Alignment tip for a characterization device

Abstract

The invention relates to an alignment tip (1) for a sample characterization device, the alignment tip comprising: - an alignment head (2) that is made of a material having an atomic weight greater than 50 and has an essentially spherical shape, and - a body (3) that is connected to the alignment head (3) and is configured to be placed in a sample support.

Description

[0001] DESCRIPTION

[0002] Title: Alignment tip for characterization device

[0003] Technical field

[0004] The present invention relates to an alignment tip for a sample characterization device.

[0005] The field of the invention is, in a non-limiting manner, that of the characterization of samples by light radiation, electrons or ions.

[0006] State of the art

[0007] In order to characterize samples using a radiation beam from a measuring or characterization device, such as diffractometers, the samples must be aligned with respect to this beam to allow correct analysis of the measurement signals.

[0008] Alignment is usually performed using a reference object, such as a target, placed in the measuring beam.

[0009] In one example, crosses made of tungsten wire, for example, are used to align samples in beamlines. The alignment is carried out using a goniometer whose rotation axis is positioned on the axis of the radiation beam, the axes of the goniometer and the beam not being parallel.

[0010] Crosses do not allow sufficient rotation to achieve alignment across the entire angular space, which is required to perform and correct all the movements necessary for sample analysis. Also, since these crosses are two-dimensional structures, a non-orthogonal incident radiation beam produces an apparent thickness greater than the actual thickness.

[0011] In another example, Siemens target or star markers are used to achieve alignment in beamlines, with a resolution of a few nanometers. However, the cost of such objects is very high. Generally, state-of-the-art reference objects are two-dimensional objects and do not allow alignment along the three axes of rotation in space. In addition, they are not suitable for mounting in a measuring device or on a goniometer in the same way as the samples to be characterized. The alignment and the resulting measurement corrections are then not sufficiently precise.

[0012] The article M. Holler et al., "X-ray ptychographic computed tomography at 16 nm isotropy 3D resolution", Scientific Reports 4, 3857 (2014) describes ptychographic measurements with three-dimensional test objects made of porous silicon dioxide. However, these objects are very fragile and their manufacture is not reproducible.

[0013] Statement of the invention

[0014] It is an object of the invention to provide an alignment tip which can be used under conditions identical to those for the characterization of samples.

[0015] Another object of the present invention is to provide an alignment tip whose manufacturing process is simple to carry out, reproducible and has a low cost.

[0016] It is also an object of the present invention to propose an alignment tip which can be implemented in various applications, and in particular for the characterization of measuring or characterization devices.

[0017] At least one of these goals is achieved with an alignment tip for a sample characterization device, the alignment tip comprising: an alignment head made of a material with an atomic weight greater than 50 and having a substantially spherical shape, and a body connected to the alignment head, configured to be placed in a sample holder.

[0018] The alignment tip according to the present invention is intended to be implemented in a characterization or measurement device, for example for measuring or characterizing samples, or for characterizing measurement devices themselves. When implemented, the alignment tip can be placed in a sample holder of the measurement device, or connected thereto, in the same manner as a sample to be measured.

[0019] Thanks to its essentially spherical shape, the head of the alignment tip can be rotated in all directions in space.

[0020] When a sample to be measured is to be aligned with respect to a measuring beam, the alignment tip is previously positioned so that the alignment head is in the axis of the beam. Since the head is a three-dimensional structure, difficulties related to non-orthogonal incidence of the beam are eliminated. Thus, the accuracy of sample positioning in this device is improved, which improves the operation of the device. The measurement time and therefore the cost can be optimized.

[0021] In this type of measuring devices, the measuring beam can be a light beam, an electron beam or an ion beam.

[0022] The alignment tip according to the invention has a simple and solid structure which can be easily manufactured and whose dimensions can be chosen to be similar or of the same order of magnitude as those of the samples to be measured or the size of a measuring beam used in a measuring or characterization device.

[0023] Also, a single alignment tip according to the invention can be used repeatedly and in different types of measuring device having a suitable sample holder in which it can be placed. Thus, the alignment tip can be implemented in many applications.

[0024] The term "essentially spherical" means that the alignment head does not represent a perfect sphere. In particular, the sphere may have a non-sphericity of up to about 10%. This means that the minimum radius and the maximum radius of the sphere may differ from each other by up to about 10%. This non-sphericity is due to the nature of the manufacturing process of the alignment tip. The quality of the sphere of the head is, however, sufficient for the applications for which it is intended. According to one embodiment, the diameter of the head may be between 5 μm and 100 μm.

