JPH06265343A - Sample surface observing apparatus and recorder/ reproducer using the same - Google Patents

Abstract

PURPOSE:To scan at a high speed and to maintain resolution simultaneously as an entire screen. CONSTITUTION:In order to approach a probe 1 to a sample surface up to an infinitesimal distance, a finely moving actuator 4 is provided on an upper surface of a cantilever 3. An optical lever type sensor having a semiconductor laser 5 for detecting a deformation of the cantilever 3 due to perpendicular or horizontal force', a quarter sensor 6 is provided above the cantilever 3. A horizontal force detector 11 for detecting a horizontal force of the cantilever 3 is connected to the sensor 4, and a scanning speed corrector 12 for correcting a scanning speed based on the horizontal force is connected to the detector 11. A scanning drive actuator 9 for driving to scan a sample 2 is connected to the corrector 12 through a scan signal generator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an apparatus for observing a sample surface by utilizing a tunnel current or force generated between a probe and a sample (Scanning Probe Microscopy, hereinafter referred to as SPM), or a sample surface using this. The present invention relates to a device for recording / reproducing information.

[0002]

2. Description of the Related Art SPMs are classified according to the physical properties they detect,
A wide variety of physical properties such as electric current, interatomic force, electrostatic force, magnetic force and the like, light, electrostatic capacitance and the like can be detected. Of these, those related to the present invention are atomic force, magnetic force, electrostatic force, etc.
A scanning force microscope (SF) that detects a force generated between sample probes in a direction perpendicular to the sample surface and detects surface information while feedback-controlling the distance between probe samples based on this signal.
M, Scanning Force Microscope), and a horizontal force, as well as a current and a horizontal force such as a frictional force generated in the in-plane direction of the sample.

FIG. 4 is a system block diagram of a conventional scanning force microscope. As shown in this figure, in SFM, a probe 101 having a sharp tip supported by a cantilever 103 as a cantilever type elastic member is brought close to a surface of the sample 102 to several tens nm to several nm. The scan drive actuator 109 is driven by the output of the scan signal generation circuit 110 to scan the sample 102 placed on the scan drive actuator 109. At this time, the elastic deformation in the vertical direction of the elastic member reflecting the atomic force generated between the probe and the sample is changed by the optical lever method including the semiconductor laser 105, the two-divided sensor 106 and the vertical direction force detection circuit 107, or the tunnel current detection method. The force is detected by a force detection sensor such as, and the fine movement actuator 104, which is a fine movement mechanism between the recording layer probes, is driven by the vertical force servo circuit 108 so that the detected force becomes constant, and the probe recording layer distance is feedback-controlled. .

In this method, the detection force may be in the attractive region (probe recording layer distance> 0) or in the repulsive region (probe recording layer distance = 0, that is, contact). Often used in excellent repulsive force area. Further, by setting the elastic constant of the elastic member to be much smaller than that of the surface of the recording layer, it is possible to keep the contact state between the probe and the recording layer substantially constant without the feedback control by the distance fine movement mechanism.

As described above, while the probe recording layer distance is controlled (including the contact state), the feedback control amount or the displacement amount of the elastic member corresponding to the change in the detection force is monitored while scanning the sample surface. An observation image that reflects the surface shape can be obtained.

On the other hand, by monitoring not only the vertical bending deformation of the cantilever type elastic member but also the horizontal bending deformation, twisting deformation, etc., a horizontal force generated in the in-plane direction of the sample such as a frictional force and a reaction force. It is possible to simultaneously acquire an observation image that reflects.

Further, the probe in the SFM is made conductive by a metal coat or the like, and the observed current reflecting the electronic state of the sample is acquired at the same time by monitoring the current generated when a bias is applied between the probe samples. Is possible.

By the method described above, a voltage pulse is applied while scanning the surface while controlling the distance between the probe and the sample, and the surface shape or electronic state is modulated by a tunnel current, a field emission current, a contact current or the like. It is also possible to apply it to a recording / reproducing apparatus by forming a recording bit.

[0009]

When a sample surface is scanned with a probe, the interaction force generated between the probe and the sample at a portion where the film thickness or film quality changes abruptly exceeds the elastic deformation yield point of the sample. , It may damage the sample. The case of contact state scanning will be described below with reference to FIG. FIG. 5 is a diagram showing a state of contact scanning in a conventional scanning force microscope.

