JPH01130457A - Scanning tunneling microscope for reflex type electron microscope - Google Patents

Abstract

PURPOSE:To allow observation of specimen by an electron microscope and ultra-precision measurement using the tunnel phenomenon by arranging a scanning tunneling type microscopic scanning mechanism in a specimen holder in which specimen is retained in such a way that the surface of specimen is in parallel with the optical axis. CONSTITUTION:A scanning tunnel type microscoping scanning mechanism equipped with a probe 5 is arranged in a specimen holder 1, in which a specimen 2 is retained in such a way as the surface of the specimen 2 is in parallel with the optical axis. A deflecting means 8 to deflect electron beam is provided, and by operating it, electron beam is allowed to run against the surface of the specimen 2, and a specimen surface image is obtained by reflex electron microscopic method, and at the same time, of the surface of specimen 2 is observed with a scanning tunnel type microscope. Thereby the field of sight can be sought with the reflex electron microscopic method, while ultra-precision observation of the surface of specimen 2 be made with scanning tunnel type microscope.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning tunneling microscope, and particularly to a scanning tunneling microscope that is incorporated into a reflection electron microscope.

[Conventional technology]

Generally, when the probe is brought close to the sample until the atom at the tip of the probe overlaps with the electron cloud of the sample's atoms by about 1 rv+, and in this state a voltage is applied between the probe and the sample, a current flows. This current is called tunneling current, and when the voltage is 1mV,
It is about 1 to 10 mA.

The magnitude of this tunneling current changes depending on the distance between the sample and the probe, and by measuring the magnitude of the tunneling current, the distance between the sample and the probe can be measured with ultra-precision. If the needle position is known, the surface shape of the sample can be determined at the atomic level. Furthermore, if the probe position is controlled so that the tunneling current is constant, the surface shape of the sample can be similarly measured from the probe position locus.

A scanning tunneling microscope (Sca
nnning tunnel microscope,
STM (abbreviated as STM) can be used in any state, such as in the atmosphere, in liquid, or in vacuum, so it has been developed in various fields in recent years.

There have been reports of a system in which such an STM is incorporated into a scanning electron microscope (SEM) for the purpose of obtaining a secondary electron image and an STM image.

[Problem that the invention seeks to solve]

By the way, when attempting to observe and evaluate images using an STM, there is a problem in that it is not possible to know which position of the sample is being observed using the STM alone. Therefore, it is conceivable to combine SEM and STM and have the SEM search the field of view.

Observation with a SEM is very effective for samples with large variations in unevenness, but it is difficult to observe samples with small unevenness because the difference in the degree of secondary electron generation is small. For this reason,
It is not very suitable for words that search for flat surfaces required for STM.

In addition, in SEM observation, in order to obtain a high-resolution image, the beam must be narrowed down, which poses problems of sample damage and contamination, and there is a high possibility of changing the surface condition, which is also unsuitable for STM. It is.

On the other hand, it has also been desired to obtain STM images using a reflection electron microscope (REV). However, REM is S
Compared to EM, the gear 7 of the objective lens pole piece is too narrow to accommodate the STM scanning section, the means to bring the sample and needle close together, the means to move the needle to a good field of view of the sample, and the possibility of hakes, stems, etc. on the sample. When processing, there is no way to prevent thin air or metal from adhering to the needle, and there is no way to increase the rigidity of the STM scanning section to improve vibration resistance, so it is difficult to incorporate STM into REM. could not.

The present invention is intended to solve the above-mentioned problems, and provides a tunneling microscope for reflection electron microscopy that incorporates STM into REV and enables observation of a sample with an electron microscope and ultra-precise measurement using tunneling phenomenon. The purpose is to

[Means for solving problems]

For this purpose, the scanning tunnel 1 for a reflection electron microscope of the present invention
The m-mirror is a scanning tunneling microscope for reflection electron microscopes in which a scanning tunneling microscope scanning mechanism equipped with a probe is placed in a sample holder that holds the sample so that the sample surface is parallel to the optical axis. It is equipped with a deflection means for deflecting the beam, and operates the polarization means to apply the electron beam to the sample surface to obtain an image of the sample surface by reflection electron microscopy, and to observe the sample surface using a scanning tunneling microscope. Features.

[Effect]

The tunneling microscope for reflection electron microscopes of the present invention searches the field of view using backscattered electron W4 microscopy, and also performs ultra-precise observation of the sample surface using a scanning tunneling microscope, and irradiates an electron beam parallel to the sample surface. By doing so, it becomes possible to measure the distance between the probe and the sample surface by obtaining a transmission image between the probe and the sample surface.

(Example〕 Examples will be described below with reference to the drawings.

Fig. 1 is a diagram showing a schematic configuration for obtaining a reflection image using a reflection type electron gli microscopic scanning tunneling microscope of the present invention, and Fig. 2 is a diagram showing the trajectory of an electron beam, in which 1 is a holder. ,
2 is the sample, 3 is the sample fixing table, 4 is the STM scanning unit, 5 is S
TM needle, 6 is an objective lens (OL) pole piece, 7 is an optical axis, 8 is a deflector, 8a and 8b are first and second deflectors, and 9 is an objective lens.

