A magnetic lens and charged particle beam device

Abstract

This invention discloses a magnetic lens and a charged particle beam device. The magnetic lens includes a first coil and a second coil coaxial with a central axis. The currents in the first and second coils originate from the same DC source, and the currents in the first and second coils are in opposite directions. The magnetomotive force (MTF) of the magnetic lens is adjusted by regulating the currents in the first and second coils. The total power of the first and second coils is equal to a preset value. This invention reduces the influence of current noise on the MMF, improves the magnetic field stability of the magnetic lens, and achieves precise and stable control of the charged particle beam. When the magnetic lens generates a MMF that meets the measurement requirements, the total power of the magnetic lens remains constant, ensuring stable lens temperature and preventing poor focusing of the charged particle beam due to thermal expansion and contraction of the magnetic lens. This guarantees the imaging quality of the sample and results in highly repeatable and reliable measurement results.

Description

Technical Field

[0001] This utility model relates to the field of electronic optics technology, and in particular to a magnetic lens and a charged particle beam device. Background Technology

[0002] With the continuous miniaturization of semiconductor devices, semiconductor devices on the order of tens of nanometers have become mainstream in recent years. In the production process of these semiconductor devices with fine structures, charged particle beam devices are widely used for defect detection of semiconductor devices due to their high resolution and ability to provide detailed images of the surface morphology of samples (e.g., wafers).

[0003] The working principle of charged particle beam devices is based on the interaction between the particle beam and the sample to generate signals, such as secondary electrons (SE) and backscattering electrons (BSE). These signals are collected by detectors and converted into images to reveal the microstructure and defects on the sample surface.

[0004] The charged particle beam device includes a magnetic lens. The magnetomotive force of the magnetic lens is adjusted by regulating the current flowing through it, ultimately achieving focused electron beam. The diameter of the irradiation area (beam spot diameter) formed by the electron beam on the sample surface determines the resolution of the charged particle beam device.

[0005] Fluctuations in current intensity cause temperature changes in the magnetic lens, resulting in thermal expansion and contraction. This expansion and contraction can alter the focal length and magnetic field distribution of the magnetic lens, leading to poor electron beam focusing and reduced image quality. Temperature-induced expansion and contraction also cause inconsistencies in measurement results, affecting repeatability and reliability. To compensate for the effects of thermal expansion and contraction, operators need to frequently adjust the parameters and position of the charged particle beam device, increasing the complexity and difficulty of operation.

[0006] The statements herein provide only background information relating to this invention and do not necessarily constitute prior art. Utility Model Content

[0007] The purpose of this invention is to provide a magnetic lens and charged particle beam device that can effectively reduce the influence of current noise on the magnetic lens, reduce the magnetic field noise generated by the magnetic lens, improve the stability of the magnetomotive force generated by the magnetic lens, and achieve precise and stable focusing of the charged particle beam. While generating a magnetomotive force that meets measurement requirements, the magnetic lens can also maintain a constant temperature, preventing changes in its performance due to thermal expansion and contraction, and ensuring the imaging quality of the sample.

[0008] To achieve the above objectives, this utility model provides a magnetic lens, comprising: a first coil and a second coil coaxial with a central axis;

[0009] The current in the first coil and the second coil comes from the same DC source, and the current in the first coil and the second coil are in opposite directions;

[0010] The magnetomotive force of the magnetic lens can be adjusted by regulating the current in the first coil and the second coil.

[0011] The total power of the first coil and the second coil is equal to a preset value.

[0012] Optionally, the magnetic lens further includes a first transistor;

[0013] The first end of the first coil is connected to the first end of the second coil; the second ends of the first coil and the second coil are electrically connected to the first transistor; the total current flowing through the first coil and the second coil is set by adjusting the first transistor.

[0014] Optionally, the magnetic lens further includes a second transistor and a third transistor;

[0015] The second transistor is electrically connected between the second end of the first coil and the first transistor; the third transistor is electrically connected between the second end of the second coil and the first transistor; the current flowing through the first coil and the current in the second coil are set by adjusting the second transistor and the third transistor.

[0016] Optionally, the first transistor, the second transistor, and the third transistor are all NMOS transistors;

[0017] The first end of the first coil and the first end of the second coil are electrically connected to the DC source;

[0018] The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is grounded.

[0019] Optionally, the first transistor, the second transistor, and the third transistor are all PMOS transistors;

[0020] The first end of the first coil and the first end of the second coil are electrically grounded;

[0021] The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is electrically connected to the DC source.

[0022] Optionally, the first transistor, the second transistor, and the third transistor are all N-type transistors;

[0023] The first end of the first coil and the first end of the second coil are electrically connected to the DC source;

[0024] The collector of the second transistor is connected to the second end of the first coil; the collector of the third transistor is connected to the second end of the second coil; the emitters of the second transistor and the third transistor are connected to the collector of the first transistor; the emitter of the first transistor is grounded.

