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74-607: Tsinghua Unigroup has five main subsidiaries, New H3C Technologies, UNISOC Communications Co , Guoxin Micro , and UniCloud Technology Co. Other subsidiaries include Unisplendour . and France-based Linxens, a design and manufacturing company of micro-connectors for smart cards , RFID antennas and inlays. U.S. technology company Intel owns a 20 percent stake in Tsinghua Unigroup's UNISOC subsidiary—a consolidation of Tsinghua Unigroup acquisitions of Spreadtrum Communications,

148-662: A big data storage joint venture, Unis WDC Storage Co. in Nanjing In 2016, Tsinghua Unigroup founded Yangtze Memory Technologies (YMTC), its IDM memory subsidiary. In 2017, Tsinghua Unigroup announced plans to build two new memory-chip factories, in Nanjing and Chengdu . Other investments include about a six percent stake in Portland, Oregon-based Lattice Semiconductor , acquired in 2017. In June 2018, Tsinghua Unigroup acquired French smart chip components maker Linxens for

222-640: A 1024   GB flash chip, with eight stacked 96-layer V-NAND chips and with QLC technology. Flash memory stores information in an array of memory cells made from floating-gate transistors . In single-level cell (SLC) devices, each cell stores only one bit of information. Multi-level cell (MLC) devices, including triple-level cell (TLC) devices, can store more than one bit per cell. The floating gate may be conductive (typically polysilicon in most kinds of flash memory) or non-conductive (as in SONOS flash memory). In flash memory, each memory cell resembles

296-489: A 16   GB flash memory chip that was manufactured with 24 stacked NAND flash chips using a wafer bonding process. Toshiba also used an eight-layer 3D IC for their 32   GB THGBM flash chip in 2008. In 2010, Toshiba used a 16-layer 3D IC for their 128   GB THGBM2 flash chip, which was manufactured with 16 stacked 8   GB chips. In the 2010s, 3D ICs came into widespread commercial use for NAND flash memory in mobile devices . In 2016, Micron and Intel introduced

370-433: A 64   MB NOR flash memory chip. In 2009, Toshiba and SanDisk introduced NAND flash chips with QLC technology storing 4 bits per cell and holding a capacity of 64   Gbit. Samsung Electronics introduced triple-level cell (TLC) technology storing 3-bits per cell, and began mass-producing NAND chips with TLC technology in 2010. Charge trap flash (CTF) technology replaces the polysilicon floating gate, which

444-586: A US$ 3.775 billion equity investment to purchase its newly issued common stock, for about a 15 percent stake in the U.S. firm. Western Digital stated, in February 2016, that Unisplendour would not move forward with its offer following a decision by the Committee on Foreign Investment in the United States (CFIUS) to investigate the deal. In 2016, Tsinghua Unigroup partnered with Western Digital to establish

518-548: A certain number of faults (NOR flash, as is used for a BIOS  ROM, is expected to be fault-free). Manufacturers try to maximize the amount of usable storage by shrinking the size of the transistors or cells, however the industry can avoid this and achieve higher storage densities per die by using 3D NAND, which stacks cells on top of each other. NAND flash cells are read by analysing their response to various voltages. NAND flash uses tunnel injection for writing and tunnel release for erasing. NAND flash memory forms

592-517: A charge-trapping mechanism for NOR flash memory cells. CTF was later commercialized by AMD and Fujitsu in 2002. 3D V-NAND (vertical NAND) technology stacks NAND flash memory cells vertically within a chip using 3D charge trap flash (CTP) technology. 3D V-NAND technology was first announced by Toshiba in 2007, and the first device, with 24 layers, was first commercialized by Samsung Electronics in 2013. 3D integrated circuit (3D IC) technology stacks integrated circuit (IC) chips vertically into

