Method for operating a particle beam system and particle beam system

Abstract

A method for operating a particle beam system includes a first operating mode and a second operating mode. The first operating mode includes: using a turbomolecular pump of the particle beam system to evacuate gas from a vacuum space into a buffer space of the particle beam system, and using a backing pump of the particle beam system to evacuate gas from the buffer space. The second operating mode includes: using the turbomolecular pump to evacuate gas from the vacuum space into the buffer space, wherein the use of the backing pump to evacuate gas from the buffer space is stopped; and when the use of the backing pump to evacuate gas from the buffer space is stopped, recording the value of a variable characterizing the operating current supplied to the turbomolecular pump, and switching back to the first operating mode if the recorded variable meets a predetermined first criterion.

Description

Technical Field

[0001] The present invention relates to a method for operating a particle beam system and a particle beam system. Background Technology

[0002] In particle beam systems (such as electron beam microscopy), a particle beam generated by a particle beam source is guided onto a sample for examination. To prevent the particles of the particle beam from interacting with the gas in the particle beam system during their journey from the particle beam source to the sample, a vacuum system is provided. This vacuum system uses multiple pumps to generate a vacuum in the vacuum space through which the particle beam passes. These multiple pumps typically include a foreground pump for generating a foreground vacuum in the vacuum space, and another pump, such as a turbomolecular pump, which further improves the foreground vacuum generated by the foreground pump.

[0003] The operation of turbomolecular pumps typically presupposes the establishment of a forevacuum, thus requiring the forevacuum to be continuously maintained. However, the operation of the forevacuum introduces vibrations into the particle beam system, degrading the quality of the particle optical image and increasing operating costs. Accordingly, a method is known whereby the forevacuum is temporarily shut down, during which time the gas is pumped by the turbomolecular pump into a evacuated buffer space to mitigate the degradation of the forevacuum. The duration of the forevacuum shutdown is controlled by the gas pressure at the buffer space, as recorded by a pressure sensor.

[0004] Typically, the vacuum system of a particle beam system is a precision system comprising a large number of expensive components that are procured, assembled, prone to failure, and require maintenance. Summary of the Invention

[0005] Therefore, the object of this invention is to provide a particle beam system with a simplified vacuum system.

[0006] The particle beam system used in the method described below includes: a particle beam source for generating a particle beam; a sample holder on which a sample intended to be irradiated by the particle beam can be arranged; a evacuable vacuum space on which the sample holder is arranged; a turbomolecular pump; a buffer space; and a backing pump.

[0007] In this context, it should be noted that a pumpable space is a space in which gas is removed, thus reducing the gas pressure. Furthermore, in the following text, the terms "connection" and "phase connection" refer to a point through which gas can flow. For example, a connection between vacuum spaces means that gas flows from one vacuum space to another. Specifically, if no gas or a very small amount of gas compared to the volume of one vacuum space can flow into another, then one vacuum space is disconnected from the other. If gas can flow from one vacuum space through an opening into another, then the two vacuum spaces are connected via the opening. Signal lines and current lines are referred to herein as electrical connections.

[0008] The proposed method for solving the above-mentioned problems includes a first operating mode and a second operating mode. The first operating mode includes: using a turbomolecular pump to evacuate gas from a vacuum space into a buffer space, and using a backing pump to evacuate gas from the buffer space. The second operating mode includes: using a turbomolecular pump to evacuate gas from a vacuum space into the buffer space, wherein the backing pump is stopped from evacuating gas from the buffer space; and when the backing pump is stopped from evacuating gas from the buffer space, recording the value of a variable characterizing the operating current supplied to the turbomolecular pump, and switching back to the first operating mode if the recorded variable meets a predetermined first criterion. According to some embodiments, if the recorded variable indicates that the power of the operating current supplied to the turbomolecular pump is higher than a first threshold, the first criterion is met; and if the recorded variable indicates that the power of the operating current supplied to the turbomolecular pump is lower than the first threshold, the first criterion is not met. According to some embodiments, in the second operating mode, the backing pump is turned off.