[0025] Optionally, the first transistor, the second transistor, and the third transistor are all P-type transistors;

[0026] The first end of the first coil and the first end of the second coil are electrically grounded;

[0027] The collector of the second transistor is connected to the second end of the first coil; the collector of the third transistor is connected to the second end of the second coil; the emitter of the second transistor is connected to the collector of the first transistor; the emitter of the first transistor is electrically connected to the DC source.

[0028] Optionally, the first transistor, the second transistor, and the third transistor are all N-type JFETs;

[0029] The first end of the first coil and the first end of the second coil are electrically connected to the DC source;

[0030] The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is electrically grounded.

[0031] Optionally, the first transistor, the second transistor, and the third transistor are all P-type JFETs;

[0032] The first end of the first coil and the first end of the second coil are electrically connected to ground;

[0033] The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is electrically connected to the DC source.

[0034] Optionally, the first transistor, the second transistor, and the third transistor all operate in the saturation region.

[0035] Optionally, the first coil and the second coil are wound in a coaxial double-strand parallel manner.

[0036] Optionally, the first coil and the second coil have the same number of turns.

[0037] Optionally, the magnetic lens is a focusing lens.

[0038] Optionally, the magnetic lens is an objective lens.

[0039] This utility model also provides a charged particle beam device, comprising:

[0040] A charged particle source, configured to emit a beam of charged particles; and

[0041] The magnetic lens as described in this utility model.

[0042] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0043] This invention relates to a magnetic lens and charged particle beam device, which provides current from the same DC source to the first and second coils (coaxial with the first coil) of the magnetic lens. The currents in the first and second coils are in opposite directions, resulting in current noise (of various causes and unavoidable) that causes the first and second coils to generate magnetic field noises in opposite directions. Since the currents in the first and second coils originate from the same DC source, their current noises are correlated, and the magnetic field noises of the first and second coils can at least partially cancel each other out, thereby reducing the magnetic field noise generated by the magnetic lens. This invention significantly improves the stability of the magnetic field generated by the magnetic lens, enabling precise and stable control of the charged particle beam.

[0044] This invention uses a first transistor to adjust the total current of the first and second coils, and a second and third transistor to adjust the current in the first and second coils respectively. Ultimately, the total power of the first and second coils equals a preset value, and the magnetic lens generates a magnetomotive force that meets the measurement requirements. Because the total power of the first and second coils is constant, the magnetic lens maintains a constant temperature, preventing changes in the focal length and magnetic field distribution due to thermal expansion and contraction. This effectively avoids poor focusing of charged particle beams, ensures sample imaging quality, and results in highly repeatable and reliable measurement results.

[0045] In this invention, the first transistor, the second transistor, and the third transistor can take various forms, resulting in high adjustment accuracy and a simple adjustment method.

[0046] The magnetic lens of this invention has wide applications and can be used as a focusing lens or objective lens for charged particle beam devices, ensuring high resolution during imaging. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of a charged particle beam device.

[0048] Figure 2 for Figure 1 A schematic diagram of the structure of a magnetic lens.

[0049] Figure 3 This is a schematic diagram of the magnetic lens in Embodiment 1 of this utility model.

[0050] Figure 4 This is a schematic diagram of the magnetic lens in Embodiment 2 of this utility model.

[0051] Figure 5 This is a schematic diagram of the magnetic lens in Embodiment 3 of this utility model.

[0052] Figure 6 This is a schematic diagram of the magnetic lens in Embodiment 4 of this utility model.

[0053] Figure 7 This is a schematic diagram of the magnetic lens in Embodiment 5 of this utility model.

[0054] Figure 8 This is a schematic diagram of the magnetic lens in Embodiment Six of this utility model.

[0055] Figure 9 This is a schematic diagram of the magnetic lens in Embodiment 7 of this utility model.

[0056] Figure 10 This is a schematic diagram of the charged particle beam device of this utility model. Detailed Implementation

[0057] The magnetic lens and charged particle beam device proposed in this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this utility model will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, only for the purpose of conveniently and clearly illustrating the embodiments of this utility model. Please refer to the drawings to make the objectives, features, and advantages of this utility model more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this utility model. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives achieved by this utility model, should still fall within the scope of the technical content disclosed in this utility model.

[0058] Figure 1 A charged particle beam device 1 is shown, which generates charged particles (e.g., electrons, ions) through a charged particle source 110, accelerates the charged particles through an electric field or the like to form a charged particle beam 105, and precisely irradiates a designated location on the surface of a sample W. Detection signals are generated by the interaction between the charged particle beam 105 and the sample W. These detection signals are collected by a detector 130 and converted into images, which are then displayed by a display unit 140 to reveal the microstructure and defects on the surface of the sample W.