666-498: A fabless semiconductor company, and semiconductor components manufacturer RDA Microelectronics. Tsinghua Unigroup operates a joint venture with Hewlett Packard Enterprise (HPE), as H3C Technologies Co, created after Tsinghua Unigroup purchased a 51 percent stake. Tsinghua Unigroup was founded in 1988 by Tsinghua Holdings , a wholly-owned business unit of Tsinghua University , a major state research university in Beijing. The company

740-828: A main factory building was completed in July 2020. On November 16, 2020, Tsinghua Unigroup defaulted on $ 198M in bonds, resulting in a credit downgrading from AA to BBB and triggering cross-defaults. It emerged on July 11, 2021, that one of the creditors of Tsinghua Unigroup - Hong King-listed Huishang Bank - has requested that the company go into bankruptcy. Defaults at that time amounted to $ 3.6 billion for several onshore and offshore bonds. According to analysts, assets of barely $ 8 billion are surmounted by $ 30 billion in debt. News agencies reported in January 2022 that Tsinghua Unigroup had scrapped its intention to build two major fabs announced in 2017, citing serious financial issues. The first

814-425: A more typical 10,000 or 100,000 erase cycles, up to 1,000,000 erase cycles. NOR-based flash was the basis of early flash-based removable media; CompactFlash was originally based on it, though later cards moved to less expensive NAND flash. NAND flash has reduced erase and write times, and requires less chip area per cell, thus allowing greater storage density and lower cost per bit than NOR flash. However,

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888-557: A plan to acquire Unigroup Liansheng, including its main asset, Linxens. However, the deal was rejected by the Chinese securities regulator the following year. Unisplendour Corporation Limited is a provider of full-stack ICT infrastructure. It provides services for digitization, networking, computing, cloud computing, and smart terminals. Its subsidiary companies include H3C Technologies Co., Limited. Unisplendour Digital (Suzhou) Group Co., Ltd. and Unicompute Technology Co., Ltd., etc. YMTC

962-518: A planar charge trap cell into a cylindrical form. As of 2020, 3D NAND flash memories by Micron and Intel instead use floating gates, however, Micron 128 layer and above 3D NAND memories use a conventional charge trap structure, due to the dissolution of the partnership between Micron and Intel. Charge trap 3D NAND flash is thinner than floating gate 3D NAND. In floating gate 3D NAND, the memory cells are completely separated from one another, whereas in charge trap 3D NAND, vertical groups of memory cells share

1036-814: A reported $ 2.6 billion. A restructuring proposal that would have Guoxin Micro acquire Unic Linxens (formerly Unigroup Liansheng) was rejected by the China Securities Regulatory Commission (CSRC) in June 2020. In 2018, Tsinghua Unigroup also announced the construction of a $ 1.9 billion Linxens plant in the Tianjin Binhai Hi-Tech Industrial Development Area in Tianjin, China. The company broke ground in September 2019, and construction of

1110-463: A separate flash memory controller chip. The NAND type is found mainly in memory cards , USB flash drives , solid-state drives (those produced since 2009), feature phones , smartphones , and similar products, for general storage and transfer of data. NAND or NOR flash memory is also often used to store configuration data in digital products, a task previously made possible by EEPROM or battery-powered static RAM . A key disadvantage of flash memory

1184-421: A separate die inside the package. The origins of flash memory can be traced back to the development of the floating-gate MOSFET (FGMOS) , also known as the floating-gate transistor. The original MOSFET was invented at Bell Labs between 1955 and 1960, after Frosch and Derick discovered surface passivation and used their discovery to create the first planar transistors. Dawon Kahng went on to develop

1258-489: A single 3D IC chip package. Toshiba introduced 3D IC technology to NAND flash memory in April 2007, when they debuted a 16   GB eMMC compliant (product number THGAM0G7D8DBAI6, often abbreviated THGAM on consumer websites) embedded NAND flash memory chip, which was manufactured with eight stacked 2   GB NAND flash chips. In September 2007, Hynix Semiconductor (now SK Hynix ) introduced 24-layer 3D IC technology, with

