Experimental study about single event functional interrupt of ferroelectric random access memory induced by 30-90 MeV proton

Abstract

Ferroelectric random access memory (FRAM) is a promising memory for space application. The performance of FRAM under irradiation environment should be investigated, especially under proton irradiation environment, which dominates the particles in the space environment. The experiments on single event effects are carried out for two types of FRAMs (FM22L16 and FM28 V100) based on the proton cyclotron of China institute of atomic energy. Both dynamic and static mode are tested for each chip under the irradiation of proton in an energy range from 30 MeV to 90 MeV. Single event upsets (SEUs) and single event functional interrupts (SEFIs) are observed only on FM22L16, where the SEFI is recorded as a significantly transient error with or without memory cell upsets. The SEFI can be subdivided into soft SEFI and hard SEFI according to whether those significantly transient errors disappear or not when the irradiation is paused. Single event effect performances of FM22L16 are accurately described, and the SEFI cross section in an energy range from 50 MeV to 90 MeV is obtained experimentally. The cross section of SEFI increases with proton energy increasing and reaches 10^-3/cm² at 90 MeV. To further study the mechanism of SEFI, the pulsed laser beam with a wavelength of 1064 nm is used to pinpoint the sensitive area of SEFI in the FRAM. Pulsed laser experiment is easy to carry out when single pulsed laser radiates on the device from the back side. Results show that a certain part in peripheral circuit is detected as a sensitive area to SEFI. The sensitive area could be a register or buffer which is vulnerable to irradiation. Only SEUs are observed when the pulsed laser radiates others area of peripheral circuit and memory cell. A hypothesis that a micro latch-up in the CMOS-based peripheral circuit leads to the SEFI is proposed to explain the test results, for the CMOS-based peripheral circuit is sensitive to irradiation. The further reason is the energy deposition in silicon substrate by protons with energies ranging from 30 MeV to 90 MeV through nuclear reaction, which triggers the silicon controlled rectifier structure in the FRAM peripheral circuit. According to the hypothesis, a transient current should be generated in the peripheral circuit when the micro latch-up happens. The transient current is observed on the output of device by using a high frequency oscilloscope which demonstrates the reasonability of the hypothesis.