Method for operating an ion beam column, computer program product and ion beam system

Abstract

The present invention relates to a method for operating an ion beam column, comprising: operating the ion beam column in a setting, wherein the ion beam column generates an ion beam and directs it towards an object such that a target location of the ion beam in a virtual working plane performs a movement along a first direction in the working plane and a movement along a second direction in the working plane, whereby a material cross-section extending in the second direction and a depth direction is formed by removing material from the object and advanced in the first direction, wherein the movement of the target location along the first direction comprises a feed component which defines a movement of a feed position, and wherein a dose distribution around the feed position is generated for each feed position.which represents a number of ions striking the working plane per feed position, resolved in the first direction; determining a deviation between the material cross-section and a target material cross-section; changing the setting of the ion beam column using the determined deviation so that a shape of the dose distribution changes; and operating the ion beam column in the changed setting, thereby advancing the material cross-section by removing material from the object in the first direction.

Description

The present invention relates to a method, a computer program product and an ion beam system which are suitable for producing a material cross section or a lamella in an object by means of ion beam etching.In the production of a semiconductor-based microstructure, such as an integrated circuit, a computer chip and the like, the quality of the produced microstructure is conventionally determined by analyzing a material cross section of the microstructure. For example, in order to determine the quality of a produced microstructure, a material cross section of the microstructure is first exposed and an image of the exposed material cross section is subsequently recorded and analyzed. For exposing the material cross section, numerous different methods and devices are known from the prior art, such as a cutting method by means of microtome, a method of chemical etching or a method of material removal by means of focused ion beam. Numerous different methods and apparatuses are likewise known from the prior art for recording the images, such as, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM).For an analysis by means of TEM, the object to be analyzed must first be prepared in the form of a so-called TEM lamella which has two surfaces which are as plane-parallel as possible at a distance of a few 10 nm to a maximum of a few 100 nm.In the production of a material cross section to have a target orientation TO and a TEM lamella to have two material cross sections with the same target orientation TO by means of focused ion beam, there is a problem which will be explained with reference to FIG. 1. To explain the problem, it is first assumed that a central axis Z of an ion beam column (not shown) that generates a focused ion beam 1 and the target orientation TO of the material cross section to be manufactured are parallel to each other. The desired orientation TO is fixed relative to the object 3 to be machined.The object 3 in which the material cross section is to be produced is rigidly arranged on a movable object table 4. The ion beam 1 is directed along the central axis Z onto the object 3 and scanned across the object 3 in a y-direction (perpendicular to the paper plane of FIGS. 1 and 2 ) around the central axis Z and slowly moved forward in an x-direction, whereby material (shaded area) is ablated (i.e. removed) from the object 3. During the removal, the object 3 is not moved and the object table 4 remains unmoved, only the ion beam 1 is deflected about the central axis Z.The removal produces a first material cross section 31, which, however, is not oriented parallel to the desired orientation TO as desired, but rather has a deviation a from the desired orientation TO that is different from zero. The deviation α is defined as an angle between a normal vector N of a surface of the first material cross section 31 and the desired orientation TO minus 90°. This deviation α is shown large in the figures for reasons of illustration, but in practice is usually only up to approximately 3°.A comparison method is described below, with which the deviation α between the orientation of the first material cross section 31 and the desired orientation TO can be reduced. In this case, the object 3 is first processed as shown in FIG. 1. Then, the deviation α is determined by measurement, and the stage 4 on which the object 3 is rigidly fixed is tilted by the measured deviation α as shown in FIG. 2. The ion beam 1 is then directed onto the object 3 in the region of the first material cross section 31 (cf. FIG. 2 ), as a result of which material (shaded region) is removed from the object 3 again and a second material cross section 32 is formed from the first material cross section 31. The ion beam column has the same setting for generating the ion beam 1 as in the processing in FIG. 1. The orientation of the second material cross section 32 is now virtually parallel to the desired orientation TO, as a result of which the second material cross section 32 is produced in the desired orientation.However, the method just described has the problem that tilting the object table 4 generally results in the first material cross section being moved out of a working region of the ion beam 1. Before the second removal of material, the first material cross section 31 must therefore first be moved back into the working region of the ion beam 1. For this purpose, the object table 4 must perform additional movements, which in turn cause drifting and further disadvantages. These additional process steps are cumbersome and time-consuming and therefore slow down the production of the material cross section.The related art includes, for example, U.S. Pat. No. 2017 / 0 002 467 A1, DE 10 2016 119 437 A1, DE 10 2010 040 324 B3 and U.S. Pat. No. 2019 / 0 348 256 A1, which disclose the use of ion beams having a specific dose distribution for material processing.In view of the above, the object of the present invention is to provide a possibility for producing a material cross section with a desired desired desired orientation in an object, which reduces the disadvantages of the conventional method.The object is achieved by the subject matters of the independent claims. Advantageous further developments are defined in the dependent claims.A method according to the invention for operating an ion beam column comprises: operating the ion beam column in a setting, whereby the ion beam column generates an ion beam and directs it onto an object such that a target location of the ion beam in a virtual working plane carries out a movement along a first direction in the working plane and a movement along a second direction in the working plane, whereby a material cross section extending in the second direction and a depth direction is generated by removing material from the object and is advanced in the first direction, wherein the movement of the target location along the first direction comprises an advancement component which determines a