Glossary Terms:

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Access time:
Time interval characteristic of a storage device that measures how long it takes to communicate to that device. For hard disk drives, access time is determined by the sum of the spin-up time, seek time, rotational delay and transfer time.

ABL (All Bit Line):
ABL (All Bit Line) memory was introduced by SanDisk at ISSCC 2008 as a significantly faster memory than "conventional" memory. While conventional memory uses, for actual operations, every other cell along a selected world line (WL), this design simultaneously exercises them all. A performance improvement of at least 100% is derived from this all bit line (ABL) architecture relative to conventional chips. Additional techniques push performance to even higher levels.

AFM:
SanDisk Adaptive Flash Management technologies contribute to the enhancement of NAND capabilities. AFM includes flash-management technology, All Bit Line (ABL) architecture and endurance metrics.

Angstrom (Å):
Unit of linear measure equal to one ten billionth of a meter. The diameter of a human hair measures about 750,000 Å.

Array:
In lithography, repetitive patterns on a die, such as an array of memory cells.

ATA 8 standard:
ATA-8 standard is designed to support the Data Set Management command. This command is the key in enabler to the TRIM feature

Bad block:
A block that was manufactured with defects or has become unusable over time.

Bad block management:
A metholodogy that marks and isolates bad blocks so that they are not used. Bad block management stores data intended for bad blocks in spare blocks.

Bit:
A single basic unit of information.

Block:
A physical division of a message that is made up of a sequence of bytes or bits having a nominal size (block length) for message transfer purposes. Dividing/Addressing data in blocks is almost universally employed when storing data to 9-track magnetic tape, to rotating media such as floppy disks, hard disks, optical discs and to NAND flash memory. In NAND flash, a block defines the smallest erase unit. In a hard disk drive, a block is the intersection of a track and a sector. Its address is specified by providing the number of the cylinder, head and sector (CHS).

Boron:
A chemical element with atomic number 5 used for p-channel doping of silicon.

Byte:
A unit of data composed of 8 bits.

Channel:
A conduit for current flow in a MOSFET between the n-type or p-type semiconductor material.

Charge trap memory transistor:
Stores charge (electrons) in a floating gate.

Circuit:
The combination of electrical elements & components to enable a particular function.

Cleanroom:
A closed area used in manufacturing with a defined class that limits contamination levels and controls humidity, temperature and particles in the air.

CMOS (Complementary Metal Oxide Semiconductor):

A fabrication process that incorporates p-channel and n-channel MOS transistors within the same silicon substrate.

Crystal:
A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts, often characterized by external planar faces.

Cylinder:
All tracks accessible on a hard disk drive without moving the head.

Data reliability
The ability of a system or component to perform required functions under stated conditions for a specified period of time. Special tests (qualification) are performed to predict performance over the lifecycle of a product.

Data retention:
The maximum period of time that written data can reliably be retrieved from the non-volatile memory.

Defect:
A chemical or structural irregularity in a crystal that degrades the ideal crystal structure or the films built over the wafer.

Die:
A combination of integrated circuits with defined functionality, hundreds of which are printed on a silicon wafer. A bare die is unpackaged.

Dielectric:
An insulator used to describe nonmetals and their interaction with electric, magnetic or electromagnetic fields, including the storage of electric and magnetic energy and its dissipation. Many phenomena in electronics, solid state and optical physics can be described using the underlying assumptions of dielectrics.

Disturb error:
Reverses the value of a bit during a Read or Write operation.

Endurance Metric
SanDisk developed the first industry metric (previously known as LDE) that expresses how much data can be written to a SSD during its lifespan in a simple, accurate and relevant number. The metric specification was developed by SanDisk and submitted to JEDEC as a benchmark to enable users to compare the data endurance of SSDs from various manufacturers. Based on typical end-user activity, the metrics provides the total number of data writes, expressed in terabytes written (TBW) that can be performed during the SSD lifespan. Data is written using typical PC transfer size distribution of writes, written at a constant rate over the life of the SSD and data is retained for at least 1 year upon TBW exhaustion. A typical client PC user writes 4GB/day, based on SanDisk internal measurements.

EEPROM (Electrically Erasable Programmable Read Only Memory):
This is early version of non-volatile memory.

Encapsulation:
The process of packaging a die with circuitry for mechanical and environmental protection.

Endurance:
The number of Write/Erase cycles that flash memory can perform without jeopardizing data reliability.

