CN208208712U - A kind of scanning electron microscope system - Google Patents

Abstract

The utility model discloses a kind of scanning electron microscope systems, comprising: Wein filter, the complex objective lens being made of electric lens and magnetic lenses, mirror retrodeviate rotary device and sample stage；Wherein, Wein filter, between the electron source for the initial electron beam for being incident to the scanning electron microscope system positioned at the upper pole shoe of magnetic lenses and generation, for making the incident initial electron beam with the first energy along axis movement, the initial electron beam with the second energy deflects to the optical axis two sides of the initial electron beam；Complex objective lens form convergence electron beam for converging to the initial electron beam acted on through the Wein filter；Mirror retrodeviates rotary device, in the lower pole shoe bore of the magnetic lenses, for changing the direction of motion of the convergence electron beam, so that the sample to be tested in the convergence electron beam oblique incidence to the sample stage.

Description

A Scanning Electron Microscope System

technical field

The utility model relates to scanning electron microscope technology, in particular to a scanning electron microscope system.

Background technique

Research progress in related fields such as materials, biology, and medicine relies heavily on efficient imaging solutions to characterize their properties, and the ability to image structural details in three dimensions is the key.

The traditional scanning electron microscope uses a mechanical sample stage to realize the sample tilting. By tilting the sample stage, images of the same position of the sample can be obtained at different angles, and the sample morphology and the region of interest can be analyzed through the images observed at different angles, or use The image algorithm reconstructs the sample surface images detected from different angles to obtain a three-dimensional image of the sample. However, when the sample is tilted through the mechanical sample stage, on the one hand, the working distance of the scanning electron microscope will be increased, thereby reducing the resolution of the scanning electron microscope and causing additional aberrations in the scanning electron microscope; on the other hand, using When the mechanical sample stage tilts the sample to image the sample at different angles, it takes a long time for the mechanical mechanism to tilt the sample to the specified angle, which seriously reduces the detection efficiency of the scanning electron microscope.

Or the scanning electron microscope uses its own electron optical device to observe the sample at an oblique angle; for example, the deflector is used to deflect the electron beam, so that the electron beam deviates from the optical axis and incidents obliquely on the sample surface to scan and observe the sample. However, compared to the condition that the electron beam is not tilted and the electron beam moves along the center of the optical axis and is incident on the sample vertically, the scanning electron microscope uses its own electron optical device to observe the sample at an oblique angle, which usually brings additional aberrations , resulting in an increase in the focused beam spot, which in turn leads to a decrease in the resolution of the scanning electron microscope. Among them, the additional aberration mainly includes: when the deflector deflects the electron beam to make it tilt, the inconsistency of the deflector’s effect on the electron beam with different energies causes deflection chromatic aberration, as shown in Figure 1; Paraxial chromatic aberration caused by different focusing capabilities, as shown in Figure 2; when the electron beam is incident from the non-central optical axis area of the lens, coma aberration caused by inconsistent focusing capabilities in areas with different distances from the central optical axis, as shown in Figure 3 .

With the development of scanning electron microscopy, more attention is paid to ensuring the resolution at low spot energy (<5keV). When the initial electron beam is focused on the sample at a lower energy, the chromatic aberration of the system usually affects the resolution of the scanning electron microscope. greater impact. Since the electrons emitted by the electron source are usually not pure electrons with a single energy V, but contain a certain energy dispersion, assuming that the electron beam emitted by the electron source contains electrons of V±ΔV, the electron energy dispersion of ΔV will bring electrons in the electron beam microscope Chromatic aberration in the optical system, the most typical is the central chromatic aberration focusing along the central optical axis of the objective lens; if there is a deflector in the system, the deflector will bring deflection chromatic aberration; the electron beam converges in the off-axis area of the objective lens, which will bring off-axis chromatic aberration . When the electron beam is incident on the sample in a low-energy state (<5keV), various chromatic aberrations will lead to an increase in the focused beam spot, resulting in a decrease in resolution.

Utility model content

In view of this, an embodiment of the present invention provides a scanning electron microscope system, which can reduce the aberration caused by the tilted electron beam and improve the resolution of the scanning electron microscope system when the sample is scanned and observed by tilting the electron beam.

