Solid-State Piezoresistive Pressure Sensor Application Guide

When semiconductor single crystal silicon material is subjected to external force and produces extremely small strain that is not noticeable to the naked eye, the electron energy level state inside its atomic structure changes, resulting in a drastic change in its resistivity, and the resistor made of the material also changes greatly. This physical effect is called piezoresistive effect. Humans began to discover and study the application value of this effect in the 1950s. Using the principle of piezoresistive effect, three-dimensional integrated circuit process technology and some special special processes, a strain gauge detection bridge composed of strain resistors is made on a specific crystal orientation on a single crystal silicon wafer. At the same time, the elastic mechanical properties of silicon are used to perform special mechanical processing on the same silicon wafer. This mechanical quantity sensor that integrates stress sensitivity and force-electric conversion detection is called a solid-state piezoresistive sensor. The solid-state piezoresistive pressure sensor that detects gas and liquid pressure is called a solid-state piezoresistive pressure sensor, which was born in the late 1960s. Obviously, it is much more advanced in technology than traditional membrane potentiometer, force balance, variable inductance, variable capacitance, metal strain gauge and semiconductor strain gauge sensors, and is still the latest generation of sensors in the field of pressure measurement. Due to their own characteristics and limitations, although it cannot completely replace the above-mentioned mechanical quantity sensors, since the mid-1980s, it has been the leading variety of pressure sensors in the sensor market in the United States, Japan, and Europe, and has almost divided the international market of acceleration sensors with piezoelectric sensors. At present, in the intelligent sensor technology characterized by the intervention of large-scale integrated circuit technology and computer software technology, it is still the most popular because it can be made into a monolithic multifunctional composite sensitive element to form the basis of intelligent sensors. Main features: 1. High sensitivity The sensitivity factor of silicon strain resistors is 50 to 100 times higher than that of metal strain gauges, so the corresponding sensor sensitivity is very high, and the full-scale output is generally about 100mv. Therefore, there are no special requirements for the interface circuit, and the application cost is relatively low. Since it is a non-mechanical structure sensor, the resolution is extremely high, which is called infinite abroad, that is, it is mainly limited by the external detection and readout instrument limitations and noise interference limitations, and generally can reach less than one hundred thousandth of the full scale of the sensor. Silicon piezoresistive sensors have no dead zone in the low-range segment near the zero point and have excellent linearity. 2. High precision Since the perception, sensitive conversion and detection of the solid-state piezoresistive pressure sensor are realized by the same component and there is no intermediate conversion link, the non-repeatability and hysteresis errors are extremely small. At the same time, since the silicon single crystal itself has great rigidity and small deformation, it ensures good linearity, so the comprehensive static accuracy is very high. 3. Small size, light weight, and high dynamic frequency response Since the core adopts an integrated process and has no transmission parts, it is small in size and light in weight. The small size chip plus the extremely high elastic modulus of silicon make the natural frequency of the sensitive element very high. In dynamic applications, the dynamic accuracy is high, the use frequency band is wide, and the use bandwidth can be from zero frequency to 100 kHz by reasonably selecting and designing the sensor appearance. 4. Stable performance and high reliability Since the working elastic deformation is as low as the micro-strain order of magnitude, the maximum displacement of the elastic film is at the sub-micron order of magnitude, so there is no wear, fatigue, or aging. The service life is up to more than 107 pressure cycles. 5. Small temperature coefficient Due to the progress of microelectronics technology, the consistency of the four strain resistors can be very high. In addition, with the progress of laser adjustment technology and computer automatic compensation technology, the zero position and sensitivity temperature coefficient of silicon piezoresistive sensors can reach the order of 10-5/℃, which has exceeded the level of strain sensors with small temperature coefficients in the field of pressure sensors. 6. Wide adaptability to media Due to the excellent chemical corrosion resistance of silicon and its good compatibility with silicone oil, the isolated structure is easy to realize. Even non-isolated piezoresistive pressure sensors have a considerable degree of adaptability to various media. 7. Safety and explosion-proof Due to its low voltage, low current and low power consumption characteristics, it is an intrinsically safe explosion-proof product that can be widely used in various chemical industry detection and control fields with the best cost performance.