METHOD FOR OPERATING AN ACOUSTIC SCRATCH MICROSCOPE AND ACOUSTIC SCRATCH MICROSCOPE

Description

[0001] The invention relates to a method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, and an acoustic scanning microscope, in particular an ultrasonic scanning microscope.

[0002] Ultrasound microscopes or acoustic microscopes, also known as scanning acoustic microscopes (SAM), are used to scan samples using ultrasound in a raster process and to process the reflected sound waves in order to generate images of the sample's structures.

[0003] These ultrasound microscopes have an ultrasound head, also known as a transducer head. The ultrasound head therefore consists of an acoustic lens and an attached sound transducer.

[0004] In acoustic microscopy, water is used as a coupling medium between the acoustic transducer and the sample under investigation to ensure good transmission of the sound waves emitted by the transducer to the sample. For this purpose, a coupling medium with good sound conductivity properties is required.

[0005] In ultrasonic microscopy, which operates in the frequency range of 1 MHz to 5 GHz, it is common practice to submerge samples in a water reservoir and place them on a sample holder, with the sample being examined using an ultrasonic microscope in immersion. Another method uses a water jet that is directed between the transducer and the sample to ensure good sound coupling into the sample.

[0006] Ultrasound microscopes, in which a sample is scanned using ultrasound and the transmitted or reflected sound waves are processed to generate an image, are known from the prior art. Image generation is non-destructive, providing information about the internal structure of a sample. The images obtained through this scanning method enable the analysis or monitoring of materials, electronic components, etc.

[0007] Furthermore, multichannel transducers are used in acoustic microscopy, in which a large number of individual elements with a fixed focal length are arranged side by side. The pixel size in the Y-direction, i.e., perpendicular to the scan direction in the X-direction, corresponds to the distance between the individual transducer elements. When using such multichannel transducers, many parallel linear scan lines are recorded simultaneously, corresponding to the number of transducer elements. In multichannel transducers, the distance between the individual elements is constant and cannot be changed, meaning that the height of a line of linear scan is fixed and the pixel size in the Y-direction, i.e., perpendicular to the scan direction in the X-direction, always corresponds to the width of the individual transducer elements and is constant. Due to the small dimension of the individual elements in the Y-direction, i.e.,Perpendicular to the scan direction in the X direction, the aperture of the lenses of the transducer elements in this direction is very small, resulting in a low resolution in the Y direction.

[0008] German patent DE 10 2006 005 448 B4 discloses an acoustic scanning microscope with at least two transducers, wherein, by means of a first device, the at least two transducers are moved to different positions along a plane for lateral scanning of a sample. The sample is scanned pixel by pixel and line by line in the XY direction, so that the entire surface of the sample is captured.

[0009] Furthermore, US patent 4,781,067 describes an acoustic scanning microscope with a balanced scanning mechanism. The transducer of the scanning microscope is moved in a meandering pattern above the sample under investigation.

[0010] Furthermore, US 2007 / 0180914 A1 generally describes an acoustic scanning microscope in which a linear motor is used to drive a transducer in the X and Y directions, while a motor is used to control the sensor movement in the Z direction.

[0011] Furthermore, US patent 2022 / 0252547 A1 discloses an acoustic inspection system. The inspection system may include a test device. In this case, a probe assembly may comprise two or more electroacoustic transducers. The transducer arrangements may follow a linear or curved contour or comprise an arrangement of elements extending along two axes, such as a matrix of transducer elements.

[0012] Furthermore, US 2017 / 0370885 A1 discloses a system for non-destructive testing using an ultrasonic immersion probe and a laser vibrometer. The immersion ultrasonic probe and a sample are immersed in a liquid contained in an immersion tank, and the laser vibrometer is positioned outside the immersion tank.

[0013] One object of the invention is to expand the application possibilities of acoustic scanning microscopy or of an acoustic microscope for examining samples, such as wafers, etc. A further object of the invention is to examine large-volume or large-area samples, particularly with high data throughput, efficiently and simply using an acoustic microscope, in particular an ultrasonic scanning microscope.

[0014] The problem is solved by a method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, wherein a sample is scanned in an XY plane by means of a transducer unit, in particular with one or more transducer elements each comprising a transducer and a lens, wherein the transducer unit is moved in the X-direction for a line-like scanning of the sample, wherein after the line-like scanning of the sample by the transducer unit the transducer unit is displaced in the Y-direction by a step size, wherein during an examination of the sample by means of the scanning method for scanning the sample the size of the step size of the transducer unit in the Y-direction is varied, wherein in particular after the displacement of the transducer unit in the Y-direction at least one further line-like scanning of the sample is carried out by means of the transducer unit in the Y-direction.

