Device for imaging and processing a sample using a clustered particle beam

Abstract

To provide a device for imaging and processing a sample using a focused particle beam.SOLUTION: The present application relates to a device which includes: (a) at least one particle source which is configured in an ultrahigh vacuum environment; (b) at least one sample chamber which is configured to image the sample in a high vacuum environment and process the sample in a medium vacuum environment; (c) at least one column which is arranged in a high vacuum environment and which has a particle-optical component; (d) at least one detection unit which is arranged within the at least one column; (e) at least one gas line system which terminates at the outlet of the at least one column and which is configured to locally provide process gas that is able to induce a local chemical reaction between a focused particle beam and the sample; and (f) at least one pressure adjustment unit through which the particle beam and particles emanating from the sample pass and which is configured to limit a pressure increase caused at the detection unit to 10 times or less, preferably to 5 times or less, more preferably to 3 times or less, and most preferably to 2 times or less.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Cross-reference This patent application claims the priority of German Patent Application No. DE102022208.597.3, titled "Vorrichtung zum Abbilden und Bearbeiten einer Probe mit einem fokussierten Teilchenstrahl", filed with the German Patent and Trademark Office on August 18, 2022, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a device for imaging and processing a sample using a focused particle beam, particularly an electron beam.

Background Art

[0003] With the progress of nanotechnology, it has become possible to manufacture components with increasingly miniaturized structural elements. For the display and processing of chip structures of microscale or nanoscale components, tools capable of imaging and modifying these chip structures are required.

[0004] A microscope is a powerful tool for imaging nanostructures. In a microscope, a particle beam usually interacts with a sample to be analyzed and / or processed. For example, a microscope that scans a sample using particles having mass, such as electrons, has a highly diffraction-limited resolution when imaging nanostructures by scanning the particle beam over the sample because the de Broglie wavelength of the particles is short in that particle beam. As an example, an electron beam can currently be focused to a diameter in the single-digit nanometer range.

[0005] Since a scanning electron microscope typically operates under vacuum, i.e., high-vacuum (HV) conditions, its electron beam is scattered by interaction with molecules along the path from the electron source to the sample and does not spread as a result. The generation of electrons for the electron beam is carried out, for example, as a result of field emission at a Schottky cathode, in an ultra-high-vacuum (UHV) environment.

[0006] A scanning electron microscope (SEM) or an ion beam (FIB) microscope or a particle beam microscope can generally be modified to be used not only for imaging a sample but also for local processing of the sample. To achieve this purpose, a process gas or a precursor gas is applied to the sample and activated with the aid of a focused particle beam so that a local etching or deposition reaction occurs. A minimum amount or a local minimum concentration of precursor gas particles is required on the sample surface so that the focused particle beam can initiate and sustain a local chemical reaction. Generally, depending on the process gas used, the reaction rate increases as the local gas concentration at the reaction site increases, so it is desirable that the local concentration of the process gas be as high as possible.

[0007] However, when a process gas is introduced into an SEM or an FIB microscope, its HV environment is impaired. As a result, some of the resulting difficulties are briefly touched upon below.

[0008] Some of the process gas and / or its reaction products may enter an optical system or a particle optical system, hereinafter also abbreviated as the particle beam column or column, where they can cause temporary or permanent damage to different components, such as, for example, the particle beam source and / or the particle detector. An SEM has a particle beam column in the form of an electron beam column, abbreviated as the column.

[0009] The cluster particle beam is scattered by the particles of the process gas and / or its reaction products. As a result, the particle beam spreads (a "beam skirt"), and the lateral spatial resolution of the local chemical reaction decreases. Furthermore, due to the resulting beam skirt, it becomes more difficult to control the local chemical reaction.

[0010] Furthermore, gas discharges in locations with high electric field strengths, such as electron optical objective lenses near the sample, can damage the objective lens and / or its voltage supply.

[0011] The process gas or precursor gas may contain harmful gases. From a safety perspective, it is not desirable to frequently replace the gas container of the SEM or FIB system due to a large gas flow.

[0012] To meet these conflicting requirements, various solutions have been developed. For example, U.S. Patent Application Publication No. 2005 / 0199086 describes a special-shaped gas line system that enables symmetrically guiding the process gas around the charged particle beam in the sample being processed. U.S. Patent No. 6872956 describes a cascade-type pump configuration with a forepump, two turbomolecular pumps, and an ion getter pump. U.S. Patent No. 9070533 discusses inserting a process shroud, which is placed on the sample and supplied with gas, into the vacuum chamber of an SEM to minimize the amount of process gas that needs to be supplied.

[0013] U.S. Patent No. 8921811 describes a process cell with a dedicated sample holder, gas inlet and outlet, and a hole for the charged particle beam. The process cell reduces the amount of gas required for sample processing. Apart from the additional expenses associated with the process cell, its use is limited to small samples.

[0014] In a further embodiment for limiting the pressure increase caused by the process gas and / or its reaction products within the column, the column of the device has one or more holes to the HV environment of the microscope. In the prior art, for example, to further protect sensitive components such as optical or particle optical components, diaphragms, ion getter pumps, etc., a pressure stage tube is used to divide the column of the microscope into two parts with respect to pressure, which are very important for continuously maintaining a high vacuum, especially for protecting the Schottky cathode used for field emission. The pressure stage tube is a long (e.g., 15 mm) and thin (e.g., 1 mm in diameter) tube that allows the passage of a collimated particle beam. The pressure stage tube significantly reduces (e.g., up to 0.01 l / sec in the case of nitrogen) the conductance of the precursor gas and / or the particles of its reaction products in the molecular flow pressure region. The proportion of the process gas that can pass through the pressure stage tube is about 0.1%. This residual component is removed from the system using an ion getter pump connected upstream of the Schottky cathode.

[0015] However, this solution still has some drawbacks. The pressure stage tube should be as long and have as small a diameter as possible so as to provide good separation with respect to the pressure from the upper part to the lower part of the column of the device. However, these requirements lead to a degradation of the beam quality of the particle beam passing through the pressure stage tube due to the adsorption of the particles of the process gas and / or its reaction products or the deposition of other contaminants from the column. As an example, these can cause scars and / or drifts of the particle beam. Due to these effects, the stability of the microscope process can be significantly reduced.

[0016] Since the diameter of the pressure stage tube is small, it is necessary to attach the detector used for imaging the sample below the pressure stage tube. The particles emitted from the sample and used for detection purposes have a significantly larger solid angle than the primary focused particle beam directed at the sample. Since the detector needs to have resistance to high-concentration corrosive gases, the placement of the detector is restricted within the microscope, limiting the number of available detector types. Furthermore, there are also problems regarding the space under the objective lens of the microscope, and the resolution can be maximized by minimizing the distance between the objective lens and the sample.

[0017] To minimize damage to the sample caused by particle collisions and limit the lateral spread of local chemical reactions, it is preferable to direct low-momentum energy particles onto the sample. However, especially when the incident energy of the particles in the particle beam on the sample is low, it is desirable to detect all particles emitted from the sample, particularly those emitted from the sample at a small polar angle with respect to the beam direction of the primary particle beam. However, for this purpose, it is necessary to spatially separate the particles moving substantially antiparallel to the particle beam from the particle beam. The long and rigid pressure stage tube described above blocks the passage of a significant portion of the particles emitted from the sample. However, shortening and / or widening the pressure stage tube causes the pressure in the region above the modified pressure stage tube to increase to a level where, for example, an ion getter pump can no longer operate.

[0018] Poor HV conditions are common in the region of the column below the pressure stage tube. This means that the particle beam is exposed to interactions with gas particles in a significant portion of the path to the sample. The resulting scattering of the particles in the particle beam leads to an increase in the width of its focal diameter.