[0059] like Figure 1 As shown, the charged particle beam device 1 includes multiple magnetic lenses 120, such as a focusing lens 121 and an objective lens 122. Each magnetic lens 120 includes a coil arranged around the path of the charged particle beam 105, and the magnetomotive force of the magnetic lens 120 is adjusted by regulating the magnitude of the current flowing through the coil.

[0060] In the charged particle beam device 1, the spacing between the components changes with the temperature of the coil. This change alters the relative position between the charged particle source 110 and the sample W, causing the irradiation position of the charged particle beam 105 on the sample W to shift (a phenomenon called drift) or the focus to become blurred, thus adversely affecting the observation of the sample W.

[0061] Furthermore, changes in coil temperature can cause varying degrees of deformation in the magnetic lens 120. This deformation alters the focal length and magnetic field distribution of the magnetic lens 120, ultimately leading to poor focusing of the charged particle beam 105 on the sample W surface and reduced image quality. Moreover, changes in coil temperature can cause inconsistencies in measurement results, affecting the repeatability and reliability of the measurements. Therefore, while generating the required magnetomotive force, the magnetic lens 120 also needs to maintain a constant power to ensure that the heat generated by the magnetic lens 120 remains constant per unit time.

[0062] Figure 2 This is a schematic diagram of a magnetic lens 120, which contains coils 120a and 120b coaxially. The currents in coils 120a and 120b originate from DC power supplies 150a and 150b, respectively. The direction of the current in coil 120a can be switched to be the same as or opposite to the direction of the current in coil 120b. In this way, the magnetic field strengths generated by coils 120a and 120b can be added together or subtracted, thus applying different magnetomotive forces to the entire magnetic lens 120. Throughout this process, the heat generated by the magnetic lens 120 remains constant.

[0063] However, the potential of the grounding wires of DC power supplies 150a and 150b is usually unstable and accompanied by voltage noise, which inevitably causes current noise in the coils 120a and 120b. The external electric field in the environment surrounding coils 120a and 120b may also generate current noise in coils 120a and 120b, which in turn leads to magnetic field noise in the magnetic lens 120.

[0064] Under the premise of ensuring a constant heat generation of the magnetic lens 120, the ideal currents configured for coils 120a and 120b are denoted as I1 and I2, respectively. Let I... N1 I N2 I represents the current noise in coil 120a and coil 120b, respectively. N1 I N2 It changes over time, and its size and direction are unpredictable.

[0065] Let μ0 represent the permeability of free space, B1 and B2 represent the magnetomotive forces generated by coils 120a and 120b respectively, and B represent the magnetomotive force output by magnetic lens 120. The number of turns of coils 120a and 120b is N. The expressions for magnetomotive forces B1, B2 and B are as follows:

[0066] B1=μ0×N×(I1+I N1 (1)

[0067] B2=μ0×N×(I2+I N2 (2)

[0068]

[0069] Since the currents in coils 120a and 120b come from different DC power supplies, the current noise I... N1 With current noise I N2 If there is no correlation, then the magnetic field noise generated by coil 120a (due to current noise I) N1 The magnetic field noise (caused by) coil 120b and generated by the current noise I N2 The magnetic field noise B′ caused by the lack of correlation between the two cannot cancel each other out.

[0070]

[0071] The magnetic field noise B′ is relatively large, which can easily make the sample image blurry or flicker, and may even affect the resolution of the charged particle beam device 1, greatly affecting the measurement effect.

[0072] Example 1

[0073] To solve the above-mentioned technical problems, this utility model provides a magnetic lens 220, such as... Figure 3 As shown, the magnetic lens 220 includes a first coil 220a and a second coil 220b (coaxial with the first coil 220a). In this embodiment, both the first coil 220a and the second coil 220b have N turns. In other embodiments, the number of turns of the first coil 220a and the second coil 220b may be different. The current in the first coil 220a and the second coil 220b comes from the same DC source 250. As an example, the DC source 250 can be a voltage source, outputting a constant voltage, and the output current can be determined by an external circuit. Figure 3 As shown, the first end of the first coil 220a and the first end of the second coil 220b are connected to the same DC source 250 (e.g., a voltage source), and the second end of the first coil 220a is connected to the second end of the second coil 220b. The currents in the first coil 220a and the second coil 220b are in opposite directions. By adjusting the currents in the first coil 220a and the second coil 220b, the magnetomotive force of the magnetic lens 220 is adjusted. The total power of the first coil 220a and the second coil 220b is equal to a preset value P. That is, the magnetic lens 220 has a constant power P, and the heat generated by the magnetic lens 220 per unit time is constant.

