International Business Machines Corporation

Rahul M Rao

Jae-Joon Kim

Aditya Bansal

Ching-Te Kent Chuang

Kevin John Nowka

Keith Aelwyn Jenkins

Rajiv V Joshi

Shih-Hsien Lo

Harmander Singh Deogun

Jente Benedict Kuang

Sani Richard Nassif

Elad Alon

Robert Matthew Senger

Jeffrey L Burns

Pong-Fei Lu

Saibal Mukhopadhyay

Amlan Ghosh

Dhruva J Acharyya

Tae-Hyoung Kim

Shao-yi Wang

Methods and systems for computing threshold voltage degradation of transistors in an array of memory cells are disclosed. In accordance with one method, a process that models an expected usage of the array is selected. In addition, a hardware processor can run the process to populate the array with data over time to simulate the expected usage of the array. The method further includes compiling data that detail different durations at which each of the memory cells in the array stores 1 or at which each of the memory cells in the array stores 0. For each separate grouping of memory cells that share a common duration of the different compiled durations, a threshold voltage degradation is determined for each transistor in the corresponding grouping of cells based on at least one biased temperature instability model.

Usage-based temporal degradation estimation for memory elements

A method for estimating delay deterioration in an integrated circuit comprising estimating degradation in at least one characteristic of each device defined within the integrated circuit using voltages and logic values monitored during a simulation of the digital circuit. Generating an end-of-life netlist in which the at least one device characteristic of each device has been modified to reflect the estimated degradation or estimating a change in timing delay of each device directly from the estimated degradation of the at least one characteristic of each device. A timing analysis is performed using the estimated change in timing delay of each device to determine circuit path delays. The timing analysis is static or statistical.

Estimating delay deterioration due to device degradation in integrated circuits

A memory circuit includes a plurality of bit line structures (each including a true and a complementary bit line), a plurality of word line structures intersecting the plurality of bit line structures to form a plurality of cell locations; and a plurality of cells located at the plurality of cell locations. Each of the cells includes a logical storage element, a first access transistor selectively coupling a given one of the true bit lines to the logical storage element, and a second access transistor selectively coupling a corresponding given one of the complementary bit lines to the logical storage element. One or both of the first and second access transistors are configured with asymmetric current characteristics to enable independent enhancement of READ and WRITE margins. Also included within the 6-T scope are one or more design structures embodied in a machine readable medium, comprising circuits as set forth herein.

Enhanced static random access memory stability using asymmetric access transistors and design structure for same

A circuit structure is provided for performing a logic function within a memory. A plurality of read word line transistors are provided that receive a read word line signal and, upon receiving the read word line signal, the plurality of read word line transistors provide a path from a plurality of bit-line transistors associated with a plurality of physically adjacent memory cells to a read bit-line. In response to an associated memory cell within the memory storing a first value, each of the plurality of read bit-line transistors turns on and provides a path to ground thereby causing a first output value to be output on the read bit-line. In response to all of the plurality of memory cells storing a second value, the plurality of read bit-line transistors turn off thereby preventing a path to ground and a second output value is output on the read bit-line.

Performing logic functions on more than one memory cell within an array of memory cells

A ring oscillator circuit for measurement of negative bias temperature instability effect and/or positive bias temperature instability effect includes a ring oscillator having first and second rails, and an odd number (at least 3) of repeating circuit structures. Each of the repeating circuit structures in turn includes an input terminal and an output terminal; a first p-type transistor having a gate, a first drain-source terminal coupled to the first rail, and a second drain source terminal selectively coupled to the output terminal; a first n-type transistor having a gate, a first drain-source terminal coupled to the second rail, and a second drain source terminal selectively coupled to the output terminal; and repeating-circuit-structure control circuitry. The ring oscillator circuit also includes a voltage supply and control block.

Monitoring negative bias temperature instability (NBTI) and/or positive bias temperature instability (PBTI)

A memory circuit includes a plurality of bit line structures (each including a true and a complementary bit line), a plurality of word line structures intersecting the plurality of bit line structures to form a plurality of cell locations and a plurality of cells located at the plurality of cell locations. Each of the cells includes a logical storage element, a first access transistor selectively coupling a given one of the true bit lines to the logical storage element, and a second access transistor selectively coupling a corresponding given one of the complementary bit lines to the logical storage element. One or both of the first and second access transistors are configured with asymmetric current characteristics to enable independent enhancement of READ and WRITE margins. Also included within the-T scope are one or more design structures embodied in a machine readable medium, comprising circuits as set forth herein.

