An electron beam metrology device
By using an electric lens and an electrostatic deflector in the electron beam measurement device, the problem of low measurement efficiency caused by the magnetic lens was solved, and faster beam current adjustment and better imaging results were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGFANG JINGYUAN ELECTRON LTD
- Filing Date
- 2023-06-29
- Publication Date
- 2026-07-21
Smart Images
Figure CN116989707B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electron beam measurement technology, and in particular to an electron beam measurement device. Background Technology
[0002] As integrated circuit manufacturing processes enter the nanometer scale, the measurement of critical dimensions in the production line exceeds the coverage of optical measurement. Since the spatial resolution of electron beam measurement devices can reach about 1nm, electron beam critical dimension measurement devices (CD-SEM) are playing an increasingly important role in semiconductor chip production.
[0003] However, in existing electron beam measurement devices, after the electrons emitted by the electron gun are accelerated, a magnetic lens is required for beam current adjustment. During beam current adjustment, due to the existence of hysteresis effect, the consistency between the excitation change and the magnetic field change of the magnetic coil of the magnetic lens is poor. In addition, the time constant of the inductor-resistor circuit of the magnetic lens is large, which leads to a long response time for beam current adjustment of the magnetic lens. In other words, the measurement efficiency of existing electron beam measurement devices is low. Summary of the Invention
[0004] This application provides an electron beam measurement device to solve the technical problem of low measurement efficiency in existing electron measurement devices.
[0005] The present invention provides an electron beam measurement device, which includes an electron gun, an electric lens, a magnetic lens, a deflector, an objective lens, and an electron detector;
[0006] An electron gun is used to generate an electron beam; an electric lens is used to generate an electric field to focus the electron beam for the first time; a magnetic lens is used to generate a magnetic field to focus the electron beam for the second time; a deflector is used to deflect the electron beam to scan the wafer; an objective lens is used to focus the electron beam onto the wafer so that the focused electron beam bombards the wafer to generate an electronic signal; and an electron detector is used to perform imaging based on the electronic signal.
[0007] Preferably, the electronic signal includes a secondary electronic signal and / or a backscattered electronic signal.
[0008] Preferably, the electron lens includes a first electrode plate, a second electrode plate, and a third electrode plate stacked and spaced apart; the first electrode plate, the second electrode plate, and the third electrode plate together form a converging channel, which is used to receive the electron beam and cause the electron beam to converge for the first time.
[0009] Preferably, the first electrode plate, the second electrode plate, and the third electrode plate are all annular plates; insulating positioning elements are respectively provided between the first electrode plate and the second electrode plate and between the second electrode plate and the third electrode plate; the first electrode plate, the second electrode plate, and the third electrode plate are provided with positioning grooves that cooperate with the insulating positioning elements so that the first electrode plate, the second electrode plate, and the third electrode plate are coaxially arranged.
[0010] Preferably, the distance between the first electrode and the second electrode is equal to the distance between the second electrode and the third electrode; when the electric lens is working, the first electrode and the third electrode are configured to be connected to zero potential, and the second electrode is configured to be connected to a non-zero potential.
[0011] Preferably, the insulating positioning element is made of one or more of ceramic, glass, or mica; and / or, the insulating positioning element is spherical in shape.
[0012] Preferably, the number of insulating positioning elements is even, and they are symmetrically distributed on both sides of the second electrode plate.
[0013] Preferably, there are 6 insulating positioning elements, which are symmetrically distributed on both sides of the second electrode plate.
[0014] Preferably, the deflector is an electrostatic deflector used to generate an electric field to deflect the electron beam; the electrostatic deflector is disposed on the upper side of the objective lens along the imaging optical axis; and / or the electrostatic deflector is disposed on the lower side of the objective lens along the imaging optical axis.
[0015] Preferably, the electric field direction of the electrostatic deflector is perpendicular to the imaging optical axis of the objective lens; the electrostatic deflector has at least one electrode plate in the direction of the imaging optical axis.
[0016] Preferably, each electrode layer includes at least two sets of electrode groups with electric field directions perpendicular to each other.
[0017] Preferably, the number of all electrode groups is even.
