Performance-screen ring oscillator with switchable features

A performance-screen ring oscillator (PSRO) test structure, the performance-screen ring oscillator (PSRO) test structure comprising:

• a ring oscillator having a plurality of stages;
• one or more selectable loads, each selectable load being coupled to an output of a corresponding one of the stages of the ring oscillator;
• and
• one or more multiplexers, each multiplexer being coupled to an output of at least one stage of the ring oscillator and being configured to select a configuration of the corresponding selectable load, wherein the selectable load in a first mode is a 180 degree out-of-phase signal.

A performance-screen ring oscillator (PSRO) test structure, the performance-screen ring oscillator (PSRO) test structure comprising:

• a ring oscillator having a plurality of stages;
• one or more selectable loads, each selectable load being coupled to an output of a corresponding one of the stages of the ring oscillator;
• and
• one or more multiplexers, each multiplexer being coupled to an output of at least one stage of the ring oscillator and being configured to select a configuration of the corresponding selectable load, wherein the selectable load in a third mode is alternating current (AC) ground.

A performance-screen ring oscillator (PSRO) test structure, the performance-screen ring oscillator (PSRO) test structure comprising:

• a ring oscillator having a plurality of stages;
• one or more selectable loads, each selectable load being coupled to an output of a corresponding one of the stages of the ring oscillator;
• and
• one or more multiplexers, each multiplexer being coupled to an output of at least one stage of the ring oscillator and being configured to select a configuration of the corresponding selectable load, wherein the selectable load in a fourth mode is a signal having a variable phase.

A performance-screen ring oscillator (PSRO) test structure, the performance-screen ring oscillator (PSRO) test structure comprising:

• a ring oscillator having a plurality of stages;
• one or more selectable loads, each selectable load being coupled to an output of a corresponding one of the stages of the ring oscillator;
• and
• one or more multiplexers, each multiplexer being coupled to an output of at least one stage of the ring oscillator and being configured to select a configuration of the corresponding selectable load, wherein the selectable load in a fifth mode is an electrical float.