Micro-displacement element, and scanning tunneling microscope ...

lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll US005268571A

United States Patent [191

[11] Patent Number:

Yamamoto et a1.

[45]

[54] MICRO-DISPLACEMENT ELEMENT, AND SCANNING TUNNELING MICROSCOPE

63-161552 7/1988 Japan. 8907256 8/1989 PCT 1m AppL.

AND INFORMATION PROCESSING APPARATUS USING SAME [75] Inventors: Keisuke Yamamoto, Yamato; Yutaka Hirai, Tokyo; Masaru Nakayama,

Atsugi; Takayuki Yagi, Machida; Yuji Kasanuki, Isehara; Yoshio Suzuki, Atsugi, all of Japan [73] Assignee: Canon Knbushiki Kaisha, Tokyo, Japan [21] App]. No.: 888,789 [22] Filed:

[30]

May 27, 1992

Dec. 7, 1993

9015986 12/1990 PCT 1m Appl. .

OTHER PUBLICATIONS Albrecht, et al., Journal of Vacuum Science And Tech nology: Part A, Microfabrication of Integrated Scan ning Tunnelling Microscope, vol. 8 No. 1 (Jan. 1980), pp. 317-318. Patent Abstracts of Japan, vol. 6, No. 25 (E-94) (903) (Feb. 13, 1982) & JP-A-56 144 585. J. Vac. Sci. Technol. A8(l), Jan/Feb. 1990, p. 317-318, Thomas R. Albrecht et al., “Microfabrication

of Integrated Scanning Tunneling Microscope.” G. Binning et a1., "Scanning tunneling microscopy,” Helvetica Physica Acta, vol. 55, No. 6, 1982, pp. 726-735.

Foreign Application Priority Data

May 28, 1991 [JP]

Date of Patent:

5,268,571

Japan ................................ .. 3-150942

Primary Examiner-Paul M. Dzierzynski

[51]

Int. Cl.5 ............................................ .. H01J 37/26

Assistant Examiner-Kiet T. Nguyen Attorney, Agent, or Firm—-Fitzpatrick, Cella, Harper &

[52]

US. Cl. ............... ..

Scinto

[58]

Field of Search .............................. .. 250/306, 307

[56]

.... .. 250/ 306; 250/ 307

References Cited U.S. PATENT DOCUMENTS 4,668,865

5/1987

Gimzewski et al. .............. .. 250/306 .... ..

4,806,755 5,043,577 5,075,548 12/1991 2/1989 8/1991 Duerig Kajimura Pohl et et al. al. .... ..

250/306

..

[57]

ABSTRACT

A micro-displacement element comprises a unimorph cantilever having a piezoelectric thin ?lm, a pair of electrodes between which the piezoelectric thin ?lm is sandwiched, and an elastic thin ?lm. One end of the cantilever is supported by a support, and the other end thereof is provided with a probe. The micro-displace

5,107,114

4/1992

Nishioka et a1. ..

.... .. 250/306

ment element can be used particularly as an array of

5,136,162

8/1992

Miyamoto ......................... .. 250/306

plural elements, for an information processing apparatus

FOREIGN PATENT DOCUMENTS 0262253 4/1988 European Pat. Off. . 0262637 4/ 1988 European Pat. Off. . 0272935 6/1988 European Pat. Off. . 0387906 9/1990 European Pat. Off. . 0472342 2/ 1992 European Pat. Off. .

in which the element faces to a recording medium such that an information recording pulse voltage or an infor mation reproducing bias voltage can be applied to be

tween the probe and the recording medium. 16 Claims, 6 Drawing Sheets

US. Patent

Dec. 7, 1993

FIG. 1

FIG. 2

Sheet 1 of 6

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U.S. Patent

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Sheet 2 of 6

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FIG. 3A

FIG. 38

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FIG. 4A

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4nm

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FIG. 4B

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US. Patent

Dec. 7, 1993

FIG. 5

FIG. 6

Sheet 3 of 6

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US. Patent

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Sheet 4 of 6

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FIG. 7

306

COMPUTER ————L l

505“ DRIVING

SERVO \

,

CIRCUIT

204

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203

cmcun

303

vms _

SERVO ‘\

CUIT

CIRCUIT 302

5 304

I TUNNEL ‘

CURRENT

‘ DETECTOR \

205 207 A ‘

k

STAGE DRIVIMG

CIRCUIT

BIAS CIRCUIT FOR

RECOR REPR

G AND CTION

US. Patent

Dec. 7, 1993

Sheet 5 of 6

5,268,571

FIG. 8A 10V

TIME

FIG. 8B DISPLACEMENT

TIME

FIG. 8C D S P l. A C E M E N T

US. Patent

Dec. 7, 1993

Sheet 6 of 6

5,268,571

FIG. 9 PRIOR ART

FIG. 10 PRIOR ART

904

902

5,268,571

1 MICRO-DISPLACEMENT ELEMENT, AND

SCANNING TUNNELING MICROSCOPE AND INFORMATION PROCESSING APPARATUS USING SAME

2

recording medium in an angstrom order. In addition, it has been suggested to simultaneously drive many

probes (multiplication of the probe) from the viewpoint of the function improvement of a recording/reproduc

tion system, particularly a high-speed processing.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-displacement

