A method for generating a three-dimensional target structure in a lithographic material using a laser lithography device.

Abstract

The invention relates to a method for generating a three-dimensional target structure (44) in a lithographic material (22) by means of a laser lithography apparatus, comprising the steps of: providing a substrate (40) on which a lithographic material is disposed; locating an interface (54) between the lithographic material and said substrate; defining a target structure by displacing a focal area (28) of a writing laser (14) by means of an optical device (16) within a writing area (34) of a scan plane (36) according to a predetermined writing instruction; applying a writing exposure dose to the lithographic material at the focal area of ​​the writing laser beam to define a structure area (46); sequentially displacing a focal area of ​​a calibration laser beam by means of the optical device to a number of test positions within the writing area of ​​the scan plane in order to locate an interface between the substrate and the lithographic material; applying a test exposure dose to the lithographic material at each test position; and determining position data of the interface (54) from a response of the lithographic material and / or the substrate to the test exposure dose. The invention also relates to a laser lithography apparatus.

Description

Technical Field

[0001] The present invention relates to a method for generating a three-dimensional target structure in a lithography material by means of a laser lithography apparatus. The present invention also relates to a laser lithography apparatus adapted and configured for said method.

Background Art

[0002] The above-described technology is applied, in particular, when generating microstructures or nanostructures in fields where high accuracy and at the same time a degree of freedom in configuration are desired for the structure to be generated. In such a laser lithography method, the writing of the structure is usually carried out by first preparing a substrate on which the lithography material is placed, and then irradiating the lithography material with an exposure dose within the focal region of the writing laser beam, whereby, for example, a structural region is locally defined by locally curing or polymerizing the lithography material. Then, by displacing the focal region in the lithography material, a three-dimensional overall structure can be generated. For this purpose, the focal region of the writing laser beam can be controllable with the accuracy required for structuring within the scan plane by means of an optical device. Such a laser lithography method is known, for example, from German Patent Application Publication No. 102017110241A1.

[0003] In order to be able to generate a structure with high accuracy by applying such a type of laser lithography method, it is necessary to establish as accurate a relationship as possible between the focal region or scan plane of the writing laser beam and the substrate surface on which the structure is to be formed. In particular, it is important to determine as accurately as possible the orientation of the substrate surface relative to the focal region or scan plane. For this purpose, it is basically known to locate the interface between the substrate and the lithography material before the actual writing of the structure and to determine the focus in this way.

[0004] According to U.S. Patent No. 7,893,410,020, a method is known in which a substrate is moved laterally with respect to the optical axis of a writing laser beam by a positioning device, and the orientation of the interface between the substrate and the lithography material is determined at multiple positions relative to the focal region of the writing laser beam. Such a method makes it possible to detect, for example, the tilt of the substrate relative to the scanning surface. [Overview of the project] [Problems that the invention aims to solve]

[0005] The objective of this invention is to generate three-dimensional structures on lithographic materials with high precision. [Means for solving the problem]

[0006] This problem is solved by the method described in claim 1. The subject here is a laser lithography method using a laser lithography apparatus, particularly so-called direct laser writing, performed in a volume portion of a laser lithography material or in a volume portion filled with a laser lithography material.

[0007] According to the above method, first, a substrate on which a lithography material is placed is prepared. The substrate is displaceable by a positioning device of a laser lithography apparatus, which is configured specifically for this purpose. In particular, the substrate is displaceable by the positioning device in all three spatial directions (x, y, z), and moreover, it is tiltable about at least one tilt axis parallel to the substrate surface (xy plane).

[0008] According to the method described above, the target structure of a lithographic material is written or defined (i.e., "written" into the lithographic material by a laser lithography apparatus) by sequentially defining multiple complementary structural regions (hereinafter also referred to as "voxels") that form the target structure as a whole. In order to write each structural region and the corresponding target structure, the focal region of the writing laser beam is displaced by an optical device, particularly perpendicular to the optical axis of the writing laser beam, while being controlled within the writing region of the scan plane defined by the optical device. In particular, the focal region passes through a scan manifold within the scan plane. The scan manifold may be a scan curve in a simple case, but may be configured in a more complex manner. For this purpose, the writing laser beam can be controlled by the optical device within the writing region with the precision required for structuring purposes. For this purpose, the optical device may include beamforming devices, beam guiding devices, and / or beam induction devices for laser beams, which are basically known from the prior art. In principle, to define the target structure, it is also conceivable that the substrate, along with the lithography material, may be displaced relative to the writing laser beam, as controlled by a positioning device.