The utility model improves a scanning electron microscope system, and the scanning electron microscope system includes:

Composite objective lens composed of electric lens and magnetic lens;

Located between the upper pole piece of the magnetic lens and the electron source that generates the initial electron beam incident to the scanning electron microscope system, the incident initial electron beam with the first energy moves along the optical axis, and the initial electron beam with the second energy an electromagnetic cross-field analyzer deflecting an initial electron beam to either side of the optical axis of said initial electron beam;

The composite objective lens is used to converge the initial electron beams acting on the electromagnetic cross-field analyzer to form a converged electron beam;

And a mirror rear deflection device located in the lower pole shoe hole of the magnetic lens, which changes the movement direction of the converged electron beam so that the converged electron beam is obliquely incident on the sample to be measured on the sample stage.

In one embodiment, the scanning electron microscope system further includes: a high-voltage tube located between the upper pole piece of the magnetic lens and the electron source, the central axis of the high-voltage tube coincides with the optical axis.

In an embodiment, the electromagnetic cross-field analyzer includes: a multi-pole magnetic deflector and a multi-pole electric deflector.

In an embodiment, the magnetic field distribution generated by the multi-pole magnetic deflector and the electric field distribution generated by the multi-pole electric deflector satisfy a first distribution condition; the first distribution condition at least includes: close to or coincident.

In one embodiment, the magnetic lens is a semi-immersed magnetic lens or a non-immersed magnetic lens excited by a current coil.

In one embodiment, the electrical lens includes: an upper pole shoe of the magnetic lens, the rear deflection device and the sample stage.

In one embodiment, the electrical lens includes: the lower end surface of the high-voltage tube, the sample stage, and the mirror rear deflection device.

In one embodiment, the deflection device behind the mirror is an electrostatic multi-pole electric deflector.

In an embodiment, the mirror deflection device has a first voltage as an electrode of the electric lens.

In one embodiment, the electromagnetic cross-field analyzer is a Wien analyzer.

In the embodiment of the utility model, the deflection device behind the mirror deflects the initial electron beam, so that the electron beam is incident on the surface of the sample to be tested at a preset inclination angle, which will increase the aberration of the focused beam spot on the surface of the sample to be tested. The electromagnetic cross-field analyzer generates electric field force and magnetic field force of appropriate size, and some electrons in the initial electron beam deviate symmetrically to both sides of the main optical axis, and the electrons deviated to both sides of the main optical axis enter the side of the composite objective lens After the axial area, the off-axis chromatic aberration is generated by the composite objective lens; by adjusting the magnitude of the current of the multi-pole magnetic deflector and the voltage of the multi-pole electric deflector in the electromagnetic cross-field analyzer, the off-axis chromatic aberration produced by the composite objective lens is consistent with that of the mirror The deflection chromatic aberration produced by the rear deflection device cancels each other out; thus, when the initial electron beam is obliquely incident on the surface of the test sample, the focused beam spot of the scanning electron microscope system on the test sample is as close as possible to the initial electron beam vertically incident on the test sample surface. The ideal beam spot on the surface of the sample (that is, central focus) reduces the aberration caused by the inclined electron beam and improves the resolution of the scanning electron microscope system; in addition, the rear deflection device not only deflects the initial electron beam, It is also an integral part of the electric lens, which participates in the formation of the deceleration lens field, and the deflection device behind the mirror is a thin deflection plate, which does not occupy the valuable space under the magnetic lens, reduces the working distance of the magnetic lens, and further improves the scanning electron microscope system. resolution.

Description of drawings

Fig. 1 is a schematic diagram of deflected chromatic aberration caused by inconsistent effects of deflectors on electron beams of different energies in the related art;

Fig. 2 is a schematic diagram of paraxial chromatic aberration caused by different focusing capabilities of electrons with different energies in the non-central optical axis region of the lens in the related art;

3 is a schematic diagram of coma aberration when an electron beam is incident from a non-central optical axis region of a lens in the related art;

4 is a schematic diagram of the composition and structure of a scanning electron microscope system according to an embodiment of the present invention;

Fig. 5 is the schematic diagram of the electric field and the magnetic field that electromagnetic cross field analyzer produces in the utility model embodiment;

Fig. 6 is a schematic diagram of the trajectory of the initial electron beam in the embodiment of the present invention after passing through the electromagnetic cross-field analyzer;

Fig. 7a is a schematic diagram of the structure of the eight-pole sheet electric deflector and the power supply of each electrode in the embodiment of the utility model;

Fig. 7b is a schematic diagram of the structure of the twelve-electrode sheet electric deflector and the power supply of each electrode in the embodiment of the present invention;

Fig. 8 is a schematic diagram of the deflection chromatic aberration produced by the deflection device behind the mirror when the electromagnetic cross-field analyzer of the embodiment of the present invention is turned off.

