The microfocus x-ray source IµS, combined D8 DISCOVER, is a new diffraction (XRD) method used for the research and characterization of modern materials. This article discusses the capabilities of the system in a micro-diffraction (µXRD) configuration to study the crystalline phase distribution, and the properties of materials with probe sizes smaller than 50µm. A second example will involve phase mapping using µXRD done on different materials, such as copper interconnect circuits and granite slices. The analysis of orientation distribution function (ODF) is also demonstrated on a 500 µm line width circuit.
The µXRD configuration is displayed in Figure 1, and the setup details are summarized in Table 1. The IµS with the integrated MONTEL optic gives a primary beam with a brilliant spot type for this application.
Figure 1. D8 DISCOVER with IµS configured for µXRD, from left to right: IµS, Montel, collimator, centric cradle, 1D and 2D detector respectively. (Top) The LYNXEYE XE is used to produce orientation dependent maps. (Bottom) The VÅNTEC-500 is used for pole figure measurements for ODF analysis.
Table 1. Typical µXRD Phase mapping instrument setup for the D8 DISCOVER with IµS.
||IµS Microfocus (Cu)
||20 µm - 1.0 mm, several intermediate sizes
||Centric Eulerian Cradle (CEC)
||Positioning Laser Video Microscope
||LYNXEYE XE or VÅNTEC-500
The final beam size can be controlled using collimators, often selected to 20 µm to 100 µm. The beam is focused on the sample using the MONTEL optic to produce a higher intensity for the smallest spot size. Precise and simple contact-free positioning of the X-ray beam on the sample is achieved using a laser-video microscope. The LYNXEYE XE detector was employed for mapping experiments, where the indication of phase existence was indicated using a single peak. Once the positioning of the detector over a peak of interest is done, an array of X translational scans is performed in Y direction. During measurement sample oscillation is done in Psi (tilting) and Phi (rotation), to minimize the orientation that is associated with poor statistics of particle, so that the intensity of the peak is representative of the concentration of the phase. After identifying an area of interest, further analysis such as textural and residual stress measurements can be done. A 2D detector like VÅNTEC-500 is used to speed up the data collection process, if numerous measurements at varying orientations of the sample are required.
Measurement of Biotite in Granite
A 20 x 20 x 5 mm granite piece was used in the experiment (Figure 2a). The phase map that was performed on this granite piece at an angle of 34 degrees (corresponding to the (131) reflection of biotite) is shown in Figure 2b. The map consists of a number of X scans with 0.1 mm step, and 0.5 second per step count time, over a range of 20 mm. The X scan is performed again over 20 mm of Y, resulting in a total scan time of 11 hours. There is a positive correlation between the black areas of the granite in the optical image, and the biotite in the µXRD phase map.
Figure 2. Optical image and µXRD phase mapping of biotite in granite with the D8 DISCOVER with IµS and LYNXEYE XE.
Measurement of 50 µm Copper Traces on a PCB
Circuit interconnection on printed circuit boards is required to connect electronic devices. The performance of the device is based on the interconnection circuit quality. When these circuits are made smaller the maintenance of the preferred orientation becomes increasingly difficult. A single 2D frame’s integration, procured from a 50 µ copper interconnect is displayed in Figure 3.
Figure 3. XRD Measurement of a printed circuit board collected with IµS and LYNXEYE XE while oscillating in X and Y over the whole surface.
The circuit that was analyzed is depicted in Figure 4a. Figure 4b shows a map of micro x-ray fluorescence of the circuit obtained using the M4 TORNADO. The sample’s µXRD phase maps (111), (200) and (220) are shown in Figures 4c-e.
Figure 4. (a) Optical image of the printed circuit board sample. (b) µXRF elemental map of Cu collected with the M4 TORNADO. (c-e) ) µXRD phase map of (111), (200) and (220) Cu collected with IµS and LYNXEYE XE.
The areas that are bright correspond to the grain at the normal orientation of the surface on the printed circuit board. Elemental mapping of barium and sulphur formed using the M4 TORNADO is shown in Figure 5a-b. Though visualization of the elements is possible, information regarding the presence of crystalline phases is absent. The (121) BaSO4 phase map in Figure 5c shows barium and sulphur in elemental mapping in the BaSO4 phase.
Figure 5. (a-b) µXRF elemental map of Ba and S collected with the M4 TORNADO. (c) µXRD phase map of (121) BaSO4 collected with IµS and LYNXEYE XE.
µXRD Measurement of Texture
Areas of interest that provide detailed analysis using µXRD phase mapping may be present. For example a material’s macroscopic properties can depend on the crystallographic orientation or texture of the existent phases. This can be used for further quantification of the texture using pole figures as well as the resulting ODF. The 2D VÅNTEC-500 detector, with its large coverage in gamma and 2q, saves time in the collection of pole figures. An optical image and a phase map of (111) Cu µXRD of a 500 µm printed circuit board is depicted in Figure 6.
Figure 6. Optical image and µXRD Cu (111) phase mapping with the D8 DISCOVER with IµS and LYNXEYE XE.
Figure 7 shows the pole figures (111) and (200) of the data set of the texture obtained at a beam size of 100 µm and 20 minute collection time. The pole figures were created using DIFFRAC.MULTEX and the texture was analyzed in the component method using the pole figure that was reconstructed. This is also displayed in Figure 7. Calculation of ODF was done based on three fibrous texture components as seen in Figure 8.
Figure 7. Measured (left) and simulated (right) pole figures using only a fiber texture components of a 500µm copper interconnect. The pole figures are of the (111) (top) and (200) (bottom) reflections of copper.
Figure 8. Orientation Distribution Function (ODF) of a 500 µm copper interconnect.
The IµS D8 DISCOVER was used for the data collection of various samples, including interconnects of copper and granite on printed circuit boards. A probe of 20 µm to 100 µm was created using the IµSMONTEL optic that helped to configure the texture analysis and µXRD phase mapping. The mapping stage X and Y of Centric Eulerin Cradle was done using LYNXEYE XE to produce the µXRD maps, while detailed analysis was achieved with the VÅNTEC-500. The combination of the DIFFRAC.MULTEX software and DAVINCI optical recognition enables the transition from LYNXEYE XE to VÅNTEC-500 within a very short span of time, and makes it possible to optimize the instrument for the experiment.
This information has been sourced, reviewed and adapted from materials provided by Bruker AXS Inc.
For more information on this source, please visit Bruker AXS Inc.