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Abstract: Neuro‐inspired computing using emerging memristors plays an increasingly significant role for the realization of artificial intelligence and thus has attracted widespread interest in the era of big data. Thanks to the maturity of technology and the superiority of device performance, phase change random access memory (PCRAM) is a promising candidate for both nonvolatile memories and neuro‐inspired computing. Recently many efforts have been carried out to achieve the biological behavior using PCRAM and to clarify the related working mechanism. In order to further improve device performances, it is helpful and urgent to summarize and discuss the PCRAM solution for neuro‐inspired computing. In this paper, fundamentals, principles, recent progresses, existing challenges, and mainstream solutions are reviewed, and a brief outlook is highlighted and introduced, with the expectation to expound future directions.

Carbon-doped Ge2Sb2Te5 (CGST) is a potential candidate in phase change random access memory (PCRAM) with superb thermal stability and ultrahigh cycle endurance. Direct observation of the microstructure evolution of CGST is desirable to uncover the phase transformation mechanism on the relationship of nucleation/crystalline behaviors of the crystalline phase at elevated temperatures and the pristine amorphous phase at room temperature. Here, we investigate the structural evolution of CGST using combined in situ techniques. Our in situ x-ray diffraction and ellipsometry results demonstrate that CGST exhibits a much higher phase transition temperature than undoped one. Temperature-dependent in situ transmission electron microscopy observations further reveal that carbon doping plays a critical role in tailoring the properties of GST by tuning the stochasticity of nucleation/crystallization, stabilizing amorphous and crystalline GST via isolating and refining the grain size at room temperature and elevated temperature. Our work provides detailed information for understanding the microscopic origin of crystallization kinetics of carbon-doped phase change materials toward high-performance PCRAM. [ABSTRACT FROM AUTHOR]

The 1S1R storage unit of 3D phase-change memory is composed of ovonic threshold switch selector (OTS) in series with the phase change memory (PCM) device. In order to solve the problems of the current OTS and PCM circuit simulation models, such as not able to accurately simulate the electrical and physical characteristics of devices, and not suitable for confined PCM, a 1S1R spice model based on Verilog-A is proposed. The model simulates the electrical characteristics of OTS and the changes of current, temperature, melting proportion, crystallization proportion and amorphous proportion in the crystallization, melting and quenching of the PCM. The model has a good convergence and fast simulation speed. The simulation results are consistent with the actual test results of the device. Compared with the traditional model, the simulation and integration of confined PCM melting process, crystal nonlinearity, melting resistivity stability and subthreshold nonlinearity, and bidirectional switching characteristics of OTS are realized. The relationship between OTS subthreshold nonlinear parameter and read voltage window is analyzed. It is found that the read window reaches its maximum when OTS threshold current is approximately equal to PCM threshold current. The results of DC simulation of 1S1R cell and transient simulation of array are displayed, providing the basis for circuit design and simulation of 3D phase-change memory.

The stability of slurries used for chemical mechanical polishing (CMP) is a crucial concern in industrial chip production, influencing both the quality and cost-effectiveness of polishing fluids. In silicon wafer polishing, the conventional use of commercial neutral silica sol combined with organic bases often leads to slurry instability. To address this issue, this study proposes organic amines—specifically ethanolamine (MEA), ethylenediamine (EDA), and tetramethylammonium hydroxide (TMAOH)—as catalysts for synthesizing alkaline silica sol tailored for silicon wafer polishing fluids. Sol–gel experiments and zeta potential measurements demonstrate the efficacy of this approach in enhancing the stability of silica sol. The quantitative analysis of surface hydroxyl groups reveals a direct correlation between enhanced stability and increased hydroxyl content. The application of the alkaline silica sol in silicon wafer polishing fluids improves polishing rates and enhances surface flatness according to atomic force microscopy (AFM). In addition, electrochemical experiments validate the capability of this polishing solution to mitigate corrosion on silicon wafer surfaces. These findings hold significant implications for the advancement of chemical mechanical polishing techniques in the field of integrated circuit fabrication. [ABSTRACT FROM AUTHOR]

In order to fulfill the complex cognitive behaviors in neuromorphic systems with reduced peripheral circuits, the reliable electronic synapses mimicked by single device that achieves diverse long‐term and short‐term plasticity are essential. Phase change random access memory (PCRAM) is of great potential for artificial synapses, which faces, however, difficulty to realize short‐term plasticity due to the long‐lasting resistance drift. This work reports the ruthenium‐doped Ge2Sb2Te5 (RuGST) based PCRAM, demonstrating a series of synaptic behaviors of short‐term potentiation, pair‐pulse facilitation, long‐term depression, and short‐term plasticity in the same single device. The optimized RuGST electronic synapse with the high transformation temperature of hexagonal phase >380°C, the outstanding endurance >108 cycles, the low resistance drift factor of 0.092, as well as the extremely high linearity with correlation coefficients of 0.999 and 0.976 in parts of potentiation and depression. Further investigations also go insight to mechanisms of Ru doping according to thorough microstructure characterization, revealing that Ru dopant is able to enter GST lattices thus changing and stabilizing atomic arrangement of GST. This leads to the short‐term plasticity realized by RuGST PCRAM. Eventually, the proposed RuGST electronic synapses performs a high accuracy of ~94.1% in a task of image recognition of CIFAR‐100 database using ResNet 101. This work promotes the development of PCRAM platforms for large‐scale neuromorphic systems. [ABSTRACT FROM AUTHOR]

Phase change materials have issues in the automotive industry and in‐memory computing due to their limited thermal stability and high power consumption. Consequently, numerous studies are conducted to enhance the performance of these materials. Uncertainty persists regarding the effects and mechanisms of various doping on the parent material. In this study, four metallic doping elements are selected, and their effects on Sb2Te3 are meticulously analyzed through experiments and ab initio calculations. The thermal stability of Sb2Te3 has been somewhat enhanced by doping these four elements, with Ta doping having the most impact. According to the ab initio molecular dynamics, this improvement results from the tetrahedral centered In and the increased coordination numbers of Ta, Ti, and Sc. Sc located at the center of the octahedron can accelerate the crystallization process. Ta, in particular, exerts the greatest influence on the migration rates of Sb and Te, resulting in the slowest grain growth rate. Simultaneously, it maximizes the delay in the transition from the cubic phase to the hexagonal phase. These features are beneficial for reducing power consumption. The elucidation of the distinct effects of doping elements sets the stage for phase change memory to adapt to various application scenarios. [ABSTRACT FROM AUTHOR]

This work presents an external capacitor‐less low‐dropout regulator (CL‐LDO) with high power supply rejection (PSR) over a wide frequency and load current (IL) range. The high PSR is implemented with an adaptive supply‐ripple cancellation (ASRC) technique. The proposed ASRC circuit consists of a buffer with diode‐connected structure and an adjusting unit. The novel buffer introduces the supply ripple through the diode‐connected transistor to the gate of the pass transistor, enhancing the PSR in the range of 1 MHz. Additionally, the adjusting unit trims the current of the buffer continuously according to the magnitude of IL to optimize the PSR adaptively. Designed in a 55 nm CMOS process with an input voltage of 1.4 V, the proposed LDO achieves −69 dB and −55 dB PSR at 100 KHz and 1 MHz for 50 mA of IL, respectively. Moreover, the maximum current efficiency of the LDO is 99.8% at a full IL of 50 mA. [ABSTRACT FROM AUTHOR]