[0009] For example, the particle beam system operates in a static mode and a standard mode, where the forepump is off in static mode and the turbomolecular pump and forepump operate in standard mode. For instance, in static mode, the operating current supplied to the turbomolecular pump is recorded. The operating current supplied to the turbomolecular pump depends on the gas pressure at the turbomolecular pump's outlet. If the gas pressure at the turbomolecular pump's outlet is high, the load on the turbomolecular pump increases due to gas backflow, thus increasing the operating current supplied to the turbomolecular pump. Accordingly, by recording the operating current supplied to the turbomolecular pump, the gas pressure at the turbomolecular pump's outlet can be inferred, or the need to operate the forepump to evacuate the buffer space can be determined. Therefore, recording the turbomolecular pump's operating current also has the effect of eliminating the need for a pressure sensor at the buffer space. Consequently, the pressure sensor and related components of the vacuum system can be eliminated, thereby simplifying the vacuum system and making it easier to assemble and maintain. It should be noted that the load on the turbomolecular pump also depends on the gas pressure at the turbomolecular pump's inlet. However, the above method is still advantageous, especially when the gas pressure at the turbomolecular pump's inlet does not increase or only slightly increases. For example, according to some embodiments, if the gas pressure at the inlet of the turbomolecular pump increases, the above method can be paused, and the backing pump can be operated until the gas pressure at the inlet of the turbomolecular pump normalizes.

[0010] According to some embodiments, the particle beam system includes a vacuum valve disposed between the buffer space and the forepump, wherein the vacuum valve is open in a first operating mode and closed in a second operating mode. This valve is also referred to hereinafter as a static mode valve and specifically prevents material from being drawn into the forepump vacuum when the forepump is not in operation.

[0011] A buffer space is the physical volume into which the turbomolecular pump pumps gas when the particle beam system operates in static mode. The buffer space can be provided by a connecting line between the turbomolecular pump and the forepump, the volume of which is typically defined by the length and cross-sectional area of ​​the connecting line. To increase the buffer space, the volume of the connecting line can be extended and / or widened, and protrusions, branch lines, and / or connecting spaces can be provided. The buffer space does not necessarily need to be provided by the entire connecting line between the turbomolecular pump and the forepump, but can also be provided solely by the connecting line from the outlet of the turbomolecular pump to the static mode valve. For example, a valve located directly at the outlet of the turbomolecular pump can also be a static mode valve, such that the buffer space is provided by the outlet of the turbomolecular pump. Different embodiments are conceivable, but the following description primarily describes the situation where, between the outlets of the turbomolecular pump, there is space connected to the connecting line to increase the buffer space. Since the volume of the connecting line may be small compared to the space connected for expansion, the buffer space may be referred to as a buffer space hereinafter, but this should not be construed as a limitation on the subject matter described above.

[0012] The aforementioned vacuum valve can also be integrated as a component in the backing pump, or it can be omitted if the backing pump design ensures a seal between the backing pump and the environment when the backing pump is shut down. As described, the vacuum valve can be located at the outlet of the turbomolecular pump.

[0013] According to some embodiments, the particle beam system includes a gas space comprising an outlet opening of a turbomolecular pump, a buffer space, and an inlet opening of a backing pump, wherein the particle beam system is not configured with a gas pressure sensor to detect the gas pressure in the gas space. For example, the gas space here is the entire pipeline connecting the outlet of the turbomolecular pump to the backing pump, along with the buffer space. The buffer space may, for example, be arranged within or connected to the aforementioned connection, allowing gas to flow from the connection into the buffer space.

[0014] According to some embodiments, the first operating mode further includes switching to a second operating mode after a predetermined time period following the commencement of the first operating mode. For example, the predetermined time period may be five minutes.

[0015] According to some embodiments, the buffer space has at least 500 cm². 3 Specifically, at least 1000 cm 3 The volume, and / or at most 5000 cm³ 3 Specifically, up to 50,000 cm 3 The volume. According to an advantageous embodiment, the buffer space has a volume of 2000 cm². 3 The volume.

[0016] According to some embodiments, the method includes guiding a particle beam generated by a particle beam source onto a sample during a first operating mode and / or during a second operating mode. According to some embodiments, the method also includes detecting a signal generated by the particle beam at the sample using a detector. For example, the sample can be scanned with the particle beam during the first operating mode and / or during the second operating mode, and a particle optical image can be generated based on the detected signal.

[0017] According to some embodiments, the first operating mode further includes recording the value of a variable characterizing the operating current supplied to the turbomolecular pump, and switching to a second operating mode if the recorded variable meets a predetermined second criterion. According to some embodiments, the second criterion is met if the recorded variable indicates that the power of the operating current supplied to the turbomolecular pump is below a second threshold, and not met if the recorded variable indicates that the power of the operating current supplied to the turbomolecular pump is above the second threshold. For example, if the particle beam system operates in standard mode for a longer period of time with the second threshold set, the operating current of the turbomolecular pump may be correspondingly a lower limit threshold of the operating current. If the foreboard pump is turned on after a static mode, it is possible to check when this lower limit threshold of the operating current is reached, and it is possible to switch back to static mode.