[0018] Preferably, the electron beam measurement device further includes an adjustment element; the adjustment element is disposed between the electric lens and the magnetic lens and is used to select and modulate the electron beam; the adjustment element is provided with multiple adjustment holes of different sizes, and the adjustment element is configured such that one of the adjustment holes moves into the electron beam path to select the electron beam.
[0019] Preferably, the electron beam measurement device further includes an electron beam accelerating plate and an alignment coil; the electron beam accelerating plate is disposed between the electron gun and the electron lens, and is used to accelerate the electron beam; the alignment coil is disposed between the magnetic lens and the objective lens, and is used to make the imaging optical axis of the electron beam coincide with that of the objective lens.
[0020] In summary, the electron beam measurement device provided in this application has at least the following beneficial effects:
[0021] This invention provides an electron beam measurement device, comprising an electron gun, an electric lens, a magnetic lens, a deflector, an objective lens, and an electron detector. The electron gun generates an electron beam; the electric lens generates an electric field for initial focusing of the electron beam; the magnetic lens generates a magnetic field for secondary focusing of the electron beam; the deflector deflects the electron beam to scan a wafer; the objective lens focuses the electron beam onto the wafer so that the focused electron beam bombards the wafer to generate an electron signal; and the electron detector performs imaging based on the electron signal. In this application, since there is no corresponding hysteresis effect in the electric field when excitation is applied to the electric lens, good consistency between excitation switching and electric field changes can be ensured. Furthermore, the time constant calculated from the capacitance and resistance of the electric field of the electric lens is much lower than the time constant calculated from the inductance and resistance of the magnetic coil of the magnetic lens. Therefore, by using the electric lens for the first focusing of the electron beam, not only can the consistency between the excitation change and the field force change be ensured, but the excitation switching time can also be shortened, improving the efficiency of beam current regulation. Attached Figure Description
[0022] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 A schematic diagram of an electron beam measurement device provided for an embodiment of this application;
[0024] Figure 2 This is a schematic diagram of the structure of an electric lens provided for an embodiment of this application.
[0025] The attached figures are labeled as follows:
[0026] 101. Electron gun; 102. Electron beam accelerator plate; 103. Electron lens; 104. Adjustment element; 105. Magnetic lens; 106. Centering coil; 107. Electron detector; 108. Objective lens; 109. Deflector; 110. Wafer; 201. First electrode plate; 202. Second electrode plate; 203. Third electrode plate; 204. Insulating positioning element. Detailed Implementation
[0027] In the description of this application, it should be understood that the use of terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" to indicate orientation or positional relationship, unless otherwise specified, is understood to be based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description, and does 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 application.
[0028] Furthermore, features specified with "first" or "second" for descriptive purposes only should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Features specified with "first" or "second" may explicitly or implicitly include at least one of the specified features. The description of "multiple" generally means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0029] In this application, unless otherwise explicitly specified and limited, terms such as "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 be 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 application based on the specific circumstances.
[0030] In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0031] Please refer to Figure 1 As shown, this application provides an electron beam measurement device, including an electron gun 101, an electric lens 103, a magnetic lens 105, a deflector 109, an objective lens 108, and an electron detector 107.
[0032] Electron gun 101 is used to generate an electron beam; electric lens 103 is used to generate an electric field to focus the electron beam for the first time; magnetic lens 105 is used to generate a magnetic field to focus the electron beam for the second time; deflector 109 is used to deflect the electron beam to scan the wafer 110; objective lens 108 is used to focus the electron beam onto the wafer 110 so that the focused electron beam bombards the wafer 110 to generate an electronic signal; electron detector 107 is used to perform imaging based on the electronic signal.
[0033] The electronic signals include secondary electronic signals and / or backscattered electronic signals generated by the electron beam bombarding the wafer 110.