Fig. 9 is a schematic diagram of the composition and structure of the scanning electron microscope system of the second embodiment of the utility model;

Fig. 10 is a schematic diagram of an optional processing flow of the sample detection method provided by the embodiment of the present invention;

Detailed ways

Below in conjunction with accompanying drawing and embodiment, the utility model is described in further detail. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

Embodiment one

An optional schematic diagram of a scanning electron microscope system provided by Embodiment 1 of the present utility model, as shown in FIG. Rear deflector 108 and sample stage 109.

In some embodiments, the function of the electromagnetic cross-field analyzer 105 can be implemented by a Wien analyzer. The electromagnetic cross-field analyzer 105 is located between the upper pole piece of the magnetic lens 107 and the electron source 101 that generates the initial electron beam incident to the scanning electron microscope, and the central area of the electromagnetic cross-field analyzer 105 coincident with the optical axis.

Here, the initial electron beam incident to the scanning electron microscope system is generated and emitted by the electron source 101, and the electrons emitted from the electron source 101 will be accelerated through the anode in the electron source 101; in some embodiments, the electrons emitted from the electron source 101 The electrons will be accelerated by a higher voltage V, such as the energy of the accelerated electron beam is greater than 5keV. The electron source 101 is a field emission electron source, such as a thermal field emission electron source or a cold field emission electron source, including Schottky, absorber, anode and other emission source structures of the field emission electron source. The electron beam emitted from the electron source 101 enters the electromagnetic cross-field analyzer 105 after being acted on by electron optical components such as an aperture, a converging lens, and a detector. The electro-optical components such as diaphragm, converging lens, and detector are omitted in each illustration of the utility model embodiment, and the electro-optical components such as diaphragm, converging lens, and detector are all grounded, that is, the diaphragm, converging lens, detecting The voltage of the electro-optical components such as the device is zero.

In some embodiments, the electromagnetic cross-field analyzer 105 is composed of an electric deflector and a magnetic deflector; wherein, the electric deflector is a multi-pole electric deflector, and the magnetic deflector is a multi-pole magnetic deflector. An optional schematic diagram of the electric field and magnetic field produced by the electromagnetic cross-field analyzer 105, as shown in Figure 5, the electric field E produced by the electromagnetic cross-field analyzer 105 is represented by a dotted line, and the electromagnetic cross-field analyzer 105 produces The magnetic field B is represented by a solid line. The magnetic field distribution generated by the multi-pole magnetic deflector 105 and the electric field distribution generated by the multi-pole electric deflector satisfy a first distribution condition; the first distribution condition at least includes: close to or coincident; that is, the electromagnetic cross-field analysis The magnetic field distribution generated by the device 105 completely coincides with or is close to the electric field distribution generated by the multipole electric deflector. When electrons pass through the electric field and magnetic field generated by the electromagnetic cross-field analyzer 105, the magnitude and direction of the magnetic force received are related to the velocity of the initial electron beam, which can also be understood as the electrons passing through the electromagnetic cross-field analyzer 105. In the case of electric field and magnetic field, the magnitude and direction of the magnetic force received are related to the energy V of the initial electron beam.

The trajectory of the initial electron beam after passing through the electromagnetic cross-field analyzer 105, as shown in Figure 6, the initial electron beam is simultaneously affected by the electric field force Fe and the magnetic field force Fm in opposite directions, and all electrons in the initial electron beam are subjected to The magnitude of the electric field force Fe is the same, and the fast-moving electrons are subject to a larger magnetic field force Fm; by adjusting the current value and voltage value of the electromagnetic cross-field analyzer 105, the electrons with the first energy (energy is V) can be subjected to The electric field force Fe and the magnetic field force Fm are equal in size and opposite in direction. Therefore, the resultant force on the electrons with energy V is 0, and the trajectory does not deflect. Electrons with the second energy (energy is V+ΔV and energy is V-ΔV) receive the resultant force of the same size and opposite direction, therefore, the trajectory of electrons with energy V+ΔV and energy V-ΔV is controlled by the electromagnetic cross field Analyzer 105 is deflected to either side of optical axis 110 . Therefore, electrons with different energies will be separated after the electron beam moving downward along the optical axis passes through the electromagnetic cross-field analyzer 105 .

