通过亚纳秒功耗动力学探测揭示相变存储器能量极限
Uncovering Phase Change Memory Energy Limits by Sub-Nanosecond Probing of Power Dissipation Dynamics
摘要：
相变存储器（PCM）是神经形态硬件的主要候选者之一，最近已经成熟为存储类存储器。然而，能量和功率消耗仍然是该技术的关键挑战，因为PCM器件的一部分必须在复位期间自加热到其熔化温度。在这里，我们表明，这种复位能量可以减少近两个数量级的脉冲宽度最小化。我们利用高速测量装置来探测具有不同脉冲宽度（0.3至40纳秒）的PCM单元中的能量消耗，并揭示功率耗散动态。一个关键的发现是，对于比PCM的短热时间常数更宽的脉冲（在50 nm直径的器件中，$τ$ $_t$ $_h$ < 1 ns），开关功率（P）保持不变，导致能量（E=P $τ$）随着脉冲宽度$τ$在该范围内减小而减小。换句话说，通过限制热扩散时间来实现短脉冲期间的热约束。我们改进的编程方案将复位能量密度降低到0.1 nJ/ $μ$ m $^2$以下，比最先进的PCM低一个数量级，可能会改变未来数据存储技术的路线图，并为节能的神经形态硬件铺平道路
英文摘要：
Phase change memory (PCM) is one of the leading candidates for neuromorphic hardware and has recently matured as a storage class memory. Yet, energy and power consumption remain key challenges for this technology because part of the PCM device must be self-heated to its melting temperature during reset. Here, we show that this reset energy can be reduced by nearly two orders of magnitude by minimizing the pulse width. We utilize a high-speed measurement setup to probe the energy consumption in PCM cells with varying pulse width (0.3 to 40 nanoseconds) and uncover the power dissipation dynamics. A key finding is that the switching power (P) remains unchanged for pulses wider than a short thermal time constant of the PCM ($τ$$_t$$_h$ < 1 ns in 50 nm diameter device), resulting in a decrease of energy (E=P$τ$) as the pulse width $τ$ is reduced in that range. In other words, thermal confinement during short pulses is achieved by limiting the heat diffusion time. Our improved programming scheme reduces reset energy density below 0.1 nJ/$μ$m$^2$, over an order of magnitude lower than state-of-the-art PCM, potentially changing the roadmap of future data storage technology and paving the way towards energy-efficient neuromorphic hardware
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