[0019] Therefore, the present invention addresses the problem of identifying a device that enables improvement in the imaging and processing of a sample using a focused particle beam.

Prior Art Documents

Patent Documents

[0020] [Patent Document 1] U.S. Patent Application Publication No. 2005 / 0199086 [Patent Document 2] U.S. Patent No. 6,872,956 [Patent Document 3] U.S. Patent No. 9,070,533 [Patent Document 4] U.S. Patent No. 8,921,811 [Summary of the Invention]

[0021] According to an exemplary embodiment of the present invention, this problem is at least partially solved by the subject matter of independent claim 1 of this application. Exemplary embodiments are described in the dependent claims.

[0022] In an embodiment, a device for imaging and processing a sample using a focused particle beam includes: (a) at least one particle source configured to generate a particle beam in an ultrahigh vacuum environment; (b) at least one sample chamber that serves to accommodate the sample, is configured to image the sample in a high vacuum environment, and is configured to process the sample in a medium vacuum environment; (c) at least one column disposed in the high vacuum environment and having at least one particle-optical component configured to shape a focused particle beam from the particle beam and direct the focused particle beam toward the sample; (d) at least one detection unit disposed within at least one column and configured to detect particles emanating from the sample; (e) at least one gas line system that terminates at an exit of the focused particle beam from the column and is configured to locally provide at least one process gas to the sample at a pressure such that the focused particle beam can induce a particle beam-induced local chemical reaction to process the sample; and (f) at least one pressure adjustment unit configured to limit a pressure increase occurring in at least one detection unit as a result of processing the sample, which is caused by passage of the particle beam and particles emanating from the sample, to 10 times or less, preferably 5 times or less, more preferably 3 times or less, and most preferably 2 times or less, without preventing access of the particles emanating from the sample to the at least one detection unit.

[0023] Since the detection unit is (at least) continuously used in a high vacuum (HV) environment, it is hardly exposed to the action of corrosive gases that may occur during sample processing. As a result of excluding this boundary condition, the range of detectors that can be used for sample imaging has increased. Furthermore, contamination of the detection unit due to adsorption of gas particles on the detector surface, for example, is effectively prevented. Additionally, highly sensitive optical components or particle optical components of the column are protected from possible contamination or even damage as a result of the unchanged HV conditions.

[0024] At the same time, the pressure adjustment unit according to the present invention enables substantially all particles emitted from the sample to access the detection unit without being hindered. This enables realistic imaging of the sample. Furthermore, the beam quality of the focused particle beam is not impaired while passing through the pressure adjustment unit. Thereby, a decrease in process stability can be avoided. Therefore, the device according to the present invention enables the sample to be processed at a high local process gas concentration and at the same time prevents contamination or even damage of highly sensitive particle optical components, thus enabling high-quality imaging of the sample.

[0025] Medium vacuum (fine vacuum; FV) includes a pressure range from 1 millibar, i.e., 100 Pa, to 10 -3 millibar, i.e., 0.1 Pa. The HV region is adjacent to the FV region and includes a pressure range from 10 -3 millibar to 10 -8 millibar. Ultra-high vacuum (UHV) has an even lower pressure, specifically from 10 -8 millibar to 10 -11Millibars occur. When proceeding from atmospheric or normal pressure and standard conditions (1013.25 millibars, 298K), the mean free path length of gas particles in the FV region reaches a value exceeding the dimensions of a typical vacuum vessel, and initially, the viscous gas flow transitions through the Knudsen flow to the region of molecular gas flow. In the molecular flow region, gas particles no longer interact with each other and only interact with the walls of the vacuum vessel. In the device according to the present invention, the pressure conditions under which the molecular flow of gas particles is formed are common everywhere except at the location where the sample is processed.

[0026] The particles of the particle beam can be particles without rest mass (m0 = 0 kg), such as photons, or can comprise particles with rest mass (m0 > 0 kg), such as electrons, ions, atoms, or molecules. Currently, an electron beam is preferred. On the one hand, electrons have a short de Broglie wavelength due to their low rest mass and can be focused to a small spot diameter. On the other hand, unlike, for example, ion bombardment, irradiating the sample with electrons does not cause damage to the sample or causes only very slight damage. The term particle optical component comprises components that can shape particles without rest mass, such as photons, and / or particles with rest mass, such as electrons, to form a focused particle beam.

[0027] The particles emitted from the sample can potentially be photons, electrons, and / or ions. The particles emitted from the sample preferably include secondary electrons (SE) and / or electrons backscattered from the sample (BE; backscattered electrons). In addition, if necessary, photons emitted by the sample can be used to analyze the sample.

[0028] The type of particles incident on the sample can be the same as the type of particles detected by the detection unit. However, when the first and second particle types indicate different particle types, it is also possible that the first particle type is incident on the sample and the second particle type is detected by the detection unit. As an example, the first particle type can include photons and / or ions, and the second particle type can include electrons.

[0029] In the region of at least one detection unit, if the processing process is not executed, at least one column has a pressure of <10 -5 mbar, preferably <3·10 -6 mbar, more preferably <10 -6 mbar, most preferably <3·10 -7 mbar and can have.

[0030] The device according to the invention enables the detection unit to operate continuously in an HV environment. This expands the range of detectors that can be used in the detection unit.

[0031] In the region of at least one particle source of at least one column, the pressure increase as a result of sample processing is <10 -8 mbar, preferably <5·10 -9 mbar, more preferably <10 -9 mbar, most preferably <10 -10 mbar and can remain.

[0032] At least one column can be provided with a vacuum pump port and / or can be provided with at least one pressure-type bypass port to the sample chamber.

[0033] The sample chamber is provided with at least one port for a vacuum pump. Without introducing process gas, the vacuum pump reduces the pressure in the sample chamber to the pressure in the HV region, usually about 10 -5Reduce from millibar to 10 -7 Reduce to millibar. Introduce a process gas and initiate a local chemical reaction to generate a reaction product of the process gas and the sample, resulting in an increase in the local pressure within the sample chamber. Unreacted process gas and a portion of the generated reaction product are removed from the sample chamber via the vacuum pump port of the sample chamber.

[0034] At least one vacuum pump port and / or at least one pressure type bypass port to the sample chamber can be arranged at the lower part of at least one column.

[0035] Since the local chemical reaction occurs immediately near the beam exit of the focused particle beam from the column, there is a possibility that a portion of the process gas and the generated reaction product may enter the column of the device. Reactive or highly reactive particles of the process gas and corrosive reaction products need to be removed from the column as quickly as possible to avoid contamination and even damage to the sensitive particle optical components arranged in the column. For this purpose, the column is provided with at least one port for a vacuum pump. This vacuum pump port is arranged as close as possible to the exit of the particle beam from the column to prevent the process gas and / or its reaction product from entering the upper part of the column. Instead of a dedicated vacuum pump, the vacuum pump port of the column can be connected to the pressure type bypass port (bypass) of the sample chamber and pumped by the vacuum pump of the sample chamber.

[0036] In the following, when referring to the lower part of the column, this means the part of the column where the focused particle beam exits the column. The upper part of the column indicates the part where the particles of the particle beam source enter the column. Using this rule, the beam direction of the particle beam passes through the column of the device from top to bottom.

[0037] This device may also include at least one turbomolecular pump that pumps into at least one sample chamber. Similarly, the turbomolecular pump may be connected to a vacuum pump port of the sample chamber. In the inlet region, the turbomolecular pump requires a pressure at which gas particles already exhibit molecular flow. This type of vacuum pump can generate pressure in the UHV region.

[0038] The sample may include a photolithography mask.