[0009] In the focal region of the writing laser beam, the writing exposure dose is irradiated onto the lithography material, and particularly utilizing multiphoton absorption, the lithography material is locally modified, thereby generating or writing structural regions. In this sense, the lithography material is locally structured. In particular, the lithography material is chemically and / or physically modified by irradiation with the writing exposure dose, for example, by hardening or polymerization. The exposure dose is, in particular, a volume dose of radiant energy. The size of the structural regions ("voxels") modified by the lithography material depends on the writing exposure dose. Therefore, by changing the writing exposure dose, the spatial extent of each structural region or voxel, particularly its structural height, can be changed.

[0010] At this time, the displacement of the writing laser beam by the optical device and the local irradiation of the writing exposure dose are performed in accordance with a set or configurable writing instruction. In particular, the writing instruction may be stored or configurable in the control device of the laser lithography apparatus. In this sense, the method includes a step of setting the writing instruction particularly before and / or during the actual writing. Preferably, the writing instruction includes a writing instruction that controls the optical device, particularly the scanning device and / or beamforming device of the optical device, based on this instruction. The writing instruction also includes an exposure instruction that sets the writing exposure dose to be irradiated onto the scan manifold in a position-dependent manner.

[0011] In the above method, the interface between the lithography material and the substrate is located, particularly before the actual writing of the structure. Specifically, the orientation of the interface relative to the scanning surface is determined. Furthermore, it is conceivable that the interface may be located, so to speak, "online" during the writing of the structure, either additionally or exclusively.

[0012] To locate the interface, it is proposed to sequentially displace the focal region of the calibration laser beam, particularly the focal region of the writing laser beam, laterally with respect to the optical axis to multiple inspection positions within the writing area of ​​the scan surface, and to locally irradiate the lithography material with an inspection exposure dose at each inspection position. Then, the position data of the interface is determined, particularly computer-aided, from the response of the lithography material and / or substrate to such inspection exposure doses. Specifically, the orientation of the interface relative to the focal region of the writing laser beam is determined for multiple positions within the scan surface. Furthermore, it is possible to determine the overall orientation of the interface relative to the scan surface from the position data determined at each individual inspection position.

[0013] According to the method, the displacement of the focal region of the calibration laser beam relative to the inspection position is performed by the same optical device that displaces the writing laser beam for the original definition of the structure. In this sense, the calibration laser beam passes through the beam guide device and / or scanning device of the optical device that deflects the writing laser beam to define the structural region within the scanning surface. In this case, it is preferable that the displacement of the calibration laser beam relative to the inspection position is performed transversely to the optical axis, i.e., in the xy plane, under a stationary substrate. In other words, the inspection position is not reached by the substrate moving transversely to the optical axis. In particular, the inspection positions are distributed and arranged across the writing region of the scanning surface.

[0014] Depending on the determined position data, at least one write instruction, or the optical device and at least one write instruction, are modified. In particular, the writing process is adapted depending on the orientation of the interface determined relative to the scan surface. This basically may include hardware (e.g., adjustment of the optical means of the optical device) and / or software (e.g., computer-aided adaptation of the write dataset). The laser lithography apparatus is then controlled to write the target structure, either by a appropriately adapted optical device or based on adapted write instructions.

[0015] Such a method not only detects errors in the interface or substrate surface from the ideal shape of a perfectly flat surface (e.g., curvature of the substrate, local undulations, inclination of the substrate relative to the scan surface), but also enables the detection of errors in the scan surface from the ideal shape of a plane (e.g., curvature of the scan surface, inclination of the scan surface relative to the substrate). In other words, it has been found that the scan surface may differ from the ideal shape of a plane parallel to the substrate surface, for example, due to errors in the optical device, and this can lead to structural errors when writing the target structure. The method described above makes it possible to detect such position-dependent changes in the orientation of the focal region relative to the substrate within the scan surface caused by the optical device, and thus determine the focal point in a position-dependent manner with relatively high accuracy. Based on the determined position data, the errors from the ideal system can be corrected, and the writing process can be appropriately adapted to generate the structure with particularly high shape accuracy.

[0016] It may be particularly preferable that the writing area is sequentially displaced relative to the substrate in a direction perpendicular to the optical axis and positioned, and that the interface between the substrate and the lithography material is positioned within the writing area each time. In this sense, it is particularly preferable that the interface is positioned relative to the substrate as described above at a first position of the writing area (i.e., multiple inspection positions are reached within the writing area), and then the writing area is displaced to a new position relative to the substrate in a direction perpendicular to the optical axis, where the interface is again positioned (i.e., multiple inspection positions are reached within the newly positioned writing area). Such a method makes it possible to distinguish between errors in the substrate from the ideal shape and errors in the scanned surface from the ideal shape, thereby enabling the writing process to be adapted with particular precision. In addition, such a method allows for particularly accurate detection of substrate curvature. The displacement of the writing area can be performed, for example, by the displacement of the substrate and / or by changing the optical device, particularly by the displacement of the objective lens module of the optical device.

