KR20220041757A - Mehtod for measuring surface characteristic of measurement object by measuring apparatus, atomic force microscope for carring out the method and computer program stored on storage medium for carring out the method - Google Patents

Abstract

The present invention relates to a method for measuring the surface characteristic of an object under measurement by means of a measurement apparatus, an atomic force microscope for executing the method thereof and a computer program stored in a computer program stored in a storage medium for executing the method thereof, which can provide a higher measurement speed, can reduce the abrasion of a tip, and can be suitable for measuring a deep and narrow trench structure. In particular, the method according to one embodiment of the present invention is a method which measures the surface characteristic of an object under measurement by means of a measurement apparatus which measures the characteristic of the object under measurement by measuring the interaction between the tip and the surface of the object under measurement. To this end, the present invention repeatedly executes steps with respect to a plurality of locations on the surface of the object under measurement, the steps comprising: an approach step of locating the tip for the tip to come in contact with the specific location of the surface of the object under measurement; and a lift step of allowing the tip which has come in contact therewith to be spaced apart from the surface of the object under measurement. In one part or the entirety of the approach step and the lift step, the tip is controlled to vibrate. The moving characteristic of the tip can be controlled in accordance with the change in the vibration characteristic of the tip.

Description

A method for measuring the properties of a surface of an object to be measured by a measuring device, an atomic force microscope for performing this method, and a computer program stored in a storage medium for performing this method FORCE MICROSCOPE FOR CARRING OUT THE METHOD AND COMPUTER PROGRAM STORED ON STORAGE MEDIUM FOR CARRING OUT THE METHOD}

The present invention relates to a method for measuring the properties of the surface of an object to be measured by a measuring device, an atomic force microscope for performing the method, and a computer program stored in a storage medium for performing the method, and more particularly, to a faster measurement A method for measuring the properties of the surface of an object to be measured by a measuring device, an atomic force microscope for carrying out this method, and a storage for carrying out this method, which can reduce the wear of the tip while having a speed and is suitable for the measurement of deep and narrow trench structures It relates to a computer program stored in a computer program stored in a medium.

A scanning probe microscope (SPM) is a microscope that measures the surface characteristics of the object to be measured and displays it as a 3D image while sweeping and passing a fine tip (probe) manufactured through the MEMS process, etc. over the surface of the sample (Scanning). say Such a scanning probe microscope is subdivided into an atomic force microscope (AFM, Atomic Force Microscope), a scanning tunneling microscope (STM, Scanning Tunneling Microscope), etc. according to a measurement method.

In scanning probe microscope, it is common to scan while the tip follows the surface of the measurement object, but even if the distance between the tip and the surface of the measurement object is feedback controlled, collision between the tip and the surface of the measurement object will occur, and the cause of tip damage do. To reduce such damage, by repeating the operation of approaching the tip to the surface of the measurement object, lifting the tip to a certain height, moving the tip to a different position, and approaching the tip to the surface of the measurement object again, only a specific point Attempts have been made to obtain the topography of the surface of the measurement object by measuring the height, respectively (see Patent Document 1).

In addition, in addition to the purpose of minimizing tip damage, there have been attempts to utilize the above-described technique so that the curved image of the surface of the measurement target is not reflected in an optional signal such as EFM or MFM (see Patent Document 2). This technology is also referred to as a so-called pinpoint mode.

On the other hand, as the miniaturization and integration of semiconductors progressed, a narrow and deep trench structure was created. In order to obtain the shape of such a narrow and deep trench, a scanning probe microscope such as an atomic force microscope is used, but due to the narrow and deep shape characteristics, at least a longer tip than the height of the trench should be selected. In addition, the tip should be as thin as possible to minimize interference with the sidewalls of the trench. Because of these tip limiting factors, it is very difficult to control the long tip to follow the surface of the narrow and deep trench.

Accordingly, the pinpoint mode is sometimes used to measure the shape of a narrow and deep trench. However, the operation of the pinpoint mode using a long tip involves excessive time required to lift the tip, which acts as a factor impairing throughput.