1332-424: A single memory product. A single-level NOR flash cell in its default state is logically equivalent to a binary "1" value, because current will flow through the channel under application of an appropriate voltage to the control gate, so that the bitline voltage is pulled down. A NOR flash cell can be programmed, or set to a binary "0" value, by the following procedure: To erase a NOR flash cell (resetting it to

1406-409: A single supply voltage and produce the high voltages that are required using on-chip charge pumps . Over half the energy used by a 1.8 V-NAND flash chip is lost in the charge pump itself. Since boost converters are inherently more efficient than charge pumps, researchers developing low-power SSDs have proposed returning to the dual Vcc/Vpp supply voltages used on all early flash chips, driving

1480-488: A standard metal–oxide–semiconductor field-effect transistor (MOSFET) except that the transistor has two gates instead of one. The cells can be seen as an electrical switch in which current flows between two terminals (source and drain) and is controlled by a floating gate (FG) and a control gate (CG). The CG is similar to the gate in other MOS transistors, but below this, there is the FG insulated all around by an oxide layer. The FG

1554-482: A technology known as CMOS Under the Array/CMOS Under Array (CUA), Core over Periphery (COP), Periphery Under Cell (PUA), or Xtacking, in which the control circuitry for the flash memory is placed under or above the flash memory cell array. This has allowed for an increase in the number of planes or sections a flash memory chip has, increasing from 2 planes to 4, without increasing the area dedicated to

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1628-843: A time. NAND flash also uses floating-gate transistors , but they are connected in a way that resembles a NAND gate : several transistors are connected in series, and the bit line is pulled low only if all the word lines are pulled high (above the transistors' V T ). These groups are then connected via some additional transistors to a NOR-style bit line array in the same way that single transistors are linked in NOR ;flash. Compared to NOR flash, replacing single transistors with serial-linked groups adds an extra level of addressing. Whereas NOR flash might address memory by page then word, NAND flash might address it by page, word and bit. Bit-level addressing suits bit-serial applications (such as hard disk emulation), which access only one bit at

1702-453: A time. Execute-in-place applications, on the other hand, require every bit in a word to be accessed simultaneously. This requires word-level addressing. In any case, both bit and word addressing modes are possible with either NOR or NAND flash. To read data, first the desired group is selected (in the same way that a single transistor is selected from a NOR array). Next, most of the word lines are pulled up above V T2 , while one of them

1776-506: A type of flash memory with a charge trap method. In 1998, Boaz Eitan of Saifun Semiconductors (later acquired by Spansion ) patented a flash memory technology named NROM that took advantage of a charge trapping layer to replace the conventional floating gate used in conventional flash memory designs. In 2000, an Advanced Micro Devices (AMD) research team led by Richard M. Fastow, Egyptian engineer Khaled Z. Ahmed and Jordanian engineer Sameer Haddad (who later joined Spansion) demonstrated

1850-450: A variation, the floating-gate MOSFET, with Taiwanese-American engineer Simon Min Sze at Bell Labs in 1967. They proposed that it could be used as floating-gate memory cells for storing a form of programmable read-only memory ( PROM ) that is both non-volatile and re-programmable. Early types of floating-gate memory included EPROM (erasable PROM) and EEPROM (electrically erasable PROM) in

1924-491: Is Anhui state-owned fund Wuhu Xinhou Yunzhi Equity Investment Partnership. In March 2023, Tsinghua Unigroup and its CEO has been accused of corruption by the Central Commission for Discipline Inspection . The anti-fraud body accused Mr. Zhao of taking a state-owned company and using it to purchase goods and services run by his relatives and friends at prices significantly higher than the market price, leading to