[0018] According to some embodiments, the particle beam system includes a controller configured to cause the particle beam system to perform the methods described above.

[0019] According to specific embodiments, multiple particle beam systems can be combined to form a larger integrated system. For example, an electron beam microscope can be combined with an ion beam system. In such an integrated system, there is at least one turbomolecular pump and at least one foreboard pump; that is, multiple turbomolecular pumps and / or multiple foreboard pumps can also be provided. Attached Figure Description

[0020] The above embodiments will now be explained in more detail with reference to the accompanying drawings.

[0021] Figure 1 The illustration shows a first electron beam microscope suitable for performing the method of the present invention.

[0022] Figure 2 A second electron beam microscope suitable for performing the method of the present invention is illustrated.

[0023] Figure 3 The illustration shows a flowchart illustrating a method according to a first embodiment.

[0024] Figure 4 The illustration shows a flowchart illustrating a method according to a second embodiment.

[0025] Figure 5The figure shows a graph illustrating the change in the operating current supplied to the turbomolecular pump over time. Detailed Implementation

[0026] Figure 1 The figure illustrates an electron beam microscope 1, which includes a source space 3, a first intermediate vacuum space 5, a second intermediate vacuum space 7, and a sample space 9. An electron beam source 11 is arranged in the source space 3. The electron beam source 11 is electrically connected to a controller 15 via a signal line 13, so that the controller 15 can supply a potential to the electron beam source 11 to generate an electron beam 17.

[0027] Source space 3 is separated from first intermediate vacuum space 5 by aperture 19. Aperture 19 has an opening 21 through which electron beam 17 passes when guided onto sample 23. First intermediate vacuum space 5 is separated from second intermediate vacuum space 7 by protection valve 25 and aperture 27. Aperture 27 has an opening 29 through which electron beam 17 passes when guided onto sample 23. Protection valve 25 includes a sealing plate 31 and an actuator 33. Actuator 33 is electrically connected to controller 15 via signal line 35. If actuator 33 is operated by controller 15 via signal line 35, the actuator moves sealing plate 31 into or out of the beam path of electron beam 17, thereby completely disconnecting or connecting the first intermediate vacuum space 5 and the second intermediate vacuum space 7, respectively. If protection valve 25 is open and electron beam 17 is guided onto sample 23, electron beam 17 passes through protection valve 25.

[0028] The electron beam microscope 1 also includes a condenser lens 37 and an objective lens 39. The condenser lens 37 includes a pole piece 41 with an opening 43 and a coil 45. The coil 45 is electrically connected to a controller 15 via a signal line 47. The controller 15 controls the condenser lens 37 by supplying current to the coil 45, which generates a magnetic field that enters the beam path of the electron beam 17 from the pole piece 41 at the opening 43 and provides a focusing effect on the electron beam 17. The electron beam 17 passes through the condenser lens 37 in the first intermediate vacuum space 5.

[0029] Objective lens 39 includes a pole piece 49 with an opening 51 and a coil 53. Coil 53 is electrically connected to controller 15 via signal line 55. Controller 15 controls objective lens 39 by supplying current to coil 53, which generates a magnetic field that enters the beam path of electron beam 17 from pole piece 49 at opening 51 and provides a focusing effect on electron beam 17. Electron beam 17 passes through objective lens 39 within the second intermediate vacuum space 7.

[0030] The second intermediate vacuum space 7 is separated from the sample space 9 by an aperture arrangement 57. The aperture arrangement 57 includes a mounting member 59 with an opening 61, and a replaceable aperture body 63 carried by the mounting member 59. The aperture body 63 has a hole 65, the cross-sectional area of ​​which differs from the cross-sectional area of ​​the opening 61 of the mounting member 59. The user of the electron beam microscope 1 removes the aperture body 63 via a vacuum lock 69 using a guide mechanism 67 and inserts another aperture body into the mounting member 59 using the guide mechanism 67, allowing the user to replace the aperture body 63. It should be noted that... Figure 1 The guide mechanism 67 is illustrated, but in some embodiments, the guide mechanism is removed from the sample space 9 or pivoted laterally relative to the image field of the electron beam microscope 1 during the guidance of the electron beam 17 onto the sample 23.

[0031] Electron beam 17 passes through opening 61 of mounting 59 and aperture 65 of aperture 63. Electron beam 17 is then incident on sample 23.