[0034] In this application, during the initial focusing of the electron beam, since there is no hysteresis effect in the electric field when excitation is applied to the electric lens 103, good consistency between the excitation switching and the change in the electric field can be guaranteed. Furthermore, the circuit of the magnetic lens is an RL circuit, and the circuit of the electric lens 103 is an RC circuit. The time constant of the RL circuit is calculated using the formula: τ = L / R, and the time constant of the RC circuit is calculated using the formula: τ = RC, where τ is the time constant of the circuit, a physical quantity that measures the speed of the transition process. The larger the time constant τ value, the longer the transition process takes. L is the inductance, R is the resistance, and C is the capacitance. Based on the above formulas, the time constant of the magnetic coil of the magnetic lens can be calculated from the inductance and resistance of the magnetic coil, typically on the order of milliseconds (ms). The time constant of the electric lens 103 can be calculated from the capacitance and resistance of the electric field, typically within picoseconds (ps). Therefore, by using the electric lens 103 to focus the electron beam for the first time, not only can the consistency between the change in excitation and the change in field force be guaranteed, but the excitation switching time can also be shortened, thereby improving the efficiency of beam current regulation.
[0035] In addition, since the electron beam is modulated by using only the electric lens 103, the image formed after the electron beam bombards the wafer 110 has large aberrations. Therefore, this application uses a magnetic lens 105 to focus the electron beam a second time, thereby improving the efficiency of beam current modulation and effectively improving aberrations.
[0036] In some embodiments, the electron lens 103 includes a first electrode 201, a second electrode 202, and a third electrode 203 stacked and spaced apart; the first electrode 201, the second electrode 202, and the third electrode 203 together form a converging channel, which is used to receive the electron beam and cause the electron beam to converge for the first time.
[0037] In some embodiments, the first electrode plate 201, the second electrode plate 202, and the third electrode plate 203 are all annular plates; insulating positioning elements are respectively provided between the first electrode plate 201 and the second electrode plate 202 and between the second electrode plate 202 and the third electrode plate 203; the first electrode plate 201, the second electrode plate 202, and the third electrode plate 203 are provided with positioning grooves that cooperate with the insulating positioning elements, so that the first electrode plate 201, the second electrode plate 202, and the third electrode plate 203 are coaxially arranged.
[0038] Please refer to Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of the electro-lens 103 in this embodiment. The electro-lens 103 has a three-layer electrode structure, including a first electrode 201 and a third electrode 203 which are two charged electrodes, and a second electrode 202 which is an intermediate electrode. The three layers are connected by an insulating positioning component and integrated into a single module. This structure can ensure the alignment of the upper and lower electrode plates by the cooperation of the insulating positioning component and the positioning groove. That is, the alignment accuracy can be guaranteed by the processing accuracy, which reduces the difficulty of aligning the electronic optical axis during the assembly process.
[0039] In some embodiments, the distance between the first electrode 201 and the second electrode 202 is equal to the distance between the second electrode 202 and the third electrode 203; when the electric lens 103 is working, the first electrode 201 and the third electrode 203 are configured to be connected to zero potential, and the second electrode 202 is configured to be connected to a non-zero potential.
[0040] Please refer to Figure 2 As shown, the first electrode 201 and the third electrode 203 are two charged electrodes with a potential of zero. The second electrode 202 is the intermediate electrode with a potential of high voltage, which can be either positive or negative. Thus, when the electron beam passes through this structure, it will converge towards the optical axis of the electron beam under the action of the electric field, thereby achieving beam current regulation. Furthermore, the distance between the first electrode 201 and the second electrode 202 is equal to the distance between the second electrode 202 and the third electrode 203, which ensures that the electron velocity in the electron beam does not change before and after passing through the electric lens 103, avoiding energy loss of the electron beam due to beam current regulation.
[0041] In some embodiments, the insulating positioning element is made of one or more of ceramic, glass, or mica; and / or, the insulating positioning element is spherical in shape.
[0042] This application lists some of the materials of the insulating positioning components. It should be understood that this application does not limit the specific material of the insulating positioning components, as long as the insulating positioning components are made of insulating materials with a certain degree of hardness. In addition, the shape of the insulating positioning components is preferably spherical, and the positioning groove that matches the spherical insulating positioning components is an arc-shaped groove. Thus, the centering accuracy of the electrode plate can be guaranteed by the machining accuracy of the spherical insulating positioning components and the arc-shaped positioning groove.
[0043] In some embodiments, the number of insulating positioning elements is even and they are symmetrically distributed on both sides of the second electrode plate 202; preferably, the number of insulating positioning elements is 6 and they are symmetrically distributed on both sides of the second electrode plate 202.
