System and method for XRF inspection

Abstract

To provide an XRF inspection system and corresponding methods.SOLUTION: A system and method are directed at inspection of a sample. The system comprises at least one X-ray source for providing X-ray radiation of a selected energy spectrum, an optical arrangement for focusing the X-ray radiation onto a selected inspection spot of a sample, and at least one detector configured to detect radiation emitted from the sample and provide output data indicative of emission spectrum from the sample, where the output data includes data indicative of L-line excitation fluorescence response of the sample.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to systems and methods for specimen inspection using X-ray fluorescence, and in particular to techniques for assessing the composition of solder bumps in circuits. [Background technology]

[0002] Typical electronic circuits and circuit boards include various arrangements of connection points. In certain circuit boards, such connection points include solder bumps, often utilizing a Ag / Sn (silver-tin) material combination. X-ray fluorescence (XRF) bump inspection is a non-destructive testing technique used primarily in the electronics manufacturing industry to evaluate the quality and composition of solder bumps on circuit boards. This technique uses XRF technology to analyze the elemental composition of solder bumps, which is important for forming reliable electrical connections in devices such as smartphones and computers.

[0003] During inspection, an X-ray source directs X-rays at selected locations on the sample, typically solder bumps. The interaction of the X-ray radiation with elements within the bumps causes fluorescence and the emission of secondary X-rays characteristic of the particular elements present in that region of the sample. By measuring the intensity and energy of the emitted X-ray radiation, the XRF system can determine the composition and thickness of the material within each bump.

[0004] Typically, conventional XRF techniques utilize K-line excitation and fluorescence detection for the inspection of Ag / Sn bumps. This technique usually operates with excitation X-rays having an energy of about 50 KeV for detection of fluorescence emission at an energy of about 25 KeV.

[0005] X-Ray Fluorescence Analytical Background: X-Ray Fluorescence Phenomenon. (http: / / cais.uga.edu / wp-content / uploads / 2019 / 01 / XRF_Background.pdf) provides an overview of the basic principles behind XRF spectroscopy.

[0006] Imashuku, S. et al., "Improvement of total reflection X-ray fluorescence spectrometer sensitivity by flowing nitrogen gas." Spectrochimia Acta Part B: Atomic Spectroscopy, volume 73, 75-78 (2012): Total reflection X-ray fluorescence (TXRF) has achieved remarkable success with its advantages of simultaneous multielement analysis, reduced background noise, absence of matrix effects, wide dynamic range, ease of operation, and the possibility of trace element analysis. Simultaneous quantitative online analysis of trace heavy metals is urgently needed by dynamic environmental monitoring and management, and TXRF has potential in this application area. However, this requires an online analytical scheme based on TXRF and a robust and rapid quantification method, which have not yet been fully explored. Furthermore, spectral overlap and background effects can lead to loss of precision or even erroneous results during practical quantitative TXRF analysis. This paper proposes an intelligent multielement quantification method using an established online TXRF analytical platform. In this intelligent quantification method, the collected characteristic curves of all existing elements and a pre-estimated background curve across the entire spectral range are used to approximate the measured spectrum. A novel hybrid algorithm, PSO-RBFN-SA, is designed to solve the curve-fitting problem using offline global optimization and fast online computing. Experimental results verify that simultaneous quantification of trace heavy metals, including Cr, Mn, Fe, Co, Ni, Cu, and Zn, can be achieved on an online TXRF analysis platform, achieving both high measurement accuracy and computational efficiency.

