Remediation for TXRF saturation effects on microdroplet residues from preconcentration methods on semiconductor wafers

Automated nanoliter solution deposition for total reflection X-ray fluorescence analysis of semiconductor samples

“…Angle scans with both the W and Ag anodes showed mostly a film-like response to the individual droplet deposition. Recent literature has shown that the linearity of the TXRF signal of a VPD residue ends around 3 ng [5,6], but for a corresponding concentration in a film-like (spun on) sample the linearity is extended [11]. By taking advantage of the programming capability of the BioDot deposition, such that the VPD residue was distributed evenly within the analysis area of the TXRF detector, the linearity could be extended beyond 3 ng.…”

“…Recent reports in the literature suggest that saturation of the TXRF signal can under-report the true value of the contamination in analyses where the contamination in the residue is greater than 3 ng [5,6], thus limiting the linear dynamic range of the technique. It has also been shown that control of the effects of the dried VPD residue's morphology on the TXRF signal is of critical importance affecting reproducibility and accuracy when matching a sample to a standard [7][8][9][10][11]. The advances in nanoliter quantity dispensing instrumentation that include rapid droplet drying time [12] and programmable dispensing patterns make it worth investigating as a novel approach for drying VPD residue on the wafer to improve the accuracy and precision of VPD-TXRF measurements.…”

Trends in total reflection X-ray fluorescence spectrometry for metallic contamination control in semiconductor nanotechnology

“…Translated into surface concentrations with application of VPD-DC this is at the order of 4 × 10 10 -3 × 10 11 at/cm 2 depending on the scanned wafer area (150-300 mm diameters), as shown in Table 1. A number of approaches have been presented to cope with the TXRF saturation effects [42]. The practice of internal standardization that is well established in the analysis of environmental samples seems not to be effective for semiconductor samples.…”

Picoliter solution deposition for total reflection X-ray fluorescence analysis of semiconductor samples

“…These procedures offer good precision of the results and therefore serve as quality assurance in the production process. However, the film-like references do not match the dried deposit specimen from the VPD process [16]. Dried deposits from the VPD process do not always dry with a predictable morphology, they either dry ring-like or spot-like or crater-shaped.…”

“…This level of automation, while possible with VPD-ICP-MS, is more difficult to achieve and thus it is usually regarded as a laboratory analysis. Even though automated VPD-TXRF systems are widely accepted in the semiconductor industry [7][8][9] there are areas for improvement such as expanding the linear dynamic range and controlling the morphology of the dried residue as that impacts the analytical signal [10][11][12][13][14][15][16][17]. The morphology has critical influence on effects like absorption of the fluorescence photons of the primary beam and therefore on the accuracy of the analysis.…”