1998-665: Is a smart chips components maker specializing in security and identification, such as flexible connectors used in smart cards and RFID antennas and inlays. In 2018, Tsinghua Unigroup, through its subsidiary Unigroup Liansheng, acquired Linxens for about US$ 2.6 billion. Founded in 1979, Linxens is headquartered in Levallois-Perret , France and, as of 2018, employs over 3,200 staff at nine production sites worldwide. It also has offices in China, Singapore and Thailand, and operates six R&D centers. In June 2019, Guoxin Micro announced

2072-480: Is an IDM memory company that designs, produces, and sells 3D NAND flash memory . The company is headquartered in Wuhan and has 6,000 employees. Tsinghua Unigroup founded YMTC in July 2016, together with Hubei provincial government and the Chinese national "Big Fund" China Integrated Circuit Industry Investment Fund with a total investment of $ 24 billion. UNISOC Too Many Requests If you report this error to

2146-444: Is an electrically insulating tunnel oxide layer between the floating gate and the silicon, so the gate "floats" above the silicon. The oxide keeps the electrons confined to the floating gate. Degradation or wear (and the limited endurance of floating gate Flash memory) occurs due to the extremely high electric field (10 million volts per centimeter) experienced by the oxide. Such high voltage densities can break atomic bonds over time in

2220-525: Is interposed between the CG and the MOSFET channel. Because the FG is electrically isolated by its insulating layer, electrons placed on it are trapped. When the FG is charged with electrons, this charge screens the electric field from the CG, thus, increasing the threshold voltage (V T ) of the cell. This means that the V T of the cell can be changed between the uncharged FG threshold voltage (V T1 ) and

2294-556: Is often employed in scenarios where cost-effective, high-capacity storage is crucial, such as in USB drives, memory cards, and solid-state drives ( SSDs ). The primary differentiator lies in their use cases and internal structures. NOR flash is optimal for applications requiring quick access to individual bytes, like in embedded systems for program execution. NAND flash, on the other hand, shines in scenarios demanding cost-effective, high-capacity storage with sequential data access. Flash memory

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2368-636: Is programmed in blocks while EEPROM is programmed in bytes. According to Toshiba, the name "flash" was suggested by Masuoka's colleague, Shōji Ariizumi, because the erasure process of the memory contents reminded him of the flash of a camera . Masuoka and colleagues presented the invention of NOR flash in 1984, and then NAND flash at the IEEE 1987 International Electron Devices Meeting (IEDM) held in San Francisco. Toshiba commercially launched NAND flash memory in 1987. Intel Corporation introduced

2442-422: Is pulled up to V I . The series group will conduct (and pull the bit line low) if the selected bit has not been programmed. Despite the additional transistors, the reduction in ground wires and bit lines allows a denser layout and greater storage capacity per chip. (The ground wires and bit lines are actually much wider than the lines in the diagrams.) In addition, NAND flash is typically permitted to contain

2516-484: Is sandwiched between a blocking gate oxide above and a tunneling oxide below it, with an electrically insulating silicon nitride layer; the silicon nitride layer traps electrons. In theory, CTF is less prone to electron leakage, providing improved data retention. Because CTF replaces the polysilicon with an electrically insulating nitride, it allows for smaller cells and higher endurance (lower degradation or wear). However, electrons can become trapped and accumulate in

2590-510: Is that it can endure only a relatively small number of write cycles in a specific block. NOR flash is known for its direct random access capabilities, making it apt for executing code directly. Its architecture allows for individual byte access, facilitating faster read speeds compared to NAND flash. NAND flash memory operates with a different architecture, relying on a serial access approach. This makes NAND suitable for high-density data storage but less efficient for random access tasks. NAND flash

2664-513: Is thus highly suitable for use in mass-storage devices, such as memory cards and solid-state drives (SSD). For example, SSDs store data using multiple NAND flash memory chips. The first NAND-based removable memory card format was SmartMedia , released in 1995. Many others followed, including MultiMediaCard , Secure Digital , Memory Stick , and xD-Picture Card . A new generation of memory card formats, including RS-MMC , miniSD and microSD , feature extremely small form factors. For example,