[0017] One preferred embodiment of the above method involves detecting an optical signal in a position-resolving manner for determining position data. In particular, it may be preferred to detect, in a position-resolving manner, the detection radiation emitted from the lithography material and / or substrate as a response to the inspection exposure dose by an optical measuring device. This detection radiation may be, in particular, radiation backscattered from the lithography material and / or substrate or generated by fluorescence. For example, radiation reflected at the interface may be detected. In particular, the detection data collected by the optical measuring device can be further processed into computational engineering formulas, for example, by a control device of a laser lithography apparatus set up for this purpose, to determine the position data. The radiation generated by fluorescence may be, for example, fluorescence radiation generated by nonlinear excitation (nonlinear fluorescence).

[0018] In particular, the position data represents the focal position of the substrate along the optical axis of the calibration laser beam when the focal region of the calibration laser beam is located at the interface between the lithography apparatus and the substrate. In this sense, the position data specifically represents the relative position of the substrate and the focal region when the scanning plane intersects the interface.

[0019] For particularly accurate positioning, it may be preferable that multiple laser pulses are irradiated onto the lithography material at each inspection position, while the substrate moves along the optical axis of the calibration laser beam, particularly along the main irradiation direction (z-direction), together with the lithography material. In this sense, the response of the lithography material and / or substrate to the inspection exposure dose can be detected for multiple z-positions of the substrate at each position, and in this way, the dependence of the response of the lithography material and / or substrate on the position of the substrate can be determined (z-sweep). It is also conceivable in principle to displace the focal region along the main irradiation direction. Then, from the measurement data obtained therefrom, for example from the reflection data or fluorescence data of an optical measurement device, the position data can be determined particularly by computational engineering formulas. For example, the measurement data can be recorded on a measurement curve, and a simulated response of an ideal system can be fitted for evaluation. In this way, particularly accurate positioning of the interface can be performed relative to the focal region. The laser pulse is, in particular, a modulated laser pulse generated by a modulation device, which is further composed of a number of unique pulses (e.g., fs laser pulses). For example, the pulse duration may be 1 μs or longer. In other words, this laser pulse is not a pulse that is specifically generated by the laser source.

[0020] To avoid structural artifacts caused by calibration measurements, it is preferable that the lithography material is not modified by the inspection exposure dose irradiation within the calibration measurement frame. For this purpose, it may be preferable that the inspection exposure dose irradiated from the calibration laser beam as a whole for each inspection position be selected to be low enough that structuring does not occur in the lithography material. In particular, a laser intensity below the threshold at which significant polymerization of the lithography material occurs (polymerization threshold) is selected. This makes it possible to perform calibration measurements multiple times without negatively affecting subsequent writing results.

[0021] Furthermore, to avoid photobleaching of the lithography material during calibration measurements, it may be preferable for the focal region of the calibration laser beam to wobble laterally, i.e., perpendicular to the direction of irradiation, when the inspection exposure dose is applied. Wobbling specifically refers to an oscillatory motion perpendicular to the optical axis.

[0022] The calibration laser beam may be a separate laser beam from the writing laser beam. In this case, the laser lithography apparatus may include a second light source, in particular, for emitting the calibration laser beam. Embodiments having such a separate calibration laser beam enable the interface to be located, so to speak, "online," even during the original definition by the writing laser beam. In this case, it is preferable that the calibration laser beam is calibrated to match the writing laser beam. For this purpose, for example, the response of the lithography material and / or substrate to the inspection exposure doses of the writing laser beam and the calibration laser beam, particularly backscatter signals or fluorescence signals, may be detected sequentially. From a comparison of the detected signals, the correlation between the writing laser beam and the calibration laser beam can be determined. It is also conceivable that the writing result of the writing laser beam, in particular the structure defined by the writing laser beam, may be correlated with the measurement result of the calibration laser beam.

[0023] Within the framework of alternative embodiments, the writing laser beam itself can also be used as a calibration laser beam. In this sense, the writing laser beam is first displaced to the inspection position by an optical device, where a localized inspection exposure dose is irradiated, and then the writing laser beam performs the original structuring of the lithography material. Such embodiments enable internal calibration, and in particular, the effective surface can be measured as a result.

[0024] One preferred embodiment of the method may be intended to adapt the local exposure dose depending on the determined position data. In particular, depending on the determined position data, for at least one subset of the scan points along the scan manifold to be traversed by the write laser beam, and particularly for only one subset, the local write exposure dose is changed. That is to say, in other words, the write exposure dose is adapted position-dependently depending on the determined position data.

