Solid state pressure sensor
AssigneeSTMicroelectronics S.r.l.
InventorsManuela Larosa, Giovanni Sicurella
Life of this patent
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Abstract
A solid state sensor to sense pressure includes a semiconductor substrate having a crystallographic design axis, and an odd number of identical inverter modules coupled in series to form a ring oscillator on the semiconductor substrate. Each inverter module includes a pair of structurally identical CMOS inverter stages. A logic input circuit starts oscillation of the ring oscillator and select a signal propagation path therein, either through CMOS inverter stage more affected by the induced mechanical stress or through CMOS inverter stages less affected by the pressure, using two logic command signals. The ring oscillator allows a reading of a frequency of oscillation based on the two logic command signals.
Claims14
A solid state sensor configured to sense pressure comprising:
- a semiconductor substrate having a crystallographic design axis;
- an odd number of identical inverter modules coupled in series to form a ring oscillator on said semiconductor substrate;
- each inverter module comprising a pair of structurally identical CMOS inverter stages comprising a plurality of MOS transistors and resistors, with each MOS transistor comprising a channel, with each resistor having a longitudinal axis, and with a spatial orientation of said plurality of transistor channels and the longitudinal axes of said plurality of resistors being oriented parallel to the crystallographic design axis at an angle from it, respectively, and having rise and fall times less affected and more affected, respectively, by pressure;
- and
- a logic input circuit configured to start oscillation of said ring oscillator and select a signal propagation path therein, either through CMOS inverter stages more affected by the induced mechanical stress or through CMOS inverter stages less affected by the pressure, using two logic command signals;
- said ring oscillator being configured to allow reading of a frequency of oscillation based on the two logic command signals.
A solid state sensor configured to sense pressure comprising:
- a semiconductor substrate having a crystallographic design axis;
- a plurality of inverter modules coupled in series to form a ring oscillator on said semiconductor substrate;
- each inverter module comprising a pair of CMOS inverter stages comprising a plurality of first and second devices, with said plurality of first devices being oriented parallel to the crystallographic design axis and with said plurality of second devices being oriented at an angle from the crystallographic design axis it, and having rise and fall times less affected and more affected, respectively, by pressure;
- and
- a logic input circuit configured to start oscillation of said ring oscillator and select a signal propagation path therein, either through CMOS inverter stages more affected by the induced mechanical stress or through CMOS inverter stages less affected by the pressure, using two logic command signals;
- said ring oscillator being configured to allow reading of a frequency of oscillation based on the two logic command signals.
A method of making a solid state sensor configured to sense pressure comprising:
- forming an odd number of identical inverter modules coupled in series to form a ring oscillator on a semiconductor substrate having a crystallographic design axis, and forming each inverter module comprising
- forming a pair of structurally identical CMOS inverter stages comprising a plurality of MOS transistors and resistors, with each MOS transistor comprising a channel, with each resistor having a longitudinal axis, and with a spatial orientation of the plurality of transistor channels and the longitudinal axes of the plurality of resistors being oriented parallel to the crystallographic design axis at an angle from it, respectively, and having rise and fall times less affected and more affected, respectively, by pressure;
- and
- forming a logic input circuit configured to start oscillation of the ring oscillator and select a signal propagation path therein, either through CMOS inverter stages more affected by the induced mechanical stress or through CMOS inverter stages less affected by the pressure, using two logic command signals;
- the ring oscillator being configured to allow reading of a frequency of oscillation based on the two logic command signals.
Dependencies are inferred from the claim text.