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Identifying Transistor Leakage Currents in the Picoampere Range which are Attributable to Defects

IP.com Disclosure Number: IPCOM000050482D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Beck, S: AUTHOR [+2]

Abstract

As the integration density increases, the margin of tolerable leakage currents in the subnanoampere range of integrated transistors becomes smaller and smaller. At the same time, the yield requirements with regard to leakage currents are increased, so that the defect probability is of the order of w = 10/-5/ for each device.

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Identifying Transistor Leakage Currents in the Picoampere Range which are Attributable to Defects

As the integration density increases, the margin of tolerable leakage currents in the subnanoampere range of integrated transistors becomes smaller and smaller. At the same time, the yield requirements with regard to leakage currents are increased, so that the defect probability is of the order of w = 10/-5/ for each device.

For detecting the defect probability in the subnanoampere range, several transistor groups as a multiple of a basic group are connected in parallel on a test chip. Leakage current measurements in these groups yielding identical mean leakage current values I1 define the basic leakage current level. Deviations from this level indicate individual defects with a calculable probability and thus the leakage current distribution of such defects.

The number of transistors n in each group is to be about 1:2:3:4, etc. The smallest group is to have about n = 0.1/w transistors. Thus, most groups are without defects but have a leakage current Il proportional to the number of transistors they include, as shown in Fig. 1.

For groups without any defects, the leakage current Il is linearly dependent on the number of transistors. This is a prerequisite for measuring the basic leakage current level. An upward deviation from the leakage current of a group indicates an additional leakage current exceeding the basic level (Fig. 2). In this case, the increased leakage...