JPH0616410B2 - Scanning tunneling microscope for transmission electron microscope - Google Patents

Description

TECHNICAL FIELD The present invention relates to a scanning tunneling microscope, and more particularly to a scanning tunneling microscope incorporated into a transmission electron microscope.

[Conventional technology]

In general, when the probe is brought close to the sample to about 1 nm where the atom at the tip of the probe and the electron cloud of the sample atom overlap, and a voltage is applied between the probe and the sample in this state, a current flows. This current is called the tunnel current, and when the voltage is several mV, 1
It is about 10 nA. The magnitude of this tunnel current is
It changes depending on the distance between the sample and the probe, and the distance between the sample and the probe can be measured ultra-precision by measuring the magnitude of the tunnel current. The surface shape of can be obtained at the atomic level. Further, if the probe position is controlled so that the tunnel current is constant, the surface shape of the sample can be similarly measured by the probe position locus.

A scanning tunneling microscope (Scann) based on this principle
ing Tunnel ling Microscope (STM for short) is
Since it can be used in any state such as air, liquid, or vacuum, it has been developed in various fields in recent years.

There is a report of the purpose of incorporating such an STM in a scanning electron microscope (SEM) to obtain a secondary electron image and an STM image.

[Problems to be solved by the invention]

By the way, when an image is observed or evaluated by the STM, there is a problem that the STM alone does not know which position of the sample is observed. Therefore, it is conceivable to combine the SEM and the STM so that the SEM can search the visual field.

The observation with the SEM is very effective for a sample with a large change in the unevenness, but the sample with a small unevenness has a small difference in the degree of generation of secondary electrons, which makes the observation difficult. For this reason,
Not very good at finding the flat surface needed for STM.

Further, in SEM observation, the beam must be narrowed down to obtain a high-resolution image, and sample damage and contamination pose a problem, and there is a great possibility that the surface condition will be changed, which is also not suitable for STM. is there.

On the other hand, it has been desired to obtain an STM image even with a transmission electron microscope (TEM). However, TEM is S
Since the resolution is higher than that of EM, the gap of the objective lens pole piece is narrow and the STM scanning part does not enter, the means for bringing the sample and the needle closer, the means for moving the needle to a good visual field of the sample, the sample bake, vapor deposition, etc. When processed, there is no means to prevent vapor or metal from adhering to the needle.
It was not possible to incorporate the STM into the TEM because there is no method for increasing the rigidity of the TM scanning unit to improve the vibration resistance.

The present invention is to solve the above-mentioned problems, and provides a scanning tunnel microscope for a transmission electron microscope which incorporates an STM in a TEM and enables observation of a sample by an electron microscope and ultra-precision measurement using tunnel development. The purpose is to do.

[Means for solving problems]

Therefore, the scanning tunneling microscope for a transmission electron microscope of the present invention is a transmission tunneling microscope in which a scanning tunnel microscope scanning mechanism having a probe is arranged in a sample holder that holds a sample so that the surface of the sample is perpendicular to the optical axis. A scanning tunneling microscope for an electron microscope, characterized in that a sample is irradiated with an electron beam to obtain a transmission image, and the surface of the sample is observed by the scanning tunneling microscope.

[Action]

The scanning tunneling microscope for a transmission electron microscope of the present invention obtains a transmission image by a transmission electron microscopy method, uses this to search for a visual field, and further performs ultra-precision observation of a sample surface with a scanning tunneling microscope. Further, the position of the probe can be known from the transmission image of the probe, that is, the shadow of the probe on the sample image.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a view showing an embodiment of the present invention when a transmission image is obtained by a scanning tunneling microscope for an electron microscope. 1 is a holder,
2 is a sample, 3 is a sample fixing base, 4 is an STM scanning unit, 5 is S
TM needle, 6 is an objective lens (OL) pole piece, 7 is an optical axis, and 8 and 9 are fixing screws.