[0039] Current photolithography masks typically have lateral dimensions of 152 mm × 152 mm. To be able to process the photomask, the sample chamber of the device according to the invention needs to be large enough to accommodate the mask. Furthermore, the sample holder in the sample chamber comprises a displacement element that can displace the photomask over an active area that is typically 142 mm × 142 mm.

[0040] The processing of the photomask, or more generally of the sample, may include local removal of material. In this case, the process gas includes at least one etching gas, for example xenon difluoride (XeF2) or nitrosyl chloride (NOCl). The processing of the sample may also include local deposition of material onto the sample. For this purpose, the process gas includes at least one precursor gas. The precursor gas may comprise metal carbonyls, such as dicobalt octacarbonyl (Co2(CO)8) or TEOS (tetraethyl orthosilicate, C8H 20 04Si). The process gas may also include an additive gas that aids in etching the sample and / or depositing material onto the sample. By way of example, the additive gas may comprise oxygen (O2) or ammonia (NH3).

[0041] At least one gas line system can be configured to locally provide at least one process gas in the sample at a pressure in the range of from 1 millibar to 0.001 millibar, preferably from 0.6 millibar to 0.003 millibar, more preferably from 0.3 millibar to 0.006 millibar, and most preferably from 0.1 millibar to 0.01 millibar.

[0042] The minimum local pressure of the process gas required for the focused particle beam to cause a local chemical reaction depends on the specific reaction. The local chemical reaction stops when it falls below the minimum gas concentration specific to the reaction. In contrast, the highest possible local pressure of the process gas is advantageous for reasons of process economics to accelerate the chemical reaction. However, the high local pressure of the process gas and its associated reaction products leads to the aforementioned adverse effects of a temporary breakdown of the HV conditions in the column and contamination or degradation of sensitive optical or particle-optical components in the column.

[0043] At least one particle source can be configured to generate a particle beam having a current intensity of from 0.1 pA to 10 nA, preferably from 0.3 pA to 3 nA, more preferably from 1 pA to 1 nA, and most preferably from 3 pA to 0.3 nA.

[0044] At least one particle-optical component can be configured to focus the particle beam to a spot diameter of <5 nm, preferably <2 nm, more preferably <1 nm, and most preferably <0.8 nm.

[0045] The spot diameter is defined as R50, which is the radius within which 50% of the beam intensity is contained. As a result of the chemical reaction induced by the particle beam, the radius of the smallest area where the focused particle beam can process the sample is about 3 to 4 times larger.

[0046] At least one detection unit may comprise a scintillation counter, in particular an Everhart-Thornley detector, and / or a semiconductor detector, in particular a direct electron detector.

[0047] The device according to the invention may further comprise at least one element from the following group: magnetic prism, magnetic chicane, and Wien filter, said at least one element being arranged in at least one column and configured to steer the particles emitted from the sample towards at least one detection unit.

[0048] Using a magnetic prism to steer the particles emitted from the sample towards the detection unit makes it possible, in particular, to detect particles whose trajectory is substantially antiparallel to the direction of the particle beam. This portion of the particles emitted from the sample cannot, for example, be detected by an in-lens detector since the in-lens detector has a hole for the passage of the particle beam directed towards the sample. To increase the lateral resolution of the particle beam, in particular an electron beam, the landing energy of the particles, i.e. the kinetic energy when the particles collide with the sample surface, is reduced as much as possible. This reduces the solid angle from which the particles are emitted from the sample. However, this also means that the portion of the particles leaving the sample antiparallel to the focused particle beam increases. The imaging quality of the recorded image of the sample is improved by the detection unit of the device according to the invention which can detect these particles.

[0049] The device according to the invention may further comprise at least one electrode arranged at the outlet of at least one column and configured to scan the focused particle beam over the sample. The at least one electrode may comprise an octupole electrode.

[0050] Furthermore, the device according to the invention may comprise a charge compensation grid arranged below the gas line system at the outlet of at least one column.

[0051] Furthermore, the column of the device according to the invention may include a liner tube (beam guiding tube), and the lower part of the liner tube is inserted into the region of the particle beam outlet and is configured to prevent or reduce contamination of the optical components by the process gas and its reaction products. The radiation tube is usually embodied in the form of a metal tube, for example an aluminum tube, and may have a diameter of several millimeters, for example from 4 mm to 5 mm. An electrostatic potential can be applied to the metal tube, and the electrostatic potential, in combination with the charge compensation grid, generates an electric field that reduces the kinetic energy of the particles of the focused particle beam as they enter the sample. By applying a voltage to the metal tube, the particles of the focused particle beam can be decelerated to a kinetic energy in the range of 100 eV to 1200 eV, preferably from 130 eV to 1000 eV, more preferably from 160 eV to 800 eV, and even more preferably from 200 eV to 600 eV.

[0052] On the one hand, when reducing the landing energy of the particles of the focused particle beam, the area where the particles cause local chemical reactions decreases. On the other hand, when reducing the kinetic energy, as a result of introducing the process gas, in the region where a large pressure or a large particle density is generated, the probability that the particles of the focused particle beam scatter on the molecules of the process gas or its reaction products increases. This impairs the (lateral) control of local chemical reactions.

[0053] Due to its large diameter, the liner tube functions only slightly like a pressure stage, and usually the pressure can be reduced by about a factor of 1.

[0054] At least one pressure adjustment unit may comprise at least one element from the following groups, namely, a differentially pumped pressure stage arranged in at least one column and at least one stop arranged on at least one gas line system at the exit of a focused particle beam from at least one column.

[0055] Both embodiments of the pressure adjustment unit enable there to be no significant breakdown of the HV conditions at the location of the detection unit in the column. That is, the detection unit and further optical components in a part of the column above it are mostly protected from corrosive gas particles. At the same time, the particles emitted from the sample are not substantially impeded along the path to the detection unit, thereby improving the quality of the imaging of the sample by the focused particle beam.

[0056] In this case, the expression "substantially" means that individual particles are scattered at a large angle away from the beam axis of the particle beam by the charge compensation grid and thus cannot enter the holes in the column. Furthermore, when a negative electrostatic potential (for example, from 20 V to 200 V) is applied to the charge compensation grid, charged particles whose kinetic energy is not sufficient to overcome this potential barrier can be prevented from leaving the sample.

[0057] In the beam direction of the particle beam, at least one differentially pumped pressure stage may be arranged in the region of the back-side focal plane of the objective lens in at least one column.

[0058] Placing the differential pump pressure stage at this beam position is advantageous because the beam waist of the beam envelope of the particles emitted from the sample is generated at this position by the objective lens or the objective lens of the device. The differential pump pressure stage reduces the ratio of the process gas entering the upper part of the column and its reaction products by about two orders of magnitude. Without the differential pump pressure stage, 1 to 2 percent of the gas particles entering the column from below may reach the upper part of the column. With the differential pump pressure stage, this ratio is reduced to about 0.02%.

[0059] The device according to the invention may further comprise a turbomolecular pump for pumping the chamber of at least one differential pump pressure stage.

[0060] Furthermore, the column may have a vacuum pump port disposed at the upper part of the column. The device according to the invention may comprise an ion getter pump for pumping the vacuum pump port at the upper part of the column.

[0061] Without the differential pump pressure stage, the pressure at this position of the column would be too high for the ion getter pump. The ion getter pump would get hot and fail. Due to the complex column structure and the problem of vibration isolation of the turbomolecular pump, if a turbomolecular pump is used instead of an ion getter pump to pump the upper part of the column, the required pressure level of <10 -6 mbar at the upper part of the column cannot be ensured.

[0062] The chamber of at least one differential pump pressure stage may comprise a pressure type bypass port to the sample chamber for pumping the inlet region of the chamber of at least one differential pump pressure stage.

[0063] With this configuration, one vacuum pump can be saved, and as a result, the design of the device according to the invention is simplified.

