Conventional Static Random Access Memory Research Articles

A novel MTCMOS based 8T2M NVSRAM design for low power applications with high temperature endurance

This research investigates, for the first time, a novel eight-transistor-two-memristor (8T2M) nonvolatile static random access memory (NVSRAM) with 7-nm technology. The key innovation in this design lies in the incorporation of multiple-threshold complementary metal oxide semiconductor (MTCMOS) technology with power gating technique, which enables efficient power management and enhanced performance with low leakage current. The implementation of multiple threshold voltage levels allows for dynamic control of transistor behavior, optimizing power consumption and read/write speeds. As compared to a traditional six-transistor (6T) static random access memory (SRAM) cell, it has been ascertained that there is a 33% enhancement in the read margin and an 18% improvement in the write margin. Moreover, the delay for read, write ‘0’ and write ‘1’ is also minimized by 63.89%, 37.99% and 42.77%. Furthermore, the power attenuation is also reduced for read and write by 63.02% and 81.6%, respectively with respect to a conventional SRAM.

A novel high-performance TG-based SRAM cell with 5 nm FinFET technology

In this study, we investigate the performance and reliability of a novel static random-access memory (SRAM) cell utilizing advanced 5 nm FinFET technology. Our research aims to address critical challenges in SRAM design by integrating transmission gates and power gated transistors. Through extensive simulations using the Cadence Virtuoso tool, we optimize the SRAM cell’s read and write paths, resulting in substantial improvements in both functionalities. Additionally, our study unveils temperature-dependent variations in the read current and write margin, emphasizing the influence of temperature on SRAM performance. Compared to conventional FinFET SRAM circuits of equivalent bit-cell area and read latency, our innovative design showcases remarkable improvements across various parameters. Specifically, we achieve a commendable increase of 6.16% in the write static noise margin (WSNM) and 5.86% in the hold static noise margin (HSNM). Moreover, our findings reveal a substantial boost in read stability, increasing from 14.75% to 18.35%. These advancements underscore the promising potential of our approach in paving the way for future innovations in high-performance memory architectures. By leveraging state-of-the-art technology and meticulous optimization techniques, our research sets a new standard for SRAM design, offering enhanced performance, reliability, and efficiency in memory systems.

A Study on the Design Method of Hybrid MOSFET-CNTFET Based SRAM – A Secondary Publication

More than 10,000 carbon nanotube field-effect transistors (CNTFETs) have been successfully integratedinto one semiconductor chip using conventional semiconductor design procedures and manufacturing processes. Thesetransistors offer advantages such as high carrier mobility, large saturation velocity, low intrinsic capacitance, flexibility, andtransparency. The three-dimensional multilayer structure of the CNTFET semiconductor chip, along with ongoing researchin CNTFET manufacturing processes, increases the potential for creating a hybrid MOSFET-CNTFET semiconductorchip. This chip combines conventional metal-oxide-semiconductor field-effect transistors (MOSFETs) and CNTFETs inone integrated system. This paper discusses a methodology to design 6T binary static random-access memory (SRAM)using a hybrid MOSFET-CNTFET. This paper introduces a method for designing a hybrid MOSFET-CNTFET SRAMby leveraging existing MOSFET SRAM or CNTFET SRAM design approaches. Additionally, this paper compares itsperformance with conventional MOSFET SRAM and CNTFET SRAM designs.