[0007] Menzel, M. et al., "Total reflection x-ray fluorescence analysis of airborne silver nanoparticles from fabrics," Analytical Chemistry, volume 86, 3053-3059 (2014): Ag nanoparticles (NPs) are commonly applied to consumer products for their antibacterial properties, making them desirable in sportswear fabrics and cleaning fabrics. Human health risks from airborne Ag NPs can arise when the NPs are inhaled. NPs are comparable in size to macromolecules and viruses and can penetrate deep into the lungs, e.g., alveoli, where, due to their large surface area, they can cause damage to cells and tissues. In this study, aerosols emitted from Ag NP-treated fabrics were collected using a low-pressure Berner impactor and analyzed by total reflection X-ray fluorescence (TXRF). We found that Ag NPs were primarily emitted in the form of larger particles, primarily 0.13–2 μm in size, likely attached to the textile material. Using an electron microprobe, we were able to identify single particles. Although the signal in energy-dispersive X-ray spectroscopy (EDX) was below the limit of detection (LOD), the detection of backscattered electrons suggested that small spots on the particles consisted of heavier elements (most likely Ag). To achieve the LOD required for Ag measurement, the Ar peak was eliminated by a nitrogen atmosphere provided by a "Picofox-box." This allowed for linear calibration and quantification of Ag. The LOD was calculated to be 0.2 ng (2.0 ppb). Following TXRF and scanning electron microscope (SEM) / EDX analysis, aerosol samples were dissolved in nitric acid and analyzed by ICPMS, successfully confirming the results obtained by TXRF measurements. Summary of the Invention

[0008] Conventional XRF techniques typically utilize K-line detection and analysis for material analysis of Ag / Sn bumps on electronic circuit boards. The excitation energy required to induce K-line fluorescence emission of these elements is relatively high and can typically be related to the maximum energy of the X-ray source used. In addition, inspection of samples using such high energies, approximately 50 keV, can result in the excitation beam penetrating the sample's underlying layer or substrate, providing output data indicative of the material of the inspection system. In addition, multiple photons emitted from the sample's underlying layer can reach the detector. In addition, the use of high-energy X-rays can cause Compton scattering at energies corresponding to the K-line of the investigated element.

[0009] More specifically, in XRF measurements, an X-ray beam is used to excite the sample being analyzed. As mentioned above, this excitation causes the sample to emit characteristic X-ray radiation at different energies corresponding to the elements present in the sample. If the sample contains sulfur (S, Z=16) and elements above the periodic table, the X-ray excitation may provide excitation of electrons from the inner shell, providing K-line excitation, or excitation of electrons from the penultimate shell, providing L-line excitation. Therefore, K-lines have higher energy than L-lines because the energy required to excite electrons from the inner shell is greater than the energy required to excite electrons from the outer shell.

[0010] Furthermore, to optimally excite an element, the X-ray beam must have an energy approximately twice its characteristic fluorescent energy. For example, to excite the K-line of tin (Sn), which has a characteristic emission energy of 25.196 KeV, the excitation X-ray beam typically requires an energy of approximately 50 KeV. Similarly, to excite the K-line of silver (Ag), which has a characteristic emission energy of 22.106 KeV, the excitation X-ray beam typically requires an energy of approximately 44 KeV.

[0011] Accordingly, the present disclosure provides an inspection system and method for inspecting specimens. The techniques of the present disclosure are typically suitable for inspecting specimens having one or more solder bumps, which are often used in electronic circuit boards to solder various elements to the substrate. Such solder bumps often contain silver (Ag) and tin (Sn). Inspection of solder bumps determines the bump's thickness and its material composition, enabling detection of inconsistencies between a circuit design and its actual structure, which can be used to identify manufacturing defects.

[0012] The system generally includes at least one X-ray source (X-ray tube) providing X-ray radiation of a selected energy spectrum, an optical device for focusing the X-ray radiation onto a selected inspection spot on the sample, and at least one detector configured to detect radiation emitted from the sample and provide output data indicative of an emission spectrum from the sample. According to the present disclosure, the output data includes data indicative of the L-line excited fluorescence response of the sample. For example, for Sn, the Lα line is 3.444 KeV, and for Ag, the Lα line is 2.984 KeV.

[0013] Typical X-ray sources used in inspection systems operate at voltages up to 50 KV. Generally, to provide K-line excitation of Ag / Sn bumps, these X-ray sources often operate at their maximum energy output. One advantage of the disclosed techniques relates to the ability to operate the X-ray source with lower energy requirements for L-line excitation. This makes L-line more suitable for analysis under standard XRF operating conditions and ensures better excitation. More specifically, energies of approximately 6.888 KV and 5.968 KV are required to excite the Lα lines of Sn and Ag, respectively, as discussed above.

