CN111398638B - Kelvin probe force microscope system and sample side wall scanning method - Google Patents

Abstract

The invention relates to a Kelvin probe force microscope system and a sample side wall scanning method based on an orthogonal probe, belonging to the technical field of Kelvin probe force microscope measurement. The invention aims to solve the problem that the existing Kelvin probe force microscope cannot realize the measurement of the surface morphology and surface potential of the side wall of the micro-nano three-dimensional structure on the semiconductor components. It designs a new orthogonal probe structure, and then uses the torsion signal of the orthogonal probe to measure the surface topography and local surface potential of the sample sidewall with a micro-nano-scale three-dimensional structure; the first step in the method realizes the surface topography of the sample sidewall In the measurement, step 2 and step 3 realize the measurement of the surface potential of the side wall of the sample, and step 4 realizes the imaging measurement of the surface of the side wall of the sample. The invention is used to realize the measurement of the surface topography of the sample side wall and the local surface potential of the micro-nano three-dimensional structure.

Description

Kelvin probe force microscope system and sample side wall scanning method

technical field

The invention relates to a Kelvin probe force microscope system based on an orthogonal probe and a sample side wall scanning method, and belongs to the technical field of Kelvin probe force microscope measurement.

Background technique

Kelvin probe force microscopy (KPFM) is a member of the scanning probe microscopy (SPM) family, which combines Kelvin technology with atomic force microscopy (AFM) to achieve Characterization of sample surface potential and surface topography. According to the different detection methods, the Kelvin probe force microscope KPFM can be divided into two working modes: amplitude modulation mode (Amplitude modulation, AM) and frequency modulation mode (Frequency modulation, FM), where AM-KPFM detects based on electrostatic force, FM-KPFM Detection is based on an electrostatic force gradient.

The surface potential of the sample can accurately reflect the surface structure characteristics and physical and chemical changes of the material, and is one of the important parameters in the process of catalyst activity, semiconductor doping and band bending, charge trapping and corrosion in the dielectric; The performance at the micro-nano scale, microbial activity, and the function of microelectronic devices are very important. Therefore, it is very meaningful to accurately measure the local surface potential of the sample. Measuring the vertical side wall surface of the sample is an important means to detect the processing performance of the sample in the semiconductor industry. Therefore, how to scan the vertical side wall surface of the sample to obtain the electrical performance parameters of the side wall has become the key to improving the micro-nano processing technology. .

The existing Kelvin probe force microscope measurement system and method based on the normal signal of the rectangular beam probe is very mature and widely used for the characterization of the topography and local surface potential of the horizontal surface of the sample. The surface topography and surface potential of the rectangular beam probe can be measured perpendicular to the normal direction of the tip of the rectangular beam probe. However, it cannot realize the characterization of the surface morphology and surface potential of the sidewalls of the micro-nano-scale three-dimensional structures commonly found on semiconductor components.

At present, for the micro-nano three-dimensional structure on semiconductor components, only the sidewall scanning of the surface topography can be realized, but the simultaneous measurement of the surface potential of the sidewall surface of the micro-nano three-dimensional structure cannot be realized at the same time.

Contents of the invention

The invention aims to solve the problem that the existing Kelvin probe force microscope cannot realize the measurement of the sidewall surface topography and surface potential of the micro-nano three-dimensional structure on the semiconductor component, and provides a Kelvin probe force microscope based on an orthogonal probe. Microscope system and sample side wall scanning method.

The Kelvin probe force microscope system based on orthogonal probes of the present invention includes a probe hand 7, and the probe hand 7 includes a probe hand base 7-1, a probe seat 7-3, an orthogonal probe 7-4, shielding sheet 7-5, orthogonal probe fixing plate 7-6 and connection terminal 7-7,

The rear end of the probe hand base 7-1 is connected to the terminal 7-7, the lower surface of the front end of the probe hand base 7-1 is connected to the probe base 7-3, and the lower surface of the probe base 7-3 passes through the orthogonal probe The fixed plate 7-6 is connected to the orthogonal probe 7-4; the shielding sheet 7-5 is set between the orthogonal probe fixed plate 7-6 and the probe seat 7-3; wherein the probe hand base 7-1 and the probe An insulating sheet is arranged between the needle base 7-3 and between the shielding sheet 7-5 and the orthogonal probe fixing plate 7-6;

The probe hand base 7-1, the shielding sheet 7-5 and the orthogonal probe fixed plate 7-6 are electrically connected to the corresponding interfaces of the terminal 7-7 respectively; the orthogonal probe fixed plate 7-6 is connected to the orthogonal probe fixed plate 7-6 Pins 7-4 are electrically connected;

The orthogonal probe 7-4 realizes mechanical vibration at the first-order torsional resonance frequency under the driving signal.

According to the orthogonal probe-based Kelvin probe force microscope system of the present invention, the orthogonal probe 7-4 includes a beam 7-4-1, a magnetic ball 7-4-2, a longitudinal beam 7-4- 3 and lordosis 7-4-4,

The beam 7-4-1 is connected to the orthogonal probe fixing plate 7-6 through the probe holder, the lower surface of the beam 7-4-1 is connected to the magnetic ball 7-4-2, and the side surface of the magnetic ball 7-4-2 The longitudinal beam 7-4-3 is connected in the vertical direction, and the outer surface of the end of the longitudinal beam 7-4-3 is connected with the protruding needle point 7-4-4.