[0064] In the beam direction of the particle beam, at least one differential pump pressure stage can be arranged upstream of the vacuum pump port of the column.

[0065] With this arrangement, it is ensured that most of the process gas entering the column and its reaction products have already been removed from the column by the vacuum pump port of the column.

[0066] The inlet region of at least one differential pump pressure stage may comprise a pressure stage tube having a diameter ranging from 1 mm to 3 mm, preferably from 1.3 mm to 2.7 mm, more preferably from 1.6 mm to 2.4 mm, and most preferably from 1.9 mm to 2.1 mm, and a length ranging from 5 mm to 25 mm, preferably from 7 mm to 183 mm, more preferably from 8 mm to 14 mm, and most preferably from 9 mm to 11 mm.

[0067] As a result of these dimensions, the pressure stage tube has a molecular conductance of 0.10 l / s in the inlet region of at least one differential pump pressure stage.

[0068] The outlet region of at least one differential pump pressure stage may comprise a pressure stage tube having a diameter ranging from 2 mm to 4 mm, preferably from 2.3 mm to 3.7 mm, more preferably from 2.6 mm to 3.4 mm, and most preferably from 2.9 mm to 3.1 mm, and a length ranging from 20 mm to 36 mm, preferably from 23 mm to 33 mm, more preferably from 26 mm to 30 mm, and most preferably from 27 mm to 29 mm.

[0069] As a result of these dimensions, the pressure stage tube has a molecular conductance of 0.12 l / s in the outlet region of at least one differential pump pressure stage. This value and the further conductance values specified in this application relate to nitrogen gas. If other gases are used to investigate the pressure-related conditions in the device, the molecular conductance values vary proportionally to the mass number of the gas used in relation to the mass number of nitrogen.

[0070] The chamber of at least one differential pump pressure stage can have a height in the range of 5 mm to 30 mm, preferably 6 mm to 20 mm, more preferably 7 mm to 15 mm, and most preferably 8 mm to 12 mm. Further, the chamber of at least one differential pump pressure stage can have a width in the range of 10 mm to 30 mm, preferably 13 mm to 27 mm, more preferably 16 mm to 24 mm, and most preferably 19 mm to 21 mm. Further, the chamber can have a length in the range of 50 mm to 200 mm, preferably 70 mm to 150 mm, more preferably 90 mm to 120 mm, and most preferably 95 mm to 110 mm.

[0071] When the height of the chamber of the differential pump pressure stage is large, the molecular conductance in the pump direction increases, and as a result, the pump cross-sectional area directly becomes large. As a result, the upper part of the column is sufficiently separated from the lower part from the viewpoint of pressure. On the other hand, when the height of the chamber is large, the path from the sample to the detection unit of the emitted particles and the accompanying beam expansion increase.

[0072] The chamber of the differential pump pressure stage can have a molecular conductance that is 10 times, preferably 15 times, more preferably 18 times, and most preferably 20 times greater than the molecular conductance of the outlet portion of the differential pump pressure stage.

[0073] Further, the chamber of at least one differential pump pressure stage can be at the potential of the metal tube inserted into the column at the beam outlet.

[0074] At least one aperture can have an adjustable aperture.

[0075] By attaching a throttle directly above the area of the gas inlet, it becomes possible to significantly reduce the volume that needs to be filled with process gas in order to carry out a local chemical reaction. This minimizes the amount of process gas required. This is advantageous in that one or more gas containers of the device according to the invention require little replacement. Furthermore, as the volume filled with process gas decreases, the time required for the accumulation and decrease of the necessary pressure at the reaction site is shortened. Furthermore, the throttle attached directly above the gas line system reduces the portion of process gas and its reaction products that need to enter and be pumped out of the column of the device.

[0076] Furthermore, by adjusting the aperture, first, substantially all particles emitted from the sample can pass through the throttle, and at the same time, the proportion of process gas and its reaction products that can enter the column can be minimized. Also, by adjusting the holes of the throttle, the aperture width of the throttle can be adapted to the distance between the throttle and the sample surface. Finally, the throttle at the outlet of the column shortens the length of the path of the high-concentration gas through which the focused particle beam must pass. Therefore, the probability that the particles scatter in the gas particles is low, and there is no expansion of the focus on the sample surface.

[0077] At least one throttle may comprise at least one piezoelectric actuator configured to adjust the aperture.

[0078] The holes of the throttle can be of any shape. It is preferably a simple geometric shape, such as rectangular or square, and the holes can be changed by a simple piezoelectric actuator configuration.

[0079] At least one piezoelectric actuator can change the area of the aperture by a factor of 1.1, preferably 1.2, more preferably 1.5, and most preferably 2.0.

[0080] The device according to the present invention may further comprise a voltage source configured to apply an electrostatic potential to at least one aperture.

[0081] By applying an electrostatic potential to the aperture, it is possible to remove or at least reduce the distortion of the electric field between the liner tube and the charge compensating grid. The voltage source may apply an electrostatic potential in the range of 20 V to 1000 V, preferably 50 V to 600 V, more preferably 100 V to 400 V, and most preferably 150 V to 300 V to at least one aperture.

[0082] The aperture of the aperture may be larger than the distance from the sample surface to the aperture, preferably 1.5 times, more preferably 1.8 times, and most preferably 2.0 times larger.

[0083] The aperture may be in the range of 100 μm to 3000 μm, preferably 130 μm to 2000 μm, more preferably 160 μm to 1000 μm, and most preferably 200 μm to 600 μm.

[0084] When the quotient of the diameter of the aperture and the distance from the sample surface is 2, if the distance between the aperture and the sample surface is small, the components of the process gas entering the column can be reduced to one-tenth. Thereby, it is possible to surely prevent the ion getter pump that pumps the upper part of the column from being overloaded.

[0085] The distance between the aperture and the sample surface may be in the range of 80 μm to 1000 μm, preferably 100 μm to 800 μm, more preferably 150 μm to 700 μm, and most preferably 200 μm to 600 μm.

[0086] The charge compensating grid may have grid openings in the range of 10 μm to 50 μm, preferably 15 μm to 45 μm, more preferably 20 μm to 40 μm, and most preferably 25 μm to 35 μm.

[0087] The distance between the charge compensation grid and the sample surface can be half the size of the grid holes in the charge compensation grid.

[0088] This device may further comprise a computer system having at least one non-volatile memory medium. The computer system may be configured to control the device during imaging of the sample and / or during processing of the sample.

[0089] The computer program may comprise instructions for prompting the computer system to image and / or process the sample. In particular, the computer system may comprise instructions for adjusting the working distance of the column from the sample and / or for controlling the adjustment of the holes in the aperture.

[0090] In the following detailed description, exemplary embodiments of the present invention that are presently preferred will be described with reference to the drawings.

Brief Description of the Drawings

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Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0092] The presently preferred embodiments of the device according to the present invention are described below. Two embodiments of the device according to the present invention are described in detail using the example of a scanning electron microscope (SEM). However, the device according to the present invention is not limited to the use of a beam of particles having mass in the form of an electron beam. Instead, any particle beam using particles in the form of bosons or fermions can be used in these devices. Further, the use of the device according to the present invention is described using the example of imaging and processing of a photolithography mask. However, this is not meant to imply any limitation. Rather, the device according to the present invention can be used to image and process any desired sample. By way of example, the devices described in the present application can be used to image and modify chip structures or semiconductor structures, MEMS (microelectromechanical systems) and / or PICs (photonic integrated circuits) on a wafer by a particle beam or by a particle beam-induced processing process.