[0014] Generally, it may be possible to use L-rays for the analysis of heavy elements, allowing for optimal excitation of the elements at relatively low voltages. However, simple testing using these energy rays can be inaccurate due to potential overlap with characteristic lines of other elements. For example, the L-α line of silver (Ag) has an energy of 2.984 keV and generally overlaps with the K-α line of argon (Ar) at 2.957 keV. Because argon is naturally present in the atmosphere, testing samples under atmospheric conditions can affect the resulting spectra at these energies.

[0015] Therefore, the present disclosure further provides for replacing the atmospheric gas composition in the present invention with a selected inert gas composition. The selected inert gas composition is typically used to exclude argon, in order to prevent normal air from affecting the test results. To this end, the system may include an inert gas source, such as a gas tank and / or pump, configured to flow the selected inert gas composition into the area where the sample is placed during testing. The selected inert gas composition may include one or more materials with energy levels that do not coincide with the L-line peaks of the material being tested, thereby avoiding interference with the testing process. More specifically, in testing Ag / Sn bumps with the L-line energies detailed above, the selected inert gas composition may include molecular nitrogen (N2) and / or helium (He), which are both chemically inert and have energy levels that are separated from the L-line levels of Ag and Sn. For example, N2 has a characteristic energy line at 0.392 keV, which is sufficiently separated from the L-alpha lines of Ag and Sn.

[0016] The selected gas composition is typically chosen to avoid interactions with materials on the wafer and with the structure of the device. Additionally, the selected inert gas composition is chosen so that no special detectors are required other than the detector used to detect L-line excitation. For example, the inspection system may include one or more (e.g., four) silicon drift detectors (SDDs).

[0017] In some embodiments, the inspection system may be operable within a sealed casing. Prior to and during inspection operations, the system may supply a selected inert gas composition within the casing to provide an overpressure condition. This eliminates, or at least significantly reduces, any interfering materials, such as Ar gas, from the casing.

[0018] Thus, according to some embodiments, the present disclosure provides the following examples.

[0019] Example 1: An XRF inspection system for inspecting a sample, comprising: at least one X-ray source providing X-ray radiation of a selected energy spectrum; an optical device for focusing the X-ray radiation onto a selected inspection spot on the sample; and at least one detector configured to detect radiation emitted from the sample and provide output data indicative of an emission spectrum from the sample, the output data including data indicative of an L-line excited fluorescence response of the sample.

[0020] Example 2: The XRF inspection system of Example 1, further comprising an inert gas source configured to flow a selected inert gas composition in a radiation path between the at least one X-ray source, the sample, and the at least one detector, thereby eliminating interference associated with excitation of components of the atmospheric composition.

[0021] Example 3: The XRF inspection system of Example 2, further comprising a casing, wherein the inert gas source is configured to provide an overpressure inert gas to thereby exclude atmospheric gas compositions from within the casing. In some examples, the inert gas is directed to excluding argon gas or other gases from interacting with the X-ray beam within the system.

[0022] Example 4: The XRF inspection system of Example 2 or 3, wherein the composition of the selected inert gas is selected so that the atmospheric conditions do not interact with the X-ray radiation provided by the at least one X-ray source.

[0023] Example 5: The XRF inspection system of any one of Examples 2-4, wherein the selected inert gas composition consists of nitrogen (N2) and / or helium (He).

[0024] Example 6: An XRF inspection system according to any one of Examples 1-5, wherein at least one X-ray source is a polychromatic X-ray source providing radiation in a selected energy spectrum.

[0025] Example 7: An XRF inspection system as described in any one of Examples 1 to 6, wherein the optical device includes a polycapillary device for focusing X-ray radiation from the at least one X-ray source into an illumination spot having a diameter in the range of 1 micrometer to 100 micrometers.

[0026] Example 8: An XRF inspection system as described in any one of Examples 1 to 7, wherein the optical device includes a Fresnel lens device for focusing X-ray radiation from the at least one X-ray source to an illumination spot having a diameter in the range of 1 micrometer to 100 micrometers.

[0027] Example 9: The XRF inspection system of any one of Examples 1-8, wherein the output data includes data indicative of sample fluorescence emission at energies in the range of 0.054 KeV to 8 KeV.

