Abstract: A method of reading a flash memory (EEPROM) device by applying zero volts to all bitlines and substrate terminal in the flash memory device, a positive voltage of between 4 to 5 volts is applied to the wordline to which the cell being read is attached and a voltage of less than equal to 2 volts is applied to the common source terminal.

Abstract: A method and apparatus for reducing band-to-band currents during the erasure of a flash EEPROM memory cell is provided. The apparatus has a back biasing connection on the substrate at which a biasing voltage is applied during erasure of the flash EEPROM memory cell. The method of applying the biasing voltage to the back biasing connection during erasure of the flash EEPROM memory cell reduces band-to-band current between the source region and the substrate during erasure of the flash memory cell. This reduction provides for gate size reduction in flash memory cells without inducing detrimental short channel effects.

Abstract: A method for erasing a flash EEPROM cell by applying a voltage differential between the control gate and the well of the memory cell. The voltage differential can be a ramped or stepped voltage applied to the control gate, a ramped or stepped voltage applied to the well, or a ramped or stepped voltage applied to the control gate and a ramped or stepped voltage applied to the well. The ramped voltages can have a constant slope or the slope can vary. The stepped voltages can be incremented equally or unequally. The voltages applied to the well or to the control gate is ramped or stepped until a selected number of memory cells verify as erased at which time the voltages applied to the well or to the control gate is clamped until the erase procedure is finished.

Abstract: A method for sensing the state of erasure of a flash (EEPROM) memory device. In one embodiment, the source voltage during erase is monitored and compared to a value determined during a characterization procedure. In a second embodiment, the rate of change of the source voltage during erase is determined and compared to a value determined during a characterization procedure. The characterization procedure correlates state of erasure with source voltages and slopes of the rate of change of source voltage versus time curve for the memory cells. The determination of the source voltage and the determination of the rate of change of the source voltage and the associated state of erasure allows modification of the erase procedure.

Abstract: A method to tighten the threshold voltage distribution curve in a memory device composed of multiple memory cells organized in rows and columns by soft programming each memory cell. Soft programming voltages that utilize the hot-carrier mechanism are selected and are applied sequentially to memory cells in wordlines. The soft programming voltages include a ramped voltage VGS of <3 volts, a VDS of <5 volts and a Vsub of <0 volts. The soft programming voltages are applied for a time period of <10 microseconds. The VT distribution is reduced to a maximum width of <2 volts. The soft programming is applied to the memory cells after the memory cells have been verified as having been erased and a having been overerase corrected.

Abstract: A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM) includes a plurality of floating gate transistor memory cells, a plurality of wordlines connected to the cells and a power supply for generating erase pulses. A controller controls the power supply to apply an erase pulse to all wordlines which are not deselected. Then, an erase verify procedure is applied to the cells in sequence. If all cells connected to a wordline pass the erase verify test, the wordline is deselected such that subsequent erase pulses will not be applied to the wordline and possibly cause the cells to become overerased. In one embodiment of the invention, erase verify is performed on all of the cells after an erase pulse is applied. The erase operation is completed when all cells pass erase verify. In another embodiment, erase verify is applied to each cell in sequence, with erase pulses being applied until each current cell passes erase verify. The wordlines can be deselected individually or in groups.

Abstract: A method of and a flash memory device for quenching bitline leakage current during programming and over-erase correction operations. The flash memory cells are organized in an array of I/O blocks with each block having columns and rows. An array of resistors is connected between the common array source connection and ground. The array of resistors is made up of sets of resistors, each set having a programming mode resistor and an APDE mode resistor. A data buffer switches either a programming mode resistor or APDE mode resistor into the circuit when a bitline is selected for either programming or APDE. The values of the resistors are selected to raise the voltage at the source above a selected threshold voltage of the memory cells so that over-erased cells will not provide leakage current to the bitline during either programming or APDE.

Abstract: A strip of a semiconductor material (for example, P type silicon) is oxidized and the resulting strip of oxide is removed leaving a depression in the upper surface of the semiconductor material which has steep sidewalls. The steep sidewalls do not have significant ion impact damage because they are formed by oxidation and not by reactive ion etching of the semiconductor material. A high quality tunnel oxide can therefore be grown on the steep sidewalls. Floating gates are then formed on the tunnel oxide, corresponding word lines are formed over the floating gates, a conductive region (for example, N type silicon) is formed into the bottom of the depression, and a number of conductive regions (for example, N type silicon) corresponding with the floating gates are formed above the rim of the depression. The resulting bit transistors have channel regions which extend in a vertical dimension under floating gates along the surface of the sidewall.

Abstract: A method and apparatus for reducing band-to-band currents during the erasure of a flash EEPROM memory cell is provided. The apparatus has a back biasing connection on the substrate at which a biasing voltage is applied during erasure of the flash EEPROM memory cell. The method of applying the biasing voltage to the back biasing connection during erasure of the flash EEPROM memory cell reduces band-to-band current between the source region and the substrate during erasure of the flash memory cell. This reduction provides for gate size reduction in flash memory cells without inducing detrimental short channel effects.

Abstract: A strip of a semiconductor material (for example, P type silicon) is oxidized and the resulting strip of oxide is removed leaving a depression in the upper surface of the semiconductor material which has steep sidewalls. The steep sidewalls do not have significant ion impact damage because they are formed by oxidation and not by reactive ion etching of the semiconductor material. A high quality tunnel oxide can therefore be grown on the steep sidewalls. Floating gates are then formed on the tunnel oxide, corresponding word lines are formed over the floating gates, a conductive region (for example, N type silicon) is formed into the bottom of the depression, and a number of conductive regions (for example, N type silicon) corresponding with the floating gates are formed above the rim of the depression. The resulting bit transistors have channel regions which extend in a vertical dimension under floating gates along the surface of the sidewall.

