JPS5952513B2 - Scanning electron microscope sample fine movement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a sample fine movement device for a scanning electron microscope.

As the range of applications of scanning electron microscopes (hereinafter referred to as SEMs) and similar devices for observing and analyzing the surface structure of objects has expanded, improvements have been required to accommodate them.

One of the most important issues is the improvement to cope with increasing sample size.

FIG. 1 is a diagram illustrating the operation of a sample fine movement mechanism and the size of a sample chamber in a conventional SEM.

When observing the entire surface of the disk-shaped sample 1, which has the outer diameter, the movement of the sample fine movement device in the X and Y directions moves la,
Since the sample 1 must be moved to positions lb, IC and 1d, the sample chamber 2 must have a circular space with a diameter of at least 2D.

If a sample with twice the diameter is to be observed, a sample chamber with four times the area is required, and the capacity of the vacuum evacuation system and sample fine movement mechanism become large and expensive, and the position of the detector 3 is placed on the sample surface. A problem has arisen in that detection sensitivity decreases as the distance increases.

FIG. 2 is a front view of a conventional SEM sample fine movement device, in which the sample 1 is placed on a Y-direction moving table 5, and the Y-direction moving table 5 is placed on an X-direction moving table 4.

These moving tables can be moved from outside the sample chamber 2 in a vacuum state by rotating the X drive shaft 13 and the X drive shaft 7 inserted through an O-ring 15 provided on the sample chamber wall 18. .

Reference numeral 8 denotes an operating knob for the X drive shaft 7. When the operating knob 8 is rotated in the forward direction, the X drive shaft 7 moves left and right, and the X direction moving base 4
Press.

When the operation knob 8 is rotated in the opposite direction, the X-direction moving table 4 returns to the right by a push spring provided on the opposite side of the X drive shaft 7.

On the other hand, when the operating knob 14 is rotated, the universal joint 12 rotates, causing the spline joint 11 and the universal joint 10 to rotate.

The shaft 16 at the tip of the universal joint 10 is fitted and supported by a bearing 9 installed on the X-direction moving table 4, and the small gear (not shown) at the tip meshes with the rack part of the Y-direction moving table 5. ing.

Therefore, by rotating the operating knob 14, the Y-direction moving table 5 can be moved in the Y-direction perpendicular to the plane of the paper.

In such a conventional sample fine movement device, as the sample becomes larger, the amount of movement of the sample moving stage increases as explained in FIG. 1.

In particular, the threaded part of the X drive shaft 7 becomes longer and protrudes to the outside.
The spline joint used in the drive system in the Y direction also becomes long, takes time to operate, and tends to operate unsmoothly.

Also, of course, the sample chamber 2 that accommodates these sample fine movement devices has a large capacity, and it takes time to create a vacuum state.
As mentioned above, the distance between the detector 3 and the sample 1 increases, resulting in a decrease in detection sensitivity.

The present invention aims to provide a small sample fine movement device suitable for observing a large sample in a sample chamber with a relatively small capacity, and is characterized by a linear movement mechanism in the X direction and a rotation mechanism. In combination with this, the entire range of the sample can be observed without increasing the size of the sample chamber.

FIG. 3 is a diagram for explaining the operation of the sample fine movement mechanism of the present invention and the size of the sample chamber, and the same parts as in FIG. 1 are given the same reference numerals.

A circular sample 1 with a diameter is installed at a position eccentric from point A, the center of the field of view, and when moved by D/2 in the X direction, 1C shown by the broken line
Move to the position.

Point B is the center of rotation of the sample 1, and if the sample 1 is rotated about point B and deflected by D/2 in the X direction, it is possible to observe the entire range of the sample.

The dimensions of the sample chamber at this time are sufficient if the width is D and the length is 1.5D, resulting in an extremely small sample chamber 2.

Furthermore, since the detector 3 is close to the observation center A, detection sensitivity is improved.

Furthermore, the moving distance in the X direction, which conventionally required ±D, is now only D/2, which has the advantage that the moving mechanism can be made smaller.

However, in this sample fine movement mechanism, when the sample stage is rotated about B instead of moving the sample 1 in the X direction, the moving distance per unit rotation amount of the sample field of view changes.

Fig. 4 is a diagram illustrating changes in the moving distance per unit rotation of the sample field of view in the sample fine movement mechanism of Fig. 3, and therefore changes in moving speed. When rotated, the field of view moves by an arc γ.

However, when sample 1 moves to position A', it only moves back through the same θ angle rotation.

That is, when the sample position moves in the X direction, the moving speed of the sample field of view differs greatly.

Since this is not preferable in observation and analysis using SEM, this drawback was solved as follows.

FIG. 5 is a diagram for explaining the operation of the SEM sample fine movement device which is an embodiment of the present invention, and the same parts as in FIG. 3 are given the same reference numerals.

In this device, a rotary drive body 20 is installed directly below the center point A of the field of view to rotate the sample stage, and this rotary drive body 20 rotates the sample stage below the point A, completely unrelated to the drive mechanism in the X direction. It contacts the bottom surface of the sample stage and rotates.

Therefore, when the rotary drive shaft 21 is rotating at a constant speed, the sample field of view moves according to the rotational speed of the rotary drive body 20, so that the field of view can always be moved at a constant speed.

FIG. 6 is a sectional view of the sample chamber showing the sample fine movement device of FIG. 5, and the same parts as in FIG. 2 are given the same reference numerals.