[0044] Specifically, the insulating positioning elements are symmetrically distributed on both sides of the second electrode plate 202, which can improve the versatility of the first electrode plate 201 and the third electrode plate 203. In a specific embodiment, three insulating positioning elements can be respectively provided on both sides of the second electrode plate 202, and the three insulating positioning elements are distributed in a triangular pattern. Thus, while ensuring the accuracy of the insulating positioning elements and the positioning grooves, the alignment accuracy of the electrode plate can be guaranteed as long as the positions of the positioning grooves correspond.
[0045] In some embodiments, the deflector 109 is an electrostatic deflector used to generate an electric field to deflect the electron beam; the electrostatic deflector is disposed on the upper side of the objective lens 108 along the imaging optical axis; and / or the electrostatic deflector is disposed on the lower side of the objective lens 108 along the imaging optical axis.
[0046] Specifically, in existing electron beam measurement devices (such as CD-SEM), the deflector 109 is a magnetic coil. When the magnetic coil scans the sample under the action of excitation, there is a hysteresis effect due to the magnetic coil under the changing excitation. Therefore, when switching the excitation, there is a problem of consistency between the change of excitation and the change of the magnetic field of the magnetic coil. However, in this application, the electrostatic deflector does not have a hysteresis effect when excitation is applied to the electrostatic deflector, thus ensuring good consistency between the switching of excitation and the change of electric field.
[0047] Similarly, the circuit for the magnetic coil is an RL circuit, while the circuit for the electrostatic deflector is an RC circuit. The time constant of the magnetic coil of the magnetic lens can be calculated from the inductance and resistance of the magnetic coil, typically on the order of milliseconds (ms). The time constant of the electrostatic lens 103 can be calculated from the capacitance and resistance of the electrostatic deflector, typically on the order of nanoseconds (ns). Therefore, using an electrostatic deflector to deflect the electron beam not only ensures the consistency between changes in excitation and changes in field force, but also shortens the excitation switching time, further improving the efficiency of scanning the sample.
[0048] In some embodiments, the electric field direction of the electrostatic deflector is perpendicular to the imaging optical axis of the objective lens 108; the electrostatic deflector has at least one electrode plate in the direction of the imaging optical axis.
[0049] Specifically, a single electrode refers to at least one electrode set perpendicular to the imaging optical axis of the objective lens 108, i.e., along the direction of the imaging optical axis of the objective lens 108. The electrode should be understood as an electrode group capable of generating an electric field. Furthermore, it should be understood that the electrode arrangement may include: in the case of multiple electrode sets along the imaging optical axis of the objective lens 108, each set may have at least one electrode group; or in the case of only one electrode set, multiple sets of mutually cooperating electrode groups may be set, where mutually cooperating refers to two electrode groups with mutually perpendicular electric field directions; or a combination of the above two methods, thereby enabling 360° adjustment of the electron beam around the optical axis of the imaging objective lens 108 to scan the wafer 110 through the cooperation of multiple electrode groups.
[0050] In some embodiments, the electron beam measurement device further includes an adjustment element 104; the adjustment element 104 is disposed between the electric lens 103 and the magnetic lens 105 for selecting and modulating the electron beam; the adjustment element 104 is provided with a plurality of adjustment holes of different sizes, and the adjustment element 104 is configured such that one of the adjustment holes moves into the electron beam path to select the electron beam.
[0051] In some embodiments, the electron beam measurement device further includes an electron beam accelerating plate 102 and a centering coil 106; the electron beam accelerating plate 102 is disposed between the electron gun 101 and the electron lens 103, and is used to accelerate the electron beam; the centering coil 106 is disposed between the magnetic lens 105 and the objective lens 108, and is used to make the electron beam coincide with the imaging optical axis of the objective lens 108.
[0052] Specifically, the multiple adjustment holes of different sizes on the adjustment element 104 can be understood as multiple aperture stops of different sizes. One of these aperture stops can be moved to the electron beam path according to the needs of those skilled in the art, allowing for further selection and modulation of the electron beam. Furthermore, this application does not specifically limit the switching method of the different sizes of adjustment holes on the adjustment element 104, as long as each of the multiple different sizes can be moved to the electron beam path. In one specific embodiment, the adjustment holes on the adjustment element 104 can be arranged in a ring, and the adjustment holes can be switched to the electron beam path by rotating the adjustment element 104. In another specific embodiment, the adjustment holes on the adjustment element 104 can be arranged in a strip shape, and the adjustment holes can be switched to the electron beam path by translating the adjustment component. Additionally, the electron beam accelerating plate 102 is provided with an accelerating channel, which can also be understood as an aperture stop, allowing for initial selection and modulation of the electron beam generated by the electron gun 101.