The Kelvin probe force microscope system based on orthogonal probes according to the present invention also includes a Kelvin sample stage 15, and the Kelvin sample stage 15 includes a Kelvin sample stage base 15-1, an inductance coil terminal 15-2, Inductance coil 15-3, sample holder 15-4, connection wire 15-5, set screw 15-6, wire harness block 15-7, copper pressing sheet 15-8 and insulating set screw 15-10,

The sample holder 15-4 is set on the Kelvin sample stage base 15-1; the upper surface of the sample holder 15-4 is used to place the sample 15-9, and an insulating sheet is arranged between the sample holder 15-4 and the sample 15-9;

The inductance coil 15-3 is fixed in the hollow inner cavity of the sample holder 15-4, and the inductance coil terminal 15-2 is drawn out from the inductance coil 15-3 for electrical connection with corresponding electrical equipment;

The copper pressing piece 15-8 is fixed on the sample holder 15-4 by the insulating fixing screw 15-10, and the copper pressing piece 15-8 is electrically connected with the sample 15-9;

The edge of the upper surface of the sample holder 15-4 also fixes the wire harness block 15-7, the connecting wire 15-5 passes through the wire harness block 15-7, and the wire harness block 15-7 is threadedly matched with the set screw 15-6 to realize alignment. Fixing of the connecting wire 15-5; the copper pressing piece 15-8 is electrically connected with the connecting wire 15-5, and the connecting wire 15-5 is used for electrically connecting with the corresponding electrical equipment;

The magnetic field generated by the inductance coil 15-3 drives the orthogonal probe 7-4 through the magnetic ball 7-4-2.

The sample sidewall scanning method of the Kelvin probe force microscope based on the orthogonal probe of the present invention is realized based on the Kelvin probe force microscope system based on the orthogonal probe, comprising the following steps:

Step 1: Mechanically excite the orthogonal probe 7-4 at the first-order torsional resonance frequency, so that the orthogonal probe 7-4 vibrates at a set torsional amplitude; make the protruding needle tip 7-4-4 move along the XYZ The Y direction of the coordinate system gradually approaches the sample 15-9 until the torsional amplitude of the orthogonal probe 7-4 decays to the set value of the torsional amplitude; the Z direction of the XYZ coordinate system is the vertical direction;

Step 2: Apply a low-frequency AC voltage and a DC compensation voltage between the orthogonal probe 7-4 and the sample 15-9, change the magnitude of the DC compensation voltage, and obtain the DC compensation voltage and the orthogonal probe 7 at the first-order torsional resonance frequency -4 the amplitude relationship curve of the torsional vibration phase signal, the change frequency of the torsional vibration phase signal is consistent with the frequency of the low-frequency AC voltage; according to the relationship curve, the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 is selected set value;

Step 3: adjusting the DC compensation voltage through the Kelvin controller, so that the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 is equal to the amplitude setting value of the torsional vibration phase signal of the orthogonal probe 7-4;

Step 4: Set the scanning step distance and the number of scanning test points of the sample 15-9, the scanning step distance and the number of scanning test points include the X direction and the Z direction; keep the position of the orthogonal probe 7-4 unchanged, and change the sample 15 in turn -9 scanning test points, corresponding to each scanning test point, under the action of mechanical excitation and electric excitation, keep the torsional amplitude of the orthogonal probe 7-4 equal to its torsional amplitude set value, and the amplitude of the torsional vibration phase signal is equal to The amplitude setting value of the torsional vibration phase signal; realize the imaging measurement of the surface topography and surface potential of the side wall of the sample 15-9.

According to the sample sidewall scanning method based on the orthogonal probe Kelvin probe force microscope of the present invention, the imaging measurement of the surface topography of the sidewall of sample 15-9 includes:

Fix the sample 15-9 on the sample holder 15-4, change the coordinate position of the sample 15-9 through the XYZ nanopositioning stage 13 connected to the Kelvin sample stage base 15-1, and realize the transformation of the scanning test point of the sample 15-9; At each scanning test point, keep the Y-direction coordinates of the orthogonal probe 7-4 unchanged, and make the torsional amplitude of the orthogonal probe 7-4 equal to its torsion by changing the Y-direction position of the Kelvin sample stage base 15-1 Amplitude setting value; sequentially record the Y-direction coordinates of the base 15-1 of the Kelvin sample stage at each scanning test point, so as to realize the imaging measurement of the surface topography of the side wall of the sample 15-9.