Next-Generation SRAM: Design and Optimization with Carbon Nanotubes

Static Random Access Memory (SRAM) serves as a critical component in modern electronic devices, offering high-speed access to stored data. As technologycontinues to advance, there's a growing demand for smaller, faster, and more energy-efficient memory solutions. Carbon nanotubes (CNTs) have emerged as apromising material for pushing the boundaries of conventional silicon-based SRAM designs. This paper presents a comprehensive exploration of the design andoptimization of next- generation SRAM utilizing carbon nanotubes. The unique properties of CNTs, suchas their exceptional electrical conductivity, mechanical strength, and nanoscale dimensions, offer a fertile ground for revolutionizing SRAM architecture. The study delves into the integration of CNTs intoSRAM cell structures, discussing variousconfigurations and layouts to harness the advantageous characteristics of carbon nanotubes. Emphasis is placed on addressing the challenges associated with CNT-based SRAM, including manufacturing scalability, reliability, and variability. In conclusion, the integration of carbon nanotubesin SRAM design offers a compelling avenue to overcome the limitations of traditional silicon-based memory technologies. This study not only highlights the promising prospects of CNTs in SRAM but also provides insights into the challenges and opportunitiesin harnessing these nanomaterials for advanced memory applications. Keywords : Static Random Access Memory (SRAM), Carbon Nanotubes (CNTs), Nanotechnology, Memory Design, Optimization, Electronic Devices, Nanomaterial Integration.

Single-Power-Supply Six-Transistor CMOS SRAM Enabling Low-Voltage Writing, Low-Voltage Reading, and Low Standby Power Consumption

We developed a self-controllable voltage level (SVL) circuit and applied this circuit to a single-power-supply, six-transistor complementary metal-oxide-semiconductor static random-access memory (SRAM) to not only improve both write and read performances but also to achieve low standby power and data retention (holding) capability. The SVL circuit comprises only three MOSFETs (i.e., pull-up, pull-down and bypass MOSFETs). The SVL circuit is able to adaptively generate both optimal memory cell voltages and word line voltages depending on which mode of operation (i.e., write, read or hold operation) was used. The write margin (VWM) and read margin (VRM) of the developed (dvlp) SRAM at a supply voltage (VDD) of 1 V were 0.470 and 0.1923 V, respectively. These values were 1.309 and 2.093 times VWM and VRM of the conventional (conv) SRAM, respectively.At a large threshold voltage (Vt) variability (=+6σ), the minimum power supply voltage (VMin) for the write operation of the conv SRAM was 0.37 V, whereas it decreased to 0.22 V for the dvlp SRAM. VMin for the read operation of the conv SRAM was 1.05 V when the Vt variability (= -6σ) was large, but the dvlp SRAM lowered it to 0.41 V. These results show that the SVL circuit expands the operating voltage range for both write and read operations to lower voltages. The dvlp SRAM reduces the standby power consumption (PST) while retaining data. The measured PST of the 2k-bit, 90-nm dvlp SRAM was only 0.957 μW at VDD = 1.0 V, which was 9.46% of PST of the conv SRAM (10.12 μW). The Si area overhead of the SVL circuits was only 1.383% of the dvlp SRAM.

Propagation Delay and Power Dissipation Analysis for a 2-Bit SRAM Using Multi-State SWS Inverter

This paper presents a study on the propagation delay and power dissipation of a 2-bit static random-access memory (SRAM) with two cross-coupled multi-state spatial wave function switching (SWS) CMOS inverters. The proposed SRAM design utilizes the advantages of the CMOS-SWS inverter, such as its small area, low power consumption, and high speed. The 2-bit SRAM circuit simulations were carried out in Cadence to analyze the power dissipation and propagation delay. An Analog Behavioral Model (ABM) and the Berkeley Short-channel IGFET Model (BSIM4.6) in 0.18-μm technology were combined to create this model. The analysis of the propagation delay shows that the multi-state CMOS-SWS SRAM significantly reduces the delay compared to other multi-state 6T SRAM memories. Additionally, the analysis of the power dissipation shows that the multi-state SWS-SRAM is comparable to conventional SRAMs. These results demonstrate the potential of multi-state SWS-SRAM for improving the performance of memory circuits and provide valuable insights for future design optimization.