In FIG. 5 (a), it is shown that the probe cannot follow the abrupt change of the uneven shape of the sample surface at the portion where the film thickness changes rapidly and the horizontal interaction force horizontal to the surface increases. Shows. When the shear stress due to this horizontal acting force exceeds the elastic deformation yield point of the sample, plastic deformation begins and the sample is damaged.

In order for the probe to sufficiently follow the uneven portion of the sample surface, the substantial signal frequency in the uneven shape determined by the scanning speed must be included in the response frequency band of the probe drive feedback control system. Therefore, since the scanning speed is determined according to the area having the maximum execution signal frequency in one screen, the observation is performed at an unnecessarily slow scanning speed even in other areas where the signal frequency is relatively low.

Therefore, even if the sample surface is flat on the average, damage such as peeling of the sample film caused by a film defect that may exist sporadically, a sharp uneven shape caused by an adsorbed substance, etc. In order to completely avoid the above, there is a problem that the scanning speed must be extremely slowed.

On the other hand, FIG. 5B shows a state in which the dynamic frictional force generated between the probe and the sample surface rapidly increases at the portion where the film quality changes rapidly. As in the case of the horizontal acting force, when the shear stress due to this dynamic friction force exceeds the elastic deformation yield point of the sample, plastic deformation begins and the sample is damaged.

The kinetic friction force is almost independent of the scanning speed, but increases in proportion to the normal force exerted by the probe. Therefore, even if the sample surface is smooth on average, it may exist sporadically, and the sample film peels off from the increase of the dynamic friction force due to the change of the adhesion force etc. due to the inhomogeneity of the film quality. In order to avoid the damage of the probe completely, it is necessary to control so that the interatomic repulsive force between the probe samples in the contact state becomes extremely small, and there are problems such as image resolution and control difficulty. is there.

The present invention has been made in view of the above problems of the prior art, and selectively reduces the scanning speed, the set repulsive force, or these at the same time only in an area where there is a rapid change, and thereby the entire screen is displayed. Another object of the present invention is to provide a surface observation device capable of simultaneously maintaining high-speed scanning and resolution, or a recording / reproducing device using the same.

[0016]

[Means for Solving the Problems] That is, the present invention for achieving the above object includes a distance control means for controlling a distance or a contact state between a probe supported by a cantilever type elastic member and a sample, and the probe. And a scanning means for scanning the sample relatively parallel to the sample surface, in a sample surface observing device, a detection means for detecting a horizontal force parallel to the sample surface generated between the probe and the sample surface; A scanning speed control means for feedback-controlling the scanning speed of the scanning means using the directional force as a servo signal, and the horizontal force detected by the detection means in the sample surface observation apparatus. A correction means for correcting the control amount in the distance control means based on the above may be provided.

Distance control means for controlling the distance or contact state between the probe and the sample supported by the cantilever type elastic member, and scanning means for relatively scanning the probe and the sample parallel to the sample surface. In the sample surface observing device including: detection means for detecting a horizontal force generated between the probe and the sample surface in parallel with the sample surface; and the distance control means based on the horizontal force detected by the detection means. It may be characterized in that a correction means for correcting the control amount is provided, and the detection means configured in any one of the above-mentioned devices is provided at different positions on a cantilever type elastic member supporting the probe. The present invention may be characterized by having a plurality of strain resistance elements provided and detecting the horizontal force based on the differential output of the plurality of strain resistance elements.

Further, there is provided a recording / reproducing apparatus using any one of the sample surface observing apparatus as described above, wherein an applying means for applying a pulse voltage to the sample and a current detecting means for detecting a current generated when the pulse voltage is applied. It may be characterized in that it is provided with a recording and reproducing means consisting of.

[0019]

In the present invention configured as described above, the distance control means controls the distance or contact state between the probe supported by the cantilever type elastic member and the sample, and the scanning means relatively moves the probe and the sample. When scanning is performed in parallel with the sample surface, when a sharp shape change or film quality change occurs between the probe and the sample surface and a horizontal force parallel to the sample surface is generated in the probe, the horizontal force is changed. It is detected by the detection means. Then, the scanning speed is feedback-controlled by the scanning speed control means by using the detected horizontal force as a servo signal, or the control amount in the distance control means is corrected by the correction means based on the horizontal force.

