Effect of HCl cleaning on InSb-Al2O3 MOS capacitors

In this work, the role of HCl treatments on InSb surfaces and InSb-Al2O3 dielectric interfaces is characterised. X-ray photoelectron spectroscopy measurements indicate that HCl diluted in and rinsed with isopropanol (IPA) results in a surface layer of InCl3 which is not present for similar HCl-water processes. Furthermore, this InCl3 layer desorbs from the surface between 200 degrees C and 250 degrees C. Metal-oxide-semiconductor capacitors were fabricated using atomic layer deposition of Al2O3 at 200 degrees C and 250 degrees C and the presence of InCl3 was associated with a +0.79 V flatband voltage shift. The desorption of the InCl3 layer at 250 degrees C reversed this shift but the increased process temperature resulted in increased interface-trapped charge (D-it) and hysteresis voltage (V-H). This shift in flatband voltage, which does not affect other figures of merit, offers a promising route to manipulate the threshold voltage of MOS transistors, allowing enhancement-mode and depletion-mode devices to be fabricated in parallel.