International Business Machines Corporation

Timothy J Koprowski

Franco Motika

Mary Prilotski Kusko

William Vincent Huott

Patrick M West, Jr

John G Rell, Jr

Timothy Gerard McNamara

James Raymond Cuffney

Cedric Lichtenau

Peilin Song

Gregory J Cook

Donald Lawrence Wheater

Pradip Patel

Brion L Keller

Richard Frank Rizzolo

Phillip J Nigh

Bryan J Robbins

Bernd K Koenemann

Ulrich Baur

Lawrence Kenneth Lange

L Owen Farnsworth

Thomas James Snethen

Paul N Keller

An apparatus for comparing strings comprises a first and a second set of input registers, a matrix of comparator circuits wherein rows of the matrix correspond to the first set of input registers and columns of the matrix correspond to the second set of input registers, a set of row control registers wherein each register corresponds to a row of the matrix of the comparator circuits, the matrix of comparator circuits configured to compare data provided by the first set of registers with data provided by the second set of registers according to the row control registers, and an error detection circuit configured to compare results from four comparator circuits corresponding to two adjacent rows and two columns of the matrix of comparator circuits. A method that invokes the above mentioned apparatus is also disclosed herein, along with a computer program product corresponding to the method.

String dataflow error detection

Embodiments relate to design-based weighting for logic built-in self-test (LBIST). An aspect includes a computer program product for implementing design-based weighting for LBIST. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes analyzing, by the processing circuit, a plurality of integrated circuit design organizational units to determine preferred weightings of the integrated circuit design organizational units that provide a highest level of failure coverage when applied to a random pattern generator. Based on determining the preferred weightings, the processing circuit creates an integrated circuit layout that includes a plurality of weighted test paths to respectively apply the preferred weightings to the integrated circuit design organizational units. The integrated circuit layout is incorporated in a device under test.

Design-Based weighting for logic built-in self-test

Embodiments relate to design-based weighting for logic built-in self-test (LBIST). An aspect includes an integrated circuit development system for implementing design-based weighting for LBIST. The system includes a memory system to create an integrated circuit layout. A processing circuit is coupled to the memory system. The processing circuit is configured to execute integrated circuit development tools to perform a method. The method includes analyzing, by the processing circuit, a plurality of integrated circuit design organizational units to determine preferred weightings of the integrated circuit design organizational units that provide a highest level of failure coverage when applied to a random pattern generator. Based on determining the preferred weightings, the processing circuit creates an integrated circuit layout that includes a plurality of weighted test paths to respectively apply the preferred weightings to the integrated circuit design organizational units. The integrated circuit layout is incorporated in a device under test.

Design-based weighting for logic built-in self-test

Flat pseudo random test patterns are provided in combination with weighted pseudo random test patterns so that the weight applied to every latch in a LSSD shift register (SR) chain can be changed on every cycle. This enables integration of on-chip weighted pattern generation with either internal or external weight set selection. WRP patterns are generated by a tester either externally or internally to a device under test (DUT) and loaded via the shift register inputs (SRIs or WPIs) into the chip's shift register latches (SRLs). A test (or LSSD tester loop sequence) includes loading the SRLs in the SR chains with a WRP, pulsing the appropriate clocks, and unloading the responses captured in the SRLs into the multiple input signature register (MISR). Each test can then be applied multiple times for each weight set, with the weight-set assigning a weight factor or probability to each SRL.

Pseudo random optimized built-in self-test

LBIST and weighted LBIST tests are performed simultaneously on different portions of the tested object. This new test methodology and design change achieves the same test coverage and test time as the traditional test strategy with dramatic power reduction during test. It can be applied at wafer, chip, MCM, and system levels of test. Most importantly, it does not need new tools for support. Current test software will work as it does with the traditional test strategy. Scheduling the LBIST and weighted LBIST tests in the same test session reduces the overall power consumption because weighted LBIST testing consumes much less power than flat LBIST testing. In the same test session, if some parts of the logic is tested using weighted LBIST while the others were tested using LBIST, the power consumed by the circuit element at any given time is reduced.