[0093] FIG. 1 represents a schematic cross-sectional view of a device 100 for imaging and processing a sample 190 using a focused electron beam as an example of a focused particle beam. The particle source 110 or electron source 110 includes a Schottky field emitter 105, from which electrons are emitted in a strong electric field in an ultra-high vacuum (UHV) environment (1·10 -10 mbar ≤ p ≤ 3·10 -9 mbar). The electron source 110 includes a vacuum port 115, and an ion getter pump (not shown in FIG. 1) can usually be connected to the vacuum port 115. The electron beam passes through an aperture 120 and enters the upper part 125 of the column 130 of the device 100.

[0094] In FIG. 1 and all subsequent figures, the particle source 110 is flanged to the column 130 at the top of the upper end of the upper part 125. The particle beam enters the column 130 at the upper end and exits the column at the lower outlet 187. Using this rule, the beam direction of the particle beam proceeds from top to bottom. The upstream means the direction opposite to the beam direction, i.e., upward, and the downstream means the beam direction of the particle beam, i.e., downward.

[0095] In the example of FIG. 1, the upper part 125 and the lower part 135 of the column 130 include electron optical components for focusing and directing the electron beam onto the sample 190. The upper part 125 and the lower part 135 of the column 130 are separated from each other by a pressure stage tube 140. The pressure stage tube 140 is designed such that the electron beam can pass through the pressure stage tube 140, but the upper part 125 of the column 130 is mostly shielded from the pressure fluctuations of the lower part 135 of the column 130. For this purpose, a long and thin pressure stage tube 140 is advantageous. Gas particles may be adsorbed on the inner wall of the long and thin pressure stage tube 140. This can lead to a degradation of the beam quality of the electron beam passing through the pressure stage tube 140. This can have an adverse effect on the imaging behavior of the electron beam of the device 100. Furthermore, the disturbance of the beam profile of the focused electron beam can have an adverse effect on the quality of the processing process.

[0096] The pressure at the upper part 125 of the column 130 is typically reduced to about 1·10 -7 mbar (usually from 5·10 -8 mbar to 5·10 -7 mbar) with the help of an ion getter pump (not shown in FIG. 1) connected to the vacuum port 145.

[0097] However, the holes in the pressure stage tube 140 are not large enough for most of the electrons 192 emerging from the sample 190 to pass through. Therefore, the device 100 of FIG. 1 has two so-called lens internal detectors 150, 160 arranged at the lower part 135 of the column 130. However, in the column 130 below the pressure stage tube 140, fluctuating pressure conditions prevail. These are caused by introducing process gas into the process chamber 170 via the gas line system 180. If no process gas is introduced via the gas line system 180, the pressure level at the lower part 135 of the column 130 is in the range of 10 -5 mbar to 10 -6 mbar, i.e., stable HV conditions prevail.

[0098] When a processing process is executed in which a focused electron beam initiates a local chemical reaction on the surface 197 of the sample 190, the pressure level increases between 10 -2 mbar and 10 -4 mbar at the lower part 135 of the column 130. Therefore, the detectors 150, 160 are exposed to a significant concentration of gas. The gas at the lower part 135 of the column 130 contains a significant amount of unreacted process gas and reaction products of the process gas. These reactive gases usually have a significant corrosion potential that can contaminate or damage the detectors 150, 160 and additional electron optical components housed in the lower part 135 of the column 130, such as the objective lens 175.

[0099] The lower part 135 of column 130 is provided with a vacuum pump port 155. Through the vacuum pump port 155, the lower part 135 of column 130 can be evacuated, for example, with the help of a turbomolecular pump (not shown in Fig. 1a). Alternatively, as schematically shown in Fig. 1, the vacuum pump port 155 may form a pressure-type bypass port to the sample chamber 170. The horizontal dashed line 172 indicates the upper end of the sample chamber 170. The sample chamber 170 is provided with a vacuum pump port 165, and through this vacuum pump port 165, the chamber can be pumped. For example, a turbomolecular pump (not reproduced in Fig. 1) can also be used for this purpose.

[0100] In addition to the detectors 150, 160, the lower part 135 of column 130 of device 100 is provided with at least one electron optical objective lens 175 or one objective lens 175 for focusing the electron beam onto the sample 190. In Fig. 200 in Fig. 2, the part of column 130 where the objective lens 175 is located is reproduced enlarged again. As an example of the focused particle beam 250, at the exit of the focused electron beam 250 from column 130, column 130 is provided with octupole electrodes 185, with the help of which the focused electron beam 250 can be scanned over the sample 190. In addition, the gas line system 180 terminates at the octupole electrodes 185. The gas line system 180 provides a process gas in the region of the incident point 260 of the focused electron beam 250 on the sample 190.

[0101] When the gas line system 180 is opened, the pressure in the region where the local chemical reaction takes place may increase between 10 -1 mbar and 10 -3 mbar, that is, in the FV region. The schematic diagram in Fig. 2 shows that most of the unreacted particles of the process gas and the locally generated reaction products can enter the column 130 of device 100.

[0102] To ensure the imaging quality of the electron beam, especially when the landing energy of the electrons is low, the components along the beam path of the electron beam in column 130 are at a potential corresponding to the potential of the electrons in column 130 up to the exit 187 of column 130. To ensure this requirement even when the exit 187 of the electron beam from column 130 is narrow, a replaceable metal tube 220 is usually inserted into the exit 187 of column 130. This metal tube is called the liner tube 220. Generally, the liner tube 220 is manufactured from a non-magnetic and corrosion-resistant material and has a diameter of 4 mm to 5 mm. The liner tube 220 limits the diameter of the column exit 187 in a defined manner and thus has the beneficial side effect of preventing contamination of the electron optical components, or generally particle optical components, accommodated in the lower part 135 of column 130.

[0103] The column 130 of the exemplary device 100 of FIGS. 1 and 2 comprises a charge compensation grid 195 which serves to minimize the influence of the electrostatic charging of the sample 190. To meet this requirement, the distance between the charge compensation grid 195 and the sample surface 197 is selected to be very small. A typical value for this distance is <70 μm. The sample 190 in the form of an electrical insulator, for example a photolithography mask 190, can become charged as a result of irradiation by the focused electron beam 250. The photolithography mask often comprises a quartz substrate which is electrically insulating.

[0104] The device 300 from FIG. 3 schematically shows a column 330 in which the detection unit 350 or detector 350 can operate at a lower pressure level compared to the detectors 150, 160 from FIG. 1. The detector 350 can be a scintillation detector 350, for example an Everhart-Thornley detector 350, and / or can comprise a semiconductor detector, in particular a direct electron detector. The sample chamber 170 from FIG. 1 is not shown in FIG. 3 or subsequent figures for the sake of simplicity.

[0105] Column 330 has a pressure stage 370 with a pressure stage tube 380 at the transition from its lower part 335 to its upper part 325. To protect the detection unit 350 from exposure to the reactive gas, the detection unit 350 is attached to the upper part 325 of the upstream column 330, unlike the detectors 150, 160 in the device 100 from FIG. 1. The holes in the pressure stage tube 380 of the pressure stage 370 are dimensioned such that substantially all electrons 390 emitted from the sample 190 can reach the detector 350. The molecular conductance of the pressure stage 370 is about 0.12 l / s (l / s represents liters per second), and is thus about 13 times greater than the molecular conductance of the pressure stage tube 140 of column 130 in device 100.

[0106] In FIG. 3, the dashed line indicates the beam envelope 395 of the electron beam 390 emitted from the sample 190 or the electron distribution 395 generated by the sample. In the device 300 exemplarily shown in FIG. 3, the pressure stage tube 380 has a diameter of 3 mm and a length of 28 mm. The pressure stage tube 380 does not impede either the primary electron beam 250 emitted from the electron source 110 and focused on the sample 190 or the electron distribution 395 generated by the sample on the path to the detection unit 350.