The holder l (details will be described later) is moved by a side entry goniometer (not shown) to set the sample 2 in a predetermined position. This holder 1
Inside, a sample 2 is attached to a sample fixing table 3 as shown in the figure, and an STM scanning section consisting of a piezo element is also housed, and an STM needle 5 is provided facing the sample 1. The number of copies of this STM scan is about 1.6 fi x 3 cranes x 5 dragons, and the structure is such that it can be sufficiently stored in the holder 1.

In such a configuration, as shown in FIG. 2, an electron beam emitted parallel to the sample surface along the optical axis passes through the objective lens 9
The beam is bent and focused by the front magnetic field of the front magnetic field and the deflector 8 installed above the objective lens, and is irradiated to the sample surface at a certain angle in the form of a spot.The beam reflected there passes on the optical axis and passes through the objective lens. A reflected image is formed downward. The reflected image is formed on a photosensitive surface (not shown), and the sample surface is observed. At this time, since the sample surface is parallel to the optical axis,
Since the uneven portion casts a shadow on the electron beam, stripes are observed corresponding to its shape. The degree of this unevenness is measured with great precision by a 37M scanning needle 5 by moving the STM scanning section. In this case, as mentioned above, the resolution of STM is at the atomic level, so the allowable amplitude of vibration of the STM needle is 0.
．． 1 Å or less, but in the present invention, the sample and needle are 1 Å or less.
Since it is fixed in one holder, it is extremely advantageous in terms of vibration resistance.

In addition, since the STM needle scans the sample surface at intervals of about Inm, it is necessary to prevent the two from colliding. By obtaining this, it is possible to measure the distance between the two, and it is possible to prevent collision between the STM needle and the sample surface.

Figure 3 shows an embodiment of the holder in the present invention, in which (a) shows the sample observation state, and (b) shows the S
This is a diagram showing a state in which the TM scanning section is separated from the sample, and the same numbers as in FIG. 1 indicate the same contents. In addition, 11 is an arm, 12 is a ball, 13, 14, 15 is an O-ring groove, 16 is a bar, 17 is an inner cylinder, 18 is a dial, 19 is a lock member,
20 is a screw, 21 is a screw, 22 is a knob, 23 is a conductor, 2
4 is a hermetic seal, 25 is a wedge, 26 is a piezo element, 27 is a pin, 28 is a screw, 29 is a spring, 30 is a conducting wire storage space, and 31 is a through hole.

The holder structure of the present invention has X, Y,
A sample moving mechanism of Z3 axes is provided, and an STM scanning section 5 is provided therein. Note that the optical axis is perpendicular to the paper surface, that is, parallel to the sample surface.

A sample fixing table 3 is fixed within the holder 1, and an inner cylinder 17 is provided in contact with the inner surface of the holder so as to be slidable in the axial direction of the holder. The sample 2 is fixed on the sample fixing table 3 so that its surface coincides with the central axis of the holder l, and the needle 5 is attached to the end of the STM scanning member opposite to this.
The TM scanning section is fixed to the scanning element 11. Inner cylinder 17
A tapered portion provided with an O-ring groove 13 for vacuum sealing is provided at the tip of the arm 11, and is configured to rotatably receive a ball 12 integrated with the arm 11 while maintaining 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 downward by a screw 21. Therefore, by turning the screw 21 and moving the free end of the bar 16 up and down, the arm 11 can be moved using the ball 12 as a fulcrum, and the needle 5 can be moved closer to or farther away from the sample. Further, a screw (not shown) similar to the screw 21 is provided perpendicularly to the plane of the paper, and by operating this screw, the needle 5 can be moved along the sample surface and the field of view can be searched.

These arm 11, ball 12, and bar 16 are provided at an eccentric position away from the central axis of the holder 1 (on the upper side in the figure),
A storage space 30 for the conducting wire 23 is formed below it. Additionally, an O-ring 1lj14 for vacuum sealing is formed between the inner cylinder 17 and the holder 1, and this and the O-ring groove 13 keep the sample side in a vacuum. A hermetic seal portion 24 for the conducting wire 23 is formed. Further, the inner cylinder 17 has a screw 20 that engages with the threaded portion of the dial 18, and when the dial 18 is turned, the inner cylinder 17 cannot be rotated by the pin 27, so it moves in the axial direction. This movement allows searching the field of view in the axial direction of the sample. Also, inner cylinder 1
7 is provided with a locking member 19 whose tapered tip extends to the ball 12 and is provided with a through hole 31 through which the screw 21 passes, and the rear end thereof is provided with a locking member 19 to which the knob 22 is attached. 28 is provided and contacts the rear end of the locking member. By turning the knob 22 and pushing the locking member 19, the taper at the tip of the locking member presses and fixes the ball 12, making it difficult for the arm 11 to move and increasing its rigidity.