[0025] As an alternative or in addition thereto, the configuration of the scan plane may be changed depending on the determined position data. In particular, depending on the determined position data, the scan plane can be aligned by changing the optical device relative to the substrate, for example, it can be straightened by beamforming and / or tilted relative to the substrate. The scan plane is preferably changed depending on the determined position data such that the scan plane is aligned parallel to the substrate surface of the substrate.

[0026] As an alternative or supplement thereto, it is also possible to change the position and / or orientation of the substrate depending on the determined position data of the boundary surface, particularly by means of a positioning device configured therefor. For example, it is conceivable that the substrate is aligned horizontally, particularly parallel to the scan plane.

[0027] The write instructions may, in particular, be stored in or be storable in at least one write dataset. The at least one write dataset may, preferably, be stored in or be storable in a memory device of the control device of the laser lithography apparatus. Then, depending on the determined position data of the interface, a modified write dataset can be determined from at least one write dataset, and the laser lithography apparatus is controlled based on this to generate the target structure. Such a method can be automated, thereby enabling simple and easy-to-operate calibration. For example, an "ideal write dataset" containing write instructions for an ideal system in which the interface and the scan plane are oriented parallel to each other in a plane can be prepared first. Then, depending on the determined position data, this "ideal write dataset" can be fitted into a computational engineering formula to correct for errors in the actual system from the ideal system (e.g., the inclination of the substrate relative to the scan plane, and / or curvature of the scan plane).

[0028] At least one write dataset may include control data for controlling an optical device. Preferably, at least one write dataset includes control data for controlling the scanning device and / or beamforming device of the optical device. In this sense, the control data can set the scan transition and / or beam shape (e.g., appropriate pulse shape) within the scanning plane, particularly for the write laser beam. For example, in embodiments of the method in which the write laser beam is used as a calibration laser beam, it may be preferable that the calibration laser beam is modified through beamforming, for example, through tilting the focus by shading on one side. This enables particularly accurate measurements.

[0029] At least one write data set may in particular also include write exposure data representing the local exposure dose for each scan point along the scan manifold of the write laser beam through the lithography material. In that sense, the write exposure data sets the exposure dose at which irradiation should be performed at a specific location of the scan manifold. The preparation of the write exposure data can in particular be carried out by determining, provided that a structure data set (for example CAD data) representing the target structure to be generated is available or stored in a control device, and then deriving the write exposure data therefrom in a computer-aided manner, for example by a control unit of a laser lithography device set up for that purpose. In one preferred development, the write exposure data can be in the form of grayscale image data representing the target structure, with different grayscale levels defining different structure heights. In that sense, the write exposure data can be visualized as a grayscale image. In that sense, at least one write data set may in particular include a grayscale image data set. In particular, the laser lithography device is controlled based on the grayscale image data. The write exposure data is preferably prepared by loading a grayscale image file into the control unit of the laser lithography device and storing it in memory.

[0030] In the type of 3D laser writing applied here, it may be particularly preferable if the exposure dose is injected by multiphoton absorption. For this reason, it is preferable that the lithography material is configured such that changes in the lithography material (e.g., local polymerization) are possible through the absorption of multiple photons, and that the writing laser beam is adapted to the lithography material. To this end, for example, the wavelength of the writing laser beam can be selected such that the energy injection required for the changes in the lithography material is achieved only by the simultaneous absorption of two or more quanta (and accordingly, the allocated quantum energy may be set in this manner). The probability of such a process occurring is nonlinearly intensity-dependent and is significantly higher in the focal region compared to other writing laser beams. From basic considerations, it becomes clear that the probability of two or more quanta being absorbed may depend on the square or higher power of the radiant intensity. In contrast, the probability of a linear absorption process occurring has a different intensity dependence, particularly with even lower powers of the radiant intensity. When a writing laser beam penetrates a lithography material, evaporation occurs (for example, based on Beer's law), which presents problems for writing in a focal region using a linear absorption process deep below the liquid surface of the lithography material. This is because, based on evaporation, even when focused below the surface in the focal region, the maximum absorption probability is not necessarily achieved. In contrast, the multiphoton absorption mechanism allows for the injection of a desired exposure dose and local modification of the lithography material even within a volume made of lithography material, i.e., relatively deep below the liquid surface. Therefore, there is no need for a device that gradually lowers a support structure in a bath made of lithography material, as is known in the prior art.

[0031] In this context, lithography materials are basically substances whose chemical and / or physical properties are variable by irradiation with a writing laser, such as so-called lithography resists. Depending on the type of modification induced by the writing beam, lithography materials can be further classified into so-called negative resists (which undergo localized hardening or have reduced solubility in the developing medium upon irradiation) and so-called positive resists (which have increased localized solubility in the developing medium upon irradiation).