[0074] Let E represent the magnetomotive force that the magnetic lens 220 theoretically needs to generate. Under the premise that the magnetic lens 220 has a constant power P, the current values ​​configured for the first coil 220a and the second coil 220b are denoted as I1 and I2, respectively.

[0075] The resistances of the first coil 220a and the second coil 220b are denoted as R1 and R2, respectively.

[0076]

[0077] Solving the system of equations formed by formulas (5) and (6) above, we get:

[0078]

[0079] In a preferred embodiment, R1 = R2 = R, then I1 and I2 are simplified to:

[0080]

[0081] Let IN1 and IN2 represent the current noise in the first coil 220a and the second coil 220b, respectively. Since the currents in the first coil 220a and the second coil 220b originate from the same DC source 250, the current noise IN1 and the current noise IN2 are correlated. The currents in the first coil 220a and the second coil 220b are in opposite directions; therefore, the current noise IN1 and the current noise IN2 can cause the first coil 220a and the second coil 220b to generate magnetic field noises in opposite directions, and the magnetic field noise of the first coil 220a and the magnetic field noise of the second coil 220b can at least partially cancel each other out. This reduces the magnetic field noise generated by the magnetic lens 220.

[0082] In this embodiment, the first coil 220a and the second coil 220b are wound in a coaxial double-strand manner. Compared with setting the first coil 220a and the second coil 220b separately, the coaxial double-strand winding method can make the magnetic field distribution of the magnetic lens 220 more uniform, and the interaction between the first coil 220a and the second coil 220b is stronger.

[0083] When the current noise IN1 and IN2 are related, the actual magnetomotive force generated by the magnetic lens 220 is E1 and the magnetic field noise is E1′.

[0084] E1=μ0×N×(I1-I2+|IN1-IN2 (11)

[0085] E1′=μ0×N×|IN1-IN2| (12)

[0086] The deviation between E1 and the theoretical magnetomotive force E is E1′, but E1′ is small. This deviation is within a reasonable range, which allows the charged particle beam device to meet the measurement requirements.

[0087] If the first coil 220a and the second coil 220b are powered by different DC power supplies, the current noise IN1 and the current noise IN2 are uncorrelated. Even if the current directions in the first coil 220a and the second coil 220b are opposite, the magnetic field noises generated by the first coil 220a and the second coil 220b cannot cancel each other out.

[0088] At this time, the magnetomotive force actually generated by the magnetic lens 220 is denoted as E2, and the magnetic field noise is E2'.

[0089]

[0090] Obviously, E1' < E2'. Therefore, through the present utility model, the magnetic field noise generated by the magnetic lens 220 can be significantly reduced, the stability of the magnetomotive force generated by the magnetic lens 220 can be improved, and precise and stable control of the charged particle beam can be achieved.

[0091] The present utility model supplies currents from the same DC source 250 to the first coil 220a and the second coil 220b of the magnetic lens 220, and the current directions in the first coil 220a and the second coil 220b are opposite. This makes the first coil 220a and the second coil 220b generate magnetic field noises in opposite directions respectively, and the current noises of the first coil 220a and the second coil 220b are correlated. Therefore, the magnetic field noise of the first coil 220a and the magnetic field noise of the second coil 220b can at least partially cancel each other out, thereby reducing the magnetic field noise generated by the magnetic lens 220. The present utility model can effectively reduce the influence of the current noise on the magnetic lens 220, significantly improve the stability of the magnetic field generated by the magnetic lens 220, and achieve precise and stable control of the charged particle beam.

[0092] The magnetic lens 220 of the present utility model is widely used and can be used as a focusing lens or an objective lens of a charged particle beam device. Since the total power of the first coil 220a and the second coil 220b is constant, when the magnetic lens 220 generates a magnetomotive force that meets the measurement requirements, the temperature can always be kept constant, avoiding the change of the focal length and magnetic field distribution of the magnetic lens 220 due to thermal expansion and contraction, effectively avoiding poor focusing of the charged particle beam, ensuring that the charged particle beam device has a high resolution during imaging, the imaging quality of the sample is high, and the measurement results have high repeatability and reliability.

[0093] Embodiment 2

[0094] The present utility model, as Figure 4As shown, the total current flowing through the first coil 220a and the second coil 220b is set by the first transistor 261, and the current flowing through the first coil 220a and the second coil 220b is set by adjusting the second transistor 262 and the third transistor 263. The first end of the first coil is connected to the first end of the second coil, the second transistor is electrically connected between the second end of the first coil and the first transistor, and the third transistor is electrically connected between the second end of the second coil and the first transistor.

[0095] In this embodiment, the first transistor 261, the second transistor 262, and the third transistor 263 are all NMOS (N-channel Metal-Oxide-Semiconductor) transistors, and all three transistors operate in the saturation region.