(Patent Document 1)

Japanese Patent Application Laid-Open No. 2004-132823 (Title of Invention: Sampling Scanning Probe Microscope and Scanning Method)

(Patent Document 2)

Korean Patent Registration No. 10-2102637 (Title of the invention: Topography signal and option signal acquisition method, apparatus, and atomic force microscope having the same)

The present invention has been devised to solve the above problems, has a faster measurement speed, can reduce tip wear, and is suitable for measuring a deep and narrow trench structure. To provide a method, an atomic force microscope for performing the method, and a computer program stored in a computer program stored in a storage medium for performing the method.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In a method according to an embodiment of the present invention for solving the above problems, the characteristic of the surface of the measurement object is measured by a measuring device that measures the characteristic of the measurement object by measuring the interaction between the tip and the surface of the measurement object way to do it The method includes an approach step of positioning the tip to be in contact with a specific position on the surface of the measurement target; and a lifting step of separating the contacted tip from the surface of the measurement target. is repeatedly performed for a plurality of positions on the surface of the measurement object, but the tip is controlled to vibrate in part or all of the approach step and the lift step, and the tip movement characteristics according to a change in the vibration characteristics of the tip This is controlled.

According to another feature of the present invention, the tip is controlled to vibrate freely, and the vibration characteristic of the tip is amplitude.

According to another feature of the present invention, the tip is controlled to vibrate freely during the approach step, and is configured to control the speed of approach of the tip to the surface of the measurement target by changing the amplitude of the tip.

According to another feature of the present invention, as the approach step proceeds, the amplitude of the tip decreases as the tip approaches the surface of the measurement object, and then the amplitude A is smaller than the amplitude during free vibration of the tip. When the amplitude of the tip is sensed, the control based on the change in the amplitude of the tip is turned off, and the tip is controlled to press the surface of the measurement object with a specific force.

According to another feature of the present invention, the tip is controlled to oscillate freely during the lifting phase and is configured to control the lift height of the tip by a change in the amplitude of the tip.

According to another feature of the present invention, the amplitude of the tip increases as the tip moves away from the surface of the measurement target while the lifting step is in progress, and then the tip becomes an amplitude B smaller than the amplitude during free vibration of the tip. When the amplitude of is detected, the lift operation is controlled to stop.

According to another feature of the present invention, the method further comprises a shifting step for positioning the tip on the different location after the lifting step at a specific location is completed and before the approach step at the other location is performed, wherein the shifting step is performed. During the step, the tip is controlled to vibrate freely, and during the shift step, the movement path of the tip is controlled so that the vibration characteristic of the tip is constant.

According to another feature of the present invention, in the approach step, the contact mode control and the non-contact mode control of the atomic force microscope are respectively performed with different sections.

According to another feature of the present invention, in the lifting step, the contact mode control and the non-contact mode control of the atomic force microscope are respectively performed with different sections.

An atomic force microscope according to an embodiment of the present invention for solving the above problems is an atomic force microscope configured to measure the surface of a measurement target by a probe having a tip and a cantilever. The atomic force microscope includes: an XY scanner configured to move the measurement object such that the tip moves relative to the surface of the measurement object in the XY direction; An optical system configured to be mounted with the probe and capable of measuring vibration or deflection of the cantilever, and data obtained by the optical system to control the distance between the tip and the surface of the measurement target. a head comprising a Z scanner configured to move in a direction; and a controller controlling the XY scanner and the head. includes The controller, an approach step of positioning the tip to be in contact with a specific position on the surface of the measurement target; and a lifting step of separating the contacted tip from the surface of the measurement target. is repeatedly performed for a plurality of positions on the surface of the measurement target, but the tip is controlled to vibrate in some or all of the approach step and the lift step, and the tip moves according to a change in the vibration property of the tip is configured to control

A computer program according to an embodiment of the present invention for solving the above problems is stored in a storage medium for performing the above-described method.

According to the method of the present invention, it is possible to reduce tip wear while having a faster measurement speed and to provide a pinpoint mode suitable for measuring a deep and narrow trench structure.

