Wednesday, October 18, 2023

Micron Unveils Breakthrough NVDRAM: A Dual-Layer 32Gbit Non-Volatile Ferroelectric Memory with Near-DRAM Performance

At the upcoming International Electron Devices Meeting (IEDM), Micron is set to present a paper on a novel 32Gbit non-volatile ferroelectric memory, termed NVDRAM. Authored by Nirmal Ramaswamy, the vice president of advanced DRAM and emerging memory at Micron, the paper is titled "NVDRAm: A 32Gbit Dual Layer 3D Stacked Non-Volatile Ferroelectric Memory with Near-DRAM Performance for Demanding AI Workloads". It introduces the world’s first dual-layer, high-performance, 32Gbit stackable ferroelectric memory technology. This technology, branded as non-volatile dynamic random access memory (NVDRAM), promises faster data movement and better energy efficiency than traditional DRAM, making it ideal for larger neural network models.

NVDRAM merges the benefits of ferroelectric memory cells – non-volatility and high endurance – with performance surpassing NAND flash memory retention and offering DRAM-like read/write speeds. The memory's architecture uses a 5.7nm ferroelectric capacitor for charge retention in a 1T1C DRAM structure, while dual-gated polycrystalline silicon transistors control access. The stacked double memory layer resides above a CMOS access circuit layer on a 48nm pitch. Despite the technological advancements, commercialization discussions remain speculative, potentially awaiting feedback from the IEDM presentation.


The images above show the final die layout (left) and SEM cross-section (center) of a 32Gb NVDRAM with 1T1C memory layers, fabricated over a CMOS array. On the right is a schematic diagram of NVDRAM memory arrays, showing polysilicon access device with orthogonal wordline (WL) and digitline (DL), and ferroelectric memory cells.

Abstract: Non-Volatile Ferroelectric w/DRAM-Like Performance, for AI & Machine Learning: Rapid growth in the size of the data models used in artificial intelligence (AI) and machine-learning (ML) applications is creating an urgent need for higher-bandwidth memory solutions. While new compute paradigms like near-memory-compute and processing-in-memory are being investigated, the best near-term opportunity is to outfit existing, traditional compute architectures with more efficient memory for faster data movement and to accommodate larger models. In this year’s Generative AI Focus Session, Micron researchers will unveil a memory technology for these uses which they call NVDRAM. It is the world’s first dual-layer, high-performance, high-density (32Gb), stackable and nonvolatile ferroelectric memory technology. It combines the non-volatile, high-endurance nature of ferroelectric memory cells with DRAM-like read/write speeds and endurance, and also surpasses the retention performance of NAND memory. NVDRAM uses an ultra-scaled (5.7nm) ferroelectric capacitor as the memory cell, and a dual-gated, stackable, polycrystalline silicon transistor as the access device. To achieve high memory density, two memory layers are fabricated above CMOS circuitry in a 48nm pitch, 4F2 architecture. Full package yield is demonstrated from -40°C to 95°C, along with reliability of 10 years (for both endurance and retention).

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