Operation of voltage termination structure in silicon n+-p-p+ detectors with Al2O3 field isolator grown by Atomic Layer Deposition method

This study focuses on evaluating the properties of voltage termination structure (VTS) with multiple guard rings in n(+)-p-p(+) silicon detectors with Al2O3 field isolation films processed by Atomic Layer Deposition (ALD) method. The dependences of the ring potential over the guard rings with respect to bias voltage were studied experimentally and compared with the results of simulations using negative charge Q(f) in Al2O3 films as a parameter. The agreement of the experimental and calculated punch-through voltages switching the ring operation verified that the punch-through model built for the p(+) -n-n(+) detectors passivated with positively charged SiO2 layers is also applicable for the n(+) -p-p(+) detectors with Al2O3 field isolator with negative charge polarity. The results indicated an efficient potential distribution over the VTS rings. The amount of the oxide charge was shown to be an essential parameter for the detector performance. From the comparison of the experimental data and simulations for Si detector with the used design and processing technology, Q(f) of -(4-7) x 10(11) cm(-2) was found to be the value explaining the properties of VTS in the detector under study. The simulations showed that Q(f) of -7 x 10(11) cm(-2) is an upper limit critical for the appearance of high electric field regions in the VTS. The increase in the silicon resistivity to 20 k Omega cm was found to be an efficient way to reduce the electric field below the value initiating the carrier avalanche multiplication.