[0053] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. An electron beam measurement device, characterized in that, It includes an electron gun (101), an electric lens (103), a magnetic lens (105), a deflector (109), an objective lens (108), and an electron detector (107); The electron gun (101) is used to generate an electron beam; The electric lens (103) is used to generate an electric field to focus the electron beam for the first time; The magnetic lens (105) is used to generate a magnetic field to converge the electron beam a second time; The deflector (109) is used to deflect the electron beam to scan the wafer (110); The objective lens (108) is used to focus the electron beam onto the wafer (110) so that the converged electron beam bombards the wafer (110) to generate an electronic signal; The electronic detector (107) is used for imaging based on the electronic signal; The electric lens (103) includes a first electrode plate (201), a second electrode plate (202), and a third electrode plate (203) stacked and spaced apart; the first electrode plate (201), the second electrode plate (202), and the third electrode plate (203) are coaxially arranged. The distance between the first electrode plate (201) and the second electrode plate (202) is equal to the distance between the second electrode plate (202) and the third electrode plate (203); When the electro-lens (103) is in operation, the first electrode (201) and the third electrode (203) are configured to be connected to zero potential, and the second electrode (202) is configured to be connected to non-zero potential.
2. The electron beam measurement device according to claim 1, characterized in that, The first electrode plate (201), the second electrode plate (202), and the third electrode plate (203) together form a converging channel, which is used to receive the electron beam and cause the electron beam to converge for the first time.
3. The electron beam measurement device according to claim 2, characterized in that, The first electrode plate (201), the second electrode plate (202), and the third electrode plate (203) are all annular plates; Insulating positioning elements are respectively provided between the first electrode plate (201) and the second electrode plate (202) and between the second electrode plate (202) and the third electrode plate (203); The first electrode plate (201), the second electrode plate (202), and the third electrode plate (203) are provided with positioning grooves that cooperate with the insulating positioning member so that the first electrode plate (201), the second electrode plate (202), and the third electrode plate (203) are coaxially arranged.
4. The electron beam measurement device according to claim 3, characterized in that, The number of insulating positioning elements is even, and they are symmetrically distributed on both sides of the second electrode plate (202).
5. The electron beam measurement device according to claim 1, characterized in that, The deflector (109) is an electrostatic deflector used to generate an electric field to deflect the electron beam; The electrostatic deflector is positioned axially on the upper side of the objective lens (108) along the imaging optical axis; and / or The electrostatic deflector is disposed on the lower side of the objective lens (108) along the axial direction of the imaging optical axis of the objective lens (108).
6. The electron beam measurement device according to claim 5, characterized in that, The electric field direction of the electrostatic deflector is perpendicular to the imaging optical axis of the objective lens (108); The electrostatic deflector has at least one layer of electrodes in the direction of the imaging optical axis.
7. The electron beam measurement device according to claim 6, characterized in that, Each layer of plates includes at least two sets of plates with electric field directions perpendicular to each other.
8. The electron beam measurement apparatus according to any one of claims 1-7, characterized in that, The electron beam measurement device also includes an adjustment element (104); The adjustment element (104) is disposed between the electric lens (103) and the magnetic lens (105) for selecting and modulating the electron beam; The adjustment element (104) is provided with a plurality of adjustment holes of different sizes, and the adjustment element (104) is configured such that one of the adjustment holes moves into the electron beam path to select the electron beam.
9. The electron beam measurement device according to claim 8, characterized in that, The electron beam measurement device also includes an electron beam accelerating plate (102) and a centering coil (106); The electron beam accelerator plate (102) is disposed between the electron gun (101) and the electron lens (103), and the electron beam accelerator plate (102) is used to accelerate the electron beam; The centering coil (106) is disposed between the magnetic lens (105) and the objective lens (108) to make the electron beam coincide with the imaging optical axis of the objective lens (108).