and scanning power source 7 for scanning primary beam 12, detector 8 for detecting secondary electrons 13 emitted from dielectric material 16 by irradiation of primary beam 12, and amplifier 9 for amplifying the detected signal And a cathode ray tube 10 or the like for imaging based on the amplified signal.

  The operation of this apparatus will be described with reference to FIG. The primary beam 12 exiting the electron gun 2 is accelerated by the anode 3 and then converged by the condenser lens 4. The primary beam 12 that has passed through the condenser lens 4 is deflected by the deflection coil 5 in accordance with the current value from the scanning power supply 7. The deflected primary beam 12 is converged so as to be focused on the dielectric material 16 placed on the sample 15 by the objective lens 6.

  When the dielectric material 16 is irradiated with the primary beam 12, secondary electrons 13 are emitted. However, a potential corresponding to the unevenness of the sample 15 is induced on the surface of the dielectric material 16 by contact charging. A contrast corresponding to a potential generated by contact charging is generated in the emitted secondary electrons.

  Here, a process in which a potential corresponding to the unevenness of the sample 15 is induced on the surface of the dielectric material 16 by contact charging will be described with reference to FIG.

FIG. 2A shows the sample 15 and the dielectric material 16 before contact. The sample 15 is not limited to a dielectric, but may be a conductor. The dielectric material 16 is a thin dielectric such as glass. At this stage, no charge appears in the sample 15 and the dielectric material 16.

FIG. 2B shows a state when the sample 15 and the dielectric material 16 are brought into contact with each other. Charge transfer occurs at the contact interface. In the embodiment, as a result of the movement of charges, a positive charge 21 is generated on the dielectric material 16 side and a negative charge 22 is generated on the sample 15 side. The polarity of the charge is not limited to the present embodiment, and a charge having a polarity corresponding to the combination of the dielectric material 16 and the material of the sample 15 is generated.

  FIG. 2C shows a state in which surface charges 23 are generated on the surface of the dielectric material 16. The electric charge generated at the contact interface forms an electric dipole, and the dielectric material 16 generates a dielectric polarization in the dielectric material 16 by a local electric field of the electric dipole. As a result, a surface charge 23 corresponding to the unevenness of the sample 15 is induced on the surface of the thin dielectric material 16. Since the surface charge 23 induced on the surface cannot move freely, it is localized on the surface. In this way, a potential corresponding to the unevenness of the sample 15 is induced on the surface of the dielectric material 16.

The inventor has confirmed that the surface charge 23 is induced using 0.7 mm thick glass as the dielectric material 16. However, the thickness of the dielectric material 16 is limited to 0.7 mm. The thickness may be any thickness that induces the surface charge 23. If it is extremely thin, it is difficult to handle, and if it is extremely thick, surface charge is not induced. Therefore, a thickness of 0.5 mm to 1 mm is considered appropriate. The dielectric material 16 can be made of glass, acrylic, PDMS, or the like, but is not limited thereto.

  Returning to FIG. When the surface of the dielectric material 16 is irradiated with the primary beam 12, secondary electrons 13 are emitted, but the surface charge 23 is localized on the surface of the dielectric material 16, and the surface charge 23 is distributed. Therefore, the emitted secondary electrons 13 have a contrast according to the distribution of the surface charges 23. At this time, the surface of the dielectric material 16 is charged up by the irradiation of the primary beam 12. However, if the irradiation amount is a general amount, the level is negligible compared to the surface charge 23, which affects the microscopic image. There is nothing.

  The emitted secondary electrons 13 are detected by the detector 8 and converted into electrical signals. The amplifier 9 amplifies the electric signal, and the amplified signal controls the luminance of the cathode ray tube 10. Since a current synchronized with the current from the scanning power supply 7 to the deflection coil 5 flows through the deflection coil 11 of the cathode ray tube 10, a contrast corresponding to the potential distribution on the surface of the dielectric material 16 is displayed on the cathode ray tube 10. Since the potential distribution on the surface of the dielectric material 16 corresponds to the unevenness on the surface of the sample 15, the unevenness on the surface of the sample 15 can be observed.

  FIG. 3 is an image of the unevenness of the sample surface actually obtained by a scanning electron microscope using the observation method of the present invention. The sample 15 was an aluminum plate, and the dielectric material 16 was 0.7 mm thick glass.

It is a schematic block diagram of the scanning electron microscope of this invention. FIG. 6 is a diagram for explaining a process in which a potential corresponding to the unevenness of a sample 15 is induced on the surface of a dielectric material 16 by contact charging. It is an image of the unevenness | corrugation of the sample surface acquired using the scanning electron microscope of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Scanning electron microscope, 2 ... Electron gun, 3 ... Anode, 4 ... Condenser lens, 5 ... Deflection coil, 6 ... Objective lens, 7 ... Scanning power supply, 8 ... Detector, 9 ... Amplifier, 10 ... CRT, 11 DESCRIPTION OF SYMBOLS ... Deflection coil, 12 ... Primary beam, 13 ... Secondary electron, 14 ... Sample mounting stand, 15 ... Sample, 16 ... Dielectric material, 21 ... Positive charge, 22 ... Negative charge, 23 ... Surface charge

Claims (3)

In a sample observation method using an electron beam apparatus that observes the state of a sample surface by irradiating the sample with an electron beam and detecting secondary electrons emitted from the sample, a dielectric material is placed on the sample, Contact charging is caused by bringing the sample into contact with the dielectric material, and the contrast of the surface potential induced on the surface of the dielectric material due to the contact charging is observed by an image using the secondary electrons. The sample observation method using the electron beam apparatus characterized by observing the unevenness | corrugation of the said sample surface by this.   The sample observation method using an electron beam apparatus according to claim 1, wherein the dielectric material is one of glass, acrylic, and PDMS.   3. The sample observation method using an electron beam apparatus according to claim 1, wherein the dielectric material has a thickness of 0.5 mm to 1 mm.