[0032] The problem described in the opening section is also solved by the laser lithography apparatus described in claim 13. The laser lithography apparatus is configured to generate a three-dimensional target structure in a lithography material. The laser lithography apparatus includes a positioning device for displacing and positioning the substrate. In particular, the positioning device is configured to displace the substrate in all three spatial directions (X, Y, Z), and preferably, in addition, to tilt it about at least one tilt axis parallel to the XY plane.

[0033] The laser lithography apparatus further includes a laser source for emitting a writing laser beam and an optical device. The optical device includes a beam guide device, which in particular includes optical means such as lenses and mirrors for defining the optical path of the writing laser beam from the laser source to the lithography material. The optical device further includes a focusing optical system configured to focus the writing laser beam to a focal region. The optical device further includes a scanning device to displace the focal region of the writing laser beam relative to the lithography material. The scanning device may be a deflection device (e.g., including a deflection mirror) for changing the position of the focal region of the writing laser beam in the lithography material. The optical device further may include a beamforming device and / or a modulation device for forming a suitable beam pulse.

[0034] Furthermore, the laser lithography apparatus includes a measuring device for detecting radiation emitted from the lithography material and / or substrate, particularly reflected or generated by fluorescence. The measuring device may include a measuring optical system preferably confocally configured with a device that generates the writing laser beam (e.g., a beam guide device). In particular, the measuring device includes a sensing device for detecting radiation backscattered, reflected or generated by fluorescence from the substrate and / or lithography material.

[0035] Furthermore, the laser lithography apparatus includes a control unit set up to carry out the method described above. The control unit includes, in particular, a computing unit and a non-volatile memory on which the dataset described above is stored or can be stored.

[0036] Next, the present invention will be described in detail with reference to the drawings.

[0037] The following diagrams are shown. [Brief explanation of the drawing]

[0038] [Figure 1] Figure 1 is a simplified schematic diagram showing a laser lithography apparatus. [Figure 2] Figure 2 is a schematic diagram illustrating the writing process using a laser lithography device. [Figure 3] Figure 3 is a schematic diagram illustrating a method for locating the interface between the substrate and the lithography material. [Figure 4] Figure 4 is a schematic diagram illustrating various methods for adapting the writing process depending on the determined position of the interface. [Figure 5] Figure 5 is a schematic diagram illustrating various methods for adapting the writing process depending on the determined position of the interface. [Figure 6]Figure 6 is a schematic diagram illustrating various methods for adapting the writing process depending on the determined position of the interface. [Figure 7] Figure 7 is a schematic diagram illustrating various methods for adapting the writing process depending on the determined position of the interface. [Modes for carrying out the invention]

[0039] In the following descriptions and drawings, the same reference numerals are used for identical or corresponding components.

[0040] Figure 1 shows a schematic diagram of a laser lithography apparatus, collectively denoted by reference numeral 10. The laser lithography apparatus 10 includes a laser source 12 for emitting a writing laser beam 14. Furthermore, the laser lithography apparatus 10 includes an optical device, collectively denoted by reference numeral 16.

[0041] The optical device 16 includes a beam guide device 18 for defining the optical path 20 of the writing laser beam 14 from the laser source 12 to the lithography material 22 to be structured. In the illustrated example, the beam guide device 18 is a micro having multiple modules that perform optical and / or mechanical functions. For example, the optical path 20 first passes through a beamforming device 24 for forming a suitable beam pulse.

[0042] Furthermore, the optical device 16 includes a focusing optical system 26 for focusing the writing laser beam 14 in a focal region 28 (see also Figure 2). The focusing optical system 26 includes, as an example, an objective lens module 30, which irradiates the writing laser beam 14 onto the lithography material 22.

[0043] Furthermore, the optical device 16 includes a scanning device 32, which allows the focal region 28 of the writing laser beam 14 to be displaced relative to the lithography material 22 within the writing region 34 of the scanning surface 36 (see Figure 2) with the precision required for structuring. In the illustrated example, the scanning device 32 includes a beam guidance module 36, which may include, for example, a galvanometer-scanner unit for controlled deflection of the laser beam 14.

[0044] As schematically shown in Figure 1, the lithography material 22 is prepared on the substrate surface 38 of the substrate 40. The substrate 40 is, as an example and preferably, displaceable to a precise position relative to the focal region 28 of the writing laser beam 14 by a positioning device 42. Each drawing also shows a coordinate system having mutually orthogonal axes x, y, and z. The positioning device 42 is configured to displace the substrate 40 in all three spatial directions x, y, and z, and is preferably configured to tilt it, in addition to this, about a first tilt axis parallel to the x axis and / or a second tilt axis parallel to the y axis.