3D SRAM Macro Design in 3D Nanofabric Process Technology

In this paper, we introduce a novel design of a 3D static random-access memory (SRAM) macro in a 3D Nanofabric process technology. The 3D Nanofabric technology is based on enabling the processing of N stack of identical layers simultaneously regardless of the number of stacked layers which consequently reduces the fabrication cost as well as the footprint of SRAM macros. To enable simultaneous patterning of stacked layers, 3D Nanofabric requires circuit topology and layout that rely on a single layer where the device channel, poly, and metal wires are all embedded without any other crossing than the gate on top of the device channel. Accordingly, we modify the layouts of the conventional SRAM bit-cell and periphery circuits which are complex and contain several metal crossings. Furthermore, we propose a new overall organization of the 3D SRAM macro that incorporates a stack of multiple identical layers each consisting of an equal size 2D array of bit-cells and the periphery circuits. We show that the proposed 3D Nanofabric SRAM macro offers 71.2% footprint gain and 36.3% read access speed improvement compared to equal size 2D SRAM macro in 3 nm FinFET.

A 128-kbit GC-eDRAM With Negative Boosted Bootstrap Driver for 11.3× Lower-Refresh Frequency at a 2.5% Area Overhead in 28-nm FD-SOI

Gain-cell embedded DRAM (GC-eDRAM) is a high-density logic-compatible alternative to conventional static random-access memory (SRAM) and embedded DRAM (eDRAM). However, GC-eDRAM suffers from a reduced data retention time (DRT) at deeply-scaled process nodes, leading to frequent power-hungry refresh operations. In order to reduce the refresh overhead, GC-eDRAM macros utilize external assist voltages which improve the bitcell write-ability, leading to an enhanced DRT. However, the requirement for external analog supply voltages creates additional overhead and is often impractical in the design of compact systems-on-chip (SoC). This work presents an on-chip write-assist technique implemented with a negative boosted bootstrap driver which generates the required wordline boosting on-chip without external components. The proposed circuitry is integrated compactly inside the GC-eDRAM macro to provide an area-efficient low-power solution which improves the bitcell’s write-ability and reduces its refresh requirement. A 128-kbit GC-eDRAM macro utilizing the proposed boosting circuitry has been fabricated in a 28-nm FD-SOI technology, demonstrating an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11.3\times $ </tex-math></inline-formula> DRT improvement at only 2.5% area overhead.

Design of Static Random-Access Memory Cell for Fault Tolerant Digital System

This paper comparatively analyzes the static random-access memory (SRAM) cell designs for fault tolerance. Since SRAM cells are sensitive to radiation-induced single event upsets, various circuit-level approaches have been applied. Compared to the conventional SRAM cell circuits, one possibility is adding redundant storage nodes by means of additional transistors. The strength and weakness of the SRAM cells in terms of various performance aspects—speed, area, power, stability, fault tolerance, etc.—according to the design approaches are compared analytically and discussed. The discussion concludes that, in the future, it is paramount to develop an SRAM cell design with a mitigated trade-off between read/write performance and SEU tolerance.

Via-Switch FPGA: 65-nm CMOS Implementation and Evaluation

Offering a combination of low latency, high energy-efficiency, and flexibility, field-programmable gate arrays (FPGAs) suit applications ranging from Internet of Things (IoT) computing to artificial intelligence (AI). The conventional static random access memory (SRAM) FPGAs face severe challenges including large standby power and low logic density due to utilization of SRAM cell and MOS switch for signal routing. In response, researchers have introduced emerging non-volatile (NV) memory technologies to solve standby power issues. However, access transistors used for NV memory cell configuration still consume a large silicon area. In this article, we introduce an NV via-switch (VS) FPGA featuring fully back-end-of-line (BEOL) signal routing and front-end-of-line (FEOL) logic computing for high logic density. The VS fabricated in BEOL is constructed by two Cu atom switches (ASs) for signal routing and two a-Si/SiN/a-Si varistors for AS configuration. We demonstrate the first implementation of the VS-FPGA at 65-nm node and evaluate its performance by various basic applications. 2.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> logic density, 1.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> energy efficiency, and 1.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> operation speed are achieved in comparison with a previous complementary AS (CAS) FPGA in which one access transistor is necessary for each CAS configuration.

