“Sensor technology is one of the indispensable types of modern technology. It is necessary for everyone to understand sensor technology. If you want to learn about sensor technology from the basic content, you can read past articles in the editor. In this article, the editor will introduce the FSI image sensor technology and analyze the four major technologies that power sensors need to break through.
Sensor technology is one of the indispensable types of modern technology. It is necessary for everyone to understand sensor technology. If you want to learn about sensor technology from the basic content, you can read past articles in the editor. In this article, the editor will introduce the FSI image sensor technology and analyze the four major technologies that power sensors need to break through.
1. FSI image sensor technology
Traditionally, image sensors are designed according to the manufacturing process. Therefore, for the final device, the light enters between the metal control lines in the front, and then is focused on the photodetector. For a long time, FSI has been very effective for larger pixels, because the ratio of the height of the pixel stack to the area of the pixel is large, resulting in a large aperture of the pixel. The shrinking pixels require a series of pixel technology innovations to solve the limitations of the previous illumination technology in terms of materials and manufacturing. For example, FSI has adopted many innovative technologies and process improvements, such as shape-optimized microlenses, color-optimized filtering, concave pixel arrays, light pipes, and anti-reflection coatings to optimize the light path of FSI pixels.
The light entering the FSI pixel is initially focused by a microlens with an anti-reflection coating, which is also used as an aperture. In mobile phones, the design of the microlens must be able to meet the requirements of lens quality and greater chief ray angle. The light passes through the microlens and is concentrated on a color filter with the best density and thickness designed for low-light response and signal-to-noise ratio (SNR) optimization, ensuring that it is completely separated into the three primary color components. The curvature and thickness of the microlens must be carefully selected so that the light transmitted by the color filter is received by the light pipe as much as possible.
Although the light pipe is designed to collect the light emitted from the microlens and make it pass through the interconnecting metal and isolation stack in the form of a narrow beam, it can still effectively shorten the height of the light stack (see the schematic diagram in the center of Figure 1) and make it parallel The light beam is directed into the photodiode area (Figure 2).
The light pipe must converge any light within the range of the cone of light and the principal angle of light (CRA) determined by the aperture. More advanced semiconductor manufacturing processes use smaller feature sizes and shift from aluminum processes to copper processes, which can provide narrower metal widths and realize wider light pipes. Combining these improvements, the pixel array can be concave, reducing the stack height above the pixel array to the thickness of only two metal layers.
Once the light pipe transmits the photons to the surface of the silicon chip, the photodiode starts to work. In view of the light absorption characteristics of silicon wafers, the area of the photodiode should extend to a depth of several microns. When designing a photodetector, the depletion depth can be extended into the silicon wafer to maximize the spatial resolution of photon collection and storage (see the schematic diagram at the far right in Figure 1). The key is to maximize the isolation between adjacent photodiodes and form a deep junction to eliminate any photocharges generated by photons of larger wavelengths that are not absorbed in the photodiodes.
Second, the breakthrough point of power sensor technology
At present, the core technologies that my country’s electric power sensors need to break through are mainly concentrated in the following four aspects:
1. Breakthrough in power sensing materials and device technology.
Develop AC and DC electrical quantity sensors to meet the requirements of DC measurement and power quality; cultivate low-cost, high-reliability, current, partial discharge, gas and vibration optical sensor components that can be integrated with primary equipment; accelerate surface acoustic wave, infrared and Research and development of non-contact temperature sensors such as thermopile.
2. Research and develop low-power, broadband and narrow-integrated wireless sensor network protocols and products to meet the needs of power perception, taking into account indicators such as ultra-low power consumption and bandwidth; establish wireless sensor network interconnection and interoperability based on consistent communication protocols and evaluation methods Evaluation system to solve the compatibility of products and agreements of different suppliers and various performance evaluation issues.
3. Aiming at the rapid response characteristics of power perception applications, an intelligent analysis technology platform is formed to realize “sensing + in-situ analysis”. Based on the “platform + application” model, it deeply integrates perception, measurement, and control to solve the fragmentation problem of power smart sensor technology and applications.
4. Master sensor energy and integrated packaging and testing technology.
Research the application and optimization of environmental micro-energy collection technology, and research and develop energy acquisition devices integrated with power sensors. According to the power system’s strong electromagnetic interference and other working conditions, integrated design, research and development of intelligent sensors integrating sensing, communication, calculation, security and energy acquisition functions, forming a series of products, and establishing a weather resistance and reliability test verification system .