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Do you know how the amazing principle of single-crystal silicon etching affects the development of technology?
In the field of micro-manufacturing, etching is an indispensable and important step. This process allows technological products to achieve precise structures. Each wafer goes through multiple etching steps during the production process. This technology not only affects the performance of electronic components, but also directly affects the electronic products we use in our daily lives, such as mobile phones and computers. What’s more interesting is, what unknown principles are hidden behind this?
Etching is a process that chemically removes layers from the surface of a wafer, which makes the material's structure finer.
During the etching process, a certain "mask" material is often used to resist the etchant, so that the etching process can be precisely controlled. Some common mask materials are photoresist and silicon nitride. Among the various etching methods, we can usually divide them into liquid phase etching (wet etching) and vapor phase etching (dry etching). The differences in these methods will profoundly affect the final material structure and its properties.
Development and Challenges of Wet Etching
Before the 1980s, liquid phase etching was the most commonly used etching method. The process requires immersing the wafer in a chemical solution, and the choice of those chemicals affects the end result. Take buffered hydrofluoric acid (BHF), for example. This chemical is often used to etch silicon dioxide, and the accuracy of the etching is controlled through specific variables.
Poor wastewater treatment and environmental damage have led to wet etching being gradually abandoned, especially in the context of today's highly developed technology.
In addition, wet etching also has the problem of isotropic etching, which makes it often impossible to control the desired structure when etching thick films. Therefore, today's microfabrication processes tend to rely on dry etching techniques, especially deep reactive ion etching (DRIE), which can achieve significant differences in horizontal and vertical etching rates.
Introduction and advantages of dry etching
With the advancement of technology, dry etching technology has gradually emerged and become the mainstream of today's very large scale integration (VLSI) process. Its working principle is to use free radicals in plasma in a low-pressure environment to achieve efficient etching of materials. This method not only increases the etching speed, but also achieves higher precision.
Plasma has replaced traditional liquid chemical etching and brought revolutionary changes to the micro-manufacturing industry.
Such a transformation undoubtedly increases the functionality of etching. Plasma etching can select different gases as source gases according to different needs, and different gases will affect the depth and accuracy of etching. This means that today's micromanufacturing technology can more flexibly adapt to diverse production needs.
Relationship between crystal orientation and etching
In the etching process of single crystal silicon, an important concept is that the crystal orientation affects the etching effect. For example, in single crystal silicon, different crystal planes (such as <100> and <111>) have different etching rates. This phenomenon is called anisotropic etching. This not only allows the final structural shape to be controlled, but also enables more complex designs.
By precisely controlling the etching directions, microfabrication technology can create ever-finer structures, which is one of the core technologies required for modern electronic devices.
For example, if a (100) crystal plane is etched, a pyramidal structure can be created through the mask material, which is critical in some semiconductor devices. Such technology opens up new possibilities, not only improving component performance but also changing the way designs are designed.
Future Outlook
The development of etching technology is not only applied to the traditional semiconductor industry, but its principles are also gradually entering emerging scientific and technological fields, such as MEMS (microelectronic electromechanical systems) and optical systems. With the rise of new materials, future etching technology may bring more innovations. And how will all this affect our upcoming technological lives?
Through continuous progress, etching technology is shaping our future, which makes us wonder what infinite possibilities future technology will have?
