JPH0532926Y2 - - Google Patents

Description

[Detailed description of the invention] This invention enables observation of high-resolution scanning electron microscope images with a single lens, observation of large samples and large-angle sample tilts,
Furthermore, the present invention relates to an objective lens for a scanning electron microscope that allows easy observation of magnetic samples.

In a scanning electron microscope, the most common objective lens has a structure as shown in FIG. 1a.
In the figure, reference numeral 1 denotes a lens yoke with an excitation coil 2 wound therein, and the magnetic flux excited by the coil passes through the yoke 1 and the upper and lower magnetic pole pieces 3 formed at the ends of the yoke. 4 parts to form a lens magnetic field between both pole pieces. Reference numeral 5 denotes an observation sample, which is placed below the lower magnetic pole piece 4 in a place where it is not affected by the lens magnetic field. Since such an objective lens places the sample away from the lens magnetic field, it is possible to observe the magnetic sample, and since the distance (working distance) between the magnetic pole piece and the sample can be large,
It is possible to tilt the sample at a large angle, observe a large sample, take out X-rays at a high angle, etc. However, it also has the disadvantage that it is not possible to observe high-resolution scanning electron microscope images because the working distance or focal length cannot be reduced.

FIG. 1b shows an objective lens for high-resolution scanning electron microscope image observation, in which a sample is placed in a strong magnetic field between the upper and lower magnetic pole pieces of the objective lens. This allows the working distance or focal length to be significantly shortened and high-resolution scanning electron microscopy images can be obtained, but since the sample is placed between narrow magnetic pole pieces, the sample is limited to very small size and large angles. Tilting, etc. becomes impossible, and magnetic samples cannot be observed.

Therefore, recently, an objective lens as shown in the specification of Japanese Patent Application Laid-open No. 118356/1983 has been developed. The lens is configured so that at least the end of the lower magnetic pole piece can be removed or replaced so that the sample is placed in the lens magnetic field from a state where no lens magnetic field is applied to the sample, and has a long working distance and a short working distance. This makes it possible to switch between stances. However, in such lenses, the lower magnetic pole piece must be replaced or removed one by one depending on the purpose of observation, which increases the size of the lens structure, and replacement requires breaking the vacuum of the scanning electron microscope lens barrel. It is very difficult to handle as it has to be carried out with a hand.

The object of the present invention is to eliminate the drawbacks of the conventional objective lenses described above and to provide an objective lens for a scanning electron microscope whose working distance can be easily switched.

In order to achieve such an object, the present invention provides a lens comprising a lens yoke, an excitation coil, and upper and lower magnetic pole pieces that form a magnetic pole gap at the lower end of the yoke, in which the center part of the lower magnetic pole piece is connected to another magnetic pole piece. The center lower magnetic pole piece is divided into parts, and a minute electron beam passage hole is bored in the divided central lower magnetic pole piece to prevent the lens magnetic field from leaking to the sample position below, and the central lower magnetic pole piece can be moved between the upper and lower magnetic pole pieces. A moving mechanism is incorporated between the two magnetic pole pieces for selectively magnetically contacting the central lower magnetic pole piece with the other part of the upper magnetic pole piece or the lower magnetic pole piece from outside the lens, and the central lower magnetic pole piece is so that the lens magnetic field formed between the central lower magnetic pole piece and the lower magnetic pole piece when magnetically contacting the upper magnetic pole piece leaks to the sample side through a hole formed in the lower magnetic pole piece; It is characterized in that the central lower pole piece is formed large.

2 and 3 are cross-sectional views showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 indicate the same components. In the present invention, the lower magnetic pole piece 4 is 4a
and 4b, with a central magnetic pole piece 4
A minute electron beam passing hole 4a' is bored in the center of a to prevent the lens magnetic field from leaking downward, and the hole 4b' in the remaining magnetic pole piece 4b allows the lens magnetic field to fully extend downward, so that the sample 5 can be The hole diameter is such that the lens is placed within the magnetic field. The central magnetic pole piece 4a can be attached to and removed from the remaining portion 4b, and is integrated with the annular male screw body 6. The annular male screw body is screwed into an annular female screw body 7 disposed on the outer periphery of the magnetic pole piece, and although not shown, the male screw body is provided with an appropriate rotation prevention mechanism, and the female screw body The male screw body is configured to move up and down by rotating the body. A bevel gear 8 is carved on the outer periphery of the annular female screw body 7, and a bevel gear 9 meshes with the bevel gear 8.
The shaft 10 is taken out to the outside of the lens, and a knob 11 is attached to the tip.