1 is a schematic perspective view of an atomic force microscope in which an XY scanner and a Z scanner are separated.
2 is a conceptual diagram illustrating a method of measuring a measurement target using an optical system.
3 is a schematic flowchart of a method for measuring a property of a surface of an object to be measured according to the present invention.
4 is a conceptual diagram schematically illustrating a method for measuring a surface characteristic of a measurement target according to the present invention.
FIG. 5 is a graph showing time series of a control method according to the execution of each step of FIG. 4 .
6 shows an FD curve and an AD curve in the approach step.
FIG. 7 is a diagram illustrating a combination curve of the FD curve and the AD curve of FIG. 6 and a VD relationship diagram thereof.
8 shows a diagram of the VD relationship in the lift phase.
9 is a graph showing a time series of a control method when an abnormal situation occurs in the shift step.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

Although the first, second, etc. are used to describe various elements, these elements are not limited by these terms, of course. These terms are only used to distinguish one component from another. Accordingly, it goes without saying that the first component mentioned below may be the second component within the spirit of the present invention. In addition, even if it is described that the second coating is performed after the first coating, it goes without saying that coating in the reverse order is also included in the technical spirit of the present invention.

In using reference numerals in the present specification, even if the drawings are different, the same reference numerals are used as much as possible when the same configuration is shown.

The size and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

Construction of an Atomic Force Microscope for Practicing the Invention

First, the configuration of an atomic force microscope as a measuring device for carrying out the method of the present invention will be described as an example.

1 is a schematic perspective view of an atomic force microscope in which an XY scanner and a Z scanner are separated, and FIG. 2 is a conceptual diagram illustrating a method of measuring a measurement target using an optical system.

Referring to FIG. 1 , an atomic force microscope 100 includes a probe unit 110 , an XY scanner 120 , a head 130 , a Z stage 140 , a fixed frame 150 , and a controller 160 . ) is included.

The probe unit 110 includes a cantilever 111 and a tip 112 , and the tip 112 is configured to follow the surface of the measurement object 1 in a contact or non-contact state. The probe unit 110 may be provided separately from other components below, and is used by being fixed to the head 130 to be described later.

The XY scanner 120 is configured to move the measurement object 1 such that the tip 112 moves relative to the surface of the measurement object 1 in the first direction. Specifically, the XY scanner 120 functions to scan the measurement object 1 in the X direction and the Y direction in the XY plane.

The head 130 is configured such that the probe unit 110 can be mounted, and based on an optical system capable of measuring vibration or deflection of the cantilever 111, and data obtained by the optical system, between the tip and the surface of the measurement target. and a Z scanner 131 configured to move the probe 110 in at least the second direction and vice versa to control the distance. The optical system will be described later with reference to FIG. 2 . Here, the Z scanner 131 moves the probe 110 with a relatively small displacement.

The Z stage 140 moves the probe unit 110 and the head 130 in the Z direction with a relatively large displacement.

The fixed frame 150 fixes the XY scanner 120 and the Z stage 140 .

The controller 160 is configured to control at least the XY scanner 120 , the head 130 and the Z stage 140 .

Meanwhile, the atomic force microscope 110 may further include an XY stage (not shown) configured to move the XY scanner 120 on the XY plane with a large displacement. In this case, the XY stage will be fixed to the fixed frame 150 .

The atomic force microscope 100 scans the surface of the measurement object 1 with the probe unit 110 to obtain images such as topography. The relative movement between the surface of the measurement object 1 and the probe unit 110 may be performed by the XY scanner 120, and moving the probe unit 110 up and down to follow the surface of the measurement object 1 is This can be done by the Z scanner 131 . Meanwhile, the probe unit 110 and the Z scanner 131 are connected by a probe arm 132 .

Referring to FIG. 2 , the XY scanner 120 supports the measurement object 1 and scans the measurement object 1 in the XY direction. The XY scanner 120 may be driven by, for example, a piezoelectric actuator, and when it is separated from the Z scanner 131 as in this embodiment, a stacked piezo may be used. . Regarding the XY scanner 120, Korean Patent Registration Nos. 10-0523031 (title of invention: XY scanner and driving method thereof in a scanning probe microscope) and No. 10-1468061 (title of invention: scanner control method and scanner device using the same).