For this control, a lamination type piezoelectric ele ment, a cylindrical piezoelectric element and the like attached on the probe or the medium have been hereto fore used (US. Pat. No. 4668865). However, these ele

scanning tunneling microscope (STM) and a large capacity and high’density information processor using

inconvenient to use these elements in the multi-probe

the micro-displacement element.

type information processor. In view of this, a method

element comprising a unimorph cantilever, as well as a 10 ments are not suitable for integration, though the use of

'

2. Related Background Art In recent years, there has been a practice tendency that while the data recording capacity in an information processor is being increased year by year, the size of a

recording unit is miniaturized and thus the recording density is heightened. For example, in a digital audio disk in which an optical recording system is utilized, the size of a recording unit is as small as l pmz. In the

background there is the active development of memory

materials, and consequently, inexpensive and high-den sity recording media using organic thin ?lms of organic dyes, photopolymers and the like have come out. On the other hand, the STM has recently been devel oped by which the electronic structure of surface atoms of a conductor can be directly observed [6. Binning et

al., Helvetica Physica Acta, 55, 726 (1982)], and as a result, the real space image can be measured with a high resolution irrespective of a single crystal or an amor phous substance. In addition, observation can be advan tageously made at a low electric power without damag ing a medium with current. Moreover, the STM can be

them permits obtaining a large displacement. Thus, it is has been contrived in which a probe is attached on a

cantilever having a length of about several hundreds pm, and this cantilever is then driven by a piezoelectric element. FIGS. 9 and 10 show an example in which a cantile ver comprising a piezoelectric bimorph is formed on an

Si substrate [Thomas R. Albrecht et al., J. Vac. Sci.

Technol, A8, p. 317, 1990]. FIG. 9 is its perspective view, and as shown in this drawing, a cantilever is formed on an Si substrate 1 by laminating two-divided lower electrodes 3, a ZnO piezoelectric thin ?lm 904, a medial electrode 902, a ZnO piezoelectric thin ?lm 904 and two-divided upper electrodes, and a portion of the

Si substrate under the cantilever is then removed by anisotropic etching so that the cantilever is held to be

overhung from the edge of the Si substrate.

The cantilever comprising this piezoelectric bimorph is provided on the tip thereof with a metallic probe 6, which detects a tunnel current through an outgoing

electrode. In this case, when voltages are independently operated even in the atmosphere and can be applied to 35 applied to the four regions including two piezoelectric regions sandwiched between the upper electrodes 5 and various materials, and for these reasons, it is expected to the medial electrode 902 of the cantilever as well as two be employed in many ?elds. piezoelectric regions sandwiched between the lower The STM utilizes the phenomenon that when a volt electrodes 3 and the medial electrode 902 as shown in age is applied to between a metallic probe (a probe electrode) and a conductive material and the probe is the sectional view of FIG. 10, the cantilever having the then brought close to a position about 1 nanometer probe 6 can be independently moved. distant from the conductive material, a tunnel current However, when the cantilever having such a piezo flows therebetween. This current is very sensitive to a electric bimorph structure as seen in the conventional distance change between them, and therefore the sur example is subjected to high-speed scanning, inconve face information of the real space can be obtained by 45 nient mechanical vibration called host vibration is liable

scanning a probe so as to constantly maintain the cur

to occur on the cantilever, which makes a correct image

rent or the average distance between them. In thisocase, the resolution in the surface direction is about 1 A. If the principle of this STM is utilized, a high-density

observation dif?cult.

gested, for example, a method which comprises chang ing the surface state of a suitable recording layer by the

the piezoelectric thin ?lms and the electrode thin films

Additionally, in the case where a plurality of cantile vers are integrally arranged, there is a problem that recording, and reproduction can be sufficiently 50 some of them bend owing to the internal stress of the achieved in an atomic order (several angstroms). This as piezoelectric thin ?lms or the electrode thin ?lms. This recording reproduction methods, there have been sug is considered to be attributable to the non-uniformity of

at the time of the formation of these ?lms by a sputter use of a particle beam (an electron beam or ion beam), 55 ing process or a vapor deposition process. or an energy beam including a high-energy electromag For the writing or reading of information in the infor netic wave such as X-ray and a visible or ultraviolet mation processor, it is necessary that all of the respec light, for recording information, and then reproducing tive cantilevers operate normally. When the precision it by the STM; and a method in which a material exhib of these cantilevers is poor, an external compensating iting a property of switching voltage-current character operation and the like are required to securing the preci istic with a memory effect, for example, a thin ?lm of a slon. u electron type organic compound or a chalcogen com

In addition, since the cantilever takes the piezoelec pound is used as the recording layer, and recording and tric bimorph structure using the two piezoelectric lay reproduction are carried out by using the STM (Japa nese Patent Appln. Laid-Open No. 63-161552 and the 65 ers, many manufacturing steps are necessary, which leads to the complication of the cantilever formation. like). As a result, it is difficult to control the stress of the thin In the information processor utilizing the STM, it is films in the respective layers. important to control the distance between a probe and a