[0015] A particular advantage of this method is that, during the scanning process, the transducer unit's step size in the Y-direction is adjusted. This allows specific areas of the sample to be scanned with higher (pixel) resolution, while other, less important areas are scanned with lower (pixel) resolution. This can reduce the time required for a complete sample scan.

[0016] A further advantage of the method is that the scanning process enables the use of transducer units with multiple transducer elements, where the lateral dimension of the transducer elements is larger than the pixel size. The method according to the invention avoids restrictions in the free choice of pixel size and losses in resolution and detection sensitivity. In particular, deviations of the individual transducer elements from a reference position are measured and, for example, entered into a calibration table. For transducer units with transducer elements of the same focal length, the area of ​​the sample to be scanned is divided, with each individual transducer element scanning the sample line by line.

[0017] The acoustic microscope, in particular an ultrasonic scanning microscope, for carrying out the method comprises a positioning system, at least one transducer unit, in particular with several transducer elements, a pulse generator unit for the transducer unit, preferably pulse generators with a number corresponding to the transducer elements, and a receiver unit, in particular a receiver device for each transducer element. Furthermore, the acoustic microscope comprises a data processing system and a module for digitizing the analog received ultrasonic signals.

[0018] In the method according to the invention, it is preferred that, in a transducer unit with multiple transducer elements, the lateral distances of the individual transducer elements are taken into account based on a (pre-)calibration, so that the area of ​​a sample to be examined and scanned is scanned in an optimized manner. In the case of continuous line-wise, i.e., linear, scanning (in the X-direction) with a predetermined and configurable number of pixels per line, the distance from line to line in the Y-direction is freely selectable.Preferably, the linear scans are performed with the same small offset increments in the Y-direction until the maximum distance between the transducer elements of the same properties is reached, and then the transducer unit is moved in the Y-direction by this distance with a larger offset increment in the Y-direction, so that a high-resolution image of the areas to be examined is produced at an increased analysis speed.

[0019] In a further development of the method, it is provided that several linear scans of the sample (in the X-direction) are carried out by the transducer unit, wherein after each linear scan of the sample the transducer unit is shifted by a small, preferably constant, offset step size in the Y-direction, and after a predetermined number n (n ≥ 2, 3, ...) of several linear scans of the sample the transducer unit is shifted by a large, preferably constant, offset step size in the Y-direction, which is larger than the small offset step size, and / or that after a linear scan of the sample the transducer unit is shifted by a large, preferably constant, offset step size in the Y-direction and after the shift of the transducer unit by the large offset step size several n (n ≥ 2, 3, ...) linear scanning of the sample by the transducer unit, wherein after each of the several linear n (n ≥ 2, 3, ...) scannings of the sample the transducer unit is shifted by a small, preferably constant, offset step size in the Y direction, which is smaller than the large offset step size.

[0020] This results in a high-resolution image of the sample areas to be examined, where, for example, the pixel size or the spacing of the linear scans (in the Y-direction) is smaller than the spacing of the individual transducer elements (in the Y-direction) of a preferably linear array of transducer elements. In particular, the ratio of pixel size or spacing of the linear scans to the spacing of the individual transducer elements (in the Y-direction) is less than 1:10, more specifically less than 1:100, and further, more specifically, less than 1:1000.

[0021] Furthermore, in this method, it is preferred if the transducer unit is moved in a meandering path in the XY plane relative to the sample. A suitable positioning system is provided for this purpose, enabling the transducer unit to be moved relative to the sample under investigation.

[0022] According to a further embodiment, the method provides that a.) the sample is scanned using a transducer unit for an acoustic scanning microscope, in particular an ultrasonic scanning microscope, with several transducer elements, each comprising a transducer and a lens, wherein at least two transducer elements have different focal lengths, or b.) that the sample is scanned using a transducer unit with several transducer elements, each comprising a transducer and a lens, preferably acoustic, wherein in particular the transducer elements have the same focal length and / or the transducer elements are arranged next to each other in a linear or rhombic arrangement in the Y-direction.