[0028] Example 10: The XRF inspection system of any one of Examples 1-9, wherein the output data includes data indicative of sample fluorescence emission at energies in the range of 2.5 KeV to 3.2 KeV.

[0029] Example 11: An XRF inspection system as described in any one of Examples 1-10, further comprising a sample stage adapted to hold the sample and to selectively translate the sample, thereby enabling scanning of the sample for inspection.

[0030] Example 12: A method for inspecting solder bumps in a sample, the method comprising: directing at least one X-ray beam to at least one illumination spot on the sample; collecting fluorescent X-ray radiation from the sample and generating fluorescent radiation data indicative of levels and energy ranges of the fluorescent radiation; and processing the fluorescent radiation data to determine data regarding material levels in one or more solder bumps according to emission peaks indicative of L-line excitation of materials in the sample.

[0031] Example 13: The method of Example 12, further comprising providing a selected inert gas composition over the sample during inspection, thereby reducing X-ray emission from one or more components of the atmospheric composition in the fluorescence emission data.

[0032] Example 14: The method of example 13, comprising inspecting a sample within the casing and providing a selected inert gas composition within the casing under pressurized conditions, thereby excluding atmospheric gas compositions from within the casing.

[0033] Example 15: The method of Example 13 or 14, wherein the selected inert gas composition is selected such that the gas atmosphere conditions do not interact with the X-ray radiation provided by the at least one X-ray source.

[0034] Example 16: The method of any one of Examples 13-15, wherein the selected inert gas composition consists of nitrogen (N2) and / or helium (He).

[0035] Example 17: The method of any one of Examples 12-16, wherein directing at least one X-ray beam comprises directing a polychromatic X-ray beam having radiation of a selected energy spectrum.

[0036] Example 18: The method of any one of Examples 12 to 17, wherein directing the at least one X-ray beam comprises directing the at least one X-ray beam through an optical device comprising a polycapillary device, and focusing the at least one X-ray beam onto an irradiation spot having a diameter in the range of 1 micrometer to 100 micrometers.

[0037] Example 19: The method of any one of Examples 12-18, wherein the fluorescence emission data includes data indicative of sample fluorescence emission at energies in the range of 0.054 KeV to 8 KeV.

[0038] Example 20: The method of any one of Examples 12-19, wherein the fluorescence emission data includes data indicative of sample fluorescence emission at energies in the range of 2.5 KeV to 3.2 KeV.

[0039] Example 21: The method of any one of Examples 12-20, further comprising providing the sample on a sample stage adapted to hold the sample, and selectively translating the sample to thereby scan at least one region of the sample. [Brief explanation of the drawings]

[0040] In order to better understand the subject matter disclosed herein, and to illustrate how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: [Figure 1] 1 schematically illustrates an inspection system according to some embodiments of the present disclosure. [Figure 2] The energy state of the atom is shown, and K excitation lines and L excitation lines are illustrated. [Figure 3] Fluorescence response spectra of the material under atmospheric and N2 conditions are shown. [Figure 4] 1 illustrates a method for inspecting a sample according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0041] 1, which schematically illustrates a system 100 for inspecting a specimen 50. The system 100 includes at least one X-ray source 110, an optical device 120 (e.g., a polycapillary device) configured to focus an X-ray beam from the at least one X-ray source 110 to a selected illumination spot on the specimen 50, and one or more detectors 130, exemplified by detectors 130a and 130b.

[0042] Typically, the system 100 may also include a sample mount 140 (e.g., a stepper) configured to mount the sample 50 and translate the sample in at least two dimensions to enable scanning of the sample to inspect different locations on the sample 50.

[0043] In some embodiments, the inspection system 100 may include a sealed casing 160. Also, in some embodiments, the inspection system includes an inert gas purging device 150 configured to flow a selected inert gas composition PG (Purge Gas) into the casing. Two inert gas sources 150a and 150b are illustrated. The selected inert gas composition is selected to purge atmospheric gases to eliminate interference of one or more atmospheric gases from interacting with x-ray radiation at energy levels near one or more energies relevant to inspection of the specimen.

