JP2001249067A - Device and method for performing contour scanning by use of scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for performing contour scanning by use of a scanning probe microscope. SOLUTION: A scanning probe tip 130 mounted to a cantilever 132 is oscillated at an exciting frequency in the Z-direction and simultaneously dithered at a dithering frequency so as to draw a circular pattern in a plane vertical to the Z-direction. The dithering frequency is far lower than the exciting frequency. As the probe tip approaches a sidewall 153 on the surface of a sample 135, the oscillation of the probe tip in the Z-direction is modulated at the dithering frequency. A phase angle θ between the modulation and one signal to drive the probe tip in a circular pattern is used to determine the angle of a normal 190 from the side wall 153 to the center of the circular pattern. As a direction to be applied is locally specified by a tangential line vertical to the normal 190, it is possible to make the probe tip scan along the contour line of the sidewall 153.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Cross Reference of Related Applications
Apparatus and Method for Determining, filed July 29, 1998, assigned to the same assignee as the present application and incorporated herein by reference.
Side Wall Profiles Using a Scanning Probe Microsco
pe Having a Probe Dithered in Lateral Directions ''
And co-pending application Ser. No. 08/124302. This co-pending application describes an apparatus for applying dithering motion to a probe tip in a plane parallel to the entire surface of a sample being scanned. The probe tip is caused to scan along a scanning line formed by applying excitation vibration in the X direction or the Y direction along this plane, or in the Z direction perpendicular to the scanning plane. In the first mode of operation,
This dithering vibration is applied to the probe tip along the scanning line. In a second mode of operation, the probe tip makes a circular motion by dithering and is used to identify the direction in which the wall extends along the sample surface. In a third mode of operation, the probe tip is dithered at different frequencies in the X and Y directions to identify this direction on the wall. In each mode, after identifying this direction, the probe will go straight up or down along the wall to get a precise contour of the wall shape.

[0002] This application is also a part of "A Scanning F," filed on September 4, 1998, assigned to the same assignee as the present application and incorporated herein by reference.
orceMicroscope with Automatic Surface Engagement a
No. 09/072230, entitled "nd Improved Amplitude Demodulation". In this application, an automatic surface engagement mechanism for a scanning probe is described, along with an amplitude demodulator for such a microscope.

[0003]

2. Description of the Related Art In a conventional scanning probe microscope, a probe attached to a distal end of a cantilever is moved when the probe moves along a sample surface during a scanning operation.
The sample is vibrated at an excitation frequency close to the natural frequency of the cantilever in a direction basically perpendicular to the surface of the sample being measured. As the height of the sample surface changes, the tip's oscillating amplitude changes, and the tip's proximal end moves toward or away from the sample surface until the probe's oscillation amplitude returns to a predetermined level. I do.

Thus, examining the topography of the surface of a sample using a prior art scanning probe microscope, for example, involves moving the earth along only a series of parallel paths extending between north and south, thereby estimating the earth's surface. It's like examining the terrain. This type of movement is effective on parts of the earth, as well as on some sample surfaces. But,
Some parts of the globe can travel around structures such as mountains, and when examining such structures, they may follow or follow several separate horizontal paths. It is particularly convenient to be able to move around. In the field of scanning probe microscopy, there is a need for a way to locate upright and downwardly extending structures and to move around them in a number of contours that are vertically spaced by an incremental distance. Have been.

FIG. 1 is a cross-sectional view showing a trench in a sample surface 1 with a very sharp probe tip 2 used in a conventional scanning probe microscope to determine surface features of the sample surface 1. This probe tip 2
Oscillates in a direction commonly referred to as the "Z-direction" perpendicular to the entire surface 1 of the sample being measured, and the relative motion between the probe 2 and the sample surface 1 moves along the sample surface along the illustrated X-direction. And so on in the scanning direction. At the end of a given scanning operation, the relative movement between the probe and the sample takes place along the sample surface in a direction perpendicular to the scanning direction. This movement is used to start a new scan line parallel to the previous scan line, so that a given portion of the sample surface will be traversed in a raster pattern. In a scanning force microscope, the probe tip 2 is fixed to the distal end of a cantilever, and the proximal end of the cantilever oscillates at a constant amplitude and frequency in the Z direction. Under these conditions, the amplitude of the resulting vibration of the tip 2 depends on the level of engagement between the probe tip 2 and the sample surface 1. Thus, a servo loop is established to move the proximal end of the cantilever in the Z direction to keep the amplitude of the probe tip 2 vibration constant. Since the resulting movement of the proximal end of the cantilever follows the sample oscillations that occur in the Z direction as the probe scans in the X direction, the drive signal generated in the servo loop to cause this movement is , Is stored as a signal representing the vibration of the sample surface 2 in the Z direction.

While this conventional method is useful for examining some types of sample surfaces that have relatively gentle upward and downward slopes, surfaces with ridges and troughs, such as trough 6 in FIG. When used to examine, serious limitations appear. The tilt angle at which the probe tip 2 can move up or down to follow the shape of the sample surface 1 is limited by the fact that the probe vibrates only in the Z direction and the physical shape of the probe. In the example of FIG. 1, the probe tip 2 that advances in the X direction first contacts the upper edge 8 of the cut-down wall surface 10.
A change in the vibration pattern indicates that the contact between the probe tip 2 and the sample surface 1 is increasing,
Move upward while in contact with the edge 8. Thus,
The actual shape of the undercut wall 10 is not reflected in the movement of the probe tip 2 used as a measurement of the surface 10.

Furthermore, in this conventional method, if the probe 2 cannot be raised fast enough to cross the wall surface while continuing the movement in the scanning direction, the probe tip 2 and the upwardly extending wall surface surface cannot be moved. There is also the possibility that a "crash" will occur. Such a situation is expected to damage both the probe 2 and the sample surface 1.

Therefore, when considering the conventional method of FIG. 1, the probe tip can follow the sample surface even when the inclination angle of the wall fluctuates, and the crash between the probe tip and the upwardly extending surface can be achieved. There is a need for a way to prevent this.

In view of the limitations of the conventional method of FIG. 1, several methods described in the patent literature have been developed for measuring wall profiles using a scanning probe microscope.

For example, US Patent No. 5,186, Nysssonen.
No. 041 describes a measurement system for measuring the depth and width of a trench in a sample to be examined with a probe that moves relative to the sample. The system detects the proximity of the probe to the surface forming the bottom of the trench and the sidewall of the trench. The system adjusts the relative position of the probe and sample vertically and horizontally relative to the output signal.

FIG. 2 is a side view of a probe 12 described in US Pat. No. 5,196,041 and having three protrusions for detecting the depth and width of a trench. The first protrusion 14 extends downward and detects the bottom of the trench. The lateral protrusion 16 extends in the opposite direction from the probe in the width direction of the trench, and detects the side wall of the trench. The device interlocked with the probe 12 includes means for vibrating the probe in the Z direction or the X direction,
And an interferometric apparatus for measuring vibrations in the Z and X directions.

FIG. 3 is a cross-sectional view showing the sample surface 18 including the trench 20 with dashed lines 22 showing the movement of the probe of FIG. 2 used to measure the trench. After measuring the height of the surface on either side of the trench at point 24, the probe tip 12 is driven downward while oscillating in the Z direction to measure the depth of the trench at a center point 26. Next, the probe 12 is moved upward by an incremental distance and alternately driven against each of the opposing side walls 28 while oscillating the probe in the X direction while taking a measurement at point 30.