A Stable Low Power Dissipating 9 T SRAM for Implementation of 4 × 4 Memory Array with High Frequency Analysis

Today’s high speed data processing and memory storage operations demand immediate data write and retrieval to meet up to benchmark. To act as a volatile or nonvolatile data storage for electronic devices such as mobile phones, laptops, the Static Random-Access Memory (SRAM) has been perfect choice for industrialists. So, memory usage is significant and more than 65% of electronic devices uses memory as its heart. Nevertheless, memory turns out to be a leading factor affecting speed, power and data retention in a handheld system. The urge for optimization in power is all time relevant. The proposed system is designed to optimize a single bit memory cell of conventional static random-access memory and hence developed a stable system with low power consumption and obtained significantly low Power-Delay-Product (PDP) by varying operating frequencies in MHz (Mega Hertz) range. Also, a comparative analysis of a 4 × 4 SRAM array is carried out between 6 T SRAM cell and 9 T SRAM cell. Here 62.83% power reduction is obtained in the proposed system as compared with the existing system at an operating frequency of 2 GHz. In this paper, a power reduction of 62.273% is obtained for the array structure. The power dissipation and Power Delay Product [PDP] of the single bit 9 T SRAM cell is also lower than the conventional 6 T SRAM. Thus, the paper implements the proposed scheme of SRAM into an array along with all connecting peripherals.

A 7T SECURITY ORIENTED SRAM BITCELL USING VLSI

Power analysis (PA) attacks have become a serious threat to security systems by enabling secret data extraction through the analysis of the current consumed by the power supply of the system. Embedded memories, often implemented with six-transistor (6T) static random access memory (SRAM) cells, serve as a key component in many of these systems. However, conventional SRAM cells are prone to side-channel power analysis attacks due to the correlation between their current characteristics and written data. To provide resiliency to these types of attacks, we propose a security-oriented 7T SRAM cell, which incorporates an additional transistor to the original 6T SRAM implementation and a two-phase write operation, which significantly reduces the correlation between the stored data and the power consumption during write operations. The proposed 7T SRAM cell was implemented in a 28 nm technology and demonstrates over 1000× lower write energy standard deviation between write ‘1’ and ‘0’ operations compared to a conventional 6T SRAM. In addition, the proposed cell has a 39%–53% write energy reduction and a 19%–38% reduced write delay compared to other power analysis resistant SRAM cells. Key Words: Power Analysis, SRAM Design, 6T SRAM, 7T SRAM, Power Dissipation Software Tools:  Tanner eda Tool

Configurable Memory With a Multilevel Shared Structure Enabling In-Memory Computing

Frequent to-and-from data transfers in the von Neumann architecture limit the overall throughput. One of the promising approaches used to overcome von Neumann bottleneck is in-memory computing (IMC) that aims to embed computing in memory to reduce the transfer of memory-processor data. This study proposes a configurable 6-transistor (6T) static random access memory (SRAM) array with a multilevel shared structure for IMC. A multilevel shared structure can effectively improve the utilization rate of the module. In addition to the conventional SRAM operation, the configurable structure can also perform the sum of absolute differences (SAD) and Hamming distance (HD) calculations. To quickly identify the minimum value among multiple calculation results, a four-input sense amplifier (SA) is proposed. The performance of the proposed memory is simulated in a 65-nm CMOS process. The post-layout simulation results show good linearity of the multirow read in the SAD and HD modes. The mean time required by the four-input SA to obtain the result is 190 ps. The SAD and HD calculations yield consumptions of 67.44 fJ/byte and 0.64 fJ/bit, respectively, at 0.8 V. Furthermore, a single column-sharing comparator consumes 2.78 and 3.41 pJ at 0.8 V in the SAD and HD modes, respectively.