[0032] Sample 23 is mounted on sample holder 73 by means of sample guide 71. Sample guide 71 includes guide rod 75 and carrier 77. In this case, the user places sample 23 on carrier 77 outside sample space 9, and then brings sample 23 to position in sample holder 73 by moving guide rod 75 through lock 79. Guide rod 75 can be detached from carrier 77 and removed from sample space 9. Instead of or attached to lock 79, electron beam microscope 1 may have an openable door in sample space 9 through which sample 23 can be mounted on sample holder 73. For example, if lock 79 and door are provided in sample space 9, samples that are too large for lock 79 can enter sample space 9 through door.

[0033] The electron beam microscope 1 also includes an actuator 81 that allows the relative position of the sample holder 73 and the aperture arrangement 57 to be changed. For this purpose, the actuator 81 is electrically connected to the controller 15 via a signal line 83.

[0034] The electron beam microscope 1 also includes a deflection arrangement 85. Figure 1 In this design, the deflection arrangement 85 is shown as an electrode pair, but it can also be implemented using an electromagnetic coil. The deflection arrangement 85 is electrically connected to the controller 15 via signal line 87. Therefore, the controller 15 can supply a potential to the deflection arrangement 85, causing it to generate an electric field in the beam path of the electron beam 17, thus deflecting the electron beam 17. This allows the electron beam 17 to be directed to different points on the sample 23.

[0035] When the electron beam 17 is incident on the sample 23, various signals are generated at the sample 23, such as secondary electrons and backscattered electrons. The electron beam microscope 1 also includes a detector 89 arranged in the sample space 9, which can record these signals and generate corresponding electrical signals. The electrical signals generated by the detector 89 are forwarded to the controller 15 via the signal line 91.

[0036] In order to capture particle optical images using electron beam microscope 1, controller 15 sequentially supplies different potentials to deflection arrangement 85, thereby guiding the electron beam to different incident positions on sample 23, and the controller stores the signal generated by detector 89 together with the incident positions on sample 23. This process is also referred to below as scanning of sample 23.

[0037] During operation of the electron beam microscope 1, vacuums of different qualities are generated in the source space 3, the first intermediate vacuum space 5, the second intermediate vacuum space 7, and the sample space 9. A high vacuum is generated in the source space 3, while a significantly poorer vacuum is maintained in the sample space 9. To generate vacuums in the source space 3, the first intermediate vacuum space 5, the second intermediate vacuum space 7, and the sample space 9, the electron beam microscope 1 also includes a pump system 93. The pump system 93 includes a foreboard pump 95, a turbomolecular pump 97, a first ion uptake pump 99, and a second ion uptake pump 101. The foreboard pump 95, for example, can reach a capacity of 10... -2 A positive displacement pump with a forestage vacuum of millibars. The turbomolecular pump 97 operates only after at least a forestage vacuum has been achieved; otherwise, the turbomolecular pump 97 may be damaged. The turbomolecular pump 97 reaches 10... -5 A vacuum of millibars. The first ion suction pump 99 and the second ion suction pump 101 require a vacuum generated by the turbomolecular pump 97 as a prerequisite and achieve a vacuum of 10. -6 millibars to 10 -10 High vacuum of millibars.

[0038] Since the foreboard pump 95 must first generate a foreboard vacuum in the source space 3, the first intermediate vacuum space 5, the second intermediate vacuum space 7, and the sample space 9, the foreboard pump 95 is connected to the sample space 9 via the foreboard pump line 103, the transition line 105, and the sample space line 107, allowing the foreboard pump 95 to evacuate the sample space 9. Furthermore, the foreboard pump 95 is connected to the second intermediate vacuum space 7 via the foreboard pump line 103, the transition line 105, the sample space line 107, and the turbopump line 109, allowing the foreboard pump 95 to evacuate the second intermediate vacuum space 7. Additionally, the foreboard pump 95 is connected to the source space 3 and the first intermediate vacuum space 5 via the foreboard pump line 103, the transition line 105, the sample space line 107, the turbopump line 109, and via the ion extraction pump line 111 and the ion extraction pump line 113, respectively, to enable evacuation of the source space and the first intermediate vacuum space. The backing pump 95 includes an outlet 114 that discharges the gas extracted from the vacuum space to the outside. The operation of the backing pump 95 is controlled by the controller 15 via signal line 116.