According to the sample sidewall scanning method based on the orthogonal probe Kelvin probe force microscope of the present invention, the imaging measurement of the surface potential of the sidewall of the sample 15-9 includes:

Obtain the local surface potential difference U _CPD between the orthogonal probe 7-4 and the scanning test point of the sample 15-9:

The total potential difference ΔU between the orthogonal probe 7-4 and the sample 15-9 is:

ΔU＝U _DC -U _CPD +U _AC sin(ω _AC t),

Wherein U _DC is the DC compensation voltage, U _AC sin (ω _AC t) is the low-frequency AC voltage, and ω _AC is the frequency of the low-frequency AC voltage;

At this time, the electrostatic force gradient _F'el between the orthogonal probe 7-4 and the surface of the sample 15-9 is:

In the formula, C is the capacitance between the orthogonal probe 7-4 and the sample 15-9, and z is the distance between the orthogonal probe 7-4 and the sample 15-9;

By recording the DC compensation voltage U _DC when the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 is equal to the set value of the amplitude of the torsional vibration phase signal, and combining the relationship curve, determine the relationship between the orthogonal probe 7-4 and Sample 15-9 scans the local surface potential difference U _CPD between the test points.

Advantages of the present invention: the system and method of the present invention are used to realize the characterization of the surface topography and local surface potential of the sample side wall. A new orthogonal probe structure is designed in the system, and then the torsion signal of the orthogonal probe is used to measure the micro Surface topography and local surface potential of the sidewalls of samples with nanoscale 3D structures.

The invention breaks through the space limitation of the traditional KPFM based on the normal signal of the rectangular beam probe to measure the surface potential, and can realize the synchronous characterization of the surface morphology and surface potential of the side wall of the micro-nano three-dimensional structure by using the torsion signal feedback of the orthogonal probe; The method of the present invention provides a new idea for further research on the surface potential of the side wall of the sample; the protruding needle tip of the orthogonal probe in the present invention can penetrate into the gap of the three-dimensional sample with high density to scan the side wall of the sample, which can avoid the traditional side wall Additive effect of the horn probe used in the topography scan.

Compared with the traditional KPFM, the method of the present invention can use the torsion signal of the orthogonal probe as feedback to realize the synchronous characterization of the surface topography and potential of the sample sidewall, which is of great significance for the monitoring and control of device performance, and does not require the KPFM test system Or Kelvin controller to make any changes, compatible with the existing KPFM test system, has high practical value in the field of KPFM test method and system research.

Description of drawings

Fig. 1 is a schematic diagram of the probe hand structure of the Kelvin probe force microscope system based on orthogonal probes according to the present invention;

Figure 2 is a schematic structural view of an orthogonal probe;

Fig. 3 is the front view of Fig. 2;

Fig. 4 is the side view of Fig. 2;

Fig. 5 is the structural representation of Kelvin sample stage;

Figure 6 is a top view of Figure 5;

Fig. 7 is a schematic diagram of the process of determining the scanning position of the orthogonal probe when the height of the side wall of the sample is small;

Fig. 8 is a scanning front view of an orthogonal probe;

Fig. 9 is a scanning side view of an orthogonal probe;

Figure 10 is a scanning axonometric view of an orthogonal probe;

Fig. 11 is the overall principle block diagram that the method control of the present invention realizes;

Figure 12 is a partial enlarged view of the position of the Kelvin sample stage in Figure 11;

Figure 13 is a schematic diagram of the overall structure of the Kelvin probe force microscope system based on orthogonal probes of the present invention; in the figure 1: frame; 2: four-quadrant position detector two-dimensional adjustment micro-platform; 3: one-dimensional adjustment micro-platform Platform I; 4: four-quadrant position detector; 5: reflected laser convex lens; 6: laser mirror; 7: probe hand; 8: XYZ micron positioning stage; 9: probe hand support; Micro-platform; 11: table top; 12: XY micro-positioning stage; 13: XYZ nano-positioning stage; 14: sample stage support; 15: Kelvin scanning sample stage; 16: incident laser focusing convex lens; 17: one-dimensional adjustment micro-stage II; 18: semiconductor laser generator; 19: laser generator angle adjustment mechanism; 20: optical microscope;

Fig. 14 is the surface topography diagram obtained by scanning the sample by the method of the present invention;

Fig. 15 is a section line diagram corresponding to the marked line in Fig. 14;

Fig. 16 is the surface potential difference diagram obtained by scanning the sample by the method of the present invention;

FIG. 17 is a graph corresponding to the statistical distribution and fitting results of the data in FIG. 16 .

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Specific Embodiment 1: The present embodiment will be described below in conjunction with FIG. 1 and FIG. 13. The orthogonal probe-based Kelvin probe force microscope system in this embodiment includes a probe hand 7,

The probe hand 7 includes a probe hand base 7-1, a probe base 7-3, an orthogonal probe 7-4, a shielding sheet 7-5, an orthogonal probe fixing plate 7-6 and a connection terminal 7 -7,

The rear end of the probe hand base 7-1 is connected to the terminal 7-7, the lower surface of the front end of the probe hand base 7-1 is connected to the probe base 7-3, and the lower surface of the probe base 7-3 passes through the orthogonal probe The fixed plate 7-6 is connected to the orthogonal probe 7-4; the shielding sheet 7-5 is set between the orthogonal probe fixed plate 7-6 and the probe seat 7-3; wherein the probe hand base 7-1 and the probe An insulating sheet is arranged between the needle base 7-3 and between the shielding sheet 7-5 and the orthogonal probe fixing plate 7-6;

The probe hand base 7-1, the shielding sheet 7-5 and the orthogonal probe fixed plate 7-6 are electrically connected to the corresponding interfaces of the terminal 7-7 respectively; the orthogonal probe fixed plate 7-6 is connected to the orthogonal probe fixed plate 7-6 Pins 7-4 are electrically connected;

The orthogonal probe 7-4 realizes mechanical vibration at the first-order torsional resonance frequency under the driving signal.