2738-485: Is used in computers , PDAs , digital audio players , digital cameras , mobile phones , synthesizers , video games , scientific instrumentation , industrial robotics , and medical electronics . Flash memory has a fast read access time but it is not as fast as static RAM or ROM. In portable devices, it is preferred to use flash memory because of its mechanical shock resistance since mechanical drives are more prone to mechanical damage. Because erase cycles are slow,

2812-554: The NOR and NAND logic gates . Both use the same cell design, consisting of floating-gate MOSFETs . They differ at the circuit level depending on whether the state of the bit line or word lines is pulled high or low: in NAND flash, the relationship between the bit line and the word lines resembles a NAND gate; in NOR flash, it resembles a NOR gate. Flash memory, a type of floating-gate memory,

2886-502: The "1" state), a large voltage of the opposite polarity is applied between the CG and source terminal, pulling the electrons off the FG through Fowler–Nordheim tunneling (FN tunneling). This is known as Negative gate source source erase. Newer NOR memories can erase using negative gate channel erase, which biases the wordline on a NOR memory cell block and the P-well of the memory cell block to allow FN tunneling to be carried out, erasing

2960-712: The 1970s. However, early floating-gate memory required engineers to build a memory cell for each bit of data, which proved to be cumbersome, slow, and expensive, restricting floating-gate memory to niche applications in the 1970s, such as military equipment and the earliest experimental mobile phones . Modern EEPROM based on Fowler-Nordheim tunnelling to erase data was invented by Bernward and patented by Siemens in 1974. And further developed between 1976 and 1978 by Eliyahou Harari at Hughes Aircraft Company and George Perlegos and others at Intel. This led to Masuoka's invention of flash memory at Toshiba in 1980. The improvement between EEPROM and flash being that flash

3034-438: The FG is charged. The binary value of the cell is sensed by determining whether there is current flowing through the transistor when V I is asserted on the CG. In a multi-level cell device, which stores more than one bit per cell, the amount of current flow is sensed (rather than simply its presence or absence), in order to determine more precisely the level of charge on the FG. Floating gate MOSFETs are so named because there

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3108-540: The I/O interface of NAND flash does not provide a random-access external address bus. Rather, data must be read on a block-wise basis, with typical block sizes of hundreds to thousands of bits. This makes NAND flash unsuitable as a drop-in replacement for program ROM, since most microprocessors and microcontrollers require byte-level random access. In this regard, NAND flash is similar to other secondary data storage devices , such as hard disks and optical media , and

3182-567: The Wikimedia System Administrators, please include the details below. Request from 172.68.168.150 via cp1114 cp1114, Varnish XID 972532109 Upstream caches: cp1114 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 11:03:29 GMT Flash memory Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash , are named for

3256-466: The cell block. Older memories used source erase, in which a high voltage was applied to the source and then electrons from the FG were moved to the source. Modern NOR flash memory chips are divided into erase segments (often called blocks or sectors). The erase operation can be performed only on a block-wise basis; all the cells in an erase segment must be erased together. Programming of NOR cells, however, generally can be performed one byte or word at

3330-502: The cell by increasing the MOSFET's threshold voltage. This, in turn, changes the drain-source current that flows through the transistor for a given gate voltage, which is ultimately used to encode a binary value. The Fowler-Nordheim tunneling effect is reversible, so electrons can be added to or removed from the floating gate, processes traditionally known as writing and erasing. Despite the need for relatively high programming and erasing voltages, virtually all flash chips today require only

3404-402: The cells are logically set to 1. Data can only be programmed in one pass to a page in a block that was erased. The programming process is set one or more cells from 1 to 0. Any cells that have been set to 0 by programming can only be reset to 1 by erasing the entire block. This means that before new data can be programmed into a page that already contains data, the current contents of the page plus