3

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information recording pulse voltage to between the

SUMMARY OF THE INVENTION An object of the present invention is to provide a

recording medium and the probe, and a means for ap

plying an information reproducing bias voltage between the recording medium and the probe.

novel micro-displacement element by which host vibra tion generated on a cantilever at the time of high-speed scanning can be remarkably decreased and by which

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a micro~displacement

image observation, recording and reproduction can be

element of the present invention. FIG. 2 is a perspective view of the micro-displace 10 ment element of the present invention. the micro-displacement element. FIGS. 3A and 3B show the responsiveness of the Another object of the present invention is to provide micro-displacement element of the present invention, a multi-type micro-displacement element array by

achieved with high precision and reproducibility, and

to provide an STM and an information processor using

and by which image observation, recording and repro duction can be achieved with high precision and repro

and FIG. '3A shows an applied voltage and FIG. 3B shows a displacement. FIGS. 4A and 4B show the responsiveness in the case that a bimorph cantilever is used, and FIG. 4A shows an

ducibility, and to provide an STM and an information

applied voltage and FIG. 4B shows a displacement.

processor using the multi-type micro-displacement ele

FIG. 5 is a perspective view of a multi-type micro displacement element array of the present invention.

which the bend and unevenness of plural cantilevers arranged on one substrate can be reduced to the utmost

ment array.

FIG. 6 is a sectional view of the micro-displacement

The above-mentioned objects can be accomplished

element of Example 2 of the present invention.

by the following present invention.

FIG. 7 is a schematic view of the recording/repro

That is, the ?rst aspect of the present invention is

ducing apparatus used in Example 2.

connected to a micro-displacement element which com

prises a unimorph cantilever having a piezoelectric thin ?lm, a pair of electrodes between which the piezoelec tric thin ?lm is sandwiched and an elastic thin ?lm, one

end of the cantilever being supported by a support, the other end thereof being provided with a probe for the input and output of information. The second aspect of the present invention is con nected to a multi-type micro-displacement element array in which at least two of the above-mentioned micro-displacement elements are arranged in a two-di

FIGS. 8A to SC show the characteristics of the mi 25

cro-displacement element of Example 4. FIG. 9 is a perspective view of a conventional micro

displacement element. FIG. 10 is a sectional view of the conventional micro

displacement element. DETAILED DESCRIPTION OF THE

PREFERRED EMBODIMENTS In the present invention, a cantilever-like displace

mensional state.

ment element for giving a micro-displacement is not

The third aspect of the present invention is connected to a scanning tunneling microscope which comprises

piezoelectric thin ?lms are each sandwiched between

the above micro-displacement element disposed so as to face, an electrical conductor, a driving means for driv

formed so as to have a bimorph structure in which two electrodes but so as to have a unimorph structure which

comprises an elastic thin ?lm and a single piezoelectric thin ?lm sandwiched between a pair of electrodes, ing the micro-displacement element, a control means for controlling the driving means, a means for applying 40 whereby host vibration at a high-speed operation can be decreased, the number of steps at the time of manufac a voltage to between the electrical conductor and the ture can be reduced, and multiple ?lm formation steps probe, a means for detecting a tunnel current which which are liable to accelerate uniformity in forming the ?ows between the electrical conductor and the probe, thin ?lms are inhibited to be small as possible. Furthermore, when a material having a linear ther surface of the electrical conductor on the basis of the 45 mal expansion coef?cient which is comparable to that detection of a tunnel current. of the piezoelectric thin ?lm is selected as a material for The fourth aspect of the present invention is con the elastic thin ?lm, the element which is thermally nected to an information processing apparatus which stable and scarcely bends can be obtained. comprises the above micro-displacement element dis The reason for selecting such a material is that it is posed so as to face to a recording medium, a driving necessary to perform the control in a molecular/atomic means for driving the micro-displacement element, a order, i.e., in an order of several nm, and when there is control means for controlling the driving means, and a a temperature difference, the cantilever tends to bend means for applying an information recording pulse volt

and a means for outputting an information as to the

inconveniently by a bimetal effect. age to between the recording medium and the probe. The ?fth aspect of the present invention is connected 55 The preferable combination of the elastic thin ?lm and the piezoelectric thin ?lm is such that the linear to an information processing apparatus which com thermal expansion coefficients of both materials are prises a micro-displacement element disposed so as to equal to each other, and at least the following relation face to a recording medium, a driving means for driving the micro-displacement element, a control means for formula may be met: controlling the driving means, and a means for applying an information reproducing bias voltage between the

recording medium and the probe. The sixth aspect of the present invention is connected

wherein A is the linear thermal expansion coefficient

of the material constituting the elastic thin ?lm, and B is to an information processing apparatus which com prises a micro-displacement element disposed so as to 65 the linear thermal expansion coef?cient of the material constituting the piezoelectric thin ?lm. The typical face to a recording medium, a driving means for driving examples of the combinations are as follows: Elastic the micro-displacement element, a control means for thin ?lm: MgO(A:l.3 X 10 -5/k) and piezoelectric thin controlling the driving means, a means for applying an

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6

?lm: ZnO(B:l.5>