The holder 1 (details will be described later) is moved by a side entry goniometer (not shown) to set the sample 2 at a predetermined position. In the holder 1, the sample 2 is attached to the sample fixing base 3 with screws 8 and 9 as shown in the figure, the STM scanning section 4 made of a piezo element is housed, and the STM needle 5 is angled as shown in the figure. It is provided so as to face the sample 1. The STM scanning unit 4 has a size of about 1.6 mm × 3 mm × 5 mm and is configured to be sufficiently housed in the holder 1.

In such a configuration, an electron beam is applied to the sample surface at a right angle, a transmission image thereof is formed on a photosensitive surface (not shown), and the sample can be observed by the transmission image. In this transmission image, even minute irregularities on the sample surface cannot be observed. Therefore, the degree of this unevenness is determined by driving the sample STM scanning unit 4 to S
Ultra-precision measurement is performed by the TM scanning needle 5. In this case, since the resolution of STM is at the atomic level as described above,
Although the allowable amplitude of vibration of the STM needle is 0.1 Å or less, in the present invention, the sample and the needle are fixed in one holder, which is extremely advantageous in terms of vibration resistance.

Further, when scanning the sample surface with the STM needle, there is a problem that it is not known at which position the observation is performed. However, if a transmission image of the probe is obtained together with the sample, the shadow of the probe will cause Since it is observed above, the observation position can be easily known.

FIG. 2 is a diagram showing an embodiment of the holder according to the present invention, FIG. 2 (a) is a diagram showing a sample observation state, and FIG. 2 (b) is a diagram showing a state in which the STM scanning unit is separated from the sample. The same numbers as those in FIG. 1 indicate the same contents. 1A and 1B
Is a window, 11 is an arm, 12 is a sphere, 13, 14 and 15 are O
Ring groove, 16 bar, 17 inner cylinder, 18 dial,
19 is a lock member, 20 is a screw, 21 is a screw, 22 is a knob, 23 is a conductor wire, 24 is a hermetically sealed portion, 25 is a wedge, 26 is a piezo element, 27 is a pin, 28 is a screw,
Reference numeral 29 is a spring, 30 is a conducting wire storage space, and 31 is a through hole.

The holder configuration of the present invention is such that X, Y,
A Z3 axis sample moving mechanism is provided, and the STM scanning unit 4,
The needle 5 is provided.

A sample fixing base 3 is fixed in the holder 1, and an inner cylinder 17 is provided in contact with the inner surface so as to be slidable in the holder axial direction. The sample 2 is fixed to the sample fixing base 3 such that the surface thereof coincides with the central axis of the holder 1, and the needle 5 is attached to the tip of the STM scanning unit 4 so as to face the sample fixing base 3.
The TM scanning unit 4 is fixed to the arm 11. Inner cylinder 17
A taper portion provided with an O-ring groove 13 for vacuum sealing is provided at a tip end of the ball so as to rotatably receive the ball 12 integrated with the arm 11 in an airtight state. A bar 16 is integrally provided on the ball 12, and its tip is free, and is urged upward by a spring 28 and pushed down by a screw 21. Therefore, by rotating the screw 21 to move the free end of the bar 16 up and down, the arm 11 can be moved around the sphere 12 as a fulcrum, and the needle 5 can be moved closer to or farther from the sample. Further, a screw (not shown) similar to the screw 21 is provided perpendicular to the paper surface, and by operating this screw, the needle 5 can be moved along the surface of the sample, and the field of view can be searched.

The arm 11, the ball 12, and the bar 16 are provided at an eccentric position (upper side in the drawing) deviated from the central axis of the holder 1,
A storage space 30 for the conducting wire 23 is formed below it. Further, an O-ring groove 14 for vacuum sealing is formed between the inner cylinder 17 and the holder 1, and this and the O-ring groove 13 are formed.
The sample side is held in vacuum by and the hermetic seal part 24 for the STM scanning part driving and tunnel current extracting conductor 23 is formed. Also, the inner cylinder 17
Has a screw 20 that meshes with the threaded portion of the dial 18,
When the dial 18 is turned, the inner cylinder 17 cannot be rotated by the pin 27, and therefore moves in the axial direction. By this movement, the visual field in the axial direction of the sample can be searched. Further, a lock member 19 having a tapered tip end portion extending to the ball 12 and a through hole 31 through which a screw 21 penetrates is provided on the inner surface of the inner cylinder 17, and a knob 22 is provided at the rear end portion. A screw 28 is provided for attachment and contacts the rear end of the locking member. Then, by rotating the knob 22 and pushing the lock member 19, the taper at the tip of the lock member pushes and fixes the ball 12, thereby making the arm 11 hard to move and increasing the rigidity.