3478-724: The company's financial issues. In the field of technology, Tsinghua Unigroup invests mainly in Integrated Circuit design and information and communication infrastructure. Tsinghua Unigroup is the controlling shareholder of dozens of technology enterprises such as Unis, UNISOC, Guoxin Micro, Linxens, etc. Unigroup Guoxin Microelectronics Co., Ltd. (002049.SZ) provides IC chips for various applications such as mobilephone SIM card, finance IC card and POS machine, automotive MCU and smart connectivity IC for industry and IoT applications. In 2021, Guoxin Micro's revenue

3552-584: The control or periphery circuitry. This increases the number of IO operations per flash chip or die, but it also introduces challenges when building capacitors for charge pumps used to write to the flash memory. Some flash dies have as many as 6 planes. As of August 2017, microSD cards with a capacity up to 400 GB (400 billion bytes) are available. The same year, Samsung combined 3D IC chip stacking with its 3D V-NAND and TLC technologies to manufacture its 512   GB KLUFG8R1EM flash memory chip with eight stacked 64-layer V-NAND chips. In 2019, Samsung produced

3626-404: The core of the removable USB storage devices known as USB flash drives , as well as most memory card formats and solid-state drives available today. The hierarchical structure of NAND flash starts at a cell level which establishes strings, then pages, blocks, planes and ultimately a die. A string is a series of connected NAND cells in which the source of one cell is connected to the drain of

3700-491: The entity known as UniSpreadtrum RDA, subsequently renamed as UNISOC. A notable development was Intel Corp .'s investment of $ 1.5 billion for a 20 percent stake in this venture. In May 2015, Tsinghua Unigroup acquired a 51 percent stake in Hewlett-Packard's H3C Technologies, a China-based data-networking company, for approximately $ 2.3 billion. In September 2015, Western Digital announced that Unisplendour would make

3774-497: The first commercial NOR type flash chip in 1988. NOR-based flash has long erase and write times, but provides full address and data buses , allowing random access to any memory location . This makes it a suitable replacement for older read-only memory (ROM) chips, which are used to store program code that rarely needs to be updated, such as a computer's BIOS or the firmware of set-top boxes . Its endurance may be from as little as 100 erase cycles for an on-chip flash memory, to

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3848-462: The flash storage device (such as SSD ), the data actually written to the flash memory may be 0011 1100. Vertical NAND (V-NAND) or 3D NAND memory stacks memory cells vertically and uses a charge trap flash architecture. The vertical layers allow larger areal bit densities without requiring smaller individual cells. It is also sold under the trademark BiCS Flash , which is a trademark of Kioxia Corporation (formerly Toshiba Memory Corporation). 3D NAND

3922-418: The floating gate. This is why data retention goes down and the risk of data loss increases with increasing degradation. The silicon oxide in a cell degrades with every erase operation. The degradation increases the amount of negative charge in the cell over time due to trapped electrons in the oxide and negates some of the control gate voltage, this over time also makes erasing the cell slower, so to maintain

3996-435: The high Vpp voltage for all flash chips in an SSD with a single shared external boost converter. In spacecraft and other high-radiation environments, the on-chip charge pump is the first part of the flash chip to fail, although flash memories will continue to work – in read-only mode – at much higher radiation levels. In NOR flash, each cell has one end connected directly to ground, and

4070-415: The higher charged FG threshold voltage (V T2 ) by changing the FG charge. In order to read a value from the cell, an intermediate voltage (V I ) between V T1 and V T2 is applied to the CG. If the channel conducts at V I , the FG must be uncharged (if it were charged, there would not be conduction because V I is less than V T2 ). If the channel does not conduct at the V I , it indicates that