[0039] A separation valve 115 is provided in the transition line 105, by means of which the forepump 95 and forepump line 103 can be separated from the sample space line 107, and thus from all vacuum spaces. The separation valve 115 is electrically connected to the controller 15 via signal line 117, allowing the controller 15 to separate the forepump 95 from the vacuum space. In the electron beam microscope 1, the transition line 105 and valve 115 are unnecessary because a vacuum can also be generated by the forepump 95 through outlet 131 and the closed turbomolecular pump 97. Furthermore, a static mode valve 119, a buffer space 121, and a separation valve 123, all electrically connected to the controller 15 via signal line 118, are provided in the forepump line 103. The static mode valve 119 and buffer space 121 allow the forepump 95 to be temporarily shut down to reduce vibration, noise, and electrical interference. Specifically, if the static mode valve 119 is closed and the forepump 95 is closed, the turbomolecular pump 97 pumps gas into the buffer space 121, causing the gas pressure in the buffer space 121 to increase slowly, and therefore the gas pressure at the outlet 131 of the turbomolecular pump 97 also increases slowly. In this case, as... Figure 1 As shown, the buffer space 121 may be a space connected to the back pump line 103, allowing gas to flow from the back pump line 103 into the buffer space 121, or the buffer space may be provided by the back pump line 103 itself.

[0040] Separation valve 123 is closed via signal line 122 through controller 15 to protect turbomolecular pump 97 before the forestage vacuum is reached.

[0041] The turbomolecular pump 97 includes a rotor 125, a stator 127, vanes 129, and an outlet 131. The stator 127 is electrically connected to a controller 15 via a signal line 133. To operate the turbomolecular pump 97, the controller 15 supplies current to the stator 127 via the signal line 133, thereby causing the rotor 125 to rotate together with the vanes 129. The vanes 129 accelerate the gas particles toward the outlet 131 by colliding with them. A current sensor 135 is arranged in the signal line 133 for recording the current supplied to the stator 127. Although the stator 127 is illustrated here without vanes, it should be noted that the stator 127 may also have vanes, for example, arranged between the multiple pairs of vanes 129 shown.

[0042] Turbomolecular pump 97 is connected to the second intermediate vacuum space 7 via turbopump line 109, to sample space 9 via turbopump line 109 and sample space line 107, and to source space 3 and first intermediate vacuum space 5 via turbopump line 109 and ion absorption pump lines 111 and 113 respectively. Furthermore, a separation valve 137 can be provided in turbopump line 109, which is electrically connected to controller 15 via signal line 139. Thus, for example, when the pre-stage pump 95 generates a forestage vacuum in the vacuum space via transition line 105, controller 15 can close separation valve 137.

[0043] The sample space line 107 also includes a separation valve 141, which is electrically connected to the controller 15 via a signal line 143. The separation valve 141 can be closed by the controller 15 to disconnect the sample space line 107 from the turbopump line 109. For example, when gas is supplied to the transition line 105 through the leak valve 151, the separation valve 141 closes to increase the gas pressure throughout the sample space 9. Thus, the separation valve 141 can be closed as needed to prevent a decrease in the gas pressure in the sample space 9 due to the operation of the turbomolecular pump 97.

[0044] A venting device 145 with a valve 147 is also provided on the sample space line 107. The valve 147 can be controlled by the controller 15 via the signal line 149. If the valve 147 is open, the venting device 145 connects the interior of the electron beam microscope 1 to the outside air, so that the electron beam microscope 1 is filled with air. This operation can be performed, for example, if damage to the electron beam microscope 1 is detected, if the user arranges a new sample 23 in the sample space 9 through the aforementioned alternative or additional door at the sample space 9, or if the electron beam microscope 1 is shut down for maintenance.

[0045] A leak valve 151 is provided on the transition line 105, and the leak valve can be controlled by a controller 15 via a signal line 153. The controller 15 can set the flow rate of the process gas at the leak valve 151, which flows into the transition line from the supply container 155 or from ambient air. The transition line 105 also has a pressure sensor 157, which records the gas pressure present in the transition line 105 and thus in the sample space 9, and generates a signal that is transmitted to the controller 15 via a signal line 159.

[0046] Ion pump lines 111 and 113 each have an ion pump 99 and an ion pump 101, respectively, as well as separation valves 161 and 163. Separation valve 161 can be controlled by controller 15 via signal line 165. Controller 167 communicates with controller 15 via signal line 169. Separation valve 163 can be controlled by controller 15 via signal line 171. Controller 167 controls the operation of ion pumps 99 and 101. If a vacuum that can be generated by turbomolecular pump 97 is reached in source space 3 and first intermediate vacuum space 5, controller 15 closes valves 161 and 163, and controller 167 supplies high voltage to ion pumps 99 and 101 via signal lines 173 and 175 to generate a high vacuum in source space 3 and first intermediate vacuum space 5. Controllers 15 and 167 can also be designed as a shared controller for controlling both valves 161 and 163, as well as supplying high voltage. Control of the corresponding components of the electron beam microscope 1 can be divided between controllers 15 and 167 in any desired manner.