movement of an advancement position, and that a dose distribution about the advancement position is generated for each advancement position, said dose distribution representing a number of ions impinging on the working plane resolved in the first direction; determining a deviation between the material cross section and a target material cross section; changing the setting of the ion beam column using the determined deviation such that a shape of the dose distribution changes; and operating the ion beam column in the changed setting, thereby advancing the material cross section in the first direction by removing material from the object.A computer program product according to the invention comprises computer-executable instructions which, when executed by a controller of an ion beam system, cause the ion beam system to carry out the methods described herein. The computer program product may be a computer program realized in an information carrier, for example in a machine readable storage device (a computer readable medium, a non-transitory computer readable storage medium, and the like), or in a signal for processing by a data processing device or for controlling a data processing device, for example a programmable processor, a computer, or a plurality of computers.An ion beam system according to the invention comprises: an ion beam column configured to generate an ion beam and deflect the ion beam in a first direction and in a second direction perpendicular to the first direction such that the ion beam can be directed to different locations of a virtual working plane spanned by the first direction and the second direction; and a controller configured to perform the methods described herein.The articles of the invention produce a cross-section of material having an orientation which is slightly different from a desired orientation. In addition, the material cross section is advanced in the first direction. The deviation of the produced material cross section is reduced by changing the setting of the ion beam column, which causes a change in the dose distribution per feed position. In addition, the disadvantages described above with reference to FIGS. 1 and 2 (repositioning of the object in the working region of the ion beam column, drifting of the object table) are avoided, since the object is not moved during the method and does not have to be moved. The material cross section can therefore also be produced more quickly in comparison with the comparison method described above.Brief Description of the DrawingsFIG. 1 shows a first removal of material from an object according to the comparison method, wherein an object table supporting the object is in a first position; FIG. 2 shows a second removal of material from the object carried out after the first removal according to the comparison method, wherein the object table is in a second position; FIG. 3 is a schematic illustration of an ion beam system according to an embodiment of the present invention; FIG. 4 is a flow chart of a method for producing and advancing a material cross section in an object using an ion beam column according to an embodiment of the present invention; FIG. 5 shows a schematic perspective illustration of an object and of feed positions; FIG. 6 shows a time profile of the feed positions; FIG. 7 shows an exemplary dose distribution per feed position; FIG. 8 shows a schematic sectional illustration of a first example of a material cross section in an object according to a first example; FIG. 9 shows a schematic sectional illustration of a second example of a material cross section in an object according to a second example; FIG. 10 shows characteristic properties of a dose distribution; FIG. 11 shows a schematic sectional representation of a first example of a material cross section which was produced starting from the situation shown in FIG. 8 ; FIG. 12 shows a schematic sectional representation of a second example of a material cross section which was produced starting from the situation shown in FIG. 9 ; FIG. 13 shows a first example of a structuring component and a dose distribution effected therewith; FIG. 14 shows a second example of a structuring component and a dose distribution effected therewith; FIG. 15 shows a third example of a structuring component and a dose distribution effected therewith.Ion beam systemReferring to FIG. 3, an ion beam system 100 is described with which the methods described herein are performed. The ion beam system 100 comprises an ion beam column 110 configured to generate and direct an ion beam 1 into a virtual working plane 6 of a working region 101 of the ion beam column 110, and a controller 120 for controlling the ion beam column 110. The ion beam system 100 further includes an object table 102 for holding an object 3 to be processed.The ion beam column 110 comprises an ion source 111, a (exchangeable) beam stop 112, a first beam deflector 113, a second beam deflector 114, a focusing lens 115, a multipole element 118 and an outlet opening 116. The ion source 111, the beam stop 112, the first beam deflector 113, the second beam deflector 114, the focusing lens 115 and the multipole element 118 are connected to the controller 120 by control connections 117. The controller 120 controls the ion beam column 110 and its components by control signals transmitted over the control links 117. The control connections 117 may be wired or wireless.The ion source 111 generates ions, for example Ga ions, from which the ion beam 1 is formed. The beam stop 112 disposed after the ion source 111 serves to adjust the current (unit ampere) of the ion beam 1. The aperture size of the jet shutter 112 may be adjusted by, for example, a motor-driven mechanical shutter. The automatic changing of the jet diaphragm 112 can be carried out, for example, by mechanically replacing the jet diaphragm 112 in a motor-driven manner.The first beam deflector 113 serves to deflect the ion beam 1 in at least one direction (for example, one or two directions). The first beam deflector 113 usually serves to deflect the ion beam 1 in two directions which are oriented perpendicular to one another and to a central axis Z of the ion beam column 110. By deflecting the ion beam 1, the target location of the ion beam 1 in the working plane 6 can be varied, whereby the location of incidence of the ion beam 1 on the object 3 is also varied. The first beam deflector 113 can be formed, for example, by electrodes or coils which generate an electric or a magnetic field in order to deflect the ion beam 1.The second beam deflector 114 is arranged behind the first beam deflector 113 in the propagation direction of the ion beam 1. The second beam deflector 114 serves to deflect the ion beam 1 in at least one direction (for example one or two directions). The second beam deflector 114 usually serves to deflect the ion beam 1 in two directions which are oriented perpendicular to one another and to the central axis Z of the ion beam column 110. By deflecting the ion beam 1, the target location of the ion beam 1 in the working plane 6 can be varied, whereby the location of incidence of the ion beam 1 on the object 3 is also varied. The second beam deflector 114 can be formed, for example, by electrodes or coils which generate an electric or a magnetic field in order to deflect the ion beam 1.If the ion beam column 110 comprises both the first beam