EPROM (Erasable Programmable Read Only Memory):
This is an early version of non-volatile memory.

Error Detection/Correction Code (EDC/ECC)
Detects errors and corrects them by reconstructing the original data using extra bits, and increases data retention.

Etching:
A micro fabrication technique to chemically remove layers from the surface of a wafer during manufacturing. Etching is a critically important process that is performed repeatedly on a wafer in many steps with the aim of achieving a minimal number of defects. Part of the wafer is protected from the etchant by using a mask that resists etching. In some cases, the mask is photo resist for use in patterning by photolithography. In other cases, silicon nitride is used, which is a more robust material

Fab (Fabrication plant):
Semiconductor wafer manufacturing facilities.

Flash Memory:
A non-volatile semiconductor memory consisting of 1-transistor memory architecture cells. The memory mechanism consists of storing charge in the gate dielectric. A second gate on the transistor enables data storage and simultaneous erasure of defined blocks of memory electronically.

Floating gate:
Stores an electrical charge for extended periods of time even without connection to power supply. Electrons stored in the floating gate are sensed by the threshold voltage.

Gate:
An electrode that regulates the current flow in a metal oxide semiconductor (MOS) transistor.

Gate oxide:
A thin layer of pure, defect-free, thermally grown oxide. It serves as the dielectric layer in MOSFET between the drain and source.

Head (also called Access arm):
Writes data to/reads from the platter surface of a hard disk drive. Each head services one side of one platter.

Ingot:
In the semiconductor industry, a material made of silicon that is processed to achieve single crystal silicon. This is then cut and polished to achieve wafers on which devices ranging from microprocessors to memory devices can be fabricated.

Input/Output Per Second (IOPS):
A measurement of the number of operations (e.g., Read or Write) performed per second. A solid state drive achieves higher IOPS when accessing random files than a hard disk drive.

JEDEC (Joint Electron Device Engineering Council)
A leading developer of standards for the solid-state industry, comprised of over 3000 participants appointed by some 295 companies working in 50 JEDEC committees.

Latency:
A delay before a given operation can be performed.

Level:
A logical method to define the analog value of a bit. 1 bit requires 2 levels.

Lithography:
An abbreviation for photolithography, a micro fabrication technique used to design the pattern for integrated circuits and micro-electromechanical systems. This term was modified from the print world, either text or artwork, where lithography refers to the use of oil or fat and gum arabic to divide the smooth surface into regions which accept the ink, and hydrophilic regions which reject it and thus become the background.

Logical Block Address (LBA):
An addressing scheme that numbers block linearly rather than by cylinder, head and sector numbers (CHS). LBA generally replaces the legacy block addressing scheme, although both are supported on current solid state drives and hard disk drives.

Mask:
A plate of glass or quartz that contains the photographic image of wafer patterns to define a single process layer. The mask is exposed onto a photosensitive layer, covers a wafer surface to expose/hide selected areas to/from various fabrication processes.

Mean time between failures (MTBF)
The average number of time until a failure is encountered.

Mean time to failure (MTTF)
The time until the first failure is encountered. Used in systems where the first failure is usually fatal.

Memory cell:
Intersection of bit line and word line identifies location where data is stored.

MOSFET (Metal Oxide Semiconductor Field Effect Transistor):
A device used to amplify or switch electronic signals. It is by far the most common field-effect transistor in both digital and analog circuits. A MOSFET is composed of a channel of n-type or p-type semiconductor material

Micrometer:
A metric unit of linear measure that equals one millionth of a meter or 10,000 angstroms.

Moore's Law:
This law, based on a prediction made in 1965, states that the density of transistors doubles every 1½ to 2 years. It enables the miniaturization of integrated circuits.

Multi Level Cell (MLC):
More than one bit is stored in a single cell; e.g., D2, D3, x4.

NAND flash:
Non-volatile memory that enables sequential access to memory cells, uses silicon more efficiently than NOR flash resulting in lower cost per gigabit, achieves faster write speed than NOR flash, suitable for mass data storage.

nCache™ Acceleration Technology1
nCache™ acceleration technology is a large Non Volatile Write Cache, a unique feature in SanDisk SSDs that improves random write performance and ensures an improved user experience. Studies show that modern operating systems mostly access the storage device using 4k access blocks. The cache is filled during these small write commands and emptied during idle time when the host is not accessing the drive, with no risk of data loss. For a typical everyday use, the write performance that the users see is the nCache™ (burst) high performance, and not steady state (sustained) SSD performance. Based on IOmeter 4K random write test

Non-volatile Memory (NVM):
A type of memory that retains data even in the absence of power.

