JPS6314813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an apparatus in which a transmission imaging type electron microscope is added with a secondary electron detection means and an X-ray analysis means.

In recent years, it has become common to incorporate secondary electron detection means into transmission imaging electron microscopes to provide scanning electron microscope functions, and to incorporate X-ray analyzers to perform elemental analysis of minute regions on samples. Summer. However, in the transmission imaging electron microscope, since the sample is placed in a narrow space between the magnetic pole pieces of the objective lens, it has been difficult to efficiently detect various signals generated from the sample. For example, when trying to detect X-rays generated from a sample through an electron beam passage hole formed in the upper magnetic pole piece of an objective lens, a sensor is placed near the electron beam passage hole in the upper magnetic pole piece in order to remove background X-rays. Although it is necessary to provide a collimator in the sample, the presence of this collimator may become an obstacle in detecting secondary electrons generated from the sample. In other words, in order to obtain a high-resolution scanning electron microscope, the objective lens is strongly excited and the lens magnetic field formed in front (above) the sample is used not only as the final focusing lens for the irradiated electron beam, but also as a final focusing lens for the irradiated electron beam. Because the system utilizes the effect of trapping weak energy secondary electrons in a helical orbit in the direction of the optical axis, the detection efficiency of secondary electrons hardly decreases even if the hole diameter of the upper magnetic pole piece becomes smaller. Who? However, in order to obtain a scanned image with low magnification, it is necessary to set the excitation of the objective lens to zero or weakly and use the focusing lens installed above it as the final stage focusing lens in order to increase the depth of focus. Often, in this case, a magnetic field is not formed between the sample and the upper magnetic pole piece of the objective lens, or the magnetic field is weak due to weak excitation, making it impossible to effectively guide the secondary electrons generated from the sample upward. If a collimator is installed near the hole of the upper magnetic pole piece to reduce its effective hole diameter, it is inevitable that the detection efficiency of secondary electrons will be reduced accordingly.

An object of the present invention is to eliminate the drawbacks of the conventional apparatus described above and to efficiently detect secondary electrons even when the excitation of the objective lens is reduced to zero. A sample 5 is placed in the gap between the upper magnetic pole piece 1 and the lower magnetic pole piece 2 of an objective lens used for the purpose, and is kept at ground potential. It is equipped with a secondary electron detector D and a collimator member 6 that is inserted into and attached to the electron beam passage hole of the upper magnetic pole piece 1, and the collimator member 6 collimates the X-rays generated from the sample 5. The collimator member has a hole 7 for guiding it to the X-ray detector 8, and a hole 18 for passing the secondary electrons generated from the sample 5 toward the secondary electron detector D side.
In an apparatus that irradiates the sample 5 with an electron beam by passing through the hole 18, a ring-shaped electrode 14 is disposed between the sample 5 and the upper magnetic pole piece 1; It is characterized by comprising means 15 and 13 for applying a negative potential to the collimator member 6 and a positive potential to the collimator member 6, and forming an electrostatic lens field above the sample, and by this lens field. The secondary electrons generated from the sample are focused and efficiently passed through the hole 18 having a small diameter.