[0045] Furthermore, the laser lithography apparatus 10 includes a control unit (not shown) which includes a computing unit and non-volatile memory.

[0046] To generate a three-dimensional target structure 44 in the lithography material 22, the focal region 28 of the laser writing beam 14 is displaced by the optical device 16, particularly by the scanning device 32, so as to pass through the volume of the lithography material 22 (enclosing the entire structure). At this time, the writing exposure dose is locally irradiated onto the lithography material 22 in the focal region 28 of the laser writing beam 14, thereby defining a structural region 46 locally, particularly by utilizing multiphoton absorption (see Figure 2). For example, the lithography material 22 polymerizes locally and is structured accordingly.

[0047] As schematically shown in Figure 2, the structure 44 can be defined by passing through the scan manifold 48 such that the focal region 28 passes through the lithography material 22 along the scan surface 36, and in the process, a sequence of laser pulses having a defined pulse repetition rate and pulse length is emitted (in Figure 2, the scan surface 36 is schematically shown in each region). This defines a row of structural regions 46 (voxels) along the scan manifold 48 that approximate the target structure 44 (shown by dashed lines in Figure 2). These structural regions 46 are similar in shape to each other or are identical in shape. The size of the structural regions 46 written at this time, and the resulting structural height, are related to the exposure dose injected.

[0048] When the desired target structure 44 is larger than the maximum writing area 34 of the laser lithography apparatus 10, the target structure 44 can be computationally decomposed into substructures, which together approximate the target structure 44. These substructures can then be written sequentially. Figure 2 shows an example in which the target structure 44 is decomposed into two substructures 50-1 and 50-2 located side by side, and these substructures are further composed of two writing layers 52-1 and 52-2 located vertically. To write the target structure 44, for example, the substructure 50-1 shown on the left side of Figure 2 can be written first, and the writing layers 52-1 and 52-2 are defined sequentially thereafter. For this purpose, for example, in order to write the second layer 52-2 after writing the first layer 52-1, the substrate 40 moves a corresponding amount downward (in the negative z direction). After the first substructure 50-1 is defined, the writing area 34 is displaced laterally with respect to the optical axis (in the x-direction in the example shown in the figure) in order to write the second substructure 50-2. The displacement of the writing area 34 can be achieved, for example, by the displacement of the substrate 40 and / or the objective lens module 30. Subsequently, the second substructure 50-2 is written in a similar manner.

[0049] The displacement of the writing laser beam 14 and the position-dependent irradiation of the writing exposure dose within the scan surface 36 are performed in accordance with predetermined writing instructions, which are preferably stored as a writing dataset in the control unit of the laser lithography apparatus 10. The writing dataset preferably includes, as an example, writing exposure data that represents the local writing exposure dose in a position-dependent manner for the scan manifold 48. In particular, the writing exposure data is grayscale image data representing the target structure 44, where different grayscales represent different exposure doses. For example, a grayscale image file can be loaded into the control unit of the laser lithography apparatus 10. The writing dataset preferably further includes control data for controlling the optical device 16. In particular, the writing dataset includes control data for controlling the scan device 32 and / or the beamforming device 24.

[0050] Before defining the structure in detail, the method described above determines the location of the interface 54 between the substrate 40 and the lithography material 22 (see Figure 1). Specifically, and preferably as an example, the position of the substrate 40 along the z-axis is determined when the focal region 28 is located inside the interface 54 (hereinafter referred to as the "focal position").

[0051] In an ideal system where the substrate surface 38 and the scan surface 36 extend parallel to each other in a plane, this focal position is the same for all scan points within the scan surface 36. However, in actual systems, the focal positions within the scan surface 36 usually differ from each other due to various factors. For example, the substrate 40 may be tilted with respect to the optical axis. In addition or alternatively, the substrate surface 38 may be bent or curved, or have local undulations. Furthermore, it has been found that the scan surface 36 may also differ from an ideal planar shape, for example, due to optical errors in the optical device 16.

[0052] Figure 2 visualizes an illustrative case in which the substrate 40 is tilted about the y-axis, and in addition, the scan plane 36 is not only curved but also tilted about the y-axis. Such errors from the ideal configuration can lead to the actually written structure 46 not accurately corresponding to the desired target structure 44, for example, being distorted or incompletely fabricated (in the example shown in Figure 2, the upper right corners of substructures 50-1 and 50-2 are not completely filled in the structure region 46).