No. 5,321,977 to Clabes et al. Describes the use of an integrated tip strain sensor in combination with a uniaxial atomic force microscope (AFM) for determining surface profiles in three dimensions. I have. The cantilever beam carries an integrated tip stem with a piezoelectric film strain sensor deposited thereon. A piezoelectric jacket with four overlapping elements is deposited on the tip stem. Piezoelectric sensors work in a plane perpendicular to the plane of the probe in an atomic force microscope. That is, when the tip contacts the sidewall surface, the tip is altered and a proportional electrical output is generated accordingly. This tip strain sensor coupled to the tip of a standard single axis AFM allows for three-dimensional measurements while avoiding catastrophic tip crashes.

US Pat. Nos. 5,283,442 and 5,347,854 to Martin et al. Describe a method and apparatus for profiling surfaces such as trenches and line sidewalls using a scanning force microscope. . This method provides improved measurement accuracy by controlling the position of the tip in response to the local slope of the surface measured in real time.

FIG. 4 illustrates the use of protrusions 34, 36 in the lower corner of probe tip 30 to establish a profile of sample surface 38 including trench 40, as described in US Pat. No. 5,283,442. FIG. 5 shows a flat probe tip 30 extending downward from a bolster 32.

FIG. 5 is a graph showing the Z-direction vibration of the probe tip 30 of FIG. 4 detected by the laser interferometer. The actual higher frequency vibration is shown by curve 42. The envelope 44 of the curve 42 represents the amplitude of the tip vibration, which is the probe tip 30 and the sample surface 38.
Fluctuates when is engaged. As the oscillating tip 30 approaches the profiling surface, the force gradient between the tip and the surface increases and the amplitude of the tip oscillation decreases. If the sample surface under measurement is flat and at the same height in the X direction, the envelope 44 does not change. When the surface is inclined in the X direction, vibration at the dithering frequency occurs in this direction, so that the amplitude envelope 44
Varies with the dithering frequency. The magnitude of the variation of the envelope 44 with the dithering frequency is indicative of the local slope of the sample surface.

FIG. 6 shows a US Pat. No. 5,528,528 for following the shape of a curved surface 46 with the protrusion 34 of the probe tip 30.
FIG. 3 is a diagram illustrating a series of operations performed by the device of No. 3442. At the initial point 47, the surface normal is indicated by an arrow 48 that forms an angle α with the Z axis. The system then proceeds with an arrow 50 perpendicular to the surface normal indicated by arrow 48.
The tip of the probe is moved by an incremental distance ending at point 52 along the scan direction indicated by. At this point, since the probe tip is far from the surface 46, the probe tip 3
The vibration in the Z direction of 0 is larger than a predetermined control value. Therefore, the probe tip 30 is positioned at the point 5 adjacent the surface 46.
Move toward 4. This movement occurs along an angle θ determined with the aid of a computer system to reduce the possibility of the tip and sample surface contacting at the corner of the trench, especially when the next measurement point is recorded. here,
Note that the tip projection 34 is generally only 20-50 Å away from the surface being profiled. The process is repeated by moving the probe tip along surface 46 using the tip-to-surface engagement and tilt measurements determined from the curves of FIG.

In the device of US Pat. No. 5,283,442,
The level of vibration in the Z-axis and X-axis (scan direction) directions of the probe tip is separated from the single signal shown in FIG. 5 using the difference between the excitation frequency and the dithering frequency, but US Pat. No. 5,347,854. The device includes a photodetector that separately detects movement in the Z and X directions and provides separate signals indicative of vibrations in these two directions. The ratio of these separate signals is used to determine the local slope of the sample surface being measured.

US Pat. Nos. 5,186,041 and 53
One problem with the apparatus and method of US Pat.
This results from the fact that the lateral scanning movement takes place in only one scanning direction. Laterally extending protrusions used to sense the side walls also extend in this direction or the opposite. Therefore, if the probe collides with a side wall extending upward or downward in a plane that is not substantially perpendicular to the scanning direction, the speed at which the probe moves upward or downward in contact with the side wall is: It does not give an accurate picture of the slope of its side walls. In particular, a problem occurs when the side wall basically extends perpendicular to the scanning direction. A probe tip shaped to provide the same type of indication that the side wall and scan direction are in contact with the side wall even when at an angle, as well as uniform contact regardless of this angle, and There is a need for a method that causes relative movement between the probe and sample to move straight up or down along the sidewall after contacting the sidewall.

US Pat. Nos. 5,107,114 and 55
No. 89686 describes an apparatus in which the probe tip of a scanning probe microscope moves a short distance in all three directions.

In particular, Nishioka et al., US Pat.
No. 14 describes a fine scanning mechanism for an atomic force microscope including a cylindrical piezoelectric element capable of three-dimensional displacement. The free end of the cylindrical piezoelectric element can be displaced in the X, Y, and Z directions. The first probe is mounted on the free end of the cylindrical piezoelectric element. The bimorph piezoelectric element is also mounted on the free end of the cylindrical piezoelectric element and is itself displaceable in the Z direction in one dimension. The cantilever is mounted to extend from the free end of the bimorph piezo element such that the free end of the cantilever is located beneath the first probe and adjacent. A second probe extends downward from the free end of the cantilever and is mounted to engage the sample surface. The stationary sample tray is arranged to face the second probe. Using this mechanism, the first and second probes are synchronously scanned across the sample surface laterally across the sample according to a predetermined pattern.

Using a probe geometry suitable for sensing anomalies close to a wall in the sample surface;
There is a need to apply dithering signals to various sections of the cylindrical piezoelectric element such that circular movement of the first and second probes is achieved. further,
What is needed is a way to move the probe laterally in a direction perpendicular to such walls as the probe moves up or down along the plane. Due to such a movement, the second probe causes a side wall of anodic
The exercise will be particularly effective in determining the presence of malies) and in determining the shape of such sidewalls. In addition, there is a need for a means for detecting dithering vibrations in the scanning direction so as to detect and trace the sudden rise and fall of the wall surface in the sample surface.

Ohara, US Pat. No. 5,589,686, discloses the location of a sensing probe for use with an alternately scanning tunneling microscope, an atomic force microscope, or a capacitive or magnetic force field sensing system. A method and apparatus for generating real-time continuous positioning data on the nanometer scale is described. This system is used to measure the distance and position of a probe from a periodically undulating surface, such as an atomic surface or other grating that moves relative to the probe. Between the probe and the surface there is a sensing field due to the rapid oscillation of the probe under the control of a sine voltage,
The phase and amplitude of the output sine voltage generated by the current in the sensing field are compared to provide a position signal indicating the direction and distance of the nearest atom or surface relief vertex. If desired, the position signal is fed back to control the relative movement of the probe and the surface.

Thus, the method of US Pat. No. 5,589,686 can only operate to determine the characteristics of a periodically undulating test sample. Another type of test sample does not generate the sinusoidal output signal required by this method from the sensed field. There is a need for a method that can determine the characteristics of abnormal wall surfaces when these wall surfaces form unknown angles and are separated from each other by an unknown aperiodic distance.

[0025]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus and method for performing a contour scan using a scanning probe microscope to overcome the above-mentioned problems.

[0026]

According to a first aspect of the present invention, there is provided a method for measuring topographical features of sidewalls within a sample surface. The method includes causing relative movement between a sample surface and a probe tip mounted on a cantilever beam that vibrates at an excitation frequency in a first direction, the relative movement comprising a first predetermined motion. A probe tip is moved along a contour path extending along the intersection of the contour surface and the side wall, wherein the engagement of the probe and the side wall along the contour path oscillates at an excitation frequency in a first direction. It is kept within a range corresponding to the variation of the measured amplitude of the tip.