The figure schematically shows the main parts of an apparatus according to an embodiment of the present invention. In the figure, reference numerals 1 and 2 indicate an upper magnetic pole piece and a lower magnetic pole piece of the objective lens, respectively, in which electron beam passage holes symmetrically shaped with respect to the optical axis 3 are bored. A sample 5 held by a sample holder 4 is installed approximately in the center between the upper and lower magnetic pole pieces, and a lens magnetic field symmetrical to the optical axis formed above the sample 5 serves as the final stage for the electron beam irradiating the sample. Acts as a focusing lens. A collimator member 6 is provided near the electron beam passage hole of the upper magnetic pole piece 1, and an electron beam passage hole 18 is bored in the center of the member 6. A hole 7 is drilled to act as a collimator. Therefore, the X-rays generated from the sample pass through the hole 7 of the collimator member 6 and enter the X-ray detector 8, where their wavelength or energy is separated into spectra.
On the other hand, when the collimator member 6 is not provided, the secondary electrons generated from the sample follow the broken line 9 in the figure.
It traces a trajectory as shown in and reaches above the upper magnetic pole piece. A secondary electron detector D is arranged above the upper magnetic pole piece, and includes a light pipe 10, a scintillator provided on the end surface of the light pipe 10, an accelerating electrode 11, a cylindrical electrode 12, and the like. An electric field for focusing secondary electrons is formed by an accelerating electrode 11 attached to the tip of the light pipe 10 and to which a voltage of about +10 KV is applied, and a cylindrical electrode 12 attached around it.
is deflected in the direction of the accelerating electrode 11 and irradiates the scintillator provided at the end face of the light pipe 10. The secondary electrons that hit the scintillator are converted into light and then converted into electrical signals by a photomultiplier tube. However, due to the presence of the collimator member 6, most of the secondary electrons generated from the sample cannot reach above the upper magnetic pole piece, which deteriorates the detection efficiency of secondary electrons. .

In order to eliminate such drawbacks, in the present invention, the collimator member 6 is electrically insulated from the surrounding members such as the upper magnetic pole piece 1, and a voltage of about several tens of volts is applied by the variable power supply 13, and the collimator member 6 is A variable power supply 15 applies a voltage of about minus several volts to a ring-shaped electrode 14 provided below the meter member 6. In this way, an electrostatic lens field is created above the sample holder 5 (or the sample) at ground potential, which lens field has a focusing effect on the secondary electrons emanating from the sample. Therefore, the secondary electrons generated from the sample are subjected to a strong focusing action as well as the focusing action received from the objective lens magnetic field, and the collimator member 6 draws a trajectory as shown by the solid line 16 instead of the trajectory shown by the broken line 9 in the figure. A cross-over image is formed at the position shown at 17 in the figure through the central hole of the electron beam, and the scintillator near the accelerating electrode 11 is irradiated. Therefore, it is possible to maintain high secondary electron detection efficiency regardless of the presence or absence of the collimator member 6.

As described above, according to the present invention, both X-ray detection and secondary electron detection can be performed with high detection efficiency, so when applied to a transmission imaging electron microscope, its utility value is significantly improved. .

[Brief explanation of the drawing]

The drawing is a schematic diagram showing the main parts of an embodiment of the device based on the present invention. 1... Upper magnetic pole piece, 2... Lower magnetic pole piece, 3... Optical axis, 4...
Sample holder, 5... sample, 6... collimator member,
8... X-ray detector, 9, 16... Secondary electron, 10... Light pipe, 11... Accelerating electrode, 12... Cylindrical electrode,
13, 15... variable power supply, 14... ring-shaped electrode.

Claims (1)

[Claims] 1 A sample 5 is placed in the gap between the upper magnetic pole piece 1 and the lower magnetic pole piece 2 of an objective lens used in a transmission imaging electron microscope and is kept at ground potential, and the sample 5 is placed above the upper magnetic pole piece 1. It is equipped with an X-ray detector 8, a secondary electron detector D, and a collimator member 6 that is inserted and attached to the electron beam passing hole of the upper magnetic pole piece 1, and the collimator member 6 is generated from the sample 5. A hole 7 is provided for collimating X-rays and guiding them to the X-ray detector 8, and the collimator member allows secondary electrons generated from the sample 5 to pass toward the secondary electron detector D side. It has a hole 18 for
In an apparatus for irradiating the sample 5 with an electron beam through the hole 18, a ring-shaped electrode 14 disposed between the sample 5 and the upper magnetic pole piece 1 and a negative potential with respect to the ring-shaped electrode 14 are provided. A signal detection device for an electron microscope, comprising means 15 and 13 for applying a positive potential to the collimator member 6.