[0047] For example, Figure 1 The valves 115, 119, 123, 137, 141, 147, 151, 161, and 163 shown may be solenoid valves. Valve 115, 119, 123, 137, 141, 147, 151, 161, and 163 may also be other valves, as long as they can be controlled by controller 15 and controller 167.

[0048] Figure 2 A second electron beam microscope 1' suitable for performing the method of the present invention is illustrated. Figure 2 In the diagram, the components and functional settings are indicated by corresponding reference numerals. For Figure 2 The accompanying figure labels and Figure 1 The same reference numerals are used for the same parts and functions as those in the accompanying drawings, and refer to the description of the parts or functions above.

[0049] Figure 2 The electron beam microscope 1' shown is Figure 1The difference in the electron beam microscope 1 shown is that the process gas flow is not supplied to the transition line 105, but is supplied directly to the sample 23 via a needle 177. The needle 177 is connected to the supply container 155 via a gas supply line 179 and a leak valve 151, allowing the process gas to be supplied directly from the supply container 155 and / or ambient air to the sample 23. In the electron beam microscope 1', a pressure sensor 181 is mounted on the sample holder 73, which is electrically connected to the controller 15 via a signal line 183. This arrangement of the pressure sensor 181 has the advantage that the pressure near the needle 177 is recorded and is not distorted by a large distance relative to the local supply point of the process gas. It should also be noted that, in the case of localized supply of process gas via the needle 177, the separation valve 141 can be opened during the measurement method.

[0050] It should be noted that particle beam systems are not limited to electron beam microscopes. For example, a particle beam system can also be an ion beam system that generates a beam of particles composed of ionized atoms. Particle beam systems can also be integrated into larger systems, such as FIB-SEMs that simultaneously generate ion beams and electron beams.

[0051] The proposed methods according to different embodiments are described in detail below. Figure 3 The figure illustrates a flowchart of a method according to a first embodiment. The method according to the first embodiment includes steps S1 to S10, wherein steps S2 to S4 form a standard mode, and steps S7 to S9 form a static mode.

[0052] In step S1, the controller 15 opens the static mode valve 119, which allows the fore-pump 95 to pump air from the fore-pump line 103 or the buffer space 121.

[0053] In step S2, controller 15 operates turbomolecular pump 97 to remove gas from the vacuum space of electron beam microscope 1, specifically from sample space 9 and second intermediate vacuum space 7. In this case, the gas removed from sample space 9 and second intermediate vacuum space 7 is discharged from outlet 131 of turbomolecular pump 97 into backing pump line 103.

[0054] In step S3, the controller 15 further operates the forepump 95 in standard mode to evacuate the forepump line 103 and buffer space 121. In this case, the gas evacuated from the forepump line 103 and buffer space 121 is discharged to the outside through the outlet 114 of the forepump 95. It should be noted that step S3 can be interchanged with step S2 or can be performed simultaneously with step S2.

[0055] In step S4, controller 15 then checks whether five minutes have elapsed since the start of standard mode. If not, controller 15 continues in standard mode and returns to step S2. If five minutes have elapsed since the start of standard mode, controller 15 proceeds to step S5.

[0056] In step S5, controller 15 closes static mode valve 119, and in step S6, it shuts down forepump 95. Accordingly, starting from step S5, forepump line 103 and buffer space 121 are no longer evacuated.

[0057] In step S7, the controller 15 continues to operate the turbomolecular pump 97 to evacuate gas from the sample space 9 and the second intermediate vacuum space 7. The gas evacuated from the sample space 9 and the second intermediate vacuum space 7 is discharged from the outlet 131 of the turbomolecular pump 97 into the forepump line 103 and the buffer space 121, where the gas gradually accumulates and the gas pressure increases.

[0058] In step S8, the controller 15 also records the operating current supplied to the turbomolecular pump 97 using the current sensor 135. In step S9, the controller 15 then checks whether the recorded operating current is greater than a predetermined threshold. The predetermined threshold may be, for example, an operating current corresponding to 50 watts of electrical power of the turbomolecular pump 97. If the operating current of the turbomolecular pump 97 is less than or equal to the predetermined threshold, the controller 15 remains in static mode and returns to step S7. On the other hand, if the operating current of the turbomolecular pump 97 is greater than the predetermined threshold, the controller 15 continues to step S10, thus switching back to standard mode.