The Z scanner 131 may be connected to the probe unit 110 to adjust the height of the probe unit 110 . The driving of the Z scanner 131 may also be performed by a piezoelectric actuator like the XY scanner 120 . For the Z scanner 131, reference is made to Korean Patent Registration No. 10-1476808 (title of the invention: scanner device and atomic force microscope including the same), which is the applicant of the present applicant. When the Z scanner 131 is contracted, the probe 110 moves away from the surface of the measurement object 1 , and when the Z scanner 131 is extended, the probe 110 moves closer to the surface of the measurement object 1 . lose

The XY scanner 120 and the Z scanner 131 may exist as separate members separated as shown in FIGS. 1 and 2 , but may be integrated into one member by a tubular piezoelectric actuator. In the case of such a tubular piezoelectric actuator, although movement in the XY direction and movement in the Z direction can be performed together, there is a problem in that the behavior in the XY direction and the behavior in the Z direction are coupled to distort the image. However, it goes without saying that such a structure can be utilized in the present invention despite these limitations. Such an XYZ integrated scanner is disclosed in US Patent Publication No. 2012-0079635A1 (title of the invention: Methods and devices for correcting errors in atomic force microscopy), and in addition, a structure of a known atomic force microscope may be used.

The head 130 has an optical system capable of measuring the vibration or bending of the cantilever 111 of the probe unit 110, and this optical system includes a laser generating unit 132 and a detector 133.

The laser generating unit 132 irradiates laser light (shown by a dotted line) to the surface of the cantilever 111 of the probe unit 110, and the laser light reflected from the surface of the cantilever 111 is PSPD (Position Sensitive Photo Detector) It is condensed on the detector (133) of the same two axes. The signal detected by this detector 133 is sent to the controller 160 for control.

The controller 160 is connected to the XY scanner 120 and the Z scanner 131 to control driving of the XY scanner 120 and the Z scanner 131 . In addition, the controller 160 converts the signal obtained from the detector 133 into a digital signal by an ADC converter, and utilizes this to determine the degree of bending, distortion, etc. of the cantilever 111 of the probe unit 110 . . A computer may be integrated into the controller 160 or may be connected to a separate computer and the controller 160 . The controller 160 may be integrated into one and put in a rack, but may exist divided into two or more.

The controller 160 sends a signal to drive the XY scanner 120 so that the measurement object 1 can be scanned in the XY direction by the XY scanner 120, while the probe unit 110 moves the measurement object 1 The Z scanner 131 is controlled to have a constant mutual force with the surface (that is, so that the cantilever 111 maintains a certain degree of bending or the cantilever 111 vibrates with a constant amplitude). That is, the controller 160 has a closed loop feedback logic of software or electrical circuit. In addition, the controller 160 measures the length of the Z scanner 131 (or the length of the actuator used in the Z scanner 131), or a voltage applied to the actuator used in the Z scanner 131. By measuring, Topography of the surface of the measurement object 1 is obtained.

Here, the tip 112 of the probe unit 110 may move relative to the surface of the measurement object 1 while in contact with the surface of the measurement object 1 (this is referred to as a 'contact mode'), and the surface It is also possible to move relative to the surface of the measurement object 1 while vibrating without contacting it (this is called a 'non-contact mode'), and also to vibrate the surface of the measurement object 1 while vibrating while hitting the surface of the measurement object (1). ) relative to the surface (this is called 'tapping mode'). Since these various modes correspond to previously developed modes, detailed descriptions thereof will be omitted.

On the other hand, the data regarding the surface of the measurement object 1 obtained by the controller 160 may be various other than the shape data. For example, by applying a magnetic force to the probe unit 110 or performing a special treatment for applying an electrostatic force, data on the magnetic force on the surface of the measurement object 1, data on the electrostatic force, and the like can be obtained. The modes of the atomic force microscope include MFM (Magnetic Force Microscopy), EFM (Electrostatic Force Microscopy), and the like, which may be implemented using a known method. In addition, the data regarding the surface of the measurement object 1 may be a voltage of the surface, a current of the surface, or the like.

On the other hand, it should be noted that the configuration of the head 130 only describes essential components for convenience of explanation, and specific configurations such as other optical systems are omitted. Configurations disclosed in No. 0646441 may be further included.

How to measure the properties of the surface of the measurement object

Hereinafter, with reference to the accompanying drawings, an embodiment of a method for measuring the characteristics of the surface of the measurement target of the present invention will be described.

3 is a schematic flowchart of a method for measuring the surface characteristics of a measurement target according to the present invention, and FIG. 4 is a conceptual diagram schematically illustrating a method for measuring the surface characteristics of the measurement target according to the present invention.