A Low-Power and High-Stability 8T SRAM Cell with Diode-Connected Transistors

This research paper proposes a low-power, high-stability 8T static random access memory (SRAM) cell. The proposed SRAM cell is a modified structure of the conventional 6T SRAM cell. The introduction of two diode-connected transistors in the pull-down network of the conventional 6T SRAM cell gives the proposed 8T SRAM cell structure. The presence of diode-connected transistors improves the power and noise performances of the proposed cell as compared to those of the conventional bit cells. The power consumption and static noise margin (SNM) of the suggested SRAM cell are calculated for write, hold and read operations. Also, the write and read delays of the proposed and conventional bit cells are observed. The power, speed, noise margin and area of the proposed 8T SRAM cell are compared with those of some of the existing SRAM cells. In comparison to conventional SRAM cells, the proposed cell consumes less power and has higher stability, according to the study. A novel dual-supply ([Formula: see text][Formula: see text]V and [Formula: see text][Formula: see text]V or 200[Formula: see text]mV) concept is applied for the existing and proposed SRAM cells. The noise and power performances of SRAM cells are well improved under the condition of dual supply as compared to the conventional supply voltage ([Formula: see text][Formula: see text]V and [Formula: see text][Formula: see text]V). A [Formula: see text] memory array of the proposed 8T SRAM cell is formed and the performance of the array structure is compared with that of [Formula: see text] array of the conventional 6T SRAM cell. The layouts of existing and proposed SRAM cells are illustrated. The simulation is carried out using the Cadence Virtuoso simulation EDA tool in 90-nm CMOS technology.

Comparative Analysis of the Design Techniques for Low Leakage SRAMs at 32nm

This paper presents a comprehensive overview of leakage reduction techniques prevailing in Static Random Access Memories (SRAMs) by classifying them in three categories namely latch, bitline and read port. The performance of the techniques are evaluated in terms of leakage reduction capability along with the impact on read performance and hold stability through extensive simulative investigations at 32 nm technology node by taking conventional SRAM cell as reference. Further, as SRAMs are susceptible to inter-die as well as intra-die process variations, the performance at different PVT corners is also captured to demonstrate the efficacy of each technique under PVT variations. It is found that among the techniques used for reducing latch leakages, Multi-threshold CMOS technique possess the highest leakage reduction capabilities followed by Drowsy mode and Substrate-bias techniques. The results also indicate that Negative word line technique is more effective at low supply voltages whereas the Leakage biased bitline technique is more effective at high supply voltages for reducing bitline leakages. Amongst the read port leakage reduction techniques, Stack-effect and Dynamic control of power supply rail techniques are capable of suppressing the leakages at high voltages whereas Virtual cell ground technique is more efficacious at low voltages. The impact of technology scaling on SRAM cell performance with leakage reduction techniques is also studied. For the sake of completeness, suggestions are put forward for adopting a particular technique to address leakages at latch, bitline and read port levels.

Low Power PPN inverter based 10T SRAM Cell

Objectives: In the present power-hungry world, the objective of this paper is to design a system that helps in the reduction of power consumption of systems. A memory cell, more specifically an SRAM cell being the major contributor to the increased power becomes an important unit to be considered in such systems for reducing power. This paper presents an improved single-ended PPN inverter based 10T SRAM cell. Methods: The proposed cell makes use of PPN-inverters. The CMOS inverter is replaced by the PPN-inverter in the conventional 8T SRAM cell giving an improved single-ended PPN-based 10T SRAM cell. Findings: The proposed work is compared with other SRAM cells based on delay, power dissipation, and power delay product (PDP). The proposed cell is designed and simulated on Cadence Virtuoso EDA tool version IC6.1.7 at a standard CMOS 45nm technology. The simulation results show that the proposed SRAM cell consumes lesser power and hence lower PDP compared to conventional 8T SRAM cell as well as other SRAM cells and with the use of high threshold voltage transistors in the read circuit a further decrease in the power consumption is observed. So, by use of PPN inverter in 8T SRAM cell a new design for low power consuming SRAM cell is achieved. Novelty: The proposed cell is optimized in terms of power dissipation making it more efficient for use in portable battery-operated devices. Keywords 10T SRAM cell, Low power, PPN inverter, Static Random­Access Memory (SRAM)