[0107] However, during the processing of the sample 190, the pressure stage 370 enables breakdown to pressure levels > 10 -5 mbar that an ion getter pump connected to the vacuum pump port 345 (not shown in FIG. 3) cannot handle in the HV environment of the part 325 of the column 330 located above it. The vacuum pump port 345 serves to evacuate the upper part 325 of the column 330 and corresponds to the vacuum pump port 145 of the device 100 from FIG. 1.

[0108] If a vacuum pump that can handle these pressure levels, for example a turbo molecular pump, is connected to the vacuum port 345 instead of an ion getter pump, < 10 -7The required residual gas pressure level in millibar is not achieved at the upper part 325 of column 330. However, this is required, firstly, to reliably protect the electron optical or particle optical components at the upper part 325 of column 330 and, secondly, to adapt the pressure level at the upper part 325 of column 330 to the UHV level of electron source 110. While the sample 190 is imaged, detector 350 "recognizes" a pressure level significantly lower than that of detectors 150, 160. However, during the processing process, the pressure level drops to an unacceptable level. More than 2% of the reactive process gas or its reaction products can pass through pressure stage 370 and proceed to the upper part 325 of column 330.

[0109] Device 400 from FIG. 4 corresponds to device 300 from FIG. 3, except that a differential pump pressure stage 450 is additionally installed. The differential pump pressure stage 450 is installed downstream of column 330, below the pressure stage 370 of device 300. This means that the outlet region 370 of the differential pump pressure stage 450 corresponds to the pressure stage 370 in device 300 from FIG. 3. The pressure stage tube 380 of the differential pump pressure stage 450 is the pressure stage tube 380 of the pressure stage 370 from FIG. 3.

[0110] The differential pump pressure stage 450 has an inlet region 470 formed by the pressure stage tube 480. Since the beam envelope 395 of the electrons 390 emitted from the sample expands in a direction opposite to the beam direction of the primary focused particle beam 250, the holes in the pressure stage tube 480 can be made slightly smaller in size than the holes in the pressure stage tube 380. This will be described in detail below with reference to FIG. 5. The differential pressure stage 450 illustratively shown in FIG. 4 comprises a pressure stage tube 480 with a hole diameter of 2 mm and a length of 10 mm. Thus, the pressure stage tube 480 has a molecular conductance of approximately 0.1 l / s.

[0111] Two opposing requirements are imposed on the chamber 410 of the differential pump pressure stage 450. First, the chamber 410 should have as large a molecular conductance as possible in order to separate the inlet portion 470 as widely as possible in terms of pressure from the outlet portion 370 of the differential pump pressure stage 450, so that the largest possible proportion of the gas particles flowing into the chamber 410 through the inlet portion 470 exits the chamber 410 through the vacuum pump port 465 of the chamber 410. For this purpose, the chamber 410 should be as high as possible. However, this requirement lengthens the path of the electrons 390 emitted from the sample 190 to the detector 350, and thus broadens its beam envelope 395. By simulation, as a good compromise, the height of the chamber was about 10 mm. Also, the chamber 410 has a width of 20 mm and a length of 100 mm.

[0112] The vacuum pump port 465 of the differential pump pressure stage 450 can be pumped, for example, using a turbomolecular pump. For example, when a turbomolecular pump having a pumping capacity of 10 l / s is connected to the vacuum port 465, the proportion of the process gas and its reaction products that can proceed to the upper part 425 of the column 430 beyond the differential pump pressure stage 450 is about 0.02%. This remaining portion can be removed without problem through the vacuum pump port 345 of the upper part 425 of the column. This means that since the pressure level of the upper part 425 of the column 430 is very low, the vacuum pump port 345 can be safely pumped, for example, by an ion getter pump.

[0113] After the installation of the differential pump pressure stage 450, the column 430 of the device 400 meets two opposing requirements. The high-sensitivity electron optical components of the column 430, especially the detection unit 350, are reliably protected against vacuum breakdown and thus against contamination. The electrons 390 leaving the sample 190 are not obstructed along the path to the detection unit 350.

[0114] In FIG. 5, FIG. 500 represents a simulation of the variation of the diameter (x-axis) of the beam envelope 395 of electrons 390 emitted from sample 190 with respect to the distance (y-axis) from the sample surface. The electrons 390 emitted from sample 190 are generated by the primary focusing electron beam 250, and the electrons have a low kinetic energy of about 200 eV at the sample surface 197. The beam envelope 395 has a beam waist 550 with a diameter of about 1 mm approximately 65 mm above the sample surface 197. This is caused by the imaging effect of the electron optical objective lens 175. The waist 550 of the beam envelope 395 marks the back focal plane of the objective lens 175.

[0115] The diameter of the beam envelope 395 is less than 2 mm at a distance from about 25 mm to 105 mm, as indicated by the dashed straight line 510. Within this distance from the sample surface 197, the pressure stage tube 480 of the differential pump pressure stage 450 allows the electrons 390 emitted from the sample 190 to access the differential pump pressure stage 450 without being obstructed. The diameter of the beam envelope 395 is less than 3 mm up to a distance of about 140 mm from the sample surface 197. This is characterized by the dashed straight line 520 in FIG. 5. This means that if the distance from the sample surface 197 to the differential pump pressure stage 450 is less than 140 mm, the electrons 390 emitted from the sample 190 can pass through the pressure stage tube 380 of the differential pump pressure stage 450 without being obstructed. The design of the differential pump pressure stage 450 can be optimized, and its optimal possible placement in the column 430 of the device 400 can be determined based on the simulation of the trajectories of the electrons 390 emitted from the sample 190.

[0116] The upper partial image 600 in FIG. 6 shows the molecular flow of gas particles through the pressure stage 370 from the lower part 335 to the upper part 325 of the column within column 330 from FIG. 3. Some basic equations for estimating the flow of molecules, i.e., the molecular flow, entering or exiting the differential pump pressure stage 450 through the pressure stage 370 are specified below. Under molecular flow conditions, the molecular conductance of nitrogen specified in liters per second (liters per second) in a tube of length L [cm] and diameter d [cm] is given by the following equation, C = 12.1·d 3 / L (see, for example, "Handbuch Vakuumtechnik", ISBN 978 - 3 - 658 - 13386 - 5).

[0117] The molecular flow Q (in units of millibar l / sec) is generated by the pressure difference or pressure gradient Δp. The proportionality constant is the molecular conductance C introduced above, and Q = C·Δp. This equation is equivalent to the basic electrical equation I = (1 / R)·U.

[0118] The molecular conductance of the pressure stage tube 380 of the pressure stage 370 was specified above as C 380 = 0.12 l / sec. A 10 -3 millibar pressure difference between the lower part 335 and the upper part 325 of the column 330 results in Q 380 = 0.12 l / sec·10 -3 millibar = 1.2·10 -4 millibar·l / sec of molecular flow, i.e., molecular flow occurs.

[0119] The lower partial image 650 in FIG. 6 shows the molecular flow, i.e., the molecular flow, in the differential pump pressure stage 450. The molecular gas flow Q 480 flows into the chamber 410 of the differential pump pressure stage 450 through the pressure stage tube 480 of the differential pump pressure stage 450. The molecular gas flow Q 480 is there the molecular flow, i.e., the molecular flow Q 465 and Q 380branches out and exits chamber 410 via vacuum port 465 and pressure stage tube 380. The molecular flow Q 465 , i.e., the molecular flow Q 465 is proportional to the suction capacity S (per second) of the vacuum pump at the pressure p in chamber 410 of the differential pump pressure stage 450, and Q 465 = S·p 410 .

