| CPC G01K 7/425 (2013.01) [G01R 31/2628 (2013.01); G01R 31/2856 (2013.01); H01L 23/34 (2013.01)] | 38 Claims |
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1. A stress sensor, comprising:
a first ring oscillator circuit on an integrated circuit comprising first one or more inverter stages, each inverter stage of the first one or more inverter stages having a first P-channel metal-oxide-semiconductor field-effect transistor (PMOS) device and a first N-channel metal-oxide-semiconductor field-effect transistor (NMOS) device connected in series between a high voltage supply level and a low voltage supply level such that the first NMOS device limits first current flowing through each inverter stage of the first one or more inverter stages relative to the first PMOS device;
a second ring oscillator circuit on the integrated circuit in proximity to the first ring oscillator circuit, the second ring oscillator circuit comprising second one or more inverter stages, each inverter stage of the second one or more inverter stages having a second PMOS device and a second NMOS device connected in series between the high voltage supply level and the low voltage supply level such that the second PMOS device limits second current flowing through each inverter stage of the second one or more inverter stages relative to the second NMOS device; and
a stress determination circuit configured to receive a first frequency signal generated by the first ring oscillator circuit and a second frequency signal generated by the second ring oscillator circuit and to determine, from the first frequency signal and the second frequency signal, a first stress value for a first stress level along a first stress direction of the integrated circuit and a second stress value for a second stress level along a second stress direction of the integrated circuit, the second stress direction being non-parallel to the first stress direction.
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