Further, as shown in Figure 2 to Figure 4, the orthogonal probe 7-4 includes a beam 7-4-1, a magnetic ball 7-4-2, a longitudinal beam 7-4-3 and a protruding needle point 7-4 -4,

The beam 7-4-1 is connected to the orthogonal probe fixing plate 7-6 through the probe holder, the lower surface of the beam 7-4-1 is connected to the magnetic ball 7-4-2, and the side surface of the magnetic ball 7-4-2 The longitudinal beam 7-4-3 is connected in the vertical direction, and the outer surface of the end of the longitudinal beam 7-4-3 is connected with the protruding needle point 7-4-4.

Further, as shown in FIG. 5 and FIG. 6, this embodiment also includes a Kelvin sample stage 15, which includes a Kelvin sample stage base 15-1, an inductance coil terminal 15-2, an inductance coil 15- 3. Sample holder 15-4, connecting wire 15-5, set screw 15-6, wire harness block 15-7, copper pressing piece 15-8 and insulating fixing screw 15-10,

The sample holder 15-4 is set on the Kelvin sample stage base 15-1; the upper surface of the sample holder 15-4 is used to place the sample 15-9, and an insulating sheet is arranged between the sample holder 15-4 and the sample 15-9;

The inductance coil 15-3 is fixed in the hollow inner cavity of the sample holder 15-4, and the inductance coil terminal 15-2 is drawn out from the inductance coil 15-3 for electrical connection with corresponding electrical equipment, and the corresponding electrical equipment includes an inductance coil A controller, as shown in Figure 11;

The copper pressing piece 15-8 is fixed on the sample holder 15-4 by the insulating fixing screw 15-10, and the copper pressing piece 15-8 is electrically connected with the sample 15-9;

The edge of the upper surface of the sample holder 15-4 also fixes the wire harness block 15-7, the connecting wire 15-5 passes through the wire harness block 15-7, and the wire harness block 15-7 is threadedly matched with the set screw 15-6 to realize alignment. Fixing of the connecting wire 15-5; the copper pressing piece 15-8 is electrically connected with the connecting wire 15-5, and the connecting wire 15-5 is used for electrically connecting with the corresponding electrical equipment, and the corresponding electrical equipment includes the signal generator in Fig. 11 2 and a signal adder for signal synthesis of DC power supply;

The magnetic field generated by the inductance coil 15-3 drives the orthogonal probe 7-4 through the magnetic ball 7-4-2.

The inductance coil 15-3 can generate a uniform magnetic field, cooperate with the magnetic ball 7-4-2 to realize the magnetic drive to the orthogonal probe 7-4.

As shown in FIG. 13 , the overall structure of the Kelvin probe force microscope system based on orthogonal probes described in this embodiment also includes: a table 11 on which a rack 1 is installed and a one-dimensional large-scale adjustment micro-platform 10 , XY micron positioning stage 12 and optical microscope 20. Among them, the Kelvin sample stage 15 is installed on the XY micron positioning stage 12 through the sample stage bracket 14 and the XYZ nanopositioning stage 13, the laser force measurement system is installed on the frame 1, and the probe hand 7 is installed on the XYZ micron positioning stage 12 through the probe hand support 9 and the XYZ micron positioning stage. The positioning platform 8 is installed on a one-dimensional large-range adjustment micro-platform 10 .

The laser force measurement system consists of a laser generator angle adjustment mechanism 19, a semiconductor laser generator 18, an incident laser focusing convex lens 16, a laser mirror 6, a reflected laser convex lens 5, a four-quadrant position detector 4, a one-dimensional adjustment micro-platform II17, The one-dimensional adjustment micro-platform I3 and the four-quadrant position detector two-dimensional adjustment micro-platform 2 are composed.

In the structure of the probe hand 7, a piezoelectric ceramic 7-2 may also be included, so that the piezoelectric ceramic 7-2 is connected between the probe hand base 7-1 and the probe seat 7-3, and the piezoelectric ceramic 7 Insulation sheets are arranged on the upper and lower surfaces of -2, and the piezoelectric ceramic 7-2 is electrically connected to the corresponding interface of the terminal 7-7; the piezoelectric ceramic 7-2 can also realize the mechanical drive of the orthogonal probe 7-4 .

In Figure 12, B in the figure is the direction of the electromagnetic field, m is the magnetization direction of the magnetic ball, τ is the direction of the torque on the magnetic ball, and the magnetically driven sample stage in the figure is the Kelvin sample stage 15; in Figure 11, ① represents piezoelectric ceramics The connection mode of the drive, ② represents the connection mode of the magnetic field drive, and one of them can be used in the actual measurement.