[0025] These dimensions correspond in particular to the typical dimensions of samples which can be measured or characterized with devices in which the alignment tip according to the invention is implemented.

[0026] These dimensions also correspond to those of a measuring beam used in measuring devices.

[0027] According to an advantageous embodiment, a collar region of the body in close proximity to the alignment head has a diameter substantially less than the diameter of the head.

[0028] The collar region, which is part of the body of the alignment tip, is located in close proximity to the sphere of the head. In this collar region, the dimensions of the body are such that the head is securely held by the body, but are substantially less than and not comparable to the diameter of the head.

[0029] When the alignment tip is implemented in a measuring or characterization device, the alignment, measurement or characterization is carried out using the substantially spherical head. When the tip is placed in a measuring beam, it is important that the collar region does not interfere with the use of the tip. The diameter of the collar region must therefore be as small as possible. In particular, the collar region must hide the measuring beam as little as possible, especially when the beam is in non-orthogonal incidence, in order to obtain a satisfactory contrast image.

[0030] According to embodiments, a diameter of the collar region may be between 2 μm and 80 μm.

[0031] Advantageously, a ratio between a length of the tapered portion of the body and a diameter of the rod-shaped portion of the body is equal to or greater than 0.5. This minimum ratio has been found to be advantageous for avoiding disturbances induced by a body that is too wide, for example when a measuring beam is in non-orthogonal incidence, and in particular for obtaining a usable contrast image.

[0032] Advantageously, the body may comprise a rod-shaped portion and a tapered portion, the tapered portion being proximate the alignment head.

[0033] The diameter of the body thus increases between the head and the other end of the body.

[0034] According to embodiments, a diameter of the body may be between 80 μm and 300 μm.

[0035] According to an advantageous embodiment, the head and the body can form a single unit.

[0036] The tip head and shaft are thus a single piece. There are no bonding points or similar that could weaken the joint between the head and the body. The monobloc withstands difficult measuring conditions, such as cryogenic conditions.

[0037] The tip material(s) are chosen for their strength, their resistance to radiation but also according to their cost.

[0038] Advantageously, the head is made of a high atomic weight material (greater than 50). The alignment head can be made of tungsten.

[0039] Indeed, in order to be able to align the alignment tip with respect to a measurement beam, it is important that the head of the tip produces a shadow when placed in the beam, in order to be able to evaluate its correct positioning. When it is a beam of electrons or X-rays, the material used for the alignment head must have a sufficiently high atomic weight so that the beam is partially or completely obscured by the head while producing contrast. According to one embodiment, the alignment tip according to the invention may comprise a removable base.

[0040] The removable base is particularly suitable for being placed in a sample holder of a measuring or characterization device.

[0041] According to a first exemplary implementation, the alignment tip according to the present invention can be used as a two-dimensional or three-dimensional reference object, under projection of a measurement beam, for the alignment of a sample in a sample characterization device or for characterizing measurement devices as a reference sample.

[0042] The alignment tip can in particular be used for centering a goniometer, for aligning the alignment tip with respect to a radiation beam, or for measuring a sample characterization device.

[0043] The alignment tip can then be used in the following manner: placing the alignment tip according to the invention in a sample holder of the goniometer,

[0044] - recording of position, displacement and dimension parameters of the alignment tip in a control module,

[0045] - centering of the alignment tip relative to the measuring beam using the dimension parameters, and replacement of the alignment tip with a sample to be characterized.

[0046] According to a second exemplary implementation, the alignment tip according to the present invention can be used as a three-dimensional reference object.

[0047] Indeed, the alignment head may have three-dimensional structures, such as hollow areas or gaps. The three-dimensional structures may be found in particular in the volume of the alignment head, but also on its surface. These generally irregular 3D structures are particularly resistant to the measuring beams implemented in the devices in which the alignment tip is to be used. An alignment tip micro-structured in this way can be used to determine the volume resolution of a measuring or characterization device, and in particular in tomography or ptychography.

[0048] Durable nanoscale structures are typically very difficult to obtain, and their fabrication (by focused ion beam (FIB)) is very expensive. An alignment tip according to the present invention constitutes a 3D structured object that is very resistant to difficult processing conditions, such as high doses of ionizing radiation or cryogenic conditions. They are compatible with permanent use, i.e., at least a hundred uses.

