Design of an Aerospace-Grade Radiation-Hardened SRAM Cell for High-Speed Read/Write Applications
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摘要: 随着CMOS工艺微缩,静态随机存取存储器(SRAM)在宇航级场景下面临严峻辐射可靠性挑战,且现有抗辐射加固(RHBD)结构难以兼顾高抗辐射能力与高速读写访问性能。为此,本文提出一种面向高速读写需求的宇航级抗辐射SRAM单元RFWF16T (Read Fast and Write Fast 16-Transistors)。该结构通过双源隔离机制,将敏感节点缩减至2个;同时,通过构建对称的反馈回路,该单元实现了100%的单节点翻转自恢复与83.3%的双节点翻转自恢复。为突破传统加固结构的速度瓶颈,RFWF16T利用短反馈路径与低阻抗电压泄放回路,在28 nm工艺下实现了20.97 ps的读访问时间与2.72 ps的写访问时间,其读写速度相比其他 8 种同类典型加固结构分别平均提升了46.65%和14.77%。蒙特卡洛与工艺角-电压-温度实验表明,该结构在宽扰动范围内具有强鲁棒性,并在综合电气质量度量评价中表现最优。结果表明,RFWF16T在保证高抗辐射能力的同时有效解决了读写速度瓶颈,具备工程应用潜力。Abstract:
Objective With the continuous scaling of CMOS technology nodes and the reduction of supply voltage, SRAMs in aerospace environments are increasingly sensitive to high-energy particle radiation, prone to Single Node Upsets (SNUs) and Double Node Upsets (DNUs). This poses a severe challenge to the reliability of spaceborne System-on-Chips (SoCs). However, existing Radiation-Hardened By Design (RHBD) structures usually struggle to balance high radiation tolerance with high-speed access performance. To resolve this contradiction, the primary objective of this work is to design an aerospace-grade radiation-hardened SRAM cell tailored for high-speed read/write applications, ensuring both superior radiation resistance and rapid access capabilities. Methods The proposed RFWF16T(Read Fast and Write Fast 16-Transistors) SRAM is based on a dual-source isolation architecture constructed with 16 transistors (8 PMOS and 8 NMOS) ( Fig. 1 ,Fig. 2 ). Structurally, by employing a symmetric recovery mechanism, the RFWF16T effectively reduces the number of key sensitive nodes to only two. Redundant transistors (P2 and P6) are utilized to create a stable high-level isolation state, isolating storage nodes from potential disturbances during the non-access phase. To achieve high-speed operation, the RFWF16T integrates a short feedback path combined with a low-impedance voltage discharge loop. Unlike traditional hardened cells that rely on stacked transistors (which increase resistance and delay), the RFWF16T adopts a parallel access topology connected to Word Lines and Bit Lines. This configuration establishes a low-impedance path during write operations, significantly accelerating node voltage switching (Fig. 3 ). Performance verification demonstrates the self-recovery capability of four data nodes. Comprehensive variation analysis includes Process-Voltage-Temperature (PVT) variations and 2000-point Monte Carlo simulations. Additionally, an improved Electrical Quality Metric (EQM) is introduced to quantitatively evaluate multi-dimensional performance.Results and Discussions The RFWF16T exhibits exceptional performance, particularly in overcoming the speed bottleneck of hardened SRAMs. In terms of access speed, the RFWF16T performs significantly better than typical models such as S8P8N, SAW16T, and RH20T. Under standard conditions (28 nm CMOS process,1.0 V, 25 ℃, TT corner), the RFWF16T achieves a Read Access Time (RAT) of 20.97 ps and a Write Access Time (WAT) of 2.72 ps, which represent average speed improvements of 46.65 % and 14.77 %, respectively, over eight comparable hardened structures ( Table 2 ). PVT analysis confirms that the RFWF16T maintains the lowest latency across varying voltages (.7 V-1.1 V) and temperatures ( -25 ℃ to 125 ℃) (Fig. 6 ). This superior write speed is attributed to the elimination of write contention via optimized discharge paths. Regarding noise margins and stability, the RFWF16T demonstrates superior robustness, achieving the highest Write Wordline Toggle Voltage (WWTV) among 9 comparative structures. Its Hold/Read Static Noise Margins (HSNM/RSNM) also rank at the forefront, ensuring stability under disturbances (Fig. 7 ). In terms of radiation hardening, the RFWF16T realizes a 100% Self-Recovery Rate for SNUs and an 83.3% recovery rate for DNUs, reaching the state-of-the-art level for DNU-recoverable units (Table 1 ). Monte Carlo simulations confirm that average recovery times for internal nodes range from 1.09 ns to 1.19 ns (Fig. 4 ,Fig. 5 ). Concerning overhead, the RFWF16T maintains a normalized area of 1.00X (4.3 μm × 1.9 μm) (Table 3 ,Fig. 2 ) and an average power consumption of 23.45 nW (Table 4 ). Although the power consumption is slightly higher, it represents a reasonable trade-off considering the significant speed advantage. Finally, in the EQM evaluation, the RFWF16T obtains the highest score, validating its comprehensive advantage in balancing reliability, speed, and stability (Fig. 7 ).Conclusions This paper proposes a radiation-hardened SRAM cell, RFWF16T, for aerospace-grade high-speed read/write applications. The cell contains only two sensitive nodes, achieving 100% self-recovery for Single Node Upsets (SNUs) and an 83.3% recovery rate for Double Node Upsets (DNUs), demonstrating strong radiation tolerance. Compared with eight other SRAM cells, the RFWF16T significantly reduces read and write delays with only a slight increase in area and power consumption, while maintaining good noise immunity and the best electrical quality metric. PVT and Monte Carlo simulations further confirm the stability and robustness of the proposed cell under various operating conditions. Future work will focus on array-level integration and tape-out verification, as well as exploring its applications in satellite-borne high-speed data processing. -
表 1 可靠性对比
表 2 标准测试下WAT与RAT对比
SRAM单元 RAT(ps) WAT(ps) PRCs(%) RAT WAT S8P8N[8] 25.36 2.88 –17.31 –5.42 QUCCE12T[9] 37.31 3.86 –43.80 –29.46 SARP12T[10] 83.06 2.88 –74.75 –5.46 SAW16T[11] 48.85 3.05 –57.07 –10.73 HRLP16T[12] 31.65 3.45 –33.74 –21.25 RH20T[13] 31.73 2.96 –33.91 –8.08 S6P8N(18T)[14] 46.89 3.34 –55.28 –18.59 S8P6N(18T)[14] 49.15 3.37 –57.33 –19.19 RFWF16T 20.97 2.72 –46.65(平均) –14.77(平均) 表 3 SRAM相对面积对比
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