[0120] The molecular conductance of the pressure stage tube 480 of the differential pump pressure stage 450 was specified above as C 480 = 0.1 l / second. When the pressure difference between the lower part 435 of column 430 and chamber 410 is 10 -3 millibar, the molecular flow Q 480 , Q 480 = 0.1 l / second · 10 -3 millibar = 10 -4 millibar·l / second, exists. As a first approximation, when the suction capacity S of the vacuum pump connected to the vacuum port 465 of the differential pump pressure stage 450 is 10 l / second, the pressure setting in chamber 410 of the said pressure stage is p 410 = Q 480 / S = 10 -4 millibar·l / second / (10 l / second) = 10 -5 millibar.

[0121] As specified above, the pressure stage tube 380 has a molecular conductance C 380 = 0.12 l / second at the outlet of the differential pump pressure stage 450. A pressure difference of 10 -5 millibar generates a molecular flow Q 480 = 0.12 l / second · 10 -5 millibar = 1.2·10 -6 millibar·l / second. This means that the differential pump pressure stage 450 reduces the molecular flow at the upper part 425 of column 430 by two digits. Q 380 / Q 480 = 1.2·10 -4 millibar·l / second / (1.2·10-6 (Millibar·l / sec)=100. Only about 1% of the gas particles flowing into the chamber 410 of the differential pump pressure stage 450 exit the chamber 410 through the exit region 370.

[0122] The electrical analogue for the differential pump pressure stage 450 is a voltage divider. The load resistance R L (equivalent to 1 / C 465 is made smaller compared to the resistance R2 (equivalent to 1 / C 480 ), so the current (molecular gas flow) flows largely through the load resistance R L and no longer through the resistance R2.

[0123] The upper partial image 700 in FIG. 7 reproduces again the lower part 335 of the column 330 of the device 300 from FIG. 3. The details of the dotted circle 750 are reproduced again magnified in the lower partial image 755 in FIG. 7. As already explained in connection with FIG. 3, when the process gas 770 is supplied to the sample surface 197 via the gas line system 180, the pressure in the exit region of the focused particle beam 250 or the electron beam 250 from the column 330 increases significantly. When the concentration of the gas particles increases significantly locally, the electrons of the focused electron beam 250 are scattered by the gas particles of the process gas 770, resulting in an unwanted beam spread indicated by the cone 760 in the partial image 755. Depending on the set gas pressure and the kinetic energy of the focused particle beam 250, up to 50% of the electrons can be scattered one or more times in the exit region 750. As a result of the scattering, the lateral size of the local chemical reaction initiated in the process gas 770 by the focused electron beam 250 increases in a difficult-to-predict manner. The limit at which the concentration of the process gas and the concentration of the electrons are no longer sufficient to maintain the local chemical reaction depends on many parameters. The local processing process performed on the sample 190 becomes difficult to control under these conditions.

[0124] The molecular gas flow entering column 335 is proportional to the process gas flow 780 of the gas line system 180. In the case of column 330 of device 300 shown in FIG. 3, about 1.5% of the particles of process gas 770, or the reaction products of process gas 770, can enter the lower part 335 of column 330.

[0125] Sub-image 755 further shows the charge compensation grid 195 from FIG. 1. The charge compensation grid 195 is typically located several tens of micrometers above the sample surface 197 during operation of device 300. To minimize the effect of charging of the sample surface 197 by the focused electron beam 250, the charge compensation grid 195 may be grounded. Further, the potential of the charge compensation grid 195 functions in combination with the potential of the liner tube 220 at the potential of the electron optical objective lens 175 to generate an electric field (not shown in FIG. 7), where the focused electron beam 250 is decelerated to a specified landing energy.

[0126] Furthermore, a voltage U2 in the range from -20 V to -200 V can be applied to the charge compensation grid 195. As a result, the electric field generated between the charge compensation grid 195 and the sample surface becomes an energy barrier or an energy filter for electrons emitted from the sample 190. Only electrons having a kinetic energy greater than the energy barrier can exit the sample 190 and enter column 330.

[0127] The upper sub-image 800 in FIG. 8 represents the lower part 335 of column 330 from FIG. 3. A diaphragm 810 is additionally inserted at the exit of column 330 in the region of the octupole electrodes 185. The region 850 at the exit of column 830 is enlarged and shown again in the lower sub-image 855.

[0128] The aperture 810 is inserted into the electrode 185 at the end of the gas line system 180. The aperture 810 and the sample 190 form a type of pressure chamber without a transverse wall. By restricting the volume of the process gas 870 on both sides, the required amount of the process gas 870 is optimized. The aperture 810 has a hole 820 with a diameter 825 so that the focused electron beam 250 impinges on the sample surface 197 and electrons 390 emitted from the sample 190 can access the lower part 835 of the column 830. The hole 820 of the aperture 810 determines the maximum angle at which electrons 390 emitted from the sample 190 can exit the sample 190. The hole diameter 825 of the aperture 810 can be in the range of, for example, 200 μm to 2000 μm.

[0129] The aperture diameter 825, i.e., the hole diameter 825, can be changed with the help of one or more piezoelectric actuators not shown in FIG. 8. Depending on the distance 840 between the sample surface 197 and the aperture 810, the diameter 825 of the aperture 810 can simply be chosen large enough so that the entry of electrons 390 emitted from the sample 190 into the column 830 is not hindered. At the same time, this ensures that the ratio of the process gas flow that inappropriately enters the column 830 and the molecular flow of the reaction products is minimized. If the distance 840 is selected such that it is half of the hole diameter 825, the aperture 810 has an opening angle of 90° with respect to the electrons 390.

[0130] The distance 830 from the sample surface 197 to the aperture 810 is usually 1 millimeter or less. The currently preferred distance 840 is in the range between 100 μm and 300 μm. The distance 840 between the aperture 810 and the sample surface 197 can be adjusted by raising or lowering the sample 190 to a value within the operating distance of the device 800 with the help of a sample holder (not shown in FIG. 8).

[0131] When the hole diameter 825 is 2 mm and the distance 840 is 1 mm, approximately 1.5% of the process gas 870 or its reaction products enters the lower part 835 of the column 830. This ratio decreases by one digit to 0.15% when the aperture 825 is 400 μm and the distance is 200 μm. When the two sizes are halved again, the ratio of the gas entering the column 830 decreases to approximately 0.05%.

[0132] Furthermore, the aperture 810 effectively shortens the length of the path of the electrons of the focused electron beam 250 under high gas pressure until the distance <1 mm as they move to the sample surface 197. Under these conditions, the focused electron beam 250 hardly experiences beam divergence 860.

[0133] Furthermore, an electrostatic potential can be applied to the aperture 810, which is indicated by U1 in FIG. 8. As a result, the distortion of the electric field between the liner tube 220 and the charge compensation grid 195 caused by the aperture 810 can be significantly avoided.

[0134] When the distance 840 from the sample surface 197 to the aperture and the aperture width 825 of the aperture are set to appropriate dimensions, the aperture 810 effectively blocks the pressure level fluctuations caused by the processing process on the sample 190 at the upper part 825 of the column 830. Therefore, in combination with the pressure stage 370 of the column 830, the aperture 810 effectively protects the high-sensitivity electron optical components, such as the detector 350, at the upper part 825 of the column 830 from the influence of the reactive particles of the process gas 870 and its reaction products. By minimizing the ratio of the process gas 870 and its reaction products, the aperture also prevents contamination and / or damage to the components, such as the objective lens 175, arranged at the lower part 835 of the column 830.

[0135] Naturally, it is also possible to combine the aperture 810 of the device 800 with the differential pump pressure stage 450 of the device 400.