[0044] The disclosed techniques and systems may be directed to the inspection of one or more solder joints within an electrical or electronic circuit board. Typically, such solder joints may be formed from silver-tin (Ag / Sn solder). The disclosed systems utilize X-ray excitation of one or more regions of a sample 50 with an X-ray beam IR, collection of a fluorescent response from the inspection location, and analysis of the energy spectrum of the collected fluorescent response FR to determine the material composition and structural parameters of the inspection region. According to the present disclosure, analysis of the fluorescent spectrum for detection and quantification of the Ag / Sn solder region utilizes a spectral range associated with L-line excitation of the material.

[0045] Figure 2 shows a schematic representation of atomic energy levels, illustrating K- and L-excitation and their respective fluorescence responses. An X-ray beam excites material in a sample when absorbed by an electron in the innermost shell (K excitation) or the penultimate shell (L excitation), ejecting an electron and leaving a vacancy. In a fluorescence response, an electron from a higher energy state relaxes into a vacancy, emitting a photon of the corresponding energy difference.

[0046] As mentioned above, the energy required for K excitation of silver (Ag) is approximately 44 keV, while the energy required for K excitation of tin (Sn) is approximately 50 keV. These energies are often at the upper end of the spectrum of typical X-ray tubes used for inspection. Alternatively, L excitation of tin (Sn) requires an energy of 6.888 keV, and L excitation of silver (Ag) requires an energy of 5.968 keV. These lower energies are more easily achieved and eliminate interference associated with Compton scattering. In addition, lower-energy X-ray beams, in the 5-7 keV range, are characterized by lower transmission, thereby enabling inspection of Ag / Sn bumps while reducing background contributions and contributions from the material matrix beneath the inspection area.

[0047] Detection of Ag / Sn bumps using L excitation allows for inspection using reduced X-ray energies and may have various advantages over detection based on K excitation. However, fluorescence data may contain emissions from additional elements in these energy ranges. More specifically, the Kα line of argon (Ar) at 2.957 keV. Because argon is naturally present in the atmosphere, inspecting samples in atmospheric conditions may affect the resulting spectra at these energies. Figure 3 (from Imashuku, et al. Spectrochim Acta Part B At Spectrosc 73, 75-78 (2012)) illustrates the fluorescence spectra of various materials and shows the effect of XRF measurements in atmospheric conditions and when the atmospheric environment is replaced with nitrogen (N2). As shown, argon (Ar) provides a relatively high fluorescence response when present, while the Ar peak is reduced in a nitrogen (N2) environment.

[0048] Therefore, to eliminate or at least significantly reduce environmental data that interferes with the collected fluorescent radiation, the system 100 may utilize an inert gas purging device 150, as described above. The inert gas purging device 150 (e.g., purging units 150a and 150b) may include a gas tank and a release valve or may be connected to an external gas source and configured to flow a selected inert gas composition through the inspection space before and during inspection of the sample. The selected inert gas composition is selected to provide an inert gas mixture that is chemically inert to the interaction of the system elements with the sample, while having an X-ray fluorescence that is separate from the L-line fluorescence response of the material being inspected, such as silver and tin. Typically, the selected inert gas composition may include one or more of nitrogen (N2) and / or helium (He).

[0049] To eliminate, or at least significantly reduce, atmospheric gas interference in the inspection data, the inert gas purging device 150 can be operated to provide a selected inert gas composition at a selected flow rate to provide an overpressure condition. The inert gas flow removes the atmospheric admixture to reduce or even eliminate the fluorescence response associated with argon gas excitation.

[0050] In some embodiments, the inert gas purging device may be connectable to an external gas source, for example, via a wall mount. Such an inert gas purging device may include one or more of the following: suitable connectors, valves, flow meters, particle filters, gas purifiers (e.g., for N2 and / or He gas), and discharge ports.

[0051] To allow for overpressure conditions of a selected inert gas composition, system 100 may be placed within a sealed casing 160. The sealed casing 160 need not be completely sealed, but typical gas flows through openings in the casing may determine the flow rate required to provide the overpressure conditions within casing 160 and the time required to sufficiently purge the atmospheric mixture from the casing.

