Abstract: The problem of bit disturb is reduced by discharging the floating bit lines of a nonvolatile memory array during programming. An illustrative virtual ground memory array uses single transistor floating gate type memory cells that are programmed using Fowler-Nordheim (“FN”) tunneling, highly conductive and lengthy bit lines, buried and relatively short sub-bit lines and a programming discharge circuit for controlling spurious voltages on the bit lines that can arise when some of the bit lines are left floating during programming. Discharge control transistor respectively coupled to the bit lines direct current into a discharge section. A discharge section may be provided for each bit line, or shared by all bit lines. The discharge section may be a fixed circuit section for use through the programming process or may be selected from multiple discharge options.

Abstract: An asymmetrical virtual ground single transistor floating gate memory cell has a floating gate that overlies a channel region in a p-well, the channel region lying between a heavily doped n+ drain region and a lightly doped n? source region. A heavily doped p+ region known as a “halo” is disposed in the channel adjacent the heavily doped n+ drain. The floating gate is spaced away from the channel region by a generally thin tunnel oxide. A lightly doped source with a graded source/channel junction reduces source side CHE generation. In one variation, a thicker oxide between the source and the floating gate reduces CHE injection from the source side. A heavily doped drain with a halo implant in the channel adjacent the drain enhances drain side CHE generation.

Abstract: A memory uses multiple threshold levels in a memory cell that are not a power of two, and further uses a cell mapping technique wherein the read mapping is only a partial function The domain of read states for a single three-level memory cell, for example, has three states, but only two of them can be uniquely mapped to a bit. The domain of read states for two three-level memory cell, for example, has nine states, but only eight of them can be uniquely mapped to three bits. Although the read mapping is only partial, the voltage margin for the three-level memory cells is larger that the voltage margin available in the commonly used four-level memory cells. This increased voltage margin facilitates memory cell threshold voltage sensing, thereby increasing the reliability of the memory.

Abstract: In nonvolatile memory cell array, the memory cells of each sector are organized into groups of successive cells, the groups preferably being of the same size and preferably isolated from one another in both the row and column directions by a suitable isolation structure such as field dielectric or trench dielectric. Because of cell group isolation, each group of column lines may be decoded by its own relatively small program column select, which preferably is replicated in essentially identical form for all groups of column lines. While each program column select preferably is used to decode one group of column lines, larger program column selects may be used if desired to decode two or more groups of column lines. Read column selects may decode one or more groups of column lines as desired. The number of column lines decoded may the same as or different than the number of column lines decoded.

Abstract: An asymmetrical virtual ground single transistor floating gate memory cell has a floating gate that overlies a channel region in a p-well, the channel region lying between a heavily doped n+ drain region and a lightly doped n− source region. A heavily doped p+ region known as a “halo” is disposed in the channel adjacent the heavily doped n+ drain. The floating gate is spaced away from the channel region by a generally thin tunnel oxide. A lightly doped source with a graded source/channel junction reduces source side CHE generation. In one variation, a thicker oxide between the source and the floating gate reduces CHE injection from the source side. A heavily doped drain with a halo implant in the channel adjacent the drain enhances drain side CHE generation.

Abstract: A memory integrated circuit includes a nonvolatile memory array that is programmed in page mode. A volatile utility memory is connected to the memory array, and is at least a page in size so that an entire page of data that is either being programmed into or read from the memory array may be stored in the utility memory, thereby providing a single readily accessible and fully functional volatile memory that supports a variety of data operations such as nonvolatile memory programming, program-verify when supplemented with a program verify detector, data compare when supplemented with a comparator, and other operations including, in particular, operations that can benefit from the availability of a fast volatile memory to store an entire page of program data or read data.