[0049] According to a third exemplary implementation, the alignment tip according to the present invention can be used as a functionalized reference object for fluorescence measurements.

[0050] For this purpose, the tip head may include a fluorescent material. The fluorescent material may in particular be introduced into hollow areas present in the alignment head.

[0051] The alignment tip thus allows, for example, the parameterization and calibration of detection in X-ray fluorescence spectrometry, functioning as a 3D marker.

[0052] According to a fourth exemplary implementation, the alignment tip according to the present invention can be used as a refractive optical element.

[0053] Indeed, the tip head may have curved crystalline areas that can function as focusing lenses for electromagnetic radiation.

[0054] Description of figures and embodiments

[0055] Other advantages and characteristics will appear on examining the detailed description of non-limiting examples, and the appended drawings in which: - [Fig.l] Figure 1 is a schematic representation of an alignment tip according to an embodiment of the invention, inserted in a support;

[0056] - [Fig.2] Figure 2 is an optical microscope image of a detail of an alignment tip according to an embodiment according to the invention; and

[0057] - [Fig.3] Figure 3 shows an image produced with an alignment tip according to the invention inserted into a hard X-ray beam.

[0058] It is understood that the embodiments described below are in no way limiting. In particular, all the variants and all the embodiments described can be combined with each other if nothing prevents this combination from a technical point of view.

[0059] In the figures, elements common to several figures may retain the same reference.

[0060] Embodiments of an alignment tip according to the invention will be described with reference to Figures 1 and 2.

[0061] The tip 1, as shown in Figure 1, comprises an alignment head 2 and a body 3 connected to the head 2.

[0062] The head 2 has a substantially spherical shape. An image of an exemplary embodiment is shown in Figure 2. It shows an alignment head 2 and a portion of the body 3 connected to the head 2, observed with an optical microscope. In this example, the head 2 and the body 3 are formed from a single piece.

[0063] The junction 4 between the head 2 and the body 3 has a diameter, or a transverse dimension when the section of the junction is not round, much smaller than the diameter of the head 2. The diameter of the head is between 5 μm and 100 μm. The diameter, or the transverse dimension, of the junction 4 between the head and the body 3 is preferably between 2 μm and 80 μm.

[0064] For example, with reference to Figure 2, the diameter of the head is approximately 30 μm, and the diameter of the junction 4 in the immediate vicinity of the head is approximately 10 μm. The body 3 of the tip 1 comprises a rod-shaped portion 8 and a conical or tapered portion 7. The conical portion 7 corresponds to a thinned region of the body 3. In the embodiment shown in Figure 2, the generatrix of the envelope of the "cone" is however not straight, but describes approximately a circular line.

[0065] For example, the length of the thinned region 7 may be between 100 pm and 1 mm.

[0066] Of course, the thinned region of the body can also have other shapes. It can, for example, be in the shape of a true cone or a rod.

[0067] The alignment tip 1 may be placed in a sample holder of a measuring or characterization device. In the embodiment as shown in Figure 1, the sample holder consists of a base 6 and a cannula 5. The cannula 5 accommodates the body 3 of the alignment tip, the inner diameter of the cannula 5 being substantially the same as the outer diameter of the end of the body 3. The cannula 5 may be considered as a removable base of the tip 1. The base 6 is adapted to be installed in a standardized measuring or characterization device.

[0068] Thus, when such an alignment tip is inserted into the measurement beam of a measuring device, with the alignment head centered on the center of the beam, an image as shown in Figure 3 is observed. Here, the measurement beam is a hard X-ray beam. To produce the image of Figure 3, the alignment tip is oriented horizontally, along the x-axis, with the head pointing to the right of the plane of the figure. The head as well as the body at the collar region partially obscure the beam, thus producing a so-called "corona" effect, i.e., a contrast image by partial occultation of the beam. A toroidal-shaped spot 10 is produced in the observation plane, with a circular shadow 11 in the center and a slit-shaped shadow 12 on the left side of the spot 10. These shadows correspond to the location of the head and the body, respectively, of the tip in the beam path.Ideally, the observed contrast image should have the shape of a perfect "donut", without the slit on the side. In this case, the alignment or centering of a sample in the measuring beam can be performed more efficiently. It is therefore very important that the transverse dimension of the collar region of the body, near the head of the alignment tip, is as small as possible, in order to obscure the measuring beam as little as possible.

