Integrated circuit with channel length indicator
AssigneeAmerican Telephone and Telegraph Company, AT&T Bell Laboratories
InventorsJohn A. Carelli, Richard A. Pedersen, Robert L. Pritchett
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Abstract
An integrated circuit includes first and second field effect transistors having differing channel lengths, and a means for comparing the channel currents flowing therethrough. An excessive difference of currents indicates "short channel" effects, which can degrade performance. A signal flag indicating this condition may be provided to a test pad on the chip, or used to disable operation of the integrated circuit, or otherwise used to provide an indication.
Claims9
An integrated circuit comprising a plurality of field effect transistors, characterized in that said integrated circuit comprises:
- a test field effect transistor (T1) having a test channel length (L1) and a reference field effect transistor (T2) having a reference channel length (L2) that is large compared to said test channel length, whereby fabrication variations that cause a change in the channel lengths produce a relatively large change in the gain of said test transistor as compared to the change in the gain of said reference transistor;
- means adapted to cause a current to flow through the channels of said test and said reference transistors;
- and a comparator having first and second inputs coupled to said test and reference transistors, respectively, whereby said comparator produces a test signal having a first output voltage state when said test channel length is less than a given amount, and a second output voltage state when said test channel length is greater than said given amount, whereby the output voltage state of said comparator is determined by the fabrication of said integrated circuit.
Dependencies are inferred from the claim text.