Abstract: A serial flash integrated circuit is provided with an integrated error correction coding (“ECC”) system that is used with an integrated volatile page memory for fast automatic data correction. The ECC code has the capability of correcting any one or two bit errors that might occur on a page of the flash memory array. One bit corrections are done automatically in hardware during reads or transfer to the page memory, while two-bit corrections are handled in external software, firmware or hardware. The ECC system uses a syndrome generator for generating both write and read syndromes, and an error trapper to identify the location of single bit errors using very little additional chip space. The flash memory array may be refreshed from the page memory to correct any detected errors. Data status is made available to the application prior to the data. The use of the ECC is optional.

Abstract: In a NOR-type flash memory of either the ETOX or virtual ground type that is programmed using electron injection and erased using FN tunneling, and that has row redundancy, the typical sequence of operations used for an embedded sector erase, namely the Preprogram, Preprogram Verify, Erase, Erase Verify, Post-Program Verify, and Post-Program operations, need not be performed for the data cells on bad or shorted rows or in unused redundant rows. Instead, the bad or shorted rows or the unused redundant rows are suitably biased so that the threshold voltages of the data cells in these rows tend to converge to a threshold voltage near the UV erased threshold.

Abstract: In an array of nonvolatile memory cells, as many memory cells as desired and indeed even the entire array of memory cells may be placed in a single region of the bulk, illustratively a p-well. Peripheral circuitry is used to in effect section the memory array into blocks and groups of blocks, and to establish suitable biasing and counter-biasing within those blocks and groups during page or block erase operations to limit erase disturb. Each group is provided with its own set of voltage switches, which furnishes the bias voltages for the various modes of operation, including erase. Each of the voltage switches furnish either a large positive voltage when its group is selected, or a large negative voltage when its group is unselected. The size of the group is established as a compromise between degree of erase disturb and substrate area required for the voltage switches.

Abstract: A memory integrated circuit includes a nonvolatile memory array that is programmed in page mode. A volatile utility memory is connected to the memory array, and is at least a page in size so that an entire page of data that is either being programmed into or read from the memory array may be stored in the utility memory, thereby providing a single readily accessible and fully functional volatile memory that supports a variety of data operations such as nonvolatile memory programming, program-verify when supplemented with a program verify detector, data compare when supplemented with a comparator, and other operations including, in particular, operations that can benefit from the availability of a fast volatile memory to store an entire page of program data or read data.

Abstract: A memory array contains memory cells designed to be erased using Fowler-Nordheim (“FN”) tunneling through the channel area, and programmed using either channel hot electron injection (“CHE”) or channel-initiated secondary electron injection (“CISEI”). To reduce disturbance of the floating gate potential of unselected memory cells during programming operations and read operations, the unselected word lines are brought to a negative potential rather than ground potential. To reduce disturbance of the floating gate potential of unselected memory cells during FN erase operations, the unselected word lines are brought to a positive potential rather than ground potential.

Abstract: A memory array contains memory cells designed to be erased using Fowler-Nordheim (“FN”) tunneling through the channel area, and programmed using either channel hot electron injection (“CHE”) or channel-initiated secondary electron injection (“CISEI”). To reduce disturbance of the floating gate potential of unselected memory cells during programming operations and read operations, the unselected word lines are brought to a negative potential rather than ground potential. To reduce disturbance of the floating gate potential of unselected memory cells during FN erase operations, the unselected word lines are brought to a positive potential rather than ground potential.

Abstract: A memory uses multiple threshold levels in a memory cell that are not a power of two, and further uses a cell mapping technique wherein the read mapping is only a partial function The domain of read states for a single three-level memory cell, for example, has three states, but only two of them can be uniquely mapped to a bit. The domain of read states for two three-level memory cell, for example, has nine states, but only eight of them can be uniquely mapped to three bits. Although the read mapping is only partial, the voltage margin for the three-level memory cells is larger that the voltage margin available in the commonly used four-level memory cells. This increased voltage margin facilitates memory cell threshold voltage sensing, thereby increasing the reliability of the memory.