This relative movement moves the probe tip along a contour path in a first plurality of straight line segments, each of which measures the vibration of the probe tip. If it is determined that the detected amplitude is out of the predetermined allowable vibration amplitude range, the process ends. The relative movement also causes the probe tip to move along a contour path in a second plurality of straight line segments, each of the second plurality of straight line segments being the first plurality of straight line segments. Extending between adjacent straight line segments, each of the first plurality of straight line segments extends along a local tangent of a line extending along the contour path.

The probe tip further includes a first signal that dithers the probe in a second direction along the plane, thereby forming a circular pattern at a dither frequency along a plane perpendicular to the first direction. Draw and dither. A phase angle is measured between the signal that modulates the measured vibration amplitude at the dither frequency and the first signal.

Determine the angle of the local normal normal to the sidewall. The local normal passes through the center of the dithering motion,
The angle of the local normal extending along a plane perpendicular to the first direction is determined as a function of the phase angle.

[0030]

FIG. 7 is a partial schematic side view of a scanning force microscope 110 constructed in accordance with the present invention. Apparatus 1
10 includes a piezoelectric actuator 112 extending between a clamped end 114 and a free end 116. Free end 11
6 responds to a voltage signal from the X-axis driver 118,
It moves in the axial direction in the Y-axis direction of arrow 120 in response to a voltage signal from the Y-axis driver 122, and in the Z-axis direction of arrow 124 in response to a voltage signal from the Z-axis driver 126.
Free end 116 also oscillates in the Z-axis direction in response to an oscillating voltage signal from excitation driver 128. X-axis driver 1
18, Y-axis driver 122, and Z-axis driver 126
Is sent to an appropriate electrode of the piezoelectric actuator 112 via a signal distribution circuit 129.

In the method described below with reference to FIGS. 8 and 9, the x-axis driver 118 and the y-axis driver 122
Is used to drive a probe tip 130 for surface sensing attached to the free end 116 of the piezoelectric actuator 112 by a cantilever 132 and a mounting plate 133 in a circular dithering pattern. This circular motion is obtained by an oscillation output signal of the oscillator 133a applied as an input to the X-axis driver 118 via the amplifier 133b. The output of the oscillator 133a is input as Y input through a delay circuit 133c and an amplifier 133d.
It is also applied to the axis driver 122. Delay circuit 133c
Derives a Y-axis drive signal having an appropriate phase angle relationship with the X-axis drive signal, thereby establishing circular motion of the probe.

During operation of the system, the probe tip 130
Is also oscillated in the Z-axis direction of the arrow 124 in a state of being engaged with the surface 134 of the sample 135 by application of the oscillation signal from the oscillator 136 to the excitation driver 128. The vibration of the probe tip 130 occurs at the drive frequency of the oscillator 136, which is preferably close to, but somewhat higher than, the resonant frequency of the cantilever 132. The vibration of the probe tip 130 in the Z-axis direction of the arrow 124 is measured by a laser detector 138 that uses optical means to generate a motion signal indicative of the motion of the probe tip 130. This optical means exhibits a change in optical path length that extends downward toward a reflective surface 139 that moves with the probe tip 130, using, for example, heterodyne interferometry.
Alternatively, while illuminating a particular photodetector, the position at which the obliquely incident laser beam is reflected by the reflective surface 139 and impinges on the array of photodetectors in the laser detector 138 is used. Determine the position of. In either case, the output signal from the laser detector 138 will be reflected by a reflective surface 139 that moves with the probe tip 130.
It is based on the motion component of the arrow 124 in the Z-axis direction. The output of the laser detector 138 is driven through a wide-pass filter 140 that passes output signals that include frequencies within the range of the drive signal, but does not pass frequencies significantly below this range. The output signal from the wide-pass filter 140 is applied to the laser detector 138.
From the excitation driver 128 to generate an output signal that reflects the average vibration amplitude of the tip motion signal at the excitation frequency.

According to a preferred embodiment of the present invention, the scanning movement in the X and Y directions applied to sample 135 is used to maintain the level of engagement between probe tip 130 and sample surface 134 within a predetermined range. You. This engagement level is indicated by the average amplitude of the vibration at the excitation frequency. Therefore, the output of demodulator 141 is provided as an input to comparison circuit 142. This is used to determine whether the average amplitude of the oscillations within the frequency range of the excitation oscillator 136 is within, above, or below this predetermined range. The output of this comparison circuit driven via the analog to digital converter 143 is
It is applied to the computer system 144 as a COMPARISON SIGNAL input. Computer system 144 also generates an output signal that is provided as an input to comparison circuit 142 via digital-to-analog converter 144a. This output signal provides the set value level and the allowable deviation level to the comparison circuit 142, whereby the output signal from the demodulator 141 is smaller than the sum of the set value level and the allowable deviation level, If greater than the difference between the deviation levels,
It is determined that it is within the predetermined range. The COMPARISON SIGNAL has three levels, a first level indicates that the output level of the demodulator 141 is lower than a predetermined range, a second level indicates that the level is within a predetermined range, and a third level.
Indicates that the level is higher than a predetermined range.

Computer system 144 includes memory 145, which is a random access memory circuit, as well as a hard disk that stores a program to be executed and data resulting from the execution of the program. In some cases. Display device 14
6 makes this data visible. The program can be loaded via a machine-readable medium 147 such as a magnetic disk.

During the contour scanning process, the computer system 1
The program executed in 44 is the X of sample 135
And a SCANNING MOTION DATA signal to control movement in the Y direction. That is, the SCANNING MOTION DATA signal includes digitally encoded data that independently indicates movement in the X and Y directions. This signal is applied as an input to a digital-to-analog converter 147, which provides separate X and Y analog signals to drive a scan motion driver 148, which drives a scan motion actuator 149. Drive.

The computer system 144 is a Z-AXIS DRIVE D
It also generates an ATA signal, which is used to drive the Z-axis driver 126 via an analog-to-digital converter 149a. This change in signal level is used, for example, to move the probe 130 in the Z direction between successive contour scans, and
It can also be used in conjunction with the relative movement between and the flat portion of the sample surface and used to find upright sidewalls.

The output of laser detector 138 also passes the portion of this output signal having a frequency within the range of the circular dither signal generated as the output of oscillator 133a, but the output signal of oscillator 136 Is also provided as an input to a low pass filter 150 that rejects portions having a frequency within the range of the excitation oscillations generated using.
The output of the low pass filter is provided as input to phase angle demodulator 151. The output of the oscillator 133a is also supplied to the demodulator 151.
Which is provided as an input to
An output is provided that indicates the phase angle between the output of Fifty and the output of oscillator 133a. The output of the phase angle demodulator 151 is supplied to the computer system 14 via an analog / digital converter 152.
4 is provided as input. This phase angle relationship is used in the manner described in connection with FIG. 8 to determine the angular relationship between the probe 130 and the side wall 153 of the adjacent sample.

FIG. 8 is a partially schematic isometric view showing the piezoelectric actuator 112 and a driving circuit associated therewith.
The piezoelectric actuator 112 includes a hollow cylinder 155 composed of a piezoelectric material, with electrodes extending along various surfaces to apply a voltage to deflect the cylinder 155 in various ways. A ground potential is applied to the inner electrode 156 extending along the inner surface of the hollow cylinder 155.