[0059] Specifically, control unit 15 reopens the forepump 95 in step S10, and then opens the static mode valve 119 in step S1. Therefore, the gas accumulated in the forepump line 103 and buffer space 121 during static mode can be pumped out by the forepump 95 and discharged to the outside. In this case, the operating current supplied to the turbomolecular pump 97 decreases again because the gas pressure at the outlet 131 of the turbomolecular pump 97 decreases.

[0060] It should be noted that Figure 3 An embodiment of the method is illustrated, wherein a switch from a standard mode to a static mode is made after a predetermined time has elapsed, and a switch back from the static mode to the standard mode is made if the operating current of the turbomolecular pump 97 exceeds a predetermined threshold. However, any desired combination and standard can be contemplated for switching between operating modes. Figure 4 The figure illustrates an exemplary alternative embodiment.

[0061] Figure 4The illustration shows a flowchart illustrating a method according to a second embodiment. Figure 4 The method shown includes steps S11 to S20, wherein steps S12 to S15 form a standard mode, and steps S18 and S19 form a static mode.

[0062] Steps S11 to S13, S16 to S18 and S20 and Figure 3 Steps S1 to S3, S5 to S7, and S10 shown are the same. For the execution of steps S11 to S13, S16 to S18, and S20, refer here accordingly to the description of steps S1 to S3, S5 to S7, and S10 above.

[0063] In the standard mode of the second embodiment, in step S14, the controller 15 uses the current sensor 135 to record the operating current supplied to the turbomolecular pump 97. This allows the controller 15 to monitor how much the operating current of the turbomolecular pump 97 has decreased when gas is pumped out from the forepump line 103 and the buffer space 121 by the forepump 95.

[0064] In step S15, the controller 15 compares the recorded operating current of the turbomolecular pump 97 with a predetermined threshold. The predetermined threshold is, for example, the operating current of the turbomolecular pump 97 corresponding to a power output of 20 watts. Specifically, the predetermined threshold in step S15 can be determined by operating the electron beam microscope 1 in standard mode and recording the operating current of the turbomolecular pump 97 after a period of time; this predetermined threshold then corresponds to the minimum operating current of the turbomolecular pump 97. If it is determined in step S15 that the operating current of the turbomolecular pump 97 is greater than or equal to the predetermined threshold, the controller remains in standard mode and returns to step S12.

[0065] On the other hand, if it is determined in step S15 that the recorded operating current of the turbomolecular pump 97 is less than a predetermined threshold, the controller 15 continues to step S16 and thus switches to static mode.

[0066] exist Figure 4 In the second embodiment shown, the operating current of the turbomolecular pump 97 is not recorded in static mode. Instead, in the second embodiment, the controller 15 checks whether a five-minute period of static mode has been executed. If no five minutes have elapsed since the start of static mode, the controller 15 remains in static mode and returns to step S18. However, if the controller 15 determines that five minutes have elapsed since the start of static mode, the controller 15 proceeds to step S20, thus switching to standard mode. It should be noted that in alternative embodiments, the operating current of the turbomolecular pump 97 can be recorded in both operating modes and compared with corresponding thresholds for switching purposes.

[0067] Figure 5 The figure shows a graph illustrating the change in operating current supplied to turbomolecular pump 97 over time. The graph illustrates curve 185, where the X-axis represents time and the Y-axis represents the operating current supplied to turbomolecular pump 97. Figure 5 The graph shown begins on the timeline in a static mode, in which turbomolecular pump 97 operates and forepump 95 is either off or isolated by static mode valve 119. During this period, as the gas discharged from turbomolecular pump 97 accumulates in forepump line 103 and buffer space 121, the gas pressure at outlet 131 of turbomolecular pump 97 increases, and the operating current supplied to turbomolecular pump 97 gradually increases. Static mode continues until the operating current of turbomolecular pump 97 reaches threshold 187 at the first boundary 191, at which point controller 15 switches to standard mode, operates forepump 95, and opens static mode valve 119.

[0068] Then the standard mode is executed until the second boundary 191, which is set five minutes after the first boundary 191. During this period, the forepump 95 evacuates the forepump line 103 and the buffer space 121, resulting in... Figure 5 In the graph, the operating current of turbomolecular pump 97 drops sharply. At the second boundary 191, controller 15 switches back to static mode.