[0052] Typically, some inspection systems operate to scan a specimen and generate output data indicative of a spectrum of fluorescent emission for each scanned location on the specimen. Accordingly, in some embodiments of the present disclosure, the inspection system 100 utilizes an inert gas purging device 150 to provide inspection conditions that enable detection and analysis of Ag / Sn solder regions using L-line fluorescence response while eliminating, or at least significantly reducing, interference from argon fluorescence response peaks. The output inspection data can then be examined and analyzed to determine compositional and structural parameters of the specimen including one or more Ag / Sn solder regions.

[0053] Furthermore, according to some embodiments, the present disclosure provides a method for inspecting a sample. FIG. 4 illustrates a method for inspecting a system according to some embodiments of the present disclosure. Specifically, the method includes providing a sample for inspection (step 4010) and generally placing the sample on a sample mount within an inspection system. Generally, prior to the inspection process, the present disclosure may include flowing a selected inert gas mixture (e.g., nitrogen and / or helium gas) into the inspection system (step 4020) to purge out the atmospheric gas mixture and eliminate or at least significantly reduce the presence of argon in the inspection system to avoid interference from argon peaks in the inspection results. Following purging of the atmospheric gas mixture, the method generally includes scanning and inspecting the sample by XRF inspection (step 4030). Scanning and inspecting the sample generally includes an inspection that may include, for each scan point, illuminating the scan point with one or more X-ray beams (having selected polychromatic or monochromatic energy ranges) (step 4032) and collecting fluorescent emission from the sample (step 4034) to generate output inspection data for each scan location. Generally, the actions of illuminating the scan point with one or more X-ray beams (step 4032) and collecting fluorescent emission data (step 4034) may occur simultaneously or nearly simultaneously. Further, in some embodiments, the method may immediately provide output data for each scan point (step 4040). The inspection process is performed by scanning all selected areas of the sample until scanning of the sample is completed (step 4038).

[0054] The inspection output data typically includes data regarding the spectrum and intensity of the fluorescent radiation for each scan point. The method includes providing the fluorescent data for analysis (step 4040), which may be done manually or using computer software. In some embodiments, the method may utilize an output of the fluorescent data for each scan point rather than generating the output data after completing a scan.

[0055] Additionally, in some embodiments, the method includes analyzing the output inspection data (step 4050) and determining the Ag / Sn solder connector based on a fluorescence peak associated with L-line excitation of the material of the sample (step 4060).

[0056] As mentioned above, L-line excitation of silver provides a peak at an energy of 2.984 keV, and L-line excitation of tin provides a peak at an energy of 3.444 keV. These energy peaks allow for a reduction in the energy of the illuminating X-ray beam; energies of 6-10 keV can be sufficient for L-line excitation. In addition, lower energy X-ray beams are generally characterized by a reduced penetration depth, reducing interference from the substrate layer and sample mount.

[0057] The inventors of the present disclosure conducted experiments to determine the effect of using an inert gas on the detection of Ag and / or Sn L lines in a sample. Experimental data was collected using an X-ray inspection system using a polychromatic tube (e.g., manufactured by MXR) with a W anode. The tube was operated at 50 kV and 950 mA using a polycapillary device (e.g., manufactured by XOS) with a focal spot of approximately 15 μm. The inspection system also used a detector array manufactured by Amptek. The inspection system was modified to support a flow of N2 gas over the detection area to purge the measurement area and remove Ar.

[0058] Two sets of measurements, each consisting of ten 60-second measurements, were performed on the 13 μm bumps. One set of measurements was performed without N2 flow to obtain a reference point, and the second set was performed with N2 flow. The measurements were carried out with a flow of N2 at a flow rate of 2.5 L / min. Table 1 below summarizes the 10 results from the different sets of measurements.

[0059] [Table 1]

[0060] From these results, the mean, standard deviation, and RSD were calculated as shown in Table 2.

[0061] As can be seen from the results, the use of N2 to purge unwanted gases from the detection area allows for a reduction in the RSD of approximately 1.7%, in this example the RSD is reduced from 8.85 to 7.18. Examination of the Ar signal shows a 55% reduction in signal.

