Research On Radiation Characteristics And Hardening Techniques Of 28 Nm SRAM Chip

There are a variety of high-energy particles in the space environment.These high-energy particles entering aerospace equipment devices will cause radiation effects and ultimately lead to device failure.Among them,total ionizing dose effects and single event effects are the two most common radiation effects.SRAM memory is not immune to space radiation effects.The radiation environment composed of high-energy protons,heavy ions and electrons makes SRAM memory prone to total ionizing dose effects and single event effects,which seriously threatens the service life of the device.At present,the influence of total ionizing dose effects on the single event upset sensitivity of deep sub-micron and nano devices is not uniform and clear enough.There is still much space to explore advanced process nodes and this subject is a real problem that the industry needs to solve.The thesis mainly focuses on the radiation characteristics and hardening techniques of the memory unit,memory array and I/O circuit of 28nm SRAM chip.The co-simulation of total ionizing dose effects and single event effects is studied and the influence of the two kinds of radiation effects on the voltage of the sensitive node of the SRAM memory cell is analyzed at the first part.Firstly,SOI Fin FET device modeling and SPICE model calibration are necessary,then according to the damage mechanism of two kinds of radiation effects,the influence of different factors on the radiation characteristics of the device is explored.TID and SEU are co-simulated to explore the effects of different energy values,different process parameters,different biases and different dose values on the voltage of SRAM sensitive nodes and the law of total ionizing dose effects and single event upset are clarified finally.In order to improve the reliability of electronic systems in aerospace and military industries,two hardened methods are proposed from the circuit level and system level respectively at the second part.In terms of circuit-level reinforcement,improved DICE structure resulted in three hardened circuits with good radiation resistance.Compared with other memory circuits,the static power has been reduced,and Static Noise Margin has been improved by approximately 13%.The switching threshold of the first two hardened circuits is close to130Me V-cm~2/mg.For multi-node upsets,the switching threshold of the DICE-II structure using the isolation unit reaches 45.2Me V-cm~2/mg,able to cope with multi-node upsets in general conditions.The DICE-III structure can effectively suppress the propagation of SET pulses in the circuit and prevent the memory from being written incorrectly or missed.In order to further improve the radiation hardened ability of the system,by improving the parallel decoding algorithm,an ECC circuit based on RS encoding and decoding is designed for the entire SRAM memory array,and finally it's realized that the ability to correct random8-bit errors occurring in the information bits.From Design Synthesis results,compared with LDPC code,the hardware overhead of RS(8,4,4)has increased by 21%,while the power consumption has been reduced by 60%,and the error correction capability has doubled.With the advancement of technology and the continuous increase of the number of I/Os,the I/O buffers have gradually become a sensitive structure for the radiation effect.In order to study the influence of the total ionizing dose effects on the behavioral characteristics of the I/O buffers of SRAM chip,the third part establishes a behavioral model of the total ionizing dose effects of the I/O buffers.this thesis studies the influence of different doses of radiation on the sensitive parameters of the I/O buffers under the premise of correct logic function,and gets two modeling method.Then the IBIS irradiation model is established by considering the total ionizing dose effects under the normal model.Finally the feasibility of the IBIS radiation effect modeling method is verified to ensure that the established model reflects the behavioral characteristics of the device under the radiation doses.