Abstract: A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM) includes a plurality of field effect transistor memory cells each having a source, drain, floating gate and control gate, and a power source for supplying a plurality of voltages to the cells. A controller controls the power source to apply at least one erase pulse to the cells. Then, at least one overerase correction or "soft programming" pulse is applied to the cells during which the source, drain and control gate voltages of the cells are such that the threshold voltages of overerased cells will be increased, but least erased cells will not be disturbed. The overerase correction pulses thereby tighten the threshold voltage distribution. A source to substrate bias voltage is applied for the duration of the overerase correction pulses which reduces the background leakage of the cells to a level at which the overerase correction operation can be effectively performed, even in applications with low supply voltages.

Abstract: A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM) includes a semiconductor substrate, and a plurality of field effect transistor memory cells each having a source, drain, floating gate and control gate formed on the substrate. A controller controls a power source to apply an operational pulse to the drain of a cell, and apply a source to substrate bias voltage to the cell while the operational pulse is being applied thereto, the bias voltage having a value selected to reduce or substantially eliminate leakage current in the cell. The operational pulse can be an overerase correction pulse. In this case, a voltage which is substantially equal to the bias voltage is applied to the control gate for the duration of the overerase correction pulse. The operational pulse can also be a programming pulse. In this case, a voltage which is higher than the bias voltage is applied to the control gate of the selected wordline for the duration of the programming pulse.

Abstract: There is provided an improved method for eliminating hot-carrier disturb during a read operation in a NAND memory architecture in which a floating gate device is used as a select gate. A first positive pulse voltage having a ramp-rate characteristic on its leading edge is applied to the drain of the floating gate device during the read operation. Simultaneously, a second positive pulse voltage is applied to the control gate of the floating gate device during the read operation so as to overlap the first positive pulse voltage.

Abstract: There is provided a novel method for performing low current channel hot-carrier programming in a NAND memory architecture. A first positive pulse voltage having a ramp-rate characteristic on its leading edge is applied to the drain of the select gate drain devices in the selected columns of bit lines during the programming operation. Simultaneously, a second positive pulse voltage is applied to the control gate of the select gate drain device and to the word lines of unselected memory cells so as to overlap the first positive pulse voltage. Further, a ramp voltage is applied to the word line of selected memory cells so as to permit fast programming thereof.

Abstract: There is provided an improved method for performing channel hot-carrier programming in an array of multiple bits-per-cell Flash EEPROM memory cells in a NOR memory architecture so as to eliminate program disturb during a programming operation. The array has a plurality of memory cells arranged in rows of word lines and columns of bit lines intersecting the rows of word lines. A programming current source is connected to the source of selected memory cells that are to be programmed in the corresponding columns of bit lines. A programming gate voltage is applied to control gates of the selected memory cells, and a programming drain voltage is applied simultaneously to the common array ground line connected to the drains of all of the memory cells. Further, a relatively low voltage is applied simultaneously to all of the control gates of non-selected memory cells in the array which are not to be programmed during the programming operation so as to eliminate the program disturb.

Abstract: An improved programming structure for performing a program operation in an array of multiple bits-per-cell flash EEPROM memory cells is provided. A memory core array (12) includes a plurality of memory cells and a reference cell array (22) having a plurality of reference core cells which are selected together with a selected memory core cell. A precharge circuit (36a) is used to precharge all of the array bit lines and the reference bit lines to a predetermined potential prior to a program operation. A reference generator circuit (134) is used for selectively generating one of a plurality of target memory core cell bit line program-verify voltages, each one corresponding to one of a plurality of programmable memory states. A switching circuit (P1,N1) is used to selectively connect a program current source to the selected certain ones of the columns of array bit lines containing the selected memory core cells which are to be programmed.

Abstract: A floating gate cell memory device, such as an EPROM or flash EEPROM, with improved discharge speed. A negative bias is applied to the effective substrate during discharge. The negative bias increases the electric field near the junction, thereby increasing the number of hot holes which can be injected to the floating gate, improving discharge speed.

Abstract: A floating gate cell memory device, such as an EPROM or flash EEPROM, with improved discharge speed. A negative bias is applied to the effective substrate during discharge. The negative bias increases the electric field near the junction, thereby increasing the number of hot holes which can be injected to the floating gate, improving discharge speed.

Abstract: Disclosed herein is a channel hot-carrier page write including an array of stacked gate flash EEPROM memory cells operating in a very low energy programming mode permitting page writing of 1024 bits within a 20-100 .mu.S programming interval. Internal programming voltage levels are derived from on-chip circuits, such as charge pumps, operated from a single +V.sub.CC source. In a preferred embodiment, a cache memory buffers data transfers between a computer bus and the page oriented storage array. In another embodiment, core doping is increased in the channel and drain regions to enhance hot carrier injection and to lower the programming drain voltage. The stacked floating gate structure is shown to exhibit a high programming efficiency in a range from 10.sup.-6 to 10.sup.-4 at drain voltages below 5.2 VDC. In another embodiment AC components of the programming current are minimized by precharging a common source line at the start of a programming cycle.

Abstract: There is provided an improved method for bulk (or byte) programming an array of flash EEPROM memory cells. A negative voltage is applied to the substrate of the array. A reference voltage of zero volts is applied simultaneously to the drain regions of selected memory cells that are to be programmed. There is also applied simultaneously the same reference voltage of zero volts to the control gates of the selected memory cells. The present invention provides for low current consumption and fast programming of the memory cell, which require only a single, low voltage power supply. The endurance reliability is greater than 100,000 cycles.