In general, when a positive voltage is applied to an electrode that extends partially around the outer surface of hollow cylinder 155, the portion of the cylinder adjacent to that electrode is compressed, and when a non-voltage is applied to such an electrode, the cylinder This part of expands. In the present application, the probe 130 is moved in either the X or Y scan direction without causing the associated movement in the Z direction.
It is particularly desirable to be able to exercise. Therefore, the movement in the X or Y direction is
12 is established by applying a predetermined voltage of opposite polarity to both sides. To obtain different polarities of the X-axis drive signal,
The output of the X-axis driver 118 is supplied via a code converter 158, and the output of the amplifier 158 is
0 is applied as an input. The output of the amplifier 160 is applied to the -X electrode 162. X-axis driver 118
Is output from the -X electrode 162 via a summing amplifier 166.
Is also supplied to the + X electrode 164 located exactly opposite to the above.

Similarly, in order to obtain Y-axis drive signals of different polarities, the output of the Y-axis driver 122 is supplied via a code converter 168, and the output of this amplifier 168 is added to the summing amplifier 1
70 is applied as an input. The output of the amplifier 170 is applied to the -Y electrode 172. Y axis driver 122
Is output through a summing amplifier 176 to a −Y electrode 172.
Is supplied also to the + Y electrode 174 located exactly opposite to the above.

When a positive voltage is applied as the output of the X-axis driver 118, the probe 130 is deflected in the X direction of arrow 180, and the distance of this deflection is basically proportional to the positive voltage. On the other hand, the negative voltage is
8, the probe 130
Is deflected in the direction opposite to the X direction of arrow 180, and the distance of this deflection is essentially proportional to its negative voltage. Similarly,
When a positive voltage is provided as the output of the Y-axis driver 122, the probe 130 deflects in the Y direction of arrow 120, and the distance of this deflection is basically proportional to the positive voltage.
When a negative voltage is provided as the output of the Y-axis driver 122, the probe 130 deflects in a direction opposite to the Y direction of arrow 120, and the distance of this deflection is essentially proportional to the negative voltage.

All X electrodes and Y electrodes 162, 16
When positive voltages are simultaneously applied to 4, 172, 174, the hollow cylinder 155 of piezoelectric material is compressed in the axial direction, and the probe 130 rises in the Z direction indicated by the arrow 124. All X and Y electrodes 162, 164,
When negative voltages are simultaneously applied to 172 and 174,
The hollow cylinder 155 extends in the axial direction and the probe 130
Falls in the direction opposite to the Z direction of arrow 124. Therefore, the output signal from the Z-axis driver 126 is supplied to all the electrodes 162, 164, 172, 174 via the summing amplifiers 160, 166, 170, 176.
Is applied to

An oscillating voltage drive signal from the excitation driver circuit 128 is also applied to the excitation electrode 184 that extends annularly around a portion of the hollow cylinder 155, causing the probe 130 to vibrate in the Z direction indicated by arrow 124. Excitation driver circuit 12
Excitation voltage signal V _E applied from 8 is given by Equation 1 below. Conventional methods of optimizing the sensitivity of a scanning probe microscope to variations in the sample surface during a measurement include:
The value of the parameter ω is selected such that the forced oscillation of the cantilever occurs near its resonant frequency.

(Equation 1) V _E = Z ₀ sin (ωt)

According to the present invention, probe 130 can be driven by signals applied from X-axis driver 122 and Y-axis driver 118 to draw a circular dithering pattern as shown by dashed line 188. preferable. The X-axis drive voltage V _X is given by the following equation (2).
The Y-axis drive voltage V _Y is given by the following equation (3). To facilitate the detection of effects caused by dithering motion, the value of parameter Ω is such that the dithering motion of probe 130 is much lower than the excitation frequency applied to actuator 112 via excitation driver 128. Selected to happen.

## EQU2 ## V _X = X ₀ sinΩt

(Equation 3)

FIG. 8 also shows an upwardly sloping wall surface 153 on the sample surface 134 to which the probe 130 normally abuts during inspection of the sample surface, to illustrate the operation of the apparatus.

FIG. 9 shows simultaneous application through the device of the present invention.
And a graph showing the various signals measured,
V_E, V_X, And V_YThe drive signal described above as
Probe 130 provided as an output of detector 138
Probe position signal V indicating the position of _PIs shown.

Referring to FIGS. 7 to 9, the vibration of the tip of the cantilever 132 close to the probe 130 is measured when inspecting a sample by the conventional operation method of the scanning probe microscope. As the probe 130 moves across the flat portion 154 of the sample surface, the tip of the cantilever oscillates at a constant amplitude and at the excitation frequency from the excitation driver circuit 128. However, as the probe 130 approaches the side wall of the sample surface, the oscillation at the excitation frequency from the excitation driver circuit 128 is attenuated, and the amplitude of the oscillation is reduced accordingly, thereby allowing the cantilever at the excitation frequency. the vibration of the tip of the is to be modulated by dithering frequency of the circular motion of the probe, the distance between the sidewall adjacent the probe by a circular dithering motion of the probe is changed periodically, the driving signal V _{X Alternatively} , either V _Y can be used with the signal generated by measuring the vibration of the tip of the cantilever to determine the orientation of the sidewall of the sample surface adjacent to the probe 130. By this process, the output signal V from the laser detector 138
_P will take the shape shown in FIG.

In the example of FIG. 8, the side wall 153 extending upward
Is located at the center 192 of the side wall 153 and the dithering path 188.
And a line 190 extending between
Is the dithering path 18 at an angle 軸 with respect to the X axis.
It extends in an orientation that intersects 8. When the height changes upward along with the start of the side wall 153, the attenuation of the excitation vibration applied to the probe 130 by the excitation driver circuit 128 increases, so that when the dithering probe 130 is rotated by an angle か ら from the X axis. , The amplitude of the excitation vibration is minimized. Therefore, when the dithering probe rotates from the X axis by the angle θ, the amplitude of the excitation vibration becomes maximum. Here, θ is given by Equation 4 below. Movement in the X direction of the probe in the dithering process, since a maximum along the X axis, theta is also a phase angle of the X-direction driving signal V _X and the probe position signal V _P of FIG.

[Equation 4] θ = Ψ−Π

[0049] Thus, using the probe position signal V _P, the direction in which the probe 130 engaged with the side wall 153 extends to be driven in a circular dithering pattern 188 is easily determined. For this purpose, the phase angle demodulator 1
51 provides an output signal indicative of the phase angle θ. This output signal is used by the analog-to-digital converter 15 for use in programs executed in the computer system 144.
It is digitally encoded within 2. This program is
The direction in which the tangent of the upright side wall impacted by the dithering probe 130 extends along a line extending perpendicular to the line of phase angle θ. That is, the angle between the direction of the X axis and the tangent extending along the side wall 153 is
It is given by Equation 5 below. Further, the X axis and the side wall 15
The angle formed by the normal extending through the center of the dithering pattern 188 that is perpendicular to
Determined by the program executed in 44. X
The angle between the axis and the normal 194 extending away from the side wall 153 is given by the phase angle θ, and the X axis and the side wall 153
Is given by the following equation (6).

(Equation 5)

数 = θ + Π

FIG. 10 shows a probe 13 for tracking a contour along an upwardly extending sidewall 200 according to the present invention.
FIG. 9 is a schematic plan view showing a path 198 along which the relative movement between 0 and the sample surface 134 takes place. While the circular dithering probe motion described above in connection with FIG. 8 continues during this tracking process, the motion of the probe due to dithering is much smaller than the tracking motion of path 198.

FIG. 11 illustrates the probe 13 during the process of finding the upright sidewall 200 and along the sidewall.
8 is a flowchart of a program executed in the computer system 144 of FIG. 7 to determine relative motion between the probe 130 and the sample 135 dithering during a subsequent process of tracking at zero.

