This paper investigates the impact of memory orientation on the bias pattern of SRAM-based PUFs. We designed and fabricated a 65nm CMOS chip that contains eleven SRAM macros that exercise different memory- and chip-level parameters. At the memory level, several parameters passed to the SRAM compiler are considered, including the number of addresses, the number of words, the aspect ratio, and the chosen bitcell. Chip-level decisions are considered during the floorplan, including the location and rotation of each SRAM macro in the testchip. In this study, we conduct a comprehensive analysis of different memory orientations and their effect on the biasing direction. Physical measurements performed on 50 fabricated chips revealed that specific memory orientations, namely R270 and MY90, exhibit a distinct negative biasing direction compared to other orientations. Importantly, this biasing direction remains consistent regardless of memory type, column mux ratio, memory size, or the utilization of SRAMs with different bitcells. Overall, this study highlights the significance of careful physical implementation and memory orientation selection in designing SRAM-based PUFs. Our findings can guide designers in the selection of SRAM memories with properties that make for better PUFs that potentially require less error correction effort to compensate for instability.

翻译：本文研究了存储器朝向对基于SRAM的物理不可克隆函数（PUF）偏置模式的影响。我们设计并制造了一款65nm CMOS芯片，其中包含十一个SRAM宏单元，这些宏单元在存储器和芯片层面采用了不同参数。在存储器层面，考虑了传递给SRAM编译器的多个参数，包括地址数量、字数量、宽高比以及所选位单元。在芯片布局规划阶段，考虑了芯片层面的决策，包括测试芯片中每个SRAM宏单元的位置和旋转角度。本研究对不同存储器朝向及其对偏置方向的影响进行了全面分析。对50块已制造芯片进行的物理测量表明，特定存储器朝向（即R270和MY90）与其他朝向相比，表现出明显的负偏置方向。重要的是，无论存储器类型、列多路复用比率、存储器大小或使用不同位单元的SRAM如何，该偏置方向始终保持一致。总体而言，本研究强调了在基于SRAM的PUF设计中，谨慎进行物理实现和存储器朝向选择的重要性。我们的发现可指导设计者选择具有更优特性的SRAM存储器，从而构建更好的PUF，这些PUF可能无需过多纠错努力即可补偿不稳定性。