Browse Prior Art Database

Array Cell Stability Monitor

IP.com Disclosure Number: IPCOM000049584D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Klein, W: AUTHOR [+4]

Abstract

Each wafer with integrated memory chips comprises, in addition to product chips, so called test sites and a plurality of test structures in the kerf. The test site is adapted to the respective product chip; i.e., it has test structures made up of the elements and circuits contained in the product chip. For deriving the chip parameters from the test structures of the test sites or the kerfs, very elaborate test systems and evaluator programs as well as experts for interpreting the test data are required.

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Array Cell Stability Monitor

Each wafer with integrated memory chips comprises, in addition to product chips, so called test sites and a plurality of test structures in the kerf. The test site is adapted to the respective product chip; i.e., it has test structures made up of the elements and circuits contained in the product chip. For deriving the chip parameters from the test structures of the test sites or the kerfs, very elaborate test systems and evaluator programs as well as experts for interpreting the test data are required.

As cell stability is a very important factor, which, in particular for MTL (merged transistor logic) array structures, is primarily determined by the dumbbell resistance and the size of the top collector, simple means are described for testing cell stability.

The test circuit to be used for the test site or kerf consists of three independent ring oscillators. Each of these oscillators is formed by an odd number of inverter stages A, an output amplifier V, and a current source I, as shown in the figure. The inverter stage A consists of suitably wired array half cells. As each cell half may have different characteristics because of the layout arrangement, both types of half cells are used for the ring oscillators. The top collector size for each of the three oscillators is varied by plus/minus one sigma of the admissible tolerance range.

The tests to be conducted with the three oscillators merely serve to determine whether and which of t...