VLSI chip test power reduction

Deterministic random Logic Built In Self Test (LBIST) is disclosed that applies Deterministic Stored Pattern Tests (DSPTs) by using random LBIST. Basically, the present invention selects the appropriate pseudorandom pattern for use with a scan cycle that needs care bits. The scan cycle may be a current or future scan cycle. In particular, the present invention determines care bits for a particular scan cycle. A pseudorandom pattern is generated that is then aligned with the particular scan cycle. If the pseudorandom pattern contains the care bits, with the correct values and in the proper positions within the pattern, this alignment tests one or more logic devices.

Deterministic random LBIST

An exemplary embodiment of the invention is a built-in self-test (BIST) method and apparatus for testing the logic circuits on an integrated circuit. Random test pattern data is generated by a random pattern generator. A random resistant fault analysis (RRFA) program is used to determine the weighting requirements, on a per channel basis, for testing the logic circuits. The weighting requirements from the RRFA program are applied to the random test pattern data resulting in weighted test pattern data. The weighted test pattern data is then programmably applied to the scan chain.

Method and apparatus for programmable LBIST channel weighting

An exemplary embodiment of the invention is a method and apparatus for delaying the start of an array built-in self-test (ABIST) until after the ABIST memory arrays have been started. The length of the delay is determined by the value in a programmable delay located on the integrated circuit. The initiation of the ABIST test is delayed by the time specified in the programmable delay.

Method and apparatus for delaying ABIST start

This invention describes a method and apparatus, contained within an integrated circuit, for isolating failure by precisely controlling the number of clocks applied during built-in self-test (BIST). A programmable clock counter, on the integrated circuit, stores a specified number of clock cycles and sends a signal to stop a BIST engine once the specified number of clock cycles have been generated. The intermediate results can then be mapped bit by bit in order to isolate the cause of failure.

Method and system for at speed diagnostics and bit fail mapping

LBIST resource parameters are used to control the data inputs for the signature generation process. These resource parameters include a LBIST pattern cycle counter, a channel input selected to input the MISR, and a channel load/unload shift counter. Properly setting one or more of these resource parameters to conditionally control those latch content values that get clocked into the MISR during the unload operation generates a three dimensional signature space.

Logic built-in self test selective signature generation

The present invention can include a method and system for testing IC chips, including the steps of performing a binary search to a first failing pattern, determining a failing sink latch, performing a back cone trace to determine all source latches, determining source latch logic states, positioning the source latch logic states in a scan chain, exercising a chip scan path by applying logic transitions on the source latches in the absence of a system L1 clock, and observing an exercised failing circuit. The invention can include the use of PICA techniques to observe the exercised failing circuit. In another embodiment, the invention can include using LBIST or a WRP technique to search for the failing pattern. In yet another it includes the step of using an algorithm to exercise the exercised failing circuit. In another embodiment, the method includes the step of creating a net pattern to be scanned including a sum of an original pattern causing a failing circuit to be exercised, and one or more shifted versions of the original pattern. The algorithm can include a step where one of the shifted versions is shifted a number of clocks wherein the number of clocks is equal to the length of the original pattern. In one embodiment, one of the shifted versions is shifted a number of clocks, wherein the number of clocks is chosen so that the sum of the original pattern and the one of the shifted versions does not cause a scan conflict. In another embodiment the method further includes the step of using an algorithm to densify the pattern set.

Technique to decrease the exposure time of infrared imaging of semiconductor chips for failure analysis

A BIST method that modifies the scan chain path and scan clocks to allow for distributed BIST test. In this distributed BIST concept, the Linear Feedback Shift Register (LFSR) and the Multiple Input Signature Register (MISR) are combined as an integral part of the scan chain, and each scan cycle is utilized as a test cycle.

Logic built-in self test

A method of LBIST testing of an entire chip (i.e. all logic and arrays are getting system clocks) enables finding intermittent fault in an area, such as the L1 cache. Latches such as GPTR latches can be set such that the L1 cache will no longer receive system clocks during LBIST testing. Logic causing an intermittent failure will no longer receive system clocks and hence will no longer cause intermittent LBIST signatures. LBIST testing can proceed on looking for the next failure, if one existed, or proving that the remaining logic contains no faults. Generally, a chip, has a basic clock distribution and control system that the chip is divided into a number (N) of functional units with each unit receiving system clocks from its own clock control macro. Each clock control macro receives an oscillator signal and a bit from the GPTR (General Purpose Test Register). All the functional units contain latches that are connected into one scan chain.

Growing community of inventors

Newburgh, NY, United States of America

Timothy J Koprowski