[0062] [Table 2]

[0063] Thus, the present disclosure provides an inspection system and method suitable for identifying one or more elements, typically Ag / Sn solder connectors, using L-line excitation of the elements of a specimen, which may utilize purging of air from the inspection region to eliminate, or at least significantly reduce, contamination of the inspection data by fluorescence peaks of environmental materials (such as argon) that have energy peaks close to the L-line excitation peaks of the specimen material.

[0064] It should be noted that the various features described in the various embodiments can be combined according to all possible technical combinations.

[0065] It is to be understood that the present invention is not limited in its application to the details set forth in the description contained herein or in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways. Accordingly, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will be able to readily utilize the conception upon which the present disclosure is based as a basis for the designing of other structures, methods and systems for carrying out some of the purposes of the subject matter of the present disclosure.

[0066] Those skilled in the art may apply various modifications and changes to the embodiments of the present invention, as described above, without departing from the scope thereof as defined in and by the appended claims.

Claims

1. 1. An XRF inspection system for inspecting a sample, comprising: at least one X-ray source providing X-ray radiation of a selected energy spectrum; an optical device for focusing the X-ray radiation onto a selected inspection spot of the sample; at least one detector configured to detect radiation emitted from the sample and provide output data indicative of an emission spectrum from the sample; Equipped with An XRF inspection system, wherein the output data includes data indicative of an L-line excited fluorescence response of the sample.

2. 10. The XRF inspection system of claim 1, further comprising an inert gas source configured to flow a selected inert gas composition into a radiation path between the at least one X-ray source, the sample, and the at least one detector, thereby eliminating interference associated with excitation of components of atmospheric composition.

3. 3. The XRF inspection system of claim 2, further comprising a casing, wherein the inert gas source is configured to provide an overpressure inert gas to thereby exclude atmospheric gas compositions from within the casing.

4. 3. The XRF inspection system of claim 2, wherein the composition of the selected inert gas is selected so that atmospheric conditions do not interact with the X-ray radiation provided by the at least one X-ray source.

5. The selected inert gas composition is nitrogen (N ２ 3. The XRF inspection system of claim 2, wherein the XRF inspection system comprises:

6. The XRF inspection system of any one of claims 1 to 5, wherein the at least one X-ray source is a polychromatic X-ray source providing radiation in a selected energy spectrum.

7. 6. The XRF inspection system of claim 1, wherein the optical device comprises a polycapillary device for focusing X-ray radiation from the at least one X-ray source into an illumination spot having a diameter in the range of 1 micrometer to 100 micrometers.

8. The XRF inspection system of any one of claims 1 to 5, wherein the output data includes data indicative of sample fluorescence emissions at energies in the range of 0.054 KeV to 8 KeV.

9. 1. A method for inspecting solder bumps in a specimen, comprising: directing at least one X-ray beam onto at least one illumination spot on the sample; collecting X-ray fluorescence radiation from the sample and generating fluorescence emission data indicative of levels and energy ranges of fluorescence emission; and processing the fluorescence emission data to determine data relating to material levels within one or more solder bumps according to emission peaks indicative of L-line excitation of material in the sample.

10. 10. The method of claim 9, further comprising providing a selected inert gas composition over the sample during inspection, thereby reducing x-ray emissions from one or more components of atmospheric composition in the fluorescence emission data.

11. 11. The method of claim 10, comprising inspecting the sample within a casing and providing the selected inert gas composition within the casing under pressurized conditions, thereby excluding atmospheric gas compositions from within the casing.

12. 11. The method of claim 10, wherein the selected inert gas composition is selected such that gas atmospheric conditions do not interact with the x-ray radiation provided by the at least one x-ray source.

13. The selected inert gas composition is nitrogen (N ２ 11. The method of claim 10, wherein the oxygen comprises:

14. The method of any one of claims 9 to 13, wherein directing at least one x-ray beam comprises directing a polychromatic x-ray beam having radiation of a selected energy spectrum.

15. A method according to any one of claims 9 to 13, wherein the fluorescence emission data comprises data indicative of sample fluorescence emission at energies in the range of 0.5 KeV to 8 KeV.

Images