The composite objective lens 11 includes a magnetic lens 107 and an electric lens 10. The magnetic field generated by the magnetic lens 107 in the composite lens 11 and the electric field generated by the electric lens 10 form a composite electromagnetic field, which is used for initial electrons passing through the electromagnetic cross field analyzer 105. The beams are converged to form a converged electron beam to ensure high resolution under low energy conditions.

In some embodiments, the magnetic lens 107 can be a semi-immersed magnetic lens excited by a current coil, or a non-immersed magnetic lens; the magnetic lens 107 is made of a wire wound into an excitation coil and an external magnetic material The casing is composed of an upper pole shoe and a lower pole shoe respectively, and the upper pole piece is located above the lower pole piece along the optical axis direction, and the magnetic field of the objective lens is between the upper and lower pole pieces. Formed; the inner diameter of the upper pole piece is Φ1, and the inner diameter of the lower pole piece is Φ2. When Φ1≥Φ2, the magnetic field of the objective lens is concentrated between the pole pieces, which is a non-immersed magnetic lens; when Φ1≤Φ2, the magnetic field of the objective lens will A portion of the sample leaks, forming a semi-immersed lens.

In some embodiments, the electric lens 10 is composed of an upper pole piece of a magnetic lens 107, a sample stage 109, and a rear deflection device 108; the rear deflection device 108 and the sample stage 109 are respectively loaded with the same voltage or close to the voltage. The electric lens generates a deceleration field between the magnetic lens and the sample, which reduces the moving speed of the electron beam, so that when the electron beam reaches the sample, the energy of the falling point is lower.

The magnetic field generated by the magnetic lens 107 in the composite lens 11 and the electric field generated by the electric lens 10 form a composite electromagnetic field, which together converge the electron beams to ensure high resolution under low energy conditions. In the embodiment of the present invention, as shown in FIG. 6 , the converging ability at the same position on the composite objective lens 11 is inversely proportional to the kinetic energy of electrons. After being deflected by the electromagnetic cross-field analyzer 105, the electrons symmetrically distributed along the optical axis 110 are converged by the composite objective lens ₁₁ , and the deflection amount of the electrons with high energy is small; The angle θ ₂ between the trajectory of the electron and the lens, that is, θ ₁ >θ ₂ . At this time, the angle difference Δθ=θ ₁ -θ ₂ is formed by the off-axis deflection chromatic aberration caused by the electromagnetic cross-field analyzer 105 and the compound objective lens 11 acting together to deflect and converge electrons with different energies.

The mirror rear deflection device 108 is located in the space formed by the pole shoe hole Φ2 under the magnetic lens 107 . The deflection field generated by the mirror rear deflection device 108 is located below the magnetic field generated by the magnetic lens 107, or partially overlaps with the lower part of the magnetic field generated by the magnetic lens 107; the mirror rear deflection device 108 is used for the convergence The moving direction of the electron beam is such that the converged electron beam is obliquely incident on the sample to be tested on the sample stage 109 .

In some implementations, the mirror rear deflection device 108 is fixed on the lower pole shoe of the magnetic lens 107 with a ceramic seat, and is located in the space of the lower pole shoe hole of the magnetic lens. At the same time, the ceramic seat is used for electrically isolating the magnetic lens 107 and the rear deflection device 108 . When the magnetic lens 107 is a non-submerged magnetic lens, the deflection sensitivity of the deflection device 108 behind the mirror is large; when the magnetic lens 107 is a semi-submerged magnetic lens, the deflection sensitivity of the deflection device 108 behind the mirror Small.