Abstract: A convergence signal includes a series of voltage pulses used to perform a convergence procedure in one or more flash EEPROM memory cells (transistors). In one instance subsequent voltage pulses in the convergence signal each have a higher voltage than the preceding pulse. In another instance, subsequent voltage pulses in the convergence signal each have a longer duration than the preceding pulse. An integrated circuit includes an array of memory cells and an erase control unit which controls the application of the convergence signal to one or more memory cells. The integrated circuit may be either serial or parallel flash EEPROM in which bulk, sector, or page mode erasing is used.

Abstract: A memory array contains memory cells designed to be erased using Fowler-Nordheim (“FN”) tunneling through the channel area, and programmed using either channel hot electron injection (“CHE”) or channel-initiated secondary electron injection (“CISEI”). To reduce disturbance of the floating gate potential of unselected memory cells during programming operations and read operations, the unselected word lines are brought to a negative potential rather than ground potential. To reduce disturbance of the floating gate potential of unselected memory cells during FN erase operations, the unselected word lines are brought to a positive potential rather than ground potential.

Abstract: A method for fabricating a tunnel window in an EEPROM cell that reduces or eliminates the initial active region overlap yet still compensates for tunnel window misalignment. The inventive method accomplishes this by removing a portion of the field oxide layer surrounding an initial active region before depositing the BN+ diffusion layer. This step is performed in order to enlarge the area in which the BN+ diffusion layer is formed to beyond the perimeter of the tunnel window forming a final active region. As a result, the method of the present invention ensures that the tunnel window is fully enclosed by the BN+ diffusion layer despite any tunnel window misalignment that may occur. Reducing the initial active region creates an EEPROM cell with a reduced cell pitch while increasing its coupling ratio.

Abstract: A semiconductor non-volatile memory device is disclosed which is based on the use of Fowler-Nordheim electron tunneling to charge and discharge the isolated gates of the storage cells. The disclosed memory device includes circuitry capable of verifying the threshold level of written storage cells and rewriting only those cells whose threshold is outside a desired threshold range. The disclosed circuit has the further advantage of being able to load data words and verify cell contents simultaneously by utilizing both ends of the bit lines.

Abstract: A high speed memory cell current measurement circuit uses an on-chip reference current circuit that generates a reference current Iref. The reference current circuit includes a first current source transistor. An on-chip current comparison circuit has a second current source transistor that is coupled to the first current source transistor so as to mirror the reference current Iref at a fixed current ratio WR. The current comparison circuit has a current connection path connecting the second current source transistor to a memory cell in the semiconductor memory device whose current is to be compared with Iref/WR. The memory cell is selected from the cells in a memory array using the device's on-chip address decoder circuitry. An on-chip result generation subcircuit, coupled to the current connection path between the second current source transistor and the memory cell, produces a Result signal that indicates whether current flowing through the memory cell is more or less than Iref/WR.

Abstract: A byte-programmable/byte-erasable flash memory system having on-chip counters and secondary storage for word line and bit line disturbance control during program and erase operations. The counters count the numbers of program/erase cycles and compare them with empirically pre-determined counter limits; when the program/erase count exceeds the counter limit, the data then carried in the system are temporarily transferred onto the secondary storage while the memory array is refreshed and the counters are reset. The lifetime of the resulting flash memory system is improved because of decreased erase and program stresses in the memory array.

Abstract: A semiconductor non-volatile memory device is disclosed which is based on the use of Fowler-Nordheim electron tunneling to charge and discharge the isolated gates of the storage cells. Furthermore, the disclosed memory device includes global decoder circuitry capable of passing either positive or negative voltages to a set of global word lines controlling-local decoder circuitry, said local controller circuitry in turn controlling row select lines or local word lines. Each local decoder controls a multiplicity of word lines. The local decoder circuitry is located in physical proximity to specific memory sectors thus resulting in an improved layout of the decoder circuitry and enabling the selection of one of the multiplicity of word lines within said sector by means of electrical control lines. The electrical control lines select one of the multiplicity of rows within a memory sector and deselect all the remaining rows. Logic control circuitry is provided to control the logic of the local row decoders.