Eon Silicon Devices, Inc.

Advanced Micro Devices Corporation

National Semiconductor Corporation

James C Yu

Yuan Tang

Chi K Chang

Chien-Sheng Su

Chih-Liang Chen

Johnny C Chen

Michael S Briner

Chung K Chang

I-Chuin Peter Chan

Suman H Patel

Pearl P Cheng

Jeffrey W Anthony

Tiao Hua Kuo

Chao-Ven Kao

A unified program method and circuitry for performing concurrently a programming and verifying operation in an array of Flash EEPROM memory cells is provided. Each of the memory cells includes a floating gate array core transistor. A single bandgap voltage is provided which corresponds to a predetermined amount of drain current at which programming is to be terminated. A program voltage is selectively connected to at least one of the columns of array bit lines containing the array core transistor which is to be programmed. A control gate bias voltage corresponding to a programmable memory state is selectively connected to the gate of the array core transistor. A core cell current flowing through the array core transistor and the predetermined amount of drain current is compared. The program voltage is disconnected so as to terminate automatically programming of the array core transistor when the core cell current falls below the predetermined amount of drain current.

Unified program method and circuitry in flash EEPROM

An output noise control circuit with significantly reduced power/ground bounce characteristics when multiple outputs thereof are being simultaneously switched is provided. The output noise control circuit includes a plurality of output buffers each being formed of an output driver stage, a first pre-driver stage, and a second pre-driver stage. Each of the output driver stages includes a pull-up drive transistor and a pull-down drive transistor. Each of the first pre-driver stages includes a first inverter, and each of said second pre-driver stages includes a second inverter. A shared pull-up resistor has its one end coupled to each of the first pre-driver stage inverters and its other end connected to a ground potential node. A shared pull-down resistor has its one end coupled to each of the second pre-driver stage inverters and its other end connected to a power supply potential node. The output noise control circuit is formed with a reduced number of circuit components than the traditional output buffer circuits currently available.

Output noise control scheme for multiple I/O's

A unified erase method used in an array of flash EEPROM memory cells arranged in a plurality of sectors for performing either a single-sector, multiple-sector, or all-sector erasing operation with a reduced amount of total erase time and a uniform V,distribution as good as that of a single-sector erase operation is provided. An erase-verify operation is performed sequentially on the plurality of sectors from a first sector to a last sector beginning with a first address of each sector if its corresponding erase-on signal is not turned OFF. The current address of each sector is stored at a point where the erase-verify operation failed. An erase pulse is applied only to all sectors simultaneously that have not passed the erase-verify operation. The erase-verify operation is then repeated beginning at the current address stored. The erasing operation is terminated when the erase-on signal has been turned OFF in all sectors in the plurality of sectors.

Unified erase method in flash EEPROM

There is provided a method of correcting overerased memory cells in a flash EEPROM memory cell after erase so as to produce a narrow threshold voltage distribution width. A ground potential is applied to all of the sources and substrates of the cells in the array of memory cells. First positive pulse voltages are simultaneously applied to each word line in a first timed sequence on a word line by word line basis. A second positive pulse voltage is simultaneously applied to each bit line in a second timed sequence in a bit line by bit line basis when the first positive pulse voltages are being applied to a first word line and is then repeated for each subsequent word line until a last word line is applied.

Method of achieving narrow V.sub.T distribution after erase in flash

A FLASH EPROM cell in accordance with the present invention is disclosed in which the erasure is accomplished under a constant electric field. The FLASH EPROM cell includes a semiconductor device including a source, a drain and a gate and a constant current circuit coupled to the source. The constant current circuit ensures that a constant field is applied to the tunneling oxide of the FLASH EPROM cell during erasure thereof. In so doing, the FLASH EPROM cell can be erased with a minimum of stress to the device. In addition, the FLASH EPROM cell of the present invention can be used with various power supplies without affecting the characteristics thereof. Finally, through the FLASH EPROM cell of the present invention, the short channel effect associated with smaller device sizes can be substantially reduced.

System for constant field erasure in a FLASH EPROM

The invention is a novel erase method for erasing flash EEPROM memory devices. A memory cell of such a memory device has a first semiconductor region of one conductivity type formed in a second region of the opposite conductivity type, source and drain regions of the opposite conductivity type formed in the first semiconductor region, and a gate. The second region is formed within a substrate of the one conductivity type. The gate includes a control gate and a floating gate, which retains charge and overlies the first semiconductor region. The erase method of the invention includes the steps of: applying a first voltage of one polarity to the source region and the first and second semiconductor regions; and simultaneously applying a second voltage of the opposite polarity to the gate, whereby any charge on the floating gate tunnels through the floating gate dielectric into both the first region and the source region, thereby removing any charge retained by the floating gate.

Method of erasing a flash EEPROM memory

A programming algorithm for a flash memory wherein programming circuitry is subdivided into a set of separately controllable groups. The algorithm detects a number of logic zeros to be programmed into a flash cell array by each group and switches among the groups such that a number of simultaneously programmed cells in the flash cell array does not exceed a predetermined number and such that maximum available programming current is used to enhance programming speed.

Program algorithm for low voltage single power supply flash memories

System for constant field erasure in a flash EPROM

To provide a boundaryless burst mode access, a memory array is divided into two or more subarrays. Each subarray has its own row and column decoders. The columns of each subarray are divided into groups. A sense amplifier circuit is provided for each group of columns. The column decoder of each subarray selects simultaneously one column from each group so that the memory locations in one row in the selected columns have consecutive addresses. The memory locations in the selected row and columns are read by the sense amplifier circuits. While the contents of the sense amplifier circuits of one subarray are transferred one by one to the memory output, consecutive memory locations of another subarray are read to the sense amplifier circuits. In some embodiments, to save power, sense amplifier circuits are disabled when their outputs are not transferred to the memory output.

Memories with burst mode access

A CMOS gate protection diode clamping the input terminal to substrate potential is prevented from injecting carriers into the substrate and causing SCR latchup by forming the diode as a well to substrate junction, surrounded by another, reverse-biased, well, to both reduce injection and collect parasitic injected carriers before they can diffuse to cause latchup.

Growing community of inventors

San Jose, CA, United States of America

James C Yu