[0023] Furthermore, a further development of the method is characterized in that the transducer unit has several transducer elements arranged in the Y-direction, preferably one behind the other and / or linearly, wherein several linear m (m ≥ 2, 3, 4, ...) scans are performed in the X-direction by means of the respective transducer elements, wherein the distances of the linear m (m ≥ 2, 3, 4, ...) scans by the respective transducer elements are equidistant in the Y-direction and after the linear m (m ≥ 2, 3, 4, ...) scans have been performed by the transducer unit, the transducer unit is moved in the Y-direction with the offset step size, which is the product of the equidistant distance of the linear scans with the number of linear m (m ≥ 2, 3, 4, ...) scans and the number of transducer elements of the The transducer unit is offset in the Y direction.

[0024] Advantageously, with this method, the achievable image resolution is independent of the distance and arrangement of the individual transducer elements, e.g., of an array. Furthermore, the individual transducer elements can be freely adjusted or optimized with regard to their resolution and signal intensity.

[0025] The image resolution achieved or to be achieved by the method is independent of the distance and arrangement of the individual transducer elements of a transducer unit or a transducer array, whereby in particular the individual transducer elements can be configured with regard to their resolution and focal length as required.

[0026] By using transducer elements with different focal lengths in a transducer unit, the surfaces or planes of a sample to be examined are scanned in one or more depth planes, which are determined by the corresponding focal lengths of the individual transducer elements of the transducer unit or transducer array, according to the method in one embodiment. Furthermore, according to another aspect, the lateral deviation of each individual transducer element is measured and the scan field is enlarged by the corresponding amount, whereby any deviations are corrected during image generation to produce complete and perfectly overlapping images.

[0027] In a further embodiment of the method, the transducer unit, preferably with several transducer elements, has a length in the Y direction, wherein after several linear scans in the X direction by the transducer unit, the transducer unit is offset in the Y direction with a displacement step size corresponding to the length of the transducer unit, wherein the respective distances of the several linear scans performed before the transducer unit is offset in the Y direction with the displacement step size corresponding to the length of the transducer unit correspond to a natural fraction of the length of the transducer unit (length of the transducer unit / t, t ≥ 2, 3, 4, ...).

[0028] Furthermore, a method according to a further development is provided in which the transducer unit has several transducer elements arranged in the Y-direction, preferably next to each other and / or linearly, wherein the transducer elements each have a, preferably constant, width in the Y-direction, wherein several linear p (p ≥ 2, 3, 4, ...) scans are carried out in the X-direction, wherein the spacing of the linear p (p ≥ 2, 3, 4, ...) scans corresponds to a fraction of the width of the transducer elements (width of the transducer elements / p, p ≥ 2, 3, 4, ...), and after the linear p (p ≥ 2, 3, 4, ...) scans have been carried out, the transducer unit is offset in the Y-direction with a displacement step size that corresponds to a multiple of the width of the transducer elements.

[0029] In one embodiment of the method, it is preferred that the, in particular large, offset step size of the transducer unit in the Y-direction is corrected by a tolerance correction value after the execution of the several line-shaped scans by the transducer unit, wherein in particular the tolerance correction value is formed such that the distance in the Y-direction of the last line-shaped scan before the offset of the transducer unit by the large offset step size to the first line-shaped scan after the offset of the transducer unit by the large offset step size corresponds to the distance of the several line-shaped scans before and / or after the offset of the transducer unit by the large offset step size in the Y-direction, or wherein in particular the tolerance correction value is formed such that the distance between all line-shaped scans by the transducer unit is constant.

[0030] In particular, the transducer unit comprises several transducer elements, which are operated in parallel. Preferably, the pulse generators for each transducer element and / or the receiving devices for each transducer element are operated in parallel. Alternatively, in one embodiment, pulse operation is achieved with a time offset of the overall decay time for the transducer signals, whereby crosstalk between the individual transducer elements is minimized and / or the signals caused by sound waves from one transducer element do not interfere with adjacent transducer elements.

[0031] Within the scope of the invention, it is possible that for carrying out the method a transducer unit with several transducer elements with a compact design with separate transducer elements or with a monolithic block for the transducer elements is provided.

[0032] Furthermore, one embodiment of the method provides for the distance between the transducer unit and the surface of the sample to be controlled by means of a transducer element. Alternatively, distance control between the transducer unit and the sample can be implemented using a weighted value, for example, using a suitable algorithm for the various transducer elements.

[0033] For carrying out the method, a transducer unit for an acoustic scanning microscope, in particular an ultrasonic scanning microscope, is provided with several transducer elements, each comprising a transducer and a lens, preferably acoustic, wherein at least two transducer elements have different focal lengths.