4144-813: The large block sizes used in flash memory erasing give it a significant speed advantage over non-flash EEPROM when writing large amounts of data. As of 2019, flash memory costs greatly less than byte-programmable EEPROM and had become the dominant memory type wherever a system required a significant amount of non-volatile solid-state storage . EEPROMs, however, are still used in applications that require only small amounts of storage, e.g. in SPD implementations on computer memory modules. Flash memory packages can use die stacking with through-silicon vias and several dozen layers of 3D TLC NAND cells (per die) simultaneously to achieve capacities of up to 1 tebibyte per package using 16 stacked dies and an integrated flash controller as

4218-659: The microSD card has an area of just over 1.5 cm , with a thickness of less than 1 mm. NAND flash has achieved significant levels of memory density as a result of several major technologies that were commercialized during the late 2000s to early 2010s. NOR flash was the most common type of Flash memory sold until 2005, when NAND flash overtook NOR flash in sales. Multi-level cell (MLC) technology stores more than one bit in each memory cell . NEC demonstrated multi-level cell (MLC) technology in 1998, with an 80   Mb flash memory chip storing 2 bits per cell. STMicroelectronics also demonstrated MLC in 2000, with

4292-422: The new data must be copied to a new, erased page. If a suitable erased page is available, the data can be written to it immediately. If no erased page is available, a block must be erased before copying the data to a page in that block. The old page is then marked as invalid and is available for erasing and reuse. This is different from operating system LBA view, for example, if operating system writes 1100 0011 to

4366-414: The next one. Depending on the NAND technology, a string typically consists of 32 to 128 NAND cells. Strings are organised into pages which are then organised into blocks in which each string is connected to a separate line called a bitline. All cells with the same position in the string are connected through the control gates by a wordline. A plane contains a certain number of blocks that are connected through

4440-474: The nitride, leading to degradation. Leakage is exacerbated at high temperatures since electrons become more excited with increasing temperatures. CTF technology however still uses a tunneling oxide and blocking layer which are the weak points of the technology, since they can still be damaged in the usual ways (the tunnel oxide can be degraded due to extremely high electric fields and the blocking layer due to Anode Hot Hole Injection (AHHI). Degradation or wear of

4514-413: The number of bits increases, the number of possible states also increases and thus the cell is less tolerant of adjustments to programming voltages, because there is less space between the voltage levels that define each state in a cell. The process of moving electrons from the control gate and into the floating gate is called Fowler–Nordheim tunneling , and it fundamentally changes the characteristics of

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4588-516: The other end connected directly to a bit line. This arrangement is called "NOR flash" because it acts like a NOR gate: when one of the word lines (connected to the cell's CG) is brought high, the corresponding storage transistor acts to pull the output bit line low. NOR flash continues to be the technology of choice for embedded applications requiring a discrete non-volatile memory device. The low read latencies characteristic of NOR devices allow for both direct code execution and data storage in

4662-435: The oxides is the reason why flash memory has limited endurance, and data retention goes down (the potential for data loss increases) with increasing degradation, since the oxides lose their electrically insulating characteristics as they degrade. The oxides must insulate against electrons to prevent them from leaking which would cause data loss. In 1991, NEC researchers including N. Kodama, K. Oyama and Hiroki Shirai described

4736-413: The performance and reliability of the NAND chip, the cell must be retired from use. Endurance also decreases with the number of bits in a cell. With more bits in a cell, the number of possible states (each represented by a different voltage level) in a cell increases and is more sensitive to the voltages used for programming. Voltages may be adjusted to compensate for degradation of the silicon oxide, and as

4810-459: The relatively thin oxide, gradually degrading its electrically insulating properties and allowing electrons to be trapped in and pass through freely (leak) from the floating gate into the oxide, increasing the likelihood of data loss since the electrons (the quantity of which is used to represent different charge levels, each assigned to a different combination of bits in MLC Flash) are normally in

