CIRCUIT STRUCTURE AS A Vt DEGRADATION MONITOR AND DIAGNOSTIC MEANS
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
Vt degradation is the continuous change of the threshold voltage of field-effect transistors (FETs). It is caused by mobile carriers in the form of impurities in semiconductor layers whose mobility increases as the operating temperature rises and which, by electric fields, are made to collect at particular points. In the absence of suitable monitoring and diagnostic means, Vt degradation eventually leads to circuit failure. (Image Omitted) The described circuit structure has three stress inverters 1, 2, 3 and one reference inverter 4 (Fig. 1) for early detection of Vt degradation. The structures, positioned on functional chips, are operated under stress conditions leading to Vt degradation. Vt degradation is precipitated when the transistors are DC operated.