Therefore, when the probe is scanned in a region having a sharp shape change or film quality change, the scanning speed and the probe sample are controlled by the scanning control means, the correction means or these so as to suppress the increase in the horizontal force. Since the repulsive force between them or these are reduced at the same time, it is possible to maintain high-speed scanning, detection resolution, or these simultaneously for the entire sample surface.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a system block diagram relating to the first embodiment of the present invention. In the present embodiment, the object of the present invention is achieved by variably controlling the scanning speed using the horizontal force as a servo signal.

The apparatus of this embodiment is an apparatus for observing the surface of a sample 2 as shown in FIG. 1, and the sample 2 is held on a scanning drive actuator 9 capable of driving and scanning in a direction substantially horizontal to the surface of the sample. There is. A cantilever 3 as a cantilever type elastic member having a probe 1 formed at its free end is provided on the sample 2, and the probe 1 can be finely moved perpendicularly to the sample surface on the upper surface of the other end of the cantilever 3. A fine movement actuator 4 is provided.

A semiconductor laser 5 and a four-division sensor 6 are provided above the cantilever 3. At the positions of the semiconductor laser 5 and the four-division sensor 6, the light beam from the semiconductor laser 5 enters the cantilever 3,
A light beam reflected by the cantilever 3 is divided into four sensors 6
The configuration is such that it is incident on the center of.

The four-division sensor 6 is composed of two pairs of division area sensors divided by division lines orthogonal to each other,
Vertical force and horizontal force can be detected independently. A pair of sensors arranged in the vertical direction detects the displacement of the beam spot due to the bending of the cantilever in the vertical direction, and a pair of sensors arranged in the other horizontal direction causes the bending of the cantilever due to the horizontal force, which causes the bending in the vertical direction. A displacement component orthogonal to the displacement is detected.

A method of controlling the distance or contact state between the probe samples in the above apparatus will be described.

The cantilever 3 as a cantilever type elastic member supporting the probe 1 acts as a force sensor. When the probe 1 is brought close to several tens nm to several nm near the sample surface, a vertical force such as an atomic force starts to be generated between the probe 1 and the sample 2. The elastic deformation of the cantilever 3 due to the vertical force is detected by the optical lever type sensor including the semiconductor laser 5 and the four-division sensor 6 as a differential output from the vertical force set value in the vertical direction detection circuit 7. Then, by performing feedback control of the fine movement actuator 4 via the vertical force servo circuit 8 so that the difference output is always zero, the inter-probe sample distance or the contact state is controlled to be substantially constant.

The vertical force detected includes an attractive region (probe recording layer distance> 0) and a repulsive region (probe recording layer distance = 0, that is, contact), which are actually used. As the method, the vertical force is often used in the repulsive force region where the detection sensitivity is excellent. Further, by setting the elastic constant of the cantilever 3 to be much smaller than that of the surface of the recording layer, the contact state between the probe and the sample can be kept substantially constant without the feedback control by the fine movement actuator 4.

Next, the variable control method of the scanning speed, which is a feature of the present invention, will be described.

At the time of scanning, the output corresponding to the horizontal force of the four-divided sensor 6 is input to the horizontal force detection circuit 11, and a differential output from the horizontal force reference set value is formed.
Then, this difference output is input to the scanning speed correction circuit 12, and the scanning speed signal correction circuit 12 calculates the difference output based on the coefficient obtained experimentally in advance and outputs the scanning speed signal.

Next, the scanning speed time integration circuit 14 calculates the time integration value of the scanning speed signal. The time integrated value of the scanning speed corresponds to the displacement amount of the probe 1, and the timing of data sampling, the return timing of scanning, etc. can be controlled based on this displacement amount.

In the scanning timing signal generating circuit 15, scanning timing signals for direction reversal are formed for each displacement amount corresponding to one scanning line and each displacement amount corresponding to one screen.

The scanning speed signal and the scanning timing signal are calculated in the scanning signal generating circuit 10 to form a scanning signal, which is output to the scanning drive actuator 9. In this way, the scanning drive is realized such that the scanning speed is variably controlled in accordance with the surface shape and the scanning direction is folded back at every constant scanning displacement corresponding to the predetermined image area size.

The image data corresponding to the variable control of the scanning speed is generated as follows.

The probe displacement amount signal output from the scanning speed time integration circuit 14 is the scanning timing signal generating circuit 1.
At the same time as 5, the data timing signal is generated by the data timing signal generation circuit 16, and a data timing signal is formed for each displacement amount corresponding to the pixel pitch.

Image data is formed by sampling the data signal output from the vertical force servo circuit 8 in the data demodulation circuit 17 using this data timing signal.