Specific embodiment 2: The present embodiment will be described below in conjunction with FIGS. The implementation of the Kelvin probe force microscope system for cross-probes includes the following steps:

Step 1: Mechanically excite the orthogonal probe 7-4 at its first-order torsional resonance frequency, so that the orthogonal probe 7-4 vibrates at a set torsional amplitude; make the protruding needle tip 7-4-4 move along the XYZ The Y direction shown in the coordinate system Figure 9 and Figure 12 gradually approaches the sample 15-9 until the torsional amplitude of the orthogonal probe 7-4 decays to the set value of the torsional amplitude; the Z direction of the XYZ coordinate system is the vertical direction ;

Step 2: Apply a low-frequency AC voltage and a DC compensation voltage between the orthogonal probe 7-4 and the sample 15-9, change the magnitude of the DC compensation voltage, and obtain the DC compensation voltage and the orthogonal probe 7 at the first-order torsional resonance frequency -4 the amplitude relationship curve of the torsional vibration phase signal, the change frequency of the torsional vibration phase signal is consistent with the frequency of the low-frequency AC voltage; according to the relationship curve, the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 is selected set value;

Step 3: Set the parameters of the Kelvin controller and turn it on, adjust the DC compensation voltage through the Kelvin controller, so that the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 is equal to that of the torsional vibration phase signal of the orthogonal probe 7-4 Amplitude setting value;

Step 4: Set the scanning step distance and the number of scanning test points of the sample 15-9, the scanning step distance and the number of scanning test points include the X direction and the Z direction; keep the position of the orthogonal probe 7-4 unchanged, and change the sample 15 in turn -9 scanning test points, corresponding to each scanning test point, under the action of mechanical excitation and electric excitation, keep the torsional amplitude of the orthogonal probe 7-4 equal to its torsional amplitude set value, and the amplitude of the torsional vibration phase signal is equal to The amplitude setting value of the torsional vibration phase signal; realize the imaging measurement of the surface topography and surface potential of the side wall of the sample 15-9. The torsional amplitude and the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 are used as feedback signals to realize displacement control and potential compensation of sample scanning.

In this embodiment, step 1 realizes the measurement of the surface topography of the sample side wall, steps 2 and 3 realize the measurement of the surface potential of the sample side wall, and step 4 realizes the imaging measurement of the sample side wall surface. Thanks to the structural characteristics of the orthogonal probe, its torsion signal can well reflect the interaction between the probe tip and the sidewall surface, thereby realizing the measurement of the surface topography and local surface potential of the sample sidewall.

The method of the present invention works under the frequency modulation mode of the microscope. During the measurement process, the probe is driven at two frequencies at the same time, including: 1. Mechanical drive of the orthogonal probe 7-4 at the first-order torsional resonance frequency; 2. Low frequency electrical excitation between orthogonal probe 7-4 and sample 15-9. The torsion signal of the orthogonal probe 7-4 can be used as feedback through the host computer to realize the displacement control and potential compensation of the scan, so as to realize the simultaneous measurement of the sample surface topography and local surface potential. The force deformation of the orthogonal probe 7-4 can be measured by a laser force measuring system.

In the test of this embodiment, the protruding needle tip 7-4-4 interacts with the surface of the three-dimensional side wall of the sample, thereby causing the force on the probe longitudinal beam 7-4-3 to cause twisting of the beam 7-4-1, and the signal is obtained by The laser force measurement system detects and is used for feedback control of the entire scanning process. The method of the invention breaks through the limitation that the surface can only be characterized in the horizontal plane based on the measurement of the normal signal of the traditional rectangular beam probe, and the simultaneous measurement of the surface topography and potential of the side wall of the sample can be realized by using the torsion signal of the orthogonal probe.

Further, in combination with what is shown in FIG. 7 , in this embodiment, the imaging measurement of the surface topography of the side wall of sample 15-9 includes:

Fix the sample 15-9 on the sample holder 15-4, change the coordinate position of the sample 15-9 through the XYZ nanopositioning stage 13 connected to the Kelvin sample stage base 15-1, and realize the transformation of the scanning test point of the sample 15-9; At each scanning test point, keep the Y-direction coordinates of the orthogonal probe 7-4 unchanged, and make the torsional amplitude of the orthogonal probe 7-4 equal to its torsion by changing the Y-direction position of the Kelvin sample stage base 15-1 Amplitude setting value; sequentially record the Y-direction coordinates of the base 15-1 of the Kelvin sample stage at each scanning test point, so as to realize the imaging measurement of the surface topography of the side wall of the sample 15-9.

In Fig. 7, the first picture shows that the orthogonal probe is servoed at the highest point of the three-dimensional side wall structure of the sample; the second picture shows that the orthogonal probe is servoed at the lowest point of the three-dimensional side wall structure of the sample; the third picture shows the sample stage The Z direction descends to a certain height; the fourth picture shows that the orthogonal probe is servoed with the side wall surface at the position point of the side wall of the sample to be tested.

Still further, in this embodiment, the imaging measurement of the surface potential of the side wall of the sample 15-9 includes:

Obtain the local surface potential difference U _CPD between the orthogonal probe 7-4 and the scanning test point of the sample 15-9:

During the test, the surface potential difference between the orthogonal probe 7-4 and the sample 15-9 is measured by taking the torsion signal of the probe due to low-frequency electrical excitation as feedback.

