A silicon multi-cathode detector (SMCD) has been developed for microanalysis and x-ray mapping applications. The SMCD has a large active area (∼0.5 cm2), excellent energy resolution, and high count rate capability. The detector utilizes novel structures that have produced very low dark current, high electric field, uniform charge collection, low noise and high sensitivity to low energy x-rays. The detector's spectral response was evaluated using a 55Fe radioisotope source, as well as by fluorescing materials with an x-ray generator. Figure 1 shows a 55Fe spectrum with an energy resolution of 125 eV FWHM at 5.9 keV collected at 12 μs peaking time. This energy resolution has been repeatably measured on many different detectors. To evaluate the high count rate x-ray performance, which is very important for fast x-ray mapping, a Cu sample was fluoresced using a Rh-anode x-ray tube.

No abstract

No abstract

This work describes recent progress in implementation and applications of synchrotron radiation total reflection x-ray fluorescence (SR-TXRF) to measure trace metals on wafer surfaces. To date, we have achieved state-of-the-art transition metal sensitivity of 3×108 atoms/cm2 (˜3fg) for 1000 sec. counting time for impurities which have an monolayer-like distribution on the surface and <1fg for droplet-like impurities. Recent instrumentation breakthroughs include reduction of detector parasitic backgrounds (particularly Cu) to below our present detection limit, 150 and 200mm whole-wafer handling, wafer-mapping capability and a cleanroom mini-environment. With these upgrades, measurements were made of wafers from various steps in the integrated circuit fabrication process. These results demonstrate that synchtron radiation brings TXRF into a new and useful regime. Further developments are underway to increase throughput and access for broader application.

The concept utilized in charge coupled devices (CCD’s) for detection and imaging of light signals involving lateral movement of charges and extremely low capacitance of the detector and readout electronics has spawned a variety of new ideas in the design of nuclear detectors. Initially, silicon drift detectors (SDD’s) were developed for high energy physics applications. More recently, a vigorous effort to develop new structures for x-ray spectroscopy and light detection has started. Drift structures have been designed in a variety of topologies and materials (such as Si, CdZnTe, and HgI2) to satisfy the requirements of many different applications. The most interesting features that can be achieved with drift structures include: a) Large active area devices with low capacitance and low electronic noise, b) Very high signal throughput, c) Operation at or near room temperature, d) High sensitivity over the large entrance electrode to low energy xrays and short wavelength light, f) Single carrier charge collection allowing for elimination of hole contribution to the spectral broadening in compound semiconductor detectors such as HgI2, CdTe, and CdZnTe, f) 2D resolution of few tens of micrometer in both directions over few cm2 active areas, and g) Possibility of using more sophisticated schemes of charge collection by switching between integration and drift mode.