[0053] In order to detect and correct such errors from the ideal configuration of the substrate 40 and / or scan surface 36, the method determines the focal position of the substrate 40 at a plurality of inspection positions 56-1 to 56-6 within the writing area 34 of the scan surface 36. When the target structure 44 is composed of a plurality of substructures 50-1, 50-2 as described above with reference to Figure 2, it is preferable that the determination of the focal position is performed separately for each substructure 50-1, 50-2. In this sense, the focal position is determined at a plurality of positions within the writing area 34, particularly after the writing area 34 has been displaced for writing to other substructures.

[0054] To this end, in the above method, the focal region 28 of the writing laser beam 14 is sequentially displaced by the optical device 16 to various inspection positions 56-1 to 56-6 within the scanning surface 36. At each of the inspection positions 56-1 to 56-6, an inspection exposure dose is locally irradiated onto the lithography material 22 (visualized by an elliptical structure in Figure 5), and detection radiation emitted from the lithography material 22 and / or substrate 40 is detected as a response to the inspection exposure dose. For this purpose, the laser lithography apparatus 10 may have a corresponding measuring device 58 (see Figure 1).

[0055] In one preferred embodiment, multiple laser pulses are irradiated at each of the inspection positions 56-1 to 56-6, during which time the substrate 40 is displaced along the z-axis by the positioning device 42. In this way, a measurement curve representing the response of the substrate 40 or the lithography material 22 can be obtained depending on the z-position of the substrate 40.

[0056] The detected radiation may be, in particular, radiation backscattered from the lithography material 22 and / or the substrate 40. In this case, the focal position of the substrate 40 can be determined, for example, by detecting the reflected signal of the laser beam 14 that strikes the interface 54 as, for example, a local intensity maximum. The detected radiation may also be radiation generated by fluorescence. In this case, the focal position can be determined, for example, by detecting the difference in the fluorescence signal when transitioning from the lithography material 22, which in particular emits fluorescence, to the substrate 40, which does not emit fluorescence. For this purpose, the measuring device 58 may have a fluorescence detector in particular.

[0057] Then, based on the focal positions determined at each of the inspection positions 56-1 to 56-6, at least one write dataset can be appropriately adapted to correct for errors from the ideal system. In particular, at least one modified write dataset can be determined computer-aidedly, for example by a control unit, and the laser lithography apparatus 10 is controlled to generate the target structure 44 based on this.

[0058] For example, the local write exposure dose may be adapted depending on the determined position data. Figure 4 shows a corresponding example in which the exposure dose is adapted in a position-dependent manner along the scan manifold 48 to ensure that the actually generated structure 46 more closely approximates the desired target structure 44 compared to the example shown in Figure 2 (the upper right corners of substructures 50-1 and 50-2 are more closely filled by the structure region 46). In such cases, the corrected write dataset may include corrected write exposure data. In embodiments not shown, the corrected write exposure data may also additionally or alternatively correct the curvature and / or local undulations of the substrate surface 38.

[0059] Depending on the determined position data, the target structure 44 may be computationally decomposed into newly defined structural regions 46. An example of this is roughly shown in Figure 5, in which the substructures 50-1 and 50-2 are composed of four writing layers 52-1 and 52-4 instead of two.

[0060] Alternatively or supplementally, the substrate 40 can be newly positioned depending on the determined position data. In that case, the modified write data may also include modified control instructions to the positioning device 42. Figure 6 visualizes an exemplary case in which the substrate 40 is aligned horizontally, based on the configuration shown in Figure 2.

[0061] Alternatively or supplementing this, depending on the determined position data, the objective lens module 30 or the objective lens of the objective lens module 30 may be newly positioned relative to the substrate 40, for example, by tilting. In this case, the modified write dataset may also include modified control instructions to the positioning device (not shown) of the objective lens module 30.

[0062] Alternatively or supplementally, the shape of the scan plane 36 may also be adapted by a beamforming or scanning device 32. Figure 7 schematically shows an exemplary case in which the scan plane 36 is straightened and aligned parallel to the substrate surface 38. In this case, the modified write dataset may include modified control data for the optical device 16, and in particular for the beamforming device 24 and / or the scanning device 32. For example, a scanning device 32 may be provided, configured to change the Z position of the focal region during scanning and adapt the shape of the scan plane 36 accordingly. For this purpose, the scanning device 32 may include, for example, an adaptive lens configured to rapidly displace the focal region along the z axis.

[0063] Within the framework of one alternative embodiment of the method described above, a calibration laser beam separate from the writing laser beam 14 may be used to irradiate the inspection exposure dose. In this case, the calibration measurement for determining the focal position is not performed using the writing laser beam 14 itself. In such an embodiment, the laser lithography apparatus may include a second laser source (not shown) in particular for emitting a calibration laser beam. The second laser source is configured and arranged such that the calibration laser beam travels through the optical device 16, and in particular through at least the beamforming device 24 and / or the scanning device 32, along the same optical path 20 as the writing laser beam 14. In such an embodiment of the method described above, the focal position can also be determined during the original writing process by the writing laser beam 14. That is, the laser writing beam 14 and the calibration laser beam can be used in parallel.