[0034] When the transducer unit is used in an acoustic scanning microscope, multiple line scans are performed simultaneously in a single, preferably one, scanning process. Due to the different focal lengths of the transducer elements, these scans occur simultaneously in different planes of the sample. Thus, different scan fields of the sample under investigation are obtained in different planes of the sample during a single scanning operation.

[0035] In addition to a transducer for generating an acoustic signal and an acoustic lens for focusing, each transducer element includes a pulse generator, a transmit / receive switch, a receiver for receiving the acoustic signals reflected or transmitted by the sample, and an analog-to-digital converter (ADC) for converting the received acoustic signals into digital values ​​for displaying (grayscale) images. The ultrasound signals reflected or transmitted by the sample are measured and converted to generate the image. Additionally, the signal propagation times or phase shifts can be acquired as further image information. In a raster scanning method, the sample is scanned pixel by pixel and line by line. During this process, the transducer unit or transducer elements are moved relative to the sample under investigation.

[0036] In a preferred embodiment of the transducer unit, it is provided that, preferably exclusively, two transducer elements with different focal lengths with respect to an XY plane are arranged in a linear arrangement next to each other in the Y direction or one behind the other in the X direction, or that, preferably exclusively, two transducer elements with different focal lengths with respect to an XY plane are arranged offset from each other in the X direction and in the Y direction, in particular diagonally.

[0037] Furthermore, another embodiment of the transducer unit is characterized by the fact that the transducer unit has several transducer elements, each with a first focal length, and several transducer elements, each with a second focal length that differs from the first focal length, relative to an XY plane. wherein an array of transducer elements with the first focal length arranged side by side in the Y-direction, in particular linearly, and an array of transducer elements with the second focal length arranged side by side in the Y-direction, in particular linearly, are arranged one after the other in the X-direction, or wherein an array of transducer elements with the first focal length arranged side by side in the Y-direction, in particular linearly, and an array of transducer elements with the second focal length arranged side by side in the Y-direction, in particular linearly, are arranged offset from each other in the X-direction and in the Y-direction, in particular diagonally, or wherein transducer elements with the first focal length and transducer elements with the second focal length are arranged one after the other in an alternating sequence in the Y-direction.

[0038] According to an advantageous embodiment, the transducer unit comprises, in particular, more than two transducer elements, each with a first focal length, and more than two transducer elements, each with a second focal length. The use of multiple arrays with multiple transducer elements for an acoustic microscope, especially with more than two transducer elements of a first focal length and more than two transducer elements of a second focal length, particularly in parallel or simultaneously, increases the application possibilities of the acoustic microscope. This is because, in a single examination of a sample, multiple images are simultaneously obtained in different planes using the transducer elements with the different focal lengths.The arrays also reduce the time required for raster scanning, as multiple transducer elements of a focal length scan the sample over a greater width in the Y direction or a wider scan field.

[0039] Furthermore, the problem is solved by an acoustic scanning microscope, in particular an ultrasonic scanning microscope, wherein the acoustic scanning microscope is configured as a transducer unit as described above, or the acoustic scanning microscope is configured to carry out the method described above for operating an acoustic microscope, in particular according to one of claims 1 to 11. To avoid repetition, explicit reference is made to the above statements.

[0040] Furthermore, the invention provides, as an independent subject matter, a method for operating an acoustic scanning microscope, in particular an ultrasonic scanning microscope, wherein a sample is scanned in an XY plane by means of a transducer unit described above, in particular with one or more transducer elements each comprising a transducer and a lens, wherein the transducer unit is moved in the X-direction for a linear scanning of the sample, wherein after the linear scanning of the sample in the X-direction by the transducer unit the transducer unit is displaced in the Y-direction by a constant displacement step size in the Y-direction, wherein in particular after the displacement of the transducer unit in the Y-direction at least one further linear scanning of the sample is carried out by means of the transducer unit in the Y-direction.

[0041] The method involves moving the sample under investigation through the transducer unit in a raster pattern with a constant displacement step in the Y-direction after each line-by-line scan in the X-direction. Preferably, the transducer unit comprises multiple transducer elements, which are operated in parallel. In particular, according to a further aspect, the transducer unit is moved in a meandering path in the XY plane relative to the sample.

[0042] Within the scope of the invention, features marked with "in particular" or "preferably" are to be understood as optional features.