(Second Embodiment) FIG. 2 is a system block diagram relating to the second embodiment of the present invention. The apparatus of this embodiment is similar in that the semiconductor laser 5 and the four-division sensor 6 are arranged above the cantilever 3, respectively, and therefore a different control configuration will be described here.
Further, in the first embodiment, the problem of the present invention is solved by variably controlling the scanning speed, but in the present embodiment, the reference setting value of the vertical force is corrected to variably control the contact state between the probe and the sample. As a result, a sharp increase in the horizontal force due to a sharp change in the surface shape, an increase in the friction coefficient due to a change in the surface film quality, and the like is suppressed, and the object of the present invention is achieved.

In the apparatus of this embodiment, as in the first embodiment, the horizontal force detection circuit 11 forms a differential signal from the reference set value based on the horizontal force detection signal from the four-division sensor 6, It is guided to the vertical force reference set value correction circuit 13. The vertical force reference set value correction circuit 13 corrects and calculates the vertical force reference set value based on the difference signal input from the horizontal force detection circuit 11 by using a coefficient obtained experimentally in advance. It is guided to the directional force detection circuit 7.

The vertical force detection circuit 7 forms a difference signal between the vertical force detection signal from the four-divided sensor 6 and the corrected reference set value signal. This differential signal is used as a servo signal to drive the fine movement actuator 4 via the vertical force servo circuit 8 to perform negative feedback control so that the differential signal becomes zero.

The image data is sent to the data demodulation circuit 17
In the above, the servo signal input from the vertical force servo circuit 8 is demodulated by performing inverse correction calculation via the phase compensation circuit according to the reference set value correction amount output from the reference set value correction circuit 13.

As described above, in this embodiment, the contact state between the probe and the sample is controlled, and the horizontal force is rapidly increased due to the sharp change of the surface shape and the increase of the friction coefficient due to the change of the surface film quality. And to achieve the object of the present invention.

(Third Embodiment) In this embodiment, an embodiment of a recording / reproducing apparatus using the surface observation apparatus of the present invention will be described. FIG. 3 is a system block diagram of an embodiment of a recording / reproducing apparatus using the surface observation apparatus of the present invention. Also in this embodiment, only the points different from the first and second embodiments will be described.

In the apparatus of this embodiment as shown in FIG. 3, the cantilever 3 supporting the conductive probe 1 is a cantilever type leaf spring, and in an actual recording / reproducing apparatus, it is on the same substrate by the micromechanics technique. Although it is composed of a plurality of cantilevers that are integrated with each other, only one is described here for simplicity.

When the apparatus of the present invention is composed of a plurality of cantilevers, the optical detection method by the four-division sensor of the above-mentioned embodiment is not suitable for the microstructure formation process by micromechanics. Therefore, in the present embodiment, it is proposed to detect the twist or the horizontal bending of the elastic body by the differential output of the plurality of strain resistance elements 18 provided on the elastic body.

In the present embodiment, as shown in FIG. 3, a pair of strain resistance elements 18 are provided on the cantilever 3 in parallel with the longitudinal direction, and the respective outputs from the pair of strain resistance elements 18 are provided. It is input to the difference circuit 19 and the addition circuit 20, respectively.

When the cantilever 3 receives a vertical force and bends only in the vertical direction, the outputs from the pair of strain resistance elements 18 are always equal and the differential output is zero. However, when the cantilever 3 receives a horizontal force and causes torsional deformation or horizontal bending deformation, each output from the pair of strain resistance elements 18 is different due to the piezoelectric effect, and a differential output is generated, depending on the degree of deformation. The difference output also becomes large.

Therefore, by forming the differential output of the pair of strain resistance elements 18 by the differential circuit 19, the horizontal force is generated, and the added output of the pair of strain resistance elements 18 is added by the addition circuit 2.
By forming 0, the vertical force can be detected.

The horizontal force detected as described above,
The vertical force is used to control the distance or contact state by using the vertical force as a servo signal during recording and reproduction.
The point that the object of the present invention is achieved by simultaneously performing the variable control of the scanning speed by the detection of the horizontal force and the variable control of the vertical reference set value at the same time is exactly the same as in the first and second embodiments. Therefore, detailed explanation is omitted.

Recording is performed by the scanning timing signal generation circuit 15
While scanning is performed based on the signal in (1), a recording voltage pulse is applied between the probe recording layers by the recording pulse generation circuit 22 based on the timing signal from the data timing signal generation circuit 16 to sequentially form recording bits.