Referring to FIGS. 7, 10 and 11, the dashed lines 202 and 204 indicate that the average amplitude of the probe motion at the excitation frequency of the excitation driver 128 can be obtained from the computer system 144 by the digital-to-analog converter 144a. The limit of the area where the comparison circuit 142 determines whether the value is within a predetermined range defined by the set value signal and the allowable deviation signal supplied through the comparator 142 is shown.

In the example apparatus of FIG. 7, the scanning motion shown in FIG. 10 occurs when the sample 135 is moved by the scanning motion actuator 149 in the X and / or Y directions. Proximal end plate 11 of piezoelectric actuator 112
4 by using a scanning motion actuator mounted on or by applying an additional scanning motion signal to the X-axis driver 118 and the Y-axis driver 122, while maintaining the sample 135 stationary. It is to be understood that can also be realized.

In each case, the relative scanning movement between the probe 130 and the sample 135 occurs at the start step 205 of the program of FIG. Next, step 208
Then, the probe 130 is scanned along the search line segment 210 of the path 198 by the relative motion. The probe slides along a relatively flat portion of the sample surface. Z-axis driver 1
The movement of the probe in the Z direction with 26 can be used to compensate for the gradually changing sample surface height. Since the sample surface is relatively flat, there is no modulation at the dithering frequency of the excitation driver 128 and the average amplitude of the probe tip vibration is relatively constant. In step 210, which is performed periodically, the comparison circuit 1
The output of 42 is checked to determine if the amplitude of the tip vibration at the excitation frequency of oscillator 136 is within a predetermined range. If it is, the program returns to step 208 and continues scanning along search line segment 210. If it is determined in step 210 that the amplitude is not within this range, it is determined in step 212 whether the amplitude is smaller than a predetermined range. If the amplitude is not less than that range, the sample surface should be sloping downward, and therefore, periodically checking the output of the comparison circuit 142 at step 210 until the amplitude returns within the predetermined range. In step 214, the Z-axis driver 12
6 moves the probe gradually downward. When the amplitude is determined to be within the predetermined range in this manner, the program returns to step 208 and restarts scanning along the search pattern.

On the other hand, if step 212 indicates that the amplitude is less than the range, the change in amplitude is due to the upward slope of the sample surface (in contrast to this). Compensates) or a collision with the side wall at a point 215 in FIG. 10 or the like. When colliding to the side wall, the amplitude of the function is modulated by the number of excitation vibration, the shape indicated by V _P in FIG. Therefore, at step 216, the output of the phase demodulator 151 is examined to see if this type of modulation is taking place. If such modulation has not occurred, the probe is moved upward in step 218 to compensate for the gentle upward slope of the sample surface. If this modulation has been performed, step 22
At 0, the output of the phase demodulator 151 is used to establish tangents and normals of adjacent sidewalls in the manner described above in connection with FIG. Then, at step 222, the process of moving along the tangent line 223 established at step 220 to scan the contour is started.

It is clear that establishing a tangent in this way offers the possibility of movement in two opposite directions. One of these directions is processor 144
The process of scanning the contours is selected by a program executed in the
l) direction.

During the continuation of the scanning process, the processor 14
The program executed in step 4 periodically checks at step 224 to determine whether the scan termination condition is satisfied. This condition may be reached, for example, by scanning to a predetermined edge location, or by scanning around a separate upright feature, such as a pillar, to return to the point where scanning of the contour started. When the end of the scan is reached, at step 226, the scanning process along the particular contour line ends. When the scanning end condition is not reached,
At step 228, a determination is made whether the amplitude is within a predetermined range. If so, the program returns to step 222 and continues scanning tangent 223. On the other hand, if it is determined that the amplitude is not within the predetermined range, such as at point 230, the program proceeds to step 232, where the output of phase demodulator 151 is again used to relate to FIGS. New tangents and normals are then determined in the manner described above.

Next, in step 234, it is determined whether the average amplitude of the vibration measured by the demodulator 141 is larger or smaller than a predetermined range. If the average amplitude of this vibration is less than a predetermined range, such as at point 230, the relative movement between sample 135 and probe tip 130 establishes step 236 and moves probe 130 away from sidewall 200 along new normal 238. Scan outward. Next, the program returns to step 222, where a new scanning motion 24 along the tangent determined in step 232 is performed.
Start 0. On the other hand, if the average amplitude of the vibration at the point 242 or the like is larger than the amplitude in the predetermined range, step 234 is executed.
If so, the program proceeds to step 244 and causes the probe 130 to scan inward along the new normal 246 toward the sidewall 200. The program then returns to step 222 to start a new scanning movement 248 along the new tangent.

As shown in the example of FIG. 10, the movement of the probe along each normal, such as lines 238 and 246, terminates when the probe 130 has completely crossed the predetermined range between lines 202 and 204. . This method limits the benefits of performing long tangent scans between normals when sidewall 200 continues to bend in the same direction. Alternatively, the movement along each normal may be terminated by also examining the average amplitude at a more central point within a predetermined range.

According to a preferred embodiment of the present invention, both the excitation oscillation and the circular dithering motion are maintained during the scanning process. Alternatively, the circular dithering motion
It can also be provided only when the tangent and normal directions need to be determined.

FIG. 12 illustrates the present invention used to inspect a portion of the side wall 250, showing several flat surfaces perpendicular to the Z direction in which the probe 130 is driven by the excitation vibration. By contour surface, contour line 2
52 have been established. The scan limit at each end of the contour 252 is predetermined, and the probe 130 moves to the next contour surface in the Z direction at each end of the scan line.

FIG. 13 is a diagram illustrating the present invention used to inspect a round upright structure 254. The scan limit at the end of contour 256 is established at the point where the line passes through its starting point, and again, probe 130 moves to the next contour surface.

Although the invention has been described in some detail as being used to determine the topographical features of upright walls, the inspection of the downwardly extending walls of the trenches can also be performed in a manner similar to that described above. It should be understood that the present invention can be used by initiating the probe motion from or by moving the probe from the overlying surface to the edge of the trench. In the subroutine example of FIG. 11, the dithering in step 216 is performed only when it is determined in step 212 that the average amplitude of the vibration of the probe at the excitation frequency is smaller than a predetermined range (indicating that the upright wall surface has started). It was determined whether there was modulation at the ring frequency, but alternatively, modulation was determined after determining whether the amplitude of the probe oscillation was greater than a predetermined range of amplitudes (indicating the beginning of the trench). You can also ask for instructions.

FIG. 14 is a diagram illustrating the present invention similarly used to inspect the sidewall surface of a downwardly extending hole 258 that progresses between several contour planes forming a contour line 260.

In the above example, the contours forming the path of the probe are formed along the intersection of the sample surface and one or more contour surfaces, each contour surface being in the Z direction where the excitation oscillation of the probe occurs. Extend in the XY plane perpendicular to

FIG. 15 illustrates several contour planes 264 and a single plane perpendicular to the Z direction that can be used in the context of the present invention as contour planes to determine the movement of the probe and establish contours. It is a figure which shows the upright cylinder which cross | intersects one slope 266.

FIG. 16 shows an upright side wall 268 having a contour 270 formed by the probe tip moving along several intersecting diagonal contour surfaces.

Although the present invention has been shown and described in detail in connection with the preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. I want to be.

In summary, the following items are disclosed regarding the configuration of the present invention.