[0043] The invention is described below, without limiting the general concept of the invention as embodied in the attached claims, by means of exemplary embodiments with reference to the drawings, whereby for all details of the invention not explained in detail in the text, express reference is made to the drawings. The drawings show: Figs. 1a, 1b are schematic perspective cross-sectional views of transducer units for an acoustic microscope; Figs. 2a, 2b are schematic perspective cross-sectional views of further transducer units for an acoustic microscope; Fig. 3 shows a single scan field of a transducer unit of an acoustic microscope for examining a sample; Fig. 4 shows an entire scan field of a transducer unit of an acoustic microscope for examining a sample; Fig. 5 shows a schematic representation of a meandering scan path of a transducer unit over a sample surface in detail; and Fig. 6 shows the scan fields for a further transducer unit.

[0044] In the drawings, identical or similar elements and / or parts are provided with the same reference numbers, so that a re-presentation is omitted.

[0045] Fig. 1a und Fig. 1b Each shows a schematic perspective view of transducer units 10 for an acoustic microscope, in particular an ultrasonic scanning microscope, in cross-section.

[0046] The transducer unit 10 in Fig. 1a The transducer unit 10 has transducer elements 1, 2, 3, 4 arranged side by side in a linear arrangement in the Y-direction, i.e., perpendicular to the scan direction of the transducer unit 10 in the X-direction, all having the same focal length. The transducer elements 1, 2, 3, 4 are identical in construction and each has a transducer 20 and an acoustic lens 21 arranged on the transducer 20 for focusing the ultrasound signals onto a sample to be examined.

[0047] In the exemplary embodiment in Fig. 1b The transducer unit 10 has transducer elements 1, 12, 3, and 14 arranged linearly in the Y-direction in an alternating sequence. Transducer elements 1 and 3 each have a (first) focal length, and transducer elements 12 and 14 each have a (second) focal length, with the focal lengths of transducer elements 1 and 3 differing from those of transducer elements 12 and 14. Transducer elements 12 and 14 each have a lens 22 whose focal length differs from the focal length of lens 21 for transducer elements 1 and 3.

[0048] In Fig. 2a und Fig. 2b are shown in schematic perspective views of transducer units 10 according to other embodiments for an acoustic microscope, in particular an ultrasonic scanning microscope, in cross-section.

[0049] The designs of the further transducer units 10 according to Fig. 2a as well as Fig. 2b differ from the designs of the transducer units 10 according to Fig. 1a as well as Fig. 1b in the arrangement of the transducer elements.

[0050] In the design of the transducer unit 10 according to Fig. 2a are compared to the transducer unit 10 in Fig. 1a Transducer elements 1 and 3 are offset in the X direction relative to transducer elements 2 and 4. Transducer elements 1, 2, 3, and 4 each have the same focal length.

[0051] In the design of the transducer unit 10 according to Fig. 2b are compared to the transducer unit 10 in Fig. 1b Transducer elements 1 and 3 are offset in the X direction relative to transducer elements 12 and 14. Transducer elements 1 and 3 each have the same focal length, which differs from the focal length of transducer elements 12 and 14.

[0052] In Fig. 3 is a single first scan field 100.1 of the transducer unit 10 according to the configuration of Fig. 1a The diagram shows a schematic representation of a sample under investigation using transducer elements 1, 2, 3, and 4, all with the same focal length. With transducer elements 1, 2, 3, and 4 positioned at Y1, a linear scan of the sample is performed, displaying, for example, on a monitor. The image lines corresponding to transducer elements 1, 2, 3, and 4 (Y1-transducer element 1, Y1-transducer element 2, Y1-transducer element 3, and Y1-transducer element 4) are acquired simultaneously from the sample during a scan in the X-direction.

[0053] Subsequently, in an end position, the transducer unit 10 is moved from the Y-position Y1 to the Y-position Y2 by a small offset step size U in the Y-direction (see figure). Fig. 5 ) is moved so that the image lines Y2-transducer element 1, Y2-transducer element 2, Y2-transducer element 3, Y2-transducer element 4 are obtained from the sample in a linear scan. Then, the transducer unit 10 is moved from Y-position Y2 to Y-position Y3 by a small displacement step U (see figure). Fig. 5 ) is moved, whereby the image lines Y3-transducer element 1, Y3-transducer element 2, Y3 transducer element 3, Y3-transducer element 4 are subsequently obtained by means of the transducer elements 1, 2, 3, 4. In an analogous manner, the transducer unit 10 is moved from the Y position Y3 to the Y position Y4 by a small displacement step U in the Y direction (see Fig. 5 ) moved further in order to then simultaneously obtain the image lines Y4-transducer element 1, Y4-transducer element 2, Y4-transducer element 3, Y4-transducer element 4 in a linear rasterization in the X direction.