In such a configuration, when performing tilted observation of a sample at a large angle or observation of a magnetic sample, the sample must be placed outside the lens magnetic field, and the central lower magnetic pole piece 4a must be placed outside the lens magnetic field as shown in 4b. In this state, since the magnetic pole piece having the minute electron beam passage hole constitutes the lower magnetic pole piece, the lens magnetic field does not leak from the passage hole 4a' and overhang in the direction of the sample 5. Therefore, by increasing the working distance, it is possible to tilt the sample at a large angle, take out X-rays at a high angle, and observe a magnetic sample.

On the other hand, if you want to observe a sample with high resolution,
When the knob 11 is rotated to rotate the annular female screw body 7 via the shaft 10 and the bevel gears 9 and 8, the annular male screw body 6 screwed therewith moves upward, as shown in FIG. The central lower magnetic pole piece 4a is magnetically joined to the upper magnetic pole piece 3 as shown in FIG. As a result, the central lower magnetic pole piece 4a
acts as an upper magnetic pole piece, and as is clear from the figure, the magnetic flux constituting the lens extends largely below the lower magnetic pole piece, and the sample 5 is placed in the lens magnetic field. Of course, the sample can also be placed within the gap between the lens magnetic poles, if necessary. As a result, the working distance of the objective lens becomes extremely short, making it possible to observe high-resolution scanning electron microscope images.

With the above configuration, you can simply connect the knob 1 from the outside.
It is possible to change the working distance by simply rotating 1, and with a simple configuration and easy handling, a single lens can be used to observe high-resolution scanning electron microscope images, observe magnetic samples, and observe large angle tilts. This provides an extremely practical objective lens that allows switching observation such as the following.

Furthermore, in the objective lens for a scanning electron microscope based on the present invention, when the central lower magnetic pole piece magnetically contacts the upper magnetic pole piece, the lens magnetic field formed between the central lower magnetic pole piece and the lower magnetic pole piece is , leaks to the sample side through the hole formed in the lower magnetic pole piece, so that the main surface of the objective lens approaches the sample side greatly. Therefore, high-resolution observation with a short working distance is possible without inserting the sample into the narrow space between the upper and lower magnetic pole pieces. Therefore, by using the objective lens of the scanning electron microscope of the present invention, there is no need to insert the sample into the narrow space between the upper and lower magnetic pole pieces, so even if the sample is large, the center lower magnetic pole piece can be magnetically attached to the upper magnetic pole piece. High-resolution observation of the sample is possible with a simple operation of bringing the sample into contact with the sample.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a conventional objective lens for a scanning electron microscope, and FIGS. 2 and 3 are sectional views showing an embodiment of the present invention. 1... Lens yoke, 2... Excitation coil, 3...
...Top pole piece, 4...Bottom pole piece, 4a...Central part of the bottom pole piece, 4b...Remaining part of the bottom pole piece, 5...Sample,
6... Annular male screw body, 7... Annular female screw body, 8,
9... bevel gear, 10... shaft, 11... knob.

Claims (1)

[Scope of utility model registration request] In a lens consisting of a lens yoke, an excitation coil, and upper and lower magnetic pole pieces that form a magnetic pole gap at the lower end of the yoke, a central portion of the lower magnetic pole piece is divided from other portions, and the divided central lower magnetic pole A minute electron beam passing hole is bored in the piece to prevent the lens magnetic field from leaking to the sample position below, and the central lower magnetic pole piece is movably supported between the upper and lower magnetic pole pieces, and the central lower magnetic pole piece is attached to the outside of the lens. A moving mechanism for selectively magnetically contacting the upper magnetic pole piece or the other part of the lower magnetic pole piece is incorporated between the two magnetic pole pieces, and when the central lower magnetic pole piece magnetically contacts the upper magnetic pole piece, The central lower magnetic pole piece is formed large so that the lens magnetic field formed between the central lower magnetic pole piece and the lower magnetic pole piece leaks to the sample side through the hole formed in the lower magnetic pole piece. Objective lens for scanning electron microscope.