(1) A method for measuring topographical features of sidewalls within a sample surface, the method comprising the steps of: between the sample surface and a probe tip attached to a cantilever beam vibrating in a first direction at an excitation frequency. Causing relative movement of the probe tip along a contour path extending along an intersection of a first predetermined contour surface and the sidewall. A method wherein the engagement of the probe and the sidewall along the contour path is maintained within a range responsive to a variation in a measured amplitude of vibration of the probe tip in the first direction at the excitation frequency. . (2) The relative movement is to move the probe tip in a first plurality of straight line segments along the contour path, and each straight line segment of the first plurality of straight line segments is The method according to (1), wherein the probe is terminated when it is determined that the measured amplitude of the vibration of the probe tip is out of a predetermined allowable vibration amplitude range. (3) the relative movement further moves the probe tip along a second one of the second plurality of straight line segments along the contour path; Extending between adjacent straight lines of the first plurality of straight line segments, each straight line segment of the first plurality of straight line segments extending along a local tangent of a line extending along the contour path ,
The method according to the above (2). (4) The probe tip is circular at a dither frequency along a plane perpendicular to the first direction by a first signal that dithers the probe in a second direction along the plane. Dithering to draw a pattern; measuring a phase angle between the signal that modulates the measured amplitude of the vibration at the dithering frequency and the first signal; Determining the angle of a vertical local normal, the local normal extending along the plane perpendicular to the first direction through the center of the dithering motion. The method according to (1), wherein the angle of the local normal is determined as a function of the phase angle. (5) The first signal is a sine function, and an angle between the local normal and a direction in which the probe tip is moved by the first signal is determined by the sum of the phase angle and π radian. , The method according to (4). (6) The method according to (4), wherein the excitation frequency is close to the natural frequency of the cantilever, and the dithering frequency is significantly lower than the excitation frequency. (7) The relative movement is to move the probe tip in a first plurality of straight line segments along the contour path, and each straight line segment of the first plurality of straight line segments is Extending perpendicular to the local normal determined near the starting point of the straight line segment, wherein each straight line segment of the first plurality of straight line segments is the measured amplitude of vibration of the probe tip. Is terminated when it is determined that is outside the predetermined allowable vibration amplitude range. (8) The relative movement further moves the probe tip in a second plurality of straight line segments along the contour path, and each straight line segment of the second plurality of straight line segments is The straight line segments extending to the adjacent straight line segments of the first plurality of straight line segments, and each straight line segment of the second plurality of straight line segments is the straight line segment of the second plurality of straight line segments. The method of (7) above, wherein the method extends along the local normal determined in the vicinity. (9) The method according to the above (1), wherein the first predetermined contour surface is a flat surface perpendicular to the first direction. (10) The method further comprising causing relative movement between the sample surface and a probe tip attached to a cantilever beam that vibrates in a first direction at an excitation frequency, wherein the relative movement is A probe tip is moved along a plurality of contour paths extending along intersection lines between a plurality of predetermined contour surfaces and the side walls, and the probe tip and the side walls are respectively moved along the plurality of contour paths. The method of claim 1, wherein the engagement along is maintained within a range responsive to a variation in a measured amplitude of vibration of the probe tip in the first direction at the excitation frequency. (11) A method for determining the direction of a tangent along a side wall of a sample surface in a plane extending perpendicular to a first direction, the method comprising: (a) in a first direction at an excitation frequency with the sample surface; Causing a relative movement between the probe tip mounted on the oscillating cantilever and the probe tip to engage the side wall while simultaneously measuring the amplitude of the probe tip vibration in the first direction. And
(B) determining whether engagement with the side wall is determined by a change in the vibration amplitude; and (b) moving the probe tip in the first direction at the excitation frequency while keeping the probe tip vibrating. In the state of being engaged with the side wall, the first
Dithering in a circular pattern in a dithering plane extending perpendicular to the direction of A method comprising: measuring a phase angle between modulation at a frequency; and (c) determining a direction of the tangent as a function of the phase angle. (12) The probe tip is the second probe according to a sine function.
(11), wherein the angle formed by the local normal and the direction in which the probe tip moves by the first signal is determined by the sum of the phase angle and π radian.
The method described in. (13) The method according to (10), wherein the excitation frequency is close to the natural frequency of the cantilever, and the dithering frequency is significantly lower than the excitation frequency. (14) A method for measuring topographical features of sidewalls within a sample surface, the method comprising: (a) a normal extending perpendicular to the side surface through a probe tip in a plane perpendicular to a first direction. And (b) moving between the sample surface and the probe tip such that the probe tip moves along a first predetermined contour surface in a direction perpendicular to the normal. Causing relative motion;
(C) determining whether the probe is within a predetermined engagement range with the side wall, is closer to the side wall than the predetermined engagement range, or is far from the side wall than the predetermined engagement range. Determining; and (d) when it is determined that the probe tip is within the predetermined engagement range with the side wall, returning to step (b) and continuing between the sample surface and the probe tip. Causing relative movement; and (e) when the probe is determined to be closer to the side wall than the predetermined engagement range, the probe tip in a plane perpendicular to the first direction. Determine the direction of a new normal that extends perpendicular to the sidewalls through, and replace the direction of the normal with the direction of the new normal, so that the probe tip moves along the new normal. Away from the side wall Causing relative movement between said probe tip and moving way the sample surface as,
Returning to step (b); and (f) when it is determined that the probe tip is farther from the side wall than the predetermined engagement range, the probe is positioned in a plane perpendicular to the first direction. Determining the direction of a new normal extending through the tip and perpendicular to the side wall, replacing the direction of the normal with the direction of the new normal, and allowing the probe tip to follow the new normal; Causing relative movement between the sample surface and the probe tip to move toward the sidewall and returning to step (b). (15) The probe tip is mounted on a cantilever beam that vibrates at the excitation frequency in the first direction, and the average amplitude of vibration of the probe tip at the excitation frequency is measured, and step (c). When it is determined that the average amplitude of the vibration is within the amplitude value allowable range, it is determined that the probe tip is within the predetermined engagement range, and the average amplitude of the vibration is determined to be within the amplitude value allowable range. When determined to be less than or equal to, it is determined that the probe tip is closer to the side wall than the predetermined engagement range, it was determined that the average amplitude of the vibration is more than the amplitude value allowable range sometimes,
The method according to (14), wherein it is determined that the probe tip is farther from the side wall than the predetermined engagement range. (16) the probe tip is further driven in a circular dither pattern at a dither frequency along the plane perpendicular to the first direction, the probe tip engaging the sidewall. Sometimes, the average amplitude is modulated at the dither frequency, and step (a)
In (e) and (f), the direction of the normal and the direction of the new normal cause the modulation of the average amplitude at the dither frequency and the movement of the probe tip in a second direction. The method according to (15), wherein the method is determined as a function of the phase angle of the dithering signal. (17) The dithering signal for moving the probe tip in the second direction is a sine function, and an angle between the local normal and the second direction is a sum of the phase angle and π radian. The method according to (16), which is determined. (18) The method according to (16), wherein the excitation frequency is close to the natural frequency of the cantilever, and the dithering frequency is significantly lower than the excitation frequency. (19) The predetermined contour surface is a first predetermined contour surface among the plurality of predetermined contour surfaces separated in the first direction, and each of the plurality of contour surfaces is the first contour surface. Steps (a) to (f) are repeated to move the probe tip along a scan line extending along the side wall and each contour surface, a flat surface perpendicular to one direction. The method of claim 14, wherein the probe tip moves in the first direction between adjacent contour surfaces of the plurality of contour surfaces. (20) A method for measuring topographical characteristics of a side wall in a sample surface, comprising: a cantilever, a probe tip attached to an end of the cantilever, and a first cantilever.
An excitation drive for oscillating in the direction of .a. Dithering drive for moving the cantilever to move the probe tip in a circular pattern along a plane perpendicular to the first direction; and a sample surface. A sample holder that holds a sample in a state where the sample holder is exposed to the probe tip, and a relative movement between the cantilever and the sample holder in a plane perpendicular to the first direction. A scan drive to cause, a first demodulator to provide a first signal indicative of an average value of the amplitude of the vibration of the probe tip in the first direction at the excitation frequency; Providing a second signal indicative of the phase angle between the modulation of the war amplitude and a dithering signal that causes a linear motion component to move the probe tip in the circular pattern. A second demodulator that includes a processor,
A program executed in the processor to determine a direction of a normal extending between the center of the circular pattern and the side wall, the normal being in the plane perpendicular to the first direction. A device extending perpendicular to said sidewalls and wherein said direction of said normal is determined as a function of said phase angle. (21) The processor controls the operation of the scan drive to cause relative movement between the sample surface and the probe tip, the relative movement causing the probe tip to move from the first predetermined contour surface to the side wall. Movement along a contour path extending along the intersection of the probe tip and the probe tip in the first direction at the excitation frequency when the probe and the side wall engage along the contour path. The apparatus according to the above (20), wherein the apparatus is held within a range corresponding to the fluctuation of the measured amplitude of the vibration. (22) The relative movement is to move the probe tip in a first plurality of straight line segments along the contour path, and each straight line segment of the first plurality of straight line segments is ,
The apparatus according to (20), wherein the probe is terminated when it is determined that the measured amplitude of the vibration of the probe tip is out of a predetermined allowable vibration amplitude range. (23) The relative movement further moves the probe tip in a second plurality of straight line segments along the contour path, and each straight line segment of the second plurality of straight line segments is Extending to the adjacent straight line segments of the first plurality of straight line segments, each straight line segment of the first straight line segment being connected to the normal line having a direction calculated at the starting point of the straight line segment. The device according to (22), extending perpendicular to the device. (24) The dithering drive moves the probe tip in the second direction according to a sine function, and an angle formed by the local normal and the second direction is a sum of the phase angle and π radian. The apparatus according to (20), wherein the apparatus is determined.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a trench in a sample surface and a conventional probe tip of a scanning probe microscope.