[0096] like Figure 4 As shown, the first end of the first coil 220a and the first end of the second coil 220b are electrically connected to the DC source 250. For example, the DC source 250 can be a voltage source. The drain D of the second transistor 262 is connected to the second end of the first coil 220a, and the drain D of the third transistor 263 is connected to the second end of the second coil 220b. The sources S of the second transistor 262 and the third transistor 263 are connected to the drain D of the first transistor 261, and the source S of the first transistor 261 is grounded.

[0097] Let I D The value represents the drain current of the NMOS transistor, μ represents the electron mobility, and C represents the drain current. ox V represents the capacitance density of the gate oxide layer, W represents the width of the NMOS transistor (the distance between the source and drain), L represents the length of the NMOS transistor (the length of the gate G), and V represents the capacitance density of the gate oxide layer. GS V represents the gate-source voltage of an NMOS transistor. T This represents the threshold voltage at which the gate (G) and source (S) of an NMOS transistor are turned on. D The expression is as follows:

[0098]

[0099] In formula (15), μ and C ox W, L and V T All are constants, indicating that the drain current I of the NMOS transistor is constant. D With gate-source voltage V GS Positive correlation.

[0100] Please refer to Figure 4The source S of the first transistor 261 is grounded. The gate-source voltage of the first transistor 261 can be adjusted by adjusting the gate voltage V1 of the first transistor 261, thereby adjusting the drain current of the first transistor 261 (that is, the total current of the first coil 220a and the second coil 220b).

[0101] It should be noted that when the first transistor 261 operates in the saturation region, its gate voltage V1 is not used to turn the first transistor 261 on or off. The gate voltage V1 does not control the presence or absence of the drain current, but rather controls the magnitude of the drain current. That is, the gate voltage V1 is used to control the conduction level of the first transistor 261, which determines the total current flowing through the first coil 220a and the second coil 220b.

[0102] Similarly, by adjusting the gate voltage V2 of the second transistor 262, the gate-source voltage of the second transistor 262 can be adjusted, thereby adjusting the drain current of the second transistor 262 (i.e., the current I1 in the first coil 220a). By adjusting the gate voltage V3 of the third transistor 263, the gate-source voltage of the third transistor 263 can be adjusted, thereby adjusting the drain current of the third transistor 263 (i.e., the current I2 in the second coil 220b).

[0103] The above adjustment process can be visualized as:

[0104] The circuit is equivalent to a water pipe, and the first transistor 261, the second transistor 262, and the third transistor 263 are equivalent to the first faucet, the second faucet, and the third faucet on the water pipe. The first faucet is located on the main pipe and is used to control the total flow rate through the first and second faucets. First, the opening degree of the first faucet is adjusted (to obtain current I), and then the opening degrees of the second and third faucets are adjusted respectively (to obtain currents I1 and I2).

[0105] The first transistor 261, the second transistor 262, and the third transistor 263 have high adjustment accuracy, simple adjustment method, and low economic cost.

[0106] Example 3

[0107] Figure 5 This is a schematic diagram of the magnetic lens 220 in Embodiment 3 of this utility model. Figure 5 As shown, the first transistor 261, the second transistor 262, and the third transistor 263 are all PMOS (P-channel Metal-Oxide-Semiconductor Field-Effect Transistor). In this embodiment, the first transistor 261, the second transistor 262, and the third transistor 263 all operate in the saturation region.

[0108] like Figure 5 As shown, the first terminal of the first coil 220a and the first terminal of the second coil 220b are electrically grounded. The drain D of the second transistor 262 is connected to the second terminal of the first coil 220a, and the drain D of the third transistor 263 is connected to the second terminal of the second coil 220b. The source S of the second transistor 262 and the source S of the third transistor 263 are connected to the drain D of the first transistor 261, and the source S of the first transistor 261 is electrically connected to the DC source 250. For example, the DC source 250 may be a voltage source.

[0109] Let I D The value represents the drain current of the PMOS transistor, μ represents the electron mobility, and C represents the drain current of the PMOS transistor. ox V represents the capacitance density of the gate oxide layer, W represents the width of the PMOS transistor (the distance between the source and drain), L represents the length of the PMOS transistor (the length of the gate G), and V represents the capacitance density of the gate oxide layer. GS V represents the gate-source voltage of a PMOS transistor. T This represents the threshold voltage at which the gate (G) and source (S) of a PMOS transistor are turned on. D The expression is as follows:

[0110]

[0111] In formula (17), μ and C ox W, L and V T Both are constants, indicating that the drain current I of the PMOS transistor is constant. D With gate-source voltage V GS Positive correlation.

