Gerard Nicolaas Anne van Veen

Silicon photodiodes for high-efficiency low-energy electron detection

Solid-state electron detectors have been fabricated using a p+n silicon photodiode where the p+ region is created by a chemical-vapor deposition (CVD) surface doping from diborane B 2 H 6 . The as-obtained nm-deep p-type layer is resistant to conventional metal etchants, which allows elimination of both entrance contacts and protection layers from the photosensitive surface. This approach lowers the dead layer energy loss, while keeping near theoretical efficiency at high electron energies. The photodiodes have outstanding performance in terms of electron signal gain at low energies achieving 60% and 74% of the theoretical gain value at 500 eV and 1 keV, respectively. The ideal I–V characteristics and the small over-the-wafer spread of the dark current indicate a defect-free p+n junction, as well as a reliable and reproducible process.

XHR SEM: enabling extreme high resolution scanning electron microscopy

The low voltage scanning electron microscope (SEM) is widely used in many industrial and research applications due to its ability to image surface details and to minimize charging and beam damage effects on sensitive samples. However, fundamental limitations in beam performance have existed, most notably in the chromatic aberration effects, which become larger as the beam voltage is reduced. The introduction of the extreme high resolution (XHR) SEM has demonstrated that sub-nanometer resolution can be achieved at low beam voltages, revealing fine surface detail. This system uses a source monochromator to reduce the effects of chromatic aberrations, resulting in a more tightly focused electron beam. Beam deceleration is available to provide a further improvement in imaging at low voltages and to give additional flexibility in optimizing the image contrast. While the monochromator is a necessary enabler of the improved imaging performance, further system elements, such as scanning, detectors, stage and environmental controls - that go into completing the SEM - are also key to the usability and throughput when it comes to practical day-to-day performance.