FIG. 2 is a partial side view showing a first type of probe tip for a scanning probe microscope according to the prior art.

3 is a cross-sectional view of a trench in a sample surface according to the prior art, with a dashed line showing a continuous movement for inspecting the trench of the probe tip of FIG. 2;

FIG. 4 is a partial view showing a second type of probe tip for a scanning probe microscope according to the prior art, in a trench in the sample surface.

FIG. 5 is a graph showing an output signal representing the vibration of the probe tip of FIG. 4 according to the prior art.

FIG. 6 shows the incremental movement of the probe of FIG. 4 for following a curved surface according to the prior art.

FIG. 7 is a schematic diagram showing an apparatus constructed according to the present invention.

FIG. 8 is an isometric view showing the probe used in the scanning force microscope of FIG. 7, along with a cantilever and a piezoelectric actuator used to move the probe in three directions orthogonal to each other.

9 is a graph showing various signals applied and measured simultaneously by the apparatus of FIG. 7;

FIG. 10 is a schematic plan view showing the path in the apparatus of FIG. 7 along which relative movement between the probe and the sample for tracking the contour along the sample sidewall occurs.

FIG. 11 is a flowchart of a program executed in the computer system of the apparatus of FIG. 7 to determine the relative movement between the probe and the sample.

FIG. 12 illustrates a pattern used by the apparatus of FIG. 7 to inspect a portion of a sidewall.

FIG. 13 illustrates a pattern used by the apparatus of FIG. 7 to inspect to inspect a round upright structure.

FIG. 14 illustrates a pattern used by the apparatus of FIG. 7 to inspect the sidewalls of a hole.

FIG. 15 shows an upright cylinder intersecting several contour planes that can be used by the device of FIG. 7 to establish a contour.

FIG. 16 shows an upright side wall having a contour formed by the movement of the probe tip of the device of FIG. 7 along several intersecting oblique contour surfaces.

[Explanation of symbols]

 112 piezoelectric actuator 118 X-axis driver 122 Y-axis driver 126 Z-axis driver 128 excitation driver 138 laser detector 140 high-pass filter 141 demodulator 142 comparison circuit 145 computer system 146 display device 150 low-pass filter 151 demodulator

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Don Chen United States 33498 Boca Raton, Florida Buena Ventura Drive 10386 (72) Inventor James Em Hammond United States 33486 Boca Raton, Florida South West Twelves Street 1365 (72) Inventor Kennis G. Roesler United States 33431 Boca Raton, Florida North West Surtees Road 2096

Claims (24)

