Effects of 3-MeV Protons on 4H-SiC Bipolar Devices and Integrated OR-NOR Gates

Abstract

Abstract-Radiation effects of 3-MeV protons on 4H-SiC bipolar devices and integrated OR-NOR gates have been investigated. The chips were irradiated from a fluence of cm until cm . Up until a fluence of cm , both the bipolar devices and the logic gates were found to be stable, but for higher fluence, they begin to degrade as a function of irradiation fluence. Using TCAD simulations, degradation of the transistor current gain has been found to be more dominated by surface states than bulk defects generated by the proton irradiation. Simulations of logic circuits using SPICE show that the gain degradation is the key contribution to the unstable performance of the circuits from the fluence of cm and above.

Total Dose Effects on 4H-SiC Bipolar Junction Transistors

“…The beam is scanned across the surface of the devices to achieve a homogeneous coverage. Static DC measurements are performed on the NPN BJT before and after the radiation [10]. Sentarus TCAD [11] simulation of the prototype device [10] is utilized to relate the excess base current recombination, generated by the irradiation, to physical mechanisms i.e.…”

Bipolar integrated circuits in SiC for extreme environment operation

“…For fluences/doses of 10 11 cm −2 3 MeV protons or 38 Mrad gamma rays, the transistor current gain degraded by only 10%. Above these levels the bipolar transistor gain degraded by 70% for 10 13 cm −2 protons [32] and 50% for 332 Mrad gamma rays [33]. However, for both of these high doses both transistors and integrated circuits (digital OR-NOR gates) were functional, even though noise margins had degraded.…”

“…Uncontrolled surface recombination leads to excessive base current and a reduced current gain. Any damage to this region is obvious in a Gummel measurement of collector and base currents [32]. The thickness of the dielectric was 1 μm, which resulted in on chip capacitors with a capacitance of 30 pF mm −2 .…”

“…All radiation tests were performed offline on chips cut from finished wafers. For 3 MeV protons, fluences from 10 8 to 10 13 cm −2 were used on separate chips [32]. For gamma rays several doses up to 332 Mrad were tested on separate chips [33].…”

“…Integrated circuits fulfilling most needed analog and digital functions in figure 1 have been investigated at extreme temperatures in the range 250 °C-600 °C. At this stage there is also some reliability data [31] and radiation testing [32,33].…”