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中国物理学会期刊

新型绝缘体上硅静态随机存储器单元总剂量效应

CSTR: 32037.14.aps.68.20190405

Total ionizing dose effects on innovative silicon-on-insulator static random access memory cell

CSTR: 32037.14.aps.68.20190405
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  • 静态随机存储器作为现代数字电路系统中常见且重要的高速存储模块, 对于提升电子系统性能具有重要作用. 到目前为止, 关于静态随机存储器单元总剂量辐射效应的数据依然有待补充完善. 本文采用130 nm绝缘体上硅工艺, 设计制备了一种基于L型栅体接触场效应晶体管器件的6晶体管静态随机存储器单元. 该L型栅体接触器件遵循静态随机存储器单元中心对称的版图特点, 使得存储单元面积相比于采用同器件尺寸的T型栅体接触器件的静态随机存储器单元减小约22%. 文中对比研究了L型栅体接触器件与其他场效应晶体管之间的电学性能差异, 以及基于不同场效应晶体管静态随机存储器单元的漏电流和读状态下静态噪声容限随辐射总剂量增加的变化规律. 测试结果表明, L型栅体接触器件与T型栅体接触器件的器件性能接近, 但前者具有面积更小的优势; 同时基于L型栅体接触场效应晶体管的静态随机存储器单元的基本电学性能以及抗总剂量辐射效应均优于传统基于浮体场效应晶体管的静态随机存储器单元, 因而具有稳定可靠的实用价值.

     

    The static random access memory (SRAM), as a common and important high-speed storage module in modern digital circuit systems, plays an important role in improving the performances of electronic systems. The data about the total ionizing dose (TID) radiation effect of SRAM cell have not been rich in the literature so far. In this work, a novel 6-transistor SRAM cell (6T LB SRAM cell) based on L-type gate body-contact (LB) MOSFET device is designed and fabricated by 130nm silicon-on-insulator (SOI) process. The LB MOSFET follows the center-symmetric layout design of the SRAM cell, reducing the area by approximately 22% compared with the SRAM cell using the T-type gate MOSFET contact device (6T TB SRAM cell) of the same device size. The electrical performance difference between LB MOSFET and other devices is compared. Besides this, the variations of the leakage current and the reading static noise margin (RSNM) of SRAM cells based on different MOSFETs under various total ionizing doses are also investigated. The test results indicate that the LB MOS successfully suppresses the floating body effect (FBE), and that the drain-induced barrier lowing (DIBL) and drain-to-source breakdown voltage (BVds) characteristics are improved. The performance of this device is similar to that of TB MOS device, but due to the special body contact design, the former has an advantage of smaller area. Due to the use of the body contact device, the leakage current of the 6T LB SRAM cell is significantly smaller than that of the conventional floating device SRAM cell (6T FB SRAM cell), which has lower static power consumption. After 60Co-γ ray irradiation, the 700 krad(Si) radiation dose only increases the leakage current of 6T LB SRAM cell by 21.9%, which is better than 41.4% of 6T FB SRAM cell. In addition, the 6T LB SRAM cell has an RSNM value similar to that of the 6T TB SRAM cell, and this is 1.93 times higher than the that of 6T FB SRAM cell. The radiation experiment causes the butterfly curve of the 6T FB SRAM cell to be asymmetrically deformed, and the stability of the SRAM cell is deteriorated due to the TID effect. However, the test results show that when the radiation dose reaches 700 krad (Si), the RSNM value of the 6T LB SRAM cell is reduced only by 11.2%. Therefore, 6T LB SRAM cell has stable and reliable practical value.

     

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