Qiwen Zheng

An Increase in TDDB Lifetime of Partially Depleted SOI Devices Induced by Proton Irradiation

The effects of proton irradiation on the subsequent time-dependent dielectric breakdown (TDDB) of partially depleted SOI devices are experimentally investigated. It is demonstrated that heavy-ion irradiation will induce the decrease of TDDB lifetime for many device types, but we are amazed to find a measurable increase in the TDDB lifetime and a slight decrease in the radiation-induced leakage current after proton irradiation at the nominal operating irradiation bias. We interpret these results and mechanisms in terms of the effects of radiation-induced traps on the stressing current during the reliability testing, which may be significant to expand the understanding of the radiation effects of the devices used in the proton radiation environment.

Hot-Carrier Effects on Total Dose Irradiated 65 nm n-Type Metal-Oxide-Semiconductor Field-Effect Transistors

The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradations on irradiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation (STI). The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.

Degradation of the front and back channels in a deep submicron partially depleted SOI NMOSFET under off-state stress

The hot-carrier effect characteristic in a deep submicron partially depleted SOI NMOSFET is investigated. Obvious hot-carrier degradation is observed under off-state stress. The hot-carrier damage is supposed to be induced by the parasitic bipolar effects of a float SOI device. The back channel also suffers degradation from the hot carrier in the drain depletion region as well as the front channel. At low gate voltage, there is a hump in the sub-threshold curve of the back gate transistor, and it does not shift in the same way as the main transistor under stress. While under the same condition, there is a more severe hot-carrier effect with a shorter channel transistor. The reasons for those phenomena are discussed in detail.

Investigating the TDDB lifetime growth mechanism caused by proton irradiation in partially depleted SOI devices

We have investigated the effects of proton irradiation on the subsequent time-dependent dielectric breakdown (TDDB) lifetimes of partially depleted (PD) SOI devices. Our results show that the TDDB lifetimes of the devices increased after proton irradiation and the amplitude increased with the intensification of the total ionizing dose (TID) damage. Moreover, the radiation-induced leakage currents (RILC) and the TDDB lifetimes of the irradiated devices by protons were dependent on TID damage but independent of energy of protons. We interpreted these results and mechanisms in terms of the effects of radiation-induced traps on the stressing current during the reliability testing, which may be significant to further expand the understanding of the radiation effects of the devices used in the space radiation environment.

Read Static Noise Margin Decrease of 65-nm 6-T SRAM Cell Induced by Total Ionizing Dose

Read static noise margin (SNM) decrease of 65-nm 6-T cell induced by total ionizing dose (TID) was observed in this paper. The static random access memory (SRAM) cell test structure allowing precise measurement of read SNM was specifically designed and irradiated by gamma ray. Experimental results show that read SNM of 65-nm 6-T cell is sensitive to TID irradiation. The largest decrease of read SNM is 48 mV after 1000 krad(Si) irradiation, which is 36% of the value before TID irradiation. Being dependent on the measurement of radiation responses of cell transistors and simulation results, we conclude that the read SNM decrease is due to a threshold voltage shift induced by TID. Because narrow width transistors are employed in SRAM cells, threshold voltage of cell transistors will be shifted by charges trapped in shallow trench isolation, known as “Radiation-Induced Narrow Channel Effect.”

Total Ionizing Dose Influence on the Single-Event Upset Sensitivity of 130-nm PD SOI SRAMs

Effect of total ionizing dose (TID) on single-event upset (SEU) hardness of 130 nm partially depleted (PD) silicon-on-insulator (SOI) static random access memories (SRAMs) is investigated in this paper. The measurable synergistic effect of TID on SEU sensitivity of 130-nm PD SOI SRAM was observed in our experiment, even though that is far less than micrometer and submicrometer devices. Moreover, SEU cross section after TID irradiation has no dependence on the data pattern that was applied during TID exposure: SEU cross sections are characterized by TID data pattern and its complement data pattern are decreased consistently rather than a preferred state and a nonpreferred state as micrometer and sub-micrometer SRAMs. The memory cell test structure allowing direct measurement of static noise margin (SNM) under standby operation was designed using identical memory cell layout of SRAM. Direct measurement of the memory cell SNM shows that both data sides’ SNM is decreased by TID, indicating that SEU cross section of 130-nm PD SOI SRAM will be increased by TID. And, the decreased SNM is caused by threshold shift in memory cell transistors induced by “radiation-induced narrow channel effect.”

Online and offline test method of total dose radiation damage on static random access memory

In this paper, for the study of static random access memory (SRAM), the online-test and offline-test are carried out on the total dose radiation damages. The differences between the two kinds of test methods and physical mechanisms are investigated. The results show that SRAM present multiple failure mode, the online-test only includes one fixed failure mode and the offline-test includes multiple failure mode. Due to the restrictions on signal integrity at test frequency, the online dynamic current test value is significantly less than offline test value. Since the existence of imprinting effect, the online-test static current is significantly less than offline-test value when the device-stored data are opposite to irradiation data. The parameters that cannot be detected online, may lapse prior to the data that could be detected online. The results are significantly important for studying the total dose radiation effect and the experimental evaluation of SRAM under radiation environment.

Hot-carrier effects on irradiated deep submicron NMOSFET

We investigate how γ exposure impacts the hot-carrier degradation in deep submicron NMOSFET with different technologies and device geometries for the first time. The results show that hot-carrier degradations on irradiated devices are greater than those without irradiation, especially for narrow channel device. The reason is attributed to charge traps in STI, which then induce different electric field and impact ionization rates during hot-carrier stress.