In some implementations, the deflection device 108 behind the mirror is a multi-pole electric deflector composed of thin-sheet multi-lobe electrodes, such as 8-pole, 12-pole, 16-pole, 20-pole, and the like. The deflection device 108 behind the mirror is loaded with a voltage as an electrode of the electric lens 10; the structure of the eight-pole sheet electric deflector and the schematic diagram of the power supply of each electrode, as shown in Figure 7a, can be loaded on each electrode The voltage used to form the deflection field, the deflection electric field that forms the diode is used for electron beam deflection or fast scanning. The potentials corresponding to the eight electrodes are: V _y +aV _x , aV _y +V _x , -aV _y +V _x , -V _y +aV _x , -V _y -aV _x , -aV _y -V _x , aV _y -V _x , V _y -aV _x ; where, a is the voltage scaling factor V _y is the y-direction component of the voltage, and V _x is the x-direction component of the voltage. The structure of the twelve-pole sheet electric deflector and the schematic diagram of the power supply of each electrode are shown in Figure 7b. The voltage is applied to each electrode according to the pressing method and direction shown in Figure 7b to generate a deflection field and form a two-pole deflection electric field For electron beam deflection or fast scanning. The potentials corresponding to the twelve electrodes are: V _y , V _x , V _y , V _x , -V _y , -V _x , -V _y , -V _x , -V _y , -V _x , V _y , - V _x . Among them, V _y is the y-direction component of the voltage, and V _x is the x-direction component of the voltage.

The deflection device behind the mirror is to arrange the deflector behind or below the objective lens. The deflection device behind the mirror can change the movement direction of the electron beam, so that when the electron beam is obliquely incident on the sample to be tested, compared with the electron beam when the rear deflection device is not working The electron beam spot formed when it is incident on the sample to be tested will produce additional deflection aberration; when the inclination angle of the electron beam incident on the sample to be tested is greater than 10°, the deflection aberration is especially obvious. The principle and structure of the deflection device behind the mirror to realize the tilting of the electron beam are relatively simple. However, the deflection device after the mirror is usually located under the objective lens, which will occupy the precious space between the objective lens and the sample to be measured, resulting in the work between the objective lens and the sample to be measured. The distance cannot be small enough, reducing the resolution of the scanning electron microscope. In the embodiment of the present utility model, the mirror rear deflection device 108 is arranged at the position of the pole shoe, and the mirror rear deflection device 108 is extremely thin, flush with or slightly protruding from the lower end of the lower pole shoe of the magnetic lens 107, but occupies too much of the magnetic lens 107 The working distance between the objective lens and the sample to be tested ensures that the working distance between the objective lens and the sample to be tested is small enough to improve the resolution of the scanning electron microscope.

When the Wien analyzer is turned off, as shown in FIG. 8 , it is a schematic diagram of the deflection chromatic aberration generated by the rear deflection device 108 . The electron beams moving downward along the optical axis 110 are converged by the composite objective lens 11 and then deflected by the rear deflection device 108 to generate oblique electron beams. Since the amount of deflection of electrons is inversely proportional to the kinetic energy of electrons, that is, the amount of deflection of fast electrons is small, and the trajectory of electrons is closer to the optical axis 110 after being deflected by the deflection device 108 after being deflected by the mirror. The beam is incident on the sample on the sample stage 109 with _a deflection angle of α1 between the beam and the optical axis 110; the slow electron deflection amount is large, and the electron track is farther away from the optical axis 110 after being deflected by the deflector 108, and the electron The included angle between the trajectory before and after the deflection is α ₂ , that is, the electron beam is incident on the sample on the sample stage 109 in the direction in which the deflection angle between the electron beam and the optical axis 110 is α ₂ . Here, α ₁ >α ₂ ; after the electron beam is deflected by the deflector 108, the slow-moving electrons are farther away from the optical axis by an angle Δα than the fast-moving electrons, where Δα=α ₁ -α ₂ , the angle difference is The deflector is formed by the deflection chromatic aberration caused by the different deflection capabilities of electrons with different energies.