The total potential difference ΔU between the orthogonal probe 7-4 and the sample 15-9 is:

ΔU＝U _DC -U _CPD +U _AC sin(ω _AC t),

Wherein U _DC is the DC compensation voltage, U _AC sin (ω _AC t) is the low-frequency AC voltage (electric excitation), and ω _AC is the frequency of the low-frequency AC voltage;

At this time, the electrostatic force gradient _F'el between the orthogonal probe 7-4 and the surface of the sample 15-9 is:

In the formula, C is the capacitance between the orthogonal probe 7-4 and the sample 15-9, z is the distance between the orthogonal probe 7-4 and the sample 15-9; it can be seen from the above formula that when U When _DC = U _CPD , the influence of the electrostatic force gradient on the orthogonal probe 7-4 at the frequency ω _AC will be eliminated. Due to the presence of the probe-sample electrostatic force gradient, the effective stiffness of the probe becomes:

k _eff = kF' _el ,

where k is the static stiffness of the probe.

Therefore, under the action of the electrostatic force gradient, the resonance frequency of the probe changes as:

where _ω0 is the first-order torsional resonance frequency of the probe. By recording the DC compensation voltage U _DC when the amplitude of the torsional vibration phase signal of the orthogonal probe 7-4 is equal to the set value of the amplitude of the torsional vibration phase signal, and combining the relationship curve, determine the relationship between the orthogonal probe 7-4 and Sample 15-9 scans the local surface potential difference U _CPD between the test points.

In the scanning method of the present invention, by recording the first-order torsional amplitude of the orthogonal probe 7-4 and the Z-direction coordinate value of the scanner when the torsional amplitude is set, the surface topography image of the sample can be obtained;

As shown in Fig. 11, in actual processing, the change of the resonance frequency of the probe is seldom directly measured by a single lock-in amplifier. Since Δω=0 when the amplitude of the probe phase signal is equal to zero. Therefore, two lock-in amplifiers are usually used to perform KPFM in FM mode: the first locks on the probe's resonant frequency (ω ₀ ), the second locks on the frequency of the AC modulating signal (ω _AC ), by adjusting U _DC zeroes the amplitude feedback signal of the phase, so U _DC = U _CPD , thus obtaining the corresponding local surface potential difference (U _CPD ) between the probe and the sample.

Shown in conjunction with Fig. 11 to Fig. 13, the specific testing process of the method of the present invention is as follows:

1. System initialization, fix the prepared sample 15-9 on the sample holder 15-4, install the orthogonal probe 7-4 on the probe hand 7, and then install the Kelvin sample table 15 and the probe hand 7 respectively On the sample stage support 14 and the probe hand support 9, at last the terminal is electrically connected to the corresponding equipment;

2. Move the XY micron positioning stage 12, initially position the sample 15-9 through the optical microscope 20, select a suitable measurement area, and move this area to the center of the field of view of the optical microscope 20;

3. Move the one-dimensional large-scale adjustment micro-platform 10 and the XYZ micron positioning stage 8, roughly align the orthogonal probe 7-4, place the probe tip above the appropriate measurement area selected in step 2, and adjust the orthogonal The laser spot of probe 7-4 is at the center of the front end of the probe beam;

4. Perform a frequency sweep operation on the orthogonal probe 7-4 by means of a frequency sweep exciter to obtain the first-order torsional resonance frequency of the orthogonal probe 7-4;

5. Determine the scanning position, which is mainly divided into two types according to the different samples: 1. For samples with a large side wall height, the needle tip will not touch the root of the side wall during the side wall scanning process. The XYZ micron positioning stage 8 coarsely adjusts and moves the orthogonal Probe 7-4 to the front of the side wall of the sample to be tested in the Y direction, and directly lower the orthogonal probe 7-4 to the position in the Z direction to be measured; 2 For samples with a small side wall height, the needle tip 7- 4-4 may touch the root of the side wall, therefore, at first respectively at the top and bottom of the side wall servo contact, obtain the height of the side wall according to the Z-direction coordinates of the XYZ nanopositioning stage 13 during the two servo contacts, and then move the XYZ nanopositioning stage 13 to make The needle tip 7-4-4 is aligned with the Z-direction of the position to be measured, and the scanning distance in the Z-direction is guaranteed to be less than the remaining side wall height;

6. Coarsely adjust the Y-direction distance between the orthogonal probe 7-4 and the sample 15-9, and readjust the laser spot of the orthogonal probe 7-4 to the front center of the probe beam, and prepare to turn on the upper computer-position servo control;

7. The probe is mechanically excited (U _m ) at the first-order torsional resonance frequency of the probe. The present invention can adopt two driving modes, but it is not limited to these two driving modes: 1) Piezoelectric ceramic drive, through sinusoidal The piezoelectric ceramic 7-2 under the voltage drive realizes the mechanical vibration of the probe at the first-order torsional resonance frequency; 2) the magnetic field drive, using the inductance coil 15-3 in the Kelvin sample stage 15 to generate alternating current under the drive of the sinusoidal voltage signal The magnetic field drives the magnetic ball 7-4-2 magnetized in a specified direction, so that the mechanical vibration of the probe at the first-order torsional resonance frequency is realized through the action of the electromagnetic torque τ. Use the laser force measuring system to detect the resonance signal generated by the orthogonal probe 7-4, and obtain the torsional amplitude and phase signal of the probe through the lock-in amplifier 1, and then start the position servo control to control the XYZ nanopositioning stage 13 in the Y-axis direction Approaching the orthogonal probe 7-4 quickly, so that the torsional amplitude of the orthogonal probe 7-4 is equal to the set value;