[0069] The alignment tip according to the present invention can be manufactured according to an electrochemical manufacturing process, the steps of which will be detailed below. As an example, the manufacture of a tungsten alignment tip is presented.

[0070] Tungsten rods can be obtained from a simple tungsten wire. The wire can have a diameter of about 250 μm. A portion of a rod is subjected to chemical attack in a soda bath via electrolysis. The submerged portion of the rod is then thinned and finally cut by the chemical reaction at the thinnest point. The electrolysis is immediately stopped to keep the thinnest part of the submerged portion of the rod. The rod is removed from the soda and immersed in an acid bath of the same concentration as the soda bath to stop any chemical reaction on the rod. The rod will thus have a pointed end whose dimensions are of the order of a few tens of nanometers.

[0071] At this stage, the achievement of the pointed end of the rod can be checked with suitable means, in order to validate the previous manufacturing steps. For this, an optical microscope, a scanning electron microscope or X-rays can be used.

[0072] Then, the pointed end of the rod is subjected to pulsed laser irradiation. For this, the end is centered on the axis of a beam of a pulsed laser. Between each pulse, the pointed end is gradually inserted into the laser beam, until a physical modification of the tip is obtained. The pointed end is in fact subjected to a partial and local melting, and takes the spherical shape. The size of the sphere obtained depends on the length of the rod irradiated by the laser. As can be seen in Figure 2, the thinned region 7 of the rod 3 between the sphere 2 and the non-immersed part of the rod 3 has an approximately conical shape. The generatrix of the envelope of the "cone" is however not straight in the example shown, but describes approximately a circular line.

[0073] The characterization of the sphere 2 obtained by irradiation with the laser can also be carried out with an optical microscope, a scanning electron microscope or X-rays. The diameter of the sphere 2 and the dimensions of the rod 3 which supports it can thus be measured. The dimensions of the rod 3 include the diameter D at the base of the rod and the diameter of the junction 4, the length L of the approximately conical part and the radius corresponding to the circular line of the thinned region 7 of the rod 3. An example of a spherical head 2 and a rod part 3 made of tungsten is shown in Figure 2.

[0074] For example, the sodium hydroxide bath (electrolyte) used for the first dipping of the rod is a NaOH bath with a concentration of 2M, used with a stainless steel electrode. Electrolysis is carried out with a voltage of approximately 12 V and an electric current that can vary between 10 pA and 1 A, for example 50 mA.

[0075] The laser used can be, for example, an Nd:YAG laser delivering pulses with an energy of 10 mJ to 20 J, and in particular 1 ms pulses with an energy of 1.5 J.

[0076] The rod and the sphere at its end then constitute the body and head of an alignment tip according to the invention. The tip can then be inserted into a suitable holder for use in a measuring or characterization device.

[0077] Examples of implementation of the alignment tip according to the present invention will be described below. According to a first example of implementation, the alignment tip according to the present invention can be used as a two-dimensional or three-dimensional reference object, under projection of a measurement beam in a sample characterization device.

[0078] The tip allows in particular to align a sample in relation to this measuring beam.

[0079] This alignment can for example be carried out using a goniometer, in which the alignment tip is positioned using a sample holder, as shown in Figure 1. Ideally, this is the same sample holder that will be used for the sample(s) to be measured subsequently. The position of the alignment tip is then adjusted relative to the measuring beam using the goniometer. An image can then be observed as shown in Figure 3. Parameters related to the position, displacement (e.g. rotation) and dimensions of the tip are recorded in a reference table. The alignment tip is then removed from the sample holder, and a sample to be measured is positioned in the same holder for measurement.

[0080] An alignment tip according to the invention can also be used to test and characterize measuring devices. In this case, the alignment tip is used as a reference sample for the successive improvement of devices such as beamlines and non-synchrotron x-ray microscopy stations. It is then possible to compare measurements from these different devices.

[0081] According to a second exemplary implementation, the alignment tip according to the invention can be used as a three-dimensional reference object.

[0082] Indeed, depending on the material used and the manufacturing process of the tip, the alignment head may have three-dimensional structures, such as hollow areas or gaps, which may be found in particular in the volume of the alignment head, but also on its surface. The 3D structures, which may be irregular, are not modifiable and are resistant to the measurement beams (electrons, ions, X-rays) implemented in the devices in which the alignment tip is to be used. The structures typically have dimensions of a few tens of nanometers.

