JPS6112332B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in backscattered electron detection devices for scanning electron microscopes and the like.

A scanning electron microscope is used as an effective device for two-dimensionally observing the unevenness of a sample surface and the distribution of constituent substances. This scanning electron microscope irradiates a sample with an electron beam having a minute diameter, and uses an electron beam detector to detect reflected electrons, secondary electrons, etc. generated from the sample by the irradiation, and detects the signal obtained from the electron beam. A concavo-convex image is obtained by using it as a brightness modulation signal of a cathode ray tube synchronized with scanning on the sample surface. Nowadays, in scanning electron microscopes, a magnetic substance is loaded into a sample chamber, and its magnetic domain structure is observed using a backscattered electron image. In this case, the magnetic domain contrast depends on the solid angle (hereinafter simply referred to as solid angle) observed by the backscattered electron detector at the electron beam irradiation point on the sample. However, in the conventional apparatus, the backscattered electron detector is directly fixed to the inner wall of the sample chamber, so the solid angle mentioned above is constant, and therefore the magnetic domain structure cannot be observed even with the optimum magnetic domain contrast.

In order to eliminate such drawbacks, the present invention provides an apparatus that can independently and arbitrarily adjust the solid angle and the detection angle of reflected electrons, and will be described in detail below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 2 is a view seen from direction A in FIG. 1, where 1 is a side wall of a sample chamber of a scanning electron microscope. 2 is the side wall 1
A sample stage is horizontally movable inside the sample stage, and a sample holder 4 holding a sample 3 on its upper surface is placed. Reference numeral 5 denotes a rotary tube that penetrates the side wall 1 in an airtight manner with an O-ring packing 6, and the axis of the rotary tube is placed to intersect with the optical axis of the electron beam. The surface of the sample 3 is placed at the intersection of the axial center and the optical axis. A shaft 8 is concentrically and movably inserted into the rotary cylinder 5 via an O-ring packing 7, and the rotary cylinder 5
A guide body 9 is fixed to one end (vacuum side), and a knob portion 10 and a male screw portion 11 are formed at the other end (atmospheric side). A movable body 12 is attached to the guide body 9 so as to be movable in a direction perpendicular to the axis of the rotary cylinder 5. A lever body 13 rotatably attached to the guide body 9 is interposed between the movable body 12 and the shaft 8, and the movable body 1
2 is constantly pressed by a spring 14 so as to engage with the lever body 13. A cap nut 15 is screwed into the male screw portion 11 formed on the rotary cylinder 5, and the cap nut 15 is connected to the shaft 8 via a screw 16.
is fixed at the end of the 17 is the moving body 12
A backscattered electron detector 18, such as a PN junction semiconductor, is attached to the bottom surface of the tip of the holding plate, that is, the surface facing the sample 3. The backscattered electron detector 18 detects backscattered electrons E generated from the sample based on electron beam irradiation, and the detected signal is amplified via an amplifier not shown and then supplied to the brightness modulation grid of the cathode ray tube. .

However, now, when the cap nut 15 is rotated, for example, clockwise, the shaft 8 moves forward (in the direction of arrow B in FIG. 1).
However, since this movement is transmitted to the movable body 12 via the lever body 13, the movable body 12, that is, the holding plate 17, moves upward as shown by the dotted line a in FIG. This moves the backscattered electron detector 18 away from the sample 3, so the solid angle becomes smaller. Furthermore, if the cap nut 15 is rotated in the opposite direction (counterclockwise) to the above, the movable body 12 (holding plate 17) descends, and the anti-electron detector 18 approaches the sample 3 in the opposite direction to the above. Therefore, the solid angle becomes larger. Therefore, by arbitrarily operating the cap nut 15, the solid angle can be arbitrarily selected at a certain take-off angle of reflected electrons.

On the other hand, when the rotary tube 5 is rotated clockwise or counterclockwise using the knob 10, the guide body 9 and the movable body 1 are rotated.
Since the backscattered electron detector 18 rotates around the electron beam irradiation point on the sample 3 via the backscattered electron detector 2 and the holding plate 17, the detection angle of backscattered electrons can be changed.

As described in detail above, according to the present invention, the backscattered electron detector can be rotated around the electron beam irradiation point on the sample, or moved closer to or away from the sample, so the detection angle of backscattered electrons can be set arbitrarily. Not only can the solid angle be set, but also the solid angle can be arbitrarily adjusted within the set angle. Therefore, the magnetic domain structure can always be observed with optimal contrast.

In addition, when observing a scanned image of a sample with high resolution, the electron beam for irradiating the sample is focused very narrowly, so the beam current becomes very small, and the output signal from the backscattered electron detector decreases, causing the S/N ratio to decrease. However, in the present invention, since the backscattered electron detector can be brought closer to the sample, the amount of backscattered electrons to the backscattered electron detector can be increased, and the S/N ratio can be improved. It has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 2 is a view of FIG. 1 viewed from direction A. In the figure, 1 is the sample chamber side wall, 2 is the sample stage, 3 is the sample, 4 is the sample holder, 5 is the rotary cylinder,
6 and 7 are O-ring packing, 8 is a shaft, 9 is a guide body, 10 is a knob part, 11 is a male thread part, 12 is a moving body, 13 is a lever body, 14 is a spring, 15
is a cap nut, 16 is a screw, 17 is a detector holding plate,
18 is a backscattered electron detector.

Claims (1)

[Claims] 1. A cylindrical rotating body installed through the sample chamber wall so that its axis is perpendicular to the optical axis of the electron beam;
a sample arranged so that its surface coincides with the point where the axis of the rotating body and the optical axis of the electron beam intersect; a guide body fixed to the rotating body on the side of the sample chamber; a movable body mounted so as to be movable; and a movable body disposed to face the sample;
and a backscattered electron detector attached to the moving body, wherein the moving direction of the moving body along the guide is perpendicular to the detection surface of the backscattered electron detector and also perpendicular to the axis of the rotating body. A backscattered electron detection device in a scanning electron microscope characterized by the following.