Claims

1. A method for generating a three-dimensional target structure (44) in a lithography material (22) using a laser lithography apparatus (10), A substrate (40) on which the lithography material (22) is placed is prepared. The interface (54) between the lithography material (22) and the substrate (40) is located, The target structure (44) is defined by the displacement of the focal region (28) of the writing laser beam (14) within the writing region (34) of the scanning surface (36) by the optical device (16) in accordance with a predetermined writing instruction. In a method in which a writing exposure dose is irradiated onto the lithography material (22) in the focal region (28) of the writing laser beam (14) to define a localized structural region (46), To locate the interface (54) between the substrate (40) and the lithography material (22), the focal region (28) of the calibration laser beam (14) is sequentially displaced by the optical device (16) to a plurality of inspection positions (56-1 to 56-6) within the writing area (34) of the scanning surface (36), an inspection exposure dose is irradiated onto the lithography material (22) at each of the inspection positions (56-1 to 56-6), the position data of the interface (54) is determined from the response of the lithography material (22) and / or the substrate (40) to the inspection exposure dose, and at least one write instruction is modified depending on the determined position data. The write instruction is stored in at least one write dataset, at least one modified write dataset is determined based on the determined position data of the interface (54), and the laser lithography apparatus (10) is controlled based on at least one modified write dataset. The write dataset includes control data for controlling the optical device (16) and / or write exposure data representing a position-dependent local exposure dose for each scan point. method.

2. The method according to claim 1, wherein the writing area (34) is sequentially displaced relative to the substrate (40) in a direction laterally with respect to the optical axis (z) and positioned, and each time the boundary surface (54) between the substrate (40) and the lithography material (22) is located in the writing area (34).

3. The method according to claim 1 or 2, wherein radiation backscattered from the lithography material (22) and / or the substrate (40) or generated by fluorescence is detected by an optical measuring device (58) for determining positional data.

4. The method according to any one of claims 1 to 3, wherein the position data represents the focal position of the substrate (40) along the optical axis (z) when the focal region (28) of the calibration laser beam (14) is located at the interface (54) between the lithography material (22) and the substrate (40).

5. The method according to any one of claims 1 to 4, wherein multiple laser pulses are irradiated at each of the aforementioned inspection positions (56-1 to 56-6), and during this time the substrate (40) moves along the optical axis (z) of the calibration laser beam (14).

6. The method according to any one of claims 1 to 5, wherein the examination exposure dose is selected to be low enough that no structuring occurs in the lithography material (22).

7. The method according to any one of claims 1 to 6, wherein the focal region (28) of the calibration laser beam (14) is wobbled laterally when irradiated with the inspection exposure dose.

8. The method according to any one of claims 1 to 7, wherein the writing laser beam (14) is used as a calibration laser beam.

9. The method according to any one of claims 1 to 8, wherein a writing laser beam (14) for defining a target structure (44) passes through a scan manifold (48) inside the writing area (34), and the local writing exposure dose is changed for at least a subset of scan points of the scan manifold (48) depending on the determined position data.

10. The method according to any one of claims 1 to 9, wherein the configuration of the scan surface (36) is changed depending on the determined position data, and the scan surface (36) is aligned relative to the substrate (40), further straightened, and / or tilted relative to the substrate (40) by the change in the optical device (16).

11. The method according to any one of claims 1 to 10, wherein the position and / or orientation of the substrate (40) is changed depending on the position data.

12. In a laser lithography apparatus (10) for generating a three-dimensional target structure (44) on a lithography material (22), A positioning device (42) for displacing and positioning the substrate (40), A laser source (12) for emitting a writing laser beam (14), The optical device (16) is, A beam guide device (18) for defining the optical path (20) of the writing laser beam (14) from the laser source (12) to the lithography material (22), A focusing optical system (26) for focusing the writing laser beam (14) in the focal region (28), A laser lithography apparatus comprising a scanning device (32) for displacing the focal region (28) of the writing laser beam (14) relative to the lithography material (22) within the scanning surface (36), A measuring device (58) for detecting radiation emitted, reflected, or generated by fluorescence from the lithography material (22) and / or the substrate (40), A laser lithography apparatus comprising a control unit set up to carry out the method according to any one of claims 1 to 11.

13. The laser lithography apparatus according to claim 12, further comprising a second laser source for emitting a calibration laser beam.

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