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Jack H. Yuan

Bio: Jack H. Yuan is an academic researcher from SanDisk. The author has contributed to research in topics: EEPROM & Trench. The author has an hindex of 21, co-authored 43 publications receiving 3178 citations.

Papers
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Patent
18 Dec 1990
TL;DR: In this article, a technique of forming capacitive coupling between the floating gate and an erase gate in a flash EEPROM array cell with improved endurance is disclosed, which allows the density of the array to be increased since the amount of semiconductor substrate area occupied by each cell is decreased without having to sacrifice the amount or quality of the capacitance.
Abstract: A memory array of PROM, EPROM or EEPROM cells has each cell formed in a trench of a thick oxide layer deposited on a silicon substrate, in a manner that a significant portion of opposing areas of the floating gate and control gate of each cell which provide capacitive coupling between them are formed vertically. This allows the density of the array to be increased since the amount of semiconductor substrate area occupied by each cell is decreased without having to sacrifice the amount or quality of the capacitive coupling. Further, a technique of forming capacitive coupling between the floating gate and an erase gate in a flash EEPROM array cell with improved endurance is disclosed.

468 citations

Patent
Jack H. Yuan1, Eliyahou Harari1
15 Mar 1989
TL;DR: In this article, spacers are formed with reference to the position of existing elements in order to form floating gates and define small areas of these gates where, in a controlled fashion, a tunnel erase dielectric is formed.
Abstract: An improved electrically erasable and programmable read only memory (EEprom) structure and processes of making it which results in a denser integrated circuit, improved operation and extended lifetime. In order to eliminate certain ill effects resulting from tolerances which must be allowed for registration of masks used in successive steps in forming the semiconductor structures, spacers are formed with reference to the position of existing elements in order to form floating gates and define small areas of these gates where, in a controlled fashion, a tunnel erase dielectric is formed. Alternatively, a polysilicon strip conductor is separated into separate control gates by a series of etching steps that includes an anisotropic etch of boundary oxide layers to define the area of the control gates that are coupled to the erase gate through an erase dielectric. In either case, the polysilicon layer strip can alternatively be separated by growing oxide thereon until it is completely consumed. A technique for forming a pure oxide dielectric layer of uniform thickness includes depositing a thin layer of an undoped polysilicon material and then oxidizing its surface until substantially the entire undoped polysilicon layer is consumed and made part of the resulting oxide layer. Overlapping doped regions are provided in the substrate by an ion implantation mask that adds spacers to the mask aperture to change its size between implants.

455 citations

Patent
Jack H. Yuan1
25 May 1994
TL;DR: In this paper, a flash EEPROM cell array with the size of individual cells being reduced, thereby increasing the number of cells which may be formed on a semiconductor substrate of a given size.
Abstract: Techniques of forming a flash EEPROM cell array with the size of individual cells being reduced, thereby increasing the number of cells which may be formed on a semiconductor substrate of a given size. Use of dielectric spacers in several steps of the process controls areas being etched or implanted with ions to something smaller than can be obtained by the highest resolution photolithography. Both split-channel and non-split-channel (no select transistor) types of memory cells are included. Example cells employ three polysilicon layers, having separate floating, control and erase gates. A technique of forming the memory cell gates with greater uniformity of conductivity level includes depositing undoped polysilicon and then using ion implantation to introduce the dopant. Field oxide is formed at an early stage in the process by CVD deposition and dry etching. The memory cell array and adjacent peripheral components are formed in a coordinated manner on a single integrated circuit chip.

391 citations

Patent
31 Oct 2002
TL;DR: In this article, the authors propose to store a level of charge corresponding to the data being stored in a dielectric material storage element that is sandwiched between a control gate and the semiconductor substrate surface over channel regions of the memory cells.
Abstract: Non-volatile memory cells store a level of charge corresponding to the data being stored in a dielectric material storage element that is sandwiched between a control gate and the semiconductor substrate surface over channel regions of the memory cells. More than two memory states are provided by one of more than two levels of charge being stored in a common region of the dielectric material. More than one such common region may be included in each cell. In one form, two such regions are provided adjacent source and drain diffusions in a cell that also includes a select transistor positioned between them. In another form, NAND arrays of strings of memory cells store charge in regions of a dielectric layer sandwiched between word lines and the semiconductor substrate.