[0054] In Fig. 4 The diagram schematically illustrates the total scan field 100 of the transducer unit 10 of an acoustic microscope for examining a sample. After acquiring the entire scan field 100.1 with four line-shaped scans in the X-direction, as shown by Fig. 3 As shown, the transducer unit 10 is offset by a displacement step size W (cf. Fig. 5 ) offset in the Y direction, which is larger than the offset step size U (see Fig. 5 ) between the Y positions Y1, Y2, Y3, Y4. In particular, the offset step size W of the transducer unit 10 in the Y direction corresponds to the length that results from the product of the equidistant distance U of the linear scans with the number of linear m (in the present case m = 4) scans and the number of (in the present exemplary case: four) transducer elements of the transducer unit 10 in the Y direction.

[0055] In another embodiment, the Y-distances of the four linear scans in positions Y1, Y2, Y3 and Y4 correspond to a fraction of the width of the transducer elements 1, 2, 3, 4, wherein, after the execution of the four linear scans in the X-direction, the transducer unit is offset in the Y-direction with the offset step size, which corresponds to a multiple of the width of the transducer elements.

[0056] After the scan field 100.1 has been acquired and fully displayed, the transducer unit 10 is activated as shown in Fig. 3 described, and after an offset in the Y direction by a large offset step size W (see Fig. 5 The transducer unit 10 moves from Y-position Y4 to Y-position Y5 to acquire a subsequent scan field 100.2. Subsequently, the transducer unit 10 moves in a meandering pattern from Y-position Y5 to the further Y-positions Y6, Y7, and Y8 to acquire a scan field 100.2. Using transducer elements 1, 2, 3, and 4, the sample is scanned linearly to generate the respective image lines for the four Y-positions Y5, Y6, Y7, and Y8. These process steps between the individual Y-positions of the transducer unit 10 and between two consecutive scan fields are repeated several times until the last scan field 100.n for Y-positions Yn, Yn+1, Yn+2, and Yn+3 has been scanned using transducer elements 1, 2, 3, and 4, and the corresponding image lines have been generated.

[0057] Within the scope of the invention, it is possible to replace the transducer unit 10 with Fig. 1a a transducer unit 10 according to the schematic configurations according to Fig. 1b or Fig. 2a oder Fig. 2b or another transducer unit with several transducer elements arranged in a predetermined arrangement in the X-direction and / or in the Y-direction and / or having different focal lengths, for capturing a total scan field 100, wherein the transducer units 10 are each moved according to a, in particular meandering, raster method with different offset step sizes in the Y-direction during the raster method.

[0058] Fig. 5 The excerpt shows a schematic representation of the scan process of transducer unit 10 (see below). Fig. 4 ) with the four transducer elements 1, 2, 3, 4 over a section of a sample area of ​​the sample. To acquire the scan fields 100.1 and 100.2, the transducer unit 10 is moved between the several Y positions Y1, Y2, Y3, Y4 and Y5, Y6, Y7, Y8 of the respective scan field 100.1 or 100.2 by the (small) displacement step U in the Y direction and, after acquiring a scan field 100.1 or 100.2, by the displacement step W, which is larger than the displacement step U.

[0059] The movement of the transducer unit 10 follows a meandering pattern 30, thereby scanning the sample in a meandering direction. The Y-step size of the meander 30 for the transducer unit 10 is varied in the Y-direction to capture the entire scan field 100 using the displacement step sizes U and W.

[0060] In the embodiment of Fig. 6 A transducer unit 10 with two transducer elements 1 and 12, as well as the combined scan fields 101 and 112 for the two transducer elements 1 and 12, are shown schematically. In this configuration, the transducer elements 1 and 12 have different focal lengths.

[0061] As from Fig. 6 As can be seen, the transducer elements 1 and 12 are arranged diagonally offset in the X and Y directions on the transducer unit 10. Consequently, when scanning a sample, the total scan field 101 for transducer element 1 and the total scan field 112 for transducer element 12 are also offset in the X and Y directions. Accordingly, the resulting total scan images 101, 102, obtained with transducer elements 1 and 12, are displayed with an offset. In one embodiment, the transducer unit 10 is moved in a meandering pattern over the sample for linear scanning using transducer elements 1 and 12, with the Y step size between two linear scans being constant.

