Imec Introduces AlGaN-on-Si Extreme Ultraviolet Imager
The hybrid design integrates an AlGaN layer acting as a sensor on a Si(111) substrate. The device would be ideally suited to solar science, EUV microscopy and advanced EUV lithography applications.
Imec, a leading research organization in nanoelectronics, has presented results of an ultra-thin hybrid AlGaN-on-Si-based extreme ultraviolet (EUV) imager. With only 10 microns pixel-to-pixel pitch the new device was presented at the International Electron Devices Meeting in San Francisco a few days go.
The wide-bandgap material (AlGaN) provides insensitivity to visible wavelengths and enhanced UV radiation hardness compared to silicon. Backside illumination in a hybrid design was used to achieve a very small pitch-to-pitch of only 10 microns. The novel imager shows an excellent detection down to a wavelength of 1nm.
Ultraviolet detection is of particular interest for solar science, EUV microscopy and advanced EUV lithography tools. Sensors using wide-bandgap materials overcome the drawbacks of Si-based sensors such as their sensitivity to UV radiation damage and the need for filters to block the unnecessary visible and infrared radiation.
Imec’s backside illuminated EUV imager is based on a state-of-the-art hybrid design integrating an AlGaN sensor on a silicon readout chip. A submicron thick AlGaN layer was grown on a Si(111) wafer using molecular beam epitaxy (MBE) and a focal plane array of 256x256 pixels with a pixel-to-pixel pitch of 10 microns was processed.
Each pixel contains a Schottky diode optimized for backside illumination. A custom read-out chip, based on capacitance transimpedance amplifiers, was fabricated in 0.35µm CMOS technology. The AlGaN wafer and read-out chip were post-processed with indium solder bumps with 10µm pixel-to-pixel pitch achieving excellent uniformity.
The focal plane array and read-out chip were assembled using flip-chip bonding and subsequently the silicon substrate was locally removed to enable backside illumination of the active AlGaN layer. Finally, the imager was packaged and wire-bonded. Measurements demonstrated an excellent response down to a wavelength of 1nm.
These results were obtained in collaboration with CRHEA/CNRS (France) and the Royal Observatory of Belgium in the framework of the BOLD project of the European Space Agency (ESA).
Imec performs world-leading research in nanoelectronics and leverages its scientific knowledge with the innovative power of its global partnerships in ICT, healthcare and energy.
Imec is headquartered in Leuven, Belgium, and has offices in Belgium, the Netherlands, Taiwan, US, China and Japan. Its staff of more than 1,750 people includes over 550 industrial residents and guest researchers. In 2009, imec's revenue (P&L) was €275 million.