353 citations

Patent
30 Jun 1999
TL;DR: In this article, an array of memory cells that individually include two floating gates, bit line source and drain diffusions, steering gates also extending along columns, and select gates forming word lines along rows of floating gates.
Abstract: An EEPROM system having an array of memory cells that individually include two floating gates, bit line source and drain diffusions extending along columns, steering gates also extending along columns and select gates forming word lines along rows of floating gates. The dual gate cell increases the density of data that can be stored. Rather than providing a separate steering gate for each column of floating gates, an individual steering gate is shared by two adjacent columns of floating gates that have a diffusion between them. The steering gate is thus shared by two floating gates of different but adjacent memory cells. In one array embodiment, the floating gates are formed on the surface of the substrate, where the added width of the steering gates makes them easier to form, removes them as a limitation upon scaling the array smaller, require fewer electrical contacts along their length because of increased conductance, are easier to contact, and reduces the number of conductive traces that are needed to connect with them. In arrays that erase the floating gates to the select gates, rather than to the substrate, the wider steering gates advantageously uncouple the diffusions they cover from the select gates. This use of a single steering gate for two floating gates also allows the floating gates, in another embodiment, to be formed on side walls of trenches in the substrate with the common steering gate between them, to further increase the density of data that can be stored. Multiple bits of data can also be stored on each floating gate.

295 citations


Cited by
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Patent
01 Aug 2008
TL;DR: In this article, the oxide semiconductor film has at least a crystallized region in a channel region, which is defined as a region of interest (ROI) for a semiconductor device.
Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

1,501 citations

Patent
25 Feb 2004
TL;DR: In this article, the memory array is read with high fidelity, not to provide actual final digital data, but rather to provide raw data accurately reflecting the analog storage state, which information is sent to a memory controller for analysis and detection of the actual digital data.
Abstract: Maximized multi-state compaction and more tolerance in memory state behavior is achieved through a flexible, self-consistent and self-adapting mode of detection, covering a wide dynamic range. For high density multi-state encoding, this approach borders on full analog treatment, dictating analog techniques including A to D type conversion to reconstruct and process the data. In accordance with the teachings of this invention, the memory array is read with high fidelity, not to provide actual final digital data, but rather to provide raw data accurately reflecting the analog storage state, which information is sent to a memory controller for analysis and detection of the actual final digital data.

934 citations

Patent
26 Jun 2002
TL;DR: In this article, the authors present a NAND type of flash EEPROM, where the memory is operated to minimize the effect of charge coupled between adjacent floating gates, by programming some cells a second time after adjacent cells have been programmed.
Abstract: A non-volatile memory system having an array of memory cells with at least one storage element each is operated with a plurality of storage level ranges per storage element. A flash electrically erasable and programmable read only memory (EEPROM) is an example, wherein the storage elements are electrically floating gates. The memory is operated to minimize the effect of charge coupled between adjacent floating gates, by programming some cells a second time after adjacent cells have been programmed. The second programming step also compacts a distribution of charge levels within at least some of the programming states. This increases the separation between states and/or allows more states to be included within a given storage window. An implementation that is described is for a NAND type of flash EEPROM.

724 citations

Patent
Jian Chen1
13 Sep 2002
TL;DR: In this article, a flash nonvolatile memory system that normally operates its memory cells in multiple storage states is provided with the ability to operate some selected or all of its memory cell blocks in two states instead.
Abstract: A flash non-volatile memory system that normally operates its memory cells in multiple storage states is provided with the ability to operate some selected or all of its memory cell blocks in two states instead. The two states are selected to be the furthest separated of the multiple states, thereby providing an increased margin during two state operation. This allows faster programming and a longer operational life of the memory cells being operated in two states when it is more desirable to have these advantages than the increased density of data storage that multi-state operation provides.

703 citations

Patent
26 Oct 2004
TL;DR: In this article, the authors present a technique to resist the development of soft errors into hard errors by maintaining the threshold voltage of each memory cell to its intended level throughout the use of the memory device.
Abstract: Soft errors occur during normal use of a solid-state memory such as EEPROM or Flash EEPROM. A soft error results from the programmed threshold voltage of a memory cell being drifted from its originally intended level. The error is initially not readily detected during normal read until the cumulative drift becomes so severe that it develops into a hard error. Data could be lost if enough of these hard errors swamps available error correction codes in the memory. A memory device and techniques therefor are capable of detecting these drifts and substantially maintaining the threshold voltage of each memory cell to its intended level throughout the use of the memory device, thereby resisting the development of soft errors into hard errors.

678 citations