deflector 113 and the second beam deflector 114, which can deflect the ion beam 1 in the same direction, an angle of incidence of the ion beam 1 on the working plane 6 (and thus also on the object 3) can be varied by cooperation of the first beam deflector 113 and the second beam deflector 114.The focusing lens 115 serves to focus the ion beam 1 into a focal plane 5. The focusing lens 115 can be formed, for example, by electrodes and / or coils which generate an electric or a magnetic field.The multipole element 118 serves to manipulate the ion beam 1. The multipole element 118 can be configured to generate a multipole field, for example a dipole field, a quadrupole field and / or an octupole field. The multipole field can be used, for example, to manipulate a stigmatism, for example, an astigmatism, of the ion beam 1. The multipole element 118 may comprise one or more electrodes for generating electric fields and / or one or more coils for generating magnetic fields.The ion beam 1 enters a vacuum chamber 130 from the ion beam column 110 through an exit opening 116. The stage 102 is located inside the vacuum chamber 130. The object 3 is rigidly arranged on the object table 102. The controller 120 controls the individual components of the ion beam column 110. The controller 120 may be operated by an operator via one or more input devices 121 (e.g., keyboard, mouse, etc.). Information used or generated in the controller 120 may be output by one or more output devices (e.g., monitor). Signals between the controller 120 and the input and output devices 121, 122 are transmitted through communication lines 124, which may be wired or wireless.The ion beam column 110 has the central axis Z, which is a central axis of the ion beam column 110. The central axis Z runs, for example, centrally within the ion beam column 110. More specifically, the central axis Z runs, for example, centrally through the components of the ion beam column 110 that manipulate (limit, deflect, focus, etc.) the ion beam 1. For example, the central axis Z runs centrally through the first beam deflector 113 and the focusing lens 115. For example, the central axis Z passes through a center point of the exit opening 116 and a center point of a field of view of the ion beam column 110. The field of view of the ion beam column 110 denotes a region in the focal plane 5, onto which the ion beam 1 can be directed by the beam deflector 113 (in the case of only one beam deflector) or the beam deflectors 113, 114 (in the case of a plurality of beam deflectors).Method for Producing and Advancing a Material Cross-SectionA method for producing and advancing a material cross section in an object according to an embodiment of the invention is described below with reference to FIG. 4.As shown in FIG. 4, the method in step S 1 comprises operating the ion beam column 110 in a setting. The adjustment causes the ion beam column 110 to generate the ion beam 1 and direct the ion beam 1 onto the object 3 in a predefined manner. By directing the ion beam 1 onto the object 3, material is ablated from the object 3, i.e. material is removed.The adjustment causes a target location of the ion beam 1 in the virtual working plane 6 to perform a movement along a first direction x in the working plane 6 and a movement along a second direction y in the working plane 6. The target location denotes that location in the working plane 6 to which the ion beam 1 is currently directed. The target location may be adjusted by the beam deflectors 113, 114.The first direction x and the second direction y are mutually different directions of the virtual working plane 6. In particular, the first direction x and the second direction y are oriented perpendicular to the central axis Z of the ion beam column 110. The first direction x and the second direction y span the working plane 6. This means that the first direction x and the second direction y lie in the working plane 6.The working plane 6 is a virtual plane that serves to describe the function of the ion beam column 110 and the deflection of the ion beam 1. The working plane 6 can coincide, for example, with the focal plane 5 of the ion beam column. An object 3 to be processed can be arranged in the working plane 6. In particular, an object 3 to be processed can be arranged such that a planar surface of the object 3 coincides with the working plane 6.By moving the target location in the second direction y, material is removed from the object 3 and a material cross section 31 is thereby produced, which extends in the second direction y and a depth direction. The depth direction approximately corresponds to the propagation direction of the ion beam 1. the movement of the target location in the second direction y is usually significantly faster than the movement of the target location in the first direction x. For example, the ion beam 1 is moved (back and forth) in the second direction y so quickly that all raster positions in the second direction y are irradiated before the next feed position in the first direction x is set. Accordingly, the ion beam 1 is moved more slowly in the first direction x than in the second direction y.By the movement of the target location in the first direction x, the material cross section 31 is advanced in the first direction x. That is, the position of the material cross section 31 relative to the object 3 changes in the first direction x (more specifically, increases in the first direction x).The movement of the target location along the first direction x comprises a feed component which defines a movement of a feed position x v. The feed position x v indicates the position in the first direction x at which the material cross section 31 is to be produced. In other words, the feed position x v indicates the desired position of the material cross section to be produced. In order to advance the material cross section 31 in the first direction x in the object 3, the feed position x v= x i is advanced in the first direction after completion of the material cross section, i.e. set to a higher value, so that a new material cross section is generated at the new feed position x v= x i+1( i is a natural number).FIG. 5 shows a schematic perspective illustration of the object 3. the object 3 is arranged such that the working plane 6 and a planar surface of the object 3 coincide. The first direction x and the second direction y lie in the working plane 6. FIG. 5 furthermore shows feed positions. A grid 7, which is represented by dashed lines in FIG. 5, is used to represent feed positions in the first direction x and the second direction y. At each vertex and each intersection point of the grid 7, there is a feed position x v, y v. The ion beam 1 extends approximately along the (negative) z direction, which is perpendicular to the first direction x and the second direction y. The feed positions x v, y v are spaced apart from each other in the first direction x by the distances dx1, dx2, dx3, etc. Typical sizes of the distances dx 1, dx 2, dx 3 are 10 nm to 1 μm.FIG. 6 shows an exemplary temporal profile of the feed position x v, y v with four feed positions x v={ x i with i=1 to 4} of the first direction x and five feed positions y v={ y j with j=1 to 5} of the second direction y, resulting in a total of 20 feed positions. This number of feed positions is selected to be small for the purpose of illustration