[0112] Please refer to Figure 5 The source voltage of the first transistor 261 is equal to the output voltage of the DC source 250. By adjusting the gate voltage V1 of the first transistor 261, the gate-source voltage of the first transistor 261 can be adjusted, thereby adjusting the drain current of the first transistor 261, so that the total current of the first coil 220a and the second coil 220b is I.

[0113] Similarly, by adjusting the gate voltage V2 of the second transistor 262, the gate-source voltage of the second transistor 262 can be adjusted, thereby adjusting the drain current of the second transistor 262 (i.e., the current I1 in the first coil 220a). By adjusting the gate voltage V3 of the third transistor 263, the gate-source voltage of the third transistor 263 can be adjusted, thereby adjusting the drain current of the third transistor 263 (i.e., the current I2 in the second coil 220b).

[0114] Example 4

[0115] Figure 6This is a schematic diagram of the magnetic lens 220 in Embodiment 4 of this utility model. Figure 6 As shown, the first transistor 261, the second transistor 262, and the third transistor 263 are all N-type transistors. In this embodiment, the first transistor 261, the second transistor 262, and the third transistor 263 all operate in the saturation region (also known as the saturation state).

[0116] like Figure 6 As shown, the first end of the first coil 220a and the first end of the second coil 220b are electrically connected to the DC source 250. For example, the DC source 250 can be a voltage source. The collector C of the second transistor 262 is connected to the second end of the first coil 220a, and the collector C of the third transistor 263 is connected to the second end of the second coil 220b. The emitters E of the second transistor 262 and the third transistor 263 are connected to the collector C of the first transistor 261, and the emitter E of the first transistor 261 is grounded.

[0117] When an N-type transistor operates in the saturation region, the collector current I... C The formula is:

[0118]

[0119] In formula (17), Is is the saturation current, which is an inherent parameter of the N-type transistor. BE It is the voltage between the base (B) and the emitter (E), V T Let I be the thermal voltage (which is constant). n is the emission coefficient. According to formula (17), the collector current I... C With voltage V BE Positive correlation; the voltage V can be adjusted by regulating the base voltage of the N-type transistor. BE This, in turn, adjusts the collector current I. C .

[0120] Please refer to Figure 6 The emitter E of the first transistor 261 is grounded. By adjusting the base voltage V1 of the first transistor 261, the voltage between the base B and the emitter E of the first transistor 261 can be adjusted, thereby adjusting the collector current of the first transistor 261 (that is, the total power of the first coil 220a and the second coil 220b).

[0121] It should be noted that when the first transistor 261 operates in the saturation region, its base voltage V1 is not used to turn the first transistor 261 on or off. The base voltage V1 does not control the "on" or "off" of the collector current, but rather controls the "large" or "small" of the collector current. That is, the base voltage V1 is used to control the conduction level of the first transistor 261, and this conduction level determines the magnitude of the total power passing through the first coil 220a and the second coil 220b.

[0122] Similarly, by adjusting the base voltage V2 of the second transistor 262, the voltage between the base (B) and emitter (E) of the second transistor 262 can be adjusted, thereby adjusting the collector current of the second transistor 262 (i.e., the current I1 in the first coil 220a). By adjusting the base voltage V3 of the third transistor 263, the voltage between the base (B) and emitter (E) of the third transistor 263 can be adjusted, thereby adjusting the collector current of the third transistor 263 (i.e., the current I2 in the second coil 220b).

[0123] Example 5

[0124] Figure 7 This is a schematic diagram of the magnetic lens 220 in Embodiment 5 of this utility model. Figure 7 As shown, the first transistor 261, the second transistor 262, and the third transistor 263 are all P-type transistors. In this embodiment, the first transistor 261, the second transistor 262, and the third transistor 263 all operate in the saturation region (saturation state).

[0125] like Figure 7 As shown, the first end of the first coil 220a and the first end of the second coil 220b are electrically grounded. The collector C of the second transistor 262 is connected to the second end of the first coil 220a. The collector C of the third transistor 263 is connected to the second end of the second coil 220b. The emitter E of the second transistor 262 is connected to the collector C of the first transistor 261. The emitter E of the first transistor 261 is electrically connected to the DC source 250. For example, the DC source 250 may be a voltage source.

[0126] When a P-type transistor operates in the saturation region, the collector current I... C The formula is:

[0127]

[0128] In formula (18), Is is the saturation current, which is an inherent parameter of the P-type transistor. BE It is the voltage between the base (B) and the emitter (E), V T Let I be the thermal voltage (which is constant). n is the emission coefficient. According to formula (18), the collector current I... C With voltage V BE Positive correlation; the voltage V can be adjusted by regulating the base voltage of the P-type transistor. BE This, in turn, adjusts the collector current I. C .

