Kioxia introduces Twin BiCS FLASH, its 3D semicircular flash memory cell structure that helps boost bit density

Kioxia announced development of the initial three-dimensional (3D) semicircular split-gate flash memory cell structure “Twin BiCS FLASH” using specially designed semicircular Floating Gate (FG) cells. Twin BiCS FLASH achieves superior program slope and a larger program/erase window at a much smaller cell size compared to conventional circular Charge Trap (CT) cells. 

These attributes make this new cell design a promising candidate to surpass four bits per cell (QLC) for significantly higher memory density and fewer stacking layers. This technology was announced at the IEEE International Electron Devices Meeting (IEDM) held in San Francisco, California.

3D flash memory technology has achieved high bit density with low cost per bit by increasing the number of cell stacked layers as well as by implementing multilayer stack deposition and high aspect ratio etching. In recent years, as the number of cell layers exceeds 100, managing the trade-offs among etch profile control, size uniformity and productivity is becoming increasingly challenging. 

To overcome this problem, Kioxia developed a new semicircular cell design by splitting the gate electrode in the conventional circular cell to reduce cell size compared to the conventional circular cell, enabling higher-density memory at a lower number of cell layers.

The circular control gate provides a larger program window with relaxed saturation problems when compared with a planar gate because of the curvature effect, where carrier injection through the tunnel dielectric is enhanced while electron leakage to the block (BLK) dielectric is lowered. In this split-gate cell design, the circular control gate is symmetrically divided into two semicircular gates to take advantage of the strong improvement in the program/erase dynamics. 

The conductive storage layer is employed for high charge trapping efficiency in conjunction with the high-k BLK dielectrics, achieving high coupling ratio to gain program window as well as reduced electron leakage from the FG, thus relieving the saturation issue. The experimental program/erase characteristics reveal that the semicircular FG cells with the high-k-based BLK exhibit significant gains in the program slope and program/erase window over the larger-sized circular CT cells. 

The semicircular FG cells, having superior program/erase characteristics, are expected to attain comparably tight QLC Vt distributions at small cell size. Further, integration of low-trap Si channel makes possible more than four bits/cell, e.g., Penta-Level Cell (PLC). These results confirm that semicircular FG cells are a viable option to pursue higher bit density.

Going forward, Kioxia’s research and development efforts aimed at innovation in flash memory will include continuing Twin BiCS FLASH development and seeking its practical applications.

KIOXIA’s PCIe 4.0 enterprise NVMe SSDs strengthens storage performance; achieves PCI-SIG compliance and NVMe certification

KIOXIA America Inc. (formerly Toshiba Memory America, Inc.), the U.S.-based subsidiary of KIOXIA Corp., announced Wednesday that its lineup of PCIe 4.0 NVMe enterprise solid state drives (SSDs) has achieved PCI-SIG compliance for PCIe 4.0 and University of New Hampshire InterOperability Laboratory (UNH-IOL) certification. 

KIOXIA’s CM6 Series passed interoperability tests at the August 2019 PCI-SIG Compliance Workshop – that includes official PCIe 4.0 specification tests. KIOXIA America will be on hand at Supercomputing 2019 later this month to showcase new levels of flash performance enabled by its CM6 Series SSDs. 

KIOXIA develops PCIe 4.0 NVM Express SSDs and continues to push the limits of flash storage performance. The CM6 Series brings planned performance improvements of three times over its PCIe 3.0 predecessors and is 12 times faster than SATA drives. KIOXIA’s lineup of Gen4 PCIe SSDs also includes the CD6 Series, which is targeted to cloud and scale-out environments.

The PCIe 4.0 NVMe enterprise SSDs utilizes KIOXIA’s 96-layer BiCS FLASH 3D flash memory, PCIe 2x2 or 1x4 lane configuration options, targeted transfer rates up to 6,900 megabytes per second; and supports SFF-TA-1001 (also known as U.3) operation with universal backplanes for simplified customer use with SAS, SATA and NVMe SSDs.

KIOXIA was at Microsoft Ignite earlier this month to demonstrate the CM6 Series running in a Microsoft Azure hyperconverged infrastructure (HCI) platform with Quanta Cloud Technologies – and enabling twice performance gains over a PCIe 3.0 solution. 

“We were able to show that our CM6 Series SSDs are capable of pushing SSD sequential read performance to over 55 gigabytes per second (GB/s) across eight drives – nearly 7GB/s per SSD – and we’re not done yet. KIOXIA will continue to push the performance envelope for our customers,” noted Alvaro Toledo, vice president of SSD marketing and product planning for KIOXIA America.

PCI-SIG hosts Compliance Workshops several times a year in various locations worldwide, giving members the opportunity to test and validate their products before entering the field. Compliance testing is completed against both PCI-SIG maintained systems and other manufacturers of PCI products. 

As the key testing and certification lab for NVMe technology and software, the UNH-IOL provides conformance and interoperability testing across various operating systems, drivers, and hardware platforms, as well as PCIe SSDs and PCIe-enabled servers. “The SSD market is quickly moving to NVM Express technology, and standards compliance is critical to ensure smooth adoption,” added Toledo.

KIOXIA’s KumoScale software offers cross-domain volume replication; boosts data protection with disaggregated NVMe flash storage

KIOXIA America Inc. (formerly Toshiba Memory America), announced that the v3.11 of its KumoScale storage software with NVM Express over Fabrics (NVMe-oF) now includes cross-domain volume replication. With this new feature, KumoScale offers data protection at the storage layer while maintaining NVMe flash performance and low latency.

KIOXIA’s KumoScale storage software makes flash storage accessible over a data center network – allowing data centers to run more efficiently. To address the inefficiencies associated with direct-attached storage (DAS) architectures, KumoScale software disaggregates high-performance NVMe SSDs from compute nodes and shares them across a network infrastructure as network-attached resources.

KumoScale software is a high-performance block storage software suite for on-premise clouds. Combining the speed and responsiveness of born-in-the-cloud software with the staying power of one of the world's largest flash memory makers, KumoScale software uses NVMe technology to enable “flash-as–a-service."

Many databases and applications require their storage systems to provide resilience against drive failure and across arbitrary failure domains. These domains can include racks, aisles – or entire data centers. KumoScale software’s cross-domain replication makes data protection available and easy to flexibly deploy.

KumoScale software’s data center-level approach to resilience against drive failure or network partition allows users to specify arbitrary failure domains using tags. When provisioning volumes, KumoScale software will create volume replicas across multiple KumoScale appliances located in different failure domains for rack-level resiliency. This addresses both equipment failure and maintenance downtime scenarios, and can be provided to only those applications or storage classes that require it.

KIOXIA designed KumoScale software to deliver NVMe flash as a service – enabling cost-effective, networked flash performance close to that of local (in-server) NVMe SSDs.

“Cloud-native applications typically offer data protection by replicating shards at the database layer,” noted Joel Dedrick, vice president and general manager, networked storage software, KIOXIA America, Inc. “However, in our experience, few customers are 100% cloud native – there are always a few legacy applications that depend on the storage layer to provide data protection. KumoScale software’s cross-domain volume replication is designed to provide the flexibility to protect data for entrenched applications while not forcing a one-size-fits-all solution across a company’s workloads.”