in the present case and is generally significantly larger in practice. During x v= x 1 the ion beam 1 is moved in the second direction y successively to the five feed positions y 1, y 2, y 3, y 4, y 5 of the second direction y and remains there in each case for an adjustable dwell time. As a result, a material cross section is produced at the current feed position x 1 which extends in the second direction y (and a depth direction). The same procedure is adopted at each further feed position of the first direction x v= x 2 or x v= x 3 or x v= x 4 respectively. In this way, material cross sections are successively produced at each of the feed positions x v of the first direction. With each further feed position in the first direction x, the material cross section is driven further in the first direction x.The feed component of the first direction x indicates, for example, at which speed the material cross section 31 is advanced in the first direction x in the object 3. The feed component essentially only defines the position of the material cross section 31 in the first direction x.However, while the target location of the ion beam 1 is set to a position in the working plane 6 (for example, the feeding positions x v, y v) the ions of the ion beam 1 meet not only the position but a limited range around the position. The distribution of the number of ions which strike the working plane 6 resolved according to the first direction x and according to the second direction y, while the feed positions x v, y v are set to a specific position, is referred to as dose distribution. In other words, the period of time during which the ions striking the working plane 6 contribute to the dose distribution of the currently set feed position is limited to the time during which the feed position is unchanged or constant.The shape of the dose distribution influences the shape of the material cross section, for example an angle of inclination of the material cross section (with respect to the central axis Z of the ion beam column 110).The shape of the dose distribution is on the one hand due to the nature of the ion beam 1, which consists of mutually repulsive ions. The ions repelling each other contribute to a scattering of the dose distribution. The shape of the dose distribution is furthermore caused by components of the ion beam column 110 which shape the ion beam 1. These components are, for example, the ion source 111, the beam stop 112 and the focusing lens 115. However, as described later, the shape of the dose distribution may be manipulated by deflecting the ion beam 1 by the beam deflectors 113, 114.FIG. 7 shows an exemplary dose distribution 40 in the first direction x for the feed position x 1. The dose distribution 40 is a usual monomodal distribution, the maximum and the centre of gravity of which lies at the feed position x 1 and which is symmetrical about the feed position x 1. The dose distribution 40 results from the ion beam 1 being directed onto the object 3 for the set dwell time, which is defined for the current feed position x 1.A half width of the dose distribution 40 denotes a width of the dose distribution 40 at half of the maximum value of the dose distribution 40. the half width of the dose distribution 40 shown in FIG. 7 is about twice the distance dx 1 between the feeding positions x 1 and x 2. In general, the half width of the dose distribution 40 is in the range of the distances between mutually adjacent feed positions. The half width of the dose distribution 40 is, for example, at most 50 nm.Operating the ion beam column 110 in the setting causes the material cross section 31 to be generated and advanced in the first direction x in the object 3 by removing material from the object 3. FIG. 8 shows a snapshot of the object 3 during the operation of the ion beam column 110 in a first setting in the form of a schematic sectional illustration through the object 3 in the x-z plane. Material which has been ablated from the object 3 by operating the ion beam column 110 is identified in each case by a shaded region in FIGS. 8 and 9. FIG. 8 shows the state after the dose distribution 40 at the feed position x 1( indicated by a broken line) is applied to the object 3. A snapshot of the object 3 during the operation of the ion beam column 110 in the first setting at a later point in time would show the material cross section 31 with the same orientation at a different position in the first direction x.The generated material cross section 31 is characterized as follows: a normal vector N 1 is orthogonal to the material cross section 31 and thus describes the orientation of the material cross section 31. The desired orientation TO denotes a desired orientation of the desired material cross section. The first angle β1 indicates, among the two angles existing between the normal vector N1 and the target orientation TO (angle β1 and its counter angle β1'=180°-β1), the angle on the side facing the ion beam column 110.A first deviation α1 is defined as: α1=90°-β1. The first deviation α 1 indicates a deviation between the actual orientation of the material cross section 31 and the target orientation TO. The smaller the deviation, the better the produced material cross section corresponds to the desired material cross section.When material (shaded area in FIGS. 8 and 9 ) is removed from the object 3, the ion beam 1 is directed onto the object 3 substantially parallel to the central axis Z of the ion beam column 110. Although the ion beam 1 is directed onto the object 3 substantially parallel to the central axis Z of the ion beam column 110 during the ablation, the non-zero deviation α 1 (and likewise an angle β 1 different from 90°) forms as a result of the ablation in practice. The deviation α1 is in practice up to approximately 3°. A magnitude and a direction (inclination tendency) of the deviation α 1 depend on the specific setting of the ion beam column 110 during the ablation, and each differ from setting to setting (or from shape to shape of the dose distribution), but are well reproducible for the respective setting.By operating the ion beam column 110 in the first setting, the material cross section 31 is formed, for example, such that the angle β 1 is, for example, in the range from 88° to 92°. Accordingly, the deviation α 1 is in the range of +2° to -2°, for example.In the example shown in FIG. 8, the first angle β 1 is, for example, 88° (not drawn to scale) and accordingly the deviation α 1=++2°. In cases where the deviation α 1 is greater than 0° (and likewise the angle β 1 is less than 90°), the inclination tendency of the material cross section 31 has a positive value (positive sign of the deviation α 1). In cases where the deviation α 1 is less than 0° (and likewise the angle β 1 is greater than 90°), the inclination tendency of the material cross section 31 has a negative value (negative sign of the deviation α 1). Such a case is shown in Fig. 9.In the example shown in FIG. 9, the angle β 1 is, for example, 92° (not drawn true to scale) and accordingly the deviation α 1=-2°.The material cross section 31 has a significant size. For example, the material cross section 31 has a dimension of at least 1 μm x 1 μm. This means that the material cross section in the second direction y has a length of at least 1 μm and likewise has a length of at least 1 μm in the depth direction (i.e. direction