8. Apply low-rate (4kHz) electric excitation (U _AC ) between the orthogonal probe 7-4 and the sample 15-9, and obtain the amplitude of the phase signal output by the lock-in amplifier 1 through the lock-in amplifier 2, and then Obtain the relationship curve between U _DC and the amplitude of the torsional vibration phase signal of the probe at the low frequency, and select the set value of the amplitude of the torsional vibration phase signal of the probe;

9. Turn on the Kelvin controller. This program uses the amplitude output by the lock-in amplifier 2 as a feedback signal to control the DC power supply to output a DC compensation voltage (U _DC ) to act between the orthogonal probe 7-4 and the sample 15-9. Thereby compensating the local potential difference (U _CPD ) between the orthogonal probe 7-4 and the surface of the sample 15-9 to ensure that the amplitude output by the lock-in amplifier 2 is equal to the set value of the amplitude of the probe torsional vibration phase signal;

10. Through the above steps, the local potential difference (U _CPD ) between the orthogonal probe 7-4 and the sample 15-9 can be obtained from the voltage (U _DC ) output by the DC power supply and the relationship curve between the torsional amplitude of the probe;

11. Set the scanning step and scanning points, and then start image scanning.

The method of the present invention is used to measure and scan the sample distributed with silicon-gold layers on the side wall; obtain Fig. 14 to Fig. 17; Fig. 14 to Fig. 17 are side wall scanning images when the silicon-gold interface is vertically placed; brightness in Fig. 14 The high part is the gold layer, and the low brightness part is the silicon substrate; the results in Figure 15 show that the sample height is 18nm; the results in Figure 17 show that the surface potential difference between the silicon layer and the gold layer on the side wall of the sample is 748mV, and the scanning range is 2μm *2μm, the number of scanning points is 200*200.

Although the invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It is therefore to be understood that numerous modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the invention as defined by the appended claims. It shall be understood that different dependent claims and features described herein may be combined in a different way than that described in the original claims. It will also be appreciated that features described in connection with individual embodiments can be used in other described embodiments.

Claims (5)

1. A Kelvin probe force microscope system comprising a probe hand (7), characterized in that,

the probe hand (7) comprises a probe hand base (7-1), a probe seat (7-3), an orthogonal probe (7-4), a shielding sheet (7-5), an orthogonal probe fixing plate (7-6) and a wiring terminal (7-7),

the rear end of the probe hand base (7-1) is connected with a wiring terminal (7-7), the lower surface of the front end of the probe hand base (7-1) is connected with a probe seat (7-3), and the lower surface of the probe seat (7-3) is connected with an orthogonal probe (7-4) through an orthogonal probe fixing plate (7-6); a shielding sheet (7-5) is arranged between the orthogonal probe fixing plate (7-6) and the probe seat (7-3); wherein insulating sheets are arranged between the probe hand base (7-1) and the probe seat (7-3) and between the shielding sheet (7-5) and the orthogonal probe fixing plate (7-6);

the probe hand base (7-1), the shielding sheet (7-5) and the orthogonal probe fixing plate (7-6) are respectively and electrically connected with corresponding interfaces of the wiring terminals (7-7); the orthogonal probe fixing plate (7-6) is electrically connected with the orthogonal probes (7-4);

the orthogonal probe (7-4) is driven by a driving signal to realize mechanical vibration at a first-order torsional resonance frequency;

the orthogonal probe (7-4) comprises a cross beam (7-4-1), a magnetic ball (7-4-2), a longitudinal beam (7-4-3) and a front convex needle point (7-4-4),

the cross beam (7-4-1) is connected with the orthogonal probe fixing plate (7-6) through the probe support, the lower surface of the cross beam (7-4-1) is connected with the magnetic ball (7-4-2), the side surface of the magnetic ball (7-4-2) is connected with the longitudinal beam (7-4-3) in the vertical direction, and the outer side surface of the tail end of the longitudinal beam (7-4-3) is connected with the front convex needle point (7-4-4).