[0069] Figure 5 The diagram also illustrates a lower threshold 189, which can be used alternatively to switch to a static mode. For example, when the first boundary 191 is reached, the controller 15 can execute a standard mode until the operating current of the turbomolecular pump 97 is reached, and therefore curve 185 drops to the lower threshold 189.

[0070] Using the method described above for operating particle beam systems 1 and 1', switching between static and standard modes can be performed even when no pressure sensor is installed at buffer space 121. Consequently, the pressure sensor and related components of the vacuum system can be omitted, thereby simplifying the vacuum system and making it easier to assemble and maintain.

Claims

1. A method for manipulating a particle beam system (1, 1'), wherein The method includes a first operating mode and a second operating mode; The particle beam system (1, 1') includes: Particle beam source (11), which is used to generate particle beam (17). A sample holder (73) on which a sample (23) intended to be irradiated by the particle beam (17) can be arranged; A vacuum space (3, 5, 7, 9) in which the sample holder (73) is arranged; turbomolecular pump (97); Buffer space (121); and Fore-pump (95); The first operating mode includes: The gas is pumped from the vacuum space (3, 5, 7, 9) into the buffer space (121) using the turbomolecular pump (97), and the gas in the buffer space (121) is pumped out using the back pump (95); The second operating mode includes: Using the turbomolecular pump (97), gas is evacuated from the vacuum space (3, 5, 7, 9) into the buffer space (121), wherein the use of the backing pump (95) to evacuate gas from the buffer space (121) is stopped; and When the forepump (95) is stopped from evacuating the gas in the buffer space (121), the value of the variable characterizing the operating current supplied to the turbomolecular pump (97) is recorded, and if the recorded variable meets a predetermined first criterion, the system switches to the first operating mode.

2. The method according to claim 1, wherein In this second operating mode, the fore-pump (95) is shut off.

3. The method according to claim 1 or 2, wherein The particle beam system (1, 1') includes vacuum valves (119; 123) disposed between the buffer space (121; 131) and the forepump (95). In this first operating mode, the vacuum valve (119) is open; In this second operating mode, the vacuum valve (119) is closed.

4. The method according to any one of claims 1 to 3, wherein, The particle beam system (1, 1') includes a gas space that includes the outlet opening (131) of the turbomolecular pump (97), the buffer space (121), and the inlet opening of the forepump (95). The particle beam system (1, 1') is not configured as a gas pressure sensor to detect the gas pressure in the gas space.

5. The method according to any one of claims 1 to 4, wherein, The recorded variables characterize the power of the operating current supplied to the turbomolecular pump (97); Wherein, if the recorded variable represents power higher than a first threshold, then the first criterion is met; and If the recorded variable represents power below the first threshold, then the first criterion is not met.

6. The method according to any one of claims 1 to 5, wherein, This first operating mode also includes: After a predetermined time period following the start of the first operating mode, switch to the second operating mode.

7. The method according to any one of claims 1 to 6, wherein The buffer space (121) has a volume of at least 500 cm 3 , in particular at least 1000 cm 3 ; and / or wherein the buffer space (121) has a volume of at most 5000 cm 3 , in particular at most 50000 cm 3 .

8. The method according to any one of claims 1 to 7, It also includes guiding a particle beam (17) generated by the particle beam source (11) onto the sample (23) during the first operating mode and / or during the second operating mode.

9. The method according to claim 8, It also includes using a detector (89) to detect the signal generated by the particle beam (17) at the sample (23).

10. The method according to any one of claims 1 to 9, wherein This first operating mode also includes: Record the value of the variable that characterizes the operating current supplied to the turbomolecular pump (97), and switch to the second operating mode if the recorded variable meets a predetermined second criterion.

11. The method according to claim 10, wherein The recorded variables characterize the power of the operating current supplied to the turbomolecular pump (97); Specifically, if the recorded variable represents power below a second threshold, then the second criterion is met; and If the recorded variable represents power higher than the second threshold, then the second criterion is not met.

12. A particle beam system (1, 1'), comprising: Particle beam source (11), which is used to generate particle beam (17). A sample holder (73) on which a sample (23) intended to be irradiated by the particle beam (17) can be arranged; A vacuum space (3, 5, 7, 9) in which the sample holder (73) is arranged; turbomolecular pump (97); Buffer space (121); Fore-pump (95); and A controller (15) configured to cause the particle beam system (1, 1') to perform the method according to any one of claims 1 to 11.

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