along the deviation α1).As shown in FIG. 4, after step S 1, the method comprises, in step S 2, determining a deviation between the material cross section 31 and a target material cross section. As a deviation between the material cross section 31 and the target material cross section, for example, the deviation α 1, i.e., the angle between the actual orientation of the material cross section 31 and the target orientation TO, is determined. As a deviation between the material cross section 31 and the target material cross section, for example, the tendency of the material cross section to tilt is determined.As shown in FIG. 4, after step S 2, the method includes determining in step S 3 whether the deviation determined in step S 2 is less than a predefined deviation limit. If the deviation is less than the predefined deviation limit (yes in step S 3), the setting of the ion beam column 110 is ideal in the sense that, by operating the ion beam column 110, a material cross section is driven through the object whose deviation from the target material cross section is unacceptably low. In this case, the ion beam column 110 may be further operated in the existing setting to further advance the material cross section in the object, as illustrated by step S 6. After step S 6, the method can continue with step S 2 in order to repeatedly check whether the current material cross section is still being generated sufficiently accurately (according to the desired material cross section) and in order to optionally adjust the setting of the ion beam column 110 (step S 4).When the deviation is not less than the predefined deviation limit (no in step S 3), the method includes changing, in step S 4, the setting of the ion beam column 110 using the deviation α determined in step S 3 so that a shape of the dose distribution changes. That is, the change in the setting of the ion beam column 110 causes a change in the shape of the dose distribution. The change in the setting of the ion beam column 110 does not need to change the feed component. Specifically, the adjustment of the ion beam column 110 is changed so that the feed component does not change. The changing of the setting is performed so that the deviation α becomes smaller.The shapes of two dose distributions are different from each other when the two dose distributions cannot be made equal by scaling. In other words, two dose distributions dependent on location have different shapes, where k is any real number and "·" is a scalar multiplication. According to this definition, the shapes of the dose distributions 40 and 41 shown in FIGS. 7 and 10 differ from one another.The shape of a dose distribution can be characterized, for example, by the following characteristic values (see FIG. 10 ): a position x max a maximum value of the dose distribution relative to a position x S an average value of the dose distribution, a scatter w of the dose distribution, a symmetry of the dose distribution (existing symmetry of the dose distribution 40 in FIG. 7 compared to no symmetry of the dose distribution 41 in FIG. 10 ) and a skewness of the dose distribution.For example, two dose distributions are different from each other when the positions of the maximum values of the two dose distributions, which are each measured relative to the position of an average value of the dose distribution, are different from each other. An example of an average is the geometric average. For example, two dose distributions are different from each other when the distributions of the dose distributions are different from each other. Examples of the dispersion are the half width, the standard deviation and the variance. For example, two dose distributions are different from each other if the symmetry of the dose distributions is unequal. For example, two dose distributions are different from each other when the slopes of the dose distributions are different from each other. Examples for realizing different dose distributions will be described later.As shown in FIG. 4, after step S 4 in step S 5, the method comprises operating the ion beam column 110 in the changed setting, whereby the material cross section 31 is advanced in the first direction x by removing material again from the object 3. In addition to the advancing of the material cross section caused by the (unchanged) feed component, the shape of the material cross section itself changes due to the changed setting of the ion beam column 110 with which a changed dose distribution is applied at each feed position.Operating the ion beam column 110 in the changed setting causes the material cross section 32 to be generated and advanced in the first direction x in the object 3 by ablating material from the object 3. FIG. 11 shows a snapshot of the object 3 during the operation of the ion beam column 110 in a second setting, which is different from the first setting (FIG. 8 ), in the form of a schematic sectional illustration through the object 3 in the x-z plane. Material which has been ablated from the object 3 by operating the ion beam column 110 is identified in each case by a shaded region in FIGS. 11 and 12. FIG. 11 shows the state after the dose distribution 41 at the feed position x 2( indicated by a broken line) is applied to the object 3. A snapshot of the object 3 during the operation of the ion beam column 110 in the second setting at a later point in time would show the material cross section 32 with the same orientation at a different position in the first direction x.The normal vector N 2 is orthogonal to the second material cross section 32 and thus describes the orientation of the second material cross section 32. the angle β 2 is the angle formed between the normal vector N 2 and the desired orientation TO. The angle β2 indicates, among the two angles existing between the normal vector N2 and the target orientation TO (angle β2 and its counter angle β2'=180°-β2), the angle on the side facing the ion beam column 110. A deviation α2is defined as: α2=90°-β2.Operating the ion beam column 110 in the changed setting (second setting) causes the deviation α 2 of the orientation of the material cross section 32 from the target orientation TO to be smaller than the deviation α 1 (i.e., |α 2|<|α 1|, where |α| denotes the absolute value of α).FIG. 12 shows a snapshot of the object 3 during the operation of the ion beam column 110 in another second setting in the form of a schematic sectional illustration through the object 3 in the x-z plane. FIGS. 11 and 12 differ from one another in different inclination tendencies of the material cross section 32.As shown in FIG. 4, after step S 5, the method can continue with step S 2. Thereby, steps S 2 to S 5 are repeatedly performed until the deviation α is less than the predetermined deviation limit (Yes at step S 3).Possibilities for Changing the Shape of the Dose DistributionThe change in the shape of the dose distribution in step S 4 of FIG. 4 can be realized in various ways, which are explained below by way of example. First, some examples of a first class of possibilities for changing the shape of the dose distribution in which the target location of the ion beam 1 is manipulated by deflecting the ion beam 1 by the beam deflectors 113, 114 will be described.According to one embodiment, the movement of the target location along the first direction x (next to the feed component) further