4884-410: The same bitline. A flash die consists of one or more planes, and the peripheral circuitry that is needed to perform all the read, write, and erase operations. The architecture of NAND flash means that data can be read and programmed (written) in pages, typically between 4 KiB and 16 KiB in size, but can only be erased at the level of entire blocks consisting of multiple pages. When a block is erased, all

4958-407: The same silicon nitride material. An individual memory cell is made up of one planar polysilicon layer containing a hole filled by multiple concentric vertical cylinders. The hole's polysilicon surface acts as the gate electrode. The outermost silicon dioxide cylinder acts as the gate dielectric, enclosing a silicon nitride cylinder that stores charge, in turn enclosing a silicon dioxide cylinder as

5032-418: The tunnel dielectric that surrounds a central rod of conducting polysilicon which acts as the conducting channel. Memory cells in different vertical layers do not interfere with each other, as the charges cannot move vertically through the silicon nitride storage medium, and the electric fields associated with the gates are closely confined within each layer. The vertical collection is electrically identical to

5106-433: The years 2013 and 2014, Tsinghua Unigroup undertook acquisitions that included Spreadtrum Communications, now recognized as UNISOC. Spreadtrum is a fabless semiconductor enterprise known for its mobile chipset platform development. During the same period, Tsinghua Unigroup also acquired RDA Microelectronics, a manufacturer of semiconductor components. These acquisitions resulted in the amalgamation of Spreadtrum and RDA, forming

5180-583: Was CN¥ 5.34 billion. Unicloud Technology Co., Ltd. is an industrial intelligent manufacturer that develops urban and industry cloud platforms for the construction and operation of smart cities in China. UNISOC is an IC design platform company. The company's products include mobilephone central processors, baseband chips, AI chips, low-power RF chips, and other IC chips for telecommunication, computing processor and controllers. Those products are used in consumer electronics and Internet of Things. In 2021, it gained an operating revenue of CN¥ 11.7 billion. Linxens

5254-417: Was first announced by Toshiba in 2007. V-NAND was first commercially manufactured by Samsung Electronics in 2013. V-NAND uses a charge trap flash geometry (which was commercially introduced in 2002 by AMD and Fujitsu ) that stores charge on an embedded silicon nitride film. Such a film is more robust against point defects and can be made thicker to hold larger numbers of electrons. V-NAND wraps

5328-674: Was founded as Tsinghua University Sci-Tech General Company, then renamed Tsinghua Unigroup in 1993. Tsinghua Unigroup is a fabless semiconductor company that is 51 percent owned by Tsinghua Holdings and 49 percent owned by Beijing Jiankun Investment Group; the latter is led by Tsinghua Unigroup chairman and CEO Zhao Weiguo. Zhao, a graduate of Tsinghua University, was also appointed CEO of Tsinghua Unigroup in 2009, then made board chairman in 2013. He chaired several of Tsinghua Unigroup's subsidiaries, including Unisplendour and Unigroup Guoxin Micro, until 2018. Zhao remains CEO and chairman of Tsinghua Unigroup and Yangtze Memory Technologies Co. (YMTC). In

5402-616: Was invented by Fujio Masuoka at Toshiba in 1980 and is based on EEPROM technology. Toshiba began marketing flash memory in 1987. EPROMs had to be erased completely before they could be rewritten. NAND flash memory, however, may be erased, written, and read in blocks (or pages), which generally are much smaller than the entire device. NOR flash memory allows a single machine word to be written – to an erased location – or read independently. A flash memory device typically consists of one or more flash memory chips (each holding many flash memory cells), along with

5476-588: Was to be a DRAM plant in Chongqing, and the second was to be a $ 24 billion facility for 3D NAND flash memory in Chengdu. On July 11, 2022, Tsinghua UniGroup has completed the registration procedures and 100% of the equity interest of Tsinghua UniGroup has been registered under Zhiguangxin. In 2022, Beijing Zhiguangxin Holding took ownership of Tsinghua Unigroup. Beijing Zhiguangxin Holding's largest shareholder

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