Further, a tapered groove is provided in a part of the contact surface of the inner cylinder 17 with the holder 1, and this groove is provided with a wedge 25 and a laminated piezo element 26 that presses the wedge, and drives the piezo element 26. By stretching the wedge 25, the wedge 25 is press-fitted between the inner cylinder 17 and the holder 1, thereby locking the inner cylinder 17 and increasing its rigidity.

In such a configuration, the holder 1 is inserted into a side entry goniometer (not shown), and by moving the holder, the sample is moved and a field of view is searched, and the sample surface is observed by the reflection image observation method. In the reflected image obtained in this way, further set the area to be observed by STM,
Move in the axial direction with the dial 18, approach the sample with the screw 21,
The needle is moved in the direction along the sample surface using a screw (not shown) that is perpendicular to the plane of the paper and is similar to the screw 21. When the needle 5 is brought close to the sample using the screw 21, as mentioned above, if the gap between the sample and the needle is observed using the TEM method and the tunnel current is detected, the needle will collide with the sample and the needle This can prevent damage to the sample. After setting the needle in this way, the ball 12 and arm 11 are fixed by turning the knob 22 and pushing the locking member 19, and the piezo element 26 is further driven to fix the inner cylinder 17, thereby increasing the overall rigidity. The vibration resistance of the 37M scan is improved to perform ultra-precise measurements using the STM method.

When processing a sample in the holder 1, turn the screw 21 to move the needle 5 away from the sample 2 so that it does not touch the surrounding area, and then turn the dial 18 to remove the needle 5 from the inner cylinder 1.
7 to the state shown in Figure 3 (mouth), and if you perform sample beta, vapor deposition, etc. in this state, the needle is away from the sample surface, preventing adverse effects such as metal or vapor adhering to the needle. be able to.

FIG. 4 is a diagram showing another embodiment of the present invention, in which a sample and an STM
The process is exactly the same as that shown in FIG. 3, except that the scanning section is orthogonal to observe the reflected image.

In addition, in the above example, an example was explained in which the needle is moved, locked, etc. using the driving force of a screw, but there are other ways to drive the needle, such as by using the principle of a lever or by using a piezo element. Any means may be used.

〔Effect of the invention〕

As described above, according to the present invention, the backscattered electrons are
After searching and observing the field of view using the gi microscopic method, the surface of the sample can be observed with ultra-precision using a scanning tunneling microscope, and the distance between the sample and the probe can be approached while being observed using the TEM method. Therefore, it is possible to prevent the probe from colliding with the sample.

[Brief explanation of the drawing]

Figure 1 shows a scanning tunnel WA for a reflection electron microscope according to the present invention.
Diagram showing the schematic configuration when obtaining a reflected image with a micromirror, Part 2
The figure shows the trajectory of the electron beam, Figure 3 shows an embodiment of the holder in the present invention, Figure (a) shows the sample observation state, and Figure (b) shows the STM scanning section. FIG. 4 shows another embodiment of the present invention in which the sample and the STM scanning section are perpendicular to each other. DESCRIPTION OF SYMBOLS 1... Holder, 2... Sample, 3... Sample fixing stand, 4... STM scanning part, 5... STM needle, 6...
Objective lens (OL) pole piece, 7... Optical axis, 11
...Arm, 12...Ball, 16...Bar, 17.
...Inner tube, 18...Dial, 19...Lock member, 22...Knob, 23...Conductor, 28...Screw. Applicant: JEOL Co., Ltd. Agent, Patent Attorney: Masanobu Hirukawa (3 others) Procedural amendment written form) January 1, 1988 Commissioner of the Japan Patent Office Kunio Ogawa 1, Indication of the case: 1988 Patent Application No. 288079-2, Title of Invention: Scanning Tunneling Microscope for Reflection Electron Microscope 3, Relationship to the Amendment Case Patent Applicant Address: 3-1-2 Musashino, Akishima City, Tokyo Name (427) JEOL Ltd. Representative Takeuchi
Takashi 4, Agent 5, Date of amendment order: February 3, 1988 Date of dispatch: February 23, 1988

Claims (2)

[Claims] (1) A scanning tunneling microscope for reflection electron microscopes, in which a scanning tunneling microscope scanning mechanism equipped with a probe is arranged in a sample holder that holds the sample so that the sample surface is parallel to the optical axis, and the electron beam The method is characterized in that it is equipped with a deflecting means for deflecting the electron beam, and operates the polarizing means to apply an electron beam to the sample surface to obtain an image of the sample surface by reflection electron microscopy, and to observe the sample surface using a scanning tunneling microscope. A tunneling microscope for reflection electron microscopy. (2) A scanning tunneling microscope for a reflection electron microscope according to claim 1, wherein an electron beam is irradiated parallel to the sample surface to obtain a transmitted image between the probe and the sample surface.