[0129] The voltage between the base B and emitter E of the first transistor 261 can be adjusted by adjusting the base voltage V1 of the first transistor 261, thereby adjusting the collector current of the first transistor 261 (that is, the total power of the first coil 220a and the second coil 220b).

[0130] Similarly, by adjusting the base voltage V2 of the second transistor 262, the voltage between the base (B) and emitter (E) of the second transistor 262 can be adjusted, thereby adjusting the collector current of the second transistor 262 (i.e., the current I1 in the first coil 220a). By adjusting the base voltage V3 of the third transistor 263, the voltage between the base (B) and emitter (E) of the third transistor 263 can be adjusted, thereby adjusting the collector current of the third transistor 263 (i.e., the current I2 in the second coil 220b).

[0131] Example 6

[0132] Figure 8 This is a schematic diagram of the magnetic lens 220 in Embodiment Six of this utility model. Figure 8 As shown, the first transistor 261, the second transistor 262, and the third transistor 263 are all N-type JFETs (Junction Field-Effect Transistors). In this embodiment, the first transistor 261, the second transistor 262, and the third transistor 263 all operate in the saturation region.

[0133] like Figure 8 As shown, the first end of the first coil 220a and the first end of the second coil 220b are electrically connected to the DC source 250. For example, the DC source 250 can be a voltage source. The drain D of the second transistor 262 is connected to the second end of the first coil 220a, and the drain D of the third transistor 263 is connected to the second end of the second coil 220b. The source S of the second transistor 262 and the source S of the third transistor 263 are connected to the drain D of the first transistor 261, and the source S of the first transistor 261 is electrically grounded.

[0134] When the N-type JFET is operating in the saturation region, the drain current I D The calculation formula is:

[0135]

[0136] In formula (19), IDSS is the maximum drain current of the N-type JFET, also known as the saturation current (which is an inherent parameter of the N-type JFET). V GS VP is the gate-source voltage, and VP is the pinch-off voltage (also known as the threshold voltage). According to formula (19), the drain current I... D With gate-source voltage V GSPositive correlation means that the gate-source voltage V can be adjusted by regulating the gate voltage of the N-type JFET. GS This adjusts the drain current I. D .

[0137] Please refer to Figure 8 In this embodiment, the gate-source voltage of the first transistor 261 can be adjusted by adjusting the gate voltage V1 of the first transistor 261, thereby adjusting the drain current of the first transistor 261 (that is, the total power of the first coil 220a and the second coil 220b).

[0138] Similarly, by adjusting the gate voltage V2 of the second transistor 262, the gate-source voltage of the second transistor 262 can be adjusted, thereby adjusting the drain current of the second transistor 262 (i.e., the current I1 in the first coil 220a). By adjusting the gate voltage V3 of the third transistor 263, the gate-source voltage of the third transistor 263 can be adjusted, thereby adjusting the drain current of the third transistor 263 (i.e., the current I2 in the second coil 220b).

[0139] Example 7

[0140] Figure 9 This is a schematic diagram of the magnetic lens 220 in Embodiment 7 of this utility model. Figure 9 As shown, the first transistor 261, the second transistor 262, and the third transistor 263 are all P-type JFETs. In this embodiment, the first transistor 261, the second transistor 262, and the third transistor 263 all operate in the saturation region.

[0141] like Figure 9 As shown, the first end of the first coil 220a and the first end of the second coil 220b are electrically connected to ground. The drain D of the second transistor 262 is connected to the second end of the first coil 220a. The drain D of the third transistor 263 is connected to the second end of the second coil 220b. The sources S of the second transistor 262 and the third transistor 263 are connected to the drain D of the first transistor 261. The source S of the first transistor 261 is electrically connected to the DC source 250. For example, the DC source 250 may be a voltage source.

[0142] When the P-type JFET is operating in the saturation region, the drain current I D The calculation formula is:

[0143]

[0144] In formula (20), IDSS is the maximum drain current of the P-type JFET, V GS VP is the gate-source voltage, and VP is the pinch-off voltage (also known as the threshold voltage). According to formula (20), the drain current I... D With gate-source voltage VGS Positive correlation means that the gate-source voltage V can be adjusted by regulating the gate voltage of the P-type JFET. GS This adjusts the drain current I. D .

[0145] Please refer to Figure 9 In this embodiment, the gate-source voltage of the first transistor 261 can be adjusted by adjusting the gate voltage V1 of the first transistor 261, thereby adjusting the drain current of the first transistor 261 (that is, the total power of the first coil 220a and the second coil 220b).