In the embodiment of the present invention, by adjusting the current value and voltage value of the composite objective lens 11, the initial electron beam emitted by the electron source 101 is focused on the surface of the sample to be tested; The voltage value on each electrode of the deflection device 108 behind the mirror, so that the electron beam can be obliquely incident on the surface of the sample to be measured at the required angle θ. In this process, the current value and the voltage value of the composite objective lens 11 can be fine-tuned, In order to keep the electron beam well focused on the sample to be tested, the deflection chromatic aberration caused by the rear deflection device 108 is determined. Afterwards, in the electromagnetic cross-field analyzer 105, the multipole magnetic deflector is loaded with a voltage and the multipole magnetic deflector is loaded with a current value, so that it works with the determined field of the objective lens to produce suitable off-axis chromatic aberration for electrons of different energies , as shown in FIG. 6 , the off-axis chromatic aberration produced by the composite objective lens 11 and the deflected chromatic aberration produced by the deflection device 108 behind the mirror can be made up for each other, thereby eliminating the deflection aberration produced by the deflecting electron beam by the deflector device 108 after the mirror, so that the electron beam can be The required angle θ is obliquely focused on the sample surface, and the area of the sample is scanned under the oblique angle to form a scanning electron beam image.

Embodiment two

The scanning electron microscope system provided by the second embodiment of the utility model is similar to the scanning electron microscope system provided by the first embodiment of the utility model, the difference is that the composition structure of the scanning electron microscope system provided by the second embodiment of the utility model, As shown in Figure 9 , it also includes a high-voltage tube 202; the high-voltage tube 202 is located between the upper pole piece of the magnetic lens 107 and the electron source that generates the initial electron beam incident to the scanning electron microscope system, and the high-voltage tube The central axis of 202 coincides with the optical axis. A higher voltage is loaded on the high-voltage tube 202, and the initial electron beam sent by the electron source 101 will maintain higher energy through the high-voltage tube 202, thereby reducing the influence of the space charge effect; the electric lens 10 is formed by the high-voltage tube 202 The lower end surface of the magnetic lens 107 is composed of the sample stage 109 and the mirror rear deflection device 108, and a decelerating electrostatic field is formed between the magnetic lens 107 and the sample to be tested. The electromagnetic cross-field analyzer 105 is located between the upper high-voltage pipe and the lower high-voltage pipe, and the central area of the electromagnetic cross-field analyzer 105 coincides with the optical axis 110. The electromagnetic cross-field analyzer 105 is composed of a multi-pole electric deflector and The multi-pole magnetic deflector is composed of multi-pole electric deflector and multi-pole magnetic deflector, and the high voltage is isolated by ceramics.

Embodiment three

Based on the scanning electron microscope system described in Embodiment 1 and Embodiment 2 above, Embodiment 3 of the present utility model also provides a sample detection method, an optional processing flow of the sample detection method, as shown in FIG. 10 , includes The following steps:

In step S101, the initial electron beam emitted by the electron source is focused and incident on the surface of the sample to be tested under the action of the composite objective lens.

In the embodiment of the present invention, before the initial electron beam is incident on the composite objective lens of the scanning electron microscope, the electromagnetic cross-field analyzer and the deflection device behind the mirror are first turned off. Turning off the electromagnetic cross-field analyzer means not loading the electromagnetic cross-field analyzer. Voltage and current, turning off the deflection device behind the mirror refers to not loading the deflection voltage for the deflection device behind the mirror; the electron source generates and emits an initial electron beam with a certain energy, and adjusts the current value and voltage value of the composite objective lens to make the initial electron beam pass through After the composite objective lens is focused and decelerated, it arrives at the sample to be measured with a low drop point energy, forming a very small focused beam spot. This process is a central focusing process of the electron beam, so that the initial electron beam forms a focused beam spot meeting the conditions on the surface of the sample to be tested.

Step S102 , the initial electron beam is incident on the sample to be tested at a set inclination angle under the action of the deflection device behind the mirror.

In some embodiments, under the condition that the electromagnetic cross-field analyzer is closed, a voltage is applied to the rear deflection device as a whole, as an electrode of the electric lens; in addition, each electrode of the rear deflection device is respectively loaded for Form the voltage of the deflection field, and form the deflection electric field of the two poles for electron beam deflection or fast scanning. By adjusting the deflection field generated by the deflection device behind the mirror, the converged electron beam is deflected, so that the electron beam is incident on the surface of the sample to be tested at a preset inclination angle. At this time, since the amount of deflection of the electrons by the deflection device behind the mirror is inversely proportional to the kinetic energy of the electrons, the deflection amount of the fast-moving electrons is small, and the trajectory of the electrons is closer to the optical axis after being deflected by the deflection device behind the mirror; The amount is large, and the electron trajectory is farther away from the optical axis after being deflected by the deflection device after the mirror. Slower electrons are farther from the optical axis than faster electrons. Therefore, compared with the centrally focused electron beam, the deflection device produces deflection chromatic aberration for electrons with different energies. The composite objective lens can be fine-tuned during this process to keep the electron beam well focused.