Further, a groove having a taper is provided in a part of the contact surface of the inner cylinder 17 with the holder 1. In this groove, a wedge 25 and a laminated piezo element 26 for pushing the wedge are provided, and the piezo element 26 is driven. Then, the wedge 25 is pushed by being extended, and the inner cylinder 17 is locked by being press-fitted between the inner cylinder 17 and the holder 1 to increase the rigidity.

In such a configuration, the holder 1 is inserted into a side-entry goniometer (not shown), and the holder is moved to move the sample to search the field of view.
Observe the sample surface by the method. In the transmission image thus obtained, an area to be further observed by the STM is set, and the dial 18 is used to move in the axial direction, the screw 21 approaches the sample, and the screw 21 similar to the screw 21 is attached to the sample surface at a right angle to the paper surface (not shown). Perform needle movement along the direction. When moving the sample, T
If the images of the sample and the needle are observed by the EM method, the observation position can be easily known from the shadow of the needle on the sample image. In this way, after setting the needle, turn the knob 22 to rotate the lock member 19
Press to fix the sphere 12 and the arm 11, and further drive the piezo element 26 to fix the inner cylinder 17, thereby increasing the rigidity as a whole and improving the vibration resistance of the STM scan to improve the STM.
Ultra-precision measurement by the method.

When the sample is processed in the holder 1, the needle 5 is separated from the sample 2 via the screw 21, and the dial 18 is rotated so that the needle 5 does not touch the surroundings.
Fig. 2 (b), and if the sample is baked or vapor-deposited in this state, the needle is away from the sample surface, so that adverse effects such as metal or vapor adhering to the needle should be prevented. You can

In the above embodiment, an example in which the needle movement, locking, and the like is performed by using the driving force of the screw has been described, but what is the driving mechanism such as using the lever principle or using the piezo element? Any means may be used.

〔The invention's effect〕

As described above, according to the present invention, by arranging the scanning tunneling microscope scanning mechanism in the sample holder that holds the sample so that the sample surface is perpendicular to the optical axis, the sample image is observed by transmission electron microscopy. After conducting a field of view search, the sample surface can be observed with a scanning tunneling microscope, and the probe can be observed by the TEM method to easily observe the position of the shadow of the needle on the sample image. You can know the probe position.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention when a transmission image is obtained by a scanning tunneling microscope for an electron microscope, FIG. 2 is a view showing an embodiment of a holder in the present invention, and FIG. The figure showing the observation state, and the figure (b) is a figure showing the state in which the STM scanning unit is separated from the sample. 1 ... Holder, 2 ... Sample, 3 ... Sample holder, 4 ...
... STM scanning part, 5 ... STM needle, 6 ... Objective lens (OL) pole piece, 7 ... optical axis, 11 ... arm,
12 ... Ball, 16 ... Bar, 17 ... Inner cylinder, 18 ... Dial, 19 ... Lock member, 22 ... Knob, 23 ...
Conductor, 28 ... screw.

Claims (2)

[Claims] 1. A scanning tunnel microscope for a transmission electron microscope, wherein a scanning tunnel microscope equipped with a probe is arranged in a sample holder that holds the sample so that the surface of the sample is perpendicular to the optical axis. A scanning tunnel microscope for a transmission electron microscope, characterized in that a sample is irradiated with an electron beam to obtain a transmission image and the surface of the sample is observed by a scanning tunnel microscope. 2. A scanning tunneling microscope for a transmission electron microscope according to claim 1, wherein the probe position is determined by the shadow of the probe on the sample image.