For reproduction, a current generated by the reproduction bias generation circuit 23 in the state where a bias voltage below the recording threshold is applied between the recording layer 2 and the conductive probe 1 is formed by a current-voltage conversion circuit and a logarithmic conversion circuit. After the detection by the detection circuit 21, the data demodulation circuit 17 forms reproduced data based on the timing signal from the data timing signal generation circuit 16.

[0051]

According to the present invention as described above, the detection means for detecting the horizontal force generated in the probe, the scanning speed control means for feedback controlling the scanning speed based on the horizontal force, or the horizontal speed control means. Since either one or both of the correction means for correcting the control amount in the distance control means based on the directional force is provided, the horizontal direction due to the abrupt shape change or film quality change which is the origin of the sample surface damage. By detecting the force increase early and decreasing the scanning speed, the interaction repulsive force between the probe samples or these simultaneously, the increase of the horizontal force is suppressed, and the film damage in the area where the film thickness and film quality change suddenly. While avoiding, it is possible to maintain high-speed scanning of the entire sample surface, detection resolution, or these at the same time.

The horizontal force detecting means outputs the twist or the horizontal bending of the elastic body to the differential output of the plurality of strain resistance elements provided at different positions on the cantilever type elastic member supporting the probe. Since it is detected by the method, it can be applied to a system having a fine structure by a micromechanics process.

[Brief description of drawings]

FIG. 1 is a system block diagram according to a first embodiment of the present invention.

FIG. 2 is a system block diagram according to a second embodiment of the present invention.

FIG. 3 is a system block diagram of an embodiment of a recording / reproducing apparatus using the surface observation apparatus of the present invention.

FIG. 4 is a system block diagram of a conventional scanning force microscope.

5A and 5B are diagrams showing a contact scanning state in a conventional scanning force microscope, FIG. 5A is a diagram showing a reaction force generated at a protrusion, and FIG. 5B is a dynamic friction force generated at a film quality change portion. FIG.

[Explanation of symbols]

 1 probe 2 sample (recording layer) 3 cantilever 4 fine actuator 5 semiconductor laser 6 four-division (or two-division) sensor 7 vertical direction force detection circuit 8 vertical direction servo circuit 9 scanning drive actuator 10 scanning signal generation circuit 11 horizontal direction force Detection circuit 12 Scanning speed correction circuit 13 Vertical force set value correction circuit 14 Scanning speed time integration circuit 15 Scan timing signal generation circuit 16 Data timing signal generation circuit 17 Data demodulation circuit 18 Distortion resistance element 19 Difference circuit 20 Addition circuit 21 Current detection Circuit 22 Recording pulse generation circuit 23 Reproduction bias generation circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiharu Yano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A distance control means for controlling a distance or a contact state between a probe and a sample supported by a cantilever type elastic member, and a scanning means for scanning the probe and the sample relatively parallel to the sample surface. In a sample surface observing apparatus including: a detecting unit for detecting a horizontal force parallel to the sample surface generated between the probe and the sample surface; and a feedback control of a scanning speed by the scanning unit using the horizontal force as a servo signal. A sample surface observing device, comprising: a scanning speed control means. 2. The sample surface observing apparatus according to claim 1, further comprising a correction unit that corrects a control amount in the distance control unit based on a horizontal force detected by the detection unit. Sample surface observation device. 3. A distance control means for controlling a distance or a contact state between a probe and a sample supported by a cantilever type elastic member, and a scanning means for scanning the probe and the sample relatively parallel to the sample surface. A sample surface observing device comprising: a detecting means for detecting a horizontal force parallel to the sample surface generated between the probe and the sample surface; and a distance control means in the distance controlling means based on the horizontal force detected by the detecting means. An apparatus for observing a sample surface, comprising a correction means for correcting the control amount. 4. The detection means has a plurality of strain resistance elements provided at different positions on a cantilever type elastic member supporting the probe, and outputs a differential output of the plurality of strain resistance elements. The sample surface observing device according to claim 1, wherein the horizontal force is detected based on the horizontal force. 5. A recording / reproducing apparatus using the sample surface observing apparatus according to claim 1, wherein the sample voltage is applied to a sample, and the pulse voltage is applied to the sample. A recording / reproducing apparatus using a sample surface observing device, which is provided with a recording / reproducing means including a current detecting means for detecting a current generated in this state.