NOR flash:
Non-volatile memory that enables direct access to each memory cell, uses silicon less efficiently than NAND flash resulting in higher cost per gigabit, achieves fast random access speed but slower write speed than NAND flash, suitable for code storage.

N-type:
A semiconductor material that has negatively charged conductivity with an excess of electrons.

One Time Programmable (OTP)
Memory that can only be written to once and cannot be erased, with no read limitations.

Page:
The smallest write unit in NAND flash.

Platter:
The spinning disk used in a hard disk drive. Data is written by the head to the top of bottom of the platter surface.

Power classes:
Power budgets are paramount in mobile computing applications. SanDisk i100 drive supports Power Classes, which provide the ability to limit SSD performance and in turn, limit power consumption. This provides the ability for optimized flexibility between power and performance and enables OEMs to take advantage of numerous SSD benefits even when maximum performance is not required.

Printed Circuit Board (PCB)
A board comprised of some specific dielectric, low-cost insulator material to mechanically support and electrically connect electronic components. A PCB uses conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate.

P-type:
A semiconductor material that has positively charged conductivity with a deficiency of electrons, usually achieved by Boron doping.

Random access:
The ability to access all elements in a sequence with no special order in the same amount of time.

Random access memory (RAM)
Volatile memory that can be read/written to/from arbitrary locations in arbitrary sequence.

Reliability:
The probability that a product will perform its intended functions within defined conditions for a specified time.

Revolutions Per Minute (RPM):
Used to measure the speed of a hard disk drive based on the number of revolutions per minute performed by the disk.

Rotational latency:
The delay in rotation for the hard disk drive to align the required sector beneath the head (calculated as half of the duration to rotate the plate a full cycle).

Back to Top

SATA uSSD™:
A SATA-IO standard for embedded solid state drives (SSDs). The SATA µSSD™ specification eliminates the module connector from the traditional SATA Interface, enabling developers to produce a single-chip SATA implementation for embedded storage applications. The Standard is implemented by SanDisk® iSSD™ integrated storage device.

Sector:
A pie-shaped slice on a hard disk drive platter that contains the minimum addressable area to/from which data can be written/read

Seek time:
The time for the head to reach the desired track on a hard disk drive.

Semiconductor:
A solid material with electrical conductivity characteristics that are between conductor and insulator.

Silicon:

An element in the periodic table used to manufacture semiconductors.

Single Level Cell (SLC):
Single bit is stored in a single cell.

Singulation:
The process of cutting a wafer into individual dies

Spin-up time :
The time required to accelerate the hard disk drive to operating speed.

Threshold voltage:
Senses the electrons in the floating gate, and acts as the gate voltage to enable current to flow.

Track:
Thin, concentric circles on the platter surface of a hard disk drive that are used to help identify the location of data.

Transistor:
A semiconductor used as an amplifier or electrically controlled switch, and the fundamental circuitry building block in computers, cellphones and other modern electronic devices. A transistor is made of a semiconductor material with at least three terminals for connection to an external circuit. Voltage or current applied to two of the terminals changes the current flowing through another pair of terminals. Because the controlled power can be much larger than the controlling power, the transistor provides amplification of a signal.

Trapped charges:
Charges trapped in the gate oxide that constitute part of the process that enables non-volatile memory.

TRIM:
TRIM contributes to a substantial gain in the product performance, by informing the SSD of the unused media space and allowing it to continuously manage its resources and retain optimized performance throughout its lifespan.

Tunneling:
A physical phenomena where electrons move across an insulating layer or a gap between two conductors. Tunneling is the basis for NAND flash write and erase operations.

Volatile memory:
A type of memory that loses data when power is off.

Wafer:
A thin slice with parallel faces cut from a semiconductor crystal such as silicon. A silicon wafer is prepared from silicon ingots.

Wear leveling:
A technology that prevents wear-out of specific blocks to extend the lifetime of flash memory by evenly distributing data from repeated Write/Erase cycles over the entire flash media. Wear leveling is particularly relevant for typical file systems (ex: DOS FAT file system) and file management algorithms that repeatedly write/erase the identical physical locations.

Yield:
Percentage of good dies on a wafer vs. the total number of dies.