Referring to FIG. 3 , in the method of measuring the surface characteristic of the measurement object according to the present invention, the atomic force microscope illustrated in FIGS. 1 and 2 measures the characteristic of the measurement object by measuring the interaction between the tip and the surface of the measurement object It is made by the same measuring device as in (100), and includes an approach step (S10), a lift step (S20), and a shift step (S30). Hereinafter, the description of the method will be referred to with reference to FIGS. 1 and 2 as well.

First, the tip 112 is placed in contact with a specific position (first position) of the surface of the measurement object (approach step, S10).

Referring to FIG. 4 , in this step ( S10 ), the measuring device sends the tip of the tip located at the point a to the point b (the first position) to make contact. Point a is an arbitrary position, and may be the position of the end of the tip 112 after the previous shifting step S30 is completed. The position (first position) of the tip 112 after the approach is an arbitrary point to be measured.

The approach step S10 is made by bringing the tip 112 close to the surface of the measurement object 1 using the Z scanner 131 . The approach step S10 is completed by causing the tip of the tip 112 to press the surface of the measurement object 1 with a specific force. When the tip of the tip 112 is pressed with a specific force, the cantilever 111 is bent, and the bending of the cantilever 111 is detected by an optical system including a laser generating unit 133 and a detector 134 . When the cantilever 111 is bent to a certain extent, the approach step S10 is completed, and data on the position of the tip of the tip 112 is collected. Such data may be obtained from the Z scanner 131 , or may be obtained by a length sensor (eg, strain gauge sensor) attached to the Z scanner 131 or the like. In addition, a specific control method in the approach step (S10) will be described later.

After the approach step (S10) is completed, when the above-described data is obtained, the contacted tip 112 is separated from the surface of the measurement object (lifting step, S20).

4, in this step (S20), the measuring device lifts the tip of the tip 112 located at the b point to the c point. For reference, point c may be the same as point a, or may not be the same as in FIG. 4 . If the Z scanner 131 that moves the tip 112 in the z direction implements complete straightness, points a and c coincide, and the path of the tip 112 by the approach step S10 and the lift step S20 The paths of the tip 112 by the can overlap each other.

The tip 112 lifted by the lifting step S20 is controlled to be positioned on a position (second position) different from the first position for data collection at another point (shifting step S30).

4, in this step (S30), the measuring device moves the tip of the tip located at the c point to the d point located above the second position. The movement of the tip 112 may be implemented by moving the tip 112 , but may be implemented by moving the measurement object 1 by the XY scanner 120 . According to the measuring apparatus shown in FIGS. 1 and 2 , the shifting step S30 can be performed by controlling the XY scanner 120 to move the measurement object 1 .

Here, the shifting step S30 may be implemented to move the tip 112 horizontally to the X direction as shown in FIG. 4 , but any path may be taken as long as it can be moved to a different planned position.

Also, since the shift step S30 is included in the lift step S20, it may not be performed as a separate step. When performing the lifting step (S20), the lifting step (S20) can be omitted by horizontally moving the tip 112 while lifting it.

The above-described approach step (S10), lift step (S20), and shift step (S30) are repeatedly performed for a plurality of positions on the surface of the measurement object 1, so that the characteristic of the measurement object 1 can be measured. Here, the characteristic of the measurement object 1 may be a topography of the surface of the measurement object 1 or the like. However, information other than topography can also be obtained by imparting special properties (magnetic properties, electrical properties, etc.) to the tip 1 in addition to this.

As shown in FIG. 4, the above-described steps (S10, S20, S30) are repeatedly performed for a plurality of positions of the surface of the measurement object 1 along the X direction to obtain data obtainable in the normal contact mode or non-contact mode. there is. In particular, in the measurement of the deep and narrow trench structure illustrated in FIG. 4 , it is necessary to find a very difficult feedback condition for the tip 112 to follow the surface of the measurement object 1 in the conventional contact mode or non-contact mode, and the feedback condition If this is not satisfied, the tip 112 collides with the measurement object 1 to obtain a poor image, and there is also a problem in that the tip 112 needs to be replaced frequently. On the other hand, if the method according to the present invention is used, an excellent image can be obtained while minimizing damage to the tip 112 even in the measurement of a deep and narrow trench structure.