[Claims] A method for measuring topographical features of sidewalls within a sample surface, said method comprising the steps of: between a sample surface and a probe tip mounted on a cantilever beam oscillating in a first direction at an excitation frequency. Causing a relative movement, wherein the relative movement causes the probe tip to move to a first position.
Movement along a contour path extending along the intersection of the predetermined contour surface and the side wall, wherein the engagement of the probe and the side wall along the contour path is performed at the excitation frequency at the excitation frequency. A method wherein the probe tip is held within a range corresponding to a variation in measured amplitude of vibration of the probe tip in one direction. 2. The method according to claim 1, wherein the relative movement moves the probe tip in a first plurality of straight line segments along the contour path. The minute ends when it is determined that the measured amplitude of the vibration of the probe tip is outside the predetermined allowable vibration amplitude range,
The method of claim 1. 3. The method of claim 2, wherein the relative movement further moves the probe tip along a second one of the second plurality of straight lines along the contour path. Extends to an adjacent straight line segment of the first plurality of straight line segments, and each straight line segment of the first plurality of straight line segments is
3. The method of claim 2, wherein the method extends along a local tangent of a line extending along the contour path. 4. Dithering the probe tip in a second direction along the plane with the probe.
Causing the first signal to dither to draw a circular pattern at a dither frequency along a plane perpendicular to the first direction; and measuring the vibration at the dither frequency. Measuring a phase angle between a signal that modulates amplitude and the first signal; and determining an angle of a local normal perpendicular to the sidewall, wherein the local normal Extends along the plane perpendicular to the first direction through the center of the dithering motion, and the angle of the local normal is determined as a function of the phase angle. The described method. 5. The method according to claim 1, wherein the first signal is a sine function, and an angle between the local normal and a direction in which the probe tip is moved by the first signal is determined by a sum of the phase angle and π radian. 5. The method of claim 4, wherein the method is performed. 6. The method of claim 4, wherein said excitation frequency is close to the natural frequency of said cantilever and said dithering frequency is substantially lower than said excitation frequency. 7. The linear motion according to claim 1, wherein the relative movement moves the probe tip along a first one of the first plurality of straight lines along the contour path. A second segment extending perpendicular to the local normal determined near the starting point of the straight line segment, wherein each straight line segment of the first plurality of straight line segments is the measurement of the vibration of the probe tip. 5. The method according to claim 4, wherein when the determined amplitude is determined to be outside the predetermined allowable vibration amplitude range, the method terminates. 8. The linear motion of claim 2, further comprising moving the probe tip along a second one of the second plurality of straight lines along the contour path. Extends to adjacent straight line segments of the first plurality of straight line segments, and each straight line segment of the second plurality of straight line segments is
The method of claim 7, wherein the method extends along the local normal determined near the straight line segment of the second plurality of straight line segments. 9. The method of claim 1, wherein said first predetermined contour surface is a flat surface perpendicular to said first direction. 10. The method of claim 1, further comprising the step of causing relative movement between the sample surface and a probe tip mounted on a cantilever beam that vibrates in a first direction at an excitation frequency. , The probe tip
Moving along a plurality of contour paths extending along intersections of a plurality of predetermined contour surfaces and the side walls, wherein the probe and the sidewalls engage along respective contour paths within the plurality of contour paths; 2. The method of claim 1, wherein is maintained within a range responsive to a measured amplitude variation of the probe tip vibration in the first direction at the excitation frequency. 11. A method for determining the direction of a tangent along a sidewall of a sample surface in a plane extending perpendicular to a first direction, the method comprising: (a) determining a first direction of the sample surface and an excitation frequency; A relative motion is caused between the probe tip mounted on the cantilever beam that oscillates in the direction and the probe tip engages the side wall, and simultaneously the amplitude of the probe tip vibration in the first direction is measured. (B) determining that engagement with the side wall is determined by a change in the vibration amplitude; and (b) continuing the vibration of the probe tip in the first direction at the excitation frequency. While the probe tip is engaged with the side wall, the probe tip is dithered in a circular pattern in a dithering plane extending perpendicularly to the first direction, and simultaneously in the dithering plane. Measuring the phase angle between the dithering motion in the direction of 2 and the modulation of the amplitude of the vibration of the probe tip at the dithering frequency; and (c) changing the direction of the tangent to the phase angle. Determining as a function of. 12. The probe tip moves in the second direction according to a sine function, and the angle formed by the local normal and the direction in which the probe tip moves by the first signal is the phase angle and π. 12. The method of claim 11, wherein the method is determined by a radian sum. 13. The method of claim 10, wherein said excitation frequency is close to a natural frequency of said cantilever and said dithering frequency is significantly lower than said excitation frequency. 14. A method for measuring topographical features of sidewalls in a sample surface, the method comprising: (a) extending perpendicularly to a side surface through a probe tip in a plane perpendicular to a first direction. Determining a direction of the normal; and (b) moving the probe tip along the first predetermined contour surface in a direction perpendicular to the normal. Causing relative movement between; and (c) the probe is within a predetermined range of engagement with the side wall, closer to the side wall than the predetermined range of engagement, or the predetermined engagement. (D) determining whether the probe tip is within the predetermined engagement range with the side wall, returning to step (b); Sample surface Causing relative movement between the probe tip and the probe tip; and (e) perpendicular to the first direction when it is determined that the probe is closer to the side wall than the predetermined engagement range. Determining the direction of a new normal extending perpendicularly to the side wall through the probe tip in a simple plane, replacing the direction of the normal with the direction of the new normal, and Causing relative movement between the sample surface and the probe tip to move away from the sidewall along a normal line; and (b)
And (f) passing through the probe tip in a plane perpendicular to the first direction when it is determined that the probe tip is farther from the side wall than the predetermined engagement range. Determining the direction of a new normal extending perpendicular to the side wall, replacing the direction of the normal with the direction of the new normal, and causing the probe tip to face the side wall along the new normal; Causing relative movement between the sample surface and the probe tip to move back and return to step (b). 15. The probe tip is mounted on a cantilever beam that vibrates at an excitation frequency in the first direction, and an average amplitude of vibration of the probe tip at the excitation frequency is measured. In c), when it is determined that the average amplitude of the vibration is within the amplitude value allowable range, it is determined that the probe tip is within the predetermined engagement range, and the average amplitude of the vibration is determined by the amplitude value. When it is determined that it is equal to or less than the allowable range, it is determined that the probe tip is closer to the side wall than the predetermined engagement range, and it is determined that the average amplitude of the vibration is equal to or greater than the amplitude value allowable range. The method of claim 14, wherein when determined, the probe tip is determined to be further from the sidewall than the predetermined engagement range. 16. The probe tip is further driven in a circular dither pattern at a dither frequency along the plane perpendicular to the first direction, the probe tip engaging the side wall. The average amplitude is modulated at the dithering frequency, and at steps (a), (e) and (f), the direction of the normal and the direction of the new normal are 16. The method of claim 15, wherein the method is determined as a function of a modulation of the average amplitude at a ring frequency and a phase angle of a dither signal that moves the probe tip in a second direction. 17. The dithering signal for moving the probe tip in the second direction is a sine function, and the angle between the local normal and the second direction is equal to the phase angle and π radian. 17. The method of claim 16, wherein the sum is determined. 18. The method according to claim 16, wherein said excitation frequency is close to a natural frequency of said cantilever and said dithering frequency is significantly lower than said excitation frequency. 19. The method according to claim 19, wherein the predetermined contour surface is a first predetermined contour surface among a plurality of predetermined contour surfaces spaced in the first direction, and each of the plurality of contour surfaces is:
Steps (a) to (f) are flat surfaces perpendicular to the first direction, wherein steps (a) to (f) are performed to move the probe tip along a scan line extending along the side wall and each contour surface. 15. The method of claim 14, wherein the probe tip is moved in the first direction between adjacent contour surfaces of the plurality of contour surfaces. 20. A method for measuring topographical features of sidewalls within a sample surface, comprising: a cantilever, a probe tip attached to an end of the cantilever, and a first cantilever. An excitation drive for oscillating in a direction, a dithering drive for moving the cantilever to move the probe tip in a circular pattern along a plane perpendicular to the first direction, and A sample holder for holding a sample in an exposed state with respect to the probe tip; and causing relative movement between the cantilever and the sample holder in a plane perpendicular to the first direction. A scanning drive; a first demodulator for providing a first signal indicative of an average value of an amplitude of vibration of the probe tip in the first direction at the excitation frequency; A second demodulation providing a second signal indicative of a phase angle between a modulation of the note amplitude of the vibration of the probe tip and a dithering signal causing a linear motion component to move the probe tip in the circular pattern. A processor, and a program executed in the processor to determine a direction of a normal extending between the center of the circular pattern and the side wall, the normal being relative to the first direction. An apparatus that extends perpendicular to the sidewall in the vertical plane, the direction of the normal being determined as a function of the phase angle. 21. The processor controls the operation of the scan drive to cause relative movement between the sample surface and the probe tip, the relative movement causing the probe tip to move with a first predetermined contour surface. Moving along a contour path extending along the intersection of the side walls,
Engagement of the probe and the side wall along the contour path is maintained within a range corresponding to a variation in a measured amplitude of vibration of the probe tip in the first direction at the excitation frequency. The device according to claim 20. 22. The relative movement comprises:
The first plurality of straight line segments are moved along the contour path, and each of the first plurality of straight line segments has a predetermined amplitude corresponding to the measured amplitude of vibration of the probe tip. 21. The apparatus according to claim 20, wherein the apparatus terminates when it is determined that the vibration amplitude is outside the allowable vibration amplitude range. 23. The method according to claim 23, wherein the relative movement further moves the probe tip along a second one of the second plurality of straight lines along the contour path. The method further comprises: extending an adjacent straight line segment between the first plurality of straight line segments, wherein each straight line segment of the first straight line segment has a direction calculated at a starting point of the straight line segment. 23. The device of claim 22, extending perpendicular to the line. 24. The dithering drive moves the probe tip in the second direction according to a sine function, and the angle formed by the local normal and the second direction is equal to the phase angle and π radian. 21. The apparatus of claim 20, wherein the apparatus is determined by a sum.