Integrated Silicon Solution Incorporated

Nexflash Technologies, Inc.

Hsi-Hsien Hung

Eungjoon Park

Eung Joon Park

Ker-Ching Liu

Fungioon Park

A row decoder for a nonvolatile memory having a low-voltage power supply that minimizes the load capacitance presented to a high voltage source without requiring additional circuitry. The row decoder accomplishes this by providing a local decoder having only one input requiring a boosted voltage higher than the power supply voltage. Further, predecoders are used to reduce the number of local decoders that receive the boosted voltage.

Row decoder for nonvolatile memory having a low-voltage power supply

A voltage pump circuit includes a native MOS device coupled as a charge transfer device (M1) between input and output stage nodes. A parallel-coupled MOS pair (M2, M3) is coupled between drain (input node) and source (output node) of the charge transfer device, in which M3 is configured as a diode. A clock generator outputs at least three non-overlapping phase signals: .phi.1 (which goes high at t1 and low at t6), .phi.2 (which goes high at t3 and low at t4), .phi.3 (which goes low qt t2 and high at t5). The t1 .phi.1 positive transient is AC-coupled to M1's drain, and a smaller fraction of the transient is coupled to M1's gate, precharging M1, which begins to turn-on. The .phi.3 t2 negative transient is AC-coupled to M1's source, increasing M1 gate-source potential, which more fully turns-on M1. The .phi.2 t3 positive transient is coupled to M1's gate, turning-on M1 very hard. A phase clock generator outputting square-wave, same-frequency signals having respective 90.degree. phase shifts that are frequency independent can be used to drive pump circuits and sequentially operated groups of pump circuits.

Charge pump system with improved programming current distribution

A sub-bit line architecture for non-volatile memory devices. Four sub-bit lines are coupled to each main bit line. The sub-bit lines are approximately one half the length of the main bit lines in each sector. This sub-bit line length provides low parasitic capacitance and high signal integrity. Each sub-bit line is coupled to a main bit line through a select transistor. A column latch is coupled to each main bit line to provide program data. Data is programmed to the memory array in a page program mode. In page program mode, the selected sub-bit line applies a programming voltage to the memory cell transistor drain terminals. The drain voltage is applied to all of the memory cell transistor drains coupled to the selected sub-bit line. Since the sub-bit lines are only half the length of the main bit lines in each sector, the number of memory cell transistors coupled to each sub-bit line is about half the number coupled to sub-bit lines that are the length of the main bit line. As a result, the number of times memory cell transistors are disturbed due to increases in drain voltage caused by the sub-bit line being selected is reduced. A further advantage of the present invention is that program disturb is reduced.

Divided bit line system for non-volatile memory devices

An improved charge transfer stage with an expanded output voltage range and high charge transfer efficiency is described. The charge transfer stage can be implemented as an output stage in a four phase clock negative charge pump system. The charge transfer stage comprises a PMOS pass transistor coupling the transfer stage input and output, a resistor between the transfer stage input and the pass transistor gate, a clock terminal, a capacitor configured PMOS transistor coupling the clock terminal to the gate of the pass transistor, and a diode from the transfer stage output to ground. When the transfer stage input goes low, charge is coupled through the resistor to pre-charge the gate of the pass transistor. The resistor has a higher junction breakdown voltage than a transistor which allows the gate of the pass transistor to be driven to a larger voltage. To provide sufficient charge to turn on the pass transistor, a logic high level greater than the power supply, such as 2 VCC, can be used for the clock signal coupled through the capacitor configured transistor to the gate of the pass transistor. To prevent the 2 VCC logic high level from forward biasing the p-n junction formed by the source and drain of the PMOS capacitor configured transistor with the well, the source, drain and well are coupled together. The charge transfer stage also includes a p-n junction diode coupled from the output of the stage to ground.

High voltage charge transfer stage

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 global decoder circuitry capable of passing either positive or negative voltages to a set of global word lines controlling, local decoder circuitry. The local decoder includes a set of word line drivers, each of which sets the voltage level of a corresponding local word line in response to the voltage levels of its associated global word line and a collection of control signals. Each word line driver includes one p-channel transistor and two n-channel transistors. These three transistors collectively establish selected local word lines at appropriate voltages for erase, program and read operations. The three transistors also establish unselected local word lines at solid bias voltages that prevent disturbance of memory cells that are not the target of a memory operation.

Local row decoder for sector-erase fowler-nordheim tunneling based flash

The present invention is a space efficient redundant column decoder circuit for use in a non-volatile memory device. The redundant column decoder compares a n-bit stored defective address with a n-bit presented address. Based on this comparison, an output signal is generated. This output signal is used both to specify the redundant column (or set of columns) associated with the redundant column decoder circuit, and to de-activate all of the other column decoders in the device. The redundant column decoder has a pull-up path and a parallel combination of n pairs of complementary pull-down paths. The pull-up path is connected to the pull-down paths at an output node, and the output signal is taken at this output node. Each pair of complementary pull-down paths has a first pull-down path and a second pull-down path. The first pull down path has a first non-volatile memory cell in series with and connected to a first address transistor. The first address transistor is also connected to the output node. The second pull-down path has a second non-volatile memory cell in series with and connected to a second address transistor. The second address transistor is also connected to the output node. At least one of the pull-down paths is conductive when the stored defective address does not match the presented address. Conversely, all of the pull-down paths are non-conductive when the stored defective address matches the presented address.

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Fremont, CA, United States of America

Hsi-Hsien Hung