On the other hand, in the deep and narrow trench structure, in the conventional non-contact mode, the tip 112 interacts with the sidewall before interacting with the bottom of the trench. This was difficult. For this, a long tip 112 must be used, and when performing a method such as the present invention with the long tip 112, it was common to completely pull the tip 112 out of the trench, which has the disadvantage of lengthening the measurement time. became However, these disadvantages are compensated for by the features described later.

5 is a graph showing the control method according to the execution of each step of FIG. 4 chronologically, FIG. 6 shows the FD curve and the AD curve in the approach step, and FIG. 7 is the FD curve and the AD curve of FIG. Fig. 8 shows the VD relation diagram in the lift stage, and Fig. 9 is a graph showing the control method in time series when an abnormal situation occurs in the shift stage.

5, the approach step (S10), the lift step (S20), and the shift step (S30) are performed in order, and the pressing force - Force Set Point and Amplitude - Set Point By setting it, the control of the contact mode and the non-contact mode is performed together.

A specific control method in the approach step S10 will be described with reference to FIGS. 5 to 7 .

In the approach step S10, the tip 112 is controlled to vibrate at a specific frequency f. Here, the specific frequency may be a resonant frequency of the cantilever 111 . Tip 112 is free oscillating and has an amplitude A _free of free oscillation.

Upon completion of this step 10 , the tip 112 vibrates, but the tip 112 is controlled to contact the surface of the measurement object 1 . That is, although the approach is performed in the contact mode, the control is performed in the approach step S10 also in the non-contact mode.

Fig. 6(a) shows a graph (F-D curve) showing the relationship between the distance D and the pressing force F between the tip of the tip 112 and the surface of the measurement object 1 in the contact mode. The tip of the tip 112 receives little force when it is far from the measurement object (1), but when it is very close, the tip of the tip 112 sticks to the surface of the measurement object (1), and when it gets closer, the tip ( 112) This measurement object (1) is pressed, and the pressing force can continue to increase.

In Fig. 6(b), a graph (AD curve) showing the relationship between the amplitude (A) of the tip 112 in the non-contact mode and the distance (D) between the tip of the tip 112 and the surface of the measurement object 1 is is shown The amplitude of the tip 112 decreases as the distance increases due to the interaction with the surface of the measurement object 1, and when the tip 112 comes into contact with the measurement object 1, the amplitude reaches 0 due to physical restraint is reduced close to

Using the behavioral characteristics of the tip 112 in the contact mode and the non-contact mode of FIG. 6 , as shown in FIG. 7 , the operation of the tip 112 approaching the surface of the measurement object 1 is controlled.

7A is a composite of the F-D curve and the A-D curve of FIG. 6 , and shows the Y-axis by synthesizing the pressing force (F) and the amplitude (A) at a certain ratio. Through this, the approach speed control method as shown in (b) of FIG. 7 is determined.

First, in the approach step S10, the control according to the contact mode is not operated, and only the control according to the non-contact mode is operated until the tip 112 and the measurement object 1 approach a specific distance d ₁ .

The specific distance d ₁ may be arbitrarily determined, but it is preferable to set a value equal to or slightly larger than the point g at which the tip of the tip 112 is attached to the surface of the measurement object 1 . The amplitude-setpoint A _setl , which is the amplitude of the tip 112 at a specific distance d ₁ , may be determined according to the type of the cantilever 111 with the tip 112 . For example, the amplitude-setpoint A _setl may be expressed as a ratio to A _free , and may be, for example, 5%, 10%, or 15%.

The control according to the non-contact mode, which is performed until the tip 112 and the measurement object 1 approaches a specific distance d ₁ , is to control the approach speed (approach speed) V as the amplitude A. That is, as shown in (b) of FIG. 7 , the approach speed V is controlled to decrease in proportion to the decrease in amplitude A.

When the amplitude reaches the amplitude-setpoint A _setl , the control according to the non-contact mode is terminated, and the control according to the contact mode is performed. That is, the approach speed V is controlled according to the force (pressing force) that the tip 112 presses against the surface of the measurement object (1), and as a result, with the pressing force-setpoint F _set , the tip 112 presses the measurement object (1) is controlled to press the surface of the

Here, the pressing force-setpoint F _set may be appropriately determined according to the characteristics of the probe unit 110 , the surface characteristics of the measurement object 1 , and the structural characteristics of the measurement object 1 , and may be, for example, several to several tens of nN. there is.