comprises a structuring component which determines a movement of the target location relative to the feed position x v and thereby influences the dose distribution around the feed position x v. Changing the shape of the dose distribution may in this case comprise changing the structuring component.FIG. 13 shows a first example of a structuring component 51 and a dose distribution 42 effected therewith. FIG. 14 shows a second example of a structuring component 52 and a dose distribution 43 effected therewith. FIG. 15 shows a third example of a structuring component 53 and a dose distribution 43 effected therewith.The movement defined by the structuring component 51 to 53 is illustrated in FIGS. 13, 14 to 15 by a diagram which specifies the position coordinate of the target location of the ion beam 1 in the first direction x as a function of time. An extent S of the movement about the feed position x v defined by the structuring component 51 to 53 is limited. This means that the movement defined by the structuring component 51 to 53 is limited to a limited spatial range around the feed position x v. The extent S of the movement defined by the structuring component 51 to 53 in the working plane 6 is, for example, at most 500 nm, in particular at most 200 nm, further in particular at most 100 nm. For example, a ratio of the extent S of the movement defined by the structuring component 51 to 53 in the working plane 6 around the feed position x v to a distance between the feed position x v and the next feed position x v+1 is at most 2, in particular at most 1.5, further in particular at most 1 or at most 0.75. In the example of FIGS. 13, 14 to 15, the structuring component 51 to 53 each defines that the target location is successively set to a plurality of grid positions 60, 61 (represented by dotted lines, not all grid positions are provided with reference symbols) distributed in the first direction x around the feed position x v. The distances between the grid positions 60, 61 are significantly smaller than the distances dx 1, dx 2, dx 3, etc. between adjacent feed positions (cf. FIG. 5 ). For example, the distances between the grid positions 60, 61 are at most 1⁄4 of the distances dx1, dx2, dx3, etc.In the example of FIGS. 13 and 14, the structuring component 51, 52 determines that the target location is repeatedly moved forward and backward in the first direction x.The deflection of the ion beam 1 about the feed position x v results in a dose distribution which has a higher scattering w compared to a dose distribution which is generated without deflection of the ion beam 1 about the feed position x v.In the example shown in FIG. 13, the dose distribution 42 is symmetrical (about the feed position x v). However, this is merely exemplary and the dose distribution may be asymmetric, as shown with dose distributions 43 and 44.In the example shown in FIG. 13, the distances between the raster positions 60 are the same. However, this is merely exemplary and the distances between the grid positions 60 may be different, as is shown by way of example in FIG. 15 by the grid positions 61.In the examples shown in FIGS. 13 and 14, the patterning components 51 and 52 each cause the target location of the ion beam to vary in the first direction x with a magnitude that repeatedly decreases and increases.The changing of the structuring component 51 to 53 can be achieved by: changing a spatial arrangement of the grid positions 60, 61. for example, by changing the structuring component 51 shown in FIG. 13 to the structuring component 53 shown in FIG. 15, the spatial arrangement of the grid positions is changed.The changing of the patterning component 51 to 53 may be achieved by: changing at least one distance between the raster positions 60, 61. for example, the distances between the raster positions may be the same, respectively, and this uniform distance may be changed. This changes the variation of the dose distribution. According to another example, the distances between the raster positions can be individually set to different values. For example, by changing the distances between the grid positions 60 shown in FIG. 13 to the distances between the grid positions 61 shown in FIG. 15, the symmetry and skewness of the dose distribution change.The changing of the structuring component 51 to 53 can be achieved by: changing dwell times of the ion beam 1 at the raster positions 60, 61. By changing the dwell times at the individual raster positions, the symmetry and the skewness of the dose distribution can be changed. An assignment of different dwell times to individual grid positions is illustrated in FIG. 15. The dwell time of a raster position denotes the time duration for which the target location of the ion beam is set to the raster position, while the feed position is constant.A second class of options for changing the shape of the dose distribution in which the target location of the ion beam 1 is not manipulated will be described below.Changing the shape of the dose distribution by changing the setting of the ion beam column 110 can be achieved, for example, by: changing a focusing of the ion beam 1; and / or changing an astigmatism of the ion beam 1 in the working plane 6; and changing a landing energy of ions of the ion beam 1 on the object 3.The astigmatism of the ion beam 1 can be configured here such that a short axis of the astigmatism in which the ion beam 100 has a short extent is oriented along the first direction x (feed direction) and a long axis of the astigmatism in which the ion beam 100 has a long extent is oriented along the second direction y. Changing the astigmatism means, for example, that the ratio of an extension of the ion beam 100 along the first direction to an extension of the ion beam 100 in the second direction is changed.The landing energy of the ion beam 1 denotes the kinetic energy with which the ions of the ion beam 1 strike the object 3. The landing energy can be set, for example, by a parameter value for controlling an electrical potential which is applied to the object 3. The landing energy of the ions of the ion beam 1 can be adjusted, for example, by a parameter value for controlling an acceleration voltage for accelerating the ion beam 1.The explained possibilities for changing the dose distribution can be combined with one another.With the method described above, by changing the setting of the ion beam column 110, which causes a change in the dose distribution per feed position, a material cross section can be produced and advanced in the object 3, the orientation of which differs only slightly from a desired orientation TO.Position and Orientation of the Object during the MethodIn the method, the object 3 does not need to be moved relative to the ion beam column 110, whereby the method can be performed faster than the comparison method described with reference to FIGS. 1 and 2. Accordingly, during the operation of the ion beam column 110, the object 3 has the same position and orientation relative to the ion beam column 110 in the setting (step S 1) and in the changed setting (step S 5). In other words, the orientation between the ion beam column 110 and the object 3 remains unchanged during steps S 1 and S 2. This makes it possible to carry out a fine and precise adaptation of the orientation of the material cross section.It may occur that the method described in FIG. 