Step S103, adjusting the voltage and current values of the electromagnetic cross-field analyzer, so that the composite objective lens produces off-axis chromatic aberration to compensate the deflection chromatic aberration produced by the deflection device behind the mirror.

In some embodiments, the electric field and the magnetic field distribution produced by the electromagnetic field cross analyzer are close to or completely coincident, and the electromagnetic cross field analyzer is adjusted to generate an electric field and a magnetic field of a suitable size; the electromagnetic field cross analyzer has no effect on the electron beam whose energy is V , the electromagnetic field cross analyzer will deviate the electrons in the electron beams with energies V+ΔV and V-ΔV to both sides of the main optical axis, and the electrons deviated to both sides of the main optical axis will enter the paraxial area of the composite objective lens Off-axis chromatic aberration is generated after being converged by the composite objective lens; by adjusting the voltage and current of the electromagnetic cross-field analyzer, the off-axis chromatic aberration generated by the composite objective lens is used to compensate the deflection chromatic aberration generated by the deflection device behind the mirror until the image is clear, thereby eliminating The aberrations produced by the deflection device behind the mirror improve the resolution of scanning electron microscopes when viewing samples with an oblique electron beam.

It should be noted that the oblique incidence of the electron beam on the sample to be tested in the embodiments of the present invention means that the electron beam is not incident perpendicular to the surface of the sample to be tested.

The above is only a specific implementation mode of the present utility model, but the protection scope of the present utility model is not limited thereto. Any skilled person familiar with the technical field can easily think of changes or modifications within the technical scope disclosed by the utility model. Replacement should be covered within the protection scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims (10)

1. a scanning electron microscope system, is characterized in that, described scanning electron microscope system comprises: Composite objective lens composed of electric lens and magnetic lens; Located between the upper pole piece of the magnetic lens and the electron source that generates the initial electron beam incident to the scanning electron microscope system, the incident initial electron beam with the first energy moves along the optical axis, and the initial electron beam with the second energy an electromagnetic cross-field analyzer deflecting an initial electron beam to either side of the optical axis of said initial electron beam; The composite objective lens is used to converge the initial electron beams acting on the electromagnetic cross-field analyzer to form a converged electron beam; And a mirror rear deflection device located in the lower pole shoe hole of the magnetic lens, which changes the movement direction of the converged electron beam so that the converged electron beam is obliquely incident on the sample to be measured on the sample stage. 2. The scanning electron microscope system according to claim 1, characterized in that, the scanning electron microscope system further comprises: a high-voltage tube positioned between the upper pole piece of the magnetic lens and the electron source, the The central axis of the high pressure tube coincides with the optical axis. 3. The scanning electron microscope system according to claim 1 or 2, wherein the electromagnetic cross-field analyzer comprises: a multi-pole magnetic deflector and a multi-pole electric deflector. 4. scanning electron microscope system as claimed in claim 3 is characterized in that, the magnetic field distribution that described multipole magnetic deflector produces and the electric field distribution that described multipole electric deflector produces satisfy the first distribution condition; A distribution condition at least includes: proximity or coincidence. 5. The scanning electron microscope system according to claim 1 or 2, wherein the magnetic lens is a semi-immersed magnetic lens or a non-immersed magnetic lens excited by a current coil. 6 . The scanning electron microscope system according to claim 1 , wherein the electrical lens comprises: an upper pole piece of the magnetic lens, the rear deflection device and the sample stage. 7 . The scanning electron microscope system according to claim 2 , wherein the electric lens comprises: the lower end surface of the high-voltage tube, the sample stage, and the mirror rear deflection device. 7 . 8. The scanning electron microscope system according to claim 1 or 2, characterized in that, the deflection device behind the mirror is an electrostatic multipolar deflector. 9. The scanning electron microscope system of claim 8, wherein The mirror rear deflection device has a first voltage as an electrode of the electric lens. 10. The scanning electron microscope system according to claim 1 or 2, wherein the electromagnetic cross-field analyzer is a Wien analyzer.