In other words, as the approach step (S10) proceeds, as the tip 112 approaches the surface of the measurement object 1, the amplitude of the tip 112 decreases, and the amplitude of the tip 112 is smaller than the amplitude at the time of free oscillation. When the amplitude of the tip 112 is detected below A _setl , the control based on the change in the amplitude of the tip 112 (non-contact mode control) is turned off, and the tip 112 is the measurement target (1). ) to perform a control (contact mode control) controlled to press the surface of , with a specific force.

Referring back to FIG. 5 , when the approach step S10 is performed, the pressing force-setpoint is set to F _set , and the amplitude-setpoint is set to A _setl . The contact mode control and the non-contact mode control are performed in different sections by these setpoints.

If this approach is performed, the approach can be performed quickly, and as the tip of the tip 112 approaches the surface of the contact object 1, the approach speed is reduced to reduce the tip of the tip 112 and the surface of the contact object 1 By reducing the amount of collision between the two, the tip 112 can be used for a long time.

Referring to FIG. 8, in the lift step (S20), the tip 112 is initially controlled to move away from the surface of the measurement object 1 at a high speed, and when it has a distance greater than d1, the speed is controlled by non-contact mode control. can As the amplitude of the tip 112 increases, the speed is controlled to decrease, and the lift height is limited so that the amplitude does not become greater than a predetermined value.

In other words, the distance D between the _tip of the tip ₁₁₂ and the surface of the measuring object 1 is Controlled. The distance d ₂ when the amplitude A is A _seth may be referred to as the lift height.

The amplitude-setpoint A _seth can be variously set to a value larger than A _setl , for example, it can be a value of 50 to 95% of the maximum amplitude A _free . Since the amplitude-setpoint A _seth is related to the lift height d ₂ , the amplitude-setpoint A _seth is set according to how much the lift height is set.

In this case, in the non-contact mode control, it is preferable to keep the gain value low. This is because, in the lifting step ( S20 ), the lifting operation is important, but the sensitive control is not.

In other words, as the tip 112 moves away from the surface of the measurement object 1 as the lifting step S20 proceeds, the amplitude of the tip 112 increases, and the amplitude of the tip 112 is smaller than the amplitude at the time of free oscillation. When the amplitude of the tip 112 is sensed with A _seth , it is controlled to stop the lift operation.

Referring back to FIG. 5 , in the lifting step ( S20 ), the pressing force-setpoint is set to 0 or a value close to it, and the amplitude-setpoint is set to the maximum A _seth to control the lift speed and height.

According to the present method, the pin-point mode can be performed by setting the minimum lift height by utilizing the non-contact mode control in the lift step S20. That is, while the conventional pin-point mode sufficiently lifts the tip 112 and then approaches at another position, according to the method of the present invention, the measurement speed can be increased by remarkably reducing the lift height while increasing the lift speed. there is.

Referring to Fig. 5, the shifting step S30 is performed by generating displacement in the X-direction (or Y-direction) while maintaining the lifted Z-direction displacement. During the shift step S30, the pressing force-setpoint is set to 0 or a value close to it, as in the lift step S20, and the amplitude-setpoint is set to A _seth . 5 illustrates a case where no obstacle is detected when the tip 112 moves, and the displacement in the Z direction is maintained while the displacement in the X direction is constantly changed.

However, during the shifting step S30 , the movement of the tip 112 in the X direction may not be possible due to an obstacle (eg, the sidewall in FIG. 9A ). These events can occur frequently when measuring deep and narrow trench structures.

Referring to FIG. 9 , in the shift step S30 , in the initial section S30 - 1 , only the movement in the X direction is made while the displacement of the tip 112 in the Z direction is not changed. When the tip 112 collides with the side wall, the amplitude A is reduced, and as shown in FIG. 5 , a control is performed to set it back to the amplitude-setpoint A _seth . Tip 112 is lifted to increase the amplitude of tip 112 . Even at this time, the movement of the tip 112 in the X direction continues. That is, the amplitude is measured to decrease in the section S30-2, but the amplitude is again controlled to A _seth in the section S30-3 due to the change in the displacement of the tip 112 in the Z direction.

For reference, the collision can be confirmed by a change in the pressing force. Referring to (b) of FIG. 9 , it can be seen that the tip 112 presses the measurement object 1 as the pressing force has a negative value during collision.