Workload-Aware Electromigration Analysis in Emerging Spintronic Memory Arrays

Electromigration (EM) has emerged as a major reliability concern for interconnects in advanced technology nodes. Most of the existing EM analysis works focus on the power lines. There exists a limited amount of work which analyzes EM failures in the signal lines. However, various emerging spintronic-based memory technologies such as the Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) and the Spin Orbit Torque Magnetic Random Access Memory (SOT-MRAM) have high current densities as compared to the conventional Static Random Access Memory (SRAM). These high current densities can lead to EM failures in the signal lines such as bit-line (BL) of these memories. Furthermore, these signal lines have workload-dependent stress as opposed to the conventional DC stress of power distribution networks. In this work, we model the EM failures in the BL of a typical STT memory array with realistic workloads. The analysis is based on physics-based EM model, which is calibrated based on industrial measurement data. The results show that the current densities in the STT arrays can be large enough to cause EM failures in the signal lines with running realistic workloads and that these failures are highly workload-dependent.

Stable organic SRAM cell with p-type access transistors

This paper demonstrates the implementation of a static random access memory (SRAM) cell that is suitable for low-voltage organic thin-film transistors (OTFTs). SRAM is an essential component in electronic systems which can store data or instructions for various applications. We use p-type OTFTs for the access transistors to gain higher areal efficiency and better robustness than those of conventional OTFT-based SRAM construction. We verify the stability of the proposed SRAM cell and optimize the transistor sizes through SPICE simulation. Using test chip measurement, the correct write/read operation of the proposed SRAM cell is confirmed under a 10× imbalance of the on-current ratio. The proposed SRAM cell achieves a 50% area reduction and a 2.5× static noise margin improvement, compared to the existing OTFT SRAM cell design.

Low power and write-enhancement RHBD 12T SRAM cell for aerospace applications

In aerospace applications, the conventional Static Random Access Memories (SRAMs) are facing high soft error problems like a single event upset. Several radiation-hardened based design (RHBD) like twelve-transistor (12T) Dice, 12T We-Quatro SRAM cells, etc., had been developed to address the soft error problems. But they all are consuming comparatively more total and static power with more delay and area. The 10T SRAM cell had been developed to reduce the power dissipation and area overhead. But the analysis of 10T cell shows a write failure at high-frequency. An RHBD 12T SRAM cell has been proposed in this paper. The proposed 12T SRAM cell consumes less total, and static power dissipation compared to 12T We-Quatro and 12T Dice cell, respectively. The critical charge and hold noise margin of the proposed SRAM cell have been improved compared to We-Quatro and Dice cell. The simulated result shows that the proposed SRAM cell has provided the less and comparable area, high write speed, and good writability under process variations. Finally, the Monte Carlo Simulation of SRAM cells under 45 nm CMOS technology validates the efficiency of the 12T proposed cell.

Monolithic 3D 6T-SRAM Based on Newly Designed Gate and Source/Drain Bottom Contact Schemes

For the first time, we suggested that the monolithic 3D (M3D) static random access memory (SRAM) with gate and S/D bottom contact (GBC and SDBC) schemes (SRAMSDGBC) and analyzed they could significantly improve the power, performance, and area (PPA) compared to the conventional M3D SRAM (SRAM3D). SRAM3D could not directly connect the top-tier device and the bottom-tier metal line. Thus two tiers had to be connected by bypassing the metal line. As a result, SRAM3D wasted the area to place the monolithic interlayer via and did not get 50 % area scaling. However, gate and S/D bottom contact schemes, GBC and SDBC, could solve these problems. Although these methods required additional process steps, they brought significant advantages in interconnect RC and PPA. Based on a 26 nm width nanosheet transistor, SRAM3D showed a 30 % area reduction compared to 2D SRAM (SRAM2D), whereas SRAMSDGBC showed a 50 % area reduction. In the ideal (worst) case which ignoring (considering) the array resistance, the read and write access time of SRAMSDGBC were improved 7.7 % (19 %) and 8.3 % (33 %) than SRAM3D, and the write dynamic power was improved by 5.9 % (5 %). Especially, SRAMSDGBC showed improved PPA in the worst case compared to SRAM2D_Cu, which had relatively small interconnect resistivity. Namely, GBC and SDBC schemes are essential to enhance the PPA of M3D cells and will be a promising scheme in M3D SRAM and other logic cells.