Gamma and proton irradiation effects and thermal stability of electrical characteristics of metal-oxide-silicon capacitors with atomic layer deposited Al2O3 dielectric

Abstract

The radiation hardness and thermal stability of the electrical characteristics of atomic layer deposited Al2O3 layers to be used as passivation films for silicon radiation detectors with slim edges are investigated. To directly measure the interface charge and to evaluate its change with the ionizing dose, metal-oxide-silicon (MOS) capacitors implementing differently processed Al2O3 layers were fabricated on p-type silicon substrates. Qualitatively similar results are obtained for degradation of capacitance-voltage and current-voltage characteristics under gamma and proton irradiations up to equivalent doses of 30 Mrad and 21.07 Mrad, respectively. While similar negative charge densities are initially extracted for all non-irradiated capacitors, superior radiation hardness is obtained for MOS structures with alumina layers grown with H2O instead of O3 as oxidant precursor. Competing effects between radiation-induced positive charge trapping and hydrogen release from the H2Ogrown Al2O3 layers may explain their higher radiation resistance. Finally, irradiated and nonirradiated MOS capacitors with differently processed Al2O3 layers have been subjected to thermal treatments in air at temperatures ranging between 100ºC and 200ºC and the thermal stability of their electrical characteristics has been evaluated. Partial recovery of the gamma-induced degradation has been noticed for O3-grown MOS structures. This can be explained by a trapped holes emission process, for which an activation energy of 1.38 ± 0.15 eV has been extracted.

Characterization of magnetic Czochralski silicon devices with aluminium oxide field insulator: effect of oxygen precursor on electrical properties and radiation hardness

“…On the other hand, the mobile interface charge increases with radiation dose for the O 3 and H 2 O + O 3 oxidants, but the increase is less for the H 2 O + O 3 combination. The observation of no change in oxide charge or saturation of positive charge accumulation resemble earlier irradiation experiments on MOS capacitors with Al 2 O 3 thin films for lower doses up to 300 kGy, where little effect of irradiation on the charge was reported [38,39]. However, in these studies films deposited with H 2 O were concluded as more radiation-hard, and accumulation of mobile charge in form of a hysteresis was not significant.…”

“…Furthermore, films deposited with O 3 have been shown to trap charges more efficiently than films deposited with water [40]. Our high-resistivity MCz substrates may also be more sensitive to interface traps and mobile charges manifested as hysteresis of MOS capacitor C-V curves, than the substrates with higher doping concentration used in [38].…”

AC-coupled n-in-p pixel detectors on MCz silicon with atomic layer deposition (ALD) grown thin film

“…On the other hand, the mobile interface charge increases with radiation dose for the O 3 and H 2 O + O 3 oxidants, but the increase is less for the H 2 O + O 3 combination. The observation of no change in oxide charge or saturation of positive charge accumulation resemble earlier irradiation experiments on MOS capacitors with Al 2 O 3 thin films for lower doses up to 300 kGy, where little effect of irradiation on the charge was reported [130,131]. However, in these studies films deposited with H 2 O were concluded as more radiation-hard, and accumulation of mobile charge in form of a hysteresis was not significant.…”

Study of surface recombination on cleaved and passivated edges of Si detectors

“…The oxide layer may gain a more positive charge during the first few Mrad of the ionizing dose, counteracting the negative charge from alumina. However, details of the sample preparation process were found to be important for the radiation resistance of the alumina layer [16], which may explain the performance variability observed at low fluences [14]. We considered both nonirradiated and irradiated samples in this study of surface recombination to find radiationinduced changes.…”