Electrical Characterization of the Operational Amplifier Consisting of 4H-SiC MOSFETs after Gamma Irradiation

Abstract

The operational amplifier (op-amp) with high gamma irradiation capability of over 30 kGy have been fabricated by 4H-SiC MOSFETs for measuring instruments which are installed in nuclear power plants. The chip size was 0.7 mm x 1.0 mm, and they consisted of five n-channel MOSFETs and three p-channel MOSFETs on the same die. The output waveform after having irradiated 50 kGy at a rate of 60 Gy/hr was amplified without distortion. On the other hand, the offset voltage became unstable when gamma integral dose was beyond 30 kGy and it at 50 kGy increased to +7.2 mV. For reduction of gamma irradiation influence, we proposed the MOSFETs structure which has field plate (FP) electrodes connected to isolation layer electrically. We indicated that the proposal device had the potential of gamma irradiation capability of 100 kGy experimentally.

Improved Offset Voltage Stability of 4H-SiC CMOS Operational Amplifier by Increasing Gamma Irradiation Resistance

“…Figure 1(a) shows the conventional active layout of the op-amp used in our previous study [8]. In the conventional layout, the gate electrode is laid across a channel region.…”

“…These results indicate that the improved op-amp can work while keeping the small offset voltage in a harsh irradiation environment without an external circuit for adjusting the offset voltage. Si-BJT [8] Conventional SiC op-amp [8]…”

“…To fabricate the ohmic contacts, the nickel layer was evaporated on the exposed surface of the 4H-SiC epitaxial layer and annealed at 1000 o C. An aluminum film was then deposited as source and drain electrodes. The op-amp circuit consisted of differential pairs, and an output stage was the same as that mentioned in our previous study [8]. Gamma-ray irradiation was carried out up to 103 kGy at a rate of 60 Gy/hr at room temperature.…”

“…Some groups showed superior characteristics of gamma-ray hardness on SiC MOS structures [1][2][3][4][5][6][7]. We previously showed the high irradiation capability of an op-amp consisting of 4H-SiC complementary MOS (CMOS) transistors and experimentally demonstrated the suppression of the total ionizing dose (TID) effect in a single transistor by optimizing the isolation structure [8].…”

Влияние протонного облучения (15 МэВ) на низкочастотный шум мощных SiC MOSFETs

“…Исследованию стойкости SiC MOSFETs по отношению к различным типам радиационного излучения уделяется значительное внимание во всех промышленно развитых странах. Наибольшее внимание до настоящего времени уделялось исследованию радиационной стойкости SiC MOSFETs по отношению к облучению γ-частицами (см., например, [2][3][4]). Значительное число работ посвящено исследованию изменения параметров SiC MOSFETs под влиянием облучения быстрыми электронами [5][6][7].…”