[0062] In another embodiment (not shown here), instead of the one in Fig. 6 The transducer unit 10 shown, for example, the one in Fig. 2b The transducer unit 10 shown is used for acquiring the total scan fields 101 and 112, wherein the transducer unit 10 is moved in the Y-direction according to a grid pattern, in particular a meandering pattern, with different displacement steps. Other embodiments of the grid pattern are also feasible using transducer units with multiple transducer elements having different focal lengths, wherein the transducer units are moved in the Y-direction according to a grid pattern, in particular a meandering pattern, with different displacement steps during the acquisition of a total scan field. Bezugszeichenliste

[0063] 1, 2, 3, 4Transducer element 10Transducer unit 12, 14Transducer element 20Transducer 21, 22Lens 30Meander 100Total scan field 101Total scan field 100.1, 100.2, ..., 100.nScan field 112Total scan field UVersetting step size Wersetting step size

Claims

1. A method for operating a scanning acoustic microscope, in particular an ultrasonic scanning microscope, wherein a sample is scanned in an X-Y plane by means of a transducer unit (10), in particular with one or more transducer elements (1, 2, 3, 4, 12, 14) comprising respectively one transducer and one lens, wherein the transducer unit (10) is moved in the X direction for a linear scanning of the sample, wherein, after the or a linear scanning of the sample by the transducer unit (10), the transducer unit (10) is displaced in the Y direction by a displacement increment, characterized in that during an examination of the sample by means of the scanning method the size of the displacement increment of the transducer unit (10) in the Y direction is varied for the scanning of the sample, wherein, in particular after the displacement of the transducer unit (10) in the Y direction, at least one further linear scanning of the sample is performed by means of the transducer unit (10) in the Y direction.

2. The method according to claim 1, characterized in that several linear scans of the sample are performed by the transducer unit (10), wherein the transducer unit (10) is displaced in each case by a small, preferably constant, displacement increment (U) in the Y direction in each case after a linear scan of the sample, and, after a predetermined number n (n ≥ 2, 3,...) of several linear scans of the sample, the transducer unit (10) is displaced in the Y direction by a large, preferably constant, displacement increment (W), which is greater than the small displacement increment (U), and / or that, after a linear scan of the sample, the transducer unit (10) is displaced in the Y direction by a large, preferably constant, displacement increment (W), and, after the displacement of the transducer unit by the large displacement increment (W), several n (n ≥ 2, 3,...) linear scans of the sample are taking place by the transducer unit (10), wherein, after each of the several linear n (n ≥ 2, 3,...) scans of the sample, the transducer unit (10) is displaced in each case by a small, preferably constant, displacement increment (U) in the Y direction, which is smaller than the large displacement increment (W).

3. The method according to claim 1 or 2, characterized in that the transducer unit (10) is moved in a meandering course in the X-Y plane relative to the sample.

4. The method according to any one of claims 1 to 3, characterized in that a.) the sample is scanned by using a transducer unit (10) for a scanning acoustic microscope, in particular an ultrasonic scanning microscope, with several transducer elements (1, 2, 3, 4, 12, 14) comprising respectively one transducer (20) and one lens (21, 22), wherein at least two transducer elements (1, 2, 3, 4, 12, 14) comprise different focal lengths, or b.) the sample is scanned by using a transducer unit (10) with several transducer elements (1, 2, 3, 4, 12, 14) comprising respectively one transducer (20) and one, preferably acoustic, lens (21, 22), wherein in particular the transducer elements (1, 2, 3, 4, 12, 14) comprise the same focal length and / or the transducer elements (1, 2, 3, 4, 12, 14) are arranged next to each other in a linear or rhombic arrangement in the Y direction.

5. The method according to any one of claims 1 to 4, characterized in that the transducer unit (10) comprises several transducer elements (1, 2, 3, 4, 12, 14) arranged in the Y direction, preferably one behind the other and / or linearly, wherein several linear m (m ≥ 2, 3, 4, ...) scans are performed in the X direction by means of the respective transducer elements (1, 2, 3, 4, 12, 14), wherein the distances of the linear m (m ≥ 2, 3, 4, ...) scans by the respective transducer elements (1, 2, 3, 4, 12, 14) are equidistant in the Y direction and, after the performance of the linear m (m ≥ 2, 3, 4, ...) scans by the transducer unit (10), the transducer unit (10) is displaced in the Y direction with the displacement increment, which corresponds to the product of the equidistant distance of the linear scans with the number of the linear m (m ≥ 2, 3, 4, ...) scans and the number of the transducer elements (1, 2, 3, 4, 12, 14) of the transducer unit (10) in the Y direction.