An electron beam 33 focused by an objective lens 34 attached to the upper part of the sample chamber 2 illuminates the center A of the field of view of the sample 1.

The sample 1 is placed on an X-direction moving table 4, and a small disk-shaped rotational drive body 20 is in contact with the lower surface of the X-direction moving table 4, just below point A.

This rotary drive body 20 is rotated by a rotary drive shaft 21 that passes through the sample chamber wall 18 in an airtight manner.

Further, the X-direction moving stage 4 moves the sample 1 in the X-direction by rotating the X-drive shaft 7.

As shown in the plan view of FIG. 6, it is possible to create a small-volume sample chamber that is long in the X direction as shown in FIG. 5, and it is possible to observe a larger sample than in the past with a sample chamber of the same volume.

The SEM sample fine movement device of this embodiment configured as described above uses a movement mechanism in the X direction and a rotation mechanism that contacts the sample movement stage directly below the center of the field of view to move the sample at a constant speed even when the sample moves. In addition to being able to scan a surface, the sample fine movement mechanism is made smaller to create a small volume sample chamber, and the distance between the detector and the field of view of the sample is shortened, making it possible to observe and analyze even large samples with high sensitivity. It has the effect of

FIG. 7 is a diagram illustrating the operation of a sample fine movement mechanism according to another embodiment of the present invention, in which the operation of the sample fine movement mechanism shown in FIG. 6 is added.

Since the rotation axis of the rotary drive body 20 is set as the center of inclination of the X-direction moving stage 4, even if the inclination angle ψ changes, there is no effect on the sample fine movement mechanism.

According to this method, the sample can be slightly moved in the X direction and rotationally while the sample 1 is tilted toward the detector 3, and the secondary electron beam generated from the detailed surface can be efficiently detected.

FIG. 8 is a sectional view of the sample chamber showing the sample tilt fine movement device of FIG. 7, and the same parts as in FIG. 6 are given the same reference numerals.

This figure also shows a Z-moving mechanism that can adjust the distance between the sample 1 and the objective lens 34 as well as the tilting mechanism.

A large opening is provided in the sample chamber wall 18, and a sample fine tilting device is attached to a face plate 25 which hermetically seals the opening.

By rotating the knob 28, this face plate 25 can be smoothly slightly moved in the vertical direction (Z direction) by the force of the compression spring 29, and can be adjusted so that the convergence point of the electron beam 33 matches the sample surface. becomes.

The sample is tilted by rotating a tilting drive shaft 24 inserted into the outer surface of the rotary drive shaft 21 with a tilting knob 23 .

The tip of the tilt drive shaft 24 engages with the X-direction moving table 4, and the sample 1 is tilted as shown in FIG.

FIG. 9 is an explanatory view of the main parts of a sample tilt fine movement device which is a modification of FIG. 8.

If the center of inclination is made to coincide with the rotary drive shaft 21 as shown in FIG. 7, the amount of movement during inclination will be large.

In FIG. 9, this defect is improved and the inclination direction of the sample 1 is tilted in the X direction, which is 90 degrees different from that in FIG. A tilting rack 36 centered at a point is attached, and a pinion 35 rotated by a tilting drive shaft 24 is meshed with this.

Therefore, there is an advantage that the distance between the surface of the sample 1 and the center of tilt is shortened, and the amount of movement of the field of view during tilting is reduced.

As described above, the sample fine tilting device of this embodiment has the effect of being able to move and tilt the field of view over the entire area of the sample for observation.

Furthermore, since this apparatus is small in size like the previous embodiment, it is of course advantageous in that relatively large samples can be observed.

The SEM sample fine movement device of the present invention has the remarkable effect of being able to scan and observe the entire area of a large sample with high sensitivity in a relatively small volume sample chamber.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the operation of the sample fine movement mechanism and the size of the sample chamber in a conventional SEM, Fig. 2 is a front view of the conventional sample fine movement device, and Fig. 3 is a diagram explaining the operation of the sample fine movement mechanism of the present invention. Figure 4 is a diagram explaining the size of the sample chamber; Figure 4 is a diagram explaining changes in the moving distance of the specimen field of view in the specimen fine movement mechanism of Figure 3;
FIG. 5 is a diagram explaining the operation of a sample fine movement mechanism that is an embodiment of the present invention, FIG. 6 is a sectional view of a sample chamber showing the sample fine movement device of FIG. 5, and FIG. 8 is a sectional view of the sample chamber showing the sample tilting fine movement device of FIG. 7, and FIG. 9 is a variation of the sample tilting fine movement mechanism of FIG. 8. FIG. 2 is an explanatory diagram of main parts of the device. DESCRIPTION OF SYMBOLS 1... Sample, 3... Detector, 4... X direction moving table, 20... Rotation drive body, 21... Rotation drive shaft, 24
... Inclined drive shaft, 33... Electron beam, 35...
Pinion, 36... inclined rack.

Claims (1)

[Claims] 1. A moving table on which a sample to be irradiated with a focused electron beam is installed, a means for moving the moving table in a direction substantially perpendicular to the electron beam, and a means for moving the moving table in a direction substantially perpendicular to the electron beam. means for rotating around a predetermined rotational axis, the rotating means includes a rotational drive body, and the rotational drive body is mounted on the lower surface of the movable base so that its center of rotation is on an extension line of the electron beam. The specimen fine movement device of the scanning electron microscope is in contact with the specimen.