Characteristics of high sensitivity MEMS pressure sensor chip for 10 kPa utilizing a novel electrical circuit are presented. The electrical circuit uses piezosensitive differential amplifier with negative feedback loop (PDA-NFL) based on two bipolar-junction transistors (BJT). The BJT has a vertical structure of n-p-n type (V-NPN) formed on a non-deformable chip area. The circuit contains eight piezoresistors located on a profiled membrane in the areas of maximum mechanical stresses. The experimental results prove that pressure sensor chip PDA-NFL with 4.0×4.0 mm2 chip area has sensitivity S = 10.1 ± 2.3 mV/V/kPa with nonlinearity of 2KNL = 0.26 ± 0.12 %/FS (pressure is applied from the back side of pressure sensor chip).

High sensitivity MEMS pressure sensor chip for different ranges (1 to 60 kPa) utilizing the novel electrical circuit of piezosensitive differential amplifier with negative feedback loop (PDA-NFL) is developed. Pressure sensor chip PDA-NFL utilizes two bipolar-junction transistors (BJT) with vertical n-p-n type structure (V-NPN) and eight piezoresistors (p-type). Both theoretical model of sensor response to pressure and temperature and experimental data are presented. Data confirms the applicability of theoretical model. Introduction of the amplifier allows for decreasing chip size while keeping the same sensitivity as a chip with classic Wheatstone bridge circuit.

The small silicon chip of Schottky diode (0.8x0.8x0.4 mm3) with planar arrangement of electrodes (chip PSD) as temperature sensor, which functions under the operating conditions of pressure sensor, was developed. The forward I-V characteristic of chip PSD is determined by potential barrier between Mo and n-Si (ND = 3 × 1015 cm-3). Forward voltage UF = 208 ± 6 mV and temperature coefficient TC = -1.635 ± 0.015 mV/⁰C (with linearity kT <0.4% for temperature range of -65 to +85 ⁰C) at supply current IF = 1 mA is achieved. The reverse I-V characteristic has high breakdown voltage UBR > 85 V and low leakage current IL < 5 μA at 25 ⁰C and IL < 130 μA at 85 ⁰C (UR = 20 V) because chip PSD contains the structure of two p-type guard rings along the anode perimeter. The application of PSD chip for wider temperature range from -65 to +115 ⁰C is proved. The separate chip PSD of temperature sensor located at a distance of less than 1.5 mm from the pressure sensor chip. The PSD chip transmits input data for temperature compensation of pressure sensor errors by ASIC and for direct temperature measurement.

Research of pressure sensor chip utilizing novel electrical circuit with bipolar-junction transistor-based (BJT) piezosensitive differential amplifier with negative feedback loop (PDA-NFL) for 5 kPa differential range was done. The significant advantages of developed chip PDA-NFL in the comparative analysis of advanced pressure sensor analogs, which are using the Wheatstone piezoresistive bridge, are clearly shown. The experimental results prove that pressure sensor chip PDA-NFL with 4.0x4.0 mm2 chip area has sensitivity S = 11.2 ± 1.8 mV/V/kPa with nonlinearity of 2KNLback = 0.11 ± 0.09 %/FS (pressure is applied from the back chip side) and 2KNLtop = 0.18 ± 0.09 %/FS (pressure is applied from the top chip side). All temperature characteristics have low errors, because the precision elements balance of PDA-NFL electric circuit was used. Additionally, the burst pressure is 80 times higher than the working range.

The theoretical model and experimental characteristics of ultra-high sensitivity MEMS pressure sensor chip for the range of -1…+1 kPa utilizing a novel electrical circuit are presented. The electrical circuit uses piezosensitive differential amplifier with negative feedback loop (PDA-NFL) based on two bipolar-junction transistors (BJT). The BJT has a vertical structure of n-p-n type (V-NPN) formed on a non-deformable chip area. The circuit contains eight piezoresistors located on a profiled membrane in the areas of maximum mechanical stresses. The circuit design provides a balance between high pressure sensitivity (S = 44.9 mV/V/kPa) and fairly low temperature dependence of zero output signal (TCZ = 0.094% FS/°C). Additionally, high membrane burst pressure of P = 550 kPa was reached.

The investigation of the pressure sensor chip’s design developed for operation in ultralow differential pressure ranges has been conducted. The optimum geometry of a membrane has been defined using available technological resources. The pressure sensor chip with an area of 6.15х6.15 mm has an average sensitivity S of 34.5 mV/кPa/V at nonlinearity 2KNL = 0.81 %FS and thermal hysteresis up to 0.6 %FS was created. Owing to the chip connection with stop elements, the burst pressure reaches 450 кPa.

A mathematical model of an ultrahigh sensitivity piezoresistive chip of a pressure sensor with a range from -0.5 to 0.5 kPa has been developed. The optimum geometrical dimensions of a specific silicon membrane with a combination of rigid islands to ensure a trade-off relationship between sensitivity (Ssamples = 34.5 mV/kPa/V) and nonlinearity (2KNL samples = 0.81 %FS) have been determined. The paper also studies the range of the membrane deflection and makes recommendations on position of stops limiting diaphragm deflection in both directions; the stops allow for increasing burst pressure Pburst up to 450 кPa. The simulated data has been related to that of experimental samples and their comparative analysis showed the relevance of the mathematical model (estimated sensitivity and nonlinearity errors calculated on the basis of average values are 1.5% and 19%, respectively).

A mathematical model of a high-sensitivity pressure sensor with a novel electrical circuit utilizing piezosensitive transistor differential amplifier with negative feedback loop (PDA-NFL) is presented. Circuits utilizing differential transistor amplifiers based on vertical n-p-n and lateral p-n-p transistors are analyzed and optimized for sensitivity to pressure and stability of output signal in operating temperature range. Parameters of fabrication process necessary for modeling of I-V characteristics of transistors are discussed. The results of the model are sufficiently close to the experimental data.

The paper presents MEMS pressure sensor chip utilizing novel electrical circuit with bipolar-junction transistor-based (BJT) differential amplifier with negative feedback loop (PDA-NFL). Pressure sensor chips with two circuits have been manufactured and tested: the first chip uses circuit with vertical n-p-n (V-NPN) BJTs and the second – circuit with horizontal p-n-p (L-PNP) BJTs. The demonstrated approach allows for increase of pressure sensitivity while keeping the same chip size. It also can be used for chip size reduction and increase of pressure overload capability while maintaining the same pressure sensitivity. Significant reduction of both noise and temperature instability of output signal has been demonstrated using transistor amplifier with negative feedback loop.