That is, when performing the shift step S30, the distance between the tip 112 and the surface of the measurement object 1 is maintained by utilizing the non-contact mode control, so the measurement time is reduced by omitting the operation of excessively lifting the tip 112. can be drastically reduced.

In other words, the movement path of the tip 112 is controlled so that the vibration characteristic (eg, amplitude) of the tip 112 is constant during the shift step S30 .

As described above, the movement characteristic of the tip 112 is controlled according to a change in the vibration characteristic of the tip 112 . Here, the movement characteristic may be an approach speed of the tip 112 exemplified above and a lift height of the tip 112 .

In addition, although only amplitude is illustrated in this embodiment as the vibration characteristic of the tip 112 , this is only an example, and includes characteristics related to vibration of the tip 112 , such as frequency and phase.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

100… atomic force microscope
110… probe
111… cantilever
112… tip
120… XY Scanner
130… head
131… scanner
132... probe arm
133… laser generating unit
134… detector
140… stage
150… fixed frame
160… controller

Claims (11)

A method of measuring a characteristic of a surface of the measurement object by a measuring device that measures the characteristic of the measurement object by measuring an interaction between a tip and a surface of the measurement object, the method comprising:
an approach step of positioning the tip to be in contact with a specific position on the surface of the measurement target; and
a lifting step of separating the contacted tip from the surface of the measurement target; Repeatedly for a plurality of positions on the surface of the measurement target,
controlled to vibrate the tip in some or all of the approach step and the lift step;
A method of measuring a property of a surface of a measurement target, wherein a movement property of the tip is controlled according to a change in the vibration property of the tip. According to claim 1,
wherein the tip is controlled to vibrate freely, and the vibration characteristic of the tip is amplitude. 3. The method of claim 2,
During the approach step the tip is controlled to vibrate freely,
and controlling the speed of approach of the tip to the surface of the measurement object by a change in the amplitude of the tip. 4. The method of claim 3,
As the approach step progresses, the amplitude of the tip decreases as the tip approaches the surface of the measurement target, and when the amplitude of the tip is sensed to be less than or equal to the amplitude A during free oscillation of the tip, the Turn off the control based on the change in the amplitude of the tip (turn off),
A method of measuring a property of a surface of a measurement object, wherein the tip is controlled to press the surface of the measurement object with a specific force. 3. The method of claim 2,
during the lifting phase the tip is controlled to vibrate freely;
and controlling the lift height of the tip by a change in the amplitude of the tip. 6. The method of claim 5,
As the lifting step progresses, the amplitude of the tip increases as the tip moves away from the surface of the measurement object. A method of measuring a property of a surface of an object to be measured, which is controlled to stop motion. 3. The method of claim 2,
a shifting step for positioning the tip on the different location after the lifting step at a specific location is completed and before the approach step at the other location is performed;
during the shifting the tip is controlled to oscillate freely;
A method of measuring a surface characteristic of a measurement object, wherein a movement path of the tip is controlled so that the vibration characteristic of the tip is constant during the shifting step. 3. The method of claim 2,
In the approach step, the contact mode control and the non-contact mode control of the atomic force microscope are respectively performed with different sections. 3. The method of claim 2,
In the lifting step, the contact mode control and the non-contact mode control of the atomic force microscope are respectively performed with different sections. An atomic force microscope configured to measure a surface of an object to be measured by a probe having a tip and a cantilever, the atomic force microscope comprising:
an XY scanner configured to move the measurement object such that the tip moves relative to the surface of the measurement object in the XY direction;
An optical system configured to be mounted with the probe, and capable of measuring vibration or bending of the cantilever, and an optical system capable of measuring a distance between the tip and the surface of the measurement target based on data obtained by the optical system. a head comprising a Z scanner configured to move in a direction; and
a controller for controlling the XY scanner and the head; including,
The controller is
an approach step of positioning the tip to be in contact with a specific position on the surface of the measurement target; and
a lifting step of separating the contacted tip from the surface of the measurement target; Repeatedly for a plurality of positions on the surface of the measurement target,
controlled to vibrate the tip in some or all of the approach step and the lift step;
and control a movement characteristic of the tip according to a change in the vibration characteristic of the tip. A computer program stored in a storage medium for performing the method of claim 1.

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