An electronic circuit includes an output terminal and at least a first measuring FET. The second drain-source terminals of a plurality of FETS to be tested are interconnected with the first drain-source terminal of the first measuring FET and the output terminal. The second drain-source terminal of the first measuring FET is interconnected with a first biasing terminal. The first drain-source terminals of the FETS to be tested are interconnected with a second biasing terminal. A state machine is coupled to the gates of the FETS to be tested and the gate of the first measuring FET. The state machine is configured to energize the gate of the first measuring FET and to sequentially energize the gates of the FETS to be tested, so that an output voltage appears on the output terminal. Circuitry to compare the output voltage to a reference value is also provided. The gate of the first measuring field effect transistor is energized; the gates of the field effect transistors to be tested are sequentially energized, whereby an output voltage appears on the output terminal; and the output voltage is compared to the reference value.

Electronic circuit for measurement of transistor variability and the like

A static pulse bus circuit and method having dynamic power supply rail selection reduces static and dynamic power consumption over that of static pulse bus designs with fixed power supply rail voltages. Every other (even) bus repeater is operated with a selectable power supply rail voltage that is selected in conformity with a state of the input signal of the bus repeater. The odd bus repeaters are operated from the lower of the selectable power supply voltages supplied to the even repeaters. The odd bus repeaters may also be operated from a selectable power supply rail voltage opposite the selectable-voltage power supply rail provided to the even bus repeaters, in which case the opposing rail of the even bus repeaters is set to the higher of the voltages selectable in the odd bus repeaters.

Static pulsed bus circuit and method having dynamic power supply rail selection

Methods of operating an electronic circuit for measurement of transistor variability and the like

In a memory circuit, data from all cells along a selected word line is read. Then, the read data is written back to half-selected cells and new data is written to the selected cells in the next cycle. In cases where a READ bit line (RBL) and WRITE bit line (WBL) are decoupled, RBL and WBL can be accessed simultaneously. Hence, the WRITE in the n-th cycle can be delayed to the n+1-th cycle as far as there is no data hazard such as reading data from memory before correct data are actually written to memory. As a result, there is no bandwidth loss, although the latency of the WRITE operation increases. WRITE stability issues in previous configurations with decoupled RBL and WBL are thus addressed.

Memory circuit with decoupled read and write bit lines and improved write stability

A ring oscillator has an odd number of NOR-gates greater than or equal to three, each with first and second input terminals, a voltage supply terminal, and an output terminal. The first input terminals of all the NOR-gates are interconnected, and each of the NOR-gates has its output terminal connected to the second input terminal of an immediately adjacent one of the NOR-gates. During a stress mode, a voltage supply and control block applies a stress enable signal to the interconnected first input terminals, and an increased supply voltage to the voltage supply terminals. During a measurement mode, this block grounds the interconnected first input terminals, and applies a normal supply voltage to the voltage supply terminals. Also included are an analogous NAND-gate based circuit, a circuit combining the NAND- and NOR-aspects, a circuit with a ring oscillator where the inverters may be coupled directly or through inverting paths, and circuits for measuring the bias temperature instability effect in pass gates.

Circuits and design structures for monitoring NBTI (negative bias temperature instability) effect and/or PBTI (positive bias temperature instability) effect

A method and circuits for measuring operating and leakage current of individual blocks within an array of test circuit blocks provides measurement free of error due to leakage currents through non-selected circuit blocks, without requiring an independent test facility for each circuit block. The circuit includes a pair of power supply grids and selection circuits at each test circuit block to select between a test power grid and a 'rest' power grid used to supply current to the non-selected circuits. The leakage currents through the non-selected circuits are thus sourced from the rest grid and error that would otherwise be introduced in the test grid current measurement is avoided. The test circuit blocks may be ring oscillators, and the measured current may be the operating and/or leakage current of the ring oscillator. The circuit blocks may also include individual devices for IV (current-voltage) characterization using an additional gate input grid.

Method and circuit for measuring operating and leakage current of individual blocks within an array of test circuit blocks

Determining a slew rate of a signal from an integrated circuit under test by comparing the signal with a first reference voltage, comparing the signal with a second reference voltage different from the first reference voltage, generating an output pulse having a pulse width indicative of a slew rate of the signal, and integrating the output pulse over time to generate an output voltage proportional to the pulse width; wherein the output voltage is indicative of the slew rate of the signal produced by the integrated circuit.

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Elmsford, NY, United States of America

Rahul M Rao