Description of the reference numerals

[0136] 100 device 105 Schottky field emitter 110 electron source, particle source 115 vacuum port 120 aperture 125 upper part of column 130 column 135 lower part of column 140 pressure stage tube 145 vacuum pump port 150 detector 155 vacuum pump port, bypass port 160 detector 165 vacuum pump port 170 process chamber, sample chamber 172 upper end of sample chamber 175 electron optical objective lens, particle optical component 180 gas line system 185 octupole electrode 187 outlet 190 sample 192 electron 195 charge compensation grid 197 sample surface 200 column part 220 liner tube 250 focused electron beam, focused particle beam 260 incidence point 300 device 310 magnetic prism 325 upper part of column 330 column 335 lower part of column 345 vacuum pump port 350 detector, detection unit 355 vacuum pump port 370 pressure stage, outlet region, outlet part 380 pressure stage tube 390 electron, particle 395 beam envelope, electron distribution 400 device 410 Chamber 425 Upper part of the column 430 Column 435 Lower part of the column 450 Differential pump pressure stage, pressure adjustment unit, differential pressure stage 465 Vacuum port, vacuum pump port, bypass port 470 Inlet region, inlet part 480 Pressure stage tube 500 Simulation of the change in the diameter (x - axis) of the beam envelope 510 Diameter of the beam envelope at a distance of about 25 mm to 105 mm 520 Diameter of the beam envelope at a distance of about 140 mm from the sample surface 550 Beam waist 600 Molecular flow 650 Molecular flow 700 Lower part of the column 750 Outlet region 755 Partial image of the lower part of the column 760 Unwanted beam spread 770 Process gas 780 Process gas flow 800 Device 810 Diaphragm, pressure adjustment unit 820 Hole 825 Diameter, width 830 Column 835 Lower part of the column 840 Distance 850 Outlet region of the column 855 Lower part of the column 860 Beam spread 870 Process gas

Claims

1. A device (400, 800) for imaging and processing a sample (190) using a focused particle beam (250), comprising: a. at least one particle source (110) configured to generate a particle beam in an ultra-high vacuum environment; b. at least one sample chamber (170) configured to house the sample (190), image the sample (190) in a high vacuum environment, and process the sample (190) in a medium vacuum environment; c. at least one column (430, 830) disposed in a high vacuum environment and having at least one particle optical component (175) configured to shape a focused particle beam (250) from the particle beam and direct the focused particle beam towards the sample (190); d. at least one detection unit (350) disposed within the at least one column (430, 830) and configured to detect particles (390) emitted from the sample (190); e. at least one gas line system (180) terminating at an exit of the focused particle beam (250) from the column (430, 830) and configured to locally provide at least one process gas (870) having a pressure such that the focused particle beam (250) can induce a locally chemical reaction induced by the particle beam to process the sample (190); f. at least one pressure adjustment unit (450, 810) disposed in the beam direction of the focused particle beam (250) in front of the at least one particle optical component (175) in the at least one column (430, 830), configured to limit a pressure increase occurring in the at least one detection unit (350) as a result of processing the sample (190) to 10 times or less, preferably 5 times or less, more preferably 3 times or less, and most preferably 2 times or less, without preventing access of the particles (390) emitted from the sample (190) to the at least one detection unit (350); Device (400, 800).

2. In the region of the at least one detection unit (350), the at least one column (430, 830) has a pressure of < 10 -5 mbar, preferably < 3·10 -6 mbar, more preferably < 10 -6 mbar, most preferably < 3·10 -7 mbar, of the device (400, 800) according to claim 1.

3. The at least one column (430, 830) comprises a vacuum pump port (155) and / or at least one pressure type bypass port (155) to the sample chamber (170), the device (400, 800) according to claim 1 or 2.

4. The sample (190) comprises a photolithography mask, the device (400, 800) according to claim 1 or 2.

5. The at least one gas line system (180) is configured to locally provide the at least one process gas (870) to the sample (190) at a pressure in the range of from 1 millibar to 0.001 millibar, preferably from 0.6 millibar to 0.003 millibar, more preferably from 0.3 millibar to 0.006 millibar, and most preferably from 0.1 millibar to 0.01 millibar, the device (400, 800) according to claim 1 or 2.

6. The at least one detection unit (350) comprises a scintillation counter, in particular an Everhart-Thornley detector, and / or a semiconductor detector, in particular a direct electron detector, the device (400, 800) according to claim 1 or 2.

7. The device (400, 800) according to claim 1 or 2 further comprises at least one element from the following group: a magnetic prism (310), a magnetic chicane, and a Wien filter, the at least one element being arranged in the at least one column (430, 830) and configured to direct the particles (390) emitted from the sample (190) to the at least one detection unit (350).

8. The at least one pressure adjustment unit (450, 810) comprises at least one element from the following group: a differential pump pressure stage (450) arranged in the at least one column (430, 830) and at least one aperture (810) arranged above the at least one gas line system (180) at the exit of the focused particle beam (250) from the at least one column (430, 830), the device (400, 800) according to claim 1 or 2.

9. In the beam direction of the particle beam (250), the at least one differential pump pressure stage (450) is arranged in the region of the back focal plane of the objective lens (175) in the at least one column (430, 830), the device (400, 800) according to claim 8.

10. The device (400, 800) according to claim 8, further comprising a turbomolecular pump for pumping the vacuum port (465) of the chamber (410) of the at least one differential pump pressure stage (450).

11. The chamber (410) of the at least one differential pump pressure stage (450) comprises a pressure type bypass port (465) to the sample chamber (170) for pumping the chamber (410) of the at least one differential pump pressure stage (450), the device (400, 800) according to claim 8.

12. In the beam direction of the particle beam, the at least one differential pump pressure stage (450) is arranged upstream of the vacuum pump port (155) of the column (430, 830), the device (400, 800) according to claim 8.

13. The inlet region (470) of the at least one differential pump pressure stage (450) comprises a pressure stage tube (480) having a diameter in the range of 1 mm to 3 mm, preferably 1.3 mm to 2.7 mm, more preferably 1.6 mm to 2.4 mm, most preferably 1.9 mm to 2.1 mm and a length in the range of 5 mm to 25 mm, preferably 7 mm to 18 mm, more preferably 8 mm to 14 mm, most preferably 9 mm to 11 mm, the device (400, 800) according to claim 8.

14. The outlet region (370) of the at least one differential pump pressure stage (450) comprises a pressure stage tube (380) having a diameter in the range of 2 mm to 4 mm, preferably 2.3 mm to 3.7 mm, more preferably 2.6 mm to 3.4 mm, most preferably 2.9 mm to 3.1 mm and a length in the range of 20 mm to 36 mm, preferably 23 mm to 33 mm, more preferably 26 mm to 30 mm, most preferably 27 mm to 29 mm, the device (400, 800) according to claim 8.

15. The device (400, 800) according to claim 8, wherein the at least one aperture (810) has an adjustable opening (820).

16. The device (400, 800) according to claim 15, wherein the at least one aperture (810) comprises at least one piezoelectric actuator configured to adjust the adjustable opening (820).

17. The device (400, 800) according to claim 8, further comprising a voltage source configured to apply an electrostatic potential to the at least one aperture (810).

18. The device (400, 800) according to claim 15, wherein the adjustable opening (820) of the aperture (810) is larger than the distance (830) from the sample surface (197) to the opening (820), preferably 1.5 times larger, more preferably 1.8 times larger, and most preferably 2.0 times larger.

19. The device (400, 800) according to claim 15, wherein the adjustable opening (820) comprises a range from 100 μm to 3000 μm, preferably from 130 μm to 2000 μm, more preferably from 160 μm to 1000 μm, and most preferably from 200 μm to 600 μm.

20. The device (400, 800) according to claim 19, wherein the charge compensation grid (195) has a distance from the surface (197) of the sample that is half the size of the grid holes of the charge compensation grid (195).

Images