4 cannot achieve a rough adaptation of the orientation of the material cross section, since only slight changes in the orientation of the material cross section can be achieved by the method described in FIG. 4. For coarse adaptation of the orientation of the material cross section, for example, an angle of incidence of the ion beam 100 on the object 3 can be adapted. The adaptation of the angle of incidence of the ion beam 100 on the object 3 can be carried out, for example, by multiple deflection of the ion beam 100 by the first beam deflector 113 and the second beam deflector 114. Additionally or alternatively, the adaptation of the angle of incidence of the ion beam 100 on the object 3 can be carried out, for example, by tilting the object table 102.Patting IncidenceDuring steps S 1 and S 5, the ion beam 1 impinges upon a surface of the object 3 with a striving incidence, from which the material cross sections are formed by the removal of material. This means that the ion beam 1 is directed onto the material cross sections with a striving incidence. The "streaking" means that an angle between the ion beam 1 and a normal vector of the surface from which material is ablated is in the range from 80° to 100°, in particular in the range from 85° to 95°, further in particular in the range from 88° to 92°.ImplementationThe method shown in FIG. 4 may be implemented, for example, as follows using the ion beam system shown in FIG. 3. The steps of the method are implemented by the controller 120 by the controller 120 executing a predefined program.Alternatively, steps S 2 and S 4 may be supported or performed by an operator.With regard to step S 2, this means, for example, that the operator controls the ion beam system 100 in such a way that an image of the material cross section is recorded, which permits the determination of the deviation by the operator. Alternatively, the controller 120 may execute a program that automatically executes these steps.Regarding step S4, for example, this means that the operator changes the setting. Alternatively, the controller 120 may execute a program that automatically executes this step. Such a program may be realized or use conventional programming or machine learning techniques, for example.Knowledge of how a certain deviation and an advantageous change in the setting of the ion beam column are related can be determined, for example, by an experimental series of experiments. The results of the series of experiments can be used to build a model of the relationship. The model can be developed, for example, using a machine learning technique, so that the model is ultimately suitable for determining, as an input variable, a suitable change in the setting in step S 4 from a deviation determined in step S 2 as an output variable.The controller 120 can manipulate the ion beam 1 in a variety of ways in order to achieve the change of the setting in step S 4 and the change of the dose distribution to be effected therewith. The current intensity of the ion beam 1 can be adjusted, for example, by a parameter value for controlling the ion source 111 or for controlling the exchangeable beam diaphragm 112. The focusing of the ion beam 1 can be adjusted, for example, by a parameter value for controlling the focusing lens 115. The kinetic energy of the ions of the ion beam 1 can be adjusted, for example, by a parameter value for controlling an acceleration voltage. The angle between the ion beam 1 and the central axis Z of the ion beam column 110 when it impinges on the working plane 6 or the object 3 (angle of incidence) can be set, for example, by a parameter value for controlling the beam deflectors 113, 114. The dwell time of the ion beam 1 per raster position can be adjusted, for example, by a parameter value for controlling the beam deflectors 113, 114. The distance between raster positions can be adjusted, for example, by a parameter value for controlling the beam deflectors 113, 114. The spatial and / or temporal arrangement of successively irradiated raster positions can be set, for example, by a parameter value for controlling the beam deflectors 113, 114.The determination of the deviation α by measurement can be carried out, for example, as follows. One or more images of the object 3 with the material cross section 31, 32 are recorded and analyzed. For example, in the region of the material cross section 31, 32 there is a previously known microstructure with a previously known shape. By comparing a sectional view of the microstructure included in the captured image with the previously known shape of the microstructure, the deviation α (in the form of an angle or the inclination tendency) can be determined. The image analysis may be performed by the controller 120, for example. The method for measuring the deviation is not limited to the above-described method.For capturing the image or for measuring the angle in general, the object 3 can be processed and analyzed with a FIB-SEM device. The FIB-SEM apparatus is an apparatus having the ion beam column 110 and a scanning electron microscope, both of which operate in a same working range. In this case, the controller 120 controls both the ion beam column 110 and the scanning electron microscope.VariantsThe method for producing a material cross section in an object has been described above. However, the process can be used to produce other articles and shapes. For example, a TEM lamella can be produced by applying the method several times. For this purpose, two material cross sections are each produced according to the described method at different positions of the object, wherein the two material cross sections have a distance in the range from approximately 10 nm to a few 100 nm. Instead of the deviation α between the orientation of the material cross section and the desired orientation, a measure for the parallelism of the two surfaces of the TEM lamella can serve as the basis for changing the dose distribution, which measure can be determined, for example, by a homogeneity of the transitivity of the TEM lamella.Embodiments of the invention have been described above. Further embodiments may be formed by omitting features or combining features.List of reference characters1 Ion beam 3 object 4 stage 5 focus plane 6 working plane 7 grid 31, 32 material cross section 40 to 44 dose distribution 51 to 53 structuring component 60, 61 grid positions 100 ion beam system 101 working region 102 stage 110 ion beam column 111 ion source 112 beam diaphragm 113 first beam deflector 114 second beam deflector 115 focusing lens 116 exit opening 117 control connections 118 multipole element 120 controller 121 input device 122 output device 124 communication lines 130 vacuum chamber N, N 1, N 2 normal vector S extent of the movement TO festgelegten orientation of the material cross section Z to be produced by the structuring component central axis of the ion beam column α, α 1, α 2 deviation β, β 1, β2 angle w dispersion x first direction x v feed position in first direction y second direction y v feed position in second direction

Claims