[0146] Similarly, by adjusting the gate voltage V2 of the second transistor 262, the gate-source voltage of the second transistor 262 can be adjusted, thereby adjusting the drain current of the second transistor 262 (i.e., the current I1 in the first coil 220a). By adjusting the gate voltage V3 of the third transistor 263, the gate-source voltage of the third transistor 263 can be adjusted, thereby adjusting the drain current of the third transistor 263 (i.e., the current I2 in the second coil 220b).

[0147] This invention also provides a charged particle beam device, such as... Figure 10 As shown, it includes:

[0148] A charged particle source 210 is configured to emit a charged particle beam 205; and a magnetic lens 220 as described in any of the preceding embodiments. The charged particle beam 205 is precisely irradiated onto a designated location on the surface of the sample W by the magnetic lens 220. The charged particle beam 205 interacts with the sample W to generate detection signals, which are collected by the detector 230 and converted into images, and displayed by the display unit 240 to reveal the microstructure and defects on the surface of the sample W.

[0149] Figure 10 In the middle, the magnetic lens 220 located at the top is the focusing lens, and the magnetic lens 220 located at the bottom is the objective lens.

[0150] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0151] In the description of this utility model, it should be understood that the terms "center," "height," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0152] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0153] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0154] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above content. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A magnetic lens, characterized in that, include: The first and second coils are on the same central axis; The current in the first coil and the second coil comes from the same DC source, and the current in the first coil and the second coil are in opposite directions; The magnetomotive force of the magnetic lens can be adjusted by regulating the current in the first coil and the second coil. The total power of the first coil and the second coil is equal to a preset value.

2. The magnetic lens as described in claim 1, characterized in that, It also includes the first transistor; The first end of the first coil is connected to the first end of the second coil; the second ends of the first coil and the second coil are electrically connected to the first transistor; the total current flowing through the first coil and the second coil is set by adjusting the first transistor.

3. The magnetic lens as described in claim 2, characterized in that, It also includes a second transistor and a third transistor; The second transistor is electrically connected between the second end of the first coil and the first transistor; the third transistor is electrically connected between the second end of the second coil and the first transistor; the current flowing through the first coil and the current in the second coil are set by adjusting the second transistor and the third transistor.

4. The magnetic lens as described in claim 3, characterized in that, The first transistor, the second transistor, and the third transistor are all NMOS transistors; The first end of the first coil and the first end of the second coil are electrically connected to the DC source; The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor. The source of the first transistor is grounded.

5. The magnetic lens as described in claim 3, characterized in that, The first transistor, the second transistor, and the third transistor are all PMOS transistors; The first end of the first coil and the first end of the second coil are electrically grounded; The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is electrically connected to the DC source.

6. The magnetic lens as described in claim 3, characterized in that, The first transistor, the second transistor, and the third transistor are all N-type transistors; The first end of the first coil and the first end of the second coil are electrically connected to the DC source; The collector of the second transistor is connected to the second end of the first coil; the collector of the third transistor is connected to the second end of the second coil; the emitters of the second transistor and the third transistor are connected to the collector of the first transistor; the emitter of the first transistor is grounded.

7. The magnetic lens as described in claim 3, characterized in that, The first transistor, the second transistor, and the third transistor are all P-type transistors; The first end of the first coil and the first end of the second coil are electrically grounded; The collector of the second transistor is connected to the second end of the first coil; the collector of the third transistor is connected to the second end of the second coil; the emitter of the second transistor is connected to the collector of the first transistor; the emitter of the first transistor is electrically connected to the DC source.

8. The magnetic lens as described in claim 3, characterized in that, The first transistor, the second transistor, and the third transistor are all N-type JFETs; The first end of the first coil and the first end of the second coil are electrically connected to the DC source; The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is electrically grounded.

9. The magnetic lens as described in claim 3, characterized in that, The first transistor, the second transistor, and the third transistor are all P-type JFETs; The first end of the first coil and the first end of the second coil are electrically connected to ground; The drain of the second transistor is connected to the second terminal of the first coil; the drain of the third transistor is connected to the second terminal of the second coil; the source of the second transistor and the source of the third transistor are connected to the drain of the first transistor; the source of the first transistor is electrically connected to the DC source.

10. The magnetic lens according to any one of claims 4-9, characterized in that, The first transistor, the second transistor, and the third transistor all operate in the saturation region.

11. The magnetic lens as claimed in claim 1, characterized in that, The first coil and the second coil are wound together in a coaxial double-strand manner.

12. The magnetic lens as claimed in claim 1, characterized in that, The first coil and the second coil have the same number of turns.

13. The magnetic lens as claimed in claim 1, characterized in that, The magnetic lens is a focusing lens.

14. The magnetic lens as claimed in claim 1, characterized in that, The magnetic lens is the objective lens.

15. A charged particle beam device, characterized in that, include: A charged particle source, configured to emit a beam of charged particles; and The magnetic lens as described in any one of claims 1 to 14.

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