Micro-nano Processing Technology: Dry Etching And Wet Etching

In the process of micro-nano processing, etching is a key step after photolithography, which is to selectively remove unnecessary etching materials from the surface of silicon wafers by chemical or physical methods, and then form circuit patterns defined by photolithography. In other words, keep what you want and remove what you don't want. The etching process in micro-nano processing technology is currently mainly divided into two etching methods: dry etching and wet etching.
Wet etching is a method of stripping off the etched substance through the chemical reaction between the chemical etching solution and the etched substance. Strong adaptability, good surface uniformity, less damage to silicon wafers, suitable for almost all metal, glass, plastic and other materials. However, due to its limitations in line width control and etching directionality: most wet etching is isotropic etching that is not easy to control, the fidelity effect of pattern etching is not ideal, and the uneven etching line width is difficult. Take control. Dry etching has become the current mainstream process.
Dry etching is to expose the surface of the silicon wafer to the plasma generated in the gaseous state. The plasma passes through the window opened by the photoresist and has a physical/chemical reaction with the silicon wafer, thereby removing the exposed surface material. Compared with wet etching, the advantage of dry etching is that the etching profile is anisotropic and has better line width control ability, so as to ensure the fidelity of fine patterns after transfer. At the same time, because no chemical reagents are used, chemical Pollution as well as issues such as material consumption and waste gas treatment costs. The disadvantage is: high cost.
Dry etching mainly includes metal etching, dielectric etching and silicon etching, among which metal etching is mainly used for aluminum alloy etching of metal interconnection lines, making tungsten plugs and contact metal etching; dielectric etching is mainly used for Make contact holes and through holes; silicon etching is mainly used to make polysilicon gates in MOS gate structures and device isolation or single crystal silicon grooves in DRAM capacitor structures.