A method of operating an ion beam column (110), comprising: operating the ion beam column (110) in a setting, whereby the ion beam column (110) generates an ion beam (1) and directs it onto an object (3) such that a target location of the ion beam (1) in a virtual working plane (6) performs a movement along a first direction (x) in the working plane (6) and a movement along a second direction (y) in the working plane (6), whereby a material cross section (31, 32) extending in the second direction (y) and a depth direction is generated by removing material from the object (3) and is advanced in the first direction (x), wherein the movement of the target location along the first direction (x) comprises a feed component which defines a movement of a feed position (x v), and in that a dose distribution (40 to 44) is generated around the feed position (x v) for each feed position (x v) which represents a number of ions per feed position (x v) impinging on the working plane (6) resolved in the first direction (x); determining a deviation (α) between the material cross section (31, 32) and a target material cross section; changing the setting of the ion beam column (110) using the determined deviation (α) such that a shape of the dose distribution (40 to 44) changes; and operating the ion beam column (110) in the changed setting, whereby the material cross section (31, 32) is advanced in the first direction (x) by removing material from the object (3).Method according to claim 1, wherein the shape of the dose distribution (40 to 44) is characterized by: a position (x max) of a maximum value of the dose distribution relative to a position (x S) of an average value of the dose distribution and / or a scatter of the dose distribution and / or a symmetry of the dose distribution and / or a skewness of the dose distribution.The method according to claim 1 or 2, wherein a half-width of the dose distribution (40 to 44) is at most 50 nm.The method according to any one of claims 1 to 3, wherein the movement of the target location along the first direction (x) further comprises a structuring component (51 to 53) per feed position (x v) which determines a movement of the target location of the ion beam (1) relative to the feed position (x v) and thereby influences the dose distribution (40 to 44), wherein an extension of the movement determined by the structuring component (51 to 53) around the feed position (x v) is limited, and wherein changing the setting of the ion beam column (110) comprises: changing the structuring component (51 to 53).Method according to Claim 4, wherein the extent (S) of the movement defined by the structuring component (51 to 53) in the working plane (6) is at most 500 nm.The method according to claim 4 or 5, wherein the structuring component (51 to 53) determines that the target location of the ion beam (1) is set successively to a plurality of raster positions (60, 61) distributed in the first direction (x) relative to the feed position (x v) wherein changing the structuring component (51 to 53) comprises: changing a spatial arrangement of the raster positions (60, 61); and / or changing at least one distance between the raster positions (60, 61); and / or changing dwell times of the ion beam (1) at the raster positions (60, 61).The method according to any one of claims 4 to 6, wherein the structuring component (51, 52) determines that the target location is repeatedly moved forward and backward in the first direction (x).The method according to any one of claims 1 to 7, wherein changing the setting of the ion beam column comprises: changing a focusing of the ion beam (1); and / or; changing an astigmatism of the ion beam (1) in the working plane (6); and / or changing a landing energy of ions of the ion beam (1) on the object (3).The method according to any one of claims 1 to 8, wherein the changing of the setting is performed so that the deviation (α) becomes smaller.The method according to any one of claims 1 to 9, wherein the determining of the deviation (α), the changing of the setting, and the operating of the ion beam column (110) in the changed setting are repeated in this order until the deviation (α) is less than a predetermined deviation limit.Method according to one of claims 1 to 10, wherein the ion beam (1) impinges on a surface of the object (3) from which the material cross section (31, 32) is formed during the removal of material from the object (3) with striving incidence.The method according to any one of claims 1 to 11, wherein determining the deviation (α) between the material cross-section (31, 32) and the target material cross-section comprises: measuring an orientation of the material cross-section (31, 32); and determining a deviation (α) of the measured orientation of the material cross-section from a target orientation (TO) as the deviation between the material cross-section (31, 32) and the target material cross-section.The method according to any one of claims 1 to 11, wherein the determining the deviation (α) between the material cross section (31, 32) and the target material cross section comprises: determining a tilt tendency of the material cross section (31, 32) as the deviation between the material cross section (31, 32) and the target material cross section, wherein the tilt tendency indicates whether a deviation of the orientation of the material cross section (31, 32) from a target orientation (TO) has a positive value or a negative value.The method according to any one of claims 1 to 13, wherein the object (3) has the same position and the same orientation relative to the ion beam column (110) during operation of the ion beam column (110) in the setting and in the changed setting.A computer program product comprising computer executable instructions which, when executed by a controller (120) of an ion beam system (100), cause the ion beam system (100) to perform the method of any one of claims 1 to 14.An ion beam system (100) comprising: an ion beam column (110) configured to generate an ion beam (1) and to deflect the ion beam (1) in a first direction (x) and in a second direction (y) such that the ion beam (1) can be directed to different locations of a virtual working plane (6) spanned by the first direction (x) and the second direction (y); and a controller (120) configured to perform the method according to any one of claims 1 to 14.A method for operating an ion beam column (110), comprising: directing an ion beam (1) onto an object (3) such that a target location of the ion beam (1) in a virtual working plane (6) performs a movement along a first direction (x) in the working plane (6) and a movement along a second direction (y) in the working plane (6), whereby a material cross section (31, 32) extending in the second direction (y) and a depth direction is generated by removing material from the object (3) and is advanced in the first direction (x), wherein the movement of the target location along the first direction (x) comprises an advancement component which determines a movement of an advancement position (x v), and that for each feed position (x v) an oblique dose distribution (40 to 44) is generated around the feed position (x v) which represents a number of ions per feed position (x v) impinging on the working plane (6) resolved in the first direction (x); wherein the movement of the target location along the first direction (x) further comprises a structuring component (51 to 53) per feed position (x v) which fixes a movement of the target location of the ion beam (1) relative to the feed position (x v) and brings about the obliqueness of the dose distribution (40 to 44).

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