Etching is a key step in the semiconductor manufacturing process, and it can be performed in two main ways: dry etching and wet etching. Dry etching uses plasma or gas to remove material from the wafer, which is very important in the manufacture of products such as DRAM and Flash memory. It can precisely control the shape and depth of the etching, achieve vertical sidewalls and high aspect ratio, and is suitable for fine feature etching.
In contrast, wet etching relies on liquid chemical solutions to remove materials. This method is more common in fields such as wafer-level packaging, MEMS, optoelectronic devices, and photovoltaics. Wet etching is simple to operate and low in cost, but side etching will occur during the etching process, which may affect the precise control of line width, so it is not very suitable for fine etching.
The advantage of dry etching is its directionality and selectivity, which can achieve anisotropic etching, such as conical or vertical shapes. Wet etching, on the other hand, has the advantages of uniformity and low cost, but is usually only isotropic, that is, the etching rate is the same in all directions.
When choosing an etching method, if the process requirements can only be achieved by dry etching, then dry etching will be used. If both methods can meet the requirements, wet etching, which is less expensive, is usually preferred. However, if precise control of line width or etching at a specific angle is required, dry etching is a better choice. In addition, some special structures, such as the inverted pyramid structure in MEMS, can only be achieved by wet etching.
In general, dry and wet etching have their own advantages and disadvantages, and the choice of which method depends on the specific process requirements and cost considerations.