2. The Kelvin probe force microscope system of claim 1, further comprising a Kelvin stage (15), the Kelvin stage (15) comprising a Kelvin stage base (15-1), an inductor winding connection terminal (15-2), an inductor winding (15-3), a sample holder (15-4), a connection wire (15-5), a set screw (15-6), a wire harness block (15-7), a copper strap (15-8), and an insulating set screw (15-10),

the sample seat (15-4) is arranged on the Kelvin sample table base (15-1); the upper surface of the sample seat (15-4) is used for placing a sample (15-9), and an insulating sheet is arranged between the sample seat (15-4) and the sample (15-9);

the inductance coil (15-3) is fixed in the hollow inner cavity of the sample seat (15-4), and the inductance coil wiring terminal (15-2) is led out from the inductance coil (15-3) and is used for being electrically connected with corresponding electrical equipment;

the copper pressing sheet (15-8) is fixed on the sample seat (15-4) through an insulating fixing screw (15-10), and the copper pressing sheet (15-8) is electrically connected with the sample (15-9);

the edge of the upper surface of the sample seat (15-4) is also fixed with a wire harness block (15-7), the connecting wire (15-5) passes through the wire harness block (15-7), and the wire harness block (15-7) is in threaded fit with the set screw (15-6) to fix the connecting wire (15-5); the copper pressing sheet (15-8) is electrically connected with the connecting wire (15-5), and the connecting wire (15-5) is used for being electrically connected with corresponding electrical equipment;

the magnetic field generated by the inductance coil (15-3) drives the orthogonal probe (7-4) through the magnetic ball (7-4-2).

3. A method of scanning a sample sidewall of a kelvin probe force microscope based on the kelvin probe force microscope system according to claim 2, characterized by comprising the steps of:

step one: mechanically exciting the quadrature probe (7-4) at a first order torsional resonance frequency to vibrate the quadrature probe (7-4) at a set torsional amplitude; gradually approaching the forward protruding tip (7-4-4) to the sample (15-9) along the Y direction of the XYZ coordinate system until the torsion amplitude of the orthogonal probe (7-4) is attenuated to a torsion amplitude set value; the Z direction of the XYZ coordinate system is the vertical direction;

step two: applying a low-frequency alternating current voltage and a direct current compensation voltage between the quadrature probe (7-4) and the sample (15-9), and changing the magnitude of the direct current compensation voltage to obtain an amplitude relation curve of the direct current compensation voltage and a torsional vibration phase signal of the quadrature probe (7-4) under a first-order torsional resonance frequency, wherein the change frequency of the torsional vibration phase signal is consistent with the frequency of the low-frequency alternating current voltage; according to the relation curve, selecting an amplitude set value of a torsional vibration phase signal of the quadrature probe (7-4);

step three: adjusting the direct current compensation voltage through a Kelvin controller to enable the amplitude of the torsional vibration phase signal of the quadrature probe (7-4) to be equal to the amplitude set value of the torsional vibration phase signal of the quadrature probe (7-4);

step four: setting a scanning step distance and a scanning test point number of the sample (15-9), wherein the scanning step distance and the scanning test point number comprise an X direction and a Z direction; the position of the quadrature probe (7-4) is kept unchanged, scanning test points of the sample (15-9) are sequentially transformed, and the torsional amplitude of the quadrature probe (7-4) is kept equal to a torsional amplitude set value under the action of mechanical excitation and electric excitation corresponding to each scanning test point, and the amplitude of a torsional vibration phase signal is equal to an amplitude set value of the torsional vibration phase signal; imaging measurement of the surface topography and surface potential of the side wall of the sample (15-9) is realized.

4. A sample sidewall scanning method of a kelvin probe force microscope according to claim 3, characterized in that the realization of the imaging measurement of the surface topography of the sidewall of the sample (15-9) comprises:

fixing a sample (15-9) on a sample seat (15-4), and changing the coordinate position of the sample (15-9) through an XYZ nanometer positioning table (13) connected with a Kelvin sample table base (15-1) to realize the conversion of a sample (15-9) scanning test point; at each scan test point, keeping the Y-direction coordinate of the quadrature probe (7-4) unchanged, and enabling the torsion amplitude of the quadrature probe (7-4) to be equal to the torsion amplitude set value by changing the Y-direction position of the Kelvin sample stage base (15-1); and (3) recording Y-direction coordinates of the Kelvin sample stage base (15-1) when each test point is scanned in sequence, and realizing imaging measurement of the surface morphology of the side wall of the sample (15-9).

5. The method of scanning the side wall of a sample in a kelvin probe force microscope according to claim 4, characterized in that the implementation of the imaging measurement of the side wall surface potential of the sample (15-9) includes:

obtaining a local surface potential difference U between the orthogonal probe (7-4) and the sample (15-9) scanning test point _CPD ：

The total potential difference DeltaU between the orthogonal probe (7-4) and the sample (15-9) is:

ΔU＝U _DC -U _CPD +U _AC sin(ω _AC t)，

wherein U is _DC For the DC compensation voltage, U _AC sin(ω _AC t) is the low frequency alternating voltage, ω _AC The frequency of the low-frequency alternating voltage; u (U) _AC An electrical excitation applied between the orthogonal probe (7-4) and the sample (15-9);

at this time, the gradient F of electrostatic force between the orthogonal probe (7-4) and the surface of the sample (15-9) _e ′ _l The method comprises the following steps:

wherein C is the capacitance between the orthogonal probe (7-4) and the sample (15-9), and z is the distance between the orthogonal probe (7-4) and the sample (15-9);

by recording the DC compensation voltage U at which the amplitude of the torsional vibration phase signal of the quadrature probe (7-4) is equal to the amplitude set point of the torsional vibration phase signal _DC And determining the local surface potential difference U between the orthogonal probe (7-4) and the sample (15-9) scanning test point by combining the relation curve _CPD 。

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