In modern industrial equipment, pressure sensors and measuring instruments play an indispensable role. Pressure sensors, as devices that convert non-electrical quantities into electrical signals, are crucial for the accuracy and stability of industrial production process control. Measuring instruments, supported by analog electronics technology, typically include sensors, sampling devices at detection points, amplifiers (for interference suppression and signal transmission), and power supplies and optional field display components. Electrical signals are mainly divided into continuous and discrete quantities, but can be further subdivided into analog quantities, switching quantities, pulse quantities, etc. Analog signal transmission usually adopts a unified signal standard, such as 4-20mA DC.
In the wave of the digital age, measurement instruments have undergone significant technological innovation and iterative development. In recent years, ASIC (Application-Specific Integrated Circuit) technology has been widely adopted, integrating sensors, microprocessors, and network interfaces into a single device to achieve integrated functions such as information acquisition, processing, transmission, and storage. In the field of automation instrumentation, measurement instruments are often referred to as transmitters, such as faulty transmitters and pressure transmitters. These transmitters not only improve measurement accuracy and stability but also enable real-time data transmission and remote monitoring, providing strong technical support for industrial production processes.
The history of pressure sensors dates back more than 70 years. Their development can be divided into the following four stages:
1. Invention Stage (1945-1960)
This stage is marked by a significant milestone: the invention of the bipolar transistor in 1947. From then on, the unique properties of semiconductor materials began to be widely applied. In 1945, C.S. Smith discovered the piezoresistive effect in silicon and germanium, demonstrating that the resistance of a semiconductor material changes significantly when an external force is applied. Based on this principle, researchers created early pressure sensors by attaching strain gauges to a thin metal film, converting force signals into electrical signals for measurement. The smallest sensors produced during this period were approximately 1 cm in size.
2. Development Stage (1960-1970)
With the continuous advancement of silicon diffusion technology, technicians can select appropriate crystal orientations on the (001) or (110) crystal planes of silicon to directly diffuse strain resistors onto the crystal planes and process them into a concave shape on the back side, forming a thin and tough silicon elastic diaphragm, which is called a silicon cup. This type of silicon cup sensor has significant advantages such as small size, light weight, high sensitivity, good stability, low cost, and easy integration. It has successfully achieved the eutectic bonding of metal and silicon, laying a solid foundation for commercial development.
3. Commercialization Phase (1970-1980)
During this stage, based on the silicon cup diffusion theory, anisotropic etching technology for silicon was widely applied. Diffused silicon sensors, with their unique processing technology and centered on anisotropic etching, have continuously developed into advanced technologies capable of automatically controlling silicon film thickness. These technologies include V-groove method, concentrated boron automatic stop method, anodizing automatic stop method, and microcomputer-controlled automatic stop method. Because etching operations can be performed simultaneously on multiple surfaces, thousands of silicon pressure diaphragms can be produced concurrently, thus achieving an integrated factory processing model, further reducing costs, and providing strong support for large-scale commercial production.
4. Micromachining stage (1980 to present)
Since the advent of nanotechnology at the end of the last century, breakthroughs have been achieved in micromachining. This process allows for the precise fabrication of structural pressure sensors under computer control, with dimensions controllable even at the micrometer level. This technology enables the etching of micrometer-scale grooves, strips, and membranes, ushering in the micrometer-scale era for pressure sensors. This advancement has significantly propelled the miniaturization and precision development of pressure sensors.
Today, pressure sensors are widely used in various industries. In recent years, with the rapid development of home appliances, automobiles, and the information industry, the demand for sensors has exploded, driving the rapid development of the sensor manufacturing industry and further boosting the prosperity of industrial equipment, especially semiconductor equipment manufacturing.