6. The method according to any one of claims 1 to 5, characterized in that the transducer unit (10), preferably with several transducer elements (1, 2, 3, 4, 12, 14), comprises a length in the Y direction, wherein, after several linear scans in the X direction by the transducer unit (10), the transducer unit (10) is displaced in the Y direction with a displacement increment that corresponds to the length of the transducer unit (10), wherein the respective distances of the several linear scans performed prior to the displacement of the transducer unit (10) in the Y direction with the displacement increment that corresponds to the length of the transducer unit (10) correspond to a natural fraction of the length of the transducer unit (10) (length of the transducer unit / t, t ≥ 2, 3, 4,...).

7. The method according to any one of claims 1 to 5, characterized in that the transducer unit (10) comprises several transducer elements (1, 2, 3, 4, 12, 14) arranged in the Y direction, preferably next to each other and / or linearly, wherein the transducer elements (1, 2, 3, 4, 12, 14) each comprise a, preferably constant, width in the Y direction, wherein several linear p (p ≥ 2, 3, 4,...) scans are performed in the X direction, wherein the distances between the linear p (p ≥ 2, 3, 4,...) scans correspond to a fraction of the width of the transducer elements (1, 2, 3, 4, 12, 14) (width of the transducer elements (1, 2, 3, 4, 12, 14) / p, p ≥ 2, 3, 4,...), and, after said performance of the linear p (p ≥ 2, 3, 4,...) scans, the transducer unit (10) is displaced in the Y direction by the displacement increment, which corresponds to a multiple of the width of the transducer elements (1, 2, 3, 4, 12, 14).

8. The method according to any one of claims 5 to 7, characterized in that the, in particular large, displacement increment (W) of the transducer unit (10) in the Y direction is corrected by a tolerance correction value after the performance of the several linear scans by the transducer unit (10), wherein in particular the tolerance correction value is formed such that the distance in the Y direction of the last linear scan prior to the displacement of the transducer unit (10) by the large displacement increment (W) to the first linear scan after the displacement of the transducer unit by the large displacement increment (W) corresponds to the distance of the several linear scans prior to and / or after the displacement of the transducer unit (10) by the large displacement increment (W) in the Y direction, or wherein in particular the tolerance correction value is formed such that the distance between all linear scans by the transducer unit (10) is constant.

9. The method according to any one of claims 1 to 8, characterized in that the transducer unit (10) comprises several transducer elements (1, 2, 3, 4, 12, 14), wherein the transducer elements (1, 2, 3, 4, 12, 14) are operated in parallel.

10. The method according to any one of claims 4 to 9, characterized in that, in particular in the case a.), preferably exclusively, two transducer elements (1, 2, 3, 4, 12, 14) with different focal lengths in relation to an X-Y plane are arranged next to each other in a linear arrangement in the Y direction or one behind the other in the X direction, or that, preferably exclusively, two transducer elements (1, 2, 3, 4, 12, 14) with different focal lengths in relation to an X-Y plane are arranged, in particular diagonally, displaced to each other in the X direction and in the Y direction.

11. The method according to any one of claims 4 to 10, characterized in that, in particular in the case a.), the transducer unit (10) comprises several transducer elements (1, 2, 3, 4, 12, 14) with respectively a first focal length and several transducer elements (1, 2, 3, 4, 12, 14) with respectively a second focal length, which differs from the first focal length in relation to an X-Y plane, wherein an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to each other, in particular linearly, in the Y direction with the first focal length and an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to each other, in particular linearly, in the Y direction with the second focal length are arranged one behind the other in the X direction, or wherein an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to each other, in particular linearly, in the Y direction with the first focal length and an array of transducer elements (1, 2, 3, 4, 12, 14) arranged next to each other, in particular linearly, in the Y direction with the second focal length are arranged, in particular diagonally, displaced to each other in the X direction and in the Y direction. or wherein transducer elements (1, 2, 3, 4, 12, 14) with the first focal length and transducer elements (1, 2, 3, 4, 12, 14) with the second focal length are arranged one behind the other, in particular linearly, in an alternating order in the Y direction.

12. A scanning acoustic microscope, in particular ultrasonic scanning microscope, comprising a transducer unit for scanning a sample in a X-Y-plane and means for moving the transducer unit in the X-direction, and means for displacing the transducer unit in the Y-direction, characterized in that the scanning acoustic microscope is configured to carry out the method according to any one of claims 1 to 11.