[0083] An alignment tip structured in this way can also be used to test and characterize measuring devices. For example, the volume resolution or contrast of measuring or characterization devices can be determined. In this case, the alignment tip is used as a reference sample for the subsequent improvement of devices such as devices for tomography or ptychography.

[0084] According to a third exemplary implementation, the alignment tip according to the invention can be used as a functionalized reference object for fluorescence measurements.

[0085] In fact, it is possible to introduce a fluorescent material into the alignment head, for example in the hollow areas present in the alignment head mentioned previously.

[0086] To fill hollow areas with fluorescent material, several techniques can be implemented:

[0087] 1. The alignment head may be dipped into a solution containing nanobeads and / or fluorescent molecules before the sphere is formed by laser irradiation. Upon partial melting, the fluorescent substances are at least partially integrated into the volume of the sphere.

[0088] 2. It is also possible to dip the formed sphere into a solution containing nanobeads and / or fluorescent molecules.

[0089] These two techniques can of course be combined. In addition, an additional galvanic electromotive force can be applied between the tip and a solution containing fluorescent nanobeads or molecules to improve the integration of fluorescent agents.

[0090] Such an alignment tip thus allows, for example, the parameterization and calibration of detection in X-ray fluorescence spectrometry. Indeed, the sphere can be subjected to a focused ion probe (FIB) to cut a part of the sphere and thus access one or more of the cavities filled with fluorescent material. With this fluorescent cavity, a fluorescence-inducing measuring beam can be scanned to measure its diameter.

[0091] According to a fourth exemplary implementation, the alignment tip according to the present invention can be used as a refractive optical element.

[0092] Indeed, the head of the alignment tip may have, or be modified to release, one or more existing crystalline zones on its surface. It is also possible to modify the head to discover or release such crystalline zones. These zones result from the manufacture of the tip, and in particular from subjecting the tip to pulsed laser irradiation. The crystalline zones are generally curved and can thus be used as focusing lenses for electromagnetic radiation. For example, such a tip can be used for the characterization of microlenses for X-rays.

[0093] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

Claims

AMENDED CLAIMS received by the International Bureau on March 22, 2024 (03.22.2024) 1. Alignment tip (1) for aligning relative to a measurement beam in a sample characterization device, the alignment tip comprising: an alignment head (2) made of material with an atomic weight greater than 50 and having a substantially spherical shape, and a body (3) connected to the alignment head (2), configured to be placed in a sample holder.

2. Alignment tip (1) according to the preceding claim, characterized in that a collar region (9) of the body (3) in the immediate vicinity of the alignment head (2) has a diameter substantially smaller than the diameter of the head.

3. Alignment tip (1) according to claim 1 or 2, characterized in that the body (3) comprises a rod-shaped portion (8) and a tapered portion (7), the tapered portion (7) being close to the alignment head (2).

4. Alignment tip (1) according to any one of the preceding claims, characterized in that the head (2) has a diameter of between 5 μm and 100 μm.

5. Alignment tip (1) according to claim 3 or 4, characterized in that a ratio between a length of the tapered portion (7) of the body (3) and a diameter of the rod-shaped portion (8) of the body (3) is equal to or greater than 0.

5.

6. Alignment tip (1) according to any one of the preceding claims, characterized in that the head (2) is made of tungsten.

7. Alignment tip (1) according to any one of the preceding claims, characterized in that the head (2) and the body (3) form a single block.

8. Use of the alignment tip (1) according to any one of the preceding claims as a two-dimensional or three-dimensional reference object in a sample characterization device. AMENDED SHEET (ARTICLE 19) 9. Use of the alignment tip (1) according to any one of claims 1 to 7 as a three-dimensional reference object in a sample characterization device, the alignment head (2) comprising microstructures.

10. Use of the alignment tip (1) according to any one of claims 1 to 7 as a functionalized reference object in a device for characterizing samples by fluorescence, the alignment head (2) comprising a fluorescent material.

11. Use of the alignment tip (1) according to any one of claims 1 to 7 as a refractive optical element, the alignment head (2) comprising at least one refractive crystalline zone. AMENDED SHEET (ARTICLE 19)

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